As silicon-based transistors face fundamental scaling limits,the search for breakthrough alternatives has led to innovations in 3D architectures,heterogeneous integration,and sub-3 nm semiconductor body thicknesses.Ho...As silicon-based transistors face fundamental scaling limits,the search for breakthrough alternatives has led to innovations in 3D architectures,heterogeneous integration,and sub-3 nm semiconductor body thicknesses.However,the true effectiveness of these advancements lies in the seamless integration of alternative semiconductors tailored for next-generation transistors.In this review,we highlight key advances that enhance both scalability and switching performance by leveraging emerging semiconductor materials.Among the most promising candidates are 2D van der Waals semiconductors,Mott insulators,and amorphous oxide semiconductors,which offer not only unique electrical properties but also low-power operation and high carrier mobility.Additionally,we explore the synergistic interactions between these novel semiconductors and advanced gate dielectrics,including high-K materials,ferroelectrics,and atomically thin hexagonal boron nitride layers.Beyond introducing these novel material configurations,we address critical challenges such as leakage current and long-term device reliability,which become increasingly crucial as transistors scale down to atomic dimensions.Through concrete examples showcasing the potential of these materials in transistors,we provide key insights into overcoming fundamental obstacles—such as device reliability,scaling down limitations,and extended applications in artificial intelligence—ultimately paving the way for the development of future transistor technologies.展开更多
The development of affordable,high-efficiency sodium-ion batteries is primarily dependent on the advancement of cathode materials.These materials need to exhibit a high cell voltage,significant storage capacity,and qu...The development of affordable,high-efficiency sodium-ion batteries is primarily dependent on the advancement of cathode materials.These materials need to exhibit a high cell voltage,significant storage capacity,and quick diffusion of sodium ions to fulfill the requirements for efficient and ecofriendly energy storage systems.In this vein,density functional theory(DFT)calculation has become instrumental in advancing the study of battery materials.This study presents a firstprinciples investigation of P2-type Na_(x)NiO_(2)and Na_(x)Ni_(0.75)M_(0.25)O_(2)(M=Cu,Fe,Mn)cathode materials for sodium-ion batteries(SIBs),focusing on Na content variation and its impact on the battery performance.For NaNiO_(2),we replaced part of the expensive Ni element with lower-cost Cu,Fe,and Mn in hopes of reducing costs and improving material performance.By employing density functional theory(DFT),we explore the relationship between lattice constants,cell volume,enthalpy of formation,and cell voltage,and how these factors influence sodium ion insertion/extraction.We provide insights into the diffusion paths and activation energies for Na ions,and assess the influence of transition metal(TM)substitution on the structural stability and electrochemical properties of the materials.Additionally,the study delves into the electronic structure,highlighting how Cu and Fe integration refines the band gap of the spin-down bands.The findings reveal that certain transition metal substitutions can enhance performance,offering a pathway to optimize sodium-ion battery electrode materials.展开更多
The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitatio...The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitation method with metal-nitrates as starting materials and mixed alkali (NaOH and Na2CO3) as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, and the crystal structure and particles morphology of the precursors which were calcined at 600, 800, 1000 ℃ for 3 h were characterized using XRD, SEM technologies. Compared with the solid state reaction of constituent oxides, when the pH value of the precipitating solution was in the range of 9.1～9.5, the LSCCF powders from the precursors caclined at 800 ℃ for 3 h had high purity, homogeneous and single perovskite phase. The electrical conductivity of the LSCCF samples sintered at 1200 ℃ for 3 h, which was measured as a function of temperatures from 100 to 800 ℃ by DC four-probe method in air, decreased with x from 0.05 to 0.20. The value of electrical conductivity was almost equal because of Ca2+, Sr2+ co-dopant resulting in the 'mix effect' while x=0.10 or 0.15. The electrical conductivity of all doped samples was higher than 100 S·cm-1 at intermediate temperatures from 500 to 800 ℃, and there was good compatibility between the LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.展开更多
Al_(0.5)CrFeNi_(2.5)high-entropy alloy(HEA)was reinforced by the small-radius Si.Al_(0.5)CrFeNi_(2.5)Six(x=0 and 0.25)HEAs were fabricated by laser melting deposition.The evolution of microstructure,nanohardness,and w...Al_(0.5)CrFeNi_(2.5)high-entropy alloy(HEA)was reinforced by the small-radius Si.Al_(0.5)CrFeNi_(2.5)Six(x=0 and 0.25)HEAs were fabricated by laser melting deposition.The evolution of microstructure,nanohardness,and wear properties of Al_(0.5)CrFeNi_(2.5)Six(x=0 and 0.25)HEAs were systematically investigated.Al_(0.5)CrFeNi_(2.5)HEA exhibits a face-centered cubic(FCC)matrix with Ni3Al-type ordered nanoprecipitates.When Si was doped,σphase and Cr-rich nanoprecipitates existed in the B2 matrix and L12 in the FCC matrix.The nanohardness was increased from 4.67 to 5.45 GPa with doping of Si,which is associated with forming the new phases and improved nanohardness of L12/FCC phases.The coefficient of friction(COF)value was reduced from 0.75 to 0.67 by adding Si.σphase and Cr-rich nanoprecipitates in B2 matrix support a decreased wear rate from 7.87×10^(-4) to 6.82×10^(-4) mm^(3)/(N m).Furthermore,the main wear mechanism of Al_(0.5)CrFeNi_(2.5)and Al_(0.5)CrFeNi_(2.5)Si0.25 HEAs is abrasive wear.展开更多
While developing nuclear materials,predicting their behavior under long-term irradiation regimes span-ning decades poses a significant challenge.We developed a novel Kinetic Monte Carlo(KMC)model to explore the precip...While developing nuclear materials,predicting their behavior under long-term irradiation regimes span-ning decades poses a significant challenge.We developed a novel Kinetic Monte Carlo(KMC)model to explore the precipitation behavior of Y-Ti-O oxides along grain boundaries within nanostructured ferritic alloys(NFA).This model also assessed the response of the oxides to neutron irradiation,even up sim-ulated radiation damage levels in the desired long dpa range for reactor components.Our simulations investigated how temperature and grain boundary sinks influenced the oxide characteristics of a 12YWT-like alloy during heat treatments at 1023,1123,and 1223 K.The oxide characteristics observed in our simulations were in good agreement with existing literature.Furthermore,the impact of grain bound-aries on precipitation was found to be minimal.The resulting oxide configurations and positions were used in subsequent simulations that exposed them to simulated neutron irradiation to a total accumu-lated dose of 8 dpa at three temperatures:673,773,and 873 K,and at dose rates of 10-3,10-4,and 10-5 dpa/s.This demonstrated the expected inverse relationship between oxide size and dose rate.In a long-term irradiation simulation at 873 K and 10-3 dpa/s was taken out to 66 dpa and found the oxides in the vicinity of the grain boundary were more susceptible to dissolution.Additionally,we conducted irradia-tion simulations of a 14YWT-like alloy to reproduce findings from neutron irradiation experiments.The larger oxides in the 14YWT-like alloy did not dissolve and displayed stability similar to the experimental results.展开更多
