Supported and colloidal single‐atom catalysts(SACs),which possess excellent catalytic properties,are particularly important in both fundamental studies and practical applications.The progress made in the preparation ...Supported and colloidal single‐atom catalysts(SACs),which possess excellent catalytic properties,are particularly important in both fundamental studies and practical applications.The progress made in the preparation methods,characterization,catalytic performances and mechanisms of SACs anchored to metal oxides,two‐dimensional materials and the surface of metal nanoclusters(NCs)are reviewed.The different techniques for SAC fabrication,including conventional solution methods based on co‐precipitation,incipient wetness co‐impregnation,and the chemical vapor deposition method,as well as the newer atom layer deposition(ALD)and galvanic replacement methods,are summarized.The main results from experimental and theoretical studies of various catalytic reactions over SACs,including oxidation reactions,hydrogenation,water gas shift,photocatalytic H2evolution and electrochemical reactions,are also discussed.Moreover,the electronic properties of the single atoms and their interactions with the supports are described to assist in understanding the origin of the high catalytic activity and selectivity of SACs.Finally,possible future research directions of SACs and their applications are proposed.展开更多
The austenite grain growth behavior in a simulated coarse-grained heat-affected zone during thermal cycling was investigated via in situ observation. Austenite grains nucleated at ferrite grain boundaries and then gre...The austenite grain growth behavior in a simulated coarse-grained heat-affected zone during thermal cycling was investigated via in situ observation. Austenite grains nucleated at ferrite grain boundaries and then grew in different directions through movement of grain boundaries into the ferrite phase. Subsequently, the adjacent austenite grains impinged against each other during the α→γtransformation. After the α→γ transformation, austenite grains coarsened via the coalescence of small grains and via boundary migration between grains. The growth process of austenite grains was a continuous process during heating, isothermal holding, and cooling in simulated thermal cycling. Abundant finely dispersed nanoscale TiN particles in a steel specimen containing 0.012wt% Ti effectively retarded the grain boundary migration, which resulted in refined austenite grains. When the Ti concentration in the steel was increased, the number of TiN particles de- creased and their size coarsened. The big particles were not effective in pinning the austenite grain boundary movement and resulted in coarse austenite grains.展开更多
Porous silicon(Si)nanostructures have aroused much interest as lithium-ion battery anodes because of the large space to accommodate the volume change in lithiation and delithiation and shorter ion transfer distance.Ho...Porous silicon(Si)nanostructures have aroused much interest as lithium-ion battery anodes because of the large space to accommodate the volume change in lithiation and delithiation and shorter ion transfer distance.However,fabrication of porous structures tends to be difficult to control and complex,so,the final electrochemical performance can be compromised.Herein,a modest magnesiothermic reduction(MMR)reaction is demonstrated to produce blackberry-like porous Si nanospheres(PSSs)controllably using magnesium silicide(Mg_(2)Si)as Mg source and SiO_(2)nanospheres as the reactant.This improved MR method provides good control of the kinetics and heat release compared to the traditional MR(TMR)method using Mg powder as the reactant.The PSSs obtained by MMR reaction has higher structural integrity than that fabricated by TMR.After encapsulation with reduced graphene oxide,the Si/C composite exhibits superior cycling stability and rates such as a high reversible capacity of 1034 mAh·g^(-1)at0.5 C(4200 mAh·g^(-1)at 1.0 C)after 1000 cycles,capacity retention of 79.5%,and high rate capacity of 497 mAh·g^(-1)at 2.0 C.This strategy offers a new route to fabricate highperformance porous Si anodes and can be extended to other materials such as germanium.展开更多
The effects of heat-treatment on corrosion behavior of Mg-15Gd-2Zn-0.39Zr alloys were investigated through microstructure characterization, corrosion tests, and scanning Kelvin probe force microscope(SKPFM) analysis. ...The effects of heat-treatment on corrosion behavior of Mg-15Gd-2Zn-0.39Zr alloys were investigated through microstructure characterization, corrosion tests, and scanning Kelvin probe force microscope(SKPFM) analysis. In long-term corrosion experiments, the corrosion rates of Mg-Gd-Zn-Zr alloys were mainly determined by the effects of micro-galvanic corrosion. During heat-treatment, the β-(Mg,Zn)3Gd eutectic phase in as-cast alloys transformed into a long-period stacking ordered(LPSO) phase, coupled with the precipitation of small precipitates. As heat-treatment proceeded, the local potential and the volume fraction of the LPSO phases reduced gradually compared with the eutectic phase, which resulted in a remarkable decrease of the micro-galvanic effect between the second phase and Mg matrix. As a result, the corrosion resistance of heat-treated alloys improved significantly.展开更多
To illuminate the corrosion behavior of MgO-based refractories under electromagnetic field(EMF),herein,the slag corrosion and penetration resistance of MgO–MgAl_(2)O_(4),MgO–CaO,and MgO–C refractories were investig...To illuminate the corrosion behavior of MgO-based refractories under electromagnetic field(EMF),herein,the slag corrosion and penetration resistance of MgO–MgAl_(2)O_(4),MgO–CaO,and MgO–C refractories were investigated using the rotary immersion slag resistance test at 1873 K for 1 h.The results showed that the order of the good slag resistance of as-tested refractories was MgO–C>MgO–CaO>MgO–MgAl_(2)O_(4).The EMF accelerated the corrosion and penetration of slag to the refractories,which caused the molten slag to be easier into the refractories by natural convection and Marangoni effect.In addition,the MgO–C refractories did not show an overwhelming advantage in slag resistance because EMF impeded the formation of the dense protection layer.Consequently,in view of the present results,the MgO–C refractories are still the most promising slag line material for refining furnace among MgO–MgAl_(2)O_(4),MgO–CaO,and MgO–C refractories.展开更多
