An Ir-catalyzed enantioselective hydrogenation of challenging tetrasubstituted exocyclic olefins is disclosed.This new catalytic system tolerates a broad substrate scope and affords valuable chiral cyclic β-amino est...An Ir-catalyzed enantioselective hydrogenation of challenging tetrasubstituted exocyclic olefins is disclosed.This new catalytic system tolerates a broad substrate scope and affords valuable chiral cyclic β-amino esters possessing two vicinal stereocenters in high yields and excellent enantioselectivities and diastereoselectivities(up to 94% yield,96% ee,99:1 dr).Control experiments and deuterium-labeling reactions reveal an iminium hydrogenation mechanism upon Brønsted acid-promoted tautomerization of the C=C double bond to cycliciminium intermediates.Density functional theory calculations showcase that the excellent selectivities are derived from C-H…π interaction between the substrate and the chiral ligand.Application in gram-scale preparation of dexmethylphenidate with up to 1500 turnover number is also demonstrated,showing the promising potential of Ir-catalyzed enantioselective hydrogenation in drug synthesis.展开更多
Development of new materials with high hydrogen storage capacity and reversible hydrogen sorp-tion performances under mild conditions has very high value in both fundamental and application aspects.In the past years,s...Development of new materials with high hydrogen storage capacity and reversible hydrogen sorp-tion performances under mild conditions has very high value in both fundamental and application aspects.In the past years,some new systems with metastable structures,such as ultra-fine nanocrystalline alloys,amorphous alloys,nanoglass alloys,immiscible alloys,high-entropy alloys,have been abundantly studied as hydrogen storage mate-rials.Many new hydrogen storage properties either from the kinetics or thermodynamics aspects have been reported.In this review,recent advances of studies on metastable alloys for hydrogen storage applications have been comprehensively reviewed.The materials preparation methods to synthesize metastable hydrogen storage alloys are firstly reviewed.Afterwards,hydrogen storage prop-erties of the metastable alloys are summarized and dis-cussed,focusing on the unique kinetics and thermodynamics properties by forming of such unique metastable structures.For examples,superior hydrogena-tion kinetics and higher hydrogen storage capacity have been achieved in Mg-based amorphous and nanoglass alloys.Destabilized thermodynamics properties can be obtained in the immiscible Mg-Mn and Mg-Zr alloys.In addition to highlighting the recent achievements of metastable alloys in the field of hydrogen storage,the remaining challenges and trends of the emerging research are also discussed.展开更多
Lithium metal has been regarded as one of the most promising anode materials for high-energy-density batteries due to its extremely high theoretical gravimetric capacity of 3860 mAh·g^-1 along with its low electr...Lithium metal has been regarded as one of the most promising anode materials for high-energy-density batteries due to its extremely high theoretical gravimetric capacity of 3860 mAh·g^-1 along with its low electrochemical potential of-3.04 V.Unfortunately,uncontrollable Li dendrite growth and repetitive destruction/formation of the solid electrolyte interphase layer lead to poor safety and low Coulombic efficiencies(CEs)for long-term utilization,which largely restricts the practical applications of lithium metal anode.In this review,we comprehensively summarized important progresses achieved to date in suppressing Li dendrite growth.Strategies for protection of Li metal anodes include designing porous structured hosts,fabricating artificial solid electrolyte interface(SEI)layers,introducing electrolyte additives,using solid-state electrolytes and applying external fields.The protection of Li metal anodes can be achieved by regulating the stripping and deposition behaviours of Li ions.Finally,the challenges remaining for lithium metal battery systems and future perspectives for Li metal anodes in practical applications are outlined,which are expected to shed light on future research in this field.展开更多
Magnesium and its alloys are the most investigated materials for solid-state hydrogen storage in the form of metal hydrides,but there are still unresolved problems with the kinetics and thermodynamics of hydrogenation...Magnesium and its alloys are the most investigated materials for solid-state hydrogen storage in the form of metal hydrides,but there are still unresolved problems with the kinetics and thermodynamics of hydrogenation and dehydrogenation of this group of materials.Severe plastic deformation(SPD)methods,such as equal-channel angular pressing(ECAP),high-pressure torsion(HPT),intensive rolling,and fast forging,have been widely used to enhance the activation,air resistance,and hydrogenation/dehydrogenation kinetics of Mg-based hydrogen storage materials by introducing ultrafine/nanoscale grains and crystal lattice defects.These severely deformed materials,particularly in the presence of alloying additives or second-phase nanoparticles,can show not only fast hydrogen absorption/desorption kinetics but also good cycling stability.It was shown that some materials that are apparently inert to hydrogen can absorb hydrogen after SPD processing.Moreover,the SPD methods were effectively used for hydrogen binding-energy engineering and synthesizing new magnesium alloys with low thermodynamic stability for reversible low/room-temperature hydrogen storage,such as nanoglasses,high-entropy alloys,and metastable phases including the high-pressureγ-MgH2 polymorph.This work reviews recent advances in the development of Mg-based hydrogen storage materials by SPD processing and discusses their potential in future applications.展开更多
A copper-ceria solid solution and ceria-supported copper catalysts were prepared and used for the catalytic hydrogenation of CO2 to CH3OH.According to site-specific classification and quantitative analyses(X-ray diffr...A copper-ceria solid solution and ceria-supported copper catalysts were prepared and used for the catalytic hydrogenation of CO2 to CH3OH.According to site-specific classification and quantitative analyses(X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,H2 temperature-programmed reduction,and CO adsorption),the interfaces of the prepared catalysts were classified as Cu incorporated into ceria(Cu-Ov-Cex),dispersed Cu O(D-Cu O-Ce O2),and bulk Cu O(B-Cu O-Ce O2)over the Ce O2 surface.These results,together with those of activity tests,showed that the Cu-Ov-Cex species was closely related to the CO2 hydrogenation activity and resulted in a much higher turnover frequency of CH3OH production than that observed with the D-Cu O-Ce O2 and B-Cu O-Ce O2 species.Thus,the copper-ceria solid solution exhibited improved activity due to the higher Cu-Ov-Cex fraction.展开更多
