The mechanical and thermodynamic properties of W-Ti alloys(including W_(15)Ti_(1),W_(14)Ti_(2),W_(12)Ti_(4) and W_(8)Ti_(8) alloys)were investigated by the first-principles approach based on density functional theory....The mechanical and thermodynamic properties of W-Ti alloys(including W_(15)Ti_(1),W_(14)Ti_(2),W_(12)Ti_(4) and W_(8)Ti_(8) alloys)were investigated by the first-principles approach based on density functional theory.The results indicate that W-Ti alloys except W_(8)Ti_(8) are thermodynamically stable.The modulus and hardness of W-Ti alloys are smaller than those of pure tungsten and gradually decrease with increasing Ti concentration.However,their B/G ratios and Poisson's ratios exceed those of pure tungsten,suggesting that the introduction of Ti decreases the mechanical strength while enhancing the ductility of W-Ti alloys.The thermal expansion coefficients for W-Ti alloys all surpass those of pure tungsten,indicating that the introduction of titanium exacerbates the thermal expansion behavior of W-Ti alloys.Nevertheless,elevated pressure has the capacity to suppress the thermal expansion tendencies in titanium-doped tungsten alloys.This study offers theoretical insights for the design of nuclear materials by exploring the mechanical and thermodynamic properties of W-Ti alloys.展开更多
Carbon fibre,steel fibre and graphite were used as conductive fillers to prepare cementitious materials with excellent electrothermal properties.The electrically conductive cementitious materials with different volume...Carbon fibre,steel fibre and graphite were used as conductive fillers to prepare cementitious materials with excellent electrothermal properties.The electrically conductive cementitious materials with different volume dosages were analysed through compressive and flexural strength,electrochemical impedance spectroscopy and temperature rise tests.An equivalent circuit model was established to study the electrically conductive heat generation mechanism in the electrically conductive cementitious composites.The results indicate that the mechanical properties of cementitious composite materials with a ternary conductive phase are better than those of pristine cementitious materials because the fibrous filler improves their mechanical properties.However,the incorporation of graphite in the material reduces its strength.Introducing fibrous and point-like conductive phase materials into the cementitious material enhances the overall conductive pathway and considerably reduces the electrical resistance of the cementitious material,enhancing its conductive properties.The volume ratios of carbon fibre,steel fibre and graphite that achieve an optimal complex doping in the cementitious material were 0.35%,0.6%and 6%,respectively.This was determined using the mutation point of each circuit element parameter as the percolation threshold.In addition,at a certain safety voltage,there is a uniform change between the internal and surface temperatures of the conductive cementitious material,and the heating effect in this materialis is considerably better than that in the pristine cementitious material.展开更多
Although poly(lactic acid)(PLA)is a good environmentally-friendly bio-degradable polymer which is used to substitute traditional petrochemical-based polymer packaging films,the barrier properties of PLA films are stil...Although poly(lactic acid)(PLA)is a good environmentally-friendly bio-degradable polymer which is used to substitute traditional petrochemical-based polymer packaging films,the barrier properties of PLA films are still insufficient for high-barrier packaging applications.In this study,oxygen scavenger hydroxyl-terminated polybutadiene(HTPB)and cobalt salt catalyst were incorporated into the PLA/poly(butylene adipate-co-terephthalate)(PLA/PBAT),followed by melting extrusion and three-layer co-extrusion blown film process to prepare the composite films.The oxygen permeability coefficient of the composite film combined with 6 wt%oxygen scavenger and 0.4 wt%catalyst was decreased significantly from 377.00 cc·mil·m^(-2)·day^(-1)·0.1 MPa^(-1) to 0.98 cc·mil·m^(-2)·day^(-1)·0.1 MPa^(-1),showing a remarkable enhancement of 384.69 times compared with the PLA/PBAT composite film.Meanwhile,the degradation behavior of the composite film was also accelerated,exhibiting a mass loss of nearly 60%of the original mass after seven days of degradation in an alkaline environment,whereas PLA/PBAT composite film only showed a mass loss of 32%.This work has successfully prepared PLA/PBAT composite films with simultaneously improved oxygen barrier property and degradation behavior,which has great potential for high-demanding green chemistry packaging industries,including food,agricultural,and military packaging.展开更多
In order to achieve the large-scale application of manufactured sand in railway high-strength concrete structure,a series of high-strength manufactured sand concrete(HMC)are prepared by taking the manufactured sand li...In order to achieve the large-scale application of manufactured sand in railway high-strength concrete structure,a series of high-strength manufactured sand concrete(HMC)are prepared by taking the manufactured sand lithology(tuff,limestone,basalt,granite),stone powder content(0,5%,10%,15%)and concrete strength grade(C60,C80,C100)as variables.The evolution of mechanical properties of HMC and the correlation between cubic compressive strength and other mechanical properties are studied.Compared to river sand,manufactured sand enhances the cubic compressive strength,axial compressive strength and elastic modulus of concrete,while its potential microcracks weaken the flexural strength and splitting tensile strength of concrete.Stone powder content displays both positive and negative effects on mechanical properties of HMC,and the stone powder content is suggested to be less than 10%.The empirical formulas between cubic compressive strength and other mechanical properties are proposed.展开更多
The microstructures and thermodynamic properties of mixed systems comprising pyridinium ionic liquid[HPy][BF_(4)]and acetonitrile at different mole fractions were studied using molecular dynamics simulation in this wo...The microstructures and thermodynamic properties of mixed systems comprising pyridinium ionic liquid[HPy][BF_(4)]and acetonitrile at different mole fractions were studied using molecular dynamics simulation in this work.The following properties were determined:density,self-diffusion coefficient,excess molar volume,and radial distribution function.The results show that with an increase in the mole fraction of[HPy][BF_(4)],the self-diffusion coefficient decreases.Additionally,the excess molar volume initially decreases,reaches a minimum,and then increases.The rules of radial distribution functions(RDFs)of characteristic atoms are different.With increasing the mole fraction of[HPy][BF_(4)],the first peak of the RDFs of HA1-F decreases,while that of CT6-CT6 rises at first and then decreases.This indicates that the solvent molecules affect the polar and non-polar regions of[HPy][BF_(4)]differently.展开更多
