5Na2O-20TiO2-32P2O5-43CaO系统玻璃在690℃核化和730℃晶体生长的热处理后,可以得到CaTi_4(PO4)6和Ca3(PO4)2两种晶相,经酸滤去Ca3(PO4)2相后,可获得主晶相为CaTi4(PO4)6的多孔微晶玻璃.本文介绍了一种扩大孔径的方法,在该组成玻璃微晶化后及酸滤析之前,在更高的温度880℃下作过析晶处理,此两析晶相能自发地进行固相反应,生成TiO2和Ca2P2O7,后者容易被酸滤析,使得更多的钙和磷自微晶玻璃体中被酸溶出,从而增大了多孔微晶玻璃的孔径.本文还应用热力学第一近似方程,对过析晶过程中的固相反应的自由焓变化作了估算,其数值为-1394kJ/mol,说明在过析晶温度下,固相反应能自发地进行,试样在过析晶前后的XRD物相分析的结果验证了此固相反应机理.本文还利用Johnson-Avirami-Mehl公式对析晶的动力学参数作了近似估算.其析晶活化能为584.7kJ/mol,晶化指数为3.2,说明试样的析晶是以整体析晶的方式进行.此计算的结果也符合试样形貌的SEM观察,即过析晶过程使得整体微晶玻璃的孔径增大.
Porous glass ceramics with CaTi4(PO4)6 as the main crystalline phase could be produced by heat-treating the 5Na2O-20TiO2-32P2O5-43CaO glass system at 690℃ and 735℃ separatively and
then by acid-leaching the crystallization product Ca3(PO4)2. In this paper, a method of enlarging the size of pores was introduced. A high temperature heat-treatment (880℃), that called post-crystallization, could be inserted
into the processes between crystallization and acid-leaching. In the post-crystallization, there was a solid reaction where the CaTi4(PO4)6 and 5Ca3(PO4)2 reacted and then products TiO2 and Ca2P2O7 produced.
The later phase could be easily leached from the glass-ceramic. The pores became larger, since more Ca and P were leached. In the present study, the change in free enthalpy of the solid reaction was estimated as --333Kcal/mol by applying the approximate
first thermodynamic equation. The phase analysis, XRD before and after post-crystallization, confirmed that this solid reaction
could happen spontaneously. The dynamic parameters for crystallization activation energy and reaction index were calculated as 584.7kJ/mol and 3.2 respectively by applying Johnson-Arirami-Mehl equation while implied that the sample was crystallized
in bulk. This calculation was also confirmed by the observation under SEM, that the pore size enlarged in the whole area of the sample after post-crystallization.
参考文献
| [1] | Hosono H, Abe Y. Mater. Res. Bull., 1994, 29 (11): 1157--1162. [2] 严建华, 冯乃谦, 封孝信. 玻璃与搪瓷, 2000, 28 (4): 15--21. [3] Kasuga T, Kume H, Abe Y. Am. Ceram. Soc., 1997, 80 (3): 777--780. [4] 王德平, 黄文#[49], 周~~萘, 等. 建筑材料学报, 2003, 6 (1): 45--50. [5] 温元凯, 邵~~俊, 王三山, 等, 金属学报,1979, 15 (1): 98--108. [6] 叶大伦. 实用无机热力学数据手册, 第一版. 北京: 冶金工业出版社,1981. 212--977. [7] 余尧楚, 姜中宏(YU Yao-Chu, et al). 无机材料学报(Journal of Inorganic Materials), 1997, 12 (3): 265--272. [8] Johnson W A, Mehl R F. Trans. AIME, 1939, 135: 416--458. [9] 作花济夫. ガラス非晶质の科学, 第一版. 日本东京: 内田老鹤圃, 1983. 263--270. [10] Marotta A, Buvi A, Pemice P. Phys. Chem. Glasses, 1980, 21 (1): 94--99. |
- 下载量()
- 访问量()
- 您的评分：
-
10%
-
20%
-
30%
-
40%
-
50%