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Graphite vs. Synthetic Sapphire

Graphite belongs to the non-oxide engineering ceramics classification, while synthetic sapphire belongs to the oxide-based engineering ceramics. There are 13 material properties with values for both materials. Properties with values for just one material (14, in this case) are not shown. Please note that the two materials have significantly dissimilar densities. This means that additional care is required when interpreting the data, because some material properties are based on units of mass, while others are based on units of area or volume.

For each property being compared, the top bar is graphite and the bottom bar is synthetic sapphire.

Metric UnitsUS Customary Units

Mechanical Properties

Compressive (Crushing) Strength, MPa 90
2700
Elastic (Young's, Tensile) Modulus, GPa 21
450
Flexural Strength, MPa 80
1090
Tensile Strength: Ultimate (UTS), MPa 18
2470

Thermal Properties

Maximum Temperature: Mechanical, °C 220
2000
Thermal Conductivity, W/m-K 6.0
30
Thermal Expansion, µm/m-K 4.9
5.3

Otherwise Unclassified Properties

Density, g/cm3 1.8
4.0

Common Calculations

Stiffness to Weight: Axial, points 6.7
63
Stiffness to Weight: Bending, points 53
64
Strength to Weight: Axial, points 2.9
170
Strength to Weight: Bending, points 8.7
100
Thermal Shock Resistance, points 12
74