Yuzuru Sato

High Quality Ferroelectric Liquid Crystal Display with Quasi-Bookshelf Layer Structure

We realized a surface stabilized ferroelectric liquid crystal display with high contrast ratio and high transmittance using a conventional rubbing method. Such remarkable electrooptical properties are based on the switching between uniform states in a cell treated with an AC electric field in the SmC*. It was confirmed by X-ray diffraction that the treatment caused a permanent change in the smectic layer structure from a chevron to a quasi-bookshelf structure. An example of multiplexing is also displayed.

Magnetic Field Effects on Preparing Thin Homogeneous Ferroelectric Smectic Cells for Electro-Optical Microsecond Switches

The effects of a magnetic field on the preparation of homogeneously aligned thin cells are examined with a 1~12 µm wedge-shaped cell of 2-methylbutyl p-(p-n-decyloxybenzylideneamino) cinnamate (DOBAMBC). Analyzing the properties of this cell, we concluded that the wide temperature range where the Sm A and the isotropic phases coexist is desirable for preparing thin cells of good quality. We actually widened this range by using an aged, degraded sample of DOBAMBC, and succeeded in obtaining a reasonably good cell of 3.5 µm thickness by applying 24 KG.

Helical Pitches and Tilt Angles in Room Temperature Ferroelectric Chiral Smectic C Liquid Crystals, MORA n and MBRA n

The helical pitches and the tilt angles are measured as a function of temperature for recently synthesized room temperature ferroelectric Sm C* liquid crystals to examine the possibility as materials for switching devices. The pitch of MBRA 8 is almost independent of temperature except in the range close to the Sm A to Sm C* phase transition, where it appears to decrease steeply as in nOBAMBC. In MORA 8 and 12, it gradually increases with temperature but does not decrease near the transition from Sm C* to isotropic. The tilt angle of MBRA 8 is relatively small as compared with the desired value of 22.5° for the best contrast. The tilt angle of MORA n could not be determined because the spontaneous polarization is too small to unwind the helix for the measurements. The present substances are not suitable for switching devices by themselves, but are pointed out to be useful as mixing components.

Anomalous Electric Field Dependence of Helical Pitches in Ferroelectric Sm C * at Temperatures Close to the Phase Transition to Sm A

The field dependence of the helical pitches in 2-methylbutyl p-(p-n-hexyloxybenzylideneamino) cinnamate has been studied optically using a homogeneously aligned cell of high quality. Near the phase transition from Sm C* to Sm A, the helical pitch depends on the applied field to a much greater extent than that predicted by the unwinding mechanism of the helicoidal structure based on the assumption that the tilt angle is independent of the field. This fact suggests that thermal fluctuations in the tilt angle play an important role in the unwinding mechanism.

Representation of the Viscosity of Molten Alloy as a Function of the Composition and Temperature

Although the viscosity of molten metal is very important, the measurement is considerably difficult for high temperature melts. The authors group has developed an oscillating viscometer for high temperature metal. The prediction of the viscosity behavior of the alloys is most useful task because the experimental data acquisition is not easy. In the prediction process, important issue is the composition and temperature dependence. The author has found that the additivity of the logarithmic viscosity was dominant criteria on the composition dependence based on the result of Fe–Si binary melt. Therefore, the logarithmic additivity was adapted to some nickel based super-alloys which were multi component systems. The viscosities of nickel based five binary melts were measured for the representation of the viscosities of super-alloys. The formulation was done by using the separation of variables method. The pre-exponential term and the activation energy were separately approximated as a function of the composition. The results of the approximation successfully represented the viscosities of molten super-alloys.

