Invasive inflammation and excessive scar formation are the main reasons for the difficulty in repairing nervous tissue after spinal cord injury.Microglia and astrocytes play key roles in the spinal cord injury micro-e...Invasive inflammation and excessive scar formation are the main reasons for the difficulty in repairing nervous tissue after spinal cord injury.Microglia and astrocytes play key roles in the spinal cord injury micro-environment and share a close interaction.However,the mechanisms involved remain unclear.In this study,we found that after spinal cord injury,resting microglia(M0)were polarized into pro-inflammatory phenotypes(MG1 and MG3),while resting astrocytes were polarized into reactive and scar-forming phenotypes.The expression of growth arrest-specific 6(Gas6)and its receptor Axl were significantly down-regulated in microglia and astrocytes after spinal cord injury.In vitro experiments showed that Gas6 had negative effects on the polarization of reactive astrocytes and pro-inflammatory microglia,and even inhibited the cross-regulation between them.We further demonstrated that Gas6 can inhibit the polarization of reactive astrocytes by suppressing the activation of the Yes-associated protein signaling pathway.This,in turn,inhibited the polarization of pro-inflammatory microglia by suppressing the activation of the nuclear factor-κB/p65 and Janus kinase/signal transducer and activator of transcription signaling pathways.In vivo experiments showed that Gas6 inhibited the polarization of pro-inflammatory microglia and reactive astrocytes in the injured spinal cord,thereby promoting tissue repair and motor function recovery.Overall,Gas6 may play a role in the treatment of spinal cord injury.It can inhibit the inflammatory pathway of microglia and polarization of astrocytes,attenuate the interaction between microglia and astrocytes in the inflammatory microenvironment,and thereby alleviate local inflammation and reduce scar formation in the spinal cord.展开更多
Background: The protein encoded by ring finger protein 157 (RNF157) is known to function as an E3 ubiquitinligase. However, whether the level of RNF157 expression in breast cancer correlates with prognosis and immune ...Background: The protein encoded by ring finger protein 157 (RNF157) is known to function as an E3 ubiquitinligase. However, whether the level of RNF157 expression in breast cancer correlates with prognosis and immune cellinfiltration among breast cancer patients remains to be further explored. Methods: In this study, publicly availabledatasets were used for evaluating RNF157 expression in different tumors compared with normal samples. Severalindependent datasets were screened for investigating the relationship between RNF157 and breast cancer survival,different mutation profiles, and tumor immune cell infiltration. We conducted a pathway enrichment analysis toidentify signaling pathways associated with RNF157. Results: Analysis of public and online databases revealed thatRNF157 expression markedly decreased in breast cancer tissue samples compared to non-carcinoma counterparts.Consistently, immunohistochemistry assays also demonstrated this RNF157 down-regulation in breast cancer samples.RNF157 up-regulation could predict the improved survival of breast cancer cases. Further, different RNF157expression level groups exhibited different mutational profiles. Pathway enrichment profiling of RNF157-related genessuggested its possible involvement in regulating breast cancer via the mitogen-activated protein kinase (MAPK)pathway. RNA sequencing (RNA-seq) data and genomic enrichment analysis showed that RNF157 downregulatedseveral genes positively associated with the MAPK signaling pathway. We also explored RNF157 expression andimmune cell infiltration in breast cancer and found that RNF157 mRNA levels were negatively related to non-Timmune cell infiltration. Conclusion: According to our work, RNF157 may be a promising diagnostic biomarker andtherapeutic target for breast cancer.展开更多
