Materials Science Forum Vols. 510-511

Abstract: TiO2 nanoparticles doped with V, Mn or Zn, respectively, were synthesized from pure TiO2 and dopants calcinating at definite temperature. The physical properties of prepared TiO2 nanoparticles were characterized by TEM, XRD and UV-vis spectrum. The TEM images showed that the diameters of the particles were 20~50 nm. There was no peak of doping elements in the XRD spectrum of nano-sized TiO2 doped, but the peak of a little amount of rutile was observed, which demonstrated that V, Mn and Zn might locate in the TiO2 octahedral lattice, or might be highly dispersed within crystalline of TiO2. In the meanwhile, doping of the TiO2 decreased the temperature for TiO2 transforming from anatase into rutile, and promoted the transforming. It was found that a little amount of V5+ may take the place of Ti4+ in the lattice of TiO2. The red-shift was clearly observed in the UV-vis spectrum of TiO2 nanopowders doped with V. As a result, the band gap was changed and the TiO2 nanopowders doped with V enable to absorb visible light. The red-shift could be assigned to the charge transfer transition between the 3d orbital of V5+ and the TiO2 conduction or valance band. The red-shift was not observed in the UV-vis spectrum of TiO2 nanopowders doped with Mn and with Zn, the shape of which was similar to that of pure TiO2. The results of the minimum inhibition concentration (MIC) for Escherichia coli and Staphylococcus aureus showed that vanadium ions doping intensely improved the antibacterial efficiency of nanocrystallites. This was attributed to the change of surface properties of metal ions doped semiconductor, such as O vacancies, Ti interstitial ions and vanadium ions which took the place of titanium.

Abstract: Nitrogen-doped titania nanoparticles were co-prepared by sol-gel and mechanical-alloying method. Raman spectroscopy was used to investigate the microstructure information of the nitrogen-doped titania nanoparticles. Besides, XPS, ESR and UV-vis absorption spectra were also analyzed as supplementary means. At first blue then red shift of 142 cm-1 peak was observed as the annealing temperatures increased. The possible reasons for the shift were discussed.

Abstract: Thin film photocatalysts of TiO2 coated on the glass were prepared to self-clean and eliminate air pollutants by spin coating process with Ti(OC3H7 i)4, including PEG. The surface structure of TiO2 films changed according to the molecular size of PEG. It was found that NOx was efficiently eliminated by the TiO2 film photocatalyst. The contact angle of water drop on the TiO2 films decreased to less than 10°. It revealed the hydrophilic property of TiO2 films. The morphology and the crystal structure of TiO2 films were affected most.

Abstract: Ceramic compound with the formula BaLi2Ti6O14 was prepared by sol-gel method at basic conditions, using ammonium hydroxide as hydrolysis catalyst. Some portions of gel sample obtained were heat treated at 200, 400, 600, and 800°C. Samples were characterized by X-ray diffraction (XRD), thermal analysis (DTA-TGA), UV-Vis and FTIR. Crystalline phase was formed when a sample was treated at 800°C for 6h. This material has been previously synthesized by solid state reaction using temperatures as high as 900-1150°C for 2 to 10 days. The crystal structure of BaLi2Ti6O14 is similar to that corresponding strontium containing phase, SrLi2Ti6O14, which has been reported as catalyst for oxidative dehydrogenation of lower alkanes.

Abstract: We prepared the surface mounted white light emitting diode (LED) chips by using yellow phosphors on the blue LED chip. The optical and electrical properties of prepared white LED chips were investigated. The yellow phosphor mixed with transparent epoxy was coated on the prepared LED chip. The optimum mixing conditions with epoxy and yellow phosphor is obtained at the mixing ration of epoxy: yellow phosphor = 97 : 3 wt %. The maximum luminance and light emitting efficiency are above 80,000 cd/m2 and 23.2 lm/W, respectively, at the bias voltage of 2.9 V. There was no distinct change in the luminance strength with changing of the yellow phosphor ratios. The flowing current of the white LED chip is about 30 mA at 2.9 V.

Abstract: In this study, we studied to find the most suitable condition for the preparation of adsorbent by hydrothermal treatment of fly ash from the municipal solid waste incinerator (MSWI). There are many variables that affect the adsorptive characteristics in our study. With the variation of which discussed the effect such as the concentration of NaOH, reaction temperature, reaction time, solid/liquid ratio, and so on. The phase of adsorbent, its morphology and cation exchange capacity (CEC) were analyzed to evaluate their effects. The phase of adsorbent after treatment was identified by X-ray diffraction (XRD), the morphology was examined by scanning electron microscopy (SEM), and the CEC was analyzed by the ammonium acetate method. The maximum CEC value was obtained under the condition of 3N NaOH, 100°C of reaction temperature, 12 hr of reaction time, and 1:10 of solid/liquid ratio. The CEC was 68 meq/100g in this condition, which was 8 times the amount of raw fly ash.

Abstract: Li1-xNi1+xO2 powder was prepared by using tartaric acid as a complexing agent. A 1 : 1 : 2 mole ratio of Li : Ni : tartaric acid was used to form carboxylate precursors which were calcined at 650–800 oC for 14–48 h. TGA of the precursors showed that formation of Li1-xNi1+xO2 initiates at 600 oC and above. By using XRD, Li1-xNi1+xO2 with 650–800 oC calcination was detected. Calculated intensity ratios of I(003)/I(104) and I(006+102)/I(101) showed that the best condition is at 750 oC for 34 h. The crystallite size was estimated using the Scherrer equation. AAS and titration techniques showed that Ni3+/(Ni3+ + Ni2+) and mean oxidation state of nickel are 66.50 wt% and 2.67 respectively. EDX showed that the powder was comprised by Ni and O. The faceted particles are shown by SEM. TEM and electron diffraction showed the results that are in accordance with the above.