Hydrogen has been widely considered as a clean energy carrier that bridges the energy producers and energy consumers in an efficient and safe way for a sustainable society.Hydrogen can be stored in a gas,liquid and so...Hydrogen has been widely considered as a clean energy carrier that bridges the energy producers and energy consumers in an efficient and safe way for a sustainable society.Hydrogen can be stored in a gas,liquid and solid states and each method has its unique advantage.Though compressed hydrogen and liquefied hydrogen are mature technologies for industrial applications,appropriate measures are necessary to deal with the issues at high pressure up to around 100 MPa and low temperature at around 20 K.Distinct from those technologies,storing hydrogen in solid-state hydrides can realize a more compact and much safer approach that does not require high hydrogen pressure and cryogenic temperature.In this review,we will provide an overview of the majormaterial groups that are capable of absorbing and desorbing hydrogen reversibly.The main features on hydrogen storage properties of each material group are summarized,together with the discussion of the key issues and the guidance of materials design,aiming at providing insights for new material development as well as industrial applications.展开更多
This study explores the impact of introducing vacancy in the transition metal layer of rationally designed Na_(0.6)[Ni_(0.3)Ru_(0.3)Mn_(0.4)]O_(2)(NRM)cathode material.The incorporation of Ru,Ni,and vacancy enhances t...This study explores the impact of introducing vacancy in the transition metal layer of rationally designed Na_(0.6)[Ni_(0.3)Ru_(0.3)Mn_(0.4)]O_(2)(NRM)cathode material.The incorporation of Ru,Ni,and vacancy enhances the structural stability during extensive cycling,increases the operation voltage,and induces a capacity increase while also activating oxygen redox,respectively,in Na_(0.7)[Ni_(0.2)V_(Ni0.1)Ru_(0.3)Mn_(0.4)]O_(2)(V-NRM)compound.Various analytical techniques including transmission electron microscopy,X-ray absorption near edge spectroscopy,operando X-ray diffraction,and operando differential electrochemical mass spectrometry are employed to assess changes in the average oxidation states and structural distortions.The results demonstrate that V-NRM exhibits higher capacity than NRM and maintains a moderate capacity retention of 81%after 100 cycles.Furthermore,the formation of additional lone-pair electrons in the O 2p orbital enables V-NRM to utilize more capacity from the oxygen redox validated by density functional calculation,leading to a widened dominance of the OP4 phase without releasing O_(2) gas.These findings offer valuable insights for the design of advanced high-capacity cathode materials with improved performance and sustainability in sodium-ion batteries.展开更多
The polymeric gel electrolytes are attractive owing to their higher ionic conductivities than those of dry polymer electrolytes and lowered water activity for enlarged potential window.However,the ionic conductivity a...The polymeric gel electrolytes are attractive owing to their higher ionic conductivities than those of dry polymer electrolytes and lowered water activity for enlarged potential window.However,the ionic conductivity and mechanical strength of the Na-ion conducting polymeric gel electrolytes are limited by below 20 mS cm−1 and 2.2 MPa.Herein,we demonstrate Na-ion conducting and flexible polymeric hydrogel electrolytes of the chemically coupled poly(diallyldimethylammonium chloride)-dextrin-N,N′-methylene-bisacrylamide film immersed in NaClO_(4) solution(ex-DDA-Dex+NaClO_(4))for flexible sodium-ion hybrid capacitors(f-NIHC).In particular,the anion exchange reaction and synergistic interaction of ex-DDA-Dex with the optimum ClO_(4)−enable to greatly improve the ionic conductivity up to 27.63 mS cm−1 at 25◦C and electrochemical stability window up to 2.6 V,whereas the double networking structure leads to achieve both the mechanical strength(7.48 MPa)and softness of hydrogel electrolytes.Therefore,the f-NIHCs with the ex-DDA-Dex+NaClO_(4) achieved high specific and high-rate capacities of 192.04 F g^(−1)at 500 mA g^(−1)and 116.06 F g^(−1)at 10000 mA g^(−1),respectively,delivering a large energy density of 120.03Wh kg^(−1)at 906Wkg^(−1)and long cyclability of 70%over 500 cycles as well as demonstrating functional operation under mechanical stresses.展开更多
In this review,we discuss the electrochemical properties of Prussian blue(PB)for Na^(+)storage by combining structural engineering and electrolyte modifications.We integrated experimental data and density functional t...In this review,we discuss the electrochemical properties of Prussian blue(PB)for Na^(+)storage by combining structural engineering and electrolyte modifications.We integrated experimental data and density functional theory(DFT)in sodium-ion battery(SIB)research to refine the atomic arrangements and crystal lattices and introduce substitutions and dopants.These changes affect the lattice stability,intercalation,electronic and ionic conductivities,and electrochemical performance.We unraveled the intricate structure-electrochemical behavior relationship by combining experimental data with computational models,including first-principles calculations.This holistic approach identified techniques for optimizing PB and Prussian blue analog(PBA)structu ral properties for SIBs.We also discuss the tuning of electrolytes by systematically adjusting their composition,concentration,and additives using a combination of molecular dynamics(MD)simulations and DFT computations.Our review offers a comprehensive assessment of strategies for enhancing the electrochemical properties of PB and PBAs through structural engineering and electrolyte modifications,combining experimental insights with advanced computational simulations,and paving the way for next-generation energy storage systems.展开更多
One of the impacts of the Fukushima disaster was the shutdown of all nuclear power plants in Japan,reaching zero production in 2015.In response,the country started importing more fossil energy including coal,oil,and n...One of the impacts of the Fukushima disaster was the shutdown of all nuclear power plants in Japan,reaching zero production in 2015.In response,the country started importing more fossil energy including coal,oil,and natural gas to fill the energy gap.However,this led to a significant increase in carbon emissions,hindering the efforts to reduce its carbon footprint.In the current situation,Japan is actively working to balance its energy requirements with environmental considerations,including the utilization of hydrogen fuel.Therefore,this paper aims to explore the feasibility and implications of using hydrogen power plants as a means to reduce emissions,and this analysis will be conducted using the energy modeling of the MARKAL-TIMES Japan framework.The hydrogen scenario(HS)is assumed with the extensive integration of hydrogen into the power generation sector,supported by a hydrogen import scheme.Additionally,this scenario will be compared with the Business as Usual(BAU)scenario.The results showed that the generation capacities of the BAU and HS scenarios have significantly different primary energy supplies.The BAU scenario is highly dependent on fossil fuels,while the HS scenario integrates hydrogen contribution along with an increase in renewable energy,reaching a peak contribution of 2,160 PJ in 2050.In the HS scenario,the target of reducing CO_(2) emissions by 80%is achieved through significant hydrogen penetration.By 2050,the total CO_(2) emissions are estimated to be 939 million tons for the BAU scenario and 261 million tons for the Hydrogen scenario.In addition,the contribution of hydrogen to electricity generation is expected to be 153 TWh,smaller than PV and wind power.展开更多
