Improving the volumetric energy density of supercapacitors is essential for practical applications,which highly relies on the dense storage of ions in carbon-based electrodes.The functional units of carbon-based elect...Improving the volumetric energy density of supercapacitors is essential for practical applications,which highly relies on the dense storage of ions in carbon-based electrodes.The functional units of carbon-based electrode exhibit multi-scale structural characteristics including macroscopic electrode morphologies,mesoscopic microcrystals and pores,and microscopic defects and dopants in the carbon basal plane.Therefore,the ordered combination of multi-scale structures of carbon electrode is crucial for achieving dense energy storage and high volumetric performance by leveraging the functions of various scale structu re.Considering that previous reviews have focused more on the discussion of specific scale structu re of carbon electrodes,this review takes a multi-scale perspective in which recent progresses regarding the structureperformance relationship,underlying mechanism and directional design of carbon-based multi-scale structures including carbon morphology,pore structure,carbon basal plane micro-environment and electrode technology on dense energy storage and volumetric property of supercapacitors are systematically discussed.We analyzed in detail the effects of the morphology,pore,and micro-environment of carbon electrode materials on ion dense storage,summarized the specific effects of different scale structures on volumetric property and recent research progress,and proposed the mutual influence and trade-off relationship between various scale structures.In addition,the challenges and outlooks for improving the dense storage and volumetric performance of carbon-based supercapacitors are analyzed,which can provide feasible technical reference and guidance for the design and manufacture of dense carbon-based electrode materials.展开更多
High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress aro...High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress arouses the deformation of large integrated die-castings.Herein,the development of non-heat treatment Al alloys is becoming the hot topic.In addition,HPDC contains externally solidified crystals(ESCs),which are detrimental to the mechanical properties of castings.To achieve high strength and toughness of non-heat treatment die-casting Al-Si alloy,we used AlSi9Mn alloy as matrix with the introduction of Zr,Ti,Nb,and Ce.Their influences on ESCs and mechanical properties were systematically investigated through three-dimensional reconstruction and thermodynamic simulation.Our results reveal that the addition of Ti increased ESCs'size and porosity,while the introduction of Nb refined ESCs and decreased porosity.Meanwhile,large-sized Al_3(Zr,Ti)phases formed and degraded the mechanical properties.Subsequent introduction of Ce resulted in the poisoning effect and reduced mechanical properties.展开更多
3D reconstruction and 2D observation were conducted to characterize the microstructure of the castings produced through high pressure die casting with different parameters.Our results indicate that shrinkage pores gen...3D reconstruction and 2D observation were conducted to characterize the microstructure of the castings produced through high pressure die casting with different parameters.Our results indicate that shrinkage pores generally co-existed with externally solidified crystals(ESCs).In specimen produced without fast slow shot speed,big net-shrinkage pores accompanied with ESCs were found in the center of the specimen.When the casting pressurization was introduced,the shrinkage pores gathered to the specimen center and became much less due to the optimization of melt feeding.Much more porosity was found near the gate rather than in the middle of the rod bar,especially gas pores.Thefilling process simulation reveals that the middle position of the bars wasfirstlyfilled and followed by the near gate position accompanied with one intense turbulentflow.展开更多
The dry sliding wear behavior of Ti_2AlC reinforced AZ91 magnesium composites was investigated at sliding velocity of 0.5 m/s under loads of 10, 20, 40 and 80 N using pin-on-disk configuration against a Cr15 steel dis...The dry sliding wear behavior of Ti_2AlC reinforced AZ91 magnesium composites was investigated at sliding velocity of 0.5 m/s under loads of 10, 20, 40 and 80 N using pin-on-disk configuration against a Cr15 steel disc. Wear rates and friction coefficients were registered during wear tests. Worn tracks and wear debris were examined by scanning electron microscopy, energy dispersive X-ray spectrometry and transmission electron microscopy in order to obtain the wear mechanisms of the studied materials. The main mechanisms were characterized as the magnesium matrix oxidation and self-lubrication of Ti_2AlC MAX phase. In all conditions, the composites exhibit superior wear resistance and self-lubricated ability than the AZ91 Mg alloy. In addition, the anisotropic mechanisms in tribological properties of textured Ti_2AlC-Mg composites were confirmed and discussed.展开更多
The microstructure, fracture morphology and mechanical properties of Al-10 Si alloy modified with Al-5 Ti were analyzed and tested by optical microscopy, scanning electron microscopy, and universal electronic testing ...The microstructure, fracture morphology and mechanical properties of Al-10 Si alloy modified with Al-5 Ti were analyzed and tested by optical microscopy, scanning electron microscopy, and universal electronic testing machine. Compared with unmodified Al-10 Si alloy, the area fraction of α-Al phase in Al-10 Si alloy modified at 740 °C increased first and then decreased with the increase of added amounts of Al-5 Ti, and reached the maximum when the added amount of Al-5 Ti was 0.5 wt.%. When the modification temperature increased from 700 to 740 °C with Al-5 Ti being fixed at 0.5 wt.%, α-Al dendrites were refined obviously and the area fraction remarkably increased. Compared with unmodified Al-10 Si alloy, the ultimate tensile strength and elongation of the alloy modified at 740 °C with 0.5 wt.% Al-5 Ti increased by 9% and 49%, respectively. The fracture surface of modified alloy predominantly exhibited ductile fracture.展开更多
To understand the relationship between the process-microstructure-mechanical properties of the high-pressure die-casting(HPDC) AE44 magnesium alloy, 3D reconstruction and 2D characterization were carried out on the HP...To understand the relationship between the process-microstructure-mechanical properties of the high-pressure die-casting(HPDC) AE44 magnesium alloy, 3D reconstruction and 2D characterization were carried out on the HPDC castings produced with different process parameters(low slow-shot speed, fast slow-shot speed, solidification pressure). Microstructural characterization revealed that the formation of shrinkage pores are closely related to ESCs, which were mainly controlled by the low slow-shot speed in shot sleeve(ESCs growth time) and fast slow-shot speed into the die cavity(distribution of ESCs). In addition, solidification pressure can significantly reduce the shrinkage porosity in the center by improving the feeding capacity of liquid metal. Tensile fracture revealed that the tearing ridge is mainly evolved from the slip band of ESCs. The quantity and distribution of ESCs determine the fracture mode of castings. The relationship between mechanical properties of castings and the morphology of ESCs and porosity is also statistically discussed.展开更多
