Papers by Keyword: Precursor Method

Abstract: SiC-Ti functionally graded material (FGM) was prepared by polymer-derived method in order to resolve connection problem between the ceramic matrix and its composite materials, as well as metal at high-temperature. Gradient materials were fabricated successfully by polymer-derived method combined with hot-press sintering process at 1300. The microstructure of the prepared samples was studied, and the results revealed that this FGM had a compact structure, without obvious interface between different layers. The distribution of elements was gradient according to the SEM and EDX results.

Abstract: Nanocrystalline Co₈₂Ni₁₈ alloy was synthesized by polyol reduction of cobalt-nickel hydroxide precursor. X-ray diffraction results indicated the formation of fcc phase alloy and the crystallite size was found to be about 19 nm. Scanning electron microscopy and transmission electron microscopy images showed the morphology of particles close to spheres and stoichiometry of the precursor and the alloy was obtained by the energy dispersive X-ray analysis. Selected area electron diffraction pattern indicated the polycrystalline nature of the alloy particles. The saturation magnetization of the nanocrystalline alloy was about 107 (emu/g) at room temperature and the M-H measurements at 300 K and 5 K indicated that the nanocrystalline alloy exhibits close to superparamagetic behaviour.

Abstract: Polymethylsilsesquioxane (PMSQ) fiber was exposed to metal chloride vapors in a controlled atmosphere or electron beam irradiation in air to promote the curing process. The cured fibers were pyrolyzed at 1273K to compare the efficiency of individual curing method. The cured fibers were investigated by FT-IR, an optical microscope and TG analysis. In the case of successful curing, averaged diameter and tensile strength were analyzed on the obtained Si-O-C fibers.

Abstract: In this paper, a new attempt of transfer heat foaming was examined on the precursor method to fabricate long scale aluminum foams. In this new method, the induction coil heater was moved along the longitudinal direction of a rod precursor to foam a part of the precursor continuously. Long scale aluminum precursor was successfully foamed by the transfer heat foaming in which heating coil was moved along the precursor to control the temperature of heated part constantly.

Abstract: The present study is aiming at investigating the possibility of producing a magnesium foam from machined chips. To produce highly porous magnesium foam, precursor producing process was investigated by hot extrusion and compressive torsion processing (CTP). The CTP could realize well-consolidated precursors and homogeneous distribution of a blowing agent. The precursor made of machined chips satisfactorily expanded, and the porosity were comparatively high by optimizing processing parameters of the CTP.

Abstract: Aluminum foam is a class of porous materials; in which closed pores are produced by a gas generation in liquid (or semi-liquid) aluminum. Aluminum foams are, generally, fabricated by heating a foamable precursor (a powder compact consisting of aluminum and TiH2 powders). Decomposition of TiH2, which is followed by a hydrogen gas release, produces bubbles in molten aluminum. In this research, aluminum foam was fabricated with the help of a chemical exothermic reaction. Titanium and boron carbide (B4C) powders were blended in the Al-TiH2 precursor as reactive powder elements. When one end of the precursor was heated, a strong exothermic reaction between titanium and B4C took place (3Ti + B4C 􀃆 2TiB2 +TiC + 761KJ), and the neighboring part of the precursor was heated by the heat of reaction. Hence, once the reaction happens at the end of the precursor, it propagates spontaneously throughout the precursor. The blowing process takes place at the same time as the reaction because aluminum melts and TiH2 decomposes by the heat of reaction. The advantage of this process is that the energy to make aluminum foam is not necessarily supplied form the external source, but generated form inside of the precursor. Therefore the blowing process is self sustainable (Self-Blowing Process). In this work, the effect of processing parameters on the Self-Blowing Process was observed. The processing parameters we focused on were blending ratio of the starting powders (aluminum, TiH2, titanium, B4C) and heating methods.