The study aims to investigate the carbonated water erosion mechanism of lining concrete in tunnels traversing karst environment and enhance its resistance.In this study,dynamic carbonated water erosion was simulated t...The study aims to investigate the carbonated water erosion mechanism of lining concrete in tunnels traversing karst environment and enhance its resistance.In this study,dynamic carbonated water erosion was simulated to assess erosion depth,microstructure,phase migrations,and pore structure in various tunnel lining cement-based materials.Additionally,Ca^(2+)leaching was analyzed,and impact of Ca/Si molar ratio in hydration products on erosion resistance was discussed by thermodynamic calculations.The results indicate that carbonated water erosion caused rough and porous surface on specimens,with reduced portlandite and CaCO_(3) content,increased porosity,and an enlargement of pore size.The thermodynamic calculations indicate that the erosion is spontaneous,driven by physical dissolution and chemical reactions dominated by Gibbs free energy.And the erosion reactions proceed more spontaneously and extensively when Ca/Si molar ratio in hydration products was higher.Therefore,cement-based materials with higher portlandite content exhibit weaker erosion resistance.Model-building concrete,with C-S-H gel and portlandite as primary hydration products,has greater erosion susceptibility than shotcrete with ettringite as main hydration product.Moreover,adding silicon-rich mineral admixtures can enhance the erosion resistance.This research offers theory and tech insights to boost cement-based material resistance against carbonated water erosion in karst tunnel engineering.展开更多
The design and synthesis of a novel π-conjugated fiuorescent framework by external ligand-assisted C-H olefination of heterocycles with excellent regioselectivity and broad substrate scope are reported herein.These n...The design and synthesis of a novel π-conjugated fiuorescent framework by external ligand-assisted C-H olefination of heterocycles with excellent regioselectivity and broad substrate scope are reported herein.These novel fiuorescent materials could present full-color-tunable emissions with large Stokes shifts. Furthermore, the protocol provides an opportunity to rapidly screen novel organic single-molecule whitelight materials with high fiuorescence quantum yields. The robust organic and low-cost white lightemitting diodes could rapidly be fabricated using the white-light-emitting material. Experimental data and theoretical calculations indicate that in the white-light dual emission the relatively short wavelength from high-lying singlet state emission and the relatively long wavelength from low-lying singlet state emission. The anti-Kasha dual-emission systems will provide a foundation for the development and application of organic single-molecule white light materials, effectively promoting the development and innovation of luminescent materials. In addition, this method demonstrated its potential application in the synthesis of new near-infrared(NIR) fiuorescence materials with large Stokes shifts based on the olefination of heterocycles.展开更多
While silicon/carbon(Si/C)is considered one of the most promising anode materials for the next generation of high-energy lithium-ion batteries(LIBs),the industrialization of Si/C anodes is hampered by high-cost and lo...While silicon/carbon(Si/C)is considered one of the most promising anode materials for the next generation of high-energy lithium-ion batteries(LIBs),the industrialization of Si/C anodes is hampered by high-cost and low product yield.Herein,a high-yield strategy is developed in which photovoltaic waste silicon is converted to cost-effective graphitic Si/C composites(G-Si@C)for LIBs.The introduction of a binder improves the dispersion and compatibility of silicon and graphite,enhances particle sphericity,and significantly reduces the loss rate of the spray prilling process(from about 25%to 5%).As an LIB anode,the fabricated G-Si@C composites exhibit a capacity of 605 mAh g^(-1) after 1200 cycles.The cost of manufacturing Si/C anode materials has been reduced to approximately$7.47 kg^(-1),which is close to that of commercial graphite anode materials($5.0 kg^(-1)),and significantly lower than commercial Si/C materials(ca.$20.74 kg^(-1)).Moreover,the G-Si@C material provides approximately 81.0 Ah/$of capacity,which exceeds the current best commercial graphite anodes(70.0 Ah/$)and Si/C anodes(48.2 Ah/$).The successful implementation of this pathway will significantly promote the industrialization of high-energydensity Si/C anode materials.展开更多
Tin dioxide(SnO_(2))with a high theoretical specific capacity of 1494 mAh g^(-1)is a promising candidate anode material for lithium storage.However,the shortcomings of serious volume expansion and low conductivity lim...Tin dioxide(SnO_(2))with a high theoretical specific capacity of 1494 mAh g^(-1)is a promising candidate anode material for lithium storage.However,the shortcomings of serious volume expansion and low conductivity limit its wide application.Herein,coaxial nano-multilayered C/SnO_(2)/TiO_(2)composites were fabricated via layerby-layer self-assembly of TiO_(2)and SnO_(2)-gel layers on the natural cellulose filter paper,followed by thermal treatment under a nitrogen atmosphere.Through engineering design of the assembly process,the optimal C/SinO_(2)/TiO_(2)composite features five alternating SnO_(2)and TiO_(2)nanolayers,with TiO_(2)as the outside shell(denoted as C/TSTST).This unique structure endows the C/TSTST with excellent structural stability and electrochemical kinetics,making it a high-performance anode for lithium-ion batteries(LIBs).The C/TSTST composite delivers a high reversible capacity of 676 mAh g^(-1)at 0.1 A g^(-1)after 200 cycles and retains a capacity of 504 mAh g^(-1)at 1.0 A g^(-1),which can be recovered to 781 mAh g^(-1)at 0.1 A g^(-1)The significantly enhanced electrochemical performance is attributed to the hierarchical hybrid structure,where the carbon core combined with coaxial TiO_(2)nanolayers serves as a structural scaffold,ameliorating volume change of SnO_(2)while creating abundant interfacial defects for enhanced lithium storage and rapid charge transport.These findings are further demonstrated by the density functional theory(DFT)calculations.This work provides an efficient strategy for designing coaxial nano-multilayered transition metal oxide-related electrode materials,offering new insights into high-performance LIBs anodes.展开更多
