Advanced Materials Research Vols. 264-265

Abstract: With the rising cost of zinc reaching historic levels, more emphasis is being placed on technologies to increase the efficient utilization of zinc. One area targeted for increased efficiency is in-house recycling of metallic zinc industrial wastes. The largest consumer of zinc is the hot-dip galvanizing of steel. Large amount of zinc slag containing more than 50% zinc, are accumulated during galvanization processes at the surface of molten zinc bath and is usually skimmed manually. At First, The pyrometallurgical recovery of zinc from slag samples was carried out, and parameters affecting recovery processes such as time, temperature, and flux percentage were studied. The results obtained revealed that zinc metal is successfully recovered from these secondary resources. The recovery efficiency is 70% for zinc waste materials having a particle size diameter of + 1.25 mm. An optimum percentage of 25% weight of ammonium chloride fluxing agent was obtained. The optimum temperature for the recovery process was 700°C.

Abstract: Cordierite ceramic of chemical composition 2MgO-2Al2O3-5SiO2 has low value of thermal expansion, excellent thermal shock resistance, high porosity and high strength. The exhibited properties resulted wide range of industrial applications, especially in the catalytic converter, kiln furniture, diesel particulate filter and high frequency insulator. It occurs rarely in nature and its formulation from the indigenous raw materials is sensitive to the peak sintering temperature and holding time. Both the parameters are again affected on the source of raw materials. Hence optimization of peak temperature and holding time is crucial for each source of raw materials. In this paper three indigenous raw materials, clay, kaolin and talc were taken and mixed with different dopants. The prepared powder batch was sintered at different peak temperature and holding time. Among the three indigenous raw materials kaolin was found to be most suitable to formulate cordierite. The peak temperature was varied within the range of 1340°C -1400°C and the holding time was considered from 30 minutes to 90 minutes. Both the parameters had significant influence on the production of cordierite. The percent of cordierite formation was affected with both the variation of holding time and peak temperature. Tough thermal shock resistance was not influenced by any of the parameters, but the influence on the porosity was quite significant. The green body was also prepared from calcined powder batch and was sintered at different peak temperature. Calcination did not exhibit any affect on cordierite formulation.

Abstract: Crack arrest model is proposed for a poled piezoceramic strip under four different mechanical and electrical yield conditions. It is assumed that developed slide zone is bigger than that of developed saturation zone. Expressions are derived for energy release rate and load required to arrest developed zones. Results obtained are applied to predict the crack arrest of strip made of PZT-4, PZT-5H and BaTiO3. Results are presented graphically.

Abstract: Determination of the flow stress curve is an important step for precisely describing material behavior in Finite Element simulations. The flow stress curve is generally determined by taking a uniaxial tensile test as a standard. In the case of very thin sheet, since the fracture is generated at a low strain, there is not enough uniaxial data obtained to be applied in the FE simulation. The reason for this is that charactering plastic deformation at a large strain values by extrapolating a flow stress curve which is based on insufficient measurement data is highly susceptible to error. Bulge test is useful method for determining the equivalent biaxial flow stress curve up to a large strain. In this paper, the biaxial flow stresses curve for very thin copper sheet with thickness 35 and 50 μm were determined using the aero-bulge test. A new empirical model was derived for the estimation of the sheet thickness at the pole. After the compatibility between uniaxial and biaxial flow stresses was verified, the uniaxial flow stress curve was determined from the aero-bulge test using reverse engineering. The methodology of extrapolation of the flow stress curve at a large strain was finally proposed for application in FE simulations.

Abstract: Dry wear properties of aluminum nitride (AlN) reinforced aluminum-11% silicon alloy (Al-11%Si) was studied using a pin-on-disc configuration wear tester. Different weight percentages of AlN (0 – 10 wt.%) powder were added to the Al-Si alloy, melt and stir cast via bottom pour technique to form composites of Al-Si alloy/AlN. The dry sliding wear test were performed at a room temperature (27°C), under 25N and 70N load with fixed velocity of 1ms-1 and sliding distance between 1 to 5 km. The addition of 10 wt% of AlN improved wear resistance of Al-Si alloy by 72% and 130% indicated by volume loss for 25N and 70N load respectively. Mixed-wear mechanism of delamination, adhesion and abrasion was observed for the composite when applied loads were 25N and 70N while delaminating mechanism was dominance for Al-Si matrix alloy. Both Al-Si alloy with and without AlN reinforced found with FE element from counter-face disk that shows material transfer was significant.

