Diamond vs Silicon carbide
Diamond and Silicon carbide are genuine alternatives to one another — a choice somebody actually makes — and differ on 3 measured properties, crystal system most clearly.
Diamond vs Silicon carbide
These are different kinds of thing (mineral, compound). Fewer properties mean the same thing across both, so a like-for-like reading may not be available.
Diamond
C
Carbon in a cubic lattice — the hardest naturally occurring substance, and one of the best thermal conductors known.
Silicon carbide
SiC
A synthetic ceramic close to diamond in hardness, and the first commercially successful manufactured abrasive.
| Property | Diamond | Silicon carbide |
|---|---|---|
| Crystal system Categorical values can be listed side by side but not ordered or subtracted. | cubic | hexagonal |
| Density | 3.5–3.53 g/cm³ higher | 3.21 g/cm³ |
| Lustre Only one of the two has a figure we can stand behind, so there is nothing to compare. | adamantine | Not known |
| Mohs hardness Mohs hardness is an ordinal scale: values can be ranked, but differences and ratios between them are not meaningful. | 10 higher | 9–9.5 |
| Molar mass Only one of the two has a figure we can stand behind, so there is nothing to compare. | Not known | 40.1 g/mol |
| Refractive index Only one of the two has a figure we can stand behind, so there is nothing to compare. | 2.417 | Not known |
| Thermal conductivity Only one of the two has a figure we can stand behind, so there is nothing to compare. | 900–2320 W/(m·K) | Not known |
Choosing between them
Diamond is recorded as a substitute for Silicon carbide — stronger.
What it gives up: Costs far more, and it reacts with iron at cutting temperature so it cannot machine steel.
In this application, on the evidence cited above.