喷雾干燥-流化床脱硝法制备Bi系超导前驱体粉末

Preparation of Bi-Based Superconductor Precursor Powder by a Spray-Dry+Fluidized Bed Denitration Technology

介绍了一种制备2212相Bi系超导前驱体粉末的新方法。首先,将组成为Bi:Pb:Sr:Ca:Cu=1.84:0.34:1.91:2.03:3.06的五种金属硝酸盐混合溶液通过喷雾干燥得到混合硝酸盐粉末蓝粉,喷雾干燥的溶液浓度按Bi3+浓度表示为0.34mol?L?1,干燥器进出口空气温度分别为563和413K。然后蓝粉在流化床中700℃下进行脱硝得到褐粉,脱硝过程为扩散控制。最后褐粉经800℃焙烧48h后得到Bi系2212相超导前驱体粉末黑粉。研究确定了各阶段粉末形成的最佳工艺条件,通过粒度分析仪、SEM和XRD等测试手段表征了粉体的形貌和晶型特征,观察了粉末由非晶型到2212相的变化过程。结果表明,新方法所制得的黑粉具有明显的2212超导相片层状结构和特征晶型,符合Bi超导材料对前驱体粉末的要求。

A novel process of synthesizing the Bi-based 2212 phase high-temperature superconductor precursor composite powder was developed. The process proposed is consisted of three preparation steps as follows. Firstly, mixed nitrate solution with nominal composition Bi：Pb：Sr：Ca：Cu - 1.84：0.34：1.91：2.03：3.06 was spray-dried to form composite nitrate powder （blue powder）. During which, according to the concentration of Bi^3＋ in the mixed solution, the mixed nitrate solution with concentration of 0.34mol Bi^3＋.L^-1 and the inlet and outlet gas temperatures of 563 and 413 K respectively were used for the spray-dry process. Secondly, the brown powder of metal oxide was prepared by denitration of the composite nitrate powder in a fluidized-bed reactor at 700℃, and it is shown that the denitration is a diffusion-controlled process. Finally, the oxide was calcined at 800℃ for 48 h to get black powder. The optimum operation conditions of the above three preparation steps were studied. The morphology, particle size, crystal structure and the phase compositions of powders in different steps were characterized by size analyzer, SEM, and XRD techniques separately. The formation of 2212 phase from amorphous-like phase during the preparation process was exhibited by SEM images and XRD patterns. Results indicate that the obtained black powder shows apparent plate-like crystal structure mainly containing 2212 phase, and it satisfies the requirement of the B i-based superconductor precursor powder.