Materials Science Forum Vols. 544-545

Abstract: The synthesis of the hydrophobic mesoporous silica MS(F) was performed using tetraethyl orthosilicate, triethoxyfluorosilane as the source of the fluoride and dodecylamine as templates. The TiO2 loaded on the hydrophobic MS(F) (TiO2/MS(F)) exhibited the efficient photocatalytic performance for the degradation of alcohols (iso-butanol) diluted in water. The photocatalytic reactivity for the degradation increased with increasing the content of fluoride ions on these photocatalysts. The hydrophobic mesoporous surface is suitable as the photocatalytic reaction field for the degradation of organic compounds diluted water.

Abstract: Mesostructured carbon (MSC) has been synthesized by the carbonization of assynthesized mesocellular siliceous foam (MCF)/P123 nanocomposite followed by the dissolution of the silica using 10 wt.% HF solution. SEM, TEM, and BET instruments were used to characterize the mesostructured carbon. Batch experiments were performed to evaluate its ability to adsorb natural organic matter (NOM) in various pH levels. MSC showed enhanced adsorption capacity for NOM than the commercial activated carbons. MSC possessed approximately 3.3 and 2.2 times greater the solid-water partitioning coefficient of NOM, Kd, at pH 7 than coal-based and coconutbased activated carbons, respectively. This increased Kd of MSC resulted from mesoporous structures in the range of 4-6 nm on the surface. The Kd value decreased with increasing initial pH levels, which is considered to be due to ionization of functional groups of NOM.

Abstract: TiO2/SiO2 hybrid film, having water resistance, for water purification photocatalyst was successfully and firmly coated on stainless steel with one dip coating and heat curing method. By controlling relative content of the TiO2 sol and the SiO2 based binder, these films were found to have a significant influence on the hardness, water-resistance, and photocatalytic activity.

Abstract: Modified polypropylene granules (MDPG) were coated by manganese dioxide and their surface and adsorptive characteristics were studied. Surface characteristics of the adsorbent were investigated by B.E.T. surface area and mercury porosimetry. Coating has significantly increased the surface area of granules from 0.12 m 2 /g B.E.T. N 2 to 15.42 m 2 /g. Gas pycnometry measurements resulted in low density of 0.13 g/cm 3 for uncoated granules, the fact ascribed to 0.65 porosity measured. Coating increased micro pore volume of raw granules by a factor of 58. Adsorption experiments were conducted in column flow-through reactors at pH 6.0 and 10 g/L sorbent dosage for mixture of four metal species, each having 5 mg/L initial concentration. More than 60 % of Pb and Cu was removed within first 20 min, whereas just over 29 and 13 % for Cd and Zn respectively. Furthermore, more than 99, 84, 40, 16 % of Pb, Cu, Cd, and Zn was removed within 1 h. Adsorption efficiencies for 5 ppm of initial metal concentration at pH 5.0 and 10 g/L sorbent/solute ratio resulted in 4.9, 3.9 mg of Pb and Cu sorbed per gram of sorbent. And these ratios for separate metal ions were substantially higher than those for the mixture of the four metal ions. For 5 g/L of sorbent under the same parameters, removal efficiencies of Cd and Zn were respectively 0.98, 0.75 mg/g, correlating well with Freundlich adsorption model. Adsorption kinetics showed relatively fast removal rates within first 5 h of sorption. Desorption resulted in eluting 57, 70, 76, 78 % of the initial feeding concentrations for Pb, Cu, Cd, Zn, respectively.

Abstract: The commercial nano-sized TiO2 powder (P25) coated with PtO2 powder by a sonochemistry method was immobilized on the foamed waste-glass substrates by using plasma spray coating technology. The immobilized TiO2-Pt coatings were applied to treat both green tide and red tide under illumination of an UV light. Their photocatalytic characterizations were evaluated as functions of the number of residual algae, transmission as well as pH value with illumination time. It’s found that the plasma sprayed Pt-doped TiO2 nanostructured coatings on foamed waste-glass showed higher photocatalytic activity, which was effective to treat the green tide and red tide.

