Oxide ceramics
The materials in this group consist mainly of single metal oxides.
The raw materials used are manufactured synthetically. This means that specifications can be made with regard to the shape and purity of the base powder. For the design of the end product, there are multiple production techniques available, these may be extrusion, injection moulding, pressing, moulding etc.
The following materials belong to the group of oxide materials:
- Aluminium Oxide Al2O3
- Zirconium Oxide ZrO2
- Other oxide ceramics
Aluminium Oxide in particular, is a frequently used material in a variety of applications.
Aluminium Oxide (Al2O3) can be produced in a wide range of modifications. Al2O3 is available in various purities (Al2O3 99.7%; Al2O3 60% etc.) Each of these Aluminium Oxide modifications has its own properties. The table below shows a number of properties associated with the different qualities.
It is important to mention that the properties of your end product are partly determined by the production method used. For example, by extrusion, injection-moulding, cold isostatic pressing, or hot isostatic pressing.
The most-frequently used material is Al2O3. This material is commonly used for a variety of reasons. The most important of these properties is its extremely high operating temperature (up to 1900 °C for Al2O3 99.7%) and its high resistance to corrosion.
A further important aspect is that a large number of techniques can be used to process the material into an end product; tubes, for example, which can be extruded in lengths of up to 4 metres.
| Hardness HV | E-modulus GPa | Bending strength MPa | Density g/cm3 | Expansion 10-6K-1 | Therm. conductivity W/(mK) | T max = K | |
| Al2O3 99.7% | 2000 | 320 | 340 | 3.83 | 7.0 | 29 | 1900 |
| Al2O3 97.6% | 1500 | 300 | 296 | 3.76 | 6.9 | 27 | 1650 |
| Al2O3 60% | 1800 | 180 | 185 | 2.6 | 3.6 | 3 | 1600 |
Zirconium Oxide (ZrO2) is the toughest and most rigid of ceramics. Of all ceramic materials, Zirconium Oxide has the highest mechanical strength and toughness. Its extraordinary characteristics remain intact at temperatures up to approximately 1000 °C.
Due to the relatively high coefficient of expansion of Zirconium Oxide, this material can be applied by press or shrink fitting as an insert in, or as a sleeve around, a metal product. Zirconium Oxide is available in different versions, by using various types of stabilisers such as Magnesium Oxide (MgO) and Ytrium (Y2O3).
Zirconium Oxide can be machined to very tight tolerances, with roughness values of 0.006 um being achievable.
| Hardness HV | E-modulus GPa | Bending strength MPa | Density g/cm3 | Expansion 10-6K-1 | Therm. conductivity W / (mK) | T max = K | |
| ZrO2 MgO stabilized | 1200 | 180 | 1000 | 5.7 | 8.0 | 3 | 900 |
| ZrO2 Y2O3 stabilized | 1300 | 205 | 1000 | 6.05 | 10 | 2 | 1200 |
| ZrO2 Y2O3 stabilized+HIP | 1350 | 205 | 1400 | 6.05 | 10 | 2 | 2000 |
| Fully stabilized ZrO2 | 180..500 | 9.3 .. 11.0 | 2300 |
Aluminium Oxide and Zirconium Oxide are important materials in the ‘oxide ceramics’ group. For the textile industry, thread guides are not only produced in Al2O3 but also in Titanium Oxide.
Titanium Oxide is used in 2 grades; electrically insulating and electrically conductive variants. The polishability of the product is important for thread guides, as it is crucial that the delicate yarn does not split. Its electric conductive quality becomes essential when static electricity in a process causes problems.
Cordierite and Steatite are both made from natural, raw materials (clay). Cordierite is a material that has excellent thermal-shock resistance. Cordierite is also used as a support for heating elements. Steatite is a material with a dense structure and excellent electrical insulating properties. Because of these properties, the material is extremely suitable for use in electrical engineering.
Aluminium Titanate (Al2TiO5) is a combination of Al2O3 and TiO2. Its porous structure, in combination with a low expansion coefficient, gives the material excellent thermal-shock resistance. Because it has a low humidification level when used with liquid, non-ferrous metals, Aluminium Titanate can be used for riser tubes or crucibles.
For specific questions, please contact a Gimex adviser.
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