燃烧合成法制备NdB6超细粉体及反应机理

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。

Preparation of Ultra-fine NdB6 Powders by Combustion Synthesis and Its Reaction Mechanism

Ultrafine powders NdB₆ were prepared by combustion synthesis with B₂O₃, Nd₂O₃ and Mg as raw materials. The effects of reaction atmosphere, sample pressure and raw materials ratio on the reaction product morphology 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.