Cobalt-based alloys with different Y2O3 contents were deposited on Q235A-carbon steel using plasma transferred arc (PTA) welding machine. The effect of Y2O3 on the microstructure and wear resistance properties of th...Cobalt-based alloys with different Y2O3 contents were deposited on Q235A-carbon steel using plasma transferred arc (PTA) welding machine. The effect of Y2O3 on the microstructure and wear resistance properties of the cobait-based alloys were investigated using an optical microscope, a scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that a cobalt-based solid solution with a face-centered cubic crystal structure was presented accompanied by the secondary phase M7C3 with a hexagonal crystal structure in the Y2O3-free cobalt-based alloy coating. Several stacking faults exist in the cobalt-based solid solution. The addition of Y2O3 leads to the existence of the Y2O3 phase in the Y2O3-modified coatings. Though stacking fault exists in the Y2O3-modified coatings, its density increases. The addition of Y2O3 can refine the microstructure and can increase the wear resistance properties when its contents are less than or equal to 0.8 wt.%. However, further increase of its contents will lead to the agglomeration of undissolved Y2O3 particles at the γ-Co grain boundary, and will lead to a coarse microstructure and lower wear resistance properties.展开更多
To improve the efficiency of cathodic oxygen reduction reaction(ORR)in zinc-air batteries(ZABs),an adsorption-complexation-calcination method was proposed to generate cobalt-based multicomponent nanoparticles comprisi...To improve the efficiency of cathodic oxygen reduction reaction(ORR)in zinc-air batteries(ZABs),an adsorption-complexation-calcination method was proposed to generate cobalt-based multicomponent nanoparticles comprising Co,Co_(3)O_(4)and CoN,as well as numerous N heteroatoms,on graphene nanosheets(Co/Co_(3)O_(4)/CoN/NG).The Co/Co_(3)O_(4)/CoN nanoparticles with the size of less than 50 nm are homogeneously dispersed on N-doped graphene(NG)substrate,which greatly improve the catalytic behaviors for ORR.The results show that the half-wave potential is as high as 0.80 V vs.RHE and the limiting current density is 4.60 mA·cm^(−2),which are close to those of commercially available platinum/carbon(Pt/C)catalysts.Applying as cathodic catalyst for ZABs,the battery shows large specific capacity and open circuit voltage of 843.0 mAh∙g^(−1) and 1.41 V,respectively.The excellent performance is attributed to the efficient two-dimensional structure with high accessible surface area and the numerous multiple active sites provided by highly scattered Co/Co_(3)O_(4)/CoN particles and doped nitrogen on the carbon matrix.展开更多
The microstructure, substructure, and wear characteristic of cobalt-basedalloy coatings obtained by plasma transferred arc (PTA) process were investigated using opticalmetallurgical microscope, X-ray diffraction (XRD)...The microstructure, substructure, and wear characteristic of cobalt-basedalloy coatings obtained by plasma transferred arc (PTA) process were investigated using opticalmetallurgical microscope, X-ray diffraction (XRD), scanning electron microscope (SEM), transmissionelectron microscope (TEM), and dry sand abrasion tester (DSAT). The aging effect on the structureand wear resistance of the cobalt-based PTA coating was also studied. The results show that theas-welded coating consists of cobalt-based solid solution with face-centered cubic structure andhexagonal (Cr,Fe)_7C_3. There are a lot of stacking faults existing in the cobalt-based solidsolution. After aging at 600 deg C for 60 h, the microstructure becomes coarse, and another carbide(Cr,Fe)_(23)C_6 precipitates. As a result, the wear mass loss of the aged sample is higher than thatof the as-welded sample.展开更多
Conversion of carbon dioxide(CO_(2))into valuable chemicals and renewable fuels via photocatalysis represents an eco-friendly route to achieve the goal of carbon neutralization.Although various types of semiconductor ...Conversion of carbon dioxide(CO_(2))into valuable chemicals and renewable fuels via photocatalysis represents an eco-friendly route to achieve the goal of carbon neutralization.Although various types of semiconductor materials have been intensively explored,some severe issues,such as rapid charge recombination and sluggish redox reaction kinetics,remain.In this regard,cocatalyst modifi cation by trapping charges and boosting surface reactions is one of the most effi cient strategies to improve the effi ciency of semiconductor photocatalysts.This review focuses on recent advances in CO_(2)photoreduction over costeff ective and earth-abundant cobalt(Co)-based cocatalysts,which are competitive candidates of noble metals for practical applications.First,the functions of Co-based cocatalysts for promoting photocatalytic CO_(2)reduction are briefl y discussed.Then,diff erent kinds of Co-based cocatalysts,including cobalt oxides and hydroxides,cobalt nitrides and phosphides,cobalt sulfi des and selenides,Co single-atom,and Co-based metal–organic frameworks(MOFs),are summarized.The underlying mechanisms of these Co-based cocatalysts for facilitating CO_(2)adsorption–activation,boosting charge separation,and modulating intermediate formation are discussed in detail based on experimental characterizations and density functional theory calculations.In addition,the suppression of the competing hydrogen evolution reaction using Co-based cocatalysts to promote the product selectivity of CO_(2)reduction is highlighted in some selected examples.Finally,the challenges and future perspectives on constructing more effi cient Co-based cocatalysts for practical applications are proposed.展开更多
Different kinds of aluminum precursors were obtained from precipitating ammonium bicarbonate, ammonium carbonate, and saturated ammonium bicarbonate, then, boehmite (AlO(OH)), ammonium alumina carbonate hydroxide (AAC...Different kinds of aluminum precursors were obtained from precipitating ammonium bicarbonate, ammonium carbonate, and saturated ammonium bicarbonate, then, boehmite (AlO(OH)), ammonium alumina carbonate hydroxide (AACH) and their mixture were obtained, and then, different kinds of alumina were obtained after calcination. Three catalysts supported on the different alumina were obtained via impregnating cobalt and ruthenium by incipient wetness. The effects of different precipitants on composition of precursors were?studied by XRD, FTIR, and TGA. The property and structure of alumina were studied by XRD and BET. The supported catalysts were studied by characterizations of XRD and H2-TPR, and the catalytic performance for Fischer-Tropsch synthesis (FTS) were evaluated at a fix-bed reactor. The relations among the composition of precursors, the property of alumina and the catalytic performance of supported catalysts were researched thoroughly.展开更多
