查看更多>>摘要：Study on the influence of temperature on the mechanical properties across multiple scales has been a focus on the research of Hastelloy-X(HX)alloys for the application in high-temperature structure com-ponents.In this work,Molecular Dynamics(MD)and Crystal Plasticity(CP)are put together to solve it from atomic scale to mesoscopic scale.MD research indicates that the deformation of HX alloy occurs in two stages at temperature below 300 K:initially,as stacking fault deforms,stacking fault can trans-form into twinning with increasing strain.When the temperature exceeds 300 K,deformation primarily forms a stacking fault.The twinning deformation path transforms from intrinsic stacking fault to extrin-sic stacking fault and then to twinning.A mesoscopic-scale CP model was developed using atomic-scale deformation mechanisms to bridge the gap between deformation mechanisms and experimental results.The CP results indicate a functional relationship between the strength of HX alloy and temperature.This relationship appears insensitive to crystal texture and grain shape.Incorporating grain morphology and texture into the model significantly impacts the strength response of calculating HX alloy.After the ten-sile deformation of HX alloy at 300 and 1173 K,the atomic scale deformation results characterized by transmission electron microscopy are aligned with the MD simulation results.The relationship between strength and temperature predicted by CP results has also been validated.A thorough investigation into the deformation behavior of HX alloys across different scales,employing MD and CP models,introduces a novel approach for predicting the mechanical properties of superalloys.
查看更多>>摘要：Neovascularization and inflammatory cell invasion within the nucleus pulposus(NP)constitute pivotal pathological changes during the acceleration stage of intervertebral disc degeneration(IDD).Mesenchy-mal stem cells(MSCs),renowned for their remarkable capacity in intervertebral disc(IVD)regeneration,also exhibit the capability to secrete pro-angiogenic factors,expediting IDD progression under hypoxic conditions.Consequently,we developed a hydrogel comprised of methacrylated hyaluronic acid(HAMA),rat tail collagen I(COL),and MSCs,incorporating the vascular endothelial growth factor receptor(VEGFR)inhibitor cabozantinib(Cabo@HAMA-COL/MSCs hydrogel).This innovative construct aimed to facilitate NP regeneration while mitigating vascularization and inflammation.Our findings revealed that the hydrogel aptly mimicked the mechanical characteristics of NP tissue,exhibiting injectability,low cytotoxicity,and the preservation of the cellular phenotype of NP cells.Co-culturing of MSCs and human umbilical vein endothelial cells(HUVECs)promoted migration,tube formation,and sprouting of HUVECs,which will be inhibited by cabozantinib.In vivo experiments demonstrated that Cabo@HAMA-COL/MSCs hydrogel main-tained disc height,protected NP,and alleviated vascularization and inflammation in a puncture-induced rat caudal IDD model.Consequently,our results substantiate that Cabo@HAMA-COL/MSCs hydrogel can prevent IDD degeneration by ameliorating the vascularization-inflammation pathological microenviron-ment,offering a promising therapeutic strategy for IDD.
查看更多>>摘要：Mechanical properties of TC17 titanium alloy undergo a significant reduction after linear friction welding(LFW),of which the strength and ductility are hard to be improved simultaneously by traditional aging heat treatment(AHT),seriously limiting the application of LFW in the manufacturing of TC17 titanium alloy blisks.To this end,the present work proposes to use electric pulse treatment(EPT)to enhance the strength and ductility of TC17 LFW joints simultaneously by improving its microstructure.The results show that,in comparison to the uneven distribution of α phases in the welding zone(WZ),heat-affected zone(HAZ),and base metal(BM)zone after AHT,EPT can selectively homogenize the α phase distribution of WZ and HAZ without impacting the BM.The selective effect of EPT is reflected as the synergistic influence of the local Joule heating effect and the electron wind effect,which promotes the diffusion of β phase stabilizing element Mo and leads to a competitive precipitation of β phase and α phase in the α phase transition temperature range.The ratio of α phase to β phase in the WZ and HAZ finally approaches an equilibrium point which is similar to that of BM,leading to a uniform distribution ofα phase and realizing the synergy of strength-ductility of LFW joint:the maximum strength increase observed is 12.9％,accompanied by a corresponding elongation increase of 122％(by AHT & EPT),and the maximum plasticity improvement is 185％,accompanied by a corresponding strength increase of 4.3％(by EPT for 1 h).This study provides essential insights for improving the strength and ductility of LFW TC17 titanium alloy blisks and enhancing the applications of LFW in aeroengine components.
