Traditional electrode manufacturing for lithium-ion batteries is well established,reliable,and has already reached high processing speeds and improvements in production costs.For modern electric vehicles,however,the n...Traditional electrode manufacturing for lithium-ion batteries is well established,reliable,and has already reached high processing speeds and improvements in production costs.For modern electric vehicles,however,the need for batteries with high gravimetric and volumetric energy densities at cell level is increasing;and new production concepts are required for this purpose.During the last decade,laser processing of battery materials emerged as a promising processing tool for either improving manufacturing flexibility and product reliability or enhancing battery performances.Laser cutting and welding already reached a high level of maturity and it is obvious that in the near future they will become frequently implemented in battery production lines.This review focuses on laser texturing of electrode materials due to its high potential for significantly enhancing battery performances beyond state-of-the-art.Technical approaches and processing strategies for new electrode architectures and concepts will be presented and discussed with regard to energy and power density requirements.The boost of electrochemical performances due to laser texturing of energy storage materials is currently proven at the laboratory scale.However,promising developments in high-power,ultrafast laser technology may push laser structuring of batteries to the next technical readiness level soon.For demonstration in pilot lines adapted to future cell production,process upscaling regarding footprint area and processing speed are the main issues as well as the economic aspects with regards to CapEx amortization and the benefits resulting from the next generation battery.This review begins with an introduction of the three-dimensional battery and thick film concept,made possible by laser texturing.Laser processing of electrode components,namely current collectors,anodes,and cathodes will be presented.Different types of electrode architectures,such as holes,grids,and lines,were generated;their impact on battery performances are illustrated.The usage of high-energy materials,which are on the threshold of commercialization,is highlighted.Battery performance increase is triggered by controlling lithium-ion diffusion kinetics in liquid electrolyte filled porous electrodes.This review concludes with a discussion of various laser parameter tasks for process upscaling in a new type of extreme manufacturing.展开更多
Herein, a low-cost, biodegradable, and high-performance microwave shielding graphite/starch material was fabricated via constructing a cation-π interaction between ammonium ions and graphite. The graphite flakes and ...Herein, a low-cost, biodegradable, and high-performance microwave shielding graphite/starch material was fabricated via constructing a cation-π interaction between ammonium ions and graphite. The graphite flakes and starch were firstly mixed with distilled water containing ammonium hydroxide to form graphite/starch slurry under an ultrasonic assistant. The cation-π interaction could improve delamination degree and dispersion of graphite in starch matrix. The slurry was first used as a coating material on the surface of wood and paper to develop shielding packages. The effect of coating thickness and coating layers on EM shielding property of the materials was investigated. Second, the composites with a high orientation of graphite were fabricated by compression at high pressures. The electrical conductivity and EM shielding effectiveness(SET) of the materials were greatly enhanced by construction of cation-πinteraction and orientation of graphite. Specifically, the EM SETvalues increased from 56.9 to 66.8 d B for the composites with 50 wt.% graphite and 2.0 mm in thickness by constructing cation-π interaction. The EM SETvalues raised from 17.4 to 66.8 d B via the graphite orientation in the materials with the same components and thickness. The shielding mechanism of the compressed composites with orientation dispersion of graphite was also discussed in comparison to the coating layer with random dispersion of graphite.展开更多
There is an increasing demand for rechargeable batteries in high-performance energy storage systems.The current dominating Li-ion batteries are limited by price,resource availability,as well as their theoretical capac...There is an increasing demand for rechargeable batteries in high-performance energy storage systems.The current dominating Li-ion batteries are limited by price,resource availability,as well as their theoretical capacities.So that the community has started to explore alternative battery chemistries.As a promising multivalent battery type,rechargeable magnesium batteries(RMBs)have attracted increasing attention because of high safety,high volumetric energy density,and low cost thanks to abundant resource of Mg.However,the development of high-performance anodes is still hampered by formation of passivating layers on the Mg surface.Additionally,dendrites can also grow under certain conditions with pure Mg anodes,which requires further studies for reliable operation window and substitutes.Therefore,this review specifically aims to provide an overview on the often overlooked yet very important anode materials of RMBs,with the hope to inspire more attention and research efforts for the achievement of over-all better performance of future RMBs.c 2020 Published by Elsevier B.V.on behalf of Chongqing University.展开更多
Herein, the electrochemical performance and the mechanism of potassium insertion/deinsertion in orthorhombic V_(2)O_(5) nanoparticles are studied. The V2O5 electrode displays an initial potassiation/depotassiation cap...Herein, the electrochemical performance and the mechanism of potassium insertion/deinsertion in orthorhombic V_(2)O_(5) nanoparticles are studied. The V2O5 electrode displays an initial potassiation/depotassiation capacity of 200 mAh g^(−1)/217 mAh g^(−1) in the voltage range 1.5–4.0 V vs. K^(+)/K at C/12 rate, suggesting fast kinetics for potassium insertion/deinsertion. However, the capacity quickly fades during cycling, reaching 54 mAh g^(−1) at the 31st cycle. Afterwards, the capacity slowly increases up to 80 mAh g^(−1) at the 200th cycle. The storage mechanism upon K ions insertion into V2O5 is elucidated. In operando synchrotron diffraction reveals that V_(2)O_(5) first undergoes a solid solution to form K_(0.6)V_(2)O_(5) phase and then, upon further K ions insertion, it reveals coexistence of a solid solution and a two-phase reaction. During K ions deinsertion, the coexistence of solid solution and the two-phase reaction is identified together with an irreversible process. In operando XAS confirms the reduction/oxidation of vanadium during the K insertion/extraction with some irreversible contributions. This is consistent with the results obtained from synchrotron diffraction, ex situ Raman, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Moreover, ex situ XPS confirms the “cathode electrolyte interphase” (CEI) formation on the electrode and the decomposition of CEI film during cycling.展开更多
Density functional methods have been used for the calculation of electronic structures, electronic transitions, vertical electron affinities and intermolecular reorganization energies for tri-aryl substituted dibenzot...Density functional methods have been used for the calculation of electronic structures, electronic transitions, vertical electron affinities and intermolecular reorganization energies for tri-aryl substituted dibenzothiophenes. These model compounds were then compared to the predicted values for dibenzo[b,d]thiophen-2-yltriphenylsilane (DBTSI 2) and to dibenzo[b,d]thiophene-2,8-diylbis(diphenylphosphine oxide) (PO15), known electron transport molecules. The results indicate that these model compounds can be used in a blue OLED system.展开更多
