To improve the overall magnetic properties of Sm(CoFeCuZr)_(z)sintered magnets,a dual-alloy sintering process that involves mixing high-iron,low-copper powders with low-iron,high-copper powders was systematically inve...To improve the overall magnetic properties of Sm(CoFeCuZr)_(z)sintered magnets,a dual-alloy sintering process that involves mixing high-iron,low-copper powders with low-iron,high-copper powders was systematically investigated.The results demonstrate that this method significantly improves the Cu-lean phenomenon at the grain boundaries,achieves multiscale uniform microstructures,greatly enhances the pinning field strength,and ultimately produces a high-performance dual-alloy magnet with a maximum energy product((BH)_(max))exceeding 240 kJ/m^(3)and an intrinsic coercivity(H_(cj))exceeding 2400 kA/m.In particular,when 35 wt.%of low-iron,high-copper alloy powder is incorporated,the dual-alloy magnet achieves a remanence of 1.13 T,H_(cj)of 2691.2 kA/m and(BH)_(max)of 248 kJ/m^(3).To evaluate the overall magnetic performance,the sum of H_(cj)(in kA/m)and(BH)_(max)(in kJ/m^(3))is used as a combined parameter,yielding a value of 2939.2.Compared with single-alloy magnets of the same composition,the dual-alloy sintering process yields magnets with a more uniform elemental distribution and superior magnetic properties.展开更多
A city is a complex giant system,in which landscape is a process,and emphasizes the regulation of social relationships in the process of creating landscape,rather than simply creating a kind of landscape.In response t...A city is a complex giant system,in which landscape is a process,and emphasizes the regulation of social relationships in the process of creating landscape,rather than simply creating a kind of landscape.In response to the slogan of high-quality development of China,communities,as the earliest developed but declining old areas in Chinese cities,are the focus of current urban renovation work.By studying the latest research theories in the process of community renewal,it is concluded that there is a close relationship between“community renewal”and“landscape justice”or“public participation”.Based on this,research related to community renewal and landscape justice were sorted out,and suggestions for future research focus were proposed.展开更多
The oxidation behavior and mechanism of Mg-Ca alloys in air and under flame exposure were studied.Results show that for the oxidation in air,the Mg-Ca-O oxide film with Ca accumulation and low Mg vapor pressure on the...The oxidation behavior and mechanism of Mg-Ca alloys in air and under flame exposure were studied.Results show that for the oxidation in air,the Mg-Ca-O oxide film with Ca accumulation and low Mg vapor pressure on the surface of Mg-Ca alloys with high Ca content shows good protective effect.However,the falling off phenomenon of the oxide film on Mg_(2)Ca results in the further oxidation.Hence,the Mg-Ca alloys with high Ca content only show good protective effect.For the oxidation in flame,the molten alloys release the Ca atoms to diffuse outward.The Mg-Ca-O oxide film with high Ca accumulation layer forms in Mg-Ca alloys with high Ca content.Despite the high Mg vapor pressure in the molten alloy,the Mg-Ca-O oxide film with high Ca accumulation layer shows excellent protective effect.展开更多
To further expand the application of Mg alloys at high temperatures,the oxidation resistance of Mg-0.3Ca and Mg-3.6Ca alloys with protective coating under flame exposure was studied.Results show that the oxidation res...To further expand the application of Mg alloys at high temperatures,the oxidation resistance of Mg-0.3Ca and Mg-3.6Ca alloys with protective coating under flame exposure was studied.Results show that the oxidation resistance of Mg-Ca alloys under flame exposure is significantly improved by the protective coating,and Mg-3.6Ca alloy shows better oxidation resistance performance.The surface temperature of Mg-Ca alloys is reduced by the coating,therefore improving the oxidation resistance under flame exposure.However,the thermal insulation effect of the coating on Mg-3.6Ca alloy is better,which can be attributed to the Ca accumulation on the surface film.In addition,the surface film with Ca accumulation layer plays a crucial role in protecting the alloy.No obvious Ca accumulation layer exists on the Mg-0.3Ca alloy surface,presenting a restricted protective effect.Nevertheless,the surface film containing Ca accumulation layer is formed on Mg-3.6 Ca alloy,which shows an excellent protective effect.展开更多
