水热法合成的介孔二氧化钛的结构表征及其对水中2,4,6-三溴苯酚的光催化降解活性

以聚丙二醇(PPG)为模板剂,采用水热法制备了可控介孔TiO2纳米晶体.醋酸水溶液为水解抑制剂和催化剂.运用X射线衍射、热重分析、扫描电镜和氮气吸附-脱附等技术对样品进行了表征.详细考察了制备过程、模板剂含量和煅烧温度等参数对样品结构和光催化活性的影响,并将样品用于紫外光下降解水体中典型溴代阻燃剂2,4,6-三溴苯酚的...     

表面具丰富羟基的介孔TiO2稳定Pt-OH-Fe(III)催化界面

在负载型金属催化剂中，载体不仅可以提高金属分散度，同时还创造了独特的金属-载体界面.在特定的反应中，这些界面位点被认为是主要活性位点.对于这些体系，其催化性能的关键在于能否构建丰富且稳定的界面活性位点.本研究中，以乙二醇-钛前驱体水解得到的超高比表面积介孔TiO₂作为载体（m-TiO₂，490 m²/g），通过紫外光照沉积得到m-TiO₂负载的高度分散的Pt纳米颗粒（1.9 wt% Pt，2.7 nm）.相较而言，在商业P25 TiO₂上负载量仅有0.2 wt%，而Pt的尺寸却达6.7 nm.通过简单的沉积沉淀法可以在Pt/m-TiO₂和Pt/P25进一步构筑超高活性和稳定性的Pt-OH-Fe（Ⅲ）界面，所得到的Fe（OH）_x-Pt/m-TiO₂在催化低温CO氧化反应中表现出超高活性和稳定性，而Fe（OH）_x-Pt/P25却会在测试过程中发生不可逆的失活.研究发现，相较于P25表面密度较小且对湿气不敏感的羟基物种，m-TiO₂的高比表面积、介孔结构以及表面具有丰富（且对湿气敏感）的羟基（10.6 mmol/g，12.5 nm^-2），可以确保Pt-OH-Fe（Ⅲ）界面在CO氧化的放热反应中不会因为脱水发生不可逆的失活.     

非对称领结型纳米孔阵列的光透射特性（英文）

本文利用数值模拟的方法研究了两种不同的非对称领结型纳米孔结构的光学特性。对于偏置间隙的领结型纳米孔,其基模共振与孔的周长呈线性关系。并且,不同的间隙尺寸对间隙偏置的敏感度不同。对于间隙的一边的结构发生变化的领结型纳米孔,基模共振可以通过改变单个几何参量(剩余部分的高度h2)进行线性调制。另外,研究中还观察到了类Fabry-Perot共振的共振峰分裂。我们在这项工作中提出的这两种打破领结型纳米孔的对称性的方法可以灵活地对领结型纳米孔结构的共振进行操控。     

Mechanical design and analysis of a low beta squeezed half-wave resonator

A superconducting squeezed type half-wave resonator （HWR） of β=0.09 has been developed at the Institute of Modern Physics, Lanzhou. In this paper, a basic design is presented for the stiffening structure for the detuning effect caused by helium pressure and Lorentz force. The mechanical modal analysis has been investigated the with finite element method （FEM）. Based on these considerations, a new stiffening structure is proposed for the HWR cavity. The computation results concerning the frequency shift show that the low beta HWR cavity with new stiffening structure has low frequency sensitivity coefficient df/dp and Lorentz force detuning coefficient KL, and stable mechanical properties.     

