This paper investigates the verb valency structure of English that is used by English as Foreign Language(EFL)learners from a corpus-driven perspective.Specifically,it focuses on the usage of the verbs“suggest”and“...This paper investigates the verb valency structure of English that is used by English as Foreign Language(EFL)learners from a corpus-driven perspective.Specifically,it focuses on the usage of the verbs“suggest”and“advise”in a selected corpus.By analyzing a sample of written and spoken texts,this study attempts to investigate the similarities and differences in the patterns of verb valency between native English speakers and Chinese EFL learners.The findings of this research can contribute to a better understanding of the challenges faced by Chinese EFL learners in acquiring accurate verb valency structures and provide insights for language teachers in designing effective pedagogical approaches.展开更多
By measuring the hardness of carburized layer of a new type supersaturated carburizing steel (35Cr3SiMnMoV) at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and t...By measuring the hardness of carburized layer of a new type supersaturated carburizing steel (35Cr3SiMnMoV) at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and the temper temperature is established. The result indicates that the hardness goes down firstly, then up and down, just like a wave consistent with the temperature increase. A secondary hardening peak appears at 570 ℃ or so. Based on Empirical Election Theory (EET) of Solids and Molecules, the valence electron structures (VESs) containing α-Fe-C, α-Fe-C-Me segregation structure units and carbide are calculated. The laws of temper process and hardness change with the temper temperature are explained, and the fact that reconstruction of θ-Fe3C is prior to that of special carbide at high tempering is analyzed with the phase structure formation factor, S, being taken into consideration. Therefore, the laws of temper process and hardness change of supersaturated carburized layer at different temper temperature can be traced back to valence electron structure (VES) level of alloy phase.展开更多
On the basis of energy and shape method for the determination of the valence bond ( VB ) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole ...On the basis of energy and shape method for the determination of the valence bond ( VB ) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is ec^29907. (sc^0.4980 + dc^2.4927) ef^1.0098 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.展开更多
The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal (CC) theory. This theory is based on cluster statistics of random alloys. By studying the correlativity betw...The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal (CC) theory. This theory is based on cluster statistics of random alloys. By studying the correlativity between energy and volume of the CC in Ta- W alloys, the valence bond structure of CC is determined by the energy and shape method. Then, following additive law of CC, the valence bond structure of Ta-W alloys is calculated. It is found that the outer shell valence electronic distribution of Ta-W Mloys shows a continuous change in the whole composition range. The covalent electrons ec (dc, sc, and pc) increase, whereas near free electrons ef decrease with increasing W concentration. The bond length and single-bond radius decrease, whereas bond energy and bond valence increase with increasing W concentration. The mechanism of solid solution strengthening of Ta-W alloys is analyzed based on their valence bond structure.展开更多
The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules (EET). A criterion for the ionic conductivity was ...The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules (EET). A criterion for the ionic conductivity was proposed, i.e. the 1/(nAnB) increases with increasing the ionic conductivity when x or y〈20% (in molar fraction).展开更多
According to EET theory, the valence electron structures of RE in the solid solution of austenite, pearlite and martensite were calculated. The influence of RE in solid solution on phase transformation of pearlite and...According to EET theory, the valence electron structures of RE in the solid solution of austenite, pearlite and martensite were calculated. The influence of RE in solid solution on phase transformation of pearlite and recrystallization of martensite was explained by the valence electron structure data of phases. Calculating results indicate that C element is favorite to enhance the number of RE in the solid solution. RE in the solute solution shortens the incubation period of proeutectoid ferrite, increases its quantity and carbon content, decreases the quantity of pearlite and thickness of its lamellas and lamellar spacing, then the strength and hardness of pearlite are improved and granular pearlite can be obtained. RE dissolved in martensite intensifies martensite, enhances tempering stability of martensite, increases its recrystallization temperature and prolongs the holding time needed during tempering.展开更多
