APPLIED SOLID STATE CHEMISTRY № 3 (8) 2019

APPLIED SOLID STATE CHEMISTRY№ 3 (8) 2019

SCIENTIFIC-PRACTICE JOURNAL. Registered at the Federal Service on the Monitoring in the Sphere of Communication, Informational Technolo-gies and Mass Communication. Published in association with the Russian Professors Assembly and Lobachevsky University Reg. PI № FS 77-939 to 13.12.2017. Published 4 times a year.

EDITOR-IN-CHIEFAlexander V. Knyazev, Lobachevsky University, RussiaEDITORIAL BOARDArtem R. Oganov, Skolkovo Institute of Science and Technology, RussiaEvgeny N. Bulanov, Lobachevsky University, RussiaMikhail F. Churbanov, G.G. Devyatykh Institute of Chemistry of High-Purity Substances, RussiaZhili Dong, Nanyang Technological University, SingaporeVladimir N. Emel’yanenko, University of Rostock, GermanyStanislav K. Filatov, Saint Petersburg University, RussiaSafri Ishmayana, Universitas Padjadjaran, IndonesiaErkki Lähderanta, Lappeenranta University of Technology, FinlandMiroslaw Mączka, Institute of Low Temperature and StructureResearch, Poland Waldeci Paraguassu, Federal University of Pará, BrazilViktor N. Serezhkin, Samara University, Russia

Address publishers / editors:Bldg. 7, 26/55, Kosmodamianskaya Emb.,Moscow, 115035. E-mail: [email protected] Subscription Centre: (495) 617-18-88 (multichannel).

Subscription in Russia:«Rospechat’» — 81038;«United catalogue» — 10618;«Russian post. Electronic catalogue» — П8320.

Size 170х252 mm. Offset printing.Offset paper № 1. Printer’s sheet 7,0.Conventional printed sheet 7,0.Passed for printing 25.06.2018.

Issue was published 30.06.2019.ISSN — 2619–0141.Circulation 3000 copies. Free market price.

Printed by “National Polygraphic Group”.Bldg. 2, street Svetlaya, Kaluga, 248031.Tel.: (4842) 70-03-37.Journal is included in the databaseof the Russian Science Citation Index.

Complete or partial reproduction of materialswithout prior written permission of authorsor the Editorial Offi ce shall be prosecuted inaccordance with law.

Channel in the telegram:https://t.me/appssc

Group Vkontakte: https://vk.com/appssc

Google Scholar: https://scholar.google.ru/citations?hl=ru&authuser=1&user=IkAt-e1YAAAAJ

Mendeley: https://www.mendeley.com/profi les/applied-solid-state-chemistry/

Website of the journal: http://appssc.me/view-articles/

Founder: Publishing Group «Jurist».

APPLIED SOLID STATE CHEMISTRY № 3 (8) 20192 APPLIED SOLID STATE CHEMISTRY № 3 (8) 2019

Contents

Korolev P.V. , Korolev A.V. , Knyazev A.V.Influence of insoluble component on C→T and Т→М phase transformations and structure formation under annealing of plasma-spray synthesized nanocrystalline powder systems (100-x)ZrO2(3Y)+xAl2O3 (x = 0 and 20 wt%). Part 2: Analysis of powders after annealing. . . . . . . . . . . . . . . . . . . . . . . . . . . 3Mamedova G.A. Synthesis and research of the zeolite of gismondine . . . . . . . . . . . . . . . . . . . .27Podzorova* L.I., Ilicheva A.A., Kutuzova V.E., Penkova O.I., Antonova O.S., Baikin A.S., Konovalov A.A.Microstructure and resistance To brittle fracture of Al2O3 – (Ce–TZP) system composites . . . . . . . . . . . . . . . . . .36Shaidurova G., Ryabinina N., Shevyakov Y. Analytical research in application of high-silica composite materials . . . . . . . . . .41Volchenkova V.A., Kazenas E.K., Andreeva N.A., Fomina A.A., Penkina T.N., Podzorova L.I., Ilyicheva A.A. Improvement of metrological characteristics of aes-icp Determination of impurity elements in zirconium ceramic Materials for medical purposes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43

3APPLIED SOLID STATE CHEMISTRY

P.V. Korolev, A.V. Korolev, A.V. Knyazev

№ 3 (8) 2019APPLIED SOLID STATE CHEMISTRY № 3 (8) 2019

Influence of insoluble component on C→T and Т→М phase transformations and structure formation under annealing of

plasma-spray synthesized nanocrystalline powder systems (100-x)ZrO2(3Y)+xAl2O3 (x = 0 and 20 wt%). Part 2: Analysis of powders after annealing.

DOI: 10.18572/2619-0141-2019-3-3-3-26

Korolev P.V., Korolev A.V. Limited Liability Company “Scientific Enterprise” High Technologies”, Po Box 6, 428018

Cheboksary, RussiaKnyazev A.V.

National Research Lobachevsky State University of Nizhny Novgorod, Gagarin Prospekt 23/2, 603950 Nizhny Novgorod, Russia

E-mail: [email protected] (P.V. Korolev)

Abstract The effect of annealing at 800–1300 °C on the phase composition and nanostruc-ture of two nanocrystalline powders (100-x)ZrO2(3Y)+xAl2O3 (x = 0 and 20 wt%) obtained by HFDP-SP was studied. It was found that the presence of Al2O3 in the system restrained the growth of CSD size of the C- and T-phases and contributed to the completion of the C→T transformation at a temperature of approximately 100 °C higher As well as the pres-ence of Al2O3 leaded to the formation of a comparable amount of the M-phase of zirconi-um dioxide at higher temperatures. The existence of a “critical size” of CSD was revealed (about 10 nm), above which a solid solution of C-ZrO2(3Y,Al) underwent transformation into a solution of T-ZrO2(3Y,Al). The transition was preceded by the growth of the unit cell parameter. Another identified “crit-ical size” (about 70 nm) corresponded to the complete decomposition of the T-ZrO2(3Y,Al)solid solution to the T-ZrO2(3Y,Al) state, which was realizing at temperatures of 1100 °C and above. Alumina formed in the T-ZrO2(3Y,Al)+20%Al2O3 system after the decomposition of T-ZrO2(3Y,Al) experienced a transformation that developed at temperatures ap-proximately 100 °C higher than in pure Al2O3 synthesized in a similar way.

Keywords: nonequilibrium solid solution of ZrO2(Y,Al); nano-Al2O3; plasma-spray pyroly-sis; critical size; nanocomposite structure.

4 APPLIED SOLID STATE CHEMISTRY


№ 3 (8) 2019

1. Introduction

In part 1 of this work [1], the phase composition of HFDP-SP powders of composition (100-x)ZrO2(3Y)+xAl2O3 (where x = 0 and 20 wt%) formed after synthesis was investigated. On the diffractorhamm of HFDP-SP powder ZrO2(3Y) after synthesis, the coexistence of "finegrained" nanocrystalline cubic (C) phase and nanocrystalline tetragonal and mono-clinic (T and M) phases with larger crystallites was observed [1]. The lattice parameters of these phases were usual for a given composition and crystallite size [1]. At the same time, on the diffractogram of HFDP-SP powder ZrO2(3Y)+20%Al2O3, C- and T- phases were observed, similar to the previous ones in CSD size, but with reduced parameters [1]. At the same time, the M-phase in this system was absent after synthesis [1]. The decrease in parameters was because of the dissolution of Al2O3 and the formation of non-equilibrium solid solutions of ZrO2(3Y,Al) of the “substitution” type [1]. It should be noted that the thermal stability of phase and structural states formed during the synthesis of the above-mentioned HFDP-SP powders of ZrO2 and ZrO2+20%Al2O3 are practically not studied. In our previous work [2], under DSC heating of HFDP-SP powders of similar composition, a number of thermal effects occurring in different temperature ranges were detected, Fig. 1.

Fig. 1 DSC heating curves for HFDP-SP powders ZrO2(3Y) (1) and ZrO2(3Y)+20%Al2O3 (2) from [2].

In the first material, intense exothermic processes were observed, occurring in the tem-perature ranges of 300–450 and 750–1300 °C, Fig. 1 (curve 1). For the second material, a relatively weak exothermic peak was detected at 840 °C, Fig. 1 (curve 2). However, the nature of the above exothermic peaks in both materials was not fully clarified in [2]. Nev-ertheless, a significant influence exerted by the presence of an “insoluble” component (Al2O3) on the structural changes that were taking place was clearly observed. It is known that when amorphous precursors based on ZrO2 and ZrO2(Y) are heated in the temperature range of 300–450 °C, crystallization processes usually occur, often accompa-nied by exoeffects [2–10]. When heated, amorphous precursors based on ZrO2-Al2O3and ZrO2-Y2O3-Al2O3 systems, under the influence of alumina, the effects of crystallization of-ten shift to temperatures of 800-900 °C and above [5-10]. In addition, in the temperature range 800–1300 °C, in nanocrystalline powder systems ZrO2(Y), ZrO2-Al2O3 and ZrO2-Y2O3-Al2O3, thermal effects associated with M→T or T→M transformations into ZrO2 can be ob-served [2] phase transformations in Al2O3 [11,12] and other physicochemical processes occurring during heating. For example, effects may be associated with the decomposition of non-equilibrium solid solutions of the ZrO2(3Y,Al) type. However, thermal effects of a different signs, flowing in parallel, and, in the nanocrystalline state, can be superimposed, as a result of which the total thermal effect can be insignificant. In this connection, an additional investigation of powders after thermal treatment with structural methods, for example, X-ray diffractometry (XRD), is required.



№ 3 (8) 2019

It is known that solid solutions of the ZrO2(Al) and ZrO2(Y,Al) types, being unstable, de-compose upon annealing. Table 1 presents literature data on the thermal stability of the ZrO2(Al) and ZrO2(Y,Al) type solid solutions in nanostructured powder systems obtained by various methods and on the sequence of phase transformations during decomposi-tion.

Table 1. Literature data of heat treatment effect on non-equilibrium solid solutions of ZrO2(Al) and ZrO2(Y,Al) and the sequence of phase transformations during their decom-

position

It can be seen that the temperature limit for the existence of nonequilibrium Al-contain-ing solid solutions with cubic and tetragonal symmetry differs significantly and depends both on the specific composition and on the synthesis method, Table 1. It is easy to see that the main phase changes in most systems occur at temperatures of 800-1300 °C. Here-with, the sequence of phase transformations and the final phase composition at maxi-mum temperatures depend on the composition and method of preparation. For example, under the influence of dissolved ions (Al3+), C→T and T→M transformations in systems with different Al2O3 contents are carried out under different conditions. It is also seen that solid solutions of ternary composition of the ZrO2(Y,Al) type are less studied than solutions of the ZrO2(Al) type. One of the most important structural indicators of the decomposition of nonequilibrium



№ 3 (8) 2019

solid solutions of the ZrO2(Al) and ZrO2(Y,Al) types is the change in their parameters with increasing heat treatment temperature. However, to the study of parameters insufficient attention was paid. Therefore, only a few works can be found to contain relevant data. For an example, in Fig. 2,a,b, data on the effect of the annealing temperature on the parame-ters and tetragonality of nonequilibrium T-ZrO2(Al) solid solutions from [15] are presented.

a) b) Fig. 2 Effect of annealing temperature on parameters (a) and tetragonality (b) of nonequilibrium

T-ZrO2(Al) solid solutions from [15].

It can be seen that the more Al2O3 dissolved in the lattice, the higher the temperature of the complete decomposition of the nonequilibrium solid solution. Evidence of decay is the approximation of the parameters of the T-phase and its tetragonality to the values characteristic for the 0 mol% Al2O3 in composition. For compositions with 15–30 mol% Al2O3 with a cubic lattice, the total decomposition temperatures were above 900 °C. The above structural changes were accompanied by an increase in the crystallite size of the T-phase. Herewith, the growth rate of crystallites decreased, and the temperature of the recrystallization onset increased with increasing amount of dissolved Al2O3 [15]. This led to the formation of the M-phase at higher annealing temperatures [15]. The nature of the annealing effect on the parameters of nonequilibrium solid solutions of the ZrO2(Y,Al) type is less known. In the most general terms it can be judged by the results of the work [10]. So, in the case of annealing of a T-ZrO2(3Y,Al) solid solution, parameter c remained at the same level up to a temperature of about 900 °C [10], Fig. 3. Further, in a narrow temperature range of 900–1000 °C, there was a sharp increase up to the value of an equilibrium solid solution T-ZrO2(3Y), which was evidence of the decomposition of a nonequilibrium solid solution [10], Fig. 3.

Fig. 3 Effect of annealing temperature on the parameter c of the nonequilibrium solid solution T-ZrO2(3Y,Al) in the ZrO2(3Y) + 10mol% Al2O3 system from [10].



№ 3 (8) 2019

However, about the effect of annealing on the crystallite size and other important param-eters of the fine crystal structure was not reported. In [17], during annealing of HFDP-SP powder with a nonequilibrium solid solution of C-ZrO2(9.4Y,Al), an increase in the parameter of the cubic phase was observed at tempera-tures above 900 °C. It also reflected the process of decomposition of this non-equilibrium solid solution. At the same time, the existence of a “critical size” of CSD (about 20 nm) was revealed, above which the C-ZrO2(9.4Y,Al) solid solution lost stability and decomposed to the C-ZrO2(9.4Y) solution [17]. The decay was preceded by an increase in the level of microstrains of the C-phase lattice [17]. Considering that these and other similar data for systems with non-equilibrium solid solu-tions like ZrO2(3Y,Al) are practically absent in the literature, repeated in-depth studies of the HFDP-SP systems (100-x)ZrO2(3Y) + xAl2O3 (x = 0 and 20 wt%) after annealing are ac-tual. In this regard, the purpose of this work was: 1) X-ray study of the structure and phase composition of (100-x)ZrO2(3Y) + xAl2O3 (x = 0 and 20 wt%) powders after annealing at 800–1300 ° C; 2) the study of the mutual influence of the main components on the phase state of each other; 3) estimation of the parameters of the unit cell and the parameters of the fine crystal structure of solid solutions ZrO2(3Y) and ZrO2(3Y,Al) type after annealing and revealing the effect of the insoluble component (Al2O3) on them; 4) study of the decomposition processes of non-equilibrium solid solutions like ZrO2(3Y,Al), and related transformations in zirconium dioxide (including T→M), occurring in the pres-ence of Al2O3, as well as transformations of Al2O3 after annealing; 5) clarification of the possible mechanisms of decomposition of nonequilibrium solid solutions of the ZrO2(3Y,Al) type.

2. Materials and experimental procedures

The powders (100-x)ZrO2(3Y)+xAl2O3 (where x = 0 and 20 wt%), which we studied earlier in [1], were investigated. In the following description, we will denote these compositions, respectively, ZrO2(3Y) and ZrO2(3Y)+20%Al2O3. The powders were annealed in air in a laboratory oven at temperatures of 800, 900, 1000, 1100, 1200 and 1300 °C. The crucible with the material was placed in an oven, subjected to heating, soaking and subsequent cooling with the furnace. The holding time at a given annealing temperature was 1 hour. The phase composition after annealing was determined by X-ray diffractometry. The sur-vey was carried out on an X-ray diffractometer “Shimadzu XRD 6000” in Cu-K -radiation. The step along the angle 2 was 0.02 degrees; the exposure at the point was 20 seconds. The profile analysis of the diffraction patterns and the overlapping lines were carried out in the program “Renex”. During the processing of the lines, their shape was analyzed, and also determined: angular position, integral intensity (area under the curve) and broaden-ing at half height. The T-phase was indexed on the basis of FC unit cell. The lattice parameters of the zirconia T-phase before and after annealing were determined by all lines up to (422) inclusive. The shift (displacement of oxygen anions from a position in the fluorite structure) was calculated using the parameters of the FC cell with helps of formula (1) from [18]:



№ 3 (8) 2019

The content of the M-phase of zirconia was determined by the ratio of the integral inten-sities of the (111) type lines by using the formulas from [19, 20]. The estimation of the average size of the coherent scattering domains (CSD) of the zirco-nia T-phase was carried out using the half-width. For evaluation, the broadening of all its lines up to (422) was taken, inclusive. Then, the Williamson-Hall plots were constructed [21]. The CSD size were determined from the approximating lines of the graphs [21]. In the course of the same procedure, the level of microstrains of the T-phase lattice was es-timated [21]. The average CSD size of the C- and M- phases of zirconia and -Al2O3 in the powders was estimated using the half-width of the low-angles lines using the Selyakov – Scherer for-mula [22]:

where D is the size of CSD, λ is the wavelength, B is the physical line broadening at half height, θ is the diffraction angle of the corresponding line. For the C-phase, the (111) line broadening was used. For the M-phase, the broadening of the lines of (-111) and (111) type was used. For -phase the broadening of line (012) was used.

