Materials Science Forum Vols. 663-665

Abstract: In this work, the influence of surfactant including the amount and the nature of the surfactant as well as alcohol solvents with different hydrocarbon chains including methanol, ethanol, 1-propanol and n-butanol on the formation of silica spheres were investigated. The morphologies and the composition of the prepared silica spheres were studied with scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) techniques. The results revealed that the size and size distribution of the spheres can be modified by changing the concentration or the nature of the surfactant additives. The influence mechanisms of surfactants additives and the alcohol solvent on the formation of silica spheres were discussed based on nucleation and growing process of the spheres.

Abstract: Considered the model of the one-dimensional photonic crystals (1-D PCs) with double defects, the refractive indexes (n2’, n3’ and n2’’, n3’’) of the double defects were 2.0, 4.0 and 4.0, 2.0 respectively. With parameter n2=1.5, n3=2.5, by theoretical calculations with characteristic matrix method, the results shown that for a certain number (14 was taken) of layers of the 1-D PCs, when the double defects abutted, there was a defect band gap in the stop band gap, while when the double defects separated, there occurred two defect band gaps in the stop band gap; besides, with the separation of the two defects, the transmittance of the double defect band gaps decreased gradually. In addition, in this progress, the frequency range of the stop band gap has a little increase from 0.092 to 0.095.

Abstract: Characteristic matrix method was used to calculate the transmittance spectra of the one-dimensional photonic crystals (1-D PCs). By theoretical calculations, the transmittance spectra of time-harmonic electromagnetic wave in the 1-D PCs with various incident angles were derived. From the transmittance spectra, it shown that along with the incident angle increased from 0o to 85o, the frequency range of stop band gap also increased from 0.085 to 0.119 for the certain periodicity N=16 of the 1-D PCs. In addition, for a certain incident angle (in this letter, the incident angle 30o was used), the transmittance spectra for different periodicity (N=2, 4, 8 and 16 respectively) were also calculated, it demonstrated that different incident angles could influence the stop band gap range markedly, but on the transmittance was minimal.

Abstract: In this letter, characteristic matrix method was used to calculate the transmittance spectra of the one-dimensional photonic crystals (1-DPCs) with single defects in the center. From altering the refractive indexes n2’ and n3’ respectively for the defect, the transmittance spectra were calculated. From them, it shown that for the certain numerical value n3’=5.0, during the course of n2’ increased from 1.1 to 3.5, when it upped to 2.0, there occurred defect band gap in the stop band gap, and the defect band gap is at frequencies between 0.24~0.30. Besides, for n2’ =2.0, when n3’ increased from 1.1 to 3.5, there also occurred defect band gap in the stop band gap, and the defect band gap is at frequencies between 0.26~0.32. In addition, in these two progresses, the transmittance increased firstly and then decreased in the defect band gap.

Abstract: The model of the one-dimensional photonic crystals (1-D PCs) with a centered defect with increasing number of layers was considered, and characteristic matrix method was used to calculate the transmittance spectra of the 1-D PCs. From the transmittance spectra, it shown that during the course of the number N of the layers of 1-D PCs’ one side symmetrical increased from 2 to 16, there occurred defect band gap in the stop band gap, when N upped to 16 , the defect band gap disappeared; besides, the defect band gap is at the frequencies around 0.30. In addition, in the progress of N increased from 3 to 16, the defect band gap reduced from the frequency range 0.0570 to 0.00, and the transmittance declined from 73.59% to 13.94% in the defect band gap.

Abstract: Smart windows were fabricated with different thicknesses of amorphous V2O5, which acts as an ion storage layer. In these devices, V2O5 was deposited by thermal evaporation at a substrate temperature of 200 oC, and an electrochromic layer (WO3) was deposited by electron beam evaporation at a substrate temperature of 250 oC. Both layers were amorphous. V2O5 was found to exhibit direct-forbidden electron transitions, whereas the WO3 layer exhibited indirect-allowed electron transitions. An increase in the thickness of V2O5 from 78 nm to 313 nm reduced the colouration efficiency from 64 to 48 cm2/C, and the time of the transmission variation curve from the coloured state to the bleached state was increased from 82.41 s to 558 s.

Abstract: Amphiphilic molecules self-assemble lamellar phase process in lyotropic liquid crystal formed by liquid dishwash was investigated with optical microscopy as concentration increases from its isotropic phase to its lamellar phase. We demonstrated that liquid dishwash molecules could assemble themselves into lamellar phase when their concentration increases between one pieces of glass substrate. We discussed the formative processes of Maltese-cross structure and phase transition from isotropic to lamellar phase.

Abstract: Based on the electro-optical property of liquid crystal (LC), an eye controlling anti-glare detector is designed in this paper. According to the transmission characteristics of SONY- LCX029 materials, the principle and working mode of anti-glare are described. The detector can get the object’s images by eye-controlling focus (ECF) module and exposure metering module. The LC can change each pixel’s transmission with the reasonably designed control circuit so that the glare is restrained. An experiment of SONY-LCX029 LCD (liquid crystal display) transmission changes with the gray level proved that the transmission of the LCD changes from 1.28% to 25.60%, reducing 2 orders of magnitude of strong light at least.

Abstract: A series of cholesterol liquid crystal compounds was synthesized. Phase-transition temperatures and mesomorphic textures of these synthesized compounds were characterized with differential scanning calorimetry and polarized optical microscopy, respectively. In these molecules the terminal ester chains CnH2n-1COO-, where n was the number of carbon atoms in the terminal ester chains, were linked to the cholesterol core. All of the synthesized cholesterol compounds exhibited mesophases for the first heating. However, as temperature decreased from their clearing points, their micrographs can also be divided into two categories, the first category exhibits branch-like mesophase textures for n in the range of 1-10 while the second category exhibits branch-like crystal textures for n in the range of 11-18.

Abstract: Polymer dispersed liquid crystal device was prepared by the method of polymerization induced phase separation. The phase separation in our PDLC device was characterized by a polarized optical microscope. Our results demonstrated that the phase-separated droplets in our PDLC device presented the four-brush radial, bipolar and axial configurations. Furthermore, these configurations were simulated by mathematica tool