|
|
|
|
| ||
|
|
| ||||
|
| |||||
Click to see Standard Catalogue items from one of the forms
|
Minerals containing Alumina represent some 15% of the earth's crust. It is therefore an abundant material and virtually inexhaustable, unlike raw materials for many alloys developed for special applications. The combination of high thermal conductivity, low thermal expansion and high compressive strength leads to good thermal shock resistance, so Alumina is suited to furnace use as crucibles, tubes and thermocouple sheaths. High purity Alumina can be used up to 1700C and is gas tight up to 1300C. Few chemicals attack Alumina. Alumina also shows good electrical insulation at high temperatures, good wear resistance and high hardness, making it suitable for components such as ball valves, piston pumps and deep drawing tools. Diamond tools are needed to machine or grind Alumina. Remarkably, continuous filament yarns have been made from alumina with reasonable but not complete success and two, similar, versions are available from Goodfellow. They are both much less flexible than normal continuous filament yarns and are rather "hairy" i.e. have broken filaments - especially the FP version.
| Chemical Resistance | ||
| Acids - concentrated | Good | |
| Acids - dilute | Good | |
| Alkalis | Good | |
| Halogens | Good | |
| Metals | Good | |
| Electrical Properties | ||
| Dielectric constant | 9.0-10.1 | |
| Dielectric strength ( kV mm-1 ) | 10-35 | |
| Volume resistivity @25C ( Ohmcm ) | >1014 | |
| Mechanical Properties | ||
| Compressive strength ( MPa ) | 2200-2600 | |
| Hardness - Knoop ( kgf mm-2 ) | 2100 | |
| Hardness - Vickers ( kgf mm-2 ) | 1500-1650 | |
| Shear strength ( MPa ) | 330 | |
| Tensile modulus ( GPa ) | 300-400 | |
| Tensile strength ( MPa ) | 260-300 | |
| Physical Properties | ||
| Apparent porosity ( % ) | 0 | |
| Density ( g cm-3 ) | 3.9 | |
| Water absorption - saturation ( % ) | 0 | |
| Thermal Properties | ||
| Coefficient of thermal expansion @20-1000C ( x10-6 K-1 ) | 8.0 | |
| Melting point ( C ) | 2100 | |
| Specific heat @25C ( J K-1 kg-1 ) | 850-900 | |
| Thermal conductivity @20C ( W m-1 K-1 ) | 26-35 | |
| Upper continuous use temperature ( C ) | 1700 | |
| Property | Value | |
|---|---|---|
| Coefficient of thermal expansion - Longitudinal | x10-6 K-1 | 5.7 |
| Density | g cm-3 | 3.9 |
| Modulus | GPa | 380 |
| Tenacity | GPa | 1.4 |
Click to see Standard Catalogue items from one of the forms
|
|
Goodfellow Cambridge Limited |
Goodfellow GmbH |
Goodfellow Corporation |
Goodfellow SARL |
