Influence of Illite Clay on Cordierite-Spinel Formation in Ceramics from Mixed Compositions

Illite clay together with dolomite can act as a precursor material for the synthesis of cordierite-spinel crystalline phases ceramics. This is confirmed by the addition of 4.5-8.2 wt.% illite clay and dolomite. The addition of 4.5 wt.% illite clay and dolomite (each of them) to stoichiometric mixture of γ Al2O3 and amorphous SiO2 results in the development of the high-temperature cordierite -indialite and spinel as the main crystalline phases at temperature 12800C and treatment time 1 h. The addition of 8.2 wt.% illite clay and dolomite (each of them) results in the formation of the spinel MgAl2O4 and enstatite MgSiO3 crystalline phases. By these additives along with the crystalline phases sufficient amount of glassy phase and evenly distributed pores with average size of 150-350m are formed. The microstructure studies have shown that the shape and size of formed cordierite crystals vary according to the additive of illite clay and dolomite. It is observed that the morphology of indialite crystals formed are perfect prismatic shaped and have a conchoidal fracture. The additional crystalline compounds are octahedral spinel and prismatic shaped enstatite. In dependence on kind of illite clay these crystals accept shapes of an imperfect nature

Catalitic Properties of Phyllosilicate in the Concentrated Oxide Suspension

Porous ceramic from clay and alumina concentrated suspensions (water content 28-35%) in the direct process of pore formation by reaction of metallic aluminium powder with water are obtained. Clay minerals form stable suspension thanks surface charge of particle surface, which is characterize by zeta potential. Clay minerals associate the developed pore structure after hydrogen elimination. After drying and sintering structure remains. Different materials structure is obtain by use kaolinite, illite or smectite because particles of these minerals have different zeta potential. Pore structure of obtained materials depends on the mineralogical composition of clay. Various admixtures (carbonate, sand) influences hydrogen elimination process and viscosity of suspension. The best catalytic properties characterises kaolinite with the highest zeta potential

Фазовый состав и свойствa муллитовой керамики при высокотемпературных испытаниях

Проведены исследовании изменения фазового состава, структуры, линейной усадки и механической прочности муллитосодержащей керамики из композиций, содержащих иллитовую (гидрослюдистую) глину и гидроокись алюминия после выскотемпературных испытаний в интервале температур 1200 -1500 0С. Показано, что в данном интервале температур происходит увеличение новообразований муллита, как и рост размеров игольчатых кристаллов муллита, что является первостепенным фактором сохранения механической прочности в пределах 28-32 MPa образцов вплоть до температуры 14000С. Установлено, что с возрастанием содержания иллитовой глины и соответственным снижением общего содержания Al2O3 в исходных композициях при выскотемпературных испытаниях при 1300-14000С возрастает содержание аморфной фазы, кристаллическая фаза муллита становится мелкодисперсной и заметно снижается механическая прочность на сжатие вплоть до разрушения образца

Porous Ceramics in Oxide and Clay Systems from Suspensions with Metallic Aluminium

Lightweight ceramic materials according to the aerated concrete technology using concentrated suspensions are produced. Pore formation in such slurries depends on rheological properties such as zeta potential, viscosity and pH. Reactions rate depends on the presence of definite minerals such as kaolinite, illite, smectite or low temperature modification of alumina. Grain size of raw materials and the sintering temperature have major influence on the pore structure of final material. These materials are used mainly as refractories but by using illitic or smectitic clays as thermal insulating materials