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Balls of
HighTech Ceramic
Ruby
Synthetic ruby and sapphire are monocrystalline aluminium oxides. Sapphire more less is pure ( 99,99% Al
2O
3), ruby’s color comes from admixture with a little chromium oxide (CrO
3). Both crystallines are hexagonal rhombohedral structured, hardness of both is ca. 2300 Vickers.
Characteristics
- inert and very resistant against aggressive media
- excellent heat conductivity (particularly at kryotemperatures)
- also excellent heat resistance and resistance against thermal shocks.
- brilliant resistance against scratching and wear
- good resistance against corrosion and abrasivity
- extreme hardness (behind diamond the most hard technical material)
- excellent electrical characteristics (high electrical resistance, high dielectric coefficient)
Technical characteristics of ruby:
chemical formula |
Al 2O3 |
structure |
exagonal rhombohedral |
molar weight |
101,94 |
mass density, g/cm³ (20 °C) |
3,98 |
dielectric coefficient at 102-108Hz at 298K
parallel
perpendicular |
|
10,55 |
8,6 |
melting point, K |
2300 |
heat conductivity, W/(m K) at 300 K
parallel
perpendicular |
|
35,1 |
33.0 |
thermal expansion, 1/K at 293 K
parallel
perpendicular |
|
5,6 x 10 -6 |
5,0 x 10-6 |
spec. thermal capacity, cal/(g K) at 298 K |
0,18 |
band gap. eV |
9,9 |
water solubility |
Keine |
Mohs hardness |
9 |
Knoop hardness, kg/mm² |
1370 |
elasticity modulus E, GPa |
335 |
shear modulusl G, GPa |
148 |
compressive modulus K, GPa at 273 K |
240 |
rupture modulusl, MPa |
350…690 |
Poisson's Ratio |
0,25 |
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