Focus I Advanced Ceramic Materials
Materials in design
Dieter Steudtner provides designers and manufacturers with an insight into advanced ceramic materials and their properties
T
oday’s advanced ceramics offer strong physical, chemical and electrical properties that make them
highly resistant to melting, bending, stretching, corrosion, wear, high voltages and currents. This has opened up development opportunities for manufacturers in a wide range of applications.
Advanced ceramics such as alumina, aluminum nitride, zirconia, silicon carbide, silicon nitride and titania-based materials, each with their own specific characteristics, provide a cost-effective, high performance alternative to traditional materials such as metals, plastics and glass. The
There are many factors that designers should consider when choosing a material including the desired properties for the application and the available materials. By fully understanding the materials, designers can then make well-informed choices. In particular when thinking about the shape, the design and the application of the part there are a lot of things to be considered in the early stages of engineering the parts. The shape of ceramic parts is often designed similar to metal parts. However this can have a negative impact on the cost and on the properties of the parts as well.
Desired properties for the application Physical properties such as strength, hardness, wear resistance, corrosion resistance and thermal stability are considered when choosing a material. Each of these characteristics is determined by specific materials. Designers look for those materials which give the best combination of characteristics for an excellent performance.
Materials
Having identified the material properties needed for individual applications, designers should then consider the various ceramic materials available to them. A number of available ceramic materials are optimised for their mechanical, electrical, thermal and/or chemical properties. Examples are detailed below:
and wear components. It has a good strength and stiffness, good hardness and resistance to wear. Alumina is available in many grades ranging from 60% to 99.9% with additives designed to enhance properties such as wear resistance or dielectric strength. It can be formed using a variety of ceramic processing methods and can be processed net-shaped or machined to produce a variety of sizes and shapes. In addition it can be readily joined to metals or other ceramics using specially developed metallising and brazing techniques. Aluminum Nitride (AlN): Aluminum nitride (AlN) has excellent thermal conductivity. Other properties include excellent thermal shock resistance and corrosion resistance. Based on these properties AlN is used in power electronics, aeronautical systems, railways, opto- electronics, semiconductor processing, microwave and military applications. Typical applications include heaters, windows, IC- packages and heat sinks. Zirconia: Zirconia offers chemical and
Alumina: Alumina is a versatile material demand posed
by new and changing applications is to improve operation at a reduced cost. New materials are constantly being developed and engineered to address the needs of individual applications.
14 February 2014
Joining of ceramics to metals also creates its own engineering challenges that require specialist expertise in the metallisation and joining of ceramics in order to provide high- integrity solutions for components of all sizes, shapes and specifications.
Components in Electronics
that offers a combination of good mechanical and electrical properties. It is suitable for a wide range of applications including laser devices, x-ray tubes, electron tubes, aerospace devices, high vacuum applications, flow meters, pressure sensors,
corrosion resistance at high temperatures up to 2400°C – well above the melting point of Alumina. In its pure form, crystal structure changes limit use in mechanical/temperature applications, but zirconia stabilised with calcium, magnesium or yttrium oxide additives can produce materials with very high strength, hardness and in particular, toughness. Morgan is a pioneer in this area of materials technology, producing Magnesia Partially Stabilised Zirconia (Mg-PSZ) and Yttria Tetragonal Poly-crystal Zirconia (Y-TZP). These belong to the group of very high strength, toughness zirconias that harness the “transformation toughening” phenomenon unique to this material. They are suited to engineering or structural applications where exceptional mechanical strength and properties such as hardness, wear and corrosion resistance are required. Meanwhile, the high temperature capability of zirconia products has led to the development of Fully Stabilised Zirconia (FSZ) grades for crucibles, nozzles and other components for molten metal applications.
Silicon Nitride: Silicon nitride has excellent high-temperature strength, creep and oxidation resistance, while its low
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