Ultrahigh-temperature ceramics were added to C/C composites to meet their application requirement in a high-temperature oxidizing environment. C/C-ZrB2-SiC composites were fabricated by high-solid-loading slurry impre...Ultrahigh-temperature ceramics were added to C/C composites to meet their application requirement in a high-temperature oxidizing environment. C/C-ZrB2-SiC composites were fabricated by high-solid-loading slurry impregnation with polymer infiltration and pyrolysis. The dispersion and rheological behavior of ZrB2 slurry and the microstructural, mechanical, and ablation properties of the C/C-ZrB2-SiC composites were investigated. Results indicated that a well-dispersed and low-viscosity ZrB2 slurry was obtained using 0.40 wt.% polyethyleneimine as a dispersant at pH 5. Ceramics were uniformly distributed in the short-cut fiber layer and needle-punched area. The flexural strength of the C/C-ZrB2-SiC composites was 309.30 MPa. The composites exhibited satisfactory ablation resistance under the oxyacetylene flame of 2500℃, and the mass and linear ablation rates were 0.40 mg/s and 0.91 μm/s, respectively. A continuous and compact Zr O2 layer, which could effectively reduce the diffusion rate of oxygen and protect the composites from being ablated, was formed.展开更多
The BiOCl(BOC)synthesized by the water bath heating method was treated with sodium borohydride(NaBH_(4))to introduce oxygen vacancies(OVs).At the same time,Au nanoparticles were loaded to prepare a series of Au/BiOCl ...The BiOCl(BOC)synthesized by the water bath heating method was treated with sodium borohydride(NaBH_(4))to introduce oxygen vacancies(OVs).At the same time,Au nanoparticles were loaded to prepare a series of Au/BiOCl samples with different ratios.OVs and Au nanoparticles can promote the light absorption of host photocatalyst in the visible region.The calculated work function of BiOCl and Au can verify the existence of Ohmic contact between the interface of them,which is conducive to the separation of charge carriers.Through a series of photoelectric tests,it was verified experimentally that the separation of charge carriers is indeed enhanced.The high-energy hot electrons produced by Au under the surface plasmon resonance(SPR)effect can increase the counts of electrons to participate in the CO_(2)reduction reaction.Especially for 1.0%-Au/BOC,the yields of CO can reach 43.16μmol g^(−1)h^(−1),which is 6.6 times more than that of BOC.Therefore,loading precious metal on semiconductors is an effective strategy to promote the photocatalytic performance of CO_(2)reduction reactions.展开更多
Surface oxygen vacancy defects and metal deposition on semiconductor photocatalysts play a critical role in photocatalytic reactions.In this work,oxygen-deficient Bi_(2)WO_(6)microspheres have been prepared by a facil...Surface oxygen vacancy defects and metal deposition on semiconductor photocatalysts play a critical role in photocatalytic reactions.In this work,oxygen-deficient Bi_(2)WO_(6)microspheres have been prepared by a facile ethylene glycol-assisted solvothermal method.Bi0 nanoparticles were reduced by in situ thermaltreatment on Bi_(2)WO_(6)microspheres to obtain Bi^(0)@Bi_(2)WO_(6)-x as well as maintaining the oxygen vacancies(OVs)under N_(2)atmosphere.Afterwards,photocatalytic NO oxidation removal activities of these photocatalysts were investigated under visible light irradiation and Bi^(0)@Bi_(2)WO_(6)-x shows the best NO removal activity than other samples.The photogenerated cha rge separation and trans fe r are promoted by Bi0 nanoparticles deposited on the surface of semiconductor catalysts.OVs defects promote the activation of reactants(H_(2)O and O_(2)),thereby enhancing the formation of the active substance.Moreover,both OVs defects and Bi0 metal have the characteristics of extending light absorption and enhancing the efficient utilization of solar energy.Besides,the photocatalytic NO oxidation mechanism of Bi^(0)@Bi_(2)WO_(6)-xwas investigated by in situ FTIR spectroscopy for reaction intermediates and final products.This work furnishes insight into the synthesis strategy and the underlying photocatalytic mecha nism of the surfacemodified Bi^(0)@Bi_(2)WO_(6)-x composite for pollutants removal.展开更多
Landscape designers increasingly prefer to use wood/bamboo-based composites for outdoor hydrophilic platforms owing to their natural surface texture,high performance,and sustainability to facilitate extensive interact...Landscape designers increasingly prefer to use wood/bamboo-based composites for outdoor hydrophilic platforms owing to their natural surface texture,high performance,and sustainability to facilitate extensive interaction between people and water and enable the full range of ecological functions of water resources.In this study,four laminated composite(LC)structures were designed and manufactured using fluffed bamboo and wood veneers.Their surface textures,profile densities,water resistances,and mechanical properties were then evaluated.The type of fluffed veneer of the surface layer determined the texture of the LC surface.The specific structures of fluffed bamboo and wood veneer laminations were found to affect the LC profile density variability,water resistance,and mechanical properties owing to the differences in the strength and interfacial properties of bamboo and wood fibers.Finally,the water resistance and mechanical properties of all four LCs were found to be much higher than the highest level specified in GB/T 20241-2006 for“laminated veneer lumber”and GB/T 30364-2013 for“bamboo scrimber flooring”,indicating that they are promising materials for structures and flooring,particularly for outdoor hydrophilic platforms.展开更多