Objective.Laser-treated surfaces for ventricular assist devices.Impact Statement.This work has scientific impact since it proposes a biofunctional surface created with laser processing in bioinert titanium.Introductio...Objective.Laser-treated surfaces for ventricular assist devices.Impact Statement.This work has scientific impact since it proposes a biofunctional surface created with laser processing in bioinert titanium.Introduction.Cardiovascular diseases are the world’s leading cause of death.An especially debilitating heart disease is congestive heart failure.Among the possible therapies,heart transplantation and mechanical circulatory assistance are the main treatments for its severe form at a more advanced stage.The development of biomaterials for ventricular assist devices is still being carried out.Although polished titanium is currently employed in several devices,its performance could be improved by enhancing the bioactivity of its surface.Methods.Aiming to improve the titanium without using coatings that can be detached,this work presents the formation of laser-induced periodic surface structures with a topology suitable for cell adhesion and neointimal tissue formation.The surface was modified by femtosecond laser ablation and cell adhesion was evaluated in vitro by using fibroblast cells.Results.The results indicate the formation of the desired topology,since the cells showed the appropriate adhesion compared to the control group.Scanning electron microscopy showed several positive characteristics in the cells shape and their surface distribution.The in vitro results obtained with different topologies point that the proposed LIPSS would provide enhanced cell adhesion and proliferation.Conclusion.The laser processes studied can create new interactions in biomaterials already known and improve the performance of biomaterials for use in ventricular assist devices.展开更多
Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+d...Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+dynamics and rapid capacity decay.In this study,we propose a medium-entropy cathode by simultaneously introducing Fe,Mg,and Li dopants into a typical P2-type Na_(0.75)Ni_(0.25)Mn_(0.75)O_(2)cathode.The modified Na_(0.75)Ni_(0.2125)Mn_(0.6375)Fe_(0.05)Mg_(0.05)Li_(0.05)O_(2)cathode predominantly exhibits a main P2 phase(93.5%)with a minor O3 phase(6.5%).Through spectroscopy techniques and electrochemical investigations,we elucidate the redox mechanisms of Ni^(2+/3+/4+),Mn^(3+/4+),Fe^(3+/4+),and O_(2)-/O_(2)^(n-)during charging/discharging.The medium-entropy doping mitigates the detrimental P2-O_(2)phase transition at high-voltage,replacing it with a moderate and reversible structural evolution(P2-OP4),thereby enhancing structural stability.Consequently,the modified cathode exhibits a remarkable rate capacity of 108.4 mAh·g^(-1)at 10C,with a capacity retention of 99.0%after 200 cycles at 1C,82.5%after 500 cycles at 5C,and 76.7%after 600 cycles at 10C.Furthermore,it also demonstrates superior electrochemical performance at high cutoff voltage of 4.5 V and extreme temperature(55 and 0℃).This work offers solutions to critical challenges in sodium ion batteries cathode materials.展开更多
Nickel-rich(Ni≥90%)layered oxides materials have emerged as a promising candidate for nextgeneration high-energy-density lithium-ion batteries(LIBs).However,their widespread application is hindered by structural fati...Nickel-rich(Ni≥90%)layered oxides materials have emerged as a promising candidate for nextgeneration high-energy-density lithium-ion batteries(LIBs).However,their widespread application is hindered by structural fatigue and lattice oxygen loss.In this work,an epitaxial surface rock-salt nanolayer is successfully developed on the LiNi_(0.9)Co_(0.1)O_(2)sub-surface via heteroatom anchoring utilizing high-valence element molybdenum modification.This in-situ formed conformal buffer phase with a thickness of 1.2 nm effectively suppresses the continuous interphase side-reactions,and thus maintains the excellent structure integrity at high voltage.Furthermore,theoretical calculations indicate that the lattice oxygen reversibility in the anion framework of the optimized sample is obviously enhanced due to the higher content of O 2p states near the Fermi level than that of the pristine one.Meanwhile,the stronger Mo-O bond further reduces cell volume alteration,which improves the bulk structure stability of modified materials.Besides,the detailed charge compensation mechanism suggests that the average oxidation state of Ni is reduced,which induces more active Li+participating in the redox reactions,boosting the cell energy density.As a result,the uniquely designed cathode materials exhibit an extraordinary discharge capacity of 245.4 mAh g^(-1)at 0.1 C,remarkable rate performance of 169.3 mAh g^(-1)at 10 C at 4.5 V,and a high capacity retention of 70.5% after 1000 cycles in full cells at a high cut-off voltage of 4.4 V.This strategy provides an valuable insight into constructing distinctive heterostructure on highperformance Ni-rich layered cathodes for LIBs.展开更多
Layer-structured Ruddlesden–Popper(RP)perovskites(RPPs)with decent stability have captured the imagination of the photovoltaic research community and bring hope for boosting the development of perovskite solar cell(P...Layer-structured Ruddlesden–Popper(RP)perovskites(RPPs)with decent stability have captured the imagination of the photovoltaic research community and bring hope for boosting the development of perovskite solar cell(PSC)technology.However,two-dimensional(2D)or quasi-2D RP PSCs are encountered with some challenges of the large exciton binding energy,blocked charge transport and poor film quality,which restrict their photovoltaic performance.Fortunately,these issues can be readily resolved by rationally designing spacer cations of RPPs.This review mainly focuses on how to design the molecular structures of organic spacers and aims to endow RPPs with outstanding photovoltaic applications.We firstly elucidated the important roles of organic spacers in impacting crystallization kinetics,charge transporting ability and stability of RPPs.Then we brought three aspects to attention for designing organic spacers.Finally,we presented the specific molecular structure design strategies for organic spacers of RPPs aiming to improve photovoltaic performance of RP PSCs.These proposed strategies in this review will provide new avenues to develop novel organic spacers for RPPs and advance the development of RPP photovoltaic technology for future applications.展开更多
While neutral aqueous metal batteries,featuring cost-effectiveness and non-flammability,hold significant potential for large-scale energy storage,their practical application is hampered by the limited specific capacit...While neutral aqueous metal batteries,featuring cost-effectiveness and non-flammability,hold significant potential for large-scale energy storage,their practical application is hampered by the limited specific capacity of cathode materials(<500 mAh g^(-1)).Herein,capacity-oriented CoS2 and rate-optimized Co9S8 cathodes are developed based on the aqueous copper ion system.The charge-storage mechanism is sys-tematically investigated through a series of ex-situ tests and density functional theory calculations,fo-cusing on the reversible transitions of Co9S8→Cu7S4→Cu9S5/Cu1.8S and CoS2→Cu7S4→Cu2S,which are associated with the redox reactions of Cu^(2+)/Cu^(+)‖Co^(2+)/Co and Cu^(2+)/Cu^(+)‖S22-/S2-,respectively.The elec-trochemical results show that CoS2 can exhibit a superior capacity of 619 mAh g^(-1) at 1 A g^(-1) after 400 cycles,while Co9S8 maintains an outstanding rate performance of 497 mAh g^(-1) at 10 A g^(-1)(the retention rate is 95%compared to 521 mAh g1 at 1 A g^(-1)).As a proof of concept,an advanced CoS2//Zn hybrid aqueous battery demonstrates a working voltage of 1.20 V and a specific energy of 663 Wh kgcathode-1.This work provides an alternative direction for developing sulfide cathodes in energetic aqueous metal batteries.展开更多