Lithium(Li)metal with high theoretical capacity and low electrochemical potential is the most ideal anode for next-generation high-energy batteries.However,the practical implementation of Li anode has been hindered by...Lithium(Li)metal with high theoretical capacity and low electrochemical potential is the most ideal anode for next-generation high-energy batteries.However,the practical implementation of Li anode has been hindered by dendritic growth and volume expansion during cycling,which results in low Coulombic efficiency(CE),short lifespan,and safety hazards.Here,we report a highly stable and dendrite-free Li metal anode by utilizing N-doped hollow porous bowl-like hard carbon/reduced graphene nanosheets(CB@rGO)hybrids as three-dimensional(3D)conductive and lithiophilic scaffold host.The lithiophilic carbon bowl(CB)mainly works as excellent guides during the Li plating process,whereas the rGO layer with high conductivity and mechanical stability maintains the integrity of the composite by confining the volume change in long-range order during cycling.Moreover,the local current density can be reduced due to the 3D conductive framework.Therefore,CB@rGO presents a low lithium metal nucleation overpotential of 18 mV,high CE of 98%,and stable cycling without obvious voltage fluctuation for over 600 cycles at a current density of 1 mA cm^(-2).Our study not only provides a good CB@rGO host and pre-Lithiated CB@rGO composite anode electrode,but also brings a new strategy of designing 3D electrodes for those active materials suffering from severe volume expansion.展开更多
Developing safer and more efficient hydrogen storage technology is a pivotal step to realizing the hydrogen economy. Owing to the lightweight, high hydrogen storage density and abundant reserves, MgH_(2) has been wide...Developing safer and more efficient hydrogen storage technology is a pivotal step to realizing the hydrogen economy. Owing to the lightweight, high hydrogen storage density and abundant reserves, MgH_(2) has been widely studied as one of the most promising solidstate hydrogen storage materials. However, defects such as stable thermodynamics, sluggish kinetics and rapid capacity decay have seriously hindered its practical application. This article reviews recent advances in catalyst doping and nanostructures for improved kinetic performance of MgH_(2)/Mg systems for hydrogen release/absorption, the tuning of their thermodynamic stability properties by alloying and reactant destabilization, and the dual thermodynamic and kinetic optimization of the MgH_(2)/Mg system achieved by nanoconfinement with in situ catalysis and ball milling with in situ aerosol spraying, aiming to open new perspectives for the scale-up of MgH_(2) for hydrogen storage applications.展开更多
Two-dimensional(2D)transition metal carbide MXene-based materials hold great potentials applied for new electromagnetic wave(EMW)absorbers.However,the application of MXenes in the field of electromagnetic wave absorpt...Two-dimensional(2D)transition metal carbide MXene-based materials hold great potentials applied for new electromagnetic wave(EMW)absorbers.However,the application of MXenes in the field of electromagnetic wave absorption(EMA)is limited by the disadvantages of poor impedance matching,single loss mechanism,and easy oxidation.In this work,MoO_(3)/TiO_(2)/Mo_(2)TiC_(2)T_(x)hybrids were prepared by the annealing-treated Mo_(2)TiC_(2)T_(x)MXene and uniform MoO_(3)and TiO_(2)oxides in-situ grew on Mo_(2)TiC_(2)T_(x)layers.At the annealing temperature of 300℃,the minimum reflection loss(RLmin)value of MoO_(3)/TiO_(2)/Mo_(2)TiC_(2)T_(x)reaches-30.76 dB(2.3 mm)at 10.18 GHz with a significantly broadening effective absorption bandwidth(EAB)of 8.6 GHz(1.8 mm).The in-situ generated oxides creating numerous defects and heterogeneous interfaces enhance dipolar and interfacial polarizations and optimize the impedance matching of Mo_(2)TiC_(2)T_(x).Considering the excellent overall performance,the MoO_(3)/TiO_(2)/Mo_(2)TiC_(2)T_(x)hybrids can be a promising candidate for EMA.展开更多
Porous ceramics were prepared from kaolinite gangue and Al（OH）3 with double addition of MgCO3 and CaCO3 by the pore-forming in-situ technique.The characterizations of porous ceramics were investigated by X-ray diffr...Porous ceramics were prepared from kaolinite gangue and Al（OH）3 with double addition of MgCO3 and CaCO3 by the pore-forming in-situ technique.The characterizations of porous ceramics were investigated by X-ray diffractometry,scanning electron microscopy,and mercury porosimetry measurements,etc.It is found that although the decomposition of MgCO3 and CaCO3 has little contribution to the porosity,the double addition of MgCO3 and CaCO3 strongly affects the formation of liquid phase,and then changes the phase compositions,pore characterization,and strength.The appropriate mode is the sample containing 1.17wt% MgCO3 and 1.17wt% CaCO3,which has high apparent porosity（41.0%）,high crushing strength（53.5 MPa）,high mullite content（76wt%）,and small average pore size（3.24 μm）.展开更多
Hydrogen energy has been recognized as “Ultimate Power Source” in the 21st century, which could be the best solution to the looming energy crisis and climate degeneration in the near future. Due to its high safety, ...Hydrogen energy has been recognized as “Ultimate Power Source” in the 21st century, which could be the best solution to the looming energy crisis and climate degeneration in the near future. Due to its high safety, low price, abundant resources and decent hydrogen storage density, magnesium based solid-state hydrogen storage materials are becoming the leading candidate for onboard hydrogen storage. However,the high operation temperature and slow reaction rate of MgH_(2), as a result of the large formation enthalpy and high reaction activation energy,respectively, are the first and most difficult problems we need to face and overcome to realize its industrialization. Herein, a state-of-the-art review on tailoring the stable thermodynamics and sluggish kinetics of hydrogen storage in MgH_(2), particularly through nanoengnieering and catalysis is presented, aiming to provide references and solutions for its promotion and application. Promising methods to overcome the challenges faced by MgH_(2)/Mg, such as bidirectional catalysts and nanoconfinement with in-situ catalysis are compared and the required improvements are discussed to stimulate further discussions and ideas in the rational design of MgH_(2)/Mg systems with ability for hydrogen release/uptake at lower temperatures and cycle stability in the near future.展开更多
The lamellar hydrates of CAC were designed with the introduction of nano CaCO_(3)or Mg-Al hydrotalcite(M-A-H),and the effects on the green strength,pore structures,and high-temperature fracture behavior of alumina-spi...The lamellar hydrates of CAC were designed with the introduction of nano CaCO_(3)or Mg-Al hydrotalcite(M-A-H),and the effects on the green strength,pore structures,and high-temperature fracture behavior of alumina-spinel castables were investigated.The results show that nano CaCO_(3)or M-A-H stimulates rapidly the hydration of CAC and the formation of lamellar C_(4)AcH_(11)or coexistence of C_(2)AH_(8)and C_(4)AcH_(11)at 25℃.The formation of lamellar hydrates can contribute to a more complicated pore structure,especially in the range of 400-2000 nm.Meanwhile,the incorporation of well-distributed CaO or MgO sources from nano CaCO_(3)or M-A-H also regulates the distribution of CA_(6)and spinel(pre-formed and in-situ).Consequently,the optimized microstructure and complicated pore structure can induce the deflection and bridging of cracks,thus facilitating the consumption of fracture energy and enhancing the resistance to thermal stress damage.展开更多