3. Results and discussion3.1 Phase composition of HFDP-SP powders ZrO2(3Y) and ZrO2(3Y)+20%Al2O3 after annealing at 800–1300 °C

а) b) Fig. 4 Diffraction patterns of ZrO2(3Y) (a) and ZrO2(3Y)+20%Al2O3 (b) powders after annealing at

temperatures of 800-1300 °C with the main lines of the identified phases (T - tetragonal, M - monoclinic, C - cubic zirconia phase; , , - intermediate modifications of Al2O3; - corundum).

In Fig. 4,a, and Fig. 5,b,d, for ZrO2(3Y) powder the diffraction patterns and their fragments after annealing at temperatures of 800–1300 °C are presented, and Table 2 shows the phases identified after annealing. With an increase in the annealing temperature, a change in the intensity of the lines of the C, T, and M phases was observed in the powder, Fig. 4,a. The cubic phase was present up to a temperature of 900 °C, Fig. 5,b,d, after which it disappeared as a result of the completion of the С→T transformation. For the M-phase, there was a decrease in the intensity of its lines in the range up to 1000 °C and a reverse growth in the range 1000-1300 °C, Fig. 4,a. In Fig. 5,b, and Fig. 5,a,c,e, for ZrO2(3Y)+20%Al2O3 powder the diffraction patterns and their fragments after annealing at temperatures of 800–1300 °C are presented, and Table 2 shows the phases identified after annealing.



№ 3 (8) 2019

Table 2 Phase composition of powders after annealing at different temperatures



№ 3 (8) 2019

At temperatures above 800 °C, the disappearance of the amorphous phase maxima (“humps” of the background) characteristic of the initial powder was observed, which indicated crystallization of the amorphous part of the material. These changes in the diffraction pattern were in good agreement with the exothermic peak (about 840 °C), which we observed earlier in the DSC study of a similar powder [2], Fig. 1 (curve 2). Also, at temperatures of 800–900 °C, a significant decrease in the asymmetry of the T-phase lines was observed. Analysis of the experimental profiles showed that this was due to the displacement of the “broad” components (the contributions of the C-phase) towards low angles, Fig.5,a,c. The cubic phase was observed up to a temperature of 1000 °C, Fig. 5,e, after which it disappeared, apparently also as a result of the C→T transformation. At 1000–1100 °C, in addition to the lines of the existing phases, very weak broad maxima, which could be attributed to the strongest lines of intermediate modifications of Al2O3 were appeared. At 2 around 45.5-46°, a line of type (400) or (400) probably were observed. At 2 about 66.5-67°, the line of the type (440) or (3.1.14) probably were observed. After annealing at 1200 °C, more numerous, but also weak lines of -Al2O3 were appeared. At 1200–1300 °C, M-phase lines were observed, Fig. 4,b, although they were significantly weaker than in the ZrO2(3Y) system after annealing at the same temperatures, Fig. 4,a. Aluminum oxide at 1300 °C was present mainly in the form of the -phase, Fig. 4,b. However, traces of the -phase also remained, Fig. 4,b, Table 2. The -Al2O3 lines in the diffractogram were relatively weak compared to the zirconia lines, Fig. 4,b, despite the fact that the nominal amount of Al2O3 in the composition was quite large. The low intensity of its lines in the diffractogram was caused by the smaller values of the atomic and structural scattering factors of alumina compared with zirconia [22]. A comparison of the two systems with each other showed that the presence of Al3+ ions in the composition was led to a delay in the С→T transformation, during annealing. Compared to the T-phase in the ZrO2(3Y) system, the complete conversion to the T-phase in the ZrO2(3Y)+20%Al2O3 system was completed at temperatures approximately 100 °C higher, Table 2. In Fig. 6 presents the results of determining the amount of M-phase in ZrO2(3Y) and ZrO2(3Y)+20%Al2O3 powders after annealing at different temperatures. In the initial state in the ZrO2(3Y) powder, the content of the M-phase was about 16%. In the range of 800–1000 °C, the M-phase content was decreased to 10%. At higher temperatures, its amount was increased again, and at a temperature of 1300 °C it reached 27%, Fig. 6 (curve 1). In the ZrO2(3Y)+20%Al2O3 powder, unlike the ZrO2(3Y) powder, the M-phase was not detected upon annealing up to 1100 °C inclusive. It was detected only at 1200-1300 °C. Wherein, the amount of M-phase in ZrO2(3Y)+20%Al2O3 powder at these temperatures was more than 2-3 times less than in ZrO2(3Y) powder, Fig. 6 (curve 2).

Fig. 6 Effect of annealing temperature on the amount of M-phase in powders: 1 - ZrO2(3Y); 2 - ZrO2(3Y)+20%Al2O3.



№ 3 (8) 2019

The common behavior of the two systems was an increase in the amount of the M-phase at temperatures above 1000 °C (in the ZrO2(3Y) system) and above 1200 °C (in the ZrO2(3Y)+20%Al2O3 system), Fig. 6 (curves 1,2). This indicated to the effect of a common factor for the two systems at these conditions, which was affects the T→M phase transformation. Such a factor could be an intensive growth of crystallite size. At lower temperatures, the second dominant factor prevailed in each of the systems, which, apparently, was own in each of the systems. A comparison of the M-phase in the two powders showed that, in general, the presence of Al3+ ions in the composition of the material had a restraining effect on the Т→M phase transformation. By analogy with [15.23], this could be considered as the “stabilizing” effect of the Al2O3 additive on the tetragonal ZrO2(3Y) solid solution. It is obvious that the additional “stabilizing” effect on the T-phase lattice of dissolved Al2O3 was the “second” factor that influenced the absence of Т→M transformation in the ZrO2(3Y)+20%Al2O3system at temperatures less than 1200 °C, Fig. 6 (curve 2). As for the possible nature of the “second” factor in the ZrO2(3Y) system, its discussion will be conducted in more detail later in another section. In turn to, a comparison of the phase state of alumina in the HFDP-SP powder ZrO2(3Y)+20%Al2O3 and in the HFDP-SP powder of pure Al2O3 from our work [24] showed that the presence of zirconia led to delay of -Al2O3 formation. If in the powder of pure Al2O3, the -phase appeared immediately after the synthesis, then in the ZrO2(3Y)+20%Al2O3 powder its traces were observed only after annealing at 1000-1100 °C, Table 2. Besides, the presence of -Al2O3 traces even after the maximum annealing temperature, Table 2, indicated that the → transformation also was not end completely under these conditions. Usually, → transformation is decisive in the formation of corundum in nanopowders [25–27]. It is known that this transformation is controlled by nucleation and growth processes [28]. At thermal influence, -Al2O3 crystallites should outgrow the “critical size” of approximately 20 nm [25-27]. Only in this case the necessary conditions for their exothermal transformation into -Al2O3 nuclei appear [25-27]. And only then does the rapid growth of -Al2O3 nuclei become possible, leading to the formation of its polycrystalline structure with crystallite sizes of about 50 nm and higher [26,29]. From the data of Table 2, it can be seen that, in the ZrO2(3Y)+20%Al2O3 system, the formation of teta-phase took place only in the temperature range 1200-1300 °C, unlike pure Al2O3 [17], where the formation of -Al2O3 was detected even after synthesis. Based on this, it was concluded that the presence of zirconia in the ZrO2(3Y)+20%Al2O3 system affected the nucleation and growth of the critical -phase nuclei, which was previously discussed when analyzing the results for the system 20%ZrO2(9.4Y)+80%Al2O3 [17]. Achieving a “critical” value of more than 20 nm occurred at a higher temperature. Apparently, even higher than in the previously studied HFDP-SP system is 20%ZrO2(9.4Y)+80%Al2O3 [17]. As a result, the transformation shifted to higher temperatures, compared with pure Al2O3 and with the system of 20%ZrO2(9.4Y)+80%Al2O3. However, after the nucleation of critical embryos under these conditions, the formation of -Al2O3 developed just as rapidly. But the formation of corundum was not finished completely. The reason for the delay of → transformation in the ZrO2(3Y)+20%Al2O3 system as compared to the 20%ZrO2(9.4Y)+80%Al2O3 system could be a percolation barrier for structural rearrangement caused by greater isolation of the -phase nuclei in the zirconia matrix due to the lower total content of alumina in the composition. The results showed that the phase composition of the ZrO2(3Y)+20%Al2O3 system was formed under conditions of significant mutual influence of the main components, which are considered “badly soluble” in each other. It was found that in the presence of the



№ 3 (8) 2019

second (insoluble) component, Al2O3, in the HFDP-SP powders based on zirconia, a delay of С→T and T→M transformations in ZrO2(3Y) is observed. According to the results of the analysis of the phase composition in the HFDP-SP system ZrO2(3Y)+20%Al2O3 after annealing at different temperatures, the following conclusion was also made. In general, the sequence of phase transformations developing in it with increasing temperature was similar to some of the main stages of the sequences observed in [15] and [16] for ZrO2-Al2O3 nanopowders synthesized by CVS and CoLAVA methods, respectively. However, wherein, a complete coincidence was not revealed either by the temperature of transformations in zirconia or by the character of the phase changes in the forming Al2O3.

3.2 Lattice parameters of the phases in the HFDP-SP powders ZrO2(3Y) and ZrO2(3Y)+20%Al2O3 after annealing at different temperatures

Fig. 7 The change in the parameters of the T-phase unit cell with an increase in the annealing tempera-ture: a) - parameters c, a, and (a2•c)1/3; b) - tetragonality c/a of the lattice; c) - shift . (Curves a - 1, c - 1,

and 1 - for ZrO2(3Y) powder, curves a - 2, c - 2, and 2 - for ZrO2(3Y)+20%Al2O3).

In Fig. 7, for the studied powders, the following graphs of dependences on the annealing temperature are presented. Changes of parameters c and a of the T-phase and the parameter of the “equivalent by volume cell of the C-phase” (a2•c)1/3, Fig. 7,a. Changes in the degree of tetragonality (c/a) of the T-phase, Fig. 7,b. Changes in the magnitude of the shift (displacements of oxygen anions from a position in the “fluorite” type structure) of the T-phase, Fig. 7,c. The lattice parameters of the M-phase in the ZrO2(3Y) and ZrO2(3Y)+20%Al2O3 systems after annealing could not be accurately measured due to the low line intensity, their significant overlap with the lines of other phases. The similarity of the change tendencies in the parameter (a2•c)1/3 in both systems before and after annealing additionally indicated the generality of the mechanisms of formation of solid



№ 3 (8) 2019

solutions based on the T-phase in both systems, Fig. 7,a. It is known that solid solutions of the T-ZrO2(3Y) type are solutions of the “substitution” type [30,31]. In the case of the ZrO2(3Y)+20%Al2O3 system, the parameter (a2•c)1/3 was slightly lower up to 1000 °C (that is, before the start of decomposition). This was in good agreement with the concepts of substitution. The replacement of cations with additionally dissolved Al3+ ions with a smaller (0.53 nm) ionic radius compared to the ionic radii of Zr4+ (0.84 nm) and Y3+ (1.015 nm) [32] should be accompanied by a decrease in the parameter (a2•c)1/3. Thus, the results of annealing additionally confirmed that solid solutions of the T-ZrO2(3Y,Al) type obtained in the work were solutions of the “substitution” type and remained so until the decomposition. The lattice parameters of the T-phase in ZrO2(3Y) and ZrO2(3Y)+20%Al2O3 powder depended on temperature differently. If in the ZrO2(3Y) powder parameters varied weakly, remaining almost at the same level, then in ZrO2(3Y)+20%Al2O3 an increase in parameter c was observed after annealing, Fig. 7,a. The difference between the parameters and the tetragonality of the T-phase lattice in ZrO2(3Y)+20%Al2O3 powder from similar parameters and tetragonality in ZrO2(3Y) was maintained up to a temperature of 1000 °C, Fig. 7,a,b. At higher temperatures, the differences in parameters did not exceed the measurement error. A similar behavior was also characteristic of the shift magnitude in the unit cell of the T-phase as a function of temperature, Fig. 7,c. The differences before the annealing completely disappeared at 1100 °C and higher.

Fig. 8 The change in the parameter of the C-phase unit cell with increasing annealing temperature: 1 - for powder ZrO2(3Y), 2 - for powder ZrO2(3Y)+20%Al2O3.

In Fig. 8 shows the change in the parameter a of the C-phase in the studied systems, depending on the annealing temperature. It can be seen that with increasing annealing temperature, the C-phase parameter in both systems was increased. However, differences between the systems also persisted until the disappearance of the C-phase. Comparison of C-phase parameters, Fig. 8, with the value of (a2•c)1/3 of the T-phase in the corresponding systems at different temperatures, Fig. 7,a, showed the following. With increasing temperature, the C-phases parameters approached the corresponding values of (a2•c)1/3 for the T-phases. This could indicate a structural reconstruction of the C-phases and an approximation of their structure to the state characteristic of the T-phases. Judging by the change of the experimental profiles shape and the “redistribution” of intensity in favor of the T-phase lines at annealing temperatures of 800–900 °C, the most likely reason for the growth of the C-phase parameter in ZrO2(3Y)+20%Al2O3 powder could be the redistribution of Al3+ ions non-equilibrium solid solution C-ZrO2(3Y,Al) during the C→T transformation. Usually, in a polycrystalline Y2O3-stabilized ceramics, the C→T transformation (and the T-phase formation process) is characterized by features of spinodal decomposition [33]. It cannot be ruled out that, in our case, in the nanocrystalline



№ 3 (8) 2019

state, diffusion processes characteristic for spinodal decomposition and leading to a phase transformation, as well as redistribution of the “insoluble” component, could have occurred. The growth of parameters and tetragonality of T-phase in ZrO2(3Y)+20%Al2O3 powder and their approximation to the corresponding values for the T-phase in ZrO2(3Y) powder in conjunction with data on the appearance of Al2O3 modifications traces at 1000-1100 °C testified decomposition of the nonequilibrium solid solution T-ZrO2(3Y,Al) according to the scheme: T-ZrO2(3Y,Al) → T-ZrO2(3Y) + Al2O3. An increase in tetragonality and the shift in the unit cell of the T-phase led to the disappearance of an additional “stabilizing” effect from the dissolution of Al2O3. As a result, at annealing temperatures above 1100 °C, a principled possibility for the formation of the M-phase in this system was appeared. According to the results of the analysis of the parameters of the C- and T-phases in the HFDP-SP system ZrO2(3Y)+20%Al2O3 after annealing at different temperatures, the following conclusions were made. The tendency to increase the C-phase parameter in HFDP-SP ZrO2(3Y)+20%Al2O3 powder after annealing coincided with the tendency to increase the parameter of cubic solid solutions after annealing in ZrO2+5mol%Al2O3 powder nanosystems [13] and 20%ZrO2(9.4Y)+80%Al2O3 [17], which were obtained by hydrolysis and HFDP-SP respectively. The effect of annealing on the parameters and tetragonality (c/a) of the T-phase in the HFDP-SP ZrO2(3Y)+20%Al2O3 powder turned out to be similar to the effect of annealing on the parameters and tetragonality of tetragonal solid solutions in CVS ZrO2+3/15 mol%Al2O3 nanopowder systems [15], Fig. 2,a,b, as well as the parameter c in the sol-gel nanopowder ZrO2(3Y)+10 mol%Al2O3 [10], Fig. 3. However, wherein, there was no complete agreement on the temperatures of the parameters changes in zirconium dioxide. The parameters of the Al2O3 lattice after annealing were succeeded to estimate only for the -phase at the maximum temperature. This was prevented by the low intensity of the Al2O3 lines observed at lower annealing temperatures. The values of the -phase parameters after annealing are presented in Table 3. In the same place, for comparison, similar parameters of the -phase in HFDP-SP powders of 20%ZrO2(9.4Y)+80%Al2O3 [17] and Al2O3 [24] are presented. It can be seen that in the ZrO2(3Y)+20%Al2O3 powder, the

-phase parameters were comparable to the parameters in the 20%ZrO2(9.4Y)+80%Al2O3 powder and were decreased from the parameters in pure Al2O3 in Table 3. Obviously, this was due to the influence of zirconia. For example, it could were due to the formation of a nanocomposite structure consisting of ZrO2(3Y) and Al2O3 grains in the particles at the maximum temperature. Thus, the data in Table 3 also showed the presence of a counter tendency. Namely: the influence of the main component (zirconium dioxide) on the parameters of the “insoluble” component (alumina) in ZrO2(3Y)+20%Al2O3 .

