Use of Ceramics

Ceramics differ from some other materials (viz. metals, plastics, wood products, textiles) in a number of individual properties, but perhaps the most distinctive difference to a designer or potential user of eeramic ware is the particularity of the individual ceramic piece. Actually ceramics are not readily shaped or worked after firing, except for some simple shapes of limited sizes. Many ceramies are manufactured as standard items refractoiy bricks and shapes, crucibles, furnace tubes, insulators, thermocouple protection tube, fibre tubes etc. 

Stoneware Natural Drain pipe, artware, kitchenware 

Technical Ceramics Electrical porcelains Low-frequency insulators 

Porcelain High strength electrical Low-frequency insulators 

Vehicle ceramic Brake discs Advanced composite ceramic Ceramic balls 

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An advantage of the use of ceramics over the use of glass as an insulator in X-ray tubes is the larger freedom in design due to better stability and more reliable quality of the ceramics. Therefore, typical markets for metal-ceramic tubes are applications where only a relatively low amount of tubes, but in special designs, are used. 

As the level of opacifier is lowered in a glass system, the level of opacification drops. This yields semi-opaque glasses which allow the development of soft pastel colors. Strong colors result from clear glasses. The clarity allows the use of ceramic pigments (qv) (mixed-metal oxides) for the development of a wide variety of colors in almost any hue, saturation, and brightness. 

As an example the use of ceramic membranes for ethane dehydrogenation has been discussed (91). The constmction of a commercial reactor, however, is difficult, and a sweep gas is requited to shift the product composition away from equiUbrium values. The achievable conversion also depends on the permeabihty of the membrane. Figure 7 shows the equiUbrium conversion and the conversion that can be obtained from a membrane reactor by selectively removing 80% of the hydrogen produced. Another way to use membranes is only for separation and not for reaction. In this method, a conventional, multiple, fixed-bed catalytic reactor is used for the dehydrogenation. After each bed, the hydrogen is partially separated using membranes to shift the equihbrium. Since separation is independent of reaction, reaction temperature can be optimized for superior performance. Both concepts have been proven in bench-scale units, but are yet to be demonstrated in commercial reactors. 

The solubilities of the various gases in [BMIM][PFg] suggests that this IL should be an excellent candidate for a wide variety of industrially important gas separations. There is also the possibility of performing higher-temperature gas separations, thanks to the high thermal stability of the ILs. For supported liquid membranes this would require the use of ceramic or metallic membranes rather than polymeric ones. Both water vapor and CO2 should be removed easily from natural gas since the ratios of Henry s law constants at 25 °C are -9950 and 32, respectively. It should be possible to scrub CO2 from stack gases composed of N2 and O2. Since we know of no measurements of H2S, SO, or NO solubility in [BMIM][PFg], we do not loiow if it would be possible to remove these contaminants as well. Nonetheless, there appears to be ample opportunity for use of ILs for gas separations on the basis of the widely varying gas solubilities measured thus far. 

Heimann, R.B. (1989). Assessing the technology of ancient pottery the use of ceramic phase diagrams. Archeomaterials 3 123-148. 

The use of ceramic membranes in gas separations is not new. Since 1950, alumina membranes were used in the separation of UF isotopes. However, the separation factor is very low in this case (theoretically 1.004 ). 

These early studies were carried out on metals of typically 90-99% purity, which sufficed to determine at least their gross properties. During the 1960s, interest diminished somewhat in actinide metallurgy due in part to the increasing use of ceramic rather than metallic fuel elements in nuclear reactors. The bulk of actinide metal research was for secret military purposes and only a fraction of the fundamental research was published. 

Infrared detection -use of ceramics [CERAMICS - ELECTRONIC PROPERTIES AND MATERIAL STRUCTURE] (Vol 5)... 

At about 1860 the first sterile surgical techniques were introduced by Lister. About 100 years ago, the research into the field of implants, notably of the hip joint, was started. In 1891 Znamensky first described the use of ceramic materials in the manufacture of implants. 

Kawamura H (2001) Practical use of Ceramic Components and Ceramic Engines. In Heinrich JG, Aldinger F (eds) Ceramic Materials and Components for Engines. Wiley-VCH, Weinheim, p 27... 

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