Alumina-based ceramics

Although beryllium oxide [1304-56-9] is in many ways superior to most commonly used alumina-based ceramics, the principal drawback of beryUia-based ceramics is their toxicity thus they should be handled with care. The thermal conductivity of beryUia is roughly about 10 times that of commonly used alumina-based materials (5). BeryUia [1304-56-9] has a lower dielectric constant, a lower coefficient of thermal expansion, and slightly less strength than alumina. Aluminum nitride materials have begun to appear as alternatives to beryUia. Aluminum nitride [24304-00-5] has a thermal conductivity comparable to that of beryUia, but deteriorates less with temperature the thermal conductivity of aluminum nitride can, theoreticaUy, be raised to over 300 W/(m-K) (6). The dielectric constant of aluminum nitride is comparable to that of alumina, but the coefficient of thermal expansion is lower. 

Goeuriot-Launay, D., Brayet, G., and Thevenot, F., Boron nitride effect on the thermal shock resistance of an alumina based ceramic composite, J. Mater. Sci. Lett., 5 940-942 (1986). 

L. M. Braun, S. J. Bennison, and B. R. Lawn, Objective Evaluation of Short-Crack Toughness Curves Using Indentation Flaws Case Study on Alumina-Based Ceramics, J. Am. Ceram. Soc., 75[11], 3049-3057 (1992). 

Inorganic membranes have been mentioned in other usage in the biotechnology and pharmaceutical industries. For example, ziiconia and alumina-based ceramic membranes have been incorporated in the following operations [Cueille and Ferreira, 1989] purification and concentration of antibiotics, vitamins, amino-acids, organic acids, enzymes, biopolymers and biopeptides for the fermentation steps in the more conventional applications human blood derivatives, vaccines, recombinant proteins, cells culture and monoclonal antibiotics in newer applications and pyrogen lemoval for ultrapure water. 

Ceramic materials are also utilized in nuclear reactor components. Applications include insulation of pressure vessels with linings fabricated from silica and alumina-base ceramic bricks or fiber insulation pressure vessels made of prestressed concrete structures that enclose the entire reactor and secondary system wear-resistant surfaces produced by means of coatings such as chromium oxide or chromium carbide and shielding applications, which include materials such as concrete, graphite, and leaded glass ... 

Masuda, M., Sato, T., Kori, T. and Chujo, Y. (1994) Cutting performance and wear mechanism for alumina-based ceramic tools when machining austempered ductile iron. Wear 174 147-153. 

Pysher, D.J., and R.E. Tressler. 1992a. Creep rupture studies of two alumina-based ceramic fibers. Journal of Materials Science 27 423—428. ... 

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