We propose the scaling rule of Morse oscillator,based on this rule and by virtue of the Her-mann-Feymann theorem,we respectively obtain the distribution of potential and kinetic ener-gy of the Morse Hamiltonian.Also,w...We propose the scaling rule of Morse oscillator,based on this rule and by virtue of the Her-mann-Feymann theorem,we respectively obtain the distribution of potential and kinetic ener-gy of the Morse Hamiltonian.Also,we derive the exact upper limit of physical energy level.Further,we derive some recursive relations for energy matrix elements of the potential and other similar operators in the context of Morse oscillator theory.展开更多
By introducing a fictitious mode to be a counterpart mode of the system mode under review we introduce the entangled state representation （η｜, which can arrange master equations of density operators p（t） in quant...By introducing a fictitious mode to be a counterpart mode of the system mode under review we introduce the entangled state representation （η｜, which can arrange master equations of density operators p（t） in quantum statistics as state-vector evolution equations due to the elegant properties of （η｜. In this way many master equations （respectively describing damping oscillator, laser, phase sensitive, and phase diffusion processes with different initial density operators） can be concisely solved. Specially, for a damping process characteristic of the decay constant k we find that the matrix element of p（t） at time t in 〈η｜ representation is proportional to that of the initial po in the decayed entangled state （ηe^-kt｜ representation, accompanying with a Gaussian damping factor. Thus we have a new insight about the nature of the dissipative process. We also set up the so-called thermo-entangled state representation of density operators, ρ = f（d^2η/π）（η｜ρ〉D（η）, which is different from all the previous known representations.展开更多
High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500℃. The main constituent was calcined gangue, fly ash ...High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500℃. The main constituent was calcined gangue, fly ash and slag, while alkali-silicate solutions were used as the diagenetic agent. The structure of gangue-containing aluminosilicate based cementitious materials was studied by the methods of IR, NMR and SEM. The results show that the mechanical properties are affected by the mass ratio between the gangue, slag and fly ash, the kind of activator and additional salt. For 28-day curing time, the compressive strength of the sample with a mass proportion of 2：1：1 （gangue： slag： fly ash） is 58.9 MPa, while the compressive strength of the sample containing 80wt% gangue can still be up to 52.3 MPa. The larger K^＋ favors the formation of large silicate oligomers with which AI（OH）4- prefers to bind. Therefore, in Na-K compounding activator solutions more oligomers exist which result in a stronger compressive strength of aluminosilicate-based cementitious materials than in the case of Na-containing activator. The reasons for this were found through IR and NMR analysis. Glauber＇s salt reduces the 3-day compressive strength of the paste, but increases its 7-day and 28-day compressive strengths.展开更多
Light and strong AlxCrNbVMo(x=0,0.5,and 1.0)refractory high-entropy alloys(RHEAs)were designed and fabricated via a the powder metallurgical process.The microstructure of the AlxCrNbVMo alloys consisted of a single BC...Light and strong AlxCrNbVMo(x=0,0.5,and 1.0)refractory high-entropy alloys(RHEAs)were designed and fabricated via a the powder metallurgical process.The microstructure of the AlxCrNbVMo alloys consisted of a single BCC crystalline structure with a sub-micron grain size of 2-3μm,and small amounts(<4 vol.%)of fine oxide dispersoids.This homogeneous microstructure,without chemical segregation or micropores was achieved via high-energy ball milling and spark-plasma sintering.The alloys exhibited superior mechanical properties at 25 and 1000℃compared to those of other RHEAs.Here,CrNbVMo alloy showed a yield strength of 2743 MPa at room temperature.Surprisingly,the yield strength of the CrNbVMo alloy at 1000℃was 1513 MPa.The specific yield strength of the CrNbVMo alloy was increased by 27%and 87%at 25 and 1000℃,respectively,compared to the AlMo_(0.5) NbTa_(0.5)TiZr RHEA,which exhibited so far the highest specific yield strength among the cast RHEAs.The addition of Al to CrNbVMo alloy was advantageous in reducing its reduce density to below 8.0 g/cm^(3),while the elastic modulus decreased due to the much lower elastic modulus of Al compared to that of the CrNbVMo alloy.Quantitative analysis of the strengthening contributions,showed that the solid solution strengthening,arising from a large misfit effect due to the size and modulus,and the high shear modulus of matrix,was revealed to predominant strengthening mechanism,accounting for over 50%of the yield strength of the AlxCrNbVMo RHEAs.展开更多
High-entropy alloy(HEA)coatings are of great importance in the fabrication of wear resistance materials.HEA coatings containing ceramic particles as reinforcement phase usually have better wear performance.In this stu...High-entropy alloy(HEA)coatings are of great importance in the fabrication of wear resistance materials.HEA coatings containing ceramic particles as reinforcement phase usually have better wear performance.In this study,AlCoCrFe Ni(TiN)_(x)(x:molar ratio;x=0,0.2,0.4,0.6,0.8,1.0)HEA coatings were fabricated on Q235 steel by plasma spray first and then subjected to laser remelting.The experimental results confirm that plasma spray together with post laser remelting could result in the in-situ formation of TiN-Al_(2)O_(3) ceramic particles and cuboidal B2 phase in the AlCoCrFeNi(TiN)_(x) HEA coatings.The in-situ TiN-Al_(2)O_(3) and nano-cuboidal B2 precipitation phase strengthened the coatings and improved their wearresistance properties.Due to the dispersion of hard phase and nano-particles resulting from second heating,the microhardness of the Al Co Cr Fe Ni(Ti N)coatings significantly increased from 493 to 851 HV after laser remelting.For the same reasons,the wear-resistance performance was also significantly promoted after laser remelting.展开更多