High-entropy alloys and ceramics containing at least five principal elements have recently received high attention for various mechanical and functional applications.The application of severe plastic deformation(SPD),...High-entropy alloys and ceramics containing at least five principal elements have recently received high attention for various mechanical and functional applications.The application of severe plastic deformation(SPD),particularly the high-pressure torsion method,combined with the CALPHAD(calculation of phase diagram) and first-principles calculations resulted in the development of numerous superfunctional high-entropy materials with superior properties compared to the normal functions of engineering materials.This article reviews the recent advances in the application of SPD to developing superfunctional high-entropy materials.These superfunctional properties include(ⅰ) ultrahigh hardness levels comparable to the hardness of ceramics in high-entropy alloys,(ⅱ) high yield strength and good hydrogen embrittlement resistance in high-entropy alloys;(ⅲ) high strength,low elastic modulus,and high biocompatibility in high-entropy alloys,(ⅳ) fast and reversible hydrogen storage in high-entropy hydrides,(ⅴ) photovoltaic performance and photocurrent generation on high-entropy semiconductors,(ⅵ) photocatalytic oxygen and hydrogen production from water splitting on high-entropy oxides and oxynitrides,and(ⅶ)CO_(2) photoreduction on high-entropy ceramics.These findings introduce SPD as not only a processing tool to improve the properties of existing high-entropy materials but also as a synthesis tool to produce novel high-entropy materials with superior properties compared with conventional engineering materials.展开更多
Introducing Ni in Ru oxide is a promising approach to enhance the catalytic activity for the oxygen evolution reaction(OER).However,the role of Ni(which has a poor intrinsic activity)is not fully understood.Here,a Ru ...Introducing Ni in Ru oxide is a promising approach to enhance the catalytic activity for the oxygen evolution reaction(OER).However,the role of Ni(which has a poor intrinsic activity)is not fully understood.Here,a Ru NiO_(x)electrode fabricated via a modified dip coating method exhibited excellent OER performance in acidic media,and neutral media for CO_(2)reduction reaction.We combined in-situ/operando X-ray absorption near-edge structure and on-line inductively coupled plasma mass spectrometry studies to unveil the role of the Ni introduced in the Ru oxide.We propose that the Ni not only transforms the electronic structure of the Ru oxide,but also produces a large number of oxygen vacancies by distorting the oxygen lattice structure at low overpotentials,increasing the participation of lattice oxygen for OER.This work demonstrates the real behavior of bimetallic oxide materials under applied potentials and provides new insights into the development of efficient electrocatalysts.展开更多
This article reports a new phosphorescent material,CaZnOS:Cu,that exhibits two types of mechano-optical conversion:mechanical quenching and mechanoluminescence.An intense mechanical quenching of phosphorescence corres...This article reports a new phosphorescent material,CaZnOS:Cu,that exhibits two types of mechano-optical conversion:mechanical quenching and mechanoluminescence.An intense mechanical quenching of phosphorescence corresponding to mechanical stimuli can be achieved in CaZnOS:Cu within a short decay time period.Over time,it gradually changes to mechanoluminescence when a mechanical load is applied.We propose that the mechanical quenching and mechanoluminescence arise from the different roles of shallow and deep traps in CaZnOS:Cu.CaZnOS:Cu has promising applications in monitoring mechanical stress in industrial plants,structures,and living bodies.展开更多
Tuning the coordination environment is the research axis of single atom catalysts (SACs). SACs are commonly stabilized by various defects from support. Here, we report a lattice confined Pd SAC using MnO_(2) as suppor...Tuning the coordination environment is the research axis of single atom catalysts (SACs). SACs are commonly stabilized by various defects from support. Here, we report a lattice confined Pd SAC using MnO_(2) as support. Compared with the Pd clusters anchored on the surface, the lattice confined Pd single atoms allows spontaneous exaction of surrounding lattice oxygen at room temperature when employed in CO oxidation. The MnO_(2) supported Pd SAC exhibited a high turnover frequency of 0.203 s^(−1) at low reaction temperature, which is higher than that of recently reported Pd SACs. Theoretical calculations also confirmed the confined monatomic Pd activate lattice oxygen with an ultralow energy barrier. Our results illustrate that the unique coordination environment of single atom provided by lattice confinement is promising to boost the activity of SACs.展开更多
Among the factors which restrict the large-scale utilization of magnesium-based hydride as a hydrogen storage medium,the high operating temperature,slow kinetics,and air stability in particular are key obstacles.In th...Among the factors which restrict the large-scale utilization of magnesium-based hydride as a hydrogen storage medium,the high operating temperature,slow kinetics,and air stability in particular are key obstacles.In this work,a novel method,namely hydriding combustion synthesis plus short-term mechanical milling followed by air exposure,was proposed to synthesize air stable and autocatalytic magnesium nickel hydride(Mg2NiH4),which shows excellent hydrogen absorption/desorption kinetics,capacity retention and oxidation resistance.The short-term-milled Mg2NiH4 can desorb 2.97 wt.%hydrogen within 500 s at 230℃.Even after exposure under air atmosphere for 67 days,it can still desorb 2.88 wt.%hydrogen within 500 s at 230℃.The experimental and theoretical results both indicated that the surface of as-milled Mg2NiH4 was easy to be oxidized under air atmosphere.However,the in-situ formed Ni during air exposure of Mg2NiH4 improved the hydrogen desorption kinetics,and the formed surface passivation layer maintained the hydrogen storage capacity and avoided further poisoning,which we called autocatalytic and self-protective effect.Such a novel dual effect modified the reaction activity and oxidation resistance of the air-exposed Mg2NiH4.Our findings provide useful insights into the design and preparation of air stable metal-based hydride for large-scale utilization and long-term storage.展开更多
The hydrogenation of CO_(2) into methanol has attracted much attention and In_(2)O_(3) is a promising catalyst.Introducing metal elements into In_(2)O_(3)(M/In_(2)O_(3))is one of the main strategies to improve its per...The hydrogenation of CO_(2) into methanol has attracted much attention and In_(2)O_(3) is a promising catalyst.Introducing metal elements into In_(2)O_(3)(M/In_(2)O_(3))is one of the main strategies to improve its performance.However,its mechanism and active sites remain unclear and need to be further elucidated.Here,the noble‐metal‐free In_(x)‐Co_(y) oxides catalysts were prepared.Much‐improved performance and obvious product selectivity shift were observed.The optimized catalyst(In_(1)‐Co_(4))(9.7 mmol g_(cat)^(–1) h^(–1))showed five times methanol yields than pure In_(2)O_(3)(2.2 mmol g_(cat)^(–1) h^(–1))(P=4.0 MPa,T=300°C,GHSV=24000 cm^(3)_(STP) g_(cat)^(–1) h^(–1),H_(2):CO_(2)=3).And the cobalt‐catalyzed CO_(2) methanation activity was suppressed,although cobalt was most of the metal element.To unravel this selectivity shift,detailed catalysts performance evaluation,together with several in‐situ and ex‐situ characterizations,were employed on cobalt and In‐Co for comparative study.The results indicated CO_(2) hydrogenation on cobalt and In‐Co catalyst both followed the formate pathway,and In‐Co reconstructed and generated a surface In_(2)O_(3)‐enriched core‐shell‐like structure under a reductive atmosphere.The enriched In_(2)O_(3) at the surface significantly enhanced CO_(2) adsorption capacity and well stabilized the intermediates of CO_(2) hydrogenation.CO_(2) and carbon‐containing intermediates adsorbed much stronger on In‐Co than cobalt led to a feasible surface C/H ratio,thus allowing the*CH_(3)O to desorb to produce CH_(3)OH instead of being over‐hydrogenated to CH_(4).展开更多
