Welding is a vital component of several industries such as automotive,aerospace,robotics,and construction.Without welding,these industries utilize aluminum alloys for the manufacturing of many components or systems.Ho...Welding is a vital component of several industries such as automotive,aerospace,robotics,and construction.Without welding,these industries utilize aluminum alloys for the manufacturing of many components or systems.However,fusion welding of aluminum alloys is challenging due to several factors,including the presence of non-heat-treatable alloys,porosity,solidification,and liquation of cracks.Many manufacturers adopt conventional in-air friction stir welding(FSW)to weld metallic alloys and dissimilar materials.Many researchers reported the drawbacks of this traditional in-air FSW technique in welding metallic and polymeric materials in general and aluminum alloys and aluminum matrix composites in specific.A number of FSW techniques were developed recently,such as underwater friction stir welding(UFSW),vibrational friction-stir welding(VFSW),and others,for welding of aluminum alloy joints to overcome the issues of welding using conventional FSW.Therefore,the main objective of this review is to summarize the recent trends in FSW process of aluminum alloys and aluminum metal matrix composites(Al MMCs).Also,it discusses the effect of welding parameters of the traditional and state-of-the-art developed FSW techniques on the welding quality and strength of aluminum alloys and Al MMCs.Comparison among the techniques and advantages and limitations of each are considered.The review suggests that VFSW is a viable option for welding aluminum joints due to its energy efficiency,economic cost,and versatile modifications that can be employed based on the application.This review also illustrated that significantly less attention has been paid to FSW of Al-MMCs and considerable attention is demanded to produce qualified joint.展开更多
In this work,molecular dynamics modeling was conducted to study hydrogen(H)-induced plastic deformation and cracking of polycrystalα-Fe.Under cyclic loading,the number of vacancies and the stress intensity increase w...In this work,molecular dynamics modeling was conducted to study hydrogen(H)-induced plastic deformation and cracking of polycrystalα-Fe.Under cyclic loading,the number of vacancies and the stress intensity increase with H atom concentration and the number of loading cycles.However,the effect of cyclic loading on cracking is not as significant as the increment of H concentration.As the H concentration increases,the dislocation generation and emission are enhanced in the{110}<111>slip system,but are inhibited in other slip systems.There is a critical H atom concentration,below which the plastic deformation ofα-Fe is facilitated by H atoms.When the critical H concentration is exceeded,the dislocation emission is inhibited by H atoms at grain boundaries,where the H atoms can pin dislocations,causing piling-up of the dislocations to generate a stress concentration.展开更多
A novel Fe/Co metal organic complex nanosheet modified by 1,4-dicarboxybenzene(BDC),i.e.,FeCo@BDC,was prepared,and highly efficient removal performance for trace lead(Ⅱ)(Pb^(2+))was demonstrated in the neutral aqueou...A novel Fe/Co metal organic complex nanosheet modified by 1,4-dicarboxybenzene(BDC),i.e.,FeCo@BDC,was prepared,and highly efficient removal performance for trace lead(Ⅱ)(Pb^(2+))was demonstrated in the neutral aqueous solutions.The removal rates were higher than 95%and the adsorption was equilibrated in 15 min.The isotherms and kinetics for the adsorption Pb^(2+)by the FeCo@BDC adsorbents followed Langmuir model and pseudo-second-order model,respectively.The maximum adsorption capacity was 220.48 mg g^(-1).The FeCo@BDC adsorbents also own a prominent regeneration performance.The prominent performance of in the removal of trace Pb^(2+)makes FeCo@BDC an ideal candidate as commercial adsorbent materials.展开更多
Based on high specific surface area,high porosity of metal-organic frameworks(MOFs)and excellent vis-ible light response of CdS,the CdS/Cd-MOF nanocomposites were constructed by in-situ sulfurization to form CdS using...Based on high specific surface area,high porosity of metal-organic frameworks(MOFs)and excellent vis-ible light response of CdS,the CdS/Cd-MOF nanocomposites were constructed by in-situ sulfurization to form CdS using Cd-MOF as precursor and the CdS loading was controlled by the dose of thioac-etamide.Under the irradiation of simulated sunlight,the degradation rate of methylene blue(MB)by 10mg MOF/CdS-6(mass ratio of MOF to thioacetamide is 6:1)was 91.9%in 100min,which was higher than that of pure Cd-MOF(62.3%)and pure CdS(67.5%).This is attributed to the larger specific surface area of the composite catalysts,which provides more active sites.Meanwhile,the loading of CdS obvi-ously broadens the light response range of Cd-MOF and improves the utilization of visible light.The Mott-Schottky model experiment shows that the formed type-Ⅱheterojunction between Cd-MOF and CdS can effectively inhibit the recombination of photogenerated electrons and holes.Meanwhile,the photocurrent intensity of MOF/CdS-6 is 8 times and 2.5 times of that of pure Cd-MOF and CdS.In addi-tion,MOF/CdS-6 showed good photocatalytic performance after five cycles,showing excellent stability and reusability.展开更多