Ti_(3)C_(2)T_(x)MXene shows great potential in the application as microwave absorbers due to its high attenuation ability.However,excessively high permittivity and self-stacking are the main obstacles that constrain i...Ti_(3)C_(2)T_(x)MXene shows great potential in the application as microwave absorbers due to its high attenuation ability.However,excessively high permittivity and self-stacking are the main obstacles that constrain its wide range of applications.To tackle these problems,herein,the microspheres of SiO_(2)@Ti_(3)C_(2)T_(x)@CoNi with the hydrangea-like core-shell structure were designed and prepared by a combinatorial electrostatic assembly and hydrothermal reaction method.These microspheres are constructed by an outside layer of CoNi nanosheets and intermediate Ti_(3)C_(2)T_(x)MXene nanosheets wrapping on the core of modified SiO_(2),engendering both homogenous and heterogeneous interfaces.Such trilayer SiO_(2)@Ti_(3)C_(2)T_(x)@CoNi microspheres are“magnetic microsize supercapacitors”that can not only induce dielectric loss and magnetic loss but also provide multilayer interfaces to enhance the interfacial polarization.The optimized impedance matching and core-shell structure could boost the reflection loss(RL)by electromagnetic synergy.The synthesized SiO_(2)@Ti_(3)C_(2)T_(x)@CoNi microspheres demonstrate outstanding microwave absorption(MA)performance benefited from these advantages.The obtained RL value was-63.95 dB at an ultra-thin thickness of 1.2 mm,corresponding to an effective absorption bandwidth(EAB)of 4.56 GHz.This work demonstrates that the trilayer core-shell structure designing strategy is highly efficient for tuning the MA performance of MXene-based microspheres.展开更多
The law of element segregation of Ti, N, Mn and S, and the sequence of selective precipitation of TiN and MnS inclusions during solidification of molten steel of SWRH82 A are studied on the basis of thermodynamics. Th...The law of element segregation of Ti, N, Mn and S, and the sequence of selective precipitation of TiN and MnS inclusions during solidification of molten steel of SWRH82 A are studied on the basis of thermodynamics. The origin of large TiN inclusions which affect the titanium inclusions point penalty in SWRH82 A wire rod is analyzed based on the research on the distribution characteristics of MnS and large size of TiN inclusions observed on metallographic specimen of SWRH82 A steel wire rod. The solidification segregation ratio of Ti is far more than that of N, and the solidification segregation ratio of S is far more than that of Mn. In the range of cooling rate of the continuous casting production, the cooling rate of solidification has little effect on the segregation ratios of Ti, N, Mn and S. MnS inclusions will precipitate earlier than TiN inclusions during solidification of the molten steel of SWRH82 A. The large TiN inclusion which is wrapped by MnS in the SWRH82 A wire rod may be foreign inclusions and it is not precipitated product during solidification in the molten steel of SWRH82 A.展开更多
MgO-CaO(40 wt.%CaO)refractory aggregates were prepared using the calcined dolomite and light-burned magnesia fine powder as raw materials and TiO_(2) as additive.The effect of TiO_(2) on their phase composition,micros...MgO-CaO(40 wt.%CaO)refractory aggregates were prepared using the calcined dolomite and light-burned magnesia fine powder as raw materials and TiO_(2) as additive.The effect of TiO_(2) on their phase composition,microstructures and properties was investigated by X-ray diffraction and scanning electron microscopy.The properties such as bulk density,apparent porosity,relative aggregate tube strength and hydration resistance were also investigated.The results showed that the CaTiO_(3) generated by the reaction between CaO and TiO_(2) was distributed around the CaO grain boundaries and intermittently distributed with MgO,which formed an isolation layer around CaO and greatly improved the hydration resistance.Meanwhile,the introduction of TiO_(2) promoted sintering and increased the grain size,further improving the strengths and hydration resistance of the materials.In addition,the most significant enhancement in the hydration resistance and strengths of the samples was achieved when 1.0-2.0 wt.%TiO_(2) was added.In this case,the relative strength of aggregate increased from 33.3% to 37.3%-43.1%,and the mass gain after the hydration test decreased from 3.13% to 1.26%-1.45%.展开更多
Due to chemical inertness of nickel and boron,the preparation of nickel borides and corresponding layered ternary transition metal borides Ni_(3)ZnB_(2)(MAB phase)has always required high-temperature and/or high-press...Due to chemical inertness of nickel and boron,the preparation of nickel borides and corresponding layered ternary transition metal borides Ni_(3)ZnB_(2)(MAB phase)has always required high-temperature and/or high-pressure conditions.Yet,an innovative and efficient approach to preparing Ni_(3)ZnB_(2)at only 600℃and without applied pressure is presented in this study.It is discovered that by simply adjusting the temperature,a phase transition from Ni_(3)ZnB_(2)to Ni4B3 with a layered structure could be induced.This transition between the binary-component and the ternary-component brings about significant variation in electromagnetic wave(EMW)shielding/absorption performance of prepared borides.For instance,Ni2B has good EMW shielding performance(42.54 dB in X band)and Ni_(3)ZnB_(2)is of weak EMW shielding(13.43 dB in X band);Ni_(3)ZnB_(2)has poor EMW absorption performance(−5 dB)while Ni4B3 has excellent EMW absorption performance(−45.19 dB)at a thickness of 2.7 mm with effective absorption bandwidth(10.4 GHz).展开更多
Studies show that manganese sulfide （MnS） inclusions in pipeline steel affect the lateral performance of steel in its rolling deformation, as well as the hydrogen induced cracking and sulfide stress corrosion cracki...Studies show that manganese sulfide （MnS） inclusions in pipeline steel affect the lateral performance of steel in its rolling deformation, as well as the hydrogen induced cracking and sulfide stress corrosion cracking resistance performance. To inhibit the precipitation of MnS and its effect on pipeline steel, a quenching experiment and a diffusion couple experiment, which investigated the evolution of MnS inclu sions in Ti bearing X80 pipeline steel, were conducted. The experimental results show that the transfor marion of the MnS inclusions during solidification is as follows： MnS→titanium sulfide （TiS） →Ti4 C2S2. The transition temperatures of MnS to TiS and TiS to Ti4C2S2 are 1673 and 1273 K, respectively, and the overall size of the sulfide decreased as well. Thermodynamic calculation results confirm that the transi tion temperatures of MnS to TiS and TiS to Ti4C2S2 are 1 623 and 1 203 K, respectively. When the sulfur content in the X80 pipeline steel is 0. 0015%, all the sulfur in the steel can be converted into Ti4C2S2 with a titanium content of more than 0.02%.展开更多
