Layered compounds play pivotal roles as precursors for producing 2D materials through mechanical exfoliation(micro-mechanical cleavage) or chemical approaches. Therefore, searching for layered compounds with sharp ani...Layered compounds play pivotal roles as precursors for producing 2D materials through mechanical exfoliation(micro-mechanical cleavage) or chemical approaches. Therefore, searching for layered compounds with sharp anisotropic chemical bonding and properties becomes emergent. In this work, the stability, electronic structure, elastic properties, and lattice dynamics of YBCwere investigated. Strong anisotropy in elastic properties is revealed, i.e., high Young’s modulus in a-b plane but low Young’s modulus in c direction. The maximum to minimum Young’s modulus ratio is 2.41 and 2.45 for YBCwith P42/mmc and P4/mbm symmetry, respectively. The most likely systems for shear sliding or microdelaminating are(001)[100] and(001)[010]. The anisotropic elastic properties are underpinned by the anisotropic chemical bonding, i.e., strong bonding within the BCnets and weak bonding between Y atom layers and BCnets. YBCis electrically conductive and the contributions to the electrical conductivity are from delocalized Y 4deas well as Bpandpzelectrons. The layered crystal structure, sharp anisotropic mechanical properties, and metallic conductivity endorse YBCpromising as a precursor for new 2D BCnets.展开更多
REB_(2)C_(2)(RE=Y and lanthanides)compounds have gained attention for their unique layered crystal structure.However,there have been few reports about Raman spectroscopy of REB_(2)C_(2) compounds up to now.Here,the Ra...REB_(2)C_(2)(RE=Y and lanthanides)compounds have gained attention for their unique layered crystal structure.However,there have been few reports about Raman spectroscopy of REB_(2)C_(2) compounds up to now.Here,the Raman spectrum of YbB_(2)C_(2) is obtained by a micro-Raman spectroscope and the first-principles calculations.Raman active vibrational modes of YbB_(2)C_(2) are confirmed as A_(1g)(627 and 1311 cm^(-1)),B_(1g)(944 and 1172 cm^(-1)),B_(2g)(330 and 885 cm^(-1))and E_(g)(357 and 530 cm^(-1)).Atomic displacements of these modes are different,they can be divided into two groups:A_(1g)’,B_(1g) and B_(2g) correspond to ring breathing(δ_(in),in the plane)of B_(2)C_(2) layer;E_(g) is due to ring deformation(δ_(oop),out of the plane)of B_(2)C_(2) layer.These results are helpful to understand the individual structure of REB_(2)C_(2).展开更多
Layered compound zirconium bis(monohydrogenphosphate)(alpha-ZrP) intercalated with rare earth complex Eu(DBM)(3)phen was prepared. The pre-intercalation of p-methoxyaniline into alpha-ZrP makes the interlayer separati...Layered compound zirconium bis(monohydrogenphosphate)(alpha-ZrP) intercalated with rare earth complex Eu(DBM)(3)phen was prepared. The pre-intercalation of p-methoxyaniline into alpha-ZrP makes the interlayer separation large enough to exchange PMA with europium complex, thus, the luminescent assembly was prepared. This was confirmed by X-ray diffraction, UV-visible spectra and elemental analysis. The fluorescence spectra and lifetime of the assembly were also presented.展开更多
Layered transition-metal compounds(LTMCs)feature stacked architectures,strong magnetic anisotropy,and tunable magnetic order,making them promising material platforms for low-power spintronic technologies and for enabl...Layered transition-metal compounds(LTMCs)feature stacked architectures,strong magnetic anisotropy,and tunable magnetic order,making them promising material platforms for low-power spintronic technologies and for enabling topological functionalities in the post-Moore era.Here we review recent progress on two-dimensional(2D)magnetism in LTMCs,emphasizing material taxonomy,intrinsic magnetic properties,and external-field controls.This review first presents a classification of LTMCs by crystal structure and chemistry—binary halides,chalcogenides,and ternary families(e.g.,MPX_(3),M_(m)X_(n)Te_(k),MnBi_(2)Te_(4))—followed by a summary of their coupling mechanisms,ordering temperatures,and dimensional effects.It then analyzes the modulation of exchange interactions,magnetic anisotropy,and topological states by electric-field gating,strain engineering,and ion intercalation,with representative experimental demonstrations.Notable advances include room-temperature ferromagnetic metals and semiconductors,observation of the quantum anomalous Hall effect(QAHE)in MnBi2Te4,and synergistic control of magnetic-topological states under multiple external stimuli.Persistent challenges involve the limited availability of intrinsic 2D magnetic semiconductors with high Curie temperatures(Tc),incomplete understanding of the microscopic couplings at interfaces and under quantum confinement,and device-level stability.We conclude by outlining opportunities that lie in the integration of multiscale characterization,first-principles theory,and cross-scale fabrication to precisely co-engineer magnetism,topology,and electronic structure,thereby advancing LTMCs toward spintronic and topological-quantum applications.展开更多