With the rapid development of globalization and information technology,intellectual property has been one of the key drivers of economic growth,and the construction of intellectual property system has become an import...With the rapid development of globalization and information technology,intellectual property has been one of the key drivers of economic growth,and the construction of intellectual property system has become an important criterion for measuring the quality of business environment.This article is intended to explore the current status of intellectual property system construction in China,the challenges,and its relationship with the business environment,to propose the corresponding countermeasures and suggestions.The study finds that the legal system of intellectual property in China is gradually improving,and judicial and administrative protection are continuously strengthened.However,the challenges still remain such as frequent infringements,rights hard to protect and insufficient international cooperation.These issues not only affect the legitimate rights and interests of innovation entities,but also for the market fairness and the level of the business environment.Therefore,this article proposes that strengthening the perfection of the intellectual property legal system,enhancing intellectual property services and support capabilities,strengthening international cooperation and exchanges,and accelerating the cultivation of composite talents.It aims to provide theoretical references for the construction of intellectual property system and the optimization of the business environment,promote the high-quality development of economy and enhance the global competitiveness of the country.展开更多
Observational data of ball lightning often contradict each other, so it was sometimes proposed to build a theory of ball lightning based on only a small number of statistically reliable observations. Work on this prin...Observational data of ball lightning often contradict each other, so it was sometimes proposed to build a theory of ball lightning based on only a small number of statistically reliable observations. Work on this principle did not bring results. The correct approach to creating the theory of ball lightning should be the desire to explain all of its properties, even those that are rare. In the database of ball lightning observations, the most valuable are the cases when it left traces available for quantitative analysis, or was filmed by video cameras. Ball lightning is a material body consisting of a shell and a multi-element core. Cases of water heating made it possible to determine energy density of ball lightning, which turned out to be higher than 1010 J/m3. A study of results of ball lightning explosion, as well as its effect on snow, made it possible to assume that it is capable of generating radiation with a wavelength of about 10 cm, the power of which can be greater than 120 kW. Ball lightning has an electric charge of 10−3 - 10−1 C. The presence of an electric charge explains the complex nature of its movement in atmosphere. Ball lightning is formed under the action of magnetic field pulse and ultraviolet radiation of linear lightning channel. A model of ball lightning in the form of a core of charged “dynamic capacitors” and a shell of polarized water molecules is considered. It is shown that this shell is capable of withstanding the force of Coulomb repulsion of the core charges and the pressure caused by the movement of charge carriers. The glow of ball lightning core occurs due to orbital motion of electrons at a speed close to light speed. The intensity of the glow is determined by the degree of uniformity of electrons arrangement along the orbit.展开更多
The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compressio...The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the aggregates.Theσ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite trend.Theε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.展开更多
A new cobalt(Ⅱ)-radical complex:[Co(im4-py)_(2)(PNB)_(2)](im4-py=2-(4'-pyridyl)-4,4,5,5-tetramethylimidazole-1-oxyl,HPNB=p-nitrobenzoic acid)has been synthesized and characterized by X-ray diffraction analysis,el...A new cobalt(Ⅱ)-radical complex:[Co(im4-py)_(2)(PNB)_(2)](im4-py=2-(4'-pyridyl)-4,4,5,5-tetramethylimidazole-1-oxyl,HPNB=p-nitrobenzoic acid)has been synthesized and characterized by X-ray diffraction analysis,elemental analysis,IR,and magnetic properties.X-ray diffraction analysis shows that the complex exists as mononuclear molecules and Co(Ⅱ)ion is four-coordinated with two radicals and two PNB-ligands.The magnetic susceptibility study indicates the complex exhibits weak ferromagnetic interactions between cobalt(Ⅱ)and im4-py radical.The magnetic property is explained by the magnetic and structure exchange mechanism.CCDC:976028.展开更多
Peanut varieties are diverse globally,with their characters and nutrition determining the product quality.However,the comparative analysis and statistical analysis of key quality indicators for peanut kernels across t...Peanut varieties are diverse globally,with their characters and nutrition determining the product quality.However,the comparative analysis and statistical analysis of key quality indicators for peanut kernels across the world remains relatively limited,impeding the comprehensive evaluation of peanut quality and hindering the industry development on a global scale.This study aimed to compare and analyze the apparent morphology,microstructure,single-cell structure,engineering and mechanical properties,as well as major nutrient contents of peanut kernels from 10 different cultivars representing major peanut-producing countries.The surface and cross-section microstructure of the peanut kernels exhibited a dense“blocky”appearance with a distinct cellular structure.The lipid droplets were predominantly spherical with a regular distribution within the cells.The single-cell structure of the kernels from these 10 peanut cultivars demonstrated varying morphologies and dimensions,which exhibited correlations with their mechanical and engineering properties.Furthermore,the mass loss versus temperature profiles of the peanut kernels revealed five distinct stages,corresponding to moisture loss,volatile loss,protein denaturation,and the degradation of various biomacromolecules.Variations were also observed in the lipid,protein,and sucrose contents,texture,bulk density,true density,porosity,geometric mean diameter,and sphericity among the diferent peanut varieties.This study establishes relationships and correlations among microstructure,engineering properties,and nutritional composition of commonly grown peanut varieties in major peanut-processing countries.The findings provide valuable insights into peanut quality evaluation,empowering the peanut industry to enhance their processing and product development efforts.展开更多
Graphene nanoplatelets(GNPs)have attracted tremendous interest due to their unique properties and bonding capabilities.This study focuses on the effect of GNP dispersion on the mechanical,thermal,and morphological beh...Graphene nanoplatelets(GNPs)have attracted tremendous interest due to their unique properties and bonding capabilities.This study focuses on the effect of GNP dispersion on the mechanical,thermal,and morphological behavior of GNP/epoxy nanocomposites.This study aims to understand how the dispersion of GNPs affects the properties of epoxy nanocomposite and to identify the best dispersion approach for improving mechanical performance.A solvent mixing technique that includes mechanical stirring and ultrasonication was used for producing the nanocomposites.Fourier transform infrared spectroscopy was used to investigate the interaction between GNPs and the epoxy matrix.The measurements of density and moisture content were used to confirm that GNPs were successfully incorporated into the nanocomposite.The findings showed that GNPs are successfully dispersed in the epoxy matrix by combining mechanical stirring and ultrasonication in a single step,producing well-dispersed nanocomposites with improved mechanical