The manufacture process of 8mol% Y-2O-3 stabilized ZrO-2(YSZ) from nano powders, including the forming and sintering stages, was studied. During the forming process of YSZ powders, the relative density of YSZ increase...The manufacture process of 8mol% Y-2O-3 stabilized ZrO-2(YSZ) from nano powders, including the forming and sintering stages, was studied. During the forming process of YSZ powders, the relative density of YSZ increases lineally with the forming press,and the sintering linear shrinkage of YSZ to the forming press compiles to the parabola trend. When the forming press exceeding 500MPa, the samples with lower shrinkage and high density were obtained. The sintering temperature of YSZ decreases greatly because of the small size and high active surface of YSZ powders. As a result, the beginning sintering temperature of YSZ made in the experiment is as low as 825℃, and the end sintering temperature is 1300-1350℃. The relative density of YSZ ceramic by solid sintering at 1300-1350℃ is more than 97%, with little and small pores in the uniform microstructure.展开更多
Yb 3+-doped TiO_2 composite nano-particles were prepared by the acid-catalyzed sol-gel method using Ti(OC_4H_9)_4 and Yb(NO_3)_3 as precursors. The effects of the amount of Yb 3+ doping and calcination temperature on ...Yb 3+-doped TiO_2 composite nano-particles were prepared by the acid-catalyzed sol-gel method using Ti(OC_4H_9)_4 and Yb(NO_3)_3 as precursors. The effects of the amount of Yb 3+ doping and calcination temperature on the phase transformation, crystallite size, surface texture of the nanopowders were investigated by XRD and BET specific surface area. Their photocatalytic activities were evaluated using the photocatalytic degradation of methylene blue in aqueous solution as a probe reaction. At the interface, titanium ions substitute for ytterbium ions in the lattice of Yb_2O_3 to form Ti-O-Yb bonds, which cause distortion and inhibit the anatase to rutile phase transformation in TiO_2. The results indicate that Yb 3+-doping can enhance the photocatalytic activity of TiO_2 nano-powders as compared with pure TiO_2. 0.125%(mass fraction) Yb 3+ doped TiO_2 nano-powders calcined at 600 ℃ for 2 h show the highest photocatalytic activity. The increase in photoactivity is due to the effects of the factors such as crystal phase, crystallite size, surface chemical property, surface density of OH groups, and surface texture properties of the TiO_2 nano-powders.展开更多
Nano 3C-SiC@multilayer graphene oxide(NS@MGO)heterostructure was in situ prepared by carbothermal reduction of pyrolyzed precursor composed of highly dispersed cured phenolic resin and silicon dioxide derived from tet...Nano 3C-SiC@multilayer graphene oxide(NS@MGO)heterostructure was in situ prepared by carbothermal reduction of pyrolyzed precursor composed of highly dispersed cured phenolic resin and silicon dioxide derived from tetraethyl orthosilicate.The heterojunction interface,number of layers of MGO,and defect content in graphene are the three most important factors for promoting photocatalytic activity.Direct contact between 3C-SiC nanograins and MGO layers facilitates the photogenerated electrons to migrate across the heterojunction interface and avoid the formation of SiO_(2) nanolayers on the surface of SiC nanograins.The number of MGO layers is supposed to be less than ten instead of over-thick MGO.The concentrations of oxygenated components,considered the defect contents,decrease with the increase of sintering temperature for NS@MGO 0.175-T-150,and relative carbon content in the multilayer graphene increases.According to the heterostructures,properties,and photocatalytic reaction performance of the NS@MGO materials,the highest photocatalytic kinetic rate constant of 0.00891/min for NS@MGO 0.175-1500-150 shows that the significant enhancement in photocatalytic degradation activity under visible light(>420 nm)irradiation is ascribed to the advantageous synergistic effects between the nano 3C-SiC particles and the direct contact multilayer graphene oxide with appropriate layers and sufficient oxygen content of 3.51%(atomic fraction)in MGO.展开更多
文摘The manufacture process of 8mol% Y-2O-3 stabilized ZrO-2(YSZ) from nano powders, including the forming and sintering stages, was studied. During the forming process of YSZ powders, the relative density of YSZ increases lineally with the forming press,and the sintering linear shrinkage of YSZ to the forming press compiles to the parabola trend. When the forming press exceeding 500MPa, the samples with lower shrinkage and high density were obtained. The sintering temperature of YSZ decreases greatly because of the small size and high active surface of YSZ powders. As a result, the beginning sintering temperature of YSZ made in the experiment is as low as 825℃, and the end sintering temperature is 1300-1350℃. The relative density of YSZ ceramic by solid sintering at 1300-1350℃ is more than 97%, with little and small pores in the uniform microstructure.
文摘Yb 3+-doped TiO_2 composite nano-particles were prepared by the acid-catalyzed sol-gel method using Ti(OC_4H_9)_4 and Yb(NO_3)_3 as precursors. The effects of the amount of Yb 3+ doping and calcination temperature on the phase transformation, crystallite size, surface texture of the nanopowders were investigated by XRD and BET specific surface area. Their photocatalytic activities were evaluated using the photocatalytic degradation of methylene blue in aqueous solution as a probe reaction. At the interface, titanium ions substitute for ytterbium ions in the lattice of Yb_2O_3 to form Ti-O-Yb bonds, which cause distortion and inhibit the anatase to rutile phase transformation in TiO_2. The results indicate that Yb 3+-doping can enhance the photocatalytic activity of TiO_2 nano-powders as compared with pure TiO_2. 0.125%(mass fraction) Yb 3+ doped TiO_2 nano-powders calcined at 600 ℃ for 2 h show the highest photocatalytic activity. The increase in photoactivity is due to the effects of the factors such as crystal phase, crystallite size, surface chemical property, surface density of OH groups, and surface texture properties of the TiO_2 nano-powders.
基金This work was supported by the National Key Research and Development Program of China(No.2021YFB3801301)the Shenyang National Laboratory for Materials Science(SYNL,China)Program for Youth Talent(No.L2022F39).
文摘Nano 3C-SiC@multilayer graphene oxide(NS@MGO)heterostructure was in situ prepared by carbothermal reduction of pyrolyzed precursor composed of highly dispersed cured phenolic resin and silicon dioxide derived from tetraethyl orthosilicate.The heterojunction interface,number of layers of MGO,and defect content in graphene are the three most important factors for promoting photocatalytic activity.Direct contact between 3C-SiC nanograins and MGO layers facilitates the photogenerated electrons to migrate across the heterojunction interface and avoid the formation of SiO_(2) nanolayers on the surface of SiC nanograins.The number of MGO layers is supposed to be less than ten instead of over-thick MGO.The concentrations of oxygenated components,considered the defect contents,decrease with the increase of sintering temperature for NS@MGO 0.175-T-150,and relative carbon content in the multilayer graphene increases.According to the heterostructures,properties,and photocatalytic reaction performance of the NS@MGO materials,the highest photocatalytic kinetic rate constant of 0.00891/min for NS@MGO 0.175-1500-150 shows that the significant enhancement in photocatalytic degradation activity under visible light(>420 nm)irradiation is ascribed to the advantageous synergistic effects between the nano 3C-SiC particles and the direct contact multilayer graphene oxide with appropriate layers and sufficient oxygen content of 3.51%(atomic fraction)in MGO.
