Efficient conversion of lignin to aromatic hydrocarbons via depolymerization and subsequent hydrodeoxygenation is important.Previously,we found that NbOx species played a key role in the activation and cleavage of C-O...Efficient conversion of lignin to aromatic hydrocarbons via depolymerization and subsequent hydrodeoxygenation is important.Previously,we found that NbOx species played a key role in the activation and cleavage of C-O bonds in lignin and its model compounds.In this study,commercial niobic acid(HY-340),niobium phosphate(NbPO-CBMM)and lab-made layered niobium oxide(Nb2O5-Layer)were chosen as supports to study the effect of Brosted and Lewis acids on the activation of C-O bonds in lignin conversion.A variety of Ru-loaded,Nb-based catalysts with different Ru particle sizes were prepared and applied to the conversion of p-cresol.The results show that all the Ru/Nb-based catalysts produce high mole yields of C7-C9 hydrocarbons(82.3%-9.1%).What's more,Ru/Nb2O5-Layer affords the best mole yield of C7-C9 hydrocarbons and selectivity for C7-C9 aromatic hydrocarbons,of up to 99.1% and 88.0%,respectively.Moreover,it was found that Lewis acid sites play important roles in the depolymerization of enzymatic lignin into phenolic monomers and the cleavage of the C-O bond of phenols.Additionally,the electronic state and particle size of Ru are significant factors which influence the selectivity for aromatic hydrocarbons.A partial positive charge on the metallic Ru surface and a smaller Ru particle size are beneficial in improving the selectivity for aromatic hydrocarbons.展开更多
A first-principles density functional approach is used to study the electronic and the elastic properties of Nb15X （X = Ti, Zr, Hf, V, Ta, Cr, Mo, and W） alloys. The elastic constants cn and c12, the shear modulus C...A first-principles density functional approach is used to study the electronic and the elastic properties of Nb15X （X = Ti, Zr, Hf, V, Ta, Cr, Mo, and W） alloys. The elastic constants cn and c12, the shear modulus CI, and the elastic modulus E（lOO） are found to exhibit similar tendencies, each as a function of valence electron number per atom （EPA）, while c44 seems unclear. Both cu and c12 of Nb15X alloys increase monotonically with the increase of EPA. The C/ and E000） also show similar tendencies. The elastic constants （except c44） increase slightly when alloying with neighbours of a higher d-transition series. Our results are supported by the bonding density distribution. When solute atoms change from Ti（Zr, Hf） to V（Ta） then to Cr（Mo, W）, the bonding electron density between the central solute atom and its first neighbouring Nb atoms is increased and becomes more anisotropic, which indicates the strong interaction and thus enhances the elastic properties of Nb-Cr（Mo, W） alloys. Under uniaxial {100） tensile loading, alloyed elements with less （more） valence electrons decrease （increase） the ideal tensile strength.展开更多
The elastic limit of single-phase alloy Nb-2Mo-2Zr-1Ti is higher as recovered state in comparison with as cold-rolled or recrystallized one.For Nb-40Ti-5.5AI alloy of age-hardening type,the elastic limit is lower as c...The elastic limit of single-phase alloy Nb-2Mo-2Zr-1Ti is higher as recovered state in comparison with as cold-rolled or recrystallized one.For Nb-40Ti-5.5AI alloy of age-hardening type,the elastic limit is lower as cold-rolled state,but increases considerably after proper aging.However,its elastic modulus changes no more,so the stored-energy (σ_e^2/E)may raise significantly.The temperature dependence on elastic modulus for pure Nb as intensely cold-worked or recrystallized state is anomalous.This anomaly may disap- pear after recovered treatment of intensely cold-worked state at 600℃ for 4 h.and may change no more after that of recrystallized state.The anomalous behaviour of elasticity was also discussed on the non-magnetic Nb.展开更多
