Tin disulfide(SnS_(2)),due to large interlayer spacing and high theoretical capacity,is regarded as a prospective anode material for lithium-ion batteries.Nevertheless,the poor electron conductivity of SnS_(2) and hug...Tin disulfide(SnS_(2)),due to large interlayer spacing and high theoretical capacity,is regarded as a prospective anode material for lithium-ion batteries.Nevertheless,the poor electron conductivity of SnS_(2) and huge volumetric change during the lithiation/delithiation process lead to a rapid capacity decay of the battery,hindering its commercialization.To address these issues,herein,SnS_(2) is in-situ grown on the surface of carbon nanotubes(CNT)and then encapsulated with a layer of porous amorphous carbon(CNT/SnS_(2)@C)by simple solvothermal and further carbonization treatment.The synergistic effect of CNT and porous carbon layer not only enhances the electrical co nductivity of SnS_(2) but also limits the huge volumetric change to avoid the pulverization and detachment of SnS_(2).Density functional theo ry calculations show that CNT/SnS_(2)@C has high Li^(+)adsorption and lithium storage capacity achieving high reaction kinetics.Consequently,cells with the CNT/SnS_(2)@C anode exhibit a high lithium storage capacity of 837mAh/g after 100 cycles at 0.1 A/g and retaining a capacity of 529.8 mAh/g under 1.0 A/g after 1000 cycles.This study provides a fundamental understanding of the electrochemical processes and beneficial guidance to design high-performance SnS_(2)-based anodes for LIBs.展开更多
Supercapacitors are promising energy storage devices in current century due to their high specific capacitance, cyclic stability, high power density, and high voltage rating. Due to their excellent electrochemical pro...Supercapacitors are promising energy storage devices in current century due to their high specific capacitance, cyclic stability, high power density, and high voltage rating. Due to their excellent electrochemical properties, supercapacitors are invariably used in a multitude of applications ranging from portable electronics to electric vehicles. The electrochemical performance of a supercapacitor mainly depends on the type of electrode-active material used in it. Thereby a careful selection is mandatory to achieve the excellency. Nanostructured electrode-active materials such as carbon nanomaterials, transition metal oxides,transition metal dichalcogenides(TMDs), electronically conducting polymers, etc. are invariably used for supercapacitor application. Among these, TMDs have received great interest, particularly transition metal disulfides such as molybdenum disulfide, tin disulfide(SnS_(2)), etc. Tin is abundant on the earth with excellent charge storage capabilities, attracted great scientific interest for application as electrode materials in supercapacitors. Good electronic conductivity, long cycling life and low-cost are its added advantages.Herein, we discuss the recent trends in layered two-dimensional(2D) SnS_(2)-based electrodes to develop low-cost supercapacitors. Initially, their crystal structure, basic properties, synthesis methods are discussed. Further, strategically designing electrode nanostructures to achieve excellent electrochemical performance is reviewed then after. This includes material design in terms of morphology, pore-size,and shape as well as preparation of 2D SnS_(2)-based nanocomposite electrodes. Furthermore, the challenges and future perspectives of 2D SnS_(2)-based supercapacitors are included.展开更多
Effects of VC/Cr3C2 on the microstructure and mechanical properties of Ti（C,N）-based cermets were studied. The microstructure was investigated by means of optical microscopy, X-ray diffractometry as well as scanning...Effects of VC/Cr3C2 on the microstructure and mechanical properties of Ti（C,N）-based cermets were studied. The microstructure was investigated by means of optical microscopy, X-ray diffractometry as well as scanning electron microscopy in combination with energy dispersive spectrometry. Mechanical properties, such as transverse rupture strength, hardness and fracture toughness, were measured. The results show that there are black core-grey rim structure and white core-grey rim structure in the microstructure. The grains become fine due to the VC/Cr3C2, and the grains of cermet added with 0.75VC/0.25Cr3C2 are refined most remarkably. The black core becomes finer with the increase of VC addition and rim phase becomes thicker with the decrease of Cr3C2 addition. The porosity increases with the increase of VC addition in VC/Cr3C2. Compared with the cermet free of VC/Cr3C2, the transverse rupture strength and hardness of cermets with VC/Cr3C2 are both improved, and the maximum values are both found for the cermet with 0.25VC/0.75Cr3C2. The fracture toughness can be effectively promoted by adding VC/Cr3C2 with an appropriate ratio of VC to Cr3C2, and the maximum value is found for the cermet with 0.5VC/0.5Cr3C2.展开更多
