均匀纺锤形α-Fe_2O_3的制备及其等电性研究

Preparation of Monodisperse Spindle-type HematiteUltra-fine Particles and Study on Its Isoelectric Phenomenon

以硝酸铁为原料,尿素为均匀沉淀剂,磷酸二氢钠为结晶助剂,用动态开放回流系统的均匀沉淀法制备了纺锤形α-Fe2O3粒子。并用XRD、TEM等进行了表征。当Fe(NO3)3、NaH2PO4、CO(NH2)2的浓度分别为0.20、0.0015、0.10mol/L,反应温度为117℃,陈化时间为13h时,制备的粒子轴比可达3.3,且分散性较好,粒径分布窄,陈化时间短,产率较高。对反应机理、结晶助剂NaH2PO4的作用等作了初步研究。并测量了不同pH值时粒子的Zeta电位值,找出了粒子的等电点,与理论估算值接近。

Uniform spindle-type hematite (α-Fe_2O_3) particles were prepared by homogeneous precipitation of boiling reflux in open system from ferric salt solution in the presence of NaH_2PO_4 using CO(NH_2)_2as homogeneous precipitant. It was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM). Spindle-type hematite particles having an axial ratio of 3.3 (mean length, 0.24 μm;mean width, 0.07 μm) were obtained by aging a solution of Fe(NO_3)_3 (0.20 mol/L)、CO(NH_2)_2 (0.10 mol/L)、NaH_2PO_4 (0.001 5 mol/L) at 117 ℃ for 13 h. The procedures had shorter aging time and higher yield and products had little size distribution and good dispersion. A reaction mechanism is offered which explains the nucleation and growth process involved in the formation of uniform particles about homogeneousprecipitation. Effects of concentration of inorganic additive on morphology of spindle-type hematite were studied in the procedures. The result shows that there is a remarkable effect of NaH_2PO_4 concentration on axial ratio of spindle-type hematite. Zeta-potential of particles was measured at different pH values. And from the platform of the two factors, the IEP (isoelectric point) can be determined, which is in accordance with theoretical value.