Coiled tube heat exchangers are widely preferred in shell structures due to their superior heat transfer performance,driven by favorable flow characteristics.This study investigates the effect of modifying coil and sh...Coiled tube heat exchangers are widely preferred in shell structures due to their superior heat transfer performance,driven by favorable flow characteristics.This study investigates the effect of modifying coil and shell configurations on heat transfer efficiency.Two key enhancements were examined:adding fins to the outer coil surface and integrating longitudinal slots within a hollowed shell.These modifications promote turbulence and extend heat transfer duration,thereby improving performance.However,they also introduce challenges,including increased pressure loss andmanufacturing complexity.Numerical simulationswere conducted usingANSYS Fluent 2024R1 under identical boundary conditions.With a fixed cold-side flow rate of 3 L/min,the input temperatures for the hot and cold fluids were 333.15 and 291.65 K,respectively.The hot-side flow rate varied between 2 and 6 L/min.Simulation outcomes were reported for the objectives of the study that included the improvement in heat exchangers’heat transfer enhancement.As it was indicated in the study outcomes,the average heat transfer rate increased by 15.56%,the overall heat transfer coefficient enhanced by about 29.51%,and the convective heat transfer coefficient improved by about 75.96%compared to the conventional shell-and-coil tube heat exchanger model.However,the modified technique resulted in a significant pressure drop.展开更多
A comparative study on the performance of gas atomized(GA)and rotating-disk atomized(RDA)aluminum alloy powders produced on industrial scale for laser directed energy deposition(L-DED)process was carried out.The powde...A comparative study on the performance of gas atomized(GA)and rotating-disk atomized(RDA)aluminum alloy powders produced on industrial scale for laser directed energy deposition(L-DED)process was carried out.The powder characteristics,the printing process window,and the quality,microstructure,and mechanical properties of printed parts were taken into account for comparison and discussion.The results demonstrate that the RDA powder is superior to the GA powder in terms of sphericity,surface quality,internal defects,flowability,and apparent density,together with a larger printing process window during the L-DED parts fabrication.Besides,the resultant parts from the RDA powder have higher dimensional accuracy,lower internal defects,more uniform and finer microstructure,and more favorable mechanical properties than those from the GA powder.展开更多
The work aims to investigate the formation and transformation mechanism of non-basal texture in the extruded Mg alloys.With this purpose a pure Mg as reference and eight Mg-Gd binary alloys with the Gd concentration r...The work aims to investigate the formation and transformation mechanism of non-basal texture in the extruded Mg alloys.With this purpose a pure Mg as reference and eight Mg-Gd binary alloys with the Gd concentration ranging from 0.5 wt.%to 18 wt.%were prepared for extrusion.This study shows that the basal fiber texture in pure Mg transited into RE(rare earth)texture in diluted Mg-Gd alloys and into the abnormal C-texture in high-concentration Mg-Gd alloys.In pure Mg,discontinuous dynamic recrystallization plays a predominant role during the extrusion process,resulting in the formation of a typical basal fiber texture.Alloying with high concentration of Gd impedes the dynamic recrystallization process,facilitating the heterogeneous nucleation of shear bands as well as the dynamic recrystallization within shear bands.Dynamic recrystallized grains within shear bands nucleate with a similar orientation to the host deformed parent grains and gradually tilt their c-axis to the extrusion direction during growth by absorbing dislocations,leading to the formation of either the REtexture orientation or the C-texture orientation,depending on the stored energy within shear bands.The analysis aided by IGMA and TEM characterization reveals that the shear bands originate from the extensive but heterogeneous activation of pyramidal I slip.Tensile tests illustrate a close correlation between the fracture elongation and texture types.A comprehensive understanding of the formation and transformation mechanism of different texture components in Mg alloys holds significant importance for the design of high-performance Mg alloys by texture engineering.展开更多
A novel approach for fabricating multi-principal element alloys with adjustable phase configurations and mechanical properties was developed using laser-aided additive manufacturing(LAAM),combining FCC-structured(face...A novel approach for fabricating multi-principal element alloys with adjustable phase configurations and mechanical properties was developed using laser-aided additive manufacturing(LAAM),combining FCC-structured(face-centered cubic)CoCrNi and BCC-structured(body-centered cubic)CoCrNiAl0.6TiFe feedstocks.During fabrication,CoCrNi powders and CoCrNiAl0.6TiFe powders were simultaneously fed into the melt pool at individually adjustable rates,allowing for controlled phase transitions.The resulting phase evolution demonstrated a gradual transition from a single FCC structure CoCrNi(A10.6TiFe)x(x=0,0.1,0.2,0.3)to a dual FCCB2 structure CoCrNi(Al0.6TiFe)x(x=0.4,0.5)as the proportion of BCC-structured powders increased.The B2 phase,enriched in Ti and Al due to their larger atomic radii and negative segregation enthalpy,precipitated around the FCC matrix,with volume fractions of 0.5%and 5.7%for CoCrNi(A10.6TiFe)0.4 and CoCrNi(A10.6TiFe)0.5,respectively.This phase transition resulted in significant mechanical enhancements.Yield and ultimate tensile strengths increased from 486.0 and 781.2 MPa(CoCrNi)to 887.2 and 1165.2 MPa(CoCrNi(A10.6TiFe)0.5).Dislocation-mediated hardening prevailed in single-phase FCC alloys,exhibiting a characteristic dislocation density of 2.5×10^(15)m^(-2)for CoCrNi(A10.6TiFe)0.3 alloy.Once the B2 phase precipitated,precipitation strengthening became dominant,as observed in transmission electron microscopy(TEM),where dislocations accumulated around B2 precipitates.This study presents an innovative alloy fabrication strategy that enables precise tuning of FCC-BCC dualphase structures,facilitating the direct fabrication of components with spatially customized properties.These findings provide valuable insights for developing multiprincipal element alloys with heterogeneous microstructures for advanced engineering applications.展开更多
All-vanadium flow batteries(VFBs)are one of the most promising large-scale energy storage technologies.Conducting an operando quantitative analysis of the polarizations in VFBs under different conditions is essential ...All-vanadium flow batteries(VFBs)are one of the most promising large-scale energy storage technologies.Conducting an operando quantitative analysis of the polarizations in VFBs under different conditions is essential for developing high power density batteries.Here,we employ an operando decoupling method to quantitatively analyze the polarizations in each electrochemical and chemical reaction of VFBs under different catalytic conditions.Results show that the reduction reaction of V^(3+)presents the largest activation polarization,while the reduction reaction of VO_(2)^(+)primarily contributes to concentration polarizations due to the formation of the intermediate product V_(2)O_(3)^(3+).Additionally,it is found that the widely used electrode catalytic methods,incorporating oxygen functional groups and electrodepositing Bi,not only enhance the reaction kinetics but also exacerbate concentration polarizations simultaneously,especially during the discharge process.Specifically,in the battery with the high oxygen-containing electrodes,the negative side still accounts for the majority of activation loss(75.3%)at 200 mA cm^(-2),but it comes down to 36,9% after catalyzing the negative reactions with bismuth.This work provides an effective way to probe the limiting steps in flow batteries under various working conditions and offers insights for effectively enhancing battery performance for future developments.展开更多
