Langmuir Blodgett films of arachidic acid and a nematic liquid crystal: Characterization and use in homeotropic alignment

We study the behavior of a mixed Langmuir monolayer consisting of a fatty acid and a nematic liquid crystal. We demonstrate that the mixed monolayer successfully transfers as a Langmuir-Blodgett film and characterize the transferred film using UV spectroscopy. An important application of Langmuir-Blodgett films is in the alignment of liquid crystals for electro-optical applications, such as displays. We show that including the liquid crystal in the Langmuir-Blodgett film produces homeotropic alignment for a system which fails to align by other standard techniques.     

Molecular dynamics simulation of pressure effect on phase transition behaviour and dynamics in the isotropic and discotic nematic phases

Molecular dynamics simulation was performed at constant temperature and pressure to investigate the effect of pressure on molecular dynamics for disc-shaped molecules. The generic Gay-Berne model, GB(0.345, 5.0, 1, 3), was used to study the phase transition behaviour, and translational and rotational dynamics, under two different reduced pressures P^?, 10.0 and 20.0. Obvious shifts were detected in the transition temperatures. Both systems have the same phase sequence with different pressures: isotropic, discotic nematic and columnar phases. Translational motion is characterised by the parallel and perpendicular components of diffusion coefficients, with respect to the director in the orientational ordered phase. With regard to rotational dynamics, the correlation time of the first-rank orientational time autocorrelation function, which corresponds to end-over-end rotational motion of a molecule, has been investigated. A clear jump in the temperature dependence of the correlation time has been found at the isotropic-nematic phase transition point. The retardation factor g_|| as a function of the reduced temperature T^?/T_NI^? shows an apparent pressure effect on the rotational dynamics.     

The role of microstructural morphology on creep properties of a [0 0 1] oriented nickel‐base single crystal superalloy

The experimentally observed microstructure of nickel‐base single crystal alloy consists of a large volume of cuboidal γ′ precipitates coherently embedded in the γ matrix. In calculation, a representative volume element is usually used to represent the whole structures due to the regular γ/γ′ topological structures. Here, three experimentally found microstructures have been extracted to generate the representative volume elements. One is constituted by one cuboidal γ′ phase surrounded by γ phase. The other two consisted of two cuboidal γ′ phases and one rectangle γ′ phase with different arrangement of the two γ′ phases. The misfit stress is taken into consideration by different thermal expansion coefficients of the two phases. The influences of different microstructures on the macro‐creep strain evolution, rafting and stress distributions are discussed.