properties.Particularly,the nanocomposites at a low GNP loading of 0.1 wt%,demonstrate superior mechanical strength,as shown by increased tensile properties,including improved Young's modulus(1.86 GPa),strength(57.31 MPa),and elongation at break(4.98).The nanocomposite with 0.25 wt%GNP loading performs better,according to the viscoelastic analysis and flexural properties(113.18 MPa).Except for the nanocomposite with a 0.5 wt%GNP loading,which has a higher thermal breakdown temperature,the thermal characteristics do not significantly alter.The effective dispersion of GNPs in the epoxy matrix and low agglomeration is confirmed by the morphological characterization.The findings help with filler selection and identifying the best dispersion approach,which improves mechanical performance.The effective integration of GNPs and their interaction with the epoxy matrix provides the doorway for additional investigation and the development of sophisticated nanocomposites.In fields like aerospace,automotive,and electronics where higher mechanical performance and functionality are required,GNPs'improved mechanical properties and successful dispersion present exciting potential.展开更多
Polyethylene glycol(PEG)with different chains was used to modify epoxy asphalt.Molecular models of PEG⁃modified epoxy asphalt were developed using molecu⁃lar simulations(MS).The thermodynamic and mechanical properties...Polyethylene glycol(PEG)with different chains was used to modify epoxy asphalt.Molecular models of PEG⁃modified epoxy asphalt were developed using molecu⁃lar simulations(MS).The thermodynamic and mechanical properties of PEG⁃modified epoxy asphalt were analyzed,and its toughening mechanisms were explored.A method based on the Dijkstra algorithm was proposed to evaluate ep⁃oxy asphalt crosslinked networks.The results show that the introduction of PEG chains into epoxy asphalt can lower the glass transition temperature and enhance its toughness be⁃cause of the extended length of the PEG chains,which can in⁃crease the free volume and improve the mobility of the epoxy resin in the epoxy asphalt.The crosslinked network quantita⁃tive evaluation method based on the Dijkstra algorithm can ef⁃fectively evaluate the distribution of epoxy asphalt crosslink⁃ing bonds,providing further explanation of the toughening mechanism of PEG⁃modified epoxy asphalt.The feasibility of designing and screening epoxy asphalt materials by MS is verified,and a guide for toughening mechanism research of epoxy asphalt at the molecular level is provided.展开更多
This study focuses on the thermophysical characterizations of composite materials made from polypropylene reinforced with residues and fibers from Borassus wood from Chad. These properties are experimentally determine...This study focuses on the thermophysical characterizations of composite materials made from polypropylene reinforced with residues and fibers from Borassus wood from Chad. These properties are experimentally determined at different temperatures using the hot wire method of the “FP2C” machine, where the hot wire probe is inserted between two specimens. The values of the thermal conductivity in powdered Borassus wood range from 0.170 W/mK to 0.182 W/mK for female wood (FNTF) and from 0.169 W/mK to 0.173 W/mK for male wood. For the female and male fibers, the thermal conductivity values range from 0.137 W/mK to 0.157 W/mK for the female and from 0.138 W/mK to 0.168 W/mK for the male. The thermal effusivity of the residues and fibers of Borassus wood varies from: 509.6 Ws1/2/m2K to 543 Ws1/2/m2K for the powder of female wood and from 524.6 Ws1/2/m2K to 547 Ws1/2/m2K for the powder of male wood. For the fibers of Borassus wood, the values range from 410.6 Ws1/2/m2K to 523.6 Ws1/2/m2K for the female wood fibers and from 420.3 Ws1/2/m2K to 480.3 Ws1/2/m2K for the male wood fibers. These results are important for the applications of Borassus wood residues and fibers in construction works regarding the thermal insulation of habitats.展开更多
Scorpions are distributed almost all over the world and inhabit rainforests,deserts,mountains,and littoral zones.Their multifunctional chelae play a key role in their biology.The chela is the pincer that has originate...Scorpions are distributed almost all over the world and inhabit rainforests,deserts,mountains,and littoral zones.Their multifunctional chelae play a key role in their biology.The chela is the pincer that has originated from the last two segments of the pedipalp.Many previous studies have focused on the morphology of the chela and the overall pincer force.The knowledge about the material properties of scorpion chelae remains rather poor.In particular,little is known about the spines located on the grasping edge of the chela.In this study,we use a combination of nanoindentation,micro-computer tomography,confocal laser scanning microscopy,scanning electron microscopy and energy-dispersive X-ray elemental analysis,to examine the mechanical properties,relative density,sclerotization level,microstructure and biomineralization of both the regular cuticle and the spine cuticle of the chela in the scorpion Androctonus bicolor.Our results show that the mechanical property values of the spine cuticle are significantly higher than those of the regular cuticle.This can reduce the risk of damage to the chela,increase the chance of indentation into the prey tissue and is very likely to result from both higher sclerotization level and biomineralization due to the accumulation of zinc.The specialized microstructure of the cuticle could contribute to the enhancement of the stiffness,strength and toughness of the chela.This study aids in better understanding the material structure,composition and properties of the scorpion chela cuticle.展开更多
With the rapid development of the world economy,complex air pollution has increasingly become a serious threat;for example,with haze events occurring frequently in various regions of the globe.Recent evidence has indi...With the rapid development of the world economy,complex air pollution has increasingly become a serious threat;for example,with haze events occurring frequently in various regions of the globe.Recent evidence has indicated that secondary aerosols play an important role in haze formation,and that heterogeneous processes are among the main forces driving their explosive growth.In this regard,this paper reviews recent advances in the understanding of the impact of heterogeneous processes on haze chemistry,including the impact on NO_(2)chemistry,marine aerosols,and the hygroscopicity and optical properties of atmospheric aerosols.It is distinguished from past reviews on this topic by focusing mainly on new insights from the past five years.We summarize the main findings of the impacts of heterogeneous processes on NO_(2)chemistry,marine aerosols,and the physicochemical properties of atmospheric aerosols,and propose several future research directions.展开更多
Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2...Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2)O_(3) ceramics have been fabricated at very high sintering temperatures,but their optical quality and sintering process still need further improvement.In this work,5%Yb:Sc_(2)O_(3)(in mass)nano-powders were obtained by co-precipitation,and then transparent ceramics were fabricated by vacuum pre-sintering and hot isostatic pressing(HIP)post-treatment.The cubic Yb:Sc_(2)O_(3) nano-powders with good dispersity and an average crystallite of 29 nm were obtained.Influence of pre-sintering temperatures(1500-1700℃)on densification process,microstructure changes,and optical transmittance of Yb:Sc_(2)O_(3) ceramics was detected.Experimental data revealed that all samples have a uniform microstructure,while the average grain sizes increase with the increase of the sintering temperatures.Impressively,the optimum in-line transmittance of Yb:Sc_(2)O_(3) ceramics,pre-sintered at 1550℃after HIP post-treatment,reaches 78.1%(theoretical value of 80%)at 1100 nm.Spectroscopic properties of the Yb:Sc_(2)O_(3) ceramics reveal that the minimum population inversion parameterβ2 and the luminescence decay time of 5%Yb:Sc_(2)O_(3) ceramics are 0.041 and 0.49 ms,respectively,which demonstrate that the optical quality of the Yb:Sc_(2)O_(3) has been improved.Meanwhile,their best vacuum sintering temperature can be controlled down to a lower temperature(1550℃).In conclusion,Yb:Sc_(2)O_(3) nano-powders are successfully synthesized by co-precipitation method,and good optical quality transparent ceramics are fabricated by vacuum pre-sintering at 1550℃and HIP post-treatment.展开更多
Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites with solidification rates of 6,20,30,and 80μm/s were prepared by a modified Bridgman directional solidification technology.The coarse Fe_(2)Ta(Al)Laves phase was precipitated...Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites with solidification rates of 6,20,30,and 80μm/s were prepared by a modified Bridgman directional solidification technology.The coarse Fe_(2)Ta(Al)Laves phase was precipitated at the eutectic colony boundary during the solidification process,which can affect the stability of microstructure and properties of the composites.The coarse Laves phase was refined using different heat treatment processes in the present paper.The influences of different heat treatment parameters on the Laves phase content,lamella/rod spacing,and mechanical properties were investigated in detail.In addition,the corrosion behaviors of Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites before and after being annealed heat treatment in a 3 g/L Na_(2)S_(2)O_(3)solution were also studied.It is shown that both the content of Laves phase and lamella/rod spacing are gradually decreased after heat treatment.Micro-hardness is decreased,while the yield strength,compressive strength,and corrosion resistance are improved.The optimum heat treatment process is selected as well.展开更多
A new type of magnesium oxychloride cement(MOC)was prepared based on calcined MgO powder from hydromagnesite in Tibet,China,with the addition of MgCl_2,a by-product of potassium extraction from the salt lake.The effec...A new type of magnesium oxychloride cement(MOC)was prepared based on calcined MgO powder from hydromagnesite in Tibet,China,with the addition of MgCl_2,a by-product of potassium extraction from the salt lake.The effect of MgO on the microstructure and properties of magnesium oxychloride cement was investigated under different calcination temperatures and time of hydromagnesite,and the hydration process,pore structure and hydration products of the materials were investigated by isothermal calorimeter,MIP,XRD,and SEM,and the mechanical properties of the materials were examined by compressive strength test.The compressive strength test shows that under the optimal conditions(800℃-2 h),the compressive strength of MOC is 75.65 MPa for 7 d and 87.98 MPa for 28 d in the indoor environment.The main exothermic period of MOC is delayed by about 10 h compared with that of 500℃-2 h and extended by about 30 h in the process of MOC preparation,which led to the alleviation of the exothermic concentration phenomenon,and the initial solidification time of the MOC specimens is 5.25 h,and the final solidification time is 11.82 h.The MOC phase maintained in indoor air for 28 d mainly consist of P5 and unreacted MgO,and the P5 in the matrix shows the slat-like shape and fills the gaps in the form of needles and rods,and the total porosity is 18.55%.展开更多
Novel ordered intermetallic compounds have stimulated much interest.Ru–Al alloys are a prominent class of hightemperature structural materials,but the experimentally reported crystal structure of the intermetallic Ru...Novel ordered intermetallic compounds have stimulated much interest.Ru–Al alloys are a prominent class of hightemperature structural materials,but the experimentally reported crystal structure of the intermetallic Ru_(2)Al_(5) phase remains elusive and debatable.To resolve this controversy,we extensively explored the crystal structures of Ru_(2)Al_(5) using first-principles calculations combined with crystal structure prediction technique.Among the calculated x-ray diffraction patterns and lattice parameters of five candidate Ru2Al5structures,those of the orthorhombic Pmmn structure best aligned with recent experimental results.The structural stabilities of the five Ru_(2)Al_(5)structures were confirmed through formation energy,elastic constants,and phonon spectrum calculations.We also comprehensively analyzed the mechanical and electronic properties of the five candidates.This work can guide the exploration of novel ordered intermetallic compounds in Ru–Al alloys.展开更多
The effects of Zr addition on the mechanical properties and in vitro degradation behavior of Mg-1.0Yb-xZr(x=0,0.2,1.0,and 1.53,wt.%)cast alloys were investigated.The results indicated that with increasing Zr addition,...The effects of Zr addition on the mechanical properties and in vitro degradation behavior of Mg-1.0Yb-xZr(x=0,0.2,1.0,and 1.53,wt.%)cast alloys were investigated.The results indicated that with increasing Zr addition,a much refined and homogeneous equiaxed grain structure was achieved from a typical columnar grain structure,in companion with the appearance and coarsening of Zr-rich particles.Subsequent electrochemical and immersion tests demonstrated that the corrosion of the alloy was Zr-addition dependent.A trace or excessive Zr addition caused severe localized corrosion attacks,whereas Zr-free and 1.0 Zr alloyed counterparts were generally corroded uniformly.The good combination of mechanical properties and corrosion resistance of the Mg-1.0Yb-1.0Zr alloy was resulted from the refined and homogeneous equiaxed grain structure and fine dispersed Zr-rich particles,thus improving the comprehensive mechanical properties by grain refinement and reducing corrosion rate by generating a more stable and compact passivation layer during long-term immersion.展开更多
基金Funded by National Key R&D Program of China(No.2021YFB3802300)the National Natural Science Foundation of China(No.52171045)the Joint Fund(No.8091B022108)。
文摘The mechanical and thermodynamic properties of W-Ti alloys(including W_(15)Ti_(1),W_(14)Ti_(2),W_(12)Ti_(4) and W_(8)Ti_(8) alloys)were investigated by the first-principles approach based on density functional theory.The results indicate that W-Ti alloys except W_(8)Ti_(8) are thermodynamically stable.The modulus and hardness of W-Ti alloys are smaller than those of pure tungsten and gradually decrease with increasing Ti concentration.However,their B/G ratios and Poisson's ratios exceed those of pure tungsten,suggesting that the introduction of Ti decreases the mechanical strength while enhancing the ductility of W-Ti alloys.The thermal expansion coefficients for W-Ti alloys all surpass those of pure tungsten,indicating that the introduction of titanium exacerbates the thermal expansion behavior of W-Ti alloys.Nevertheless,elevated pressure has the capacity to suppress the thermal expansion tendencies in titanium-doped tungsten alloys.This study offers theoretical insights for the design of nuclear materials by exploring the mechanical and thermodynamic properties of W-Ti alloys.