A large aspect ratio vibration reducing tool holder based on passive damping vibration reduction technology is designed to solve the vibration problem that occurs in deep hole machining of vertical lathes.A dynamic mo...A large aspect ratio vibration reducing tool holder based on passive damping vibration reduction technology is designed to solve the vibration problem that occurs in deep hole machining of vertical lathes.A dynamic model of passive damping vibration reduction tool holder was established,and the optimal damping ratio,optimal frequency ratio,and maximum relative amplitude were derived.Modal analysis of the passive damping vibrationreduction tool holder was conducted using software.The results showed that the maximum response amplitude of the passive damping vibration reduction tool holder decreased significantly compared to the original one.展开更多
The extrusion deformation process of L-shaped aluminum profiles was numerically simulated using the finite element program Deform-3D.The simulation findings revealed that the deformation of the profiles was mostly cau...The extrusion deformation process of L-shaped aluminum profiles was numerically simulated using the finite element program Deform-3D.The simulation findings revealed that the deformation of the profiles was mostly caused by unequal material flow velocity,which resulted in the profiles bending.Determine the impact of extrusion parameters on the bending deformation of the profile after studying various parameters that may affect the material flow mode(hole position,extrusion speed).展开更多
This paper takes the boring head of 20 roll mill as the research object,optimizes the vibration inside the boring head through a differential damping structure,and then conducts the 3 d model inside the boring head th...This paper takes the boring head of 20 roll mill as the research object,optimizes the vibration inside the boring head through a differential damping structure,and then conducts the 3 d model inside the boring head through SolidWorks,and checks the interference of the boring head model.Finally,Ansys workbench finite element analysis software is used to analyze and verify the vibration damping characteristics of the differential damping structure.展开更多
To promote the utilization of renewable energy,such as photovoltaics,this paper proposes an optimal flexibility dispatch method for demand-side resources(DSR)based on the Stackelberg game theory.First,the concept of t...To promote the utilization of renewable energy,such as photovoltaics,this paper proposes an optimal flexibility dispatch method for demand-side resources(DSR)based on the Stackelberg game theory.First,the concept of the generalized DSR is analyzed and flexibility models for various DSR are constructed.Second,owing to the characteristics of small capacity but large-scale,an outer approximation is proposed to describe the aggregate flexibility of DSR.Then,the optimal flexibility dispatch model of DSR based on the Stackelberg game is established and a decentralized solution algorithm is designed to obtain the Stackelberg equilibrium.Finally,the actual data are utilized for the case study and the results show that,compared to the traditional centralized optimization method,the proposed optimal flexibility dispatch method can not only reduce the net load variability of the DSR aggregator but is beneficial for all DSR owners,which is more suitable for practical applications.展开更多
Background:Cardiopulmonary resuscitation(CPR)strategies in COVID-19 patients differ from those in patients suffering from cardiogenic cardiac arrest.During CPR,both healthcare and non-healthcare workers who provide re...Background:Cardiopulmonary resuscitation(CPR)strategies in COVID-19 patients differ from those in patients suffering from cardiogenic cardiac arrest.During CPR,both healthcare and non-healthcare workers who provide resuscitation are at risk of infection.The Working Group for Expert Consensus on Prevention and Cardiopulmonary Resuscitation for Cardiac Arrest in COVID-19 has developed this Chinese Expert Consensus to guide clinical practice of CPR in COVID-19 patients.Main recommendations:1)A medical team should be assigned to evaluate severe and critical COVID-19 for early monitoring of cardiac-arrest warning signs.2)Psychological counseling and treatment are highly recommended,since sympathetic and vagal abnormalities induced by psychological stress from the COVID-19 pandemic can induce