The hot extrusion die is a key tool for determining the surface quality and dimensional accuracy of extruded products.Because its service process is subject to high temperature,high pressure,and wear,it must be resist...The hot extrusion die is a key tool for determining the surface quality and dimensional accuracy of extruded products.Because its service process is subject to high temperature,high pressure,and wear,it must be resistant to these conditions.In this paper,the high-temperature friction and wear properties of a cobalt(Co)-based alloy were investigated and compared with those of a titanium carbide(TiC)cemented material.The results show that the high-temperature wear performance of the Co-based alloy is better than that of the TiC cemented material,and that Co-based materials have the potential for replacing TiC cemented materials as hot-extrusion-die materials.Due to the high density and good combination of the matrix and carbide,the carbides do not easily peel off from the matrix during the wear process.Due to the higher impact toughness of the Co-based alloys,microcracks that can cause worn-surface peeling are not easily generated.As a result,the high-temperature wear performance of Co-based alloys is found to be better than that of TiC cemented materials.展开更多
Electrocatalytic water splitting is an essential and effective means to produce green hydrogen energy structures,so it is necessary to develop non-precious metal catalysts to replace precious metals.Cobalt-based catal...Electrocatalytic water splitting is an essential and effective means to produce green hydrogen energy structures,so it is necessary to develop non-precious metal catalysts to replace precious metals.Cobalt-based catalysts present effective alternatives due to the diverse valence states,adjustable electronic structures,and plentiful components.In this review,the catalytic mechanisms of hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)for electrocatalytic water splitting are described.Then,the synthesis strategies of various cobalt-based catalysts are systematically summarized,followed by the relationships between the structure and performance clarified.Subsequently,the effects of d-band center and spin regulation for cobalt-based catalysts are also discussed.Furthermore,the dynamic electronic and structural devolution of cobalt-based catalysts are elucidated by combining a series of in-situ characterizations.Finally,we highlight the challenges and future developed directions of cobalt-based catalysts for electrocatalytic water splitting.展开更多
The double minimum creep,characterized by two creep rate minima,in Co-based superalloy is investigated using a phase-field model coupled with a crystal plasticity model.The constitutive modeling,based on the dislocati...The double minimum creep,characterized by two creep rate minima,in Co-based superalloy is investigated using a phase-field model coupled with a crystal plasticity model.The constitutive modeling,based on the dislocation slip theory considering dislocation interaction,is applied to simulate microstructural evolution and deformation behavior.Rafting process commences at the beginning of creep until the global minimum of creep rate is reached,demonstrating a strengthening effect from N-type rafts under compressive creep.The high shear strain rate of(111)[011]slip system in the intersections of horizontal and verticalγchannels leads to a slight increase of creep rate after the first local minimum.The evolution of stress field shows that the softening effect is the combined effect of the increase of resolved shear stress and the decrease of hardening stress in the intersections.Further,these changes in stress are primarily caused by the dislocation annihilation and the inhomogeneous plastic deformation.This study indicates that the intermediate local softening stage during creep may be eliminated if the initial inter-distance betweenγ’precipitates is decreased.展开更多
Potassium-ion batteries(KIBs)are regarded as one of the most promising replacements for lithium-ion batteries because of their low cost and high performance.Exploring suitable anode materials to stably and effectively...Potassium-ion batteries(KIBs)are regarded as one of the most promising replacements for lithium-ion batteries because of their low cost and high performance.Exploring suitable anode materials to stably and effectively store potassium is critical for the development of KIBs.Given their high theoretical specific capacity,cobalt-based compounds have been extensively investigated as an anode material in recent years;however,specific reviews summarizing the research progress in the application of cobaltbased compounds as anode materials for high-performance KIBs are lacking.Consequently,this review systematically summarizes the recent states of cobalt-based anode materials in KIBs starting at the potassium storage mechanism,followed by strategies and applications to improve the electrochemical performance.The current challenges are also discussed,and corresponding prospects are proposed.This work may facilitate the realization of various applications of cobalt-based compound anodes for highperformance rechargeable batteries and is expected to provide some guidance for developing other metal-based compounds for KIBs anodes.展开更多
The release of debris and ions from metallic artificial joints during bio-tribocorrosion posed a severe threat to patient health.In this work,the lifecycle of a Co Cr Mo alloy was presented by investigating the subsur...The release of debris and ions from metallic artificial joints during bio-tribocorrosion posed a severe threat to patient health.In this work,the lifecycle of a Co Cr Mo alloy was presented by investigating the subsurface microstructure transformation in-vitro.The results showed that the originally coarse grains changed to nano-grains(NGs)on the top region of the alloy,and nanoparticles(NPs)were torn off the surface,which were then blocked by the tribo-film.The agglomerated alloy NPs contained in the tribofilm transformed into debris after being removed from the alloy surface.The majority of the torn-off NPs were corroded and released ions into solution due to their high chemical activities.展开更多