The energies and the magnetization of an electron in a piece of metal in the structure of Metal/Insulator/Metal/Insulator… (M/I/M/I…), in a magnetic field, at high temperature, and in range of quantum size thickness...The energies and the magnetization of an electron in a piece of metal in the structure of Metal/Insulator/Metal/Insulator… (M/I/M/I…), in a magnetic field, at high temperature, and in range of quantum size thickness of the piece of metal layer have been obtained. The results show that when the thickness of the metal layer becomes smaller, the orbital magnetism of the charged particles which collide with the wall of the metal layer is to vary from diamagnetism to paramagnetism. The smaller the thickness of the metal layer becomes, the more particles will collide with the boundary of the metal layer, and then the paramagnetism becomes stronger. Finally, when the thickness of the metal layer becomes very small (<100 nm), all of the orbital diamagnetism will reverse to paramagnetism, and then the paramagnetization will be almost a maximum constant.展开更多
Three kinds of new layered perovskite compounds with Ruddlesden-Popper （R-P） phase, AgrNa2-xLa2Ti3O10 （x = 0.2, 0.3 and 0.5）, were synthesized by an ion-exchange reaction of Na2La2Ti3O10 with AgNO3 solution. The s...Three kinds of new layered perovskite compounds with Ruddlesden-Popper （R-P） phase, AgrNa2-xLa2Ti3O10 （x = 0.2, 0.3 and 0.5）, were synthesized by an ion-exchange reaction of Na2La2Ti3O10 with AgNO3 solution. The structures of the compounds were characterized by EDX and XRD, and their antibacterial activity and light-resistance property were evaluated. The results indicated that the molecular formula of AgxNa2-xLa2Ti3O10 （x = 0.2, 0.3 and 0.5） was confirmed, and that the crystalline structure of Na2La2Ti3O10 was not obviously affected by exchange of silver ion. The minimum inhibitory concentrations （MICs） of Ag0.3Na1.7La2Ti3O10 against Escherichia coli （E. coli）, Staphylococcus aureus （S. aureus） were 180 μg/mL and 240 μg/mL, respectively, while its discoloration was not observed after 24 h light ageing test.展开更多
The growth kinetics of intermetallic compound layer between molten In-Sn alloy and Cu40Zr44Al8Ag8 bulk metallic glass substrate was examined by solid state isothermal aging at the temperature range between 333 and 393...The growth kinetics of intermetallic compound layer between molten In-Sn alloy and Cu40Zr44Al8Ag8 bulk metallic glass substrate was examined by solid state isothermal aging at the temperature range between 333 and 393 K.The aged samples were characterized by scanning electron microscopy and energy dispersive spectrometry.It is found that the intermetallic compound layer is composed of Zr,Cu and Sn.The layer growth of the intermetallic compound is mainly controlled by a diffusion mechanism over the temperature range and the value of the time exponent is approximately 0.5.The apparent activation energy for the growth of total intermetallic compound layers is 98.35 kJ /mol calculated by the Arrhenius equation.展开更多
The preparation of ZnAlLa-hydrotalcite-like compounds [ZnAlLa-HTLcs] wasstudied. ZnAlLa-HTLcs were synthesized by a method of variable pH with the raw materials ofZn(NO_3)_2, Al(NO_3)_3, La(NO_3)_3, and NaOH. The eS&#...The preparation of ZnAlLa-hydrotalcite-like compounds [ZnAlLa-HTLcs] wasstudied. ZnAlLa-HTLcs were synthesized by a method of variable pH with the raw materials ofZn(NO_3)_2, Al(NO_3)_3, La(NO_3)_3, and NaOH. The eS'ccts of some factors (i.e. pH values, the moleratio of Al^(3+) to La^(3+), temperature and the period of hydrothermal treatment) on thepreparation of HTLcs were discussed systematically. XRD, TG-DTA, FT-IR spectroscopy, and ICP wereperformed to characterize ZnAlLa-HTLcs samples, and the thermal stability of HTLcs was alsodiscussed. It was shown that unique ZnAlLa-HTLcs with high crystallinity can be prepared, under theconditions of pH = 5.5-6.5, n(Zn^(2+))/n(Al^(3+) + La^(3+))=2 and the atomic ratio of La^(3+) toAl^(3+) ranging from 0.07 to 2, hydrothermal treatment at 120 ℃ for 5 h. When the calcination ofthe HTLcs is performed at temperatures above 200 ℃, ZnO phase is detected with Al_2O_3 and La_2O_3spreading on its top. The complex metal oxides derived from ZnAlLa-HTLcs at 500 ℃ have highercatalytic activity and selectivity than those from ZnAl-HTLcs for the esterification of acetic acidwith n-butanol under the same reaction conditions.展开更多
Infrared spectra of (n-C_9H_(19)NH_3)_2CuCl_4 in three solid phases were investigated. It was found that the phase transition at T_(cl)(25℃) arises from the change of the interaction and packing structure of the chai...Infrared spectra of (n-C_9H_(19)NH_3)_2CuCl_4 in three solid phases were investigated. It was found that the phase transition at T_(cl)(25℃) arises from the change of the interaction and packing structure of the chain. The phase transition at T_(c2)(34℃)is related to the change of a partial conformational order-disorder. The GTC or GTG' and small concentration of TG structure near CH_3 group exist in phase Ⅲ (above 38℃).展开更多
