二氧化钒薄膜的光学特性及应用前景

本文着重介绍二氧化钒（ＶＯ２）薄膜的性质，相变原理，若干制备工艺对ＶＯ２薄膜相变特性的影响并给出ＶＯ２薄膜的应用方向。     

Deposition of Er：A12O3 Films and Photoluminescence Characteristics

Er^3 -doped Al2O3 films were deposited on silicon substrates by reactive closed-field unbalanced magnetron sput-tering. The process parameters, such as target bias voltage, substrate bias voltage, O2 gas flows, sputtering gas pressure, were studied. The 1.53μm photoluminescence characteristics from Er^3 were measured. The relations among the PL peak intensity, annealing temperatures, and pump power were experimentally investigated.     

Chemical Structure of HfO2/Si Interface with Angle-Resolved Synchrotron Radiation Photoemission Spectroscopy

Interracial chemical structure of HfO2/Si （100） is investigated using angle-resolved synchrotron radiation photoemission spectroscopy （ARPES）. The chemical states of Hf show that the Hf 4f binding energy changes with the probing depth and confirms the existence of Hf-Si-O and Hf Si bonds. The Si 2p spectra are taken to make sure that the interracial structure includes the Hf silicates, Hf silicides and SiOx. The metallic characteristic of the Hf-Si bonds is confirmed by the valence band spectra. The depth distribution model of this interface is established.     

离子束辅助沉积二氧化铪薄膜紫外光学特性研究

利用离子束辅助沉积方法制备单层二氧化铪薄膜,对薄膜样品的折射率、吸收特性进行了研究。实验结果表明,薄膜特性与制备工艺参数有着密切的关系,沉积速率、烘烤温度、离子束流、氧气流量均对单层二氧化铪薄膜紫外光学特性有着不同程度的影响。实验分析了不同工艺因素对单层二氧化铪薄膜的影响,并且找到了在一定范围内的最佳工艺参数。针对可能对紫外波段造成较大散射吸收损耗的微观表面形貌,利用SEM分析了典型工艺因素对表面形貌的影响。     

CeO2掺杂的Mn/Al催化剂的物化、表面及催化性能

Pure and CeO2-doped Mn/Al mixed oxides were prepared by the wet impregnation method using finely powdered alumina, manganese, and cerium nitrates. The physicochemical, surface, and catalytic properties of the thermally treated solids (at 500, 800, and 900 ℃) were investigated using XRD, nitrogen adsorption at -196 ℃, and hydrogen peroxide decomposition in an aqueous solution at 30 - 50 ℃. The Mn oxidation state changed from Mn4 to Mn2 on increasing the calcination temperature. There were two unique features associated with CeO2 that are of interest. The first was that it favored the dispersion of manganese oxides deposited on the γ-Al2O3 catalyst calcined at 500 ℃. The second was that it enhanced the formation of Mn3O4 species from Mn2O3 deposited initially on the alumina support calcined at 800 and 900 ℃. Consequently, the specific surface area of the Mn/Al mixed oxides calcined at 500 ℃ was increased by increasing the amount of dopant added. An opposite effect was observed by increasing the calcination temperature from 500 to 900 ℃. The doping followed by calcination at different temperatures brought about an increase in the catalytic activity of mixed oxides. Pretreatments did not modify the mechanism of the catalyzed reaction but changed the number of catalytically active sites without changing the nature of these sites.     

团簇Au/CeO2的制备及其催化CO氧化反应构效关系的研究

负载型Au催化剂因其在诸多反应过程中的高催化活性而备受研究者关注.然而针对负载型催化剂中Au物种结构的有效调控,以及催化过程中真实构-效关系的探索一直充满了挑战.用CeO₂为Au物种担载基底,通过简单煅烧处理引起的CeO₂结构变化,进而实现Au/CeO₂之间界面作用力的调控.此研究发现Au纳米颗粒中Au⁰物种具备更为高效的催化室温CO氧化活性,结合多种原位表征分析,其室温条件下催化转化效率更依赖于CO吸附能力.而相比于单原子Au₁和纳米Au颗粒,所制备的团簇Au/CeO₂催化剂在较高温度(>50℃)展现出优异的催化CO氧化反应性能.随着温度升高,催化剂表界面O参与的MvK反应路径更易发生,因此具有更多表界面活性O物种和Au^δ+位点的团簇Au/CeO₂催化剂展现出最为优异的催化CO氧化性能.这些发现为高效负载型Au催化剂的制备提供了新思路并深化了对Au/CeO₂催化作用机制的理解.     