Exploring the anodic reaction to substitute conventional oxygen evolution reaction(OER)for the synthesis of complex pharmaceutical molecules is highly attractive.Here,we report an electrocatalytic strategy for dehydro...Exploring the anodic reaction to substitute conventional oxygen evolution reaction(OER)for the synthesis of complex pharmaceutical molecules is highly attractive.Here,we report an electrocatalytic strategy for dehydrogenative[4+2]cycloaddition of N,N-dialkylanilines with maleimides via dual functionalization of both C(sp3)-H and C(sp2)-H bonds,by using an electrochemically activated cobalt carbonate hydroxide hydrate supported on carbon cloth(CCHH-A/CC),affording various tetrahydroquinolines with high yields.This electrochemical transformation proceeds with high activity and stability,as well as good substrate compatibility.Mechanism study shows thatα-aminoalkyl radical exists in the electrooxidation reaction.This strategy shows significant potential for the synthesis of valuable chemicals by using an electrocatalytic strategy.展开更多
With the rapid economic growth and the deepening awareness of sustainable development,the demand for green and efficient energy storage equipment increases.As a promising energy storage and conversion device,zinc-air ...With the rapid economic growth and the deepening awareness of sustainable development,the demand for green and efficient energy storage equipment increases.As a promising energy storage and conversion device,zinc-air batteries(ZABs)have the advantages of high theoretical specific energy density,low cost,and environmental friendliness.Nevertheless,the efficiency of ZABs is closely related to the electrocatalytic capacity of the air electrode due to its sluggish kinetics for oxygen reduction and evolution reaction(ORR/OER).Therefore,it is necessary to develop efficient catalysts to promote the reaction rate.Recently,cobalt-based materials have become a research hotspot for oxygen electrocatalysts owing to their rich natural content,high catalytic activity,and stability.In this review,the mechanisms of the OER/ORR reaction process,the catalyst's performance characterization,and the various combination methods with the current collector are systematically introduced and analyzed.Further,a broad overview of cobalt-based materials used as electrocatalysts for ZABs is presented,including cobalt-based perovskite,cobalt-nitrogen-carbon(Co-N-C)materials,cobalt oxides,cobalt-containing composite oxides,and cobalt sulfides/phosphides.Finally,various strategies for developing efficient electrocatalysts for ZABs are summarized,highlighting the challenges and future perspectives in designing novel catalysts.展开更多
The present work investigates the thermal stability and mechanical properties of a Co-20 Cr-15 W-10 Ni(wt%) alloy with a bimodal grain(BG) structure.The BG structure consisting of fine grains(FGs) and coarse grains(CG...The present work investigates the thermal stability and mechanical properties of a Co-20 Cr-15 W-10 Ni(wt%) alloy with a bimodal grain(BG) structure.The BG structure consisting of fine grains(FGs) and coarse grains(CGs) is thermally stable under high-temperature exposure treatments of 760℃ for 100 h and 870℃ for 100-1000 h.The size of both FGs and CGs remains no significant changes after thermal exposure treatments.The microstructural stability is associated with the slow kinetics of grain growth and the pinning of carbides.The thermal stability enables to maintain the BG structures,leading to the same mechanical properties as the sample without thermal exposure treatment.In particular,the BG alloy samples after thermal exposure treatment exhibit superior mechanical properties of both high strength and high ductility compared to the unimodal grain(UG) structured ones.The BG structure of the alloy samples after thermal exposure is capable of avoiding severe loss of ductility and retaining high strength.More specifically,the ductility of the BG alloy samples after thermal exposure treatments of 870℃ for 500-1000 h is ten times higher(44.6% vs.3.5% and 52.6% vs.5.0%) than that of the UG ones.The finding in the present work may give new insights into high-temperature applications of the Co-20 Cr-15 W-10 Ni alloy and other metallic materials with a BG structure.展开更多
Fabrication of selective adsorption coatings plays a crucial role in solid-phase microextraction(SPME).Herein,new strategies were developed for the in-situ fabrication of novel cobalt-based carbonaceous coatings on th...Fabrication of selective adsorption coatings plays a crucial role in solid-phase microextraction(SPME).Herein,new strategies were developed for the in-situ fabrication of novel cobalt-based carbonaceous coatings on the nickel-titanium alloy(Ni Ti)fiber substrate using ZIF-67 as a precursor and template through the chemical reaction of ZIF-67 with glucose,dopamine(DA)and melamine,respectively.The adsorption performance of the resulting coatings was evaluated using representative aromatic compounds coupled to high-performance liquid chromatography(HPLC)with ultraviolet detection(HPLC-UV).The results clearly demonstrated that the adsorption selectivity was subject to the surface elemental composition of the fiber coatings.The cobalt and nitrogen co-doped carbonaceous coating showed better adsorption selectivity for ultraviolet filters.In contrast,the cobalt-doped carbonaceous coating exhibited higher adsorption selectivity for polycyclic aromatic hydrocarbons.The fabricated fibers present higher mechanical stability and higher adsorption capability for model analytes than the commercial polydimethylsiloxane and polyacrylate fibers.These new strategies will continue to expand the Ni Ti fibers as versatile fiber substrates for metal-organic frameworks(MOFs)-derived coating materials with controllable nanostructures and tunable properties.展开更多
