共查询到20条相似文献,搜索用时 15 毫秒
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B. Picart A. Arranz G. Oustry B. Tromeur 《Quality and Reliability Engineering International》1991,7(4):249-254
The complexity of present VLSI chips requires powerful tools to detect possible defects. For such a purpose, internal contactless testing methods such as electron beam or laser testing, have been developed to help the precise localization of the electrical defect. The aim of this paper is to describe the liquid crystals test method, used at the IBM COMPEC laboratory for failure analysis. The electro-optical properties of these materials allow the visualization of electric signals on the chips surface. 相似文献
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通过热引发聚合制备了聚甲基丙烯酸甲酯基网络稳定铁电液晶(PNSFLC)材料。采用热台偏光显微镜观察了由不同含量的甲基丙烯酸甲酯(MMA)制备的PNSFLC样品的网络织构。采用紫外分光光度计在0~30V的电压条件下研究了PNSFLC样品的电光性能。采用阿贝折射仪在0~70℃范围内,研究了PSFLC的折射率随温度变化的关系。结果表明:随着(MMA)含量的增加,聚合物网络结构由稀疏至致密。当MMA含量为7%时,所制备的PNSFLC样品的电光响应比小分子液晶的电光性能成线性好,且该MMA含量的PNSFLC样品的热稳定性较好。 相似文献
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Electro-optic and dielectric studies have been carried out on two ferroelectric liquid crystalline materials: namely, the commercial mixture possessing low spontaneous polarization and pure material with high spontaneous polarization on cells with planar alignment. The calculated values of spontaneous polarization, response time and rotational viscosity were found ~ 240 nC/cm2, 20 nC/cm2, 1600 μs, 500 μs, 230 kg/ms and 19 kg/ms for high and low polarization ferroelectric liquid crystalline materials, respectively. For the ferroelectric liquid crystal with high polarization, the effect of temperature, frequency and bias field on the dielectric properties have been studied and the obtained results were compared to those obtained on the ferroelectric liquid crystalline mixture with low spontaneous polarization. 相似文献
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N V Madhusudana 《Bulletin of Materials Science》1988,10(1-2):53-59
After briefly describing the usually observed defects in nematic liquid crystals, we give a summary of our observations on
high strength line defects and a regular network of point disclinations on the nematic-isotropic interface. 相似文献
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铁电液晶空间光调制器响应特性的研究 总被引:4,自引:0,他引:4
以铁电液晶为非线性介质建立了光寻址空间光调制器的等效电路,并以写入光和擦除光为控制参变量,利用电路分析软件Pspice模拟了该光调制器的光电响应特性。结果表明,电路方法得到的上升时间在微秒(μs)量级上,擦除效应的临界值在毫瓦每平方米(mW/cm^2)量级上;光电响应速度随写入光强(擦除光强)的增大而加快(减慢),均与相关文献的实验结果吻合。 相似文献
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Alignment of liquid crystals doped with nickel nanoparticles containing different morphologies 总被引:1,自引:0,他引:1
Zhao D Zhou W Cui X Tian Y Guo L Yang H 《Advanced materials (Deerfield Beach, Fla.)》2011,23(48):5779-5784
Uniform homeotropic and homogeneous alignment of liquid crystals (LCs) is facilely achieved by dispersing Ni nanoparticles (Ni NPs) into the LCs. The alignment mode depends on the morphology of the Ni NPs. The mechanism of NP-induced LC alignment is elucidated clearly, indicating that the perfect orientation arises from the adsorption of Ni NPs on the substrate. 相似文献
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Carbon nanotubes are the best of known materials with a combination of excellent mechanical, electronic, and thermal properties. To fully exploit individual nanotube properties for various applications, the grand challenge is to fabricate macroscopic ordered nanotube assemblies. Liquid-crystalline behavior of the nanotubes provides a unique opportunity toward reaching this challenge. In this Review, the recent developments in this area are critically reviewed by discussing the strategies for fabricating liquid-crystalline phases, addressing the solution properties of liquid-crystalline suspensions, and exploiting the practical techniques of liquid-crystal routes to prepare macroscopic nanotube fibers and films. 相似文献
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The helicoidal structures in ferroelectric liquid crystals can be utilized to realize a special phase matching for the second-harmonic
generation (SHG) when two counter-propagating fundamental waves are normally incident and the wavelength of the second-harmonic
wave is near the selective reflection band edge. In this paper, we report the thickness and polarization dependences of the
SHG thus observed. By comparing the experimental results with the theoretical ones developed, good agreement was confirmed. 相似文献
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S. S. Sarman P. T. Cummings D. J. Evans 《International Journal of Thermophysics》1994,15(6):1125-1134
During the last 15 years, noneyuilibrium molecular dynamics (NEMD) has been successfully applied to study transport phenomena in fluids that are isotropic at equilibrium. A natural extension is therefore to study liquid crystals, which are anisotropic al equilibrium. The lower symmetry of these systems means that the linear transport coefficients are considerably more complicated than in an isotropic system. Part of the reason for this is that there are crosscouplings between tensors of different rank and parity. Such couplings arc symmetry-forbidden in isotropic phases. In this paper. we review some of fundamental theoretical results we have derived concerning the rheology of liquid crystals. report NEMD simulations of thermal conductivity and shear viscosity of liquid crystals, and present NEMD simulations of shear cessation phenomena. All of the NEMD results are presented for a model liquid crystal fluid which is a modification of the Gay-Borne fluid. The results obtained are in qualitative agreement with experimental measurements on liquid crystal systems.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
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The first experimental evidence of director fluctuations in a micellar lyotropic liquid crystal, studied by 1H spin-lattice relaxation rate, is reported. The system is constituted by the ternary mixture: potassium laurate/1-decanol/water. With the aim to test the slow dynamics, the experiment has been performed over a broad range of Larmor frequencies (2 ×
103− 6.6 × 106 Hz), using fast field-cycling NMR relaxometry. The results evidence that in the nematic and isotropic mesophases and the
poliphasyc region, director fluctuations are responsible for the spin-lattice relaxation dispersion in the low Larmor frequency
range (<105 Hz). By increasing the intermicellar water content, a crossover was found between a quasi-isotropic 3D director fluctuations
behavior to a 2D pseudo-lamellar undulation fluctuations. In order to explain the higher frequency range (>105 Hz), two relaxation mechanisms are assigned: i) molecular reorientation by translational diffusion on the micellar surface,
and ii) molecular exchange between the micelle and the bulk.