A novel SnO2-based gas anode was developed for aluminum electrolysis in molten cryolite at 850 ＆#176;C to reduce energy consumption and decrease CO2 emissions. Hydrogen was introduced into the anode, participating in...A novel SnO2-based gas anode was developed for aluminum electrolysis in molten cryolite at 850 ＆#176;C to reduce energy consumption and decrease CO2 emissions. Hydrogen was introduced into the anode, participating in the anode reaction. Carbon and aluminum were used as the cathode and reference electrodes, respectively. Cyclic voltammetry was applied in the cell to investigate the electrochemical behavior of oxygen ion on platinum and SnO2-based materials. The potential for oxygen evolution on these electrode materials was determined. Then, galvanostatic electrolysis was performed on the gas anode, showing a significant depolarization effect （a decrease of ~0.8 V of the anode potential） after the introduction of hydrogen, compared with no gas introduction or the introduction of argon. The results indicate the involvement of hydrogen in the anode reaction （three-phase-boundary reaction including gas, electrolyte and electrode） and give the possibility for the utilization of reducing gas anodes for aluminum electrolysis.展开更多
通过水热法制备了SnS_(2)/还原氧化石墨烯(SnS_(2)/RGO)复合材料,采用X射线衍射谱(XRD)、拉曼光谱(Raman)、X射线光电子能谱(XPS)和N2吸附-脱附表征SnS_(2)/RGO复合材料的物相晶型、化学基团、元素组成和比表面积与孔隙孔径。SnS_(2)/RG...通过水热法制备了SnS_(2)/还原氧化石墨烯(SnS_(2)/RGO)复合材料,采用X射线衍射谱(XRD)、拉曼光谱(Raman)、X射线光电子能谱(XPS)和N2吸附-脱附表征SnS_(2)/RGO复合材料的物相晶型、化学基团、元素组成和比表面积与孔隙孔径。SnS_(2)/RGO复合材料作为锂离子电池负极材料组装纽扣电池。结果表明:电流密度100 m A/g条件下,SnS_(2)/RGO复合材料的充放电比容量明显高于纯SnS_(2),SnS_(2)/RGO复合材料第一次放电比容量高达2803 m Ah/g,表现出优异的电化学性能。循环100次后放电比容量仍然可以达到941 mAh/g,而循环100次后纯SnS_(2)的放电比容量远低于SnS_(2)/RGO复合材料,仅为198 m Ah/g,表现出良好的循环稳定性。1 000 m A/g的高电流密度下,SnS_(2)/RGO复合材料放电比容量依然可以达到696 mAh/g,表现出良好的倍率性能。展开更多
A series of SnO2‐based catalysts modified by Mn, Zr, Ti and Pb oxides with a Sn/M （M=Mn, Zr, Ti and Pb） molar ratio of 9/1 were prepared by a co‐precipitation method and used for CH4 and CO oxidation. The Mn3＋, ...A series of SnO2‐based catalysts modified by Mn, Zr, Ti and Pb oxides with a Sn/M （M=Mn, Zr, Ti and Pb） molar ratio of 9/1 were prepared by a co‐precipitation method and used for CH4 and CO oxidation. The Mn3＋, Zr4＋, Ti4＋and Pb4＋cations are incorporated into the lattice of tetragonal rutile SnO2 to form a solid solution structure. As a consequence, the surface area and thermal stability of the catalysts are improved. Moreover, the oxygen species of the modified catalysts become easier to be reduced. Therefore, the oxidation activity over the catalysts was improved, except for the one modified by Pb oxide. Manganese oxide demonstrates the best promotional effects for SnO2. Using an X‐ray diffraction extrapolation method, the lattice capacity of SnO2 for Mn2O3 was 0.135 g Mn2O3/g SnO2, which indicates that to form stable solid solution, only 21%Sn4＋cations in the lattice can be maximally replaced by Mn3＋. If the amount of Mn3＋cations is over the capacity, Mn2O3 will be formed, which is not favorable for the activity of the catalysts. The Sn rich samples with only Sn‐Mn solid solution phase show higher activity than the ones with excess Mn2O3 species.展开更多
Thermoelectric materials,enabling the directing conversion between heat and electricity,are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-co...Thermoelectric materials,enabling the directing conversion between heat and electricity,are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-consumption of fossil fuels.Bi2Te3-based alloys are the classical thermoelectric materials working near room temperature.Due to the intensive theoretical investigations and experimental demonstrations,significant progress has been achieved to enhance the thermoelectric performance of Bi2Te3-based thermoelectric materials.In this review,we first explored the fundamentals of thermoelectric effect and derived the equations for thermoelectric properties.On this basis,we studied the effect of material parameters on thermoelectric properties.Then,we analyzed the features of Bi2Te3-based thermoelectric materials,including the lattice defects,anisotropic behavior and the strong bipolar conduction at relatively high temperature.Then we accordingly summarized the strategies for enhancing the thermoelectric performance,including point defect engineering,texture alignment,and band gap enlargement.Moreover,we highlighted the progress in decreasing thermal conductivity using nanostructures fabricated by solution grown method,ball milling,and melt spinning.Lastly,we employed modeling analysis to uncover the principles of anisotropy behavior and the achieved enhancement in Bi2Te3,which will enlighten the enhancement of thermoelectric performance in broader materials展开更多
