Solid State Phenomena Vols. 124-126

Abstract: Al foams with high porosity were fabricated via melt foaming method. In this process, Ca and TiH2 are used as thickening and foaming agent. The macrostructure of aluminum foams exhibited homogeneous distribution of fine pore sizes at shorter holding time. From comparison of the actual pore sizes with ones calculated with modified Ostwald ripening, the measured pore sizes were well fitted to the calculated ones. These results suggest that hydrogen diffusion through pore walls from smaller pores to a larger one is the main process of pore evolution at least in the later period of holding. The detailed are discussed in the context.

Abstract: We have been investigated application of the lotus type porous metal that is manufactured by the unidirectional solidification of the melt in pressurized gas atmosphere such as hydrogen or nitrogen for an air bearing development. In this study, wear properties of porous copper having cylindrical pores have been investigated. Generally, wear test is influenced by a shape, a wear test method, atmosphere and a way of lubrication. Wear test used pin on disk type's wear test.

Abstract: ZSM-5 was modified by alkaline and acidic solution to introduce mesoporosity in the crystals. Heterogenized Co(III) salen was prepared in the mesopores of ZSM-5 by ‘ship-in-a-bottle’ method. Phenolic ring opening of epoxides was performed successfully by using encapsulated chiral salen catalysts. Very high enantioselectivity and conversion were obtained in PKR reaction by immobilized catalysts.

Abstract: Self-organization of a two-dimensional array of nanopores, which was formed by anodic oxidation of aluminum, was investigated quantitatively using scanning electron microscopy (SEM) images and their fast Fourier transformation analysis. The highly ordered array of nanopores with diameters of ~60 nm was obtained by two-step anodization at an anodizing voltage of 40 V for an anodizing time of 36 h in a 0.3 M oxalic acid. A two-dimensional ordered array of ferroelectric PbTiO3 nanotubes was successfully fabricated by a spin coating of sol-gel solution into porous anodic alumina template. SEM and transmission electron microscopy images show that the nanotubes have a relatively constant wall thickness of ~15 nm with an outer diameter of ~60 nm. The present method has a high efficiency to fabricate an ordered nanotube array of a variety of functional metal oxide materials in a large area.

Abstract: The fluorine-modified mesoporous silica HMS(F20) was synthesized by using the mixture of TEFS(SiF(OC2H5)3) and TEOS(Si(OC2H5)4) as the silica source. The specific surface and pore size distribution were characterized by N2 adsorption and the hydrophilic-hydrophobic property was measured by water adsorption. The photocatalytic activities of TiO2 nanoparticles loaded on HMF(F20) and HMS were investigated for the degradation of iso-butanol diluted in water. The results show that the fluorine-modified mesoporous silica HMS(F20) has higher hydrophobic property than HMS and the TiO2/HMS(F20) exhibits the higher photocatalytic activity than TiO2/HMS. The hydrophobic mesopores benefit the condensation of hydrophobic organic compounds diluted in water, which results in higher photocatalytic degradation efficiency.

Abstract: Graphite nanofibers (GNFs)–supported platinum (Pt) catalysts had been prepared by an electrochemical deposition by controlling an applied potential to a potential of Pt reduction. Pt nanoparticles were successfully deposited by using potential sweep methods. The catalyst prepared by 18 sweep times showed the lowest resistance and the highest electroactivity. These electrochemical properties were dependent on the size, loading level, and morphology of catalysts. The influences of electrochemical condition on the sizes and loading level of catalysts were also investigated.

Abstract: Although glass wool and polyurethane foam are the most widely used sound-absorber and insulating materials, there are some critical problems related to the environmental issues. In this reason, there is a lot of attention on the aluminum foam as a sound absorption material, therefore, in this research, sound absorption and transmission loss properties were studied. The results showed that low density aluminum foam performed better in both sound absorption and transmission loss and the properties were improved as increased air cavity and space.

Abstract: The change in dielectric constant of ferroelectric materials as a function of electric field is the key to wide range of microwave application such as tunable filter, impedance matching network, and phase shifter. In this study, ferroelectric Ba0.5Sr0.5TiO3 (BST) films were grown on r-cut sapphire and polycrystalline sapphire (poly-sapphire) substrates by RF sputtering. The results of comprehensive structural diagnostics of the films are correlated with the dielectric constant and dielectric loss of a co-planar BST varactor, measured at a frequency range of 1~3 GHz. Textured BST films approximately 500 nm thick, grown on r-cut sapphire substrates, are characterized by high dielectric constant ≥ 650. However, polycrystalline BST films, grown on poly-sapphire substrates, are less strained, having dielectric constant range of 430 ~ 640.

Abstract: In this study, the synthesis of the bulky and dense mesoporous silica such as FSM was attempted by a hydrothermal hot-pressing (HHP) with a surfactant as a template and a subsequent calcination. According to TEM observation, the dense bulks obtained by HHP had a hexagonal mesopore structure. Also, these dense FSM bulks possessed high specific surface areas. Furthermore, Ag-supported dense FSM bulks were successfully synthesized by HHP with Ag salt and a subsequent calcination in H2. Thus, this HHP method is useful for synthesizing dense bulks and simultaneous supporting novel metals such as Ag on bulky FSM.

Abstract: Pitch based activated carbon fibers(ACFs) were characterized by electric decomposition method in the various kinds of acid electrolyte. The felt-type commercialized ACFs were used as raw material and the acids such as HCl, H2SO4, HNO3 and HF were used as electrolytes for electric decomposition. ACFs were treated with 0.7 ~ 2.0A/g-ACF of DC as an anode material for few hours in the acid electrolyte bath and voltage was varied 10~50V according to the condition of current and electrolyte. The pore properties of surface characterized ACFs were measured by adsorption analyzer and changes of surface morphology were also observed by scanning electron microscope and transmitting electron microscope. In order to estimate possibility of use as hydrogen storage material, hydrogen adsorption amount was measured with high pressure thermogravimetric analyzer. In the result the pore size distribution of surface characterized ACFs were changed with respect to electric decomposition condition, especially species and concentration of electrolytes and hydrogen adsorption amount also changed according to pore properties of ACFs.