Advanced Materials Research Vols. 11-12

Abstract: With the certain deposition process, the conversion coatings by four different pretreatments on LF21 were studied. The morphology and the chemical composition of the conversion coatings were examined by scanning electron microscopy (SEM). The corrosion resistance was investigated by electrochemical impedance spectroscopy (EIS) and the salt spray test. The results showed that the different pretreatments had obvious effect on the cerium conversion coatings. For the certain deposition process, the optimal pretreatment process was identified.

Abstract: Recently, the increase in production, consumption causes the shortage of the natural resources and the increase in waste disposal. In order to build up a sustainable society, the input and the output of the natural system should be reduced by the recirculation of materials and energy. We have tried to develop high performance building materials by solidification technology at low temperature. The starting materials were the inorganic wastes or soil. These solidified inorganic waste and solidifying soil have good mechanical strength for paving tile. Solidifying soil called as Tataki works has good performance of mitigating urban heat islands. Numerical simulation method based on heat transfer model was studied to estimate performance of mitigating urban heat islands of solidifying soil. Numerical model was calculated by the surface temperature changes in the outside with air temperature changes. Simulation result was compared with experimental measurement.

Abstract: Attempts have been made to sinter hexagonal boron nitride (h-BN) by pressureless-sintering in air. In order to achieve this purpose, feldspar has been selected as a sintering aid to produce sintered compacts at a temperature above the melting point of feldspar. Even though h-BN was not wetted by the molten feldspar in nitrogen, the wettability was significantly improved in air. Through the heating process, the h-BN powder disappeared owing to the oxidation of the powder followed by sublimation of the boron oxide. The decomposition of BN was prevented effectively by the presence of molten feldspar in the h-BN/feldspar (30 vol.%) compact. It was shown that h-BN/feldspar composite can be sintered in air under normal pressure, although the bulk density of h-BN/feldspar composites (1.40 to 1.51 g/cm3) was not satisfactory enough.

Abstract: The electrochemical behaviors of anodized and sealed aluminum alloys in NaCl solution were studied by potentiodynamic polarization, the open-circuit-potential and EIS. The results show that anodic oxidization of aluminum increases its corrosion resistance greatly. Different sealing methods have different influences on corrosion behavior of the anodized alloys in NaCl solution; corrosion resistance increases in the order: no sealing < water sealing < dichromate sealing < nickel fluoride sealing. The modulus of the porous film sealed by dichromate solution increases with the immersion time in NaCl solution, which is similar to the self-sealing effect of unsealed anodic films.

Abstract: Surface modification of low-density polyethylene (LDPE) films was carried out via a novel photografting polymerization technique with acrylamide (AAm) as the monomer. The photografting polymerization can be achieved via one-step method and two-step method. The photografting polymerization reactivity of AAm was examined with benzophenone (BP) as the photoinitiator and low-density polyethylene (LDPE) film as the substrate with “sandwich” assembly. Moreover, the occurrence and evolution of grafting polymerization of AAm on the substrate was demonstrated XPS analysis and SEM pictures.

Abstract: A process for preparing of the delaminated kaolinite was developed with intercalation of hydrazine, urea or potassium acetate followed by removing the chemical assistants. Delaminated kaolinite was characterized by XRD, solid-state NMR, thermal analyses, particle-size distribution analyses, etc. The particle size was reduced to ca. 440 nm in diameter and ca.15 nm in thickness in contrast to about 7 μm and 800 nm for untreated precursor respectively. The dehydroxylation temperature of kaolinite was shifted from 514°C to 490°C by the delamination. Additionally, a greater mass lost was also observed for the delaminated particles by dehydroxylation.

Abstract: Supramolecular 2,3-pyridinedicarboxylate intercalated NiAl-layered double hydroxides (2,3-pyridinedicarboxylate-NiAl-LDHs) has been prepared by direct coprecipitation method. The solid product was found to have a greatly expanded LDH structure. Possible orientation of 2,3-pyridinedicarboxylate between the interlayer region has been proposed. Furthermore, its thermal decomposition process was studied by the use of TG-MS and in situ HT-XRD.

Abstract: Polyacrylonitrile (PAN) tow were continuously pretreated with cuprous chloride on line. The structure and properties of untreated and treated PAN precursors were characterized by IR, DSC, X-ray diffraction and other analysis, and the paper made a preliminary discussion on the effect of modification on PAN precursors. It was suggested that PAN precursors pretreated with CuCl can enhance the rate of cyclization, lower the temperature of cyclization reaction, reduce the time required for stabilization. At the same time the resulting oxidized fibers achieved an elongation of 17.6% for the temperature range of exothermic process, and an improvement in tensile strength of 46%.

Abstract: A novel tube-form asymmetrical carbon membrane based on phenol-formaldehyde resin (PFR) is proposed in this paper. The membrane is composed of Ni-P alloy on exterior surface of carbon support membrane by electroless plating method after adding ferrous powders (<20&m) as active particles inside the membrane procurer. The results show that the H2, N2 and CO2 permeation rate through the composite Ni-P carbon membrane decrease and gas separation factors increase with increase of Fe content, and H2, N2 and CO2 permeation rates reach 0.44, 0.10 and 0.08 m3.m-2.s-1.MPa-1, respectively; H2/N2 and H2/CO2 separation factors are 4.2 and 5.5, respectively. The morphology of the membrane is measured by Scanning Electron Microscope (SEM).