In order to investigate the effect of the relative motion of nano CaCO_(3)reinforced bamboo pulp fiber(BPF)/HDPE composite components on the mechanical performance,a comparative study was performed.BPF was treated by ...In order to investigate the effect of the relative motion of nano CaCO_(3)reinforced bamboo pulp fiber(BPF)/HDPE composite components on the mechanical performance,a comparative study was performed.BPF was treated by nano CaCO_(3)blending(BM)and impregnation modification(IM)technology.The composites were produced using hot press(HPMP),extrusion(EMP)and injection molding process(IMP).The physical morphology of BPF was similar at different manufacturing processes.Compared to the samples manufactured by HPMP,a decrease in the(specific)flexural strength of BPF/HDPE composites and an increase in those of composites treated by nano CaCO_(3)manufactured by EMP and IMP were observed.The injection molded composites exhibited the best values in the(specific)impact strength,(specific)tensile properties.IM had a greater effect on the rheological behavior of the composites than BM,and nano CaCO_(3)treatment most effectively affected the performance of the extrusion molded composites.展开更多
This work systematically studied the effect of volumetric energy density E on the densification,mi-crostructures,tensile mechanical properties,and shape memory performance of a Fe-Mn-Si-Cr-Ni shape memory alloy(SMA)fa...This work systematically studied the effect of volumetric energy density E on the densification,mi-crostructures,tensile mechanical properties,and shape memory performance of a Fe-Mn-Si-Cr-Ni shape memory alloy(SMA)fabricated by laser powder bed fusion(L-PBF).An E of 90-265 J/mm3 is suggested to fabricate the Fe-Mn-Si-Cr-Ni SMA with minor metallurgical defects and a high relative density of above 99%.The increase in E can promote the formation of the primaryγaustenite and the solid phase trans-formation from the primaryδferrite to theγaustenite,which helps to achieve a nearly complete y austenitic microstructure.The increase in E also contributes to fabricating the Fe-Mn-Si-Cr-Ni SMA with superior comprehensive mechanical properties and shape memory performance by L-PBF.The Fe-Mn-Si-Cr-Ni SMA with a combination of good ductility of around 30%,high yield strength of above 480 MPa,an ultrahigh ultimate tensile strength of above 1 GPa,and large recovery strain of about 6%was manu-factured by L-PBF under a high E of 222-250 J/mm^(3).The good shape memory effect,excellent compre-hensive mechanical properties,and low cost of Fe-Mn-Si-Cr-Ni SMAs,as well as the outstanding ability to fabricate complex structures of L-PBF technology,provide a solid foundation for the design and fabri-cation of novel intelligent structures.展开更多
The efficient and stable operation of proton exchange membrane fuel cells(PEMFCs)in practical applications can be adversely affected by various contaminants.This study delves into the impact of Cr_(2)(SO_(4))_(3)conta...The efficient and stable operation of proton exchange membrane fuel cells(PEMFCs)in practical applications can be adversely affected by various contaminants.This study delves into the impact of Cr_(2)(SO_(4))_(3)contamination on the gas diffusion layer(GDL)and PEMFC performance,systematically analyzing the physicochemical property changes and their correlation with electrochemical performance.The results indicate that after post-treatment,the GDL surface exhibited exposed carbon fibers,cracks,and large pores in the microporous layer(MPL),with a noticeable detachment of PTFE.There was a marked reduction in C and F element signals,an increase in O element signals,deposition of Cr_(2)(SO_(4))_(3),formation of C=O and C=C bonds,appearance of Cr_(2)(SO_(4))_(3)characteristic peaks,and changes in pore structure—all suggesting significant alterations in the GDL's surface morphology,structure,and chemical composition.The decline in mechanical strength and thermal stability,and increased surface roughness and resistance negatively impacted fuel cell performance.At high current densities,the emergence of water flooding increased mass transfer resistance from 0.1Ωcm^(2)to 1.968Ωcm^(2),with a maximum power density decay rate reaching 71.17%.This study reveals the significant negative impact of Cr_(2)(SO_(4))_(3)contamination on GDL and fuel cell performance,highlighting that changes in surface structure,reduced hydrophobicity,and increased mass transfer resistance are primary causes of performance degradation.The findings provide crucial insights for improving GDL materials,optimizing fuel cell manufacturing and operation processes,and addressing contamination issues in practical applications.展开更多
This study investigates the electrochemical behavior of molybdenum disulfide(MoS_(2))as an anode in Li-ion batteries,focusing on the extra capacity phenomenon.Employing advanced characterization methods such as in sit...This study investigates the electrochemical behavior of molybdenum disulfide(MoS_(2))as an anode in Li-ion batteries,focusing on the extra capacity phenomenon.Employing advanced characterization methods such as in situ and ex situ X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,and transmission electron microscopy,the research unravels the complex structural and chemical evolution of MoS_(2) throughout its cycling.A key discovery is the identification of a unique Li intercalation mechanism in MoS_(2),leading to the formation of reversible Li_(2)MoS_(2) phases that contribute to the extra capacity of the MoS_(2) electrode.Density function theory calculations suggest the potential for overlithiation in MoS_(2),predicting Li5MoS_(2) as the most energetically favorable phase within the lithiation–delithiation process.Additionally,the formation of a Li-rich phase on the surface of Li_(4)MoS_(2) is considered energetically advantageous.After the first discharge,the battery system engages in two main reactions.One involves operation as a Li-sulfur battery within the carbonate electrolyte,and the other is the reversible intercalation and deintercalation of Li in Li_(2)MoS_(2).The latter reaction contributes to the extra capacity of the battery.The incorporation of reduced graphene oxide as a conductive additive in MoS_(2) electrodes notably improves their rate capability and cycling stability.展开更多
High levels of Al and Ti in superalloy compositions normally lead to cracking formation during the laser powder bed fusion process,while these elements are key constituents of strengthening phases.In the current study...High levels of Al and Ti in superalloy compositions normally lead to cracking formation during the laser powder bed fusion process,while these elements are key constituents of strengthening phases.In the current study,a novel Co-based superalloy with the basic chemical composition of Co-Al-W-Ta-Ti resolved this contradiction,indicating that the part was formed without cracking and simultaneously contained a large amount of strengthening precipitates in the microstructure fabricated via laser powder bed fusion.The printability,microstructures,and mechanical properties of the sample were analysed before and after heat treatment,providing a potential superalloy that can replace Ni-based superalloys fabricated by additive manufacturing in aerospace and other industries with higher temperature and more efficiency.展开更多
