Materials Science Forum Vols. 783-786

Abstract: In this study, the friction and wear properties of the siliconized, chromized and borochromized SS 400 steel/Si₃N₄ tribopairs were investigated in ethyl alcohol at 298 K. The surface of the siliconized plate specimens mainly consisted of Fe₃Si, while the surfaces of the chromized and borochromized steel plate specimens were mainly composed of Fe-Cr alloy and Cr₂B phases, respectively. The borochromized specimens exhibited the highest microvickers hardness of all the plate specimens. Also, it was found that both the chromized and borochromized steel specimens exhibited friction coefficients as low as 0.2 in ethyl alcohol, and that the friction coefficients of the siliconized steel specimens were slightly lower than those of the non-coated steel specimens.

Abstract: Self-ordered nanoporous α-alumina membrane having uniformly sized straight pore arrays was fabricated by anodization of aluminum and subsequent through-hole and heat treatment. The detachment of thick anodic oxide film formed in oxalic acid was performed by combining preliminary loaded heating before stepwise voltage drop and cathodic polarization in phosphoric acid to prevent excess dissolution at the through-hole process. Suppression of excess dissolution of the upper layer of anodic alumina membrane acted an important role to provide symmetrical evenness of top and bottom pore density for the prevention of deformation such as warp and cracking during subsequent heating for crystallization. Thus, a thick, robust and chemically resistant nanoporous crystalline α-alumina membrane was successfully obtained by optimizing preparation conditions.

Abstract: The layers near the interface of explosively welded plates were investigated by means of microscopic observations, mostly with the use of transmission electron microscopy (and Focus Ion Beam technique for the thin foils preparation) equipped with energy dispersive spectrometry. The metal compositions based on steels and Ti, Zr, Ta or Cu, were analyzed. The study was focused on the identification of the intermetallic phases inside the melted zones, the possible interdiffusion between the bonded metals and the changes in the dislocation structure.

Abstract: Self-assembled monolayer (SAM) was adsorbed on the surface of vanadate conversion coated AZ31 magnesium alloy. The SAM thin film was deposited using (Tridecafluoro-1, 1, 2, 2-tetrahydrooctyl) trimethoxysilane (FAS13) and Tetrakis (trimethylsiloxy) titanium as a catalyst. Contact angles measurement, SEM, XRD, EDS and XPS were employed to analyze the surface morphologies, molecular composition, phase structure and wettability of the coatings formed on Mg alloy substrate. Corrosion resistance property of the coatings was also examined using the anodic polarization method and salt spray test. The anticorrosion property was improved with SAM post treatment. Furthermore, the contact angle increases from 12 deg. to 165 deg. indicating to production of super hydrophobic surface with SAM post treatment.

Abstract: It is known that the TiO2 has some photocatalytic functions, even though they are relatively weak and their further enhancements are necessary for wider practical usages. On the other hand, improving materials surface functions by introducing microtextures is of great interest in various fields. Under such circumstances, the present study is aiming at developing a high-functional photocatalytic surface by earning the real surface area and reducing the light reflection and so on with the support of microtexturing technique. In this work, a pure Ti plate surface, which was covered with numerous micro impressions and micro pile-ups formed by the vibration-assisted microscratching, was anodized in order to obtain a regularly microtextured TiO2 film on the uppermost surface of Ti plate, and its wettabilty was evaluated in order to investigate its potential as the photocatalyst. As a result, it was found that the wettability of the TiO2 film surface regularly microtextured by the vibration-assisted microscratching was superior to those of the mirror finished one under the irradiation environment by the ultraviolet rays.

Abstract: State of the Art

Abstract: A structure and morphology of the fabricated nanocomposite materials composed of carbon nanotubes and platinum nanoparticles is reported in the paper. High quality CNTs obtained in the CVD process with a long of 100-200 mm and diameter of 10-20 nm were used in the research. Raw CNTs did not contain metallic impurities or amorphous carbon deposits. An indirect method of bonding the earlier produced platinum nanoparticles to the surface of functionalised carbon nanotubes was used to produce carbon nanotubes – platinum nanoparticles system. The main aim of current research was structure and morphology investigation of obtained nanocomposite using Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM) and X-ray structure analysis (XRD).

Abstract: In the present study, needle like micro-Co₃O₄ rods were synthesized on the cell walls of open celled Al foam_. The microstructure and phase composition of micro-rods and sound absorption properties of resultant samples were characterized. Compared with original Al foams, the modified ones showed enhanced sound absorption capacities, particularly at low frequencies, which were more obvious as the length of Co₃O₄ rods increased. The improvement is related to increased air flow resistance owing to increased roughness of the cell walls.

Abstract: During the solidification of a liquid containing dispersed second phase particles, particles are either rejected or engulfed by the advancing solid-liquid interface. Theories have been proposed on the mechanisms on particle pushing by a freezing front. However, the critical growth velocities predicted are much smaller than actually found experimentally. This article evaluates mechanisms on particle pushing. A specially selected alloy system, an Al-Ti-B master alloy, was chosen to evaluate particle pushing under various solidification conditions. The final distribution of the particles in ingots was examined. It is concluded that most of the particles are pushed by the dendritic solid liquid interface under cooling conditions varying a few orders of magnitude. Mechanical disturbance, such as fluid flow in the remaining liquid of the mushy zone, promotes particle pushing by the growing solid. Keywords: Particle pushing, solidification, Aluminum alloys, and metal-matrix composites

Abstract: Carbon fiber-reinforced plastics (CFRP) composite is most attractive materials to reduce the weight of transportations. To increase the production volume and the efficiency in the field of CFRP component, fast, highly precise and cost-efficient technologies are required. Although laser cutting meets these requirements, it is not used because of insufficient knowledge about the effect of thermal damage on the material behavior. In this study, the effect of several cutting processes on the static tensile strength and the fatigue strength was evaluated for CFRP consisting of thermoset resin matrix and carbon fibers. The CFRP was cut using two different-type of lasers; a CO₂ gas laser and single-mode fiber lasers, and a conventional mechanical tool. The mechanical cutting specimen produced a cut of high quality. While, the laser cutting specimens clearly showed a heat-affected zone (HAZ). The static tensile strength and the fatigue strength by laser cutting specimens clearly decreased in comparison with mechanical cutting specimen. The laser cutting specimen exhibited a linear dependency of the tensile strength on the HAZ, indicating that the main effect resulted from thermal destruction of CFRP within the HAZ.