In order to improve the anti-explosion performance ofρ-Al_(2)O_(3) bonded corundum castables,H_(2)O_(2) was added(0,0.025%,0.050%,0.075%,0.100%and 0.125%,by mass)as the anti-explosion agent.After mixing and casting,s...In order to improve the anti-explosion performance ofρ-Al_(2)O_(3) bonded corundum castables,H_(2)O_(2) was added(0,0.025%,0.050%,0.075%,0.100%and 0.125%,by mass)as the anti-explosion agent.After mixing and casting,specimens were prepared.Some specimens were cured at room temperature for 12 h and demoulded for the anti-explosion performance test at different temperatures(450,500,550,600,650,700,750 and 800℃);the other specimens were cured,dried and fired,and tested in terms of the apparent porosity,the density,the cold mechanical properties,the air permeability and the pore size distribution.The results show that:(1)with the increase of the H_(2)O_(2) addition,the anti-explosion performance of castables increases gradually,the average pore size increases gradually,and the density and the strength decrease gradually;(2)by comprehensive consideration,the appropriate addition of H_(2)O_(2) shall be within 0.075%.展开更多
In the scope of developing new electrochemical concepts to build batteries with high energy density,chloride ion batteries(CIBs)have emerged as a candidate for the next generation of novel electrochemical energy stora...In the scope of developing new electrochemical concepts to build batteries with high energy density,chloride ion batteries(CIBs)have emerged as a candidate for the next generation of novel electrochemical energy storage technologies,which show the potential in matching or even surpassing the current lithium metal batteries in terms of energy density,dendrite-free safety,and elimination of the dependence on the strained lithium and cobalt resources.However,the development of CIBs is still at the initial stage with unsatisfactory performance and several challenges have hindered them from reaching commercialization.In this review,we examine the current advances of CIBs by considering the electrode material design to the electrolyte,thus outlining the new opportunities of aqueous CIBs especially combined with desalination,chloride redox battery,etc.With respect to the developing road of lithium ion and fluoride ion batteries,the possibility of using solid-state chloride ion conductors to replace liquid electrolytes is tentatively discussed.Going beyond,perspectives and clear suggestions are concluded by highlighting the major obstacles and by prescribing specific research topics to inspire more efforts for CIBs in large-scale energy storage applications.展开更多
The effect of nano-carbon black content(O,8 and 12 wt.%)on the wettability of molten steel on Al_(2)O_(3)-C substrates was investigated by the sessile drop wetting method at 1500℃ under argon atmosphere.At the beginn...The effect of nano-carbon black content(O,8 and 12 wt.%)on the wettability of molten steel on Al_(2)O_(3)-C substrates was investigated by the sessile drop wetting method at 1500℃ under argon atmosphere.At the beginning of the wetting experiment,the contact angle decreased with the increase in nano-carbon black content.As the wetting experiment progressed,FeAl_(2)0_(4) layer and sheet Al_(2)O_(3) layer were found at the interface between the molten steel and the Al_(2)O_(3)-C substrates with O and 8 wt.% nano-carbon black content,and the contact angle deceased with time.When the content of nano-carbon black was 12 wt.%,a large number of nano-Al_(2)O_(3) whiskers were observed,which made the contact angle between the molten steel and Al_(2)O_(3)-C substrate become large.Based on the scanning electron microscope and energy dispersive spectrometry results,the formation mechanism of FeAl2O4 layer and Al_(2)O_(3) layer and the interfacial reaction mechanism were proposed.展开更多
Magnesia-calcia refractories are widely used in the production process of clean steel due to their excellent high-tem-perature stability,slag resistance and ability to purify molten steel.However,there are still probl...Magnesia-calcia refractories are widely used in the production process of clean steel due to their excellent high-tem-perature stability,slag resistance and ability to purify molten steel.However,there are still problems such as difficult sintering and easy hydration.Magnesia-calcia materials with various calcium oxide contents were prepared by using induction sintering,and the sintering property combined with the hydration resistance of the materials was investigated.The experimental results showed that the magnesia-calcia materials prepared under induction field had higher density,microhardness and hydration resistance.In particular,the relative density of induction sintered magnesia-calcia materials with 50 mo1%CaO was greater than 98%,and the average grain size of CaO was 4.56μm,which was much larger than that of traditional sintered materials.In order to clarify the densification and microstructure evolution mechanism of the magnesia-calcia materials,the changes in temperature and magnetic field throughout the sintering process were analyzed by using finite element simulation.The results showed that the larger heating rate and higher sintering temperature under the induction sintering mode were beneficial to the rapid densification.In addition,the hot spots generated within the material due to the difference in high-temperature electric conductivity between MgO and CaO were the critical factor to realize selective sintering in MgO-CaO system,which provides a novel pathway to solve the problem of difficult sintering and control the microstructure of high-temperature composite material used in the field of high-purity steel smelting.展开更多
基金supported by the National Natural Science Foundation of China(51472184 and 51472185)the Science and Technology Support Program of Hubei Province(2013BHE003)the Program for Innovative Teams of Outstanding Young and Middle-Aged Researchers in the Higher Education Institutions of Hubei Province(T201602)~~
文摘Supported and colloidal single‐atom catalysts(SACs),which possess excellent catalytic properties,are particularly important in both fundamental studies and practical applications.The progress made in the preparation methods,characterization,catalytic performances and mechanisms of SACs anchored to metal oxides,two‐dimensional materials and the surface of metal nanoclusters(NCs)are reviewed.The different techniques for SAC fabrication,including conventional solution methods based on co‐precipitation,incipient wetness co‐impregnation,and the chemical vapor deposition method,as well as the newer atom layer deposition(ALD)and galvanic replacement methods,are summarized.The main results from experimental and theoretical studies of various catalytic reactions over SACs,including oxidation reactions,hydrogenation,water gas shift,photocatalytic H2evolution and electrochemical reactions,are also discussed.Moreover,the electronic properties of the single atoms and their interactions with the supports are described to assist in understanding the origin of the high catalytic activity and selectivity of SACs.Finally,possible future research directions of SACs and their applications are proposed.
