Lattice constants and electronic structures of diluted magnetic semiconductors ( In, Mn ) As were investigated using the first principles LMTO-ASA band calculation by assuming supercell structures. Three concentrati...Lattice constants and electronic structures of diluted magnetic semiconductors ( In, Mn ) As were investigated using the first principles LMTO-ASA band calculation by assuming supercell structures. Three concentrations of the 3 d impurities were studied ( x = 1/2, 1/4, 1/8). The effect of varying Mn coucentrations on the lattice constants and the electronic structures are shown.展开更多
PZT(Zr/Ti=52/48) ferroelectric films are prepared by a new modified Sol-Gel method from three stable-separated Pb2+, Zr4+, Ti4+ precursor–monomers. This method needs no distillation and has the advantage of easy chan...PZT(Zr/Ti=52/48) ferroelectric films are prepared by a new modified Sol-Gel method from three stable-separated Pb2+, Zr4+, Ti4+ precursor–monomers. This method needs no distillation and has the advantage of easy change of the Pb2+/Zr4+/Ti4+ stoichiometric. In the paper we also investigate PT seeds influence on ferroelectric properties, crystallographic structures and surface morphologies, and find the bottom/up PT seeds structure prompte PZT crystallization and have superior ferroeletric properties. The paper introduce a method to deduce and calculate lattice constant α by ‘least square method’, then the more accurate lattice constant a0 can be got from X-ray diffractometer (XRD) analysis data. We also discover that grain sizes of PZT film calculated from XRD data are much closed to those of AFM, and the film a0 is relatively small due to crushing stress.展开更多
Cerium oxide possesses intrinsic hydrophobic properties ascribed to the unique electronic structure.However,the relationship between the crystal structure and hydrophobicity of cerium oxide has not been systematically...Cerium oxide possesses intrinsic hydrophobic properties ascribed to the unique electronic structure.However,the relationship between the crystal structure and hydrophobicity of cerium oxide has not been systematically studied.Herein,it is experimentally and theoretically demonstrated that the water contact angle(105.9°)of the(111)surface is higher than that(91.7°)of the(220)surface,associated with the lower surface free energy(28.44 mN/m)of(111)surface than that(38.48 mN/m)of(220)surface.Furthermore,cerium oxide films with(111)-terminated surface are annealed at 300℃ and 600℃ for1 h,respectively.The lattice constant increases(5.4594Å<5.4613Å<5.4670Å)with decreasing the annealing temperature(600℃>300℃>the as-deposited),leading to the increased water contact angle(96.7°<96.8°<99.0°).The First-principles calculation provides microscopic insights into the wetting mechanism,originating from the weakened adsorption capacity of the(111)surface for water molecules with the increasing lattice constant.展开更多
The lattice constants and chemical composition of Ti,Nb and V precipitates with different particle sizes have been measured hy means of CBED and EDAX.It was obtained that the concentration ratio Of Nb and V,C_(Nb)/C_V...The lattice constants and chemical composition of Ti,Nb and V precipitates with different particle sizes have been measured hy means of CBED and EDAX.It was obtained that the concentration ratio Of Nb and V,C_(Nb)/C_V,and the lattice constants in the Nb-V steel de- crease with the decrease of the particle size of the precipitates,but there is no regularity for tattice constant of Ti,N b and V precipitate against their particle size in the Ti-V-Nb steel.展开更多
Initially, all that was known about diffraction in quasicrystals was its point group symmetry;nothing was known about the mechanism. The structure was more evident, and was called quasiperiodic. From mapping the Mn at...Initially, all that was known about diffraction in quasicrystals was its point group symmetry;nothing was known about the mechanism. The structure was more evident, and was called quasiperiodic. From mapping the Mn atoms by phase-contrast, optimum-defocus, electron microscopy, the progress towards identifying unit cell, cluster, supercluster and extensive hierarchic structure is evident. The structure is ordered and uniquely icosahedral. From the known structure, we could calculate structure factors. They were all zero. The quasi structure factor is an iterative procedure on the hierarchic structure that correctly calculates diffraction beam intensities in 3-dimensional space. By a creative device, the diffraction is demonstrated to occur off the Bragg condition;the quasi-Bragg condition implies a metric that enables definition and measurement of the lattice constant. The reciprocal lattice is the 3-dimensional diffraction pattern. Typically, it builds on Euclidean axes with coordinates in geometric series, but it also transforms to Cartesian coordinates.展开更多
