Hollow CuO-CeO2-ZrO2nano-particles were prepared with supercritical anti-solvent apparatus by using methanol as sol-vent and supercritical carbon dioxide as anti-solvent. Two key factors （i.e., pressure and temperat...Hollow CuO-CeO2-ZrO2nano-particles were prepared with supercritical anti-solvent apparatus by using methanol as sol-vent and supercritical carbon dioxide as anti-solvent. Two key factors （i.e., pressure and temperature） were investigated to explore the effects of catalyst structure and physic-chemical properties （i.e., morphology, reducing property, oxygen storage capacity and specific surface area）. The resulting materials were characterized with X-ray diffraction （XRD）, high resolution transmission electron micros-copy （HRTEM）, Brunauer-Emmett-Teller （BET）,hydrogen temperature programmed reduction （H2-TPR） and oxygen storage capac-ity （OSC） measurement, respectively. The experimental results showed that lower temperatures promoted production of hollow struc-ture nano-particulates. The particle morphology also changed significantly, i.e. the solid construction was first transferred to hollow structure then back to solid construction. The optimal conditions for obtaining hollow nano-particles were determined at 45 °C, 18.0–24.0 MPa.展开更多
The interaction between Pt and its various supports can regulate the intrinsic electronic structure of Pt particles and their catalytic performance.Herein,Pt/CeO2 and Pt/SiC catalysts were successfully prepared via a ...The interaction between Pt and its various supports can regulate the intrinsic electronic structure of Pt particles and their catalytic performance.Herein,Pt/CeO2 and Pt/SiC catalysts were successfully prepared via a facile Pt colloidal particle deposition method,and their catalytic performance in CO oxidation was investigated.XRD,TEM,XPS and H2-TPR were used to identify the states of Pt particles on the support surface,as well as their effect on the performance of the catalysts.Formation of the Pt-O-Ce interaction is one of the factors controlling catalyst activity.Under the oxidative treatment at low temperature,the Pt-O-Ce interaction plays an important role in improving the catalytic activity.After calcining at high temperature,enhanced Pt-O-Ce interaction results in the absence of metallic Pt0 on the support surface,as evidenced by the appearance of Pt2+species.It is consistent with the XPS data of Pt/CeO2,and is the main reason behind the deactivation of the catalyst.By contrast,either no interaction is formed between Pt and SiC or Pt nanoparticles remain in the metallic Pt0 state on the SiC surface even after aging at 800℃in an oxidizing atmosphere.Thus,the Pt/SiC shows better thermal stability than Pt/CeO2.The interaction between Pt and the active support may be concluded to be essential for CO oxidation at low temperature,but strong interactions may induce serious deactivation of catalytic activity.展开更多
High temperature heat-treatment of wood, which is value-added green product, is one of the altematives to chemical treatment. It has better dimensional stability, thermal insulating properties and biological resistanc...High temperature heat-treatment of wood, which is value-added green product, is one of the altematives to chemical treatment. It has better dimensional stability, thermal insulating properties and biological resistance compared to kiln dried wood. It also has dark brown color which is very important for decorative purposes. Unfortunately, this color changes during weathering. Developing a transparent and non-toxic coating for the protection of heat-treated wood against discoloration without changing its natural appearance is the main objective of this study. For this purpose, waterborne acrylic polyurethane base was chosen because of its durability against weathering and non-toxic nature. Natural antioxidants which are extracted from barks and CeO2 nano particles （alone or together with lignin stabilizer） were used as additives to develop different coatings. The protective characteristics of these coatings were compared with highly pigmented and toxic industrial coating under accelerated weathering conditions. The results showed that acrylic polyurethane coatings protected wood better compared to commercially available coating tested in this study. The chemical modifications during accelerated weathering of coated and heat-treated wood surfaces were monitored by X-ray photoelectron spectroscopy analysis. The morphological changes took place during weathering were studied by fluorescence microscope analysis.展开更多
Nano-Y2O3 and nano-CeO2 of different weight ratio mixed with deionizing water were doped into MoO2 powder by liquid-solid doping method. The diameter 1.80 and 0.18 mm alloy wires of Mo-0.3Y, Mo-0.3Ce, and Mo-0.15Y-0.1...Nano-Y2O3 and nano-CeO2 of different weight ratio mixed with deionizing water were doped into MoO2 powder by liquid-solid doping method. The diameter 1.80 and 0.18 mm alloy wires of Mo-0.3Y, Mo-0.3Ce, and Mo-0.15Y-0.15Ce were prepared through reduction, iso- static pressing, sintering, and drawing. Tensile properties, second phase microstructure and fracture surface appear- ance of wires were analyzed. The better refining effect for Mo alloy powder can be gotten after two kinds of nano- particle oxide doped into MoO2 than only one doped. Nano-Y2O3 and nano-CeO2 have different influences on sintering process. For nano-CeO2, the constraining effect of grain growth focuses on the initial sintering stage, nano- Y2O3 plays refining grains roles in the later densification stage. Nano-Y2O3 is undistorted and keeps intact in the process of drawing; and nano-CeO2 is elongated and bro- ken into parts in the drawing direction. The strengthening effect of nano-Y2O3 and nano-CeO2 keeps the finer grains and superior tensile properties for Mo-0.15Y-0.15Ce wire.展开更多