The oilseed cake, vetch, rapeseed straw, wheat straw and corn straw were buried in tobacco-planted soil. The decomposition rates, the variation of active organic C and N contents in the residues and the relationship b...The oilseed cake, vetch, rapeseed straw, wheat straw and corn straw were buried in tobacco-planted soil. The decomposition rates, the variation of active organic C and N contents in the residues and the relationship between active organic C and N contents and decomposition rate were investigated. The results showed the decomposition rates of different organic materials were all high in the early period and then low in the late period. Among the organic materials, the decomposition rates ranked as oilseed cake 〉 vetch 〉 wheat straw and rapeseed straw 〉 corn straw. The decomposition rate was positively related to total N content （P〈0.01）, but was negatively related to the active organic C/N ratio （P〈0.01）. However, there was no significant relationship between decomposition ratio and active organic C content. With the proceeding of decomposition, the active organic C content and the total N content in rapeseed straw, vetch, wheat straw and corn straw all trended to increase, but the active organic C/N ratio trended to decrease. However, the variation of active organic C content, total N content and active organic C/N ratio in oilseed cake was on the contrary.展开更多
The LiMnPO4/C composite material was synthesized via a sol-gel method based on the citric acid. The X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical performance tests were adopted to...The LiMnPO4/C composite material was synthesized via a sol-gel method based on the citric acid. The X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical performance tests were adopted to characterize the properties of LiMnPO4/C. The XRD studies show that the pure olivine phase LiMnPO4 can be obtained at a low temperature of 500 °C. The SEM analyses illustrate that the citric acid used as the chelating reagent and carbon source can restrain the particle size of LiMnPO4/C well. The LiMnPO4/C sample synthesized at 500 °C for 10 h performs the highest initial discharge capacity of 122.6 mA-h/g, retaining 112.4 mA-h/g over 30 cycles at 0.05C rate. The citric acid based sol-gel method is favor to obtain the high electrochemical performance of LiMnPO4/C.展开更多
Silicon/flake graphite/carbon （Si/FG/C） composites were synthesized with different dispersants via spray drying and subsequent pyrolysis, and effects of dispersants on the characteristics of the composites were inve...Silicon/flake graphite/carbon （Si/FG/C） composites were synthesized with different dispersants via spray drying and subsequent pyrolysis, and effects of dispersants on the characteristics of the composites were investigated. The structure and properties of the composites were determined by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and electrochemical measurements. The results show that samples have silicon/flake graphite/amorphous carbon composite structure, good spherical appearances, and better electrochemical performance than pure nano-Si and FG/C composites. Compared with the Si/FG/C composite using washing powder as dispersant, the Si/FG/C composite using sodium dodecyl benzene sulfonate （SDBS） as dispersant has better electrochemical performance with a reversible capacity of 602.68 mA·h/g, and a capacity retention ratio of 91.58 % after 20 cycles.展开更多
In order to enhance electrochemical properties of LiFePO4 （LFP） cathode materials, spherical porous nano/micro structured LFP/C cathode materials were synthesized by spray drying, followed by calcination. The result...In order to enhance electrochemical properties of LiFePO4 （LFP） cathode materials, spherical porous nano/micro structured LFP/C cathode materials were synthesized by spray drying, followed by calcination. The results show that the spherical precursors with the sizes of 0.5-5 μm can be completely converted to LFP/C when the calcination temperature is higher than 500 ℃. The LFP/C microspheres obtained at calcination temperature of 700 ℃ are composed of numerous particles with sizes of -20 nm, and have well-developed interconnected pore structure and large specific surface area of 28.77 mE/g. The specific discharge capacities of the LFP/C obtained at 700 ℃ are 162.43, 154.35 and 144.03 mA.h/g at 0.5C, 1C and 2C, respectively. Meanwhile, the capacity retentions can reach up to 100% after 50 cycles. The improved electrochemical properties of the materials are ascribed to a small Li＋ diffusion resistance and special structure of LFP/C microspheres.展开更多
Researching for interphase materials that can protect SiC fibers from oxygen and water vapor attacks has become one of the most important issues for the applications of SiC_f/SiC composites in high-temperature combust...Researching for interphase materials that can protect SiC fibers from oxygen and water vapor attacks has become one of the most important issues for the applications of SiC_f/SiC composites in high-temperature combustion environment. However, such kinds of interphase materials are not available yet. Herein,we report theoretically predicted properties of two promising interphase materials Y_5Si_3 C and Y_3Si_2C_2.Although crystallizing in different structures, they share the common features of layered structure,anisotropic chemical bonding, anisotropic electrical and mechanical properties, and low shear deformation resistance. The bulk moduli for Y_5Si_3C and Y_3Si_2C_2 are 78 and 93 GPa, respectively; while their shear moduli are 52 and 50GPa, respectively. The maximum to minimum Young's modulus ratios are1.44 for Y_5Si_3C and 3.27 for Y_3Si_2C_2. Based on the low shear deformation resistance and low Pugh's ratios(G/B = 0.666 forY_5Si_3C and 0.537 for Y_3Si_2C_2; G: shear modulus; B: bulk modulus), they are predicted as damage tolerant and soft ceramics with predicted Vickers hardness of 9.6 and 6.9 GPa, respectively.The cleavage plane and possible slip systems are(000 l) and(0001)[1120] and(1010)[0001] forY_5Si_3C,and those for Y_3Si_2C_2 are {h00} and(010)[101]. Since the oxidation products are water-vapor resistant Y2 Si2 O7, Y2 SiO5 and/or Y_2 O_3 upon oxidation, and the volume expansions are ca 140% and ca 26% for Y_5Si_3C and Y_3Si_2C_2, they are expected to seal the interfacial cracks in SiC_f/SiC composites. The unique combination of easy cleavage, low shear deformation resistance, volume expansions upon oxidation, and the resistance of the oxidation products to water vapor attack warrant them promising as interphase materials of SiC_f/SiC composites for water-vapor laden environment applications.展开更多
