致密ZrO2陶瓷板表面金属层的熔盐电解法制备

Preparation of Metal Layer on Surface of Dense ZrO2 Ceramics Plate by Molten Salts Electrolysis

致密ZrO2陶瓷具有良好高温强度、耐磨性,以及导电、导热特性,而致密ZrO2陶瓷板的表面金属化是改善其与金属间的钎焊润湿性,促进其应用的重要途径。熔盐电解法是一种通过加载电压直接将金属从其氧化物中还原实现金属冶炼的方法。在CaCl2-NaCl混合熔盐中,以致密ZrO2陶瓷板为阴极,石墨为阳极,在850℃,3.1 V电压条件下对致密ZrO2陶瓷板进行电解,表面原位生成致密的锆金属层。采用X射线衍射（XRD）研究了不同电解时间、不同表层深度的物相组成,并计算分析表层不同深度电解产物的含量。结果显示,ZrO2的电解脱氧冶金反应由外向内进行,形成ZrO2,Zr3O和Zr共存的电解脱氧层。随电解时间增加,脱氧层的深度增加,表面氧含量减小。当电解时间超过8 h,在致密ZrO2陶瓷板表面形成锆金属层。初步探讨了熔盐电解法机制,提出氧化锆陶瓷表面氧的离子化是受到了强制双电层吸引的设想。

The dense ZrO2 ceramics have good high temperature strength, abrasion resistance, as well as conductive and thermal con- ductivity. Surface metallization of dense ZrO2 ceramic plates is an important way to improve the brazing wettability between them and the metal. The molten salts electro-deoxidization is a metal smelting method to produce metal directly from metal oxide by loading volt- age. By using CaCl2-NaCl molten salts as electrolyte, dense ZrO2 ceramics as cathode and graphite rod as anode, the ceramic plates were electrolyzed at 850 ℃ and 3.1 V, and a Zr metal layer was obtained on the ZrO2 ceramic plate by in-situ electro-deoxidization. The phase constitutions of the ceramics surfaces layers with different electro-deoxidization time, as well as in different depth, were studied by means of X-ray diffraction （XRD） techniques, and the contents of various phases were calculated. The result showed that the electro-deoxidization took place from surface of the ceramic plate, and an electro-deoxidization layer containing ZrO2, Zr30 and Zr formed. With increasing electrolysis time, the thickness of electro-deoxidization layer increased, and oxygen content decreased. When the electrolysis time exceeded 8 h, the zirconium metal layer was formed on the surface of the compact ZrO2 ceramic plate. The mecha- nism of the electro-deoxidization was analyzed preliminarily. The hypothesis was proposed that the ionization of oxygen atoms resulted from zirconia surface being attracted by the forced electric double layer.