Upload
gladys-williams
View
215
Download
0
Tags:
Embed Size (px)
Citation preview
38th ICACC Daytona Beach Conference 26th - 31st January, 2014
Assessing the Carbon Concentration in Boron Carbide: A Combined X-Ray Diffraction and
Chemical AnalysisKanak Kuwelkar, Vladislav Domnich, Richard Haber
Unit Name
Current understanding of the variations in the boron carbide stoichiometry based on literature.
Determination of the various phases present in commercial boron carbide and quantification based on Rietveld refinement.
Investigation of the variation in the carbon concentration of commercial/standard and RU produced dense boron rich boron carbide based on the lattice parameters.
Developing an improved methodology for the determination of the free carbon content by X-ray diffraction.
Chemical characterization of selected commercial/standard and RU powders. Stoichiometric variations in commercial boron carbide samples based on chemical analysis and X-ray diffraction.
OUTLINE
Unit Name
BORON CARBIDE: CRYSTAL STRUCTURE
Rhombohedral symmetry with single phase carbon has a solubility varying from ~8 at% to ~20 at%. The unit cell consists of B11C icosahedra and C-B-C intericosahedral chains for 20 at% carbon.
Variations in the carbon concentrations have been estimated to B4.3C, B3.6C and B4.0 on the carbon rich side.
Schwetz proposed the limit of the B:C ratio to be B4.3C on the carbon rich side based on combined chemical analysis and EPMA.
• Seminar on boron carbide, 23.01.2003.,Schwetz.K ,• Schewtz.K., J. Less-Common Met.,1991.175: p. 1-11 ,• Conde, O.,et al, Surface and Coatings Technology, 2000. 125(1): p. 141-146. ,• Domnich, V., et al.,JECerS., 2011. 94(11): p. 3605-3628.
18.8
Unit Name
Phase Identification of SG-010813 (Superior Graphite) and quantitative analysis by Rietveld Refinement
B4C-97.5% Graphite-2.5%
Boron Carbide
Graphite
PHASE IDENTIFICATION OF COMMERCIAL SAMPLES In
tens
ity (
Cou
nts)
Two-theta(deg)
Unit Name
0
Inte
nsity
(C
ount
s)
Two-theta(deg)
Boron Carbide
Graphite
Aluminum Nitride
Boron Nitride
Phase Identification of Pad-Tile 8(Coorstek) and quantitative analysis by Rietveld Refinement
B4C-96.9%Graphite-0.3%Aluminum Nitride-0.4%Boron Nitride-0.3%
Unit Name
Superior Graphite sampleESK sampleCeradyne sample
% Carbon Concentration
a la
ttic
e pa
ram
eter
(Å
)
• Aselage, T.L. and R.G. Tissot, . J. Am. Ceram. Soc., 1992. 75(8): p. 2207-2212.
c la
ttic
e pa
ram
eter
(Å
)
% Carbon Concentration
VARIATION IN LATTICE PARAMETERS OF COMMERCIAL SAMPLES
Superior Graphite sampleESK sampleCeradyne sample
Unit Name
X-RAY DIFFRACTION PATTERNS OF DENSE BORON RICH SAMPLESIn
tens
ity (
Cou
nts)
Two-theta(deg)
Two-theta(deg) Two-theta(deg)
Inte
nsity
(C
ount
s)
Inte
nsity
(C
ount
s)
25% Excess Boron
10% Excess Boron
1% Excess Boron
5% Excess Boron
25% Excess Boron
10% Excess Boron
1% Excess Boron
5% Excess Boron
25% Excess Boron
10% Excess Boron
1% Excess Boron
5% Excess Boron
No Free CarbonPeak
MAJOR BORON CARBIDE PEAKS
35% Excess Boron
35% Excess Boron35% Excess Boron
Peak Shift
Unit Name
VARIATION IN LATTICE PARAMETERS OF DENSE BORON RICH SAMPLES
1% Excess Boron5% Excess Boron10% Excess Boron25% Excess Boron35% Excess Boron
1% Excess Boron5% Excess Boron10% Excess Boron25% Excess Boron35% Excess Borona
latt
ice
para
met
er (
Å)
c la
ttic
e pa
ram
eter
(Å
)
% Carbon Concentration % Carbon Concentration
•Aselage, T.L. and R.G. Tissot, . J. Am. Ceram. Soc., 1992. 75(8): p. 2207-2212.
Unit Name
OVIERVIEW OF THE CURRENT CHARACTERIZATION TECHNIQUES USED
FREE CARBON : Spiking technique or Rietveld refinement
TOTAL CARBON : Combustion of total carbon followed by detection of carbon by infrared detection (CS 230)
TOTAL OXYGEN : Combustion of total oxygen followed by detection of oxygen by infrared detection (TC 600)
TOTAL NITROGEN : Combustion of total nitrogen followed by detection of nitrogen by thermal conductivity detection (TC 600)
TOTAL BORON : Boric acid titration after dissolution of boron carbide in molten sodium carbonate
Unit Name
METHODS FOR THE DETERMINATION OF THE FREE CARBON CONTENT
Combustion methods can be used but the boron carbide will oxidize at the same rate as the carbon and the formed oxide will seal some of the free carbon.