基金Funded by the Key R&D Projects of Shanxi Province(No.201903D321113)the Shanxi Provincial Natural Science Foundation(No.202303021212359)the General Research Projects of Taiyuan University(No.23TYYB07)。
文摘Carbon fibre,steel fibre and graphite were used as conductive fillers to prepare cementitious materials with excellent electrothermal properties.The electrically conductive cementitious materials with different volume dosages were analysed through compressive and flexural strength,electrochemical impedance spectroscopy and temperature rise tests.An equivalent circuit model was established to study the electrically conductive heat generation mechanism in the electrically conductive cementitious composites.The results indicate that the mechanical properties of cementitious composite materials with a ternary conductive phase are better than those of pristine cementitious materials because the fibrous filler improves their mechanical properties.However,the incorporation of graphite in the material reduces its strength.Introducing fibrous and point-like conductive phase materials into the cementitious material enhances the overall conductive pathway and considerably reduces the electrical resistance of the cementitious material,enhancing its conductive properties.The volume ratios of carbon fibre,steel fibre and graphite that achieve an optimal complex doping in the cementitious material were 0.35%,0.6%and 6%,respectively.This was determined using the mutation point of each circuit element parameter as the percolation threshold.In addition,at a certain safety voltage,there is a uniform change between the internal and surface temperatures of the conductive cementitious material,and the heating effect in this materialis is considerably better than that in the pristine cementitious material.
基金financial support of this work by the National Natural Science Foundation of China(Nos.22378332,52003219)the Open Fund of Zhejiang Key Laboratory of Flexible Electronics(No.2022FE008)+1 种基金the Natural Science Foundation of Ningbo(NO.2022J058)Ministry of Industry and Information Technology high quality development project(TC220A04A-206).
文摘Although poly(lactic acid)(PLA)is a good environmentally-friendly bio-degradable polymer which is used to substitute traditional petrochemical-based polymer packaging films,the barrier properties of PLA films are still insufficient for high-barrier packaging applications.In this study,oxygen scavenger hydroxyl-terminated polybutadiene(HTPB)and cobalt salt catalyst were incorporated into the PLA/poly(butylene adipate-co-terephthalate)(PLA/PBAT),followed by melting extrusion and three-layer co-extrusion blown film process to prepare the composite films.The oxygen permeability coefficient of the composite film combined with 6 wt%oxygen scavenger and 0.4 wt%catalyst was decreased significantly from 377.00 cc·mil·m^(-2)·day^(-1)·0.1 MPa^(-1) to 0.98 cc·mil·m^(-2)·day^(-1)·0.1 MPa^(-1),showing a remarkable enhancement of 384.69 times compared with the PLA/PBAT composite film.Meanwhile,the degradation behavior of the composite film was also accelerated,exhibiting a mass loss of nearly 60%of the original mass after seven days of degradation in an alkaline environment,whereas PLA/PBAT composite film only showed a mass loss of 32%.This work has successfully prepared PLA/PBAT composite films with simultaneously improved oxygen barrier property and degradation behavior,which has great potential for high-demanding green chemistry packaging industries,including food,agricultural,and military packaging.
基金Funded by the National Natural Science Foundation of China(Nos.U1934206,52108260)China Academy of Railway Sciences Fund(No.2021YJ078)+1 种基金Railway Engineering Construction Standard Project(No.2023-BZWW-006)New Cornerstone Science Foundation through the XPLORER PRIZE。
文摘In order to achieve the large-scale application of manufactured sand in railway high-strength concrete structure,a series of high-strength manufactured sand concrete(HMC)are prepared by taking the manufactured sand lithology(tuff,limestone,basalt,granite),stone powder content(0,5%,10%,15%)and concrete strength grade(C60,C80,C100)as variables.The evolution of mechanical properties of HMC and the correlation between cubic compressive strength and other mechanical properties are studied.Compared to river sand,manufactured sand enhances the cubic compressive strength,axial compressive strength and elastic modulus of concrete,while its potential microcracks weaken the flexural strength and splitting tensile strength of concrete.Stone powder content displays both positive and negative effects on mechanical properties of HMC,and the stone powder content is suggested to be less than 10%.The empirical formulas between cubic compressive strength and other mechanical properties are proposed.
文摘The microstructures and thermodynamic properties of mixed systems comprising pyridinium ionic liquid[HPy][BF_(4)]and acetonitrile at different mole fractions were studied using molecular dynamics simulation in this work.The following properties were determined:density,self-diffusion coefficient,excess molar volume,and radial distribution function.The results show that with an increase in the mole fraction of[HPy][BF_(4)],the self-diffusion coefficient decreases.Additionally,the excess molar volume initially decreases,reaches a minimum,and then increases.The rules of radial distribution functions(RDFs)of characteristic atoms are different.With increasing the mole fraction of[HPy][BF_(4)],the first peak of the RDFs of HA1-F decreases,while that of CT6-CT6 rises at first and then decreases.This indicates that the solvent molecules affect the polar and non-polar regions of[HPy][BF_(4)]differently.
基金Guizhou Provincial University Humanities and Social Sciences Research Project in 2024"Enhancing the Development of New Productive Forces through University Technological Innovation and Intellectual Property Management"(2024RW256)Guizhou University of Commerce Research Project in 2022"Study on the Ideas and Pathways to Drive Agricultural Powerhouse through Digital Economy"(2022XJZX315)。
文摘With the rapid development of globalization and information technology,intellectual property has been one of the key drivers of economic growth,and the construction of intellectual property system has become an important criterion for measuring the quality of business environment.This article is intended to explore the current status of intellectual property system construction in China,the challenges,and its relationship with the business environment,to propose the corresponding countermeasures and suggestions.The study finds that the legal system of intellectual property in China is gradually improving,and judicial and administrative protection are continuously strengthened.However,the challenges still remain such as frequent infringements,rights hard to protect and insufficient international cooperation.These issues not only affect the legitimate rights and interests of innovation entities,but also for the market fairness and the level of the business environment.Therefore,this article proposes that strengthening the perfection of the intellectual property legal system,enhancing intellectual property services and support capabilities,strengthening international cooperation and exchanges,and accelerating the cultivation of composite talents.It aims to provide theoretical references for the construction of intellectual property system and the optimization of the business environment,promote the high-quality development of economy and enhance the global competitiveness of the country.