The(Cu−10Sn)−Ni−MoS2 composites,prepared by powder metallurgy,were studied for the effects of Ni-coated MoS2 on the microstructure,mechanical properties and lubricating properties.The mechanism of effects of Ni and Mo...The(Cu−10Sn)−Ni−MoS2 composites,prepared by powder metallurgy,were studied for the effects of Ni-coated MoS2 on the microstructure,mechanical properties and lubricating properties.The mechanism of effects of Ni and MoS2 on the properties of composites was analyzed through a comparative experiment by adding Ni and MoS2 separately.The results show that the nickel wrapping around the MoS2 particles decreases the reaction rate of MoS2 with the copper matrix,and greatly improves the bonding of the matrix.The composites with 12 wt.%Ni-coated MoS2(C12)show the optimum performance including the mechanical properties and tribological behaviors.Under oil lubrication conditions,the friction coefficient is 0.0075 with a pressure of 8 MPa and a linear velocity of 0.25 m/s.The average dry friction coefficient,sliding against 40Cr steel disc,is measured to be 0.1769 when the linear velocity and pressure are 0.25 m/s and 4 MPa,respectively.展开更多
Tin sulfide(SnS_(2))anodes have garnered significant attention within emerging energy storage technologies.However,the application of SnS_(2)is curtailed due to its inherent limitations,including poor cyclic stability...Tin sulfide(SnS_(2))anodes have garnered significant attention within emerging energy storage technologies.However,the application of SnS_(2)is curtailed due to its inherent limitations,including poor cyclic stability and inevitable volumetric expansion upon cycling.This study reports the successful fabrication of an innovative SnS_(2)-based composite,featuring an eggshell-like structured nitrogen-doped carbon coating,referred to as SnS_(2)@NxC.This novel architecture,wherein SnS_(2)acts as the core encapsulated by a nitrogen-doped carbon shell,characterized by a void space between the shell and core,is crucial in mitigating volumetric expansion.This configuration contributes to maintaining the structural integrity of the composite materials,even under the stresses of continuous cycling.Nitrogen within the carbon matrix enhances conductivity and promotes the formation of a more robust and stable solid electrolyte interphase(SEI)layer.Experimental investigations have substantiated the electrochemical superiority of the SnS_(2)@NxC electrode,demonstrating a specific capacity of 701.8 mA·h·g^(-1)after 1000 cycles at 0.5 A·g^(-1)and maintaining a capacity of 597.2mA·h·g^(-1)after 400 cycles at a heightened current density of 2 A·g^(-1).These findings underscore the exceptional cyclic performance and durability of the SnS_(2)@NxC electrode.展开更多
We investigated the influence of soaking time on the semi-conductivity and nonlinear electrical properties of TiO2- based varistor ceramic samples. We used a single sintering process and fabricated six disk samples of...We investigated the influence of soaking time on the semi-conductivity and nonlinear electrical properties of TiO2- based varistor ceramic samples. We used a single sintering process and fabricated six disk samples of （Sr, Bi, Si, Ta）-doped TiO2- based varistor ceramics sintered at 1 250℃ for 0.5 h, 1.0 h, 2.0 h, 3.0 h, 4.0 h, and 5.0 h, respectively. The samples were characterized by X-ray diffraction, breakdown voltage, and complex impedance. The results show that as the soaking time increases from 0.5 h to 5.0 h, the breakdown voltage drops before rising while the nonlinear coefficient increases and then decreases. We suggest that, considering both grain semi-conductivity and nonlinear electrical properties of the TiO2-based varistor ceramics, the optimal soaking time is between 2.0 h and 3.0 h.展开更多
