金属离子掺杂对金红石型纳米TiO2的稳定性影响

以TiCl4为原料,采用低温水热法制备不同金属离子掺杂的纳米TiO2粉末,结合扫描电子显微镜(SEM)、X射线粉末衍射仪(XRD)、孔径分析仪等分析金属离子掺杂对产物晶型、晶粒尺寸、形貌及比表面积的影响,以及不同金属掺杂纳米TiO2的高温稳定性。结果表明:掺入Ce^3+、Re^7+、La^3+和Co^2+等金属离子时,制备的纳米TiO2仍为金红石结构,掺入Zr^4+时,纳米TiO2为金红石和锐钛矿混晶结构;Ce-TiO2、Re-TiO2、La-TiO2的初级粒子均为棒状,但直径和长度不同,CoTiO2、Zr-TiO2的初级粒子大部分呈颗粒状,且Zr-TiO2颗粒具有高分散性,比表面积高达198.0 m^2/g;高温煅烧后,掺杂Zr^4+、Ce^3+、Re^7+、Co^2+等金属离子的纳米TiO2粉末均出现新的晶相,其中Ce^3+和Co^2+掺杂出现锐钛矿相,Zr^4+和Re^7+掺杂出现板钛矿相;La^3+、Co^2+促进TiO2粉末高温烧结,而Ce^3+和Re^7+的掺杂可以抑制高温烧结。整体上,金属离子掺杂对烧结影响较小,掺杂样品的晶粒尺寸仍会明显增大,比表面积显著降低。

Effects of metal ions doping on the stability of nano-sized rutile TiO_2

The nano-TiO2 powders doped with different metal ions were prepared by low-temperature hydrothermal method using TiCl4 as raw material. The powders were characterized by scanning electron microscopy(SEM),X-ray powder diffraction(XRD),specific surface area and pore size analyzer. The effect of different metal ion doping on crystal structure,crystallite size,morphology and specific surface area of the samples,and the high temperature stability of nano-TiO2 doped with different metals was investigated. The results demonstrate that the nano-TiO2 prepared by the addition of metal ions such as Ce^3+,Re^7+,La^3+ and Co^2+ retain rutile structure. When Zr^4+ is doped,the nano-TiO2 exhibits a mixed structure of rutile and anatase. The primary particles of Ce-TiO2,Re-TiO2 and La-TiO2 are rod-shaped,but the diameter and length are different. The primary particles of Co-TiO2 and Zr-TiO2 are mostly granular,and Zr-TiO2 has high dispersibility and a specific surface area of 198.0 m^2/g. After calcination at high temperature,the nano-TiO2 powder doped with Zr^4+,Ce^3+,Re^7+ and Co^2+emerges a new crystal phase,Ce^3+ and Co^2+ doping appears anatase phase,and Zr^4+ and Re^7+doping appears brookite phase. La^3+ and Co^2+ promote the high temperature sintering of TiO2 powder,whereas the doping of Ce^3+ and Re^7+ can inhibit high temperature sintering. In general,metal ion doping has a little effect on sintering,and the grain size of the doped sample still increases significantly,and the specific surface area is remarkable reduced.