da Silva Antonio N, Pinto Raffael C F, Freire Paulo T C, Junior Jose Alves L, Oliveira Alcineia C, Filho Josué M
Universidade Federal do Ceará, Campus do Pici-Bloco 922, Departamento de Física, Fortaleza, Ceará, Brazil.
Universidade Federal do Ceará, Campus do Pici-Bloco 940, Departamento de Química Analítica e Físico-Química, Fortaleza, Ceará, Brazil.
Spectrochim Acta A Mol Biomol Spectrosc. 2015 Mar 5;138:763-73. doi: 10.1016/j.saa.2014.11.081. Epub 2014 Nov 29.
Structural characterizations of nanostructured oxides were studied by X-ray diffraction (XRD), Raman and infrared spectroscopy. The oxides catalysts namely, SnO2, ZrO2, CeO2, MnOx, Al2O3 and TiO2 were prepared by a nanocasting route and the effect of the temperature and pressure on the stability of the solids was evaluated. Raman spectra showed that ZrO2 and TiO2 exhibited phase transitions at moderate temperatures whereas CeO2, SnO2 and MnOx had an effective creation of defects in their structures upon annealing at elevated temperatures. The results suggested also that the effect of the temperature on the particles growth is related to the type of oxide. In this regard, phase transition by up to 600°C accelerated the sintering of ZrO2 and CeO2 grains compared to TiO2, SnO2 and MnOx counterparts. Under hydrostatic pressures lower than 10GPa, rutile TiO2 and tetragonal ZrO2 exhibited pressure induced phase transition whereas CeO2 and SnO2 were stable at pressures close to 15GPa. The experiments revealed that the nanostructured SnO2 oxide exhibited stable performance at relatively high temperatures without phase transition or sintering, being suitable to be used as catalysts in the range of temperature and pressure studied.
通过X射线衍射（XRD）、拉曼光谱和红外光谱对纳米结构氧化物的结构特征进行了研究。通过纳米铸造法制备了氧化物催化剂，即SnO₂、ZrO₂、CeO₂、MnOₓ、Al₂O₃和TiO₂，并评估了温度和压力对固体稳定性的影响。拉曼光谱表明，ZrO₂和TiO₂在中等温度下表现出相变，而CeO₂、SnO₂和MnOₓ在高温退火后其结构中有效地产生了缺陷。结果还表明，温度对颗粒生长的影响与氧化物的类型有关。在这方面，与TiO₂、SnO₂和MnOₓ相比，高达600°C的相变加速了ZrO₂和CeO₂晶粒的烧结。在低于10GPa的静水压力下，金红石型TiO₂和四方相ZrO₂表现出压力诱导相变，而CeO₂和SnO₂在接近15GPa的压力下是稳定的。实验表明，纳米结构的SnO₂氧化物在相对较高的温度下表现出稳定的性能，无相变或烧结，适合在所研究的温度和压力范围内用作催化剂。