查看更多>>摘要：Niobium(Nb)is sensitive to even minute quantities of silicon(Si)solutes,which are known to induce pronounced hardening.However,the underlying mechanism for hardening remains elusive since the ef-fect of Si solutes on dislocation behavior is unclear.Here,using tensile testing,in-situ microscopy and nanomechanical testing,the behavior of dislocations in dilute Nb-Si alloys,containing from 0 at.％to 0.8 at.％Si,is investigated.We show that the hardness,strength and strain hardening rate increase from two to four times,while the uniform elongation in tension only reduces 50％as the Si content increases.Dislocations evolve from complex entangled patterns in Nb to parallel long-straight screw dislocation-dominated structures in Nb-Si alloys.In-situ indentation reveals that the origins of the marked harden-ing in Nb-Si alloy are the reduction of dislocation mobility and cross-slip propensity.Large densities of dislocation debris-superjogs and loops introduced throughout the sample during warm rolling and an-nealing are found to provide active internal dislocation sources,which explain the minimal ductility loss seen in these Nb-Si alloys.These findings can help guide the alloy design of high-performance refractory materials for extreme temperature applications.
查看更多>>摘要：Research into the atomic structures of metal materials in the liquid state,their dynamic evolution versus temperature until the onset of crystal nucleation has been a central research topic in condensed matter physics and materials science for well over a century.However,research and basic understanding of the atomic structures of liquid metals are far less than those in the solid state of the same compositions.This review serves as a condensed collection of the most important research literature published so far in this field,providing a critical and focused review of the historical research development and progress in this field since the 1920s.In particular,the development of powerful synchrotron X-ray sources and the as-sociated experimental techniques and sample environments for studying in-situ the atomic structures of different metallic systems.The key findings made in numerous pure metals and metallic alloy systems are critically reviewed and discussed with the focus on the results and new understandings of structural het-erogeneities found inside a bulk liquid,at the liquid surface or liquid-solid interface.The possible future directions of research and development on the most advanced experimental and modeling techniques are envisaged and briefly discussed as well.
查看更多>>摘要：Flexible supercapacitors with high mechanical strength,excellent flexibility,and high performance are highly desired to meet the increasing demands of flexible electronics.However,the trade-off between mechanical and electrochemical properties remains challenging.In this context,an interface-engineered strategy approach was proposed to construct polylactic acid(PLA)/polyaniline(PANI)/MXene(PPM)film electrodes for flexible supercapacitor applications.In the PPM electrode,the porous PLA prepared from the nonsolvent-induced-phase-separation method served as an ideal flexible substrate,providing excel-lent flexibility and high mechanical strength,whereas PANI as the coupling agent,enhanced the interfa-cial strength between PLA and the electroactive MXene that was firmly anchored and deposited on PLA through a facile layer-by-layer dip coating method.The tensile strength at break,elongation at break,and toughness of PPM are 53.09 MPa,11.09％,and 4.12 MJ/m3,respectively,much higher than those of pure MXene(29.36 MPa,4.62％,and 0.75 MJ/m3).At an optimum mass loading density of 3 mg cm-2 for MXene,the fabricated PPM3 film electrode achieved a high specific capacitance of 290.8 F g-1 at a cur-rent density of 1 A g-1 in the three-electrode setup,approximately 1.5 times that of 190.8 F g-1 for pure MXene.Meanwhile,the symmetric all-solid-state supercapacitor based on PPM3 film electrodes delivers a high specific capacitance of 193.7 F g-1 at a current density of 0.25 A g-1,with a corresponding high energy density of 9.3 Wh kg-1at a power density of 291.3 W kg-1.The SC retains 86％of its original ca-pacitance even bent at 120° and also possesses an excellent fire-retardant ability,demonstrating its great potential for flexible and safe wearable electronics.
查看更多>>摘要：Owing to its exceptional casting performance,substantial utilization of recycled sand,and environmen-tally sustainable characteristics,frozen sand mold casting technology has found extensive application across diverse sectors,including aerospace,power machinery,and the automotive industry.The focus of the present study was on the development of frozen sand mold formulations tailored for efficient machin-ing,guided by the performance and cutting fracture mechanism of frozen sand molds.A regional tem-perature control device was developed for the purpose of conducting cryogenic cutting experiments on frozen sand molds with varying geometrical characteristics and molding materials.The impact of milling process parameters on the dimension accuracy of both sand molds and castings,as well as castings'surface roughness,were systematically investigated by a whole-process error flow control method.The findings indicate that precise and efficient processing of complicated sand molds was achievable by using sand particles with sizes ranging from 106 to 212 μm,and water content between 4 and 5 wt.％,freezing temperature below-25 ℃,and cutting temperature within the range of-5 to 0 ℃.Through the frozen-casting of representative components,it was validated that the machining error of the frozen sand mold was within±0.25 mm.Additionally,the dimensional accuracy of the flywheel shell casting conformed to the CT8 specifications.This study provides theoretical guidance for the selection of frozen-casting sand formulations and close-loop control of process size chains for complex metal parts,as well as an overall solution for the realization of sustainable development of green casting.