The study provided a systematic investigation into the creep behavior of aγʹ-strengthened Co-based single crystal superalloy Co-7Al-8W-1Ta-4Ti(at.%)under compressive creep conditions at 1000℃and 137 MPa.Simultaneous...The study provided a systematic investigation into the creep behavior of aγʹ-strengthened Co-based single crystal superalloy Co-7Al-8W-1Ta-4Ti(at.%)under compressive creep conditions at 1000℃and 137 MPa.Simultaneously,the microstructural changes during thermal exposure at 1000℃ were thor-oughly examined.The microstructure analysis of the creep samples revealed the presence ofγ/γʹrafts,twins,stacking faults,and dislocation networks.Statistical analyses were conducted to assess the dimen-sions and volume fractions ofγʹ,alongside Vickers hardness tests and nanoindentation experiments.Re-sults show thatγʹdissolution in the creep samples with substantially higher dissolution rates compared to thermal exposure.Localized Co depletion and Ti enrichment in twin is observed in creep sample,po-tentially initiating localized phase transformations.Concurrently,lattice rotation occurred during creep,resulting in a progressive deviation of crystal orientation away from the[001]direction.Stacking faults transitioned from network-like structures to parallel configurations,and twins played a significant role in creep deformation,particularly in samples subjected to 382 h creep.The study also explored the evo-lution of Vickers hardness and the elastic modulus,introducing a systematic linear model to describe Vickers hardness changes during both thermal exposure and creep conditions.展开更多
Owing to its low cost,short process and low energy consumption,semi-solid processing(SSP)of aluminum(Al)and magnesium(Mg)alloys has been considered as a competitive approach to fabricate complicated components with ex...Owing to its low cost,short process and low energy consumption,semi-solid processing(SSP)of aluminum(Al)and magnesium(Mg)alloys has been considered as a competitive approach to fabricate complicated components with excellent performance.Over the past decade,significant progress has been achieved in deeply understanding the SSP process,the microstructure and performance of the fabricated components in China.This paper starts with a retrospective overview of some common slurry preparation methods,followed by presenting the performance and the underlying mechanisms of SSP fabricated alloys.Then,the mainstream opinions on the microstructure evolution and rheological flow behavior of semi-solid slurry are discussed.Subsequently,the general situation and some recent examples of industrial applications of SSP are presented.Finally,special attention is paid to the unresolved issues and the future directions in SSP of Al and Mg alloys in China.展开更多
A complete mathematical model for logarithmic spiral type sprag one-way clutch design and analysis is given.It assumes that the motion of all clutch components can be expressed by a model of epicyclic gearing.It takes...A complete mathematical model for logarithmic spiral type sprag one-way clutch design and analysis is given.It assumes that the motion of all clutch components can be expressed by a model of epicyclic gearing.It takes advantage of Hunt-Crossley contact impact theory to calculate the contact forces between sprags and races,and it can be used for optimization of design and comparison with other types of sprag clutches.A good deal of analysis shows that the parameters of the steady windup angle,the steady contact force,the natural frequency and natural cycle of clutch have nothing to do with the initial velocity of outer race,while the parameters of the maximum transient windup angle,the maximum transient impact force and the steady engagement time increase linearly in the mode of engaging operation of clutch.It is also shown that the strut angle has great influence on the dynamic engagement performance of clutch.The parameters of the steady windup angle,the maximum transient windup angle,the steady engaging time,the steady contact force,the maximum transient impact force and the natural cycle of clutch decrease linearly nearly with the inner strut angle,while the natural frequency of the system increases linearly with the inner strut angle.展开更多
Taking wall-flow diesel particulate filter(DPF) as the research objective and separately assuming its filtering wall to be composed of numerous spherical or cylindrical elements, two different mathematical models of s...Taking wall-flow diesel particulate filter(DPF) as the research objective and separately assuming its filtering wall to be composed of numerous spherical or cylindrical elements, two different mathematical models of steady filtration for wall-flow diesel particulate filter were developed and verified by experiments as well as numerically solved. Furthermore, the effects of the macroand micro-structural parameters of filtering wall and exhaust-flow characteristic parameters on trapping efficiency were also analyzed and researched. The results show that: 1) The two developed mathematical models are consistent with the prediction of variation of particulate size; the influence of various factors on the steady trapping efficiency is exactly the same. Compared to model 2, model 1 is more suitable for describing the steady filtration process of wall-flow diesel particulate filter; 2)The major influencing factors on steady trapping efficiency of wall-flow diesel particulate filter are the macro-and micro-structural parameters of filtering wall; and the secondary influencing factors are the exhaust-flow characteristic parameters and macro-structural parameters of filter; 3)The steady trapping efficiency will be improved by increasing filter body volume, pore density as well as wall thickness and by decreasing exhaust-flow, but effects will be weakened when particulate size exceeds a certain critical value; 4) The steady trapping efficiency will be significantly improved by increasing exhaust-flow temperature and filtering wall thickness, but effects will be also weakened when particulate size exceeds a certain critical value; 5) The steady trapping efficiency will approximately linearly increase with reducing porosity, micropore aperture and pore width.展开更多
The additive manufacturing(AM)of Ni-based superalloys has attracted extensive interest from both academia and industry due to its unique capabilities to fabricate complex and high-performance components for use in hig...The additive manufacturing(AM)of Ni-based superalloys has attracted extensive interest from both academia and industry due to its unique capabilities to fabricate complex and high-performance components for use in high-end industrial systems.However,the intense temperature gradient induced by the rapid heating and cooling processes of AM can generate high levels of residual stress and metastable chemical and structural states,inevitably leading to severe metallurgical defects in Ni-based superalloys.Cracks are the greatest threat to these materials’integrity as they can rapidly propagate and thereby cause sudden and non-predictable failure.Consequently,there is a need for a deeper understanding of residual stress and cracking mechanisms in additively manufactured Ni-based superalloys and ways to potentially prevent cracking,as this knowledge will enable the wider application of these unique materials.To this end,this paper comprehensively reviews the residual stress and the various mechanisms of crack formation in Ni-based superalloys during AM.In addition,several common methods for inhibiting crack formation are presented to assist the research community to develop methods for the fabrication of crack-free additively manufactured components.展开更多
The growth kinetics of microarc oxidation(MAO)coatings on Ti6Al4V alloy was studied by designing an electrolyte with low PO_(4)^(3−)content and high B_(4)O_(7)^(2−)content,using scanning electron microscopy,transmissi...The growth kinetics of microarc oxidation(MAO)coatings on Ti6Al4V alloy was studied by designing an electrolyte with low PO_(4)^(3−)content and high B_(4)O_(7)^(2−)content,using scanning electron microscopy,transmission electron microscopy,X-ray diffraction,and potentiodynamic polarization.The results showed that B_(4)O_(7)^(2−)increased the spark intensity and dissolved most of the oxides at high temperatures.Then,a thicker barrier layer at the coating/substrate interface was produced,which increased the polarization resistance of the coating.PO_(4)^(3−)at a low concentration also promoted the uniform growth of the MAO coating and the formation of hat-shaped holes in the outer deposition layer.The thickness of the MAO coatings obtained in Na_(2)B_(4)O_(7) electrolytes exhibited an exponential increase with time at spark discharge stage,while that of the MAO coating obtained in phosphate–tetraborate electrolytes showed a linear trend as the PO_(4)^(3−)content increased.展开更多