cardiac arrest.3)Healthcare workers should wear personal protective equipment(PPE).4)Mouth-to-mouth ventilation should be avoided on patients suspected of having or diagnosed with COVID-19.5)Hands-only chest compression and mechanical chest compression are recommended.6)Tracheal-intubation procedures should be optimized and tracheal-intubation strategies should be implemented early.7)CPR should be provided for 20-30 min.8)Various factors should be taken into consideration such as the interests of patients and family members,ethics,transmission risks,and laws and regulations governing infectious disease control.Changes in management:The following changes or modifications to CPR strategy in COVID-19 patients are proposed:1)Healthcare workers should wear PPE.2)Hands-only chest compression and mechanical chest compression can be implemented to reduce or avoid the spread of viruses by aerosols.3)Both the benefits to patients and the risk of infection should be considered.4)Hhealthcare workers should be fully aware of and trained in CPR strategies and procedures specifically for patients with COVID-19.展开更多
After the construction of cascade reservoirs in the upper reaches of the Three Gorges Reservoir(TGR),the sediment load outflow of the upper Yangtze River Basin(YRB)has been significantly altered,decreasing from 491.8 ...After the construction of cascade reservoirs in the upper reaches of the Three Gorges Reservoir(TGR),the sediment load outflow of the upper Yangtze River Basin(YRB)has been significantly altered,decreasing from 491.8 Mt/yr(1956–2002)to 36.1 Mt/yr(2003–2017)at Yichang station.This has widely affected river hydrology,suspended sediment grain size distribution,and channel morphology.This study analyzed hydrological variations in water discharge and sediment load of the upper YRB over the past 62 years(1956–2017)by employing a double mass curve.The variations in the source areas of sediment yielding for the upper YRB were quantified,and field measurement data of the cross-channel profile were collected to investigate the sedimentation process in the TGR from 2003 to 2017.More than 90%of the sediment load reduction in the upper YRB may be explained by human activities.The Jinshajiang River was no longer the largest sediment source area for the Zhutuo station(accounting for 5.23%)in the 2013–2017 time span,and the sediment rating rates for the inflow and outflow of the TGR shifted to negatively correlated.A longitudinal fining trend was revealed in the suspended sediment size.Still,the mean median grain size of suspended sediment in the TGR had an increasing trend in the 2013–2017 period.This result may be closely related to sediment regulation in reservoirs and incoming sediment load reduction.Sedimentation in the TGR decreased sharply from 299.8 Mt/yr in 2003–2012 to 47.2 Mt/yr in 2013–2017,but the sedimentation rate of the TGR remained at>80%annually.Moreover,some cross sections in the fluctuating backwater zone experienced scouring.展开更多
In the present research,the gas-assisted laser(GAL)and water-jet guided laser(WGL)processing technologies were applied to machine the ultrathin kerf in the wrought Ti-6Al-4V alloy.The microstructure,microhardness,and ...In the present research,the gas-assisted laser(GAL)and water-jet guided laser(WGL)processing technologies were applied to machine the ultrathin kerf in the wrought Ti-6Al-4V alloy.The microstructure,microhardness,and wear properties of the superficial layer were investigated.The results reveal that the GAL processing could machine the kerf with a high depth-to-width ratio of 12–15,but the increased processing times enhance the depth little.Due to the oxygen entrainment and relatively low heat and mass transferring efficiency,the assisted gas promotes the formation of a scaled recast layer containingβ-Ti phase and oxides,which increases the roughness to 20μm.The WGL processed kerf has a low depth-to-width ratio with a value of 1.9–2.5 and the depth could be increased by increasing the WGL processing times.With the assistance of the water jet,the remelted debris and heat could be eliminated immediately,which restrains the formation of the recast layer and heat-affected zone.The ultrathin oxide outer layer with hundreds