To attain an enhanced combination of mechanical properties for low alloyed steel, the current study has been made to fulfill that growing need in the industry. Its results are introduced within this paper. One step Qu...To attain an enhanced combination of mechanical properties for low alloyed steel, the current study has been made to fulfill that growing need in the industry. Its results are introduced within this paper. One step Quenching and Partitioning (Q&P) heat treatment has been applied on Niobium-based microalloyed steel alloy with 0.2 %C, in the form of 2 mm thickness sheets. The target of this study is to investigate the viability of applying that significantly recommended, results-wise, heat treatment on the highly well-suited alloy steel samples, to achieve the main target of enhanced properties. A single temperature of 275°C was used as quenching and Partitioning temperature. Four Partitioning periods (30, 200, 500, and 1000 Seconds) were used for soaking at the same temperature. The results were analyzed in the light of microstructural investigation and mechanical testing. All applied cycles did not enhance the strength but moderately improved the ductility and toughness, mainly caused by the slightly high soaking temperature used. Niobium impact of grain refining was apparent through all cycles. The cycle of 500 Seconds Partitioning time obtained optimum values at that particular temperature. The 1000 Seconds Cycle obtained the worst combination of properties. A set of recommendations are set. More research is required at this point, where a lower Partitioning temperature is advised. In the light of the applied combination of parameters, the Partitioning period at such temperature is advised to be between 500 and 1000 Seconds. A high probability that periods closer to 500 than 1000 Seconds will produce better results. More research is needed between those two values of Partitioning time to precisely determine the optimum time at that temperature on that specific alloy.展开更多
【目的】城市绿色基础设施政策工具是由政府主导实施的促进城市绿色基础设施建设的重要手段。【方法】以绿色基础设施政策工具为研究对象,借助Bibliometrix R Package软件和CiteSpace软件,以文本检索、计量分析、编码分类为研究线索,深...【目的】城市绿色基础设施政策工具是由政府主导实施的促进城市绿色基础设施建设的重要手段。【方法】以绿色基础设施政策工具为研究对象,借助Bibliometrix R Package软件和CiteSpace软件,以文本检索、计量分析、编码分类为研究线索,深入剖析了12项代表性城市绿色基础设施政策工具的发展历程,对比其发展历程、指标体系、绩效评估方式和政策管控路径的优势和劣势,探究绿色基础设施建设管理与生态系统服务目标有机结合的途径和方式。【结果】1)城市绿色基础设施政策工具的目标定位从解决单一雨水问题转向评估生态系统服务多重效益。2)政策指标初期包括植物、水系和土壤元素,后期逐步形成包括地表复层植被、地表蓝绿设施、建筑垂直绿化、建筑绿色屋顶项目元素,以及直接干预、动物介入管理元素的层级体系。3)城市绿色基础设施政策工具有强制约束土地利用的“一致性”和间接鼓励的“描述性”2种模式,结合了标准权重和绩效阈值2种互补的城市开发项目筛选机制,工具应用于规划、建设、管控、监测全周期过程。4)结合生态系统服务需求,校准城市绿色基础设施政策工具的绩效评估权重已成为迫切需求。【结论】城市绿色基础设施政策工具将成为应对全球问题和城市挑战的有力手段,揭示其管控落实过程的多元思路,可为城市绿色基础设施优化与完善提供政策指引和技术支持。展开更多
Dielectric capacitors are the ideal energy storage devices because they have excellent power density,high working voltages,and a long lifespan.With its lower size and better energy storage density,film capacitors make...Dielectric capacitors are the ideal energy storage devices because they have excellent power density,high working voltages,and a long lifespan.With its lower size and better energy storage density,film capacitors make them simpler to incorporate into circuits than traditional dielectric capacitor devices.Lead-free Nb-based perovskite ferroelectric/antiferroelectric films have strong orbital hybridization with O 2p orbitals due to unfilled d orbitals of Nb elements,forming a series of energy storage film materials with potential application value.Here,we provide an overview of the state-of-the-art lead-free Nb-based films for energy storage applications,which include K_(0.5)Na_(0.5)NbO_(3)-based,K_(0.5)Na_(0.5)Bi_(4)NbTi_(3)O_(15)-based,AgNbO_(3)-based and NaNbO_(3)-based films.An overview of the benefits and drawbacks of each kind of Nb-based perovskite ferroelectric/antiferroelectric films is provided,along with a description of the design tactics used to achieve high energy storage performances.展开更多