Effects of equal channel angular pressing(ECAP)extrusion on the microstructure,mechanical properties and biodegradability of Mg–2Zn–xGd–0.5Zr(x=0,0.5,1,2 wt%)alloys were studied in this work.Microstructure analysis...Effects of equal channel angular pressing(ECAP)extrusion on the microstructure,mechanical properties and biodegradability of Mg–2Zn–xGd–0.5Zr(x=0,0.5,1,2 wt%)alloys were studied in this work.Microstructure analysis,tensile test at ambient temperature,immersion test and electrochemical test in Hank’s solution were carried out.The results showed that Gd could further enhance the grain refinement during the ECAP extrusion.Both Gd addition and ECAP extrusion could improve the mechanical properties of the alloys,and the extrusion played the dominant role.Minor addition of Gd(0.5–1 wt%)could obviously enhance the corrosion resistance of the alloys.To some extent,ECAP extrusion improved the corrosion resistance of the alloys due to the change of second phases distribution and the refinement of grains.Further increase in extrusion pass was detrimental to the improvement of the corrosion resistance as a result of increment of the grain boundaries.展开更多
Magnesium composites reinforced by N-deficient Ti_(2)AlN MAX phase were first fabricated by non-pressure infiltration of Mg into three-dimensional(3D)co-continuous porous Ti_(2)AlN_(x)(x=0.9,1.0)preforms.The relations...Magnesium composites reinforced by N-deficient Ti_(2)AlN MAX phase were first fabricated by non-pressure infiltration of Mg into three-dimensional(3D)co-continuous porous Ti_(2)AlN_(x)(x=0.9,1.0)preforms.The relationship between their mechanical properties and micro-structure is discussed with the assessment of 2D and 3D characterization.X-ray diffraction(XRD)and scanning electron microscopy detected no impurities.The 3D reconstruction shows that the uniformly distributed pores in Ti_(2)AlN_(x) preforms are interconnected,which act as infiltra-tion tunnels for the melt Mg.The compressive yield strength and microhardness of Ti_(2)AlN_(0.9)/Mg are 353 MPa and 1.12 GPa,respectively,which are 8.55%and 6.67%lower than those of Ti_(2)AlN/Mg,respectively.The typical delamination and kink band occurred in Ti_(2)AlN_(x) under compressive and Vickers hardness(V_(H))tests.Owing to the continuous skeleton structure and strong interfacial bonding strength,the crack ini-tiated in Ti_(2)AlN_(x) was blocked by the plastic Mg matrix.This suggests the possibility of regulating the mechanical performance of Ti_(2)AlN/Mg composites by controlling the N vacancy and the hierarchical structure of Ti_(2)AlN skeleton.展开更多
To clarify the relationship between externally solidified crystals(ESCs)and other defects,e.g.,defect bands and pores,two dimensional(2D)and three dimensional(3D)characterization methods were adopted to analyze castin...To clarify the relationship between externally solidified crystals(ESCs)and other defects,e.g.,defect bands and pores,two dimensional(2D)and three dimensional(3D)characterization methods were adopted to analyze castings produced using a modified ingate system equipped with and without an ESC collector.The reduction of ESCs strongly reduced defect band width and shrinkage pore quantity.By reducing the quantity and size of ESCs,net-shrinkage pores were transformed into isolated island-shrinkage pores.We determined via statistical analysis that the mechanical properties of high pressure die castings were strongly related to the size and fraction of the ESCs rather than porosity volume.The reduction of ESCs also caused tensile transgranular fracture modes to transform into intergranular fracture modes.Additionally,casting pressurization strongly reduced pore morphology,volume,and size.展开更多
The solidification microstructure,fracture morphologies,and mechanical properties of an Al-18Si alloy and alloys modified with Al-5Ti and Al-3P master alloys were investigated using an optical microscope,scanning elec...The solidification microstructure,fracture morphologies,and mechanical properties of an Al-18Si alloy and alloys modified with Al-5Ti and Al-3P master alloys were investigated using an optical microscope,scanning electron microscope,and an electronic universal testing machine.The results show that additions of Al-5Ti and Al-3P have significant effects on the size and area fraction of the primary Si and the mechanical properties of the Al-18Si alloy.Compared to the Al-18Si alloy modified with 0.6 wt%Al-5Ti at 850°C,when the Al-18Si alloy was modified with 0.3 wt%Al-5Ti and 0.5 wt%Al-3P at the same temperature,the average size of the primary Si decreased from 39 to 14μm and the area fraction increased from 9.5%to 11.6%.The biggest influencing factor on the tensile strength and elongation of the Al-18Si alloy is the addition of Al-3P,followed by the modification temperature and the addition of Al-5Ti.At a modification temperature of 850°C,the tensile strength and elongation of the Al-18Si alloy modified with 0.3 wt%Al-5Ti+0.5 wt%Al-3P increased by 19.6%and 88.6%,respectively compared to that of the Al-18Si alloy modified with 0.6 wt%Al-5Ti.展开更多
A series of Mg_(2-x)Nd_xNi (x=0.05, 0.1, 0.2, 0.3) alloys and Mg_(1.95)RE_(0.05)Ni (RE= La, Ce, Pr, Nd, Y) ternary alloys were prepared by ball milling of mixted powder of Mg,Ni,RE and sintering under the protection o...A series of Mg_(2-x)Nd_xNi (x=0.05, 0.1, 0.2, 0.3) alloys and Mg_(1.95)RE_(0.05)Ni (RE= La, Ce, Pr, Nd, Y) ternary alloys were prepared by ball milling of mixted powder of Mg,Ni,RE and sintering under the protection of argon. XRD analysis shows that Mg_(2-x)Nd_xNi (x=0.05, 0.1) and Mg_(1.95)RE_(0.05)Ni consist of single phase with the same crystal structure as Mg_2Ni. While three-phase alloys including Mg_2Ni, NdNi and NdMgNi_4 were formed in Mg_(1.8)Nd_(0.2)Ni and Mg_(1.7)Nd_(0.3)Ni alloys respectively. The lattice constants of Mg_2Ni in those ternary alloys were calculated. The decomposition of Mg_2Ni occurs in the milling process of Mg_2Ni and Mg_(1.95)RE_(0.05) Ni alloys respectively. For the latter, another earlier reaction occurs in milling process, which means that atoms of RE are separated from crystal structure of Mg_2Ni and form relevant oxides by combination with oxygen existed in argon atmosphere.展开更多