In this paper, we present Continuous Multiple Center(CMC) d-p πbond in TS_2 slabs on the basis of Extended Huckle calculation for incommensurate misfit compounds (MS)_xTS_2(where M=Pb, Sn and La; T=V,Nb,Ta, Cr), and ...In this paper, we present Continuous Multiple Center(CMC) d-p πbond in TS_2 slabs on the basis of Extended Huckle calculation for incommensurate misfit compounds (MS)_xTS_2(where M=Pb, Sn and La; T=V,Nb,Ta, Cr), and put forwards the trigonal prismatic coordination CMC d-p π conductive model. According to this model the conductivity of (MS)_xTS_2 series and the similarity between (MS)_xTS_2 and Na_xTS_2 series compounds in metallic behaviors can be explained successfully. Some relations between metallic behaviors and CMC d-p π bond (or band) are found.展开更多
Thin heavily Mg-doped InGaN and GaN compound contact layer is used to form Ni/Au Ohmic contact to p-GaN. The growth conditions of the compound contact layer and its effect on the performance of Ni/Au Ohmic contact to ...Thin heavily Mg-doped InGaN and GaN compound contact layer is used to form Ni/Au Ohmic contact to p-GaN. The growth conditions of the compound contact layer and its effect on the performance of Ni/Au Ohmic contact to p-GaN are investigated. It is confirmed that the specific contact resistivity can be lowered nearly two orders by optimizing the growth conditions of compound contact layer. When the flow rate ratio between Mg and Ga gas sources of p＋＋-InGaN layer is 10.6% and the thickness of p＋＋-InGaN layer is 3 nm, the lowest specific contact resistivity of 3.98× 10-5 Ω cm2 is achieved. In addition, the experimental results indicate that the specific contact resistivity can be further lowered to 1.07 × 10-7Ω.cm2 by optimizing the alloying annealing temperature to 520 ℃.展开更多
With the Uddeholm self restricted method, the effect of compound layer of plasma nitriding on thermal fatigue behavior of 4Cr5MoSiV1 steel was studied by the way of adding Ar during plasma nitriding to remove the com...With the Uddeholm self restricted method, the effect of compound layer of plasma nitriding on thermal fatigue behavior of 4Cr5MoSiV1 steel was studied by the way of adding Ar during plasma nitriding to remove the compound layer. The results show that the compound layer of plasma nitriding can delay the nucleation of heat cracks and hold back the propagation of heat cracks from surface to substrate because of its high hardness and strength. On the other land, the heat checking expands faster with the compound layer on the surface than that without it. After 3000 cycles of thermal fatigue test, both heat cracks with the compound layer are wider than the another without compound layer and the number of heat cracks of the former is more from the view of cross section.展开更多
A silicon-on-insulator （SOI） high performance lateral double-diffusion metal oxide semiconductor （LDMOS） on a compound buried layer （CBL） with a step buried oxide （SBO CBL SOI） is proposed. The step buried oxi...A silicon-on-insulator （SOI） high performance lateral double-diffusion metal oxide semiconductor （LDMOS） on a compound buried layer （CBL） with a step buried oxide （SBO CBL SOI） is proposed. The step buried oxide locates holes in the top interface of the upper buried oxide （UBO） layer. Furthermore, holes with high density are collected in the interface between the polysilicon layer and the lower buried oxide （LBO） layer. Consequently, the electric fields in both the thin LBO and the thick UBO are enhanced by these holes, leading to an improved breakdown voltage. The breakdown voltage of the SBO CBL SOI LDMOS increases to 847 V from the 477 V of a conventional SOI with the same thicknesses of SOI layer and the buried oxide layer. Moreover, SBO CBL SOI can also reduce the self-heating effect.展开更多
The bonding of solid steel plate to liquid aluminum was studied using rapidsolidification. The surface of solid steel plate was defatted, descaled, immersed (in K_2ZrF_6 fluxaqueous solution) and stoved. In order to d...The bonding of solid steel plate to liquid aluminum was studied using rapidsolidification. The surface of solid steel plate was defatted, descaled, immersed (in K_2ZrF_6 fluxaqueous solution) and stoved. In order to determine the thickness of Fe-Al compound layer at theinterface of steel-aluminum solid to liquid bonding under rapid solidification, the interface ofbonding plate was investigated by SEM (Scanning Electron Microscope) experiment. The relationshipbetween bonding parameters (such as preheat temperature of steel plate, temperature of aluminumliquid and bonding time) and thickness of Fe-Al compound layer at the interface was established byartificial neural networks (ANN) perfectly. The maximum of relative error between the output and thedesired output of the ANN is only 5.4%. From the bonding parameters for the largest interfacialshear strength of bonding plate (226℃ for preheat temperature of steel plate, 723℃ for temperatureof aluminum liquid and 15.8 s for bonding time), the reasonable thickness of Fe-Al compound layer10.8 μm was got.展开更多