The electrochemical corrosion behavior of Ti（C,N）-based cermets with different Mo2C additions was investigated in freely aerated 10% H2SO4 and potentiodynamic polarization of all the materials was conducted from -0....The electrochemical corrosion behavior of Ti（C,N）-based cermets with different Mo2C additions was investigated in freely aerated 10% H2SO4 and potentiodynamic polarization of all the materials was conducted from -0.5 to 1.5 V. There are two passive regions for all polarization curves. The first should be attributed to passive film formation due to Ti（C,N）, while the second may be due to the presence of Ni. Corrosion current density increases with M02C content increasing, from 2.06×10^-3 to 6.70×10^-3 mA/cm2. It is indicated that the corrosion resistance of Ti（C,N）-based cermets decreases with the increase of Mo2C addition. A skeleton of Ti（C,N） gains is observed after dissolution of Ni. The inner rim of cermets, rich in Mo2C, is corroded along with Ni binder and is more serious with the increase of Mo2C content. The secondary carbide Mo2C can be oxidized and dissolved in sulphuric acid.展开更多
In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent ...In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiC np advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vo1% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730＋ 95 MPa and fracture toughness is 5.6 ± 0.6 MPa.m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.展开更多
基金the financial support from the Australian Research CouncilCentre for Materials Science,Queensland University of Technology。
文摘Tin disulfide(SnS_(2)),due to large interlayer spacing and high theoretical capacity,is regarded as a prospective anode material for lithium-ion batteries.Nevertheless,the poor electron conductivity of SnS_(2) and huge volumetric change during the lithiation/delithiation process lead to a rapid capacity decay of the battery,hindering its commercialization.To address these issues,herein,SnS_(2) is in-situ grown on the surface of carbon nanotubes(CNT)and then encapsulated with a layer of porous amorphous carbon(CNT/SnS_(2)@C)by simple solvothermal and further carbonization treatment.The synergistic effect of CNT and porous carbon layer not only enhances the electrical co nductivity of SnS_(2) but also limits the huge volumetric change to avoid the pulverization and detachment of SnS_(2).Density functional theo ry calculations show that CNT/SnS_(2)@C has high Li^(+)adsorption and lithium storage capacity achieving high reaction kinetics.Consequently,cells with the CNT/SnS_(2)@C anode exhibit a high lithium storage capacity of 837mAh/g after 100 cycles at 0.1 A/g and retaining a capacity of 529.8 mAh/g under 1.0 A/g after 1000 cycles.This study provides a fundamental understanding of the electrochemical processes and beneficial guidance to design high-performance SnS_(2)-based anodes for LIBs.
基金Sunway University for supporting this research work under Sunway University Internal Grant Scheme 2022 (grant no. GRTIN-IGS(02)-GAMRG-03-2022)。
文摘Supercapacitors are promising energy storage devices in current century due to their high specific capacitance, cyclic stability, high power density, and high voltage rating. Due to their excellent electrochemical properties, supercapacitors are invariably used in a multitude of applications ranging from portable electronics to electric vehicles. The electrochemical performance of a supercapacitor mainly depends on the type of electrode-active material used in it. Thereby a careful selection is mandatory to achieve the excellency. Nanostructured electrode-active materials such as carbon nanomaterials, transition metal oxides,transition metal dichalcogenides(TMDs), electronically conducting polymers, etc. are invariably used for supercapacitor application. Among these, TMDs have received great interest, particularly transition metal disulfides such as molybdenum disulfide, tin disulfide(SnS_(2)), etc. Tin is abundant on the earth with excellent charge storage capabilities, attracted great scientific interest for application as electrode materials in supercapacitors. Good electronic conductivity, long cycling life and low-cost are its added advantages.Herein, we discuss the recent trends in layered two-dimensional(2D) SnS_(2)-based electrodes to develop low-cost supercapacitors. Initially, their crystal structure, basic properties, synthesis methods are discussed. Further, strategically designing electrode nanostructures to achieve excellent electrochemical performance is reviewed then after. This includes material design in terms of morphology, pore-size,and shape as well as preparation of 2D SnS_(2)-based nanocomposite electrodes. Furthermore, the challenges and future perspectives of 2D SnS_(2)-based supercapacitors are included.