Spherical LiFePO4 and LiFePO4/C composite powders for lithium ion batteries were synthesized by a novel processing route of co-precipitation and subsequent calcinations in a nitrogen and hydrogen atmosphere. The precu...Spherical LiFePO4 and LiFePO4/C composite powders for lithium ion batteries were synthesized by a novel processing route of co-precipitation and subsequent calcinations in a nitrogen and hydrogen atmosphere. The precursors of LiFePO4, LiFePO4/C composite and the resultant products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and the electrochemical performances were investigated by galvanostatic charge and discharge tests. The precursors composed of amorphous Fe3(PO4)2·xH2O and crystalline Li3PO4 obtained in the co-precipitation processing have a sphere-like morphology. The spherical LiFePO4 derived from the calcinations of the precursor at 700 ℃ for 10 h in a reduction atmosphere shows a discharge capacity of 119 mAh·g-1 at the C/10 rate, while the LiFePO4/C composite with 10wt.% carbon addition exhibits a discharge capacity of 140 mAh·g-1. The electrochemical performances indicate that the LiFePO4/C composite has a higher specific capacity and a more stable cycling performance than the bare olivine LiFePO4 due to the carbon addition enhancing the electronic conductivity.展开更多
Thermal contact resistance plays a very important role in heat transfer efficiency and thermomechanical coupling response between two materials,and a common method to reduce the thermal contact resistance is to fill a...Thermal contact resistance plays a very important role in heat transfer efficiency and thermomechanical coupling response between two materials,and a common method to reduce the thermal contact resistance is to fill a soft interface material between these two materials.A testing system of high temperature thermal contact resistance based on INSTRON 8874 is established in the present paper,which can achieve 600 C at the interface.Based on this system,the thermal contact resistance between superalloy GH600 material and three-dimensional braid C/C composite material is experimentally investigated,under different interface pressures,interface roughnesses and temperatures,respectively.At the same time,the mechanism of reducing the thermal contact resistance with carbon fiber sheet as interface material is experimentally investigated.Results show that the present testing system is feasible in the experimental research of high temperature thermal contact resistance.展开更多
Data-mining techniques using machine learning are powerful and efficient for materials design, possessing great potential for discovering new materials with good characteristics. Here, this technique has been used on ...Data-mining techniques using machine learning are powerful and efficient for materials design, possessing great potential for discovering new materials with good characteristics. Here, this technique has been used on composition design for La（Fe,Si/Al）（13）-based materials, which are regarded as one of the most promising magnetic refrigerants in practice. Three prediction models are built by using a machine learning algorithm called gradient boosting regression tree（GBRT） to essentially find the correlation between the Curie temperature（TC）, maximum value of magnetic entropy change（（？SM）（max））,and chemical composition, all of which yield high accuracy in the prediction of TC and（？SM）（max）. The performance metric coefficient scores of determination（R^2） for the three models are 0.96, 0.87, and 0.91. These results suggest that all of the models are well-developed predictive models on the challenging issue of generalization ability for untrained data, which can not only provide us with suggestions for real experiments but also help us gain physical insights to find proper composition for further magnetic refrigeration applications.展开更多
Ti3C2Tx,a novel two-dimensional layer material,is widely used as electrode materials of supercapacitor due to its good metal conductivity,redox reaction active surface,and so on.However,there are many challenges to be...Ti3C2Tx,a novel two-dimensional layer material,is widely used as electrode materials of supercapacitor due to its good metal conductivity,redox reaction active surface,and so on.However,there are many challenges to be addressed which impede Ti3C2Tx obtaining the ideal specific capacitance,such as restacking,re-crushing,and oxidation of titanium.Recently,many advances have been proposed to enhance capacitance performance of Ti3C2Tx.In this review,recent strategies for improving specific capacitance are summarized and compared,for example,film formation,surface modification,and composite method.Furthermore,in order to comprehend the mechanism of those efforts,this review analyzes the energy storage performance in different electrolytes and influencing factors.This review is expected to predict redouble research direction of Ti3C2Tx materials in supercapacitors.展开更多
Thermal deformation of aluminum alloy casting materials for manufacturing the tire mold was numerically investigated.The AC7A and AC4C casting material was selected as casting material and the metal casting device was...Thermal deformation of aluminum alloy casting materials for manufacturing the tire mold was numerically investigated.The AC7A and AC4C casting material was selected as casting material and the metal casting device was used in order to manufacture the mold product of automobile tire in the actual industrial field.The temperature distribution and the cooling time of casting materials were numerically calculated by finite element analysis (FEA).Also,the thermal deformation such as displacement and stress distribution was calculated from the temperature results.The thermal deformation was closely related to the temperature difference between the surface and inside of the casting.The numerical analysis results reveal that the thermal deformation of AC7A casting material is higher than that of AC4C casting material.Also,the thermal deformation results at the central part are larger than that on the side of casting because of the shrinkage caused by the cooling speed difference.展开更多
Silicon monoxide(SiO)is considered as a promising anode material for lithium-ion batteries(LIBs)due to its higher capacity and longer cycle life than those of graphite and silicon,respectively.In this study,glucose wa...Silicon monoxide(SiO)is considered as a promising anode material for lithium-ion batteries(LIBs)due to its higher capacity and longer cycle life than those of graphite and silicon,respectively.In this study,glucose was developed as a suitable and inexpensive carbon source to synthesize SiO/C composite with a high performance.In addition,the effects of the calcination temperature and the amount of c arbon source on the electrochemical performance of the SiO/C composite were investigated.The addition of 5 wt%glucose and a calcination temperature of 800℃ demonstrated the optimum conditions for SiO/C synthesis.The resultant SiO/C showed an initial charge capacity of 1259 mAh·g^(-1) and a high initial coulombic efficiency of 71.9%.A charge capacity of 850 mAh·g^(-1) after 100 cycles at 200 mA·g^(-1) was achieved,demonstrating the best value of the SiO/C-based materials.The composition changes of SiO under the calcination temperature played a significant role in the electrochemical performance.Overall,the obtained SiO/C material with a high capacity and good stability is suitable for LIB applications as an anode material.展开更多