In the electrochemical process,Pt nanoparticles(NPs)in Pt-based catalysts usually agglomerate due to Oswald ripening or lack of restraint,ultimately resulting in reduction of the active sites and catalytic efficiency....In the electrochemical process,Pt nanoparticles(NPs)in Pt-based catalysts usually agglomerate due to Oswald ripening or lack of restraint,ultimately resulting in reduction of the active sites and catalytic efficiency.How to uniformly disperse and firmly fix Pt NPs on carbon matrix with suitable particle size for catalysis is still a big challenge.Herein,to prevent the agglomeration and shedding of Pt NPs,Ni species is introduced and are evenly dispersed in the surface of carbon matrix in the form of Ni-N-C active sites(Ni ZIF-NC).The Ni sites can be used to anchor Pt NPs,and then effectively limit the further growth and agglomeration of Pt NPs during the reaction process.Compared with commercial Pt/C catalyst,Pt@Ni ZIF-NC,with ultralow Pt loading(7 wt%)and ideal particle size(2.3 nm),not only increases the active center,but also promotes the catalysis kinetics,greatly improving the ORR and HER catalytic activity.Under acidic conditions,its half-wave potential(0.902 V)is superior to commercial Pt/C(0.861 V),and the mass activity(0.38 A per mg Pt)at 0.9 V is 4.7 times that of Pt/C(0.08 A per mg Pt).Besides,it also shows outstanding HER performance.At 20 and 30 mV,its mass activity is even 2 and 6 times that of Pt/C,respectively.Whether it is under ORR or HER conditions,it still shows excellent durability.These undoubtedly indicate the realization of dual-functional catalysts with low-Pt and high-efficiency properties.展开更多
To have an insight into the occurrence of inverse Hall-Petch relationship in ultrafine-grained(UFG) aluminum alloys produced by severe plastic deformation(SPD),ultra-SPD(i.e.inducing several ten thousand shear strains...To have an insight into the occurrence of inverse Hall-Petch relationship in ultrafine-grained(UFG) aluminum alloys produced by severe plastic deformation(SPD),ultra-SPD(i.e.inducing several ten thousand shear strains via high-pressure torsion,HPT) followed by aging is applied to an Al-La-Ce alloy.Average nanograin sizes of 40 and 80 nm are successfully achieved together with strain-induced Lomer-Cottrell dislocation lock formation and aging-induced semi-coherent Al_(11)(La,Ce)_3 precipitation.Analysis of hardening mechanisms in this alloy compared to SPD-processed pure aluminum with micrometer grain sizes,SPD-processed Al-based alloys with submicrometer grain sizes and ultra-SPD-processed Al-Ca alloy with nanograin sizes reveals the presence of two breaks in the Hall-Petch relationship.First,a positive upbreak appears when the grain sizes decrease from micrometer to submicrometer which is due to extra hardening by solute-dislocation interactions.Second,a negative down-break and softening occur by decreasing the grain sizes from submicrometer to nanometer which is caused by weakening the dislocation hardening mechanism with minor contribution of the inverse Hall-Petch mechanism.Detailed analyses confirm that nanograin formation is not necessarily a solution for extra hardening of Al-based alloys and other accompanying strategies such as grain-boundary segregation and precipitation are required to overcome such a down-break and softening.展开更多
Since first establishing thermal measurement techniques for micrometer-scale wires,various methods have been devised and improved upon.However,the uncertainty of different measurements on the same sample has not yet b...Since first establishing thermal measurement techniques for micrometer-scale wires,various methods have been devised and improved upon.However,the uncertainty of different measurements on the same sample has not yet been discussed.In this work,a round robin test was performed to compare the thermal conductivity and thermal diffusivity measurement methods for a fine metal wire.The tested material was a pure gold wire,with a diameter of 30μm.The wire was cut into certain lengths and distributed to four institutions using five different measurement methods:the direct current(DC)self-heating method,the DC heating T-type method,the 3ωmethod for thermal conductivity,the scanning laser heating alternating current(AC)method,and the spot periodic heating radiation thermometry method for thermal diffusivity.After completing the measurements,the reported thermal conductivity and thermal diffusivity at room temperature,i.e.,317 W·m^(-1)·K^(-1)and 128×10^(-6)m^(2)·s^(-1),respectively,were adopted as references for comparison with the measurement results.The advantages and disadvantages of each method are described in terms of the effect of electrical and thermal junctions fabricated on a wire,such as an electrode,a thermocouple,and a heat bath.The knowledge obtained from the tested methods will be useful for selecting and designing a measurement technique for various wire-like materials.展开更多
Fast fluid transport on graphene has attracted a growing body of research due to a wide range of potential applications including thermal management,water desalination,energy harvesting,and lab-on-a-chip.Here,we criti...Fast fluid transport on graphene has attracted a growing body of research due to a wide range of potential applications including thermal management,water desalination,energy harvesting,and lab-on-a-chip.Here,we critically review the theoretical,simulational,and experimental progress regarding the fluid slippage on graphene.Based on the summary of the past studies,we give perspectives on future research directions towards complete understanding and practical applications of slip flow on graphene.展开更多
基金The National Natural Science Foundation of China(grant no.21991113)the Stable Support Plan Program of Shenzhen Natural Science Fund(program contract no.20200925161222002)+1 种基金Guangdong Basic and Applied Basic Research Foundation(grant nos.2021A1515110808 and 2021B1515020062)Guangdong Provincial Key Laboratory of Catalysis(grant no.2020B121201002).
文摘An Ir-catalyzed enantioselective hydrogenation of challenging tetrasubstituted exocyclic olefins is disclosed.This new catalytic system tolerates a broad substrate scope and affords valuable chiral cyclic β-amino esters possessing two vicinal stereocenters in high yields and excellent enantioselectivities and diastereoselectivities(up to 94% yield,96% ee,99:1 dr).Control experiments and deuterium-labeling reactions reveal an iminium hydrogenation mechanism upon Brønsted acid-promoted tautomerization of the C=C double bond to cycliciminium intermediates.Density functional theory calculations showcase that the excellent selectivities are derived from C-H…π interaction between the substrate and the chiral ligand.Application in gram-scale preparation of dexmethylphenidate with up to 1500 turnover number is also demonstrated,showing the promising potential of Ir-catalyzed enantioselective hydrogenation in drug synthesis.
