低温固相反应法制备NiFe_2O_4纳米粉及机理研究

采用机械研磨方法制备前驱体,再将前驱体进行煅烧得到NiFe2O4纳米粉.重点研究了煅烧温度对粉体物相和形貌的影响以及固相反应过程与机理.结果表明:煅烧过程中晶粒长大活化能为12.08 k J·mol-1,主要以界面扩散为主;煅烧温度为700℃时粉体团聚严重,颗粒之间存在片状非晶态化合物,结晶度低;750℃煅烧1 h得到的NiFe2O4纳米粉物相单一,粒径分布在35~85 nm之间,温度过高时晶粒明显长大;机械研磨洗涤后前驱体主要由Fe2O3,NiO和NiFe2O4组成,反应产物结晶度低,反应不完全;盐颗粒的存在能抑制晶粒生长,减小产物粒径.

Synthesis of NiFe2 O4 Nanopowder by Low-Temperature Solid-State Reaction and Its Mechanism

The precursors ground by planetary ball milling at room temperature were calcined to obtain NiFe₂O₄ nanopowder. The effect of calcination temperature on the particle phase and morphology and the mechanisms of solid-state reaction were studied in detail. The results show that the activation energy of grain growth during calcination process is 12.08kJ·mol^-1， indicating that the predominant mass transport mechanism is interfacial diffusion. The particles calcined at 700℃ showed strong agglomeration and low crystallinity with flaky amorphous compounds. The NiFe₂O₄ nanopowder calcined at 750℃ for 1h is of single phase with a particle size range of 35-85nm. The grains grew obviously when the calcination temperature increased to over 800℃. The main compositions of the precursor are Fe₂O₃， NiO and NiFe₂O₄. The low crystallinity of reaction products indicates the solid state reaction is not complete. The existence of salt particles can suppress grain growth， and thus decrease the particle size.