Advanced Materials Research Vol. 893

Abstract: Submicron magnetic polymeric particle (MPP) and/or Janus magnetic polymeric particle (JMPP) were successfully prepared via the miniemulsion polymerization of styrene (St)/acrylic acid (AA) monomers consisting of superparamagnetic iron oxide nanoparticles (IONPs) coated with oleic acid. Since the particle nucleation occurs primarily within the monomer droplet, not only the size of particle could be controlled at the beginning but also its morphology was manipulated by using different types of initiator. The MPPs with homogeneous distribution of IONPs (41%) in P(St-DVB-AA) were obtained with using potassium persulfate (KPS) as initiator and divinyl benzene (DVB) as crosslinking agent. To obtain anisotropic JMPP, an oil-soluble initiator 2,2-azobis (2-isobutyronitrile) was used instead. The controllable phase separation between P(St-AA) and the encapsulated IONPs caused the stable spherical Janus particles containing IOPNs (15%) located on one side of polymer particle. Both MPPs and JMPPs could be easily separated by an external magnet. The MPPs were functionalized with chitosan (CS) acting as spacer and then chemical immobilized with fluorescein isothiocyanate (FITC) to produce fluorescent-MPPs. When applying as imaging device for cancer cells labeling i.e., HeLa, cells, results showed that MPPs/CS-FITC could be located inside cells with low cytotoxicity.

Abstract: 2-((phenylcarbamoyl) oxy) ethyl acrylate (Monomer 1) was synthesized based on the raw materials of N-Z-ethanolamine (NSC), acryloyl chloride (AOC), triethylamine (TEA) and dichloromethane (DCM). The chemical structure of Monomer 1 was characterized and confirmed by FTIR and 1H NMR, and the light-curing polymerization behavior was also investigated. Results showed that Monomer 1 had prospective chemical structure. Compared to commercial monomer TEGDMA, Monomer 1 had better reaction speed and conversion rate.

Abstract: This paper presents the results of an experimental investigation on the turning of Al/SiC (LM-13) composite using Cryogenic Liquid Nitrogen (LN₂) as coolant. The influence of machining performance parameters such as cutting force, cutting temperature and surface finish were investigated under wet and cryogenic machining. The results proved that the application of cryogenic LN₂ coolant reduced the cutting temperature and the cutting force for about 19 to 30% and 24 to 35% respectively. The surface finish of the machined part is about 10 to 23% better than in the conventional coolant. Thus it was proved that the application of cryogenic coolants reduced the cutting force and temperature which resulted in an appreciable improvement in surface finish in machining of Al/SiC MMC.

Abstract: Machining processed with various conditions form the surface characteristics of materials. Material processes needed for forming parts such as bone screws. This paper presents surface characteristics of bone screw for orthopedic implant that processed by conventional turning machine with various conditions. Manufacturing production in conventional way of bone screw connector is expected to produce same geometry, dimensions and quality as well as the product from abroad. The screws design type that used for cortical bone orthopedic implant known as cortical bone screw. Cortical screws have fine threads along the shaft and are designed to anchor in cortical bone. In this research, screws were made of stainless steel 316L which mounted on the horizontal lathe and the head manufactured by punching machine. Bone screws which used for interfragmentary bone surgery manufactured by lathe machine with various conditions such as various thread per inch, various cutting tools angle, various cutting tools properties and also various depth of cut. So this research focus on the extent to which the influence of machining parameters namely cutting speed, depth of cut, feed rate, cutting angle, number of thread and tool selection to the surface characteristic of the bone screw. Based on the result from the different machining parameter, they are affecting to the quality of the cortical screw on the microstructure, and the surface roughness.

Abstract: Effect of strontium (Sr) addition on the microstructure and the mechanical properties of semi-solid A356 aluminum alloy produced by GISS process were investigated in this study. Strontium addition resulted in both grain refinement and modification of eutectic Si. The maximum average ultimate tensile strength and elongation of 291.06 MPa and 17.31%, respectively, were obtained from the T6 heat-treated specimen containing 0.08wt%Sr. The excessive addition of strontium (0.2wt%Sr), however, seemed to deteriorate the mechanical properties of the alloy as a result of the Al₂Si₂Sr particle formation.