By calculating the electron structures of the phases that phosphor, sulfur and alloying elements dissolving inγ-Fe, the reason why alloying elements can bring centerline segregation in continuous casting slab (CCS) w...By calculating the electron structures of the phases that phosphor, sulfur and alloying elements dissolving inγ-Fe, the reason why alloying elements can bring centerline segregation in continuous casting slab (CCS) with nA, the number of electrons on the strongest covalent bonds, and the structure formation factor S were investigated, and an electron structural criterion to control and to eliminate the centerline segregation was advanced. Basing on this, the electron structures of a part of rare earth phosphides and sulfides are calculated, the physical mechanism that rare earth elements can control the segregation of phosphor and sulfur is analyzed, and the criterion is well verified.展开更多
The Eu-doped Cu(In, Eu)Te2 semiconductors with chalcopyrite structures are promising materials for their applications in the absorption layer for thin-film solar cells due to their wider band-gaps and better optical...The Eu-doped Cu(In, Eu)Te2 semiconductors with chalcopyrite structures are promising materials for their applications in the absorption layer for thin-film solar cells due to their wider band-gaps and better optical properties than those of CuInTe2. In this paper, the Eu-doped CuInTe2 (CuIn1-xEuxTe2, x = 0, 0.1, 0.2, 0.3) are studied systemically based on the empirical electron theory (EET). The studies cover crystal structures, bonding regularities, cohesive energies, energy levels, and valence electron structures. The theoretical values fit the experimental results very well. The physical mechanism of a broadened band-gap induced by Eu doping into CuInTe2 is the transitions between different hybridization energy levels induced by electron hopping between s and d orbitals and the transformations from the lattice electrons to valence electrons for Cu and In ions. The research results reveal that the photovoltaic effect induces the increase of lattice electrons of In and causes the electric resistivity to decrease. The Eu doping into CuInTe2 mainly influences the transition between different hybridization energy levels for Cu atoms, which shows that the 3d electron numbers of Cu atoms change before and after Eu doping. In single phase CuIn1-xEuxTe2, the number of valence electrons changes regularly with increasing Eu content, and the calculated band gap Eg also increases, which implies that the optical properties of Eu-doped CuIn1-xEuxTe2 are improved.展开更多
Based on the empirical electronic theory of solids and molecules (EET), the actual model for unit cell of cementite (0-FeaC) was built and the valence electron structures (VES) of cementite with specified site a...Based on the empirical electronic theory of solids and molecules (EET), the actual model for unit cell of cementite (0-FeaC) was built and the valence electron structures (VES) of cementite with specified site and a number of Fe atoms substituted by alloying atoms of M ( M=Cr, V, W, Mo, Mn ) were computed by statistical method. By defining P as the stability factor, the stability of alloyed cementite with different numbers and sites of Fe atoms substituted by M was calculated. Calculation results show that the density of lattice electrons, the symmetry of distribution of covalent electron pairs and bond energy have huge influence on the stability of alloyed cementite. It is more stable as M substitutes for FeE than for Fe1. The alloyed cementite is the most stable when Cr, Mo, W and V substitute for 2 atoms of Fe2 at the sites of Nos. 2 and 3 (or No. 6 and No. 7). The stability of alloyed cementite decreases gradually as being substitutional doped by W, Cr, V, Mo and Mn.展开更多
Formate is an important liquid chemical,which can be produced by electrocatalytic carbon dioxide reduction reaction(CO_(2) RR).Most of the metal catalysts for CO_(2) RR to formate are toxic or noble metals,such as Cd,...Formate is an important liquid chemical,which can be produced by electrocatalytic carbon dioxide reduction reaction(CO_(2) RR).Most of the metal catalysts for CO_(2) RR to formate are toxic or noble metals,such as Cd,Hg,Pb and Pd,leading to the environmental pollution or increased production costs.Herein,we develop an environmentally friendly and low-cost NiZn alloy catalyst for CO_(2) RR to formate.The X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM) confirm the alloy structure of the prepared NiZn catalyst. As for a catalyst for CO_(2) RR,the NiZn alloy exhibits the FE_(HCOO)^(-)(Faraday efficiency of HCOO^(-)) of 36±0.7% at-0.9 V vs.RHE in 0.1 M KHCO_(3), and remarkable stability for 40,000 s at-0.8,-0.9,-1.0 and-1.1 V vs.RHE,respectively.Theoretical calculation results indicate that the NiZn alloy exhibits the middle valence electron structure between the Zn and Ni metal,resulting in the favorable pathway for HCOOH formation but unfavorable for the hydrogen evolution reaction and CO production.The Ultraviolet Photoelectron Spectroscopy results verify the modulated valence electron structure for NiZn alloy as compared to Ni and Zn,consistent with the theoretical calculation results.This work provides new insights into design of alloy catalysts for CO_(2) RR to formate.展开更多
