HDPE-Quasicrystal Composite: Fabrication and Wear Resistance

TECHNICAL PAPER

HDPE-Quasicrystal Composite: Fabrication and Wear Resistance

Ankush Kothalkar • Amit S. Sharma •

Garima Tripathi • Bikramjit Basu •

Krishanu Biswas

Received: 2 November 2010 / Accepted: 4 March 2011 / Published online: 30 March 2012

� Indian Institute of Metals 2012

Abstract The present paper reports, for the first time the

processing, characterization and wear property of novel

HDPE-decagonal quasicrystal (QC) composite prepared by

the compression molding technique. The composites are

prepared at 130�C at applied pressure of 735 kPa with

different holding time to obtain fully dense product. It has

been found that a holding time of 60 min is the optimum at

the specified molding temperature and pressure. The sec-

ond phase (QC) content is varied from 5 to 20 wt% to

obtain optimum mechanical properties. SEM observations

indicate well-dispersed QC particles within the HDPE

matrix, with fine scale distribution for 20 wt% QC. Ball-

on-disc wear test reveals that composites showing better

wear resistance than pure HDPE sample. The results are

discussed using currently available literature.

Keywords HDPE � Quasicrystals � Microstructure �Friction � Wear

1 Introduction

The study of the effect of fillers to polymeric materials has

emerged lately as one of the important fields of research

activities in polymer science. The polymer industry has

long been using fillers as one of the additives to reduce the

cost of the plastics by replacing a more expensive resin

(with non-expensive materials such as CaCO3, SiO2, clays,

talc etc.) [1]. In addition to saving, the addition of fillers

leads to value-added properties. The fillers are reported to

improve the physical, mechanical, rheological as well as

chemical properties [1, 2]. For example, the addition of

fillers, such as talc, leads to higher stiffness and better

creep resistance. Similarly, the electrical and thermal

conductivities of polymers can be improved by addition of

metallic filler [3]. Thus, properties of the filled polymers

can be tailored by addition of many such types of filler.

Hence, new filler materials have continuously been inves-

tigated in the polymer research with the promise of

developing material with the combination of the properties

of the fillers and processibility.

The role of fillers in the design of high strength wear

resistant plastics can be thought of quite similar to their

function in the development of ceramic reinforced metal-

matrix composite [2]. The addition of a particulate filler

leads to the production of materials with increased strength

and wear resistance, when compared to their unfilled

counterparts. In practical applications, it has commonly

been observed that machinery contains parts made from

various alloys and hard ceramics. Therefore, a filler that

improves wear resistance of a polymer while having the

ability to slide against these materials without causing

significant damage is desirable. To address this issue, new

quasicrystalline Al–Co–Ni fillers are evaluated in the

present study.

The focus of the present work is therefore to use novel

quasicrystalline (QC) particulate fillers in high density

polyethylene (HDPE) matrix. QCs discovered in 1984 [4],

are complex metallic alloys that possess distinct physical

properties such as low co-efficient of friction (0.05–0.2)

[5], high hardness (HV0.2 *800) [6], low surface energy

(*25 mJ/m2) [7] etc. The novel physico-chemical prop-

erties of these materials stem from their unusual quasi-

periodic lattice structure. The name QC originates from the

A. Kothalkar � A. S. Sharma � G. Tripathi �B. Basu � K. Biswas (&)

Department of Materials Science and Engineering, Indian

Institute of Technology, Kanpur, Kanpur 208016, UP, India

e-mail: [email protected]

123

Trans Indian Inst Met (February 2012) 65(1):13–20

DOI 10.1007/s12666-012-0120-2

unique rotational symmetries arising out of their aperiodic

atomic structure. QCs exhibit symmetries that are forbid-

den by classical crystallography, such as fivefold, eight-

fold, tenfold and 12-fold. Since their discovery [8], several

hundred alloys have been found to exhibit QC phases. Al–

Ni–Co system forms stable decagonal quasicrystalline

phases, exhibiting unique tenfold symmetry [9]. The Al–

Ni–Co system is the most attractive and remarkable alloy

system, because it forms stable decagonal phase with a

wide range of compositions (Al72NixCo28-x with x varying

from 8 to 20) [8]. In addition, the brittle nature [6] of the

QC phase allows us to obtain fine powder with low cost.