Plasmonic bismuth(Bi^0)nanoparticle-decorated flower-like CeO2-δ(Bi^0/CeO2-δ)photocatalysts with abundant oxygen vacancies(OVs)were synthesized via a solvothermal method.The OVs can not only improve the separation o...Plasmonic bismuth(Bi^0)nanoparticle-decorated flower-like CeO2-δ(Bi^0/CeO2-δ)photocatalysts with abundant oxygen vacancies(OVs)were synthesized via a solvothermal method.The OVs can not only improve the separation of electron-hole pairs,but also facilitate the adsorption and activation of gas molecules(NO/O2).In addition,the Bi^0 nanoparticles can enhance the visible light response and prevent the recombination of charge carriers by virtue of the surface plasmon resonance(SPR)effect,achieving an excellent ability for NO elimination and NO2 inhibition under visible light irradiation.Density functional theory(DFT)calculations confirm that the Schottky barrier between Bi^0 and CeO2-δaccompanied with the OVs are pivotal for the migration of photogenerated charge carriers to involve in the photocatalytic NO removal.Trapping experiments and in situ FTIR spectroscopy were conducted to explore the mechanism of the photocatalytic NO removal,suggesting that the photocatalytic NO removal can be significantly enhanced by introducing abundant OVs and the involvement of Bi^0 metal nanoparticles.展开更多
In this work,a novel Z-scheme Bi_(5)O_(7-δ)I/CeO_(2-δ)heterojunction photocatalyst was prepared by combining hydrothermal synthesis and thermal treatment methods.Oxygen vacancies were in situ generated on the surfac...In this work,a novel Z-scheme Bi_(5)O_(7-δ)I/CeO_(2-δ)heterojunction photocatalyst was prepared by combining hydrothermal synthesis and thermal treatment methods.Oxygen vacancies were in situ generated on the surface of Bi_(5)O_(7-δ)I and CeO_(2-δ)nanostructures.The existence of oxygen vacancies significantly improved the light absorption of CeO_(2-δ)and inhibited the recombination of photogenerated carriers.Based on the photocatalytic activity,the as-prepared Bi_(5)O_(7-δ)I/CeO_(2-δ)photocatalyst exhibited excellent photocatalytic NO removal performance under visible light irradiation.The results of the capture experiment and electron spin resonance(ESR)spectroscopy show that super oxygen radicals(·O_(2)^(-))and hydroxyl radicals(·OH)are the main active species in the overall photocatalytic reaction process.Density functional theory(DFT)calculations and ESR results demonstrate that a Z-scheme heterojunction is formed between Bi_(5)O_(7-δ)I and CeO_(2-δ).Compared with the traditional type-Ⅱ heterojunction,the Z-scheme heterojunction exhibited more efficient charge separation and robust redox capacity in the photocatalytic reaction.展开更多
Fast recombination and slow transfer of photogenerated charge carriers impede the photo-oxidation process of NOx.Herein,the K_(0.5)Bi_(0.5)TiO_(3) with oxygen vacancies(KBT-O)realized the enhancement of charge separat...Fast recombination and slow transfer of photogenerated charge carriers impede the photo-oxidation process of NOx.Herein,the K_(0.5)Bi_(0.5)TiO_(3) with oxygen vacancies(KBT-O)realized the enhancement of charge separation caused by the effect of spontaneous polarization.In addition to spontaneous polarization,oxygen vacancies introduced intentionally under UV light irradiation act as hubs for capturing the photogenerated electrons to further enhance the separation of charge carriers due to a surface local electric field.Oxygen vacancies can also serve as active sites to enhance the adsorption of NO and O_(2).In particular,the built-in electric field in the KBT-O because of spontaneous polarization improves the separation efficiency of photogenerated charge carriers,resulting in an increased removal rate of NO(53.6%)and a reduced concentration of formed NO_(2)(2.1 ppb).This work unravels the important role of spontaneous polarization along with oxygen vacancies in enhancing the deep oxidation of NO over ferroelectric KBT-O photocatalyst under visible light irradiation.展开更多
基金Project(GFZX0101040101-2012C20X) supported by the National Basic Research Program of ChinaProject(2017JJ2320) supported by the Natural Science Foundation of Hunan Province,China
文摘Ultrahigh-temperature ceramics were added to C/C composites to meet their application requirement in a high-temperature oxidizing environment. C/C-ZrB2-SiC composites were fabricated by high-solid-loading slurry impregnation with polymer infiltration and pyrolysis. The dispersion and rheological behavior of ZrB2 slurry and the microstructural, mechanical, and ablation properties of the C/C-ZrB2-SiC composites were investigated. Results indicated that a well-dispersed and low-viscosity ZrB2 slurry was obtained using 0.40 wt.% polyethyleneimine as a dispersant at pH 5. Ceramics were uniformly distributed in the short-cut fiber layer and needle-punched area. The flexural strength of the C/C-ZrB2-SiC composites was 309.30 MPa. The composites exhibited satisfactory ablation resistance under the oxyacetylene flame of 2500℃, and the mass and linear ablation rates were 0.40 mg/s and 0.91 μm/s, respectively. A continuous and compact Zr O2 layer, which could effectively reduce the diffusion rate of oxygen and protect the composites from being ablated, was formed.