The 3D needled C/SiC brake materials modified with graphite were prepared by a combined process of the chemical vapor infiltration,slurry infiltration and liquid silicon infiltration process.The microstructure and fri...The 3D needled C/SiC brake materials modified with graphite were prepared by a combined process of the chemical vapor infiltration,slurry infiltration and liquid silicon infiltration process.The microstructure and frictional properties of the brake materials were investigated.The density and open porosity of the materials as-received were about(2.1±0.1)g/cm3and(5±1)%,respectively.The brake materials were composed of 59%C,39%SiC,and 2%Si(mass fraction).The content of Si in the C/SiC brake materials modified with graphite was far less than that in the C/SiC brake materials without being modified with graphite,and the Si was dispersed.The braking curve of the 3D needled C/SiC modified with graphite was smooth,which can ensure the smooth and comfortable braking.The frictional properties under wet condition of the 3D needled C/SiC modified with graphite showed no fading.And the linear wear rate of the C/SiC modified with graphite was lower than that of the C/SiC unmodified.展开更多
Composites Li1-xVxCryFe1-yPO4/C（x=0.01, 0.02; y = 0.01, 0.02） were synthesized by solid-state reaction method. The influence of the content of doping vanadium and chromium on the structure of Li1-xVxCryFe1-yPO4/C wa...Composites Li1-xVxCryFe1-yPO4/C（x=0.01, 0.02; y = 0.01, 0.02） were synthesized by solid-state reaction method. The influence of the content of doping vanadium and chromium on the structure of Li1-xVxCryFe1-yPO4/C was investigated by XRD, while the morphology of powders was observed by SEM. The investigation of the electrochemical performances showed that the Li0.99V0.01Cr0.02Fe0.98PO4/C material has a higher capacity. At 0.1 C discharging rate, it is capable of delivering reversible specific capacity of 163.8 mAh/g with fairly stable cycleability.展开更多
The mechanical properties of ceramic cutting tool materials can be modified by introducing proper content of nanoparticles or whiskers.However,the process of adding whiskers or nanoparticles has the disadvantages of h...The mechanical properties of ceramic cutting tool materials can be modified by introducing proper content of nanoparticles or whiskers.However,the process of adding whiskers or nanoparticles has the disadvantages of high cost and health hazard as well as the agglomeration;although a new in-situ two-step sintering process can solve the above problems to some extent,yet the problems of low conversion ratio of the raw materials and the abnormal grain growth exist in this process.In this paper,an in-situ one-step synthesis technology is proposed,which means the growth of whiskers or nanoparticles and the sintering of the compact can be accomplished by one time in furnace.A kind of Ti（C,N）-based ceramic cutting tool material synergistically toughened by TiB_2 particles and whiskers is fabricated with this new process.The phase compositions,relationships between microstructure and mechanical properties as well as the toughening mechanisms are analyzed by means of X-ray diffraction（XRD）and scanning electron microscopy（SEM）.The composite which is sintered under a pressure of 32 MPa at a temperature of 1700℃in vacuum holding for 60 min can get the optimal mechanical properties.Its flexural strength,fracture toughness and Vickers hardness are 540 MPa,7.81 MPa·m（1/2）and 20.42 GPa,respectively.The composite has relatively high density,and the in-situ synthesized TiB_2 whiskers have good surface integrity,which is beneficial for the improvement of the fracture toughness.It is concluded that the main toughening mechanisms of the present composite are whiskers pulling-out and crack deflection induced by whiskers,crack bridging by whiskers/particles and multi-scale particles synergistically toughening.This study proposes an in-situ one-step synthesis technology which can be well used for fabricating particles and whiskers synergistically toughened ceramic tool materials.展开更多
Magnesium-based materials have been regarded as promising candidates for large-scale,high-efficiency thermoelectric applications,owing to their excellent dimensionless figure of merit,high abundance,and low cost.In th...Magnesium-based materials have been regarded as promising candidates for large-scale,high-efficiency thermoelectric applications,owing to their excellent dimensionless figure of merit,high abundance,and low cost.In this review,we comprehensively summarize the recent advances of Mg-based thermoelectrics,including Mg_(2)X(X=Si,Ge,Sn),Mg3(Sb,Bi)_(2),andα-MgAgSb,from both material and device level.Their electrical and thermal transport properties are first elucidated based on the crystallographic characteristics,band structures,and phonon dispersions.We then review the optimization strategies towards higher thermoelectric performance,as well as the device applications of Mg-based thermoelectric materials and the related engineering issues.By highlighting the challenges and possible solutions in the end,this review intends to offer perspectives on the future research work to further enhance the performance of Mg-based materials for practical applications.展开更多
基金Project(2021YJ059)supported by the Research Project of China Academy of Railway Sciences。
文摘The study aims to investigate the carbonated water erosion mechanism of lining concrete in tunnels traversing karst environment and enhance its resistance.In this study,dynamic carbonated water erosion was simulated to assess erosion depth,microstructure,phase migrations,and pore structure in various tunnel lining cement-based materials.Additionally,Ca^(2+)leaching was analyzed,and impact of Ca/Si molar ratio in hydration products on erosion resistance was discussed by thermodynamic calculations.The results indicate that carbonated water erosion caused rough and porous surface on specimens,with reduced portlandite and CaCO_(3) content,increased porosity,and an enlargement of pore size.The thermodynamic calculations indicate that the erosion is spontaneous,driven by physical dissolution and chemical reactions dominated by Gibbs free energy.And the erosion reactions proceed more spontaneously and extensively when Ca/Si molar ratio in hydration products was higher.Therefore,cement-based materials with higher portlandite content exhibit weaker erosion resistance.Model-building concrete,with C-S-H gel and portlandite as primary hydration products,has greater erosion susceptibility than shotcrete with ettringite as main hydration product.Moreover,adding silicon-rich mineral admixtures can enhance the erosion resistance.This research offers theory and tech insights to boost cement-based material resistance against carbonated water erosion in karst tunnel engineering.