文摘Observational data of ball lightning often contradict each other, so it was sometimes proposed to build a theory of ball lightning based on only a small number of statistically reliable observations. Work on this principle did not bring results. The correct approach to creating the theory of ball lightning should be the desire to explain all of its properties, even those that are rare. In the database of ball lightning observations, the most valuable are the cases when it left traces available for quantitative analysis, or was filmed by video cameras. Ball lightning is a material body consisting of a shell and a multi-element core. Cases of water heating made it possible to determine energy density of ball lightning, which turned out to be higher than 1010 J/m3. A study of results of ball lightning explosion, as well as its effect on snow, made it possible to assume that it is capable of generating radiation with a wavelength of about 10 cm, the power of which can be greater than 120 kW. Ball lightning has an electric charge of 10−3 - 10−1 C. The presence of an electric charge explains the complex nature of its movement in atmosphere. Ball lightning is formed under the action of magnetic field pulse and ultraviolet radiation of linear lightning channel. A model of ball lightning in the form of a core of charged “dynamic capacitors” and a shell of polarized water molecules is considered. It is shown that this shell is capable of withstanding the force of Coulomb repulsion of the core charges and the pressure caused by the movement of charge carriers. The glow of ball lightning core occurs due to orbital motion of electrons at a speed close to light speed. The intensity of the glow is determined by the degree of uniformity of electrons arrangement along the orbit.
基金financially supported by the National Natural Science Foundation of China(Nos.52174092,51904290,and 52374147)the Natural Science Foundation of Jiangsu Province,China(No.BK20220157)+2 种基金the Fundamental Research Funds for the Central Universities,China(No.2022YCPY0202)the National Key Research and Development Program of China(No.2023YFC3804204)the Major Program of Xinjiang Uygur Autonomous Region S cience and Technology(No.2023A01002)。
文摘The mechanical behavior of cemented gangue backfill materials(CGBMs)is closely related to particle size distribution(PSD)of aggregates and properties of cementitious materials.Consequently,the true triaxial compression tests,CT scanning,SEM,and EDS tests were conducted on cemented gangue backfill samples(CGBSs)with various carbon nanotube concentrations(P_(CNT))that satisfied fractal theory for the PSD of aggregates.The mechanical properties,energy dissipations,and failure mechanisms of the CGBSs under true triaxial compression were systematically analyzed.The results indicate that appropriate carbon nanotubes(CNTs)effectively enhance the mechanical properties and energy dissipations of CGBSs through micropore filling and microcrack bridging,and the optimal effect appears at P_(CNT)of 0.08wt%.Taking PSD fractal dimension(D)of 2.500 as an example,compared to that of CGBS without CNT,the peak strength(σ_(p)),axial peak strain(ε_(1,p)),elastic strain energy(Ue),and dissipated energy(U_(d))increased by 12.76%,29.60%,19.05%,and90.39%,respectively.However,excessive CNTs can reduce the mechanical properties of CGBSs due to CNT agglomeration,manifesting a decrease inρ_(p),ε_(1,p),and the volumetric strain increment(Δε_(v))when P_(CNT)increases from 0.08wt%to 0.12wt%.Moreover,the addition of CNTs improved the integrity of CGBS after macroscopic failure,and crack extension in CGBSs appeared in two modes:detour and pass through the aggregates.Theσ_(p)and U_(d)firstly increase and then decrease with increasing D,and porosity shows the opposite trend.Theε_(1,p)andΔε_(v)are negatively correlated with D,and CGBS with D=2.150 has the maximum deformation parameters(ε_(1,p)=0.05079,Δε_(v)=0.01990)due to the frictional slip effect caused by coarse aggregates.With increasing D,the failure modes of CGBSs are sequentially manifested as oblique shear failure,"Y-shaped"shear failure,and conjugate shear failure.
文摘A new cobalt(Ⅱ)-radical complex:[Co(im4-py)_(2)(PNB)_(2)](im4-py=2-(4'-pyridyl)-4,4,5,5-tetramethylimidazole-1-oxyl,HPNB=p-nitrobenzoic acid)has been synthesized and characterized by X-ray diffraction analysis,elemental analysis,IR,and magnetic properties.X-ray diffraction analysis shows that the complex exists as mononuclear molecules and Co(Ⅱ)ion is four-coordinated with two radicals and two PNB-ligands.The magnetic susceptibility study indicates the complex exhibits weak ferromagnetic interactions between cobalt(Ⅱ)and im4-py radical.The magnetic property is explained by the magnetic and structure exchange mechanism.CCDC:976028.
基金supported by the National Key R&D Program of China(2021YFD2100400,2023YFE0104900)Xinjiang Agriculture Research System-Oil Crop Research System,China(XJARS-05)+3 种基金Taishan Industrial Experts Programme,China(tscx202306075)the Scientific and Technological Assistance Projects to Developing Countries,China(KY202201003)the Agricultural Science and Technology Innovation Program,Institute of Food Science and Technology,Chinese Academy of Agricultural Sciences(CAAS-ASTIP-2024-IFST)The authors are grateful for the financial support from the Arawana Charity Foundation,China.
文摘Peanut varieties are diverse globally,with their characters and nutrition determining the product quality.However,the comparative analysis and statistical analysis of key quality indicators for peanut kernels across the world remains relatively limited,impeding the comprehensive evaluation of peanut quality and hindering the industry development on a global scale.This study aimed to compare and analyze the apparent morphology,microstructure,single-cell structure,engineering and mechanical properties,as well as major nutrient contents of peanut kernels from 10 different cultivars representing major peanut-producing countries.The surface and cross-section microstructure of the peanut kernels exhibited a dense“blocky”appearance with a distinct cellular structure.The lipid droplets were predominantly spherical with a regular distribution within the cells.The single-cell structure of the kernels from these 10 peanut cultivars demonstrated varying morphologies and dimensions,which exhibited correlations with their mechanical and engineering properties.Furthermore,the mass loss versus temperature profiles of the peanut kernels revealed five distinct stages,corresponding to moisture loss,volatile loss,protein denaturation,and the degradation of various biomacromolecules.Variations were also observed in the lipid,protein,and sucrose contents,texture,bulk density,true density,porosity,geometric mean diameter,and sphericity among the diferent peanut varieties.This study establishes relationships and correlations among microstructure,engineering properties,and nutritional composition of commonly grown peanut varieties in major peanut-processing countries.The findings provide valuable insights into peanut quality evaluation,empowering the peanut industry to enhance their processing and product development efforts.