For the purpose of high-temperature service and the weight reduction in aviation engineering applications,the dissimilar joining of Ti3Al-based alloy to Ni-based superalloy(GH536)was conducted using Au-17.5Ni(wt%)braz...For the purpose of high-temperature service and the weight reduction in aviation engineering applications,the dissimilar joining of Ti3Al-based alloy to Ni-based superalloy(GH536)was conducted using Au-17.5Ni(wt%)brazing filler metal.The microstructure and chemical composition at the interfaces were investigated by scanning electron microscope,X-ray diffraction and transmission electron microscope.The diffusion behaviors of elements were analyzed as well.The results indicated that the Ti_(3)Al/GH536 joint microstructure was characterized by multiple layer structures.Element Ni from Au-Ni filler metal reacted with Ti3Al base metal,leading to the formation of AlNi2Ti and NiTi compounds.Element Ni from Ti3Al base metal reacted with Ni and thus Ni3Nb phase was detected in the joint central area.Due to the dissolution of Ni-based superalloy,(Ni,Au)solid solution((Ni,Au)ss)and Ni-rich phase were visible adjacent to the superalloy side.The average tensile strength of all the joints brazed at 1253 K for 5-20 min was above 356 MPa at room-temperature.In particular,the joints brazed at 1253 K/15 min presented the maximum tensile strength of434 MPa at room-temperature,and the strength of 314 MPa was maintained at 923 K.AlNi2Ti compound resulted in the highest hardness area and the fracture of the samples subjected to the tensile test mainly occurred in this zone.展开更多
Maximum bubble pressure measurement was employed to evaluate surface tension of Sn-8Zn-3Bi- (00.15)Nd and Sn-8Zn-3Bi-(00.15)La solder melts. Wetting balance method was used to measure wetting force and wetting time on...Maximum bubble pressure measurement was employed to evaluate surface tension of Sn-8Zn-3Bi- (00.15)Nd and Sn-8Zn-3Bi-(00.15)La solder melts. Wetting balance method was used to measure wetting force and wetting time on Cu substrate of the two group solders. The experimental results show that minute amount of Nd or La addition to Sn-8Zn-3Bi solder causes significant decrease of the surface tension of the solder melts at 200240℃ and Nd addition is more effective on reduction of surface tension than that of La. Nd or La addition has the effect on enhancing the wetting force of the solder melts on Cu substrate, which results from the decrease of interfacial tension between the solder melt and Cu substrate. The wetting force reaches the maximum when 0.1% Nd is added to the base alloy. The contact angle between Sn-8Zn-3Bi base solders and Cu substrate decreases with the addition of Nd or La and the minimum of the contact angle is obtained from the solder with 0.1% Nd addition.展开更多
Konjac glucomannan （KGM） was crosslinked with sodium tripolyphosphate （STPP） to synthesize hydrogels. The crosslinking reaction was confirmed by FT-IR. The results of degradation test show that the hydrogels retai...Konjac glucomannan （KGM） was crosslinked with sodium tripolyphosphate （STPP） to synthesize hydrogels. The crosslinking reaction was confirmed by FT-IR. The results of degradation test show that the hydrogels retain the enzymatic degradation character of KGM and can be degraded for 74.45% in 5 days by cellulase E0240.展开更多
Niobium (Nb)-clad stainless steels(SS) produced via roll bonding are being considered for use in the bipolar plates of polymer electrolyte membrane fuel cell(PEMFC) stacks. Because the roll bonding process induces sub...Niobium (Nb)-clad stainless steels(SS) produced via roll bonding are being considered for use in the bipolar plates of polymer electrolyte membrane fuel cell(PEMFC) stacks. Because the roll bonding process induces substantial work hardening in the constituent materials, thermal annealing is used to restore ductility to the clad sheet so that it can be subsequently blanked, stamped and dimpled in forming the final plate component. Two roll bonded materials, niobium clad 340L stainless steel (Nb/340L SS) and niobium clad 434 stainless steel (Nb/434 SS) were annealed under optimized conditions prescribed by the cladding manufacturer. Comparative mechanical testing conducted on each material before and after annealing shows significant improvement in ductility in both cases. However, corresponding microstructural analyses indicate an obvious difference between the two heat treated materials. During annealing, an interlayer with thick less than 1 μm forms between the constituent layers in the Nb/340L SS, whereas no interlayer is found in the annealed Nb/434 SS material. Prior work suggests that internal defects potentially can be generated in such an interlayer during metal forming operations. Thus, Nb/434 SS may be the preferred candidate material for this application.展开更多
Direct quenching and tempering （DQ-T） of hot rolled steel section has been widely used in steel mill for the sake of improvement of mechanical properties and energy saving. Temperature history and microstructural ev...Direct quenching and tempering （DQ-T） of hot rolled steel section has been widely used in steel mill for the sake of improvement of mechanical properties and energy saving. Temperature history and microstructural evolution during hot rolling plays a major role in the properties of direct quenched and tempered products. The mathematical and physical modeling of hot forming processes is becoming a very important tool for design and development of required products as well as predicting the microstructure and the properties of the components. These models were mostly used to predict austenite grain size （AGS）, dynamic, recta-dynamic and static recrystallization in the rods immediately after hot rolling and prior to DQ process. The hot compression tests were carried out on 42CrMo4 steel in the temperature range of 900-1 100 ℃ and the strain rate range of 0. 05-1 s^-1 in order to study the high tempera- ture softening behavior of the steel. For the exact prediction of flow stress, the effective stress-effective strain curves were obtained from experiments under various conditions. On the basis of experimental results, the dynamic recrystallization fraction （DRX）, AGS, hot deformation and activation energy behavior were investigated. It was found that the calculated results were in good agreement with the experimental flow stress and microstructure of the steel for different conditions of hot deformation.展开更多
Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700 ℃ and repressing at 500 MPa. Four k...Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700 ℃ and repressing at 500 MPa. Four kinds composites with different compositions were produced, and the mechanical properties and electrical wear performance were investigated. The results showed that the composite added with carbon nanotubes had a higher hardness and strength, a lower contact voltage drop and an excellent anti-wear property in electrical sliding wear, because of the reinforcement ability of carbon nanotubes. Adding graphite to the composite also decreased the wear loss and contact voltage drop, because graphite had an electrical current conducting ability which not only made the current pass the lubricating films easily but also eliminated and reduced the arc and spark effectively.展开更多
The effects of Ca and Sr addition on the microstructure and creep properties of Mg-4Al-2Sn alloys were examined. Tensile tests at 25 ℃ and 200 ℃ and creep tests at 150 ℃ and 200 ℃ were carried out to estimate the ...The effects of Ca and Sr addition on the microstructure and creep properties of Mg-4Al-2Sn alloys were examined. Tensile tests at 25 ℃ and 200 ℃ and creep tests at 150 ℃ and 200 ℃ were carried out to estimate the room temperature and high temperature mechanical properties of these alloys. The microstrueture of the Mg-4Al-2Sn alloy showed dendritic a-Mg, Mg17Al12 and Mg2Sn phases. The latter two phases precipitated along the grain boundaries. The addition of Ca and Sr resulted in the formation of ternary CaMgSn and SrMgSn phases within the grain. The grain size was reduced slightly with the addition of Sr and Ca. The tensile strength was decreased by the addition of Ca and Sr at room temperature. However, the high temperature tensile strength was increased. The creep strength was improved by the addition of Ca and Sr.展开更多
It is pointed out that the quantum mechanical Hamiltonian of two L-C circuits with mutual-inductance is equivalent to a pair of harmonic oscillators with a kinetic coupling term.We then diagonalize the Hamiltonian.It ...It is pointed out that the quantum mechanical Hamiltonian of two L-C circuits with mutual-inductance is equivalent to a pair of harmonic oscillators with a kinetic coupling term.We then diagonalize the Hamiltonian.It is shown that instantaneously switching on the external sources may result in a two-mode squeezed state of the system,which actually arises from the effect of mutual-inductance.The quantum fluctuation for the case of l_(1)c_(1)=l_(2)c_(2 ) is analysed and it is found that the current fluctuation in the circuits increases with the increment of the mutual-inductance.展开更多
The microstructure and mechanical properties of friction stir welded 2. 5 mm 7050-T7451 aluminum alloy natural aging 72 h and 17 520 h were investigated, respectively. The uniaxial tensile test showed that yield stren...The microstructure and mechanical properties of friction stir welded 2. 5 mm 7050-T7451 aluminum alloy natural aging 72 h and 17 520 h were investigated, respectively. The uniaxial tensile test showed that yield strength, tensile strength and elongation of the joints 17 520 h natural aging were about 20%, 12% and 24% higher than those joints natural aging 72 h. Hardness profile of natural aging 17 520 h joint witnessed significant enhancement in nugget zone, compared with 72 h natural aging. Differential scanning calorimetry （ DSC ） and transmission electron microscopy （TEM） test revealed that more Guinier-Preston zone, η＇ and 71 phase emerged in nugget zone as natural aging duration increased, high density of dislocation located within grain boundary in nugget zone of joints natural aging 72 h. It is concluded that natural aging was feasible to enhalwe strength and plasticity of FSW joints simultaneously.展开更多
The nanocrystalline Fe-Ni-Cr coatings were electrodeposited by using the pulse current technique.The SEM results showed that the coatings had a mixed morphology of small nodules and fine cauliflower structures at low ...The nanocrystalline Fe-Ni-Cr coatings were electrodeposited by using the pulse current technique.The SEM results showed that the coatings had a mixed morphology of small nodules and fine cauliflower structures at low current densities.Also,the Cr content was increased at expense of Fe and Ni contents at high current densities.XRD patterns confirmed that the pulse current density had a positive effect on the grain refinement.The results of vibrating sample magnetometer(VSM)measurements demonstrated that by increasing the current density,the saturation magnetization was decreased and the coercivity was increased due to the enhancement of Cr content and the reduction of the grain size.The friction coefficient and wear rate values were decreased by increasing the pulse current density.Also,both the adhesive and abrasive wear mechanisms were observed on the worn surfaces.The abrasive grooves and the amount of wear debris were decreased by increasing the pulse current density.展开更多
基金supported by the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(MSIT),South Korea(RS-2024-00421181)financially supported in part by National R&D Program(2021M3H4A3A02086430)through NRF(National Research Foundation of Korea)funded by Ministry of Science and ICT+2 种基金the National Research Council of Science&Technology(NST)grant by the Korea government(MSIT)(No.GTL25021-210)The Inter-University Semiconductor Research Center,Institute of Engineering Research,and Soft Foundry Institute at Seoul National University provided research facilities for this workhe grant by the National Research Foundation of Korea(NSF)supported by the Korea government(MIST)(RS-2025-16903034)。
文摘As silicon-based transistors face fundamental scaling limits,the search for breakthrough alternatives has led to innovations in 3D architectures,heterogeneous integration,and sub-3 nm semiconductor body thicknesses.However,the true effectiveness of these advancements lies in the seamless integration of alternative semiconductors tailored for next-generation transistors.In this review,we highlight key advances that enhance both scalability and switching performance by leveraging emerging semiconductor materials.Among the most promising candidates are 2D van der Waals semiconductors,Mott insulators,and amorphous oxide semiconductors,which offer not only unique electrical properties but also low-power operation and high carrier mobility.Additionally,we explore the synergistic interactions between these novel semiconductors and advanced gate dielectrics,including high-K materials,ferroelectrics,and atomically thin hexagonal boron nitride layers.Beyond introducing these novel material configurations,we address critical challenges such as leakage current and long-term device reliability,which become increasingly crucial as transistors scale down to atomic dimensions.Through concrete examples showcasing the potential of these materials in transistors,we provide key insights into overcoming fundamental obstacles—such as device reliability,scaling down limitations,and extended applications in artificial intelligence—ultimately paving the way for the development of future transistor technologies.
