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