基金Project (090414185) supported by the Natural Science Foundation of Anhui Province, China
文摘Effects of VC/Cr3C2 on the microstructure and mechanical properties of Ti（C,N）-based cermets were studied. The microstructure was investigated by means of optical microscopy, X-ray diffractometry as well as scanning electron microscopy in combination with energy dispersive spectrometry. Mechanical properties, such as transverse rupture strength, hardness and fracture toughness, were measured. The results show that there are black core-grey rim structure and white core-grey rim structure in the microstructure. The grains become fine due to the VC/Cr3C2, and the grains of cermet added with 0.75VC/0.25Cr3C2 are refined most remarkably. The black core becomes finer with the increase of VC addition and rim phase becomes thicker with the decrease of Cr3C2 addition. The porosity increases with the increase of VC addition in VC/Cr3C2. Compared with the cermet free of VC/Cr3C2, the transverse rupture strength and hardness of cermets with VC/Cr3C2 are both improved, and the maximum values are both found for the cermet with 0.25VC/0.75Cr3C2. The fracture toughness can be effectively promoted by adding VC/Cr3C2 with an appropriate ratio of VC to Cr3C2, and the maximum value is found for the cermet with 0.5VC/0.5Cr3C2.
基金Project(51404001)supported by the National Natural Science Foundation of ChinaProject([2014]1685)supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education,China
文摘A novel SnO2-based gas anode was developed for aluminum electrolysis in molten cryolite at 850 ＆#176;C to reduce energy consumption and decrease CO2 emissions. Hydrogen was introduced into the anode, participating in the anode reaction. Carbon and aluminum were used as the cathode and reference electrodes, respectively. Cyclic voltammetry was applied in the cell to investigate the electrochemical behavior of oxygen ion on platinum and SnO2-based materials. The potential for oxygen evolution on these electrode materials was determined. Then, galvanostatic electrolysis was performed on the gas anode, showing a significant depolarization effect （a decrease of ~0.8 V of the anode potential） after the introduction of hydrogen, compared with no gas introduction or the introduction of argon. The results indicate the involvement of hydrogen in the anode reaction （three-phase-boundary reaction including gas, electrolyte and electrode） and give the possibility for the utilization of reducing gas anodes for aluminum electrolysis.
文摘通过水热法制备了SnS_(2)/还原氧化石墨烯(SnS_(2)/RGO)复合材料,采用X射线衍射谱(XRD)、拉曼光谱(Raman)、X射线光电子能谱(XPS)和N2吸附-脱附表征SnS_(2)/RGO复合材料的物相晶型、化学基团、元素组成和比表面积与孔隙孔径。SnS_(2)/RGO复合材料作为锂离子电池负极材料组装纽扣电池。结果表明:电流密度100 m A/g条件下,SnS_(2)/RGO复合材料的充放电比容量明显高于纯SnS_(2),SnS_(2)/RGO复合材料第一次放电比容量高达2803 m Ah/g,表现出优异的电化学性能。循环100次后放电比容量仍然可以达到941 mAh/g,而循环100次后纯SnS_(2)的放电比容量远低于SnS_(2)/RGO复合材料,仅为198 m Ah/g,表现出良好的循环稳定性。1 000 m A/g的高电流密度下,SnS_(2)/RGO复合材料放电比容量依然可以达到696 mAh/g,表现出良好的倍率性能。
基金supported by the National Natural Science Foundation of China (21263015,21567016 and 21503106)the Education Department Foundation of Jiangxi Province (KJLD14005 and GJJ150016)the Natural Science Foundation of Jiangxi Province (20142BAB213013 and 20151BBE50006),which are greatly acknowledged by the authors~~
文摘A series of SnO2‐based catalysts modified by Mn, Zr, Ti and Pb oxides with a Sn/M （M=Mn, Zr, Ti and Pb） molar ratio of 9/1 were prepared by a co‐precipitation method and used for CH4 and CO oxidation. The Mn3＋, Zr4＋, Ti4＋and Pb4＋cations are incorporated into the lattice of tetragonal rutile SnO2 to form a solid solution structure. As a consequence, the surface area and thermal stability of the catalysts are improved. Moreover, the oxygen species of the modified catalysts become easier to be reduced. Therefore, the oxidation activity over the catalysts was improved, except for the one modified by Pb oxide. Manganese oxide demonstrates the best promotional effects for SnO2. Using an X‐ray diffraction extrapolation method, the lattice capacity of SnO2 for Mn2O3 was 0.135 g Mn2O3/g SnO2, which indicates that to form stable solid solution, only 21%Sn4＋cations in the lattice can be maximally replaced by Mn3＋. If the amount of Mn3＋cations is over the capacity, Mn2O3 will be formed, which is not favorable for the activity of the catalysts. The Sn rich samples with only Sn‐Mn solid solution phase show higher activity than the ones with excess Mn2O3 species.