Table 3 Corundum crystal lattice parameters in various HFDP-SP powders after annealing at 1300 °C



№ 3 (8) 2019

3.3 CSD size of C, T and M phases and the level of microstrains of the T-phase lattice after annealing at different temperatures

a) b)

c)Fig. 9 Dependence on annealing temperature: a) – for the average CSD size of the T- and C- phases;

b) – for the average CSD size of M-phase; c) for the level of the microstrains of T-phase (1 - for ZrO2(3Y) powder; 2 - for ZrO2(3Y)+20%Al2O3 powder).

In Fig. 9a,b, are the dependences on the annealing temperature: for the average CSD size of the T- and C- phases (Fig. 9,a), for microstrains of the T-phase lattice (Fig. 9,c), as well as for the average CSD size M- phases (Fig. 9,b) in both studied powders. It is seen that with an increase in the annealing temperature, the CSD of the T-phase in the ZrO2(3Y) system significantly increased compared with the initial state, Fig. 9,a (curve 1-1). For the ZrO2(3Y)+20%Al2O3 system, despite the greater initial value, the increase in CSD was less significant, Fig. 9,a (curve 2-1). The CSD size of the C-phase in both systems slightly increased up to the completion temperatures of the corresponding C→T transformations, Fig. 9,a (curve 1-2 and curve 2-2). Wherein, the difference in the CSD size between the two systems was retained up to the completion temperatures of C→T transformations, Fig. 9,a (curve 1-2 and curve 2-2). The average CSD size of the M-phase in the ZrO2(3Y) system, estimated from the broadening of two single-type lines (-111) and (111), remained approximately at the same level, Fig. 9,b (curve 1 and curve 2). The sizes of CSD of the M-phase in the ZrO2(3Y)+20%Al2O3 powder after annealing at 1200-1300 °C were smaller than the analogous sizes of the CSD in the ZrO2(3Y) powder, Fig. 9b (curve 1 and curve 2). The level of T-phase microstrains were changed in both systems in different ways. If in the ZrO2(3Y) powder it decreased with an increase in the annealing temperature, Fig. 9,c (curve 1), then in ZrO2(3Y)+20%Al2O3 powder at 800–1000 °C it increased significantly as compared to the initial state, and became much larger than in the ZrO2(3Y) system, Fig. 9,c (curve 2). Only in the interval of 1100–1300 °C, microstrains were decreased, approaching at 1300 °C to the level characteristic of the ZrO2(3Y) system, Fig. 9,c (curve 2). The temperature region of 800-1100 °C, in which there was a significant increase in the level of micro-distortions of the T-phase in the ZrO2(3Y)+20%Al2O3 system compared



№ 3 (8) 2019

to the ZrO2(3Y) system, coincided with the temperature regions of the most significant changes in the parameters of C and T phases, Fig. 7,a, 7,c, Fig. 8 (curve 2), as well as the disappearance of the C-phase, Table 2. The data from this part of our work showed that the presence of Al3+ ions in the composition provided an additional “increase” in the level of microstrains of the T-phase lattice in the ZrO2(3Y)+20%Al2O3 system compared to ZrO2(3Y) during annealing. From the literature it is known about the existence of a relationship between the level of microstrains of the T-phase and the amount of stabilizing oxide in the composition. For example, it was observed for such systems as: ZrO2-Y2O3 and ZrO2-CeO2 [34]. Oxides Y2O3 and CeO2 are considered “well soluble” in zirconium dioxide and “stabilizing” its T-phase. According to [34], the more “well soluble” oxide is dissolved in the lattice, the greater the level of microstrains. At the same time, for the case of "badly soluble" aluminum oxide, we could not find such data in the literature. However, from our data, Fig. 9,c, it follows that when a nonequilibrium solid solution ZrO2(3Y,Al) was formed, the effect of alumina was similar to the effect of “well soluble” oxides, considered to be “stabilizing”. The approximation of the T-phase microstrains in the ZrO2(3Y)+20%Al2O3 system to the values characteristic for the ZrO2(3Y) system annealed under the same conditions indicated the decomposition of nonequilibrium solid solution ZrO2(3Y,Al) at temperatures above 1100 °C. Thus, the presence of Al3+ ions in the composition of ZrO2(3Y)+20%Al2O3 powder provided a higher level of microstrains of the tetragonal zirconia lattice at medium annealing temperatures and reflected the redistribution of the “insoluble component” before the decomposition (and after decomposition) of the nonequilibrium solid solution. At the maximum temperature, the effect of the “insoluble component” limited the CSD size of T- and M- phases compared to ZrO2(3Y) powder. The data obtained in our article made it possible to clarify in more detail the picture of the decomposition of described in the literature [9,10,14,15,16] nonequilibrium tetragonal solid solutions ZrO2(Al) and ZrO2(3Y,Al). The ratio of CSD sizes of the T- and M-phases in HFDP-SP powders after annealing was somewhat "atypical", especially at maximum temperatures. So, after annealing at 1300 °C in both systems, the CSD size of the M-phase was less than the CSD of the T-phase. Using as an example the HFDP-SP powder ZrO2(3Y), it was possible to trace the cause of such an CSD size ratio. As noted above, the CSD size of the T-phase at temperatures of 1000 °C substantially increased, reflecting the grain growth usually observed under these conditions (Fig. 9,a, curve 1). At the same time, the average CSD size of the M-phase, estimated from the broadening of two single-type lines (-111) and (111), remained approximately at the same level (Fig.9,b, curve 1 and curve 2). As a result, if the CSD size of the M-phase in ZrO2(3Y) powder was slightly larger before annealing, then after annealing at 1300 °C, the CSD size of the T-phase more than 2 times was exceed the CSD size of the M-phase, Fig. 9,a,b. A discussion of the reasons for the observed ratio of the CSD size in ZrO2(3Y) powder will be carried out below when analyzing the features of the T→M transformation developed during cooling. According to the estimate, the CSD size of the -phase forming at 1200 °C was about 15 nm. It was somewhat less than the critical size of the embryos (about 20 nm) required for intensive developing of → transformation [25-28]. This indicated a mechanism for the delay of → transformation in this system, under the influence of zirconia associated with the restriction of the growth of the -phase nuclei. The CSD size of the -phase formed at 1300 °C was about 70 nm. It was smaller than the CSD size of the -phase (about 78 nm) formed at this temperature in pure Al2O3, which we studied earlier in [24]. It also pointed to the mechanism of grain growth restriction associated with the influence of a



№ 3 (8) 2019

polycrystalline matrix consisting of zirconia nanograins.

3.4 Main factors affecting the development of T→M transformation in HFDP-SP powders ZrO2(3Y) and ZrO2(3Y)+20%Al2O3 after annealing

It was noted above that the amount of M-phase in the HFDP-SP ZrO2(3Y) and ZrO2(3Y)+20%Al2O3 powders was different, both in the initial state and after annealing at different temperatures, Fig. 6. The system ZrO2(3Y) was particularly outstanding for its behavior, Fig. 6 (curve 1). In this system, at 900 and 1000 °С a decrease in the amount of the M-phase was observed as compared with the initial state. This was happened against the background of an increase in the CSD size of the T-phase from 28 to 50 nm. Then, with a further increase in the annealing temperature (or the CSD size of the T-phase), an increase in the amount of the M-phase to a maximum was occurred, Fig. 9,a (curve 1-1). A similar dependence of the M-phase content on the annealing temperature, with a “dip” at medium temperatures, was little described in the literature for ZrO2-Y2O3 nanostructured powder systems. Only in some papers, such as [35], was it possible to encounter similar behavior. For example, in [35], for the ZrO2+4mol%Y2O3 nanocrystalline system synthesized by the hydrothermal method, during annealing at 400–1200 °C, a decrease in the amount of the M-phase was observed, up to complete disappearance, against an increase in the CSD size of the T-phase from 9.5 up to 64 nm. With further increase in temperature to 1400 °C, the amount of M-phase was increased again. In [35], the explanation of such non-monotonous behavior was reduced to the complex influence of various factors. We used the concept of the “critical size” of T-phase to explain the experimental data obtained after annealing, as in the analysis of the as-synthesized state of the HFDP-SP powders ZrO2(3Y) and ZrO2(3Y)+20%Al2O3. In accordance with these concepts, the formation of the M-phase occurred as a result of the development of T→M martensitic transformation in crystallites exceeding the “critical size” [36] when cooled from the annealing temperature. The above reasoning can be confirmed by the dependences of the M-phase amount on the average CSD size of the T-phase in the HFDP-SP powders ZrO2(3Y) and ZrO2(3Y)+20%Al2O3, Fig. 10 (curves 1 and 2). The data on the plots include the values before and after annealing. The obtained correlations showed that exceeding the “critical size” was caused an increase of the M-phase content in the studied powders, Fig. 10 (right sides of curves 1 and 2). Exceeding the “critical size” in its pure form took place at annealing temperatures of 1000-1300 °C (for the ZrO2(3Y) system) and 1200-1300 °C (for the ZrO2(3Y)+20%Al2O3 system). Factor of the “critical size” exceeding was common for the two systems. It was the “first” factor, discussed above in section 3.1. As can be seen, for the ZrO2(3Y)+20%Al2O3 system, the “critical” size was about 52 nm, and for the ZrO2(3Y) system, it should be about 40 nm (if we realize a linear extrapolation of the right side of curve 1 to zero M-phases in the material). The formation of a significant M-phase amount in ZrO2(3Y) powder at a size below the expected “critical”, Fig. 10 (left side of curve 1) was associated with the action of the “second” factor, which lowered the “critical” size value of T-phase crystallites. Such a factor could be the effect of bound and crystallization water inherited from the original water precursor during the synthesis [37]. As is known, the introduction of water into the surface layers of zirconia contributes to the distortion of the lattice of the T-phase and its transformation into the M-phase [37]. The confirmation of the presence of various types of water was irreversible mass loss, which was observed during a thermogravimetric and DSC study of a similar ZrO2(3Y) powder in [38]. Complex exoeffects 300–450 °C and 750–1300 °C, Fig. 1 (curve 1), which we observed earlier in the DSC study of a similar ZrO2(3Y) powder [2], was also confirmed the loss of various types



№ 3 (8) 2019

of water during annealing. The effect of this factor in ZrO2(3Y) powder decreased with increasing temperature in the range of 800-1000 °C (and, accordingly, the size of CSD). Bound and crystallization water, exerting a destabilizing effect on the lattice of the surface layers of T-phase grains, contributed to a decrease in the “critical size” and the development of T→M transformation in crystallites with a “near-critical” size during synthesis. A decrease in the water content at annealing, contributed to the approximation of the critical size of T-phase crystallites to the natural level for a given composition and a decrease in the amount of the M-phase.

Fig. 10 The dependence of the M-phase amount on the average CSD size of T-phase (1 - for ZrO2(3Y) powder; 2 - for ZrO2(3Y)+20%Al2O3 powder).

In the ZrO2(3Y)+20%Al2O3 system, when the CSD size was less than 52 nm, bound and crystallization water inherited from the initial water precursor could also be present. However, the effect of dissolved Al2O3 (increasing the “critical” size) was more significant. As a result, after synthesis the T→M transformation was completely suppressed, despite the “near-critical” CSD size of the T-phase. Upon annealing, the effect of bound and crystallization water only decreased, which only contributed to an increase in the “critical” size of the T-phase and a shift in the T→M transformation to higher temperatures. In Fig. 11 for the two systems studied, the dependences of the volume of the unit cell of the T-phase on the level of microstrains of its lattice are presented. It is seen that in the case of the ZrO2(3Y) system, a higher level of microstrains was correspond to a larger volume of the T-phase unit cell. At the same time, in the ZrO2(3Y)+20%Al2O3 system, a higher level of microstrains was correspond to a smaller unit cell volume of the T-phase. Usually in zirconia partially stabilized by Y2O3, the volume of the T-phase unit cell is larger than that of the C-phase, but smaller than that of the M-phase [30,31]. The correlations shown in Fig. 11, allowed to demonstrate the nature of the “stabilizing” effect of dissolved Al2O3 in the ZrO2(3Y)+20%Al2O3 system and the “destabilizing” effect of H2O in the ZrO2(3Y) system. The general “compression” of the unit cell during the dissolution of Al2O3 brought it closer to the cubic phase, making it difficult to turn into the M-phase. The “expansion” of the T-phase cell under the influence of H2O brought its volume closer to the volume of the M-phase, facilitating T→M transformation. Dependencies, Fig. 11, made it possible to better understand the physicochemical nature of the increase in the “critical size” of T-phase crystallites in the ZrO2(3Y)+20%Al2O3 system and its decrease in the ZrO2(3Y) system.



№ 3 (8) 2019

Fig. 11 Dependence of the T-phase unit cell volume on the level of microstrains of its lattice in the HF-DP-SP powders: ZrO2(3Y) (1) and ZrO2(3Y)+20%Al2O3 (2).

The positive effect of Al2O3 on the “stability” of the T-phase in the ZrO2(3Y)+20%Al2O3 system was preserved, apparently, after the decomposition of a nonequilibrium solid solution of T-ZrO2(3Y,Al). This is evidenced by a significantly smaller amount of M-phase in this system, even after maximum annealing temperatures, Fig. 6. This was evidenced by a significantly smaller amount of M-phase in this system, even after maximum annealing temperatures, Fig. 6. It could be associated with the influence of grain-boundary precipitates and forming Al2O3 grains. Based on the data on the CSD size ratio of T- and M-phases after annealing obtained in the work, a number of assumptions can be made about the T→M transformation mechanism realized in the studied systems during cooling from the annealing temperature. Above, in section 3.1, it was noted that in HFDP-SP systems ZrO2(3Y) (at temperatures above 1000 °C) and ZrO2(3Y)+20%Al2O3 (at temperatures 1200-1300 °C) the average CSD size of the M-phase was smaller than the CSD size of the T-phase, Fig. 9,a,b. This could be due to the development of martensitic T→M transformation not according to the scheme “monodomain crystallite of T-phase into monodomain crystallite of M-phase”, but realization of the scheme “monodomain crystallite of T-phase into polydomain crystallite of M-phase” [37]. The cause of the fragmentation of the crystallites of the daughter M-phase could be the realization of the transformation in “constrained” conditions [39] due to the presence of neighbors in the walls of the particles. This conclusion was supported by the fact that at the same annealing temperatures, the CSD size of the M-phase in the ZrO2(3Y)+20%Al2O3 system was less than the CSD size in the ZrO2(3Y) system, Fig. 6. The presence of more hard Al2O3 inclusions in the polycrystalline matrix, first, limited the growth of crystallites. Second, it led to an increase in the “constraint” of the M-phase grain during the transformation process. As a result, the size of the M-phase domains formed in the ZrO2(3Y)+20%Al2O3 system was smaller. Studies have confirmed the conclusion about the deterrent effect of the “insoluble” component (Al2O3) on the growth of T-phase crystallites and its tendency to turn into the M-phase in the HFDP-SP powders, previously identified in [1,2]. The effect obtained coincided with the analogous effect previously revealed in ZrO2+3/30mol% Al2O3nanosized powder systems synthesized by CVS [15].