To investigate the influences of Cr_(2)AlC mass fraction and supersonic plasma spraying process on the microstructure and mechanical properties of Cr_(2)AlC reinforced 410 stainless steel composite coatings,the coatin...To investigate the influences of Cr_(2)AlC mass fraction and supersonic plasma spraying process on the microstructure and mechanical properties of Cr_(2)AlC reinforced 410 stainless steel composite coatings,the coatings containing different mass fractions of Cr_(2)AlC were prepared and investigated.The composite coating exhibited low porosity and high adhesion strength.The addition of Cr_(2)AlC significantly enhanced the hardness of the composite coatings through particle strengthening.However,when the mass fraction of Cr_(2)AlC was 20%,the aggregation of Cr_(2)AlC resulted in a strong decrease in the coating preparation efficiency,as well as a decline in adhesion strength.In the supersonic plasma spraying process,the Ar flow rate mainly influenced the flight velocity of the particles,while the H_(2) flow rate and the current mainly affected the temperature of the plasma torch.Consequently,all of them influenced the melting degree of particles and the quality of the coating.The lowest porosity and the highest hardness and adhesion strength could be obtained when the Ar flow rate is 125 L/min,the H_(2) flow rate is 25 L/min,and the current is 385 A.展开更多
In recent decades, the demand for lightweight and high specific strength materials brings about the development of magnesium matrix composites. Different from some traditional binary ceramic particles, such as SiC, Al...In recent decades, the demand for lightweight and high specific strength materials brings about the development of magnesium matrix composites. Different from some traditional binary ceramic particles, such as SiC, Al_(2)O_(3), the novel ternary nano-layered M_(n+1)AX_(n)(MAX)phase carbide or nitride ceramics exhibit metal-like properties and self-lubricate capacity(where “M” is an early transition metal, “A” belongs to the group A element, “X” is C or/and N, and n = 1–3). Ti_(2)AlC, as the representative of the MAX phase, was interestingly introduced into the magnesium matrix. Layered Ti_(2)AlC MAX phased reinforced AZ91D magnesium composites manufactured through the stir casting exhibit sufficient deformation capacity due to unique deformation behaviors of MAX, namely delamination and the formation of kinking band. Further,the Ti_(2)AlC-AZ91D composites exhibit a distinctive characteristic in strengthening mechanism, damping mechanism and tribological capacity due to the other special properties of MAX phase, such as self-lubricated property. Accordingly, to give a comprehensive understanding, we overviewed the fabrication process, microstructural characterization, mechanical properties, damping property and tribological capacity on these composites. In order to understand the A-site effect in MAX phase on the microstructure, we introduced another representative Ti_(3)SiC_(2)MAX phase to explain the interfacial evolution. In addition, due to the high aspect ratio of MAX, MAX particles could be orientationally regulated in Mg matrix by plastic deformation such as hot extrusion. Herein, we discussed the anisotropic mechanical and physical properties of the textured composites produced by hot extrusion. Moreover, the potential applications and future development trends of MAX phases reinforced magnesium matrix composites were also given and prospected.展开更多
In order to enhance the ablation-resistant performance of stainless-steel conductive rails,Mo coating,410 stainless steel coating and 15 wt%Cr_(2)AlIC particles reinforced 410 stainless steel composite coating were pr...In order to enhance the ablation-resistant performance of stainless-steel conductive rails,Mo coating,410 stainless steel coating and 15 wt%Cr_(2)AlIC particles reinforced 410 stainless steel composite coating were prepared and evaluated.Different from the weak interfacial strength caused by the dissimilar metals between Mo and steel rails,410 stainless steel coating has better interfacial contact with steel rails.The introduction of Cr_(2)AlC into 410 stainless steels further strengthened the mechanical properties of coating by alloy strengthening effect and particle strengthening effect,as the decomposition of Cr_(2)AlC into nano CrC particles is accompanied with the diffusion of Al atoms into 410 stainless steels.It was found that the composite coating can still resist arc erosion at 150 A current,as a dense oxide film formed during the ablation process and the decomposition of Cr_(2)AlC contributed to the heat absorption.展开更多
The structure, microstructure, thermal stability and hydriding characteristics of amorphous La0.95-Mg2.05Ni9 have been investigated with differential thermal analysis, X-ray diffraction, scanning electron microscopy a...The structure, microstructure, thermal stability and hydriding characteristics of amorphous La0.95-Mg2.05Ni9 have been investigated with differential thermal analysis, X-ray diffraction, scanning electron microscopy and battery test. It is found that the increase in mechanical alloying time leads to enhancement in thermal stabilities of amorphous La0.95Mg2.05Ni9 alloy. The amorphous alloy has good charge/discharge ability at room temperature(430 mA·h·g-1), but the discharge capacity decreases seriously during cycling tests due to the crystallization of amorphous and oxidization of magnesium on the particle surface in alkaline aqueous solution.展开更多
3D reconstruction was adopted to characterize the microstructural morphologies of Mg-3.0Nd-0.3Zn-0.6Zr alloy castings produced by high pressure die casting(HPDC)processes with different parameters,including low slow-s...3D reconstruction was adopted to characterize the microstructural morphologies of Mg-3.0Nd-0.3Zn-0.6Zr alloy castings produced by high pressure die casting(HPDC)processes with different parameters,including low slow-shot speed,solidification pressurization and fast slow-shot speed.At low slow-shot speeds of 0.1 m·s^(-1),0.2 m·s^(-1) and 0.3 m·s^(-1),the porosity is concentrated in the center of the castings with one spiral staggered shape along the liquid flow direction.The porosity volume simultaneously decreases with the reduction of quantity and size of externally solidified crystals(ESCs),while the shrinkage pores become more and more dispersed with the increasing low slow-shot speed.Pressurization not only reduces the porosity volume due to the improvement of feeding ability,but also transformes the center gathered porosity into one layer-by-layer distribution form.Accompanied with the increasing fast slow-shot speed,the central porosity dramatically decreases and transforms into a large-scale spiral staggered shape along the liquid flow direction.However,the porosity is much more dispersed when the speed is increased from 2 m·s^(-1) to 3 m·s^(-1).展开更多
Carbonitride MXenes,such as Ti_(3)CNT_(x),Ti_(2)C_(0.5)N_(0.5)T_(x),and Ti_(4)(C_(0.2)N_(0.8))_(3)T_(x),have attracted much interest in the large family of two-dimensional(2D)nanomaterials.Like their carbide MXene cou...Carbonitride MXenes,such as Ti_(3)CNT_(x),Ti_(2)C_(0.5)N_(0.5)T_(x),and Ti_(4)(C_(0.2)N_(0.8))_(3)T_(x),have attracted much interest in the large family of two-dimensional(2D)nanomaterials.Like their carbide MXene counterparts,the nanolayered structure and functional groups endow carbonitride MXenes with an attractive combination of physical and chemical properties.More interestingly,the replacement of C by N changes the lattice parameters and electron distribution of carbonitride MXenes due to the greater electronegativity of N as compared to C,thus resulting in significantly enhanced functional properties.This paper reviews the development of carbonitride MXenes,the preparation of 2D carbonitride MXenes,and the current understanding of the microstructure,electronic structure,and functional properties of carbonitride MXenes.In addition,applications,especially in energy storage,sensors,catalysts,electromagnetic wave shielding and absorption,fillers,and environmental and biomedical fields,are summarized.Finally,their current limitations and future opportunities are presented.展开更多