基金financially supported by the Postdoctoral Science Foundation of China (No. 2014M550415)the National Natural Science Foundation of China (No. 50734004)
文摘The austenite grain growth behavior in a simulated coarse-grained heat-affected zone during thermal cycling was investigated via in situ observation. Austenite grains nucleated at ferrite grain boundaries and then grew in different directions through movement of grain boundaries into the ferrite phase. Subsequently, the adjacent austenite grains impinged against each other during the α→γtransformation. After the α→γ transformation, austenite grains coarsened via the coalescence of small grains and via boundary migration between grains. The growth process of austenite grains was a continuous process during heating, isothermal holding, and cooling in simulated thermal cycling. Abundant finely dispersed nanoscale TiN particles in a steel specimen containing 0.012wt% Ti effectively retarded the grain boundary migration, which resulted in refined austenite grains. When the Ti concentration in the steel was increased, the number of TiN particles de- creased and their size coarsened. The big particles were not effective in pinning the austenite grain boundary movement and resulted in coarse austenite grains.
基金the National Natural Science Foundation of China(Nos.51974208 and51504171)the Major Project of Technology Innovation of Hubei Province(No.2018AAA011)+4 种基金the Special Project of Central Government for Local Science and Technology Development of Hubei Province(No.2019ZYYD024)the Innovation Group of Natural Science Foundation of Hubei Province(No.2019CFA020)Wuhan Yellow Crane Talents ProgramCity University of Hong Kong Applied Research Grant(ARG)(No.9667122)Hong Kong Research Grants Council(RGC)General Research Funds(GRF)(No.City U 11205617)。
文摘Porous silicon(Si)nanostructures have aroused much interest as lithium-ion battery anodes because of the large space to accommodate the volume change in lithiation and delithiation and shorter ion transfer distance.However,fabrication of porous structures tends to be difficult to control and complex,so,the final electrochemical performance can be compromised.Herein,a modest magnesiothermic reduction(MMR)reaction is demonstrated to produce blackberry-like porous Si nanospheres(PSSs)controllably using magnesium silicide(Mg_(2)Si)as Mg source and SiO_(2)nanospheres as the reactant.This improved MR method provides good control of the kinetics and heat release compared to the traditional MR(TMR)method using Mg powder as the reactant.The PSSs obtained by MMR reaction has higher structural integrity than that fabricated by TMR.After encapsulation with reduced graphene oxide,the Si/C composite exhibits superior cycling stability and rates such as a high reversible capacity of 1034 mAh·g^(-1)at0.5 C(4200 mAh·g^(-1)at 1.0 C)after 1000 cycles,capacity retention of 79.5%,and high rate capacity of 497 mAh·g^(-1)at 2.0 C.This strategy offers a new route to fabricate highperformance porous Si anodes and can be extended to other materials such as germanium.
基金financial support from the National Natural Science Foundation of China (Nos. 51531007 and 51771050)the National program for the Young Top-notch Professionalsthe Fundamental Research Funds for the Central Universities (N170205002)
文摘The effects of heat-treatment on corrosion behavior of Mg-15Gd-2Zn-0.39Zr alloys were investigated through microstructure characterization, corrosion tests, and scanning Kelvin probe force microscope(SKPFM) analysis. In long-term corrosion experiments, the corrosion rates of Mg-Gd-Zn-Zr alloys were mainly determined by the effects of micro-galvanic corrosion. During heat-treatment, the β-(Mg,Zn)3Gd eutectic phase in as-cast alloys transformed into a long-period stacking ordered(LPSO) phase, coupled with the precipitation of small precipitates. As heat-treatment proceeded, the local potential and the volume fraction of the LPSO phases reduced gradually compared with the eutectic phase, which resulted in a remarkable decrease of the micro-galvanic effect between the second phase and Mg matrix. As a result, the corrosion resistance of heat-treated alloys improved significantly.
基金The authors gratefully acknowledge the support of the open research fund for State Key Laboratory of Advance Refractories(Grant Nos.SKLAR201904 and SKLAR202001)National Natural Science Foundation of China(Grant No.51772277).
文摘To illuminate the corrosion behavior of MgO-based refractories under electromagnetic field(EMF),herein,the slag corrosion and penetration resistance of MgO–MgAl_(2)O_(4),MgO–CaO,and MgO–C refractories were investigated using the rotary immersion slag resistance test at 1873 K for 1 h.The results showed that the order of the good slag resistance of as-tested refractories was MgO–C>MgO–CaO>MgO–MgAl_(2)O_(4).The EMF accelerated the corrosion and penetration of slag to the refractories,which caused the molten slag to be easier into the refractories by natural convection and Marangoni effect.In addition,the MgO–C refractories did not show an overwhelming advantage in slag resistance because EMF impeded the formation of the dense protection layer.Consequently,in view of the present results,the MgO–C refractories are still the most promising slag line material for refining furnace among MgO–MgAl_(2)O_(4),MgO–CaO,and MgO–C refractories.
基金supported by the National Natural Science Foundation of China(Nos.52072323 and 51872098)the“Double-First Class”Foundation of Materials and Intelligent Manufacturing Discipline of Xiamen University,as well as Postdoctoral Foundation of China(2018M632929).
