Materials Science Forum Vol. 724

Abstract: The (Na_0.52K_0.44)(Nb_0.9Sb_0.06)O₃-0.04LiTaO₃ (NKNS-LT) ceramics doped with various Cu₂O contents were prepared by the conventional solid state reaction method. The Cu₂O content was varied in the range of 0.1~0.4 wt%. The effects of Cu on microstructure, crystallographic phase transition, and piezoelectric properties were investigated. The material with perovskite structure had a tetragonal phase (T1) when Cu₂O concentration was less than 0.3 wt% and it was transformed to another tetragonal phase (T2) when the Cu₂O amount was greater than 0.3 wt%. The phase boundary between T1 and T2 phases was appeared at around 0.3 wt% of Cu₂O concentration. The piezoelectric properties were shown the maximum values at the composition of the phase boundary. The electro-mechanical coupling factor (k_p) was 0.42 and the piezoelectric charge constant (d₃₃) was 245 pC/N at the 0.3 wt% of Cu₂O concentration.

Abstract: In this paper, SAF2507 duplex stainless steel (DSS) was welded by GTAW with ER2594 as filler wire, and Ar + N₂ as shielding gas. The results show that, with increasing the content of N₂ in the shielding gas, the amount of austenite in weld metal increase, the micro-hardness drops and impact energy increases; the use of Ar +2 ~ 3% N₂ welding parameters, the microstructure and mechanical properties of welded joints are the best, the austenitic rates and impact energy of weld metals are 51%~53% and 75~88 J, respectively, and the welding process is easy to control; when the content of N₂ reach 5%, the impact energy of weld metal decreases obviously and the welding arc is unstable.

Abstract: The purpose of present study was to increase productivity and to reduce the polution of dust for making of endmill by conventional method such as grinding process. The micro scale endmill manufactured by powder injection molding, the molding (green part) was debinded and sintered. After that decreasing the porosities of the parts sintered, HIP process was adapted. After HIP process the relative density was shown more than 99% of the tools sintered. Finally, the micro cutting experiment using manufactured tool by PIM and HIP were implemented for verifying the feasibility of the tool. The ware of zirconia micro tool was observed very small, but the concentricity is less than the conventional tool made by grinding process. This type of tool is adequate to use in rough milling.

Abstract: Aluminum dross is forms at the surface of the molten metal as the latter reacts with the furnace atmosphere and it was an unavoidable by-product of the aluminum production process. However, it has not been sufficiently recycled yet. Approximately 95% of the Al dross was land filled without innocent treatment. Therefore, Al-dross is positively necessary to recycling. The purpose of this study is to investigate the compressive strength of Selective Catalyst Reduction (SCR) prepares using recycled Al-dross and compared commercial SCR catalyst. Recycled Al-dross was as support material to increase strength. As to experimental procedures, Al dross was classified according to its size. The recycled Al dross was made into SCR catalyst by mixing with WO₃, V₂O₅, and TiO₂. After V₂O₅-WO₃-TiO₂-Al₂O₃ SCR strength was measured by Universal Testing Machine (UTM). And then NOx removal activity of V₂O₅-WO₃-TiO₂-Al₂O₃ SCR and commercial SCR catalyst were observed by MR(Micro-Reactor).

Abstract: In this study, we tried to reveal the presence of a cytokine that is regulated by weight, food intake, body fat, the hypothalamus-pituitary-adrenal axis, and corticosterone. The experiment group was given a high calorie diet and the control group was fed a normal calorie diet, and both groups were exposed to various stresses. The behavioral and hormonal change by the kinds and severity of stresses were measured via their immunologic aspect as well as their stress alleviation by voluntary high calorie food intake. After sacrificing the animal, the adrenal gland fat tissues were weighed, and the high calorie diet group showed heavier adrenal glands than those of the control group. In particular, the CVS A group had lighter adrenal gland weight than the Res B and CVS B groups, and the other groups had heavier adrenal glands. The comparison of plasma ACTH concentration to the corticosteroid secretion ratio showed that the CVS A group had decreased ACTH and an increased corticosteroid/ACTH ratio. This fact shows that the adrenal gland was highly active and, in spite of a normal corticosteroid concentration, induced too much negative feedback inhibition.