Lithium metal batteries(LMBs)with high energy density are impeded by the instability of solid electrolyte interface(SEI)and the uncontrolled growth of lithium(Li)dendrite.To mitigate these challenges,optimizing the SE...Lithium metal batteries(LMBs)with high energy density are impeded by the instability of solid electrolyte interface(SEI)and the uncontrolled growth of lithium(Li)dendrite.To mitigate these challenges,optimizing the SEI structure and Li deposition behavior is the key to stable LMBs.This study novelty proposes a facile synthesis of MgF_(2)/carbon(C)nanocomposite through the mechanochemical reaction between metallic Mg and polytetrafluoroethylene(PTFE)powders,and its modified polypropylene(PP)separator enhances LMB performance.The in-situ formed highly conductive fluorine-doped C species play a crucial role in facilitating ion/electron transport,thereby accelerating electrochemical kinetics and altering Li deposition direction.During cycling,the in-situ reaction between MgF_(2)and Li leads to the formation of LiMg alloy,along with a LiF-rich SEI layer,which reduces the nucleation overpotential and reinforces the interphase strength,leading to homogeneous Li deposition with dendrite-free feature.Benefiting from these merits,the Li metal is densely and uniformly deposited on the MgF_(2)/C@PP separator side rather than on the current collector side.Furthermore,the symmetric cell with MgF_(2)/C@PP exhibits superb Li plating/stripping performance over 2800 h at 1 mA cm^(-2)and 2 mA h cm^(-2).More importantly,the assembled Li@MgF_(2)/C@PPILiFePO4full cell with a low negative/positive ratio of 3.6delivers an impressive cyclability with 82.7%capacity retention over 1400 cycles at 1 C.展开更多
The novel core−shell SiC@CoCrFeNiMn high-entropy alloy(HEA)matrix composites(SiC@HEA)were successfully prepared via mechanical ball milling and vacuum hot-pressing sintering(VHPS).After sintering,the microstructure wa...The novel core−shell SiC@CoCrFeNiMn high-entropy alloy(HEA)matrix composites(SiC@HEA)were successfully prepared via mechanical ball milling and vacuum hot-pressing sintering(VHPS).After sintering,the microstructure was composed of FCC solid solution,Cr_(23)C_(6) carbide phases,and Mn_(2)SiO_(4) oxy-silicon phase.The relative density,hardness,tensile strength,and elongation of SiC@HEA composites with 1.0 wt.%SiC were 98.5%,HV 358.0,712.3 MPa,and 36.2%,respectively.The core−shell structure had a significant deflecting effect on the cracks.This effect allowed the composites to effectively maintain the excellent plasticity of the matrix.As a result,the core−shell SiC@HEA composites obtained superior strength and plasticity with multiple mechanisms.展开更多
Electric vehicles are pivotal in the global shift toward decarbonizing road transport,with lithium-ion batteries at the heart of this technological evolution.However,the pursuit of batteries capable of extremely fast ...Electric vehicles are pivotal in the global shift toward decarbonizing road transport,with lithium-ion batteries at the heart of this technological evolution.However,the pursuit of batteries capable of extremely fast charging that also satisfy high energy and safety criteria,poses a significant challenge to current lithium-ion batteries technologies.Additionally,the increasing demand for aluminum(Al)and copper(Cu)in electrification,solar energy technologies,and vehicle light-eighting is driving these metals toward near-critical status in the medium term.This study introduces metalized polythylene terephthalate(mPET)polymer films by depositing an Al or Cu thin layer onto two sides of a polyethylene terephthalate film—named mPET/Al and mPET/Cu,as lightweight,cost-effective alternatives to traditional metal current collectors in lithium-ion batteries.We have fabricated current collectors that significantly reduce weight(by 73%),thickness(by 33%),and cost(by 85%)compared with traditional metal foil counterparts.These advancements have the potential to enhance energy density to 280 Wh kg^(-1) at the electrode level under 10-min charging at 6 C.Through testing,including a novel extremely fast charging protocol across various C-rates and long-term cycling(up to 1000 cycles)in different cell configurations,the superior performance of these metalized polymer films has been demonstrated.Notably,mPET/Cu and mPET/Al films exhibited comparable capacities to conventional cells under extremely fast charging,with the mPET cells showing a 27%improvement in energy density at 6 C and maintaining significant energy density after 1000 cycles.This study underscores the potential of mPET films to revolutionize the roll-to-roll battery manufacturing process and significantly advance the performance metrics of lithium-ion batteries in electric vehicles applications.展开更多
Sustainable aviation fuel(SAF)production from biomass and biowaste streams is an attractive option for decarbonizing the aviation sector,one of the most-difficult-to-electrify transportation sectors.Despite ongoing co...Sustainable aviation fuel(SAF)production from biomass and biowaste streams is an attractive option for decarbonizing the aviation sector,one of the most-difficult-to-electrify transportation sectors.Despite ongoing commercialization efforts using ASTM-certified pathways(e.g.,lipid conversion,Fischer-Tropsch synthesis),production capacities are still inadequate due to limited feedstock supply and high production costs.New conversion technologies that utilize lignocellulosic feedstocks are needed to meet these challenges and satisfy the rapidly growing market.Combining bio-and chemo-catalytic approaches can leverage advantages from both methods,i.e.,high product selectivity via biological conversion,and the capability to build C-C chains more efficiently via chemical catalysis.Herein,conversion routes,catalysis,and processes for such pathways are discussed,while key challenges and meaningful R&D opportunities are identified to guide future research activities in the space.Bio-and chemo-catalytic conversion primarily utilize the carbohydrate fraction of lignocellulose,leaving lignin as a waste product.This makes lignin conversion to SAF critical in order to utilize whole biomass,thereby lowering overall production costs while maximizing carbon efficiencies.Thus,lignin valorization strategies are also reviewed herein with vital research areas identified,such as facile lignin depolymerization approaches,highly integrated conversion systems,novel process configurations,and catalysts for the selective cleavage of aryl C-O bonds.The potential efficiency improvements available via integrated conversion steps,such as combined biological and chemo-catalytic routes,along with the use of different parallel pathways,are identified as key to producing all components of a cost-effective,100%SAF.展开更多
Conventional annealing is a slow, high temperature process that involves heating atoms uniformly, i.e., in both defective and crystalline regions. This study explores an electrical alternative for energy efficiency,wh...Conventional annealing is a slow, high temperature process that involves heating atoms uniformly, i.e., in both defective and crystalline regions. This study explores an electrical alternative for energy efficiency,where moderate current density is used to generate electron wind force that produces the same outcome as the thermal annealing process. We demonstrate this on a zirconium alloy using in-situ electron back scattered diffraction(EBSD) inside a scanning electron microscope(SEM) and juxtaposing the results with that from thermal annealing. Contrary to common belief that resistive heating is the dominant factor, we show that 5 × 10~4 A/cm^2 current density can anneal the material in less than 15 min at only135?C. The resulting microstructure is essentially the same as that obtained with 600?C processing for360 min. We propose that unlike temperature, the electron wind force specifically targets the defective regions, which leads to unprecedented time and energy efficiency. This hypothesis was investigated with molecular dynamics simulation that implements mechanical equivalent of electron wind force to provide the atomistic insights on defect annihilation and grain growth.展开更多
