Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional ceramics.Most of the current method...Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional ceramics.Most of the current methods,however,are complicated and time-consuming,the mass production remains a chal-lenge.Herein,we proposed a new high-efficiency strategy for synthesis of MMB_(2)using molten aluminum as the medium for the first time.The prepared Al-containing multi-component borides(TiZrHfNbTa)B_(2)microcrystals had a homogeneous composition with a hexagonal AlB_(2)structure and ultra-high hardness value of∼35.3 GPa,which was much higher than data reported in the literature and the rule of mix-ture estimations.Furthermore,combined with the First-principles calculation results,we found that the Poisson’s ratio(v)values exhibit a clearly ascending trend from 0.17 at VEC=3.5 to 0.18 at VEC=3.4,then to 0.201 at VEC=3.2 with the increasing of Al content.This indicates that the intrinsic toughness of multi-component boride microcrystals is obviously enhanced by the trace-doped Al elements.Besides,the fabricated Al-containing multi-component boride microcrystals have superior oxidation activation en-ergy and structural stability.The enhanced oxidation resistance is mainly attributed to the formation of a protective Al2 O3 oxide layer and the lattice distortion,both of which lead to sluggish diffusion of O_(2).These findings propose a new unexplored avenue for the fabrication of MMB_(2)materials with supe-rior comprehensive performance including ultra-hardness and intrinsically improved thermo-mechanical properties.展开更多
Hypoeutectic Al-Si alloys are becoming increasingly popular in automotive and aerospace engineering fields due to their excellent overall performance,and grain refinement is regarded as an important way to improve cas...Hypoeutectic Al-Si alloys are becoming increasingly popular in automotive and aerospace engineering fields due to their excellent overall performance,and grain refinement is regarded as an important way to improve casting and mechanical properties.Titanium(Ti)is a basic element for grain refinement;thus,a certain amount of Ti is often included in Al-Si alloys.In the present work,the changes in the grain re-finement,mechanical,and casting properties of Al-Si alloys with different Ti concentration levels under various grain refinement conditions were systematically investigated.The specific roles of Ti in the het-erogeneous nucleation ofα-Al grains were summarized,and the formation mechanism of Ti-rich zones in Al-Si alloys was revealed.Excess Ti concentration could not efficiently reduce the grain size of Al-Si alloys and eventually resulted in inferior mechanical and casting qualities;hence,the recommended Ti concentration level for the aluminum alloy grades of A356 and A357 is≤0.1 wt%.Furthermore,an opti-mized technique for the grain refinement of hypoeutectic Al-Si alloys was presented.A small amount of an Al-TCB master alloy was introduced to achieve the best grain refinement and mechanical properties in a trace Ti environment.The addition of 0.5 wt%of the Al-TCB master alloy at the Ti concentration level of 0.06 wt%increased the ultimate tensile strength,elongation,and quality index of the Al-7Si-0.45Mg alloy to 328.8±5.0 MPa,14.4%±0.6%,and 970.7±33.1 MPa,respectively.展开更多
The manufacturing of heterogeneous high-temperature material components is challenging for use in practical applications.Three-dimensional(3D)printing provides solutions to programmable constructing ceramic architectu...The manufacturing of heterogeneous high-temperature material components is challenging for use in practical applications.Three-dimensional(3D)printing provides solutions to programmable constructing ceramic architectures.However,the development of heterogeneous ceramics is limited by low flexibil-ity of heterogeneity,geometrical complexity,structural resolution,manufacturing efficiency,and mate-rial diversity.In this study,we demonstrated flexible and rapid approaches for fabricating complicated and precise heterogeneous ceramics by shape-changing(4D)or shape-keeping(3D)additive-subtractive manufacturing(ASM)methods.The shape-changing strategy for heterogeneous ceramics was achieved by global ceramization of heterogeneous precursors,while the shape-keeping strategy for heterogeneous ceramics was achieved by local receramization of homogeneous ceramics.Finite element analysis(FEA)simulations of the influence of the thermal shrinkage dominant in the shape-changing strategy on the shape deformation of heterogeneous ceramics could be valuable predictions of the experimental results.The 3D/4D ASM methods are generic for high-temperature materials and extendable to metallic and dia-mond materials.展开更多