Autothermal reforming of methane over Ni catalysts supported over ZrO2-CeO2-Al2O3

Ni catalysts supported on Al2O3, ZrO2-Al2O3, CeO2-Al2O3 and ZrO2-CeO2-Al2O3 were prepared by coprecipitation method, and their catalytic performances for autothermal reforming of methane to hydrogen were investigated. The Ni-supported catalysts were characterized by XRD, TPR and XPS. The relationship between the structures and catalytic activities of the catalysts was discussed. The results showed that the catalytic activity and stability of the Ni/ZrO2-CeO2-Al2O3 catalyst was better than those of other catalysts with the highest CH4 conversion, H2/CO and H2/COx ratio at 750 ℃. The catalyst showed a little deactivation along the reaction time during its 72 h on stream with the mean deactivation rate of 0.08%/h. The catalytic performance of the Ni/ZrO2-CeO2-Al2O3 catalyst was also affected by reaction temperature, no2 ： nCH4 molar ratio and nH2O ： nCH4 molar ratio. TPR, XRD and XPS measurements indicated that the formation of ZrO2-CeO2 solid solution could improve the dispersion of NiO, and inhibit the formation of NiAl2O3, and thus significantly promoted the catalytic activity of the Ni/ZrO2-CeO2-Al2O3 catalyst.     

SBA-15负载CeO2纳米晶的溶胶-凝胶一步合成

以P123为模板剂, 正硅酸乙酯和硝酸铈为前驱体, 通过溶胶-凝胶路线在酸性条件下合成了SBA-15负载氧化铈(CeO2与SiO2质量比为28.7%)有序介孔材料. 采用热重/差热分析(TGA/DTA)、X射线衍射(XRD)、透射电镜(TEM)和氮气吸附等手段对所合成材料进行了表征. 结果表明, 合成的材料具有类似于SBA-15的结构, 孔径、孔容和比表面积分别为38.7 Å, 0.46 cm3/g和570 m2/g. X射线衍射(XRD)、透射电镜(TEM)、X射线能谱(EDS)和选区电子衍射花样联合表征证实了铈物种以高分散的CeO2纳米晶的形式分布在介孔基体中.     

PuO2体系的分子反应动力学研究

基于ＰｕＯ２分子（Ｘ＾５Σｇ＾＋）的多体展式分析势能函数,用准经典的Ｍｏｎｔｅ－Ｃａｒｌｏ轨迹法研究了Ｏ（＾３Ｐｇ）＋ＰｕＯ（０,０）和Ｐｕ（＾７Ｆｇ）＋Ｏ２（０,０）的分子反应动力学过程。结果表明：Ｏ（＾３Ｐｇ）＋ＰｕＯ（０,０）碰撞生成少量稳定络合物ＰｕＯ２（Ｘ＾５Σｇ＾＋）,该反应是无阈能反应;而Ｐｕ（＾７Ｆｇ）＋Ｏ２（０,０）碰撞生成稳定络合物的同时,主要还发生了Ｐｕ（＾７Ｆｇ）＋Ｏ２（０     

中性团簇(CeO2)m(m=1~3)活化甲烷C—H的密度泛函理论计算

采用密度泛函理论(DFT)计算了CH₄在电中性(CeO₂)_m(m=1~3)团簇上的活化情况, 并对其机理进行了探讨. 计算结果表明, 甲烷C—H键在团簇上的活化为亲核加成模式, 电子由团簇流向甲烷C—H反键轨道, 使甲烷C—H键削弱而得以活化, 反应的过渡态为四中心结构. 团簇的桥氧位活化甲烷C—H键的活性大于端氧位, 而三重桥氧位的活性高于二重桥氧位. 团簇中作用位点Ce和O原子的电荷布居与其活化甲烷C—H的能力密切相关. 溶剂的存在不仅降低了甲烷C—H活化自由能垒, 而且使与甲烷作用的团簇各位点的活性差异缩小.