The aim of this work is to investigate microstructure,corrosion resistance characteristics and nanohardness of the oxide layer on AZ91 Mg alloy by applying different voltage with KMnO4 contained solution.There are lot...The aim of this work is to investigate microstructure,corrosion resistance characteristics and nanohardness of the oxide layer on AZ91 Mg alloy by applying different voltage with KMnO4 contained solution.There are lots of closed pores that are filled with another oxide compound compared with the typical surface morphology with pore coated until 350 V of coating voltage.The thickness of oxide layer increases with increasing coating voltage.The oxide layer formed on AZ91 Mg alloy in electrolyte with potassium permanganate consists of MgO and Mn2O3.Corrosion potential of the oxide layer on AZ91 Mg alloy obtained at different plasma electrolytic oxidation(PEO) reaction stages increases with increasing coating voltage.The corrosion resistance of AZ91 Mg alloy depends on the existence of the manganese oxide in the oxide layer.The inner barrier layer composed of the MgO and Mn2O3 may serve as diffusion barrier to enhance the corrosion resistance and may partially explain the excellent anti-corrosion performance in corrosion test.Nanohardness values increase with increasing coating voltage.The increase in the nanohardness may be due to the effect of manganese oxide in the oxide layer on AZ91 Mg alloy coated from electrolyte containing KMnO4.展开更多
Anneal hardening has been one of the approaches to improve mechanical properties of solid solution alloys with the face-centered cubic(FCC) structure,whereby a considerable strengthening can be attained by annealing o...Anneal hardening has been one of the approaches to improve mechanical properties of solid solution alloys with the face-centered cubic(FCC) structure,whereby a considerable strengthening can be attained by annealing of cold-worked alloys below the recrystallization temperature(T_(rx)).Microscopically,this hardening effect has been ascribed to several mechanisms,i.e.solute segregation to defects(dislocation and stacking fault) and short-range chemical ordering,etc.However,none of these mechanisms can well explain the anneal hardening recently observed in phase-pure and coarse-grained FCC-structured high-entropy alloys(HEAs).Here we report the observations,using high-resolution electron channeling contrast imaging and transmission electron microscopy,of profuse and stable dislocation substructures in a cold-rolled CoCrFeMnNi HEA subject to an annealing below T_(rx).The dislocation substructures are observed to be thermally stable up to T_(rx),which could arise from the chemical complexity of the high-entropy system where certain elemental diffusion retardation occurs.The microstructure feature is markedly different from that of conventional dilute solid solution alloys,in which dislocation substructures gradually vanish by recovery during annealing,leading to a strength drop.Furthermore,dilute addition of 2 at.% Al leads to a reduction in both microhardness and yield strength of the cold-rolled and subsequently annealed(≤500℃) HEA.This Al induced softening effect,could be associated with the anisotropic formation of dislocation substructure,resulting from enhanced dislocation planar slip due to glide plane softening effect.These findings suggest that the strength of HEAs can be tailored through the anneal hardening effect from dislocation substructure strengthening.展开更多
Quest for bio-based halogen-free green flame retardant has attracted many concerns in recent years.Herein a reactive functional flame retardant containing phosphorus VDP is synthesized from vanillin,9,10-dihydro-9-oxa...Quest for bio-based halogen-free green flame retardant has attracted many concerns in recent years.Herein a reactive functional flame retardant containing phosphorus VDP is synthesized from vanillin,9,10-dihydro-9-oxa-10-phosphophene-10-oxide(DOPO)and phenol via a facile way.VDP is characterized with^(1)H NMR,^(31)P NMR,FTIR and Time of Flight Mass Spectrometry,and used as a new reactive flame retardant for bisphenol epoxy thermosets.Thermogravimetry analysis shows that when the VDP loading is only 0.5P%(based on phosphorus content),the residue increases from 14.2%to 21.1%at 750℃ in N_(2)compare with neat DGEBA.Correspondingly,the limit oxygen index increased to 29.6%,and flame retardancy reaches UL-94 V0 grade.Micro combustion calorimetry(MCC)and cone calorimetry analyses demonstrate that VDP can significantly lower flammability of the epoxy thermoset.With only 0.5P%of VDP,the heat release rate,total heat release rate and smoke production are reduced markedly.At the same time,the mechanical properties of the modified epoxy thermosets are also improved.The impact strength increases by 34%and the flexural strength increased by 23%,with 1.5P%of VDP.In short,VDP not only improves the flame retardancy,but also improves the mechanical properties of the epoxy thermosets.展开更多
基金The research to anode material development received funding from the German Research Foundation(DFG,project No.392322200)the development of cathode materials and upscaling strategies was funded by the Federal Ministry of Education and Research(Project NextGen-3DBat,03XP0198F).
文摘Traditional electrode manufacturing for lithium-ion batteries is well established,reliable,and has already reached high processing speeds and improvements in production costs.For modern electric vehicles,however,the need for batteries with high gravimetric and volumetric energy densities at cell level is increasing;and new production concepts are required for this purpose.During the last decade,laser processing of battery materials emerged as a promising processing tool for either improving manufacturing flexibility and product reliability or enhancing battery performances.Laser cutting and welding already reached a high level of maturity and it is obvious that in the near future they will become frequently implemented in battery production lines.This review focuses on laser texturing of electrode materials due to its high potential for significantly enhancing battery performances beyond state-of-the-art.Technical approaches and processing strategies for new electrode architectures and concepts will be presented and discussed with regard to energy and power density requirements.The boost of electrochemical performances due to laser texturing of energy storage materials is currently proven at the laboratory scale.However,promising developments in high-power,ultrafast laser technology may push laser structuring of batteries to the next technical readiness level soon.For demonstration in pilot lines adapted to future cell production,process upscaling regarding footprint area and processing speed are the main issues as well as the economic aspects with regards to CapEx amortization and the benefits resulting from the next generation battery.This review begins with an introduction of the three-dimensional battery and thick film concept,made possible by laser texturing.Laser processing of electrode components,namely current collectors,anodes,and cathodes will be presented.Different types of electrode architectures,such as holes,grids,and lines,were generated;their impact on battery performances are illustrated.The usage of high-energy materials,which are on the threshold of commercialization,is highlighted.Battery performance increase is triggered by controlling lithium-ion diffusion kinetics in liquid electrolyte filled porous electrodes.This review concludes with a discussion of various laser parameter tasks for process upscaling in a new type of extreme manufacturing.