This has made them ideal materials for evaluation as

reinforcing fillers in polymeric materials. Earlier study [2,

3, 10] carried out on the addition of Al–Cu–Fe icosahedral

quasicrystals to various polymeric materials (both ther-

moplastics and thermosets) to prepare a wear-resistant fil-

ler. It was shown that Al–Cu–Fe QC filled polymers could

exhibit wear resistance behavior with nominal improve-

ments in other mechanical properties associated with rigid

low- aspect ratio fillers. In addition, the QC powder in the

polymer matrix has been reported to cause almost no

abrasion to the steel counterface materials during the wear

testing [10].

In the present contribution, we have reported the pro-

cessing, characterization and wear resistance of Al–Ni–Co

decagonal QC filled HDPE composites. The process opti-

mization to obtain fully dense composite with various

amount of QC filler will be discussed. One of important

aspects of this work is also to understand the wear resis-

tance of QC filled polymers in comparison to the pure

polymer.

2 Experimental Details

2.1 Materials

Quasicrystalline (Al72Ni8Co20) decagonal phase powders

were prepared in our laboratory by ball milling alloy but-

tons. The alloy buttons were made by arc melting pure

elements (99.9% purity) in argon atmosphere in a vacuum

arc-melting furnace. These buttons were then crushed by

mortars followed by dry balling milling (P7, Fritsch, Ger-

many) at 100 rpm with ball-to-powder weight ratio of 7:1

for 2 h to obtain fine powders. Low rpm was used so that no

structural change would occur in the alloy powder during

milling operation. The powders thus obtained have been

found to contain only decagonal phase (confirmed by X-ray

diffraction analysis). Commercially available high-density

polyethylene (HDPE) powder of density 0.948 gm/cc

(Pohong Industries, China) was used for matrix. Differen-

tial scanning calorimetric (TGA/DSC1, Mettler Toledo,

Switzerland) observations of HDPE powder shows melting

temperature of 130�C. Scanning electron microscopic

observation showed that the average particle size of QC and

HDPE were 20 ± 2 and 174 ± 4 lm, respectively.

2.2 Composite Fabrication

The pure HDPE and Al–Ni–Co alloy powder of different

compositions (HDPE with 0, 5, 10, 15 and 20 wt% QC

powder) were mechanically mixed by dry milling in a ball

mill (P7, Fritsch, Germany) operating at rpm of 200 for

6 h. The ball-to-powder ratio maintained was 7:1. The

resulting QC/Polymer powder mixture was placed in a die

mold (diameter of 2.5 cm and height of 4 cm). The powder

mixture was then compressed using a compression molding

set up SCM30 (SANTEC Laboratory, India) at a pressure

of 735 kPa and temperature of 130�C. The mold tempera-

ture was monitored with a thermocouple attached to the

mold wall. The samples were held at the set temperature

for different time duration ranging from 15 to 90 min

before cooling under pressure to room temperature. The

resulting composite pellets were polished with 400-grade

emery paper followed by washing in distilled water.

2.3 Characterization

The density of all pellets was measured according to

Archimedes’ principle using distilled water. The theoretical

density for the compression molding composition was cal-

culated following the rule of mixtures, considering the theo-

retical densities of pure HDPE and QC as 0.948 [11] and

3.939 gm/cc [9], respectively. The phase identification of the

polished and flat samples was performed by X-ray diffraction

(XRD) (Seifert, USA) using Cu-Ka (k = 0.154056 nm)

