ガラス結晶化物の化学的耐久性

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Glasses of the compositions, Li_2O・1.5 SiO_2,Li_2O・2SiO_2,Li_2O・ 3SiO_2,and Li_2O・3SiO_2・0.1 M_mO_n (M_mO_n=Na_2O K_2O, Al_2O_3 or ZrO_2) in mole ratio, each with or without platinum, were prepared in a form of rectangular plate of 20x40x2mm. After polished with 1500-grit Al_2O_3 powder to make smooth surfaces, these glasses were reheated up to 900℃ at the constant rate of 5℃/min. The polycrystalline materials thus obtained were exposed to various solutions, mainly to 5% HCl solution of 90°±2℃ for various times. The chemical durability was reported in terms of weight loss per unit surface exposed. Identification of crystalline phases in the specimens by an X-ray diffractometer and electron microscopicobservation of the surface of specimens were made before and after the durability test in order to correlate the durability to the microstructure of the crystallized specimens. The results obtained were summarized as follows : 1 ) Effects of the basic composition. For the two component system, i. E., Li_2O・ 1.5 SiO_2,Li_2O・2SiO_2,and Li_2O・3SiO_2,the durability, in general, increased with the increase in SiO_2 content, regardless of the presence of Pt. The durability of the crystallized specimens was much higher than that of their mother glasses. An exception was the Li_2O・2SiO_2 crystallized specimen without Pt, which showed the very poor durability. 2) Effects of the addition of Pt. The poor durability of the specimen above described was found to be due to the presence of micro-cracks on the surface of the crystallized specimen. The addition of Pt as a nucleating agent in an appropriate amount (0.005-0.01% in weight) was found effective for suppressing the development of the cracks during reheating, thus improving the durability. 3) Effects of addition of the third components. Of the four components, e. G., Na_2O, K_2O, Al_2O_3,and ZrO_2,Na_2O and K_2O lowered the durability markedly. This was attributed to the concentration of these components in crystal grain boundaries (matrix glass) of the crystallized specimens, which was confirmed by an electron microscope. The matrix glass was easily attacked by 5% HCl. 4) Effects of the kind of test reagent. The durability to various test reagents such as pure water, 5% H_2SO_4,5% NaCl, 5% NaOH and 5% Na_2CO_3,besides 5% HCl, was also measured with the glass of the composition Li_2O・3SiO_2 with 0.01% Pt. In general, the attack of the alkaline solutions was much more severe than that of pure water and the acid solutions.
社団法人日本セラミックス協会の論文
1963-07-01

ガラス結晶化物の化学的耐久性

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