of nanometers and ultrafineα-Ti grain inner layer are formed on the surface,which decreases the roughness to 12μm.Compared with the as-received Ti-6Al-4V alloy,the microhardness of GAL processed kerf surface is increased to 382.8 HV accompanied by residual tensile stress,while the microhardness of WGL processed kerf surface is increased to 481.6 HV accompanying with residual compressive stress.In addition,the GAL processing increases the wear rate at room temperature but decreases the wear rate at high temperatures.Comparatively,the WGL processing decreases the wear rate at room and high temperatures,simultaneously.Such wear behaviors could be ascribed to their different superficial microstructures and phase constituents.展开更多
Ag-Cu bimetallic nanoalloy,integrating the advantages of reducing migration and cost of nano-Ag and alleviating oxidation of nano-Cu,is a prospective bonding material for power electronic packaging.The Ag-coated Cu na...Ag-Cu bimetallic nanoalloy,integrating the advantages of reducing migration and cost of nano-Ag and alleviating oxidation of nano-Cu,is a prospective bonding material for power electronic packaging.The Ag-coated Cu nanoparticles(Cu@Ag NPs)paste can execute bonding with high quality at 250℃,and the achieved supersaturated Ag-Cu nanoalloy joint with ultrahigh shear strength(152 MPa)dramatically exceeds most nano-paste joints.The interstitial solid solutions with atomic-level metallurgical bonds at the interface dominantly promoted the shear strength.Besides,the numerous ultrafine nanograin,high proportion of low angle grain boundaries(7.44%)without deformation,and the Cu nanoprecipitates in the joint would improve subordinately.Furthermore,the high content(16.8%)of∑3 twin boundaries would contribute to the electrical and thermal conductivity.Thus,the multiple strengthening mechanisms with the solid solution,the second precipitated phase,and ultrafine nanograin can dramatically enhance shear strength and electro-thermal conductivity of joints for high-temperature device packaging.展开更多
基金supported by the National Natural Science Foundation of China, Nos.81971151 (to YW), 82102528 (to XL), 82102583 (to LW)the Natural Science Foundation of Guangdong Province, China, Nos.2020A1515010265 (to YW), 2020A1515110679 (to XL), and 2021A1515010358 (to XL)
文摘Invasive inflammation and excessive scar formation are the main reasons for the difficulty in repairing nervous tissue after spinal cord injury.Microglia and astrocytes play key roles in the spinal cord injury micro-environment and share a close interaction.However,the mechanisms involved remain unclear.In this study,we found that after spinal cord injury,resting microglia(M0)were polarized into pro-inflammatory phenotypes(MG1 and MG3),while resting astrocytes were polarized into reactive and scar-forming phenotypes.The expression of growth arrest-specific 6(Gas6)and its receptor Axl were significantly down-regulated in microglia and astrocytes after spinal cord injury.In vitro experiments showed that Gas6 had negative effects on the polarization of reactive astrocytes and pro-inflammatory microglia,and even inhibited the cross-regulation between them.We further demonstrated that Gas6 can inhibit the polarization of reactive astrocytes by suppressing the activation of the Yes-associated protein signaling pathway.This,in turn,inhibited the polarization of pro-inflammatory microglia by suppressing the activation of the nuclear factor-κB/p65 and Janus kinase/signal transducer and activator of transcription signaling pathways.In vivo experiments showed that Gas6 inhibited the polarization of pro-inflammatory microglia and reactive astrocytes in the injured spinal cord,thereby promoting tissue repair and motor function recovery.Overall,Gas6 may play a role in the treatment of spinal cord injury.It can inhibit the inflammatory pathway of microglia and polarization of astrocytes,attenuate the interaction between microglia and astrocytes in the inflammatory microenvironment,and thereby alleviate local inflammation and reduce scar formation in the spinal cord.
基金funded by the Innovation Team Project of Hainan Natural Science Foundation(820CXTD446)the Technology Program of Qingyuan(No.2022KJJH027 to Linhai Li).