High-strength Al-Si alloys are important lightweight materials,but their optimal design is hindered by scarce-imbalance data,and complex compositional-process-property relationships.Traditional trialand-error experime...High-strength Al-Si alloys are important lightweight materials,but their optimal design is hindered by scarce-imbalance data,and complex compositional-process-property relationships.Traditional trialand-error experimentation fails to explore this multi-dimensional design space,where processing routes(PRs)and composition must be co-optimized to achieve superior strength.This study introduces a process-synergistic active learning(PSAL)framework leveraging a conditional Wasserstein autoencoder(c-WAE)to enable the data-efficient design.By encoding PRs as conditional variables,the PSAL framework reveals exceptional synergistic effects across diverse PRs,significantly outperforming single-process approaches.The process-aware latent representation facilitates the efficient exploration of potential compositions across multi-PRs simultaneously.Through iterative active learning cycles integrating machine learning predictions with experimental validations,ultimate tensile strength is greatly improved:459.8MPa for gravity casting with T6 heat treatment within three iterations and 220.5MPa for gravity casting with hot extrusion in a single iteration.This framework handles sparse datasets effectively,capturing complex processcomposition-property relationships and establishing a new paradigm for accelerated multi-objective material design.展开更多
Remote,rural ethnic-minority communities face greater disaster-related public health risks due to their lack of resources and limited access to health care.The Ethnic Minority Health Project(EMHP) was initiated in 200...Remote,rural ethnic-minority communities face greater disaster-related public health risks due to their lack of resources and limited access to health care.The Ethnic Minority Health Project(EMHP) was initiated in 2009 to work with remote,disaster-prone ethnic-minority villages that live in extreme poverty.One of the project's aims is to develop and evaluate bottom-up health risk reduction efforts in emergency and disaster risk management(HealthEDRM).This article shares project updates and describes field intervention results from the Yi ethnic community of Hongyan village in China's Sichuan Province,an area that experiences recurrent floods.It was found that 64% of the village respondents had never considered any form of disaster preparation,even with the recurrent flood risks.Health intervention participants showed sustained knowledge retention and were nine times more likely to know the correct composition of oral rehydration solution(ORS) after the intervention.Participants also retained the improved knowledge on ORS and disaster preparedness kit ownership12 months after the intervention.展开更多
Ma'an Qiao Village, a Dai and Yi ethnic minority-based community in Sichuan Province, China sustained complete infrastructure devastation during the 2008 Panzhihua earthquake. Health emergency and disaster risk ma...Ma'an Qiao Village, a Dai and Yi ethnic minority-based community in Sichuan Province, China sustained complete infrastructure devastation during the 2008 Panzhihua earthquake. Health emergency and disaster risk management(Health-EDRM) education intervention programs were implemented in 2010 and 2011. This serial cross-sectional survey study aimed to examine the immediate and long-term impacts of the Health-EDRM interventions in this remote rural community. The findings demonstrate knowledge improvement in areas of water and sanitation, food and nutrition, and disaster preparedness immediately after the Health-EDRM education interventions. Temporal stability of knowledge retention was observed in household hygiene and waste management and smoking beliefs in 2018, 7 years after the interventions.Other important findings include knowledge uptake pattern differences of oral rehydration solution(ORS) between earthquake-prone and flood-prone communities. Usage of Internet and mobile technology for accessing disaster-related information was found to be independent of gender and income. Overall, this study demonstrated the knowledge improvement through Health-EDRM education interventions in a remote rural community. Promoting behavioral changes through interventions to raise awareness has the potential to reduce health risks in transitional post-disaster settings. Future programs should aim to identify evidence-based practices and explore how technology can support Health-EDRM education among vulnerable subgroups.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.52271033 and 52071179)the Key program of National Natural Science Foundation of China(No.51931003)+2 种基金Natural Science Foundation of Jiangsu Province,China(No.BK20221493)Jiangsu Province Leading Edge Technology Basic Research Major Project(No.BK20222014)Foundation of“Qinglan Project”for Colleges and Universities in Jiangsu Province.
