Nb_2O_5·nH_2O的制备研究

Preparation of Nb_2O_5 · nH_2O

以草酸铌为前驱体,分别在水溶液体系、乙二醇-水的混合体系中水解制备水合氧化铌。通过XRD,TG/DSC,SEM等分析方法表征了在不同体系中所合成产物的物理化学特性,用FTIR,UV等分析方法表征了反应体系的光谱特征以及合成过程的特点。研究表明:两种体系均可合成无定型态水合氧化物,但产物特征及反应过程特征有较大区别;水溶液反应体系中,反应快速,电导率呈阶跃式变化,合成产物形貌不规则、表面粗糙、粒度均匀性差;乙二醇-水的混合反应体系中,反应易于控制,电导率变化平缓,合成产物为规则的棒状或片状、表面光滑、粒度均匀。两种反应体系得到的产物均含有吸附水、结晶水和结构水,但乙二醇-水体系产物的总含水量比水体系产物的总含水量高13.1%,并且乙二醇-水体系产物的结构水脱除起始温度点较水体系产物的结构水脱除起始温度点提高50℃左右;在700℃热处理后,二者都完全失去水份并转变为T-T相氧化铌晶体结构。反应体系光谱学特征分析表明,两种反应体系反应过程和反应产物的差别主要是由于乙二醇与草酸铌可能形成了新的更复杂的配位结构,提高了配合物中心离子的稳定性。

By hydrolysis method,Nb2O5 · nH2O was prepared in the aqueous solution system,the aqueous solution and glycol mixed system respectively using niobium oxalate as precursor.The physical-chemical characteristics of product were studied by XRD,TG/DSC and SEM.The spectral characteristics of different reaction systems and the characters during synthetic reaction process were characterized by FTIR,UV etc.The results showed that,amorphous Nb2O5 · nH2O could be prepared in both reaction systems;however,in the two reaction systems,the characteristics of product and reaction process were different.In aqueous solution system,the reaction rate was faster,the conductance took on step change,the surface morphology of product was anomalous and rough,and the particle size was badly asymmetric.In aqueous solution and glycol mixed system,the reaction process was easy to control,the conductance changed mildly,the shape of Nb2O5 · nH2O was symmetric and took on piece or stick,the surface was smooth,and the particle size was uniformity.In the two reaction systems,both products contained adsorbed water,crystal water and structural water.The total water content of the product in the aqueous solution and glycol mixed system was 13.1%,higher than that in aqueous solution system.The initial temperature at which structural water of the product in the aqueous solution and glycol mixed system was removed was 50 ℃,higher than that in aqueous solution system.After heat treatment at 700 ℃,the water was lost completely in both samples,and they both formed T-T Nb2O5 crystalloid.The spectral characteristics of both reaction systems showed that,reaction process and reaction product between both reaction systems were difference,because niobium oxalate and glycol could form a new complicated ligand,which could improve the stability of central ion.