Advanced Materials Research Vol. 717

Abstract: In this paper, we introduced a P-buried (P_b) layer under trench gate which relieved the electric field crowding in the Non Punch Through Trench gate Insulated Gate Bipolar Transistor (NPT-TIGBT) structure. The P_b layer, with carrier concentration of 5x10¹⁶ cm^-3, was created underneath the trench gate within the n-drift layer. In this way, the concentration of electric field at the trench bottom corner decreased. As a result, the breakdown voltage characteristics of NPT-TIGBT improved. The structures were proposed and verified by T-CAD Sentuarus simulation. From the simulation results, the breakdown voltage increased by approximately 30% compared with conventional NPT-TIGBT.

Abstract: This study reports on the use of Fuzzy-Grey systems, with a Taguchi designed experiment to enhance the quality characteristics of yttria stabilized zirconia (ZrO₂/8%Y₂O₃) coatings, made by a plasma-sprayed process. Eight control factors were designed in an L18 orthogonal array experiment, and the effects of the control parameters on the surface properties were critically evaluated in the experiments. Multi-response characteristic terms-surface roughness, hardness and wear depth values in the sprayed ZrO₂/8%Y₂O₃ coatings through the optimization were studied comparatively. A Fuzzy-Grey approach, based on the Taguchi orthogonal experiments for optimizing multi-response performance in the coatings, was reported. In addition, the influence of control factors on the Fuzzy-Grey systems for spraying processes was investigated by analysis of variance. In addition, a confirmation experiment was conducted. Experimental results have shown that the hardness increased by 18.67%, while the surface roughness decreased by 32.01%and the wear rate improved by 30.52%. It is clear that the multi-response quality characteristics for plasma sprayed coatings are greatly improved through Taguchi-Fuzzy-Grey analysis, and that these findings achieved the desired values in regard to the mechanical properties.

Abstract: This paper introduces the research content, methods and progress of integrating the water distribution network, and has done a comprehensive overview from basic concepts to several typical methods for designing water-using networks such as water pinch analysis, mathematical programming, internal water main technique and experience-based design methodology. It has an advance view of the future developments direction as well.

Abstract: In this work the microscopic morphology of titanium carbide thin films, obtained by pulsed laser ablation, are studied. A target of TiC has been ablated in vacuum with a laser Twinkle of Light Conversion Ltd. capable to furnish impulses of 250 fs, with a repetition frequency of 10 Hz at the wavelength of 527 nm. The ablated material has been deposited on (111) oriented silicon substrates, maintained at ambient temperature during the film deposition. Digital images of the films have been acquired through scanning electron microscopy. Numerical codes have been developed in Matlab environment, to obtain a three-dimensional reconstruction of the film surfaces starting from the bidimensional images. On such reconstruction a multi-scale analysis has been performed by hilbertian methods, for the characterization of the surface roughness and to study the distribution of the deposited nanoparticles. The results show that the free surface of the film has a characteristics scale invariance that allow the description by multi-fractal techniques. In particular the fractal dimension of the surface has been calculated in nanometric range. The investigation allows to identify some proper morphological indicators to characterize the film geometry and parameterize the tribological properties of the interface. These indicators, if opportunely employed together with classical methods of analysis, furnish a further tool for better understanding the complex nature of the deposits.

Abstract: The melting temperature-pressure phase diagram [T_m(P)-P] for wustite (FeO) is predicted through the Clapeyron equation where the pressure-dependent volume difference is modeled by introducing the effect of surface stress induced pressure. FeO plays an important role in many metallurgical processes and in the Earths mantle mineralogy. FeO is also of great interest in the field of state solid physics and chemistry because of its electrical, magnetic, structural and non-stoichiometric properties.