文摘Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional ceramics.Most of the current methods,however,are complicated and time-consuming,the mass production remains a chal-lenge.Herein,we proposed a new high-efficiency strategy for synthesis of MMB_(2)using molten aluminum as the medium for the first time.The prepared Al-containing multi-component borides(TiZrHfNbTa)B_(2)microcrystals had a homogeneous composition with a hexagonal AlB_(2)structure and ultra-high hardness value of∼35.3 GPa,which was much higher than data reported in the literature and the rule of mix-ture estimations.Furthermore,combined with the First-principles calculation results,we found that the Poisson’s ratio(v)values exhibit a clearly ascending trend from 0.17 at VEC=3.5 to 0.18 at VEC=3.4,then to 0.201 at VEC=3.2 with the increasing of Al content.This indicates that the intrinsic toughness of multi-component boride microcrystals is obviously enhanced by the trace-doped Al elements.Besides,the fabricated Al-containing multi-component boride microcrystals have superior oxidation activation en-ergy and structural stability.The enhanced oxidation resistance is mainly attributed to the formation of a protective Al2 O3 oxide layer and the lattice distortion,both of which lead to sluggish diffusion of O_(2).These findings propose a new unexplored avenue for the fabrication of MMB_(2)materials with supe-rior comprehensive performance including ultra-hardness and intrinsically improved thermo-mechanical properties.
基金financially supported by the National Natu-ral Science Foundation of China(Nos.52071189,U2241230,and 52301167).
文摘Hypoeutectic Al-Si alloys are becoming increasingly popular in automotive and aerospace engineering fields due to their excellent overall performance,and grain refinement is regarded as an important way to improve casting and mechanical properties.Titanium(Ti)is a basic element for grain refinement;thus,a certain amount of Ti is often included in Al-Si alloys.In the present work,the changes in the grain re-finement,mechanical,and casting properties of Al-Si alloys with different Ti concentration levels under various grain refinement conditions were systematically investigated.The specific roles of Ti in the het-erogeneous nucleation ofα-Al grains were summarized,and the formation mechanism of Ti-rich zones in Al-Si alloys was revealed.Excess Ti concentration could not efficiently reduce the grain size of Al-Si alloys and eventually resulted in inferior mechanical and casting qualities;hence,the recommended Ti concentration level for the aluminum alloy grades of A356 and A357 is≤0.1 wt%.Furthermore,an opti-mized technique for the grain refinement of hypoeutectic Al-Si alloys was presented.A small amount of an Al-TCB master alloy was introduced to achieve the best grain refinement and mechanical properties in a trace Ti environment.The addition of 0.5 wt%of the Al-TCB master alloy at the Ti concentration level of 0.06 wt%increased the ultimate tensile strength,elongation,and quality index of the Al-7Si-0.45Mg alloy to 328.8±5.0 MPa,14.4%±0.6%,and 970.7±33.1 MPa,respectively.
基金supported by the Shenzhen-Hong Kong Sci-ence and Technology Innovation Cooperation Zone Shenzhen Park Project(grant No.HZQB-KCZYB-2020030)the Shenzhen Science and Technology Program:No.JCYJ20220818101204010+4 种基金the Re-search Grants Council of the Hong Kong Special Administrative Region,China(grant No.CityU PDFS2223-1S05)the Guangdong Provincial Department of Science and Technology(Key-Area Re-search and Development Program of Guangdong Province)(grant No.2020B090923002)the Major Program of Changsha Science and Technology Project(grant No.kh2003023)the Hong Kong In-novation and Technology Commission via the Hong Kong Branch of National Precious Metals Material Engineering Research Centerthe Research Grants Council of Hong Kong Special Administrative Region,China(grant No.AoE/M-402/20).
文摘The manufacturing of heterogeneous high-temperature material components is challenging for use in practical applications.Three-dimensional(3D)printing provides solutions to programmable constructing ceramic architectures.However,the development of heterogeneous ceramics is limited by low flexibil-ity of heterogeneity,geometrical complexity,structural resolution,manufacturing efficiency,and mate-rial diversity.In this study,we demonstrated flexible and rapid approaches for fabricating complicated and precise heterogeneous ceramics by shape-changing(4D)or shape-keeping(3D)additive-subtractive manufacturing(ASM)methods.The shape-changing strategy for heterogeneous ceramics was achieved by global ceramization of heterogeneous precursors,while the shape-keeping strategy for heterogeneous ceramics was achieved by local receramization of homogeneous ceramics.Finite element analysis(FEA)simulations of the influence of the thermal shrinkage dominant in the shape-changing strategy on the shape deformation of heterogeneous ceramics could be valuable predictions of the experimental results.The 3D/4D ASM methods are generic for high-temperature materials and extendable to metallic and dia-mond materials.
