燃烧合成法制备NdB6超细粉体及反应机理

Preparation of Ultra-fine NdB_6 Powders by Combustion Synthesis and Its Reaction Mechanism

以B2O3、Nd2O3和Mg为原料,采用燃烧合成法制备出NdB6超细粉体。考察了反应气氛、制样压力和物料配比对反应产物微观形貌和物相的影响。采用XRD、SEM对产物进行了表征,结果表明:燃烧产物由NdB6、MgO以及少量Mg3B2O6和Nd2B2O6组成,稀硫酸处理去除可溶性成分后,产物为单一的NdB6相,纯度为99.1%。随着制样压力的增大,NdB6颗粒尺寸逐渐变小。制样压力为20 MPa时,制备的NdB6粉末平均粒度小于500 nm。Mg-B2O3-Nd2O3三相反应历程:首先Mg还原Nd2O3生成单质Nd和MgO,然后引发Mg还原B2O3生成单质B和MgO,同时生成的Nd和B反应得到NdB6,反应的表观活化能为691.59 kJ/mol,反应级数为3.2。

Ultrafine powders NdB6 were prepared by combustion synthesis with B2O3, Nd2O3 and Mg as raw mate- rials. The effects of reaction atmosphere, sample pressure and raw materials ratio on the reaction product morphol- ogy and phases were studied. Characterizations by XRD and SEM show that the products consist of NdB6, MgO and a little amount of Mg3B2O6 and Nd2B2O6. After reaction with sulphuric acid at low concentration to eliminate the latter three components, the pure NdB6 is obtained （purity 99.1%）. As the preparation pressure increases, the NdB6 particle sizes become small. When the sample pressure is 20 MPa, the average particle size is less than 500 nm. The preparation reaction process is as follows： firstly, Mg reduces Nd2O3 to generate Nd and MgO; and then, the reaction between Mg and B2O3 are ignited to generate B and MgO; at the same time, the generated Nd and B are reacted to produce NdB6. The apparent activation energy of the reaction is 691.59 kJ/mol and the reaction order is 3.2.