In the wet chemical oxidation method, the rate of oxidation of free carbon and carbon in boron carbide will be too similar to differentiate for superfine boron carbide powders.
The spiking or the addition technique is used to determine the amount of free carbon where the free carbon is less than 5% by weight.
• Beauvy, M. et al, J. Less-Common Met., 1981. 80(2): p. 227-233.• Schwetz, K. et al, J. Less-Common Met., 1986. 117(1–2): p. 7-15.• Alizadeh, A.et al, J European Cer Soc, 2004. 24(10): p. 3227-3234.
Unit Name
• Beauvy, M. et al, J. Less-Common Met., 1981. 80(2): p. 227-233.
FREE CARBON CONTENT BY THE SPIKING TECHNIQUE (M.BEAUVY & R.ANGERS)
Spiking technique involves determining the free carbon content less than 10% from the ratio of the intensities of the carbon and boron carbide peaks.
Linear relationship exists between free carbon and boron carbide peak.
This technique can be used only if the carbon is completely crystallized as graphite.
Powder A Powder A (after grinding)
Unit Name
Experimental PatternDerived Pattern
Carbon Peak
Boron Carbide Peak
MODELLING THE ASSYMETRY OF THE CARBON PEAK
Two-Theta (deg)
Inte
nsity
(C
ount
s)
Two-Theta (deg)
3) Graphitic Peak
2) Disordered Carbon Peak
1) Amorphous Peak
Experimental PatternDerived Pattern
Inte
nsity
(C
ount
s)
CARBON PEAK
ST-HD20 (H.C.STARCK) SAMPLE WITH 0.5%
ADDED CARBON
Unit Name
3) Graphitic Peak
2) Disordered Carbon Peak
1) Amorphous Peak
Experimental PatternDerived Pattern
Inte
nsity
(C
ount
s)
Two-Theta (deg)
Carbon Peak
Experimental PatternDerived Pattern
Inte
nsity
(C
ount
s)
Two-Theta (deg)
ATD-2012-6-41 CERADYNE INC. SAMPLE WITH 0.5%
ADDED CARBON
CARBON PEAK
Boron Carbide Peak
Kα2 Peak
Unit Name
VARIATION IN THE FREE CARBON BASED ON BACKGROUND SUBTRACTED1) Cubic Spline
2) Linear
Bo
ron
Ca
rbid
e P
eak
Car
bo
n P
eak
Bo
ron
Ca
rbid
e P
eak
IC/IB4C = 0.17
IC/IB4C = 0.15
Car
bo
n P
eak
Background 1
Background 2IC/IB4C = 0.20
Unit Name
FREE CARBON CONTENT
ATD-2012-6-41 (CERADYNE INC.)
SAMPLE
ST-HD20 (H.C.STARCK)
SAMPLE
ST-HD20
ATD-2012-6-41
Free Carbon = 0.96%
Free Carbon = 2.78%
Unit Name
European Reference Material ERM® - ED102 Boron Carbide Powder
Characterized at Rutgers University - ED102 Boron Carbide Powder
Unit Name
CHEMICAL ANALYSIS OF COMMERCIAL BORON CARBIDE SAMPLES
http://www.cesaroni.com/industries/medical/Leco_Corporation_TC600- 500_Nitrogen_Oxygen_Determinator.php
http://www.leco.com/products/analytical-sciences/carbon-sulfur-analyzers/230-series
Oxygen/Nitrogen Analyser (TC600) Carbon/SulphurAnalyser (CS230)
Unit Name
Chemical Analysis (LECO) Total Oxygen Total Nitrogen
X-Ray Diffraction (Spiking Technique) Free Carbon
Boron Titration Total Boron
DETERMINATION OF THE STOICHIOMETRY
Total Boron = Boron in Boron Carbide + Boron in Boron Nitride + Boron in Boron Oxide
Total Carbon = Carbon in Boron Carbide + Free Carbon
Stoichiometry of Boron Carbide = Moles of Boron in Boron carbide Moles of Carbon in Boron carbide
Chemical Analysis (LECO) Total Carbon
Step 1 Step 2
Step 3 Step 4
Unit Name
VARIATION IN THE STOICHIOMETRY OF COMMERCIAL SAMPLES
Unit Name
CONCLUSIONS AND FUTURE WORK
Improvement of the correlation of the bound carbon concentrations to the lattice parameters.
Improvement and establishment of a standardized procedure for the characterization of boron carbide.
Development of a novel technique for the determination of the free carbon. Validation of the stoichiometry of the commercial/RU produced boron carbide samples with the aid of electron microprobe analysis.
The goal is to establish the preferred composition and purity of boron carbide for extreme environments and to develop a standardized procedure to analyze boron carbide samples.
Unit Name
Acknowledgements
Thank You
Ceramic, Composite, and Optical Materials Center