A visible light-active photoelectrocatalyst,ZnFe-layered double oxide(LDO)/cobalt(II,III)oxide(Co_(3)O_(4))composites were obtained by calcining the Co loaded ZnFe-layered double hydroxide(LDH)prepared by a hydrotherm...A visible light-active photoelectrocatalyst,ZnFe-layered double oxide(LDO)/cobalt(II,III)oxide(Co_(3)O_(4))composites were obtained by calcining the Co loaded ZnFe-layered double hydroxide(LDH)prepared by a hydrothermal and microwave hydrothermal method.The morphological studies revealed that the ZnFe-LDO/Co_(3)O_(4) composites exhibited a flower-like structure comprising Co_(3)O_(4) nanowires and ZnFe-LDO nanosheets.Further,when the mass ratio of Co(NO_(3))_(2)·6H_(2)O/LDH was 1:1.8 and the calcination temperature was 550℃,the ZnFe-LDO/Co_(3)O_(4) composite exhibited 93.3%degradation efficiency for methylene blue(MB)at the applied voltage of 1.0 V under visible light after 3 h.Furthermore,the Mott-Schottky model experiments showed that the formation of a p-n heterojunction between ZnFe-LDO and Co_(3)O_(4) could effectively inhibit the recombination of electrons and holes in the photoelectrocatalytic process.Meanwhile,free radical scavenging experiments showed that the active radicals of⋅OH played an important role in the degradation of MB.Therefore,the photoelectrocatalytic effect of ZnFe-LDO/Co_(3)O_(4) provides a simple and effective strategy for the removal of organic pollutants.展开更多
The work combined scanning Kelvin probe force microscopy measurements and finite element modelling to study the diffusion and distribution of hydrogen(H)atoms at metallurgical microphases contained in X52 pipeline ste...The work combined scanning Kelvin probe force microscopy measurements and finite element modelling to study the diffusion and distribution of hydrogen(H)atoms at metallurgical microphases contained in X52 pipeline steel.Results show that the pearlite contained in the steel is more stable than the ferrite during electropolishing,as indicated by the measured topographic profiles and Volta potentials.The hydrogen(H)-charging enhances the electrochemical activity of both pearlite and ferrite,as shown by increased Volta potential and thus the decreased work function.As the H-charging time increases,the Volta potentials of both phases further increase,implying that their activities increase with the H-charging time.The pearlite has a greater Volta potential and thus a lower work function than the ferrite.This is associated with more H atoms accumulating at the pearlite than at the ferrite.The H atom diffusion and accumulation are affected by H diffusivity at phase boundaries,H-trap binding energy and the number of traps in the steel.展开更多
NiFe_(2)O_(4)/polypyrrole(NiFe_(2)O_(4)/PPy)nanocomposites are prepared by a simple surface-initiated polymerization method and demonstrate negative permittivity in the low frequency regions.These nanocomposites also ...NiFe_(2)O_(4)/polypyrrole(NiFe_(2)O_(4)/PPy)nanocomposites are prepared by a simple surface-initiated polymerization method and demonstrate negative permittivity in the low frequency regions.These nanocomposites also exhibit significantly enhanced electromagnetic wave(EMW)absorption property in the high frequency regions.Compared with pure PPy,the enhanced negative permittivity is observed in the NiFe_(2)O_(4)/PPy nanocomposites with a NiFe_(2)O_(4)loading of 5.0,10.0,20.0 and 40.0 wt%,indicating the formation of metal-like electrical conducting network in NiFe_(2)O_(4)/PPy nanocomposites.Moreover,the negative permittivity could be tuned by changing the NiFe_(2)O_(4)loading.The minimum reflection loss(RL)of-40.8 dB is observed in the 40.0 wt%NiFe_(2)O_(4)/PPy composites with a thickness of only 1.9 mm.The effective absorption bandwidth below-10.0 and-20.0 dB reaches 6.08 and 2.08 GHz,respectively.The enhanced EMW absorption performance benefits from the improved independence matching,EMW attenuation capacity,and synergistic effects of conduction loss,dielectric loss(interfacial and dipole polarizations)and magnetic loss(exchange and natural resonances).This research work provides a guidance for the fabrication of nanocomposites with an excellent EMW absorption.展开更多
基金United Arab Emirates University (UAEU), Al-Ain, UAE, and Sultan Qaboos University (SQU), Muscat, Sultanate of Oman, for providing research support through a collaborative research project (UAEU: 31N270)。
