To improve light absorption ability in the visible light region and the efficiency of the charge transfer reaction, Pd nanoparticles decorated with reduced TiO2 nanotube photocatalyst were synthesized. The reduced TiO2 nanotube photocatalyst was fabricated by anodic oxidation of Ti plate, followed by an electrochemical reduction process using applied cathodic potential. For TiO2 photocatalyst electrochemically reduced using an applied voltage of -1.3 V for 10 min, 38% of Ti4+ ions on TiO2 surface were converted to Ti3+ ion. The formation of Ti3+ species leads to the decrease in the band gap energy, resulting in an increase in the light absorption ability in the visible range. To obtain better photocatalytic efficiency, Pd nanoparticles were decorated through photoreduction process on the surface of reduced TiO2 nanotube photocatalyst (r10-TNT). The Pd nanoparticles decorated with reduced TiO2 nanotube photocatalyst exhibited enhanced photocurrent response, and high efficiency and rate constant for aniline blue degradation; these were ascribed to the synergistic effect of the new electronic state of the TiO2 band gap energy induced by formation of Ti3+ species on TiO2, and by improvement of the charge transfer reaction.

For the purpose of manufacturing a high efficiency TiO2 photocatalyst, B-doped TiO2 photocatalysts are synthesized using a plasma electrolytic oxidation method in 0.5 M H2SO4 electrolyte with different concentrations of H3BO3 as additive. For the B doped TiO2 layer fabricated from sulfuric electrolyte having a higher concentration of H3BO3 additive, the main XRD peaks of (101) and (200) anatase phase shift gradually toward the lower angle direction, indicating volume expansion of the TiO2 anatase lattice by incorporation of boron, when compared with TiO2 layers formed in sulfuric acid with lower concentration of additive. Moreover, XPS results indicate that the center of the binding energy peak of B1s increases from 191.45 eV to 191.98 eV, which suggests that most of boron atoms are doped interstitially in the TiO2 layer rather than substitutionally. The B doped TiO2 catalyst fabricated in sulfuric electrolyte with 1.0 M H3BO3 exhibits enhanced photocurrent response, and high efficiency and rate constant for dye degradation, which is ascribed to the synergistic effect of the new impurity energy band induced by introducing boron to the interstitial site and the improvement of charge transfer reaction.

To improve photocatalytic performance, CdS nanoparticle deposited TiO2 nanotubular photocatalysts are synthesized. The TiO2 nanotube is fabricated by electrochemical anodization at a constant voltage of 60 V, and annealed at 500 for crystallization. The CdS nanoparticles on TiO2 nanotubes are synthesized by successive ionic layer adsorption and reaction method. The surface characteristics and photocurrent responses of TNT/CdS photocatalysts are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis spectrometer and LED light source installed potentiostat. The bandgaps of the CdS deposited TiO2 photocatalysts are gradually narrowed with increasing of amounts of deposited CdS nanoparticles, which enhances visible light absorption ability of composite photocatalysts. Enhanced photoelectrochemical performance is observed in the nanocomposite TiO2 photocatalyst. However, the maximum photocurrent response and dye degradation efficiency are observed for TNT/CdS30 photocatalyst. The excellent photocatalytic performance of TNT/CdS30 catalyst can be ascribed to the synergistic effects of its better absorption ability of visible light region and efficient charge transport process.

To improve photocatalytic performance, a PbS/ZnO/TiO2 nanotube catalyst was synthesized, and its surface characteristics and photocatalytic efficiency were investigated. The hybrid photocatalysts were produced by anodic oxidation and successive ionic layer adsorption and reaction(SILAR). The photocatalytic efficiency was evaluated using the dye degradation rate. The PbS/ZnO/TiO2 photocatalyst significantly enhanced the photocatalytic activity for dye degradation, which was ascribed to the synergistic effect of their better absorption of solar light and a decrease in the rate of excited electron-hole recombination.

To synthesize a high-performance photocatalyst, N doped TiO2 nanotubes deposited with Ag nanoparticles were synthesized, and surface characteristics, electrochemical behaviors, and photocatalytic activity were investigated. The TiO2 nanotubular photocatalyst was fabricated by anodization; the Ag nanoparticles on the TiO2 nanotubes were synthesized by a reduction reaction in AgNO3 solution under UV irradiation. The XPS results of the N doped TiO2 nanotubes showed that the incorporated nitrogen ions were located in interstitial sites of the TiO2 crystal structure. The N doped titania nanotubes exhibited a high dye degradation rate, which is effectively attributable to the increase of visible light absorption due to interstitial nitrogen ions in the crystalline TiO2 structure. Moreover, the precipitated Ag particles on the titania nanotubes led to a decrease in the rate of electron-hole recombination; the photocurrent of this electrode was higher than that of the pure titania electrode. From electrochemical and dye degradation results, the photocurrent and photocatalytic efficiency were found to have been significantly affected by N doping and the deposition of Ag particles.

The present study is intended to comparatively investigate the changes in microstructure and tensile properties at room and elevated temperatures in commercial AM50(Mg-5%Al-0.3%Mn) and 0.3 wt%CaO added ECO-AM50 alloys produced by permanent mould casting. The typical microstructure of AM50 alloy was distinctively characterized using two intermetallic compounds, β(Mg17Al12) and Al8Mn5, along with α-(Mg) matrix in an as-cast state. The addition of a small amount of CaO played a role in reducing dendrite cell size and quantity of the β phase in the AM50 alloy. It is interesting to note that the added CaO introduced a small amount of Al2Ca adjacent to the β compounds, and that inhomogeneous enrichment of elemental Ca was observed within the β phase. The ECO-AM50 alloy showed higher hardness and better YS and UTS at room temperature than did the AM50 alloy, which characteristics can be mainly ascribed to the finer-grained microstructure that originated from the CaO addition. At 175˚C, higher levels of YS and UTS and higher elongation were obtained for the ECO-AM50 alloy, demonstrating that even 0.3 wt%CaO addition can be beneficial in promoting the heat resistance of the AM50 alloy. The combinational contributions of enhanced thermal stability of the Ca-containing β phase and the introduction of a stable Al2Ca phase with high melting point are thought to be responsible for the improvement of the high temperature tensile properties in the ECO-AM50 alloy.

Ti 과 AI의 고순도 원소 박판을 이용하여 열간프레스장치에서 고온자전합성법으로 TiAI계 금속간화합물을 제조하였다. 원소 박판에서 TiAl3 금속간화합물을 제조하는 데 승온속도, 압력, 온도 등의 변수가 고온자전합성에 영향을 미치는 중요한 인자다. 특히 승온속도는 반응합성온도를 결정하는 인자로서 본 실험에서 DTA 분석을 이용하여 공정변수를 결정하였다. DTA 분석결과에 따르면, Ti와 AI의 계면에서 반응합성은 AI의 용융점 이하와 이상의 온도에서 두 번 발생함을 알 수 있다. 또한 승온속도가 증가할수록 두 반응합성온도는 증가하였다. 10층의 Ti 박판과 9층의 AI 박판을 20˚C/min의 승온속도로 고온자전합성시킨 후, 810˚C와 240MPa의 압력에서 4시간 동안 열처리한 결과 700μm 두께의 TiAI계 금속간화합물 판재를 제조하였으며, XRD 회절과 SEM으로 확인하였다.