In order to study rock breaking characteristics of tunnel boring machine(TBM) disc cutter at different rock temperatures,thermodynamic rock breaking mathematical model of TBM disc cutter was established on the basis o...In order to study rock breaking characteristics of tunnel boring machine(TBM) disc cutter at different rock temperatures,thermodynamic rock breaking mathematical model of TBM disc cutter was established on the basis of rock temperature change by using particle flow code theory and the influence law of interaction mechanism between disc cutter and rock was also numerically simulated.Furthermore,by using the linear cutting experiment platform,rock breaking process of TBM disc cutter at different rock temperatures was well verified by the experiments.Finally,rock breaking characteristics of TBM disc cutter were differentiated and analyzed from microscale perspective.The results indicate the follows.1) When rock temperature increases,the mechanical properties of rock such as hardness,and strength,were greatly reduced,simultaneously the microcracks rapidly grow with the cracks number increasing,which leads to rock breaking load decreasing and improves rock breaking efficiency for TBM disc cutter.2) The higher the rock temperature,the lower the rock internal stress.The stress distribution rules coincide with the Buzin Neske stress circle rules: the maximum stress value is below the cutting edge region and then gradually decreases radiant around; stress distribution is symmetrical and the total stress of rock becomes smaller.3) The higher the rock temperature is,the more the numbers of micro,tensile and shear cracks produced are by rock as well as the easier the rock intrusion,along with shear failure mode mainly showing.4) With rock temperature increasing,the resistance intrusive coefficients of rock and intrusion power decrease obviously,so the specific energy consumption that TBM disc cutter achieves leaping broken also decreases subsequently.5) The acoustic emission frequency remarkably increases along with the temperature increasing,which improves the rock breaking efficiency.展开更多
Additive manufacturing(AM)has emerged as an advanced technique for the fabrication of complex near-net shaped and lightweight metallic parts with acceptable mechanical performance.The strength of AM metals has been co...Additive manufacturing(AM)has emerged as an advanced technique for the fabrication of complex near-net shaped and lightweight metallic parts with acceptable mechanical performance.The strength of AM metals has been confirmed comparable or even superior to that of metals manufactured by conventional processes,but the fatigue performance is still a knotty issue that may hinder the substitution of currently used metallic components by AM counterparts when the cyclic loading and thus fatigue failure dominates.As essential complements to high-cost and time-consuming experimental fatigue tests of AM metals,models for fatigue performance prediction are highly desirable.In this review,different models for predicting the fatigue properties of AM metals are summarized in terms of fatigue life,fatigue limit and fatigue crack growth,with a focus on the incorporation of AM characteristics such as AM defect and processing parameters into the models.For predicting the fatigue life of AM metals,empirical models and theoretical models(including local characteristic model,continuum damage mechanics model and probabilistic method)are presented.In terms of fatigue limit,the introduced models involve the Kitagawa–Takahashi model,the Murakami model,the El-Haddad model,etc.For modeling the fatigue crack growth of AM metals,the summarized methodologies include the Paris equation,the Hartman-Schijve equation,the NASGRO equation,the small-crack growth model,and numerical methods.Most of these models for AM metals are similar to those for conventionally processed materials,but are modified and pay more attention to the AM characteristics.Finally,an outlook for possible directions of the modeling and prediction of fatigue properties of AM metals is provided.展开更多
Silicon/carbon composites are promising alternatives to current graphite anodes in commercial lithiumion batteries(LIBs)because of their high capacity and excellent safety.Nevertheless,the unsatisfactory fastcharging ...Silicon/carbon composites are promising alternatives to current graphite anodes in commercial lithiumion batteries(LIBs)because of their high capacity and excellent safety.Nevertheless,the unsatisfactory fastcharging capability and cycle stability of Si/C composites caused by slow charge transport capability and huge volume change under industrial electrode conditions severely hamper their development.Here,a novel Si/C anode was fabricated by homogeneously depositing amorphous C-Si nanolayers on graphite(C-Si@graphite).C-Si nanolayers with uniformly dispersed sub-nanometer Si particles in 3D carbon skeleton significantly boost electron and Li-ion transport and efficiently relieve Si's agglomeration and volume change.As a result,the tailored C-Si@graphite electrodes show an excellent rate capacity(760.3 mAh·g^(-1)at 5.0C)and long cycle life of over 1000 cycles at 1.0C and800 cycles at 2.0C under industrial electrode conditions.In addition,the assembled full cells(C-Si@graphite,anode;Li[Ni_(0.8)Co_(0.1)Mn_(0.1)]O_(2),cathode)present superior fastcharging capability(240.4 Wh·kg^(-1),charging for16.2 min,3.0C)and long cycle life(80.7%capacity retention after 500 cycles at 1.0C),demonstrating the massive potential of C-Si@graphite for practical application.展开更多
Diamond is a promising material for the modern industry. It is widely used in different applications, such as cutting tools, optical windows, heat dissipation, and semiconductors.However, these application areas requi...Diamond is a promising material for the modern industry. It is widely used in different applications, such as cutting tools, optical windows, heat dissipation, and semiconductors.However, these application areas require exceptionally flattened and polished diamond surfaces.Unfortunately, due to the extreme hardness and chemical inertness of diamond, the polishing of diamond is challenging. Since the 1920s, various conventional and modern mechanical,chemical, and thermal polishing techniques have been proposed and developed for finishing diamond surfaces. Therefore, to impart proper guidance on selecting a good polishing technique for production practice, this paper presents an in-depth and informative literature survey of the current research and engineering developments regarding diamond polishing. At first, a brief review of the general developments and basic material removal principles is discussed. This review concludes with a detailed analysis of each techniques' polishing performance and critical challenges, and a discussion of the new insights and future applications of diamond polishing.展开更多
文摘Coiled tube heat exchangers are widely preferred in shell structures due to their superior heat transfer performance,driven by favorable flow characteristics.This study investigates the effect of modifying coil and shell configurations on heat transfer efficiency.Two key enhancements were examined:adding fins to the outer coil surface and integrating longitudinal slots within a hollowed shell.These modifications promote turbulence and extend heat transfer duration,thereby improving performance.However,they also introduce challenges,including increased pressure loss andmanufacturing complexity.Numerical simulationswere conducted usingANSYS Fluent 2024R1 under identical boundary conditions.With a fixed cold-side flow rate of 3 L/min,the input temperatures for the hot and cold fluids were 333.15 and 291.65 K,respectively.The hot-side flow rate varied between 2 and 6 L/min.Simulation outcomes were reported for the objectives of the study that included the improvement in heat exchangers’heat transfer enhancement.As it was indicated in the study outcomes,the average heat transfer rate increased by 15.56%,the overall heat transfer coefficient enhanced by about 29.51%,and the convective heat transfer coefficient improved by about 75.96%compared to the conventional shell-and-coil tube heat exchanger model.However,the modified technique resulted in a significant pressure drop.