基金financially supported by the National Natural Science Foundation of China(No.52173264)the Natural Scienceof Chongqing(No.cstc2020jcyjmsxmX0401)。
文摘Herein, a low-cost, biodegradable, and high-performance microwave shielding graphite/starch material was fabricated via constructing a cation-π interaction between ammonium ions and graphite. The graphite flakes and starch were firstly mixed with distilled water containing ammonium hydroxide to form graphite/starch slurry under an ultrasonic assistant. The cation-π interaction could improve delamination degree and dispersion of graphite in starch matrix. The slurry was first used as a coating material on the surface of wood and paper to develop shielding packages. The effect of coating thickness and coating layers on EM shielding property of the materials was investigated. Second, the composites with a high orientation of graphite were fabricated by compression at high pressures. The electrical conductivity and EM shielding effectiveness(SET) of the materials were greatly enhanced by construction of cation-πinteraction and orientation of graphite. Specifically, the EM SETvalues increased from 56.9 to 66.8 d B for the composites with 50 wt.% graphite and 2.0 mm in thickness by constructing cation-π interaction. The EM SETvalues raised from 17.4 to 66.8 d B via the graphite orientation in the materials with the same components and thickness. The shielding mechanism of the compressed composites with orientation dispersion of graphite was also discussed in comparison to the coating layer with random dispersion of graphite.
基金the German Research Foundation DFG project(LI 2839/1-1)National Natural Science Foundation of China(51971044)MF acknowledges funding from EU research and innovation framework programme via ttE-MAGIC,project(ID:824066)。
文摘There is an increasing demand for rechargeable batteries in high-performance energy storage systems.The current dominating Li-ion batteries are limited by price,resource availability,as well as their theoretical capacities.So that the community has started to explore alternative battery chemistries.As a promising multivalent battery type,rechargeable magnesium batteries(RMBs)have attracted increasing attention because of high safety,high volumetric energy density,and low cost thanks to abundant resource of Mg.However,the development of high-performance anodes is still hampered by formation of passivating layers on the Mg surface.Additionally,dendrites can also grow under certain conditions with pure Mg anodes,which requires further studies for reliable operation window and substitutes.Therefore,this review specifically aims to provide an overview on the often overlooked yet very important anode materials of RMBs,with the hope to inspire more attention and research efforts for the achievement of over-all better performance of future RMBs.c 2020 Published by Elsevier B.V.on behalf of Chongqing University.
基金This work contributes to the research performed at CELEST(Center for Electrochemical Energy Storage Ulm-Karlsruhe)and was funded by the German Research Foundation(DFG)under Project ID 390874152(POLiS Cluster of Excellence)Our research work has gained benefit from beamtime allocation(2017092405-qfu)at BL04-MSPD at ALBA Synchrotron,Barcelona,Spain and(I-20170977)at PETRA-III beamline P65 at DESY,Hamburg,Germany.The in operando XAS work was performed by using the Biologic potentiostat of PETRA-Ⅲ beamline P02.1.We thank Dr.Francois Fauth from Experiments Division at ALBA for his technical help during synchrotron diffraction measurement.We appreciate Dr.Anna-Lena Hansen(IAM-ESS)for the helpful discussion regarding to the crystal sturcture of V_(2)O_(5).Dr.Kristina Pfeifer(IAM-ESS),Dr.Noha Sabi(IAM-ESS),and Dr.Thomas Bergfeldt(IAM-AWP)are gratefully acknowledged for SEM/EDX,FTIR,and ICP-OES measurements,respectively.The TEM characterization was carried out at the Karlsruhe Nano Micro Facility(KNMF),a Helmholtz research infrastructure operated at the KIT.
文摘Herein, the electrochemical performance and the mechanism of potassium insertion/deinsertion in orthorhombic V_(2)O_(5) nanoparticles are studied. The V2O5 electrode displays an initial potassiation/depotassiation capacity of 200 mAh g^(−1)/217 mAh g^(−1) in the voltage range 1.5–4.0 V vs. K^(+)/K at C/12 rate, suggesting fast kinetics for potassium insertion/deinsertion. However, the capacity quickly fades during cycling, reaching 54 mAh g^(−1) at the 31st cycle. Afterwards, the capacity slowly increases up to 80 mAh g^(−1) at the 200th cycle. The storage mechanism upon K ions insertion into V2O5 is elucidated. In operando synchrotron diffraction reveals that V_(2)O_(5) first undergoes a solid solution to form K_(0.6)V_(2)O_(5) phase and then, upon further K ions insertion, it reveals coexistence of a solid solution and a two-phase reaction. During K ions deinsertion, the coexistence of solid solution and the two-phase reaction is identified together with an irreversible process. In operando XAS confirms the reduction/oxidation of vanadium during the K insertion/extraction with some irreversible contributions. This is consistent with the results obtained from synchrotron diffraction, ex situ Raman, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Moreover, ex situ XPS confirms the “cathode electrolyte interphase” (CEI) formation on the electrode and the decomposition of CEI film during cycling.
文摘Density functional methods have been used for the calculation of electronic structures, electronic transitions, vertical electron affinities and intermolecular reorganization energies for tri-aryl substituted dibenzothiophenes. These model compounds were then compared to the predicted values for dibenzo[b,d]thiophen-2-yltriphenylsilane (DBTSI 2) and to dibenzo[b,d]thiophene-2,8-diylbis(diphenylphosphine oxide) (PO15), known electron transport molecules. The results indicate that these model compounds can be used in a blue OLED system.
文摘Objective.Laser-treated surfaces for ventricular assist devices.Impact Statement.This work has scientific impact since it proposes a biofunctional surface created with laser processing in bioinert titanium.Introduction.Cardiovascular diseases are the world’s leading cause of death.An especially debilitating heart disease is congestive heart failure.Among the possible therapies,heart transplantation and mechanical circulatory assistance are the main treatments for its severe form at a more advanced stage.The development of biomaterials for ventricular assist devices is still being carried out.Although polished titanium is currently employed in several devices,its performance could be improved by enhancing the bioactivity of its surface.Methods.Aiming to improve the titanium without using coatings that can be detached,this work presents the formation of laser-induced periodic surface structures with a topology suitable for cell adhesion and neointimal tissue formation.The surface was modified by femtosecond laser ablation and cell adhesion was evaluated in vitro by using fibroblast cells.Results.The results indicate the formation of the desired topology,since the cells showed the appropriate adhesion compared to the control group.Scanning electron microscopy showed several positive characteristics in the cells shape and their surface distribution.The in vitro results obtained with different topologies point that the proposed LIPSS would provide enhanced cell adhesion and proliferation.Conclusion.The laser processes studied can create new interactions in biomaterials already known and improve the performance of biomaterials for use in ventricular assist devices.
基金supported by the National Natural Science Foundation of China(No.21805018)by Sichuan Science and Technology Program(Nos.2022ZHCG0018,2023NSFSC0117 and 2023ZHCG0060)Yibin Science and Technology Program(No.2022JB005)and China Postdoctoral Science Foundation(No.2022M722704).
