Electro-crystallization behavior

According to the previous discussions, the above mentioned PEVD composite anode microstructure is largely based on PEVD s unique electro-crystallization behavior.Thus, PEVD has the capability of fabricating composite anodes to meet all the criteria for theoretically ideal anodes as illustrated in Figure 29. Furthermore, with regard to cost efficiency, PFVD is a single step process for composite anode formation. It can be conducted in situ to coat the pure metallic anodes, or even to repair damaged composite anodes for SOFCs. 

In the commercial application, the drop tube method, as mentioned above, is suitable for mass production. The detailed investigations, such as temperature measurement of each small droplet and in situ observation of microstructure formation are not easy to attain because each droplet is in free fall. Here, the levitation method, where an Si droplet with a diameter of mm can be levitated by electromagnetic force using an electro-magnetic levitator (EML), as shown in Fig. 8.5, is a powerful investigation technique because the controlled droplet position enables us to measure the surface temperature of the droplet by pyrometer and to observe the crystallization behavior in situ by a high-speed video camera (HSV) [16-18]. 

Electro-Optic Behavior of Twisted-Nematic Liquid Crystals... 

Conventional AMLCDs use nematic liquid crystals in a twisted configuration between two sheets of glass or plastic, one of which is the backplane containing the TFTs. The space between the two sheets is called the cell gap. Display operation relies on some subtle features of the electro-optic behavior of nematic liquid crystals... 

Chiang, Y. C., Jamieson, A. M., Campbell, S., Tong, T. H., Sidocky, N. D., Chien, L. C., Kawasumi, M., and Percec, V, Electro-rheological behavior of hqnid crystal polymers (LCPs) dissolved in a nematic solvent dependence on temperatnre and LCP structure. Polymer, 41, 4127-4135 (2000). 

A new class of liquid crystal/polymer network composite with very small amounts of polymer network (3 Wt%) is described. These composites are formed by photopolymerization of the monomers in-situ from a solution of monomer dissolved in low-molar-mass liquid crystals. Several techniques have proven useful to characterize these polymer networks. This review describes polymer network structure and its influence on electro-optic behavior of liquid crystals. Structural formation in these composites begins with the phase separation of polymer micronetworks, which aggregate initially by reaction-limited, and then by diffusion-limited modes. The morphology can be manipulated advantageously by controlling the crossover condition between such modes, the order of the monomer solution prior to photopolymerization, and the molecular structure of monomers or comonomers. 

D. Kang, J.E. Maclennan, N.A. Clark, A.A. Zakhidov, R.H. Baughman, Electro-optic behavior of liquid-crystal-filled silica opal photonic crystals Effect of liquid-crystal alignment Phys. Rev. Lett. 86, 4052-4055 (2001)... 

The structures of extra-chain liquid crystalline polymers present applicative interest today for other reasons than those of intra-chain LCP. Coupling of the mesogene with basic chain caused a classical liquid crystal behavior. On the other hand, these structures exhibit characteristics of processability and a mechanical behavior similar with that of polymers, having the same sensitivity to various external sohcitations (electric and/or magnetic field) as simple mesogenes, which recommends the utilization of liquid crystaline polymers with extra-chain mesophase for electro-optic applications [29-32]. 

The dielectric properties of LC polymers are thus direcdy correlated with the electro-optical behavior of polymer systems in the mesophase. Nevertheless, the large set of different molecular motions which take place in comb-shaped LC polymers serve as a graphic example of the manifestation of a set of properties of the polymer and low-molecular-weight crystal combined in one system. 

Liquid crystals (LCs) have been the focus of considerable research for many years and have been developed for use in a wide array of applications. Recently, the development and application of polymer/LC composites has become an area of great interest in LC research. Introducing polymers in LC systems increases the inherent mechanical strength and may dramatically change the LC phase behavior and electro-optic properties (7). Conversely, the directional ordering present in liquid crystals forms a fascinating media in which to study polymerizations (2). 

To produce novel LC phase behavior and properties, a variety of polymer/LC composites have been developed. These include systems which employ liquid crystal polymers (5), phase separation of LC droplets in polymer dispersed liquid crystals (PDLCs) (4), incorporating both nematic (5,6) and ferroelectric liquid crystals (6-10). Polymer/LC gels have also been studied which are formed by the polymerization of small amounts of monomer solutes in a liquid crystalline solvent (11). The polymer/LC gel systems are of particular interest, rendering bistable chiral nematic devices (12) and polymer stabilized ferroelectric liquid crystals (PSFLCs) (1,13), which combine fast electro-optic response (14) with the increased mechanical stabilization imparted by the polymer (75). 

D. Eden and C. Sunshine, in Dynamic Behavior of Macromolecules, Colloids, Liquid Crystals and Biological Systems by Optical and Electro-Optical Methods (H. Watanabe, ed.), pp. 000-000, Hirokawa, Tokyo (1989). 

Switching systems based on photochromic behavior,I29 43,45 77-100 optical control of chirality,175 76 1011 fluorescence,[102-108] intersystem crossing,[109-113] electro-chemically and photochemical induced changes in liquid crystals,l114-119 thin films,170,120-1291 and membranes,[130,131] and photoinduced electron and energy transfer1132-1501 have been synthesized and studied. The fastest of these processes are intramolecular and intermolecular electron and energy transfer. This chapter details research in the development and applications of molecular switches based on these processes. 

In the following sections, we shah demonstrate that the observed behavior of electro-optic activity with chromophore number density can be quantitatively explained in terms of intermolecular electrostatic interactions treated within a self-consistent framework. We shall consider such interactions at various levels to provide detailed insight into the role of both electronic and nuclear (molecular shape) interactions. Treatments at several levels of mathematical sophistication will be discussed and both analytical and numerical results will be presented. The theoretical approaches presented here also provide a bridge to the fast-developing area of ferro- and antiferroelectric liquid crystals [219-222]. Let us start with the simplest description of our system possible, namely, that of the Ising model [223,224]. This model is a simple two-state representation of the to-... 

This research resulted in a substantial gain in the imderstanding of powders at the molecular level and the way in which the surface properties of powders affect their behavior at the bulk level for not only small molecules obtained from chemical synthesis "as is" but can be extended to the engineered particles like the spherical-shaped crystalline particles obtained by novel methods such as supercritical fluids, electro-hydrodynamic spraying, and sono-crystallization. 

In this section, we discuss the behavior of liquid crystal suspensions under the action of an external electric field. The behavior of colloidal suspensions in electric fields is of considerable technological interest with the so-called Electro-Rheological (ER) fluids [17, 18]. The main features of this behavior are now rather well understood. When an external field is applied, particles suspended in an isotropic fluid become polarized. Resultant dipole-dipole interactions between the particles lead to their chaining along the direction of the applied field. When suspended in a liquid crystal host, colloidal particles are also expected to be polarized upon the application of an electric field. However, new phenomena may take place because of the specific response of the liquid crystal. In this case, the external field is likely to alter the distortions of the liquid crystal alignment... 

Besides electricity-induced oxidation-reduction and heating mechanisms, there are other electrochromic mechanisms that give rise to the electrochromic behavior, such as electro-introduced conformational changes of conjugated polymers, reorientation of liquid crystals and change of lattice constant in opals. 

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