基金the Fundamental Research Funds for the Central Universities (Nos. 2024CDJXY0022023CDJYGRH-YB17+4 种基金2022CDJXY-025)the Venture & Innovation Support Program for Chongqing Overseas Returnees (No. cx2022061)the Natural Science Foundation of Chongqing (No. CSTB2022NSCQ-MSX1123)the Chongqing Talents: Exceptional Young Talents Project (No. cstc2021ycjh-bgzxm0067)the Hongshen Young Scholars Program from Chongqing University (No. 0247001104426) for financial support。
文摘The design and synthesis of a novel π-conjugated fiuorescent framework by external ligand-assisted C-H olefination of heterocycles with excellent regioselectivity and broad substrate scope are reported herein.These novel fiuorescent materials could present full-color-tunable emissions with large Stokes shifts. Furthermore, the protocol provides an opportunity to rapidly screen novel organic single-molecule whitelight materials with high fiuorescence quantum yields. The robust organic and low-cost white lightemitting diodes could rapidly be fabricated using the white-light-emitting material. Experimental data and theoretical calculations indicate that in the white-light dual emission the relatively short wavelength from high-lying singlet state emission and the relatively long wavelength from low-lying singlet state emission. The anti-Kasha dual-emission systems will provide a foundation for the development and application of organic single-molecule white light materials, effectively promoting the development and innovation of luminescent materials. In addition, this method demonstrated its potential application in the synthesis of new near-infrared(NIR) fiuorescence materials with large Stokes shifts based on the olefination of heterocycles.
基金supported by the Major Science and Technology Projects in Yunnan Province(Grant No.202402AF080005)National Natural Science Foundation of China(Grant Nos.52274408,22468029,52274412)+2 种基金Yunnan Fundamental Research Projects(Grant No.202201AW070014)the Program for Innovative Research Team in University of Ministry of Education of China(Grant No.IRT 17R48)the German Research Foundation(DFG,Project number 501766751).
文摘While silicon/carbon(Si/C)is considered one of the most promising anode materials for the next generation of high-energy lithium-ion batteries(LIBs),the industrialization of Si/C anodes is hampered by high-cost and low product yield.Herein,a high-yield strategy is developed in which photovoltaic waste silicon is converted to cost-effective graphitic Si/C composites(G-Si@C)for LIBs.The introduction of a binder improves the dispersion and compatibility of silicon and graphite,enhances particle sphericity,and significantly reduces the loss rate of the spray prilling process(from about 25%to 5%).As an LIB anode,the fabricated G-Si@C composites exhibit a capacity of 605 mAh g^(-1) after 1200 cycles.The cost of manufacturing Si/C anode materials has been reduced to approximately$7.47 kg^(-1),which is close to that of commercial graphite anode materials($5.0 kg^(-1)),and significantly lower than commercial Si/C materials(ca.$20.74 kg^(-1)).Moreover,the G-Si@C material provides approximately 81.0 Ah/$of capacity,which exceeds the current best commercial graphite anodes(70.0 Ah/$)and Si/C anodes(48.2 Ah/$).The successful implementation of this pathway will significantly promote the industrialization of high-energydensity Si/C anode materials.
基金financially supported by the National Natural Science Foundation of China(Nos.22302133 and 22405161)Central Guidance on Local Science and Technology Development Fund of Hebei Province,China(No.236Z4406G)+5 种基金the Natural Science Foundation of Hebei Education Department,China(No.BJ2025100)the Natural Science Foundation of Hebei Province,China(No.B2021210001)the Natural Science Foundation of Xinjiang Uygur Autonomous Region(No.2024D01A157)the Key R&D Plan of Karamay(No.2024zdyf0009)Karamay Innovation Environment Construction Plan(Innovative Talents)Project(No.2024hjcxrc0029)the Research Foundation of China University of Petroleum-Beijing at Karamay(No.XQZX20240023)
文摘Tin dioxide(SnO_(2))with a high theoretical specific capacity of 1494 mAh g^(-1)is a promising candidate anode material for lithium storage.However,the shortcomings of serious volume expansion and low conductivity limit its wide application.Herein,coaxial nano-multilayered C/SnO_(2)/TiO_(2)composites were fabricated via layerby-layer self-assembly of TiO_(2)and SnO_(2)-gel layers on the natural cellulose filter paper,followed by thermal treatment under a nitrogen atmosphere.Through engineering design of the assembly process,the optimal C/SinO_(2)/TiO_(2)composite features five alternating SnO_(2)and TiO_(2)nanolayers,with TiO_(2)as the outside shell(denoted as C/TSTST).This unique structure endows the C/TSTST with excellent structural stability and electrochemical kinetics,making it a high-performance anode for lithium-ion batteries(LIBs).The C/TSTST composite delivers a high reversible capacity of 676 mAh g^(-1)at 0.1 A g^(-1)after 200 cycles and retains a capacity of 504 mAh g^(-1)at 1.0 A g^(-1),which can be recovered to 781 mAh g^(-1)at 0.1 A g^(-1)The significantly enhanced electrochemical performance is attributed to the hierarchical hybrid structure,where the carbon core combined with coaxial TiO_(2)nanolayers serves as a structural scaffold,ameliorating volume change of SnO_(2)while creating abundant interfacial defects for enhanced lithium storage and rapid charge transport.These findings are further demonstrated by the density functional theory(DFT)calculations.This work provides an efficient strategy for designing coaxial nano-multilayered transition metal oxide-related electrode materials,offering new insights into high-performance LIBs anodes.