文摘Layered transition metal oxides have emerged as promising cathode materials for sodium ion batteries.However,irreversible phase transitions cause structural distortion and cation rearrangement,leading to sluggish Na+dynamics and rapid capacity decay.In this study,we propose a medium-entropy cathode by simultaneously introducing Fe,Mg,and Li dopants into a typical P2-type Na_(0.75)Ni_(0.25)Mn_(0.75)O_(2)cathode.The modified Na_(0.75)Ni_(0.2125)Mn_(0.6375)Fe_(0.05)Mg_(0.05)Li_(0.05)O_(2)cathode predominantly exhibits a main P2 phase(93.5%)with a minor O3 phase(6.5%).Through spectroscopy techniques and electrochemical investigations,we elucidate the redox mechanisms of Ni^(2+/3+/4+),Mn^(3+/4+),Fe^(3+/4+),and O_(2)-/O_(2)^(n-)during charging/discharging.The medium-entropy doping mitigates the detrimental P2-O_(2)phase transition at high-voltage,replacing it with a moderate and reversible structural evolution(P2-OP4),thereby enhancing structural stability.Consequently,the modified cathode exhibits a remarkable rate capacity of 108.4 mAh·g^(-1)at 10C,with a capacity retention of 99.0%after 200 cycles at 1C,82.5%after 500 cycles at 5C,and 76.7%after 600 cycles at 10C.Furthermore,it also demonstrates superior electrochemical performance at high cutoff voltage of 4.5 V and extreme temperature(55 and 0℃).This work offers solutions to critical challenges in sodium ion batteries cathode materials.
基金financially supported by the National Natural Science Foundation of China(No.52202228,52402298)funded by the Science Research Project of Hebei Education Department(No.BJK2022011)+3 种基金the Central Funds Guiding the Local Science and Technology Development of Hebei Province(No.236Z4404G)the Beijing Tianjin Hebei Basic Research Cooperation Special Project(No.E2024202273)the Science and Technology Correspondent Project of Tianjin(24YDTPJC00240)supported by the U.S.Department of Energy’s Office of Science,Office of Basic Energy Science,Materials Sciences and Engineering Division。
文摘Nickel-rich(Ni≥90%)layered oxides materials have emerged as a promising candidate for nextgeneration high-energy-density lithium-ion batteries(LIBs).However,their widespread application is hindered by structural fatigue and lattice oxygen loss.In this work,an epitaxial surface rock-salt nanolayer is successfully developed on the LiNi_(0.9)Co_(0.1)O_(2)sub-surface via heteroatom anchoring utilizing high-valence element molybdenum modification.This in-situ formed conformal buffer phase with a thickness of 1.2 nm effectively suppresses the continuous interphase side-reactions,and thus maintains the excellent structure integrity at high voltage.Furthermore,theoretical calculations indicate that the lattice oxygen reversibility in the anion framework of the optimized sample is obviously enhanced due to the higher content of O 2p states near the Fermi level than that of the pristine one.Meanwhile,the stronger Mo-O bond further reduces cell volume alteration,which improves the bulk structure stability of modified materials.Besides,the detailed charge compensation mechanism suggests that the average oxidation state of Ni is reduced,which induces more active Li+participating in the redox reactions,boosting the cell energy density.As a result,the uniquely designed cathode materials exhibit an extraordinary discharge capacity of 245.4 mAh g^(-1)at 0.1 C,remarkable rate performance of 169.3 mAh g^(-1)at 10 C at 4.5 V,and a high capacity retention of 70.5% after 1000 cycles in full cells at a high cut-off voltage of 4.4 V.This strategy provides an valuable insight into constructing distinctive heterostructure on highperformance Ni-rich layered cathodes for LIBs.
基金funding from National Science Foundation of China(52202337 and 22178015)the Young Taishan Scholars Program of Shandong Province(tsqn202211082)+1 种基金Natural Science Foundation of Shandong Province(ZR2023MB051)Independent Innovation Research Project of China University of Petroleum(East China)(22CX06023A).
文摘Layer-structured Ruddlesden–Popper(RP)perovskites(RPPs)with decent stability have captured the imagination of the photovoltaic research community and bring hope for boosting the development of perovskite solar cell(PSC)technology.However,two-dimensional(2D)or quasi-2D RP PSCs are encountered with some challenges of the large exciton binding energy,blocked charge transport and poor film quality,which restrict their photovoltaic performance.Fortunately,these issues can be readily resolved by rationally designing spacer cations of RPPs.This review mainly focuses on how to design the molecular structures of organic spacers and aims to endow RPPs with outstanding photovoltaic applications.We firstly elucidated the important roles of organic spacers in impacting crystallization kinetics,charge transporting ability and stability of RPPs.Then we brought three aspects to attention for designing organic spacers.Finally,we presented the specific molecular structure design strategies for organic spacers of RPPs aiming to improve photovoltaic performance of RP PSCs.These proposed strategies in this review will provide new avenues to develop novel organic spacers for RPPs and advance the development of RPP photovoltaic technology for future applications.
基金supported by the National Natural Science Foundation of China(Nos.52301282 and 52072256)Shanxi Province Science and Technology Program Unveiled Bidding Program(No.20201101016)+2 种基金Key Research and Development Program of Shanxi Province(Nos.202102030201006 and 202202070301016)Central Guidance for Local Science and Technology Development Funds Program(No.YDZJSX2021B005)Science and Technology Innovation Base Construction Program of Shanxi Province(No.YDZJSX2022B003).
文摘While neutral aqueous metal batteries,featuring cost-effectiveness and non-flammability,hold significant potential for large-scale energy storage,their practical application is hampered by the limited specific capacity of cathode materials(<500 mAh g^(-1)).Herein,capacity-oriented CoS2 and rate-optimized Co9S8 cathodes are developed based on the aqueous copper ion system.The charge-storage mechanism is sys-tematically investigated through a series of ex-situ tests and density functional theory calculations,fo-cusing on the reversible transitions of Co9S8→Cu7S4→Cu9S5/Cu1.8S and CoS2→Cu7S4→Cu2S,which are associated with the redox reactions of Cu^(2+)/Cu^(+)‖Co^(2+)/Co and Cu^(2+)/Cu^(+)‖S22-/S2-,respectively.The elec-trochemical results show that CoS2 can exhibit a superior capacity of 619 mAh g^(-1) at 1 A g^(-1) after 400 cycles,while Co9S8 maintains an outstanding rate performance of 497 mAh g^(-1) at 10 A g^(-1)(the retention rate is 95%compared to 521 mAh g1 at 1 A g^(-1)).As a proof of concept,an advanced CoS2//Zn hybrid aqueous battery demonstrates a working voltage of 1.20 V and a specific energy of 663 Wh kgcathode-1.This work provides an alternative direction for developing sulfide cathodes in energetic aqueous metal batteries.
基金financially supported by the Natural Science Foundation of China(52277218)the Hubei Provincial Natural Science Foundation of China(2024AFA094)+1 种基金the Excellent Discipline Cultivation Project by JHUN(2023XKZ009)the Graduate Student Innovation Fund of JHUN(KYCXJJ202422).