In order to investigate the effect of die wall thickness on morphologies of defect band,a stepped mold with a wall thickness of 5 mm,4 mm,3 mm,2 mm,and 1 mm was designed to carry out high pressure die casting experime...In order to investigate the effect of die wall thickness on morphologies of defect band,a stepped mold with a wall thickness of 5 mm,4 mm,3 mm,2 mm,and 1 mm was designed to carry out high pressure die casting experiments with AlSi10 MgMn alloy.For castings with wall thickness of 2-4 mm,the ratio of the mean defect band width(w)and mean grain size(d)in the defect band(w/d)ranges 7-18,while it increases to 24.47 for the 5 mm-thick casting.This difference is related with the filling speed and the distribution of externally solidified crystals(ESCs).The mold flow analysis indicates that the filling speed decreases from 25.41 m·s^(-1)to 11.07 m·s^(-1)when wall thickness increases from 2 mm to 5 mm.Due to the decreasing filling speed along the wall thickness,ESCs gradually diffuse from the center to the defect band,which keep the shear strength in the defect band at a high-level during filling.Meanwhile,the shear strength generated during the filling also decreases as the shear rate drops.Finally,the defect bands in the 5 mm-thick region become widen and indistinct,and the porosity is as high as 5.25%.展开更多
Owing to their unique mechanical properties and excellent thermal and chemical stability,Al_(2)O_(3)nanofibers are highly desirable for practical applications as functional and structural building blocks.However,the s...Owing to their unique mechanical properties and excellent thermal and chemical stability,Al_(2)O_(3)nanofibers are highly desirable for practical applications as functional and structural building blocks.However,the scalable production of Al,O3 nanofibers has always faced significant challenges,namely,high cost and complicated processes.This work explores a feasible and straightforward dealloying strategy for the batch synthesis of Al_(2)O_(3)nanofibers.When a binary Al-Li alloy is immersed in alcohol,the alkoxide nanofibers spontaneously grow following the mechanism of boundary strain energy minimization.The results indicate that by dissolving Li in Al-Li alloys,the continuous exposure of a fresh Al surface renders the remaining unsaturated bonds of Al sufficiently reactive,providing the conditions for the subsequent reaction with alcohols and thus inducing the formation of alcohol-aluminum compounds.These nanofibers were calcined in air to obtain monocrystallineα-Al_(2)O_(3)and polycrystalline y-Al_(2)O_(3)nanofibers.We investigated the evolution of the alloy into nanofibers in dry ethanol and the influence of different Al-Li alloy compositions and calcination temperatures on the crystal structure and morphology of the resulting Al_(2)O_(3)nanofibers.The study revealed thatγ-Al_(2)O_(3)with diameters of approximately 50-80 nm and lengths of approximately 20-30μm andα-Al_(2)O_(3)with diameters of approximately 100-150 nm and lengths of approximately 15-20μm were successfully prepared via this technique route.The approach reported in this study is anticipated to open new paths for the efficient and economical synthesis of advanced metal oxide nanofibers and lay the foundation for their extensive application in current industrial sectors.展开更多
Two-dimensional(2D)MoB metal borides(MoB MBene)have attracted much attention due to their fascinating properties and functional applications.So far,work on the synthesis of 2D MoB nanosheets by acid or alkaline etchin...Two-dimensional(2D)MoB metal borides(MoB MBene)have attracted much attention due to their fascinating properties and functional applications.So far,work on the synthesis of 2D MoB nanosheets by acid or alkaline etching of MoAlB has not been very successful.It has been proposed that the 2D MoB MBene may be fabricated by chemical etching of a Mo_(2)AlB_(2) precursor,but further investigations were not performed possibly due to the difficult preparation of the metastable Mo_(2)AlB_(2) compound at high temperatures by solid-state reactions.Here,we report on the successful synthesis of the Mo_(2)AlB_(2) compound and 2D MoB nanosheets by the deintercalation of Al from MoAlB through a ZnCl_(2) molten salt etching approach at relatively low temperatures.The influence of etching temperature,etching time,and starting mixtures on the formation of desirable phases have been investigated.A pure Mo_(2)AlB_(2) compound was synthesized at temperatures below 600℃,while the 2D MoB MBene nanosheets were obtained at 700℃through the molten salt etching of MoAlB.In addition,the present work further confirms that the MoB MBene can be prepared by etching the as-synthesized Mo_(2)AlB_(2) precursor in LiF–HCl solution.Our work demonstrates that the molten salt etching is an effective method to prepare 2D MoB MBene.展开更多
基金funded by the Joint Fund for Regional Innovation and Development of National Natural Science Foundation of China(U21A20143)the National Science Fund for Excellent Young Scholars(52322607)the Excellent Youth Foundation of Heilongjiang Scientific Committee(YQ2022E028)。
文摘Improving the volumetric energy density of supercapacitors is essential for practical applications,which highly relies on the dense storage of ions in carbon-based electrodes.The functional units of carbon-based electrode exhibit multi-scale structural characteristics including macroscopic electrode morphologies,mesoscopic microcrystals and pores,and microscopic defects and dopants in the carbon basal plane.Therefore,the ordered combination of multi-scale structures of carbon electrode is crucial for achieving dense energy storage and high volumetric performance by leveraging the functions of various scale structu re.Considering that previous reviews have focused more on the discussion of specific scale structu re of carbon electrodes,this review takes a multi-scale perspective in which recent progresses regarding the structureperformance relationship,underlying mechanism and directional design of carbon-based multi-scale structures including carbon morphology,pore structure,carbon basal plane micro-environment and electrode technology on dense energy storage and volumetric property of supercapacitors are systematically discussed.We analyzed in detail the effects of the morphology,pore,and micro-environment of carbon electrode materials on ion dense storage,summarized the specific effects of different scale structures on volumetric property and recent research progress,and proposed the mutual influence and trade-off relationship between various scale structures.In addition,the challenges and outlooks for improving the dense storage and volumetric performance of carbon-based supercapacitors are analyzed,which can provide feasible technical reference and guidance for the design and manufacture of dense carbon-based electrode materials.