文摘Lithium(Li)metal with high theoretical capacity and low electrochemical potential is the most ideal anode for next-generation high-energy batteries.However,the practical implementation of Li anode has been hindered by dendritic growth and volume expansion during cycling,which results in low Coulombic efficiency(CE),short lifespan,and safety hazards.Here,we report a highly stable and dendrite-free Li metal anode by utilizing N-doped hollow porous bowl-like hard carbon/reduced graphene nanosheets(CB@rGO)hybrids as three-dimensional(3D)conductive and lithiophilic scaffold host.The lithiophilic carbon bowl(CB)mainly works as excellent guides during the Li plating process,whereas the rGO layer with high conductivity and mechanical stability maintains the integrity of the composite by confining the volume change in long-range order during cycling.Moreover,the local current density can be reduced due to the 3D conductive framework.Therefore,CB@rGO presents a low lithium metal nucleation overpotential of 18 mV,high CE of 98%,and stable cycling without obvious voltage fluctuation for over 600 cycles at a current density of 1 mA cm^(-2).Our study not only provides a good CB@rGO host and pre-Lithiated CB@rGO composite anode electrode,but also brings a new strategy of designing 3D electrodes for those active materials suffering from severe volume expansion.
基金financially supported by Research Funds for the Central Universities (No. 2023CDJXY-019)the Fundamental Guiding Project of Scientific Research Program in Ministry of Education of Hubei Province (No. B2021025)+2 种基金Shenzhen Municipal Science and Technology Innovation Commission (No. JCYJ20210324141613032)the Innovative Research Group Project of the Natural Science Foundation of Hubei Province (No. 2019CFA020)Special Projects for Local Science and Technology Development Guided by the Chinese Central Government (No. 2019ZYYD024)。
文摘Developing safer and more efficient hydrogen storage technology is a pivotal step to realizing the hydrogen economy. Owing to the lightweight, high hydrogen storage density and abundant reserves, MgH_(2) has been widely studied as one of the most promising solidstate hydrogen storage materials. However, defects such as stable thermodynamics, sluggish kinetics and rapid capacity decay have seriously hindered its practical application. This article reviews recent advances in catalyst doping and nanostructures for improved kinetic performance of MgH_(2)/Mg systems for hydrogen release/absorption, the tuning of their thermodynamic stability properties by alloying and reactant destabilization, and the dual thermodynamic and kinetic optimization of the MgH_(2)/Mg system achieved by nanoconfinement with in situ catalysis and ball milling with in situ aerosol spraying, aiming to open new perspectives for the scale-up of MgH_(2) for hydrogen storage applications.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.U2004177 and U21A2064)Outstanding Youth Fund of Henan Province(No.212300410081)Support Plan for Scientific and Technological Innovation Talents in Colleges and Universities of Henan Province(No.22HASTIT001)。
文摘Two-dimensional(2D)transition metal carbide MXene-based materials hold great potentials applied for new electromagnetic wave(EMW)absorbers.However,the application of MXenes in the field of electromagnetic wave absorption(EMA)is limited by the disadvantages of poor impedance matching,single loss mechanism,and easy oxidation.In this work,MoO_(3)/TiO_(2)/Mo_(2)TiC_(2)T_(x)hybrids were prepared by the annealing-treated Mo_(2)TiC_(2)T_(x)MXene and uniform MoO_(3)and TiO_(2)oxides in-situ grew on Mo_(2)TiC_(2)T_(x)layers.At the annealing temperature of 300℃,the minimum reflection loss(RLmin)value of MoO_(3)/TiO_(2)/Mo_(2)TiC_(2)T_(x)reaches-30.76 dB(2.3 mm)at 10.18 GHz with a significantly broadening effective absorption bandwidth(EAB)of 8.6 GHz(1.8 mm).The in-situ generated oxides creating numerous defects and heterogeneous interfaces enhance dipolar and interfacial polarizations and optimize the impedance matching of Mo_(2)TiC_(2)T_(x).Considering the excellent overall performance,the MoO_(3)/TiO_(2)/Mo_(2)TiC_(2)T_(x)hybrids can be a promising candidate for EMA.
基金Puyang Re-fractories Co. Ltd. for financially supporting
文摘Porous ceramics were prepared from kaolinite gangue and Al（OH）3 with double addition of MgCO3 and CaCO3 by the pore-forming in-situ technique.The characterizations of porous ceramics were investigated by X-ray diffractometry,scanning electron microscopy,and mercury porosimetry measurements,etc.It is found that although the decomposition of MgCO3 and CaCO3 has little contribution to the porosity,the double addition of MgCO3 and CaCO3 strongly affects the formation of liquid phase,and then changes the phase compositions,pore characterization,and strength.The appropriate mode is the sample containing 1.17wt% MgCO3 and 1.17wt% CaCO3,which has high apparent porosity（41.0%）,high crushing strength（53.5 MPa）,high mullite content（76wt%）,and small average pore size（3.24 μm）.
基金funded by Chongqing Special Key Project of Technology Innovation and Application Development(Grant No.cstc2019jscx-dxwt BX0016)Guiding Project of Scientific Research Program in Ministry of Education of Hubei Province (No. B2021025)Fundamental Research Funds for the Central Universities (2022CDJXY-010 and 2022CDJQY-013)。
文摘Hydrogen energy has been recognized as “Ultimate Power Source” in the 21st century, which could be the best solution to the looming energy crisis and climate degeneration in the near future. Due to its high safety, low price, abundant resources and decent hydrogen storage density, magnesium based solid-state hydrogen storage materials are becoming the leading candidate for onboard hydrogen storage. However,the high operation temperature and slow reaction rate of MgH_(2), as a result of the large formation enthalpy and high reaction activation energy,respectively, are the first and most difficult problems we need to face and overcome to realize its industrialization. Herein, a state-of-the-art review on tailoring the stable thermodynamics and sluggish kinetics of hydrogen storage in MgH_(2), particularly through nanoengnieering and catalysis is presented, aiming to provide references and solutions for its promotion and application. Promising methods to overcome the challenges faced by MgH_(2)/Mg, such as bidirectional catalysts and nanoconfinement with in-situ catalysis are compared and the required improvements are discussed to stimulate further discussions and ideas in the rational design of MgH_(2)/Mg systems with ability for hydrogen release/uptake at lower temperatures and cycle stability in the near future.
