凝胶-溶胶法制备纳米二氧化钛的pH控制

pH control on preparation of nano-TiO_2 by gel-sol process

利用凝胶-溶胶法制备纳米二氧化钛,采用透射电镜(TEM)和X射线衍射(XRD)对产物进行了表征,考察了体系pH变化和电解质(高氯酸钠)对它的影响,以及初始pH(pH0)对二氧化钛形貌及体系组成的影响。结果表明,产物为锐钛矿型二氧化钛,平均粒径5-15 nm;体系pH变化是由于OH-(或H+)在氢氧化钛或二氧化钛表面的吸附和脱附,添加0.1 mol/L高氯酸钠能促进OH-(或H+)的吸附和脱附过程。pH0显著影响二氧化钛形貌和体系组成,pH0=1.0时为球状晶体,pH0=9.4时为较规则的立方晶体,至pH0=11.5变为椭球形。pH0>9.4时,二氧化钛物质的量分数显著下降,至pH0=12.0时无二氧化钛生成,因此应控制pH0<9.4。

Nano - TiO2 was prepared by gel - sol method and were characterized by transmission electron microscopy （TEM） and X - ray diffraction patterns （ XRD ）. The pH change and the effects of electrolyte （ NaClO4 ） on it were studied. The effects of initial pH value （ pH0 ） on the shapes of TiO2 and the system composition were also investigated. The resuits showed that the synthesized products were anatase TiO2 with the average diameter of 5 - 15 nm. The change in pH value was mainly governed by the adsorption and desorption process of H^＋ and OH^- on the surface of Ti （ OH ） 4 or TiO2. This process can be enhanced by adding 0.1 mol/L NaClO4. The shapes of TiO2 and the system composition were greatly influenced by different pH0. The spheroidal crystals of TiO2 at pH0 = 1.0 became cubeidal at pH0 = 9.4 and ellipsoidal at pH0 = 11.5. The fraction of a mount of substance of TiO2 decreased significantly at pH0 〉 9.4 and no TiO2 was produced at pH0 = 12.0, so pH0 below 9.4 is the optimum parameter for TiO2 preparation in our experiments.