Extensive efforts have been made to pursue a low-friction state with promising applications in many fields,such as mechanical and biomedical engineering.Among which,the load capacity of the low-friction state has been...Extensive efforts have been made to pursue a low-friction state with promising applications in many fields,such as mechanical and biomedical engineering.Among which,the load capacity of the low-friction state has been considered to be crucial for industrial applications.Here,we report a low friction under ultrahigh contact pressure by building a novel self-assembled fluorinated azobenzene layer on an atomically smooth highly-oriented pyrolytic graphite(HOPG)surface.Sliding friction coefficients could be as low as 0.0005 or even lower under a contact pressure of up to 4 GPa.It demonstrates that the low friction under ultrahigh contact pressure is attributed to molecular fluorination.The fluorination leads to effective and robust lubrication between the tip and the self-assembled layer and enhances tighter rigidity which can reduce the stress concentration in the substrate,which was verified by density functional theory(DFT)and molecular dynamics(MD)simulation.This work provides a new approach to avoid the failure of ultralow friction coefficient under relatively high contact pressure,which has promising potential application value in the future.展开更多
提出了金属 -半导体欧姆接触退化的快速评估方法——温度斜坡快速评价法 ,并建立了自动评估系统 ,用该方法和系统测得的欧姆接触退化激活能 ,和传统方法相比 ,耗时少 ,所需样品少 ,所得结果和传统方法一致 .针对传统 Au Ge Ni/Au欧姆接...提出了金属 -半导体欧姆接触退化的快速评估方法——温度斜坡快速评价法 ,并建立了自动评估系统 ,用该方法和系统测得的欧姆接触退化激活能 ,和传统方法相比 ,耗时少 ,所需样品少 ,所得结果和传统方法一致 .针对传统 Au Ge Ni/Au欧姆接触系统的缺点 ,提出了加 Ti N扩散阻挡层的新型欧姆接触系统 .实验表明新型欧姆接触系统的可靠性远远优于传统 Au Ge Ni/Au欧姆接触系统 .展开更多
The existence of narrow and brittle white etching layers(WELs)on the rail surface is often linked with the formation of rail defects such as squats and studs,which play the key roles in rail surface degradation and tr...The existence of narrow and brittle white etching layers(WELs)on the rail surface is often linked with the formation of rail defects such as squats and studs,which play the key roles in rail surface degradation and tribological performance.In the present study,a systematic investigation on stress/strain distribution and fatigue life of the WEL during wheel-rail rolling contact was conducted based on a numerical model considering the realistic wheel geometry.This is the first study considering the influence of rail materials,loading pressure,frictional condition,WEL geometry(a/b),and slip ratio(Sr)in the practical service conditions at the same time.The results revealed much higher residual stress in WEL than in rail matrix.Stress changes along the rail depth matched with the previously reported microstructure evolutions.The current work revealed that the maximum difference in contact stress between the wheel passages of rail matrix and the WEL region(noted as stress variation)rises with the increase of loading pressure,the value of a/b,and Sr;but drops with the friction coefficient(μ).In addition,a critical length–depth ratio of 5 for a/b has been found.The fatigue parameter,FP,of the WEL decreased quickly with the length–depth ratio when it was less than 5 and then increased slightly when it was larger than 5.This study also revealed that the fatigue life of the WEL was reduced for high strength head hardened(HH)rail compared with standard carbon(SC)rail.展开更多
Perovskite-based photovoltaic materials have been attracting attention for their strikingly improved performance at converting sunlight into electricity.The beneficial and unique optoelectronic characteristics of pero...Perovskite-based photovoltaic materials have been attracting attention for their strikingly improved performance at converting sunlight into electricity.The beneficial and unique optoelectronic characteristics of perovskite structures enable researchers to achieve an incredibly remarkable power conversion efficiency.Flexible hybrid perovskite photovoltaics promise emerging applications in a myriad of optoelectronic and wearable/portable device applications owing to their inherent intriguing physicochemical and photophysical properties which enabled researchers to take forward advanced research in this growing field.Flexible perovskite photovoltaics have attracted significant attention owing to their fascinating material properties with combined merits of high efficiency,light-weight,flexibility,semitransparency,compatibility towards roll-to-roll printing,and large-area mass-scale production.Flexible perovskite-based solar cells comprise of 4 key components that include a flexible substrate,semi-transparent bottom contact electrode,perovskite(light absorber layer)and charge transport(electron/hole)layers and top(usually metal)electrode.Among these components,interfacial layers and contact electrodes play a pivotal role in influencing the overall photovoltaic performance.In this comprehensive review article,we focus on the current developments and latest progress achieved in perovskite photovoltaics concerning the charge selective transport layers/electrodes toward the fabrication of highly stable,efficient flexible devices.As a concluding remark,we briefly summarize the highlights of the review article and make recommendations for future outlook and investigation with perspectives on the perovskite-based optoelectronic functional devices that can be potentially utilized in smart wearable and portable devices.展开更多
基金the support of the National Natural Science Foundation of China(51922058).
