High purity alumina products can withstand very high temperatures under reducing, inert or high vacuum conditions. They remain good chemical resistance under high temperatures, and have excellent wear and abrasion resistance. We offer alumina products with purity >99% which can withstand high temperature up to 1700°C (3092°F)
| Volume Density | g/cm3 | 3.85 |
| Rockwell Hardness | HRA | 90 |
| Flexural Strength | MPa | 350 |
| Maximum Service Temperature | °C ≥ | 1700 |
| Air-Tightness | | Qualified |
| Coefficient of Thermal Expansion (CTE) | 10-6/K | 5.3 |
| Coefficient of Linear Expansion | X10-6/°C | 8.2 |
| Dielectric Constant | Ꜫ r20°C, 1MHz | 9.2 |
| Dielectric Loss Tangent | tanδ X 10-4 | 2 |
| Volume Resistivity | Ω.cm20°C | 1015 |
| Disruptive Strength | KV/mm, DC ≥ | 20 |
| Acid Resistance | Mg/cm2 ≤ | 0.7 |
| Alkali Resistance | Mg/cm2 ≤ | 0.1 |
| Abrasion Resistance | g/cm2 ≤ | 0.1 |
| Compressive Strength | MPa ≥ | 2800 |
| Tensile Strength | MPa | 210 |
| Elasticity Modulus | GPa | 350 |
| Poisson's Ratio | | 0.22 |
| Thermal Conductivity | W/m °k (20°C) | 26.7 |
Guidelines for Using Alumina Products
- Alumina products are fragile. Please handle them carefully and avoid collisions during unpacking, transportation, handling and cleaning.
- Check whether any micro-cracks exist before using alumina products. Products with micro-cracks should not be used.
- Alumina products should be completely dry before usage. If they get wet, let the alumina products dry naturally before using them. If drying alumina products by placing them in a dryer or oven, make sure that the drying process goes slowly.
- Do not load too many materials in alumina crucibles, which can increase the possibility of uneven heating.
- Alumina products are sensitive to thermal shock. Try to warm up the furnace chamber slowly. A heating rate of 150°C/hour is recommended for the first 1-1.5 hours so that the alumina products can be evenly heated to reduce the impact of thermal shock. It usually takes about 3 hours to increase to high temperature. A temperature change rate no more than 3°C/minute is preferred. Larger alumina products are more sensitive to thermal shock.
- Lower the temperature as gradually as possible. The cooling down rate is often half of the heating rate. If possible, arrange for consecutive heating of the furnace to maintain a hot crucible. If taking the crucibles out of the furnace into room temperature to pour the melted material, try to control the process as short as possible.
- Avoid contact of heated alumina products with a cold surface. Use insulation materials as support under alumina products .
- Alumina products should not be heated by torches or furnaces that cannot control temperature change rate. The uneven heating can cause cracks.