Abstract: In this research, the SiC/Al/h-BN composite ceramics with different SiC grain size were fabricated by the method of preparing the machinable pre-sintered body through Plasma Activated Sintering (PAS), which has the advantage of complex shape formation for precision parts. By hardening treatment, the SiC/Al/h-BN composite ceramics would be changed to SiC/AlN composites, and the relatively higher hardness and mechanical properties could be obtained accordingly. The phase transformation and microstructure were observed and the mechanical and other properties were also measured. The results showed that, for different matrix SiC particle size, change tendency of the bending strength was different with the heat treatment temperature change. And the bending strength of composites with larger SiC grain size was higher than that with smaller SiC grain size.

Abstract: Recently, increasing of impervious surface as concrete or asphalt pavement with urban development brought increasing of air temperature in city. So many researchers have explored ways to reduce the urban heat island effect and water-retentive or water absorbing pavements have been found to be very effective. In this study, to evaluate the reduction effects of urban heat reduction of water-retentive pavement, surface temperature of pavement, air temperature, wind speed and albedo were measured for 3 years (2008~2010, summer period). And the intensity of sensible heat flux was calculated to estimate a influence on air temperature. Experimental results indicated that water-retentive was effective to reduction of air temperature by decreasing of surface temperature of pavement compare to other pavements. This is showed that water-retentive pavement can be contributed to mitigation of urban heat island.

Abstract: The use of turbochargers improves engine power, reduces the rate of fuel consumption. The vane lever is an important part of a turbocharger that regulates the volume of hot exhaust gas. Until now it has been produced by a 4 cavity fine blanking tool, but it requires the use of an 8 cavity fine blanking tool for better productivity. In this paper, we conducted structural simulation of an 8 cavity fine blanking tool and predicted the deformation of fine blanking tool elements. The maximum vertical deformation of the die was 0.01222mm and the maximum horizontal deformation of the die was 0.00096mm. This deformation led to a clearance change in the 8 cavity fine blanking tool. According to the simulation results, the calculated clearance was increased to a maximum of 45.9%, decreased to a minimum of 49.0%. Through the fine blanking experiment with the manufactured 8 cavity fine blanking tool, we demonstrated that 8 vane levers could be simultaneously produced by the 8 cavity fine blanking tool.

Abstract: The size of pipe network accident caused by aging of water distribution system, rapid urbanization, abnormal climate or a disaster such as an earthquake is gradually becoming larger. Accordingly, it is required to improve the technology to maintain the water distribution system so that the related technologies can be scientifically and systematically applied. The paradigm of Korean water supply service is changing from supply era to maintenance era, and it is required to apply equipment and method to effectively check, diagnose and test the internal condition of the pipe without stopping water supply. If photographing and diagnosis of the burial environment around the water service pipeline and inside the pipe can be carried out without stopping water supply effectively utilizing the surrounding facilities such as straight piping and air valve to the maximum, decrepit pipe (defective pipe) improvement projects can be effectively carried out by making adequate decisions. Also, a systematic and more efficient water supply service maintenance system can be established by building a database of surrounding pipeline directly investigated and selecting priority of direct/indirect evaluation. This study has raised accuracy of a diagnosis by applying a camera capable of securing high resolution without generation of distortion in case of photographing the inside of a pipe, and suggested an application method of the pipe endoscope camera using an inspection hole inside a pipe.

Abstract: The influences of processing parameters on the tensile strength (TS) of KGM/CaCO₃ composite films (KCaCF) were investigated through orthogonal experiment method. Calcium carbonate and KCaCF were characterized, respectively, by XRD, laser diffraction particle size analyzer, zeta potential analyzer and SEM. The results showed that micron-sized calcite CaCO₃ crystals with-16.4 mv of Zeta potential were synthesized. Calcium carbonate dispersion was blended with KGM to fabricate KCaCF. The mass of CaCO₃, KGM and swelling time affected TS of composite films differently, but didnt reach the significant level (p>0.05). The optimal preparation process for KCaCF is that 5.0% (wt) of KGM powder is added into the dispersion with 2.0% (wt) of CaCO₃, swelling for 1.0 hour at 50 °C and pH 8.0 and then poured onto plate and dried at 50 °C for 15 h.