Formation of Mullite Basedon Hydromica Clay – Aluminum Oxide Compositions

Ceramic item deformation during firing: effects of composition and microstructure (review)

“…In the two-component Al 2 O 3 -SiO 2 system, mullite is formed at temperatures above 1400°C and with a molar ratio Al 2 O 3 /SiO 2 » 1.5; the region of solid solutions extends [25,26] from the composition corresponding to mullite as 3Al 2 O 3 × 2SiO 2 to the composition 2Al 2 O 3 × SiO 2 . In threecomponent systems (and with a larger number of components), containing K 2 O, Na 2 O, CaO, Fe 2 O 3 (FeO) or TiO 2 , the temperature for mullite formation is reduced because of the acceleration of reactions on account of the liquid phase, which appears at relatively low temperatures.…”

“…In [30], as the Al 2 O 3 source use was made of the cheaper bauxite. It has been suggested [25,26] that instead of alumina and other oxide additives one should use a mixture of hydromica clay (50 -60%) with Al(OH) 3 , in which it has been shown that mullite is most rapidly formed at 1150 -1200°C, which is 150 -200°C lower than in the formation of mullite from oxides.…”

“…Extensive research has been done on the sintering parameters and also the structure formation from mineralizing additives TiO 2 , ZnO, and CaF 2 [39], or a mixture containing zinc oxide and magnesium carbonate [40]; other studies have been made on the production of mullite in alumosilicate systems in the presence of Fe 2 O 3 (FeO) [25,26]; on the effects of pyrite nodules on the sintering and high-temperature viscosity of a refractory clay [41]; and on features of the phase transformations on firing clay materials with elevated contents of iron oxides [42].…”

Aluminosilicate ores processed by a fluoride method

“…For all its superior thermophysical properties and large natural mineral reserves, mullite production in Russia is still in the early stage of development. The demands of the domestic mullite market are at present mainly satisfied by the supply of ready-made mullite refractories purchased from foreign manufacturers [1,2].In Russia, a few manufacturers are concerned with the production of mullite-based refractory materials. Mullite materials are available from Ogneupory Joint-Stock Co. (Tula Region) and Semiluki Refractory Plant Joint-Stock Co. (Semiluki, Voronezh Region); however, they contain less than 62% Al 2 O 3 and their refractoriness is much inferior to that of pure mullite materials.…”

“…For all its superior thermophysical properties and large natural mineral reserves, mullite production in Russia is still in the early stage of development. The demands of the domestic mullite market are at present mainly satisfied by the supply of ready-made mullite refractories purchased from foreign manufacturers [1,2].…”