Estudo de soluções sólidas da mulita: fabricação e propriedades.

AUTOR(ES)

Gislayne Elisana Gonçalves Coutinho Herculano

DATA DE PUBLICAÇÃO

2007

RESUMO

In the present work a study is made about manufacture of mullite ceramic compacts by synthesis from mechanical mixture of silica (SiO2) and alumina (Al2O3) powders with different compositions by sintering. The silica powder used as starting material for the mullite production was obtained from the calcination of chemically treated rice husk, at temperatures of 550oC during 4h and 700oC, for comparison. The powders were initially mixed mechanically, uniaxially pressed, and sintered at 1650C in a muffle type furnace, for approximately 4h, in air atmosphere. Some samples were re-sintered in order to verify the time influence in the mullitization process during the sintering. The mixture process was optimized using the orbital disc mill coated with alumina and calcination of the mixed α- alumina and silica powder at temperature of 1100 C during 4h. The microstructure of the sintered ceramic compacts was characterized by Scanning Electron Microscopy (SEM). The phase characterization of the sintered compacts was carried out by X-ray diffraction. The relation between the alumina content in the sintered mullite and the lattice parameter a was calculated by the relation m = 144.5a 1029.5, where a is the lattice parameter. The effect of the composition to the electric conductivity of the mullite was analyzed by measures of electric resistivity at room temperature. This study shows that working with the experimental conditions described is possible to manufacture mullite with low density, microstructure presenting equiaxial grains with sizes varying in the range of 2 to 3 μm, and the composition varying of 70 to 74 wt.% of alumina that corresponds the mullite 3:2 and 1.64:1, respectively. These results also show that sintering time is an essential factor to be considered in order to reach a high mullitization content when it is intended to get mullite by sintering of α-alumina and silica powders at temperature of 1650C.

ASSUNTO(S)

processos de fabricacao fabricação de corpos cerâmicos,pó de sílica,sinterização,microestrutura dos corpos cerâmicos,calcinação.

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