基金financially supported by the National Natural Science Foundation of China(Nos.52175284 and 52474396)the National Key Research and Development Program of China(No.2022YFB3404201)。
文摘High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress arouses the deformation of large integrated die-castings.Herein,the development of non-heat treatment Al alloys is becoming the hot topic.In addition,HPDC contains externally solidified crystals(ESCs),which are detrimental to the mechanical properties of castings.To achieve high strength and toughness of non-heat treatment die-casting Al-Si alloy,we used AlSi9Mn alloy as matrix with the introduction of Zr,Ti,Nb,and Ce.Their influences on ESCs and mechanical properties were systematically investigated through three-dimensional reconstruction and thermodynamic simulation.Our results reveal that the addition of Ti increased ESCs'size and porosity,while the introduction of Nb refined ESCs and decreased porosity.Meanwhile,large-sized Al_3(Zr,Ti)phases formed and degraded the mechanical properties.Subsequent introduction of Ce resulted in the poisoning effect and reduced mechanical properties.
基金financially supported by the National Natural Science Foundation of China (No. 52175284)the State Key Lab of Advanced Metals and Materials (2021-ZD08)technical support of BL13W1 Beamline in Shanghai Synchrotron Radiation Facility (SSRF) and Gaomi Xiangyu company
文摘3D reconstruction and 2D observation were conducted to characterize the microstructure of the castings produced through high pressure die casting with different parameters.Our results indicate that shrinkage pores generally co-existed with externally solidified crystals(ESCs).In specimen produced without fast slow shot speed,big net-shrinkage pores accompanied with ESCs were found in the center of the specimen.When the casting pressurization was introduced,the shrinkage pores gathered to the specimen center and became much less due to the optimization of melt feeding.Much more porosity was found near the gate rather than in the middle of the rod bar,especially gas pores.Thefilling process simulation reveals that the middle position of the bars wasfirstlyfilled and followed by the near gate position accompanied with one intense turbulentflow.
基金supported by the National Natural Science Foundation of China (No. 51701010)the Beijing Jiaotong University Foundation for youth scientists (No. No.2017RC013)+1 种基金the Project National United Engineering Laboratory for Advanced Bearing Tribology-Henan University of Science and Technology (No. 201805)the Beijing Government Funds for the Constructive Project of Central Universities (No. 353139535)
文摘The dry sliding wear behavior of Ti_2AlC reinforced AZ91 magnesium composites was investigated at sliding velocity of 0.5 m/s under loads of 10, 20, 40 and 80 N using pin-on-disk configuration against a Cr15 steel disc. Wear rates and friction coefficients were registered during wear tests. Worn tracks and wear debris were examined by scanning electron microscopy, energy dispersive X-ray spectrometry and transmission electron microscopy in order to obtain the wear mechanisms of the studied materials. The main mechanisms were characterized as the magnesium matrix oxidation and self-lubrication of Ti_2AlC MAX phase. In all conditions, the composites exhibit superior wear resistance and self-lubricated ability than the AZ91 Mg alloy. In addition, the anisotropic mechanisms in tribological properties of textured Ti_2AlC-Mg composites were confirmed and discussed.
基金financially supported by the National Natural Science Foundation of China(No.51571039)
文摘The microstructure, fracture morphology and mechanical properties of Al-10 Si alloy modified with Al-5 Ti were analyzed and tested by optical microscopy, scanning electron microscopy, and universal electronic testing machine. Compared with unmodified Al-10 Si alloy, the area fraction of α-Al phase in Al-10 Si alloy modified at 740 °C increased first and then decreased with the increase of added amounts of Al-5 Ti, and reached the maximum when the added amount of Al-5 Ti was 0.5 wt.%. When the modification temperature increased from 700 to 740 °C with Al-5 Ti being fixed at 0.5 wt.%, α-Al dendrites were refined obviously and the area fraction remarkably increased. Compared with unmodified Al-10 Si alloy, the ultimate tensile strength and elongation of the alloy modified at 740 °C with 0.5 wt.% Al-5 Ti increased by 9% and 49%, respectively. The fracture surface of modified alloy predominantly exhibited ductile fracture.
