Agrawal A, Cizeron J, Colvin VL
Department of Chemistry, MS 60, Rice University, 6100 Main Street, Houston, TX 77005
Microsc Microanal. 1998 May;4(3):269-277. doi: 10.1017/s1431927698980278.
: In this work, the high-temperature behavior of nanocrystalline TiO2 is studied using in situ transmission electron microscopy (TEM). These nanoparticles are made using wet chemical techniques that generate the anatase phase of TiO2 with average grain sizes of 6 nm. X-ray diffraction studies of nanophase TiO2 indicate the material undergoes a solid-solid phase transformation to the stable rutile phase between 600 degrees and 900 degreesC. This phase transition is not observed in the TEM samples, which remain anatase up to temperatures as high as 1000 degreesC. Above 1000 degreesC, nanoparticles become mobile on the amorphous carbon grid and by 1300 degreesC, all anatase diffraction is lost and larger (50 nm) single crystals of a new phase are present. This new phase is identified as TiC both from high-resolution electron microscopy after heat treatment and electron diffraction collected during in situ heating experiments. Video images of the particle motion in situ show the nanoparticles diffusing and interacting with the underlying grid material as the reaction from TiO2 to TiC proceeds.
在这项工作中，利用原位透射电子显微镜（TEM）研究了纳米晶TiO₂的高温行为。这些纳米颗粒采用湿化学技术制备，生成平均粒径为6 nm的TiO₂锐钛矿相。纳米相TiO₂的X射线衍射研究表明，该材料在600℃至900℃之间经历了固-固相变，转变为稳定的金红石相。在TEM样品中未观察到这种相变，这些样品在高达1000℃的温度下仍保持锐钛矿相。高于1000℃时，纳米颗粒在非晶碳网格上开始移动，到1300℃时，所有锐钛矿衍射消失，出现了新相的较大（50 nm）单晶。通过热处理后的高分辨率电子显微镜以及原位加热实验期间收集的电子衍射，确定这个新相为TiC。原位颗粒运动的视频图像显示，随着从TiO₂到TiC的反应进行，纳米颗粒扩散并与底层网格材料相互作用。