The electronic structures of pure Ti, Zr and Hf metals with hcp structure were determined by one atom (OA) theory. According to the electronic structures of these metals,their potential curves, cohesive energies, latt...The electronic structures of pure Ti, Zr and Hf metals with hcp structure were determined by one atom (OA) theory. According to the electronic structures of these metals,their potential curves, cohesive energies, lattice constants, elasticities and the temperature dependence of linear thermal expansion coefficients were calculated. The electronic structures and characteristic properties of these metals with bcc and fcc structures and liquids were also studied. The results show that the electronic structures of Ti, Zr and Hf metals are respectively [Ar](3d n) 0.481 0 (3d c) 2.085 7 (4s c) 1.000 0 (4s f) 0.433 3 , [Kr](4d n) 0.396 8 (4d c) 2.142 8 (5s c) 1.262 0 (5s f) 0.198 4 , [Xe](5d n) 0.368 0 (5d c) 2.041 4 (6s c) 1.406 6 (6s f) 0.184 0 . It is explained why the pure Ti, Zr and Hf metals with hcp and bcc structures can exist naturally, while those with fcc structure can not.展开更多
A series of Ba8Ga16Si30 clathrate samples were prepared by arc melting, ball milling, acid washing, and spark plasma sintering (SPS). X-ray diffraction analysis revealed that the lattice of the Ba8Ga16Si30 samples e...A series of Ba8Ga16Si30 clathrate samples were prepared by arc melting, ball milling, acid washing, and spark plasma sintering (SPS). X-ray diffraction analysis revealed that the lattice of the Ba8Ga16Si30 samples expanded as the SPS temperature was increased from 400 to 750℃. Lattice contraction recurred when the SPS temperature was further increased in the range of 750-1000℃. This phenomenon can be explained by the variation of Ga content in the lattice. The thermoelectric figure of the merit ZT value of clathrates increased with the increase in SPS temperature and reached a maximum when the sample was subjected to SPS at 800℃. A further increase in SPS temperature did not contribute to the improvement of ZT. The variation of the lattice parameter a vs. SPS temperature T was similar to the variation ob-served in the ZT-T curve.展开更多
Using the new developed valence bond theory of metals,the electronic structure,crystal structure and physical properties of Au metal have been systematically analysed.It has been determined that its electronic structu...Using the new developed valence bond theory of metals,the electronic structure,crystal structure and physical properties of Au metal have been systematically analysed.It has been determined that its electronic structure is(5d_(n))^(4.65)(5d_(c))^(4.71)(6s_(c))^(0.62)(6s_(f))^(1.02).According to this electronic structure,lattice constant,cohesive energy.potential curve,bulk modulus and temperature dependence of liner thermal expansion coeCHcient have been calculated.The theoretical values of properties are all in good agreement with experimental results.This electronic structure has been verified in part by linear rigorous cellular method of band theory.It shows that the valence bond theory has been reached perfectly.展开更多
The anisotropy of the microstructure, thermal expansion behavior, corrosion resistance and magnetic properties of AISI 1045 steel was investigated. The distribution of Fe3C lameUae in the investigation plane parallel ...The anisotropy of the microstructure, thermal expansion behavior, corrosion resistance and magnetic properties of AISI 1045 steel was investigated. The distribution of Fe3C lameUae in the investigation plane parallel to the radial directions of molds was observed to differ from that in the investigation plane perpendicular to the radial directions by transmission electron microscopy. The lattice constants a0 of α-Fe deduced from the XRD patterns of samples prepared using a sand (S)-mold and cut parallel to the radial direction of the mold (S//) and using a metal (M)-mold and cut parallel to the radial direction (M//), the corrosion resistance measured using an electrochemical work- station, and the magnetic permeability obtained by vibrating sample magnetometry also indicated the existence of anisotropy in the tested samples. The anisotropic change of corrosion potential (Eeorr), pitting potential (Epit) and magnetic permeability (μ) of the samples was observed to depend on the orientation factorF200 of α-Fe in the measured samples, which is controlled by the distribution of Fe3C lamellae in the eutectoid structure.展开更多
he expressions of the composition space and the dependent properties of the lattice constant, the energy bandgap and the Gibbs energy were presented for the (Ga,In)(As,Sb) quaternary compound semiconductor. On the bas...he expressions of the composition space and the dependent properties of the lattice constant, the energy bandgap and the Gibbs energy were presented for the (Ga,In)(As,Sb) quaternary compound semiconductor. On the basis of these expressions, a computer aided analysis system is set up for the design of ⅢⅤ compound semiconductor materials and growth processes. By using this system, a comprehensively optimized diagram is constructed through the projection of the optoelectronic properties (energy bandgap or wave length), in which the composition relations are matched to substrates and the miscibility gaps.展开更多