3.5 "Size" effects and the supposed mechanism of decomposition of nonequilibrium solid solutions C-ZrO2(3Y,Al) and T-ZrO2(3Y,Al) during the synthesis and annealing of the HFDP-SP powder ZrO2(3Y)+20%Al2O3

In Fig. 12 for the ZrO2(3Y)+20%Al2O3 system, three dependencies on the average CSD size are presented. Dependence of the parameter a of a solid solution C-ZrO2(3Y,Al), Fig. 12



№ 3 (8) 2019

(line I). Dependence of value (a2•c)1/3 for T-ZrO2(3Y,Al) solid solution, Fig. 12 (line II). And the dependence of the value (a2•c)1/3 for T-ZrO2(3Y) solid solution, Fig. 12 (line III). It can be seen that the dependence common for the parameters of three types solid solutions has “kinks” at CSD sizes about 10 nm and about 70 nm. A relatively small size region (less than 10 nm) belongs to the «stability» region of the solid solution C-ZrO2(3Y,Al). The average, relatively broad range of size (10 - 70 nm) belongs to the existence region of T-ZrO2(3Y,Al). The range of size above 70 nm refers to the states of complete decomposition of T-ZrO2(3Y,Al) to the state T-ZrO2(3Y). In the range of size 2–10 nm, the dependence with a sufficiently high correlation coefficient (R = 0.75) was approximated by the function a = 0.5044 + D*9.11792*10–4 nm, where D is the average CSD size in nanometers. The growth rate of the parameter a for C-ZrO2(3Y,Al) with an increase in the size of CSD was significantly higher than for the solid solution C-ZrO2(9.4Y,Al) from [17], which indicated a lower stability of the first solution.

Fig. 12 Dependence on the average size of CSD: parameter a of the C-phase lattice in the ZrO2(3Y)+20%Al2O3 system (I); value (a2•c)1/3 of the T-phase in the ZrO2(3Y)+20%Al2O3 system (II) and

value (a2•c)1/3 of the T-phase in the ZrO2(3Y) system (III).

In Fig. 13 shows the dependences of the parameters a and c of the T-phase on its average CSD size for the two studied HFDP-SP powders. It can be seen that the parameters a and c of the ZrO2(3Y) system, as well as the parameter a of the ZrO2(3Y)+20%Al2O3 system, were practically independent of the CSD size. At the same time, the parameter c of the ZrO2(3Y)+20%Al2O3 system, in the size range of 40-70 nm, was increased, approaching to the level of the parameter in the ZrO2(3Y) powder. The values from this region refer to a nonequilibrium solid solution of the ZrO2(3Y,Al) type. The dependence on the size in this region was approximated by a function с = 0.5121+D*9.02520*10-5 nm, where D is the average size of CSD in nanometers. For large values of CSD, the data could be interpolated by a constant function c = 0.5174 nm. The saturation of dependence was observed at CSD size about 70 nm, Fig. 13. The growth rate of the parameter c of T-ZrO2(3Y,Al) with an increase in the size of CSD was significantly lower than for the parameter a of a solid solution C-ZrO2(3Y,Al), Fig. 12. This was indicated to a lower «stability» of the second solution.



№ 3 (8) 2019

Fig. 13 Dependence of the T-phase lattice parameters on its average CSD size: a - 1, c - 1 - for ZrO2(3Y) powder; a - 2, c - 2 - for ZrO2(3Y)+20%Al2O3 powder.

In Fig. 14 shows the dependence of the lattice microstrains of T-phase on its average CSD size, constructed according to the data before and after annealing at different temperatures for the systems ZrO2(3Y) (curve 1) and ZrO2(3Y)+20%Al2O3 (curve 2). It can be seen that both systems were characterized by a decrease in the level of microstrains with an increase in the size of CSD. Wherein, the values in the ZrO2(3Y) system decreased smoothly in a relatively wide range of sizes, and in the ZrO2(3Y)+20%Al2O3 system, the values decreased more sharply in a narrower size range. In Fig. 14, areas related to the equilibrium solid solution ZrO2(3Y) (region I) and non-equilibrium solid solution ZrO2(3Y,Al) (region II) were also outlined. It can be seen that a non-equilibrium solid solution of ZrO2(3Y,Al) was characterized by a higher level of microstrains of the lattice. However, with the growth of CSD, it decreased and approached the values characteristic of ZrO2(3Y) solid solution at about 67 nm, which reflected the process of complete decomposition.

Fig. 14 Dependence of the microstrains of the zirconia T-phase lattice on its average CSD size: 1 - for ZrO2(3Y) powder; 2 - for ZrO2(3Y)+20%Al2O3 powder; I - values related to the nonequilibrium solid solu-

tion ZrO2(3Y,Al); II - values related to the equilibrium solid solution ZrO2(3Y).

In our opinion, the dependencies shown in Fig. 12, 13 and 14, reflected the “dimensional” sequence of decomposition of various types of nonequilibrium solid solutions of ZrO2(3Y,Al) type in the process of synthesis and subsequent heat treatment, according to the following scheme: C-ZrO2(3Y,Al) (about 10 nm) → T-ZrO2(3Y,Al) (about 70 nm) → T-ZrO2(3Y) + Al2O3. In favor of this, the following arguments were proposed. For C-ZrO2(3Y,Al) solid solution, they are as follows. As already noted, the C-phase in a nanosize state can be stabilized by oxygen vacancies even in the absence of stabilizing



№ 3 (8) 2019

additives [40–42]. In this regard, the rapid growth of the C-phase parameter in a narrow size range of less than 10 nm, Fig. 12, could be interpreted in terms of the restructuring of the vacancy subsystem of the oxygen sublattice of a nonequilibrium C-ZrO2(3Y,Al) solid solution. That is, the smaller the number of vacancies at similar sizes of CSD, the greater was the parameter and less stability of the C-phase [40-42]. In itself, the rearrangement of the oxygen vacancy subsystem could be due to the redistribution of ions of the insoluble component in the C-ZrO2(3Y,Al) solid solution during processes similar to spinodal-like decomposition known for coarse-grained materials in the ZrO2(3Y) system [33]. The decomposition process of the tetragonal solid solution ZrO2(3Y,Al) as the crystallites grow reflects the approximation of the parameter c of the ZrO2(3Y)+20%Al2O3 system to the level of the parameter c in the ZrO2(3Y) powder, in the size range of 40-70 nm, Fig. 13. And, a similar tendency for the parameter (a2•c)1/3, Fig. 12. The same process was reflected by the dependence of the level of microstrains on the CSD size of the the solid solution ZrO2(3Y,Al), Fig. 14. For nanocrystalline powders based on ZrO2 and other nanocrystalline oxides, there is a well-known inverse ratio between the level of crystal lattice microstrains and the size of CSD [43,44]. The larger size of CSD corresponds to smaller values of microstrains [43,44]. This is attributed to the fact that in a polycrystalline structure consisting of interconnected crystallites, the boundaries of crystallites make the main contribution to the level of lattice microstrains [44]. Accordingly, as the grain grows occur, the length of the boundaries and their total contribution to the level of microstrains recorded by the X-ray method, decreases. As can be seen from our data, Fig. 14, it was precisely this dependence that was observed in our case in both systems. Wherein, in the case of a nonequilibrium solid solution of T-ZrO2(3Y,Al), the contribution from the processes occurring at the boundaries of zirconia crystallites was of decisive importance. It can be assumed that the gradual decomposition of a nonequilibrium solid solution T-ZrO2(3Y,Al) was accompanied by the precipitation of Al2O3 clusters along the grain boundaries. A similar mechanism has already been discussed earlier in the analysis of the decomposition of a nonequilibrium solid solution C-ZrO2(9.4Y,Al) [17]. The formation of grain-boundary clusters served to the beginning of the formation of a nanocomposite structure with full valued Al2O3 inclusions. Based on the foregoing, the following scheme was proposed for processes involving solid solutions C-ZrO2(3Y,Al) and T-ZrO2(3Y,Al) in ZrO2(3Y)+20%Al2O3 powder, Fig. 15. The primary cubic zirconia grain (state 1), as it grew, experienced aging of a non-equilibrium solid solution of the spinodal-like decomposition type with the formation of Guinier-Preston zones [22] with an increased concentration of Al3+ ions in the composition (states 2, 3), Fig. 15. A solid solution of C-ZrO2(3Y,Al) aged in such a way, upon reaching a size of about 10 nm, experienced a transformation into a more poor solid solution of T-ZrO2(3Y,Al) with the precipitation of clusters of Al2O3 along the boundaries (state 4), Fig. 15. Further, as the T-phase grain grew, a further depletion of the tetragonal solid solution occurred with the migration of Al3+ ions to the grain boundaries. The clusters «fed» by the influx of Al3+ ions grew at the boundaries (state 5), Fig. 15. After the complete decomposition of the T-ZrO2(3Y,Al) solid solution to the T-ZrO2(3Y) solution state, the Al2O3 clusters were consolidated and formed first small crystallites of the - and -phase, and then, nuclei of the -phase of aluminum oxide (state 5, 6). Later, by association, the -phase nuclei were formed (state 7), which, absorbing other Al2O3 grains, developed rapidly and formed

-Al2O3 inclusions in the polycrystalline structure consisting of zirconia nanograins: of T-phase and of polydomain M-phase (state 8), Fig 15.



№ 3 (8) 2019

Fig. 15 The proposed scheme for the formation of a structure with the participation of non-equilibrium solid solutions (ss) C-ZrO2(3Y,Al) and T-ZrO2(3Y,Al) according to XRD data. 1,2,3,4,5,6,7 — structural

states of a zirconia grain as it grows; C - cubic phase; T - tetragonal phase, M pd. - polydomain mono-clinic phase; CL. - grain boundary clusters Al2O3; N. - phase nuclei; - -Al2O3; - corundum.

4. Conclusion

In the work, nanocrystalline HFDP-SP powders of (100-x)ZrO2(3Y)+xAl2O3 compositions (where x = 0 and 20 wt%) after annealing at temperatures of 800-1300 °C were investigated. In the ZrO2(3Y) system, as the annealing temperature increases, the C-ZrO2(3Y) phase was disappears as a result of the C→T transformation. Then, a phase transition of T-ZrO2(3Y) to the M-ZrO2(3Y) phase took place. In the ZrO2(3Y)+20%Al2O3 system after annealing, the crystalline C-ZrO2(3Y,Al) phase based on zirconium dioxide, with the structure of a non-equilibrium solid solution of the “substitution” type, also subjected to C→T transformation. Under the influence of the “insoluble component” (Al2O3), the completion temperature of the C→T transformation in the ZrO2(3Y)+20%Al2O3 system increased by approximately 100 °C compared to the ZrO2(3Y) system. The "daughter" non-equilibrium solid solution of T-ZrO2(3Y,Al) of the “substitution” type decomposed with increasing temperature. Only after this, the formation of the M-ZrO2(3Y) phase was observed, which was carried out at maximum annealing temperatures. In general, under the influence of the "insoluble component", the T→M transformation in zirconium dioxide was significantly inhibited. The following sequence of phase transformations during annealing was typical for the ZrO2(3Y) system: C-ZrO2(3Y) → (at 800-900 °C) T-ZrO2(3Y) → (at 1000-1300 °C) T-ZrO2(3Y) + M-ZrO2(3Y). At the same time, in the ZrO2(3Y)+20%Al2O3 system, the sequence of phase transformations was more complex. Amorphous phase → (at 800-900 °C) C-ZrO2(3Y,Al) → (at 900-1000 °C) T-ZrO2(3Y,Al) + Al2O3 (traces) → (at 1100 °C) T-ZrO2(3Y) + Al2O3 (traces) → (at 1200 °C) T-ZrO2(3Y) + M-ZrO2(3Y) (traces) + -Al2O3 → (at 1300 °C) T-ZrO2(3Y) + -Al2O3 + M-ZrO2(3Y) + -Al2O3 (traces). It was established that in the ZrO2(3Y)+20%Al2O3 system under the influence of zirconia, the implementation of the final stage → of the Al2O3 transformation was observed at higher temperatures, compared to pure Al2O3 , obtained by a similar method. Wherein, the formation of -Al2O3 was carried out in a narrow temperature range above the temperature of complete decomposition of the nonequilibrium solid solution T-ZrO2(3Y,Al). The presence of zirconia in the ZrO2(3Y)+20%Al2O3 system was reduced the CSD size of the

-phase formed after the annealing as compared with pure Al2O3. It was revealed that with an increase in the annealing temperature, the parameter a of the nonequilibrium solid solution C-ZrO2(3Y,Al) was increased, which reflected the redistribution of Al3+ ions and related oxygen vacancies during the C→T transformation.



№ 3 (8) 2019

It was established that for a nonequilibrium solid solution T-ZrO2(3Y,Al) with increasing annealing temperature, parameter c, tetragonality (c/a) and shift (characterizing the position of oxygen anions in the unit cell) were increased. This, apparently, contributed to the loss of the previously identified "stabilizing" effect of dissolving Al2O3 and facilitating the formation of the M-phase. The microstrains of the crystal lattice of the zirconia T-phase in the ZrO2(3Y)+20%Al2O3 system after annealing was decreased with an increase in the CSD size, approaching the values for the T-phase in the ZrO2(3Y) system at 67 nm. This was corresponded to the complete decomposition of a nonequilibrium solid solution T-ZrO2(3Y,Al) to the state of an equilibrium solid solution T-ZrO2(3Y). On the dependence of the lattice parameters of the C- and T-phases on the size of the CSD, “kinks” were also found at about 10 and about 70 nm. The latter, in order of magnitude, was very close to the critical size of the complete decomposition on the dependence of microstrains on the size of the CSD. Both obtained “size” dependences were reflected the stages of the decomposition process of the nonequilibrium solid solution ZrO2(3Y,Al) during the C→T transformation and subsequent structural changes in the daughter T-phase. The above results should be considered when using HFDP-SP nanocrystalline systems (100-x)ZrO2(3Y)+xAl2O3 (where x = 0 and 20 wt%) as starting materials for obtaining composite ceramic materials, functional products and coatings based on them.