γ-A12O3-supported CeO2 catalysts were pre- pared by microemulsion and impregnation methods and characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM） techniques. At the same time, the des...γ-A12O3-supported CeO2 catalysts were pre- pared by microemulsion and impregnation methods and characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM） techniques. At the same time, the desulfurization activity of catalysts was investigated. The results show that nanoscale active substances and a high desulfurization effect are achieved by microemulsion, exhibiting a significant dominance compared with traditional impregnation method. The optimal preparation condition is temperature of 30 ℃ and ratio of [H20]/[surface active agent] of 7 with slow demulsification. The activated catalysts still keep high and stable desulfurization activity during a wide temperature range of 450-600 ℃. Among a series of prepared catalysts, the desulfurization rate of 6CeOz/γ-A1203 is the highest, reaching up to 80 % when temperature is higher than 550℃. The catalytic reduction mechanism of SO2 over nano-CeOz/γ-A1203 follows redox mechanism.展开更多
In this study,aquatic toxic effect of atrazine,and nano-CeO2,the accumulation,reproduction and adsorp-tion of atrazine onto nano-CeO2 and the facilitated transport of atrazine into D.magna by nano-CeO2 were exam-ined....In this study,aquatic toxic effect of atrazine,and nano-CeO2,the accumulation,reproduction and adsorp-tion of atrazine onto nano-CeO2 and the facilitated transport of atrazine into D.magna by nano-CeO2 were exam-ined.The results showed that atrazine concentrations of 3.0,4.0,and 10.0 mg/L exhibited 43%,56%,68% mortali-ties,respectively,which indicated the mortality was 56% while the concentration of nano-CeO2 was 4.0 mg/L.D.magna accumulated considerably more atrazine when exposed to atrazine-contaminated water in the presence of nano-CeO2.At the same time,atrazine and nano-CeO2 yielded a significant reduction of the reproduction rate at all concentrations tested.What is more,the co-exposure of nano-CeO2 and atrazine was observed to significantly de-crease the reproduction rate of D.magna,and atrazine adsorbed on nano-CeO2 quickly.Therefore,attention should be paid to their associations with other contaminants for the risk assessment of nano-CeO2 and it is worthy of notice that the sorption of atrazine on nano-CeO2 would enhance the toxicity of atrazine to D.magna.展开更多
Thermally stable Zr4+, Al3+, and Si4+ cations were incorporated into the lattice of CeO2 nano‐rods (i.e., CeO2‐NR) in order to improve the specific surface area. The undoped and Zr4+, Al3+, and Si4+ doped nano‐rods...Thermally stable Zr4+, Al3+, and Si4+ cations were incorporated into the lattice of CeO2 nano‐rods (i.e., CeO2‐NR) in order to improve the specific surface area. The undoped and Zr4+, Al3+, and Si4+ doped nano‐rods were used as supports to prepare MnOx/CeO2‐NR, MnOx/CZ‐NR, MnOx/CA‐NR, and MnOx/CS‐NR catalysts, respectively. The prepared supports and catalysts were comprehensively characterized by transmission electron microscopy (TEM), high‐resolution TEM, X‐ray diffraction, Raman and N2‐physisorption analyses, hydrogen temperature‐programmed reduction, ammonia temperature‐programmed desorption, in situ diffuse reflectance infrared Fourier‐transform spectroscopic analysis of the NH3 adsorption, and X‐ray photoelectron spectroscopy. Moreover, the catalytic performance and H2O+SO2 tolerance of these samples were evaluated through NH3‐selective catalytic reduction (NH3‐SCR) in the absence or presence of H2O and SO2. The obtained results show that the MnOx/CS‐NR catalyst exhibits the highest NOx conversion and the lowest N2O concentration, which result from the largest number of oxygen vacancies and acid sites, the highest Mn4+ content, and the lowest redox ability. The MnOx/CS‐NR catalyst also presents excellent resistance to H2O and SO2. All of these phenomena suggest that Si4+ is the optimal dopant for the MnOx/CeO2‐NR catalyst.展开更多
基金supported by the National Natural Science Foundation of China(20976120)Natural Science Foundation of Tianjin(09JCYBJC06200)
文摘Hollow CuO-CeO2-ZrO2nano-particles were prepared with supercritical anti-solvent apparatus by using methanol as sol-vent and supercritical carbon dioxide as anti-solvent. Two key factors （i.e., pressure and temperature） were investigated to explore the effects of catalyst structure and physic-chemical properties （i.e., morphology, reducing property, oxygen storage capacity and specific surface area）. The resulting materials were characterized with X-ray diffraction （XRD）, high resolution transmission electron micros-copy （HRTEM）, Brunauer-Emmett-Teller （BET）,hydrogen temperature programmed reduction （H2-TPR） and oxygen storage capac-ity （OSC） measurement, respectively. The experimental results showed that lower temperatures promoted production of hollow struc-ture nano-particulates. The particle morphology also changed significantly, i.e. the solid construction was first transferred to hollow structure then back to solid construction. The optimal conditions for obtaining hollow nano-particles were determined at 45 °C, 18.0–24.0 MPa.