Multi-metal porous crystalline materials(MPCM),integrating the functions of both multi-metal centres and porous crystalline materials(e.g.,metal-organic frameworks(MOFs)and covalent organic frameworks(COFs)),are an ex...Multi-metal porous crystalline materials(MPCM),integrating the functions of both multi-metal centres and porous crystalline materials(e.g.,metal-organic frameworks(MOFs)and covalent organic frameworks(COFs)),are an extended class of porous materials that have attracted much attention for a broad range of applications.Owing to the advantages of these materials,they generally display high porosity,multimetal active sites,well-tuned functions,and pre-designable structures,etc.,serving as desired platforms for the study of structure-property relationships.In view of the clean and sustainable target,a series of MPCM have been explored as electrocatalysts for electrocatalytic reactions like hydrogen evolution reaction,oxygen evolution reaction and electrocatalytic CO_(2)reduction reaction.Concerning the progress achieved for MPCM in electrocatalytic field during past years,this review will provide a brief introduction on the recent breakthrough of MPCM based electrocatalysts including their synthesis methods,structure design,component/morphology tuning,electrocatalytic property and structure-property relationship,etc.Besides,it will also conclude the current challenges and present perspectives for the MPCM based electrocatalysts,which might promote the development of porous crystalline materials in electrocatalysis and hope to provide new insights for scientists in related fields.展开更多
In this work,we proposed a method to enhance the magnetic properties of(Nd,Ce)-Fe-B magnets with Ce/TRE ratios below 25 wt%by introducing a moderate amount of La elements.The segregation behavior of La elements toward...In this work,we proposed a method to enhance the magnetic properties of(Nd,Ce)-Fe-B magnets with Ce/TRE ratios below 25 wt%by introducing a moderate amount of La elements.The segregation behavior of La elements towards grain boundaries(GBs)was utilized to optimize the GB phase structure.Incorporation of La atoms into the main phase induces lattice expansion,leading to an increased formation of Ce^(3+)ions with enhanced magnetic moments.Comparative analysis with the original magnet(La/Ce=0 wt%)demonstrates that the magnet with a La/Ce ratio of 10 wt%exhibits improvements of 0.3%in remanence,12.6%in coercivity,and 0.6%in maximum energy produ ct.These results underscore that the moderate addition of La elements enhances the fluidity of the rare earth-rich phase and optimizes the distribution of lamellar GB,consequently reinforcing the magnetic isolation effect.Furthermore,the promotion of the transformation from Ce^(4+)to Ce^(3+)ons contributes to the comprehensive enhancement of the magnetic properties.This research offers a novel strategy for fabricating high-performance and resource-e fficient sintered magnets based on LaCe alloys.展开更多
基金supported by the National Key Research and Development Program for Young Scientists,China(No.2023YFB3508400)the National Natural Science Foundation of China(Nos.51871005,51931007)+1 种基金the Key Program of Science and Technology Development Project of Beijing Municipal Education Commission of China(No.KZ202010005009)the Program of Top Disciplines Construction in Beijing,China(No.PXM2019_014204_500031)。
文摘To improve the overall magnetic properties of Sm(CoFeCuZr)_(z)sintered magnets,a dual-alloy sintering process that involves mixing high-iron,low-copper powders with low-iron,high-copper powders was systematically investigated.The results demonstrate that this method significantly improves the Cu-lean phenomenon at the grain boundaries,achieves multiscale uniform microstructures,greatly enhances the pinning field strength,and ultimately produces a high-performance dual-alloy magnet with a maximum energy product((BH)_(max))exceeding 240 kJ/m^(3)and an intrinsic coercivity(H_(cj))exceeding 2400 kA/m.In particular,when 35 wt.%of low-iron,high-copper alloy powder is incorporated,the dual-alloy magnet achieves a remanence of 1.13 T,H_(cj)of 2691.2 kA/m and(BH)_(max)of 248 kJ/m^(3).To evaluate the overall magnetic performance,the sum of H_(cj)(in kA/m)and(BH)_(max)(in kJ/m^(3))is used as a combined parameter,yielding a value of 2939.2.Compared with single-alloy magnets of the same composition,the dual-alloy sintering process yields magnets with a more uniform elemental distribution and superior magnetic properties.
基金Sponsored by the Project of Research on Humanities and Social Sciences of Chongqing Education Commission(22SKGH161)Urban Management Scientific Research Project of Chongqing City(Chengguankezi 2024,No.34).
文摘A city is a complex giant system,in which landscape is a process,and emphasizes the regulation of social relationships in the process of creating landscape,rather than simply creating a kind of landscape.In response to the slogan of high-quality development of China,communities,as the earliest developed but declining old areas in Chinese cities,are the focus of current urban renovation work.By studying the latest research theories in the process of community renewal,it is concluded that there is a close relationship between“community renewal”and“landscape justice”or“public participation”.Based on this,research related to community renewal and landscape justice were sorted out,and suggestions for future research focus were proposed.