Compounds that crystallize in the layered CaAl_(2)Si_(2)structural pattern have rapidly emerged as an exciting class of thermoelectric materials with attractive n-and p-type properties.More than 100 AM_(2)X_(2)compoun...Compounds that crystallize in the layered CaAl_(2)Si_(2)structural pattern have rapidly emerged as an exciting class of thermoelectric materials with attractive n-and p-type properties.More than 100 AM_(2)X_(2)compounds that form this structure type-characterized by anionic M_(2)X_(2)slabs sandwiched between layers of octahedrally coordinated A cations-provide numerous potential paths to chemically tune every aspect of thermoelectric transport.This review highlights the chemical diversity of this structure type,discusses the rules governing its formation and stability relative to competing AM_(2)X_(2)structures(e.g.,ThCr_(2)Si_(2)and BaCu_(2)S_(2)),and attempts to bring some of the most recently discovered compounds into the spotlight.The discussion of thermoelectric transport properties in AM_(2)X_(2)compounds focuses primarily on the intrinsic parameters that determine the potential for a high figure of merit:the band gap,effective mass,degeneracy,carrier relaxation time,and lattice thermal conductivity.We also discuss routes that have been used to successfully control the carrier concentration,including controlling the cation vacancy concentration,doping,and isoelectronic alloying(approaches that are highly interdependent).Finally,we discuss recent progress made towards n-type doping in this system,highlight opportunities for further improvements,as well as open questions that still remain.展开更多
Two types of layered hydroxide zinc m-aminobenzoate compounds with structures of layered basic metal salt （LBMS） were prepared by the reaction of zinc hydroxide with m-aminobenzoic acid solution in the temperature r...Two types of layered hydroxide zinc m-aminobenzoate compounds with structures of layered basic metal salt （LBMS） were prepared by the reaction of zinc hydroxide with m-aminobenzoic acid solution in the temperature range of 40----120℃. The formation reactions, structures, chemical compositions, and exfoliation reactions of the layered compounds in alcohol solvents were investigated by XRD, TG-DTA, SEM, and TEM. One layered phase with a basal spacing of 1.08 nm has a a-Ni（OH）2-1ike structure, and its chemical formula can be written as Zn（OH）0.67（m-NH2C6HaCOO）l.33. This phase has strip-like particle morphology and cannot be exfoliated into its nanosheets in alcohol solvents. The other layered phase with a basal spacing of 2.66 nm has a zinc hydrox- ide-nitrate-like structure, and can be exfoliated in alcohol solvents.展开更多
A two-dimensional lead complex, [Pb（C14N3O2H12S）（NO3）]n·nH2O, was prepared by the reaction of salicylyl-4-phenyl thiosemicarbazide and lead nitrate. The compound （C14H13N4O6PbS, Mr = 572.53） crystallizes in...A two-dimensional lead complex, [Pb（C14N3O2H12S）（NO3）]n·nH2O, was prepared by the reaction of salicylyl-4-phenyl thiosemicarbazide and lead nitrate. The compound （C14H13N4O6PbS, Mr = 572.53） crystallizes in the monoclinic space group P21/c with a = 11.2984（2）, b = 15.6628（7）, c = 11.1118（2）A,β= 113.564（2）°, V = 1802.43（10）A3, Dc= 2.110 g/cm3, Z = 4,μt（MoKα） = 9.515 mm-1, F（000） = 1084, the final R = 0.0394 and wR = 0.0701 for 2552 observed reflections with I 〉 2σ（I）. The Pb（Ⅱ） ion displays a distorted octahedron in which the hypothesized stereochemically active lone pair occupies the apex. The compound exhibits a two-dimensional network structure formed by the zigzag one-dimensional chains joined by two μ-O of two nitrate groups in overlapping. A large ring exists in the two-dimensional layers. The TGA of the title compound has been studied.展开更多
Plasma radical nitriding was performed to harden the surface of SCM440 steel for 1-10 h at temperature range of 450-550℃. This process involved the use of NH3 gas instead of N2 gas employed for the well-established p...Plasma radical nitriding was performed to harden the surface of SCM440 steel for 1-10 h at temperature range of 450-550℃. This process involved the use of NH3 gas instead of N2 gas employed for the well-established plasma nitriding method. No compound layer was formed during this process except the experiment carried out at 500℃ for 10 h. The main phase produced in the diffusion zone was identified to be γ＇-Fe4（N, C）. A diffusion depth increased with increasing treatment temperature and time （up to about 250 μm）. The surface hardness of radical nitrided layer was about two times higher than that of the untreated surface. The tensile test was carried out to estimate the mechanical properties of surface-hardened SCM440 steel prepared at various plasma radical nitriding treatment time and temperature. The influence of radical nitriding treatment on the tensile strength of the specimen was found to be insignificant. The highest value of the ultimate tensile strength was obtained in the experiment carried out at 500℃ for 1 h. However, the elongation was greatly affected by the radical nitriding processing parameters. The maximum value of elongation, which is equal to about 18.1%, was also obtained under the condition of 500℃ for 1 h.展开更多
