Alumina ceramic thermocouple protection tubes are mainly used for the conditions that high temperature resistance is required.They are always used as protective tubes. Their operating temperature can be up to 1800° C.
Alumina thermocouple protection tubes also have outstanding corrosion resistance and are highly chemically resistant to acids, solvents, and salts.
Additionally,ceramic thermocouple protection tubes have high hardness, wear resistance, insulation property,can be used as fuse insulating tube on the electric and electronic appliances.
Properties of Alumina Ceramics
Alumina has a high melting point, high hardness and high mechanical strength, although mechanical strength is reduced at temperatures above 1000°C. Due to the relatively large coefficient of thermal expansion, thermal shock resistance is reduced. Alumina is an electrically insulating material, with a high electrical resistivity, increasing with purity.Good chemical stability of alumina, leads to a high corrosion resistance. It is insoluble in water and only slightly soluble in strong acid and alkaline solution.
| Characteristics | Unit | 95 Al2O3 | 99 Al2O3 | ZrO2 | GPSi3N4 | BN | Glass Ceramic |
| Crystal Structure | - | hexagonal | hexagonal | tetragonal | hexagonal | hexagonal | - |
| Color | - | white | ivory | white | gray | white | white |
| Density | g/cm3 | 3.65 | 3.88 | 5.95 | 3.22 | 2.26 | 2.55 |
| Water Absorption | % | 0 | 0 | 0 | 0 | 0.0-1.0 | 0 |
| Young's Modulus | Gpa | 280 | 350 | 205 | 295 | 670 | 65 |
| Vickers Hardness | Gpa | 14 | 20 | 12 | 18-20 | - | - |
| Flexural Strength @R.T. | Mpa | 280 | 300 | 900 | 650 | 51 | 100 |
| Compressive Strength @R.T. | Mpa | 2000 | 2500 | 2200 | 2200 | 230 | 500 |
| Thermal Conductivity @R.T. | W/(m*k) | 18-25 | 30 | 2.2 | 25 | 20 | 1.7 |
| Thermal shock resistance | Δ(℃) | 220 | 180-200 | 280-350 | 450-650 | >1500 | 25-100 |
| Max. Working Temperature @R.T. | ℃ | 1500 | 1700 | 850 | 1200 | 960 | 800 |
| Volume Resistivity @R.T. | Ω*cm | >10^15 | >10^14 | >10^12 | >10^14 | 10^13 | 10^16 |
| Dielectric Constant (1 MHz @R.T. ) | - | 9.5 | 9.8 | 26 | 8.2 | 4.08 | 6.02 |
| Dielectric Strength | kV/mm | 16 | 22 | - | 16 | 375 | 40 |
Various Application of Alumina Ceramics
*Seal rings
*Medical prostheses
*Laser tubes
*Electronic substrates
*Ballistic armour
*Thermocouple tubes
*Electrical insulators
*Grinding media
*Threadguides
*Wear components
About UniPreTec
UniPreTec provides high-performance ceramic products in Alumina, Zirconia, Boron Nitride, Machinable Glass Ceramic, Silicon Nitride and further special materials. Along with these materials, we offer several machining from which to choose such as cutting, drilling, sawing, turning, grinding, polishing etc.. Furthermore, our technologies and equipments allow us to provide various and flexible forming processes, like dry pressing, isostatic pressing, extrusion, injection moulding and slip casting.