基金Project supported by the National Natural Science Foundation of China(21506194,21676255)the Natural Science Foundation of Zhejiang Province,China(Y16B070025).
文摘The interaction between Pt and its various supports can regulate the intrinsic electronic structure of Pt particles and their catalytic performance.Herein,Pt/CeO2 and Pt/SiC catalysts were successfully prepared via a facile Pt colloidal particle deposition method,and their catalytic performance in CO oxidation was investigated.XRD,TEM,XPS and H2-TPR were used to identify the states of Pt particles on the support surface,as well as their effect on the performance of the catalysts.Formation of the Pt-O-Ce interaction is one of the factors controlling catalyst activity.Under the oxidative treatment at low temperature,the Pt-O-Ce interaction plays an important role in improving the catalytic activity.After calcining at high temperature,enhanced Pt-O-Ce interaction results in the absence of metallic Pt0 on the support surface,as evidenced by the appearance of Pt2+species.It is consistent with the XPS data of Pt/CeO2,and is the main reason behind the deactivation of the catalyst.By contrast,either no interaction is formed between Pt and SiC or Pt nanoparticles remain in the metallic Pt0 state on the SiC surface even after aging at 800℃in an oxidizing atmosphere.Thus,the Pt/SiC shows better thermal stability than Pt/CeO2.The interaction between Pt and the active support may be concluded to be essential for CO oxidation at low temperature,but strong interactions may induce serious deactivation of catalytic activity.
文摘High temperature heat-treatment of wood, which is value-added green product, is one of the altematives to chemical treatment. It has better dimensional stability, thermal insulating properties and biological resistance compared to kiln dried wood. It also has dark brown color which is very important for decorative purposes. Unfortunately, this color changes during weathering. Developing a transparent and non-toxic coating for the protection of heat-treated wood against discoloration without changing its natural appearance is the main objective of this study. For this purpose, waterborne acrylic polyurethane base was chosen because of its durability against weathering and non-toxic nature. Natural antioxidants which are extracted from barks and CeO2 nano particles （alone or together with lignin stabilizer） were used as additives to develop different coatings. The protective characteristics of these coatings were compared with highly pigmented and toxic industrial coating under accelerated weathering conditions. The results showed that acrylic polyurethane coatings protected wood better compared to commercially available coating tested in this study. The chemical modifications during accelerated weathering of coated and heat-treated wood surfaces were monitored by X-ray photoelectron spectroscopy analysis. The morphological changes took place during weathering were studied by fluorescence microscope analysis.
基金financially supported by the National Tungsten and Molybdenum Value-added Utilization Tech-nology Industry Development(No.2012BAE06B02)Shanxi Province Science and Technology Innovation Plan(No.2012KTCQ01-08)
文摘Nano-Y2O3 and nano-CeO2 of different weight ratio mixed with deionizing water were doped into MoO2 powder by liquid-solid doping method. The diameter 1.80 and 0.18 mm alloy wires of Mo-0.3Y, Mo-0.3Ce, and Mo-0.15Y-0.15Ce were prepared through reduction, iso- static pressing, sintering, and drawing. Tensile properties, second phase microstructure and fracture surface appear- ance of wires were analyzed. The better refining effect for Mo alloy powder can be gotten after two kinds of nano- particle oxide doped into MoO2 than only one doped. Nano-Y2O3 and nano-CeO2 have different influences on sintering process. For nano-CeO2, the constraining effect of grain growth focuses on the initial sintering stage, nano- Y2O3 plays refining grains roles in the later densification stage. Nano-Y2O3 is undistorted and keeps intact in the process of drawing; and nano-CeO2 is elongated and bro- ken into parts in the drawing direction. The strengthening effect of nano-Y2O3 and nano-CeO2 keeps the finer grains and superior tensile properties for Mo-0.15Y-0.15Ce wire.