基金Supported by National Key Technology Research and Development Program(2012BAD40B02Yunnan Provincial Tobacco Company Plan Project(2012YN48)~~
文摘The oilseed cake, vetch, rapeseed straw, wheat straw and corn straw were buried in tobacco-planted soil. The decomposition rates, the variation of active organic C and N contents in the residues and the relationship between active organic C and N contents and decomposition rate were investigated. The results showed the decomposition rates of different organic materials were all high in the early period and then low in the late period. Among the organic materials, the decomposition rates ranked as oilseed cake 〉 vetch 〉 wheat straw and rapeseed straw 〉 corn straw. The decomposition rate was positively related to total N content （P〈0.01）, but was negatively related to the active organic C/N ratio （P〈0.01）. However, there was no significant relationship between decomposition ratio and active organic C content. With the proceeding of decomposition, the active organic C content and the total N content in rapeseed straw, vetch, wheat straw and corn straw all trended to increase, but the active organic C/N ratio trended to decrease. However, the variation of active organic C content, total N content and active organic C/N ratio in oilseed cake was on the contrary.
基金Project (0991025) supported by Natural Science Foundation of Guangxi, ChinaProject (51164007) supported by the National Natural Science Foundation of ChinaProject (201101ZD008) supported by Educational Commission of Guangxi, China
文摘The LiMnPO4/C composite material was synthesized via a sol-gel method based on the citric acid. The X-ray diffraction （XRD）, scanning electron microscopy （SEM） and electrochemical performance tests were adopted to characterize the properties of LiMnPO4/C. The XRD studies show that the pure olivine phase LiMnPO4 can be obtained at a low temperature of 500 °C. The SEM analyses illustrate that the citric acid used as the chelating reagent and carbon source can restrain the particle size of LiMnPO4/C well. The LiMnPO4/C sample synthesized at 500 °C for 10 h performs the highest initial discharge capacity of 122.6 mA-h/g, retaining 112.4 mA-h/g over 30 cycles at 0.05C rate. The citric acid based sol-gel method is favor to obtain the high electrochemical performance of LiMnPO4/C.
基金Project(2011FJ1005)supported by the Science and Technology Programs of Hunan Province,China
文摘Silicon/flake graphite/carbon （Si/FG/C） composites were synthesized with different dispersants via spray drying and subsequent pyrolysis, and effects of dispersants on the characteristics of the composites were investigated. The structure and properties of the composites were determined by X-ray diffractometry （XRD）, scanning electron microscopy （SEM） and electrochemical measurements. The results show that samples have silicon/flake graphite/amorphous carbon composite structure, good spherical appearances, and better electrochemical performance than pure nano-Si and FG/C composites. Compared with the Si/FG/C composite using washing powder as dispersant, the Si/FG/C composite using sodium dodecyl benzene sulfonate （SDBS） as dispersant has better electrochemical performance with a reversible capacity of 602.68 mA·h/g, and a capacity retention ratio of 91.58 % after 20 cycles.
基金Project(2013AA050901)supported by the National High-tech Research and Development Program of China
文摘In order to enhance electrochemical properties of LiFePO4 （LFP） cathode materials, spherical porous nano/micro structured LFP/C cathode materials were synthesized by spray drying, followed by calcination. The results show that the spherical precursors with the sizes of 0.5-5 μm can be completely converted to LFP/C when the calcination temperature is higher than 500 ℃. The LFP/C microspheres obtained at calcination temperature of 700 ℃ are composed of numerous particles with sizes of -20 nm, and have well-developed interconnected pore structure and large specific surface area of 28.77 mE/g. The specific discharge capacities of the LFP/C obtained at 700 ℃ are 162.43, 154.35 and 144.03 mA.h/g at 0.5C, 1C and 2C, respectively. Meanwhile, the capacity retentions can reach up to 100% after 50 cycles. The improved electrochemical properties of the materials are ascribed to a small Li＋ diffusion resistance and special structure of LFP/C microspheres.
基金supported financially by the National Natural Science Foundation of China (Nos. U1435206 and 51672064)the Beijing Municipal Science & Technology Commission (No. D161100002416001)
文摘Researching for interphase materials that can protect SiC fibers from oxygen and water vapor attacks has become one of the most important issues for the applications of SiC_f/SiC composites in high-temperature combustion environment. However, such kinds of interphase materials are not available yet. Herein,we report theoretically predicted properties of two promising interphase materials Y_5Si_3 C and Y_3Si_2C_2.Although crystallizing in different structures, they share the common features of layered structure,anisotropic chemical bonding, anisotropic electrical and mechanical properties, and low shear deformation resistance. The bulk moduli for Y_5Si_3C and Y_3Si_2C_2 are 78 and 93 GPa, respectively; while their shear moduli are 52 and 50GPa, respectively. The maximum to minimum Young's modulus ratios are1.44 for Y_5Si_3C and 3.27 for Y_3Si_2C_2. Based on the low shear deformation resistance and low Pugh's ratios(G/B = 0.666 forY_5Si_3C and 0.537 for Y_3Si_2C_2; G: shear modulus; B: bulk modulus), they are predicted as damage tolerant and soft ceramics with predicted Vickers hardness of 9.6 and 6.9 GPa, respectively.The cleavage plane and possible slip systems are(000 l) and(0001)[1120] and(1010)[0001] forY_5Si_3C,and those for Y_3Si_2C_2 are {h00} and(010)[101]. Since the oxidation products are water-vapor resistant Y2 Si2 O7, Y2 SiO5 and/or Y_2 O_3 upon oxidation, and the volume expansions are ca 140% and ca 26% for Y_5Si_3C and Y_3Si_2C_2, they are expected to seal the interfacial cracks in SiC_f/SiC composites. The unique combination of easy cleavage, low shear deformation resistance, volume expansions upon oxidation, and the resistance of the oxidation products to water vapor attack warrant them promising as interphase materials of SiC_f/SiC composites for water-vapor laden environment applications.