基金financially supported by the Fundamental Research Funds for the Central Universities (M22JBMC0060)the National Natural Science Foundation of China (No.52175284)the State Key Lab of Advanced Metals and Materials (No.2021-ZD08)。
文摘To understand the relationship between the process-microstructure-mechanical properties of the high-pressure die-casting(HPDC) AE44 magnesium alloy, 3D reconstruction and 2D characterization were carried out on the HPDC castings produced with different process parameters(low slow-shot speed, fast slow-shot speed, solidification pressure). Microstructural characterization revealed that the formation of shrinkage pores are closely related to ESCs, which were mainly controlled by the low slow-shot speed in shot sleeve(ESCs growth time) and fast slow-shot speed into the die cavity(distribution of ESCs). In addition, solidification pressure can significantly reduce the shrinkage porosity in the center by improving the feeding capacity of liquid metal. Tensile fracture revealed that the tearing ridge is mainly evolved from the slip band of ESCs. The quantity and distribution of ESCs determine the fracture mode of castings. The relationship between mechanical properties of castings and the morphology of ESCs and porosity is also statistically discussed.
基金financially supported by the Key Program of China on Biomedical Materials Research and Tissue and Organ Replacement(Nos.2016YFC1101804 and 2016YFC1100604)the Shenyang Key R&D and Technology Transfer Program(No.Z18-0-027)+2 种基金the National Natural Science Foundation of China(No.51801220)the Top-notch Academic Programs Project of Jiangsu Higher Education Institutions(TAPP)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘Effects of equal channel angular pressing(ECAP)extrusion on the microstructure,mechanical properties and biodegradability of Mg–2Zn–xGd–0.5Zr(x=0,0.5,1,2 wt%)alloys were studied in this work.Microstructure analysis,tensile test at ambient temperature,immersion test and electrochemical test in Hank’s solution were carried out.The results showed that Gd could further enhance the grain refinement during the ECAP extrusion.Both Gd addition and ECAP extrusion could improve the mechanical properties of the alloys,and the extrusion played the dominant role.Minor addition of Gd(0.5–1 wt%)could obviously enhance the corrosion resistance of the alloys.To some extent,ECAP extrusion improved the corrosion resistance of the alloys due to the change of second phases distribution and the refinement of grains.Further increase in extrusion pass was detrimental to the improvement of the corrosion resistance as a result of increment of the grain boundaries.
基金financially supported by the National Natural Science Foundation of China(No.52175284)the State Key Lab of Advanced Metals and Materials(No.2021-ZD08)the Beijing Government Funds for the Cons tructive Project of Central Universities(No.353139535)。
文摘Magnesium composites reinforced by N-deficient Ti_(2)AlN MAX phase were first fabricated by non-pressure infiltration of Mg into three-dimensional(3D)co-continuous porous Ti_(2)AlN_(x)(x=0.9,1.0)preforms.The relationship between their mechanical properties and micro-structure is discussed with the assessment of 2D and 3D characterization.X-ray diffraction(XRD)and scanning electron microscopy detected no impurities.The 3D reconstruction shows that the uniformly distributed pores in Ti_(2)AlN_(x) preforms are interconnected,which act as infiltra-tion tunnels for the melt Mg.The compressive yield strength and microhardness of Ti_(2)AlN_(0.9)/Mg are 353 MPa and 1.12 GPa,respectively,which are 8.55%and 6.67%lower than those of Ti_(2)AlN/Mg,respectively.The typical delamination and kink band occurred in Ti_(2)AlN_(x) under compressive and Vickers hardness(V_(H))tests.Owing to the continuous skeleton structure and strong interfacial bonding strength,the crack ini-tiated in Ti_(2)AlN_(x) was blocked by the plastic Mg matrix.This suggests the possibility of regulating the mechanical performance of Ti_(2)AlN/Mg composites by controlling the N vacancy and the hierarchical structure of Ti_(2)AlN skeleton.
基金financially supported by the National Natural Science Foundation of China(No.52175284)the State Key Lab of Advanced Metals and Materials in University of Science and Technology Beijing(No.2021-ZD08)。
文摘To clarify the relationship between externally solidified crystals(ESCs)and other defects,e.g.,defect bands and pores,two dimensional(2D)and three dimensional(3D)characterization methods were adopted to analyze castings produced using a modified ingate system equipped with and without an ESC collector.The reduction of ESCs strongly reduced defect band width and shrinkage pore quantity.By reducing the quantity and size of ESCs,net-shrinkage pores were transformed into isolated island-shrinkage pores.We determined via statistical analysis that the mechanical properties of high pressure die castings were strongly related to the size and fraction of the ESCs rather than porosity volume.The reduction of ESCs also caused tensile transgranular fracture modes to transform into intergranular fracture modes.Additionally,casting pressurization strongly reduced pore morphology,volume,and size.
基金Project(51571039) supported by the National Natural Science Foundation of China
文摘The solidification microstructure,fracture morphologies,and mechanical properties of an Al-18Si alloy and alloys modified with Al-5Ti and Al-3P master alloys were investigated using an optical microscope,scanning electron microscope,and an electronic universal testing machine.The results show that additions of Al-5Ti and Al-3P have significant effects on the size and area fraction of the primary Si and the mechanical properties of the Al-18Si alloy.Compared to the Al-18Si alloy modified with 0.6 wt%Al-5Ti at 850°C,when the Al-18Si alloy was modified with 0.3 wt%Al-5Ti and 0.5 wt%Al-3P at the same temperature,the average size of the primary Si decreased from 39 to 14μm and the area fraction increased from 9.5%to 11.6%.The biggest influencing factor on the tensile strength and elongation of the Al-18Si alloy is the addition of Al-3P,followed by the modification temperature and the addition of Al-5Ti.At a modification temperature of 850°C,the tensile strength and elongation of the Al-18Si alloy modified with 0.3 wt%Al-5Ti+0.5 wt%Al-3P increased by 19.6%and 88.6%,respectively compared to that of the Al-18Si alloy modified with 0.6 wt%Al-5Ti.