The valence electron structure of alloying austenite of 3C-15Cr high chromium white cast iron with different Mn contents from 1% to 6% is analyzed by BLD method and EET. Results show that the addition of Mn has major ...The valence electron structure of alloying austenite of 3C-15Cr high chromium white cast iron with different Mn contents from 1% to 6% is analyzed by BLD method and EET. Results show that the addition of Mn has major influence on the valence electron structure of the alloying austenite, especially on that of Fe-C, Fe-C-Cr and Fe-C-Cr-Mn unit cells of it. The effect becomes weak when Mn content is over 4%. Based on the effect of n~, F~~, the weighting of each unit cell and the degree of undercooling on phase transition of the aus- tenite, we can calculate the retained austenite content of as-cast structure of the high chromium white cast iron. The calculation results coincide well with those of the experiment. The phase transition characters of the austenite in high chromium white cast iron can be forecasted through valence electron structure analysis of alloying austenite by BLD method and EET on the basis of Fe-C-Cr equilibrium phase diagram.展开更多
Based on the analysis and processing on relative empirical formula and data, C-values in Larson-Miller (P) expression, P= T(C + Igt), have determined for pearlitic heat resistant steel 12Cr1MoV and 15CrMo(20.62 and 20...Based on the analysis and processing on relative empirical formula and data, C-values in Larson-Miller (P) expression, P= T(C + Igt), have determined for pearlitic heat resistant steel 12Cr1MoV and 15CrMo(20.62 and 20.30). The simulation experiments of high temperature aging, heated from 1.5 to 873 hours, have been designed and performed for its verification. And in combination with published information and the present nearly quantitative works, it has further been verified that both the degradations of microstructures and mechanical properties show a good accuracy and practicability using the Larson-Miller parameter with the present determined C-values. Finally, the effects of carbon content on C-value are analyzed by the empirical electron theory of solids and molecules (EET).展开更多
The differences of grain-refining effect between Sc and Ti additions in aluminum,which cannot be substantially explained by traditional theories,were carefully studied.The empirical electron theory(EET) of solids and ...The differences of grain-refining effect between Sc and Ti additions in aluminum,which cannot be substantially explained by traditional theories,were carefully studied.The empirical electron theory(EET) of solids and molecules was employed to calculate the valence electron structures(VES) of Al3Ti and Al3Sc.The conclusions can be drawn that,in the two alloys Al-Ti and Al-Sc,the different valence electron structures of Al3Ti and Al3Sc and the consequent differences of growth habit of the two particles,and the different interfacial electron density between particles and matrix fundamentally lead to the differences of grain-refining effect between Sc and Ti additions on aluminum and make Sr the better grain-refiner of aluminum.展开更多
Based on the empirical electron theory of solids and molecules of S. H. Yu, this paper proposes (i) the calculating model of valence electron structures in L_2~'-type substitutional and interstitial complex solid ...Based on the empirical electron theory of solids and molecules of S. H. Yu, this paper proposes (i) the calculating model of valence electron structures in L_2~'-type substitutional and interstitial complex solid solutions; (ii) the bond length difference analysis (BLD) method of unknown bond length structure solid solutions; (iii) the treatment of uncertainty of BLD analysis solution.展开更多
The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent,met...The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent,metallic and ionic characters. For a quantitative analysis of the relative strength of these components,their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN,which coincides to that de-duced from the first-principles method.展开更多
The heterogeneous distribution of C and metallic alloying elements as well as the phase com- position changes before and after cold deformation of an Fe-Mn-Cr-C alloy have been stu- died by the use of Mssbauer spectro...The heterogeneous distribution of C and metallic alloying elements as well as the phase com- position changes before and after cold deformation of an Fe-Mn-Cr-C alloy have been stu- died by the use of Mssbauer spectroscopy.The austenites without and with C and metallic alloying elements are found in the alloy in as-solid solution state.While the martensites with- out and with C and alloying elements may be induced by cold deformation.The transforma- tion from austenite to martensite in the alloy is confirmed via theoretical computation and ex- periments to be controlled by the number of covalent electron pairs forming covalent bond in austenitic crystal cell of the alloy.The formation of strong covalent bond between C and me- tallic elements can vigorously retard the γ/α' transformation.展开更多