Nowadays,finding cheap and non-toxic materials able to reversibly store high amounts of hydrogen is a challenge in the renewable energy field.Metal sulfides seem to be promising candidates to this purpose.Titanium sul...Nowadays,finding cheap and non-toxic materials able to reversibly store high amounts of hydrogen is a challenge in the renewable energy field.Metal sulfides seem to be promising candidates to this purpose.Titanium sulfides are reported to be particularly interesting but their ability to store hydrogen remains unclear.In this work,titanium based sulfides TiS2 and TiS3 with two-dimensional nanostructures have been synthesized by solid-gas reaction between titanium powder and sulfur at temperatures between 500-600℃.The morphology and crystal structure of Ti-sulfides were characterized by SEM(scanning electronic microscopy)equipped with EDX(energy dispersion X-ray)and XRD(X-ray diffraction),respectively.Their thermal stability was examined by TGA(thermal gravimetric analysis).Their hydrogenation properties have been determined by manometric means using a Sieverts system and by DSC-HP(high-pressure differential scanning calorimetric).Ti-sulfides hardly absorb/adsorb hydrogen for hydrogen pressures up to 80 bar and reaction temperatures up to 300℃.展开更多
The appearance of adhenng layer formed on tool face, its composition and distributionare analysed when Ca-S free-cutting stainless steel is machined. Cutting temperature field and itsrelation with formation of the lay...The appearance of adhenng layer formed on tool face, its composition and distributionare analysed when Ca-S free-cutting stainless steel is machined. Cutting temperature field and itsrelation with formation of the layer is also studied. The result shows that, the layer can be formed under proper temperature condition, the stable cutting temperature field keeps the stable layer, itsthickness and composition distribution along rake face depend on the corresponding cutting tem-perature field. The theoretical model of the layer formation is set up.展开更多
基金supported by the National Science Foundation of China under Grant No. U1435206 and No. 51672064the Beijing Municipal Science & Technology Commission under grant number Z151100003315012 and D161100002416001
文摘Layered compounds play pivotal roles as precursors for producing 2D materials through mechanical exfoliation(micro-mechanical cleavage) or chemical approaches. Therefore, searching for layered compounds with sharp anisotropic chemical bonding and properties becomes emergent. In this work, the stability, electronic structure, elastic properties, and lattice dynamics of YBCwere investigated. Strong anisotropy in elastic properties is revealed, i.e., high Young’s modulus in a-b plane but low Young’s modulus in c direction. The maximum to minimum Young’s modulus ratio is 2.41 and 2.45 for YBCwith P42/mmc and P4/mbm symmetry, respectively. The most likely systems for shear sliding or microdelaminating are(001)[100] and(001)[010]. The anisotropic elastic properties are underpinned by the anisotropic chemical bonding, i.e., strong bonding within the BCnets and weak bonding between Y atom layers and BCnets. YBCis electrically conductive and the contributions to the electrical conductivity are from delocalized Y 4deas well as Bpandpzelectrons. The layered crystal structure, sharp anisotropic mechanical properties, and metallic conductivity endorse YBCpromising as a precursor for new 2D BCnets.
基金financially supported by the National Natural Science Foundation of China under Contract Nos.50802099 and 51072201。
文摘REB_(2)C_(2)(RE=Y and lanthanides)compounds have gained attention for their unique layered crystal structure.However,there have been few reports about Raman spectroscopy of REB_(2)C_(2) compounds up to now.Here,the Raman spectrum of YbB_(2)C_(2) is obtained by a micro-Raman spectroscope and the first-principles calculations.Raman active vibrational modes of YbB_(2)C_(2) are confirmed as A_(1g)(627 and 1311 cm^(-1)),B_(1g)(944 and 1172 cm^(-1)),B_(2g)(330 and 885 cm^(-1))and E_(g)(357 and 530 cm^(-1)).Atomic displacements of these modes are different,they can be divided into two groups:A_(1g)’,B_(1g) and B_(2g) correspond to ring breathing(δ_(in),in the plane)of B_(2)C_(2) layer;E_(g) is due to ring deformation(δ_(oop),out of the plane)of B_(2)C_(2) layer.These results are helpful to understand the individual structure of REB_(2)C_(2).
文摘Layered compound zirconium bis(monohydrogenphosphate)(alpha-ZrP) intercalated with rare earth complex Eu(DBM)(3)phen was prepared. The pre-intercalation of p-methoxyaniline into alpha-ZrP makes the interlayer separation large enough to exchange PMA with europium complex, thus, the luminescent assembly was prepared. This was confirmed by X-ray diffraction, UV-visible spectra and elemental analysis. The fluorescence spectra and lifetime of the assembly were also presented.
基金supported by the National KeyR&D Program of China(Grant No.2024YFB3817400)the National Natural Science Foundation of China(Grants No.12274276 and No.U24A6002)+1 种基金the Natural Science Foundation of Shanxi Province(China)(Grant No.202403021223008)Supported by Scientific and Technology Innovation Programs of Higher Education Institutions in Shanxi(Grant No.2024Q017 and No.2025L043).
