硼砂对自蔓延高温合成ZrB2粉体的影响

以ZrO_2、Mg、B_2O_3及Na_2B4O_7为原料,采用自蔓延高温合成技术制备ZrB2粉体。通过FactSage7.0软件计算,从热力学角度研究了该反应体系发生自蔓延反应的可能性。采用X射线粉末衍射物相分析仪、场发射电子扫描电镜-能谱分析对最终产物的物相组成及显微形貌进行检测。分析结果显示,过量的Mg、B_2O_3可有效提高产物中ZrB_2的含量,Mg和B_2O_3分别过量40%(质量分数)、30%(质量分数)为Mg-ZrO_2-B_2O_3体系的较佳配比。基于上述优化配比,研究了用无水硼砂(Na_2B_4O_7)替换原料中B_2O_3对产物ZrB_2含量及晶粒尺寸的影响,当替换量达到15%(质量分数)时,ZrB_2的含量最高,并且随着Na_2B_4O_7替换量的增加,产物的晶粒尺寸由2μm减小至不足0.5μm。

Effect of Na2B4O7 on ZrB2 Powder Prepared by Self-propagating High-temperature Synthesis

ZrB2 powders were prepared by the self-propagating high-temperature synthesis (SHS) using ZrO2 ,Mg ,B2 O3 and Na2B4O7 as main raw materials .Based on thermodynamic calculation ,the feasibility of the SHS was studied by FactSage7.0. The phase composition and microstructure of the final product were characterized with X-ray diffraction (XRD ) and field-emission scanning electron microscopy (FESEM) with energy dispersive spectrometer (EDS) .The ZrB2 purity of the final product could be improved when the raw materials were mixed with extra amount of Mg and B2O3 ,it was found that the optimum extra amounts of Mg and B2O3 were 40wt％ and 30wt％ ,respectively .Based on the optimum ratio ,the effect of replacing B2O3 by Na2B4O7 on purity and microstructure of ZrB2 was studied .When the replacement ratio was 15％ ,the purity of ZrB2 was the best ,the grain size of ZrB2 decreased from 2 μm to less than 0.5 μm with the increasing Na2B4O7 replacement ratio .