Advanced Materials Research Vol. 909

Abstract: The paper deals with analysis of influence of pressing speed, of melt temperature and of casting position in a mold upon ultimate tensile strength R_m of die casting from aluminium. The monitored parameters of die casting are very important in terms of production efficiency and quality of casting, which is positively reflected in economic indicators of the production.

Abstract: Submarine structural steels, such as SM 400, SM 490, and SM 520, have the same structural properties and same grades as general structural steels, but those have better weldability than general structural steels. For that reason, their usage is increasing. However, their fire resistance is not well defined, except for individual fire resistance, such as column and beam. The fire resistance of H-section made of submarine structural steels can be applied with various column lengths. The fire resistance of them is not clear to engineers and residents. To determine the fire resistance, in this paper an analysis was conducted using their mechanical properties at high temperature and related theories with a standard fire curve. As the strength of submarine structural steels is increased, the structural stability showed a rapid decrease while the longer the length of column, the less structural stability of the column represented.

Abstract: High-Birefringence Nematic Liquid Crystals Mixtures (HBNLCM) recently developed in the Military University of Technology (Poland) are presented in this paper. Dielectric, refractometric, viscosimetric and elastomeric characteristic were determined. The properties are discussed in terms of their applicability to electro-optical devices. Applying HBNLCM of LCM to space mission (Phobos Ground) applications for a space-borne laser rangefinder was developed, manufactured and tested under cooperation between Military University of Technology (MUT) in Poland and Vavilov State Optical Institute (Vavilov SOI) in Russia. Transmission T of Liquid Crystal Cell (LCC) at λ=1.064 μm was not smaller than 95% at the aperture diameter not less than 15 mm. Switching on and switching off times in 2.5 μm thick LCC driven by voltage 10 V were not larger than 0.7 ms. Applying HBNLCM of LCM3 to refractive index matched twisted Nematic Liquid Crystal Cell of type LCNP4 for Thomson diagnostics of dense plasma was developed, manufactured and tested under cooperation between MUT in Poland and the National Research University of Information Technologies, Mechanics and Optics in Russia. Transmission T of LCNP4 at λ=1.064 μm was not smaller than 97% at the aperture diameter not less than 30 mm. Switching on time in 2.5 μm thick LCNP4 driven by voltage 200 V was not larger than 3 μs. LCNP4 can easily tolerate 0.42 J/cm².

Abstract: (Ti,V)₂AlC solid solutions with Al₂O₃ addition were produced by solid state combustion involving aluminothermic reduction in the mode of self-propagating high-temperature synthesis (SHS). Starting materials included Ti/V₂O₅/Al/Al₄C₃ and TiO₂/V₂O₅/Al/Al₄C₃ powder mixtures. Attempts were made to obtain (Ti_1-xV_x)₂AlC with a broad substitution percentage. Combustion exothermicity was increased by increasing V₂O₅ for the yield of a higher proportion of V at the substitution site, which not only increased the combustion temperature and reaction front velocity, but also facilitated the evolution of (Ti,V)₂AlC. The Ti-containing samples showed higher reaction exothermicity and better product formation than those adopting TiO₂. As a result, (Ti_1-xV_x)₂AlC with x from 0.2 to 0.8 was produced from the samples composed of the Ti/V₂O₅/Al/Al₄C₃ mixture. The (Ti,V)₂AlC/Al₂O₃ composites synthesized in this study exhibited a laminated microstructure with closely-stacked (Ti,V)₂AlC slabs of about 0.30.8 μm.

Abstract: Currently many different types of protective garments are used designed to protect the wearer against biological contamination (e.g., bacteria) and mechanical impurities (such as dust, drops of technical fluids, etc.). Their disadvantage is that, thanks to the materials used in the requirement of a high level of protection for the user, a very low permeability even to zero, so that for example, do not allow to remove moisture and heat from the user's body and thus their use is quite uncomfortable, and conversely, in case of the requirement of good breathability and high comfort of application have very little effectiveness in detecting biological and mechanical impurities, which is not sufficient for a number of disciplines.

Abstract: The experimental trials were conducted by design of experiments (DOE) technique to find an anisotropic wet etching condition that achieves 90° wall angle on silicon (100) orientation wafer. Three considered factors assigned to the DOE were NaOH concentration, solution temperature, and stirring speed. The response aimed for this study was not only targeting at 90° wall but also providing highest etch rate. The experimental results showed that in order to fabricate the 90° wall angle, the best etching condition using was 30% wt NaOH concentration, 80°C solution temperature, and 300 rpm stirring speed. This condition gave an etch rate of 1245 nm/min with surface roughness (R_a) of 701.48 nm.

Abstract: The melting behaviors of Co_nCu_55-n(n=0~55) bimetallic cluster were studied by using semi-empirical Gupta potential combined with molecular dynamics simulations. The melting point of the Co_nCu_55-n(n=0~55) cluster shows itself the trend of going up, accompanied by the increasing of the Cobalt atomicity. However, it is between Co₅₅ and Cu₅₅ elementary cluster for melting point overall. Meanwhile the variation in the width of pre-melting temperature is greater, if around n0 or n55, but it is lesser nearly n55/2(namely Co and Cu at the same atomicity). In addition, the saturation point of specific heat capacity can be determined corresponding to the peak of Lindemann index.

Abstract: Electromigration (EM) is the phenomenon of atomic diffusion in a metallic film with a high-density electron flow. Our group used EM to fabricate Al micro-materials. The EM technique can be used to fabricate micro-materials with a high aspect ratio, pure metal components, an arbitrary form, and a single-crystal structure. Recently, two micro-materials have been simultaneously fabricated using an array pattern consisting of parallel or series connections. However, multiple micro-materials have not been fabricated simultaneously thus far. In this study, a new comb sample pattern was used with a conductive passivation film to produce multiple Al micro-materials.

Abstract: The liquidus temperature of molten salt NaCl-KCl-NaWO₃F system was measured by differential thermal analysis. The results show that in the molten salt system when :=1:1, X_NaWO3F <0.5 the liquidus temperature decreased with the increase of NaWO₃F content; when :=1:1, X_NaWO3F>0.5 the liquidus temperature increased with the increase of NaWO₃F content; the eutectic temperature is 615.9 °C, the eutectic composition is =0.25, =0.25, X_NaWO3F=0.5.