基金This work was financially supported by the National Natural Science Foundation of China (No.50134020)
文摘Spherical LiFePO4 and LiFePO4/C composite powders for lithium ion batteries were synthesized by a novel processing route of co-precipitation and subsequent calcinations in a nitrogen and hydrogen atmosphere. The precursors of LiFePO4, LiFePO4/C composite and the resultant products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and the electrochemical performances were investigated by galvanostatic charge and discharge tests. The precursors composed of amorphous Fe3(PO4)2·xH2O and crystalline Li3PO4 obtained in the co-precipitation processing have a sphere-like morphology. The spherical LiFePO4 derived from the calcinations of the precursor at 700 ℃ for 10 h in a reduction atmosphere shows a discharge capacity of 119 mAh·g-1 at the C/10 rate, while the LiFePO4/C composite with 10wt.% carbon addition exhibits a discharge capacity of 140 mAh·g-1. The electrochemical performances indicate that the LiFePO4/C composite has a higher specific capacity and a more stable cycling performance than the bare olivine LiFePO4 due to the carbon addition enhancing the electronic conductivity.
基金supported by the Fundamental Research Funds for the Central Universities (FRF-BR-10-007A and FRF-AS-09-001A)the National Natural Science Foundation of China (10872104)
文摘Thermal contact resistance plays a very important role in heat transfer efficiency and thermomechanical coupling response between two materials,and a common method to reduce the thermal contact resistance is to fill a soft interface material between these two materials.A testing system of high temperature thermal contact resistance based on INSTRON 8874 is established in the present paper,which can achieve 600 C at the interface.Based on this system,the thermal contact resistance between superalloy GH600 material and three-dimensional braid C/C composite material is experimentally investigated,under different interface pressures,interface roughnesses and temperatures,respectively.At the same time,the mechanism of reducing the thermal contact resistance with carbon fiber sheet as interface material is experimentally investigated.Results show that the present testing system is feasible in the experimental research of high temperature thermal contact resistance.
基金supported by the National Basic Research Program of China(Grant No.2014CB643702)the National Natural Science Foundation of China(Grant No.51590880)+1 种基金the Knowledge Innovation Project of the Chinese Academy of Sciences(Grant No.KJZD-EW-M05)the National Key Research and Development Program of China(Grant No.2016YFB0700903)
文摘Data-mining techniques using machine learning are powerful and efficient for materials design, possessing great potential for discovering new materials with good characteristics. Here, this technique has been used on composition design for La（Fe,Si/Al）（13）-based materials, which are regarded as one of the most promising magnetic refrigerants in practice. Three prediction models are built by using a machine learning algorithm called gradient boosting regression tree（GBRT） to essentially find the correlation between the Curie temperature（TC）, maximum value of magnetic entropy change（（？SM）（max））,and chemical composition, all of which yield high accuracy in the prediction of TC and（？SM）（max）. The performance metric coefficient scores of determination（R^2） for the three models are 0.96, 0.87, and 0.91. These results suggest that all of the models are well-developed predictive models on the challenging issue of generalization ability for untrained data, which can not only provide us with suggestions for real experiments but also help us gain physical insights to find proper composition for further magnetic refrigeration applications.
基金National Natural Science Foundation of China with Grant No.21905304Natural Science Foundation of Shandong Province(No.ZR2019BEM031)the Fundamental Research Funds for the Central Universities(Nos.18CX02158A and 19CX05001A).
文摘Ti3C2Tx,a novel two-dimensional layer material,is widely used as electrode materials of supercapacitor due to its good metal conductivity,redox reaction active surface,and so on.However,there are many challenges to be addressed which impede Ti3C2Tx obtaining the ideal specific capacitance,such as restacking,re-crushing,and oxidation of titanium.Recently,many advances have been proposed to enhance capacitance performance of Ti3C2Tx.In this review,recent strategies for improving specific capacitance are summarized and compared,for example,film formation,surface modification,and composite method.Furthermore,in order to comprehend the mechanism of those efforts,this review analyzes the energy storage performance in different electrolytes and influencing factors.This review is expected to predict redouble research direction of Ti3C2Tx materials in supercapacitors.
基金Project supported by Research Funds from Chosun University(2009),Korea
文摘Thermal deformation of aluminum alloy casting materials for manufacturing the tire mold was numerically investigated.The AC7A and AC4C casting material was selected as casting material and the metal casting device was used in order to manufacture the mold product of automobile tire in the actual industrial field.The temperature distribution and the cooling time of casting materials were numerically calculated by finite element analysis (FEA).Also,the thermal deformation such as displacement and stress distribution was calculated from the temperature results.The thermal deformation was closely related to the temperature difference between the surface and inside of the casting.The numerical analysis results reveal that the thermal deformation of AC7A casting material is higher than that of AC4C casting material.Also,the thermal deformation results at the central part are larger than that on the side of casting because of the shrinkage caused by the cooling speed difference.