文摘Welding is a vital component of several industries such as automotive,aerospace,robotics,and construction.Without welding,these industries utilize aluminum alloys for the manufacturing of many components or systems.However,fusion welding of aluminum alloys is challenging due to several factors,including the presence of non-heat-treatable alloys,porosity,solidification,and liquation of cracks.Many manufacturers adopt conventional in-air friction stir welding(FSW)to weld metallic alloys and dissimilar materials.Many researchers reported the drawbacks of this traditional in-air FSW technique in welding metallic and polymeric materials in general and aluminum alloys and aluminum matrix composites in specific.A number of FSW techniques were developed recently,such as underwater friction stir welding(UFSW),vibrational friction-stir welding(VFSW),and others,for welding of aluminum alloy joints to overcome the issues of welding using conventional FSW.Therefore,the main objective of this review is to summarize the recent trends in FSW process of aluminum alloys and aluminum metal matrix composites(Al MMCs).Also,it discusses the effect of welding parameters of the traditional and state-of-the-art developed FSW techniques on the welding quality and strength of aluminum alloys and Al MMCs.Comparison among the techniques and advantages and limitations of each are considered.The review suggests that VFSW is a viable option for welding aluminum joints due to its energy efficiency,economic cost,and versatile modifications that can be employed based on the application.This review also illustrated that significantly less attention has been paid to FSW of Al-MMCs and considerable attention is demanded to produce qualified joint.
基金supported by National Natural Science Foundation of China(Nos.52374072,No.52004323)CNPC Innovation Foundation(No.2022DQ02-0502)+1 种基金Natural Science Foundation of Shandong Province(Nos.ZR2020ME094,ZR2019BEE006 and ZR2019MEE108)the Senior Foreign Expert Project Fund(No.G2022152003L).
文摘In this work,molecular dynamics modeling was conducted to study hydrogen(H)-induced plastic deformation and cracking of polycrystalα-Fe.Under cyclic loading,the number of vacancies and the stress intensity increase with H atom concentration and the number of loading cycles.However,the effect of cyclic loading on cracking is not as significant as the increment of H concentration.As the H concentration increases,the dislocation generation and emission are enhanced in the{110}<111>slip system,but are inhibited in other slip systems.There is a critical H atom concentration,below which the plastic deformation ofα-Fe is facilitated by H atoms.When the critical H concentration is exceeded,the dislocation emission is inhibited by H atoms at grain boundaries,where the H atoms can pin dislocations,causing piling-up of the dislocations to generate a stress concentration.
文摘A novel Fe/Co metal organic complex nanosheet modified by 1,4-dicarboxybenzene(BDC),i.e.,FeCo@BDC,was prepared,and highly efficient removal performance for trace lead(Ⅱ)(Pb^(2+))was demonstrated in the neutral aqueous solutions.The removal rates were higher than 95%and the adsorption was equilibrated in 15 min.The isotherms and kinetics for the adsorption Pb^(2+)by the FeCo@BDC adsorbents followed Langmuir model and pseudo-second-order model,respectively.The maximum adsorption capacity was 220.48 mg g^(-1).The FeCo@BDC adsorbents also own a prominent regeneration performance.The prominent performance of in the removal of trace Pb^(2+)makes FeCo@BDC an ideal candidate as commercial adsorbent materials.
文摘Based on high specific surface area,high porosity of metal-organic frameworks(MOFs)and excellent vis-ible light response of CdS,the CdS/Cd-MOF nanocomposites were constructed by in-situ sulfurization to form CdS using Cd-MOF as precursor and the CdS loading was controlled by the dose of thioac-etamide.Under the irradiation of simulated sunlight,the degradation rate of methylene blue(MB)by 10mg MOF/CdS-6(mass ratio of MOF to thioacetamide is 6:1)was 91.9%in 100min,which was higher than that of pure Cd-MOF(62.3%)and pure CdS(67.5%).This is attributed to the larger specific surface area of the composite catalysts,which provides more active sites.Meanwhile,the loading of CdS obvi-ously broadens the light response range of Cd-MOF and improves the utilization of visible light.The Mott-Schottky model experiment shows that the formed type-Ⅱheterojunction between Cd-MOF and CdS can effectively inhibit the recombination of photogenerated electrons and holes.Meanwhile,the photocurrent intensity of MOF/CdS-6 is 8 times and 2.5 times of that of pure Cd-MOF and CdS.In addi-tion,MOF/CdS-6 showed good photocatalytic performance after five cycles,showing excellent stability and reusability.