This article puts forward a new method in calculating the band structures of low-dimensional semiconductor structures. In this study, the valence band structures of InAs/GaAs quantum ring and lens-shaped quantum dot a...This article puts forward a new method in calculating the band structures of low-dimensional semiconductor structures. In this study, the valence band structures of InAs/GaAs quantum ring and lens-shaped quantum dot are calculated with four-band model, in the framework of effective-mass envelope function theory. To determine the Hamiltonian matrix elements, this article develops the numerical Fourier transform method instead of the widely used analytical integral method. The valence band mixing is considered. The hole energy levels change dramatically with the geometrical parameters of the quantum ring and quantum dot. It is demonstrated that numerical Fourier transform method can be adopted in low-dimensional structures with any shape. The results of Fourier transform method are consistent with the ones of analytical integral in literature; and they are helpful for studying and fabricating optoelectronic devices.展开更多
The valence band structure and hole effective mass of silicon under a uniaxial stress in (001) surface along the [110] direction were detailedly investigated in the framework of the k. p theory. The results demonstr...The valence band structure and hole effective mass of silicon under a uniaxial stress in (001) surface along the [110] direction were detailedly investigated in the framework of the k. p theory. The results demonstrated that the splitting energy between the top band and the second band for tmiaxial compressive stress is bigger than that of the tensile one at the same stress magnitude, and of all common used crystallographic direction, such as [110], [001], [110] and [100], the effective mass for the top band along [110] crystallographic direction is lower under uniaxial compressive stress compared with other stresses and crystallographic directions configurations. In view of suppressing the scattering and reducing the effective mass, the [110] crystallographic direction is most favorable to be used as transport direction of the charge carrier to enhancement mobility when a uniaxial compressive stress along [110] direction is applied. The obtained results can provide a theory reference for the design and the selective of optimum stress and crystallorgraphic direction configuration ofuniaxial strained silicon devices.展开更多
hethesisanalysesthevalenceelectronstructuresof phase Γin Fe Zn transitionallayerof heat galvanized sheet used in cars by applying the Empirical Electron Theory of Solids andMolecules, and calculatesthebond energy o...hethesisanalysesthevalenceelectronstructuresof phase Γin Fe Zn transitionallayerof heat galvanized sheet used in cars by applying the Empirical Electron Theory of Solids andMolecules, and calculatesthebond energy ofthe major bondsand cohesiveenergy ofcrystals,from which we draw theconclusion:sincecrystal has alargercohesiveenergy, it has higherhardness, butsinceitsbondenergyisratherlow ,itiseasytobreak under pressurefrom out side, and thecrackiseasytocome up andspreadin phase Γ.展开更多
A modern valence bond approach, namely bonded tableau unitary group approach, is applied to ozone, sulphur dioxide and nitrite systems, respectively. It is shown that the biradical structure is in the primary position...A modern valence bond approach, namely bonded tableau unitary group approach, is applied to ozone, sulphur dioxide and nitrite systems, respectively. It is shown that the biradical structure is in the primary position in descrbing the molecular structure of ozone. Thus three instead of two resonance structures are needed to describe the ground state of ozone. The case of sulphur dioxide is similar to that of ozone. It is found that, however, for the nitrite anion four resonance structures are needed.展开更多
文摘This paper investigates the verb valency structure of English that is used by English as Foreign Language(EFL)learners from a corpus-driven perspective.Specifically,it focuses on the usage of the verbs“suggest”and“advise”in a selected corpus.By analyzing a sample of written and spoken texts,this study attempts to investigate the similarities and differences in the patterns of verb valency between native English speakers and Chinese EFL learners.The findings of this research can contribute to a better understanding of the challenges faced by Chinese EFL learners in acquiring accurate verb valency structures and provide insights for language teachers in designing effective pedagogical approaches.
