用溶胶-凝胶法制备Al_2O_3涂层工程陶瓷的表面改性研究

STUDY OF MODIFICATION OF Al_2O_3-COATED ENGINEERING CERAMICS BY SOL-GEL PROCESS

分析了溶胶 -凝胶法制备Al2 O3 溶胶的适宜工艺条件 ,在氧化铝基陶瓷基体上成功地制备了Al2 O3 涂层 ;利用X射线衍射分析和差热分析 (DTA)方法对Al2 O3 凝胶粉末的相变过程进行了研究 .通过分析精磨、热处理、Al2 O3 一次和二次溶胶涂层 4种试样的抗弯强度测量值对材料总体性能进行了估计 .结果表明 :Al2 O3 涂层工程陶瓷可以提高基体的抗弯强度而降低其分散性 ,效果好于单纯的热处理 .

The Al2O3 sols were selected and prepared under the optimized conditions. The phase development of Al2O3 gel powders during heat treatment was investigated by XRD and DTA. The mono-layer and double-layer coatings were prepared by using dipping method on carefully cleaned ceramics substrate. The strength of the coated materials was estimated on the basis of flexural strength. The theoretical model was put forward with the help of SEM observation on the free surface of uncoated, heat-treated and coated specimens and the cross-section of coated specimens. The results show that the clear stale sols can be obtained at 70-90°C with (100-200):1 of n(H2O):n(Al3+) and (0.2-0.28):1 of n(H+):n(Al3+). After heat treatment at 1200°C for 1 h, the strength of the specimens with double-layer and mono-layer coatings is increased by 33% and 29% respectively and the strength distribution is decreased considerably. The smooth and crack-free coatings combine with the substrates tightly without clear interface. Compared with mono-layer coating, double-layer coating can fill in surface microcracks more effectively. The strengthening mechanism of sol-gel coatings is attributed to the decreased crack length and/or the blunted crack tip.