Aluminum oxide sintering

Manufactured abrasives include silicon carbide, fused aluminum oxide, sintered aluminum oxide, sol-gel sintered aluminum oxide, fused zirco-nia-alumina, synthetic diamond, cubic boron nitride, boron carbide, slags, steel shot, and grit. 

Sol—Gel Sintered Aluminum Oxide. A new and much more versatile sintered alumina abrasive is now produced from aluminum monohydrate, with or without small additions of modifiers such as magnesia, by the sol—gel process (see Sol-gel technology). The first modified sol—gel abrasive on the market, Cubitron, was patented (27) and produced by the 3M Corporation for products such as coated belts and disks. The success of this material promoted intensive research into sol—gel abrasives. 

The predominate role of the 2inc and aluminum oxides in the ICI catalyst is to reduce the rate of sintering and loss of metallic copper surface area, which, in addition to poisoning, is one of the modes of activity loss with time for this catalyst. 

Rigid Porous Media These are available in sheets or plates and tubes. Materials used include sintered stainless steel and other metals, graphite, aluminum oxide, silica, porcelain, and some plastics—a gamut that allows a wide range of chemical and temperature resistance. Most applications are for clarification. 

The measures of solid state reactivity to be described include experiments on solid-gas, solid-liquid, and solid-solid chemical reaction, solid-solid structural transitions, and hot pressing-sintering in the solid state. These conditions are achieved in catalytic activity measurements of rutile and zinc oxide, in studies of the dissolution of silicon nitride and rutile, the reaction of lead oxide and zirconia to form lead zirconate, the monoclinic to tetragonal transformation in zirconia, the theta-to-alpha transformation in alumina, and the hot pressing of aluminum nitride and aluminum oxide. 

The mostly applied porous separator in laboratory cells is sintered glass ( fritted glass ). It can be simply and leakproof mounted by the glassblower into the walls of glass cells and then it is very easy to handle. It is available - like similar ceramic materials, for example, sintered aluminum oxide or unglazed porcelain... 

J.M. Dynys. Sintering Mechanisms and Surface Diffusion for Aluminum Oxide. PhD thesis, Department of Materials Science and Engineering, Massachusetts Institute of Technology, 1982. 

Aluminum oxide sols are successfully used for application of films [1794, 1793], such as high area films for hybrid circuits [1236]. The same technique was used for the preparation of J-A1203 (NaAlnO,7) in this case alcoholic solutions of NaOR were added to aluminum alkoxide solutions [1795, 1038]. To increase the stability of sols, aluminum alkoxides are frequently modified with acetic acid [1570] or (3-diketones [1659]. Alumina sheets are commercially produced by the sintering of high-purity fine A1203 powders prepared by hydrolysis of modified Al(OPr )3 [1236]. To prepare powders with spherical species from dilute solutions, hydroxopropylcellulose was added to prevent... 

The product is poured into ice water, thoroughly extracted yith benzene, and the benzene solution washed with water. Benzene is then removed by distillation until a volume of 25-50 cc. is reached and the resulting deep-red solution is passed through a 12 by 2 cm. column of aluminum oxide. The column is developed with ordinary, undried benzene, and that portion of the eluate which runs through before the strawberry-red zone reaches the bottom of the tube is discarded. The solution that follows is collected, and a pale yellow crystalline mass is obtained upon removal of the solvent. Recrystallization from ethanol gives 1.24-1.37 g. (60-65%) of pale yellow crystals that sinter at 119° and melt at 122.7-123.2° (cor.). 

The product is then poured into ice water, extracted with benzene, and washed with water, aqueous sodium hydroxide, and finally with water. After removal of the solvent, the residue is sublimed at 1 mm. and a bath temperature of 160-190°. The pale yellow crystals so obtained are dissolved in benzene, and the solution is passed through a short column of aluminum oxide. Removal of the solvent gives 0.2-0.23 g. (40-45%) of white crystals which begin to sinter at 245° and melt at 252-254° (cor.). 

Roberts, R.M. et al.. Hydrogen permeability of sintered aluminum oxide. Journal of the American Ceramic Society, 62, 495 (1979). 

Researchers at Argonne National Laboratory have devoted considerable effort to the development of anodized aluminum oxide (AAO) membrane reactors. AAO membrane pores are generally synthesized with diameters of >50 nm. However, using ALD, the membrane pores are decreased by overcoating with Al Oj or another material which can act as a support for metal clusters [83]. Sintering is reduced in the AAO membrane reactors because the clusters are effectively trapped in the AAO pores in much the same manner that small metal particles... 

The industrial manufacture of aluminum hydroxide and aluminum oxide currently proceeds almost exclusively by the Bayer process i.e. by wet digestion of bauxite. The sinter- and melt-digestion processes with sodium carbonate and/or lime only have minor industrial importance. 

The starting point for the suspension process is a finely divided aluminum oxide powder suspended in water. An additive provides the necessary viscosity. Spinning of this finely divided suspension with the help of additives provides raw aluminum oxide fibers, which by calcining and treatment at high temperature is converted into non-porous sintered a-aluminum oxide fibers. 

The industrially most important oxide-ceramic material is sintered aluminum oxide. The raw materials used are so-called calcined alumina and melted corundum. 

In recent years sintered titanium(IV) oxide has been utilized in addition to aluminum oxide in the textile industry in which it is utilized as an abrasion-resistant material for thread guides. 

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