This study,a core-shell CoPt@C assembled hierarchical catalyst(named CoPt@C)was prepared using a unique CH_(4)deposition strategy for highly efficient overall water splitting.CoPt@C is composed of dense CoPt@C core-sh...This study,a core-shell CoPt@C assembled hierarchical catalyst(named CoPt@C)was prepared using a unique CH_(4)deposition strategy for highly efficient overall water splitting.CoPt@C is composed of dense CoPt@C core-shell nanoparticles(NPs)and a minor proportion of curled CoPt@nanotubes(CoPt@CNTs).Moreover,by adjusting the CH_(4)deposition time,the carbon shell thickness can be effectively regulated.Benefiting from the synergistic interaction between CoPt alloy and carbon shell,coupled with the high conductivity of the carbon shell,the overpotential of hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)for CoPt@C is 15 and 120 mV at 10 mA cm^(-2).In addition,CoPt@C requires only 1.58 V to achieve 10 mA cm^(-2)for overall water splitting and maintains excellent stability over 80 h of continuous electrolysis.Density functional theory(DFT)calculations suggest that electrons transfer from the CoPt alloy NPs to the carbon shell,rendering the carbon shell electron-rich.Additionally,the hydrogen adsorption energy(ΔG*H)and the rate-determining step(ΔG*OOH)on CoPt@C are only-0.22 and 1.9 eV,respectively.展开更多
Nickel-based superalloys fabricated by wire-arc directed energy deposition,also known as wire arc ad-ditive manufacturing(WAAM),usually exhibit inherent columnar grain structure,micro-segregation,and rough surface.A n...Nickel-based superalloys fabricated by wire-arc directed energy deposition,also known as wire arc ad-ditive manufacturing(WAAM),usually exhibit inherent columnar grain structure,micro-segregation,and rough surface.A novel deposition strategy,integrating an oscillating arc and forced interlayer cooling,was developed in WAAM of Inconel(IN)718 components.The influences of deposition modes on geometrical characteristics,defects,microstructure,and mechanical properties were systematically evaluated.The re-sults showed that the oscillation mode,compared to the standard parallel mode,can effectively promote the molten pool’s spread and wettability,as well as prevent overflow,finally resulting in high geometric accuracy.In addition,the voids-like defects were reduced by 77.78%,while most common crack defects were not observed.Meanwhile,the forced interlayer cooling process further increased the cooling rate,leading to the reduction of the element segregation as well as the proportion of long-chain-like Laves phases.After a short-process modified heat treatment,the anisotropic mechanical behaviors of the as-deposited samples were almost eliminated.Compared with the parallel mode samples,the yield strength and ultimate tensile strength of the oscillation path samples increased by 5.75%and 9.25%,respectively,while the elongation increased significantly by 51.20%.This signifies that their strength and ductility were simultaneously improved.The strengthening mechanisms were further analyzed based on the distribution of the strengthening phases,as well as the residual Laves phases and porosity.展开更多
Laser Directed Energy Deposition (LDED) marks a critical advance in intelligent manufacturing, enabling efficient near-net shape production of metal parts. This method is especially beneficial for aerospace and defens...Laser Directed Energy Deposition (LDED) marks a critical advance in intelligent manufacturing, enabling efficient near-net shape production of metal parts. This method is especially beneficial for aerospace and defense applications that require high precision. However, issues such as deformation and heat accumulation during production still affect the quality of the final products, necessitating further optimization of process parameters. This paper studies the effects of three deposition strategies on 316L stainless steel parts using LDED. The three strategies based on unidirectional scanning (US), zigzag scanning (ZS), and square spiral scanning (SS) are investigated by solid samples and samples with a central hole. The surface smoothness, defects, and mechanical properties of 316L samples manufactured with the above strategies are discussed by means of surface topography tests and metallographic characterization. Experimental results indicate that the zigzag scanning strategy yielded better results for solid components, and the square spiral scanning strategy is suitable for samples with a central hole.展开更多
基金financially supported by the Natural Science Foundation of National(No.NSFC22208179)the Key Laboratory of Laser Technology and Optoelectronic Functional Materials of Hainan Province(No.2024LTOM05)
文摘This study,a core-shell CoPt@C assembled hierarchical catalyst(named CoPt@C)was prepared using a unique CH_(4)deposition strategy for highly efficient overall water splitting.CoPt@C is composed of dense CoPt@C core-shell nanoparticles(NPs)and a minor proportion of curled CoPt@nanotubes(CoPt@CNTs).Moreover,by adjusting the CH_(4)deposition time,the carbon shell thickness can be effectively regulated.Benefiting from the synergistic interaction between CoPt alloy and carbon shell,coupled with the high conductivity of the carbon shell,the overpotential of hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)for CoPt@C is 15 and 120 mV at 10 mA cm^(-2).In addition,CoPt@C requires only 1.58 V to achieve 10 mA cm^(-2)for overall water splitting and maintains excellent stability over 80 h of continuous electrolysis.Density functional theory(DFT)calculations suggest that electrons transfer from the CoPt alloy NPs to the carbon shell,rendering the carbon shell electron-rich.Additionally,the hydrogen adsorption energy(ΔG*H)and the rate-determining step(ΔG*OOH)on CoPt@C are only-0.22 and 1.9 eV,respectively.
基金financial sup-port from the National Natural Science Foundation of China(Nos.52275374 and 51805415)the Young Elite Scientists Sponsorship Program by CAST:2021QNRC001.
文摘Nickel-based superalloys fabricated by wire-arc directed energy deposition,also known as wire arc ad-ditive manufacturing(WAAM),usually exhibit inherent columnar grain structure,micro-segregation,and rough surface.A novel deposition strategy,integrating an oscillating arc and forced interlayer cooling,was developed in WAAM of Inconel(IN)718 components.The influences of deposition modes on geometrical characteristics,defects,microstructure,and mechanical properties were systematically evaluated.The re-sults showed that the oscillation mode,compared to the standard parallel mode,can effectively promote the molten pool’s spread and wettability,as well as prevent overflow,finally resulting in high geometric accuracy.In addition,the voids-like defects were reduced by 77.78%,while most common crack defects were not observed.Meanwhile,the forced interlayer cooling process further increased the cooling rate,leading to the reduction of the element segregation as well as the proportion of long-chain-like Laves phases.After a short-process modified heat treatment,the anisotropic mechanical behaviors of the as-deposited samples were almost eliminated.Compared with the parallel mode samples,the yield strength and ultimate tensile strength of the oscillation path samples increased by 5.75%and 9.25%,respectively,while the elongation increased significantly by 51.20%.This signifies that their strength and ductility were simultaneously improved.The strengthening mechanisms were further analyzed based on the distribution of the strengthening phases,as well as the residual Laves phases and porosity.
文摘Laser Directed Energy Deposition (LDED) marks a critical advance in intelligent manufacturing, enabling efficient near-net shape production of metal parts. This method is especially beneficial for aerospace and defense applications that require high precision. However, issues such as deformation and heat accumulation during production still affect the quality of the final products, necessitating further optimization of process parameters. This paper studies the effects of three deposition strategies on 316L stainless steel parts using LDED. The three strategies based on unidirectional scanning (US), zigzag scanning (ZS), and square spiral scanning (SS) are investigated by solid samples and samples with a central hole. The surface smoothness, defects, and mechanical properties of 316L samples manufactured with the above strategies are discussed by means of surface topography tests and metallographic characterization. Experimental results indicate that the zigzag scanning strategy yielded better results for solid components, and the square spiral scanning strategy is suitable for samples with a central hole.
