Materials Science Forum Vols. 544-545

Abstract: This study focuses on the development of novel catalysts for simultaneous adsorption and oxidation of micropollutants in aqueous phase. Molecular catalysts were physically immobilized on the surface or pore of amberlite IRA-400 or powdered activated carbon (PAC). Comparison of different combinations of catalysts and adsorbents showed that the Fe(III)-TsPc combined with amberlite had the highest removal efficiency for target compounds. Although the catalyst was immobilized by electrical attraction, no dissociation of catalyst from adsorbent occurred during the tests. Amberlite-supported Fe(III)-TsPc shows more than 98% removal efficiency in 40 min. In homogenous system (suspension of Fe(III)-TsPc in aqueous solution), the oxidation reaction occurred only in acidic conditions (pH ~ 4.5) and the catalyst deactivation rate was fast. On the contrary, the reaction was fast in neutral pH and catalytic deactivation was negligible using the amberlite-supported Fe(III)-TsPc.

Abstract: TiO2 nanoparticles were synthesized with using N2-diluted and O2-enriched coflow hydrogen diffusion flames. We investigated the effects of the flame temperature on the crystalline phases and particle characteristics of the TiO2 nanoparticles that were formed. For the higher temperature conditions, the maximum centerline temperatures that were measured were greater than approximately 1,600K, and TiO2 nanoparticles, which had spherical shapes with diameters of approximately 60nm, were synthesized. For the lower temperature conditions, the maximum centerline temperatures that were measured were less than approximately 1,600K, and the diameters of the nanoparticles that were formed had unclear boundaries that ranged from 35 to 50nm. From the XRD analyses, it was believed that the crystalline structures of the nanoparticles that were formed were divided into two types. For the higher temperature cases, the fractions of the TiO2 nanoparticles that were synthesized, which had anatase-phase crystalline structures, increased with the increase of the flame temperatures. On the contrary, for the lower temperature cases, the fraction of anatase-phase nanoparticles increased with the decrease of the flame temperatures.

Abstract: In the area of biomaterials, the structures with negative Poisson’s ratio are able to be applied to the polymer component of prosthesis, artificial blood-vessel and catheter. To induce its characteristic, previous studies postulated many structural shapes such as non-convex shape with reentrant corners and re-entrant honeycomb. In this study, we proposed the rotational particle structures and investigated the Poisson’s ratio and the ratio (Ee/E) of the elastic modulus of these structures based on structural design variables using finite element method. The auto-meshing preprocessor was coded using MATLAB in order to construct numerical models as design variables and perform finite element analysis (FEA) effectively. Three selected design variables were the ratio of fibril’s length to particle’s diameter (0.2~2.0), the ratio of fibril’s length to its width (0.02~0.2) and the angle of fibril about horizontal axis (0 degree ~ tangential angle). Finite element model has 2D plain stress quadratic element and composed of 515 particles and 6-linked fibrils per each particle. For all of 213 cases, one side of each model is applied a tension, 0.1% strain and analyze Poisson’s ratio and the ratio (Ee/E) of the elastic modulus. As the ratio of fibril’s length to particle’s diameter increased and the ratio of fibril’s diameter to fibril’s length decreased fixing the fibril’s angle with 45 degree, the negative Poisson effect of rotational particle structures increased. The ratio of elastic modulus of these structures decreased with Poisson’s ratio. The results show the reasonable values as compared with the previous analytical results.

Abstract: The post-dynamic softening of Nb micro-alloyed steel and plain carbon steel was investigated through stress relaxation method. Meanwhile, By comparison with C-Mn steel, the effect of deformation temperature and strain on post dynamic recrystallization of Nb steel was studied . The result shows that element Nb in solution state can dramatically improve the apparent activation energy of static recrystallization. At lower temperature, the recrystallization can be retarded and precipitation of Nb(C, N) occured. If strain is more than the critical strain of dynamic recrystallization, the metadynamic recrystallization takes place. If fully metadynamic recrystallization takes place, the kinetics is no longer dependent on strain of the kind of steels.

Abstract: Effects of mixing dye sensitizer for the photocatalytic activity of dye-sensitized Pt/K0.95Ta0.92Zr0.08O3 was investigated. It was found that the photocatalytic activity was greatly improved by mixing dye sensitizer on the catalyst, and among the examined combination of organic dyes, the highest photocatalytic activity was obtained by mixing Cr-tetraphenylporphyrin (Cr-TPP) and Pentametylene bis[4-(10, 15, 20-triphenylporphine-5-yl)benzoate] dizinc(ΙΙ) (Zn-TPP dimer). In order to identify the effect of dye sensitizer, photovoltaic behavior of the dye-sensitized KTaO3 was investigated. The lifetime of the photo-exited electron and hole can be improved by coating with dye sensitizer. Thus, the effect of porphyrinoids would be explained by the improved efficiency of charge separation.