基金the financial support from the National Natural Science Foundation of China(No.52072379)the Recruitment Program of Global Experts,and the Fundamental Research Funds for the Central Universities(WK2060000016)。
文摘The development of affordable,high-efficiency sodium-ion batteries is primarily dependent on the advancement of cathode materials.These materials need to exhibit a high cell voltage,significant storage capacity,and quick diffusion of sodium ions to fulfill the requirements for efficient and ecofriendly energy storage systems.In this vein,density functional theory(DFT)calculation has become instrumental in advancing the study of battery materials.This study presents a firstprinciples investigation of P2-type Na_(x)NiO_(2)and Na_(x)Ni_(0.75)M_(0.25)O_(2)(M=Cu,Fe,Mn)cathode materials for sodium-ion batteries(SIBs),focusing on Na content variation and its impact on the battery performance.For NaNiO_(2),we replaced part of the expensive Ni element with lower-cost Cu,Fe,and Mn in hopes of reducing costs and improving material performance.By employing density functional theory(DFT),we explore the relationship between lattice constants,cell volume,enthalpy of formation,and cell voltage,and how these factors influence sodium ion insertion/extraction.We provide insights into the diffusion paths and activation energies for Na ions,and assess the influence of transition metal(TM)substitution on the structural stability and electrochemical properties of the materials.Additionally,the study delves into the electronic structure,highlighting how Cu and Fe integration refines the band gap of the spin-down bands.The findings reveal that certain transition metal substitutions can enhance performance,offering a pathway to optimize sodium-ion battery electrode materials.
基金the National High-Tech Development Plan (2006AA05Z417)the Natural Science Foundation of Lia-oning Province (20062145)the Education department of Liaoning Province (05L073)
文摘The precursors of La0.7Sr0.3-xCaxCo0.9Fe0.1O3-δ(LSCCF, x=0.05, 0.10, 0.15, 0.20) as the cathode materials for intermediate temperature solid oxide fuel cell (ITSOFC) were prepared by reverse titration co-precipitation method with metal-nitrates as starting materials and mixed alkali (NaOH and Na2CO3) as a precipitating agent. The formation process of LSCCF from the precursors was monitored by TG-DSC, and the crystal structure and particles morphology of the precursors which were calcined at 600, 800, 1000 ℃ for 3 h were characterized using XRD, SEM technologies. Compared with the solid state reaction of constituent oxides, when the pH value of the precipitating solution was in the range of 9.1～9.5, the LSCCF powders from the precursors caclined at 800 ℃ for 3 h had high purity, homogeneous and single perovskite phase. The electrical conductivity of the LSCCF samples sintered at 1200 ℃ for 3 h, which was measured as a function of temperatures from 100 to 800 ℃ by DC four-probe method in air, decreased with x from 0.05 to 0.20. The value of electrical conductivity was almost equal because of Ca2+, Sr2+ co-dopant resulting in the 'mix effect' while x=0.10 or 0.15. The electrical conductivity of all doped samples was higher than 100 S·cm-1 at intermediate temperatures from 500 to 800 ℃, and there was good compatibility between the LSCCF cathode and Ce0.8Sm0.2O2 electrolyte.
基金supported by the China Scholarship Council(No.202208210253)the Natural Science Foundation of Liaoning Province(2022-MS-272)the Scientific Research Funding Project of the Education Department of Liaoning Province(LJKMZ20220463).
文摘Al_(0.5)CrFeNi_(2.5)high-entropy alloy(HEA)was reinforced by the small-radius Si.Al_(0.5)CrFeNi_(2.5)Six(x=0 and 0.25)HEAs were fabricated by laser melting deposition.The evolution of microstructure,nanohardness,and wear properties of Al_(0.5)CrFeNi_(2.5)Six(x=0 and 0.25)HEAs were systematically investigated.Al_(0.5)CrFeNi_(2.5)HEA exhibits a face-centered cubic(FCC)matrix with Ni3Al-type ordered nanoprecipitates.When Si was doped,σphase and Cr-rich nanoprecipitates existed in the B2 matrix and L12 in the FCC matrix.The nanohardness was increased from 4.67 to 5.45 GPa with doping of Si,which is associated with forming the new phases and improved nanohardness of L12/FCC phases.The coefficient of friction(COF)value was reduced from 0.75 to 0.67 by adding Si.σphase and Cr-rich nanoprecipitates in B2 matrix support a decreased wear rate from 7.87×10^(-4) to 6.82×10^(-4) mm^(3)/(N m).Furthermore,the main wear mechanism of Al_(0.5)CrFeNi_(2.5)and Al_(0.5)CrFeNi_(2.5)Si0.25 HEAs is abrasive wear.