基金supported by the National Natural Science Foundation of China(No.52074157)Department of Education of Guangdong Province,China(No.2023KTSCX121)Shenzhen Science and Technology Programs,China(Nos.JSGG20210802154210032,JCYJ20210324104608023,JSGG20180508152608855)。
文摘A comparative study on the performance of gas atomized(GA)and rotating-disk atomized(RDA)aluminum alloy powders produced on industrial scale for laser directed energy deposition(L-DED)process was carried out.The powder characteristics,the printing process window,and the quality,microstructure,and mechanical properties of printed parts were taken into account for comparison and discussion.The results demonstrate that the RDA powder is superior to the GA powder in terms of sphericity,surface quality,internal defects,flowability,and apparent density,together with a larger printing process window during the L-DED parts fabrication.Besides,the resultant parts from the RDA powder have higher dimensional accuracy,lower internal defects,more uniform and finer microstructure,and more favorable mechanical properties than those from the GA powder.
基金funding from the National Natural Science Foundation of China under Grant No 52275327。
文摘The work aims to investigate the formation and transformation mechanism of non-basal texture in the extruded Mg alloys.With this purpose a pure Mg as reference and eight Mg-Gd binary alloys with the Gd concentration ranging from 0.5 wt.%to 18 wt.%were prepared for extrusion.This study shows that the basal fiber texture in pure Mg transited into RE(rare earth)texture in diluted Mg-Gd alloys and into the abnormal C-texture in high-concentration Mg-Gd alloys.In pure Mg,discontinuous dynamic recrystallization plays a predominant role during the extrusion process,resulting in the formation of a typical basal fiber texture.Alloying with high concentration of Gd impedes the dynamic recrystallization process,facilitating the heterogeneous nucleation of shear bands as well as the dynamic recrystallization within shear bands.Dynamic recrystallized grains within shear bands nucleate with a similar orientation to the host deformed parent grains and gradually tilt their c-axis to the extrusion direction during growth by absorbing dislocations,leading to the formation of either the REtexture orientation or the C-texture orientation,depending on the stored energy within shear bands.The analysis aided by IGMA and TEM characterization reveals that the shear bands originate from the extensive but heterogeneous activation of pyramidal I slip.Tensile tests illustrate a close correlation between the fracture elongation and texture types.A comprehensive understanding of the formation and transformation mechanism of different texture components in Mg alloys holds significant importance for the design of high-performance Mg alloys by texture engineering.
基金financially supported by the following sources:Guangdong Basic and Applied Basic Research Foundation(No.2023B1515120045)Yangjiang City Key Industry Talent Revitalization Plan Project for Alloy Materials and Hardware Scissors(No.RCZX202302)+7 种基金GDAS'Project of Science and Technology Development(Nos.2022GDASZH-2022010108,2022GD ASZH-2022010107 and 2024GD ASZH-2024010102)GDAS'Young Talent Project(No.2024GDASQNRC-0314)Guangzhou Basic and Applied Basic Research Foundation(No.2023A04J1628)the National Key R&D Program of China(No.2022YFB4600700)National Natural Science Foundation of China(No.52371110)Guangdong Basic and Applied Basic Research Foundation(No.2023A1515011510)Shenzhen Science and Technology Program(Nos.JCYJ20220530115011026 and JCYJ20230807093410021)Shanxi Province Key R&D Project(No.202302050201011)
文摘A novel approach for fabricating multi-principal element alloys with adjustable phase configurations and mechanical properties was developed using laser-aided additive manufacturing(LAAM),combining FCC-structured(face-centered cubic)CoCrNi and BCC-structured(body-centered cubic)CoCrNiAl0.6TiFe feedstocks.During fabrication,CoCrNi powders and CoCrNiAl0.6TiFe powders were simultaneously fed into the melt pool at individually adjustable rates,allowing for controlled phase transitions.The resulting phase evolution demonstrated a gradual transition from a single FCC structure CoCrNi(A10.6TiFe)x(x=0,0.1,0.2,0.3)to a dual FCCB2 structure CoCrNi(Al0.6TiFe)x(x=0.4,0.5)as the proportion of BCC-structured powders increased.The B2 phase,enriched in Ti and Al due to their larger atomic radii and negative segregation enthalpy,precipitated around the FCC matrix,with volume fractions of 0.5%and 5.7%for CoCrNi(A10.6TiFe)0.4 and CoCrNi(A10.6TiFe)0.5,respectively.This phase transition resulted in significant mechanical enhancements.Yield and ultimate tensile strengths increased from 486.0 and 781.2 MPa(CoCrNi)to 887.2 and 1165.2 MPa(CoCrNi(A10.6TiFe)0.5).Dislocation-mediated hardening prevailed in single-phase FCC alloys,exhibiting a characteristic dislocation density of 2.5×10^(15)m^(-2)for CoCrNi(A10.6TiFe)0.3 alloy.Once the B2 phase precipitated,precipitation strengthening became dominant,as observed in transmission electron microscopy(TEM),where dislocations accumulated around B2 precipitates.This study presents an innovative alloy fabrication strategy that enables precise tuning of FCC-BCC dualphase structures,facilitating the direct fabrication of components with spatially customized properties.These findings provide valuable insights for developing multiprincipal element alloys with heterogeneous microstructures for advanced engineering applications.
基金supported by the Guangdong Major Project of Basic and Applied Basic Research(2023B0303000002)the National Natural Science Foundation of China(No.52206089)+3 种基金the Guangdong Basic and Applied Basic Research Foundation(2024A1515010288,2023B1515120005)the Natural Science Foundation of Shenzhen(JCYJ20230807093315033)the Shenzhen Engineering Research Center,Southern University of Science and Technology(No.XMHT20230208003)high level of special funds(G03034K001)。
文摘All-vanadium flow batteries(VFBs)are one of the most promising large-scale energy storage technologies.Conducting an operando quantitative analysis of the polarizations in VFBs under different conditions is essential for developing high power density batteries.Here,we employ an operando decoupling method to quantitatively analyze the polarizations in each electrochemical and chemical reaction of VFBs under different catalytic conditions.Results show that the reduction reaction of V^(3+)presents the largest activation polarization,while the reduction reaction of VO_(2)^(+)primarily contributes to concentration polarizations due to the formation of the intermediate product V_(2)O_(3)^(3+).Additionally,it is found that the widely used electrode catalytic methods,incorporating oxygen functional groups and electrodepositing Bi,not only enhance the reaction kinetics but also exacerbate concentration polarizations simultaneously,especially during the discharge process.Specifically,in the battery with the high oxygen-containing electrodes,the negative side still accounts for the majority of activation loss(75.3%)at 200 mA cm^(-2),but it comes down to 36,9% after catalyzing the negative reactions with bismuth.This work provides an effective way to probe the limiting steps in flow batteries under various working conditions and offers insights for effectively enhancing battery performance for future developments.
基金This study is financially supported by the Basic Research Operating Expenses Program of International Centre for Bamboo and Rattan(1632021002).
