由硝酸盐尿素配合物前驱体制备过渡金属氮化物粉体的研究

采用硝酸盐尿素配合物为原料,在氨气中氮化,制备了氮化铬(CrN)和氮化铁(ζ-Fe₂N)粉体.结果表明该配合物是一种有用的前驱体,可用于制备其它过渡金属氮化物.采用红外光谱(FTIR),热分析(TG-DSC)等方法对硝酸盐尿素配合物的性质进行了表征.在配合物分子中,尿素取代了结晶水的位置,与金属离子通过氧原子形成配位键(C=O→M),在加热时分解形成多孔隙的氧化物颗粒聚集体,并与氨气发生气固反应,生成过渡金属氮化物.对不同反应温度和反应时间合成的粉体用X射线衍射(XRD)和扫描电镜(SEM)进行了表征.研究了反应温度和反应时间对不同金属的硝酸盐尿素配合物在氨气中氮化反应的影响,结果表明FeOC(NH₂)₂]₆(NO₃)₃转变成ζ-Fe₂N的反应速度快,反应温度低,CrOC(NH₂)₂]₆(NO₃)₃完全转变成CrN则需要较长的反应时间.

Synthesis of Transition Metal Nitride Powders from Metal-urea NitrateComplex Precursors

A novel and general route to synthesize transition metal nitrides (CrN and ζ-Fe₂N) from metal-urea nitrate complexes was presented. Metal-urea nitrate complex is proved to be a useful precursor to prepare transition metal nitrides. FTIR and TG-DSC were adopted for the characterization of the complexes. Urea molecules bond with metal ion through oxygen-to-metal coordinate bonds. The transformation from metal-urea nitrate to metal nitride is thought through the reaction between oxide powder and ammonia gas after its pyrolysis. The influences of the reaction temperature and the holding time on the nitridation of different metal-urea nitrate were investigated by using XRD. The holding time for the complete nitridation of iron-urea nitrate is shorter, compared with that for chromium-urea nitrate, and the temperature needed by the former is lower. The morphology of nitride powders was observed by using SEM.