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Hydrothermal preparation and formation mechanism of titanium dioxide microcrystallites 总被引:2,自引:0,他引:2
Hydrothermal preparation experiments of TiO_2 microcrystallites were carried out. The formation of TiO_2 microcrystallites of polymorpbic forms was related to the precursor types and the basicity or acidity of reaction mediums under hydrothermal conditions. Based on the "growth unit" model, the space lattice graphs of growth units responding to different polymorphs were established. The stable energy of growth unit was calculated for different basicity or acidity of reaction mediums. The formation of polymorphic TiO_2 microcrystallites under hydrothermal conditions was discussed based on the experimental results. 相似文献
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采用双坩埚提拉法(DCCZ)生长了各种不同成分的近化学计量比LiNbO3晶体,并用腐蚀法观察了其电畴结构.结果表明,化学成分对未经极化处理晶体的电畴结构起决定性作用,当Li2O含量处于49.4mol%附近时,晶体z面电畴呈现特殊的三次对称反畴;当晶体中Li2O含量为49.7mol%时,晶体为完全单畴.本文对其形成机理进行了探讨,认为在由顺电相向铁电相转变时,局部铁电畴的极性方向与该处沿z轴方向的温度梯度正负密切相关,z轴生长晶体时,由于相变发生所处位置离生长界面的距离受LiNbO3晶体计量比影响,所处温场固有温梯也随之不同,在此基础上解释了不同成分晶体的电畴结构形成原因.最后讨论了控制铁电畴结构的工艺措施. 相似文献
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为了能够更好地利用过渡区的数据,寻求一种新的全区电阻率定义方法,在CSAMT的基本理论上,通过迭代求解方式计算求解得到全区视电阻率定义公式。使用CSAMT1D程序进行了不同层状模型水平电偶源激发的电磁场的计算,模型成图,分析,以此为基础计算Ex和Ex/Hy全区视电阻率。分析和比较6种模型改变不同参数得出的卡尼亚视电阻率和全区视电阻率对比,分析了不同参数下迭代效果,得出全区视电阻率能够充分利用过渡带数据和近场数据,具有更好的分层特性和实际应用价值。 相似文献
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The formation of titania polymorphs under hydrothermal condition 总被引:1,自引:0,他引:1
The formation process of crystal polymorphs of titania under hydrothermal condition is studied. According to the experimental results and theoretic analysis, the formation process of crystal polymorphs can be described as a unit process. It includes the formation of growth units, the formation of nuclei through the polymerization of growth unit, and the growth of crystallites. The influence of the environmental phase and growth conditions on the formation of polymorphs is reflected in the changes of the structures of growth units. For example, when changing the pH of the reaction medium, the structure of growth unit with the highest stable energy in the hydrothermal system changes. Then different titania polymorphs can be prepared. The absorption, movement, crystallization or desorption of the growth unit are related to crystalline structure. On the other hand, the formation of crystal inner defects is related to the disturbance of the crystallizing process. 相似文献