The microstructures of platinum (111) facets were studied by reflection electron microscopy, and the features on facets, for example, growth steps, slip steps, and dislocations emerging through the surfaces, etc., wer...The microstructures of platinum (111) facets were studied by reflection electron microscopy, and the features on facets, for example, growth steps, slip steps, and dislocations emerging through the surfaces, etc., were analysed. In the following annealing at about 1100°C for 1 h in the atmosphere, the migration of crystal surface atoms resulted in the transformation of stepped configuration on (111) facets. Differently high and sized ?111? terraces or small planes distributed on facets constructed frustum structures.展开更多
In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas(2DEG)electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-depen...In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas(2DEG)electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-dependent Hall measurement and theoretical fitting method. The results of our analysis clearly indicate that the Ga N cap layer thickness of an Al N/Ga N heterostructure has influences on the 2DEG electron density and the electron mobility. For the Al N/Ga N heterostructures with a 3-nm Al N barrier layer, the optimized thickness of the Ga N cap layer is around 4 nm and the strained a-axis lattice constant of the Al N barrier layer is less than that of Ga N.展开更多
We have carried out density functional theory to study the lattice constants and electronic properties of LaB<sub>6</sub>, NdB<sub>6</sub>, Nd-doped LaB<sub>6</sub>, and La-doped Nd...We have carried out density functional theory to study the lattice constants and electronic properties of LaB<sub>6</sub>, NdB<sub>6</sub>, Nd-doped LaB<sub>6</sub>, and La-doped NdB<sub>6</sub>. The lattice constant, intra-octahedral bond, inter-octahedral boron bond, and positional parameter (z) were calculated for LaB<sub>6</sub>, La<sub>7</sub>Nd<sub>1</sub>B<sub>6</sub>, La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub>, and NdB<sub>6</sub>. Our results show that the doped Nd increases the lattice constant of La<sub>7</sub>Nd<sub>1</sub>B<sub>6</sub>. Likewise, La-doping leads to an increase in the lattice constant of the La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub>. The PDOSs of LaB<sub>6</sub>, B of LaB<sub>6</sub>, La<sub>7</sub>Nd<sub>1</sub>B<sub>6</sub>, B of La<sub>7</sub>Nd<sub>1</sub>B<sub>6</sub>, La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub>, B of La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub>, NdB<sub>6</sub>, and B of NdB<sub>6</sub> were calculated. La d-electron bands cross the Fermi energy, showing classical conductor behavior. The charge density results indicate that light and dark colors show high and low-intensity zones, respectively. La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub> has a low-density region and LaB<sub>6</sub> has a high-density region. The LaB<sub>6</sub> midpoint has strong charge density peaks. Weak peaks are also observed for La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub>. Thus, ternary REB<sub>6</sub> has good potential for many applications. This article reports an investigation of the electronic features and structural parameters of binary and ternary hexaborides.展开更多
Ti(C,N)concentration was found to be lower on the hearth sidewall of a blast furnace and increased gradually toward the bottom of the blast furnace.The Ti(C,N)protective layer in a blast furnace is thin.Therefore,the ...Ti(C,N)concentration was found to be lower on the hearth sidewall of a blast furnace and increased gradually toward the bottom of the blast furnace.The Ti(C,N)protective layer in a blast furnace is thin.Therefore,the formation of a Ti(C,N)protective layer was promoted by studying the heterogeneous nucleation principle of titanium compounds on different substances and regulation measures for the deposition process of titanium compounds on refractories or impurities.The lattice disregistry between the titanium compounds and the main components in the refractory or the main impurities in the protective layer was calculated using a two-dimensional disregistry equation to study the heterogeneous nucleation principle of titanium compounds.The results revealed that in refractory materials,the heterogeneous nucleation of carbonitride is weak when C,SiO_(2),and Al_(2)O_(3) are used as heterogeneous nucleation substrates,and the heterogeneous nucleation of carbonitride is strong when TiO_(2) and SiC are used as heterogeneous nucleation substrates.As nucleation phases,TiC,TiN,Ti(C_(0.3),N_(0.7)),and Ti(C_(0.5),N_(0.5))have similar heterogeneous nucleation ability in single component refractory,and the type of carbonitride has little effect on the lattice disregistry.The impurities in the protective layer as the substrate phases are not conducive to the heterogeneous nucleation of carbonitride.When CaS was used as the substrate phase,the heterogeneous nucleation ability of carbonitride was the worst.Both carbon and alumina were not conducive to the heterogeneous nucleation of carbonitride,but carbon was more unfavourable than alumina.展开更多