References

[1] P.V. Korolev, A.V. Korolev, A.V. Knyazev, G.M. Sorokin, Influence of insoluble component on C→T and Т→М phase transformations and structure formation under annealing of plasma-spray synthesized nanocrystalline powder system (100-x)ZrO2(3Y)+xAl2O3 (x = 0 and 20 wt.%). Part 1: Analysis of as-synthesized powders, Applied Solid State Chemistry. 1(2019)6-22. [2] P.V. Korolev, A.V. Knyazev, I.R. Gavrilov, M.R. Gavrilov, A.V. Korolev, X-Ray Diffraction and Calorimetric Studies of Powder Nanocrystalline Systems Based on ZrO2(Y) and Al2O3 with Second Insoluble Component, Physics of the Solid State. 54(2) (2012) 267–272. [3] A.P. Surzhikov, S.A. Ghyngazov, T.S. Frangulyan, I.P. Vasil’ev, Thermal transformations in ultrafine plasmochemical zirconium dioxide powders, J. Therm. Anal. Calorim. 119 (2015) 1603–1609. [4] V. F. Petrunin, V. V. Popov, Zhu Hongzhi, and S. A. Korovin, Stability of High-Temperature Phases of Ultrafine Zirconia, Glass Physics and Chemistry. 31(4) (2005) 459–464. [5] O. Yamaguchi, M. Shirai, and M. Yoshinaka, Formation and Transformation of Cubic ZrO2 Solid Solutions in the System ZrO2-Al2O3, J. Am. Ceram. Soc.. 71(12) (1988) C–510–C–512. [6] S. Inamura, H. Miyamoto, Y. Imaida, M. Takagawa, K. Hirota, O. Yamaguchi, Formation and hot isostatic pressing of ZrO2 solid solution in the system ZrO2-Al2O3, J. Mater. Sci.. 29 (1994) 4913-4917. [7] K. Ishida, K. Hirota, O. Yamaguchi, H. Kume, S. Inamura and H. Miyamoto, Formation of zirconia solid solutions containing alumina prepared by new preparation method, J. Am. Ceram. Soc.. 77(5) (1994) 1391-1395. [8] M.L. Balmer, F.F. Lange, and C.G. Levi, Metastable Phase Selection and Partitioning for Zr(1-x)AIxO(2-x/2) Materials Synthesized with Liquid Precursors, J. Am. Ceram. Soc.. 77(8) (1994) 2069–2075. [9] G. Štefanić, S. Musić, & R. Trojko, The influence of thermal treatment on the phase development in HfO2–Al2O3 and ZrO2–Al2O3 systems, Journal of Alloys and Compounds. 388(1) (2005) 126–137. [10] M. Yoshimura, S.-T. Oh, M. Sando, & K. Niihara, Crystallization and microstructural



№ 3 (8) 2019

characterization of ZrO2 (3 mol% Y2O3) nano-sized powders with various Al2O3 contents, Journal of Alloys and Compounds. 290(1-2) (1999) 284–289. [11] L.A.Xue, I.W.Chen, Influence of additives on the –to- transition of alumina, J. Mater. Sci. Lett.. 11(8) (1992) 443-445.[12] F.S. Yen, M.Y. Wang, J.L. Chang, Temperature reduction of θ- to -phase transformation induced by high-pressure pretreatments of nano-sized alumina powders derived from boehmite, J. Cryst. Growth. 236(1-3) (2002) 197–209. [13] A. Mondal, S. Ram, Al3+-stabilized c-ZrO2 nanoparticles at low temperature by forced hydrolysis of dispersed metal cations in water, Solid State Ionics. 160(1-2) (2003) 169–181. [14] S. Moreau, M. Gervais, A.Douy, Formation of metastable solid solution in the ZrO2-rich part of the system ZrO2-Al2O3, Solid State Ionics. 101-103 (1997) 625–631. [15] V.V. Srdic, M. Winterer, Aluminum-doped zirconia nanopowders: Cemical vapor synthesis and structural analysis by Rietveld refinement of X-ray diffraction data, Chem. Mater.. 15 (2003) 2668-2674. [16] J.F. Bartolomé, A. Smirnov, H.-D. Kurland, J. Grabow and F.A. Müller. New ZrO2/Al2O3 Nanocomposite Fabricated from Hybrid Nanoparticles Prepared by CO2 Laser Co-Vaporization, Scientific Reports. 6(1) (2016) 1-11. [17] P.V. Korolev, A.V. Korolev, A.V. Knyazev, O.V. Khristoforov, Influence of annealing on plasma-spray synthesized amorphous-nanocrystalline powder system 80wt.%Al2O3+20wt.%ZrO2(Y) with nonequilibrium solid solution ZrO2(Y,Al) in content, Applied Solid State Chemistry. 3(4) (2018) 19-35. [18] C.J.Howard, B.A.Hunter, & D.-J.Kim, Oxygen Position and Bond Lengths from Lattice Parameters in Tetragonal Zirconias, J. Am. Ceram. Soc.. 81(1), (1998) 241–243. [19] H.Toraya, M.Yoshimura, S.Somiya, Calibration Curve for Quantitative Analysis of the Monoclinic-Tetragonal ZrO2 System by X-Ray Diffraction, J. Am. Ceram. Soc.. 67(6) (1984) C–119–C–121. [20] H. Toraya, M. Yoshimura, S. Somiya, Quantitative Analysis of Monoclinic-Stabilized Cubic ZrO2 Systems by X-Ray Diffraction, J. Am. Ceram. Soc.. 67(9) (1984) C–183–C–184.[21] G.K. Williamson and W.H. Hall, X-ray line broadening from filed aluminium and wolfram, Acta Metall. 1 (1953) 22-31. [22] Y.S. Umansky. Yu.A. Skakov, A.N. Ivanov, L.N. Rastorguev, Kristallografiya, rentgenografiya i elektronnaya mikroskopiya (Crystallography, X-ray diffraction and electron microscopy), Moscow: Metallurgy, 1982. [in Russian] [23] J. Grabis, I. Steins, D. Rasmane, A. Krumina and M. Berzins, Preparation and characterization of ZrO2-Al2O3 particulate nanocomposites produced by plasma technique, Proc. Estonian Acad. Sci. Eng.. 12(4) (2006) 349–357 [24] P.V. Korolev, A.V. Knyazev, A.V. Korolev, Investigation of (100-x)%Al2O3+x%MgO (x = 0 and 1,5 wt.%) powder nanocrystalline systems synthesized by plasmochemical method, Applied Solid State Chemistry. 1 (2018) 7-17. [25] H.L. Wen, F.S. Yen, Growth characteristics of boehmite-derived ultrafine theta and alpha-alumina particles during phase transformation, J. Cryst. Growth. 208 (2000) 696–708.[26] P.-L. Chang, F.-S. Yen, K.-C. Cheng, H.-L. Wen, Examinations on the Critical and Primary Crystallite Sizes during θ- to α-Phase Transformation of Ultrafine Alumina Powders, Nano Letters. 1(5) (2001) 253–261. [27] F.S. Yen, M.Y. Wang, J.L. Chang, Temperature reduction of θ- to -phase transformation induced by high-pressure pretreatments of nano-sized alumina powders derived from boehmite, J. Cryst. Growth. 236(1-3) (2002) 197–209. [28] F.W. Dynys, J.W. Halloran, Alpha Alumina Formation in Alum-Derived Gamma Alumina. J. Am. Ceram. Soc.. 65(9) (1982) 442–448.

APPLIED SOLID STATE CHEMISTRY № 3 (8) 201926 APPLIED SOLID STATE CHEMISTRY


№ 3 (8) 2019

[29] R.B. Bagwell, G.L. Messing, P.R. Howell, The formation of -Al2O3 from θ-Al2O3: The relevance of a “critical size” and: Diffusional nucleation or “synchro-shear”? J. Mater. Sci.. 36 (2001) 1833–1841. [30] [25] N.G. Scott Phase relationship in the zirconia-yttria system, J. Mater. Sci.. 10(9) (1975) 1527–1535. [31] E.H. Kisi, C.J. Howard, Crystal Structures of Zirconia Phases and their Inter-Relation, Key Engineering Materials. 153-154 (1998) 1–36. [32] R.D. Shannon, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides, Acta Crystallogr. Section A. 32(5) (1976) 751–767. [33] T.Sakuma, The cubic-to-tetragonal transformations in zirconia alloys, pp. 86-98, in “Science and Technology of Zirconia V” edited by: S.P.S. Badwal, M.J. Bannister, R.H.J. Hannink. Lancaster: “Technomic Publishing Company, Inc.” (1993). [34] J. D. Lin and J. G. Duh, “Crystallite Size and Microstrain of Thermally Aged Low-Ceria- and Low-Yttria-Doped Zirconia,” J. Am. Ceram. Soc.. 81 [4] 853–60 (1998). [35] G. Xu, Y.-W. Zhang, C.-S. Liao, & C.-H. Yan, Tetragonal-to-Monoclinic Phase Transitions in Nanocrystalline Rare-Earth-Stabilized Zirconia Prepared by a Mild Hydrothermal Method, J. Am. Ceram. Soc.. 87(12) (2004) 2275–2281. [36] R.C. Garvie, The Occurrence of Metastable Tetragonal Zirconia as a Crystallite Size Effect. The Journal of Physical Chemistry, 69(4) (1965) 1238–1243. [37] Y. Murase, E. Kato, Role of Water Vapor in Crystallite Growth and Tetragonal-Monoclinic Phase Transformation of ZrO2, J. Am. Ceram. Soc.. 66(3) (1983) 196-200. [38] S.A. Ghyngazov, I.P. Vasiliev, T.S. Frangulyan, V.M. Khaidukova, T.S. Mylnikova, Investigation of the structural–phase state of ultrafine plasmochemical ZrO2(Y) powders, IOP Conf. Series: Materials Science and Engineering. 66 (2014) 012021 1-6 [39] Lange F F Transformation toughening: Рart 3: Experimental observations in the ZrO2–Y2O3 system, J. Mater. Sci.. 17 (1982) 240-246. [40] S. Tsunekawa, S. Ito, Y. Kawazoe, & J.-T. Wang, Critical Size of the Phase Transition from Cubic to Tetragonal in Pure Zirconia Nanoparticles, Nano Letters. 3(7), (2003) 871–875. [41] S. Jayakumar, P.V. Ananthapadmanabhan, T.K. Thiyagarajan, K. Perumal, S.C. Mishra, G. Suresh, L.T. Su, A.I.Y. Tok, Nanosize stabilization of cubic and tetragonal phases in reactive plasma synthesized zirconia powders, Materials Chemistry and Physics. 140 (2013) 176-182. [42] Y.L. Soo, P.J. Chen, S.H. Huang, T.J. Shiu, T.Y. Tsai, Y.H. Chow, Y.C. Lin, S.C.Weng, S.L.Chang, G.Wang, C.L. Cheung, R.F. Sabirianov, W.N. Mei, F. Namavar, H. Haider, K.L. Garvin, J.F. Lee, H.E. Lee, P.P. Chu, Local structures surrounding Zr in nanostructurally stabilized cubic zirconia: Structural origin of phase stability, J. Appl. Phys.. 104(11) (2008) 113535. [43] N.H. Brett, M. Gonzalez, J. Bouillot, J.C. Niepce, Neutron and X-ray diffraction studies on pure and magnesia-doped zirconia gels decomposed in vacuo, J. Mater. Sci.. 19 (1984) 1349-1358. [44] J.M. Criado, M. González, C. Real, Correlation between crystallite size and microstrains in materials subjected to thermal and/or mechanical treatments, J. Mater. Sci. Lett.. 5(4) (1986) 467–469.


Mamedova G.A.


SYNTHESIS AND RESEARCH OF THE ZEOLITE OF GISMONDINE TYPE ON THE BASIS OF NATURAL MINERAL NAKHCHIVAN

DOI: 10.18572/2619-0141-2019-3-3-27-35Mamedova G.A.

Nakhchivan Department of the Azerbaijan National Academy of Sciences, Institute of natural resources, AZ 7000, Heydar Aliyev avenue 76, Nakhchivan, Azerbaijan

[email protected]

Abstract Zeolite of gismondine was synthesized on the basis of the natural zeolite of Na-khchivan and its physicochemical properties were studied. The mineralogical composi-tion of Nakhchivan zeolite tuffs takes from the Kyukyuchai field was as follow: mordenite 78.5%, quartz 19.5% and anortite 2.00%. It was established that the area of existence of gismondine is wide and the optimal conditions for its hydrothermal synthesis were a tem-perature of 100°C, a concentration of a thermal solution of 10–20% KOH and a processing time of 50 hours. It was established that the resulting zeolite of gismondine is dehydrated in the temperature range of 80–250°C and stable up to 620°C, and a further increase in temperature leads to the destruction of its structure and crystallization of sanidine. It was shown that dehydrated gismondine is completely rehydrated within 24 hours, which once again proves its zeolitic character.

Keywords: Nakhchivan mineral, zeolite, gismondine, natural mineral, X-ray phase analysis, hydrothermal synthesis.

1. Introduction

The study of the structure and properties of frame-class aluminosilicates class minerals obtained from available and widely distributed natural raw materials is an important scientific task aimed at creating new multifunctional materials. This is mainly due to the uniqueness of the physicochemical properties of the frame aluminosilicates, manifested in the developed specific surface area, the presence of active centers of different nature, adsorption and ion exchange capacity. It opens up wide opportunities for their use, for ex-ample, when creating new effective materials for water treatment and wastewater treat-ment [1-4], sorbents in pharmacology [5-8]. The path to the development of a new gener-ation of catalysts lies through the production of synthetic zeolites. Zeolite-based catalysts can be used for almost any chemical process [9-12]. Questions about their industrial use are based on the technological and economic features of the process.Conducting research in the field of the synthesis of zeolites based on natural minerals, as well as the study of the Nakhchivan zeolite is a promising and urgent task of our time. The fact is that conducting research on the basis of natural minerals reduces the country's dependence on foreign raw materials, contributes to the rational use of natural resources of the Nakhchivan Autonomous Republic (NAR), its use in various areas of the national economy, which leads to the development of the country's economy. It is known that ze-olites, synthetic or natural, have a wide range of applications - starting with a catalyst and ending with additives in animal husbandry and crop production.One of the defining goals of modern science is to reunite it with production and thereby contribute to the development of the country's economy.The need to study the hydrothermal recrystallization of zeolite-containing rocks is asso-ciated with the possibility of using them to obtain zeolites of other structural types with practically important properties.The development of the scientific foundations of the synthesis and areas of existence of


Mamedova G.A.

№ 3 (8) 2019

zeolites, as well as the implementation of crystallization based on local mineral raw mate-rials is currently one of the important areas of basic research.The use of local mineral raw materials (low-cost materials) in the synthesis of zeolites be-comes an area of great interest and plays an active role in advancing technological ad-vances related to scientific research and production technologies of zeolite materials in optimized experimental conditions.A series of zeolites was synthesized in hydrothermal conditions, both pure phase-wise and in the form of associations, on the basis of the natural zeolite of the Kyukyuchai de-posit of the Nakhchivan AR [13–15]. It has been established that the use of local natural raw materials from the Kyukyuchai deposit contributes to the process under moderate conditions, obtaining phase-crystalline products that are clean.Considering the above, the purpose of this research work is to study the hydrothermal modification of the natural sample of Nakhchivan with the production of practically im-portant zeolite such as gismondine, the establishment of optimal conditions for its syn-thesis using local natural raw materials from the Kyukyuchai deposit of the Nakhchivan AR.

2. Materials and Methods2.1. Materials2.1.1. Chemicals

Potassium hydroxide (flake, 99% purity, Alfa Aesar GmbH & Co KG, Germany) was used as received without further purification.

2.1.2. Natural zeolite

The natural sample was obtained from the zeolite-containing horizon in the North-West of the river of Kyukyuchai where its content varies with the range of 75−80%. Zeolitic tuffs of Nakhchivan were used as samples sources, 78.5% of which is taken by the ma-jor mineral - mordenite (Ca2Na2K2.8Al8.8Si39.2O96 ∙ 34H2O), 19.5% falls onto quartz (SiO2), and 2.00% goes to anortite (Ca0.86Na0.14Al1,94Si2.06O8.01). The sample was thoroughly washed with distilled water and dried at the temperature of 100°C for three days. The chemical compo-sition of the natural zeolite of Nakhchivan is given in the Table 1.

Table 1. The percentage of oxides and elements in the composition of the natural sample of zeolite


Mamedova G.A.

№ 3 (8) 2019

2.2. Synthesis

The hydrothermal synthesis was conducted in autoclaves of the Morey type made of the stainless steel of the 45MNFT grade, in a volume of 18 cm3, and with the filling coefficient of F = 0.8. The hydrothermal crystallization experiments were taken without creating the gradient of temperature ∆Т = 0 and without stirring of the reaction mass. Solid phase and liquid phase was ratio 1:10.

2.2.1. Synthesis of gismondine

The hydrothermal synthesis experiments of zeolite of the gismondine type were conduct-ed for 3−7 days, at the temperature of 100−200°C. NaOH with the concentration varying in the range of 1−3 N. The optimal temperature for the synthesis of the ZSM-5 zeolite is 120°C, the thermal solution concentration is 2 N, and the crystallization process takes 6 days.

2.2. Methods2.2.1. XRD analysis Those experiments involved using the X-ray analyzer 2D PHASER "Bruker" (Cu Kα radi-ation, 2θ = 20−80°), using of NaCl, SiO2 (quartz) and pure zeolites internal and external standards. Samples were placed on a front mounted plastic sample holder. The measuring conditions were as follows: step size 0.15 s/step, nickel filter as incident beam, aperture slit 0.3° and scan range from 0.5° to 10° 2θ.

2.2.2. IR spectraIR spectroscopy was conducted with IR-spectrometer «Nicolete IS-10» within the frequen-cy range of 400−5000 cm–1 provided by US Thermo Scientific. The samples of the studied zeolites were prepared through tableting with KBr in the aerial medium, using the Spec-troscopic Creativity Pike Technologies Hand press, in the proportion of 1 mg of zeolite per 400 mg of KBr. The resulting powder was pressed into a tablet with the diameter of 1 mm. The pill was pressed with two ramps and placed in the space of the measuring cuvette. The second cuvette (comparison) remained free, i.e. the reference is air.