基金financially supported by Guangdong Basic and Applied Basic Research Foundation (No. 2019A1515011985)the National Natural Science Foundation of China (Nos.52071157,51801078,52001070 and 52001079)+3 种基金the Natural Science Foundation of Jiangsu Province (No.BK20180986)the Natural Science Foundation of Guangxi Province (No. 2019GXNSFB A185004)Guangzhou Science and Technology Association Young Talent Lifting Project (No.X20200301071)the Open Fund of the Guangdong Provincial Key Laboratory of Advance Energy Storage Materials (No.AESM202102)
文摘Development of new materials with high hydrogen storage capacity and reversible hydrogen sorp-tion performances under mild conditions has very high value in both fundamental and application aspects.In the past years,some new systems with metastable structures,such as ultra-fine nanocrystalline alloys,amorphous alloys,nanoglass alloys,immiscible alloys,high-entropy alloys,have been abundantly studied as hydrogen storage mate-rials.Many new hydrogen storage properties either from the kinetics or thermodynamics aspects have been reported.In this review,recent advances of studies on metastable alloys for hydrogen storage applications have been comprehensively reviewed.The materials preparation methods to synthesize metastable hydrogen storage alloys are firstly reviewed.Afterwards,hydrogen storage prop-erties of the metastable alloys are summarized and dis-cussed,focusing on the unique kinetics and thermodynamics properties by forming of such unique metastable structures.For examples,superior hydrogena-tion kinetics and higher hydrogen storage capacity have been achieved in Mg-based amorphous and nanoglass alloys.Destabilized thermodynamics properties can be obtained in the immiscible Mg-Mn and Mg-Zr alloys.In addition to highlighting the recent achievements of metastable alloys in the field of hydrogen storage,the remaining challenges and trends of the emerging research are also discussed.
基金the financial support from the National Natural Science Foundation of China(51831009)the National Materials Genome Project(2016YFB0700600)the National Youth Top-Notch Talent Support Program。
文摘Lithium metal has been regarded as one of the most promising anode materials for high-energy-density batteries due to its extremely high theoretical gravimetric capacity of 3860 mAh·g^-1 along with its low electrochemical potential of-3.04 V.Unfortunately,uncontrollable Li dendrite growth and repetitive destruction/formation of the solid electrolyte interphase layer lead to poor safety and low Coulombic efficiencies(CEs)for long-term utilization,which largely restricts the practical applications of lithium metal anode.In this review,we comprehensively summarized important progresses achieved to date in suppressing Li dendrite growth.Strategies for protection of Li metal anodes include designing porous structured hosts,fabricating artificial solid electrolyte interface(SEI)layers,introducing electrolyte additives,using solid-state electrolytes and applying external fields.The protection of Li metal anodes can be achieved by regulating the stripping and deposition behaviours of Li ions.Finally,the challenges remaining for lithium metal battery systems and future perspectives for Li metal anodes in practical applications are outlined,which are expected to shed light on future research in this field.
基金supported in part by the Light Metals Educational Foundation of Japan,and in part by the MEXT,Japan through Grants-in-Aid for Scientific Research on Innovative Areas(Nos.JP19H05176&JP21H00150)the Challenging Research Exploratory(Grant No.JP22K18737)+6 种基金W.J.Botta is grateful to the Brazilian agencies FAPESP(Grant No.2013/05987-8)CNPq(Grant Nos.421181-2018-4 and 307397-2019-0)the financial support and to the Laboratory of Structural Characterization(LCE-DEMa-UFSCar)for general electron microscopy facilities.R.Floriano thanks for the financial support from FAPESP(Grant No.2022/01351-0)support from the French State through the ANR-21-CE08-0034-01 project as well as the program“Investment in the future”operated by the National Research Agency(ANR)referenced under No.ANR-11-LABX-0008-01(Labex DAMAS)support from the National Natural Science Foundation of China(Grant No.52171205)support from the National Natural Science Foundation of China(Grant No.52071157).
文摘Magnesium and its alloys are the most investigated materials for solid-state hydrogen storage in the form of metal hydrides,but there are still unresolved problems with the kinetics and thermodynamics of hydrogenation and dehydrogenation of this group of materials.Severe plastic deformation(SPD)methods,such as equal-channel angular pressing(ECAP),high-pressure torsion(HPT),intensive rolling,and fast forging,have been widely used to enhance the activation,air resistance,and hydrogenation/dehydrogenation kinetics of Mg-based hydrogen storage materials by introducing ultrafine/nanoscale grains and crystal lattice defects.These severely deformed materials,particularly in the presence of alloying additives or second-phase nanoparticles,can show not only fast hydrogen absorption/desorption kinetics but also good cycling stability.It was shown that some materials that are apparently inert to hydrogen can absorb hydrogen after SPD processing.Moreover,the SPD methods were effectively used for hydrogen binding-energy engineering and synthesizing new magnesium alloys with low thermodynamic stability for reversible low/room-temperature hydrogen storage,such as nanoglasses,high-entropy alloys,and metastable phases including the high-pressureγ-MgH2 polymorph.This work reviews recent advances in the development of Mg-based hydrogen storage materials by SPD processing and discusses their potential in future applications.
文摘A copper-ceria solid solution and ceria-supported copper catalysts were prepared and used for the catalytic hydrogenation of CO2 to CH3OH.According to site-specific classification and quantitative analyses(X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,H2 temperature-programmed reduction,and CO adsorption),the interfaces of the prepared catalysts were classified as Cu incorporated into ceria(Cu-Ov-Cex),dispersed Cu O(D-Cu O-Ce O2),and bulk Cu O(B-Cu O-Ce O2)over the Ce O2 surface.These results,together with those of activity tests,showed that the Cu-Ov-Cex species was closely related to the CO2 hydrogenation activity and resulted in a much higher turnover frequency of CH3OH production than that observed with the D-Cu O-Ce O2 and B-Cu O-Ce O2 species.Thus,the copper-ceria solid solution exhibited improved activity due to the higher Cu-Ov-Cex fraction.
基金support by the program of studying/visiting abroad(No.450404).