文摘A series of Mg_(2-x)Nd_xNi (x=0.05, 0.1, 0.2, 0.3) alloys and Mg_(1.95)RE_(0.05)Ni (RE= La, Ce, Pr, Nd, Y) ternary alloys were prepared by ball milling of mixted powder of Mg,Ni,RE and sintering under the protection of argon. XRD analysis shows that Mg_(2-x)Nd_xNi (x=0.05, 0.1) and Mg_(1.95)RE_(0.05)Ni consist of single phase with the same crystal structure as Mg_2Ni. While three-phase alloys including Mg_2Ni, NdNi and NdMgNi_4 were formed in Mg_(1.8)Nd_(0.2)Ni and Mg_(1.7)Nd_(0.3)Ni alloys respectively. The lattice constants of Mg_2Ni in those ternary alloys were calculated. The decomposition of Mg_2Ni occurs in the milling process of Mg_2Ni and Mg_(1.95)RE_(0.05) Ni alloys respectively. For the latter, another earlier reaction occurs in milling process, which means that atoms of RE are separated from crystal structure of Mg_2Ni and form relevant oxides by combination with oxygen existed in argon atmosphere.
基金supported by the Beijing Natural Science Foundation(Grant No.3232011)the Joint Fund of the Ministry of Education for Equipment Pre-research(Grant No.8091B02022306)the National Natural Science Foundation of China(Grant No.52175284).
文摘To investigate the influences of Cr_(2)AlC mass fraction and supersonic plasma spraying process on the microstructure and mechanical properties of Cr_(2)AlC reinforced 410 stainless steel composite coatings,the coatings containing different mass fractions of Cr_(2)AlC were prepared and investigated.The composite coating exhibited low porosity and high adhesion strength.The addition of Cr_(2)AlC significantly enhanced the hardness of the composite coatings through particle strengthening.However,when the mass fraction of Cr_(2)AlC was 20%,the aggregation of Cr_(2)AlC resulted in a strong decrease in the coating preparation efficiency,as well as a decline in adhesion strength.In the supersonic plasma spraying process,the Ar flow rate mainly influenced the flight velocity of the particles,while the H_(2) flow rate and the current mainly affected the temperature of the plasma torch.Consequently,all of them influenced the melting degree of particles and the quality of the coating.The lowest porosity and the highest hardness and adhesion strength could be obtained when the Ar flow rate is 125 L/min,the H_(2) flow rate is 25 L/min,and the current is 385 A.
基金supported by the National Natural Science Foundation of China (No. 52175284, 52130509 and 52075543)the State Key Lab of Advanced Metmals and Materials (2021-ZD08)。
文摘In recent decades, the demand for lightweight and high specific strength materials brings about the development of magnesium matrix composites. Different from some traditional binary ceramic particles, such as SiC, Al_(2)O_(3), the novel ternary nano-layered M_(n+1)AX_(n)(MAX)phase carbide or nitride ceramics exhibit metal-like properties and self-lubricate capacity(where “M” is an early transition metal, “A” belongs to the group A element, “X” is C or/and N, and n = 1–3). Ti_(2)AlC, as the representative of the MAX phase, was interestingly introduced into the magnesium matrix. Layered Ti_(2)AlC MAX phased reinforced AZ91D magnesium composites manufactured through the stir casting exhibit sufficient deformation capacity due to unique deformation behaviors of MAX, namely delamination and the formation of kinking band. Further,the Ti_(2)AlC-AZ91D composites exhibit a distinctive characteristic in strengthening mechanism, damping mechanism and tribological capacity due to the other special properties of MAX phase, such as self-lubricated property. Accordingly, to give a comprehensive understanding, we overviewed the fabrication process, microstructural characterization, mechanical properties, damping property and tribological capacity on these composites. In order to understand the A-site effect in MAX phase on the microstructure, we introduced another representative Ti_(3)SiC_(2)MAX phase to explain the interfacial evolution. In addition, due to the high aspect ratio of MAX, MAX particles could be orientationally regulated in Mg matrix by plastic deformation such as hot extrusion. Herein, we discussed the anisotropic mechanical and physical properties of the textured composites produced by hot extrusion. Moreover, the potential applications and future development trends of MAX phases reinforced magnesium matrix composites were also given and prospected.
基金supported by Beijing Natural Science Foundation(3232011)the Pre-Research Program in National 14th Five-Year Plan(80923010304)the National Natural Science Foundation of China(52130509).
文摘In order to enhance the ablation-resistant performance of stainless-steel conductive rails,Mo coating,410 stainless steel coating and 15 wt%Cr_(2)AlIC particles reinforced 410 stainless steel composite coating were prepared and evaluated.Different from the weak interfacial strength caused by the dissimilar metals between Mo and steel rails,410 stainless steel coating has better interfacial contact with steel rails.The introduction of Cr_(2)AlC into 410 stainless steels further strengthened the mechanical properties of coating by alloy strengthening effect and particle strengthening effect,as the decomposition of Cr_(2)AlC into nano CrC particles is accompanied with the diffusion of Al atoms into 410 stainless steels.It was found that the composite coating can still resist arc erosion at 150 A current,as a dense oxide film formed during the ablation process and the decomposition of Cr_(2)AlC contributed to the heat absorption.
文摘The structure, microstructure, thermal stability and hydriding characteristics of amorphous La0.95-Mg2.05Ni9 have been investigated with differential thermal analysis, X-ray diffraction, scanning electron microscopy and battery test. It is found that the increase in mechanical alloying time leads to enhancement in thermal stabilities of amorphous La0.95Mg2.05Ni9 alloy. The amorphous alloy has good charge/discharge ability at room temperature(430 mA·h·g-1), but the discharge capacity decreases seriously during cycling tests due to the crystallization of amorphous and oxidization of magnesium on the particle surface in alkaline aqueous solution.
基金financially supported by the National Training Programs of Innovation and Entrepreneurship for Undergraduates and the State Key Lab of Advanced Metals and Materials(No.2021-ZD08)the National Natural Science Foundation of China(No.52175284)。
文摘3D reconstruction was adopted to characterize the microstructural morphologies of Mg-3.0Nd-0.3Zn-0.6Zr alloy castings produced by high pressure die casting(HPDC)processes with different parameters,including low slow-shot speed,solidification pressurization and fast slow-shot speed.At low slow-shot speeds of 0.1 m·s^(-1),0.2 m·s^(-1) and 0.3 m·s^(-1),the porosity is concentrated in the center of the castings with one spiral staggered shape along the liquid flow direction.The porosity volume simultaneously decreases with the reduction of quantity and size of externally solidified crystals(ESCs),while the shrinkage pores become more and more dispersed with the increasing low slow-shot speed.Pressurization not only reduces the porosity volume due to the improvement of feeding ability,but also transformes the center gathered porosity into one layer-by-layer distribution form.Accompanied with the increasing fast slow-shot speed,the central porosity dramatically decreases and transforms into a large-scale spiral staggered shape along the liquid flow direction.However,the porosity is much more dispersed when the speed is increased from 2 m·s^(-1) to 3 m·s^(-1).
