リン酸塩埋没材の熱的挙動 : 第 4 報 MgO-NH_4H_2PO_4-SiO_2 系水和硬化体の熱的挙動
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Thermal behavior of experimental and commercial phosphate bonded investments, which had various compositions of MgO, NH_4H_2PO_4 and SiO_2, was investigated by using TG-DTA, X-ray diffraction and IR spectrum. The products after setting of the experimental investments were MgNH_4PO_4・6H_2O (6H), Mg(NH_4)_2H_2(PO_4)_2・4H_2O (4H) and Mg_3(NH_4)_2H_4(PO_4)_4・8H_2O (8H). As the contents of SiO_2 or the ratio of MgO to NH_4H_2PO_4 in the investments became high, 6H was mainly formed. The kinds of products after heating up to 900℃ depended on the molar ratio (R) of (MgO)_2 to P_2O_5 in the investments. Mg_2P_4O_<12>(MP_2) Mg_2P_2O_7 (MP) and Mg_3(PO_4)_2 (M_3P_2) were formed in investments A(R=0.5), B(R=1) and D(R=3), respectively. MP and M_3P_2 were formed in investment C(R=2). In TG curves for any of the experimental investments, a rapid weight decrease occurred around 100℃ and then gradual decrease continued up to 500℃ and several endothermic peaks were observed in their DTA curves, which corresponded to decomposition of the products after setting. Crystallization of MP_2 occurred above 400℃ in investment A. However, that of MP and M_3P_2, which caused one or two exothermic peaks in the DTA curves of investments B, C and D, occurred above about 650℃. The ratio of MgO to NH_4H_2PO_4 was between 1.3 and 3 in the commercial investments. Thermal behavior of the investments was similar to that of the experimental investments C and D with high SiO_2 content.
- 九州歯科学会の論文
- 1987-02-25
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- リン酸塩埋没材の熱的挙動 : 第 4 報 MgO-NH_4H_2PO_4-SiO_2 系水和硬化体の熱的挙動 : 主論文の要旨
- リン酸塩埋没材の熱的挙動 : 第 4 報 MgO-NH_4H_2PO_4-SiO_2 系水和硬化体の熱的挙動