radiation at a scan rate of 1�/min. The phase distribution of all

the polished samples were observed using a field emission

scanning electron microscope (FESEM, Carl Zeiss SUPRA

40VP), operated at 10 kV. The compositional analysis of the

phases were conducted using energy dispersive x-ray spec-

troscopic (EDS) analyzer attached to the SEM. Differential

scanning calorimetry (DSC) as well as thermogravimetric

(TGA) analysis were performed on a Mettler-Toledo TGA/

DSC1 under argon purge at a heating rate of 10 K/min. Wear

test of the developed composites was performed in a ball-on-

disc type commercial tribometer (DUCOM, India) under

mode-I fretting condition. The compression-molded pellets

were used as flat materials (moving) and the alumina ball of

9 mm in diameter with mirror finish surfaces was the count-

erbody material. Before the fretting tests, alumina balls were

ultrasonically cleaned in acetone. The testing parameters

included a normal load of 5 N, frequency of 5 Hz, stroke of

100 lm and testing duration of 60,000 cycles. In fretting

tribometer, an inductive displacement transducer monitored

14 Trans Indian Inst Met (February 2012) 65(1):13–20

123

the displacement of the flat sample. The friction force was

recorded with a piezoelectric transducer attached to the holder

that supports the counterbody. The friction coefficient was

obtained from the online measured tangential force. After a

wear test was performed, the laser surface profilometry

(MAHR, Perthometer, Germany) was utilized to obtain

3-dimenional shape of the wear scar. These data were utilized

to obtain wear volume of all samples. The hardness of the

pellets was measured on polished compression molded sam-

ples using Vickers hardness tester (Bareiss Prufgeratebau,

GmbH) with 10 gm load. At least 5 indentations were taken

for each sample and hardness value was reported as the

average of all the measurements with error bars.

3 Results and Discussion

3.1 Optimization of Densification

We shall first discuss the process optimization to prepare

dense composite using compression molding. The com-

pression molding of the composite powder mixture has

been carried out at 130�C and pressure of 735 kPa for

different holding time ranging from 15 to 90 min to opti-

mize the densification. The selection of holding tempera-

ture has been done based on differential scanning

calorimetry results, which will be discussed later. Figure 1

shows the variation of relative density of the composite

with time for HDPE-5 wt% QC compression molded at

735 kPa. The relative density of the composite increases as

a function of holding time up to 60 min reaching

99.9% qth, where qth is the theoretical density of the

composite calculated using rule of mixture. The relative

density decreases with further increase in holding time

(90 min). Similar trend in densification behavior has been

observed for other compositions. Therefore, the holding

time of 60 min and applied pressure of 735 kPa at 130�C

has been used as optimized processing conditions in the

compression molding experiments in the present investi-

gation. Table 1 shows the relative density of all the com-

posite compression molded with same applied pressure and

temperature. It is clear that pellets can be fully sintered

irrespective the composition of the composite.

3.2 X-ray Diffraction (XRD) Study

X-ray diffraction analysis of all the composites (5, 10, 15

and 20 wt%) as well as pure HDPE pellets has been carried

out. However, we shall present representative XRD anal-

ysis of HDPE-10 wt% QC composite. Figure 2 shows such

analysis. The XRD patterns obtained from individual

powder are shown in Fig. 2a, b, whereas Fig. 2d is the

XRD pattern obtained from the compression-molded pellet.

Figure 2c reveals XRD pattern from the mixed powder.

Figures 2c, d show that all peaks in the XRD patterns can

be indexed using the characteristic peaks of decagonal

quasicrystal and pure HDPE. The observation of rather

Fig. 1 The relative density of HDPE-5 wt% QC composite is plotted

against holding time. The pellet was compression molded at 130�C at

735 kPa pressure. q is the measured density of the composite and qth

is the theoretical density of the composite calculated using rule of

mixture

Table 1 Relative density of the

composite pellets with different

QC content

Wt% of QC

in HDPE

Relative

density

(=qmeasured

qtheoretical)

0 99.8

5 99.9

10 99.9

15 99.9

20 99.8

20 30 40 50 60 70 80 90 100

Carbon

Inte

nsit

y (a

rb. u

nits

)

HDPEAl-Co-NiAl-Co-Ni(10wt %)+HDPE compositeAl-Co-Ni(10wt %)+HDPE Pellet

(a)

(b)

(c)

(d)

2θ (in degrees)

decagonal

Fig. 2 X-ray diffraction patterns: a pure HDPE powder,

b Al72Co20Ni8 QC powder, c HDPE-10 wt% QC powder mixture

and d HDPE-10 wt% QC composite pellet

Trans Indian Inst Met (February 2012) 65(1):13–20 15

123

broad HDPE peak can be ascribed to the semi-crystalline

nature of the polymer. The presence of any unwanted phase

or reaction product cannot be detected in the compression-

molded pellet. As amount of QC phase increases in the

composite, there is concomitant increase in intensity of QC

peaks. Therefore, it is possible to retain the constituent

phases in the compression-molded pellets.