Abstract: The influence of the titania photocatalyst particle of the nanometer region on the human being and biology’s to be doubted. Removing the uneasiness will expand further uses for the photocatalyst nanoparticle. Then, we attempted to examine the effect of several titania photocatalyst nanoparticles to the artificial skin like the human body under the UV and visible light irradiation conditions. The decomposition degree of the artificial skin was evaluated from the monitoring of the amount of carbon dioxide generated from them by the titania photocatalyst nanoparticle activity. Under the UV irradiation condition, it was almost found the carbon dioxide emergence from the artificial skin by the activity of the titania photocatalyst nanoparticle. On the other hand, under visible light condition it was mostly detected.

Abstract: Tantalum dioxide and nitrogen co-doped titanium dioxide nanopowders, denoted as (Ta2O5, N) co-doped TiO2, were fabricated by a high-energy ball miller using TiO2, Ta2O5 and urea as raw materials. Experiments on the photocatalytic activities of the (Ta2O5, N) co-doped TiO2 were carried out in the form of photodegradation of methylene blue (MB) in aqueous solution under visible light irradiation. Enhanced photocatalytic activities were observed for the (Ta2O5, N) co-doped TiO2 than commercial Degussa P25. Besides, physical, chemical and optical properties, including XRD, DRS, and XPS were detected to analyze the origins for the enhanced photocatalytic activities of the prepared samples.

Abstract: High purity nanowires are successfully synthesized by chemical vapor deposition. In this work, we have tried synthesis of GaP nanowires with copper oxide catalyst using chemical vapor deposition method involving a metal oxide-assisted vapor-liquid-solid (VLS) growth mechanism. The synthesis process is the same as that described in existing work except for a catalyst. The mixture of GaP and Ga powder was used as GaP source for synthesis of GaP nanowires. And the mixture powder was directly vaporized in the range of 700~1000°C under argon ambient in a furnace. The wire-like products was observed in the range of 800~950°C. The diameter of nanowires increases with increasing synthesis temperature, but reversely, the length of nanowires decreases steadily. The nanowires prepared at 850°C possess perfect wire-like shape and uniform distribution of diameter. The average diameter and length of nanowires are about 50
 and 150, respectively. HRTEM and EDX analysis were carried out to obtain more detailed information of its microstructure. Nevertheless, all condition of processing was set for making the high purity GaP nanowires as existing reported method, the nanowires were identified as well-crystallized gallium oxide nanowires with an amorphous outer layer. It does not accord with existing reported results. This result means that the catalysts play a key role in the growth of nanowires.

Abstract: Titanium of 99.7% purity was anodized in 1M potassium phosphate monobasic (KH2PO4) water solution with 0.15M NH4F. Titanium oxide nanotubes were fabricated at anodization potential of 20 V and 4.64 pH. To control the pH of the solution, we have added weak acid such as citric acid because it has three dissociation constants (pKa) of 3.09, 4.75, and 5.41. Citric acid was very useful to control the pH of the 1M KH2PO4 water electrolyte solution within 3 to 5. The diameter and length of the titanium oxide nanotubes were independent on anodization time. The diameter of 120 nm and length of 2.8 μm at anodization time of 5 hrs were observed by field emission scanning electron microscope (FESEM). Undesired thin oxide layer blocking the top of titanium oxide nanotubes was wiped out by increasing the anodization potential with the multi step voltage by 1 V reached to 25 V. The titanium oxide nanotubes having a very large surface area are very attractive for the battery, gas sensor, photocatalytic application, and biomaterials.

Abstract: TiO2 nanoparticles were prepared using the hydrolysis of titanium tetraisopropoxide (TTIP) using TENOH as a peptizing agent in the hydrothermal method. The physical properties of prepared nanosized TiO2 particles were investigated. The photocatalytic degradation of orange II has been studied using a batch reactor in the presence of UV light. The crystallite size of the anatase phase is increased from 15 to 30 nm as the molar ratio of TENOH/TTIP increases from 0.1 to 1.0. The titania particle prepared at TENOH/TTIP molar ratio=0.1 shows the highest activity on the photocatalytic decomposition of orange II and the photocatalytic activity decreases according to an increase in TENOH/TTIP molar ratio. In addition, the titania particles prepared at 160oC shows the highest activity on the photocatalytic decomposition of orange II