文摘Layered transition-metal compounds(LTMCs)feature stacked architectures,strong magnetic anisotropy,and tunable magnetic order,making them promising material platforms for low-power spintronic technologies and for enabling topological functionalities in the post-Moore era.Here we review recent progress on two-dimensional(2D)magnetism in LTMCs,emphasizing material taxonomy,intrinsic magnetic properties,and external-field controls.This review first presents a classification of LTMCs by crystal structure and chemistry—binary halides,chalcogenides,and ternary families(e.g.,MPX_(3),M_(m)X_(n)Te_(k),MnBi_(2)Te_(4))—followed by a summary of their coupling mechanisms,ordering temperatures,and dimensional effects.It then analyzes the modulation of exchange interactions,magnetic anisotropy,and topological states by electric-field gating,strain engineering,and ion intercalation,with representative experimental demonstrations.Notable advances include room-temperature ferromagnetic metals and semiconductors,observation of the quantum anomalous Hall effect(QAHE)in MnBi2Te4,and synergistic control of magnetic-topological states under multiple external stimuli.Persistent challenges involve the limited availability of intrinsic 2D magnetic semiconductors with high Curie temperatures(Tc),incomplete understanding of the microscopic couplings at interfaces and under quantum confinement,and device-level stability.We conclude by outlining opportunities that lie in the integration of multiscale characterization,first-principles theory,and cross-scale fabrication to precisely co-engineer magnetism,topology,and electronic structure,thereby advancing LTMCs toward spintronic and topological-quantum applications.
基金Supported by the National Natural Science Foundation of China(5 96 0 2 0 0 4)
文摘The energies and the magnetization of an electron in a piece of metal in the structure of Metal/Insulator/Metal/Insulator… (M/I/M/I…), in a magnetic field, at high temperature, and in range of quantum size thickness of the piece of metal layer have been obtained. The results show that when the thickness of the metal layer becomes smaller, the orbital magnetism of the charged particles which collide with the wall of the metal layer is to vary from diamagnetism to paramagnetism. The smaller the thickness of the metal layer becomes, the more particles will collide with the boundary of the metal layer, and then the paramagnetism becomes stronger. Finally, when the thickness of the metal layer becomes very small (<100 nm), all of the orbital diamagnetism will reverse to paramagnetism, and then the paramagnetization will be almost a maximum constant.
文摘Three kinds of new layered perovskite compounds with Ruddlesden-Popper （R-P） phase, AgrNa2-xLa2Ti3O10 （x = 0.2, 0.3 and 0.5）, were synthesized by an ion-exchange reaction of Na2La2Ti3O10 with AgNO3 solution. The structures of the compounds were characterized by EDX and XRD, and their antibacterial activity and light-resistance property were evaluated. The results indicated that the molecular formula of AgxNa2-xLa2Ti3O10 （x = 0.2, 0.3 and 0.5） was confirmed, and that the crystalline structure of Na2La2Ti3O10 was not obviously affected by exchange of silver ion. The minimum inhibitory concentrations （MICs） of Ag0.3Na1.7La2Ti3O10 against Escherichia coli （E. coli）, Staphylococcus aureus （S. aureus） were 180 μg/mL and 240 μg/mL, respectively, while its discoloration was not observed after 24 h light ageing test.
基金Project (2011CB606301) supported by the National Basic Research Program of ChinaProject (20212339) supported by the Doctor Startup Foundation Program of Shenyang University,China
文摘The growth kinetics of intermetallic compound layer between molten In-Sn alloy and Cu40Zr44Al8Ag8 bulk metallic glass substrate was examined by solid state isothermal aging at the temperature range between 333 and 393 K.The aged samples were characterized by scanning electron microscopy and energy dispersive spectrometry.It is found that the intermetallic compound layer is composed of Zr,Cu and Sn.The layer growth of the intermetallic compound is mainly controlled by a diffusion mechanism over the temperature range and the value of the time exponent is approximately 0.5.The apparent activation energy for the growth of total intermetallic compound layers is 98.35 kJ /mol calculated by the Arrhenius equation.
基金Supported by Shanxi Province Natural Science Funds.(20001015)
文摘The preparation of ZnAlLa-hydrotalcite-like compounds [ZnAlLa-HTLcs] wasstudied. ZnAlLa-HTLcs were synthesized by a method of variable pH with the raw materials ofZn(NO_3)_2, Al(NO_3)_3, La(NO_3)_3, and NaOH. The eS'ccts of some factors (i.e. pH values, the moleratio of Al^(3+) to La^(3+), temperature and the period of hydrothermal treatment) on thepreparation of HTLcs were discussed systematically. XRD, TG-DTA, FT-IR spectroscopy, and ICP wereperformed to characterize ZnAlLa-HTLcs samples, and the thermal stability of HTLcs was alsodiscussed. It was shown that unique ZnAlLa-HTLcs with high crystallinity can be prepared, under theconditions of pH = 5.5-6.5, n(Zn^(2+))/n(Al^(3+) + La^(3+))=2 and the atomic ratio of La^(3+) toAl^(3+) ranging from 0.07 to 2, hydrothermal treatment at 120 ℃ for 5 h. When the calcination ofthe HTLcs is performed at temperatures above 200 ℃, ZnO phase is detected with Al_2O_3 and La_2O_3spreading on its top. The complex metal oxides derived from ZnAlLa-HTLcs at 500 ℃ have highercatalytic activity and selectivity than those from ZnAl-HTLcs for the esterification of acetic acidwith n-butanol under the same reaction conditions.