3.3 Differential Scanning Calorimetric (DSC)

and Thermogravitometry (TGA) Study

Differential scanning calorimetric and TGA were carried

out for five samples (0, 5, 10, 15 and 20 wt% QC in HDPE)

to study crystallinity of HDPE in the pellets and to under-

stand the stability of the composites. It has been observed

that pure HDPE pellet melts at 130.5�C, which is the

equilibrium melting temperature, reported in the literature

[9]. As far as processing temperature of the composites are

concerned, the compression molding experiments have

been carried out at 130�C so that QC particles get well

mixed during the holding time and we can obtain well

dispersed QC particles in the pellet. The crystallinity of the

pure HDPE and composite pellets can be calculated using

normalized enthalpy of melting of the composite from DSC

measurements and comparing it with the enthalpy of pure

HDPE with 100% crystallinity (234.2 J/g) [10]. Table 2

provides the results obtained from such analysis. It is clear

that the samples are not 100% crystalline, rather they show

semi-crystalline nature. The crystallinity of the composite

decreases by addition of QC particles. TGA measurements

indicate the % change in mass of the samples during mea-

surement. TGA results show that the mass of the samples

does not change appreciably. Therefore, the samples are

found to be not reactive with the atmospheric oxygen during

the measurement and hence these composites are very sta-

ble during heating to high temperatures.

3.4 Scanning Electron Microscopic (SEM) Analysis

of Composite

Scanning electron microscopic observations of the com-

posite pellets are presented in Fig. 3. These are back-

Fig. 3 BSE SEM micrographs of the composites samples with

a 5 wt% QC, b 10 wt% QC, c 15 wt% QC and d 20 wt% QC. The

inset in each figure shows higher magnification micrographs revealing

distribution of QC particles in HDPE matrix

Table 2 DSC-TGA results of the composites and pure HDPE pellets

Wt% of QC

in HDPE

% Crystallinity Wt. change in

TGA (% initial weight)

0 46.41 1.571

5 41.19 1.328

10 44.83 0.996

15 45.64 0.756

20 43.44 1.329


123

scattered electron (BSE) micrographs, depicting distribu-

tion of QC particles within HDPE matrix. Figure 3a–d

reveals the BSE micrographs with varying QC content

(5–20 wt%) in the composite, clearly showing the well-

dispersed QC particles in the composite. The inset in each

micrograph reveals higher magnification micrographs to

reveal the size and shape of QC particles. One can clearly

observe (marked by broken arrows in the inset of Fig. 3a,

b) the presence of finer scale QC particles (\1 lm) in case

of HDPE- 5 wt% QC composite. It is to be noted that SEM

micrographs (not shown here) of QC powder indicate the

average particle size to be 20 ± 2 lm. The dispersion of

quasicrystalline particles in the polymer matrix is found to

be uniform. However, as concentration of the QC increa-

ses, QC particles form agglomerates, as indicated by white

arrows in Fig. 3c, d as well as in the insets of the figures.

The agglomeration of QC particles is mainly due to the

close proximity in HDPE melting during compression-

molding experiments.

3.5 Hardness and Friction Measurements

Figure 4 shows the hardness of the composites as a func-

tion of QC content. The hardness measurements have been

carried out using Vickers hardness tester. Pure HDPE pellet

shows a hardness of 55 MPa. There is a steady increase in

the hardness of composites as we increase the QC content

from 5 to 20 wt%. In fact, the hardness of the HDPE-

20 wt% QC is more than twice that of pure HDPE.

Therefore, the addition of harder QC particles to softer

HDPE matrix leads to substantial improvement of hardness

of the composite. The hardness values obtained in the

present investigation are comparable with earlier studies on

Al–Cu–Fe QC filled ultrahigh molecular polyethylene as

well as epoxy composites [2–4].

The coefficient of friction (COF) of all samples has been

measured using ball-on-disc type commercial tribometer

under mode-I fretting condition. We shall present the

results obtained from representative samples to elucidate

the salient results of the test. The evolution in frictional

response of pure HDPE and HDPE-10 wt% QC pellets,

measured using 4.9 N load, 100 lm stroke and 5 Hz fre-

quency with Al2O3 as counterbody, is shown in Fig. 5a.

