Applied Mechanics and Materials Vol. 376

Abstract: The temperature distribution in the reactor, especially on the surface of the wafer, is the important factors influencing the chemical reaction in CVD and PECVD process. This paper focused on a typical cylindrical PECVD reactor carrying with a wafer, and established the combination calculation model, which divided the chamber system into two calculation domains according to the rarefied degree of the gases. A one-dimensional thermal model was developed to calculate the temperature profiles in the narrow gap between the wafer and the heater, considering the heat conduction, radiation and thermal accommodation phenomenon between the gas and the surfaces in low pressure conditions; a two-dimensional axisymmetric model was applied to calculate the temperature profiles in the chamber above the wafer, considering the heat conduction, radiation and mass transfer. We verified the validity of the model through the experimental measurement in different pressure with the aluminum matrix pedestal and the one without. The experiment and numerical calculation both pointed out that there are 15~30K temperature drop in the narrow gap between the wafer and heater with the pressure of 1~10Torr at the outlet of the chamber, the mass flow of 5000sccm at the inlet, and the fixed temperature of 673K within the heater. The lower the pressure was, the greater the differences were, and it presented a negative exponential relation. In addition, this paper predicted the response of the wafer surface temperature to the change of the narrow gap height and chamber pressure via numerical calculation model. The results showed a negative linear relationship between the wafer top surface temperature and the narrow gap height. When the narrow gap height was changed in the range of 0.15~2mm and chamber pressure of 1~10Torr, the temperature of wafer will drop 0.5~5.5K.

Abstract: The Urea SCR system is a promising approach to reduce NOx in order to meet stringent limits on Euro 1V and Euro V standards. Apart from thermodynamic properties (temperature, pressure,heat and mass transfer), the cell geometry of SCR also got significant role in reduction of NOx. The current study focuses on the calculation of NOx conversion by varying the Open Frontal area of monolith, volume of monolith, cell density thereby to choose best cell geometry which will result in maximum DeNOx efficiency. It has been found that as the cell density increases the NOx conversion efficiency also increases. In the current analysis, a cell density varying from 200 CPSI to 400 CPSI is considered. One dimensional steady state and transient kinetic analysis are carried out using AVL BOOST software. The monolith volume is varied from 0.002m³ to 0.008m³ and the effects on DeNOx efficiency are discussed. The Open frontal area of SCR catalyst also been varied, and the effects on NOx conversion is studied. It has been found that as the cell density, monolith volume increases, the NOx conversion efficiency also increases, where as it decreases with increase in Open frontal area. The results are validated through experimental results obtained from the literature.

Abstract: Effects of 20-40 vol.% SiC_p additions on microstructure and hardness of aluminum composites have been investigated in this research. The composites were produced via powder injection molding at 170°C followed by solvent debinding and sintering at 700-820°C. After sintering, composite microstructures and properties were influenced by SiC_p additions and sintering temperatures. Higher SiC_p additions required higher effective sintering temperatures. Furthermore, increasing SiC_p content promoted SiC_p agglomeration along aluminum grain boundaries and caused SiC_p pull-out during metallurgical preparation. This resulted in higher porosity observed from the sintered microstructures. Variation in macro Vickers hardness values were obtained due to opposing effects of increasing contents of SiC_p and porosity. Optimum hardness values were obtained when sintering was carried out at 740, 780 and 800°C for 20, 30 and 40 vol.% SiC_p additions respectively.

Abstract: Manufacturing and characterization of U-Zr alloys for PWR fuel types have been conducted. At first U-Zr alloy ingot was made by melting U and Zr metal in the electric arc furnace that is equipped with a water cooler and in an atmosphere of argon gas. Ingot manufacturing of U-Zr alloy was done at Zr concentration 35%, 45%, 55% and 65% weight respectively. U-Zr ingot result was cut for testing, such as: density, hardness, microstructure and phases. Density testing was done by using Autopicnometer, hardness by using microhardness, microstructure by using optical microscope, and phase by XRD. The density test results showed that the increase of Zr will decrease the density, while the hardness tends to increase. At Zr concentration amount 35 % (U-35Zr) the U-35Zr density is 11.2409 g/cc and at concentration amount of 65% (U-65Zr) the U-65 Zr density to be 8.4673 g/cc, while the hardness at 35% of Zr (U-35Zr) the hardness is 374 HV and will be 400 HV at concentration of Zr amount 65%. The microstructure observation result showed that increasing of Zr will increase the amount of grain and δ1 phases, while the result of phases testing showed that the U-Zr alloy tested had been dominated by the δ1 phases. From this experiment can be concluded that adding of Zr will influence the physical properties, mechanical, and microstructure formed. Keywords: Manufacturing, characterization, U-Zr , fuel, PWR.