Line width(i.e.,critical dimension,CD)is a crucial parameter in integrated circuits.To accurately control the CD in manufacturing,a reasonable CD measurement algorithm is required.We develop an automatic and accurate ...Line width(i.e.,critical dimension,CD)is a crucial parameter in integrated circuits.To accurately control the CD in manufacturing,a reasonable CD measurement algorithm is required.We develop an automatic and accurate method based on a two-dimensional discrete Fourier transform for measuring the lattice spacings from high-resolution transmission electron microscopy images.Through the two-dimensional inverse discrete Fourier transform of the central spot and a pair of symmetrical diffraction spots,an image containing only a set of lattice spacings is obtained.Then,the pixel span of the lattice spacing is calculated through the centre of gravity method.Finally,we estimate the standard CD value according to the half-intensity method.The silicon crystal lattice constant guarantees the accuracy and traceability of the CD value.Through experiments,we demonstrate the efficiency of the proposed method,which can be conveniently applied to accurately measure CDs in practical applications.展开更多
This paper designs the thermal crystals composed of alloy materials with air holes and analyzes their properties of band structures,heat transmission,and flux spectra.Thermal crystals composed of Si-A(A=Ge,Sn,Pb)alloy...This paper designs the thermal crystals composed of alloy materials with air holes and analyzes their properties of band structures,heat transmission,and flux spectra.Thermal crystals composed of Si-A(A=Ge,Sn,Pb)alloys as background materials and air holes with square array are used to construct an elastic-constant periodic structure and their high-frequency phononic band is calculated by deploying finite element methods.Moreover,this paper investigates heat transmission through a finite array of thermally excited phonons and presents the thermal crystal with maximum heat transport.The results show that a wider bandgap could be achieved by increasing the air hole radius and decreasing the lattice constant.In the alloy materials,with increasing atomic radius and thus atomic mass(Ge,Sn,Pb),the frequency range(contributed to thermal conductivity)shifts towards lower frequency.Hence,the bandgap frequencies also shift toward low frequency,but this decreasing rate is not constant or in order,so former may have a faster or slower decreasing rate than the later.Thus,the frequency range for the contribution of heat transportation overlaps with the bandgap frequency range.The development of thermal crystals is promising for managing heat and controlling the propagation of the thermal wave.展开更多
According to the correlativity between energy, volume and electronic structure of characteristic crystals and bound conditions of OA theory, the Gibbs energy function, atomic volume function and electronic structure o...According to the correlativity between energy, volume and electronic structure of characteristic crystals and bound conditions of OA theory, the Gibbs energy function, atomic volume function and electronic structure of Ag Cu alloys have been determined. Then the electronic structure and properties of disordered alloys with any composition and ordered alloys with any ordering degree can be calculated. The number of d c covalent electrons in the states of Ag characteristic atoms decreases with the increase of Cu atoms in the nearest neighbouring shell. The number of d c covalent electrons in the states of Cu characteristic atoms decreases with the increase of Ag atoms in the nearest neighbouring shell. Such changes lead to the tendencies of atomic segregation and partition into two phases in the Ag Cu system.展开更多
Nine functions of atomic volume interaction have been established. The values of average atomic volumes and lattice constants of Ag-Cu alloys obtained from each V-function are, respectively, equal to each other and in...Nine functions of atomic volume interaction have been established. The values of average atomic volumes and lattice constants of Ag-Cu alloys obtained from each V-function are, respectively, equal to each other and in good agreement with experimental values. But the average atomic volumes of components and the volumes of characteristic atoms obtained from each V-function are different from each other. Only after the correlative study of energy, volume and electronic structure is carried out, can the V-function be correctly chosen, can a knowledge system about the alloys be established, thus providing the base for scientific design of new alloys. The relationships between lattice parameters of metastable phases of Ag-Cu alloys and composition and between average properties and partial molar properties of components are discussed.展开更多
基金Funded by the National Natural Science Foundation of China(No.60476047) ,the Key Teacher Foundation of the EducationalBureau of Henan Province ,and the Natural Science Foundation ofthe Educational Bureau of Henan Province , China ( No:2003140027 ,2004140004)
文摘Lattice constants and electronic structures of diluted magnetic semiconductors ( In, Mn ) As were investigated using the first principles LMTO-ASA band calculation by assuming supercell structures. Three concentrations of the 3 d impurities were studied ( x = 1/2, 1/4, 1/8). The effect of varying Mn coucentrations on the lattice constants and the electronic structures are shown.