基金Fundamental Research Funds for the Central Universities,Grant/Award Numbers:2023YJS061,2023JBZY019。
文摘Carbonitride MXenes,such as Ti_(3)CNT_(x),Ti_(2)C_(0.5)N_(0.5)T_(x),and Ti_(4)(C_(0.2)N_(0.8))_(3)T_(x),have attracted much interest in the large family of two-dimensional(2D)nanomaterials.Like their carbide MXene counterparts,the nanolayered structure and functional groups endow carbonitride MXenes with an attractive combination of physical and chemical properties.More interestingly,the replacement of C by N changes the lattice parameters and electron distribution of carbonitride MXenes due to the greater electronegativity of N as compared to C,thus resulting in significantly enhanced functional properties.This paper reviews the development of carbonitride MXenes,the preparation of 2D carbonitride MXenes,and the current understanding of the microstructure,electronic structure,and functional properties of carbonitride MXenes.In addition,applications,especially in energy storage,sensors,catalysts,electromagnetic wave shielding and absorption,fillers,and environmental and biomedical fields,are summarized.Finally,their current limitations and future opportunities are presented.
基金supported by the National Natural Science Foundation of China(No.52474396 and 52175284)the National Key Research and Development Program of China(Grant No.2022YFB3404201)。
文摘In order to investigate the effect of die wall thickness on morphologies of defect band,a stepped mold with a wall thickness of 5 mm,4 mm,3 mm,2 mm,and 1 mm was designed to carry out high pressure die casting experiments with AlSi10 MgMn alloy.For castings with wall thickness of 2-4 mm,the ratio of the mean defect band width(w)and mean grain size(d)in the defect band(w/d)ranges 7-18,while it increases to 24.47 for the 5 mm-thick casting.This difference is related with the filling speed and the distribution of externally solidified crystals(ESCs).The mold flow analysis indicates that the filling speed decreases from 25.41 m·s^(-1)to 11.07 m·s^(-1)when wall thickness increases from 2 mm to 5 mm.Due to the decreasing filling speed along the wall thickness,ESCs gradually diffuse from the center to the defect band,which keep the shear strength in the defect band at a high-level during filling.Meanwhile,the shear strength generated during the filling also decreases as the shear rate drops.Finally,the defect bands in the 5 mm-thick region become widen and indistinct,and the porosity is as high as 5.25%.
基金supported by the National Natural Science Foundation of China(No.U2469213)the Beijing Natural Science Foundation(Nos.2252051 and 2234093)+1 种基金the Fundamental Research Funds for the Central Universities(No.2022XKRC016),the Hebei Natural Science Foundation(No.E2024105074)the Research Fund for Commercialization of Major Scientific and Technological Achievements of Hebei Province(No.22281006Z and 23267601Z).
文摘Owing to their unique mechanical properties and excellent thermal and chemical stability,Al_(2)O_(3)nanofibers are highly desirable for practical applications as functional and structural building blocks.However,the scalable production of Al,O3 nanofibers has always faced significant challenges,namely,high cost and complicated processes.This work explores a feasible and straightforward dealloying strategy for the batch synthesis of Al_(2)O_(3)nanofibers.When a binary Al-Li alloy is immersed in alcohol,the alkoxide nanofibers spontaneously grow following the mechanism of boundary strain energy minimization.The results indicate that by dissolving Li in Al-Li alloys,the continuous exposure of a fresh Al surface renders the remaining unsaturated bonds of Al sufficiently reactive,providing the conditions for the subsequent reaction with alcohols and thus inducing the formation of alcohol-aluminum compounds.These nanofibers were calcined in air to obtain monocrystallineα-Al_(2)O_(3)and polycrystalline y-Al_(2)O_(3)nanofibers.We investigated the evolution of the alloy into nanofibers in dry ethanol and the influence of different Al-Li alloy compositions and calcination temperatures on the crystal structure and morphology of the resulting Al_(2)O_(3)nanofibers.The study revealed thatγ-Al_(2)O_(3)with diameters of approximately 50-80 nm and lengths of approximately 20-30μm andα-Al_(2)O_(3)with diameters of approximately 100-150 nm and lengths of approximately 15-20μm were successfully prepared via this technique route.The approach reported in this study is anticipated to open new paths for the efficient and economical synthesis of advanced metal oxide nanofibers and lay the foundation for their extensive application in current industrial sectors.
基金supported by the Fundamental Research Funds for the Central Universities(Grant No.2022YJS088)the National Natural Science Foundation of China(Grant No.52275171).
文摘Two-dimensional(2D)MoB metal borides(MoB MBene)have attracted much attention due to their fascinating properties and functional applications.So far,work on the synthesis of 2D MoB nanosheets by acid or alkaline etching of MoAlB has not been very successful.It has been proposed that the 2D MoB MBene may be fabricated by chemical etching of a Mo_(2)AlB_(2) precursor,but further investigations were not performed possibly due to the difficult preparation of the metastable Mo_(2)AlB_(2) compound at high temperatures by solid-state reactions.Here,we report on the successful synthesis of the Mo_(2)AlB_(2) compound and 2D MoB nanosheets by the deintercalation of Al from MoAlB through a ZnCl_(2) molten salt etching approach at relatively low temperatures.The influence of etching temperature,etching time,and starting mixtures on the formation of desirable phases have been investigated.A pure Mo_(2)AlB_(2) compound was synthesized at temperatures below 600℃,while the 2D MoB MBene nanosheets were obtained at 700℃through the molten salt etching of MoAlB.In addition,the present work further confirms that the MoB MBene can be prepared by etching the as-synthesized Mo_(2)AlB_(2) precursor in LiF–HCl solution.Our work demonstrates that the molten salt etching is an effective method to prepare 2D MoB MBene.