基金supported by the Nuclear Regulatory Commission Fellowship Grant No.NRC-HQ-84-14-G-0035.
文摘While developing nuclear materials,predicting their behavior under long-term irradiation regimes span-ning decades poses a significant challenge.We developed a novel Kinetic Monte Carlo(KMC)model to explore the precipitation behavior of Y-Ti-O oxides along grain boundaries within nanostructured ferritic alloys(NFA).This model also assessed the response of the oxides to neutron irradiation,even up sim-ulated radiation damage levels in the desired long dpa range for reactor components.Our simulations investigated how temperature and grain boundary sinks influenced the oxide characteristics of a 12YWT-like alloy during heat treatments at 1023,1123,and 1223 K.The oxide characteristics observed in our simulations were in good agreement with existing literature.Furthermore,the impact of grain bound-aries on precipitation was found to be minimal.The resulting oxide configurations and positions were used in subsequent simulations that exposed them to simulated neutron irradiation to a total accumu-lated dose of 8 dpa at three temperatures:673,773,and 873 K,and at dose rates of 10-3,10-4,and 10-5 dpa/s.This demonstrated the expected inverse relationship between oxide size and dose rate.In a long-term irradiation simulation at 873 K and 10-3 dpa/s was taken out to 66 dpa and found the oxides in the vicinity of the grain boundary were more susceptible to dissolution.Additionally,we conducted irradia-tion simulations of a 14YWT-like alloy to reproduce findings from neutron irradiation experiments.The larger oxides in the 14YWT-like alloy did not dissolve and displayed stability similar to the experimental results.
基金supported by the National Natural Science Foundation of China(No.10874174)。
文摘We propose the scaling rule of Morse oscillator,based on this rule and by virtue of the Her-mann-Feymann theorem,we respectively obtain the distribution of potential and kinetic ener-gy of the Morse Hamiltonian.Also,we derive the exact upper limit of physical energy level.Further,we derive some recursive relations for energy matrix elements of the potential and other similar operators in the context of Morse oscillator theory.
基金supported by President Foundation of Chinese Academy of Sciences and National Natural Science Foundation of China under Grant Nos. 10775097 and 10874174
文摘By introducing a fictitious mode to be a counterpart mode of the system mode under review we introduce the entangled state representation （η｜, which can arrange master equations of density operators p（t） in quantum statistics as state-vector evolution equations due to the elegant properties of （η｜. In this way many master equations （respectively describing damping oscillator, laser, phase sensitive, and phase diffusion processes with different initial density operators） can be concisely solved. Specially, for a damping process characteristic of the decay constant k we find that the matrix element of p（t） at time t in 〈η｜ representation is proportional to that of the initial po in the decayed entangled state （ηe^-kt｜ representation, accompanying with a Gaussian damping factor. Thus we have a new insight about the nature of the dissipative process. We also set up the so-called thermo-entangled state representation of density operators, ρ = f（d^2η/π）（η｜ρ〉D（η）, which is different from all the previous known representations.
基金This work was supported by the National High-Tech Research and Development Program of China (No.2003AA332020), the Nation-al Natural Science Foundation of China (No.50474002) and the Key Project of the Ministry of Education of China (No.104231).
文摘High performance aluminosilicate based cementitious materials were produced using calcined gangue as one of the major raw materials. The gangue was calcined at 500℃. The main constituent was calcined gangue, fly ash and slag, while alkali-silicate solutions were used as the diagenetic agent. The structure of gangue-containing aluminosilicate based cementitious materials was studied by the methods of IR, NMR and SEM. The results show that the mechanical properties are affected by the mass ratio between the gangue, slag and fly ash, the kind of activator and additional salt. For 28-day curing time, the compressive strength of the sample with a mass proportion of 2：1：1 （gangue： slag： fly ash） is 58.9 MPa, while the compressive strength of the sample containing 80wt% gangue can still be up to 52.3 MPa. The larger K^＋ favors the formation of large silicate oligomers with which AI（OH）4- prefers to bind. Therefore, in Na-K compounding activator solutions more oligomers exist which result in a stronger compressive strength of aluminosilicate-based cementitious materials than in the case of Na-containing activator. The reasons for this were found through IR and NMR analysis. Glauber＇s salt reduces the 3-day compressive strength of the paste, but increases its 7-day and 28-day compressive strengths.
