纳米晶Fe_2O_3和TiO_2结构相变的尺寸效应(英)

SIZE EFFECT IN THE STRUCTURAL PHASE TRANSITION OF NANOCRYSTAL Fe_2O_3 AND TiO_2

用DTA（差热分析）、TG（热重分析）和X射线衍射分析，研究了Fe2O3和TiO2纳米晶粒的结构相变．结果表明，对于Fe2O3纳米晶粒，只要没有发生γ→α转变，纳米晶粒就保持其原来的尺寸不变，而一旦发生了相变，晶粒的尺寸就会迅速长大．同样，对TiO2纳米晶粒，在从锐钛矿相→板钛矿相→金红石相的相变过程中，在相变发生以前，不管温度多高，纳米晶粒都保持其原来的尺寸不变，只要发生了相变，晶粒的尺寸就会迅速长大．对于纳米晶粒，依赖于晶粒尺寸的结构相变和依赖于结构相交的晶粒生长过程都是存在的．这是纳米晶的一种新的尺寸效应．

Structure phase transition of nanocrystalline Fe2O3 and TiO2(n-Fe2O3 and n-TiO2) had been studied by DTA (difFerencial thermal analysis), TG(thermal gravity ) and X-ray differential method, it was found that n-Fe2O3 particles keep their original size if the transition from γ-phase to α-phase has not taken place. As the transition occurs, the nanocrystals grow up quickly. Similarly.in the case of TiO2, before the transition from the brookite→the anatase → the rutile phase, the nanocrystalline particles keep their original size even at high temperature. While-the transition takes place, n-TiO2 particles grow up quickly. Combining with the research work of P. Ayyue et al., it is suggeSted that both of the size dependence of structure phase transition and the transition dependence of the nanocrystals' growth are possible for the nanocrystals. It is a new size effect of nanocrystals.