基金Supported by the Ferroelectric Films Part of 973 Projects (No.51310Z02)
文摘PZT(Zr/Ti=52/48) ferroelectric films are prepared by a new modified Sol-Gel method from three stable-separated Pb2+, Zr4+, Ti4+ precursor–monomers. This method needs no distillation and has the advantage of easy change of the Pb2+/Zr4+/Ti4+ stoichiometric. In the paper we also investigate PT seeds influence on ferroelectric properties, crystallographic structures and surface morphologies, and find the bottom/up PT seeds structure prompte PZT crystallization and have superior ferroeletric properties. The paper introduce a method to deduce and calculate lattice constant α by ‘least square method’, then the more accurate lattice constant a0 can be got from X-ray diffractometer (XRD) analysis data. We also discover that grain sizes of PZT film calculated from XRD data are much closed to those of AFM, and the film a0 is relatively small due to crushing stress.
基金financially supported by the National Natural Science Foundation of China(Nos.51901062 and U1908220)the Natural Science Foundation of Zhejiang Province(No.LR18E010001)+1 种基金the Key R&D Project of Zhejiang Province(Nos.2019C01121 and 2021C01023)the LiaoNing Revitalization Talents Program(No.XLYC1807177)。
文摘Cerium oxide possesses intrinsic hydrophobic properties ascribed to the unique electronic structure.However,the relationship between the crystal structure and hydrophobicity of cerium oxide has not been systematically studied.Herein,it is experimentally and theoretically demonstrated that the water contact angle(105.9°)of the(111)surface is higher than that(91.7°)of the(220)surface,associated with the lower surface free energy(28.44 mN/m)of(111)surface than that(38.48 mN/m)of(220)surface.Furthermore,cerium oxide films with(111)-terminated surface are annealed at 300℃ and 600℃ for1 h,respectively.The lattice constant increases(5.4594Å<5.4613Å<5.4670Å)with decreasing the annealing temperature(600℃>300℃>the as-deposited),leading to the increased water contact angle(96.7°<96.8°<99.0°).The First-principles calculation provides microscopic insights into the wetting mechanism,originating from the weakened adsorption capacity of the(111)surface for water molecules with the increasing lattice constant.
文摘The lattice constants and chemical composition of Ti,Nb and V precipitates with different particle sizes have been measured hy means of CBED and EDAX.It was obtained that the concentration ratio Of Nb and V,C_(Nb)/C_V,and the lattice constants in the Nb-V steel de- crease with the decrease of the particle size of the precipitates,but there is no regularity for tattice constant of Ti,N b and V precipitate against their particle size in the Ti-V-Nb steel.
文摘Initially, all that was known about diffraction in quasicrystals was its point group symmetry;nothing was known about the mechanism. The structure was more evident, and was called quasiperiodic. From mapping the Mn atoms by phase-contrast, optimum-defocus, electron microscopy, the progress towards identifying unit cell, cluster, supercluster and extensive hierarchic structure is evident. The structure is ordered and uniquely icosahedral. From the known structure, we could calculate structure factors. They were all zero. The quasi structure factor is an iterative procedure on the hierarchic structure that correctly calculates diffraction beam intensities in 3-dimensional space. By a creative device, the diffraction is demonstrated to occur off the Bragg condition;the quasi-Bragg condition implies a metric that enables definition and measurement of the lattice constant. The reciprocal lattice is the 3-dimensional diffraction pattern. Typically, it builds on Euclidean axes with coordinates in geometric series, but it also transforms to Cartesian coordinates.