文摘Lithium metal batteries(LMBs)with high energy density are impeded by the instability of solid electrolyte interface(SEI)and the uncontrolled growth of lithium(Li)dendrite.To mitigate these challenges,optimizing the SEI structure and Li deposition behavior is the key to stable LMBs.This study novelty proposes a facile synthesis of MgF_(2)/carbon(C)nanocomposite through the mechanochemical reaction between metallic Mg and polytetrafluoroethylene(PTFE)powders,and its modified polypropylene(PP)separator enhances LMB performance.The in-situ formed highly conductive fluorine-doped C species play a crucial role in facilitating ion/electron transport,thereby accelerating electrochemical kinetics and altering Li deposition direction.During cycling,the in-situ reaction between MgF_(2)and Li leads to the formation of LiMg alloy,along with a LiF-rich SEI layer,which reduces the nucleation overpotential and reinforces the interphase strength,leading to homogeneous Li deposition with dendrite-free feature.Benefiting from these merits,the Li metal is densely and uniformly deposited on the MgF_(2)/C@PP separator side rather than on the current collector side.Furthermore,the symmetric cell with MgF_(2)/C@PP exhibits superb Li plating/stripping performance over 2800 h at 1 mA cm^(-2)and 2 mA h cm^(-2).More importantly,the assembled Li@MgF_(2)/C@PPILiFePO4full cell with a low negative/positive ratio of 3.6delivers an impressive cyclability with 82.7%capacity retention over 1400 cycles at 1 C.
基金supported by Key Laboratory of Infrared Imaging Materials and Detectors,Shanghai Institute of Technical Physics,Chinese Academy of Sciences(No.IIMDKFJJ-21-10)China Postdoctoral Science Foundation(No.2018T110993)。
文摘The novel core−shell SiC@CoCrFeNiMn high-entropy alloy(HEA)matrix composites(SiC@HEA)were successfully prepared via mechanical ball milling and vacuum hot-pressing sintering(VHPS).After sintering,the microstructure was composed of FCC solid solution,Cr_(23)C_(6) carbide phases,and Mn_(2)SiO_(4) oxy-silicon phase.The relative density,hardness,tensile strength,and elongation of SiC@HEA composites with 1.0 wt.%SiC were 98.5%,HV 358.0,712.3 MPa,and 36.2%,respectively.The core−shell structure had a significant deflecting effect on the cracks.This effect allowed the composites to effectively maintain the excellent plasticity of the matrix.As a result,the core−shell SiC@HEA composites obtained superior strength and plasticity with multiple mechanisms.
文摘Electric vehicles are pivotal in the global shift toward decarbonizing road transport,with lithium-ion batteries at the heart of this technological evolution.However,the pursuit of batteries capable of extremely fast charging that also satisfy high energy and safety criteria,poses a significant challenge to current lithium-ion batteries technologies.Additionally,the increasing demand for aluminum(Al)and copper(Cu)in electrification,solar energy technologies,and vehicle light-eighting is driving these metals toward near-critical status in the medium term.This study introduces metalized polythylene terephthalate(mPET)polymer films by depositing an Al or Cu thin layer onto two sides of a polyethylene terephthalate film—named mPET/Al and mPET/Cu,as lightweight,cost-effective alternatives to traditional metal current collectors in lithium-ion batteries.We have fabricated current collectors that significantly reduce weight(by 73%),thickness(by 33%),and cost(by 85%)compared with traditional metal foil counterparts.These advancements have the potential to enhance energy density to 280 Wh kg^(-1) at the electrode level under 10-min charging at 6 C.Through testing,including a novel extremely fast charging protocol across various C-rates and long-term cycling(up to 1000 cycles)in different cell configurations,the superior performance of these metalized polymer films has been demonstrated.Notably,mPET/Cu and mPET/Al films exhibited comparable capacities to conventional cells under extremely fast charging,with the mPET cells showing a 27%improvement in energy density at 6 C and maintaining significant energy density after 1000 cycles.This study underscores the potential of mPET films to revolutionize the roll-to-roll battery manufacturing process and significantly advance the performance metrics of lithium-ion batteries in electric vehicles applications.
基金supported by the Center for Bioenergy Innovation(CBI)supported by the Office of Biological and Environmental Research in the DOE Office of Science and led by Oak Ridge National Laboratory.Oak Ridge National Laboratory is managed by UT-Battelle,LLC for the US DOE under Contract Number DE-AC05-00OR22725+2 种基金authored in part by the Na-tional Renewable Energy Laboratory,operated by Alliance for Sustainable Energy,LLC,for the U.S.Department of Energy(DOE)under Contract No.DE-LC-000L054provided by the U.S.Department of Energy(DOE),Office of Energy Efficiency and Renewable Energy(EERE),and Bioenergy Technologies Office(BETO)at the Pacific Northwest National Laboratory(PNNL)under Contract No.DE-AC05-76RL01830supported by Laboratory Directed Research and Development(LDRD)funding from Argonne National Laboratory,provided by the Director,Office of Science,of the U.S.Department of Energy under Contract No.DE-AC02-06CH11357。
文摘Sustainable aviation fuel(SAF)production from biomass and biowaste streams is an attractive option for decarbonizing the aviation sector,one of the most-difficult-to-electrify transportation sectors.Despite ongoing commercialization efforts using ASTM-certified pathways(e.g.,lipid conversion,Fischer-Tropsch synthesis),production capacities are still inadequate due to limited feedstock supply and high production costs.New conversion technologies that utilize lignocellulosic feedstocks are needed to meet these challenges and satisfy the rapidly growing market.Combining bio-and chemo-catalytic approaches can leverage advantages from both methods,i.e.,high product selectivity via biological conversion,and the capability to build C-C chains more efficiently via chemical catalysis.Herein,conversion routes,catalysis,and processes for such pathways are discussed,while key challenges and meaningful R&D opportunities are identified to guide future research activities in the space.Bio-and chemo-catalytic conversion primarily utilize the carbohydrate fraction of lignocellulose,leaving lignin as a waste product.This makes lignin conversion to SAF critical in order to utilize whole biomass,thereby lowering overall production costs while maximizing carbon efficiencies.Thus,lignin valorization strategies are also reviewed herein with vital research areas identified,such as facile lignin depolymerization approaches,highly integrated conversion systems,novel process configurations,and catalysts for the selective cleavage of aryl C-O bonds.The potential efficiency improvements available via integrated conversion steps,such as combined biological and chemo-catalytic routes,along with the use of different parallel pathways,are identified as key to producing all components of a cost-effective,100%SAF.
