Materials Science Forum Vols. 510-511

Abstract: Langasite (La3Ga5SiO14: denoted by LGS) single crystal is one of the lead free piezoelectric materials with high piezoelectricity that is maintained up to its melting point (1470°C). Although LGS single crystals have usually been grown by Czochralski (CZ) method in oxygen contained atmosphere to prevent evaporation of Ga, they were grown by the vertical Bridgman (VB) method in Ar atmosphere without oxygen, and their properties were evaluated in this work. Transparent and colorless LGS single crystals were successfully obtained without Ga evaporation by the VB method in Ar atmosphere, and their resistivity at room temperature was much higher than that grown by conventional CZ method. Piezoelectric constant d11 of the crystal grown by the VB method was 6 x 10-12 C/N, which was close to that of the crystal grown by CZ method. The colorless transparent LGS single crystal turned to orange and its resistivity decreased by annealing in air. Since an orange-colored transparent LGS single crystal has been grown by conventional CZ method, this indicates that color change and the resistivity decrease of LGS crystal is caused by extra interstitial oxygen atoms in the crystal.

Abstract: A novel route is developed to prepare a new type of Sr-contained hydroxyapatite bone cement. Tetracalcium phosphate, strontium hydrogen phosphate or anhydrous strontium chlorite, dicalcium phosphate, phosphoric and water are used as precursors. XRD, FTIR and EDXS are used to characterize the incorporation of 5% or 10% Sr2+ into the crystal lattice of hydroxyapatite. Results indicate that the Sr-contained CPC system of TTCP/DCPA/DSPA can set in 0.5M diluted phosphate acid with a final product of non-stoichiometric Sr-contained hydroxyapatite.

Abstract: Sericite has the intermediate nature of the muscovite and illite, which has been used as the additive of the cosmetics, the ceramic industry, welding rods, and other various pigments and the paint. In this study, the characteristics of sericite were examined using XRD(X-ray diffractometer), XRF(X-ray fluorescence spectrometer), TG-DTA(Thermal Analyzer), SEM(Scanning Electron Microscope) and PSA(Particle Size Analyzer). The raw ore is composed of 60.90wt% SiO2, 7.88wt% K2O, 0.36wt% TiO2, 24.80wt% Al2O3, 1.64wt% Fe2O3, 2.39wt% CaO, and 0.83wt% MgO. After sericite was purified, the content of SiO2 decreased from 60.9wt% to 51.4wt%, and in the crystal phase the intensity of quartz decreased significantly. For the high grade purification of sericite, the removal of iron and separation of quartz for the raw ore (sericite), the hydrocyclone were used with the magnetic separator. The content of iron was reduced from 1.64wt% to 0.91wt%.

Abstract: High strength Al-8Fe-2Mo-2V-1Zr (wt.%) alloys fabricated by a melt spinning and a hot extrusion process were produced to correlate the microstructure and mechanical property. Melt spun ribbon prepared by single roll melt spinner showed a cellular structure with an average size of 10nm and Al-Fe based intermetallic dispersoid of less than 10nm in particle size. The melt spun ribbon obtained was then pulverized to make a powder shape followed by hot extrusion at 648K, 673K, 723K and 773K in extrusion ratio of 5 to 1, respectively. Equiaxed grain structure containing Al-Fe based intermetallic phase was observed in all extruded specimens. According to increasing extrusion temperature, the grain size increased and particle size of intermetallic dispersoid. The lattice parameter increased from 0.4051nm to 0.4059 nm with increasing extrusion temperature from 648K to 773K, those values were larger than that obtained in pure Al (0.4049nm). Yield strength of the specimen extruded at 648K measured to 956MPa at room temperature, 501MPa at 573K and 83MPa at 773K, respectively. With increasing extrusion temperature yield strength decreased significantly at room temperature and even in the intermediate temperature range, while no noticeable difference in yield strength was observed at 773K.

Abstract: We report on advanced β-titanium alloys having excellent biocompatibility without containing V or Al that has been known as a toxic element for human body, and on a low elastic modulus to be used in the fields of artificial joint and dental implant in the replacement of natural human bone. Martensite structure with α’ (hcp) or α”(orthorhombic) was observed in Ti-xNb-1.5at.%Si, where x=10-20at.%. The crystal structure of martensite formed from water quenching process was largely dependent upon Nb content but does not on Si content. On the basis of experimental results obtained, it is suggested that Si has an effective role to suppress the precipitation of ω phase leading to reduction in elastic modulus in the metastable β phase region. Metastable β phase region was superior to reduce the elastic modulus than stable β phase region in the present alloy system. The minimum value of elastic modulus was measured to 48GPa.

Abstract: Surface modification process was employed to enhance the thickness of film and avoid crack propagation during ambient drying for the smart glazing. To eliminate the hydrocarbon on the surface of glass, UV was irradiated on the glass slide under oxygen atmosphere. The wetting angle was reduced to the optimal condition for dip-coating when UV irradiation with oxygen time was kept for 10minutes. The thickness of the surface modification samples have almost double value compared to the sample of non-surface treatment. The thickness of the film after heat treatment of the substrate was highly increased.

Abstract: Aluminum dross is presented as a potential material to form AlON using thermite reaction. The commercial MgAl powder, active carbon, and titania were prepared to make a chemical furnace (self-propagation combustion). The preheating temperature of 300
is enough to intitate ignition of the mixture as fuel and oxidizer. The addition of Y2O3 (1wt. %) is effective to enhance solid solution products between Al2O3 and AlN in the Aluminum dross. The level of contamination like an alkali metal oxide in the Aluminum dross was reduced highly by the heat from chemical furnace.

Abstract: We propose a new PDMS microfluidic system including microvalves and a micropump that are easily integrated on the same substrate with the same process steps. The pumping rate of the fabricated microfluidic system was measured under various frequency and duty-ratio of applied power. The maximum pumping rate of about 26 nl/min is measured under the duty ratio of 1 % at 2 Hz of the applied pulse voltage. The dynamic response of the microvalve in the microfluidic system is measured under the on/off alternation with the applied power of 100 mW.

Abstract: Porous n-HA/PVA hydrogel composite was prepared through in-situ hydrothermal treatment under normal pressure and emulsion foam freeze-drying method, which was used to fabricate porous hydrogel. The pores exhibited interconnection-pore structure owing to the injection of air bubbles and the removal of emulsifier (OP). The porous hydrogels were investigated by using IR, XRD, TEM and SEM. The results indicated that n-HA in the composite could disperse uniformly, and there were chemical bonding with PVA. In addition, nano-hydroxyapatite existed in the composite in the shape of short-rod. The pores were interconnection with narrowly pore size and highly porosity. And the pore size and size distribution were influenced by the weight of OP. The emulsion foam freeze-drying method can be used to prepare porous hydrogel scaffold for tissue engineering, or to contain proteins scaffold, because of operating at a low temperature. The method displayed a vast potential of applied foreground.