Abstract: In recent years, the studies of the pigment dyeing have gained more and more attention since it is directly related to environmental protection. The Pigment Dyeing is one way, which fabrics modified by cationic modification were dyed with pigment. The aim of this research is to study the pigment dyeing process of selected blended fabrics by measuring the K/S value in order to get the optimum process for different dyeing conditions. It is found that the K/S value property of the dyed fabrics is influenced by blinder concentrations, pigment concentrations, dyeing time, dyeing temperature. Through the data fitting and correlation coefficient, we can observe the optimum process conditions were as follows: blinder 5~10g/L, pigment 16~20g/L, temperature 60~70and dyeing time 50~70mins.

Abstract: Open sun drying is one of the oldest techniques employed for processing agricultural products. The local practice of drying the seaweed is by spreading it over a plastic sheet on the ground and exposing it to the sun. Unfortunately, such traditional practice of drying seaweed has led to increased risk of contamination of seaweed by dust and sand particles and other impurities, as well as seaweed often suffer from lower quality. This research was conducted to examine the effect of application of table type sun drying on quality of dried seaweed, through indicators of water content, level of impurities, and brightness. The dryer was designed by using aluminum as a drying surface, with holes for circulation. The surface of aluminum is blackened to increase temperature. The results of study showed that table type sun drying reduced water content rapidly, reduce level of impurities, and improve brightness of dried seaweed.

Abstract: Due the rapid heating rate combined with high pressure by the Spark Plasma Sintering (SPS) technologies possible manufacture a wide range of novel materials with exceptional properties that cannot be achieved using conventional sintering techniques. Hard metals are, from a technical point of view, one of the most successful composite materials. An overview of the metallurgical reactions during the SPS sintering process of powder mixtures for the manufacture of hard metals is presented. The relatively complex phase reactions in the multi-component system TiC-Mo-W-Ni are discussed. There were elaborated a new technology for the fabrication of nanocrystalline hard metals of a new class assigned for the production of articles with high different characteristics. Elaborated materials are characterized by high melting temperature, hardness, wear-resistance, and satisfactory strength at high temperature and corrosive resistance. Through the use of developed technology and the appropriate structural condition gives possibility to achieve high physical-mechanical characteristics. Obtaining of composite materials via elaborated technology is available from the corresponding complex compounds and directly consisting elements too. In this case High-temperature Self-propagation Synthesis (SHS) and spark plasma sintering/synthesis (SPS) process are united and during a single operation it is possible to get not only the powder materials but at the same time obtain required details.

Abstract: Many engineering applications in aerospace and automotive field require joining of dissimilar 5xxx to 6xxx Al alloys. Dissimilar Al alloy joints are used for industrial applications due to technical & economic reasons. However, due to different metallurgical behaviour & mechanical properties, joining of dissimilar Al alloys presents a number of challenges. Due to high temperature generation most of the fusion welding techniques are not suitable. In addition, other pressure welding techniques such as – Ultrasonic welding, Roll bonding, Diffusion bonding and Friction welding have some limitation. Hence, friction stir welding (FSW) can be considered to be the most suitable method to join dissimilar Al alloys due to solid-state nature of the process. Since invention, friction stir welding has been a matter of research and investigation for years. In its history of two decades, Friction Stir welding was investigated for joining dissimilar Al alloys during the last decade. Most of studies demonstrated that good quality joints between dissimilar Al alloys can be produced by the Friction Stir Welding (FSW) process. The present study is a chronological & critical review of recent studies on joining of dissimilar 5xxx to 6xxx Al alloys by friction stir welding.

Abstract: Dense Nb/Nb₅Si₃ composites were fabricated via spark plasma sintering technology using Nb, Si, and Al elemental powders as raw materials. The microstructures of the synthesised composites were analysed through scanning electron microscopy, X-ray diffraction, and electron probe microanalysis. The results show that the composites consisted of residual Nb particle phase and Nb₅Si₃ phase. The microstructure of the Nb/ Nb₅Si₃ in situ composites was evidently affected by Al addition, which prompted the formation of the Al₃Nb₁₀Si₃ phase. The oxidation resistance of the Nb/Nb₅Si₃ in situ composites significantly improved with the increase in Al addition. Pesting oxidation behaviour was exhibited at 800°C by the Nb-20Si composites when exposed to air for 4h. This pest oxidation behaviour is not exhibited by the Nb-20Si-10Al and Nb-20Si-15Al composites after exposure to air for ~10h. The composite exhibits the best oxidation resistance at 15at% Al.