Aprotic lithium-oxygen(Li-O_(2))batteries represent a promising next-generation energy storage system due to their extremely high theoretical specific capacity compared with all known batteries.Their practical realiza...Aprotic lithium-oxygen(Li-O_(2))batteries represent a promising next-generation energy storage system due to their extremely high theoretical specific capacity compared with all known batteries.Their practical realization is impeded,however,by the sluggish kinetics for the most part,resulting in high overpotential and poor cycling performance.Due to the high catalytic activity and favorable stability of Co-based transition metal oxides,they are regarded as the most likely candidate catalysts,facilitating researchers to solve the sluggish kinetics issue.Herein,this review first presents recent advanced design strategies for Co-based transition metal oxides in Li-O_(2)batteries.Then,the fundamental insights related to the catalytic processes of Co-based transition metal oxides in traditional and novel Li-O_(2)electrochemistry systems are summarized.Finally,we conclude with the current limitations and future development directions of Co-based transition metal oxides,which will contribute to the rational design of catalysts and the practical applications of Li-O_(2)batteries.展开更多
Effect of revert cycles on microstructure and fatigue properties of cast cobalt base superalloy K640S has been investigated. The results show that: at 70 times of cool heat cycles, there were microcracks found in seve...Effect of revert cycles on microstructure and fatigue properties of cast cobalt base superalloy K640S has been investigated. The results show that: at 70 times of cool heat cycles, there were microcracks found in seven times revert and ten times revert. With the increasing of thermal fatigue cycles, the crack of revert grows a little faster than virgin. When the cycle time reaches 200, the crack length for both virgin and reverts have been as long as 2mm. The low cycle fatigue life has no remarkable change, with the increase of revert cycles at 815℃, 360MPa ,0 5Hz. With the times of cycles increasing, it is found that the content of impurity and gas in alloy change a little, and there is no obvious change for dendrite microstructure.展开更多
Secondary M23C6 precipitation around primary MC carbide in a directionally solidified cobalt-base saperalloy was investigated duriny aging at 850℃. The results show that it was closely related to the decomposition of...Secondary M23C6 precipitation around primary MC carbide in a directionally solidified cobalt-base saperalloy was investigated duriny aging at 850℃. The results show that it was closely related to the decomposition of the MC. Two mechanisms were suggested,i.e. the in situ reaction, MC+γ→M23C6+C, and the direct reaction, M+C→M23C6,in which MC acted as a carbon source.展开更多
Nano-sized γ-alumina (γ-Al2O3) was first prepared by a precipitation method. Then, active component of cobalt and a series of alkaline- earth metal promoters or nickel (Ni) with different contents were loaded on...Nano-sized γ-alumina (γ-Al2O3) was first prepared by a precipitation method. Then, active component of cobalt and a series of alkaline- earth metal promoters or nickel (Ni) with different contents were loaded on the γ-Al2O3 support. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD) and thermogravimetry analysis (TGA). The activity and selectivity of the catalysts in catalytic partial oxidation (CPO) of methane have been compared with Co/γ-Al2O3, and it is found that the catalytic activity, selectivity, and stability are enhanced by the addition of alkaline-earth metals and nickel. The optimal loadings of strontium (Sr) and Ni were 6 and 4 wt%, respectively. This finding will be helpful in designing the trimetallic Co-Ni-Sr/γ-Al2O3 catalysts with high performance in CPO of methane展开更多
Non-porous carbon sphere was used as support to synthesize supported cobalt Fischer-Tropsch catalysts with high activity and durability. Strong metal-support interaction was avoided and intrinsic activity of pristine ...Non-porous carbon sphere was used as support to synthesize supported cobalt Fischer-Tropsch catalysts with high activity and durability. Strong metal-support interaction was avoided and intrinsic activity of pristine cobalt nano-particles was studied. Thermal decomposition synthesis method was applied to obtain cobalt catalysts with high dispersion and narrow particle size distribution. Furthermore the cobalt size can be controlled by the molar ratio of o-dichlorobenzene/benzylamine. Compared with supported cobalt catalysts prepared by incipient wetness impregnation method and ultrasonic impregnation method,the catalyst prepared by thermal decomposition method showed higher catalytic activity, higher long chain hydrocarbons selectivity and lower methane selectivity.展开更多
Active non-noble metal catalysts plays a decisive role for water electrolysis,however,the rational design and development of cost-efficient electrocatalysts with Pt/IrO2-like activity is still a challenging task.Herei...Active non-noble metal catalysts plays a decisive role for water electrolysis,however,the rational design and development of cost-efficient electrocatalysts with Pt/IrO2-like activity is still a challenging task.Herein,a facile one-step electrodeposition route in deep eutectic solvents(DESs) is developed for morphology-controllable synthesis of cobalt oxide/phosphate-carbon nano hybrids on nickel foam(CoPO@C/NF).A series of CoPO@C/NF nanostructures including cubes,octahedrons,microspheres and nanoflowers are synthesized,which show promising electrocatalytic properties toward oxygen and hydrogen evolution reactions(OER/HER).Such surface self-organized microstructure with accessible active sites make a significant contribution to the enhanced electrochemical activity,and hybridizing cobalt oxide with cobalt pyrophosphates and carbon can result in enhanced OER performance through synergistic catalysis.Among all nanostructures,the obtained microspherical CoPO@C/NF-3 catalyst exhibits excellent catalytic activities for OER and HER in 1.0 M KOH,affording an anodic current density of 10 mA cm^(-2) at overpotentials of 293 mV for OER and 93 mV for HER,with good long-time stability.This work offers a practical route for engineering the high-performance electrocatalysts towards efficient energy conversion and storage devices.展开更多
基金This work is financially supported by the Scientific Research Foundation for Young Teachers of Anhui Province, China (No. 2006jql082).