基金the financial supports from the Natural Science Foundation of Hunan Province, China (Nos. 2020JJ4114, 2016JJ3151)the National Natural Science Foundation of China (No. 51601229)+2 种基金the Young Elite Scientist Sponsorship Program by CAST, China (No. 2015QNRC001)the Hunan Province Innovation Platform and Talent Plan Project, China (No. 2015RS4001)the Open-end Fund for the Valuable and Precision Instruments of Central South University, China (No. CSUZC201815)。
基金financially supported by the Natural Science Foundation of Hunan Province,China(Nos.2020JJ4114,2016JJ3151)the National Natural Science Foundation of China(No.51601229)+2 种基金the Young Elite Scientist Sponsorship Program by CAST,China(No.2015QNRC001)the Hunan Province Innovation Platform and Talent Plan,China(No.2015RS4001)the Open-End Fund for the Valuable and Precision Instruments of Central South University,China(No.CSUZC201815)。
基金supported by the National Science Foundation (DMR 1609060)the US Department of Energy funding (DENE0008259)+1 种基金Funding by the Powder Metal Initiative (PMI) through the Pennsylvania Department of Community and Economic Development (DCED),grant # C-000057477the Engineering Technology and Commonwealth Engineering (ETCE),Pennsylvania State University
文摘Conventional annealing is a slow, high temperature process that involves heating atoms uniformly, i.e., in both defective and crystalline regions. This study explores an electrical alternative for energy efficiency,where moderate current density is used to generate electron wind force that produces the same outcome as the thermal annealing process. We demonstrate this on a zirconium alloy using in-situ electron back scattered diffraction(EBSD) inside a scanning electron microscope(SEM) and juxtaposing the results with that from thermal annealing. Contrary to common belief that resistive heating is the dominant factor, we show that 5 × 10~4 A/cm^2 current density can anneal the material in less than 15 min at only135?C. The resulting microstructure is essentially the same as that obtained with 600?C processing for360 min. We propose that unlike temperature, the electron wind force specifically targets the defective regions, which leads to unprecedented time and energy efficiency. This hypothesis was investigated with molecular dynamics simulation that implements mechanical equivalent of electron wind force to provide the atomistic insights on defect annihilation and grain growth.
基金supported by a grant from the Center of Advanced Materials Processing(CAMP) of the 21st Centry Froniter R&D Program Funded by the Ministry of Knowledge Economy(MKE),Koreasupported by the Korea Science and Engineering Foundation (No.2009-0079807)
文摘The aim of this work is to investigate microstructure,corrosion resistance characteristics and nanohardness of the oxide layer on AZ91 Mg alloy by applying different voltage with KMnO4 contained solution.There are lots of closed pores that are filled with another oxide compound compared with the typical surface morphology with pore coated until 350 V of coating voltage.The thickness of oxide layer increases with increasing coating voltage.The oxide layer formed on AZ91 Mg alloy in electrolyte with potassium permanganate consists of MgO and Mn2O3.Corrosion potential of the oxide layer on AZ91 Mg alloy obtained at different plasma electrolytic oxidation(PEO) reaction stages increases with increasing coating voltage.The corrosion resistance of AZ91 Mg alloy depends on the existence of the manganese oxide in the oxide layer.The inner barrier layer composed of the MgO and Mn2O3 may serve as diffusion barrier to enhance the corrosion resistance and may partially explain the excellent anti-corrosion performance in corrosion test.Nanohardness values increase with increasing coating voltage.The increase in the nanohardness may be due to the effect of manganese oxide in the oxide layer on AZ91 Mg alloy coated from electrolyte containing KMnO4.
基金financially supported by the National Natural Science Foundation of China (No. 52001120)the Fundamental Research Funds for the Central Universities (No. 531118010450)+10 种基金the Hundred Talent Program of Hunan Provincethe State Key Laboratory of Powder Metallurgy,Central South University,Changshathe State Key Laboratory of Advanced Metals and Materials(No. 2021-Z09)University of Science&Technology Beijing,Chinasupported by the National Natural Science Foundation of China (No. 51801060)supported by the Swedish Research Councilsupported by the National Science Foundation under Contract (No. DMR-1408722)sponsored by the Whiting School of EngineeringJohns Hopkins Universityfunded by the National Key Research and Development Program of China (No. 2016YFB0300801)the National NaturalScience Foundation of China (Nos. 51831004, 11427806, 51671082,51471067)。
文摘Anneal hardening has been one of the approaches to improve mechanical properties of solid solution alloys with the face-centered cubic(FCC) structure,whereby a considerable strengthening can be attained by annealing of cold-worked alloys below the recrystallization temperature(T_(rx)).Microscopically,this hardening effect has been ascribed to several mechanisms,i.e.solute segregation to defects(dislocation and stacking fault) and short-range chemical ordering,etc.However,none of these mechanisms can well explain the anneal hardening recently observed in phase-pure and coarse-grained FCC-structured high-entropy alloys(HEAs).Here we report the observations,using high-resolution electron channeling contrast imaging and transmission electron microscopy,of profuse and stable dislocation substructures in a cold-rolled CoCrFeMnNi HEA subject to an annealing below T_(rx).The dislocation substructures are observed to be thermally stable up to T_(rx),which could arise from the chemical complexity of the high-entropy system where certain elemental diffusion retardation occurs.The microstructure feature is markedly different from that of conventional dilute solid solution alloys,in which dislocation substructures gradually vanish by recovery during annealing,leading to a strength drop.Furthermore,dilute addition of 2 at.% Al leads to a reduction in both microhardness and yield strength of the cold-rolled and subsequently annealed(≤500℃) HEA.This Al induced softening effect,could be associated with the anisotropic formation of dislocation substructure,resulting from enhanced dislocation planar slip due to glide plane softening effect.These findings suggest that the strength of HEAs can be tailored through the anneal hardening effect from dislocation substructure strengthening.
基金This work is supported by the National Natural Science Foundation of China(NSFC)under the agreements of 21875131 and 21773150The Natural Science Basic Research Plan in Shaanxi Province of China(2020JM-283)the Fundamental Research Funds for the Central Universities(GK202003044 and GK201902014)are also acknowledged for partial support。
文摘Quest for bio-based halogen-free green flame retardant has attracted many concerns in recent years.Herein a reactive functional flame retardant containing phosphorus VDP is synthesized from vanillin,9,10-dihydro-9-oxa-10-phosphophene-10-oxide(DOPO)and phenol via a facile way.VDP is characterized with^(1)H NMR,^(31)P NMR,FTIR and Time of Flight Mass Spectrometry,and used as a new reactive flame retardant for bisphenol epoxy thermosets.Thermogravimetry analysis shows that when the VDP loading is only 0.5P%(based on phosphorus content),the residue increases from 14.2%to 21.1%at 750℃ in N_(2)compare with neat DGEBA.Correspondingly,the limit oxygen index increased to 29.6%,and flame retardancy reaches UL-94 V0 grade.Micro combustion calorimetry(MCC)and cone calorimetry analyses demonstrate that VDP can significantly lower flammability of the epoxy thermoset.With only 0.5P%of VDP,the heat release rate,total heat release rate and smoke production are reduced markedly.At the same time,the mechanical properties of the modified epoxy thermosets are also improved.The impact strength increases by 34%and the flexural strength increased by 23%,with 1.5P%of VDP.In short,VDP not only improves the flame retardancy,but also improves the mechanical properties of the epoxy thermosets.
