辅助剂对合成WO3纳米棒形貌和光吸收特性的影响

以六氯化钨为原料,以乙二醇、尿素为辅助剂,在酸性反应体系通过醇热法合成了纳米氧化钨.利用XRD、SEM对产物进行了表征,结果表明:控制乙二醇及尿素的加入量,可获得不同形貌的纳米氧化钨.对不同条件下合成的WO3进行紫外可见光光谱分析可知,当反应体系加入乙二醇和尿素,纳米氧化钨的紫外吸收不同程度的减弱,单独加入乙二醇吸收峰发生蓝移,两者同时加入时吸收峰也发生蓝移.     

两种侧链偶氮聚电解质自组装膜中生色团取向研究

用偏振紫外光谱研究了两种侧链偶氮聚电解质静电逐层自组装膜中偶氮生色团的初始取向 .讨论了不同的组装条件对自组装膜中偶氮生色团取向的影响 .进一步探讨了偶氮聚电解质自组装膜的结构特点 .研究表明 ,侧链偶氮聚电解质自组装膜中的偶氮生色团存在一定程度的面内取向 ,自组装的各种影响条件和聚合物结构等 (pH值、侧链柔性间隔基团长度、以及偶氮生色团官能度等 )与自组装膜中偶氮生色团的面内取向程度存在一定的相关性 .通过研究偶氮生色团的取向和影响因素 ,可以深入认识侧链偶氮聚电解质的自组装行为     

具有螺旋结构的金属镍有机-无机配位聚合物的合成及表征

在水热体系中合成了3个中心金属为镍离子, 以六配位扭曲八面体构型形成的具有螺旋结构的配位聚合物{[Ni₂L₂(bib)₂·2H₂O]·5H₂O}_n(1), [Ni₂L₂(bpy)]_n(2)和{[Ni₂L₂(bibpip)₂·2H₂O]·6H₂O}_n(3)[H₂L=4,4'-三苯胺二甲酸; bib=1,3-二(咪唑基)苯; bpy=4,4-联吡啶; bibpip=1,4-二(4-咪唑苄基)哌嗪]. 通过单晶及粉末X射线衍射、 红外光谱、 元素分析和热重分析对这3种化合物进行了表征. 结果表明, 化合物1属于单斜晶系, C2/c空间群, 其骨架为具有{4²·6⁵·8}拓扑结构的二维层结构; 化合物2属于斜方晶系, Fdd2空间群, 其骨架为具有{4⁸·5⁴·6³}拓扑结构的三维超分子网络; 化合物3属于三斜晶系, P\begin{array}{c}\bar{1}\end{array}空间群, 为1个五重穿插的三维超分子网络, 其骨架具有{4⁴·6²}拓扑结构.     

Landau damping of collective modes in a harmonically trapped Bose--Einstein condensate

This paper proposes a method for calculating the Landau damping of a low-energy collective mode in a harmonically trapped Bose--Einstein condensate. Based on the divergence-free analytical solutions for ground-state wavefunction of the condensate and eigenvalues and eigenfunctions for thermally excited quasiparticles, obtained beyond Thomas--Fermi approximation, this paper calculates the coupling matrix elements describing the interaction between the collective mode and the quasiparticles. With these analytical results this paper evaluates the Landau damping rate of a monopole mode in a spherical trap and discusses its dependence on temperature, particle number and trapping frequency of the system.     

取代苯环结构活性指标的能量密度标度法

取代苯是有机化学中一类很重要的化合物,其独特的苯环结构决定了它们参与化学反应的特殊性。苯环上取代基的不同对环结构产生了不同程度的影响,进而反映在化学反应活     

Dark Lump Excitations in Bose—Einstein Condensates

We investigate the dynamics of two-dimensional matter-wave pulses in a Bose-Einstein condensate with diskshaped traps.For the case of repulsive atom-atom interactions,a Kadomtsev-Petviashvili equation with positive dipersion is derived using the method of multiple scales.The results show that it is possible to excite dark lump-like two-dimensional nonlinear excitations in the Bose-Einstein condensate.     

矩形谐振器中非传播重力-表面张力孤波的理论研究

本文用多重尺度微扰方法研究了外加驱动下,计及表面张力时矩形谐振器中有限深流体重力-表面张力驻波模的弱非线性调制。对吴君汝等人所发现的非传播表面孤波现象进行了较为详细的分析计算,修正和发展了Larraza,Putterman和Miles的非传播孤波理论,得到了正确的二次谐波共振条件。在σ-kd图上对非传播表面孤波的存在区域进行了仔细的理论分析,发现除静态液面深度外,流体的表面张力是产生和控制非传播表面孤波的另一重要参数。最后讨论了矩形谐振器的非线性共振曲线特性,并与实验进行了比较。 关键词：     

水热老化对Cu改性的W/CeTi催化剂NH3-SCR性能的影响

采用浸渍法制备了CuW/CeTi和W/CuCeTi催化剂,考察了催化剂中Cu的不同作用方式对氨气选择性催化还原NO_x （NH₃-SCR）反应脱硝性能的影响。新鲜的CuW/CeTi和W/CuCeTi在低温下显示出优异的活性。经过800℃、10 h水热老化后,W/CuCeTi表现出比CuW/CeTi更优异的脱硝性能,证明W/CuCeTi具有更高的水热稳定性。通过透射电子显微镜（TEM）、X射线衍射（XRD）、拉曼光谱（Raman）、N₂物理吸附-脱附、X射线光电子能谱（XPS）、氨气程序升温脱附（NH₃-TPD）和氢气程序升温还原（H₂-TPR）表征,发现Cu的掺杂形成的Cu-O-Ce结构能够提高CeTi的抗烧结能力,同时削弱W-CeO₂相互作用,抑制老化过程中Ce₂（WO₄）₃物质的形成,使W/CuCeTi表现出更优异的水热稳定性。     

Effect of Cu doping on the secondary electron yield of carbon films on Ag-plated aluminum alloy

Reducing the secondary electron yield (SEY) of Ag-plated aluminum alloy is important for high-power microwave components. In this work, Cu doped carbon films are prepared and the secondary electron emission characteristics are studied systematically. The secondary electron coefficient δ_max of carbon films increases with the Cu contents increasing at first, and then decreases to 1.53 at a high doping ratio of 0.645. From the viewpoint of surface structure, the higher the content of Cu is, the rougher the surface is, since more cluster particles appear on the surface due to the small solid solubility of Cu in the amorphous carbon network. However, from viewpoint of the electronic structure, the reduction of the sp² hybrid bonds will increase the SEY effect as the content of Cu increases, due to the decreasing probability of collision with free electrons. Thus, the two mechanisms would compete and coexist to affect the SEY characteristics in Cu doped carbon films.