2.2.3. Thermogravimetric method Thermogravimetric analysis of samples was carried out on the Q-Derivatograf 1500-D of the Hungarian company MOM in a dynamic mode in the temperature range 20-10000С, and also in a derivatograph of the German firm NETZSCH STA 449F3 STA449F3A-0757-M. Shooting mode: heating rate 100/min; paper speed 2.5 mm/min; the sensitivity of DTA, DTG and TG is 500 mV; ceramic crucibles; standard - Al2O3.

2.2.4. Scanning electron microscopy Scanning electron microscopic analysis of the starting materials and reaction products was performed on a high resolution microscope (an increase of 30000 times) Hitachi 3000 TM. Low vacuum mode allows you to explore samples without pre-deposition. The sam-ple is placed on a double-sided adhesive tape glued onto a metal disk and vacuum to a pressure of 10-4 Pa and then the sample is viewed on a microscope to obtain micrographs.


Mamedova G.A.

№ 3 (8) 2019

3. ResultsThe obtained hydrothermal modification of natural mineral raw of Nakhchivan gismon-dine crystallizes in the monoclinic crystal system with the unit cell parameters a = 9.84 Å, b = 10.02 Å, c = 10.62 Å, which agrees well with the reference data [16]. The synthesis conditions were studied in the temperature range of 100-300°C, the concentration of the KOH thermal solution is 10-30%, and the processing time is 10-100 hours. This suggests that the area of existence of gismondine is large. But under the above conditions, the opti-mum, i.e. phase pure gismondine are temperature − 100°C, concentration of KOH 10-20%, processing time − 50 hours.The diffractogram and IR spectrum of natural mineral raw materials of Nakhchivan and synthesized gismondine are presented in Figures 1-3, and the tabulated data of X-ray dif-fraction analysis of gismondine is given in Table 2.

Figure 1. XRD patterns of Nakhchivan natural zeolite

Figure 2. IR spectra of Nakhchivan natural zeolite

Figure 3. XRD patterns of gismondine


Mamedova G.A.

№ 3 (8) 2019

Table 2. X-ray data of synthesized gismondine

When comparing diffraction experimental data with literature data [17], it was established that the sample under study is a zeolite – mordenite and the synthesized product of gismondine (Table 2). The interference maxima characteristic of the mordenite phase correspond to the values of the Bragg angle 2θ = 6.5, 9.8, 13.5, 14, 19.5, 22, 25.5, 26, 27, 28, etc. The relative intensity and interplanar distances obtained experimentally correspond to the literature data (within the experimental error), which indicates that mordenite is the main phase of the sample. The interplanar distances (d) and the intensities of the diffraction lines (I) equal to d=3.34Å (100), 2.45Å (30), 2.28Å (201) and 2.12 Å (20) indicate that that the sample contains silicon dioxide, i.e. α-quartz. According to the diffractogram anorthite (4.30Å, 3.60Å, 3.40Å, 3.19Å) is also present in the sample composition in small quantities. The absorption bands in the frequency range of 250–1400 cm–1 correspond to the main vibrations of the aluminum-silicon tetrahedron of the skeleton structure of zeolites. The main vibrations of alumina-silicon tetrahedron of zeolites belong to two groups of vibrations. Oscillations of the first group are not sensitive to changes in the frame structure. The second type of oscillations depends on the nature of the junction of the tetrahedron


Mamedova G.A.

№ 3 (8) 2019

in the secondary structural units and the peculiarities of the cavities of the zeolites [18].The IR-spectra of the resultant zeolites (Figure 2) shows that the most intensive absorption banks registered within the range of 440−480, 570−650, 990, 1045−1160 cm-1 are consistent with the volatility of bonds Si–O–Si. The absorption banks within the range of 700−780 cm-1 are referred to the bond stretching of Al–O, while 650−900 cm1 relates to the bending vibration of Al–O4. The value of 1610−1660 cm-1 constitutes a band of the bending vibrations of water molecules [19]. The absence of the absorption bands of 960 cm-1 as well as within 3720−3740 cm-1 in the IR-spectra [20] of all synthesized zeolites says for the high crystallinity and evidences that there are no amorph impurity phases in the composition of the resultant zeolites (as shown in the XRD of the resultant zeolites). The area of dehydration, water content and thermal stability of gismondine are determined by the method of thermographic analysis. The DTA and TG curves are presented in Figure 4.DTA curves are characterized by two endothermic and one exothermic effects.The first endothermic effect with a maximum of 115°C refers to the removal of adsorption water. The second endothermic effect with a maximum of 200°C refers to the complete dehydration of gismondine and occurs with a loss in weight of 21%. The whole process of dehydration occurs in the temperature range of 80–250°С.

Figure 4. DTA and TG curves of gismondine

According to X-ray phase analysis after dehydration, the gismondine carcass does not undergo structural changes. The dehydrated gismondine is fully rehydrated within 24 hours. The reversibility or irreversibility of the process of dehydration of zeolites was estimated by the level of restoration of the original diffraction pattern after rehydration. When zeolites are dehydrated [21], water being removed from the cavities is concentrated in the form of a hydration shell around the cation and, as a result, the cations in hydrate form can also be removed from the system. For this reason, in the diffractogram of dehydrated gismondine, small changes are observed in both the intensities of the bands and the displacements in the values of the interplanar distances (Fig. 5).


Mamedova G.A.

№ 3 (8) 2019

Figure 5. XRD patterns of dehydrated gismondine

The exothermic effect found on the DTA curve (440-620°С) with a maximum of 470°С refers to the destruction of the gismondine structure. X-ray phase analysis after the exothermic effect showed that the structure of gismondine is destroyed and crystallizes the potassium feldspar of sanidine (Fig. 6).

Figure 6. XRD patterns of sanidine

Sanidine refers to feldspars, crystallizes in the monoclinic crystal system with the unit cell parameters a = 8.6 Å, b = 13.03 Å, c = 7.17 Å, which agrees well with the reference data [16]. Figure 7 shows the micrograph of the synthesized gismondine. As can be seen from Figure 7, the resulting alkaline treatment of gismondine has a triangular morphology in the form of nanoparticles.

Figure 7. Micrograph of gismondine

4. Conclusions

Thus, the hydrothermal modification of natural mineral raw materials of Nakhchivan was carried out for the first time and a practically important zeolite of gismondine type was synthesized. A hydrothermal modification was carried out in a wide range of temperature, concentration of thermal solution and treatment time, and it was found that the optimal


Mamedova G.A.

№ 3 (8) 2019

conditions for the synthesis of phase-pure gismondine were a temperature of 100°C, a concentration of thermal solution of 10-20% KOH, and a treatment time of 50 hours. It was established that the resulting zeolite of gismondine is dehydrated in the temperature range of 80-250°C and stable up to 620°C, and a further increase in temperature leads to the destruction of its structure and crystallization of sanidine. It was shown that dehydrated gismondine is completely rehydrated within 24 hours, which once again proves its zeolite character.

5. References

1. М.В. Обуздина, Процессы очистки сточных вод от нефтепродуктов с использовани-ем модифицированных цеолитов. Авт. дис. ….. кан.тех.наук, Томск, 2011.2. К.Т. Оспанов, Г.Н. Муханова, Обезвреживание осадков сточных вод от тяжелых металлов с помощью природного цеолита, Вода и экология: проблемы и решение 4 (2015) 56−61.3. Е.Г. Филатова, Ю.Н. Пожидаев, О.И. Помазкина, Использование природных цеоли-тов в технологии очистки сточных вод, Вода: химия и экология 11 (2014) 83−88.4. E. Erdem, N. Karapinar, R. Donat, The removal of heavy metal cations by natural zeolites, J. Colloid Interf. Sci. 280 (2004) 309−314.5. А.М. Паничев, Н.И. Богомолов, Н.П. Бгатова, С.Н. Силкин, А.Н. Гульков, Цеолиты в хирургии, ДВГТУ, Владивосток, 2004. 6. А.М. Паничев, А.Н. Гульков, Природные минералы и причинная медицина будуще-го, ДВГТУ, Владивосток, 2001.7. L. Bacakova, M. Vandrovcova, I. Kopova, I. Jirka, Applications of zeolites in biotechnology and medicine – a review, Biomat. Sci. 6 (2018) 974−989.8. О.Ю. Голубева, Пористые алюмосиликаты со слоистой и каркасной структурой: синтез, свойства и разработка композиционных материалов на их основе для реше-ния задач медицины, экологии и катализа. Дисс. ….. д.х.н., Санкт-Петербург, 2016.9. K. Jonghyun, J.C. Sung, K. Do Heui, Facile Synthesis of KFI-type Zeolite and Its Application to Selective Catalytic Reduction of NOx with NH3, ACS Catal. 7 (2017) 6070−6081.10. J.R. Christopher, The Properties and Applications of Zeolites, Sci. Prog. 93 (2010) 223−284.11. В.П. Доронин, Т.П. Сорокина, Химический дизайн катализаторов крекинга, Рос. Хим. Журн. 4 (2007) 23−28.12. Б.Б. Митыпов, Э.Л. Зонхоева, Н.М. Кожевникова, Б.В. Пашинова, Сорбция ионов лантана (III) природным морденитсодержащим туфом, Журн. прикл. химии, 74 (2001) 564−567.13. G.A. Mamedova, Modification of a Nakhchivan natural zeolite in the alkaline environment, Mosc. Univ. Chem. Bull. 74 (2019) 46−53. 14. Г.А. Мамедова, Гидротермальный синтез цеолита ZSM-10, Вестник МГТУ им. Н.Э. Баумана. 80 (2018) 125−133. 15. Г.А. Мамедова, Ф.М. Новрузова, Химическая модификация природного минерала Нахчывана, Перспективные материалы. 6 (2018) 54−61. 16. M.M. Treacy, J.B. Higgins, Collection of simulated XRD powder patterns for zeolites, fourth ed., Elsevier, New York, 2001. 17. P. Sánchez-López, J. Antúnez-García, S. Fuentes-Moyado, D. Galván, V. Petranovskii, Analysis of theoretical and experimental X-ray diffraction patterns for distinct mordenite frameworks, J. Mat. Sci. 54 (2019) 7745–7757. 18. H. Bekkum, E. Flanigen, P. Jacobs, J. Jansen, Introduction to Zeolite Science and Practice, second ed., Elsevier , New York, 2001.


Mamedova G.A.

№ 3 (8) 2019

19. G. Coudurier, C. Naccache, J. Vedrine, Spectroscopy in Identifying ZSM Zeolite Structure, J. Chem. Soc. Chem. Com. 24 (1982) 1413−1415. 20. S. Khabtou, T. Chevreau, J. Lavalley, Quantitative infrared study of the distinct acidic hydroxyl groups contained in modified Y zeolites, Microp. Mat. 3 (1994) 133−148. 21. Д.И. Мирзаи, Физико-химические закономерности дегидратации и регидратации природных цеолитов. Авт. дис. …. д.х.н., Москва, 1989.


L.I.Podzorova*, A.A.Ilicheva, V.E.Kutuzova, O.I.Penkova, O.S.Antonova, A.S.Baikin, A.A.Konovalov

№ 3 (8) 2019

MICROSTRUCTURE AND RESISTANCE TO BRITTLE FRACTURE OF Al2O3 – (Сe–TZP) SYSTEM COMPOSITES

DOI: 10.18572/2619-0141-2019-3-3-36-40Podzorova* L.I.,Ilicheva A.A., Kutuzova V.E., Penkova O.I.,

Antonova O.S., Baikin A.S., Konovalov A.A.Baikov Institute of Metallurgy and Materials Science, 49 Leninskii pr-t., Moscow, Russia

[email protected]

Abstract This work presents an investigation of composites of 75%Al2O3-25%[ZrO2 -СeO2] system with the variable content of oxide of calcium from 1 to 6%. It is established the introduction of calcium oxide in the amount of 1% contributes to increase resistance to brittle fracture of the composites due to the formation of the microstructure that contain long-prismatic shaped grain that performs the function of dispersion strengthening.

Keywords: ceramic composites, aluminium oxide, zirconium dioxide, bending strength, fracture toughness

1. Introduction

Ceramic materials based on aluminum and zirconium oxides, due to chemical stabili-ty, high mechanical strength, resistance to brittle fracture, and biological inertness, are widely used both in engineering and in medicine. Currently, intensive research has been conducted to develop ceramic composites based on them, which have improved perfor-mance, especially important to medical applications: high service life without the need of revision surgery.Ceramic materials based on individual aluminum and zirconium oxides suffer from several disadvantages. Ceramic materials based on ZrO2 have a low heat conductivity, which hin-ders heat removal in tribotechnical products. Ceramic based on Al2O3 has a low resistance to brittle fracture, which significantly compromise the quality of its structural character-istics [1-3]. So far different technological approaches have been developed for ensuring the parameter increment with the use of nanoscale initial powders and inclusion of phase composites that have the effects of transformation and/or dispersion strengthening in to composition [4-8]. As a transformation-toughened phase, the solid solutions based on tetragonal zirconia are the most frequently used. Dispersion hardening is carried out by introducing the phases crystallizing in the form of fibers, filaments, pins or highly anisotropic crystallites. As one of the leaders in the field of technical ceramics production, CeramTec through re-search has developed a composite in the Al2O3- ZrO2 system, which combines both mech-anisms of increasing resistance to brittle fracture [9]. In this composite, tetragonal zirconia stabilized with yttrium oxide is the transformation-toughened phase and the strontium hexaaluminate is dispersion strengthening phase. The experimental procedure and prop-erties of similar composites are described in detail in publications [10,11]. It was shown in our publications [12,13] that in the process of sintering nanopowders of the ZrО2 – Al2O3 – СеО2 system modified with alkaline-earth elements a three-grain composition microstructure is formed, including anisotropic grains corresponding to the phase of complex hexaaluminates. To clarify the possibility of increasing the crack resistance of composites with an aluminum oxide matrix by increasing the content of the phase that crystallizes in the long-prismatic form could be of interest. This paper provides the results of studying the grain composition microstructure of Al2O3 –– ZrO2(Ce–TZP) composites with the Al2O3 matrix influence on their resistance to brittle



№ 3 (8) 2019

fracture.

2. Experimental procedure and testing methods

The basic composition of 75%Al2O3-25% [88%ZrO2 + 12%СeO2] (mol.%)1 system (without modifying additive) and compositions modified by CaO with a variation of its content from 1% to 6% have been studied in this work.Synthesis of nanopowder precursors was performed by the hydrolysis sol-gel method us-ing 1 M solution of ZrOCl2, Al(NO3)3, Ce(NO3)3, Ca(NO3)2 crystalline salts. The process was carried out according to the scheme of components codepositions described in [14]. Sam-ples were named as follows: basic "75Al" and modified "75AlСa1", "75AlСа3", "75AlСа6". Hydrogel precipitates were dried, and then the xerogels were obtained after heat treat-ment at a temperature of 1050°C. The green compacts with dimensions of 4x4x32 mm were formed by semi-dry pressing in hydrostatic press (50 t) with specific pressure of 200 MPa. The optimum sintering temperature was set by heat treatment of the green com-pacts in air within the range of 1600 to 1650°C in electric furnaces. To measure the powders specific surface area, the method of low-temperature adsorption (automated gas adsorption analyzer TriStar-3000) was used. The granulometric compo-sition of powders was determined by the laser diffraction method on the Analizette-22 device. The surface analysis of composites was carried out with the scanning electron mi-croscope Tescan Vega II SBU. The relative density and voids rating were measured by the hydrostatic weighting method (the Archimedean method) [15]. The bending strength was determined by the three-point bending method on the multipurpose testing machine Instron 5581. The test machine’s crosshead rate was 0.5 mm/min. The fracture toughness coefficient K1c was determined by the method of CTOD test (Crack Tip Opening Displace-ment). Young's modulus (E) was estimated by the scanning impulse acoustic microscopy.

3. Results and DiscussionAfter the heat treatment at the temperature of 1050°C, the main crystalline phases composition of nanopowders comes in a form of solid solution based on tetragonal zirconia (JCPDS card. № 50-1089). As additional phases, solid solution of – Al2O3 transition oxide phase and traces of monoclinic zirconium dioxide (M-ZrO2) are registered. This fact is illustrated by fragments of the 75Al and 75AlCa powders XRD patterns presented in Figure 1.