基金Funded by the Science and Technology Foundation of Retuned Students Studying Abroad of Shanxi Province of China(No. 1995-26)
文摘By measuring the hardness of carburized layer of a new type supersaturated carburizing steel (35Cr3SiMnMoV) at different temper temperature for 2 h, the relationship curve between the carburized layer hardness and the temper temperature is established. The result indicates that the hardness goes down firstly, then up and down, just like a wave consistent with the temperature increase. A secondary hardening peak appears at 570 ℃ or so. Based on Empirical Election Theory (EET) of Solids and Molecules, the valence electron structures (VESs) containing α-Fe-C, α-Fe-C-Me segregation structure units and carbide are calculated. The laws of temper process and hardness change with the temper temperature are explained, and the fact that reconstruction of θ-Fe3C is prior to that of special carbide at high tempering is analyzed with the phase structure formation factor, S, being taken into consideration. Therefore, the laws of temper process and hardness change of supersaturated carburized layer at different temper temperature can be traced back to valence electron structure (VES) level of alloy phase.
基金supported by the National Natural Science Foundation of China(No.50271085).
文摘On the basis of energy and shape method for the determination of the valence bond ( VB ) structures of crystal, the valence bond structure of titanium is redetermined at room temperature and calculated in the whole temperature range of 0-1943K. The outer shell electronic distribution of Ti is ec^29907. (sc^0.4980 + dc^2.4927) ef^1.0098 in crystal. The temperature dependences of the VB structures of hcp and bcc phases are the same. The VB structures of hcp and bcc phases monotonically increase or decrease with the increase in temperature, but show discontinuous changes at the phase-transformation temperature 1155K.
基金supported by Xiangtan University Doctor Research Foundation(GrantNo.08QDZ32)
文摘The valence bond structure of substitutional BCC based Ta-W alloys is studied using characteristic crystal (CC) theory. This theory is based on cluster statistics of random alloys. By studying the correlativity between energy and volume of the CC in Ta- W alloys, the valence bond structure of CC is determined by the energy and shape method. Then, following additive law of CC, the valence bond structure of Ta-W alloys is calculated. It is found that the outer shell valence electronic distribution of Ta-W Mloys shows a continuous change in the whole composition range. The covalent electrons ec (dc, sc, and pc) increase, whereas near free electrons ef decrease with increasing W concentration. The bond length and single-bond radius decrease, whereas bond energy and bond valence increase with increasing W concentration. The mechanism of solid solution strengthening of Ta-W alloys is analyzed based on their valence bond structure.
文摘The valence electron structures of Sr- and Mg-doped LaGaO3 ceramics with different compositions were calculated by Empirical Electron Theory of Solids and Molecules (EET). A criterion for the ionic conductivity was proposed, i.e. the 1/(nAnB) increases with increasing the ionic conductivity when x or y〈20% (in molar fraction).
文摘According to EET theory, the valence electron structures of RE in the solid solution of austenite, pearlite and martensite were calculated. The influence of RE in solid solution on phase transformation of pearlite and recrystallization of martensite was explained by the valence electron structure data of phases. Calculating results indicate that C element is favorite to enhance the number of RE in the solid solution. RE in the solute solution shortens the incubation period of proeutectoid ferrite, increases its quantity and carbon content, decreases the quantity of pearlite and thickness of its lamellas and lamellar spacing, then the strength and hardness of pearlite are improved and granular pearlite can be obtained. RE dissolved in martensite intensifies martensite, enhances tempering stability of martensite, increases its recrystallization temperature and prolongs the holding time needed during tempering.