文摘Infrared spectra of (n-C_9H_(19)NH_3)_2CuCl_4 in three solid phases were investigated. It was found that the phase transition at T_(cl)(25℃) arises from the change of the interaction and packing structure of the chain. The phase transition at T_(c2)(34℃)is related to the change of a partial conformational order-disorder. The GTC or GTG' and small concentration of TG structure near CH_3 group exist in phase Ⅲ (above 38℃).
文摘In this paper, we present Continuous Multiple Center(CMC) d-p πbond in TS_2 slabs on the basis of Extended Huckle calculation for incommensurate misfit compounds (MS)_xTS_2(where M=Pb, Sn and La; T=V,Nb,Ta, Cr), and put forwards the trigonal prismatic coordination CMC d-p π conductive model. According to this model the conductivity of (MS)_xTS_2 series and the similarity between (MS)_xTS_2 and Na_xTS_2 series compounds in metallic behaviors can be explained successfully. Some relations between metallic behaviors and CMC d-p π bond (or band) are found.
基金support by the National Natural Science Foundation of China(Grant Nos.61474110,61377020,61376089,61223005,and 61176126)the National Science Fund for Distinguished Young Scholars,China(Grant No.60925017)
文摘Thin heavily Mg-doped InGaN and GaN compound contact layer is used to form Ni/Au Ohmic contact to p-GaN. The growth conditions of the compound contact layer and its effect on the performance of Ni/Au Ohmic contact to p-GaN are investigated. It is confirmed that the specific contact resistivity can be lowered nearly two orders by optimizing the growth conditions of compound contact layer. When the flow rate ratio between Mg and Ga gas sources of p＋＋-InGaN layer is 10.6% and the thickness of p＋＋-InGaN layer is 3 nm, the lowest specific contact resistivity of 3.98× 10-5 Ω cm2 is achieved. In addition, the experimental results indicate that the specific contact resistivity can be further lowered to 1.07 × 10-7Ω.cm2 by optimizing the alloying annealing temperature to 520 ℃.
文摘With the Uddeholm self restricted method, the effect of compound layer of plasma nitriding on thermal fatigue behavior of 4Cr5MoSiV1 steel was studied by the way of adding Ar during plasma nitriding to remove the compound layer. The results show that the compound layer of plasma nitriding can delay the nucleation of heat cracks and hold back the propagation of heat cracks from surface to substrate because of its high hardness and strength. On the other land, the heat checking expands faster with the compound layer on the surface than that without it. After 3000 cycles of thermal fatigue test, both heat cracks with the compound layer are wider than the another without compound layer and the number of heat cracks of the former is more from the view of cross section.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.60806025 and 60976060)in part by the State Key Laboratory of Electronic Thin Films and Integrated Devices,China (Grant No.CXJJ201004)
文摘A silicon-on-insulator （SOI） high performance lateral double-diffusion metal oxide semiconductor （LDMOS） on a compound buried layer （CBL） with a step buried oxide （SBO CBL SOI） is proposed. The step buried oxide locates holes in the top interface of the upper buried oxide （UBO） layer. Furthermore, holes with high density are collected in the interface between the polysilicon layer and the lower buried oxide （LBO） layer. Consequently, the electric fields in both the thin LBO and the thick UBO are enhanced by these holes, leading to an improved breakdown voltage. The breakdown voltage of the SBO CBL SOI LDMOS increases to 847 V from the 477 V of a conventional SOI with the same thicknesses of SOI layer and the buried oxide layer. Moreover, SBO CBL SOI can also reduce the self-heating effect.
基金This project is financially supported by National Natural Science Foundation of China (No.50274047) and Advanced Technical Committee of China(No. 715-009-060)
文摘The bonding of solid steel plate to liquid aluminum was studied using rapidsolidification. The surface of solid steel plate was defatted, descaled, immersed (in K_2ZrF_6 fluxaqueous solution) and stoved. In order to determine the thickness of Fe-Al compound layer at theinterface of steel-aluminum solid to liquid bonding under rapid solidification, the interface ofbonding plate was investigated by SEM (Scanning Electron Microscope) experiment. The relationshipbetween bonding parameters (such as preheat temperature of steel plate, temperature of aluminumliquid and bonding time) and thickness of Fe-Al compound layer at the interface was established byartificial neural networks (ANN) perfectly. The maximum of relative error between the output and thedesired output of the ANN is only 5.4%. From the bonding parameters for the largest interfacialshear strength of bonding plate (226℃ for preheat temperature of steel plate, 723℃ for temperatureof aluminum liquid and 15.8 s for bonding time), the reasonable thickness of Fe-Al compound layer10.8 μm was got.
文摘Compounds that crystallize in the layered CaAl_(2)Si_(2)structural pattern have rapidly emerged as an exciting class of thermoelectric materials with attractive n-and p-type properties.More than 100 AM_(2)X_(2)compounds that form this structure type-characterized by anionic M_(2)X_(2)slabs sandwiched between layers of octahedrally coordinated A cations-provide numerous potential paths to chemically tune every aspect of thermoelectric transport.This review highlights the chemical diversity of this structure type,discusses the rules governing its formation and stability relative to competing AM_(2)X_(2)structures(e.g.,ThCr_(2)Si_(2)and BaCu_(2)S_(2)),and attempts to bring some of the most recently discovered compounds into the spotlight.The discussion of thermoelectric transport properties in AM_(2)X_(2)compounds focuses primarily on the intrinsic parameters that determine the potential for a high figure of merit:the band gap,effective mass,degeneracy,carrier relaxation time,and lattice thermal conductivity.We also discuss routes that have been used to successfully control the carrier concentration,including controlling the cation vacancy concentration,doping,and isoelectronic alloying(approaches that are highly interdependent).Finally,we discuss recent progress made towards n-type doping in this system,highlight opportunities for further improvements,as well as open questions that still remain.