基金supported by the National Natural Science Foundation of China(Nos.51772183.52072230)the Yulin Science and Technology Project(No.CXY-2020-040)。
文摘The BiOCl(BOC)synthesized by the water bath heating method was treated with sodium borohydride(NaBH_(4))to introduce oxygen vacancies(OVs).At the same time,Au nanoparticles were loaded to prepare a series of Au/BiOCl samples with different ratios.OVs and Au nanoparticles can promote the light absorption of host photocatalyst in the visible region.The calculated work function of BiOCl and Au can verify the existence of Ohmic contact between the interface of them,which is conducive to the separation of charge carriers.Through a series of photoelectric tests,it was verified experimentally that the separation of charge carriers is indeed enhanced.The high-energy hot electrons produced by Au under the surface plasmon resonance(SPR)effect can increase the counts of electrons to participate in the CO_(2)reduction reaction.Especially for 1.0%-Au/BOC,the yields of CO can reach 43.16μmol g^(−1)h^(−1),which is 6.6 times more than that of BOC.Therefore,loading precious metal on semiconductors is an effective strategy to promote the photocatalytic performance of CO_(2)reduction reactions.
基金supported by the National Natural Science Foundation of China(No.51772183)the key Research and Development Program of Shaanxi Province(No.2018ZDCXL-SF-02-04)the Fundamental Research Funds for the Central Universities(Nos.GK201903023 and GK201801005)。
文摘Surface oxygen vacancy defects and metal deposition on semiconductor photocatalysts play a critical role in photocatalytic reactions.In this work,oxygen-deficient Bi_(2)WO_(6)microspheres have been prepared by a facile ethylene glycol-assisted solvothermal method.Bi0 nanoparticles were reduced by in situ thermaltreatment on Bi_(2)WO_(6)microspheres to obtain Bi^(0)@Bi_(2)WO_(6)-x as well as maintaining the oxygen vacancies(OVs)under N_(2)atmosphere.Afterwards,photocatalytic NO oxidation removal activities of these photocatalysts were investigated under visible light irradiation and Bi^(0)@Bi_(2)WO_(6)-x shows the best NO removal activity than other samples.The photogenerated cha rge separation and trans fe r are promoted by Bi0 nanoparticles deposited on the surface of semiconductor catalysts.OVs defects promote the activation of reactants(H_(2)O and O_(2)),thereby enhancing the formation of the active substance.Moreover,both OVs defects and Bi0 metal have the characteristics of extending light absorption and enhancing the efficient utilization of solar energy.Besides,the photocatalytic NO oxidation mechanism of Bi^(0)@Bi_(2)WO_(6)-xwas investigated by in situ FTIR spectroscopy for reaction intermediates and final products.This work furnishes insight into the synthesis strategy and the underlying photocatalytic mecha nism of the surfacemodified Bi^(0)@Bi_(2)WO_(6)-x composite for pollutants removal.
基金the Science and Technology Project of Zhejiang Province(2021C02012)the Science Foundation of Zhejiang Provincial Department of Education(113429A4F21070)the Science Foundation of Zhejiang Sci-Tech University(11340031282014 and 11343132612052).