基金the Natural Science Foundation of Liaoning under grant No.20022150 the National Natural Science Foundation of China under grant No.50271030.
文摘By calculating the electron structures of the phases that phosphor, sulfur and alloying elements dissolving inγ-Fe, the reason why alloying elements can bring centerline segregation in continuous casting slab (CCS) with nA, the number of electrons on the strongest covalent bonds, and the structure formation factor S were investigated, and an electron structural criterion to control and to eliminate the centerline segregation was advanced. Basing on this, the electron structures of a part of rare earth phosphides and sulfides are calculated, the physical mechanism that rare earth elements can control the segregation of phosphor and sulfur is analyzed, and the criterion is well verified.
基金supported by the National Natural Science Foundation of China(Grant No.1 1274110)
文摘The Eu-doped Cu(In, Eu)Te2 semiconductors with chalcopyrite structures are promising materials for their applications in the absorption layer for thin-film solar cells due to their wider band-gaps and better optical properties than those of CuInTe2. In this paper, the Eu-doped CuInTe2 (CuIn1-xEuxTe2, x = 0, 0.1, 0.2, 0.3) are studied systemically based on the empirical electron theory (EET). The studies cover crystal structures, bonding regularities, cohesive energies, energy levels, and valence electron structures. The theoretical values fit the experimental results very well. The physical mechanism of a broadened band-gap induced by Eu doping into CuInTe2 is the transitions between different hybridization energy levels induced by electron hopping between s and d orbitals and the transformations from the lattice electrons to valence electrons for Cu and In ions. The research results reveal that the photovoltaic effect induces the increase of lattice electrons of In and causes the electric resistivity to decrease. The Eu doping into CuInTe2 mainly influences the transition between different hybridization energy levels for Cu atoms, which shows that the 3d electron numbers of Cu atoms change before and after Eu doping. In single phase CuIn1-xEuxTe2, the number of valence electrons changes regularly with increasing Eu content, and the calculated band gap Eg also increases, which implies that the optical properties of Eu-doped CuIn1-xEuxTe2 are improved.
基金Project(2014CFB801)supported by Natural Science Foundation of Hubei Province of ChinaProject(11304236)supported by the National Natural Science Foundation of China
文摘Based on the empirical electronic theory of solids and molecules (EET), the actual model for unit cell of cementite (0-FeaC) was built and the valence electron structures (VES) of cementite with specified site and a number of Fe atoms substituted by alloying atoms of M ( M=Cr, V, W, Mo, Mn ) were computed by statistical method. By defining P as the stability factor, the stability of alloyed cementite with different numbers and sites of Fe atoms substituted by M was calculated. Calculation results show that the density of lattice electrons, the symmetry of distribution of covalent electron pairs and bond energy have huge influence on the stability of alloyed cementite. It is more stable as M substitutes for FeE than for Fe1. The alloyed cementite is the most stable when Cr, Mo, W and V substitute for 2 atoms of Fe2 at the sites of Nos. 2 and 3 (or No. 6 and No. 7). The stability of alloyed cementite decreases gradually as being substitutional doped by W, Cr, V, Mo and Mn.