基金Project supported by the Australian Research CouncilZhi-Gang Chen thanks the USQ start-up grantstrategic research grant
文摘Thermoelectric materials,enabling the directing conversion between heat and electricity,are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-consumption of fossil fuels.Bi2Te3-based alloys are the classical thermoelectric materials working near room temperature.Due to the intensive theoretical investigations and experimental demonstrations,significant progress has been achieved to enhance the thermoelectric performance of Bi2Te3-based thermoelectric materials.In this review,we first explored the fundamentals of thermoelectric effect and derived the equations for thermoelectric properties.On this basis,we studied the effect of material parameters on thermoelectric properties.Then,we analyzed the features of Bi2Te3-based thermoelectric materials,including the lattice defects,anisotropic behavior and the strong bipolar conduction at relatively high temperature.Then we accordingly summarized the strategies for enhancing the thermoelectric performance,including point defect engineering,texture alignment,and band gap enlargement.Moreover,we highlighted the progress in decreasing thermal conductivity using nanostructures fabricated by solution grown method,ball milling,and melt spinning.Lastly,we employed modeling analysis to uncover the principles of anisotropy behavior and the achieved enhancement in Bi2Te3,which will enlighten the enhancement of thermoelectric performance in broader materials
基金Projects(51371099,51501091)supported by the National Natural Science Foundation of China。
文摘The(Cu−10Sn)−Ni−MoS2 composites,prepared by powder metallurgy,were studied for the effects of Ni-coated MoS2 on the microstructure,mechanical properties and lubricating properties.The mechanism of effects of Ni and MoS2 on the properties of composites was analyzed through a comparative experiment by adding Ni and MoS2 separately.The results show that the nickel wrapping around the MoS2 particles decreases the reaction rate of MoS2 with the copper matrix,and greatly improves the bonding of the matrix.The composites with 12 wt.%Ni-coated MoS2(C12)show the optimum performance including the mechanical properties and tribological behaviors.Under oil lubrication conditions,the friction coefficient is 0.0075 with a pressure of 8 MPa and a linear velocity of 0.25 m/s.The average dry friction coefficient,sliding against 40Cr steel disc,is measured to be 0.1769 when the linear velocity and pressure are 0.25 m/s and 4 MPa,respectively.
文摘Tin sulfide(SnS_(2))anodes have garnered significant attention within emerging energy storage technologies.However,the application of SnS_(2)is curtailed due to its inherent limitations,including poor cyclic stability and inevitable volumetric expansion upon cycling.This study reports the successful fabrication of an innovative SnS_(2)-based composite,featuring an eggshell-like structured nitrogen-doped carbon coating,referred to as SnS_(2)@NxC.This novel architecture,wherein SnS_(2)acts as the core encapsulated by a nitrogen-doped carbon shell,characterized by a void space between the shell and core,is crucial in mitigating volumetric expansion.This configuration contributes to maintaining the structural integrity of the composite materials,even under the stresses of continuous cycling.Nitrogen within the carbon matrix enhances conductivity and promotes the formation of a more robust and stable solid electrolyte interphase(SEI)layer.Experimental investigations have substantiated the electrochemical superiority of the SnS_(2)@NxC electrode,demonstrating a specific capacity of 701.8 mA·h·g^(-1)after 1000 cycles at 0.5 A·g^(-1)and maintaining a capacity of 597.2mA·h·g^(-1)after 400 cycles at a heightened current density of 2 A·g^(-1).These findings underscore the exceptional cyclic performance and durability of the SnS_(2)@NxC electrode.