基金the Puncak RM for the project under the grant 6733204-13069 to carry out the experiments。
文摘Graphene nanoplatelets(GNPs)have attracted tremendous interest due to their unique properties and bonding capabilities.This study focuses on the effect of GNP dispersion on the mechanical,thermal,and morphological behavior of GNP/epoxy nanocomposites.This study aims to understand how the dispersion of GNPs affects the properties of epoxy nanocomposite and to identify the best dispersion approach for improving mechanical performance.A solvent mixing technique that includes mechanical stirring and ultrasonication was used for producing the nanocomposites.Fourier transform infrared spectroscopy was used to investigate the interaction between GNPs and the epoxy matrix.The measurements of density and moisture content were used to confirm that GNPs were successfully incorporated into the nanocomposite.The findings showed that GNPs are successfully dispersed in the epoxy matrix by combining mechanical stirring and ultrasonication in a single step,producing well-dispersed nanocomposites with improved mechanical properties.Particularly,the nanocomposites at a low GNP loading of 0.1 wt%,demonstrate superior mechanical strength,as shown by increased tensile properties,including improved Young's modulus(1.86 GPa),strength(57.31 MPa),and elongation at break(4.98).The nanocomposite with 0.25 wt%GNP loading performs better,according to the viscoelastic analysis and flexural properties(113.18 MPa).Except for the nanocomposite with a 0.5 wt%GNP loading,which has a higher thermal breakdown temperature,the thermal characteristics do not significantly alter.The effective dispersion of GNPs in the epoxy matrix and low agglomeration is confirmed by the morphological characterization.The findings help with filler selection and identifying the best dispersion approach,which improves mechanical performance.The effective integration of GNPs and their interaction with the epoxy matrix provides the doorway for additional investigation and the development of sophisticated nanocomposites.In fields like aerospace,automotive,and electronics where higher mechanical performance and functionality are required,GNPs'improved mechanical properties and successful dispersion present exciting potential.
基金The Major Science and Technology Project of Nan⁃jing(No.202209012)the Postgraduate Research and Practice Innova⁃tion Program of Jiangsu Province(No.KYCX22⁃0277).
文摘Polyethylene glycol(PEG)with different chains was used to modify epoxy asphalt.Molecular models of PEG⁃modified epoxy asphalt were developed using molecu⁃lar simulations(MS).The thermodynamic and mechanical properties of PEG⁃modified epoxy asphalt were analyzed,and its toughening mechanisms were explored.A method based on the Dijkstra algorithm was proposed to evaluate ep⁃oxy asphalt crosslinked networks.The results show that the introduction of PEG chains into epoxy asphalt can lower the glass transition temperature and enhance its toughness be⁃cause of the extended length of the PEG chains,which can in⁃crease the free volume and improve the mobility of the epoxy resin in the epoxy asphalt.The crosslinked network quantita⁃tive evaluation method based on the Dijkstra algorithm can ef⁃fectively evaluate the distribution of epoxy asphalt crosslink⁃ing bonds,providing further explanation of the toughening mechanism of PEG⁃modified epoxy asphalt.The feasibility of designing and screening epoxy asphalt materials by MS is verified,and a guide for toughening mechanism research of epoxy asphalt at the molecular level is provided.
文摘This study focuses on the thermophysical characterizations of composite materials made from polypropylene reinforced with residues and fibers from Borassus wood from Chad. These properties are experimentally determined at different temperatures using the hot wire method of the “FP2C” machine, where the hot wire probe is inserted between two specimens. The values of the thermal conductivity in powdered Borassus wood range from 0.170 W/mK to 0.182 W/mK for female wood (FNTF) and from 0.169 W/mK to 0.173 W/mK for male wood. For the female and male fibers, the thermal conductivity values range from 0.137 W/mK to 0.157 W/mK for the female and from 0.138 W/mK to 0.168 W/mK for the male. The thermal effusivity of the residues and fibers of Borassus wood varies from: 509.6 Ws1/2/m2K to 543 Ws1/2/m2K for the powder of female wood and from 524.6 Ws1/2/m2K to 547 Ws1/2/m2K for the powder of male wood. For the fibers of Borassus wood, the values range from 410.6 Ws1/2/m2K to 523.6 Ws1/2/m2K for the female wood fibers and from 420.3 Ws1/2/m2K to 480.3 Ws1/2/m2K for the male wood fibers. These results are important for the applications of Borassus wood residues and fibers in construction works regarding the thermal insulation of habitats.
基金financially supported by the Grant GO995/48-1 to S.N.G.from the National Priority Program SPP2416″Code-Chi-Chitin,chitosan and chitooligosaccharides and their interaction with proteins of the extracellular matrix and cellular signaling”of the German Science Foundation(DFG).
文摘Scorpions are distributed almost all over the world and inhabit rainforests,deserts,mountains,and littoral zones.Their multifunctional chelae play a key role in their biology.The chela is the pincer that has originated from the last two segments of the pedipalp.Many previous studies have focused on the morphology of the chela and the overall pincer force.The knowledge about the material properties of scorpion chelae remains rather poor.In particular,little is known about the spines located on the grasping edge of the chela.In this study,we use a combination of nanoindentation,micro-computer tomography,confocal laser scanning microscopy,scanning electron microscopy and energy-dispersive X-ray elemental analysis,to examine the mechanical properties,relative density,sclerotization level,microstructure and biomineralization of both the regular cuticle and the spine cuticle of the chela in the scorpion Androctonus bicolor.Our results show that the mechanical property values of the spine cuticle are significantly higher than those of the regular cuticle.This can reduce the risk of damage to the chela,increase the chance of indentation into the prey tissue and is very likely to result from both higher sclerotization level and biomineralization due to the accumulation of zinc.The specialized microstructure of the cuticle could contribute to the enhancement of the stiffness,strength and toughness of the chela.This study aids in better understanding the material structure,composition and properties of the scorpion chela cuticle.
基金supported by the National Key Research and Development Program of China(No.2022YFC3701000)the National Natural Science Foundation of China(Nos.42130606 and 41931287)+1 种基金the Beijing National Laboratory for Molecular Sciences(BNLMS-CXXM-202011)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.Y2021013).
文摘With the rapid development of the world economy,complex air pollution has increasingly become a serious threat;for example,with haze events occurring frequently in various regions of the globe.Recent evidence has indicated that secondary aerosols play an important role in haze formation,and that heterogeneous processes are among the main forces driving their explosive growth.In this regard,this paper reviews recent advances in the understanding of the impact of heterogeneous processes on haze chemistry,including the impact on NO_(2)chemistry,marine aerosols,and the hygroscopicity and optical properties of atmospheric aerosols.It is distinguished from past reviews on this topic by focusing mainly on new insights from the past five years.We summarize the main findings of the impacts of heterogeneous processes on NO_(2)chemistry,marine aerosols,and the physicochemical properties of atmospheric aerosols,and propose several future research directions.
