Titanium-Containing Precipitates in Corundum of Brown Aluminous Abrasives after Heat-Treatments in Air

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  • 褐色アルミナ質研削材 (Ti<sup>3+</sup>固溶コランダム) を酸化加熱した場合にコランダム結晶中に析出する結晶相
  • カッショク アルミナシツ ケンサクザイ Ti3 コヨウ コランダム オ サンカ カネツ シタ バアイ ニ コランダム ケッショウ チュウ ニ セキシュツ スル ケッショウソウ

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The corundum grains of single crystal 60 to 80μm in size, which were prepared from commercial brown aluminous abrasives by removing their impurity phases, were heated in air at temperatures between 1, 200° and 1, 630°C for various hours. Phases of the precipitates given by the oxidation of Ti3+ ions in the corundum were examined by the X-ray diffraction method and by optical microscopy. Only rutile was found within the corundum crystals in any of the specimens, although β-Al2TiO5 is stable above about 1, 300°C. β-Al2TiO5 was found on the surfaces of the corundum crystals after long heat-treatments at high temperatures. The β-Al2TiO5 was given by the titanium moving out to the surfaces from the rutile which had precipitated within the corundum crystals. The cause of the fact that the rutile did not give β-Al2TiO5 within the corundum crystals was discussed. Formation of β-Al2TiO5 from a mixture of Al2O3 and TiO2 powders was found to be supressed by the addition of a small amount of CuO. A trace of Cu was contained in the corundum grains.

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