Advanced Materials Research Vols. 378-379

Abstract: This study presents the configuration and modeling of an electro-rheological (ER) fluid-based haptic master device for minimally invasive surgery (MIS). The haptic master device can produce a 3-DOF rotational motion which is realized by ER bi-directional clutch/brake for X and Y axes and ER brake for Z axis. In order to transmit a complex rotation from the handle of the device to three rotary movements, a gimbal structure is adopted. Before manufacturing the proposed haptic master, two case of design parameters are detemined from the viewpoint of compact size and extensive workspace, respectively.

Abstract: The effects of Sn addition on the cast microstructure, mechanical properties, and corrosion behavior were comprehensively investigated. Cast AM60 alloy mainly consisted of primary Mg matrix and Mg17Al12 phase, and the microstructure virtually remained unchanged by the Sn additions up to 2%. Most of added Sn solute atoms were observed to dissolve into the Mg17Al12 phase and only a few fine MgAlSn precipitates were found in the high Sn alloys. Tensile strength at both room and 175oC was rather deteriorated by increasing Sn content, however the creep strength was significantly enhanced by it. Polarization characteristics of cast AM60 based alloys were not remarkably affected by the Sn content.

Abstract: In this study, we have fabricated a fiber-optic dosimeter using an organic scintillator and a plastic optical fiber for measuring percentage depth doses with radiotherapeutic high energy photon beams. The scintillating light generated in an organic dosimeter probe embedded in a solid water phantom is guided by a plastic optical fiber to the light-measuring device. Using this fiber-optic dosimeter, percentage depth doses are measured with 6 and 15 MV energies of photon beams whose field sizes are 2 x 2 and 10 x 10 cm2, and the results are compared with those measured using conventional dosimeters such as an ionization chamber and EBT films used in radiotherapy dosimetry.

Abstract: In Thailand, commercial orthodontic stainless steel wires are imported from overseas and expensive. However, lower cost general purpose stainless steel wires, the same type and number as commercial orthodontic stainless steel wires may be used for orthodontic purposes. Objective: This study aimed to determine the physical, mechanical and chemical properties of general purpose stainless steel wire compared with commercial orthodontic stainless steel wires. Materials and Method: Two commercial orthodontic stainless steel wires (Ormco and Highland) and general purpose stainless steel wire (SUS 304H) were evaluated. The physical and mechanical properties were studied according to ISO 15841:2006 and corrosion resistance was studied according to ISO 10271:2001. Surface characteristics and composition were studied by scanning electron microscope (SEM) and electron probe micro analyzer, respectively. Results: The experiment indicated that SUS 304H had the diameter and mechanical properties in the range of orthodontic stainless steel wires. The surface characteristics SUS 304H were similar from observation by SEM magnifications but SUS 304H had lower corrosion resistance due to lower nickel content. The composition confirmed that the three samples wires were genuine type 304. Conclusion: SUS 304H properties are comparable to commercial orthodontic wire properties.

Abstract: Hydroxyapatite (HAP) and tricalcium phosphate (TCP) nanoparticles (NPs) are in current use covering a wide range of medical applications, hence, it is indispensable to study the potential side effect acting on living organism, and to figure out the biocompatibility evaluation model of nanoparticles for standardization and methodology. In the present study, HAP and TCP NPs were selected and their diameters were within 30-80nm. Cytotoxicity in vitro was analyzed by agar overlay and direct contact exposure test was conducted to evaluate potential toxicity to SD rat macrophages, and hemolysis test of NPs was performed in compliance with ISO 10993-12 guidelines. The results showed that both HAP and TCP NPs could inhibit proliferation of macrophages when their concentration was reached to 20 µg/ml, and the extent of haemolysis would be increased more than 5% while 1000µg/ml NPs were contacted with rabbit blood cells. Furthermore, TCP NPs could induce obvious hemolysis reaction and inhibit proliferation of macrophages compared with group of HAP NPs at the same concentration.

Abstract: In this paper, we have investigated the structural stability and elastic properties of four tungsten borides with the hexagonal structure by the first principle calculations. The results indicated that m-WB2 and c-WB2 were stable in thermodynamics and structure. The stiffness coefficient and modulus of the stable compounds were also calculated and were compared with those of the typical MAX ceramics. The computed ratios of bulk-to-shear-modulus and bulk-modulus-to-c44 showed that m-WB2 and c-WB2 were ductile.

Abstract: The processing and recycling experiments of dust from Electric Arc Furnace (EAF) in industrial conditions aimed at highlighting the minimizing possibility of this waste by transforming it into a by-product that can represent either a secondary raw material for steel making in EAF or to recover iron, zinc and lead (the Waltz process). Electric-arc furnace dust (EAFD) is a by-product of steel production and recycling. This fine-grained material contains high amounts of zinc and iron as well as significant amounts of potentially toxic elements such as lead, cadmium and chromium. Therefore, the treatment and stabilization of this industrial residue is necessary. Leaching test is a method of evaluating the impact of waste that is stored (soil, water table).

Abstract: The purpose of this study is to identify and quantify the effect of the mixing features of concrete such as size of coarse aggregate, high strength and steel fiber reinforcement on chloride penetration through micro-cracks. In examining the effect of size of coarse aggregate on chloride penetration through cracks, the cracks should not impact on chloride penetration directly, although small size of coarse aggregate can lead to complicated micro-cracks in concrete. On the contrary, chloride should easily penetrate through micro-cracks concentrated at the surface of coarse aggregates. In examining the effect of high strength concrete on chloride penetration through cracks, high strength concrete has an excellent performance to resist with chloride penetration. If cracks are generated in high strength concrete, however, its performance is reduced up to the level of ordinary concrete.

Abstract: The nature of high specific strength compared with other structural materials has led to wide application of Mg alloys. However, Mg alloys often exhibit relatively low strength and/or low surface stability, which can limit the practical application of the alloy system. In order to achieve high strength, the commercial AZ61 alloys were extruded, so that the application of the alloy system can be extended towards new structural parts for requiring the light nature of the alloy system. In this study, a high temperature extrusion has been carried out for the commercial Mg alloys (AZ61). The productivity and mechanical properties of the alloy were critically affected by the extrusion conditions such as temperature, extrusion ratio and extrusion speed. The texture development and alloy strengths with respect to the extrusion conditions have been discussed in terms of microstructural observations and phase analyses.

Abstract: Mn doped ZnO films with different doping concentration were synthesized by sol gel method using the spin coating technique. Zn1-xMnxO thin films are prepared using 2-methoxyethanol solution of zinc acetate dehydrate and manganese acetate tetrahydrate. The quantity of Mn in the sol was synthesized with undoped ZnO, 2%, 4%, 6% and 8 % of Mn doped ZnO with an annealing temperature of 500°C. The FESEM images showed many spherical shaped nanoparticles on the cross-sectional of the films. The optical properties were characterized using UV-Vis where the transmittance and band gap value were affected by certain amount of Mn concentration. These films achieve tunable band gap characteristics by means of changing the dopant concentration. It shows an initial decrease of band gap for small concentrations of Mn, followed by an increase at higher Mn doping concentrations.