文摘A visible light-active photoelectrocatalyst,ZnFe-layered double oxide(LDO)/cobalt(II,III)oxide(Co_(3)O_(4))composites were obtained by calcining the Co loaded ZnFe-layered double hydroxide(LDH)prepared by a hydrothermal and microwave hydrothermal method.The morphological studies revealed that the ZnFe-LDO/Co_(3)O_(4) composites exhibited a flower-like structure comprising Co_(3)O_(4) nanowires and ZnFe-LDO nanosheets.Further,when the mass ratio of Co(NO_(3))_(2)·6H_(2)O/LDH was 1:1.8 and the calcination temperature was 550℃,the ZnFe-LDO/Co_(3)O_(4) composite exhibited 93.3%degradation efficiency for methylene blue(MB)at the applied voltage of 1.0 V under visible light after 3 h.Furthermore,the Mott-Schottky model experiments showed that the formation of a p-n heterojunction between ZnFe-LDO and Co_(3)O_(4) could effectively inhibit the recombination of electrons and holes in the photoelectrocatalytic process.Meanwhile,free radical scavenging experiments showed that the active radicals of⋅OH played an important role in the degradation of MB.Therefore,the photoelectrocatalytic effect of ZnFe-LDO/Co_(3)O_(4) provides a simple and effective strategy for the removal of organic pollutants.
基金supported by Mitacs,InnoTech Alberta and Natural Science and Engineering Research Council(NSERC),CanadaStudy of hydrogen atom distribution at metallurgical microphases of X52 steel by scanning Kelvin probe force microscopy and finite element modelling.
文摘The work combined scanning Kelvin probe force microscopy measurements and finite element modelling to study the diffusion and distribution of hydrogen(H)atoms at metallurgical microphases contained in X52 pipeline steel.Results show that the pearlite contained in the steel is more stable than the ferrite during electropolishing,as indicated by the measured topographic profiles and Volta potentials.The hydrogen(H)-charging enhances the electrochemical activity of both pearlite and ferrite,as shown by increased Volta potential and thus the decreased work function.As the H-charging time increases,the Volta potentials of both phases further increase,implying that their activities increase with the H-charging time.The pearlite has a greater Volta potential and thus a lower work function than the ferrite.This is associated with more H atoms accumulating at the pearlite than at the ferrite.The H atom diffusion and accumulation are affected by H diffusivity at phase boundaries,H-trap binding energy and the number of traps in the steel.
基金supported by the Research Starting Foundation of Shaanxi University of Science and Technology(Program No.2019QNBJ-01)the Research Foundation for Thousand Young Talent Plan of Shaanxi province of China。
文摘NiFe_(2)O_(4)/polypyrrole(NiFe_(2)O_(4)/PPy)nanocomposites are prepared by a simple surface-initiated polymerization method and demonstrate negative permittivity in the low frequency regions.These nanocomposites also exhibit significantly enhanced electromagnetic wave(EMW)absorption property in the high frequency regions.Compared with pure PPy,the enhanced negative permittivity is observed in the NiFe_(2)O_(4)/PPy nanocomposites with a NiFe_(2)O_(4)loading of 5.0,10.0,20.0 and 40.0 wt%,indicating the formation of metal-like electrical conducting network in NiFe_(2)O_(4)/PPy nanocomposites.Moreover,the negative permittivity could be tuned by changing the NiFe_(2)O_(4)loading.The minimum reflection loss(RL)of-40.8 dB is observed in the 40.0 wt%NiFe_(2)O_(4)/PPy composites with a thickness of only 1.9 mm.The effective absorption bandwidth below-10.0 and-20.0 dB reaches 6.08 and 2.08 GHz,respectively.The enhanced EMW absorption performance benefits from the improved independence matching,EMW attenuation capacity,and synergistic effects of conduction loss,dielectric loss(interfacial and dipole polarizations)and magnetic loss(exchange and natural resonances).This research work provides a guidance for the fabrication of nanocomposites with an excellent EMW absorption.