Received: 30 March 2000 相似文献
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Abstract This paper deals with the enmicrocapsulation of cholesteric liquid crystals by the colloid coaversation process. This incident light reflection study reveals that the encapsulated liquid crystal films sustain highly sensitive and precise temperature gradients with responding abilities determined by their iridescent coloration. 相似文献
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Supattra Wongsaenmai Rattikorn Yimnirun Supon Ananta Amar S. Bhalla 《Materials Letters》2008,62(3):352-356
Thermal expansion was measured for the ceramic compositions (1 − x)Pb(In0.5Nb0.5)O3-(x)PbTiO3 (x = 0.0, 0.1, 0.2 and 0.3) prepared via the wolframite method. The deviation from the straight line below Burns temperature for all the compositions was due to the dynamic polarization fluctuations. Burns temperature was determined and found to increase with increasing PT concentration. The local polarization was calculated from the thermal expansion data. The calculated local polarization and the measured reversible spontaneous polarization were compared and the relaxor behavior of the PIN-PT compositions was analyzed. 相似文献
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推导出了0-3/1-3混合连通型铁电陶瓷-铁电聚合物的热释电系数表达式, 并详细讨论了陶瓷体积分数 v2和陶瓷颗粒粒径与膜厚比(G/t)分别对复合材料的热释电系数pc及pc/εc(εc为复合材料的介电常数)的影响。结果表明: 当G/t≥0.5时, 不同陶瓷体积分数复合材料的热释电系数pc均趋向于某个定值, 说明此时G/t对热释电系数的影响可忽略不计; 另外当陶瓷体积分数为0.1时, 随着G/t的增大, pc /εc出现一个极大值, 且当G/t=0.9时, pc /εc比纯PZT陶瓷的大8倍, 表明此条件为最佳工艺条件。而且, 在低陶瓷体积分数和低G/t比时, 理论曲线与实验数据符合较好。 相似文献
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A new liquid crystal of a siloxane dimer with an achiral swallow-tail, C11Si2C11, D, was synthesized and mixed with a chiral material as a chiral dopant, 4′-[11-(1,1,2,2,3,3,3-heptamethyltrisiloxanyl)undecyloxy]biphenyl-4-carboxylate, C11Si3, C, to prepare binary mixtures for this study. All mixtures possess the ferroelectric chiral smectic C phase over a broad temperature range. For respect compound C11Si3, the temperature range of the SmC* phase was only 72.6 °C, and was increased upon the addition of dimer C11Si2C11. The electro-optical properties of the SmC* phase, such as tilt angle, dielectric permittivity and switching behavior were also measured. It appeared that the mixtures had a similar viscosity, but the switching time was decreased due to the larger Ps, which was caused by an increased proportion of C11Si3. Therefore, the mixtures revealed a similar tilt angle at around 37.5° at temperatures within their respective mesophase temperature ranges. As a consequence, the correlation between the electro-optical properties and mixture proportion was determined. 相似文献
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Honglawan A Beller DA Cavallaro M Kamien RD Stebe KJ Yang S 《Advanced materials (Deerfield Beach, Fla.)》2011,23(46):5519-5523
SU-8 pillar-assisted epitaxial assembly of toric focal conic domains (TFCDs) arrays of smectic-A liquid crystals is studied. The 3D nature of the pillar array is crucial to confine and direct the formation of TFCDs on the top of each pillar and between neighboring pillars, leading to highly ordered square and hexagonal array TFCDs. Excellent agreement between the experimentally obtained critical pillar diameter and elasticity calculation is found. 相似文献