基金Funded by the Natural Science Foundation of China (No. 50872001 and No. 50642038)the Scientific Research Foundation of Education Ministry of Anhui Province (No. 2005KJ224 and No. KJ2007B132)the Graduate Student Innovation Programs of Anhui University (No. 20072006)
文摘We investigated the influence of soaking time on the semi-conductivity and nonlinear electrical properties of TiO2- based varistor ceramic samples. We used a single sintering process and fabricated six disk samples of （Sr, Bi, Si, Ta）-doped TiO2- based varistor ceramics sintered at 1 250℃ for 0.5 h, 1.0 h, 2.0 h, 3.0 h, 4.0 h, and 5.0 h, respectively. The samples were characterized by X-ray diffraction, breakdown voltage, and complex impedance. The results show that as the soaking time increases from 0.5 h to 5.0 h, the breakdown voltage drops before rising while the nonlinear coefficient increases and then decreases. We suggest that, considering both grain semi-conductivity and nonlinear electrical properties of the TiO2-based varistor ceramics, the optimal soaking time is between 2.0 h and 3.0 h.
基金Project(51074110) supported by the National Natural Science Foundation of ChinaProject(10GGZD080GX-268) supported by Chengdu Science and Technology Program, China
文摘The electrochemical corrosion behavior of Ti（C,N）-based cermets with different Mo2C additions was investigated in freely aerated 10% H2SO4 and potentiodynamic polarization of all the materials was conducted from -0.5 to 1.5 V. There are two passive regions for all polarization curves. The first should be attributed to passive film formation due to Ti（C,N）, while the second may be due to the presence of Ni. Corrosion current density increases with M02C content increasing, from 2.06×10^-3 to 6.70×10^-3 mA/cm2. It is indicated that the corrosion resistance of Ti（C,N）-based cermets decreases with the increase of Mo2C addition. A skeleton of Ti（C,N） gains is observed after dissolution of Ni. The inner rim of cermets, rich in Mo2C, is corroded along with Ni binder and is more serious with the increase of Mo2C content. The secondary carbide Mo2C can be oxidized and dissolved in sulphuric acid.
基金Supported by National Natural Science Foundation of China(Grant No.51175305)
文摘In recent decades, many additives with different characteristics have been applied to strengthen and toughen Al2O3-based ceramic cutting tool materials. Among them, SiC whiskers and SiC nanoparticles showed excellent performance in improving the material properties. While no attempts have been made to add SiC whiskers and SiC nanoparticles together into the ceramic matrix and the synergistically toughening effects of them have not been studied. An Al2O3-SiCw-SiC np advanced ceramic cutting tool material is fabricated by adding both one-dimensional SiC whiskers and zero-dimensional SiC nanoparticles into the Al2O3 matrix with an effective dispersing and mixing process. The composites with 25 vol% SiC whiskers and 25 vol% SiC nanoparticles alone are also investegated for comparison purposes. Results show that the Al2O3-SiCw-SiCnp composite with both 20 vo1% SiC whiskers and 5 vol% SiC nanoparticles additives have much improved mechanical properties. The flexural strength of Al2O3-SiCw-SiCnp is 730＋ 95 MPa and fracture toughness is 5.6 ± 0.6 MPa.m1/2. The toughening and strengthening mechanisms of SiC whiskers and nanoparticles are studied when they are added either individually or in combination. It is indicated that when SiC whiskers and nanoparticles are added together, the grains are further refined and homogenized, so that the microstructure and fracture mode ratio is modified. The SiC nanoparticles are found helpful to enhance the toughening effects of the SiC whiskers. The proposed research helps to enrich the types of ceramic cutting tool and is benefit to expand the application range of ceramic cutting tool.
