二阶非线性弹光张量的旋转不变性

基于群论原理,用Matlab语言编制了用于计算具有SO(2)群对称性的任意阶弹光系数张量的通用软件.在编程中,采用由非对称化的恒等表示基函数构造出具有弹光系数张量本征对称性的对称化恒等表示基函数的方法,以便于编制通用软件.利用该软件得到了具有SO(2)群对称性的二阶非线性应变和应力弹光系数张量的形式,并经坐标变换验证,该张量形式确实具有围绕物理坐标系中Z轴的任意旋转不变性.     

晶体和准晶旋声性质的旋转不变性

依据群论原理对计算张量的群论方法作了改进,采用非对称化基函数取代对称化基函数,以便于编程.用MATLAB编制了用于计算属于SO(2)群各阶张量的软件.借助于该软件得到了具有SO(2)群对称性的旋声张量的形式.指出晶体中属于六角系的6、6 mm和622晶类和准晶中属于五角系的5、52、5 m晶类的旋声性质具有围绕晶体或准晶中唯一高次轴的任意旋转不变性.该结果对于旋声性的应用有重要意义.     

鹿角形状钛酸钡制备及其介电共振现象研究

不同形貌钛酸钡通过将氧化钛前驱体球和钡盐在碱性条件下进行水热和高温烧结制备出来,其与石蜡混合物(75 wt;)在12 GHz微波频率附近发生了介电共振现象.由于钛酸钡是晶格常数降低的顺电立方相/四方相,发生原因是电致伸缩/逆压电效应产生的弹性纵波在晶粒内部的共振吸收.不同条件制备钛酸钡晶粒尺寸(219 nm)趋于一致,共振频率相近,经过110℃水热和1100℃烧结制备的鹿角形状钛酸钡晶粒较大(657 nm)并且相互联接使得共振加强.本工作证明了通过改变钛酸钡晶粒尺寸和形貌从而改变微波介电性能.     

一种锥光干涉和近光轴调制结合测量晶体电光系数的方法

提出了一种测量晶体电光系数的简易方法,即在近光轴电光调制的基础上,通过采用散射程度合适的毛玻璃,同时获得了透射光点和锥光干涉图样.根据透射光点在锥光干涉图样中的位置确定激光通过晶体后产生的相位差,并结合理论可计算出相应的电光系数.该方法对光强以及环境稳定性要求较低,所用设备简单、调节方便.用此方法测量计算了铌酸锂晶体的电光系数,与其他方法测得的结果进行了比较,并且分析估算了其误差来源及大小.结果表明该方法和其他方法相比,测量结果相差不超过5;.对测量误差进行简单分析,主要来自对相位差的判断,此误差不超过4.2;.     

WO3薄膜的电致变色与响应时间机理研究

采用直流反应磁控溅射方法制备了纳米WO3薄膜,研究了溅射气压对WO3薄膜的表面形貌和微结构的影响.利用X射线衍射仪和扫描电子显微镜对WO3的微结构进行了表征.采用紫外-可见分光光度计和循环伏安测试系统对样品的电致变色及响应时间性能进行了研究.结果表明,纳米WO3薄膜的微孔结构特征具有较大的比表面积,有利于改善其电致变色性能.当溅射气压为4Pa时,WO3薄膜在可见光区的电致变色平均调色范围达到了71.6;,并且其着色响应时间为5 s,漂白响应时间为16 s.     

全薄膜电致变色元件的制备及其光学性能研究

采用磁控溅射法在单层玻璃基片上制备了由多层薄膜构成的电致变色元件,通过XRD、SEM等对薄膜及元件的晶体结构、表面形貌等进行了表征分析.采用可见光透射谱,研究了元件的电致变色性能.结果表明,较低的基片温度和较大的靶基距是采用磁控溅射制备电致变色元件的两个很重要的因素.所制备的全薄膜电致变色元件在处于漂白态和着色态时,对可见光的透过率分别达到了47.19;和15.67;,对光的透射率调节范围为31.52;.该全薄膜电致变色元件在电致变色智能窗领域具有较大的应用潜力.     

WO3基电致变色器件的制备及性能研究

本文采用真空热蒸发法,在ITO基底上制备WO3薄膜,之后在空气气氛中对其进行了400℃,1 h的退火处理.SEM测试结果表明,退火后的WO3薄膜变得更为致密平整.将退火后的WO3薄膜,及通过溶胶凝胶法制得的TiO2-CeO2对电极薄膜和PC-PEO-LiClO4凝胶态电解质封装得到电致变色器件,以探索该退火处理对WO3薄膜电致变色性能的影响.结果表明,该WO3基电致变色器件在632.8 nm处的光学调制幅度达56.8;,记忆时间超过24 h,且具有良好的循环稳定性.本研究表明WO3薄膜的后期退火处理对制备高性能WO3基电致变色器件具有重要的意义.     

