Applied Mechanics and Materials Vols. 548-549

Abstract: A novel synthetic approach to ultrathin (< 5 nm) multilayered single crystalline gold nanosheets using amphiphilic comb-like polymer as template was presented. The poly (oxyethylene) containing decyl-tri (oxyethylene) amphiphile as well as the thioether linking group in the side chain was synthesized via polymer analogous reaction. The polymer and the gold precursor, LiAuCl₄, were mixed and dried to afford a homogeneous complex. The gold precursors were reduced to gold crystals by photoreduction using long wave UV light (> 350 nm). The gold nanosheets with multilayered structure, where the layer spacing is about 3.6 nm, were obtained after 24 h. The formation of the multilayered nanosheets is due to the layered structure of the gold complex of the polymer and precursor.

Abstract: This paper describes the design, manufacturing and welding sequence for the aluminum alloy vacuum chamber for Taiwan Photon Source. The vacuum chamber composes of aluminum extrusion chamber of A6063 and BPM chamber of A6061 aluminum alloys. The straightness and flatness of these extrusion chambers are controlled under 0.1mm/m and 0.2mm/m, respectively. The BPM chambers are manufactured precisely in oil-free environment, which provide clean surface and a precise sealing surface after machining. All the components are assembled in pre-aligned support system through the welding process, and then the results show the straightness of < 0.15mm/m, flatness of < 0.3mm/m, and leakage rates of < 2 × 10^-10 mbar‧l/sec. were achieved.

Abstract: This present paper is aims to study the influence of cold rolling process on the microstructure and corrosion behaviors of 316L stainless steel using potentiodynamics polarization testing techniques. The steel with initial thickness of 2.0 mm was unidirectional cold rolled to 10%, 30% and 50% reduction in thickness. The corrosion behaviors of the cold rolled steels were evaluated in phosphate buffered saline (PBS) as their simulated body fluids environment. The pH and temperature of the solution was maintained at 7.31 and 37°C and took approximately 5 hours for each individual test. The microstructure observations of the steels were studied using optical microscope and scanning electron microscopy (SEM). The results showed that the cold rolling process has modified the microstructure of 316L stainless steel by producing extensive surface defects. The microstructure modifications of the cold-rolled steel caused to enhance the corrosion resistance by lowering its corrosion rate to 23% and reduce the pitting resistance by lowering its breakdown potential to 61%. The pit corrosion was extensively appeared after reaching the breakdown potential.

Abstract: Steam methane reforming has been a conventional process to produce synthesis gas which is an important feedstock to many chemicals. However, for gas to liquid (GTL) applications this reforming process is not suitable as it produces synthesis gas with very high hydrogen to carbon monoxide ratio than required by the Fischer Tropsch synthesis in GTL line. In this work, a GTL process is designed in which synthesis gas is produced by steam reforming from a natural gas feedstock containing relatively substantial carbon dioxide contents in it. Synthesis gas composition is tailored by tail gas recycling from the Fischer Tropsch products. Process simulation and optimization is performed on Aspen HYSYS to produce synthesis gas with hydrogen to carbon monoxide ratio of 2 which is desired in GTL technology.

Abstract: A novel synthetic approach for gold nanocrystals using triblock copolymer as a polymeric template was described. The triblock copolymer used in this study was poly (ethylene oxide)₂₀-poly (propylene oxide)₇₀-poly (ethylene oxide)₂₀ with hydroxy or thiol end-functional groups. The complexes of HAuCl₄ and triblock copolymers were prepared by mixing and drying. After exposed to the sunlight for a few days, the gold nanocrystals, which have different sizes and shapes according to the ripening time, end functional groups, and gold salt concentrations, were obtained. The optical properties of the gold nanocrystals were also discussed.

