方形锐钛矿TiO2纳米晶的合成及表征

在不添加任何模板剂或形状控制剂的条件下,以TiCl₄为前体,经氨水沉淀、乙醇洗涤和超临界干燥(AS制备法)选择性地合成了方形锐钛矿TiO₂纳米单晶.热稳定性研究结果表明,当焙烧温度不超过650℃时,方形锐钛矿TiO₂纳米晶的表面积、孔容、晶粒/颗粒尺寸基本保持不变.XRD和拉曼光谱分析表明,方形锐钛矿TiO₂纳米晶在800℃下焙烧后仍能保持晶相不变,表现出很强的抗晶相转变能力.但在1000℃焙烧后,样品可以完全转变成金红石相TiO₂.

Synthesis and Characterization of Nanosized Anatase TiO2 Cuboids

Anatase TiO₂ nanocrystals with cuboidal morphology were successfully prepared in the absence of any templates or shape-protectors by changing Ti(OH)₄ precipitate(hydrogel) into its corresponding ethanol-gels(viz., by extensive washing with absolute ethanol), followed by supercritical drying in ethanol medium and then calcination in air(named as AS preparation). The cuboidal crystals were subject to calcination at different temperatures and were characterized by N₂ physisorption, XRD, Raman spectroscopy, and TEM/HRTEM. The change of the calcination temperature in the range from 270 to 650 ℃ showed little effect on the surface area, pore volume and crystal/particle sizes of the sample. A further increase of the calcination temperature up to 800 ℃ resulted in a significant sintering of the TiO₂ nanocrystals but the sample crystal phase remained in the anatase structure. These results suggest that the as-prepared anatase TiO₂ cuboids are highly resistant to the well-known thermal effect on the phase transformation(anatase-to-rutile) of titania. However, the calcination of the sample at 1 000 ℃ resulted in a complete anatase-to-rutile phase transformation, which was companied by severe sintering growth of the TiO₂ crystals as well as a drastic change in the sample texture.