基金supported financially by the Natural Science Foundation of Qinghai(2022-ZJ-928)the Special Project for Transformation of Scientific and Technological Achievements of Qinghai Province(2023-GX-102).
文摘The lamellar hydrates of CAC were designed with the introduction of nano CaCO_(3)or Mg-Al hydrotalcite(M-A-H),and the effects on the green strength,pore structures,and high-temperature fracture behavior of alumina-spinel castables were investigated.The results show that nano CaCO_(3)or M-A-H stimulates rapidly the hydration of CAC and the formation of lamellar C_(4)AcH_(11)or coexistence of C_(2)AH_(8)and C_(4)AcH_(11)at 25℃.The formation of lamellar hydrates can contribute to a more complicated pore structure,especially in the range of 400-2000 nm.Meanwhile,the incorporation of well-distributed CaO or MgO sources from nano CaCO_(3)or M-A-H also regulates the distribution of CA_(6)and spinel(pre-formed and in-situ).Consequently,the optimized microstructure and complicated pore structure can induce the deflection and bridging of cracks,thus facilitating the consumption of fracture energy and enhancing the resistance to thermal stress damage.
基金supported by the National Natural Science Foundation of China(U2004177)the Outstanding Youth Fund of Henan Province(212300410081)the Support Plan for Scientific and Technological Innovation Talents in Colleges and Universities of Henan Province(22HASTIT001)。
文摘Ti_(3)C_(2)T_(x)MXene shows great potential in the application as microwave absorbers due to its high attenuation ability.However,excessively high permittivity and self-stacking are the main obstacles that constrain its wide range of applications.To tackle these problems,herein,the microspheres of SiO_(2)@Ti_(3)C_(2)T_(x)@CoNi with the hydrangea-like core-shell structure were designed and prepared by a combinatorial electrostatic assembly and hydrothermal reaction method.These microspheres are constructed by an outside layer of CoNi nanosheets and intermediate Ti_(3)C_(2)T_(x)MXene nanosheets wrapping on the core of modified SiO_(2),engendering both homogenous and heterogeneous interfaces.Such trilayer SiO_(2)@Ti_(3)C_(2)T_(x)@CoNi microspheres are“magnetic microsize supercapacitors”that can not only induce dielectric loss and magnetic loss but also provide multilayer interfaces to enhance the interfacial polarization.The optimized impedance matching and core-shell structure could boost the reflection loss(RL)by electromagnetic synergy.The synthesized SiO_(2)@Ti_(3)C_(2)T_(x)@CoNi microspheres demonstrate outstanding microwave absorption(MA)performance benefited from these advantages.The obtained RL value was-63.95 dB at an ultra-thin thickness of 1.2 mm,corresponding to an effective absorption bandwidth(EAB)of 4.56 GHz.This work demonstrates that the trilayer core-shell structure designing strategy is highly efficient for tuning the MA performance of MXene-based microspheres.
基金support from the Science Research Plan (201210321098) of Wuhan Science and Technology Bureau
文摘The law of element segregation of Ti, N, Mn and S, and the sequence of selective precipitation of TiN and MnS inclusions during solidification of molten steel of SWRH82 A are studied on the basis of thermodynamics. The origin of large TiN inclusions which affect the titanium inclusions point penalty in SWRH82 A wire rod is analyzed based on the research on the distribution characteristics of MnS and large size of TiN inclusions observed on metallographic specimen of SWRH82 A steel wire rod. The solidification segregation ratio of Ti is far more than that of N, and the solidification segregation ratio of S is far more than that of Mn. In the range of cooling rate of the continuous casting production, the cooling rate of solidification has little effect on the segregation ratios of Ti, N, Mn and S. MnS inclusions will precipitate earlier than TiN inclusions during solidification of the molten steel of SWRH82 A. The large TiN inclusion which is wrapped by MnS in the SWRH82 A wire rod may be foreign inclusions and it is not precipitated product during solidification in the molten steel of SWRH82 A.
基金the Key Project of the National Natural Science Foundation of China(Grant Nos.U21A2058 and 51802235)the Hubei Science and Technology Innovation Talent Project(Grant No.2023DJC087).
文摘MgO-CaO(40 wt.%CaO)refractory aggregates were prepared using the calcined dolomite and light-burned magnesia fine powder as raw materials and TiO_(2) as additive.The effect of TiO_(2) on their phase composition,microstructures and properties was investigated by X-ray diffraction and scanning electron microscopy.The properties such as bulk density,apparent porosity,relative aggregate tube strength and hydration resistance were also investigated.The results showed that the CaTiO_(3) generated by the reaction between CaO and TiO_(2) was distributed around the CaO grain boundaries and intermittently distributed with MgO,which formed an isolation layer around CaO and greatly improved the hydration resistance.Meanwhile,the introduction of TiO_(2) promoted sintering and increased the grain size,further improving the strengths and hydration resistance of the materials.In addition,the most significant enhancement in the hydration resistance and strengths of the samples was achieved when 1.0-2.0 wt.%TiO_(2) was added.In this case,the relative strength of aggregate increased from 33.3% to 37.3%-43.1%,and the mass gain after the hydration test decreased from 3.13% to 1.26%-1.45%.
基金supported by the National Natural Science Foundation of China(No.U2004177)Henan Province Key Research Project for Higher Education Institutions(No.23B430017)+1 种基金the Outstanding Youth Fund of Henan Province(No.212300410081)the Science and Technology Innovation Talents in Universities of Henan Province(CN)(No.22HASTIT001).
