This paper analyses the effect of surface treatment on fretting fatigue specimen by numerical simulations using Finite Element Analysis.The processed specimen refers to artificially adding a cylindrical pit to its con...This paper analyses the effect of surface treatment on fretting fatigue specimen by numerical simulations using Finite Element Analysis.The processed specimen refers to artificially adding a cylindrical pit to its contact surface.Then,the contact radius between the pad and the specimen is controlled by adjusting the radius of the pit.The stress distribution and slip amplitude of the contact surface under different contact geometries are compared.The critical plane approach is used to predict the crack initiation life and to evaluate the effect of processed specimen on its fretting fatigue performance.Both crack initiation life and angle can be predicted by the critical plane approach.Ruiz parameter is used to consider the effect of contact slip.It is shown that the crack initial position is dependent on the tensile stress.For same type of model,three kinds of critical plane parameters and Ruiz method provide very similar position of crack initiation.Moreover,the improved sample is much safer than the flat-specimen.展开更多
Electrocatalytic urea oxidation reaction(UOR)is regarded as an effective yet challenging approach for the degradation of urea in wastewater into harmless N2 and CO_(2).To overcome the sluggish kinetics,catalytically a...Electrocatalytic urea oxidation reaction(UOR)is regarded as an effective yet challenging approach for the degradation of urea in wastewater into harmless N2 and CO_(2).To overcome the sluggish kinetics,catalytically active sites should be rationally designed to maneuver the multiple key steps of intermediate adsorption and desorption.Herein,we demonstrate that metal-organic frameworks(MOFs)can provide an ideal platform for tailoring binary active sites to facilitate the rate-determining steps,achieving remarkable electrocatalytic activity toward UOR.Specifically,the MOF(namely,NiMn_(0.14)-BDC)based on Ni/Mn sites and terephthalic acid(BDC)ligands exhibits a low voltage of 1.317 V to deliver a current density of 10 mA cm^(-2).As a result,a high turnover frequency(TOF)of 0.15 s^(-1) is achieved at a voltage of 1.4 V,which enables a urea degradation rate of 81.87%in 0.33 M urea solution.The combination of experimental characterization with theoretical calculation reveals that the Ni and Mn sites play synergistic roles in maneuvering the evolution of urea molecules and key reaction intermediates during the UOR,while the binary Ni/Mn sites in MOF offer the tunability for electronic structure and d-band center impacting on the intermediate evolution.This work provides important insights into active site design by leveraging MOF platform and represents a solid step toward highly efficient UOR with MOF-based electrocatalysts.展开更多
基金the National Natural Science Foundation of China(Grant Nos.11372138 and 11572157)the Research Foundation-Flanders(FWO),The Luxembourg National Research Fund(FNR)and Slovenian Research Agency(ARRS)in the framework of the FWO Lead Agency project:G018916N‘Multi-analysis of fretting fatigue using physical and virtual experiments.'The authors would like to acknowledge thefinancial support of the grants from the China Scholarship Council(201806840127)。
文摘This paper analyses the effect of surface treatment on fretting fatigue specimen by numerical simulations using Finite Element Analysis.The processed specimen refers to artificially adding a cylindrical pit to its contact surface.Then,the contact radius between the pad and the specimen is controlled by adjusting the radius of the pit.The stress distribution and slip amplitude of the contact surface under different contact geometries are compared.The critical plane approach is used to predict the crack initiation life and to evaluate the effect of processed specimen on its fretting fatigue performance.Both crack initiation life and angle can be predicted by the critical plane approach.Ruiz parameter is used to consider the effect of contact slip.It is shown that the crack initial position is dependent on the tensile stress.For same type of model,three kinds of critical plane parameters and Ruiz method provide very similar position of crack initiation.Moreover,the improved sample is much safer than the flat-specimen.
基金This work is finically supported by the National Key R&D Program of China(Grant No.2017YFE0120500)the National Natural Science Foundation of China(Grant Nos.51972129,21725102)+3 种基金the Bintuan Science and Technology Program(Grant Nos.2020DB002,2022DB009)the Key Research and Development Program of Hubei(Grant No.2020BAB079)the Science and Technology Innovation Committee Foundation of Shenzhen(Grant No.JCYJ20210324141613032)the Natural Science Foundation of Jiangsu Province of China(BK20211609).
文摘Electrocatalytic urea oxidation reaction(UOR)is regarded as an effective yet challenging approach for the degradation of urea in wastewater into harmless N2 and CO_(2).To overcome the sluggish kinetics,catalytically active sites should be rationally designed to maneuver the multiple key steps of intermediate adsorption and desorption.Herein,we demonstrate that metal-organic frameworks(MOFs)can provide an ideal platform for tailoring binary active sites to facilitate the rate-determining steps,achieving remarkable electrocatalytic activity toward UOR.Specifically,the MOF(namely,NiMn_(0.14)-BDC)based on Ni/Mn sites and terephthalic acid(BDC)ligands exhibits a low voltage of 1.317 V to deliver a current density of 10 mA cm^(-2).As a result,a high turnover frequency(TOF)of 0.15 s^(-1) is achieved at a voltage of 1.4 V,which enables a urea degradation rate of 81.87%in 0.33 M urea solution.The combination of experimental characterization with theoretical calculation reveals that the Ni and Mn sites play synergistic roles in maneuvering the evolution of urea molecules and key reaction intermediates during the UOR,while the binary Ni/Mn sites in MOF offer the tunability for electronic structure and d-band center impacting on the intermediate evolution.This work provides important insights into active site design by leveraging MOF platform and represents a solid step toward highly efficient UOR with MOF-based electrocatalysts.