文摘Cobalt-based alloys with different Y2O3 contents were deposited on Q235A-carbon steel using plasma transferred arc (PTA) welding machine. The effect of Y2O3 on the microstructure and wear resistance properties of the cobait-based alloys were investigated using an optical microscope, a scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). It was found that a cobalt-based solid solution with a face-centered cubic crystal structure was presented accompanied by the secondary phase M7C3 with a hexagonal crystal structure in the Y2O3-free cobalt-based alloy coating. Several stacking faults exist in the cobalt-based solid solution. The addition of Y2O3 leads to the existence of the Y2O3 phase in the Y2O3-modified coatings. Though stacking fault exists in the Y2O3-modified coatings, its density increases. The addition of Y2O3 can refine the microstructure and can increase the wear resistance properties when its contents are less than or equal to 0.8 wt.%. However, further increase of its contents will lead to the agglomeration of undissolved Y2O3 particles at the γ-Co grain boundary, and will lead to a coarse microstructure and lower wear resistance properties.
基金financially supported by the National Natural Science Foundation of China (No. 52102100)the Industry-University-Research Cooperation Project of Jiangsu Province, China (No. BY2021525)the Postgraduate Research & Practice Innovation Program of Jiangsu Province, China (No. SJCX22_1944)
文摘To improve the efficiency of cathodic oxygen reduction reaction(ORR)in zinc-air batteries(ZABs),an adsorption-complexation-calcination method was proposed to generate cobalt-based multicomponent nanoparticles comprising Co,Co_(3)O_(4)and CoN,as well as numerous N heteroatoms,on graphene nanosheets(Co/Co_(3)O_(4)/CoN/NG).The Co/Co_(3)O_(4)/CoN nanoparticles with the size of less than 50 nm are homogeneously dispersed on N-doped graphene(NG)substrate,which greatly improve the catalytic behaviors for ORR.The results show that the half-wave potential is as high as 0.80 V vs.RHE and the limiting current density is 4.60 mA·cm^(−2),which are close to those of commercially available platinum/carbon(Pt/C)catalysts.Applying as cathodic catalyst for ZABs,the battery shows large specific capacity and open circuit voltage of 843.0 mAh∙g^(−1) and 1.41 V,respectively.The excellent performance is attributed to the efficient two-dimensional structure with high accessible surface area and the numerous multiple active sites provided by highly scattered Co/Co_(3)O_(4)/CoN particles and doped nitrogen on the carbon matrix.
文摘The microstructure, substructure, and wear characteristic of cobalt-basedalloy coatings obtained by plasma transferred arc (PTA) process were investigated using opticalmetallurgical microscope, X-ray diffraction (XRD), scanning electron microscope (SEM), transmissionelectron microscope (TEM), and dry sand abrasion tester (DSAT). The aging effect on the structureand wear resistance of the cobalt-based PTA coating was also studied. The results show that theas-welded coating consists of cobalt-based solid solution with face-centered cubic structure andhexagonal (Cr,Fe)_7C_3. There are a lot of stacking faults existing in the cobalt-based solidsolution. After aging at 600 deg C for 60 h, the microstructure becomes coarse, and another carbide(Cr,Fe)_(23)C_6 precipitates. As a result, the wear mass loss of the aged sample is higher than thatof the as-welded sample.
基金supported by the National Natural Science Foundation of China(Nos.21905049,22178057)the Natural Science Foundation of Fujian Province(Nos.2020J01201,2021J01197)+1 种基金the Research Foundation of the Academy of Carbon Neutrality of Fujian Normal University(TZH2022-07)the Award Program for Minjiang Scholar Professorship。
文摘Conversion of carbon dioxide(CO_(2))into valuable chemicals and renewable fuels via photocatalysis represents an eco-friendly route to achieve the goal of carbon neutralization.Although various types of semiconductor materials have been intensively explored,some severe issues,such as rapid charge recombination and sluggish redox reaction kinetics,remain.In this regard,cocatalyst modifi cation by trapping charges and boosting surface reactions is one of the most effi cient strategies to improve the effi ciency of semiconductor photocatalysts.This review focuses on recent advances in CO_(2)photoreduction over costeff ective and earth-abundant cobalt(Co)-based cocatalysts,which are competitive candidates of noble metals for practical applications.First,the functions of Co-based cocatalysts for promoting photocatalytic CO_(2)reduction are briefl y discussed.Then,diff erent kinds of Co-based cocatalysts,including cobalt oxides and hydroxides,cobalt nitrides and phosphides,cobalt sulfi des and selenides,Co single-atom,and Co-based metal–organic frameworks(MOFs),are summarized.The underlying mechanisms of these Co-based cocatalysts for facilitating CO_(2)adsorption–activation,boosting charge separation,and modulating intermediate formation are discussed in detail based on experimental characterizations and density functional theory calculations.In addition,the suppression of the competing hydrogen evolution reaction using Co-based cocatalysts to promote the product selectivity of CO_(2)reduction is highlighted in some selected examples.Finally,the challenges and future perspectives on constructing more effi cient Co-based cocatalysts for practical applications are proposed.