文摘Hydrogen has been widely considered as a clean energy carrier that bridges the energy producers and energy consumers in an efficient and safe way for a sustainable society.Hydrogen can be stored in a gas,liquid and solid states and each method has its unique advantage.Though compressed hydrogen and liquefied hydrogen are mature technologies for industrial applications,appropriate measures are necessary to deal with the issues at high pressure up to around 100 MPa and low temperature at around 20 K.Distinct from those technologies,storing hydrogen in solid-state hydrides can realize a more compact and much safer approach that does not require high hydrogen pressure and cryogenic temperature.In this review,we will provide an overview of the majormaterial groups that are capable of absorbing and desorbing hydrogen reversibly.The main features on hydrogen storage properties of each material group are summarized,together with the discussion of the key issues and the guidance of materials design,aiming at providing insights for new material development as well as industrial applications.
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education,Science and Technology(NRF-2020R1A6A1A03043435,NRF-2023R1A2C2003210,and NRF-2022M3H4A1A04096478)by Technology Innovation Program(Alchemist Project,20012196,Al based supercritical materials discovery)funded by the Ministry of Trade,Industry&Energy,Korea.support from the“Bundesministerium fur Bildung und Forschung”(BMBF)and the computing time granted through JARA-HPC on the supercomputer JURECA at Forschungszentrum Julich.
文摘This study explores the impact of introducing vacancy in the transition metal layer of rationally designed Na_(0.6)[Ni_(0.3)Ru_(0.3)Mn_(0.4)]O_(2)(NRM)cathode material.The incorporation of Ru,Ni,and vacancy enhances the structural stability during extensive cycling,increases the operation voltage,and induces a capacity increase while also activating oxygen redox,respectively,in Na_(0.7)[Ni_(0.2)V_(Ni0.1)Ru_(0.3)Mn_(0.4)]O_(2)(V-NRM)compound.Various analytical techniques including transmission electron microscopy,X-ray absorption near edge spectroscopy,operando X-ray diffraction,and operando differential electrochemical mass spectrometry are employed to assess changes in the average oxidation states and structural distortions.The results demonstrate that V-NRM exhibits higher capacity than NRM and maintains a moderate capacity retention of 81%after 100 cycles.Furthermore,the formation of additional lone-pair electrons in the O 2p orbital enables V-NRM to utilize more capacity from the oxygen redox validated by density functional calculation,leading to a widened dominance of the OP4 phase without releasing O_(2) gas.These findings offer valuable insights for the design of advanced high-capacity cathode materials with improved performance and sustainability in sodium-ion batteries.
基金National Research Foundation,Grant/Award Number:NRF-2020R1A3B2079803Korea Institute for Advancement of Technology,Grant/Award Number:P0026069。
文摘The polymeric gel electrolytes are attractive owing to their higher ionic conductivities than those of dry polymer electrolytes and lowered water activity for enlarged potential window.However,the ionic conductivity and mechanical strength of the Na-ion conducting polymeric gel electrolytes are limited by below 20 mS cm−1 and 2.2 MPa.Herein,we demonstrate Na-ion conducting and flexible polymeric hydrogel electrolytes of the chemically coupled poly(diallyldimethylammonium chloride)-dextrin-N,N′-methylene-bisacrylamide film immersed in NaClO_(4) solution(ex-DDA-Dex+NaClO_(4))for flexible sodium-ion hybrid capacitors(f-NIHC).In particular,the anion exchange reaction and synergistic interaction of ex-DDA-Dex with the optimum ClO_(4)−enable to greatly improve the ionic conductivity up to 27.63 mS cm−1 at 25◦C and electrochemical stability window up to 2.6 V,whereas the double networking structure leads to achieve both the mechanical strength(7.48 MPa)and softness of hydrogel electrolytes.Therefore,the f-NIHCs with the ex-DDA-Dex+NaClO_(4) achieved high specific and high-rate capacities of 192.04 F g^(−1)at 500 mA g^(−1)and 116.06 F g^(−1)at 10000 mA g^(−1),respectively,delivering a large energy density of 120.03Wh kg^(−1)at 906Wkg^(−1)and long cyclability of 70%over 500 cycles as well as demonstrating functional operation under mechanical stresses.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(NRF-2022R1C1C1011058)。
文摘In this review,we discuss the electrochemical properties of Prussian blue(PB)for Na^(+)storage by combining structural engineering and electrolyte modifications.We integrated experimental data and density functional theory(DFT)in sodium-ion battery(SIB)research to refine the atomic arrangements and crystal lattices and introduce substitutions and dopants.These changes affect the lattice stability,intercalation,electronic and ionic conductivities,and electrochemical performance.We unraveled the intricate structure-electrochemical behavior relationship by combining experimental data with computational models,including first-principles calculations.This holistic approach identified techniques for optimizing PB and Prussian blue analog(PBA)structu ral properties for SIBs.We also discuss the tuning of electrolytes by systematically adjusting their composition,concentration,and additives using a combination of molecular dynamics(MD)simulations and DFT computations.Our review offers a comprehensive assessment of strategies for enhancing the electrochemical properties of PB and PBAs through structural engineering and electrolyte modifications,combining experimental insights with advanced computational simulations,and paving the way for next-generation energy storage systems.
文摘One of the impacts of the Fukushima disaster was the shutdown of all nuclear power plants in Japan,reaching zero production in 2015.In response,the country started importing more fossil energy including coal,oil,and natural gas to fill the energy gap.However,this led to a significant increase in carbon emissions,hindering the efforts to reduce its carbon footprint.In the current situation,Japan is actively working to balance its energy requirements with environmental considerations,including the utilization of hydrogen fuel.Therefore,this paper aims to explore the feasibility and implications of using hydrogen power plants as a means to reduce emissions,and this analysis will be conducted using the energy modeling of the MARKAL-TIMES Japan framework.The hydrogen scenario(HS)is assumed with the extensive integration of hydrogen into the power generation sector,supported by a hydrogen import scheme.Additionally,this scenario will be compared with the Business as Usual(BAU)scenario.The results showed that the generation capacities of the BAU and HS scenarios have significantly different primary energy supplies.The BAU scenario is highly dependent on fossil fuels,while the HS scenario integrates hydrogen contribution along with an increase in renewable energy,reaching a peak contribution of 2,160 PJ in 2050.In the HS scenario,the target of reducing CO_(2) emissions by 80%is achieved through significant hydrogen penetration.By 2050,the total CO_(2) emissions are estimated to be 939 million tons for the BAU scenario and 261 million tons for the Hydrogen scenario.In addition,the contribution of hydrogen to electricity generation is expected to be 153 TWh,smaller than PV and wind power.