基金supported by the open subject of the State Key Laboratory of Powder Metallurgy,Central South University(SKLPM-KF-003)a grant from the National Natural Science Foundation of China(52471142 and 52301167)+4 种基金the National Youth Talent Program,Ministry of Industry and Information Technology of China(GQQNKP005)the open subject of the State Key Laboratory of Solidification Processing,Northwestern Polytechnical University(SKLSP202403)the National Natural Science Foundation of China(12302140)the Fundamental Research Funds for the Central Universities of China(sxzy012023213)'China Postdoctoral Science Foundation(2023M732794)Postdoctoral Fellowship Program(Grade B)of China Postdoctoral Science Foundation(GZB20230575).
文摘High-strength Al-Si alloys are important lightweight materials,but their optimal design is hindered by scarce-imbalance data,and complex compositional-process-property relationships.Traditional trialand-error experimentation fails to explore this multi-dimensional design space,where processing routes(PRs)and composition must be co-optimized to achieve superior strength.This study introduces a process-synergistic active learning(PSAL)framework leveraging a conditional Wasserstein autoencoder(c-WAE)to enable the data-efficient design.By encoding PRs as conditional variables,the PSAL framework reveals exceptional synergistic effects across diverse PRs,significantly outperforming single-process approaches.The process-aware latent representation facilitates the efficient exploration of potential compositions across multi-PRs simultaneously.Through iterative active learning cycles integrating machine learning predictions with experimental validations,ultimate tensile strength is greatly improved:459.8MPa for gravity casting with T6 heat treatment within three iterations and 220.5MPa for gravity casting with hot extrusion in a single iteration.This framework handles sparse datasets effectively,capturing complex processcomposition-property relationships and establishing a new paradigm for accelerated multi-objective material design.
基金funded by the CCOUC field research fundthe Chow Tai Fook Charitable Foundation+1 种基金the I-CARE Programme (The Chinese University of Hong Kong)Wu Zhi Qiao Charitable Foundation
文摘Remote,rural ethnic-minority communities face greater disaster-related public health risks due to their lack of resources and limited access to health care.The Ethnic Minority Health Project(EMHP) was initiated in 2009 to work with remote,disaster-prone ethnic-minority villages that live in extreme poverty.One of the project's aims is to develop and evaluate bottom-up health risk reduction efforts in emergency and disaster risk management(HealthEDRM).This article shares project updates and describes field intervention results from the Yi ethnic community of Hongyan village in China's Sichuan Province,an area that experiences recurrent floods.It was found that 64% of the village respondents had never considered any form of disaster preparation,even with the recurrent flood risks.Health intervention participants showed sustained knowledge retention and were nine times more likely to know the correct composition of oral rehydration solution(ORS) after the intervention.Participants also retained the improved knowledge on ORS and disaster preparedness kit ownership12 months after the intervention.
基金Wu Zhi Qiao Foundation for all their supportfunded by the CCOUC Disaster and Medical Research Fund+5 种基金the School of Public Health and Primary Care Research Fundthe Wu Zhi Qiao Charitable Foundationthe Lee Hysan FoundationIáCAREThe Chinese University of Hong KongJockey Club Disaster Preparedness and Response Institute
文摘Ma'an Qiao Village, a Dai and Yi ethnic minority-based community in Sichuan Province, China sustained complete infrastructure devastation during the 2008 Panzhihua earthquake. Health emergency and disaster risk management(Health-EDRM) education intervention programs were implemented in 2010 and 2011. This serial cross-sectional survey study aimed to examine the immediate and long-term impacts of the Health-EDRM interventions in this remote rural community. The findings demonstrate knowledge improvement in areas of water and sanitation, food and nutrition, and disaster preparedness immediately after the Health-EDRM education interventions. Temporal stability of knowledge retention was observed in household hygiene and waste management and smoking beliefs in 2018, 7 years after the interventions.Other important findings include knowledge uptake pattern differences of oral rehydration solution(ORS) between earthquake-prone and flood-prone communities. Usage of Internet and mobile technology for accessing disaster-related information was found to be independent of gender and income. Overall, this study demonstrated the knowledge improvement through Health-EDRM education interventions in a remote rural community. Promoting behavioral changes through interventions to raise awareness has the potential to reduce health risks in transitional post-disaster settings. Future programs should aim to identify evidence-based practices and explore how technology can support Health-EDRM education among vulnerable subgroups.
