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38 th ICACC Daytona Beach Conference 26 th - 31 st January, 2014

Assessing the Carbon Concentration in Boron Carbide: A Combined X-Ray Diffraction and Chemical Analysis. Kanak Kuwelkar, Vladislav Domnich, Richard Haber. 38 th ICACC Daytona Beach Conference 26 th - 31 st January, 2014. OUTLINE.

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38 th ICACC Daytona Beach Conference 26 th - 31 st January, 2014

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  1. Assessing the Carbon Concentration in Boron Carbide: A Combined X-Ray Diffraction and Chemical Analysis Kanak Kuwelkar, Vladislav Domnich, Richard Haber 38th ICACC Daytona Beach Conference 26th - 31st January, 2014

  2. OUTLINE • 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.

  3. 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. 18.8 • 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.

  4. PHASE IDENTIFICATION OF COMMERCIAL SAMPLES Phase Identification of SG-010813 (Superior Graphite) and quantitative analysis by Rietveld Refinement B4C-97.5% Graphite-2.5% Intensity (Counts) Boron Carbide Graphite Two-theta(deg)

  5. 0 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% Intensity (Counts) Boron Carbide Graphite Aluminum Nitride Boron Nitride Two-theta(deg)

  6. VARIATION IN LATTICE PARAMETERS OF COMMERCIAL SAMPLES c lattice parameter (Å) a lattice parameter (Å) Superior Graphite sample ESK sample Ceradyne sample Superior Graphite sample ESK sample Ceradyne sample % Carbon Concentration % Carbon Concentration • Aselage, T.L. and R.G. Tissot, . J. Am. Ceram. Soc., 1992. 75(8): p. 2207-2212.

  7. X-RAY DIFFRACTION PATTERNS OF DENSE BORON RICH SAMPLES 35% Excess Boron Intensity (Counts) 25% Excess Boron 10% Excess Boron 5% Excess Boron 1% Excess Boron Two-theta(deg) MAJOR BORON CARBIDE PEAKS No Free Carbon Peak 35% Excess Boron 35% Excess Boron 25% Excess Boron 25% Excess Boron 10% Excess Boron Intensity (Counts) 10% Excess Boron Intensity (Counts) 5% Excess Boron 5% Excess Boron 1% Excess Boron 1% Excess Boron Peak Shift Two-theta(deg) Two-theta(deg)

  8. VARIATION IN LATTICE PARAMETERS OF DENSE BORON RICH SAMPLES a lattice parameter (Å) c lattice parameter (Å) 1% Excess Boron 5% Excess Boron 10% Excess Boron 25% Excess Boron 35% Excess Boron 1% Excess Boron 5% Excess Boron 10% Excess Boron 25% Excess Boron 35% Excess Boron % Carbon Concentration % Carbon Concentration • Aselage, T.L. and R.G. Tissot, . J. Am. Ceram. Soc., 1992. 75(8): p. 2207-2212.

  9. 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

  10. 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 techniqueis 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.

  11. FREE CARBON CONTENT BY THE SPIKING TECHNIQUE (M.BEAUVY & R.ANGERS) Powder A Powder A (after grinding) • 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. • Beauvy, M. et al, J. Less-Common Met., 1981. 80(2): p. 227-233.

  12. MODELLING THE ASSYMETRY OF THE CARBON PEAK ST-HD20 (H.C.STARCK) SAMPLE WITH 0.5% ADDED CARBON Experimental Pattern Derived Pattern Boron Carbide Peak Intensity (Counts) Carbon Peak Two-Theta (deg) CARBON PEAK Experimental Pattern Derived Pattern 3) Graphitic Peak 2) Disordered Carbon Peak Intensity (Counts) 1) Amorphous Peak Two-Theta (deg)

  13. MODELLING THE ASSYMETRY OF THE CARBON PEAK ATD-2012-6-41 CERADYNE INC. SAMPLE WITH 0.5% ADDED CARBON Experimental Pattern Derived Pattern Boron Carbide Peak Intensity (Counts) Carbon Peak Two-Theta (deg) CARBON PEAK Experimental Pattern Derived Pattern 3) Graphitic Peak 2) Disordered Carbon Peak Intensity (Counts) 1) Amorphous Peak Kα2 Peak Two-Theta (deg)

  14. VARIATION IN THE FREE CARBON BASED ON BACKGROUND SUBTRACTED 1) Cubic Spline Carbon Peak Boron Carbide Peak Background 1 IC/IB4C = 0.17 IC/IB4C = 0.20 Background 2 2) Linear Carbon Peak Boron Carbide Peak IC/IB4C = 0.15

  15. FREE CARBON CONTENT ST-HD20 ST-HD20 (H.C.STARCK) SAMPLE Free Carbon = 0.96% ATD-2012-6-41 (CERADYNE INC.) SAMPLE ATD-2012-6-41 Free Carbon = 2.78%

  16. CHEMICAL ANALYSIS OF COMMERCIAL BORON CARBIDE SAMPLES Oxygen/Nitrogen Analyser (TC600) Carbon/SulphurAnalyser (CS230) 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

  17. DETERMINATION OF THE STOICHIOMETRY Step 1 Step 2 Chemical Analysis(LECO) Total Oxygen Total Nitrogen Boron Titration Total Boron Total Boron = Boron in Boron Carbide + Boron in Boron Nitride + Boron in Boron Oxide Total Carbon = Carbon in Boron Carbide + Free Carbon Step 3 Step 4 X-Ray Diffraction (Spiking Technique) Free Carbon Chemical Analysis(LECO) Total Carbon Stoichiometry of Boron Carbide = Moles of Boron in Boron carbide Moles of Carbon in Boron carbide

  18. VARIATION IN THE STOICHIOMETRY OF COMMERCIAL SAMPLES

  19. 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.

  20. Acknowledgements Thank You Ceramic, Composite, and Optical Materials Center

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