基金the Hosokawa Powder Technology Foundation of Japan for a grantsupported by the MEXT, Japan through Grants-in-Aid for Scientific Research on Innovative Areas (Nos. JP19H05176 and JP21H00150)in part by the MEXT, Japan through Grant-in-Aid for Challenging Research Exploratory (No. JP22K18737)。
文摘High-entropy alloys and ceramics containing at least five principal elements have recently received high attention for various mechanical and functional applications.The application of severe plastic deformation(SPD),particularly the high-pressure torsion method,combined with the CALPHAD(calculation of phase diagram) and first-principles calculations resulted in the development of numerous superfunctional high-entropy materials with superior properties compared to the normal functions of engineering materials.This article reviews the recent advances in the application of SPD to developing superfunctional high-entropy materials.These superfunctional properties include(ⅰ) ultrahigh hardness levels comparable to the hardness of ceramics in high-entropy alloys,(ⅱ) high yield strength and good hydrogen embrittlement resistance in high-entropy alloys;(ⅲ) high strength,low elastic modulus,and high biocompatibility in high-entropy alloys,(ⅳ) fast and reversible hydrogen storage in high-entropy hydrides,(ⅴ) photovoltaic performance and photocurrent generation on high-entropy semiconductors,(ⅵ) photocatalytic oxygen and hydrogen production from water splitting on high-entropy oxides and oxynitrides,and(ⅶ)CO_(2) photoreduction on high-entropy ceramics.These findings introduce SPD as not only a processing tool to improve the properties of existing high-entropy materials but also as a synthesis tool to produce novel high-entropy materials with superior properties compared with conventional engineering materials.
基金supported by institutional program grants from the Korea Institute of Science and Technology and Korea Institute of Energy Technology Evaluation and Planning(KETEP)granted financial resource from the Ministry of Trade,Industry&Energy,Republic of Korea(No.20224C10300020)“Carbon to X Project”(2020M3H7A1098229)through the National Research Foundation(NRF)funded by the Ministry of Science and ICT,Republic of Korea+1 种基金supported by the National Research Council of Science&Technology(NST)grant by the Korean government(MSIT)(No.CAP21011-100)National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIT)(NRF-2021R1A2C2093467)。
文摘Introducing Ni in Ru oxide is a promising approach to enhance the catalytic activity for the oxygen evolution reaction(OER).However,the role of Ni(which has a poor intrinsic activity)is not fully understood.Here,a Ru NiO_(x)electrode fabricated via a modified dip coating method exhibited excellent OER performance in acidic media,and neutral media for CO_(2)reduction reaction.We combined in-situ/operando X-ray absorption near-edge structure and on-line inductively coupled plasma mass spectrometry studies to unveil the role of the Ni introduced in the Ru oxide.We propose that the Ni not only transforms the electronic structure of the Ru oxide,but also produces a large number of oxygen vacancies by distorting the oxygen lattice structure at low overpotentials,increasing the participation of lattice oxygen for OER.This work demonstrates the real behavior of bimetallic oxide materials under applied potentials and provides new insights into the development of efficient electrocatalysts.
基金This work was partly supported by a Grant-in-Aid for Scientific Research(A)(Grant number:25249100)from the Japan Society for the Promotion of Science.
文摘This article reports a new phosphorescent material,CaZnOS:Cu,that exhibits two types of mechano-optical conversion:mechanical quenching and mechanoluminescence.An intense mechanical quenching of phosphorescence corresponding to mechanical stimuli can be achieved in CaZnOS:Cu within a short decay time period.Over time,it gradually changes to mechanoluminescence when a mechanical load is applied.We propose that the mechanical quenching and mechanoluminescence arise from the different roles of shallow and deep traps in CaZnOS:Cu.CaZnOS:Cu has promising applications in monitoring mechanical stress in industrial plants,structures,and living bodies.
基金X.Liao gratefully thanks the support from the National Natural Science Foundation of China(No.21706216)the Sichuan Science and Technology Program(2020YFG0162)+3 种基金the Young Scholar Project in Xihua University.X.Li acknowledges the support from the National Natural Science Foundation of China(No.21972163)the Fundamental Research Funds for the Central Universities and DHU Distinguished Young Professor Program,and the Development Fund for Shanghai Talents.Z.Jiang acknowledges financial support from the Joint Fund U1732267.M.Y.thanks the JSPS KAKENHI(No.JP 18H05517)JST-CREST for financial supports,and Riken SPring-8 for the approval of the SRXRD measurement(20190028)EXAFS studies were carried out at the BL14W1 beamline in the Shanghai Synchrotron Radiation Facility[63],Shanghai Institute of Applied Physics,China(16ssr-f00787).X.Liao gratefully thanks the useful discussion with Ya Wang and Yanmin Liu.
文摘Tuning the coordination environment is the research axis of single atom catalysts (SACs). SACs are commonly stabilized by various defects from support. Here, we report a lattice confined Pd SAC using MnO_(2) as support. Compared with the Pd clusters anchored on the surface, the lattice confined Pd single atoms allows spontaneous exaction of surrounding lattice oxygen at room temperature when employed in CO oxidation. The MnO_(2) supported Pd SAC exhibited a high turnover frequency of 0.203 s^(−1) at low reaction temperature, which is higher than that of recently reported Pd SACs. Theoretical calculations also confirmed the confined monatomic Pd activate lattice oxygen with an ultralow energy barrier. Our results illustrate that the unique coordination environment of single atom provided by lattice confinement is promising to boost the activity of SACs.
基金the National Natural Science Foundation of China(Nos.51771092,52071177,and 21975125)Six Talent Peaks Project in Jiangsu Province(No.2018-XNY-020)the Priority Academic Program Development(PAPD)of Jiangsu Higher Education Institutions.
文摘Among the factors which restrict the large-scale utilization of magnesium-based hydride as a hydrogen storage medium,the high operating temperature,slow kinetics,and air stability in particular are key obstacles.In this work,a novel method,namely hydriding combustion synthesis plus short-term mechanical milling followed by air exposure,was proposed to synthesize air stable and autocatalytic magnesium nickel hydride(Mg2NiH4),which shows excellent hydrogen absorption/desorption kinetics,capacity retention and oxidation resistance.The short-term-milled Mg2NiH4 can desorb 2.97 wt.%hydrogen within 500 s at 230℃.Even after exposure under air atmosphere for 67 days,it can still desorb 2.88 wt.%hydrogen within 500 s at 230℃.The experimental and theoretical results both indicated that the surface of as-milled Mg2NiH4 was easy to be oxidized under air atmosphere.However,the in-situ formed Ni during air exposure of Mg2NiH4 improved the hydrogen desorption kinetics,and the formed surface passivation layer maintained the hydrogen storage capacity and avoided further poisoning,which we called autocatalytic and self-protective effect.Such a novel dual effect modified the reaction activity and oxidation resistance of the air-exposed Mg2NiH4.Our findings provide useful insights into the design and preparation of air stable metal-based hydride for large-scale utilization and long-term storage.
