Crystals2013, 3(4), 530-553; doi:10.3390/cryst3040530 - published online 26 November 2013 Show/Hide Abstract
Abstract: In our studies, it was confirmed that the cause of image sticking on liquid crystal (LC) cells is based on attacks of electrostatic discharge (ESD), which can be greatly relieved by doping with a small amount of tin-doped indium oxide (ITO) nanoparticles. Our proposed remedy allows the residual time of image sticking to be significantly reduced by more than an order and may protect the LC displays against any adverse ESD conditions, thus enhancing the overall display quality and reliability. In this study, conventional voltage-transmittance (V-T) characterization, voltage holding ratio (VHR) measurement, and ESD testing were employed to investigate the properties of the ITO-doped LCs. Based on our low voltage measurement results, it is interesting to find that ITO nanoparticles do not evidently alter the intrinsic properties of the LC. Namely, ITO additive initiates an early breakdown of the doped LC samples exposed to high electric fields. A model is proposed in this paper to depict the possible role of ITO particles applied in LCs.
Crystals2013, 3(4), 517-529; doi:10.3390/cryst3040517 - published online 22 October 2013 Show/Hide Abstract
Abstract: Intermetallide phase formation was studied in a powdered Fe–Al system under layer by layer laser cladding with the aim of fabricating the gradient of properties by means of changing the Fe–Al concentration ratio in the powder mixture from layer to layer. The relationships between the laser cladding parameters and the intermetallic phase structures in the consecutively cladded layers were determined. In order to study the structure formation an optical microscopy, X-ray diffraction analysis, measurement of microhardness, scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) spectroscopy analysis were used after the laser synthesis of intermetallic compounds.
Crystals2013, 3(3), 504-516; doi:10.3390/cryst3030504 - published online 3 September 2013 Show/Hide Abstract
Abstract: Exploratory synthesis in the area of polar intermetallics has yielded a rich variety of structures that offer clues into the transition in bonding between Zintl and Hume-Rothery phases. In this article, we present a bonding analysis of one such compound, Ca10Pt7Si3, whose large Ca content offers the potential for negative formal oxidation states on the Pt. The structure can be divided into a sublattice of Ca cations and a Pt–Si polyanionic network built from Pt7Si3 trefoil units linked through Pt–Pt contacts of 3.14 Å. DFT-calibrated Hückel models reveal that the compound adheres well to a Zintl-like electron counting scheme, in which the Pt–Si and Pt–Pt contacts are equated with two-center two-electron bonds. The experimental electron count is in excess of that predicted by 2%, a discrepancy which is attributed to the electron transfer from the Ca to the Pt–Si network being incomplete. For the Pt–Pt contacts, the occupancy of the bonding orbitals is dependent on the participation of the surrounding Ca atoms in bridging interactions. This use of multi-center interactions isolobal to classical two-center two-electron bonds may illustrate one path by which the bonds delocalize as one moves from the Zintl phases toward the Hume-Rothery domain.
Crystals2013, 3(3), 483-503; doi:10.3390/cryst3030483 - published online 3 September 2013 Show/Hide Abstract
Abstract: We reviewrecent progress in the development of high birefringence (Δn ≥ 0.12) negative dielectric anisotropy (Δε < 0) liquid crystals (LCs) for direct-view and projection displays. For mobile displays, our UCF-N2 (low viscosity, negative Δε, high Δn) based homogeneous alignment fringe-field switching (called n-FFS) mode exhibits superior performance to p-FFS in transmittance, single gamma curve, cell gap insensitivity, and negligible flexoelectric effect. For projection displays using a vertical alignment liquid-crystal-on-silicon (VA LCOS), our high birefringence UCF-N3 mixture enables a submillisecond gray-to-gray response time, which is essential for color sequential displays without noticeable color breakup. Our low viscosity UCF-N2 also enables multi-domain VA displays to use a thinner cell gap for achieving faster response time.
Crystals2013, 3(3), 443-482; doi:10.3390/cryst3030443 - published online 3 September 2013 Show/Hide Abstract
Abstract: Liquid crystals, compounds and mixtures with positive dielectric anisotropies are reviewed. The mesogenic properties and physical chemical properties (viscosity, birefringence, refractive indices, dielectric anisotropy and elastic constants) of compounds being cyano, fluoro, isothiocyanato derivatives of biphenyl, terphenyl, quaterphenyl, tolane, phenyl tolane, phenyl ethynyl tolane, and biphenyl tolane are compared. The question of how to obtain liquid crystal with a broad range of nematic phases is discussed in detail. Influence of lateral substituent of different kinds of mesogenic and physicochemical properties is presented (demonstrated). Examples of mixtures with birefringence ∆n in the range of 0.2–0.5 are given.
Crystals2013, 3(3), 431-442; doi:10.3390/cryst3030431 - published online 26 August 2013 Show/Hide Abstract
Abstract: Twobarium phosphide halides, Ba2P7Br and Ba2P7I, were synthesized and structurally characterized by single crystal X-ray diffraction. Both compounds crystallize in the monoclinic space group P21/m (No. 11) and are isostructural to Ba2P7Cl. The crystal structures of Ba2P7X (X = Cl, Br, I) feature the presence of heptaphosphanortricyclane P73− clusters along with halogen anions and barium cations. According to the Zintl concept, Ba2P7X compounds are electron-balanced semiconductors. Quantum-chemical calculations together with UV-Visible spectroscopy confirm the title compounds are wide bandgap semiconductors. The bonding in the P73− clusters was analyzed by means of electron localization function. The elemental compositions were confirmed using energy dispersive X-ray spectroscopy.