文摘In order to investigate the effect of the relative motion of nano CaCO_(3)reinforced bamboo pulp fiber(BPF)/HDPE composite components on the mechanical performance,a comparative study was performed.BPF was treated by nano CaCO_(3)blending(BM)and impregnation modification(IM)technology.The composites were produced using hot press(HPMP),extrusion(EMP)and injection molding process(IMP).The physical morphology of BPF was similar at different manufacturing processes.Compared to the samples manufactured by HPMP,a decrease in the(specific)flexural strength of BPF/HDPE composites and an increase in those of composites treated by nano CaCO_(3)manufactured by EMP and IMP were observed.The injection molded composites exhibited the best values in the(specific)impact strength,(specific)tensile properties.IM had a greater effect on the rheological behavior of the composites than BM,and nano CaCO_(3)treatment most effectively affected the performance of the extrusion molded composites.
基金supported by the Chinese National Natural Science Fund (No.U1864208)the National Science and Technology Major Project (No.2017-VII-0011-0106)+8 种基金the Youth Science Fund Project of National Natural Science Foundation of China (No.52105396)the Postdoctoral Research Foundation of China (No.2020M682410)Postdoctoral Science and Technology Activity Program of Hubei Province (No.0106110134)the Project Supported by Jiangsu Key Laboratory of 3D Printing Equipment and Manufacturing (No.3DL202104)the Science and Technology Planning Project of Tianjin (No.20ZYJDJC00030)the Key Program of Research and Development of Hebei Province (No.202030507040009)the Fund for Innovative Research Groups of Natural Science Foundation of Hebei Province (No.A2020202002)the Natural Science Foundation of Chongqing (No.cstc2021jcyj-msxmX0241)the Key Project of Natural Science Foundation of Tianjin (No.S20ZDF077).
文摘This work systematically studied the effect of volumetric energy density E on the densification,mi-crostructures,tensile mechanical properties,and shape memory performance of a Fe-Mn-Si-Cr-Ni shape memory alloy(SMA)fabricated by laser powder bed fusion(L-PBF).An E of 90-265 J/mm3 is suggested to fabricate the Fe-Mn-Si-Cr-Ni SMA with minor metallurgical defects and a high relative density of above 99%.The increase in E can promote the formation of the primaryγaustenite and the solid phase trans-formation from the primaryδferrite to theγaustenite,which helps to achieve a nearly complete y austenitic microstructure.The increase in E also contributes to fabricating the Fe-Mn-Si-Cr-Ni SMA with superior comprehensive mechanical properties and shape memory performance by L-PBF.The Fe-Mn-Si-Cr-Ni SMA with a combination of good ductility of around 30%,high yield strength of above 480 MPa,an ultrahigh ultimate tensile strength of above 1 GPa,and large recovery strain of about 6%was manu-factured by L-PBF under a high E of 222-250 J/mm^(3).The good shape memory effect,excellent compre-hensive mechanical properties,and low cost of Fe-Mn-Si-Cr-Ni SMAs,as well as the outstanding ability to fabricate complex structures of L-PBF technology,provide a solid foundation for the design and fabri-cation of novel intelligent structures.
基金funded by Key Laboratory of Energy Conversion and Storage Technology(Southern University of Science and Technology)Ministry of Education+1 种基金Guangdong Innovative and Entrepreneurial Research Team Program(grant No.2016ZT06N500)Guangdong Provincial Key Laboratory of Energy Materials for Electric Power(grant No.2018B030322001).
文摘The efficient and stable operation of proton exchange membrane fuel cells(PEMFCs)in practical applications can be adversely affected by various contaminants.This study delves into the impact of Cr_(2)(SO_(4))_(3)contamination on the gas diffusion layer(GDL)and PEMFC performance,systematically analyzing the physicochemical property changes and their correlation with electrochemical performance.The results indicate that after post-treatment,the GDL surface exhibited exposed carbon fibers,cracks,and large pores in the microporous layer(MPL),with a noticeable detachment of PTFE.There was a marked reduction in C and F element signals,an increase in O element signals,deposition of Cr_(2)(SO_(4))_(3),formation of C=O and C=C bonds,appearance of Cr_(2)(SO_(4))_(3)characteristic peaks,and changes in pore structure—all suggesting significant alterations in the GDL's surface morphology,structure,and chemical composition.The decline in mechanical strength and thermal stability,and increased surface roughness and resistance negatively impacted fuel cell performance.At high current densities,the emergence of water flooding increased mass transfer resistance from 0.1Ωcm^(2)to 1.968Ωcm^(2),with a maximum power density decay rate reaching 71.17%.This study reveals the significant negative impact of Cr_(2)(SO_(4))_(3)contamination on GDL and fuel cell performance,highlighting that changes in surface structure,reduced hydrophobicity,and increased mass transfer resistance are primary causes of performance degradation.The findings provide crucial insights for improving GDL materials,optimizing fuel cell manufacturing and operation processes,and addressing contamination issues in practical applications.
基金the financial support from the Science, Technology, and Innovation Funding Authority (STIFA, STDF previously) through project number 42691 entitled “Microstructure-Based, Multi-Physics Simulation and Optimization to Improve Battery Performance”supported by the U.S. DOE (Department of Energy), Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357supported by the U.S. DOE Vehicle Technologies office, under contract number DE-AC02-06CH11357
文摘This study investigates the electrochemical behavior of molybdenum disulfide(MoS_(2))as an anode in Li-ion batteries,focusing on the extra capacity phenomenon.Employing advanced characterization methods such as in situ and ex situ X-ray diffraction,Raman spectroscopy,X-ray photoelectron spectroscopy,and transmission electron microscopy,the research unravels the complex structural and chemical evolution of MoS_(2) throughout its cycling.A key discovery is the identification of a unique Li intercalation mechanism in MoS_(2),leading to the formation of reversible Li_(2)MoS_(2) phases that contribute to the extra capacity of the MoS_(2) electrode.Density function theory calculations suggest the potential for overlithiation in MoS_(2),predicting Li5MoS_(2) as the most energetically favorable phase within the lithiation–delithiation process.Additionally,the formation of a Li-rich phase on the surface of Li_(4)MoS_(2) is considered energetically advantageous.After the first discharge,the battery system engages in two main reactions.One involves operation as a Li-sulfur battery within the carbonate electrolyte,and the other is the reversible intercalation and deintercalation of Li in Li_(2)MoS_(2).The latter reaction contributes to the extra capacity of the battery.The incorporation of reduced graphene oxide as a conductive additive in MoS_(2) electrodes notably improves their rate capability and cycling stability.
基金supported by the Shenzhen-Hong Kong Sci-ence and Technology Innovation Cooperation Zone Shenzhen Park Project(Grant No.HZQB-KCZYB-2020030)the RGC Theme-based Research Scheme(Grant No.AoE/M-402/20)+1 种基金National Nat-ural Science Foundation of China(Grant No.52250710160)Shenzhen Science and Technology Innovation Committee(Grant Nos.KQTD20170328154443162,JCYJ20210324104610029,and JCYJ20220818100613028).