Abstract: The suspension stability was investigated as the function of particle number concentration, applied force, and the distance between cathode and anode. The suspension was prepared by using BaTiO3 nanoparticles in a mixed solution with ethanol and acetylacetone. The highest zeta potential value was 30 mV, when the mixing ratio of EtOH and Acac was 75 : 25. EPD conditions of BaTiO3 nanoparticles suspension with 0.05 wt% were settled at the conditions of an applied dc field of 20 V/
and an electrode distance of 1.5
at 300 seconds of deposition time.

Abstract: A pulsed spark-discharge aerosol generator using air as a carrier gas was successfully applied to the titania nanoparticle production. The titanium vapor evaporated by spark discharge was subsequently supersaturated and condensed to titania nanoparticles by nucleation and condensation. The size and concentration of the particles can be controlled easily using air as a carrier gas by altering the repetition frequency, capacitance, gap distance, and flow rate of the spark-discharge system. TEM observation shows that the generated particles were aggregates, which primary particle sizes are a few nanometers. The element composition of the nanoparticles was titanium and the crystal phase was amorphous. XPS analysis shows that oxidation state of generated particles corresponded to TiO2. These XPS data indicates that some fraction of the evaporated titanium vapor could be oxidized in an air atmosphere by the oxidation with oxygen. However, enough time for crystallization was lacked because of raid cooling.

Abstract: TiO2 and V-doped TiO2 gel were synthesized and coated onto porous α-Al2O3 beads to study the thermal catalytic activities of oxidation reactions. Titanium isopropoxide (Ti(OPr)4) and 1,2-butadiol(Bu(OH)2) were used as starting chemicals for preparation of TiO2 gel without Vdoping. After aging at ambient temperature for one week, a TiO2 gel was obtained. The concentration of Ti(OPr)4 was varied, 0.2, 0.3, 0.7 and 2.4 M was used. For V-doping of the TiO2 gel, 0.05, 0.20 and 0.75 mole% of V was prepared by ultrasonically dissolving vanadium acetylacetone (V(acac)2) in 1,2-butadiol. The solutions were then added to Ti(OPr)4. Finally, the mixed solutions were kept under ambient temperature for one week to form the V-doped TiO2 gel. TiO2 and V-doped TiO2 were calcined at 300, 400, 500, 600, 700, and 800 °C. XRD analysis, SEM and TEM in conjunction with EDS analysis were used to identify the phases present, grain size and morphology. The TiO2 grains have a particle size in the nano-scale range. Doping TiO2 with V could retard growth of the TiO2 particles and affect phase transformation at higher calcination temperatures. Both the TiO2 and V-doped TiO2 gels were prepared and coated onto α-Al2O3 beads to test oxidation reactions in a purpose-designed reactor. The results of the catalytic reactions indicated that V-doped TiO2 had a higher oxidation activity than the undoped TiO2 gel. The content of vanadium was related to the reaction efficiency.

Abstract: In case of the low carbon chromium steel that have widely been used for the carburized gears or rolling bearings, the austenite grain coarsening may be occasionally occurred during carburizing. To restrain this phenomenon, most of hot forged parts have been given to an isothermal heat treatment or normalizing immediately after hot forging and/or prior to carburizing. Therefore, their production cost includes unexpected additional expenses caused by such a non-value added process. To confirm the possibility of an energy saving, as well as attaining a superior fatigue life, in the production of automotive parts to be carburized, the austenite grain coarsening with the manufacturing process of the microalloyed steel, containing Nb and B as a grain refining elements, was investigated. The heat treatment characteristics and rolling contact fatigue behavior of the carburized specimens with the isothermal heat treatment were also investigated. In spite of omitting the isothermal heat treatment after hot forging, the abnormally coarse austenite grains were not found out in the carburized specimens. However, the rolling contact fatigue life of the carburized specimens, in which the isothermal heat treatment was omitted, was shorter than that of isothermally heat-treated specimens.