基金National Key R&D Program of China(2023YFE3812005)International Partnership Program of Chinese Academy of Sciences(121631KYSB20200039)+1 种基金National Center for Research and Development(WPC2/1/SCAPOL/2021)Chinese Academy of Sciences President’s International Fellowship Initiative(2024VEA0005,2024VEA0014)。
文摘Sc_(2)O_(3),as a host for solid-state laser gain materials,has advantage of high thermal conductivity and easy matching with activating ions,which is promising in high-power laser applications.Currently,Yb-doped Sc_(2)O_(3) ceramics have been fabricated at very high sintering temperatures,but their optical quality and sintering process still need further improvement.In this work,5%Yb:Sc_(2)O_(3)(in mass)nano-powders were obtained by co-precipitation,and then transparent ceramics were fabricated by vacuum pre-sintering and hot isostatic pressing(HIP)post-treatment.The cubic Yb:Sc_(2)O_(3) nano-powders with good dispersity and an average crystallite of 29 nm were obtained.Influence of pre-sintering temperatures(1500-1700℃)on densification process,microstructure changes,and optical transmittance of Yb:Sc_(2)O_(3) ceramics was detected.Experimental data revealed that all samples have a uniform microstructure,while the average grain sizes increase with the increase of the sintering temperatures.Impressively,the optimum in-line transmittance of Yb:Sc_(2)O_(3) ceramics,pre-sintered at 1550℃after HIP post-treatment,reaches 78.1%(theoretical value of 80%)at 1100 nm.Spectroscopic properties of the Yb:Sc_(2)O_(3) ceramics reveal that the minimum population inversion parameterβ2 and the luminescence decay time of 5%Yb:Sc_(2)O_(3) ceramics are 0.041 and 0.49 ms,respectively,which demonstrate that the optical quality of the Yb:Sc_(2)O_(3) has been improved.Meanwhile,their best vacuum sintering temperature can be controlled down to a lower temperature(1550℃).In conclusion,Yb:Sc_(2)O_(3) nano-powders are successfully synthesized by co-precipitation method,and good optical quality transparent ceramics are fabricated by vacuum pre-sintering at 1550℃and HIP post-treatment.
基金Funded by the Key Industry Innovation Chain(Group)Project of Shaanxi Province,China(No.2019ZDLGY 04-04)the Project of Yulin Science and Technology Bureau(No.2023-CXY-197)。
文摘Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites with solidification rates of 6,20,30,and 80μm/s were prepared by a modified Bridgman directional solidification technology.The coarse Fe_(2)Ta(Al)Laves phase was precipitated at the eutectic colony boundary during the solidification process,which can affect the stability of microstructure and properties of the composites.The coarse Laves phase was refined using different heat treatment processes in the present paper.The influences of different heat treatment parameters on the Laves phase content,lamella/rod spacing,and mechanical properties were investigated in detail.In addition,the corrosion behaviors of Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites before and after being annealed heat treatment in a 3 g/L Na_(2)S_(2)O_(3)solution were also studied.It is shown that both the content of Laves phase and lamella/rod spacing are gradually decreased after heat treatment.Micro-hardness is decreased,while the yield strength,compressive strength,and corrosion resistance are improved.The optimum heat treatment process is selected as well.
基金Funded by the Xining Key R&D and Transformation Program(No.2024-Y-11)the Qinghai Province“Kunlun Talents-Highend Innovation and Entrepreneurship Talents”Top Talents。
文摘A new type of magnesium oxychloride cement(MOC)was prepared based on calcined MgO powder from hydromagnesite in Tibet,China,with the addition of MgCl_2,a by-product of potassium extraction from the salt lake.The effect of MgO on the microstructure and properties of magnesium oxychloride cement was investigated under different calcination temperatures and time of hydromagnesite,and the hydration process,pore structure and hydration products of the materials were investigated by isothermal calorimeter,MIP,XRD,and SEM,and the mechanical properties of the materials were examined by compressive strength test.The compressive strength test shows that under the optimal conditions(800℃-2 h),the compressive strength of MOC is 75.65 MPa for 7 d and 87.98 MPa for 28 d in the indoor environment.The main exothermic period of MOC is delayed by about 10 h compared with that of 500℃-2 h and extended by about 30 h in the process of MOC preparation,which led to the alleviation of the exothermic concentration phenomenon,and the initial solidification time of the MOC specimens is 5.25 h,and the final solidification time is 11.82 h.The MOC phase maintained in indoor air for 28 d mainly consist of P5 and unreacted MgO,and the P5 in the matrix shows the slat-like shape and fills the gaps in the form of needles and rods,and the total porosity is 18.55%.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11965005 and 11964026)the Natural Science Basic Research Plan in Shaanxi Province,China(Grant Nos.2023-JC-YB-021 and 2022JM-035)+1 种基金the Fundamental Research Funds for the Central Universitiesthe 111 Project(Grant No.B17035)。
文摘Novel ordered intermetallic compounds have stimulated much interest.Ru–Al alloys are a prominent class of hightemperature structural materials,but the experimentally reported crystal structure of the intermetallic Ru_(2)Al_(5) phase remains elusive and debatable.To resolve this controversy,we extensively explored the crystal structures of Ru_(2)Al_(5) using first-principles calculations combined with crystal structure prediction technique.Among the calculated x-ray diffraction patterns and lattice parameters of five candidate Ru2Al5structures,those of the orthorhombic Pmmn structure best aligned with recent experimental results.The structural stabilities of the five Ru_(2)Al_(5)structures were confirmed through formation energy,elastic constants,and phonon spectrum calculations.We also comprehensively analyzed the mechanical and electronic properties of the five candidates.This work can guide the exploration of novel ordered intermetallic compounds in Ru–Al alloys.
基金the financial supports from the China Scholarship Council(No.201808505057)。
文摘The effects of Zr addition on the mechanical properties and in vitro degradation behavior of Mg-1.0Yb-xZr(x=0,0.2,1.0,and 1.53,wt.%)cast alloys were investigated.The results indicated that with increasing Zr addition,a much refined and homogeneous equiaxed grain structure was achieved from a typical columnar grain structure,in companion with the appearance and coarsening of Zr-rich particles.Subsequent electrochemical and immersion tests demonstrated that the corrosion of the alloy was Zr-addition dependent.A trace or excessive Zr addition caused severe localized corrosion attacks,whereas Zr-free and 1.0 Zr alloyed counterparts were generally corroded uniformly.The good combination of mechanical properties and corrosion resistance of the Mg-1.0Yb-1.0Zr alloy was resulted from the refined and homogeneous equiaxed grain structure and fine dispersed Zr-rich particles,thus improving the comprehensive mechanical properties by grain refinement and reducing corrosion rate by generating a more stable and compact passivation layer during long-term immersion.