文摘Different kinds of aluminum precursors were obtained from precipitating ammonium bicarbonate, ammonium carbonate, and saturated ammonium bicarbonate, then, boehmite (AlO(OH)), ammonium alumina carbonate hydroxide (AACH) and their mixture were obtained, and then, different kinds of alumina were obtained after calcination. Three catalysts supported on the different alumina were obtained via impregnating cobalt and ruthenium by incipient wetness. The effects of different precipitants on composition of precursors were?studied by XRD, FTIR, and TGA. The property and structure of alumina were studied by XRD and BET. The supported catalysts were studied by characterizations of XRD and H2-TPR, and the catalytic performance for Fischer-Tropsch synthesis (FTS) were evaluated at a fix-bed reactor. The relations among the composition of precursors, the property of alumina and the catalytic performance of supported catalysts were researched thoroughly.
文摘The hot extrusion die is a key tool for determining the surface quality and dimensional accuracy of extruded products.Because its service process is subject to high temperature,high pressure,and wear,it must be resistant to these conditions.In this paper,the high-temperature friction and wear properties of a cobalt(Co)-based alloy were investigated and compared with those of a titanium carbide(TiC)cemented material.The results show that the high-temperature wear performance of the Co-based alloy is better than that of the TiC cemented material,and that Co-based materials have the potential for replacing TiC cemented materials as hot-extrusion-die materials.Due to the high density and good combination of the matrix and carbide,the carbides do not easily peel off from the matrix during the wear process.Due to the higher impact toughness of the Co-based alloys,microcracks that can cause worn-surface peeling are not easily generated.As a result,the high-temperature wear performance of Co-based alloys is found to be better than that of TiC cemented materials.
基金support of this research by the National Natural Science Foundation of China(Nos.U20A20250 and 22179034)the Natural Science Foundation of Heilongjiang Province(No.ZD2023B002).
文摘Electrocatalytic water splitting is an essential and effective means to produce green hydrogen energy structures,so it is necessary to develop non-precious metal catalysts to replace precious metals.Cobalt-based catalysts present effective alternatives due to the diverse valence states,adjustable electronic structures,and plentiful components.In this review,the catalytic mechanisms of hydrogen evolution reaction(HER)and oxygen evolution reaction(OER)for electrocatalytic water splitting are described.Then,the synthesis strategies of various cobalt-based catalysts are systematically summarized,followed by the relationships between the structure and performance clarified.Subsequently,the effects of d-band center and spin regulation for cobalt-based catalysts are also discussed.Furthermore,the dynamic electronic and structural devolution of cobalt-based catalysts are elucidated by combining a series of in-situ characterizations.Finally,we highlight the challenges and future developed directions of cobalt-based catalysts for electrocatalytic water splitting.
基金the supports provided by the National Key Research and Development Program of China(Nos.2017YFB0702902 and 2016YFB0701405)the National Science and Technology Major Project(Nos.2017-VI-0001-0070 and 2017-Ⅵ-0002-0072)+1 种基金the National Natural Science Foundation of China(Nos.51971174 and 51771148)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2020JM-121)。
文摘The double minimum creep,characterized by two creep rate minima,in Co-based superalloy is investigated using a phase-field model coupled with a crystal plasticity model.The constitutive modeling,based on the dislocation slip theory considering dislocation interaction,is applied to simulate microstructural evolution and deformation behavior.Rafting process commences at the beginning of creep until the global minimum of creep rate is reached,demonstrating a strengthening effect from N-type rafts under compressive creep.The high shear strain rate of(111)[011]slip system in the intersections of horizontal and verticalγchannels leads to a slight increase of creep rate after the first local minimum.The evolution of stress field shows that the softening effect is the combined effect of the increase of resolved shear stress and the decrease of hardening stress in the intersections.Further,these changes in stress are primarily caused by the dislocation annihilation and the inhomogeneous plastic deformation.This study indicates that the intermediate local softening stage during creep may be eliminated if the initial inter-distance betweenγ’precipitates is decreased.
基金financially supported by the National Natural Science Foundation of China(Nos.22008053 and 52002111)Key Research and Development Program of Hebei Province(Nos.20310601D and 205A4401D)+3 种基金the Natural Science Foundation of Hebei Province(No.B2021208061)the High Level Talents Funding of Hebei Province(No.A202005006)the Science Foundation of University of Hebei Province(Nos.BJ2020026 and BJ2021001)Liaoning Revitalization Talents Program(No.XLYC2008014)。
文摘Potassium-ion batteries(KIBs)are regarded as one of the most promising replacements for lithium-ion batteries because of their low cost and high performance.Exploring suitable anode materials to stably and effectively store potassium is critical for the development of KIBs.Given their high theoretical specific capacity,cobalt-based compounds have been extensively investigated as an anode material in recent years;however,specific reviews summarizing the research progress in the application of cobaltbased compounds as anode materials for high-performance KIBs are lacking.Consequently,this review systematically summarizes the recent states of cobalt-based anode materials in KIBs starting at the potassium storage mechanism,followed by strategies and applications to improve the electrochemical performance.The current challenges are also discussed,and corresponding prospects are proposed.This work may facilitate the realization of various applications of cobalt-based compound anodes for highperformance rechargeable batteries and is expected to provide some guidance for developing other metal-based compounds for KIBs anodes.
基金the National Natural Science Foundation of China under grants No.51971035 and No.51801016。
文摘The release of debris and ions from metallic artificial joints during bio-tribocorrosion posed a severe threat to patient health.In this work,the lifecycle of a Co Cr Mo alloy was presented by investigating the subsurface microstructure transformation in-vitro.The results showed that the originally coarse grains changed to nano-grains(NGs)on the top region of the alloy,and nanoparticles(NPs)were torn off the surface,which were then blocked by the tribo-film.The agglomerated alloy NPs contained in the tribofilm transformed into debris after being removed from the alloy surface.The majority of the torn-off NPs were corroded and released ions into solution due to their high chemical activities.