Both the materials have qualitatively similar frictional

response in a sense that the COF reaches a peak value of

0.16 during the running-in period (first 1,000 cycle) and

thereafter, drops to steady state value. The steady state

COF of QC composites is comparable with that of pure

HDPE. It is clear that the COF of the decagonal QC

composite is slightly (0.15) higher than that of pure HDPE

pellets tested under identical conditions. It is reported in

the literature that the Al–Ni–Co decagonal QC has higher

COF (0.2) [12, 13] than pure HDPE (0.1) [11]. The addi-

tion of QC, in the present case, therefore does not lead to

substantial change of COF of the composite as compared to

pure HDPE. COF measured for all the composites, as listed

Fig. 4 Hardness of the pellets is plotted as a function of QC content

of the composites

Fig. 5 a Coefficient of friction versus no of cycles plot for HDPE-

20 wt% QC composite, b wear volume versus wt% QC


123

in Table 3, shows similar trend. This is one of the advan-

tages of addition of harder QC particles in HDPE as

compared to other metallic or ceramic fillers [1]. Figure 5b

shows the wear volume measured with the HDPE-based

pellets. The wear volume of the pellets has been calculated

using 3-dimensional wear scars profiles obtained from LSP

measurements. The results clearly indicate that wear vol-

ume of the composites is at least one order of magnitude

lower than that of pure HDPE samples. The wear volume

decreases as the wt% QC phase increases in the composite.

At least four times less wear volume is measured with

HDPE-20 wt% QC composite as compared to unfilled

HDPE. This clearly shows the efficacy of the addition of

harder QC particles for enhancement of wear resistance.

To understand the wear mechanism, the wear tracks are

closely observed in SEM. Figure 6 shows the BSE SEM

micrographs of the wear tracks of pure HDPE as well as

composite. The insets of figures depict the higher magni-

fication micrographs. The wear damage region on each

sample has been marked on the figure. Figure 6a shows the

wear track of unfilled HDPE with inset showing higher

magnification micrograph. The track contains wavy areas

of polymer with waves normal to the sliding direction. It

also indicates that pure HDPE surface has undergone sig-

nificant viscoelastic deformation. The track is relatively

deeper and presence of abrasive grooves can be seen on the

wear signifying the occurrence of abrasive wear.

The wear tracks on three composite pellets are shown in

Fig. 6b–d. Al–Co–Ni particles appear brighter in the SEM

micrographs as compared to the surrounding carbon-based

matrix due to atomic number contrast. The Al–Co–Ni

particles appear to be worn down leaving a flat smooth

exposed surface. The brighter contrast in the wear scar as

compared to the unworn surrounding area suggests that

some of the Al–Co–Ni has been embedded in the wear

track. Morphologically, these areas look very smooth in

Fig. 6b. The wear tracks of the composites also reveal that

the QC particles are broken (inset of Fig. 6b, c) down into

smaller pieces, which are embedded in the surrounding

matrix. Therefore, QC particles, being harder, bear the

fretting load during the wear test. In the process of wear,

QC particles fractures (due to brittleness) and produces

smaller particles. This is a typical characteristic of all worn

tracks of the composite samples.

The elemental mapping of the wear tracks has been

carried out in SEM with energy dispersive X-ray spec-

troscopy (EDS) analysis to know the origin of the atomic

number contrast of the worn tracks. The SEM micrograph

Table 3 Coefficient of friction

of the composites and HDPE

pellets

Wt% of QC

in HDPE

COF

0 0.15

5 0.15

10 0.16

15 0.17

20 0.16

Fig. 6 Wear tracks: a neat HDPE, b HDPE-10 wt% QC and

c HDPE-20 wt% composites. The wear track diameter is indicated

on the figure. The inset in figure shows higher magnification

micrograph revealing the detailed wear behavior


123

on Fig. 7a reveals the QC particle has been worn during

wear test. The X-ray map of this area (marked by pink box)

clearly shows the presence of aluminum (Fig. 7b), cobalt

(Fig. 7b), nickel (Fig. 7c) and oxygen (Fig. 7d) as well as

carbon (not shown here). Therefore, during wear test, the

QC particles appear to be broken down into very small

particles that are embedded in the polymer matrix to pro-

duce a smooth, metal-oxide rich wear track. It has been

reported that Al-based QC particles are always covered

with an aluminum oxide shell [9]. During fretting wear this

oxide layer is continuously broken, making the virgin QC

surface in contact with atmosphere and further oxidized.