拓扑结构优化晶体网络实现WO3电致变色性能的提升

利用水热合成法,根据晶体生长特性,分别改变水热反应液中HCl和草酸的浓度,在旋涂有WO3种子层颗粒的FTO导电玻璃上,生长多尺度WO3晶体网络结构,即微米花1、微米花2以及微米海胆.利用扫描电子显微镜(SEM)、X射线衍射(XRD)分析表征样品形貌特征以及晶体结构.最后利用电化学工作站表征WO3的电致变色性能.结果表明,在四种结构中微米海胆由于其有序的针状结构,有利于电解液离子在其中通透,使得离子能够在电场作用下,在纳米针之间较小的运输阻力和路径下定向脱嵌,导致更高的颜色对比度和更好的电致变色性能.     

铝/铁掺杂的非晶碳/铝结构的电致电阻效应研究

采用脉冲激光沉积方法在石英玻璃衬底上沉积铁掺杂的非晶碳膜(a-C:Fe),然后使用真空热蒸发设备在膜上镀铝(Al)电极层,形成Al/a-C:Fe/Al结构的器件.该器件在±5 V测试电压范围内显示出可逆电致电阻效应,具有较好的开关电压、开关比等参数,可用作电阻型随机存储器.     

Theoretical Study of Intragranular Heterogeneity of Deformation and Crystal Rotation

The paper deals with the problem of the intragranular heterogeneous deformation. The grains of a deformed polycrystal are divided in general into subgrains (or deformation zones). In each subgrain a different set of slip systems and consequently a different crystal rotation may occur. We have examined theoretically both the homogeneous and the heterogeneous deformation in tension of a grain using the model of the plastic inclusion(s) in an elastic matrix. The crystal structure and orientation as well as the interactions between slip systems have been taken into account. For both situations (homogeneous and heterogeneous) we have compared resulting deformation energies, active slip systems and crystal rotations. We conclude that for some configurations of heterogeneity it is possible to minimize the total deformation energy.     

Order Parameter and Refractive Index of Cholesteryl Linoleate

Refractive indices of cholesteryl linoleate are determined at different temperatures and order parameters have been calculated in smectic and cholesteric phases.     

Dielectric Anisotropy and the Order Parameter of HXBBA

Abstract

Measurements of dielectric anisotropy (Δ?), refractive indices (n _e , n _o), birefringence (Δn) and density (ρ) have been made in the nematic and smectic phases of N(-p-hexyloxybenzylidene)-p-butylaniline (HXBBA). The results indicate that the various transitions are of the first order type except smectic B-smectic G, which may be a second order transition. The order parameter S has been determined using the isotropic internal field model (Vuks approach) and the anisotropic internal field model (Neugebauer's approach) and both the values agree fairly well. The dielectric anisotropy (Δ?) increases strongly in the smectic phases whle S increases only slowly. It is interpreted by an increase of dipole-dipole correlations.     

Molecular Properties and Order Parameters of Schiff's Base Compounds

The refractive indices n_o, n_c and the order parameters are measured as a function of temperature for the Schiffs base compound PBBA. From the experimental data the molecular polarisabilities and its anisotropies at different wavelengths are calculated using different internal field models. The merits of each model are discussed. Order parameters (P ₂), (P ₄) and other molecular parameters of PBBA and EBBA are also calculated using X-ray diffraction techniques at different temperatures. Comparison with theoretical values shows the relative merits of different experimental techniques. The (P ₂) and (P ₄) values of other members of the Schiff's base compounds, already reported from our laboratory, have been given herewith to show the disagreement with the simple mean field theory. Possible causes for such disagreement have been discussed.     

Order Parameter and the Performance of Nematic Guest-Host Displays

A simple model of a nematic guest-host display is presented in which the limiting “on” and “off” states are considered to be uniform arrays of molecules oriented perpendicular and parallel (or at a small tilt angle), respectively, to the plane of the display. Calculated contrast ratio and brightness curves are presented for several angles of view and of all planes of view as functions of dye order parameter, pretilt andploarizer efficiency. The effects of host refractive index and front surface reflectivity are discussed.     

Birefringence and Order Parameter of Some Alkyl and Alkoxycyanobiphenyl Liquid Crystals

The refractive indices and densities of six liquid crystals—two alkylcyanobiphenyls, three alkoxycyanobiphenyls and one mixture of two alkylcyanobiphenyls have been reported as a function of temperature. The effective polarizabilities α_eand α_o in the nematic phase calculated using the methods due to Neugebauer, Vuks and Saupe and Maier, are found to be appreciably different, though the order parameter S evaluated with those values of (α_e - α_o) are in good agreement. The preference of one method over the other two is discussed.