基金Financial support was provided by the National Natural Science Foundation of China(21978147,21935001,22090030,22105015)the China Postdoctoral Science Foundation(2019M660421)State Key Laboratory of Catalytic Materials and Reaction Engineering(RIPP,SINOPEC).
文摘Exploring the anodic reaction to substitute conventional oxygen evolution reaction(OER)for the synthesis of complex pharmaceutical molecules is highly attractive.Here,we report an electrocatalytic strategy for dehydrogenative[4+2]cycloaddition of N,N-dialkylanilines with maleimides via dual functionalization of both C(sp3)-H and C(sp2)-H bonds,by using an electrochemically activated cobalt carbonate hydroxide hydrate supported on carbon cloth(CCHH-A/CC),affording various tetrahydroquinolines with high yields.This electrochemical transformation proceeds with high activity and stability,as well as good substrate compatibility.Mechanism study shows thatα-aminoalkyl radical exists in the electrooxidation reaction.This strategy shows significant potential for the synthesis of valuable chemicals by using an electrocatalytic strategy.
基金supported by the National Key Research and Development Program of China(No.2020YFB1506002)National Natural Science Foundation of China(No.21975143).
文摘With the rapid economic growth and the deepening awareness of sustainable development,the demand for green and efficient energy storage equipment increases.As a promising energy storage and conversion device,zinc-air batteries(ZABs)have the advantages of high theoretical specific energy density,low cost,and environmental friendliness.Nevertheless,the efficiency of ZABs is closely related to the electrocatalytic capacity of the air electrode due to its sluggish kinetics for oxygen reduction and evolution reaction(ORR/OER).Therefore,it is necessary to develop efficient catalysts to promote the reaction rate.Recently,cobalt-based materials have become a research hotspot for oxygen electrocatalysts owing to their rich natural content,high catalytic activity,and stability.In this review,the mechanisms of the OER/ORR reaction process,the catalyst's performance characterization,and the various combination methods with the current collector are systematically introduced and analyzed.Further,a broad overview of cobalt-based materials used as electrocatalysts for ZABs is presented,including cobalt-based perovskite,cobalt-nitrogen-carbon(Co-N-C)materials,cobalt oxides,cobalt-containing composite oxides,and cobalt sulfides/phosphides.Finally,various strategies for developing efficient electrocatalysts for ZABs are summarized,highlighting the challenges and future perspectives in designing novel catalysts.
基金financially supported by the Fundamental Research Program of Korea Institute of Materials Science,Republic of Korea(No.PNK7140)the National Key Research and Development Project,China(No.2020YFC1107200)。
文摘The present work investigates the thermal stability and mechanical properties of a Co-20 Cr-15 W-10 Ni(wt%) alloy with a bimodal grain(BG) structure.The BG structure consisting of fine grains(FGs) and coarse grains(CGs) is thermally stable under high-temperature exposure treatments of 760℃ for 100 h and 870℃ for 100-1000 h.The size of both FGs and CGs remains no significant changes after thermal exposure treatments.The microstructural stability is associated with the slow kinetics of grain growth and the pinning of carbides.The thermal stability enables to maintain the BG structures,leading to the same mechanical properties as the sample without thermal exposure treatment.In particular,the BG alloy samples after thermal exposure treatment exhibit superior mechanical properties of both high strength and high ductility compared to the unimodal grain(UG) structured ones.The BG structure of the alloy samples after thermal exposure is capable of avoiding severe loss of ductility and retaining high strength.More specifically,the ductility of the BG alloy samples after thermal exposure treatments of 870℃ for 500-1000 h is ten times higher(44.6% vs.3.5% and 52.6% vs.5.0%) than that of the UG ones.The finding in the present work may give new insights into high-temperature applications of the Co-20 Cr-15 W-10 Ni alloy and other metallic materials with a BG structure.
基金the National Natural Science Foundation of China(Nos.21765020 and 21265019)。
文摘Fabrication of selective adsorption coatings plays a crucial role in solid-phase microextraction(SPME).Herein,new strategies were developed for the in-situ fabrication of novel cobalt-based carbonaceous coatings on the nickel-titanium alloy(Ni Ti)fiber substrate using ZIF-67 as a precursor and template through the chemical reaction of ZIF-67 with glucose,dopamine(DA)and melamine,respectively.The adsorption performance of the resulting coatings was evaluated using representative aromatic compounds coupled to high-performance liquid chromatography(HPLC)with ultraviolet detection(HPLC-UV).The results clearly demonstrated that the adsorption selectivity was subject to the surface elemental composition of the fiber coatings.The cobalt and nitrogen co-doped carbonaceous coating showed better adsorption selectivity for ultraviolet filters.In contrast,the cobalt-doped carbonaceous coating exhibited higher adsorption selectivity for polycyclic aromatic hydrocarbons.The fabricated fibers present higher mechanical stability and higher adsorption capability for model analytes than the commercial polydimethylsiloxane and polyacrylate fibers.These new strategies will continue to expand the Ni Ti fibers as versatile fiber substrates for metal-organic frameworks(MOFs)-derived coating materials with controllable nanostructures and tunable properties.
