頁籤選單縮合
題名 | Studying the Divitrification of Calcium Phosphate Glasses with Various Ca/P Molar Ratios |
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作者 | Dong,Guo-chung; Yao,Chun-hsu; Lee,Jinn-shing; Huang,Chin-wang; | 書刊名 | 醫學工程 |
卷期 | 10:6 1998.12[民87.12] |
頁次 | 頁39-44 |
分類號 | 410.1644 |
關鍵詞 | Calcium phosphate glasses; Devitrification; Crystalline morphology; |
語文 | 英文(English) |
英文摘要 | The purpose of this study was to investigate the crystalliztion proerty of calcium phosphate glasses with different Ca/p molar ratios. In the current research, various calcium phosphate glasses were prepared with a series of Ca/p molar ratios ranged from 0.25 to 0.70. After the preparation of these materials, the devitrification mechanism was determined by suing non-isothermal DTA (differential thermal analysis ) and XRD (x-ray diffraction analysis). In addition, the crystalline morphology and characteristics were examined by SEM (scanning electron microscopy), and EDX (energy dispersive spectrometer). In this work, it was found that the devitrification mechanism changed from bulk nucleation to surface nucleation. The transition was due to the descent of Ca/P molar ratio in calcium phosphate glasses composition. In the DTA analysis. the major part of exothermic peaks showed sharp form in the illustation, which indicated that the crystallization process was mainly dominated by bulk nucleation mechanism. However, few broad peaks in the analysis were still observed, the appearance of these board peaks revealed that the surface nucleation mechanism was credibly occurred in these glasses, too. The modified Kissinger equation has been widely used for the kinetic study of the non-isothermal crystallization glasses in the recent researches. In this study, the tendency was also confirmed by comparing the difference of exothermic peak on fine and coarse powder samples. Thus, the experimental condition could be modified appropriately to calculate the activation energty (Ea.) of surface nucleation by Kissinger equation. The results in our study showed that the activation energy (Ea.) increases with the decreasing Ca/P molar ratio. These values ranged from 254 KJ/mole to 351 KJ/mole and this result was agreed with that of Y. Abe's research, 459.8 KJ/mole ∼ 125.4KJ/mole. In addition, different morphologies of the -Ca(PO3)2 crystal were observed on the surface of glasses with different nucleation mechanism and compostion. |
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