基金TheNaturalScienceFoundationofHunanProvince (No .99JZY10 0 5 )
文摘The electronic structures of pure Ti, Zr and Hf metals with hcp structure were determined by one atom (OA) theory. According to the electronic structures of these metals,their potential curves, cohesive energies, lattice constants, elasticities and the temperature dependence of linear thermal expansion coefficients were calculated. The electronic structures and characteristic properties of these metals with bcc and fcc structures and liquids were also studied. The results show that the electronic structures of Ti, Zr and Hf metals are respectively [Ar](3d n) 0.481 0 (3d c) 2.085 7 (4s c) 1.000 0 (4s f) 0.433 3 , [Kr](4d n) 0.396 8 (4d c) 2.142 8 (5s c) 1.262 0 (5s f) 0.198 4 , [Xe](5d n) 0.368 0 (5d c) 2.041 4 (6s c) 1.406 6 (6s f) 0.184 0 . It is explained why the pure Ti, Zr and Hf metals with hcp and bcc structures can exist naturally, while those with fcc structure can not.
基金supported by the National Natural Science Foundation of China(No.51072023)the National Science Foundation of US(No.DMR-0821284)the National Aeronautics and Space Administration of US(Nos.NNX10AM80H and NNX07AO30A)
文摘A series of Ba8Ga16Si30 clathrate samples were prepared by arc melting, ball milling, acid washing, and spark plasma sintering (SPS). X-ray diffraction analysis revealed that the lattice of the Ba8Ga16Si30 samples expanded as the SPS temperature was increased from 400 to 750℃. Lattice contraction recurred when the SPS temperature was further increased in the range of 750-1000℃. This phenomenon can be explained by the variation of Ga content in the lattice. The thermoelectric figure of the merit ZT value of clathrates increased with the increase in SPS temperature and reached a maximum when the sample was subjected to SPS at 800℃. A further increase in SPS temperature did not contribute to the improvement of ZT. The variation of the lattice parameter a vs. SPS temperature T was similar to the variation ob-served in the ZT-T curve.
基金supported by China National Nonferrous Metals Industry Corporation
文摘Using the new developed valence bond theory of metals,the electronic structure,crystal structure and physical properties of Au metal have been systematically analysed.It has been determined that its electronic structure is(5d_(n))^(4.65)(5d_(c))^(4.71)(6s_(c))^(0.62)(6s_(f))^(1.02).According to this electronic structure,lattice constant,cohesive energy.potential curve,bulk modulus and temperature dependence of liner thermal expansion coeCHcient have been calculated.The theoretical values of properties are all in good agreement with experimental results.This electronic structure has been verified in part by linear rigorous cellular method of band theory.It shows that the valence bond theory has been reached perfectly.
基金supported by the Beijing Natural Science Foundation (No. 1112005)the National Major Fundamental Research Program of China,Ministry of Science and Technology China (No. 2010CB833100)
基金financially supported by the National Natural Science Foundation of China (Nos. 51171091 and 51471099)the Excellent Youth Project of Natural Science Foundation of Shandong (No. JQ201012)the Major State Basic Research Development Program of China (No. 2012CB825702)
文摘The anisotropy of the microstructure, thermal expansion behavior, corrosion resistance and magnetic properties of AISI 1045 steel was investigated. The distribution of Fe3C lameUae in the investigation plane parallel to the radial directions of molds was observed to differ from that in the investigation plane perpendicular to the radial directions by transmission electron microscopy. The lattice constants a0 of α-Fe deduced from the XRD patterns of samples prepared using a sand (S)-mold and cut parallel to the radial direction of the mold (S//) and using a metal (M)-mold and cut parallel to the radial direction (M//), the corrosion resistance measured using an electrochemical work- station, and the magnetic permeability obtained by vibrating sample magnetometry also indicated the existence of anisotropy in the tested samples. The anisotropic change of corrosion potential (Eeorr), pitting potential (Epit) and magnetic permeability (μ) of the samples was observed to depend on the orientation factorF200 of α-Fe in the measured samples, which is controlled by the distribution of Fe3C lamellae in the eutectoid structure.
