NIST Structural Ceramics Database(SCD) Database - NIST Ceramics Data Portal

NIST Structural Ceramics Database (SCD) Database

NIST Standard Reference Database 30

Last Update to Data Content: 2002

DOI: http://dx.doi.org/10.18434/T4F30D

SCD Citation Number: Z00501

Bibliographic Information

Reference:

"Material Properties of a Sintered α-SiC," R.G. Munro, Journal of Physical and Chemical Reference Data, Vol. 26 [5], pp. 1195-1203 (1997), published by American Chemical Society.

Language: English

General Materials Processing Notes

"Sintered α-SiC ceramics typically are produced using submicrometer powders that have been extracted from an Acheson furnace and ground to a fine particle size. Boron and carbon are used as sintering aids to achieve improved densification during sintering which is typically conducted at a temperature on the order of 2500 °C. The resulting microstructure consists predominantly of fine, equiaxed grains of the hexagonal SiC polytype 6H. A small amount of free carbon and isolated B₄C grains may be present also as remnant artifacts of the sintering aids. ... the density is approximately (98 ± 1)% of the density of single crystal SiC(6H) with a mean grain size of (6 ± 2) µm. The mass fractions of boron and free carbon in the sintered composition are (0.4 ± 0.1)% and (0.5 ± 0.1)%, respecitively."

Measurement Methods

Analysis

"A self-consistent, single-valued representation of the major physical, mechanical, and thermal properties of a sintered α-SiC is presented. This comprehensive set of properties is achieved by focusing on a narrowly defined material specification... Percentages in parentheses are estimated relative combined standard uncertainties, i.e., the quantity 3.0(5%) is equivalent to 3.0 ± 0.15. Property values in parentheses are extrapolated values."

Index of Materials and Properties

Material Number 1: SiC

Material Specification and Properties for SiC

Material number 1 of 1
in SCD Citation Number: Z00501
Chemical Class: Carbide
Chemical Family: Si-C
Formula: SiC
Informal Name: silicon carbide
Structure Type: Polycrystalline
Manufacturer: Typical
Process: Sintering

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Bulk Modulus
Temperature ( °C )	Bulk Modulus ( GPa )
20	203 (3%)
500	197
1000	191
1200	188
1400	186
1500	184

Measurement Method: Analysis
Evaluation Status: Validated by models

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Creep Activation Energy
Temperature Range ( °C )	Creep Activatn Energy ( kJ mol^-1 )
≤ 1600	442
> 1600	944

Measurement Method: Analysis
Evaluation Status: Validated by models
Cautions:

"... when the results... are examined in an Arrhenius type plot... there is clear distinction between the results from above and below 1600 °C, suggesting a significant change in the creep mechanism at that temperature."

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Creep Rate
Temperature ( °C )	Creep Rate ( 10^-9 s^-1 )
20	0
500	0
1000	0
1200	0.004
1400	0.27
1500	1.6

Measurement Method: Analysis
Evaluation Status: Validated by models
Cautions:

"The steady state creep rate... is... of the form dε/dt = A σⁿ exp(-E_act/RT), where the independent variables are stress, σ, and the absolute temperature, T; R = 8.3145 J/(mol K); and A, n, and E_act are parameters... n is called the creep stress exponent, and E_act is the creep activation energy. ... A = 7.35 s^-1 MPa^-1.36, n = 1.36, E_act = 442 kJ/mol for T ≤ 1600 °C; and A = 4.5 x 10¹⁴ s^-1 MPa^-1.32, n = 1.32, E_act = 944 kJ/mol for T > 1600 °C. These parameters yield an estimate combined standard uncertainty of 17% for the creep rate."

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Creep Rate Exponent
Temperature Range ( °C )	Creep Rate Exponent ( no unit )
≤ 1600	1.36
> 1600	1.32

Measurement Method: Analysis
Evaluation Status: Validated by models
Cautions:

"... when the results... are examined in an Arrhenius type plot... there is clear distinction between the results from above and below 1600 °C, suggesting a significant change in the creep mechanism at that temperature."

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Crystal Cell Axes
Axis	Temperature ( °C )	Axis Length ( Å )
a	20	3.0815 (0.01%)
a	500	3.0874
a	1000	3.0950
a	1200	(3.0984)
a	1400	(3.1021)
a	1500	(3.1040)
c	20	15.117 (0.02%)
c	500	15.144
c	1000	15.179
c	1200	(15.194)
c	1400	(15.210)
c	1500	(15.218)

Measurement Method: Analysis
Evaluation Status: Validated by models
Cautions:

Extrapolated values for T > 1000 °C are shown in parentheses.

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Density (mass)
Temperature ( °C )	Density ( g cm^-3 )
20	3.16 (1%)
500	3.14
1000	3.11
1200	3.10
1400	3.09
1500	3.08

Measurement Method: Analysis
Evaluation Status: Validated by models

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Elastic Modulus
Temperature ( °C )	Elastic Modulus ( GPa )
20	415 (3%)
500	404
1000	392
1200	387
1400	383
1500	380

Measurement Method: Analysis
Evaluation Status: Validated by models

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Flexural Strength
Temperature ( °C )	Flexural Strength ( MPa )
20	359 (15%)
500	359
1000	397
1200	437
1400	446
1500	446

Measurement Method: Analysis
Evaluation Status: Validated by models
Cautions:

"Sintered α-SiC exhibits the somewhat unusual behavior of increasing flexural strength with increasing temperature... when tests are conducted in an air environment. This phenomenon is generally attributed to short-term crack healing as a result of the formation of an oxide, SiO₂, on the surface of the silicon carbide specimen. For other environments and long-term exposures, the strength may be expected to diminish."