基金Project supported by the Shaanxi Provincial Natural Science Foundation （No. 2007B24）, and the Education Office of Shaanxi Province （No. 2010JK409） of China.
文摘Two types of layered hydroxide zinc m-aminobenzoate compounds with structures of layered basic metal salt （LBMS） were prepared by the reaction of zinc hydroxide with m-aminobenzoic acid solution in the temperature range of 40----120℃. The formation reactions, structures, chemical compositions, and exfoliation reactions of the layered compounds in alcohol solvents were investigated by XRD, TG-DTA, SEM, and TEM. One layered phase with a basal spacing of 1.08 nm has a a-Ni（OH）2-1ike structure, and its chemical formula can be written as Zn（OH）0.67（m-NH2C6HaCOO）l.33. This phase has strip-like particle morphology and cannot be exfoliated into its nanosheets in alcohol solvents. The other layered phase with a basal spacing of 2.66 nm has a zinc hydrox- ide-nitrate-like structure, and can be exfoliated in alcohol solvents.
基金supported by the Science Foundation of Huaqiao University (07BS509)
文摘A two-dimensional lead complex, [Pb（C14N3O2H12S）（NO3）]n·nH2O, was prepared by the reaction of salicylyl-4-phenyl thiosemicarbazide and lead nitrate. The compound （C14H13N4O6PbS, Mr = 572.53） crystallizes in the monoclinic space group P21/c with a = 11.2984（2）, b = 15.6628（7）, c = 11.1118（2）A,β= 113.564（2）°, V = 1802.43（10）A3, Dc= 2.110 g/cm3, Z = 4,μt（MoKα） = 9.515 mm-1, F（000） = 1084, the final R = 0.0394 and wR = 0.0701 for 2552 observed reflections with I 〉 2σ（I）. The Pb（Ⅱ） ion displays a distorted octahedron in which the hypothesized stereochemically active lone pair occupies the apex. The compound exhibits a two-dimensional network structure formed by the zigzag one-dimensional chains joined by two μ-O of two nitrate groups in overlapping. A large ring exists in the two-dimensional layers. The TGA of the title compound has been studied.
文摘Plasma radical nitriding was performed to harden the surface of SCM440 steel for 1-10 h at temperature range of 450-550℃. This process involved the use of NH3 gas instead of N2 gas employed for the well-established plasma nitriding method. No compound layer was formed during this process except the experiment carried out at 500℃ for 10 h. The main phase produced in the diffusion zone was identified to be γ＇-Fe4（N, C）. A diffusion depth increased with increasing treatment temperature and time （up to about 250 μm）. The surface hardness of radical nitrided layer was about two times higher than that of the untreated surface. The tensile test was carried out to estimate the mechanical properties of surface-hardened SCM440 steel prepared at various plasma radical nitriding treatment time and temperature. The influence of radical nitriding treatment on the tensile strength of the specimen was found to be insignificant. The highest value of the ultimate tensile strength was obtained in the experiment carried out at 500℃ for 1 h. However, the elongation was greatly affected by the radical nitriding processing parameters. The maximum value of elongation, which is equal to about 18.1%, was also obtained under the condition of 500℃ for 1 h.
文摘Nowadays,finding cheap and non-toxic materials able to reversibly store high amounts of hydrogen is a challenge in the renewable energy field.Metal sulfides seem to be promising candidates to this purpose.Titanium sulfides are reported to be particularly interesting but their ability to store hydrogen remains unclear.In this work,titanium based sulfides TiS2 and TiS3 with two-dimensional nanostructures have been synthesized by solid-gas reaction between titanium powder and sulfur at temperatures between 500-600℃.The morphology and crystal structure of Ti-sulfides were characterized by SEM(scanning electronic microscopy)equipped with EDX(energy dispersion X-ray)and XRD(X-ray diffraction),respectively.Their thermal stability was examined by TGA(thermal gravimetric analysis).Their hydrogenation properties have been determined by manometric means using a Sieverts system and by DSC-HP(high-pressure differential scanning calorimetric).Ti-sulfides hardly absorb/adsorb hydrogen for hydrogen pressures up to 80 bar and reaction temperatures up to 300℃.
文摘The appearance of adhenng layer formed on tool face, its composition and distributionare analysed when Ca-S free-cutting stainless steel is machined. Cutting temperature field and itsrelation with formation of the layer is also studied. The result shows that, the layer can be formed under proper temperature condition, the stable cutting temperature field keeps the stable layer, itsthickness and composition distribution along rake face depend on the corresponding cutting tem-perature field. The theoretical model of the layer formation is set up.
