Liyi Shi

Morphology and properties of ultrafine SnO2–TiO2 coupled semiconductor particles

In this paper, a new method to synthesize ultrafine SnO2–TiO2 coupled particles is presented. The coupled particles are synthesized by homogeneous precipitation and characterized by EDS, XRD, TEM, HREM and BET surface area analysis. The coupled particles, pure ultrafine TiO2, commercial TiO2, and pure SnO2 are employed for photocatalytic degradation of azo dye active red X-3B in aerated solution. The results show that a very rapid and complete decolorization of the azo dye can be achieved, and the photoactivity of the coupled particles is higher than that of pure ultrafine TiO2 and commercial TiO2 particles, and the optimum loading of SnO2 on TiO2 is 18.4%. The enhanced degradation rate of X-3B using SnO2–TiO2 coupled photocatalysts is attributed to increased charge separation in these systems.

Morphology and structure of nanosized TiO2 particles synthesized by gas-phase reaction

Abstract Nanosized titania particles are synthesized by the gas-phase oxidation of titanium tetrachloride in a high temperature tubular aerosol flow reactor that consists of two preheaters for oxygen and vaporized titanium tetrachloride, a reaction zone, and a cooling zone for particles. The effect of process parameters on the morphology and structure of titania particles is studied. As the preheating temperature of oxygen increases, the average particle size of titania decreases and the size distribution becomes more uniform. The addition of AlCl 3 can reduce the particle size, and enhance the rutile weight fraction. The effect of reaction temperature ( T ) on the characteristics of nanosized titania particles is also investigated. The results show that the particle size increases with increasing temperature, and a maximum rutile fraction is attained at 1200°C and AlCl 3 and TiCl 4 feed ratio ( X inlet ) of 0.09. Pure rutile titania particles is formed when T =1373xa0K and X inlet =0.25. The average grain size of the particles is 29.0xa0nm, and the BET specific surface area is 23.4xa0m 2 xa0g −1 .

Preparation and CO conversion activity of ceria nanotubes by carbon nanotubes templating method

Abstract Ceria nanotubes with high CO conversion activity by means of carbon nanotubes as removable templates in the simple liquid phase process were fabricated under moderate conditions. The pristine CNTs were first pretreated by refluxing in a 30% nitric acid solution at 140 °C for 24 h, then dispersed in an ethanolic Ce(NO 3 ) 3 ·6H 2 O solution with ultrasonic radiation at room temperature for 1 h. Under vigorous stirring, NaOH solution was added drop by drop into the above ethanolic solution until the pH value was 10. The product was collected and repeatedly washed with ethanol and on drying at 60 °C, the CeO 2/ CNT composites were obtained. Then, the as-prepared composites were heated at 450 °C in an air atmosphere for 30 min to remove CNTs. The ceria nanotubes were characterized by X-Ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and X-Ray Photoelectron Spectrum (XPS). The results showed that the ceria nanotubes were polycrystalline face-centered cubic phase and were composed of lots of dense ceria nanoparticles. The diameter of ceria nanotubes was about 40–50 nm. Catalytic activity of the product for CO oxidation was carried out at the region of 30–300 °C in a U-shaped quartz reactor with feeding about 0.15 g of the catalyst, which was loaded on Al 2 O 3 carrier. The inlet gas composition was 1.0% CO and 28% O 2 with N 2 as balance, and the rate of flow was kept at 40 ml/min. The catalytic products were analyzed by gas chromatography. The as-prepared CeO 2 nanotubes showed higher CO oxidation activity, which indicated that the morphology of ceria products affected the catalytic performance. The ceria nanotubes supported on Al 2 O 3 demonstrated that conversion temperature for CO oxidation to CO 2 was lower than that for bulk catalysts.

The Effect of SnO2 on the Photocatalytic Activity of Aerosol-Made TiO2 Particles

Ultrafine titania particles were prepared by gas-phase oxidation of titanium tetrachloride in a high-temperature tubular aerosol flow reactor. Homogeneous precipitation method was used to deposit SnO2 on the surface of lab-made TiO2. The composite particles were characterized by TEM, ICP, XRD, and BET surface area analysis. The composite particles, pure ultrafine TiO2, commercial TiO2, and pure SnO2 were employed for photocatalytic degradation of azo dye active red X-3B in aerated solutions. The result showed that the photoactivity of the composite particles was higher than that of pure ultrafine TiO2 and commercial TiO2, and the optimum loading of SnO2 on TiO2 is 15.3%. The enhanced degradation rate of X-3B using SnO2-TiO2 composite particles was attributed to increased charge separation in these systems.

Poly(ethylene terephalate) prepolymer graft modification of nano-TiO2 and its effect on mechanical property of polycarbonate nanocomposites

Abstract Nano-TiO2 particles were modified by the poly(ethylene terephalate) prepolymer (pre-PET) via polycondensation. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy results showed that pre-PET was successfully grafted on the surface of the nano-TiO2 particles. Thermogravimetric analysis results indicated that the grafting efficiency depended on the vacuum degree. Compared to the original nano-TiO2, the grafted nano-TiO2 had better compatibility with the polycarbonate (PC) matrix and could be dispersed more homogeneously in PC. Hence, interfacial adhesion between TiO2 and PC was enhanced. The mechanical properties of the resultant PC/nano-TiO2 composites like tensile strength and notched impact strength were greatly improved. Calculated respectively from tensile yield stress PC/nano-TiO2 composites, the interfacial interaction parameter B was employed to quantitatively characterise the effective interfacial interaction between the nano-TiO2 and PC matrix. It demonstrated that the nano-TiO2 grafted with pre-PET had stronger effective interfacial interaction with PC matrix than original nano-TiO2.