Electrowinning of Lithium from Molten Salt Containing LiOH for Hydrogen Storage and Transportation

Introduction Hydrogen is expected to contribute in energy saving by the improvement of energy efficiency with use of fuel cell and in reduction of environment burden matters such as CO2 and NOx. However, an effective supply system of hydrogen has not yet been established at this stage. The authors have investigated the system for storage and transportation of hydrogen by using lithium hydride (LiH) as a storage medium [1]. The schematic illustration of the system is shown in Fig. 1. In this system, LiH is synthesized by the reaction of lithium metal with hydrogen gas (H2) produced by conventional methods, e.g. steam reforming of natural gas (hydrogenation process). LiH has great hydrogen storage capacity and is chemically stable at ambient temperatures and pressures. LiH transported from supplier to user is reacted with water, and H2 gas corresponding to 25% of mass of LiH is then released with following reaction: LiH(s) + H2O(l) = H2(g) + LiOH(s) (hydrolysis process). LiOH formed after H2 generation is returned to supplier in which lithium is reproduced by molten salt electrolysis (electrolysis process). The regeneration of lithium metal from LiOH by electrolysis is the most important process in the system, and its fundamental investigation was carried out in this study.

Brillouin Spectra and Structural Relaxation in ZnCl2–KCl Binary Melts

The Brillouin scattering experiment has been carried out for molten ZnCl2-KCl binary melts over the composition range 0–45 mol% KCl. The complete profiles of Rayleigh-Brillouin spectra were obtained at scattering angle of 90°, and at temperatures ranging from 550 to 1000 K by the use of carefully purified samples. Marked change in the shape of the spectrum with variations in temperature and composition has been observed and has been concluded to be due to structural relaxation in the melts. A dispersion of sound wave propagation was observed in the melts in the hypersonic region. The spectra have been analyzed based on the viscoelastic theory on the assumption of single relaxation. The sound velocities at the limiting low and high frequencies and the relaxation time have been determined.

Production of Tantalum Fine Powder by Reduction of Tantalum Chloride with Zinc

Tantalum (Ta) capacitor are mainly used on the mobile devices due to its excellent characteristic such as high capacity per unit volume and high stability. Performance of the tantalum capacitor has close connection to the size and form of the tantalum powder, and these characteristic have been improved by the studies of reduction condition. Tantalum powder is produced industrially by sodiothermic reduction of K2TaF7 in the molten salt consitsting of KCl-NaCl-NaF (Hunter process) This process contains problems such as high reaction temperature and discharge wastes including fluorine. It is also mentioned that it is technically-difficult to reduce the diameter of powder by this process furthermore, therefore a new process is expected to improve the performance of tantalum capacitor. The authors proposed a new process for the production of fine tantalum powder. The process is based on the reduction of TaCl5 by metalic zinc (Zn). The authors previously studied to produce fine powder by the reduction of TaCl5 vapor with Zn vapor, represented by the equation of TaCl5 (g) + 5/2Zn (g) = Ta (s) + 5/2ZnCl2 (g). In the previous study, it was successful to obtain a fine powder which primary particle was smaller than 1μm. However, gas phase reaction is poor in reaction efficiency and is difficult to control the deposition region. For industrialization of the process, it is necessary to improve the reaction efficiency and to facilitate the collection of product. Therefore, the authors propose to use molten salt as a reaction medium, and to inject the vaporized reactant into the molten salt with a carrier gas in this study. By using molten salt as a reaction medium, the reaction efficiency improves due to extend residence time, moreover deposition region can be limited in the molten salt and it can be easier to collect the product. The reaction apparatus used in this study is shown in Fig.1. Reaction apparatus is consist of two reactant vaporized part and one reaction part. TaCl5 (4.4g) and Zn (6.9g) were contained in the vaporized part and molten mixture of NaCl-LiCl (91.4g) was contained in the reaction part made of quartz. These setups were separately heated under purified Ar, the vaporized reactant was injected into the molten salt with a carrier gas (rate of carrier gas : 20ml/min ) after the salt has melted. Temperature of TaCl5 vaporized part was about 500K (pTaCl5 =0.086 MPa ) and that of Zn vaporized part was about 1000K (pZn = 0.012MPa ). The reaction temperature was about 1000K and reaction time was 30min. The setups were cooled in the furnace under Ar after the reaction. The solidified salt and residual Zn were removed in a distilled water and HCl aqueous solution. The sample powder was rinsed with distilled water and ethanol, and dried under vacuum. After the reaction, tantalum powder formed was stored in the molten salts, and deposition region was effectively limited, which served easy collection of the products. Fig.2 shows a representative TEM image of the tantalum powder obtained. As shown in the figure, Ta aggregation of primary particles with diameter of 10100nm was successfully obtained.