| Summary: | 碩士 === 遠東技術學院 === 機械研究所 === 94 === In general, the glasses are not heated by microwave induction. It was found that some raw materials of phosphate glass could be heated directly by microwave. The purposes of this research are to study on the glass-formation mechanism, relative constituents and its chemical durability properties.
Based on the basic composition 80NH4H2PO4-15Li2CO3-5Ca(OH)2 (wt%), the phosphate glass phase can be formed by 900W microwave heating for 6min with additional water. The chemical reactions between raw materials and water are found at room temperature. At first, H3PO4 and NH3 were produces due to the reaction between NH4H2PO4 powder and water. In The corrosion resistance of advanced, the product H3PO4 could be reacted with Li2CO3 and then to result CO2 gas, which cause the weight loss of the mixed powders.
The microwave heating process is divided into three steps. First of all NH4H2PO4 is melted and about 190℃ and then NH3 gas is decomposed. The weight loss is 15% due to NH3 gas out. The second reaction is that Ca (OH) 2 powder is reduced to CaO and H2O. The last one is the decomposition reaction of Li2CO3. After three dissolution reactions the phosphate glass phase can be formed by the residual products about 700℃ in microwave melting process.
Based on the compositions 80NH4H2PO4-15Li2CO3-5Ca(OH)2(in wt%) and 80H4P2O7-15Li2CO3-5 Ca(OH)2 , The effect of microwave time on the densities of the phosphate glass have the same trends, that the densities are decreased as the microwave time increased. The density of the former is decrease from 3.83 g/cm3 to 2.746 g/cm3, and the one of the latter is from 2.65g/cm3 to 2.05 g/cm3. But the variation tendency of the hardness is different from the density, the hardness of the former is dropped to 285HK from average hardness value 337.1HK, and the latter rises from 210HK to 285HK. The corrosion resistance of the phosphate glass is improved by adding the boehmite powder in the aqueous solution, but is useless in acid and alkali solution. The corrosion resistance of the phosphate glass adding with boehmite gel is invalid in aqueous, acid and alkali solutions.
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