20 25 30 35 40 45 50

020406080

100120140160180200220240260280300

y-Al2O3

M-ZrO2

y-Al2O3

2Θ, град.

инте

нсив

ност

ь, у

сл.е

д.

75Al

75AlCa

T-ZrO2

M-ZrO2

Figure 1. Fragments of the 75Al and 75AlCa powders XRD patterns (T=1050°C) – Al2O3 Т– ZrO2 М– ZrO2

1 Further everywhere mol.%



№ 3 (8) 2019

It should be noted that despite the prevalence of Al2O3 in the compositions, T-ZrO2 is identified as the main phase of XDR pattern, which is linked to differences in the absorption coefficients ( ) [16] of aluminum oxide and zirconium dioxide, = 31,2 and 108,9 units, respectively.The obtained powders of all compositions with different content of the modifier have high dispersity, belong to nanoscale systems and have a developed porous structure with hierarchical structuring. Results are presented in Table 1. The samples of composites with basic composition containing 1% CaO had a relative density not lower than 99% of the theoretical density value in the absence of open porosity after sintering at a temperature of 1650°C. Increasing of CaO content led to the appearance of open porosity. This fact can be correlated with the presence of a significant number of large agglomerates in the powders 75AlСа3 and 75AlСа6. The characteristics of sintered samples are presented in Table 2.

Table 1. Dimensional characteristics of “75Al”, “75AlСа1”, “75AlСа3”, “75AlСа6” powders

Table 2. Characteristics of materials obtained after sintering at 1650 ° C

The high porosity of the 75Al6Ca sample did not allow to prepare proper polished specimen, therefore the samples microstructure of the obtained composites was analyzed only for the compositions "75Al", "75AlCa1" and "75AlCa3", which are presented in Figure 2 (a,b,c).

Figure 2. Microstructure of composites a - 75Al; b - 75AlCa; c- 75Al3Ca

The microstructure of the base composition 75Al is represented by two types of grains: dark ones, corresponding to corundum and streamlined globular corresponding to T-ZrO2 light ones. Furthermore, the sizes of corundum grains are higher than the ZrO2 grains and fall within the range up to 2 μm. ZrO2 grains are in the range up to 1 μm, with a



№ 3 (8) 2019

predominance of 500 nm. In the modified composites microstructures, a third type is added to the described types of grains, corresponding to the aluminous grains with a long prismatic habit. In our publication [13] it was shown that the formation of such grains is determined by the crystallization of complex calcium-cerium hexaaluminates in the process of heat treatment of nanopowders. The volume fraction of the long-prismatic crystals of the grains is increased equally to the amount of calcium oxide. Consequently, the greatest amount of the analogous grains would be in the composite 75Al6Са. This fact is also influenced the attaining of the certain specific strength. Strength characteristics of base and modified composites are presented in Table 3.

Table 3. Strength characteristics of ceramic composition materials

According to the obtained results, strength characteristics of the ceramic materials demonstrate high structural sensitivity. The strength of ceramics is influenced significantly by the quantitative ratio of crystalline phases, grain sizes and habitus, as well as the presence of porosity. The pores don’t only reduce the cross-sectional area, but also function as stress concentrators.The dependence of ceramics strength on porosity is described by the Ryszkiewicz’s formula:

It follows from that dependence that with a porosity of 5%, the failure resistance can decrease by more than 40% compared to the strength of the densified material. This thesis is confirmed by the obtained results. With a content of 3% CaO, the strength of the 75Al3Ca composite decreases by 42% and even more for the 75Al6Ca composite. The densified samples of 75Al1Са, modified with 1% CaO, show an increase in resistance to brittle fracture in comparison with the base composite 75Al, the value of К1с increased from 7 to 9.5 МPа ·m ½. This fact is explained by the combination of the effect of two stabilizing mechanisms: transformation and dispersion strengthening, as well as the densely-sintered state of the composite.

4. ConclusionOn the basis of synthesized by the sol-gel method nanopowders, ceramic composites were obtained in the 75%Al2O3-25%[ZrO2 -СeO2] system, with the variability of CaO content modifier from 0% to 6%. It is shown that the introduction of calcium oxide causes the



№ 3 (8) 2019

composites formation that have a three-grain microstructure. It was found that an increase in the content of the phase formed in long-prismatic grains and performing the function of dispersion strengthening does not lead to an increase in strength characteristics since it makes it difficult to obtain densely-sintered samples. It is established that the introduction of CaO in the amount of 1% contributes to stability improvement of the composites to brittle fracture due to the summation of the effects of transformation and dispersion strengthening, fracture toughness К1с increases to 10.5 МPа ·m ½. This work was carried out within the framework of the state task No. 075-00746-19-00.

References[1] Barinov SM, Shevchenko V.Ya. Strength of technical ceramics// M. Nauka.1996. 159p.[2] Garshin AP, Gropyanov VM, Zaitsev GP, Semenov SS Ceramics for machine building// M. Nauchtekhlitizdat. 2003. 380p[3] Bakunov VS, Belyakov AV, Lukin ES, Shayakhmetov U.Sh. Oxide ceramics: sintering and creep// Mendeleev University of Chemical Technology. 2007. 584p.[4] Yang G, Li J, Wang G, Yashima M, Min S: Influences of ZrO2 nanoparticles on the microstructure and mechanical behavior of Ce-TZP/Al2O3 nanocomposites. J Mater Sci. 2005, V.40. I.23. P. 6087–6090.[5] Piconi C., Maccauro G., Muratori F. Alumina Matrix Composites in Arthroplasty// K. Engineering Mater. 2005. V. 284-286. P.979-982[6] Palmero P., Naglieri V., Spina G., Lombardi M. Microstructural design and elaboration of multiphase ultra-fine ceramics// Ceram. Int. 2011.V 37. No.1. P.139–144[7] Naglieri, V.; Palmero, P.; Montanaro, L.; Chevalier, J. Elaboration of Alumina-Zirconia Composites: Role of the Zirconia Content on the Microstructure and Mechanical Properties//J. Materials. 2013. I.6. P.2090–2102[8] N. A. Rejab, A. Zahirani, A. Azhar, Khoo Seng Kian. Effects of MgO addition on the phase, mechanical properties, and microstructure of zirconiа- toughened alumina added with CeO2(ZTACeO2) ceramic composite//Materials Science and Engineering. 2014. A 02. 595. P.18–24[9] Information on https://www.ceramtec.ru/ceramic-materials/mixed-dispersion-ceramics/ (accessed 14 May 2019).[10] W. Burger and H.G. Richter, High Strength and Toughness Alumina Matrix Composites by Transformation Toughening and 'In Situ' Platelet Reinforcement (ZPTA) - The New Generation of Bioceramics// K. Engineering Mater. 2001. V. 192-195, P. 545-548[11] S.J. Lee, S.Y.Chun, C.H.Lee. In situ fabrication of multi- component ceramic compositites by steric organic entrapment route// J. Mater. Lett. 2004. V.58. P.2646-2649[12] L. I. Podzorova, L. I. Shvorneva, A. A. Il’icheva, N. A. Alad’ev, O. I. Pen’kova Microstructure and phase composition of ZrO2-CeO2-Al2O3 materials modified with MgO and Y2O3. Inorganic Materials April 2013, V. 49, I. 4. P. 376-381[13] L. I. Podzorova, A. A. Il’icheva, O. I. Pen’kova, V. P. Sirotinkin, O. S. Antonova, and A. A. Konovalov Phase Formation in Al2O3–ZrO2–CeO2 Nanopowders Modified with Calcium Cations// Inorg. Mater. 2018. V. 54. No. 5. P. 454–459.[14] Podzorova L.I., llyichova A.A., Mikhailina N.A., Penkova O.I., Shvorneva L.I., Talanova G.V Strength Properties of Al203 and T-Zr02 based Ceramics when Changing the Matrix// Refractories and Industrial Ceramics. 2007. V. 48. No 2. P.6-9.[15] Praktikum po technologii keramiki I ogneuporov [A workshop on technology of ceramics and ogneupor] under edition D.N.Poluboyarinova and R. Ya.Popil’skogo. Moscow, Izd. lit. po stroitelstvu, 1972, P.352(P.106 – 109)[16] L. I. Podzorova, A. A. Il’icheva and L. I. Shvorneva Effect of the precipitation sequence on phase formation in the ZrO2-CeO2-Al2O3 system//Inorganic Materials. 2007. V. 43. No. 9. P. 972-975


Galina Shaidurovaa, Natalia Ryabininaa, Yakov Shevyakova


Analytical Research in Application of High-silica Composite Materials

DOI: 10.18572/2619-0141-2019-3-3-41-42Shaidurova G., Ryabinina N., Shevyakov Y.

Department of Mechanics of Composite Materials and Structures at Perm National Research Poly-technic University, Russia, 614013, Perm, Complex of PNRPU, st. Academician Korolev,

15 (building D) to. 402"[email protected]

Keywords: High-silica coatings, Composite materials, Matrix, Fire resistance, Liquid glass

1. IntroductionThis article presents analytical studies on the use of high-silica composite materials. The use and development of new materials is an important factor in solving economic prob-lems. One of the promising are high-silica composite materials. In the case of the use of an alkaline component as a binder — liquid glass in combination with silica-containing nanofillers with the presence of chopped fiberglass — you can obtain fire-resistant ma-terials with a high intrinsic heat capacity. These materials can be successfully applied in flame retardant structures with a fire resistance of more than 240 minutes, which is ex-tremely important in the case of an emergency situation in habitable objects. Primary tests carried out confirm the effectiveness of the use of high-temperature building mate-

rials for a liquid glass binder.

Discussion It is known that when changing the conditions or under impulse action, composites with programmable behavior or intelligent composites can change their properties and turn into other forms of materials that have new properties. At the same time, the formation of nanophases and nanostructures is of great importance in modern macrosystems. With the introduction of nanoparticles into the polymer matrix, its macromolecules gather around the nanoparticles, forming a fairly dense nucleus. The number of macromolecules around is determined by the surface energy of the nanoparticle or the charge distributed on its surface and its fluctuations on the surface of the nanoparticle. Numerous strength material tests for various purposes confirm the positive effect on macromolecules and their mutual organization. Among the majority of nanostructures a significant place belongs to silicon-containing formations. Silicon dioxide, for example, has been used in formulations of various new materials (SiO2 is silica, known in medicine as Polysorb, SiO2 is Aerosil, as a thixotropic filler, silicon carbide is a key component of high-temperature ceramic-matrix compounds). The use of compositions with a high sil-icon content is promising for creating materials remaining fire resistant for a long time, which is now quite important in the designs of fire resistant doors high-temperature fur-naces and other units. The material must have its own high heat capacity. Intermolecular bonds between silicon and binding fire-resistant compositions, known in a wide range of fire resistance up to 240 minutes, are of great practical interest. However, the mechanism of their physicochemical transformations is reduced to thermal decom-position of the polymer binder with the formation of a foamed product, which affects the increase in thermal conductivity, equal to


Galina Shaidurovaa, Natalia Ryabininaa, Yakov Shevyakova

№ 3 (8) 2019

In the process of destruction, the free volume fraction (FVF) is formed, which is calculated by the formula:

FVF = (ν - 1.3 νw) / ν,Where ν is free volume of the polymer; νw is specific van der Waltz volume.

The value 1.3 is an empirical parameter, where 1.3 = 1 / кcr, where кcr is the molecular packing coefficient of ideal crystals. Naturally, macropores are characterized by less dense packaging. Due to the fact that polymer matrices require generally the use of flammable solvents during processing, their use for fire protection is practically unacceptable. Polymers and their water-based com-positions do not have sufficient moisture resistance. Although high-silicon compositions with liquid glass (gel - fractions) are used, they require an instrumental investigation of physical and chemical transformations during high-temperature heating, typical for each added component. In addition, it is necessary to take into account the thermomechanical behavior of the cured composition. The essence of the method developed by V.A. Kargin and T.I. Sogelova is as follows: a polymer body is subjected to a constant or variable load, its deformation being recorded at each temperature. Creep develops, if is subjected to a constant voltage.When using liquid glass in combination with silica-containing nanofillers with the pres-ence of chopped fiberglass as a binding alkaline component, it is possible to obtain fire-resistant materials with a high intrinsic heat capacity. These materials can be success-fully applied in flame-retardant structures with a fire resistance of more than 240 minutes, which is extremely important in the case of an extreme situation in inhabited objects. The initial tests confirm the effectiveness of high-temperature building materials with the liquid-glass binder.

References1. Askadsky A.A. Physical Chemistry of Polymeric Materials and Methods for their Research / A.A. Askadsky, M.N. Popov, V.I. Kondrashchenko - Moscow: “ACB Publishing House” - 2015.- p.p.105-120. 2. Certificate of Authorship №697429, MKL. S04B 7/14, 18.11.793. Patent RU 2296724 С04B 7/153 Binders (versions)4. Khodakov G.S. On the Mechanism of Finely Ground Lime-sand Binder Hardening with-out Hydrothermal Treatment / G.S. Khodakov - Moscow: State Publishing House of Litera-ture on Construction Materials - 1957. – p.p.3-5.5. Klimenko N. N., Mikhaylenko N. Y. Building Material Based on Liquid Glass and the Pro-cesses of Its Hardening // The World of Technology and Technology. - 2012. - № 7. - P. 60–63.6. Mikhaylenko N. Y., Klimenko N. N. Optimization of the TechnoloGical Parameters of the Synthesis of High-silica Liquid Glass Composites for Construction Purposes // Glass and Ceramics. - 2013. - № 5. - P. 11–17.7. Typical Diagrams of the State of Three-component Systems: a teaching aid / N. V. Gol-ubev, E. S. Ignatieva, S. V. Kirsanova, etc. - Moscow, RCTU of Art. D.I. Mendeleev, 2017. - 72 p.


Volchenkova V.A., Kazenas E.K., Andreeva N.A., Fomina A.A., Penkina T.N., Podzorova L.I., Ilyicheva A.A.


IMPROVEMENT OF METROLOGICAL CHARACTERISTICS OF AES-ICP DETERMINATION OF IMPURITY ELEMENTS IN ZIRCONIUM CERAMIC

MATERIALS FOR MEDICAL PURPOSESDOI: 10.18572/2619-0141-2019-3-3-43-56


Baikov Institute of Metallurgy and Materials Science of the Russian Academy of Sciences (IMET RAS). Russia, Moscow, Leninsky prospect, [email protected]; [email protected]

Abstract: New methods have been developed for simultaneous quantifying of the con-tents of impurity elements: Al, Ag, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Sn, Sr, Ti, Y, Yb, Hf, V, Zn in ceramic materials based on ZrO2. Various schemes for dissolving samples were offered for different types of ceramic connections. Elements were determinate with founded optimal analytical parameters. The influence and meth-ods elimination of matrix element (Zr) were studied. It allowed to determine elements in a wide range of concentration from 1∙10-3 to n∙10% without preliminary separation of the matrix and improve metrological characteristics. The relative standard deviation (Sr) does

not exceed 0,12.

Keywords: zirconium ceramic, AES-ICP, determination, impurity elements.



№ 3 (8) 2019

1. Introduction

The development of materials for medicine is one of the most important tasks in modern material science. Zirconium dioxide is wide used as a ceramic material for medical purpos-es due to biological inertness. Using zirconium ceramic compounds as materials with high biocompatibility and wear resistance is very promising [1,2] for applications in arthroplas-ty of joints, restoration, and orthopedic dentistry. So analytical control of such materials is very important. Quantitative analysis of impurities is contained in the feedstock and introduced during the synthesis process can be very useful for practical use of functional materials. Medical materials are also subject of high purity requirements for the content of harmful impurities (As, Cr, Cd, Li, Pb), which are regulated by international standards.The purpose of this work is the development of methods for determination of impurities in the following compositions of different purity ceramic materials: ZrO2, ZrO2-СеО2, ZrO2-Y2О3, ZrO2-СеО2-Al2O3, ZrO2-Yb2О3, Al2O3-ZrO2-Yb2О3 with improved metrological charac-teristics. Determination of the contents impurities in compounds of this composition is have not been adequately covered in the literature.

