Efeito do tratamento superficial na devitrificação e dissolução da silica vitrea / Effect of surface treatment on devitrification and dissolution of vitreous silica

AUTOR(ES)
DATA DE PUBLICAÇÃO

1997

RESUMO

The effect of surface stress and roughness, produced by polishing process with abrasive powder, was investigated on the devitrification and dissolution of silica glass. The characterization studies of the silica glass treated by grinding, polishing and etching and their effect on the devitrification were conducted by X-ray diffraction, optical and electronic microscopy, inftared spectroscopy and small-angle X-ray scattering. The samples were heat treated at 1250°C for a period of 15 min and 150 mino X-ray diffraction and optical microscopy observation showed more intense devitrification effect into a-cristobalite for higher degree of surface roughness, and the samples treated with HF etching presented the lowest devitrification effect. The silica glass surfaces exposed to the furnace atmosphere (air) presented a much bigger crystallization effect, inversely to the bottom surface in contact with a silica base. The dissolution of silica glass by chemical etching (HF solutions) was studied, and the results showed that dissolution rate is dependent on the surface roughness, HF concentration and etching time. For example, the dissolution rate of samples treated with SiC #320 and ?Ce IND. 2??O IND. 3?, were estimated as 0.16 ?mu?m/min and 0.14 ?mu?m/min, respectively. The results showthat sampleswith longtime etching(~1000 min) revealed grain-like etch pattern of 4 to 10 11min diameter, which suggests reveals the existence of micro-stress in the amorphous structure. This "amorphous grains or sub-grains" might be correlated with atomic into inhomogeneities of amorphous silica structure

ASSUNTO(S)

microscopia eletronica raios x - difração microscopia otica cristalização raios x - espalhamento a baixo angulo x-rays silica vitreo retificação e polimento vitreous silica electron microscopy grinding and polishing optical microscopy crystallization espectroscopia de infravermelho x-ray small-angle scattering infrared spectroscopy

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