基金the National Research Foundation(NRF)grant funded by the Ministry of Science and ICT of Korea through contracts NRF-2018K2A9A1A06069970,NRF2020R1A5A6017701the Asian Office of Aerospace Research and Development(AOARD)grant funded by the Air Force Office of Scientific Research(AFOSR)through a grant FA2386-19-1-4009。
文摘Light and strong AlxCrNbVMo(x=0,0.5,and 1.0)refractory high-entropy alloys(RHEAs)were designed and fabricated via a the powder metallurgical process.The microstructure of the AlxCrNbVMo alloys consisted of a single BCC crystalline structure with a sub-micron grain size of 2-3μm,and small amounts(<4 vol.%)of fine oxide dispersoids.This homogeneous microstructure,without chemical segregation or micropores was achieved via high-energy ball milling and spark-plasma sintering.The alloys exhibited superior mechanical properties at 25 and 1000℃compared to those of other RHEAs.Here,CrNbVMo alloy showed a yield strength of 2743 MPa at room temperature.Surprisingly,the yield strength of the CrNbVMo alloy at 1000℃was 1513 MPa.The specific yield strength of the CrNbVMo alloy was increased by 27%and 87%at 25 and 1000℃,respectively,compared to the AlMo_(0.5) NbTa_(0.5)TiZr RHEA,which exhibited so far the highest specific yield strength among the cast RHEAs.The addition of Al to CrNbVMo alloy was advantageous in reducing its reduce density to below 8.0 g/cm^(3),while the elastic modulus decreased due to the much lower elastic modulus of Al compared to that of the CrNbVMo alloy.Quantitative analysis of the strengthening contributions,showed that the solid solution strengthening,arising from a large misfit effect due to the size and modulus,and the high shear modulus of matrix,was revealed to predominant strengthening mechanism,accounting for over 50%of the yield strength of the AlxCrNbVMo RHEAs.
基金Natural Science Foundation of Liaoning Province(No.2019-MS-247)Liao Ning Revitalization Talents Program(No.XLYC1807178)+1 种基金Research Fund of the State Key Laboratory of Solidification Processing(No.SKLSP202011)International Cooperation Project of Guangdong Province(No.2021A0505030052)。
文摘High-entropy alloy(HEA)coatings are of great importance in the fabrication of wear resistance materials.HEA coatings containing ceramic particles as reinforcement phase usually have better wear performance.In this study,AlCoCrFe Ni(TiN)_(x)(x:molar ratio;x=0,0.2,0.4,0.6,0.8,1.0)HEA coatings were fabricated on Q235 steel by plasma spray first and then subjected to laser remelting.The experimental results confirm that plasma spray together with post laser remelting could result in the in-situ formation of TiN-Al_(2)O_(3) ceramic particles and cuboidal B2 phase in the AlCoCrFeNi(TiN)_(x) HEA coatings.The in-situ TiN-Al_(2)O_(3) and nano-cuboidal B2 precipitation phase strengthened the coatings and improved their wearresistance properties.Due to the dispersion of hard phase and nano-particles resulting from second heating,the microhardness of the Al Co Cr Fe Ni(Ti N)coatings significantly increased from 493 to 851 HV after laser remelting.For the same reasons,the wear-resistance performance was also significantly promoted after laser remelting.
基金sponsored by the National Natural Science Foundation of China(No.51705489)the State Key Laboratory of Advanced Brazing Filler Metals and Technology,Zhengzhou Research Institute of Mechanical Engineering(No.SKLABFMT201603)
文摘For the purpose of high-temperature service and the weight reduction in aviation engineering applications,the dissimilar joining of Ti3Al-based alloy to Ni-based superalloy(GH536)was conducted using Au-17.5Ni(wt%)brazing filler metal.The microstructure and chemical composition at the interfaces were investigated by scanning electron microscope,X-ray diffraction and transmission electron microscope.The diffusion behaviors of elements were analyzed as well.The results indicated that the Ti_(3)Al/GH536 joint microstructure was characterized by multiple layer structures.Element Ni from Au-Ni filler metal reacted with Ti3Al base metal,leading to the formation of AlNi2Ti and NiTi compounds.Element Ni from Ti3Al base metal reacted with Ni and thus Ni3Nb phase was detected in the joint central area.Due to the dissolution of Ni-based superalloy,(Ni,Au)solid solution((Ni,Au)ss)and Ni-rich phase were visible adjacent to the superalloy side.The average tensile strength of all the joints brazed at 1253 K for 5-20 min was above 356 MPa at room-temperature.In particular,the joints brazed at 1253 K/15 min presented the maximum tensile strength of434 MPa at room-temperature,and the strength of 314 MPa was maintained at 923 K.AlNi2Ti compound resulted in the highest hardness area and the fracture of the samples subjected to the tensile test mainly occurred in this zone.
文摘Maximum bubble pressure measurement was employed to evaluate surface tension of Sn-8Zn-3Bi- (00.15)Nd and Sn-8Zn-3Bi-(00.15)La solder melts. Wetting balance method was used to measure wetting force and wetting time on Cu substrate of the two group solders. The experimental results show that minute amount of Nd or La addition to Sn-8Zn-3Bi solder causes significant decrease of the surface tension of the solder melts at 200240℃ and Nd addition is more effective on reduction of surface tension than that of La. Nd or La addition has the effect on enhancing the wetting force of the solder melts on Cu substrate, which results from the decrease of interfacial tension between the solder melt and Cu substrate. The wetting force reaches the maximum when 0.1% Nd is added to the base alloy. The contact angle between Sn-8Zn-3Bi base solders and Cu substrate decreases with the addition of Nd or La and the minimum of the contact angle is obtained from the solder with 0.1% Nd addition.
基金The authors are grateful for the financial support of the National Science Foundation of China(Grant No.20174029)National Key Basic Research and Development Program(G1999064703).
文摘Konjac glucomannan （KGM） was crosslinked with sodium tripolyphosphate （STPP） to synthesize hydrogels. The crosslinking reaction was confirmed by FT-IR. The results of degradation test show that the hydrogels retain the enzymatic degradation character of KGM and can be degraded for 74.45% in 5 days by cellulase E0240.
