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铈基氧化物催化剂上氧物种的EPR研究 总被引:2,自引:0,他引:2
选择CeO2、20%(mol)Ce/Sr及SrCO33种甲烷氧化偶联催化剂,进行了吸附氧的EPR及骤冷EPR研究,对氧物种的形式、吸附方式及在反应中的作用进行了深入讨论.实验发现,氧化铈及复合催化剂很容易吸附氧分子产生O2-超氧离子,而碳酸锶表面不利于O-2的生成.O-2可以不同方式吸附于催化剂表面,不同方式吸附的O-2具有不同的氧化能力和稳定性.不同温度下骤冷可以在复合催化剂上得到几乎相同强度的O-2EPR信号,因此O-2可能不是甲烷的选择活化中心,而是在反应条件下转化成了O2-2或O-选择性物种.复合催化剂中的SrCO3,对CeO2中氧的流动性及产生氧中间体的能力起到了调节作用,抑制了过氧化. 相似文献
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直接利用甲烷氧化偶联产物中的稀乙烯制环氧乙烷刘育,徐法强,沈师孔(中国科学院兰州化学物理研究所,兰州,730000)关键词乙烯环氧化,甲烷氧化偶联,负载银催化剂1.前言甲烷氧化偶联(OCM)是一个产物较为复杂的反应,从目前研究结果来看,产物中C2烃总... 相似文献
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利用同步辐射光电子能谱(SRPES)和X射线光电子能谱(XPS)技术,系统研究了室温下Fe/ZnO界面形成过程中Fe薄膜与氧结尾的ZnO(000 1 )衬底之间的相互作用,结果显示初始沉积的Fe明显被表面氧氧化为Fe2+离子,在Fe覆盖度为0—3 nm的范围内,分别观察到与界面电荷传输、化学反应以及薄膜磁性相关的三个有意义的临界厚度,这一结果将有助于基于Fe/ZnO界面的相关器件的设计和研发. 相似文献
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利用全势线性Muffin-tin轨道(FP-LMTO)理论方法,计算了ZnO及其几种本征点缺陷的电子结构.计算的结果表明,ZnO中的Zn3d电子对其成键起重要作用. O2p与Zn3d的轨道杂化使价带变宽,带隙变小.Zn空位和O填隙分别在价带顶0.3和0.4 eV处产生浅受主能级.而Zn填隙在导带底0.5 eV处产生浅施主能级.但O空位则在导带底1.3 eV处产生深施主能级.根据以上结果,证明了Zn填隙是引起ZnO本征n型导电性的主要原因. 相似文献
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Detection of Fe 3d electronic states in valence band and magnetic properties of Fe-doped ZnO film 下载免费PDF全文
Fe-doped ZnO film has been grown by laser molecular beam epitaxy (L-MBE) and structurally characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), all of which reveal the high quality of the film. No secondary phase was detected. Resonant photoemission spectroscopy (RPES) with photon energies around the Fe 2p-3d absorption edge is performed to detect the electronic structure in the valence band. A strong resonant effect at a photon energy of 710 eV is observed. Fe3+ is the only valence state of Fe ions in the film and the Fe 3d electronic states are concentrated at binding energies of about 3.8 eV and 7 eV~ 8 eV. There are no electronic states related to Fe near the Fermi level. Magnetic measurements reveal a typical superparamagnetic property at room temperature. The absence of electronic states related to Fe near the Fermi level and the high quality of the film, with few defects, provide little support to ferromagnetism. 相似文献
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采用循环伏安法在GaAs(100)单晶表面电沉积了铁族金属单质薄膜. 扫描电子显微镜(SEM)结果显示, Fe族金属薄膜的晶粒较小, 薄膜平整度较高。通过X射线衍射(XRD)谱分析了Fe, Co, Ni在GaAs(100)晶面上的外延生长. 使用磁光克尔效应装置研究了Fe族金属薄膜的宏观磁性, 用同步辐射圆偏振软X射线测量了铁族单质磁性薄膜的吸收谱, 获得了X射线磁性圆二色谱, 并通过加和定则计算了磁性薄膜中Fe族金属原子的轨道磁距和自旋磁矩. 相似文献
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We have studied the band structure and optical properties of 4H-SiC by using a full potential linearized augmented plane waves (FPLAPW) method. The density of states (DOS) and band structure are presented. The imaginary part of the dielectric function has been obtained directly from the band structure calculation. With band gap correction, the real part of the dielectric function has been derived from the imaginary part by the Kramers-Kronig (KK) dispersion relationship. The values of reflectivity for normal incidence as a function of photon energy have also been calculated. We found the theoretical results are in good agreement with the experimental data. 相似文献