文摘he expressions of the composition space and the dependent properties of the lattice constant, the energy bandgap and the Gibbs energy were presented for the (Ga,In)(As,Sb) quaternary compound semiconductor. On the basis of these expressions, a computer aided analysis system is set up for the design of ⅢⅤ compound semiconductor materials and growth processes. By using this system, a comprehensively optimized diagram is constructed through the projection of the optoelectronic properties (energy bandgap or wave length), in which the composition relations are matched to substrates and the miscibility gaps.
文摘The microstructures of platinum (111) facets were studied by reflection electron microscopy, and the features on facets, for example, growth steps, slip steps, and dislocations emerging through the surfaces, etc., were analysed. In the following annealing at about 1100°C for 1 h in the atmosphere, the migration of crystal surface atoms resulted in the transformation of stepped configuration on (111) facets. Differently high and sized ?111? terraces or small planes distributed on facets constructed frustum structures.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11174182 and 61306113)the Specialized Research Fund for the Doctoral Program of Higher Education,China(Grant No.20110131110005)
文摘In this study, we investigate the effects of Ga N cap layer thickness on the two-dimensional electron gas(2DEG)electron density and 2DEG electron mobility of Al N/Ga N heterostructures by using the temperature-dependent Hall measurement and theoretical fitting method. The results of our analysis clearly indicate that the Ga N cap layer thickness of an Al N/Ga N heterostructure has influences on the 2DEG electron density and the electron mobility. For the Al N/Ga N heterostructures with a 3-nm Al N barrier layer, the optimized thickness of the Ga N cap layer is around 4 nm and the strained a-axis lattice constant of the Al N barrier layer is less than that of Ga N.
文摘We have carried out density functional theory to study the lattice constants and electronic properties of LaB<sub>6</sub>, NdB<sub>6</sub>, Nd-doped LaB<sub>6</sub>, and La-doped NdB<sub>6</sub>. The lattice constant, intra-octahedral bond, inter-octahedral boron bond, and positional parameter (z) were calculated for LaB<sub>6</sub>, La<sub>7</sub>Nd<sub>1</sub>B<sub>6</sub>, La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub>, and NdB<sub>6</sub>. Our results show that the doped Nd increases the lattice constant of La<sub>7</sub>Nd<sub>1</sub>B<sub>6</sub>. Likewise, La-doping leads to an increase in the lattice constant of the La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub>. The PDOSs of LaB<sub>6</sub>, B of LaB<sub>6</sub>, La<sub>7</sub>Nd<sub>1</sub>B<sub>6</sub>, B of La<sub>7</sub>Nd<sub>1</sub>B<sub>6</sub>, La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub>, B of La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub>, NdB<sub>6</sub>, and B of NdB<sub>6</sub> were calculated. La d-electron bands cross the Fermi energy, showing classical conductor behavior. The charge density results indicate that light and dark colors show high and low-intensity zones, respectively. La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub> has a low-density region and LaB<sub>6</sub> has a high-density region. The LaB<sub>6</sub> midpoint has strong charge density peaks. Weak peaks are also observed for La<sub>1</sub>Nd<sub>7</sub>B<sub>6</sub>. Thus, ternary REB<sub>6</sub> has good potential for many applications. This article reports an investigation of the electronic features and structural parameters of binary and ternary hexaborides.
基金financially supported by the National Natural Science Foundation of China(No.52204334).
