A Summary of Aluminum Titanate
At temperatures greater than 1350 °C, solid-state reaction of titania and alumina leads to the synthesis of aluminum titanate. Depending on its reactivity, the synthesized powder can be sintered at temperatures of 1400 °C–1600 °C in air. The crystal structure of aluminum titanate is pseudobrookite.
Ceramics that are made from aluminum titanate exhibit excellent thermal shock resistance. This is mostly due to its extremely low thermal expansion coefficient caused by the substantial anisotropy in the material’s properties.
Expansion along the a- and b-axes direction is positive, while the same in the c-axis direction is negative. Apart from producing almost zero thermal expansion, this causes microcracks in the sintered material, leading to moderately low material strength. SiO2 and MgO are additives used to prevent strength degradation. Strengths up to 100 MP have been specified for experimental materials.
The material has excellent thermal shock resistance, low thermal conductivity, and optimal chemical resistance to molten metals. These properties enable the material (mainly aluminum) to satisfy several metal-contact applications in the foundry sector such as crucibles, plugs, riser tubes, ladles, launders, and pouring spouts.
When compared to competing materials like calcium silicate and fused silica, components manufactured using aluminum titanate products have significantly longer service life.
Moreover, aluminum titanate is utilized as an insulating liner in the automotive sector for exhaust manifolds, where there is a need to reduce heat loss before a turbocharger. In this article, the metal exhaust manifold is cast over the molded aluminum titanate liner. The difference in the thermal expansion between the steel and aluminum titanate manifold during cooling maintains the ceramic in compressed state. This helps in resolving the problems associated with its low strength.
When ordering mica tubes, don’t envision a standard cylindrical tube. Mica tubes can be customized in terms of shape, thickness, length, diameter, and material. Since mica tubes are formed by multiple layers of mica paper, customizing mica tubes is very manageable.
Silicon Nitride (Si3N4) Properties and Applications
Silicon nitride (Si3N4) was developed in the 1960s and '70s in a search for fully dense, high strength and high toughness materials. A prime driver for its development was to replace metals with ceramics in advanced turbine and reciprocating engines to give higher operating temperatures and efficiencies. Although the ultimate goal of a ceramic engine has never been achieved, silicon nitride has been used in a number of industrial applications, such as engine components, bearings and cutting tools.
Silicon nitride has better high temperature capabilities than most metals combining retention of high strength and creep resistance with oxidation resistance. In addition, its low thermal expansion coefficient gives good thermal shock resistance compared with most ceramic materials.
Pure silicon nitride is difficult to produce as a fully dense material. This covalently bonded material does not readily sinter and cannot be heated over 1850oC as it dissociates into silicon and nitrogen. Dense silicon nitride can only be made using methods that give bonding through indirect methods, such as small chemical additions to aid densification. These chemicals are known as sintering aids, which commonly induce a degree of liquid phase sintering.
Alumina ceramic (Aluminum Oxide or Al2O3) is an excellent electrical insulator and one of the most widely used advanced ceramic materials. Additionally, it is extremely resistant to wear and corrosion. Alumina components are used in a wide range of applications such as electronics, pump components and automotive sensors.
Elan Technology offers a variety of alumina compositions, including 94% Alumina Low CaO, 94% Alumina High CaO2, and 85% Alumina 14% SiO2, but the 96% Alumina Ceramic is one of the most widely used materials.
Alumina components can be formed by a variety of manufacturing techniques such as uniaxial pressing, isostatic pressing, injection molding and extrusion. Finishing can be accomplished by precision grinding and lapping, laser machining and a variety of other processes.
The alumina ceramic components produced by Elan Technology are suitable for metallization in order to create a component that is easily brazed with many materials in subsequent operations. Elan Technology offers a range of alumina compositions to meet your most demanding applications.