Abstract: The influence in optimization of processing, calcinations and sintering parameter on the physical properties and characteristic of CaCu₃Mn₄O₁₂ were investigated. The stoichiometric CaCu₃Mn₄O₁₂ powders were successfully prepared by the citric gel method. Dried gel with three dimension network consisted of molar ratio of [citrates/metallic ion]; 1:2 was formed. The precursor gel formed was calcined and sintered at range 400 °C to 800 °C. A single-phase CaCu₃Mn₄O₁₂ fairly well densified at relative low temperature under atmospheric sintering condition. FESEM results turned out that CaCu₃Mn₄O₁₂ powder particle is submicron in size and highly agglomerates due to high calcinations temperature. The smaller particle size with higher grain boundary and less of porosity were found for the sample sintered at 700 °C to 800 °C. The samples show the ‘superparamagnetism’ behavior where the M-H curves are linear with the field and have a smaller value of coercivity at room temperature. Sintering at 800 °C produced the sample with lowest Hc value due to the phenomenon of over grown magnetocrystallites, grain size and grain boundaries.

Abstract: The way is developed by the combined process of finishing machining. In this method, surface treatment is due to the combined effects of cutting tool and anodic dissolution of metal under the influence of an electric current in the electrolytic solution. Applying of this method allow the processing of aluminum and copper alloys to obtain higher quality parameters of the obtained surface, including special material.

Abstract: Milling is a common machining process with high cutting speed and material removal rate. High cutting speed tends to generate heat at the interface between tool and workpiece. This may reduce the surface quality of the workpiece and reduce the tool life. The application of conventional cutting fluid to reduce friction and heat between tool and workpiece may produce numerous environmental problems. The vegetable-based lubricant as an alternative for measuring the effect on surface quality during milling operation is studied. The relation between machining parameters such as spindle speed, feed rate, depth of cut and lubricants is analyzed by using Analysis of Variance (ANOVA) and Response Surface Methodology (RSM). The optimization of surface quality is analyzed by using Box-Behnken Design of RSM. The research focused on using sunflower oil as lubricant during machining process using mild steel solid block with TiCN coated HSS tools and using synthetic oil as comparison. Surface roughness for using sunflower oil as lubricant is 0.457 μm which lower compared to synthetic oil with 0.679 μm. Feed rate and spindle speed give the most significant effect to the surface roughness during milling operation. The application of vegetable-based oil as lubricant gives better surface quality, prevent tool wear and offer environmental advantages.

Abstract: The ability of polymeric coatings to self-heal from mechanical damage is explored in this paper. Polymeric coatings with self-healing property is one of the important aspects in science. It can be used in industries such as oil industry (protect against corrosion), mechanical engineering, aircraft, etc. The PU microparticles were synthesized on the basis of PPG and TDI with a method of interfacial polycondensation at the interface water-benzene. Further to study the surface morphology of the microcapsules with healing agent (TMPTA) obtained PU was applied the method of scanning electron and atomic force microscopy. The PU microparticles hollow inside have regular spherical shape with a diameter of 5-10 μm with a dense and smooth polymeric shell. The resulting polyimide – polyurethane (PI – PU) composites have high potential to regenerate damaged surfaces not only on the surface and also in the volume of composite.

Abstract: The aim of this work is to study the low temperature annealing effect on the electrical properties of p-type multicrystalline silicon grown by Heat Exchanger Method (HEM).The minority carrier lifetime variation, the transition metal elements behavior, the sheet resistivity and the interstitial oxygen concentration after different temperatures annealing under N₂ ambient were investigated using quasi-steady state photoconductance technique (QSSPC), secondary ion mass spectroscopy (SIMS), four-probe measurement and Fourier transform infrared spectrometer (FTIR), respectively. The obtained results indicate in the temperature range of 300°C to 700°C that the effective lifetime increases and reaches its maximum values of 28 μs at 500 °C and decreasing to 6 μs at 700 °C. This amelioration is due probably to metallic impurities internal gettering in the extended defects and in the oxygen precipitates as observed on SIMS profiles and the FTIR spectra. From 300 °C to 500 °C the sheet resistivity values rest unchanged at 30 Ω.cm^-2 and rises significantly to reach 45 Ω.cm^-2 for T> 500 °C.