Solid State Phenomena Vols. 124-126

Abstract: Lotus-type porous NiAl and Ni3Al intermetallic compounds, possessing cylindrical pores aligned in the direction parallel to the solidification direction, were fabricated by using a unidirectional solidification technique in a pressurized hydrogen atmosphere of 2.5MPa. The porosity of lotus NiAl is 24.2 %, and the porosity of lotus Ni3Al is 3.2%; the porosity of the porous NiAl is larger than that of Ni3Al. This is because the solubility gap of hydrogen between liquid and solid phases of NiAl is larger than that of Ni3Al.

Abstract: We investigated the pore morphology in lotus-type porous copper fabricated by continuous casting technique as a function of transference velocity range from 1 to 100 mm･min-1 under hydrogen gas pressure of 1.0 MPa. Lotus-type porous copper with long cylindrical pores aligned in one direction parallel to the transference direction was fabricated, which posses a sufficient uniformity of the porosity and pore size. The pores formed at transference velocity of 1 mm･min-1 were larger than other condition. Necks were observed in these pores, whose formation may be attributed to bubbling in the melt. The pore size decreased with increasing transference velocity, while the porosity was not varied much by transference velocity.

Abstract: A network structure of gold nanowires was prepared from a template synthesis method, in which gold metal nanowires were first deposited into a polycarbonate track-etched membrane with pore diameter of 100 or 220 nm via auto-catalytic deposition (i.e., electroless deposition), followed by thermal treatment to remove the polycarbonate template membrane.

Abstract: Ceramic membranes having nano sized pores have great potential for gas separation at high temperature due to their good thermal stability. Moreover, nanoporous silicon carbide membrane has potential application under hydrothermal condition at high temperature. In this research, nanoporous SiC membrane has been developed on the porous alumina plate using preceramic polymers as CVD precursor at 850oC. The preceramic polymer was characterized with Si29 NMR, FT-IR, GC and TGA. The prepared SiC membrane was characterized with SEM and EDS. The hydrogen permeability and selectivity toward nitrogen gas were measured using a GC.

Abstract: A series of Cu-Zn-Al catalysts from the precursors with the hydrotalcite-like structure were prepared, and these catalysts admixed with γ-Al2O3 were tested for DME synthesis in a fixed bed flow reactor in a single step. DME synthesis rates were well correlated with the Cu metal surface of the Cu-Zn-Al catalysts in the admixed catalysts, indicating that DME synthesis rates would be controlled by methanol synthesis rates.

Abstract: In the present work, TiO2 and Ag-TiO2 catalysts were prepared by an ultrasonic assisted sol-gel method. The physico-chemical characteristics studies of the newly synthesized catalysts were carried out by XRD, TEM, EDX, XPS, UV-Visible absorption spectra and an optical ellipsometry. In order to find out the optical absorption properties of the catalysts, theoretical simulations have been carried out by using the Tauc-Lorentz oscillator model. Photodegradation and mineralisation of the chlorophenols were confirmed by the HPLC and TOC measurements. The rate of a mineralisation trend was observed in the order of P < 2-CP < 2,4-DCP < 2,6-DCP < 4-CP < 2,4,6-TCP by using the Ag-TiO2 catalyst. The concentration of the main aromatic intermediate products was considerably lower for the Ag-TiO2 photocatalysts than for pure TiO2. This experiment demonstrated that the presence of Ag on TiO2 catalysts could enhance the photocatalytic oxidation of chlorophenols in an aqueous suspension. It was found that the degradation of the chlorphenols by these catalysts followed the pseudo- first order kinetic model.

Abstract: Au/CeO2 catalysts prepared by a deposition-precipitation and a co-precipitation method were applied to CO oxidation in the absence and presence of hydrogen. The transmission electron microscope (TEM), the temperature programmed reduction (TPR), and the X-ray absorption near edge structure (XANES) were conducted to probe structural and electronic properties of gold. Au2O3 was determined to be mainly present when Au/CeO2 was prepared by a deposition-precipitation method. However, the metallic gold was observed in a co-precipitated Au/CeO2 catalyst. Au/CeO2 containing oxidized gold species, prepared by a deposition-precipitation method, showed the decreasing CO conversion with a reaction time, which accompanied the reduction of gold from Au(+3) to Au(0). However, co-precipitated Au/CeO2 showed the stable CO conversion. The effect of pretreatment condition on CO oxidation was also examined. These results support that Au/CeO2 catalyst containing oxidized gold species was superior to Au/CeO2 catalyst containing the metallic gold for CO oxidation. This Au/CeO2 catalyst was also active for the selective CO oxidation in the presence of hydrogen.

Abstract: The synthesis of dimethyl carbonate(DMC) was investigated using four differently supported quaternary ammonium salt catalysts to facilitate their separation after the reaction. The different catalysts are (1) C1 on poly(ST-co-VBC), (2) C2 on poly(ST-DVB-VBC), (3) C3 on macroporous poly(ST-DVB-VBC), (4) C4 on modified MCM-41. The synthesis of DMC was performed in an autoclave under carbon dioxide pressure. The main byproduct was propylene glycol. The immobilized quaternary ammonium salt catalysts showed good catalytic activity for the synthesis of DMC. The order of the reactivity for the catalysts of different support was C1>C3>C2>C4. The catalysts can be reused for four successive runs without considerable loss of their initial reactivity.

Abstract: Applicability of Al-MCM-48 as a catalyst for the linear low density polyethylene (LLDPE) degradation was investigated using a thermogravimetric analyzer as well as a batch reactor. The degradation products were analyzed by GC/MS, GC-TCD and GC-FID. The activation energy of LLDPE degradation was lowered by the addition of Al-MCM-48. The oil and gas yields were higher over Al-MCM-48 than those over Si-MCM-48. Al-MCM-48 generated mainly C7-C10 hydrocarbons, while Si-MCM-48 exhibited the relatively broader distribution of the oil products (C8-C14). Al-MCM-48 showed high catalytic stability for the LLDPE degradation.