文摘The hydrogenation of CO_(2) into methanol has attracted much attention and In_(2)O_(3) is a promising catalyst.Introducing metal elements into In_(2)O_(3)(M/In_(2)O_(3))is one of the main strategies to improve its performance.However,its mechanism and active sites remain unclear and need to be further elucidated.Here,the noble‐metal‐free In_(x)‐Co_(y) oxides catalysts were prepared.Much‐improved performance and obvious product selectivity shift were observed.The optimized catalyst(In_(1)‐Co_(4))(9.7 mmol g_(cat)^(–1) h^(–1))showed five times methanol yields than pure In_(2)O_(3)(2.2 mmol g_(cat)^(–1) h^(–1))(P=4.0 MPa,T=300°C,GHSV=24000 cm^(3)_(STP) g_(cat)^(–1) h^(–1),H_(2):CO_(2)=3).And the cobalt‐catalyzed CO_(2) methanation activity was suppressed,although cobalt was most of the metal element.To unravel this selectivity shift,detailed catalysts performance evaluation,together with several in‐situ and ex‐situ characterizations,were employed on cobalt and In‐Co for comparative study.The results indicated CO_(2) hydrogenation on cobalt and In‐Co catalyst both followed the formate pathway,and In‐Co reconstructed and generated a surface In_(2)O_(3)‐enriched core‐shell‐like structure under a reductive atmosphere.The enriched In_(2)O_(3) at the surface significantly enhanced CO_(2) adsorption capacity and well stabilized the intermediates of CO_(2) hydrogenation.CO_(2) and carbon‐containing intermediates adsorbed much stronger on In‐Co than cobalt led to a feasible surface C/H ratio,thus allowing the*CH_(3)O to desorb to produce CH_(3)OH instead of being over‐hydrogenated to CH_(4).
基金supported by the National Natural Science Foundation of China(22075223,51701146)the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing(Wuhan University of Technology)(2021-ZD-4)。
文摘In the electrochemical process,Pt nanoparticles(NPs)in Pt-based catalysts usually agglomerate due to Oswald ripening or lack of restraint,ultimately resulting in reduction of the active sites and catalytic efficiency.How to uniformly disperse and firmly fix Pt NPs on carbon matrix with suitable particle size for catalysis is still a big challenge.Herein,to prevent the agglomeration and shedding of Pt NPs,Ni species is introduced and are evenly dispersed in the surface of carbon matrix in the form of Ni-N-C active sites(Ni ZIF-NC).The Ni sites can be used to anchor Pt NPs,and then effectively limit the further growth and agglomeration of Pt NPs during the reaction process.Compared with commercial Pt/C catalyst,Pt@Ni ZIF-NC,with ultralow Pt loading(7 wt%)and ideal particle size(2.3 nm),not only increases the active center,but also promotes the catalysis kinetics,greatly improving the ORR and HER catalytic activity.Under acidic conditions,its half-wave potential(0.902 V)is superior to commercial Pt/C(0.861 V),and the mass activity(0.38 A per mg Pt)at 0.9 V is 4.7 times that of Pt/C(0.08 A per mg Pt).Besides,it also shows outstanding HER performance.At 20 and 30 mV,its mass activity is even 2 and 6 times that of Pt/C,respectively.Whether it is under ORR or HER conditions,it still shows excellent durability.These undoubtedly indicate the realization of dual-functional catalysts with low-Pt and high-efficiency properties.
基金financially supported by the Light Metals Educational Foundation of Japan,the Ministry of Education,Culture,Sports,Science and Technology (MEXT) of Japan (No. 19H05176,21H00150)the Russian Science Foundation (No. 17-19-01311)。
文摘To have an insight into the occurrence of inverse Hall-Petch relationship in ultrafine-grained(UFG) aluminum alloys produced by severe plastic deformation(SPD),ultra-SPD(i.e.inducing several ten thousand shear strains via high-pressure torsion,HPT) followed by aging is applied to an Al-La-Ce alloy.Average nanograin sizes of 40 and 80 nm are successfully achieved together with strain-induced Lomer-Cottrell dislocation lock formation and aging-induced semi-coherent Al_(11)(La,Ce)_3 precipitation.Analysis of hardening mechanisms in this alloy compared to SPD-processed pure aluminum with micrometer grain sizes,SPD-processed Al-based alloys with submicrometer grain sizes and ultra-SPD-processed Al-Ca alloy with nanograin sizes reveals the presence of two breaks in the Hall-Petch relationship.First,a positive upbreak appears when the grain sizes decrease from micrometer to submicrometer which is due to extra hardening by solute-dislocation interactions.Second,a negative down-break and softening occur by decreasing the grain sizes from submicrometer to nanometer which is caused by weakening the dislocation hardening mechanism with minor contribution of the inverse Hall-Petch mechanism.Detailed analyses confirm that nanograin formation is not necessarily a solution for extra hardening of Al-based alloys and other accompanying strategies such as grain-boundary segregation and precipitation are required to overcome such a down-break and softening.
文摘Since first establishing thermal measurement techniques for micrometer-scale wires,various methods have been devised and improved upon.However,the uncertainty of different measurements on the same sample has not yet been discussed.In this work,a round robin test was performed to compare the thermal conductivity and thermal diffusivity measurement methods for a fine metal wire.The tested material was a pure gold wire,with a diameter of 30μm.The wire was cut into certain lengths and distributed to four institutions using five different measurement methods:the direct current(DC)self-heating method,the DC heating T-type method,the 3ωmethod for thermal conductivity,the scanning laser heating alternating current(AC)method,and the spot periodic heating radiation thermometry method for thermal diffusivity.After completing the measurements,the reported thermal conductivity and thermal diffusivity at room temperature,i.e.,317 W·m^(-1)·K^(-1)and 128×10^(-6)m^(2)·s^(-1),respectively,were adopted as references for comparison with the measurement results.The advantages and disadvantages of each method are described in terms of the effect of electrical and thermal junctions fabricated on a wire,such as an electrode,a thermocouple,and a heat bath.The knowledge obtained from the tested methods will be useful for selecting and designing a measurement technique for various wire-like materials.
基金the JST CREST Grant Number JPMJCR18I1,Japan,JST FOREST Program(Grant Number JPMJFR212M,Japan)JSPS KAKENHI(Grant Nos.JP20H02089,JP20H02090,and JP21K18693)。
文摘Fast fluid transport on graphene has attracted a growing body of research due to a wide range of potential applications including thermal management,water desalination,energy harvesting,and lab-on-a-chip.Here,we critically review the theoretical,simulational,and experimental progress regarding the fluid slippage on graphene.Based on the summary of the past studies,we give perspectives on future research directions towards complete understanding and practical applications of slip flow on graphene.
