Black alumina ceramic tube is a high-temperature industrial ceramic tube made primarily from aluminum oxide (Al₂O₃) with a black ceramic body or surface treatment that adds light-absorbing properties. It combines the core advantages of alumina—high mechanical strength, electrical insulation, wear resistance, and thermal stability up to about 1600–1750 °C—with low reflectivity for optical shielding. Black alumina ceramic tubes are widely used for thermocouple protection, furnace components, sensor housings, wear-resistant liners, and optical or electronic shielding in high-temperature and corrosive environments.
Black Alumina Ceramic Tube Benefits
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Combined high-temperature and optical performance – Black alumina ceramics retain the strength and insulation of alumina while providing strong light absorption and low reflectivity, suitable for thermal and optical environments in one component.
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Stable strength at elevated temperature – Alumina ceramics maintain high flexural strength from room temperature to around 1100 °C and remain functional up to 1600–1750 °C in suitable atmospheres.
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Low thermal expansion and good dimensional stability – The low thermal expansion of alumina supports dimensional stability during repeated heating and cooling cycles, reducing the risk of warping or misalignment in assemblies.
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Electrical insulation and wear resistance in one tube – Black alumina ceramic tube provides high electrical resistivity together with abrasion resistance, allowing it to act as both insulator and wear liner in mechanical or electrical systems.
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Resistance to many industrial chemicals – Alumina ceramics show strong resistance against many acids, alkalis, and process gases, making black alumina suitable for aggressive furnace and process atmospheres when correctly selected.
Black Alumina Ceramic Tube Properties
| Property | Unit | 96% Al₂O₃ | 99% Al₂O₃ | 99.5% Al₂O₃ | 99.6% Al₂O₃ | 99.7% Al₂O₃ | 99.8% Al₂O₃ | 99.9% Al₂O₃ | 99.99% Al₂O₃ |
| Alumina content | % | 96 | 96 | 99.5 | 99.6 | 99.7 | 99.8 | 99.9 | 99.99 |
| Density | g/cm³ | 3.6-3.75 | 3.83 | 3.89 | 3.91 | 3.92 | 3.93 | 3.94 | 3.98 |
| Color | – | white | Ivory | Ivory | Ivory | Ivory | Ivory | Ivory | Ivory |
| Water absorption | % | 0 | 0 | – | 0 | 0 | 0 | 0 | 0 |
| Young’s modulus (Elastic modulus) | GPa | 0 | 0 | 375 | 356 | 357 | 358 | 359 | 362 |
| Shear modulus | GPa | – | – | 152 | – | – | – | – | – |
| Bulk modulus | GPa | – | – | 228 | – | – | – | – | – |
| Poisson’s ratio | – | – | – | 0.22 | – | – | – | – | – |
| Compressive strength | MPa | 1910 | 2210 | 2600 | 2552 | 2554 | 2556 | 2558 | 2570 |
| Flexural strength | MPa | 260 | 300 | 379 | 312 | 313 | 314 | 315 | 320 |
| Fracture toughness | MPa·m¹ᐟ² | – | – | 4 | – | – | – | – | – |
| Hardness | GPa | 14.5 | 17 | 17 | 23 | 24 | 25 | 26 | 30 |
| Thermal conductivity | W/m·K | 22 | 24 | 35 | 32–37 | 33–38 | 34–39 | 35–40 | 36–42 |
| Thermal shock resistance ΔT | °C | – | – | – | 222 | 223 | 224 | 225 | 228 |
| Maximum use temperature (no load) | °C | 1450 | 1680 | ≤1750 | 1755 | 1760 | 1765 | 1770 | 1800 |
| Coefficient of thermal expansion | 10⁻⁶/°C | 7.6 | 7.6 | 8.4 | – | – | – | – | – |
| Volume resistivity | Ω·cm | >1×10¹⁴ | >1×10¹⁴ | >1×10¹⁴ | >1×10¹⁴ | >1×10¹⁴ | >1×10¹⁴ | >1×10¹⁴ | >1×10¹⁴ |
| Dielectric constant (relative permittivity) | – | 9.2 | 9.5 | 9.8 | 9.83 | 9.84 | 9.85 | 9.86 | 9.92 |
| Dielectric strength | kV/mm | 15 | 19 | 16.9 | 23.2 | 23.4 | 23.6 | 23.8 | 24 |
| Dissipation factor (loss factor @ 1 kHz) | – | – | – | 0.0002 | – | – | – | – | – |
Black Alumina Ceramic Tube Specifications
| Item No. | Outer Diameter（mm） | Inner Diameter（mm） | Length（mm） | Purity（%） |
| AT-AO-HG001 | 3 | 1 | 2 | 95-99 |
| AT-AO-HG002 | 10 | 6 | 30 | 95-99 |
| AT-AO-HG003 | 18 | 11 | 36 | 95-99 |
| AT-AO-HG004 | 20 | 12 | 50 | 95-99 |
| AT-AO-HG005 | 25 | 15 | 100 | 95-99 |
Black Alumina Tube Packaging
- Each tube is individually wrapped using foam and placed inside a rigid cardboard casing. Long isolates are cushioned with corrugated inserts.