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Fracture Toughness
Temperature ( °C )	Fracture Toughness ( MPa m^1/2 )
20	3.1 (10%)
500	3.1
1000	3.1
1200	3.1
1400	3.1
1500	3.1

Measurement Method: Analysis
Evaluation Status: Validated by models
Cautions:

"The fracture toughness... results vary considerably among the distinct methods, but several independent studies have concluded that sharp crack techniques provide the more reliable results. ... results... from the surface crack in flexure (SCF) method. ... also known as the controlled surface flaw or controlled microflaw method. ... are shown."

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Friction Coefficient
Temperature ( °C )	Friction Coefficient ( no unit )
20	0.7 (21%)
500	0.4
1000	0.4

Measurement Method: Analysis
Evaluation Status: Validated by models
Cautions:

"Laboratory results for friction and wear, therefore, may depend significantly on both the design of the measurement apparatus and the specific procedure that is applied to the measurement. ... Results... under dry sliding conditions, involving four different sources of the test materials, are shown..." The results assume a sliding speed of 0.2 m/s under a load of 5 N.

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Hardness
Temperature ( °C )	Hardness ( GPa )
20	32 (15%)
500	17
1000	8.9
1200	(6.9)
1400	(5.3)
1500	(4.6)

Measurement Method: Analysis
Evaluation Status: Validated by models
Cautions:

Vickers indentation, 1 kg load. Extrapolated values for T > 1000 °C are shown in parentheses.

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Poisson's Ratio
Temperature ( °C )	Poisson's Ratio ( no unit )
20	0.16 (25%)
500	0.159
1000	0.157
1200	0.157
1400	0.156
1500	0.156

Measurement Method: Analysis
Evaluation Status: Validated by models

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Shear Modulus
Temperature ( °C )	Shear Modulus ( GPa )
20	179 (3%)
500	174
1000	169
1200	167
1400	166
1500	165

Measurement Method: Analysis
Evaluation Status: Validated by models

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Sound Velocity
Mode	Temperature ( °C )	Sound Velocity ( km/s )
Longitudinal	20	11.82 (2%)
Longitudinal	500	11.69
Longitudinal	1000	11.57
Longitudinal	1200	11.52
Longitudinal	1400	11.47
Longitudinal	1500	11.44
Shear	20	7.52 (2%)
Shear	500	7.45
Shear	1000	7.38
Shear	1200	7.35
Shear	1400	7.32
Shear	1500	7.31

Measurement Method: Analysis
Evaluation Status: Validated by models

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Specific Heat
Temperature ( °C )	Specific Heat ( J kg^-1 K^-1 )
20	715 (5%)
500	1086
1000	1240
1200	1282
1400	1318
1500	1336

Measurement Method: Analysis
Evaluation Status: Validated by models

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Tensile Strength
Temperature ( °C )	Tensile Strength ( MPa )
20	250 (6%)
500	250
1000	250
1200	250
1400	250
1500	250

Measurement Method: Analysis
Evaluation Status: Validated by models

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Thermal Conductivity
Temperature ( °C )	Thermal Conductivity ( W m^-1 K^-1 )
20	114 (8%)
500	55.1
1000	35.7
1200	31.3
1400	27.8
1500	26.3

Measurement Method: Analysis
Evaluation Status: Validated by models

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Thermal Diffusivity
Temperature ( °C )	Thermal Diffusivity ( cm² s^-1 )
20	0.50 (12%)
500	0.16
1000	0.092
1200	0.079
1400	0.068
1500	0.064

Measurement Method: Analysis
Evaluation Status: Validated by models

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Thermal Expansion
Temperature ( °C )	Thermal Expansion ( 10^-6 K^-1 )
20	1.1 (10%)
500	4.4
1000	5.0
1200	5.2
1400	5.4
1500	5.5

Measurement Method: Analysis
Evaluation Status: Validated by models
Cautions:

Cumulative expansion from 0 °C.

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Wear Coefficient Log
Temperature ( °C )	Log Wear Coefficient ( no unit )
20	-4.0 (5%)
500	-3.6
1000	-3.6

Measurement Method: Analysis
Evaluation Status: Validated by models
Cautions:

"Laboratory results for friction and wear, therefore, may depend significantly on both the design of the measurement apparatus and the specific procedure that is applied to the measurement. ... Results... under dry sliding conditions, involving four different sources of the test materials, are shown..." The results assume a sliding speed of 0.2 m/s under a load of 5 N.

SiC

Material number 1 of 1
in SCD Citation Number: Z00501

Weibull Modulus
Temperature ( °C )	Weibull Modulus ( no unit )
20	11 (27%)
500	11
1000	11
1200	11
1400	11
1500	11

Measurement Method: Analysis
Evaluation Status: Validated by models