Yanping Jin

Preparation and characterization of silica-doped titania photocatalyst through sol-gel method

Silica-doped nanocrystalline titania powders were prepared using the sol–gel technique. The influence of dopant concentration on the phase transition and grain growth was studied. Subsequently the sample was studied at a constant dopant concentration to investigate the effect of calcination temperature on the photoactivity of titania. It was found that 30SiO2/TiO2 (30 denotes the weight percent of SiO2) fired at 800 °C has a higher photoactivity than other samples with different silica content and different calcination temperature. The effect of addition of silica was to increase the photoactivity by suppressing the phase transformation of titania from anatase to rutile and forming oxygen vacancies in titania.

Optical properties of silver-dispersed PVP thin film

Abstract Silver-dispersed PVP (Ag/PVP) thin films were prepared by spin coating from an alcohol solution of polyvinylpyrrolidone (PVP) in which silver nitrate were dissolved. A peak formed at 430–450 nm in the UV/VIS-spectra resulted from the surface plasma resonance of the silver nanoparticles. With the increase of annealing temperature, the plasma resonance absorption peak was broadened and intensities increased. The peak position of the surface plasma resonance also shifted to a high wavelength. XRD results confirmed the presence of silver particles in thin films. The absorption peak position calculated from the absorption spectrum is in very good agreement with Maxwell-Garnet (MG) theory using the dielectric constant of silver particles to calculate results of the absorption coefficient, α, of the silver particles.

Preparation, structure and properties of TiO2–PVP hybrid films

Abstract The organic–inorganic hybrid films of TiO 2 –PVP have been prepared by the sol-gel process. The TiO 2 was obtained by the hydrolysis of titanium n -butoxide (TNBT) under the catalysis of HCl. The hybrid film has a smooth surface with average roughness less than 3 nm. The thermal stability and structure of the gels have been studied by TGA and FTIR spectra, respectively. The TiO 2 –PVP films are transparent and their transmittance is high up to 93% in the visible light range. The microhardness and dielectric properties for the hybrid material films are dependent on the annealing temperature. The microhardness of the film reaches 2.65 GPa after heat treatment at 270°C for 0.5 h.

Effects of PVP on structure of TiO2 prepared by the sol-gel process

Abstract The synthesis of nanocrystalline TiO 2 powders obtained from the hydrolysis of Ti(OBu n ) 4 in the presence of polyvinylpyrrolidone (PVP) was investigated. Porous titania with a Brunauer–Emmett–Teller surface area up to 65 m 2 g −1 and distribution of pores in the range of mesopores were obtained after heat treatment at 500 °C devoted to the removal of PVP from TiO 2 /PVP composites. The influence of PVP on the phase transformation of TiO 2 from anatase to rutile was investigated by using X-ray diffraction and Raman spectra. It was found that PVP could noticeably enhance the transformation by reducing the onset transformation temperature. The obtained powders were also characterized by differential scanning calorimeter, transmission electron microscopy and high-resolution electron microscopy.

Effect of PVP on the photocatalytic behavior of TiO2 under sunlight

Abstract TiO 2 prepared by the sol–gel method and adding 30 wt.% of polyvinylpyrrolidone (PVP) has been proved to be efficient in the photodegradation of methylene red under ultraviolet (UV) light. The same powder was also found to be photoactive under sunlight in this research. TiO 2 powders with various contents of added PVP were prepared and characterized by XRD, diffuse reflectance spectroscopy (DRS), etc. It was found that the presence of PVP in the sol–gel process can reduce the transformation temperature from anatase to rutile phase and the crystallite size of TiO 2 . At the same time, a unique coexistence structure of the anatase and rutile phases was obtained in these materials.

Effect of surface modification on the rheological behavior of concentrated, aqueous SiC suspensions

Abstract Surface modification of SiC powder leached by deionized water, acid, and base leaching and the effect on the rheological behavior of concentrated aqueous SiC suspensions were investigated. The SiC powders were well dispersed irrespective of the surface treatment. However, the viscosity was affected by the surface treatment. The experimental results indicated that base leaching caused a lower viscosity. The reason of the leaching effect on viscosity was discussed. The influence of SiC oxidative thermal treatment was determined for SiC suspensions. It was found that calcination of the SiC powder was observed to result in partial oxidation of SiC to amorphous SiO 2 and effectively reduced the viscosity of SiC suspensions.

STUDIES ON THE CHARGING OF GRADED SIZE SINTERS IN A MODEL FURNACE

Abstract It is a new fascinating technology to charge graded size sinters in a blast furnace (BF). Some work has been done with this technology on cold state in a model furnace in a laboratory. The parameters were tested in the different ways to charge graded size sinters such as charge column resistance loss, distribution of the relative airflow velocity and pressure field of a scattered charge bed. The result shows that the technology can make relatively uniform and controllable sinters ameliorate permeability and decrease the resistance loss. A few laws and the preferable charging system to the model furnace were obtained. It is a new fascinating technology to charge graded size sinters in a blast furnace (BF). Some work has been done with this technology on cold state in a model furnace in a laboratory. The parameters were tested in the different ways to charge graded size sinters such as charge column resistance loss, distribution of the relative airflow velocity and pressure field of a scattered charge bed. The result shows that the technology can make relatively uniform and controllable sinters ameliorate permeability and decrease the resistance loss. A few laws and the preferable charging system to the model furnace were obtained. C’est une technologie nouvelle et fascinante que celle du chargement d’agglomérés à taille calibrée dans un haut-fourneau. On a effectué une certaine quantité de travail au moyen de cette technologie dans un fourneau modèle en laboratoire, à l’état froid. On a évalué les paramètres reliés aux différentes façons de charger les agglomérés à taille calibrée, incluant la perte de résistance de la colonne de charge, la distribution de la vitesse relative de l’écoulement d’air et le champ de pression d’un lit à charge dispersée. Le résultat montre que la technologie peut produire des agglomérés relativement uniformes et contrôlables, peut améliorer la perméabilité et diminuer la perte de résistance. Au cours de ce travail, on a obtenu quelques lois ainsi que le système préférable de chargement du fourneau modèle.C’est une technologie nouvelle et fascinante que celle du chargement d’agglomérés à taille calibrée dans un haut-fourneau. On a effectué une certaine quantité de travail au moyen de cette technologie dans un fourneau modèle en laboratoire, à l’état froid. On a évalué les paramètres reliés aux différentes façons de charger les agglomérés à taille calibrée, incluant la perte de résistance de la colonne de charge, la distribution de la vitesse relative de l’écoulement d’air et le champ de pression d’un lit à charge dispersée. Le résultat montre que la technologie peut produire des agglomérés relativement uniformes et contrôlables, peut améliorer la perméabilité et diminuer la perte de résistance. Au cours de ce travail, on a obtenu quelques lois ainsi que le système préférable de chargement du fourneau modèle.