Abstract: Fine blanking is a press-working process that permits the production of precise finished components which are cleanly sheared through the whole cutting surface. It can be eliminated secondary operations, such as milling, grinding, etc. Recently, many studies on the weight reduction of automobile for fuel saving were underway. Especially, there are many examples which new materials were applied for automotive parts. Eco-Al is the new material which is replaced Mg of aluminum alloy with Mg+Al₂Ca, therefore Eco-Al material has improved mechanical properties and formability. In this paper, the shear characteristics of Eco-Al 5052 and Al 5052 parts which had been blanked by fine blanking process were analyzed and compared. As a result, even though Eco-Al and Al sheets were not treated for fine blanking, the cutting surface of Eco-Al and Al parts had the shear surface of more than 85% and dimensional accuracy of more than ISO accuracy grade 9.

Abstract: Erosive wear is one of the major failure modes in metal and plastic injection moulding. Certain regions such as gate, runner and some areas on the cavity wall, are particularly susceptible to erosive wear damage, leading to the reduction in the mould lifetime. Several parameters such as pressure, injection velocity, melting temperature, including various contaminants during material processing, have influenced to decrease the surface quality of the mould. Hence, the wear test and prediction are necessary information for the life extension of the mould material, and were carried out in present work. This work therefore aims to determine slurry erosion wear behaviour of the mould material, and presents a new semi-empirical approach to estimate the wear coefficient of material itself as a function of impact angles via an erosion test apparatus. It was found that the maximum wear coefficient of the tool material is around ~ 2.51 x 10^-7 at the impact angle of 60^o. While that the minimum value was found to be ~ 4.70 x 10^-8 at the angle of impingement of 30^o. Therefore, the effect of the different angle of impact on the impact energy, can also represent the failure modes in the tool steel material as ductile failures.

Abstract: In the paper a flow stress model based on internal variables is shortly presented. The multiplicative model contains three parts. In the model, the normalized dislocation density ρ_m was considered, as a strain function only, independently to the strain rate and the temperature. Influence of varying processing conditions (the strain rate and the temperature) is introduced as a factor. The first one is a model of so called master curve. It is an internal variable model based on dislocation density and its output value strongly depends on strain and very weakly on temperature and strain rate. The second factor introduces varying deformation conditions. Changes of flow stress do not occur instantly with the change of deformation conditions, but it requires some strain for transition. The third part considers influence of recrystallization. The results of the model parameters identification and verification in varying deformation conditions are presented in this paper.

Abstract: GaN semiconductor was one of the most promising semiconductor materials with direct wide band gap transition. It was regarded as one of the most desirable materials to prepare short wavelength optoelectronic devices for the good optoelectronic properties and excellent mechanical behavior. In this paper, n and p-type GaN films were prepared on Al₂O₃ substrates by MOCVD. Through the optimization of parameters, we obtained effective in doped Mg and carrier concentration for 10¹⁹_. MSM structural ultraviolet photoelectric devices were prepared on GaN film by two step epitaxy growth method. The highest transmittance and best epitaxial growth quality has been gained at 570°C for buffer layer of the samples.

Abstract: Duplex stainless steel (DSS) offers an alternative to the austenitic stainless steels especially at temperatures between –50 and 300°C and is suitable for structural applications. The research was study the effect of post weld aging (PWA) parameters on microstructure in heat affected zone. The specimen was duplex stainless steel (DSS) UNS31803 which thickness of 10 mm. The PWA sample were tested the microstructure and phase analysis. The factors used in this study were PWA temperature of 650, 750, and 850 ^๐C with PWA time of 1, 2, 4 and 8 hours. The welded specimens were tested by microstructure and phase analysis testing according to ASTM E3-11 code. The result showed that both of PWA temperature and PWA time can greatly affect microstructure and phase analysis in heat affected zone (HAZ). The ferrite that was austenite with a grain and an austenite scattered throughout. The microstructures of PWA 650 °C with PWA 1, 2, 4 and 8 hours in ferrite phase which ferrite phase was not different. The widmanstätten structures were observed high PWA temperatures were also distributed at grain. At high PWA temperature, ferrite at the grain boundary tended to decrease. Moreover excessive aging temperature can result in increasing austenite intensity and size in parent phase. Definitely, at high PWA temperature and time, over-aging of HAZ resulted in corrosion resistance reduce.