基金National Natural Science Foundation of China,Grant/Award Number:52002247Natural Science Foundation of Guangdong Province,Grant/Award Number:2019A1515011344。
文摘Aprotic lithium-oxygen(Li-O_(2))batteries represent a promising next-generation energy storage system due to their extremely high theoretical specific capacity compared with all known batteries.Their practical realization is impeded,however,by the sluggish kinetics for the most part,resulting in high overpotential and poor cycling performance.Due to the high catalytic activity and favorable stability of Co-based transition metal oxides,they are regarded as the most likely candidate catalysts,facilitating researchers to solve the sluggish kinetics issue.Herein,this review first presents recent advanced design strategies for Co-based transition metal oxides in Li-O_(2)batteries.Then,the fundamental insights related to the catalytic processes of Co-based transition metal oxides in traditional and novel Li-O_(2)electrochemistry systems are summarized.Finally,we conclude with the current limitations and future development directions of Co-based transition metal oxides,which will contribute to the rational design of catalysts and the practical applications of Li-O_(2)batteries.
文摘Effect of revert cycles on microstructure and fatigue properties of cast cobalt base superalloy K640S has been investigated. The results show that: at 70 times of cool heat cycles, there were microcracks found in seven times revert and ten times revert. With the increasing of thermal fatigue cycles, the crack of revert grows a little faster than virgin. When the cycle time reaches 200, the crack length for both virgin and reverts have been as long as 2mm. The low cycle fatigue life has no remarkable change, with the increase of revert cycles at 815℃, 360MPa ,0 5Hz. With the times of cycles increasing, it is found that the content of impurity and gas in alloy change a little, and there is no obvious change for dendrite microstructure.
文摘Secondary M23C6 precipitation around primary MC carbide in a directionally solidified cobalt-base saperalloy was investigated duriny aging at 850℃. The results show that it was closely related to the decomposition of the MC. Two mechanisms were suggested,i.e. the in situ reaction, MC+γ→M23C6+C, and the direct reaction, M+C→M23C6,in which MC acted as a carbon source.
基金supported by the Open Foundation of State Key Laboratory of Physical Chemistry of Solid Surfaces, Xiamen University (No.200906)the Natural Science Foundation of Jiangxi Province (No.2010GZH0048)+1 种基金the National Natural Science Foundation of China (No. 21067004)the Young Science Foundation of Jiangxi Province Education Office (No. GJJ10150)
文摘Nano-sized γ-alumina (γ-Al2O3) was first prepared by a precipitation method. Then, active component of cobalt and a series of alkaline- earth metal promoters or nickel (Ni) with different contents were loaded on the γ-Al2O3 support. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction (XRD) and thermogravimetry analysis (TGA). The activity and selectivity of the catalysts in catalytic partial oxidation (CPO) of methane have been compared with Co/γ-Al2O3, and it is found that the catalytic activity, selectivity, and stability are enhanced by the addition of alkaline-earth metals and nickel. The optimal loadings of strontium (Sr) and Ni were 6 and 4 wt%, respectively. This finding will be helpful in designing the trimetallic Co-Ni-Sr/γ-Al2O3 catalysts with high performance in CPO of methane
基金supported by the Key Program project of the NSFC and China Petrochemical Corporation Joint Fund (Grant No. U1463210)the Natural Science Foundation of Hubei Province of China (2013CFA089)the Fundamental Research Funds for the Central Universities, South-Central University for Nationalities (CZZ13002 and CZW15099)
文摘Non-porous carbon sphere was used as support to synthesize supported cobalt Fischer-Tropsch catalysts with high activity and durability. Strong metal-support interaction was avoided and intrinsic activity of pristine cobalt nano-particles was studied. Thermal decomposition synthesis method was applied to obtain cobalt catalysts with high dispersion and narrow particle size distribution. Furthermore the cobalt size can be controlled by the molar ratio of o-dichlorobenzene/benzylamine. Compared with supported cobalt catalysts prepared by incipient wetness impregnation method and ultrasonic impregnation method,the catalyst prepared by thermal decomposition method showed higher catalytic activity, higher long chain hydrocarbons selectivity and lower methane selectivity.
基金supported by the National Natural Science Foundation of China (21421001, 21875118)the Natural Science Foundation of Xinjiang Autonomous Region (2016D01A009)+1 种基金the 111 project (B12015)the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering (2020-KF-22)。
文摘Active non-noble metal catalysts plays a decisive role for water electrolysis,however,the rational design and development of cost-efficient electrocatalysts with Pt/IrO2-like activity is still a challenging task.Herein,a facile one-step electrodeposition route in deep eutectic solvents(DESs) is developed for morphology-controllable synthesis of cobalt oxide/phosphate-carbon nano hybrids on nickel foam(CoPO@C/NF).A series of CoPO@C/NF nanostructures including cubes,octahedrons,microspheres and nanoflowers are synthesized,which show promising electrocatalytic properties toward oxygen and hydrogen evolution reactions(OER/HER).Such surface self-organized microstructure with accessible active sites make a significant contribution to the enhanced electrochemical activity,and hybridizing cobalt oxide with cobalt pyrophosphates and carbon can result in enhanced OER performance through synergistic catalysis.Among all nanostructures,the obtained microspherical CoPO@C/NF-3 catalyst exhibits excellent catalytic activities for OER and HER in 1.0 M KOH,affording an anodic current density of 10 mA cm^(-2) at overpotentials of 293 mV for OER and 93 mV for HER,with good long-time stability.This work offers a practical route for engineering the high-performance electrocatalysts towards efficient energy conversion and storage devices.