2.Experimental part.Lack of standard composition samples to determine the list of impurity elements Al, Ag, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Sn, Sr, Ti, Y, Hf, V, Zn limits the choice of analysis method. We used atomic emission spectrometry with inductively coupled plasma (AES-ICP). This method has the following advantages: low detection lim-its, expressivity, reliable measurement of analytical signals, linearity of calibration in the range of 5-6 orders with high reproducibility, possibility of simultaneous determination of elements in a wide range of contents, relatively small level of influence of accompanying elements and ability to work without solid standard samples of the composition [3,4].

2.1 Sample preparation.It is necessary to transfer the analyzed samples to solution to perform elemental analysis using method AES-ICP. Zirconium materials are rather complex objects of investigation because of difficulties transferring samples to solution and obtaining stable solutions of high concentrations of readily hydrolyzed elements of zirconium and hafnium [5,6]. Opti-mal schemes for sample dissolution and methods of retaining elements in solution have been found (table 1).



№ 3 (8) 2019

Table 1. Methods of dissolution of zirconium ceramic materials.

Different temperature regimes could be used for producing ceramic compounds. Open systems were used to dissolve ceramics obtained without decrepitation. Accelerated techniques were developed, using the microwave system Mars 5 (CEM Corporation, USA) to translate difficult-to-open oxide ceramics obtained with decrepitation to 500°C into the solution. To confirm completeness of the dissolution of oxides, a classical scheme of alloy fusion with alkali metal salts was used [5]. The most effective was autoclaved microwave dissolution using the MARS 5 module. A 100 mg sample was completely dissolved for 50 minutes in a mixture of concentrated nitric, chloric and hydrofluoric acids at temperature of 210°C. Classical schemes of samples melting with alkali metal salts were used to transfer



№ 3 (8) 2019

to the solution of ceramic compounds, obtained with decrepitation above 500°C. These ceramic compounds failed to dissolve in the microwave system MARS 5 for several days even using rigid regimes (P, T) (table 1). The solutions residues were transferred with 4M HCl after dissolving the samples and removing hydrofluoric acid. Such high concentration of acid is necessary for obtaining stable solutions of zirconium and hafnium [6]. Before measurement on the plasma spectrometer the solutions obtained were diluted 10 times with 1 M HCI. This method of sample preparation is not suitable to determine silicon, so the wet-fusion method was also used [5]. At the same time, blank experiments were con-ducted to control the purity of the reagents. All used reagents were of the high purity. Samples of ceramic compounds are the most difficult soluble compounds.

2.2 Optimal analytical parameters for the determination of elements. Atomic-emission spectrometer with inductively coupled plasma from the firm "HORIBA JOBIN YVON", the model "ULTIMA 2" (France- Japan) was used for investigation. The high optical resolution (5 рm) of spectrometer provides the best signal to the background ra-tio, which leads to low detection limits of elements. The following optimal analytical pa-rameters for determination of elements were experimentally found: discharge power - 1,2 kW; cooling argon flow - 14 l/min; transporting - 0,80 l/min; plasma - 0,5 l/min; observation height - 14 mm above the top turn of the induction coil; the speed rate samples - 1,0 ml/min [7]. Analytical lengths of waves were chosen for determination of elements to provide suitable detection limits, a minimum of adjustments for background and overlapping of spectral lines [7]. Optimal analytical lengths of waves for determination are presented in table 2.

Table 2. Characteristics of analytical lines of elements.



№ 3 (8) 2019

It is very important to find the concentration of the matrix element in the solution, which is not violated the stability for the system burner - nebulizer. Concentration should be not more than 500 ррm for zirconium.

2.3 The influence of the matrix and methods of it removal.The possibility to determine low concentrations of impurity elements on the background of zirconium was established by studying of the spectral interference from the base ele-ment at the scan-out of the spectrum from 190 to 800 nm. Solutions of pure zirconium (500 or 1000 ppm) and impurity elements (5, 10, or 100 ppb) were introduced in the plas-ma. The detection limits of elements were estimated using the formula [9]:LOD = k∙BEC∙RSD0LOD - limit of detection; k - coefficient equal to 3 for detection 3σ limits; BEC - the concen-tration of noise; RSD0 – relative standard deviation at zero standard.Calibration curve was built for two points 0 and 5 ppm to evaluate detection limits. Cali-bration was used to determine the concentration of the noise BEC. The relative standard deviation RSD0 was determined as results of the zero standard analysis for 5 minutes. The standard solution 500 or 1000 ppm of zirconium (prepared from high purity metals [6]) was used as the zero calibration solution. The second calibration solution was prepared for the background solution of zirconium 500 ppm or 1000 ppm. Concentrations of the determined elements (Al, Ag, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Sn, Sr, Ti, Y, Yb, Hf, V, Zn) were 5 ppm.Calculated detection limits for the impurity elements in the presence of matrix element are presented in table 2. Detection limits against the 500 or 1000 ppm zirconium back-ground are significantly different from those in pure solutions. The mutual influences of the determined elements were studied. It has been established that no mutual effects occur when the content of the elements up to 10 ppm. The main problem of the emission analysis is to find the influence of the matrix. The back-ground of zirconium has very complex matrix. Determination of trace elements is espe-cially difficult because of temporal drift of the background, sophisticated form of back-ground in area of analytical lines and weak signal intensity. Increasing integration time reduces the detection limits but does not solve the problem of the influence matrix [4]. The influence of the matrix element (Zr) was studied. Allowable ratios of zirconium matrix elements to determined elements are presented in table 3.



№ 3 (8) 2019

Table 3. Allowable ratios of the zirconium matrix element to the determined elements.

It was determined effect of zirconium for different elements. Such effect is especially sig-nificant for high contents of matrix elements and low concentrations of the elements. It was observed that the slope and shift of the calibration curve depend from concentration



№ 3 (8) 2019

of matrix element in the solution. The concentration of the matrix element up to 100 ppm did not affect the analytic signals of the impurity elements (more than 10 ppb). Concentra-tion increase of Zr in the solution from 100 ppm to 500 ppm leads to change in the slope and a shift of the calibration curves. Such changes are particularly noticeable for high matrix contents (1000 ppm) and low concentrations of the detectable elements (less than 5 ppb) (Fig. 1-5). The method of interactive concordance of matrix [4] was applied to elim-inate the matrix interference due to the changing concentration of the matrix element. It is particularly difficult to determine the elements near the limits of their detection on the level of the background of complex matrices. On Fig. 1-5 are presented the calibration graphs of Nb, As, Sn, W and Pb for pure solutions and containing 300 -1000 ppm Zr. There is a distortion (see Fig. 1-5) of the calibration curves and, consequently, a deterioration in metrological characteristics of the determination of elements at Nb concentration below 10 ppb. When determining the elements near detection limits (5 ppb), other impurity el-ements (at a content of more than 10 ppm) begin to affect analytical signals. There are many publications regarding calibration functions for the analysis of high concentrations but practically no work on reducing errors of determination low concentrations [10]. We used the orthorecursive expansions method (ORE) in overcomplete systems, which bases on embedded spaces [11] to construct gauge functions with various sets of matrix effects. Due to orthorecursive expansions in overcrowded systems withstand any finite number of computational errors, the application of this method in the construction of gauge functions provides the following possibilities: significantly reducing errors of calculations, taking into consideration the influence of many matrices, accelerate the conduct of ana-lytical measurements, and determinate elements from 1∙10-3% without separation of the zirconium matrix. In the case of smaller concentrations should be provided a preliminary separation of the matrix or should be used methods of mathematical modeling.

-2000

0

2000

4000

6000

8000

10000

12000

0 2 4 6 8 10

c(Nb), ppb

Inte

nsity

, I 0 ppm Zr300 ppm Zr

Fig. 1 Calibration curves Nb for pure solutions and containing 300 ppm Zr.

-20000

0

20000

40000

60000

80000

100000

0 1 2 3 4 5 6

с (As), ppm

Inte

nsity

, I

0 ppm Zr500 ppm Zr

Fig.2 Calibration curves As for pure solutions and containing 500 ppm Zr.



№ 3 (8) 2019

-10000

0

10000

20000

30000

40000

50000

60000

70000

80000

0 200 400 600 800 1000 1200

c (Sn), ppb

Inte

nsity

, I

0 ppm Zr500 ppm Zr

Fig. 3 Calibration curves Sn for pure solutions and containing 500 ppm Zr.

-5000

0

5000

10000

15000

20000

25000

30000

35000

40000

0 50 100 150 200 250

с (W), ppb

Inte

nsity

, I

0 ppm Zr1000 ppm Zr

Fig. 4 Calibration curves W for pure solutions and containing 1000 ppm Zr.

-10000

0

10000

20000

30000

40000

50000

0 20 40 60 80 100 120

с (Pb), ppb

Inte

nsity

, I

0 ppm Zr1000 ppm Zr

Fig. 5 Calibration curves Pb for pure solutions and containing 1000 ppm Zr.

2.4 The influence of acids.The influence of the concentration effect of HCl, HNO3, H2SO4 acids on the analytical sig-nals of elements were studied. The dependence curves of analytical Al signals from the nature and concentration of acids in the analyzed solution are shown on Fig. 6. Changes in the acid concentration of the analyzed solution lead to changes in analytical signal. The degree of signal change depends on the nature and concentration of acid. The solution of 2M HCI decreases the analytical signal Al and the sulfuric acid of the same concentration accordingly on 3% and 11%. When HCL and HNO3 concentration increases from 0,01 M to 1 M, analytical signals of the elements change not more than 3%. Analytical signals of the elements depend significantly on concentrations of sulfuric acid in solution. Depress-ing action of acids is due to changes in the spray or the sample introduction systems. Change in the acid concentration leads to alteration in the effectiveness of spraying and, consequently, sensitivity. However, the methodical error can be avoided by maintaining adequate acid content in tests and standard solutions. Uncontrolled fluctuations in the concentration of acids, especially sulphuric, can lead to significantly greater errors than instrumental.



№ 3 (8) 2019

[Al]

160000

180000

200000

220000

0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6 1,8 2Acid concentration, mole/l

Inten

sity,

I

HСL

HNO3

H2SO4

Fig. 6 The dependence of the intensity of the signal Al from nature and concentration of acid.

3.The results.Samples were analyzed according to developed programs. In the solutions obtained the contents of the impurity elements were determined: Al, Ce, Y, Yb, As, Ba, Be, Bi, Ca, Cd, Co, Cr, Cu, Fe, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Sn, Sr, Ti, Hf, V, Zn. To reduce the error in determin-ing elements, calibration solutions were prepared for the same composition and content of acids as solutions of the analyzed samples. The results of the analysis of the samples are shown in tables 4-6. Findings were compared with the data of atomic absorption methods of analysis and inductively coupled plasma mass spectrometry to confirm correctness of the obtained results. Good convergence of the results received using different methods of analysis was obtained.The improvement of the metrological characteristics of AES–ICP determination of impuri-ty elements was achieved due to: • optimization of chemical sample preparation conditions;• ensuring completeness of the transfer of all elements into the solution;• obtaining low values of the blank experience, solutions stability in time, etc.;• optimization of conditions for the determination of elements in the plasma;• optimization of operating parameters;• optimization concentration of matrix element in the solution;• optimization of the choice of free analytical lines of elements;• taking into consideration influence of matrix elements on the values of analytical signals;• taking into consideration the contribution of accompanying elements to the an-alytical signal of each identified elements;• taking into consideration the influence of the nature and concentration of the acid on the signal intensity of elements; •using methods of mathematical modeling to eliminate the matrix interference.New methods allowed carry out the rapid chemical control of harmful (As, Cr, Cd, Li, Pb), "coloring" (Co, Cu, Fe, Mn, Ni), and functional (Al, Ba, Ca, Ce, Hf, K, Mg, Na, Sr, Y, Zn) impuri-ties in zirconium ceramic materials. Analytical control has been used during research and development of new generation ceramic biomaterials, in particular, medical composite materials, for bone repair.The source of ceramic compounds contamination with harmful impurities (As, Cr, Cd, Li, Pb), obtained in the IMET RAS by the sol-gel synthesis method, was found. Recommenda-tions were given to reduce the content of these elements in obtained samples.



№ 3 (8) 2019

Table 4. Results of determination of the elements contents in powders zirconium oxide

ceramics, obtained by various methods of analysis (n = 10, P = 0.95)



№ 3 (8) 2019

Table 5. Results of determination of the elements contents in powders zirconium-cerium and zirconium-ytterbium ceramics, obtained by various methods of analysis

(n = 10; P = 0,95).



№ 3 (8) 2019

Table 6. Results of AES-ICP determination of the elements contents of in powders

zirconium ceramics, obtained by with using method ОRE



№ 3 (8) 2019

4.Conclusion..With using of atomic-emission spectrometry with inductively coupled plasma the meth-ods with improved metrological characteristics were developed for determination: Al, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cu, Cr, Fe, Hf, K, Li, Mg, Mn, Mo, Na, Ni, Pb, Si, Sn, Sr, Ti, V, Y, Yb, Zn in ceramic compounds of the composition: ZrO2, ZrO2-СеО2, ZrO2-Y2О3, ZrO2-СеО2-Al2O3, ZrO2-Yb2О3, allowing express determination of these elements in a wide range of con-centrations from 1·10-3 to 10∙n%, using limited amount of samples (from 1 mg), without preliminary separation of the matrix and without using solid standard samples. The al-gorithms for mathematical accounting of the matrix effects when AES–ICP determining low concentrations of impurity elements in the studied compounds were proposed. The relative standard deviation (Sr) is 0,05-0,005 at the content of elements from 1 to 50% and does not exceed 0,12 at the elements content from 0,001 to 0,1%.This work allows us to assess the compliance of the developed ceramics with the require-ments of international standards for medical materials.

This work was carried out within the framework of the project on the fundamental re-search program of the Presidium of the Russian Academy of Sciences: “Development of methods for diagnosing and studying the structure and properties of metallic functional and nanoscale materials”.



№ 3 (8) 2019

References. [1] C. Piconi, G. Maccauro, Zirconia as a ceramic biomaterial, J.Biomaterials. 20 (1999) 1-25.[2] L.I. Podzorova, A.A. Il’icheva, O.I. Pen’kova, N.A. Aladev, V.A. Volchenkova, S.V. Kutzev, L.I. Shvorneva, Modified composites of Al2O3–(Ce-TZP) system as materials for medical use, Inorg. Mater. Appl. Res. 7 (2016) 724-729.[3] Atomic–emission analysis with inductive plasma. The results of science and technolo-gy. Ser. Analytical chemistry (Moscow: VINITI), vol. 2, 1990.[4] M.P. Thompson and J.N. Walsh, Handbook of Inductively Coupled Plasma Spectrome-try, New York: Blackie, 1989.[5] R.A. Bock, Handbook of Decomposition Methods in Analytical Chemistry, New York: John Wiley and Sons, 1979.[6] A.I. Lazarev, I.P. Kharlamov and P.Ya. Yakovlev, Handbook of chemist-analyst. M.: metal-lurgy, 1976.[7] V.I. Otmakhov, E.V. Petrova, N.V. Varlamova, Yu.V Anyushkina, Optimization of the con-ditions of the atomic emission analysis of zirconia and corundum nanoceramics by sim-ulating physicochemical processes in spectrum excitation sources, Journal of Analytical Chemistry. Т. 66 № 9 (2011) 815-819.[8] P.W.J.M. Boumans, Coincidence tables for inductively coupled plasma. Atomic emission spectrometry vol. 1, 2 (Oxford Pergamon Press), 1984.[9] V.A. Volchenkova, E.K. Kazenas, N.N. Dergunova, A.P. Degtyareva and I.I. Kraskov J. Per-spective materials. 9 (2010) 128-131. [10] D.D. Nygaard, D.S. Chase and D.A. Leighty, 1983 J.Appl. Spectrosc. 37 vol 5 (1983) 432-435.[11] A.K. Paunov, Orthorecursive expansions, Materials X1 of the Russian annual confer-ence of young researchers and graduate students "Physical chemistry and technology of inorganic materials" Moscow, IMET RAS (2014) 159.

Documents

APPLIED SOLID STATE CHEMISTRY № 3 (8) 2019