文摘Ti(C,N)concentration was found to be lower on the hearth sidewall of a blast furnace and increased gradually toward the bottom of the blast furnace.The Ti(C,N)protective layer in a blast furnace is thin.Therefore,the formation of a Ti(C,N)protective layer was promoted by studying the heterogeneous nucleation principle of titanium compounds on different substances and regulation measures for the deposition process of titanium compounds on refractories or impurities.The lattice disregistry between the titanium compounds and the main components in the refractory or the main impurities in the protective layer was calculated using a two-dimensional disregistry equation to study the heterogeneous nucleation principle of titanium compounds.The results revealed that in refractory materials,the heterogeneous nucleation of carbonitride is weak when C,SiO_(2),and Al_(2)O_(3) are used as heterogeneous nucleation substrates,and the heterogeneous nucleation of carbonitride is strong when TiO_(2) and SiC are used as heterogeneous nucleation substrates.As nucleation phases,TiC,TiN,Ti(C_(0.3),N_(0.7)),and Ti(C_(0.5),N_(0.5))have similar heterogeneous nucleation ability in single component refractory,and the type of carbonitride has little effect on the lattice disregistry.The impurities in the protective layer as the substrate phases are not conducive to the heterogeneous nucleation of carbonitride.When CaS was used as the substrate phase,the heterogeneous nucleation ability of carbonitride was the worst.Both carbon and alumina were not conducive to the heterogeneous nucleation of carbonitride,but carbon was more unfavourable than alumina.
基金supported by Basic Scientific Research Operating Fund of NIM(Grant No.AKYZD2007-1).
文摘Line width(i.e.,critical dimension,CD)is a crucial parameter in integrated circuits.To accurately control the CD in manufacturing,a reasonable CD measurement algorithm is required.We develop an automatic and accurate method based on a two-dimensional discrete Fourier transform for measuring the lattice spacings from high-resolution transmission electron microscopy images.Through the two-dimensional inverse discrete Fourier transform of the central spot and a pair of symmetrical diffraction spots,an image containing only a set of lattice spacings is obtained.Then,the pixel span of the lattice spacing is calculated through the centre of gravity method.Finally,we estimate the standard CD value according to the half-intensity method.The silicon crystal lattice constant guarantees the accuracy and traceability of the CD value.Through experiments,we demonstrate the efficiency of the proposed method,which can be conveniently applied to accurately measure CDs in practical applications.
基金National Natural Science Foundation of China(No.61975119)。
文摘This paper designs the thermal crystals composed of alloy materials with air holes and analyzes their properties of band structures,heat transmission,and flux spectra.Thermal crystals composed of Si-A(A=Ge,Sn,Pb)alloys as background materials and air holes with square array are used to construct an elastic-constant periodic structure and their high-frequency phononic band is calculated by deploying finite element methods.Moreover,this paper investigates heat transmission through a finite array of thermally excited phonons and presents the thermal crystal with maximum heat transport.The results show that a wider bandgap could be achieved by increasing the air hole radius and decreasing the lattice constant.In the alloy materials,with increasing atomic radius and thus atomic mass(Ge,Sn,Pb),the frequency range(contributed to thermal conductivity)shifts towards lower frequency.Hence,the bandgap frequencies also shift toward low frequency,but this decreasing rate is not constant or in order,so former may have a faster or slower decreasing rate than the later.Thus,the frequency range for the contribution of heat transportation overlaps with the bandgap frequency range.The development of thermal crystals is promising for managing heat and controlling the propagation of the thermal wave.
基金Project supported by the Na tional Natural Science Foundation of Chi m(Grant Nos.59371029,59671030
文摘According to the correlativity between energy, volume and electronic structure of characteristic crystals and bound conditions of OA theory, the Gibbs energy function, atomic volume function and electronic structure of Ag Cu alloys have been determined. Then the electronic structure and properties of disordered alloys with any composition and ordered alloys with any ordering degree can be calculated. The number of d c covalent electrons in the states of Ag characteristic atoms decreases with the increase of Cu atoms in the nearest neighbouring shell. The number of d c covalent electrons in the states of Cu characteristic atoms decreases with the increase of Ag atoms in the nearest neighbouring shell. Such changes lead to the tendencies of atomic segregation and partition into two phases in the Ag Cu system.
基金Project supported by the Na tional Na tu ral Science Foundation of Chim(Grant No.59371029).
文摘Nine functions of atomic volume interaction have been established. The values of average atomic volumes and lattice constants of Ag-Cu alloys obtained from each V-function are, respectively, equal to each other and in good agreement with experimental values. But the average atomic volumes of components and the volumes of characteristic atoms obtained from each V-function are different from each other. Only after the correlative study of energy, volume and electronic structure is carried out, can the V-function be correctly chosen, can a knowledge system about the alloys be established, thus providing the base for scientific design of new alloys. The relationships between lattice parameters of metastable phases of Ag-Cu alloys and composition and between average properties and partial molar properties of components are discussed.