Abstract: High performance automotive, aerospace, electronics and other industrial and commercial applications are finding tremendous advantages in using metal matrix composites. The reinforcement is very important because it determines the mechanical properties, cost and performance of a given composite. An excellent in mechanical properties, combined with the ease of formability and low cost makes the application of metal matrix composite of aluminium-11.8% silicon reinforced SiO2 to increase steadily. This paper investigates the interrelationships between thermal properties and reinforcement content, microstructure and hardness of LM6 reinforced SiO2 composites. Specimens were fabricated by casting technique for 5, 10, 15 and 20% weight fractions of SiO2 particulate and mesh of: 65 micron. The experimental results show that the thermal diffusivity and thermal conductivity decreases as SiO2 wt.% of the composite increases and under hardness test, it was found that the hardness value had increased gradually with the increased addition of quartz particulate by weight fraction percentage.

Abstract: In this paper, effect of AlCl3 addition as process control agent (PCA) during high energy ball milling of Al and TiO2 powder mixture was studied. This mechanical activation is aimed at to synthesize an ultra fine grained TiAl/Al2O3 composite. Experimental results show that AlCl3 significantly prevents severe cold welding of Al particles to milling media. Sublimation of this compound by local temperature increase due to balls collisions seems to be the main reason in prevention of severe cold welding. Samples were characterized by XRD, SEM and DTA. Mean crystallite sizes in particles of this sample and those milled with no PCA and milled with stearic acid were calculated and the results showed that smaller crystallite size is obtained in presence of AlCl3. However, DTA results revealed that addition of AlCl3, shifts aluminothermic reduction of TiO2 by Al to higher temperatures and therefore, final composite phases form at higher temperatures. Phase evolutions during further heat treatment of the powder sample milled with AlCl3 were also thoroughly studied.

Abstract: Batai (paraserianthes moluccana) tropical wood species was impregnated with three levels of polyvinyl alcohol (PVA) solutions (25%, 50% and 75%) for composite manufacturing. Manufactured wood polymer composites (WPCs) were characterized using Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), free-free vibration testing, and the dimensional stability analysis. The dynamic Young’s modulus (Ed) was calculated using the free-free flexural vibration method. Impregnation of PVA solutions into wood samples was confirmed through FTIR and SEM. WPC from 75% PVA solution showed lower water absorption and improved dimensional stability. The fabricated WPC yielded a higher Young’s modulus compared with the raw one.

Abstract: In the present study, the effects of deformation speeds, sheet thickness, and widths on the springback were investigated experimentally and numerically using a 60o V-shaped bending for DP600 steel. Results reveal that the springback was significantly decreased with increasing thicknesses and deformation speed including 125 mm/min in the range of 5-500 mm/min. The effects of widths on springback were found to be inconsiderable.

Abstract: Natural rubber (NR) was reinforced with three types of filler: carbon black, calcium carbonate, and sisal fiber. NR composites were prepared on a two-roll mill. Filler content was 20 phr. Mechanical properties and cure characteristics of NR composites were studied. All NR composites had higher maximum torque than NR. NR filled with carbon black showed the highest maximum torque. However, scorch time and cure time of the NR composites were not much affected by filler types. In addition, influence of fiber treatment (alkalization) on mechanical properties and cure characteristics of sisal fiber-NR composites was investigated. Alkali treated sisal fiber-NR composite exhibited higher tensile properties and hardness than untreated sisal fiber- NR composite due to improved adhesion between the fiber and NR matrix. Moreover, alkali treated sisal fiber-NR composite had superior specific modulus and strength than NR composites filled with carbon black and calcium carbonate.