CaO-BaO-SiO_2-TiO_2系统溶胶涂液的制备和凝胶化过程

Study on the Sol Preparation for Dip coating and Gel Formation Process in CaO BaO SiO 2 TiO 2 System

采用溶胶－凝胶工艺制备０．１ＣａＯ－０．１ＢａＯ－ＸＳｉＯ２－（０．８－Ｘ）ＴｉＯ２和ＹＣａＯ－（０．３－Ｙ）ＢａＯ－０．３ＳｉＯ２－０．４ＴｉＯ２（Ｘ＝０～０．５，Ｙ＝０～０．３摩尔分数）两组四元系统浸涂液。根据粘度变化和凝胶时间研究了组成、水和醋酸加入量对溶胶涂液稳定性的影响，得出了配制稳定期长的浸涂液的配比。利用红外光谱和Ｘ－射线衍射（ＸＲＤ）探讨溶胶形成过程和凝胶向玻璃态转变过程中的结构变化。结果表明：溶液中ＣＨ３ＣＯＯ－取代醇盐中的ＯＲ基团分别与Ｓｉ４＋和Ｔｉ４＋配位，形成反应活性不同于原醇盐的新的前驱体醇盐；经５００°Ｃ热处理后凝胶的红外光谱中出现由Ｔｉ—Ｏ—Ｓｉ伸缩振动所引起的吸收带。ＸＲＤ谱证实６０°Ｃ干凝胶中有醋酸盐晶体，５００°Ｃ热处理后，这种晶体消失，凝胶中生成Ｂａ２ＴｉＯ４晶相。

The aim of this paper is to prepare an alkaline resistant coating by sol gel method for glass fibre used in cement reinforcement. Two groups of sols for dip coating: 0.1CaO 0.1BaO X SiO 2 (0.8- X )TiO 2 and Y CaO (0.3- Y )BaO 0.3SiO 2 0.4TiO 2 ( X =0￣ 0.5 , Y =0￣ 0.3 mol fraction) were synthesized by sol gel. The effect of composition, water and acetid acid amount on the stability of the sol was studied according to sol viscosity and gelling time. The optimum technology for obtaining stable sols has been investigated. The process of sol preparation and gel to glass transition has been discussed by using IR and X ray diffraction spectra. The results indicated that acetate replaced OR group to coordinated with Si 4+ and Ti 4+ and formed new precursors having reactivity different from the former. In addition the streching vibration peak due to Ti—O—Si was observed from the IR speetrum of these gels heated at 500°C. XRD spectra illustrated that acetate crystals were formed in the gels at 60°C. After heat treating at 500°C the acetate crystals disappeared and Ba 2TiO 4 crystal was formed.