文摘Due to chemical inertness of nickel and boron,the preparation of nickel borides and corresponding layered ternary transition metal borides Ni_(3)ZnB_(2)(MAB phase)has always required high-temperature and/or high-pressure conditions.Yet,an innovative and efficient approach to preparing Ni_(3)ZnB_(2)at only 600℃and without applied pressure is presented in this study.It is discovered that by simply adjusting the temperature,a phase transition from Ni_(3)ZnB_(2)to Ni4B3 with a layered structure could be induced.This transition between the binary-component and the ternary-component brings about significant variation in electromagnetic wave(EMW)shielding/absorption performance of prepared borides.For instance,Ni2B has good EMW shielding performance(42.54 dB in X band)and Ni_(3)ZnB_(2)is of weak EMW shielding(13.43 dB in X band);Ni_(3)ZnB_(2)has poor EMW absorption performance(−5 dB)while Ni4B3 has excellent EMW absorption performance(−45.19 dB)at a thickness of 2.7 mm with effective absorption bandwidth(10.4 GHz).
基金supported by the National Natural Science Foundation of China(Grant No.51604201)
文摘Studies show that manganese sulfide （MnS） inclusions in pipeline steel affect the lateral performance of steel in its rolling deformation, as well as the hydrogen induced cracking and sulfide stress corrosion cracking resistance performance. To inhibit the precipitation of MnS and its effect on pipeline steel, a quenching experiment and a diffusion couple experiment, which investigated the evolution of MnS inclu sions in Ti bearing X80 pipeline steel, were conducted. The experimental results show that the transfor marion of the MnS inclusions during solidification is as follows： MnS→titanium sulfide （TiS） →Ti4 C2S2. The transition temperatures of MnS to TiS and TiS to Ti4C2S2 are 1673 and 1273 K, respectively, and the overall size of the sulfide decreased as well. Thermodynamic calculation results confirm that the transi tion temperatures of MnS to TiS and TiS to Ti4C2S2 are 1 623 and 1 203 K, respectively. When the sulfur content in the X80 pipeline steel is 0. 0015%, all the sulfur in the steel can be converted into Ti4C2S2 with a titanium content of more than 0.02%.
文摘In order to improve the anti-explosion performance ofρ-Al_(2)O_(3) bonded corundum castables,H_(2)O_(2) was added(0,0.025%,0.050%,0.075%,0.100%and 0.125%,by mass)as the anti-explosion agent.After mixing and casting,specimens were prepared.Some specimens were cured at room temperature for 12 h and demoulded for the anti-explosion performance test at different temperatures(450,500,550,600,650,700,750 and 800℃);the other specimens were cured,dried and fired,and tested in terms of the apparent porosity,the density,the cold mechanical properties,the air permeability and the pore size distribution.The results show that:(1)with the increase of the H_(2)O_(2) addition,the anti-explosion performance of castables increases gradually,the average pore size increases gradually,and the density and the strength decrease gradually;(2)by comprehensive consideration,the appropriate addition of H_(2)O_(2) shall be within 0.075%.
基金the support of the National Energy-Saving and Low-Carbon Materials Production and Application Demonstration Platform Program (TC220H06N)the National Natural Science Foundation of China (51832004,51972259,52127816)the Natural Science Foundation of Hubei Province (2022CFA087)。
文摘In the scope of developing new electrochemical concepts to build batteries with high energy density,chloride ion batteries(CIBs)have emerged as a candidate for the next generation of novel electrochemical energy storage technologies,which show the potential in matching or even surpassing the current lithium metal batteries in terms of energy density,dendrite-free safety,and elimination of the dependence on the strained lithium and cobalt resources.However,the development of CIBs is still at the initial stage with unsatisfactory performance and several challenges have hindered them from reaching commercialization.In this review,we examine the current advances of CIBs by considering the electrode material design to the electrolyte,thus outlining the new opportunities of aqueous CIBs especially combined with desalination,chloride redox battery,etc.With respect to the developing road of lithium ion and fluoride ion batteries,the possibility of using solid-state chloride ion conductors to replace liquid electrolytes is tentatively discussed.Going beyond,perspectives and clear suggestions are concluded by highlighting the major obstacles and by prescribing specific research topics to inspire more efforts for CIBs in large-scale energy storage applications.
基金This work was funded by the National Natural Science Foundation of China(No.51974214)the Natural Science Funds of Hubei Province for Distinguished Young Scholars(Grant No.2020CFA088).
文摘The effect of nano-carbon black content(O,8 and 12 wt.%)on the wettability of molten steel on Al_(2)O_(3)-C substrates was investigated by the sessile drop wetting method at 1500℃ under argon atmosphere.At the beginning of the wetting experiment,the contact angle decreased with the increase in nano-carbon black content.As the wetting experiment progressed,FeAl_(2)0_(4) layer and sheet Al_(2)O_(3) layer were found at the interface between the molten steel and the Al_(2)O_(3)-C substrates with O and 8 wt.% nano-carbon black content,and the contact angle deceased with time.When the content of nano-carbon black was 12 wt.%,a large number of nano-Al_(2)O_(3) whiskers were observed,which made the contact angle between the molten steel and Al_(2)O_(3)-C substrate become large.Based on the scanning electron microscope and energy dispersive spectrometry results,the formation mechanism of FeAl2O4 layer and Al_(2)O_(3) layer and the interfacial reaction mechanism were proposed.
基金The authors would like to express the gratitude for the financial support from the National Natural Science Foundation of China(U20A20239).
文摘Magnesia-calcia refractories are widely used in the production process of clean steel due to their excellent high-tem-perature stability,slag resistance and ability to purify molten steel.However,there are still problems such as difficult sintering and easy hydration.Magnesia-calcia materials with various calcium oxide contents were prepared by using induction sintering,and the sintering property combined with the hydration resistance of the materials was investigated.The experimental results showed that the magnesia-calcia materials prepared under induction field had higher density,microhardness and hydration resistance.In particular,the relative density of induction sintered magnesia-calcia materials with 50 mo1%CaO was greater than 98%,and the average grain size of CaO was 4.56μm,which was much larger than that of traditional sintered materials.In order to clarify the densification and microstructure evolution mechanism of the magnesia-calcia materials,the changes in temperature and magnetic field throughout the sintering process were analyzed by using finite element simulation.The results showed that the larger heating rate and higher sintering temperature under the induction sintering mode were beneficial to the rapid densification.In addition,the hot spots generated within the material due to the difference in high-temperature electric conductivity between MgO and CaO were the critical factor to realize selective sintering in MgO-CaO system,which provides a novel pathway to solve the problem of difficult sintering and control the microstructure of high-temperature composite material used in the field of high-purity steel smelting.