This is clearly observed in case of HDPE- 20 wt% QC

composite surface (inset of Fig. 6c). The wear debris par-

ticles adjacent to the wear track of the composite samples

are collected and investigated in SEM. The wear debris

particles have been found to contain small fragmented

particles, which appears similar in composition to the worn

areas as composite pellet. EDS analysis as well as com-

positional mapping (not shown here) show the presence of

ubiquitous Al, Co, Ni and O throughout the debris. Thus,

the oxide particles form on the virgin surface of the QC

particles and get fragmented during fretting wear. It is to be

noted here that no debris has been found during wear test of

HDPE pellet.

As expected, no observable wear damage could be

recorded on worn Al2O3 ball surface after testing with all

the investigated materials. Figure 8a, b show low and high

magnification micrographs of the surface of the ball,

illustrating almost no sign of wear.

The excellent wear resistance of HDPE-QC composites

in combination with low counter-body abrasion can be

attributed to the unique properties of Al–Co–Ni QC; low

surface energy [7], low COF [5] and high hardness [6]. In

addition, the presence of hard particulate fillers in the

polymer is known to increase the shear strength and thus

wear resistance of the polymer composite [13, 14]. The low

COF of the QC originates from reduced electronic inter-

actions, whereas higher electronic interactions in materials

like steels contributes to sticking effect, which increases

Fig. 7 SEM image and

elemental mapping of

aluminum, cobalt, nickel and

oxygen in the wear track of

HDPE-10 wt% QC composite


123

friction. It is to be noted that the presence of newly formed

smooth metal-oxide layer at the worn surface may also

contribute to enhancement of wear resistance. The wear

resistance of the composite increases as the wt% of QC

increases from 5 to 20. This is due to the increase of the

volume of hard QC particles. Moreover, the uniform dis-

tribution of the QC particles also leads to wear resistance.

The wear resistance improves with the increase in hardness

of the material. This is typically observed in case of

abrasive and adhesive wear of metallic materials, which is

primarily worn by extensive plastic deformation. The

present experimental results however indicate that an

increase in hardness also leads to improvement in wear

resistance in case of materials undergoing viscoelastic

deformation.

4 Concluding Remarks

The following conclusions can be drawn from the present

study:

(i) HDPE-decagonal QC composite can be obtained with

near theoretical density by compression moulding at

130�C for 1 h at 735 kPa pressure. Longer curing time

leads to a decrease in density.

(ii) The QC addition (up to 20 wt%) leads to consider-

able improvement in hardness with 120 MPa Vickers

hardness being measured with HDPE-20 wt% QC

composite.

(iii) The wear resistance of the newly developed com-

posites is superior to the pure HDPE without

compromising on frictional properties. The frictional

response as well as steady state COF of the

composite remains almost similar to that of pure

HDPE.

(iv) The high wear resistance can be attributed to high

hardness and uniform distribution of QC phase.

References

1. Zebarjad S M, Sajjadi S A, Tahani M, and Lazzeri A, J AchievMater Manuf Eng 17 (2006) 173.

2. Bloom P D, Baikerikar K G, Otaigbe J U, and Sheares V V,

Mater Sci Eng A 294–296 (2000) 156.

3. Bloom P D, Baikerikar K G, Anderegg J W, and Sheares V V,

Mater Sci Eng A 360 (2003) 46.

4. Shechtman D, Blech I, Gratias D and Cahn J W, Phy Rev Lett 53(1984) 1951.

5. Dubois J M, Kang S S and Perrot A, Mater Sci Eng A 179/180(1994) 122.

6. Koster U, Liu W, Liebertz H and Michel M, J Non-Cryst Solids153/154 (1993) 446.

7. Jenks C J and Thiel P, MRS Bull 22 (1997) 55.

8. Tsai A P, Acc Chem Res 36 (2003) 31.

9. Tsai A P, Phil Mag Lett 74 (1996) 233.

10. Anderson B C, Bloom P D, Baikerikar K G, Sheares V V and

Mallapragada S K, Biomaterials 23 (2002) 1761.

11. Hutchings I M, Tribology: Friction and wear of engineering

materials, Edward Arnold, London (1992), p 261

12. Schurack F, Eckert J and Schultz L, Phil Mag 83 (2003) 807.

13. Bandyopadhyay P P and Siegmann S, Surf Coat Technol 197(2005) 1.

14. Woishnis W, Polypropylene, PDI publisher, New York (1998),

p 68

Fig. 8 SEM image of surface of Al2O3 ball (used as counterbody):

a low magnification and b high magnification micrograph


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Documents

HDPE-Quasicrystal Composite: Fabrication and Wear Resistance