固相反应合成Ba_(1.0)Co_(0.7)Fe_(0.2)Nb_(0.1)O_(3-δ)的动力学(英文)

Kinetics of Synthesis of Ba_(1.0)Co_(0.7)Fe_(0.2)Nb_(0.1)O_(3-δ) through Solid-Solid Reaction

依据新的固相反应模型,采用非等温热重和差示扫描量热法研究了由BaCO3和Co3O4、Fe2O3、Nb2O5粉末固相反应合成Ba1.0Co0.7Fe0.2Nb0.1O3-δ的动力学.考察了高速机械搅拌方式混料和球磨方式混料对合成动力学的影响.结果表明,反应过程分为两个阶段:第一阶段为BaCO3和Co3O4、Fe2O3、Nb2O5之间的加成反应;第二阶段为加成反应生成的BaCoO3、BaFeO3和BaNbO3三相之间固溶生成均相的Ba1.0Co0.7Fe0.2Nb0.1O3-δ,此过程中伴随有氧的脱出.应用修正的模型对实验结果进行了拟合,实验数据和理论模型符合良好.高速机械搅拌样品加成反应阶段的活化能为376.76kJ·mol-1,仅为球磨样品加成反应阶段活化能494.76kJ·mol-1的3/4.高速机械搅拌工艺促进了离子的扩散,有利于后续反应的进行,是更为有效、节能、环保的混料方式.

The mechanism of solid-solid reaction between BaCO3 and Co3O4/Fe2O3/Nb2O5 has been investigated by means of non-isothermal thermogravimetry and differential scanning calorimetry （DSC） under flowing air gas conditions at atmospheric pressure with a new solid-solid reaction model. The effects of high speed agitating mixing and ball-milling mixing processes on the synthesis kinetics were also studied. The synthesis kinetics of Ba1.0Co0.7Fe0.2Nb0.1O3-δ from the BaCO3 and Co3O4/Fe2O3/Nb2O5 particles was calculated by applying the modified model. The results indicated that the overall reaction process was considered involving two stages： addition reaction between BaCO3 and Co3O4/Fe2O3/Nb2O5 particles in the first stage and solution reaction between BaCoO3, BaFeO3, and BaNbO3 to form a homogeneous Ba1.0Co0.7Fe0.2Nb0.1O3-δ phase in the second stage. The new model matched well with the experimental data. The apparent activation energy of addition reaction stage of the high speed agitating mixing sample was estimated to be 376.76 kJ·mol-1, which was only 3/4 of that of the ball-milling mixing sample （494.76 kJ·mol-1）. These results indicated that the high-speed agitating process could enhance atomic diffusion and facilitate the subsequent reaction, thus it is believed as a more effective, energy saving, and environmentally benign mixing process.