文摘Extensive efforts have been made to pursue a low-friction state with promising applications in many fields,such as mechanical and biomedical engineering.Among which,the load capacity of the low-friction state has been considered to be crucial for industrial applications.Here,we report a low friction under ultrahigh contact pressure by building a novel self-assembled fluorinated azobenzene layer on an atomically smooth highly-oriented pyrolytic graphite(HOPG)surface.Sliding friction coefficients could be as low as 0.0005 or even lower under a contact pressure of up to 4 GPa.It demonstrates that the low friction under ultrahigh contact pressure is attributed to molecular fluorination.The fluorination leads to effective and robust lubrication between the tip and the self-assembled layer and enhances tighter rigidity which can reduce the stress concentration in the substrate,which was verified by density functional theory(DFT)and molecular dynamics(MD)simulation.This work provides a new approach to avoid the failure of ultralow friction coefficient under relatively high contact pressure,which has promising potential application value in the future.
文摘提出了金属 -半导体欧姆接触退化的快速评估方法——温度斜坡快速评价法 ,并建立了自动评估系统 ,用该方法和系统测得的欧姆接触退化激活能 ,和传统方法相比 ,耗时少 ,所需样品少 ,所得结果和传统方法一致 .针对传统 Au Ge Ni/Au欧姆接触系统的缺点 ,提出了加 Ti N扩散阻挡层的新型欧姆接触系统 .实验表明新型欧姆接触系统的可靠性远远优于传统 Au Ge Ni/Au欧姆接触系统 .
基金Authors Qinglin LIAN,Xi WANG,and Zhiming LIU would like to acknowledge the National Key R&D Program of China(2016YFB1200501-008)for the financial support.Author Hongtao ZHU would like to acknowledge the support of Australian Research Council Training Centre for Advanced Technologies in Rail Track Infrastructure(ARC ITTC-Rail).
文摘The existence of narrow and brittle white etching layers(WELs)on the rail surface is often linked with the formation of rail defects such as squats and studs,which play the key roles in rail surface degradation and tribological performance.In the present study,a systematic investigation on stress/strain distribution and fatigue life of the WEL during wheel-rail rolling contact was conducted based on a numerical model considering the realistic wheel geometry.This is the first study considering the influence of rail materials,loading pressure,frictional condition,WEL geometry(a/b),and slip ratio(Sr)in the practical service conditions at the same time.The results revealed much higher residual stress in WEL than in rail matrix.Stress changes along the rail depth matched with the previously reported microstructure evolutions.The current work revealed that the maximum difference in contact stress between the wheel passages of rail matrix and the WEL region(noted as stress variation)rises with the increase of loading pressure,the value of a/b,and Sr;but drops with the friction coefficient(μ).In addition,a critical length–depth ratio of 5 for a/b has been found.The fatigue parameter,FP,of the WEL decreased quickly with the length–depth ratio when it was less than 5 and then increased slightly when it was larger than 5.This study also revealed that the fatigue life of the WEL was reduced for high strength head hardened(HH)rail compared with standard carbon(SC)rail.
基金the CSIRO Low Emissions Technologies Program for the support of this studythe financial support from the Australian Research Council(ARC)for the Future Fellowship(FT130101337)+4 种基金QUT core funding(QUT/322120-0301/07)supported by NSF MRI(1428992)U.S.-Egypt Science and Technology(S&T)Joint FundSDBoR R&D ProgramEDA University Center Program(ED18DEN3030025)。
文摘Perovskite-based photovoltaic materials have been attracting attention for their strikingly improved performance at converting sunlight into electricity.The beneficial and unique optoelectronic characteristics of perovskite structures enable researchers to achieve an incredibly remarkable power conversion efficiency.Flexible hybrid perovskite photovoltaics promise emerging applications in a myriad of optoelectronic and wearable/portable device applications owing to their inherent intriguing physicochemical and photophysical properties which enabled researchers to take forward advanced research in this growing field.Flexible perovskite photovoltaics have attracted significant attention owing to their fascinating material properties with combined merits of high efficiency,light-weight,flexibility,semitransparency,compatibility towards roll-to-roll printing,and large-area mass-scale production.Flexible perovskite-based solar cells comprise of 4 key components that include a flexible substrate,semi-transparent bottom contact electrode,perovskite(light absorber layer)and charge transport(electron/hole)layers and top(usually metal)electrode.Among these components,interfacial layers and contact electrodes play a pivotal role in influencing the overall photovoltaic performance.In this comprehensive review article,we focus on the current developments and latest progress achieved in perovskite photovoltaics concerning the charge selective transport layers/electrodes toward the fabrication of highly stable,efficient flexible devices.As a concluding remark,we briefly summarize the highlights of the review article and make recommendations for future outlook and investigation with perspectives on the perovskite-based optoelectronic functional devices that can be potentially utilized in smart wearable and portable devices.