文摘Background: The protein encoded by ring finger protein 157 (RNF157) is known to function as an E3 ubiquitinligase. However, whether the level of RNF157 expression in breast cancer correlates with prognosis and immune cellinfiltration among breast cancer patients remains to be further explored. Methods: In this study, publicly availabledatasets were used for evaluating RNF157 expression in different tumors compared with normal samples. Severalindependent datasets were screened for investigating the relationship between RNF157 and breast cancer survival,different mutation profiles, and tumor immune cell infiltration. We conducted a pathway enrichment analysis toidentify signaling pathways associated with RNF157. Results: Analysis of public and online databases revealed thatRNF157 expression markedly decreased in breast cancer tissue samples compared to non-carcinoma counterparts.Consistently, immunohistochemistry assays also demonstrated this RNF157 down-regulation in breast cancer samples.RNF157 up-regulation could predict the improved survival of breast cancer cases. Further, different RNF157expression level groups exhibited different mutational profiles. Pathway enrichment profiling of RNF157-related genessuggested its possible involvement in regulating breast cancer via the mitogen-activated protein kinase (MAPK)pathway. RNA sequencing (RNA-seq) data and genomic enrichment analysis showed that RNF157 downregulatedseveral genes positively associated with the MAPK signaling pathway. We also explored RNF157 expression andimmune cell infiltration in breast cancer and found that RNF157 mRNA levels were negatively related to non-Timmune cell infiltration. Conclusion: According to our work, RNF157 may be a promising diagnostic biomarker andtherapeutic target for breast cancer.
基金Science and Technology Research Project of Liaoning Provincial Department of Education:Research on the Application of Damping and Vibration Reduction Technology in Key Components of Machine Tools(JYTMS20230066)The Fund of Liaoning Provincial Natural Science and Technology Foundation Regional Joint(No.2021-YKLH-08).
文摘A large aspect ratio vibration reducing tool holder based on passive damping vibration reduction technology is designed to solve the vibration problem that occurs in deep hole machining of vertical lathes.A dynamic model of passive damping vibration reduction tool holder was established,and the optimal damping ratio,optimal frequency ratio,and maximum relative amplitude were derived.Modal analysis of the passive damping vibrationreduction tool holder was conducted using software.The results showed that the maximum response amplitude of the passive damping vibration reduction tool holder decreased significantly compared to the original one.
基金the Natural Science Foundation of Liaoning(Grant:2021-YKLH-032021-YKLH-04)The 2023 Key scientific research project of Yingkou Institute of Technology(Grant:ZDIL202302).
文摘The extrusion deformation process of L-shaped aluminum profiles was numerically simulated using the finite element program Deform-3D.The simulation findings revealed that the deformation of the profiles was mostly caused by unequal material flow velocity,which resulted in the profiles bending.Determine the impact of extrusion parameters on the bending deformation of the profile after studying various parameters that may affect the material flow mode(hole position,extrusion speed).
基金2022 Liaoning Provincial Natural Science Foundation Plan(Yingkou Joint Fund),New Style Design and Optimization of Bore Head Drive Structure(Fund No.:2022-YKLH-17)In 2023,the key scientific research project of Yingkou Institute of Technology is the Design and Optimization of Smoke Drainage Pipe for New Mining Truck(Fund No.:ZDIL202306)2021 Natural Science Foundation ofLiaoning Province(Yingkou Joint Fund)Research on Dynamic Characteristics of Damped Vertical Shack(Fund No.:2021-YKLH-08).
文摘This paper takes the boring head of 20 roll mill as the research object,optimizes the vibration inside the boring head through a differential damping structure,and then conducts the 3 d model inside the boring head through SolidWorks,and checks the interference of the boring head model.Finally,Ansys workbench finite element analysis software is used to analyze and verify the vibration damping characteristics of the differential damping structure.
基金supported by Science and Technology Project of State Grid Hebei Electric Power Company(SGHE0000DKJS2000228)
文摘To promote the utilization of renewable energy,such as photovoltaics,this paper proposes an optimal flexibility dispatch method for demand-side resources(DSR)based on the Stackelberg game theory.First,the concept of the generalized DSR is analyzed and flexibility models for various DSR are constructed.Second,owing to the characteristics of small capacity but large-scale,an outer approximation is proposed to describe the aggregate flexibility of DSR.Then,the optimal flexibility dispatch model of DSR based on the Stackelberg game is established and a decentralized solution algorithm is designed to obtain the Stackelberg equilibrium.Finally,the actual data are utilized for the case study and the results show that,compared to the traditional centralized optimization method,the proposed optimal flexibility dispatch method can not only reduce the net load variability of the DSR aggregator but is beneficial for all DSR owners,which is more suitable for practical applications.