The artificial nitrogen(N_(2)) reduction reaction(NRR) via electrocatalysis is a newly developed methodology to produce ammonia(NH3) at ambient conditions,but faces the challenges in N_(2)activation and poor reaction ...The artificial nitrogen(N_(2)) reduction reaction(NRR) via electrocatalysis is a newly developed methodology to produce ammonia(NH3) at ambient conditions,but faces the challenges in N_(2)activation and poor reaction selectivity.Herein,Nb-based MXenes are developed to remarkably enhance the NRR activity through the engineering of the stretched 3D structure and oxygen vacancies(VO).The theoretical studies indicate that N_(2)could be initially adsorbed on VOwith an end-on configuration,and the potential determining step might be the first hydrogenation step.The catalysts achieve an NH3production rate of 29.1 μg h^(-1)mg_(cat)^(-1)and excellent Faradic efficiency of 11.5%,surpassing other Nbbased catalysts.The selectivity of NRR is assigned to the unique structure of the catalysts,including(1) the layered graphitic structure for fast electron transfer and active site distribution,(2) the reactive VOfor N_(2)adsorption and activation,and(3) the expanded interlayer space for mass transfer.展开更多
基金supported by the National Natural Science Foundation of China(21832002,21872050,21808063)the Natural Science Foundation of Shanghai(18ZR1408500)~~
文摘Efficient conversion of lignin to aromatic hydrocarbons via depolymerization and subsequent hydrodeoxygenation is important.Previously,we found that NbOx species played a key role in the activation and cleavage of C-O bonds in lignin and its model compounds.In this study,commercial niobic acid(HY-340),niobium phosphate(NbPO-CBMM)and lab-made layered niobium oxide(Nb2O5-Layer)were chosen as supports to study the effect of Brosted and Lewis acids on the activation of C-O bonds in lignin conversion.A variety of Ru-loaded,Nb-based catalysts with different Ru particle sizes were prepared and applied to the conversion of p-cresol.The results show that all the Ru/Nb-based catalysts produce high mole yields of C7-C9 hydrocarbons(82.3%-9.1%).What's more,Ru/Nb2O5-Layer affords the best mole yield of C7-C9 hydrocarbons and selectivity for C7-C9 aromatic hydrocarbons,of up to 99.1% and 88.0%,respectively.Moreover,it was found that Lewis acid sites play important roles in the depolymerization of enzymatic lignin into phenolic monomers and the cleavage of the C-O bond of phenols.Additionally,the electronic state and particle size of Ru are significant factors which influence the selectivity for aromatic hydrocarbons.A partial positive charge on the metallic Ru surface and a smaller Ru particle size are beneficial in improving the selectivity for aromatic hydrocarbons.
基金Project supported by the National Natural Science Foundation of China(Grant No.50771004)
文摘A first-principles density functional approach is used to study the electronic and the elastic properties of Nb15X （X = Ti, Zr, Hf, V, Ta, Cr, Mo, and W） alloys. The elastic constants cn and c12, the shear modulus CI, and the elastic modulus E（lOO） are found to exhibit similar tendencies, each as a function of valence electron number per atom （EPA）, while c44 seems unclear. Both cu and c12 of Nb15X alloys increase monotonically with the increase of EPA. The C/ and E000） also show similar tendencies. The elastic constants （except c44） increase slightly when alloying with neighbours of a higher d-transition series. Our results are supported by the bonding density distribution. When solute atoms change from Ti（Zr, Hf） to V（Ta） then to Cr（Mo, W）, the bonding electron density between the central solute atom and its first neighbouring Nb atoms is increased and becomes more anisotropic, which indicates the strong interaction and thus enhances the elastic properties of Nb-Cr（Mo, W） alloys. Under uniaxial {100） tensile loading, alloyed elements with less （more） valence electrons decrease （increase） the ideal tensile strength.
文摘The elastic limit of single-phase alloy Nb-2Mo-2Zr-1Ti is higher as recovered state in comparison with as cold-rolled or recrystallized one.For Nb-40Ti-5.5AI alloy of age-hardening type,the elastic limit is lower as cold-rolled state,but increases considerably after proper aging.However,its elastic modulus changes no more,so the stored-energy (σ_e^2/E)may raise significantly.The temperature dependence on elastic modulus for pure Nb as intensely cold-worked or recrystallized state is anomalous.This anomaly may disap- pear after recovered treatment of intensely cold-worked state at 600℃ for 4 h.and may change no more after that of recrystallized state.The anomalous behaviour of elasticity was also discussed on the non-magnetic Nb.