文摘High levels of Al and Ti in superalloy compositions normally lead to cracking formation during the laser powder bed fusion process,while these elements are key constituents of strengthening phases.In the current study,a novel Co-based superalloy with the basic chemical composition of Co-Al-W-Ta-Ti resolved this contradiction,indicating that the part was formed without cracking and simultaneously contained a large amount of strengthening precipitates in the microstructure fabricated via laser powder bed fusion.The printability,microstructures,and mechanical properties of the sample were analysed before and after heat treatment,providing a potential superalloy that can replace Ni-based superalloys fabricated by additive manufacturing in aerospace and other industries with higher temperature and more efficiency.
基金supported by the China Post-doctoral Science Foundation(No.2023M731500)the Shen-zhen Science and Technology Innovation Commission,China(Nos.JCYJ20210324104610029,KQTD20170328154443162,and JCYJ20220818100613028)+1 种基金the National Natural Science Foundation of China(No.52250710160),the National Key Research and De-velopment Program of China(No.2017YFB0702901)the Shenzhen Key Laboratory for Additive Manufacturing of High-performance Materials(No.ZDSYS201703031748354)。
文摘The study provided a systematic investigation into the creep behavior of aγʹ-strengthened Co-based single crystal superalloy Co-7Al-8W-1Ta-4Ti(at.%)under compressive creep conditions at 1000℃and 137 MPa.Simultaneously,the microstructural changes during thermal exposure at 1000℃ were thor-oughly examined.The microstructure analysis of the creep samples revealed the presence ofγ/γʹrafts,twins,stacking faults,and dislocation networks.Statistical analyses were conducted to assess the dimen-sions and volume fractions ofγʹ,alongside Vickers hardness tests and nanoindentation experiments.Re-sults show thatγʹdissolution in the creep samples with substantially higher dissolution rates compared to thermal exposure.Localized Co depletion and Ti enrichment in twin is observed in creep sample,po-tentially initiating localized phase transformations.Concurrently,lattice rotation occurred during creep,resulting in a progressive deviation of crystal orientation away from the[001]direction.Stacking faults transitioned from network-like structures to parallel configurations,and twins played a significant role in creep deformation,particularly in samples subjected to 382 h creep.The study also explored the evo-lution of Vickers hardness and the elastic modulus,introducing a systematic linear model to describe Vickers hardness changes during both thermal exposure and creep conditions.
基金financial supports from the Shenzhen Science and Technology Innovation Commission, China (Nos. KQTD20170328154443162, JCYJ20180305123432756)。
文摘Owing to its low cost,short process and low energy consumption,semi-solid processing(SSP)of aluminum(Al)and magnesium(Mg)alloys has been considered as a competitive approach to fabricate complicated components with excellent performance.Over the past decade,significant progress has been achieved in deeply understanding the SSP process,the microstructure and performance of the fabricated components in China.This paper starts with a retrospective overview of some common slurry preparation methods,followed by presenting the performance and the underlying mechanisms of SSP fabricated alloys.Then,the mainstream opinions on the microstructure evolution and rheological flow behavior of semi-solid slurry are discussed.Subsequently,the general situation and some recent examples of industrial applications of SSP are presented.Finally,special attention is paid to the unresolved issues and the future directions in SSP of Al and Mg alloys in China.
基金Project(2011CB706800)supported by the National Basic Research Program of China
文摘A complete mathematical model for logarithmic spiral type sprag one-way clutch design and analysis is given.It assumes that the motion of all clutch components can be expressed by a model of epicyclic gearing.It takes advantage of Hunt-Crossley contact impact theory to calculate the contact forces between sprags and races,and it can be used for optimization of design and comparison with other types of sprag clutches.A good deal of analysis shows that the parameters of the steady windup angle,the steady contact force,the natural frequency and natural cycle of clutch have nothing to do with the initial velocity of outer race,while the parameters of the maximum transient windup angle,the maximum transient impact force and the steady engagement time increase linearly in the mode of engaging operation of clutch.It is also shown that the strut angle has great influence on the dynamic engagement performance of clutch.The parameters of the steady windup angle,the maximum transient windup angle,the steady engaging time,the steady contact force,the maximum transient impact force and the natural cycle of clutch decrease linearly nearly with the inner strut angle,while the natural frequency of the system increases linearly with the inner strut angle.
基金Projects(5117604551276056)supported by the National Natural Science Foundation of China+1 种基金Projects(201208430262201306130031)supported by the National Studying Abroad Foundation of the China Scholarship Council
文摘Taking wall-flow diesel particulate filter(DPF) as the research objective and separately assuming its filtering wall to be composed of numerous spherical or cylindrical elements, two different mathematical models of steady filtration for wall-flow diesel particulate filter were developed and verified by experiments as well as numerically solved. Furthermore, the effects of the macroand micro-structural parameters of filtering wall and exhaust-flow characteristic parameters on trapping efficiency were also analyzed and researched. The results show that: 1) The two developed mathematical models are consistent with the prediction of variation of particulate size; the influence of various factors on the steady trapping efficiency is exactly the same. Compared to model 2, model 1 is more suitable for describing the steady filtration process of wall-flow diesel particulate filter; 2)The major influencing factors on steady trapping efficiency of wall-flow diesel particulate filter are the macro-and micro-structural parameters of filtering wall; and the secondary influencing factors are the exhaust-flow characteristic parameters and macro-structural parameters of filter; 3)The steady trapping efficiency will be improved by increasing filter body volume, pore density as well as wall thickness and by decreasing exhaust-flow, but effects will be weakened when particulate size exceeds a certain critical value; 4) The steady trapping efficiency will be significantly improved by increasing exhaust-flow temperature and filtering wall thickness, but effects will be also weakened when particulate size exceeds a certain critical value; 5) The steady trapping efficiency will approximately linearly increase with reducing porosity, micropore aperture and pore width.
基金This work was supported by Shenzhen-Hong Kong Science and Technology Innovation Cooperation Zone Shenzhen Park Project:HZQB-KCZYB-2020030the National Natural Science Foundation of China(No.91860131and No.52074157)+2 种基金Guangdong Provincial Department of Science and Technology,Key-Area Research and Development Program of Guangdong Province(No.2020B090923002)the National Key Research and Development Program of China(No.2017YFB0702901)the Shenzhen Science and Technology Innovation Commission(No.JCYJ20170817111811303,No.KQTD20170328154443162and No.ZDSYS201703031748354).
文摘The additive manufacturing(AM)of Ni-based superalloys has attracted extensive interest from both academia and industry due to its unique capabilities to fabricate complex and high-performance components for use in high-end industrial systems.However,the intense temperature gradient induced by the rapid heating and cooling processes of AM can generate high levels of residual stress and metastable chemical and structural states,inevitably leading to severe metallurgical defects in Ni-based superalloys.Cracks are the greatest threat to these materials’integrity as they can rapidly propagate and thereby cause sudden and non-predictable failure.Consequently,there is a need for a deeper understanding of residual stress and cracking mechanisms in additively manufactured Ni-based superalloys and ways to potentially prevent cracking,as this knowledge will enable the wider application of these unique materials.To this end,this paper comprehensively reviews the residual stress and the various mechanisms of crack formation in Ni-based superalloys during AM.In addition,several common methods for inhibiting crack formation are presented to assist the research community to develop methods for the fabrication of crack-free additively manufactured components.