文摘Background:Cardiopulmonary resuscitation(CPR)strategies in COVID-19 patients differ from those in patients suffering from cardiogenic cardiac arrest.During CPR,both healthcare and non-healthcare workers who provide resuscitation are at risk of infection.The Working Group for Expert Consensus on Prevention and Cardiopulmonary Resuscitation for Cardiac Arrest in COVID-19 has developed this Chinese Expert Consensus to guide clinical practice of CPR in COVID-19 patients.Main recommendations:1)A medical team should be assigned to evaluate severe and critical COVID-19 for early monitoring of cardiac-arrest warning signs.2)Psychological counseling and treatment are highly recommended,since sympathetic and vagal abnormalities induced by psychological stress from the COVID-19 pandemic can induce cardiac arrest.3)Healthcare workers should wear personal protective equipment(PPE).4)Mouth-to-mouth ventilation should be avoided on patients suspected of having or diagnosed with COVID-19.5)Hands-only chest compression and mechanical chest compression are recommended.6)Tracheal-intubation procedures should be optimized and tracheal-intubation strategies should be implemented early.7)CPR should be provided for 20-30 min.8)Various factors should be taken into consideration such as the interests of patients and family members,ethics,transmission risks,and laws and regulations governing infectious disease control.Changes in management:The following changes or modifications to CPR strategy in COVID-19 patients are proposed:1)Healthcare workers should wear PPE.2)Hands-only chest compression and mechanical chest compression can be implemented to reduce or avoid the spread of viruses by aerosols.3)Both the benefits to patients and the risk of infection should be considered.4)Hhealthcare workers should be fully aware of and trained in CPR strategies and procedures specifically for patients with COVID-19.
基金funded by the National Natural Science Foundation of China(Grant No.5210090851)the Opening Fund of State Key Laboratory of Water Simulation and Safety,Tianjin University(No.HESS-1720)the Special funded project for basic scientific research business expenses of central public welfare scientific research institutes(No.TKS 190104).
文摘After the construction of cascade reservoirs in the upper reaches of the Three Gorges Reservoir(TGR),the sediment load outflow of the upper Yangtze River Basin(YRB)has been significantly altered,decreasing from 491.8 Mt/yr(1956–2002)to 36.1 Mt/yr(2003–2017)at Yichang station.This has widely affected river hydrology,suspended sediment grain size distribution,and channel morphology.This study analyzed hydrological variations in water discharge and sediment load of the upper YRB over the past 62 years(1956–2017)by employing a double mass curve.The variations in the source areas of sediment yielding for the upper YRB were quantified,and field measurement data of the cross-channel profile were collected to investigate the sedimentation process in the TGR from 2003 to 2017.More than 90%of the sediment load reduction in the upper YRB may be explained by human activities.The Jinshajiang River was no longer the largest sediment source area for the Zhutuo station(accounting for 5.23%)in the 2013–2017 time span,and the sediment rating rates for the inflow and outflow of the TGR shifted to negatively correlated.A longitudinal fining trend was revealed in the suspended sediment size.Still,the mean median grain size of suspended sediment in the TGR had an increasing trend in the 2013–2017 period.This result may be closely related to sediment regulation in reservoirs and incoming sediment load reduction.Sedimentation in the TGR decreased sharply from 299.8 Mt/yr in 2003–2012 to 47.2 Mt/yr in 2013–2017,but the sedimentation rate of the TGR remained at>80%annually.Moreover,some cross sections in the fluctuating backwater zone experienced scouring.