基金Natural Science Foundation of China (21872174,22002189,U1932148)the International Science and Technology Cooperation Program (2017YFE0127800,2018YFE0203402)+5 种基金the Hunan Provincial Science and Technology Program(2017XK2026)the Hunan Province Key Field R&D Program(2020WK2002)the Hunan Provincial Natural Science Foundation of China (2020JJ2041,2020JJ5691)the Shenzhen Science and Technology Innovation Project (JCYJ20180307151313532)the Hunan Provincial Science and Technology Plan Project(2017TP1001)the Fundamental Research Funds for the Central Universities of Central South University。
文摘Formate is an important liquid chemical,which can be produced by electrocatalytic carbon dioxide reduction reaction(CO_(2) RR).Most of the metal catalysts for CO_(2) RR to formate are toxic or noble metals,such as Cd,Hg,Pb and Pd,leading to the environmental pollution or increased production costs.Herein,we develop an environmentally friendly and low-cost NiZn alloy catalyst for CO_(2) RR to formate.The X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS) and transmission electron microscopy(TEM) confirm the alloy structure of the prepared NiZn catalyst. As for a catalyst for CO_(2) RR,the NiZn alloy exhibits the FE_(HCOO)^(-)(Faraday efficiency of HCOO^(-)) of 36±0.7% at-0.9 V vs.RHE in 0.1 M KHCO_(3), and remarkable stability for 40,000 s at-0.8,-0.9,-1.0 and-1.1 V vs.RHE,respectively.Theoretical calculation results indicate that the NiZn alloy exhibits the middle valence electron structure between the Zn and Ni metal,resulting in the favorable pathway for HCOOH formation but unfavorable for the hydrogen evolution reaction and CO production.The Ultraviolet Photoelectron Spectroscopy results verify the modulated valence electron structure for NiZn alloy as compared to Ni and Zn,consistent with the theoretical calculation results.This work provides new insights into design of alloy catalysts for CO_(2) RR to formate.
文摘The valence electron structure of alloying austenite of 3C-15Cr high chromium white cast iron with different Mn contents from 1% to 6% is analyzed by BLD method and EET. Results show that the addition of Mn has major influence on the valence electron structure of the alloying austenite, especially on that of Fe-C, Fe-C-Cr and Fe-C-Cr-Mn unit cells of it. The effect becomes weak when Mn content is over 4%. Based on the effect of n~, F~~, the weighting of each unit cell and the degree of undercooling on phase transition of the aus- tenite, we can calculate the retained austenite content of as-cast structure of the high chromium white cast iron. The calculation results coincide well with those of the experiment. The phase transition characters of the austenite in high chromium white cast iron can be forecasted through valence electron structure analysis of alloying austenite by BLD method and EET on the basis of Fe-C-Cr equilibrium phase diagram.
文摘Based on the analysis and processing on relative empirical formula and data, C-values in Larson-Miller (P) expression, P= T(C + Igt), have determined for pearlitic heat resistant steel 12Cr1MoV and 15CrMo(20.62 and 20.30). The simulation experiments of high temperature aging, heated from 1.5 to 873 hours, have been designed and performed for its verification. And in combination with published information and the present nearly quantitative works, it has further been verified that both the degradations of microstructures and mechanical properties show a good accuracy and practicability using the Larson-Miller parameter with the present determined C-values. Finally, the effects of carbon content on C-value are analyzed by the empirical electron theory of solids and molecules (EET).
基金Project(20050003042) supported by Research Fund for the Doctoral Program of Higher Education of China
文摘The differences of grain-refining effect between Sc and Ti additions in aluminum,which cannot be substantially explained by traditional theories,were carefully studied.The empirical electron theory(EET) of solids and molecules was employed to calculate the valence electron structures(VES) of Al3Ti and Al3Sc.The conclusions can be drawn that,in the two alloys Al-Ti and Al-Sc,the different valence electron structures of Al3Ti and Al3Sc and the consequent differences of growth habit of the two particles,and the different interfacial electron density between particles and matrix fundamentally lead to the differences of grain-refining effect between Sc and Ti additions on aluminum and make Sr the better grain-refiner of aluminum.
基金Project supported by the National Natural Science Foundation of China.
文摘Based on the empirical electron theory of solids and molecules of S. H. Yu, this paper proposes (i) the calculating model of valence electron structures in L_2~'-type substitutional and interstitial complex solid solutions; (ii) the bond length difference analysis (BLD) method of unknown bond length structure solid solutions; (iii) the treatment of uncertainty of BLD analysis solution.
基金Supported by the National Natural Science Foundation of China (Grant No. 10702060)the Ministry of Science and Technology of China (2005CB724400 and 2005CB724404)
文摘The valence electronic structures of tantalum carbide (TaC) and tantalum nitride (TaN) are studied by using the empirical electronic theory (EET). The results reveal that the bonds of these compounds have covalent,metallic and ionic characters. For a quantitative analysis of the relative strength of these components,their ionicities have been calculated by implanting the results of EET to the PVL model. It has been found that the ionicity of tantalum carbide is smaller than that of tantalum nitride. The EET results also reveal that the covalent electronic number of the strongest bond in the former is larger than that of the latter. All these suggest that the covalent bond of TaC is stronger than that of TaN,which coincides to that de-duced from the first-principles method.