基金financially supported by the Natural Science Foundation of Hubei Province, China(No. 2009CDB246)the Applied Basic Research Project of Wuhan City (No. 2015060101010068)
文摘γ-A12O3-supported CeO2 catalysts were pre- pared by microemulsion and impregnation methods and characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM） techniques. At the same time, the desulfurization activity of catalysts was investigated. The results show that nanoscale active substances and a high desulfurization effect are achieved by microemulsion, exhibiting a significant dominance compared with traditional impregnation method. The optimal preparation condition is temperature of 30 ℃ and ratio of [H20]/[surface active agent] of 7 with slow demulsification. The activated catalysts still keep high and stable desulfurization activity during a wide temperature range of 450-600 ℃. Among a series of prepared catalysts, the desulfurization rate of 6CeOz/γ-A1203 is the highest, reaching up to 80 % when temperature is higher than 550℃. The catalytic reduction mechanism of SO2 over nano-CeOz/γ-A1203 follows redox mechanism.
基金supported by Chongqing Key Laboratory of Micro/Nano Materials Engineering and Technology (No. KFJJ1106)Jiangsu Provincial Key Laboratory of Coastal Wetland Bioresources and Environmental Protection (No.JLCBE11004)Jiangsu Marine Resources Development Research Institute (No. JSIMR10E04)
文摘In this study,aquatic toxic effect of atrazine,and nano-CeO2,the accumulation,reproduction and adsorp-tion of atrazine onto nano-CeO2 and the facilitated transport of atrazine into D.magna by nano-CeO2 were exam-ined.The results showed that atrazine concentrations of 3.0,4.0,and 10.0 mg/L exhibited 43%,56%,68% mortali-ties,respectively,which indicated the mortality was 56% while the concentration of nano-CeO2 was 4.0 mg/L.D.magna accumulated considerably more atrazine when exposed to atrazine-contaminated water in the presence of nano-CeO2.At the same time,atrazine and nano-CeO2 yielded a significant reduction of the reproduction rate at all concentrations tested.What is more,the co-exposure of nano-CeO2 and atrazine was observed to significantly de-crease the reproduction rate of D.magna,and atrazine adsorbed on nano-CeO2 quickly.Therefore,attention should be paid to their associations with other contaminants for the risk assessment of nano-CeO2 and it is worthy of notice that the sorption of atrazine on nano-CeO2 would enhance the toxicity of atrazine to D.magna.
基金supported by National Natural Science Foundation of China (21876168, 21507130)Youth Innovation Promotion Association of CAS (2019376)the Chongqing Science & Technology Commission (cstc2016jcyjA0070, cstckjcxljrc13)~~
文摘Thermally stable Zr4+, Al3+, and Si4+ cations were incorporated into the lattice of CeO2 nano‐rods (i.e., CeO2‐NR) in order to improve the specific surface area. The undoped and Zr4+, Al3+, and Si4+ doped nano‐rods were used as supports to prepare MnOx/CeO2‐NR, MnOx/CZ‐NR, MnOx/CA‐NR, and MnOx/CS‐NR catalysts, respectively. The prepared supports and catalysts were comprehensively characterized by transmission electron microscopy (TEM), high‐resolution TEM, X‐ray diffraction, Raman and N2‐physisorption analyses, hydrogen temperature‐programmed reduction, ammonia temperature‐programmed desorption, in situ diffuse reflectance infrared Fourier‐transform spectroscopic analysis of the NH3 adsorption, and X‐ray photoelectron spectroscopy. Moreover, the catalytic performance and H2O+SO2 tolerance of these samples were evaluated through NH3‐selective catalytic reduction (NH3‐SCR) in the absence or presence of H2O and SO2. The obtained results show that the MnOx/CS‐NR catalyst exhibits the highest NOx conversion and the lowest N2O concentration, which result from the largest number of oxygen vacancies and acid sites, the highest Mn4+ content, and the lowest redox ability. The MnOx/CS‐NR catalyst also presents excellent resistance to H2O and SO2. All of these phenomena suggest that Si4+ is the optimal dopant for the MnOx/CeO2‐NR catalyst.
