Introduction
Alumina ceramics (Al₂O₃), or aluminum oxide, are advanced non-metallic materials valued for their hardness, thermal stability, and electrical insulation. Available in purities of 95%, 97.5%, 99%, and 99.5% Al₂O₃, these ceramics provide a spectrum of properties for material science research. This article examines the key properties of alumina ceramics, supported by a comparative table, to highlight their significance in research applications.
Properties of Alumina Ceramics
Alumina ceramics exhibit a range of properties that make them ideal for material science studies. Below are their key characteristics:
- High Hardness: Vickers hardness from 13.7 GPa (95% Al₂O₃) to 17.5 GPa (99.5% Al₂O₃), suitable for wear resistance studies.
- Thermal Conductivity: Ranges from 24 W/(m·K) (95% Al₂O₃) to 34 W/(m·K) (99.5% Al₂O₃), ideal for heat transfer research.
- Electrical Insulation: Volume resistivity >10¹⁴ ohm-cm across all grades, supporting electrical behavior studies.
- Chemical Stability: Minimal weight loss in acids (e.g., 0.03 mg/cm²/day in HNO₃ for 99.5% Al₂O₃), perfect for corrosion studies.
- Low Dielectric Loss: Decreases from 38 × 10⁻⁴ (95% Al₂O₃) to 10 × 10⁻⁴ (99.5% Al₂O₃), reducing energy loss in high-frequency applications.
Detailed Properties Table
The table below compares the properties of alumina ceramics across 95%, 97.5%, 99%, and 99.5% Al₂O₃ grades.
Property | 95% Al₂O₃ | 97.5% Al₂O₃ | 99% Al₂O₃ | 99.5% Al₂O₃ |
Main Characteristics | ||||
Color | White | White | White | White |
Main Applications | Metallization, wear resistance | High wear resistance | High temperature, wear resistance | High temperature, wear resistance |
Characteristics | High strength, wear resistance, corrosion resistance, and insulation | High strength, corrosion resistance | High strength, corrosion resistance | High strength, corrosion resistance |
Mechanical Properties | ||||
Bulk Density (g/cm³) | 3.7 | 3.8 | 3.9 | 3.9 |
Water Absorption (%) | 0 | 0 | 0 | 0 |
Vickers Hardness (GPa) | 13.7 | 15.2 | 17.2 | 17.5 |
Flexural Strength (MPa) | 350 | 310 | 380 | 400 |
Compressive Strength (MPa) | — | — | — | 3800 |
Young’s Modulus (GPa) | 320 | 360 | 380 | 380 |
Poisson’s Ratio | 0.23 | 0.23 | 0.23 | 0.23 |
Fracture Toughness (MPa m¹/²) | 3–4 | 5–6 | — | — |
Thermal Properties | ||||
Specific Heat Capacity (J/(kg·K) × 10⁻³, 400°C) | 7.2 | 7.2 | 7.2 | 7.2 |
Thermal Conductivity (W/(m·K)) | 24 | 25 | 32 | 34 |
Thermal Shock Resistance (ΔT°C) | 200 | 200 | 200 | 200 |
Electrical Properties | ||||
Volume Resistivity (ohm-cm) | >10¹⁴ | >10¹⁴ | >10¹⁴ | >10¹⁴ |
Dielectric Strength (kV/mm) | 15 | 15 | 15 | 15 |
Dielectric Constant (1 MHz) | 9.4 | 9.9 | 9.9 | 9.9 |
Dielectric Loss (×10⁻⁴) | 38 | 20 | 10 | 10 |
Chemical Properties | ||||
Nitric Acid (60%) Weight Loss (mg/cm²/day) | 0.10 | 0.05 | 0.03 | 0.03 |
Sulfuric Acid (95%) Weight Loss (mg/cm²/day) | 0.33 | 0.22 | 0.19 | 0.19 |
Caustic Soda (30%) Weight Loss (mg/cm²/day) | 0.06 | 0.04 | 0.03 | 0.03 |
Table Notes:
- Mechanical Properties: Higher-purity grades show increased hardness and stiffness, offering insights into composition effects.
- Electrical Properties: Lower dielectric loss with higher purity enhances performance in high-frequency applications.
- Chemical Stability: Reduced weight loss in acids with higher purity provides a benchmark for corrosion resistance.
Conclusion
Alumina ceramics, with their diverse properties across 95% to 99.5% Al₂O₃ grades, are ideal for material science research. Their hardness, thermal conductivity, and chemical stability provide valuable insights into the effects of purity on ceramic performance.
Heeger Materials is a leading manufacturer and supplier of high-quality alumina ceramic products in forms of plates, sheets, rods, tubes, crucibles, substrates, and customized parts, offering customized solutions for various industrial and research applications.