文摘The heterogeneous distribution of C and metallic alloying elements as well as the phase com- position changes before and after cold deformation of an Fe-Mn-Cr-C alloy have been stu- died by the use of Mssbauer spectroscopy.The austenites without and with C and metallic alloying elements are found in the alloy in as-solid solution state.While the martensites with- out and with C and alloying elements may be induced by cold deformation.The transforma- tion from austenite to martensite in the alloy is confirmed via theoretical computation and ex- periments to be controlled by the number of covalent electron pairs forming covalent bond in austenitic crystal cell of the alloy.The formation of strong covalent bond between C and me- tallic elements can vigorously retard the γ/α' transformation.
基金supported by the Hi-Tech Research and Development Program of China (2009AA03Z405)the National Natural Science Foundation of China (60908028)+1 种基金the National Natural Science Foundation of China (60971068)the High School Innovation and Introducing Talent Project of China (B07005)
文摘This article puts forward a new method in calculating the band structures of low-dimensional semiconductor structures. In this study, the valence band structures of InAs/GaAs quantum ring and lens-shaped quantum dot are calculated with four-band model, in the framework of effective-mass envelope function theory. To determine the Hamiltonian matrix elements, this article develops the numerical Fourier transform method instead of the widely used analytical integral method. The valence band mixing is considered. The hole energy levels change dramatically with the geometrical parameters of the quantum ring and quantum dot. It is demonstrated that numerical Fourier transform method can be adopted in low-dimensional structures with any shape. The results of Fourier transform method are consistent with the ones of analytical integral in literature; and they are helpful for studying and fabricating optoelectronic devices.
基金Project supported by the National Ministries and Commissions of China(Nos.51308040203,6139801)the Fundamental Research Funds for the Central Universities of China(No.72105499)the Natural Science Basic Research Plan in Shaanxi Province of China(No. 2010JQ8008)
文摘The valence band structure and hole effective mass of silicon under a uniaxial stress in (001) surface along the [110] direction were detailedly investigated in the framework of the k. p theory. The results demonstrated that the splitting energy between the top band and the second band for tmiaxial compressive stress is bigger than that of the tensile one at the same stress magnitude, and of all common used crystallographic direction, such as [110], [001], [110] and [100], the effective mass for the top band along [110] crystallographic direction is lower under uniaxial compressive stress compared with other stresses and crystallographic directions configurations. In view of suppressing the scattering and reducing the effective mass, the [110] crystallographic direction is most favorable to be used as transport direction of the charge carrier to enhancement mobility when a uniaxial compressive stress along [110] direction is applied. The obtained results can provide a theory reference for the design and the selective of optimum stress and crystallorgraphic direction configuration ofuniaxial strained silicon devices.
文摘hethesisanalysesthevalenceelectronstructuresof phase Γin Fe Zn transitionallayerof heat galvanized sheet used in cars by applying the Empirical Electron Theory of Solids andMolecules, and calculatesthebond energy ofthe major bondsand cohesiveenergy ofcrystals,from which we draw theconclusion:sincecrystal has alargercohesiveenergy, it has higherhardness, butsinceitsbondenergyisratherlow ,itiseasytobreak under pressurefrom out side, and thecrackiseasytocome up andspreadin phase Γ.
基金State Major Key Project for Basic Researches also supported by the National Natural Science Foundation of China
文摘A modern valence bond approach, namely bonded tableau unitary group approach, is applied to ozone, sulphur dioxide and nitrite systems, respectively. It is shown that the biradical structure is in the primary position in descrbing the molecular structure of ozone. Thus three instead of two resonance structures are needed to describe the ground state of ozone. The case of sulphur dioxide is similar to that of ozone. It is found that, however, for the nitrite anion four resonance structures are needed.