文摘The growth kinetics of microarc oxidation(MAO)coatings on Ti6Al4V alloy was studied by designing an electrolyte with low PO_(4)^(3−)content and high B_(4)O_(7)^(2−)content,using scanning electron microscopy,transmission electron microscopy,X-ray diffraction,and potentiodynamic polarization.The results showed that B_(4)O_(7)^(2−)increased the spark intensity and dissolved most of the oxides at high temperatures.Then,a thicker barrier layer at the coating/substrate interface was produced,which increased the polarization resistance of the coating.PO_(4)^(3−)at a low concentration also promoted the uniform growth of the MAO coating and the formation of hat-shaped holes in the outer deposition layer.The thickness of the MAO coatings obtained in Na_(2)B_(4)O_(7) electrolytes exhibited an exponential increase with time at spark discharge stage,while that of the MAO coating obtained in phosphate–tetraborate electrolytes showed a linear trend as the PO_(4)^(3−)content increased.
基金Projects(51274252,51074180)supported by the National Natural Science Foundation of ChinaProject(2013CB035401)supported by the National Basic Research Program of China+1 种基金Projects(2012AA0418012012AA041803)supported by the High-Tech Research and Development Program of China
文摘In order to study rock breaking characteristics of tunnel boring machine(TBM) disc cutter at different rock temperatures,thermodynamic rock breaking mathematical model of TBM disc cutter was established on the basis of rock temperature change by using particle flow code theory and the influence law of interaction mechanism between disc cutter and rock was also numerically simulated.Furthermore,by using the linear cutting experiment platform,rock breaking process of TBM disc cutter at different rock temperatures was well verified by the experiments.Finally,rock breaking characteristics of TBM disc cutter were differentiated and analyzed from microscale perspective.The results indicate the follows.1) When rock temperature increases,the mechanical properties of rock such as hardness,and strength,were greatly reduced,simultaneously the microcracks rapidly grow with the cracks number increasing,which leads to rock breaking load decreasing and improves rock breaking efficiency for TBM disc cutter.2) The higher the rock temperature,the lower the rock internal stress.The stress distribution rules coincide with the Buzin Neske stress circle rules: the maximum stress value is below the cutting edge region and then gradually decreases radiant around; stress distribution is symmetrical and the total stress of rock becomes smaller.3) The higher the rock temperature is,the more the numbers of micro,tensile and shear cracks produced are by rock as well as the easier the rock intrusion,along with shear failure mode mainly showing.4) With rock temperature increasing,the resistance intrusive coefficients of rock and intrusion power decrease obviously,so the specific energy consumption that TBM disc cutter achieves leaping broken also decreases subsequently.5) The acoustic emission frequency remarkably increases along with the temperature increasing,which improves the rock breaking efficiency.
基金the support from National Science and Technology Major Project(J2019-IV-0014-0082)National Key Research and Development Program of China(2022YFB4600700)+2 种基金15th Thousand Youth Talents Program of China,the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures(MCMS-I-0419G01)the Fundamental Research Funds for the Central Universities(1001-XAC21021)a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘Additive manufacturing(AM)has emerged as an advanced technique for the fabrication of complex near-net shaped and lightweight metallic parts with acceptable mechanical performance.The strength of AM metals has been confirmed comparable or even superior to that of metals manufactured by conventional processes,but the fatigue performance is still a knotty issue that may hinder the substitution of currently used metallic components by AM counterparts when the cyclic loading and thus fatigue failure dominates.As essential complements to high-cost and time-consuming experimental fatigue tests of AM metals,models for fatigue performance prediction are highly desirable.In this review,different models for predicting the fatigue properties of AM metals are summarized in terms of fatigue life,fatigue limit and fatigue crack growth,with a focus on the incorporation of AM characteristics such as AM defect and processing parameters into the models.For predicting the fatigue life of AM metals,empirical models and theoretical models(including local characteristic model,continuum damage mechanics model and probabilistic method)are presented.In terms of fatigue limit,the introduced models involve the Kitagawa–Takahashi model,the Murakami model,the El-Haddad model,etc.For modeling the fatigue crack growth of AM metals,the summarized methodologies include the Paris equation,the Hartman-Schijve equation,the NASGRO equation,the small-crack growth model,and numerical methods.Most of these models for AM metals are similar to those for conventionally processed materials,but are modified and pay more attention to the AM characteristics.Finally,an outlook for possible directions of the modeling and prediction of fatigue properties of AM metals is provided.
基金financially supported by Guangdong Basic and Applied Basic Research Foundation (No.2020A1515110762)。
文摘Silicon/carbon composites are promising alternatives to current graphite anodes in commercial lithiumion batteries(LIBs)because of their high capacity and excellent safety.Nevertheless,the unsatisfactory fastcharging capability and cycle stability of Si/C composites caused by slow charge transport capability and huge volume change under industrial electrode conditions severely hamper their development.Here,a novel Si/C anode was fabricated by homogeneously depositing amorphous C-Si nanolayers on graphite(C-Si@graphite).C-Si nanolayers with uniformly dispersed sub-nanometer Si particles in 3D carbon skeleton significantly boost electron and Li-ion transport and efficiently relieve Si's agglomeration and volume change.As a result,the tailored C-Si@graphite electrodes show an excellent rate capacity(760.3 mAh·g^(-1)at 5.0C)and long cycle life of over 1000 cycles at 1.0C and800 cycles at 2.0C under industrial electrode conditions.In addition,the assembled full cells(C-Si@graphite,anode;Li[Ni_(0.8)Co_(0.1)Mn_(0.1)]O_(2),cathode)present superior fastcharging capability(240.4 Wh·kg^(-1),charging for16.2 min,3.0C)and long cycle life(80.7%capacity retention after 500 cycles at 1.0C),demonstrating the massive potential of C-Si@graphite for practical application.
基金financial support for this work from the Guangdong Basic and Applied Basic Research Foundation (2019A1515111133)the National Natural Science Foundation of China (Grant Nos. 52035009, 52005243)the research fund for International Cooperation (GJHZ20180928155412525) from the Science and Technology Innovation Committee of Shenzhen Municipality, Shenzhen, China。
文摘Diamond is a promising material for the modern industry. It is widely used in different applications, such as cutting tools, optical windows, heat dissipation, and semiconductors.However, these application areas require exceptionally flattened and polished diamond surfaces.Unfortunately, due to the extreme hardness and chemical inertness of diamond, the polishing of diamond is challenging. Since the 1920s, various conventional and modern mechanical,chemical, and thermal polishing techniques have been proposed and developed for finishing diamond surfaces. Therefore, to impart proper guidance on selecting a good polishing technique for production practice, this paper presents an in-depth and informative literature survey of the current research and engineering developments regarding diamond polishing. At first, a brief review of the general developments and basic material removal principles is discussed. This review concludes with a detailed analysis of each techniques' polishing performance and critical challenges, and a discussion of the new insights and future applications of diamond polishing.
