Alumina crucibles are widely used in high-temperature applications due to their excellent thermal and mechanical properties. The temperature they can withstand depends on the alumina content and the specific conditions of use. Generally, high-purity alumina crucibles (99% or higher) can withstand temperatures up to 1750°C in both oxidizing and reducing atmospheres, with short-term use reaching up to 1800°C. Lower purity alumina crucibles (e.g., 85%) are suitable for temperatures up to 1400°C for short-term use. These crucibles exhibit high thermal conductivity, low thermal expansion, and resistance to chemical reactions, making them ideal for demanding high-temperature environments.
Key Points Explained:
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Temperature Resistance Based on Alumina Content:
- High-Purity Alumina (99% or higher): Can withstand temperatures up to 1750°C in both oxidizing and reducing atmospheres. For short-term use, they can handle temperatures up to 1800°C.
- Lower Purity Alumina (e.g., 85%): Suitable for temperatures up to 1400°C for short-term use, with long-term use recommended in stable environments where temperature changes are gradual.
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Thermal Properties:
- Thermal Conductivity: Alumina crucibles have large thermal conductivity, which helps in evenly distributing heat and preventing localized overheating.
- Thermal Expansion: They exhibit low thermal expansion, which reduces the risk of cracking or deformation under rapid temperature changes.
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Chemical Resistance:
- Alumina crucibles are inert to hydrogen, carbon, and refractory metals, and do not react with air, water vapor, hydrogen, or CO even at high temperatures (up to 1700°C). This makes them suitable for a wide range of chemical environments.
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Mechanical Strength:
- Alumina crucibles have high mechanical strength, making them harder than materials like iron or graphite. This allows them to withstand higher internal pressures and mechanical stresses during high-temperature operations.
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Application Considerations:
- Short-Term vs. Long-Term Use: The maximum working temperature for short-term use is higher than for long-term use. For example, a 99% alumina crucible can be used at 1800°C for short periods but is recommended for long-term use at lower temperatures.
- Environmental Stability: Lower purity alumina crucibles are suitable for environments where temperature changes are not too rapid, ensuring long-term durability and performance.
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Material Composition:
- The high-form alumina crucible with 1000 ml capacity is made of >99.6% Alumina (Al2O3), which provides excellent high-temperature performance and chemical inertness, making it ideal for demanding applications.
In summary, the temperature an alumina crucible can withstand depends on its alumina content and the specific conditions of use. High-purity alumina crucibles offer superior temperature resistance and chemical stability, making them suitable for the most demanding high-temperature applications.
Summary Table:
| Property | High-Purity Alumina (99%+) | Lower Purity Alumina (e.g., 85%) |
|---|---|---|
| Max Temperature (Short-Term) | Up to 1800°C | Up to 1400°C |
| Max Temperature (Long-Term) | Up to 1750°C | Lower than 1400°C |
| Thermal Conductivity | High | Moderate |
| Thermal Expansion | Low | Low |
| Chemical Resistance | Excellent | Good |
| Mechanical Strength | High | Moderate |
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