基金supported by 2008 research fund by TP,Ulsan,Korea
文摘Niobium (Nb)-clad stainless steels(SS) produced via roll bonding are being considered for use in the bipolar plates of polymer electrolyte membrane fuel cell(PEMFC) stacks. Because the roll bonding process induces substantial work hardening in the constituent materials, thermal annealing is used to restore ductility to the clad sheet so that it can be subsequently blanked, stamped and dimpled in forming the final plate component. Two roll bonded materials, niobium clad 340L stainless steel (Nb/340L SS) and niobium clad 434 stainless steel (Nb/434 SS) were annealed under optimized conditions prescribed by the cladding manufacturer. Comparative mechanical testing conducted on each material before and after annealing shows significant improvement in ductility in both cases. However, corresponding microstructural analyses indicate an obvious difference between the two heat treated materials. During annealing, an interlayer with thick less than 1 μm forms between the constituent layers in the Nb/340L SS, whereas no interlayer is found in the annealed Nb/434 SS material. Prior work suggests that internal defects potentially can be generated in such an interlayer during metal forming operations. Thus, Nb/434 SS may be the preferred candidate material for this application.
文摘Direct quenching and tempering （DQ-T） of hot rolled steel section has been widely used in steel mill for the sake of improvement of mechanical properties and energy saving. Temperature history and microstructural evolution during hot rolling plays a major role in the properties of direct quenched and tempered products. The mathematical and physical modeling of hot forming processes is becoming a very important tool for design and development of required products as well as predicting the microstructure and the properties of the components. These models were mostly used to predict austenite grain size （AGS）, dynamic, recta-dynamic and static recrystallization in the rods immediately after hot rolling and prior to DQ process. The hot compression tests were carried out on 42CrMo4 steel in the temperature range of 900-1 100 ℃ and the strain rate range of 0. 05-1 s^-1 in order to study the high tempera- ture softening behavior of the steel. For the exact prediction of flow stress, the effective stress-effective strain curves were obtained from experiments under various conditions. On the basis of experimental results, the dynamic recrystallization fraction （DRX）, AGS, hot deformation and activation energy behavior were investigated. It was found that the calculated results were in good agreement with the experimental flow stress and microstructure of the steel for different conditions of hot deformation.
基金supported by National Natural Science Foundation of China(No50741003)Key Project of Science and Technology of Ministry of Education of China (No107066)Anhui Provincial Natural Science Foundation(No070414181)
文摘Silver matrix composite brushes were fabricated by means of powder metallurgy, which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700 ℃ and repressing at 500 MPa. Four kinds composites with different compositions were produced, and the mechanical properties and electrical wear performance were investigated. The results showed that the composite added with carbon nanotubes had a higher hardness and strength, a lower contact voltage drop and an excellent anti-wear property in electrical sliding wear, because of the reinforcement ability of carbon nanotubes. Adding graphite to the composite also decreased the wear loss and contact voltage drop, because graphite had an electrical current conducting ability which not only made the current pass the lubricating films easily but also eliminated and reduced the arc and spark effectively.
基金supported by a grant from the Metals Bank by the Ministry of Knowledge Economy and a grant-in-aid for the National Core Research Center Program (No.R15-2006-022-02001-0)
文摘The effects of Ca and Sr addition on the microstructure and creep properties of Mg-4Al-2Sn alloys were examined. Tensile tests at 25 ℃ and 200 ℃ and creep tests at 150 ℃ and 200 ℃ were carried out to estimate the room temperature and high temperature mechanical properties of these alloys. The microstrueture of the Mg-4Al-2Sn alloy showed dendritic a-Mg, Mg17Al12 and Mg2Sn phases. The latter two phases precipitated along the grain boundaries. The addition of Ca and Sr resulted in the formation of ternary CaMgSn and SrMgSn phases within the grain. The grain size was reduced slightly with the addition of Sr and Ca. The tensile strength was decreased by the addition of Ca and Sr at room temperature. However, the high temperature tensile strength was increased. The creep strength was improved by the addition of Ca and Sr.
基金Supported by the National Natural Science Foundation of China under Grant No.19574045。
文摘It is pointed out that the quantum mechanical Hamiltonian of two L-C circuits with mutual-inductance is equivalent to a pair of harmonic oscillators with a kinetic coupling term.We then diagonalize the Hamiltonian.It is shown that instantaneously switching on the external sources may result in a two-mode squeezed state of the system,which actually arises from the effect of mutual-inductance.The quantum fluctuation for the case of l_(1)c_(1)=l_(2)c_(2 ) is analysed and it is found that the current fluctuation in the circuits increases with the increment of the mutual-inductance.
文摘The microstructure and mechanical properties of friction stir welded 2. 5 mm 7050-T7451 aluminum alloy natural aging 72 h and 17 520 h were investigated, respectively. The uniaxial tensile test showed that yield strength, tensile strength and elongation of the joints 17 520 h natural aging were about 20%, 12% and 24% higher than those joints natural aging 72 h. Hardness profile of natural aging 17 520 h joint witnessed significant enhancement in nugget zone, compared with 72 h natural aging. Differential scanning calorimetry （ DSC ） and transmission electron microscopy （TEM） test revealed that more Guinier-Preston zone, η＇ and 71 phase emerged in nugget zone as natural aging duration increased, high density of dislocation located within grain boundary in nugget zone of joints natural aging 72 h. It is concluded that natural aging was feasible to enhalwe strength and plasticity of FSW joints simultaneously.
文摘The nanocrystalline Fe-Ni-Cr coatings were electrodeposited by using the pulse current technique.The SEM results showed that the coatings had a mixed morphology of small nodules and fine cauliflower structures at low current densities.Also,the Cr content was increased at expense of Fe and Ni contents at high current densities.XRD patterns confirmed that the pulse current density had a positive effect on the grain refinement.The results of vibrating sample magnetometer(VSM)measurements demonstrated that by increasing the current density,the saturation magnetization was decreased and the coercivity was increased due to the enhancement of Cr content and the reduction of the grain size.The friction coefficient and wear rate values were decreased by increasing the pulse current density.Also,both the adhesive and abrasive wear mechanisms were observed on the worn surfaces.The abrasive grooves and the amount of wear debris were decreased by increasing the pulse current density.