文摘Landscape designers increasingly prefer to use wood/bamboo-based composites for outdoor hydrophilic platforms owing to their natural surface texture,high performance,and sustainability to facilitate extensive interaction between people and water and enable the full range of ecological functions of water resources.In this study,four laminated composite(LC)structures were designed and manufactured using fluffed bamboo and wood veneers.Their surface textures,profile densities,water resistances,and mechanical properties were then evaluated.The type of fluffed veneer of the surface layer determined the texture of the LC surface.The specific structures of fluffed bamboo and wood veneer laminations were found to affect the LC profile density variability,water resistance,and mechanical properties owing to the differences in the strength and interfacial properties of bamboo and wood fibers.Finally,the water resistance and mechanical properties of all four LCs were found to be much higher than the highest level specified in GB/T 20241-2006 for“laminated veneer lumber”and GB/T 30364-2013 for“bamboo scrimber flooring”,indicating that they are promising materials for structures and flooring,particularly for outdoor hydrophilic platforms.
基金supported by the National Natural Science Foundation of China(51772183,21673118 and 21972067)the Key Research and Development Program of Shaanxi Province(2018ZDCXL-SF-02-04)+1 种基金the Natural Science Foundation of Hubei Province(2019CFB225)the Fundamental Research Funds for the Central Universities(GK201903023 and GK201801005)。
文摘Plasmonic bismuth(Bi^0)nanoparticle-decorated flower-like CeO2-δ(Bi^0/CeO2-δ)photocatalysts with abundant oxygen vacancies(OVs)were synthesized via a solvothermal method.The OVs can not only improve the separation of electron-hole pairs,but also facilitate the adsorption and activation of gas molecules(NO/O2).In addition,the Bi^0 nanoparticles can enhance the visible light response and prevent the recombination of charge carriers by virtue of the surface plasmon resonance(SPR)effect,achieving an excellent ability for NO elimination and NO2 inhibition under visible light irradiation.Density functional theory(DFT)calculations confirm that the Schottky barrier between Bi^0 and CeO2-δaccompanied with the OVs are pivotal for the migration of photogenerated charge carriers to involve in the photocatalytic NO removal.Trapping experiments and in situ FTIR spectroscopy were conducted to explore the mechanism of the photocatalytic NO removal,suggesting that the photocatalytic NO removal can be significantly enhanced by introducing abundant OVs and the involvement of Bi^0 metal nanoparticles.
基金supported by the National Natural Science Foundation of China(Grant No.51772183 and 52072230)the Fundamental Research Funds for the Central Universities(2020TS028).
文摘In this work,a novel Z-scheme Bi_(5)O_(7-δ)I/CeO_(2-δ)heterojunction photocatalyst was prepared by combining hydrothermal synthesis and thermal treatment methods.Oxygen vacancies were in situ generated on the surface of Bi_(5)O_(7-δ)I and CeO_(2-δ)nanostructures.The existence of oxygen vacancies significantly improved the light absorption of CeO_(2-δ)and inhibited the recombination of photogenerated carriers.Based on the photocatalytic activity,the as-prepared Bi_(5)O_(7-δ)I/CeO_(2-δ)photocatalyst exhibited excellent photocatalytic NO removal performance under visible light irradiation.The results of the capture experiment and electron spin resonance(ESR)spectroscopy show that super oxygen radicals(·O_(2)^(-))and hydroxyl radicals(·OH)are the main active species in the overall photocatalytic reaction process.Density functional theory(DFT)calculations and ESR results demonstrate that a Z-scheme heterojunction is formed between Bi_(5)O_(7-δ)I and CeO_(2-δ).Compared with the traditional type-Ⅱ heterojunction,the Z-scheme heterojunction exhibited more efficient charge separation and robust redox capacity in the photocatalytic reaction.
基金supported by the National Natural Science Foundation of China(grant no.51772183 and 52072230).
文摘Fast recombination and slow transfer of photogenerated charge carriers impede the photo-oxidation process of NOx.Herein,the K_(0.5)Bi_(0.5)TiO_(3) with oxygen vacancies(KBT-O)realized the enhancement of charge separation caused by the effect of spontaneous polarization.In addition to spontaneous polarization,oxygen vacancies introduced intentionally under UV light irradiation act as hubs for capturing the photogenerated electrons to further enhance the separation of charge carriers due to a surface local electric field.Oxygen vacancies can also serve as active sites to enhance the adsorption of NO and O_(2).In particular,the built-in electric field in the KBT-O because of spontaneous polarization improves the separation efficiency of photogenerated charge carriers,resulting in an increased removal rate of NO(53.6%)and a reduced concentration of formed NO_(2)(2.1 ppb).This work unravels the important role of spontaneous polarization along with oxygen vacancies in enhancing the deep oxidation of NO over ferroelectric KBT-O photocatalyst under visible light irradiation.