文摘To attain an enhanced combination of mechanical properties for low alloyed steel, the current study has been made to fulfill that growing need in the industry. Its results are introduced within this paper. One step Quenching and Partitioning (Q&P) heat treatment has been applied on Niobium-based microalloyed steel alloy with 0.2 %C, in the form of 2 mm thickness sheets. The target of this study is to investigate the viability of applying that significantly recommended, results-wise, heat treatment on the highly well-suited alloy steel samples, to achieve the main target of enhanced properties. A single temperature of 275°C was used as quenching and Partitioning temperature. Four Partitioning periods (30, 200, 500, and 1000 Seconds) were used for soaking at the same temperature. The results were analyzed in the light of microstructural investigation and mechanical testing. All applied cycles did not enhance the strength but moderately improved the ductility and toughness, mainly caused by the slightly high soaking temperature used. Niobium impact of grain refining was apparent through all cycles. The cycle of 500 Seconds Partitioning time obtained optimum values at that particular temperature. The 1000 Seconds Cycle obtained the worst combination of properties. A set of recommendations are set. More research is required at this point, where a lower Partitioning temperature is advised. In the light of the applied combination of parameters, the Partitioning period at such temperature is advised to be between 500 and 1000 Seconds. A high probability that periods closer to 500 than 1000 Seconds will produce better results. More research is needed between those two values of Partitioning time to precisely determine the optimum time at that temperature on that specific alloy.
文摘【目的】城市绿色基础设施政策工具是由政府主导实施的促进城市绿色基础设施建设的重要手段。【方法】以绿色基础设施政策工具为研究对象,借助Bibliometrix R Package软件和CiteSpace软件,以文本检索、计量分析、编码分类为研究线索,深入剖析了12项代表性城市绿色基础设施政策工具的发展历程,对比其发展历程、指标体系、绩效评估方式和政策管控路径的优势和劣势,探究绿色基础设施建设管理与生态系统服务目标有机结合的途径和方式。【结果】1)城市绿色基础设施政策工具的目标定位从解决单一雨水问题转向评估生态系统服务多重效益。2)政策指标初期包括植物、水系和土壤元素,后期逐步形成包括地表复层植被、地表蓝绿设施、建筑垂直绿化、建筑绿色屋顶项目元素,以及直接干预、动物介入管理元素的层级体系。3)城市绿色基础设施政策工具有强制约束土地利用的“一致性”和间接鼓励的“描述性”2种模式,结合了标准权重和绩效阈值2种互补的城市开发项目筛选机制,工具应用于规划、建设、管控、监测全周期过程。4)结合生态系统服务需求,校准城市绿色基础设施政策工具的绩效评估权重已成为迫切需求。【结论】城市绿色基础设施政策工具将成为应对全球问题和城市挑战的有力手段,揭示其管控落实过程的多元思路,可为城市绿色基础设施优化与完善提供政策指引和技术支持。
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.12074204,11864028)Natural Science Foundation of Inner Mongolia(Grant No.2022ZD06,2021BS01004,2021BS05006)Foundation of Inner Mongolia University of Technology(ZZ202003,ZY202008).
文摘Dielectric capacitors are the ideal energy storage devices because they have excellent power density,high working voltages,and a long lifespan.With its lower size and better energy storage density,film capacitors make them simpler to incorporate into circuits than traditional dielectric capacitor devices.Lead-free Nb-based perovskite ferroelectric/antiferroelectric films have strong orbital hybridization with O 2p orbitals due to unfilled d orbitals of Nb elements,forming a series of energy storage film materials with potential application value.Here,we provide an overview of the state-of-the-art lead-free Nb-based films for energy storage applications,which include K_(0.5)Na_(0.5)NbO_(3)-based,K_(0.5)Na_(0.5)Bi_(4)NbTi_(3)O_(15)-based,AgNbO_(3)-based and NaNbO_(3)-based films.An overview of the benefits and drawbacks of each kind of Nb-based perovskite ferroelectric/antiferroelectric films is provided,along with a description of the design tactics used to achieve high energy storage performances.
基金financially supported by China Postdoctoral Science Foundation (2019M652305)Qingdao Postdoctoral Application Research Project。
文摘The artificial nitrogen(N_(2)) reduction reaction(NRR) via electrocatalysis is a newly developed methodology to produce ammonia(NH3) at ambient conditions,but faces the challenges in N_(2)activation and poor reaction selectivity.Herein,Nb-based MXenes are developed to remarkably enhance the NRR activity through the engineering of the stretched 3D structure and oxygen vacancies(VO).The theoretical studies indicate that N_(2)could be initially adsorbed on VOwith an end-on configuration,and the potential determining step might be the first hydrogenation step.The catalysts achieve an NH3production rate of 29.1 μg h^(-1)mg_(cat)^(-1)and excellent Faradic efficiency of 11.5%,surpassing other Nbbased catalysts.The selectivity of NRR is assigned to the unique structure of the catalysts,including(1) the layered graphitic structure for fast electron transfer and active site distribution,(2) the reactive VOfor N_(2)adsorption and activation,and(3) the expanded interlayer space for mass transfer.