查看更多>>摘要：Herein,a novel TiO2/CN heterojunction material has been prepared by one-step bubble template-assisted calcination to enhance the hydrogen storage capability of LiAlH4.The TEM,XPS and UPS analysis confirm that a heterostructure is formed between TiO2 and g-C3N4 successfully.The experimental findings indi-cate that the TiO2/CN significantly enhances the dehydrogenation performance of LiAlH4.For instance,the LiAlH4-7 wt％TiO2/CN starts to dehydrogenize at 76 ℃(94 ℃ less than pure LiAlH4)and releases 6.5 wt％H2 at 200 ℃.Meanwhile,LiAlH4-7 wt％TiO2/CN releases 4.9 wt％H2 at 120 ℃ within 50 min.The mech-anism analysis illustrates that AlTi3N is formed in situ during ball-milling.And density functional theory(DFT)calculation results reveal that the AlTi3N can weaken the Al-H bonds in LiAlH4 through interfacial charge transfer.Furthermore,the TiO2/CN heterostructure creates an internal electric field that generates an electron-rich layer.As a result,the negative electron layer at one end of the TiO2/CN heterojunction has an increased affinity for H,which enhances the dehydrogenation reaction of LiAlH4.Clearly,both the TiO2/CN heterostructure and AlTi3N contribute to the improvement of the dehydrogenation properties of LiAlH4.
查看更多>>摘要：Nowadays,there is a growing global demand for high-performance room temperature gas sensing de-vices.In this context,we aim to explore the advancements in two-dimensional(2D)Ti3C2 MXene role for toxic NO2 gas sensing at room temperature.The distinctive advantages of 2D Ti3C2 MXene,including high electrical conductivity,ample surface area,surface termination groups,and layer structure have garnered significant attention towards NO2 gas adsorption.Further,the compatible regularity of Ti3C2 MXene at the interface of various semiconductors directed the development of potential room-temperature NO2 gas sensing devices.Further,the leveraging gas sensing(selectivity,response,and recovery)characteristics be-come increasing attention on Ti3C2 MXene/semiconductor interfaces than pure Ti3C2 MXene.Elaborative control on the depletion layer through the Schottky barrier formation distinguished the room tempera-ture NO2 gas sensing and led to the evolution of electrophilic NO2 gas molecule interaction.Remarkably,the great processability of Ti3C2 MXene/semiconductor interface is sensitive to the low detection limit(LOD)of NO2 gas at parts per billion(ppb)conditions.On the other hand,this review demonstrates the room temperature optoelectronic NO2 gas sensing capabilities of Ti3C2-based composites for emphasiz-ing selectivity and recovery.Interestingly,the Ti3C2 MXene/semiconductor composite builds immunity against the atmosphere humidity and achieves stable NO2 gas sensing.Finally,we have provided conclu-sions and key points to advance the research on room temperature NO2 gas sensing of Ti3C2 integrated semiconductors.
查看更多>>摘要：Water-assisted proton hopping(WAPH)plays an important role in the aqueous-phase hydrogenation of levulinic acid(LA)to y-valerolactone(GVL).In this study,based on a strategy of spontaneously polarized ceramic(SPCE)-reinforced WAPH,a Ni-Co/SPCE-C catalyst was constructed by high-temperature calci-nation of a dual mechanical activation-treated precursor.Ni-Co/SPCE-C with favorable structural char-acteristics,intimate interfacial compatibility,and unique spontaneous polarization effect enhanced the migration efficiency of active hydrogen and activated water to form small water clusters,contributing to outstanding catalytic activity for aqueous-phase hydrogenation of L.A to produce GVL at relatively low re-action temperature and H2 pressure.A LA conversion of 99.9％and a GVL yield of 92.3％were achieved at 160 ℃ and 1.5 MPa H2 over the Ni-Co/SPCE-C catalyst,which were significantly higher than those catalyzed by contrastive catalysts.A variety of tests and theoretical calculations reveal that SPCE with far-infrared emission and surface electric field was conducive to the reduction in the hydrogen spillover energy barrier,the stabilization of the transition state,and the facile exchange of H2 and water for ac-celerating WAPH.Moreover,a reasonable SPCE-reinforced WAPH mechanism was proposed to explain the enhanced aqueous hydrogenation of LA.This research can provide valuable insights into the design and development of high-performance non-noble metal catalysts for aqueous hydrogenation applications.
NETL
NSTL
万方数据