基金National Natural Science Foundation of China(52405425)Project of Natural Science Research in Higher Education Institutions in Jiangsu Province(23KJB430039)+1 种基金Major Natural Science Research Project of Higher Education Institutions in Jiangsu Province(21KJA460007)333 High Level Talent Training Project in Jiangsu Province(2022-3-12-182)。
文摘The oxidation behavior and mechanism of Mg-Ca alloys in air and under flame exposure were studied.Results show that for the oxidation in air,the Mg-Ca-O oxide film with Ca accumulation and low Mg vapor pressure on the surface of Mg-Ca alloys with high Ca content shows good protective effect.However,the falling off phenomenon of the oxide film on Mg_(2)Ca results in the further oxidation.Hence,the Mg-Ca alloys with high Ca content only show good protective effect.For the oxidation in flame,the molten alloys release the Ca atoms to diffuse outward.The Mg-Ca-O oxide film with high Ca accumulation layer forms in Mg-Ca alloys with high Ca content.Despite the high Mg vapor pressure in the molten alloy,the Mg-Ca-O oxide film with high Ca accumulation layer shows excellent protective effect.
基金General Project of Natural Science Research in Higher Education Institutions in Jiangsu Province(23KJB430039)Major Natural Science Research Project of Higher Education Institutions in Jiangsu Province(21KJA460007)National Natural Science Foundation of China(51905462)。
文摘To further expand the application of Mg alloys at high temperatures,the oxidation resistance of Mg-0.3Ca and Mg-3.6Ca alloys with protective coating under flame exposure was studied.Results show that the oxidation resistance of Mg-Ca alloys under flame exposure is significantly improved by the protective coating,and Mg-3.6Ca alloy shows better oxidation resistance performance.The surface temperature of Mg-Ca alloys is reduced by the coating,therefore improving the oxidation resistance under flame exposure.However,the thermal insulation effect of the coating on Mg-3.6Ca alloy is better,which can be attributed to the Ca accumulation on the surface film.In addition,the surface film with Ca accumulation layer plays a crucial role in protecting the alloy.No obvious Ca accumulation layer exists on the Mg-0.3Ca alloy surface,presenting a restricted protective effect.Nevertheless,the surface film containing Ca accumulation layer is formed on Mg-3.6 Ca alloy,which shows an excellent protective effect.
基金supported by the National Key R&D Program of China(No.2023YFA1507204)the National Natural Science Foundation of China(Nos.22171139,22225109,22309054,22071109,22371080,21775048)+2 种基金Natural Science Foundation of Guangdong Province(No.2023B1515020076)China Postdoctoral Science Foundation(No.2023M731154)China National Postdoctoral Program for Innovative Talents(No.BX20220116)。
文摘Multi-metal porous crystalline materials(MPCM),integrating the functions of both multi-metal centres and porous crystalline materials(e.g.,metal-organic frameworks(MOFs)and covalent organic frameworks(COFs)),are an extended class of porous materials that have attracted much attention for a broad range of applications.Owing to the advantages of these materials,they generally display high porosity,multimetal active sites,well-tuned functions,and pre-designable structures,etc.,serving as desired platforms for the study of structure-property relationships.In view of the clean and sustainable target,a series of MPCM have been explored as electrocatalysts for electrocatalytic reactions like hydrogen evolution reaction,oxygen evolution reaction and electrocatalytic CO_(2)reduction reaction.Concerning the progress achieved for MPCM in electrocatalytic field during past years,this review will provide a brief introduction on the recent breakthrough of MPCM based electrocatalysts including their synthesis methods,structure design,component/morphology tuning,electrocatalytic property and structure-property relationship,etc.Besides,it will also conclude the current challenges and present perspectives for the MPCM based electrocatalysts,which might promote the development of porous crystalline materials in electrocatalysis and hope to provide new insights for scientists in related fields.
基金Project supported by the National Natural Science Foundation of China(52071004,52301228,51971005,52171168)the Program of Top Disciplines Construction in Beijing(PXM2019_014204_500031)the International Research Cooperation Seed Fund of Beijing University of Technology(2021B23)。
文摘In this work,we proposed a method to enhance the magnetic properties of(Nd,Ce)-Fe-B magnets with Ce/TRE ratios below 25 wt%by introducing a moderate amount of La elements.The segregation behavior of La elements towards grain boundaries(GBs)was utilized to optimize the GB phase structure.Incorporation of La atoms into the main phase induces lattice expansion,leading to an increased formation of Ce^(3+)ions with enhanced magnetic moments.Comparative analysis with the original magnet(La/Ce=0 wt%)demonstrates that the magnet with a La/Ce ratio of 10 wt%exhibits improvements of 0.3%in remanence,12.6%in coercivity,and 0.6%in maximum energy produ ct.These results underscore that the moderate addition of La elements enhances the fluidity of the rare earth-rich phase and optimizes the distribution of lamellar GB,consequently reinforcing the magnetic isolation effect.Furthermore,the promotion of the transformation from Ce^(4+)to Ce^(3+)ons contributes to the comprehensive enhancement of the magnetic properties.This research offers a novel strategy for fabricating high-performance and resource-e fficient sintered magnets based on LaCe alloys.
