| Alumina, Al2O3, is available from Ceramaret with a purity of up to 99.9%. It is a polycrystalline material with a grain size of 1 to 5 microns, an average density of 3.95 g/cm³ and a hardness of about 2000 Vickers. %20-%20Physical,%20Mechanical,%20Thermal,%20Electrical%20and%20Chemical%20Properties%20-%20Supplier%20Dat_files/image004.jpg)
Physical Properties | | | Atomic composition | >99% | | Crystalline structure | Corundum | | Grain size (microns) | 1-5 | | Density (g/cm3) | 3.95 | | Water absorption (%) | 0 | Mechanical Properties at 20°C | | | Vickers hardness (Hv 500g) | 1800-2000 | | Tensile strength (N/mm2) | 200-250 | | Bending strength (N/mm2) | 200-600 | | Compressive strength (N/mm2) | 1900-2000 | | Young’s modulus (N/mm2) | 3.8x105 | | Poisson’s ratio | 0.25-0.30 | | Fracture toughness KIC -½ (MPa.m) | 4-5 | Thermal Properties | | | Dilation co-efficient (20-2000°C) (°C-1) | 8.4x10-6 | | Specific heat 100°C (J/kg.K) | 930 | | Thermal conductivity at 20°C (W/m.K) | 40 | | Thermal shock resistance (°C) | 200 | Electrical Properties | | | Resistivity at 20°C (ohm.cm) | >1014 | | Dielectric constant at 20°C and 1GHz | 9.5 | | Dielectric rigidity at 50Hz (KV/mm) | 30 | Chemical Properties | | | HCl | 35% | Boiling | 30 min | A | | HNO3 | 70% | Boiling | 30 min | A | | H2SO4 | 98% | Boiling | 30 min | A | | H3PO4 | 90% | Boiling | 30 min | B | | HF | 60% | 20 | 24 hr | C | | KOH solution | 10% | 80 | 7 day | A | | KOH boiling | | 500 | 24 hr | C | | NaOH boiling | | 500 | 24 hr | B | | Na2CO3 boiling | | 900 | 24 hr | B | | Na2SO4 boiling | | 1000 | 24 hr | A | | KF boiling | | 90 | 4 hr | D | A: no corrosion observed B: slightly corroded C: middle degree of corrosion D: heavily corroded Note: The values quoted are typical. Ceramic property values can vary with the method of manufacture. |