排序方式: 共有68条查询结果,搜索用时 15 毫秒
61.
62.
63.
宋晓岚 《武汉理工大学学报(材料科学英文版)》2010,25(6):929-934
Monodispersed spheroidal SnO2 nanocrystals with the grain size of 8–30 nm were synthesized by the precipitation method using SnCl4·5H2O (stannic chloride hydrate) as raw materials. Differential scanning calorimetry/thermogravimetry (DSC/TG), X-ray diffraction
(XRD) and transmission electron microscope (TEM) were used to characterize the structure of SnO2 nanocrystals. The influences of the calcination temperature and time on the lattice constant, the lattice distortion and
the grain size of SnO2 nanocrystals were discussed based on the XRD results. The grain growth kinetics of SnO2 nanocrystals during calcination process was simulated with a conventional grain growth model which only took into account
of diffusion and with a new isothermal model proposed by our group, which took into account of both diffusion and surface
reactions. Using conventional model, the grain growth rate constant of SnO2 crystals is 1.55×104 nm5/min with a pre-exponential factor of 5 and an activation energy of 108.62 kJ/mol. Compared with the convention model, the
new isothermal model is more realistic in reflecting the grain growth behavior of SnO2 nanocrystals during the calcination process. This indicates that the grain growth of SnO2 nanocrystals is controlled by both diffusion and reaction factors, and the effect of surface reactivity on the grain growth
of SnO2 nanocrystals could not be ignored. A combined activation energy estimated with the new isothermal model is 53.46 kJ/mol. 相似文献
64.
采用电子自旋共振(ESR)方法研究了钛在BaO-SiO2-B2O3-TiO2系统玻璃中的价态及Ti3+的结构状态.结果表明:在正常空气气氛下熔制的玻璃中,钛主要以Ti4+形式存在,所产生的顺磁信号归因于玻璃的本征缺陷和熔制时TiO2中氧的逸出而形成的氧空位捕获电子引起,且随温度升高,氧空位浓度减少;在微还原性气氛下,有部分Ti3+形成,出现g┃=1.9954,g┸=1.9823两处顺磁峰,它们对温度有着不同的依从性,即随温度升高:g┃ 峰增强,g┸峰降低;根据Ti3+的g┃ 、g┸)参数的性质,认为Ti3+是处于带四方畸变的八面体配位场中,形成[TiO6];即便在液氮温度下,也难以观察到Ti3+的超精细结构谱线. 相似文献
65.
66.
67.
水相体系纳米γ-Al2O3浆料的分散稳定性能研究 总被引:4,自引:0,他引:4
为确定配制稳定的纳米γ-Al2O3化学机械抛光(CMP)浆料的工艺条件,通过润湿性、Zeta电位及黏度的测定,研究了溶液pH值及添加分散剂等因素对水相体系纳米γ-Al2O3悬浮液分散稳定性能的影响.结果表明,在纳米γ-Al2O3固含量为6%的浆料中,加入异丙醇胺作为分散剂,其用量为γ-Al2O3粉体质量的1%,同时控制浆料的pH值约为4时,纳米γ-Al2O3粉末的润湿性能最佳,此时浆料Zeta电位值较高,黏度较小;在该条件下成功获得长时间不沉降的稳定浆料. 相似文献
68.