基金financially supported by a Fund Project from Education Department of Jiangxi Province(No.KJLD14008)the Special Fund Project for Graduate Innovation of Nanchang University(No.CX2017005)。
文摘Silicon monoxide(SiO)is considered as a promising anode material for lithium-ion batteries(LIBs)due to its higher capacity and longer cycle life than those of graphite and silicon,respectively.In this study,glucose was developed as a suitable and inexpensive carbon source to synthesize SiO/C composite with a high performance.In addition,the effects of the calcination temperature and the amount of c arbon source on the electrochemical performance of the SiO/C composite were investigated.The addition of 5 wt%glucose and a calcination temperature of 800℃ demonstrated the optimum conditions for SiO/C synthesis.The resultant SiO/C showed an initial charge capacity of 1259 mAh·g^(-1) and a high initial coulombic efficiency of 71.9%.A charge capacity of 850 mAh·g^(-1) after 100 cycles at 200 mA·g^(-1) was achieved,demonstrating the best value of the SiO/C-based materials.The composition changes of SiO under the calcination temperature played a significant role in the electrochemical performance.Overall,the obtained SiO/C material with a high capacity and good stability is suitable for LIB applications as an anode material.
基金Project(46-QP-2009)supported by the Research Fund of State Key Laboratory of Solidification Processing(NWPU),ChinaProject supported by the Program for Changjiang Scholars and Innovative Research Team in Chinese University
文摘The 3D needled C/SiC brake materials modified with graphite were prepared by a combined process of the chemical vapor infiltration,slurry infiltration and liquid silicon infiltration process.The microstructure and frictional properties of the brake materials were investigated.The density and open porosity of the materials as-received were about(2.1±0.1)g/cm3and(5±1)%,respectively.The brake materials were composed of 59%C,39%SiC,and 2%Si(mass fraction).The content of Si in the C/SiC brake materials modified with graphite was far less than that in the C/SiC brake materials without being modified with graphite,and the Si was dispersed.The braking curve of the 3D needled C/SiC modified with graphite was smooth,which can ensure the smooth and comfortable braking.The frictional properties under wet condition of the 3D needled C/SiC modified with graphite showed no fading.And the linear wear rate of the C/SiC modified with graphite was lower than that of the C/SiC unmodified.
文摘Composites Li1-xVxCryFe1-yPO4/C（x=0.01, 0.02; y = 0.01, 0.02） were synthesized by solid-state reaction method. The influence of the content of doping vanadium and chromium on the structure of Li1-xVxCryFe1-yPO4/C was investigated by XRD, while the morphology of powders was observed by SEM. The investigation of the electrochemical performances showed that the Li0.99V0.01Cr0.02Fe0.98PO4/C material has a higher capacity. At 0.1 C discharging rate, it is capable of delivering reversible specific capacity of 163.8 mAh/g with fairly stable cycleability.
基金Supported by National Natural Science Foundation of China(Grant No.51175305)Key Special Project of Numerical Control Machine Tool of China(Grant No.2012ZX04003-051)China Postdoctoral Science Special Foundation(Grant No.2012T50610)
文摘The mechanical properties of ceramic cutting tool materials can be modified by introducing proper content of nanoparticles or whiskers.However,the process of adding whiskers or nanoparticles has the disadvantages of high cost and health hazard as well as the agglomeration;although a new in-situ two-step sintering process can solve the above problems to some extent,yet the problems of low conversion ratio of the raw materials and the abnormal grain growth exist in this process.In this paper,an in-situ one-step synthesis technology is proposed,which means the growth of whiskers or nanoparticles and the sintering of the compact can be accomplished by one time in furnace.A kind of Ti（C,N）-based ceramic cutting tool material synergistically toughened by TiB_2 particles and whiskers is fabricated with this new process.The phase compositions,relationships between microstructure and mechanical properties as well as the toughening mechanisms are analyzed by means of X-ray diffraction（XRD）and scanning electron microscopy（SEM）.The composite which is sintered under a pressure of 32 MPa at a temperature of 1700℃in vacuum holding for 60 min can get the optimal mechanical properties.Its flexural strength,fracture toughness and Vickers hardness are 540 MPa,7.81 MPa·m（1/2）and 20.42 GPa,respectively.The composite has relatively high density,and the in-situ synthesized TiB_2 whiskers have good surface integrity,which is beneficial for the improvement of the fracture toughness.It is concluded that the main toughening mechanisms of the present composite are whiskers pulling-out and crack deflection induced by whiskers,crack bridging by whiskers/particles and multi-scale particles synergistically toughening.This study proposes an in-situ one-step synthesis technology which can be well used for fabricating particles and whiskers synergistically toughened ceramic tool materials.
基金financial support from the National Natural Science Foundation of China(Grant Nos.52125103,52071041,12104071,11874356,U21A2054)。
文摘Magnesium-based materials have been regarded as promising candidates for large-scale,high-efficiency thermoelectric applications,owing to their excellent dimensionless figure of merit,high abundance,and low cost.In this review,we comprehensively summarize the recent advances of Mg-based thermoelectrics,including Mg_(2)X(X=Si,Ge,Sn),Mg3(Sb,Bi)_(2),andα-MgAgSb,from both material and device level.Their electrical and thermal transport properties are first elucidated based on the crystallographic characteristics,band structures,and phonon dispersions.We then review the optimization strategies towards higher thermoelectric performance,as well as the device applications of Mg-based thermoelectric materials and the related engineering issues.By highlighting the challenges and possible solutions in the end,this review intends to offer perspectives on the future research work to further enhance the performance of Mg-based materials for practical applications.