基金the financial support for this research by the National Key Research and Develop-ment Program of China(No.2018YFC1106702)the Natural National Science Foundation of China(NSFC)(No.51805525)+5 种基金the Natural Science Foundation of Zhejiang Province(Nos.LY21E050018,LY18E050027)the Innovation Guidance Foun-dation of Innovation Academy for Light-duty Gas Turbine of Chinese Academy of Sciences(No.CXYJJ20-QN-10)the Zhejiang Basic Public Welfare Research Program(No.LGG20E050009)the Ningbo 2025 Major Science and Technology Project(No.2022Z013)the Guangdong Basic and Applied Basic Research Foundation(Nos.2020A1515011301,2019A1515110067,and 2020A1515110055)the Shenzhen Basic Research Project(Nos.JCYJ20210324120001003,JCYJ20200109144608205,and JCYJ20200109144604020).
文摘In the present research,the gas-assisted laser(GAL)and water-jet guided laser(WGL)processing technologies were applied to machine the ultrathin kerf in the wrought Ti-6Al-4V alloy.The microstructure,microhardness,and wear properties of the superficial layer were investigated.The results reveal that the GAL processing could machine the kerf with a high depth-to-width ratio of 12–15,but the increased processing times enhance the depth little.Due to the oxygen entrainment and relatively low heat and mass transferring efficiency,the assisted gas promotes the formation of a scaled recast layer containingβ-Ti phase and oxides,which increases the roughness to 20μm.The WGL processed kerf has a low depth-to-width ratio with a value of 1.9–2.5 and the depth could be increased by increasing the WGL processing times.With the assistance of the water jet,the remelted debris and heat could be eliminated immediately,which restrains the formation of the recast layer and heat-affected zone.The ultrathin oxide outer layer with hundreds of nanometers and ultrafineα-Ti grain inner layer are formed on the surface,which decreases the roughness to 12μm.Compared with the as-received Ti-6Al-4V alloy,the microhardness of GAL processed kerf surface is increased to 382.8 HV accompanied by residual tensile stress,while the microhardness of WGL processed kerf surface is increased to 481.6 HV accompanying with residual compressive stress.In addition,the GAL processing increases the wear rate at room temperature but decreases the wear rate at high temperatures.Comparatively,the WGL processing decreases the wear rate at room and high temperatures,simultaneously.Such wear behaviors could be ascribed to their different superficial microstructures and phase constituents.
基金This work was financially supported by the National Natu-ral Science Foundation of China(No.NSFC 51775140)A part of the work was also supported by the National Science and Technology Major Project(No.2017-VI-0009-0080)+2 种基金the Guangdong Province key research and development program(No.2019B010935001)the Shenzhen Science and Technology Plan(No.JCYJ20180507183511908)Bureau of Industry and Information Technology of Shenzhen through the Innovation Chain and Industry Chain(No.201806071354163490).
文摘Ag-Cu bimetallic nanoalloy,integrating the advantages of reducing migration and cost of nano-Ag and alleviating oxidation of nano-Cu,is a prospective bonding material for power electronic packaging.The Ag-coated Cu nanoparticles(Cu@Ag NPs)paste can execute bonding with high quality at 250℃,and the achieved supersaturated Ag-Cu nanoalloy joint with ultrahigh shear strength(152 MPa)dramatically exceeds most nano-paste joints.The interstitial solid solutions with atomic-level metallurgical bonds at the interface dominantly promoted the shear strength.Besides,the numerous ultrafine nanograin,high proportion of low angle grain boundaries(7.44%)without deformation,and the Cu nanoprecipitates in the joint would improve subordinately.Furthermore,the high content(16.8%)of∑3 twin boundaries would contribute to the electrical and thermal conductivity.Thus,the multiple strengthening mechanisms with the solid solution,the second precipitated phase,and ultrafine nanograin can dramatically enhance shear strength and electro-thermal conductivity of joints for high-temperature device packaging.
