1. 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

2. 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

3. 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 B 11 C icosahedra and C-B-C intericosahedral chains for 20 at% carbon.  Variations in the carbon concentrations have been estimated to B 4.3 C, B 3.6 C and B 4.0 on the carbon rich side.  Schwetz proposed the limit of the B:C ratio to be B 4.3 C 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

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

5. Unit Name 0 Intensity (Counts) Two-theta(deg) Boron Carbide Graphite Aluminum Nitride Boron Nitride Phase Identification of Pad-Tile 8 (Coorstek) and quantitative analysis by Rietveld Refinement B 4 C-96.9% Graphite-0.3% Aluminum Nitride-0.4% Boron Nitride-0.3%

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

7. Unit Name X-RAY DIFFRACTION PATTERNS OF DENSE BORON RICH SAMPLES Intensity (Counts) Two-theta(deg) Intensity (Counts) 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 Carbon Peak MAJOR BORON CARBIDE PEAKS 35% Excess Boron Peak Shift

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

9. 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

10. 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.

11. 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 (after grinding)

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

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

14. Unit Name VARIATION IN THE FREE CARBON BASED ON BACKGROUND SUBTRACTED 1) Cubic Spline 2) Linear Boron Carbide Peak Carbon Peak Boron Carbide Peak I C /I B4C = 0.17 I C /I B4C = 0.15 Carbon Peak Background 1 Background 2 I C /I B4C = 0.20

15. 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%

16. Unit Name European Reference Material ERM ® - ED102 Boron Carbide Powder Characterized at Rutgers University - ED102 Boron Carbide Powder

17. 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)

18. 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

19. Unit Name VARIATION IN THE STOICHIOMETRY OF COMMERCIAL SAMPLES

20. 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.

21. Unit Name Acknowledgements Thank You Ceramic, Composite, and Optical Materials Center