Zr-B固相反应中B的扩散动力学研究

Diffusion Kinetics of B Element in Zr-B Solid State Reactions

将金属Zr块埋在B粉末中在800~1500℃温度下反应2~16 h,使用XRD法研究金属Zr块表面反应产物的物相构成,使用SEM观察抛光截面的产物层形貌,采用EDS分析Zr、B元素分布,测量产物层厚度,根据菲克第二定律采用线性拟合法计算B向金属Zr中反应扩散动力学。研究结果表明:在800℃2 h条件下进行反应,金属Zr块表面生成少量ZrB_(2),抛光截面上未观察到明显的产物层生成。当温度升高到1200~1500℃反应时间延长到4~16 h时,抛光截面上生成了厚度均匀连续的ZrB_(2)产物层,其厚度随反应温度升高和反应时间延长而增加。计算得出产物层增厚的时间指数n=0.434,B元素扩散激活能Q=152.0 kJ/mol,扩散系数指前项D_(0)=1743.4×10^(-12)m^(2)/s。

Metallic Zr bulks were set in B powder beds to carry out solid state reactions at temperatures ranging from 800 to 1500℃for different times between 2 and 16 h.Phase components in the reaction products formed on the Zr bulk surfaces was checked by XRD.Morphology of the product layers was observed by SEM on polished sections.Distribution of Zr and B elements was analyzed by EDS.Thickness of the product layers were measured.Reaction diffusion kinetics of B element was calculated according to the Fick's second law.The results showed that a small amount of ZrB_(2) was formed on the Zr bulk surfaces after reaction at 800℃ for 2 h.But the polished sections of the corresponding samples observed no formation of a product layer.When the temperatures were raised to 1200℃and above(but below 1500℃),reactions for 4~16 h could generate continuous ZrB_(2) product layers with uniform thickness which increased both with time and with temperature.Time index of thickening effect of the product layer was calculated to be n=0.434;the diffusion activation energy of element B was Q=152.0 kJ/mol;The diffusion coefficient term D_(0)=1743.4×10^(-12) m^(2)/s.