Abstract: We reported a systematic study of the effect of Zr content on the structural and magnetic properties of rapidly quenched Sm (Co_balFe_0.11Cu_0.10Zr_x)₇ alloys with x varying from 0 to 0.04. The results show that the addition of Zr greatly affected the microstructure and magnetic properties of the heat-treated ribbons. The Zr-free ribbon had crystallized as the 1:7H structure as the main phase while the ribbon with Zr addition adopted the 2:17R structure type. A Sm₂Co₇ phase was observed in the heat-treated ribbons when the Zr content x increased to 0.04. It is found that while the Zr content was increased from 0 to 0.04, saturation magnetization of the heat-treated ribbons was decreased from 11.9kGs to 3.3 kGs, and the intrinsic coercivity was increased from 0.07 kOe to 11.7 kOe. The highest intrinsic coercivity, H_ci=11.7 kOe, was obtained in the ribbon with Zr content of 0.03.

Abstract: Although friction stir welded joints of similar or dissimilar metals exhibit good mechanical properties, the nugget zone in the weld region usually shows a deviation in the properties from the rest of the region due to grain coarsening. The effect of grain coarsening at the nugget zone is further aggravated when the friction stir welded joints are subjected to annealing treatment resulting to a wide variation in the properties. In order to overcome the above problem, in the present study an attempt has been made to retard grain coarsening at the nugget zone by the addition of suitable ceramic particles in the nugget zone during welding. SiC particles of 12 microns size is added at the nugget zone in the weld region during friction stir welding of Al 6351 aluminium alloy. The test results reveal that the addition of reinforcement particles resulted in the improvement of uniformity of properties across the weld region both in the as-weld and in the annealed condition.

Abstract: In this work, effects of temperature and strain rate on microstructure development of a Nickel Aluminum Bronze (NAB) alloy during hot compression were investigated. The temperatures between 750°C and 900°C, strain rates between 0.1 s^-1 and 10 s^-1 and a deformation degree of 60% were considered. Microstructure analyses were performed for the samples after the compression using scanning electron microscopy technique. The results showed that microstructure of as-cast NAB alloy consisted of α, β' and κ phase. After homogenization β' phase transformed to the α and κ phase. Furthermore, different heating temperatures led to varying initial microstructures before forming and subsequent deformation, forming rates and cooling caused precipitation of various intermetallic phases. The α phase was found in the final microstructures of all forming conditions. At high forming temperatures, some intermetallic κ phases tended to dissolve and precipitated during cooling according to applied strain rate. However, at lower temperatures of 750-850°C, no significant effect of the strain rate on alteration of intermetallic κ phases.

Abstract: Microstructure of post-homogenization is significant to prevent particle stimulated nucleation of recrystallization. This paper investigated microstructure evolution in alloy 7050 during cooling from homogenization. Two intermetallic phases, Al₇Cu₂Fe and Mg₂Si were insoluble during homogenization. Cooling to 460 °C and 400 °C follow by quenching, precipitates nucleated discontinuously on the grain boundaries, no precipitates was found within the grains. The precipitates were found near the grain boundaries when quenching from 350 °C, and precipitated uniformly within the center of the grains when quenching from 250 °C. The sizes of the precipitates increased with the decreased of the quenching temperature. Controlling of the post-homogenization microstructure is beneficial to prevent particle stimulated nucleation of recrystallization.

Abstract: In this study, the effect of the long natural aging on the precipitation sequence of Al-Mg-Si alloy was investigated by differential scanning calorimetry and hardness examinations. This investigation revealed that the natural aging has a negative effect on the artificial aging. The reason behind the influence of natural aging on precipitation behavior of the Al-Mg-Si alloy is assumed to be the formation of clusters and G.P. zone during natural aging. The hardening mechanism during artificial aging was explained.