The effect of ZnO-B2O3（ZB） glass addition on the sintering behavior, microstructures and microwave dielectric properties of BaO-Nd2O3-TiO2-Bi2O3 （BNTB） system was investigated with the aid of X-ray diffraction, sc...The effect of ZnO-B2O3（ZB） glass addition on the sintering behavior, microstructures and microwave dielectric properties of BaO-Nd2O3-TiO2-Bi2O3 （BNTB） system was investigated with the aid of X-ray diffraction, scanning electron microscopy and capacitance meter. It is found that the ZB glass addition, acting as a sintering aid, can effectively lower the sintering temperature of BNTB system to 850 ℃. The dielectric constant of BNTB-ZB ceramics increases with the increase of soaking time and the value of dielectric loss decreased with increasing soak time. The optical dielectric properties at 1 GHz of ε=74, tan δ=4×10^-4, and TCC=25 ppm/℃ were obtained for the BNTB system doped with 25 wt% ZB glass sintered at 850 ℃ for 2 h, representing that the BNTB-ZB ceramics could be promising for multilayer low temperature co-fired ceramics applications.展开更多
V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for N...V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for NOx conversion using NH3 as the reductant. Hydrothermal ageing decreased the NOx conversion of V2O5/WO3‐TiO2 catalyst severely over the entire measured tem‐perature range. Interestingly, the NH3‐SCR activity of the silica‐modified catalyst at 220–480℃ is enhanced after ageing. The catalysts were characterized by X‐ray diffraction, nitrogen adsorption, X‐ray fluorescence, Raman spectroscopy, H2 temperature‐programmed reduction, and NH3 temper‐ature‐programmed desorption. The addition of silica inhibited the phase transition from anatase to rutile titania, growth of TiO2 crystallite size and shrinkage of catalyst surface area. Consequently, the vanadia species remained highly dispersed and the hydrothermal stability of the V2O5/WO3‐TiO2 catalyst was significantly improved.展开更多
基金Funded by the Tianjin Natural Science Foundation of China (No.06YFJMJC01000)
文摘The effect of ZnO-B2O3（ZB） glass addition on the sintering behavior, microstructures and microwave dielectric properties of BaO-Nd2O3-TiO2-Bi2O3 （BNTB） system was investigated with the aid of X-ray diffraction, scanning electron microscopy and capacitance meter. It is found that the ZB glass addition, acting as a sintering aid, can effectively lower the sintering temperature of BNTB system to 850 ℃. The dielectric constant of BNTB-ZB ceramics increases with the increase of soaking time and the value of dielectric loss decreased with increasing soak time. The optical dielectric properties at 1 GHz of ε=74, tan δ=4×10^-4, and TCC=25 ppm/℃ were obtained for the BNTB system doped with 25 wt% ZB glass sintered at 850 ℃ for 2 h, representing that the BNTB-ZB ceramics could be promising for multilayer low temperature co-fired ceramics applications.
基金supported by the National Natural Science Foundation of China (51372137)the National High Technology Research and Development Program of China (863 Program,2015AA034603)~~
文摘V2O5/WO3‐TiO2 and V2O5/WO3‐TiO2‐SiO2 catalysts were prepared by a wetness impregnation method, and both the catalysts were hydrothermally aged at 750℃ in 10 vol%H2O/air for 24 h. The catalysts were evaluated for NOx conversion using NH3 as the reductant. Hydrothermal ageing decreased the NOx conversion of V2O5/WO3‐TiO2 catalyst severely over the entire measured tem‐perature range. Interestingly, the NH3‐SCR activity of the silica‐modified catalyst at 220–480℃ is enhanced after ageing. The catalysts were characterized by X‐ray diffraction, nitrogen adsorption, X‐ray fluorescence, Raman spectroscopy, H2 temperature‐programmed reduction, and NH3 temper‐ature‐programmed desorption. The addition of silica inhibited the phase transition from anatase to rutile titania, growth of TiO2 crystallite size and shrinkage of catalyst surface area. Consequently, the vanadia species remained highly dispersed and the hydrothermal stability of the V2O5/WO3‐TiO2 catalyst was significantly improved.