正方形纳米线及纳米孔阵列辐射特性研究

晶体硅纳米线及纳米孔阵列结构不仅有着优异的增吸收特性,而且与传统的硅膜电池相比能大幅降低原料成本,因而在光伏市场中有着巨大发展前景。本文采用严格耦合波分析(RCWA)研究了晶体硅正方形纳米线和纳米孔阵列结构的辐射特性,证明了两种结构的应用潜力。在AM1.5太阳能光谱辐射强度下,纳米线和纳米孔阵列结构最终效率都大于24%,高出同等厚度晶体硅薄膜70%P以上。两种纳米结构在周期600 nm附近达到最高,其中纳米线阵列结构有着更低的最优填充率。不同角度混合极化入射下,两种结构的最终效率能够维持在大的角度范围内(0~60°),表现了良好的角度特性。     

SBA-15表面改性及其对介孔La0.8Sr0.2CoO3钙钛矿型催化剂结构和性能的影响

Mesoporous SBA-15 with mesopore diameter up to 10.1 nm was prepared by a hydrothermal method, and was further functionalized to obtain different surface properties. Thus-prepared SBA-15 was employed as a template to synthesize rhombohedrally crystallized mesoporous La_0.8Sr_0.2CoO₃ perovskite via a nanocasting method. The surface properties of the SBA-15 were adjusted by treatment with concentrated hydrochloric acid, trimethylchlorosilane (TMCS), and 3-aminopropyltriethoxysilane (APTES). A series of characterization techniques verified that all the synthesized templates possessed ordered two-dimensional hexagonal mesoporous structure, and the surface was successfully modified with methyl and amino groups. The mesoporous perovskite structure was formed in the samples and the surface properties of SBA-15 significantly influenced the structure and properties of La_0.8Sr_0.2CoO₃ perovskite oxides. Wide-angle X-ray diffraction patterns suggested that the modified silica templates were conducive to the formation of pure perovskite frameworks with good crystallinity. The catalysts also possessed mesoporous structure, as confirmed by small-angle XRD patterns, high-resolution transmission electron microscopy images, and nitrogen adsorption analysis. Moreover, the La_0.8Sr_0.2CoO₃ materials synthesized using surface-functionalized templates exhibited relatively higher catalytic activity and stability in CO oxidation. Complete CO conversion could be achieved at 140℃ using the thus-prepared La_0.8Sr_0.2CoO₃ materials, and no significant loss in catalytic activity was observed after 100 h of on-stream reaction experiments. X-ray photoelectron spectroscopy, H₂ temperature-programmed reduction, and O₂ temperature-programmed desorption experiments revealed that the existence of Co⁴⁺, Sr enrichment in the perovskite structure, and high content of adsorbed oxygen species play a critical role in the enhanced catalytic activity of the catalysts. We also proposed the possible reasons for the effect of surface properties of the silica templates on the structure and properties of the La_0.8Sr_0.2CoO₃ nanomaterials.     

压电体椭圆孔边的力学分析

基于复变函数的方法,以PZT-4材料为例,分别采用精确电边界条件和非导通电边界条件进行了远场均匀载荷作用下的横观各向同性压电体椭圆孔的力学分析并与相关结果进行对比。结果表明当椭圆孔退化为圆孔时,无论在远场作用力载荷或电载荷,两种电边界条件下的结果均能完全吻合。随着椭圆孔的愈加尖锐化,非导通电边界条件逐渐不能适用。     

椭圆孔外作用集中力螺旋弹性平面解

 运用复变函数保角变换与解析延拓方法，获得含椭圆孔无限弹性平面任意位置作 用集中力螺旋的基本解，并由此获得含有限长裂纹的相应基本解，可作为弹性力学典型问题. 该方法较以往文献简捷.     

切槽爆破中V形切槽产生的力学效应研究

本文详细研究了切槽爆破中V形切槽在爆炸冲击波的动态压力和爆生气体的准静态压力作用下产生的力学效应。在此基础上,进一步阐明了V形切槽对岩石定向破裂的控制机理,提出了切槽爆破中裂缝扩展的力学判据。最后,对所得结论用实验结果进行了验证。     

偏振旋转孔散斑照相法

文提出动态散斑技术中一种新的孔径:偏振旋转孔。在旋转孔径处适当布置偏振片能使衍射晕能量分布均匀,信息存储合理,散斑条纹清晰度提高。偏振转孔法能在一张散斑图上记录下全部动态过程,并连续地再现出来。本文介绍了偏振菱位孔,偏振平移孔,偏振四扇孔,论述了它们的全场分析和逐点分析功能,给出了理论分析和实验证明。