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
Ti-V-based alloys are proved of huge potential in storing hydrogen,but the incomplete reversible hydrogen storage capacity caused by overstability of V hydride has limited the large-scale application.In this study,Ti_...Ti-V-based alloys are proved of huge potential in storing hydrogen,but the incomplete reversible hydrogen storage capacity caused by overstability of V hydride has limited the large-scale application.In this study,Ti_(32)V_(40+x)Fe_(23-x)Mn_(5)(x=0,4,8,12,at.%)alloys were designed,and the effects of V/Fe ratio on phase constitution and hydrogen storage properties were investigated.The main phase of the alloys is body-centered cubic(BCC)phase,and the lattice constants of the BCC phase decrease with the decrease of V/Fe ratio.Moreover,C14 Laves phase exists in alloys with a Fe content of 19at.%to 23at.%.For hydrogenation,the C14 Laves phase can accelerate the hydrogen absorption rate,but the hydrogen absorption capacity is reduced.With the decrease of V/Fe ratio,the hydride gradually destabilizes.Owing to its large lattice constant and high hydrogen absorption phase content,the Ti_(32)V_(52)Fe_(11)Mn_(5)alloy shows the most enhanced hydrogen storage properties with hydrogenation and dehydrogenation capacities of 3.588wt.%at 298 K and 1.688wt.%at 343 K,respectively.The hydrogen absorption capacity of this alloy can be reserved to 3.574wt.%after 20 cycles of hydrogen absorption and desorption.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
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
AgGa_(1-x)In_(x)Se_(2)polycrystals were synthesized by the method of mechanical oscillation and temperature oscillation.X-ray diffraction spectra of polycrystal powder are conformable with the JCPDS cards.Lattice cons...AgGa_(1-x)In_(x)Se_(2)polycrystals were synthesized by the method of mechanical oscillation and temperature oscillation.X-ray diffraction spectra of polycrystal powder are conformable with the JCPDS cards.Lattice constants a and c calculated from the XRD were found to obey Vegard's law.The melting point of AgGa_(0.8)In_(0.2)Se_(2)obtained by means of differential scanning calorimetry(DSC)is 796.53℃.The DSC curve also show that there are no other transformation points below the melting point.The results indicate that polycrystalline materials synthesized by the method mentioned above are high-quality and can be used to grow single crystals by the vertical Bridgman technology.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
Bulk Mn_(1.2)Fe_(0.8)P_(0.76)Ge_(0.24) alloy was prepared by mechanical milling and subsequent spark plasma sintering technique.Effect of annealing on the structure and magneto-caloric properties of the alloy was inve...Bulk Mn_(1.2)Fe_(0.8)P_(0.76)Ge_(0.24) alloy was prepared by mechanical milling and subsequent spark plasma sintering technique.Effect of annealing on the structure and magneto-caloric properties of the alloy was investigated.XRD results show that both sintered and annealed samples possess a hexagonal Fe_2P-type crystal structure.After annealing,ferromagnetic impurity Fe_3Mn_4Ge_6,which exists in the sintered sample,was eliminated from the alloy.Furthermore,the lattice constants a and c change noticeably,leading to a decrease in c/a ratio,while the cell volume almost remains invariable.As a result,the Curie temperature of the alloy increases from 253 K to 298 K,but the maximum magnetic entropy change decreases from 37.5 to 11.7 J·kg·K^(-1) for 2 T magnetic field change.On the other hand,the thermal hysteresis of M-T curves around T_C upon heating and cooling is 14 and 8 K for the as-sintered and the annealed sample,respectively,showing evident change.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
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
Using the plane-wave expansion (PWE)method , the band gaps of the two-dimension phononic crystals composed of square, triangle and honeycomb arrays aluminum cylinders in the air are calculated numerically. The band st...Using the plane-wave expansion (PWE)method , the band gaps of the two-dimension phononic crystals composed of square, triangle and honeycomb arrays aluminum cylinders in the air are calculated numerically. The band structures of three lattices were compared and analyzed. It is concluded that the band-gap of honeycomb lattices is located at lower frequency fields, compared with square and triangle lattices. When the filling fraction is between 0.091 and 0.6046, the honeycomb lattices have larger band gaps and gain an advantage over square and triangle lattices. In addition, the gap map is introduced to illustrate the influences of filling fraction on the number, the relative width and the limit frequency of the band-gap.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
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
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
Al-1.1%Sc and A1-2%Sc （mass fraction） alloys were prepared using gas atomized alloy particles. Samples from consolidated alloys were analyzed by XRD for the determination of lattice parameters. Using these lattice p...Al-1.1%Sc and A1-2%Sc （mass fraction） alloys were prepared using gas atomized alloy particles. Samples from consolidated alloys were analyzed by XRD for the determination of lattice parameters. Using these lattice parameters, the mechanical properties of the alloys were calculated theoretically with WIEN2k and EMTO programs, respectively. The elasticity moduli of the experimentally produced alloys were compared with the theoretical calculation results. The calculated mechanical properties of A13Sc phase and A1-Sc alloys were discussed to determine the optimum Sc content of Al-Sc alloys. It may be concluded that the Sc content should be the maximum about 1.0%, much more Sc addition could not improve the mechanical properties of the alloys.展开更多
Liquid mixtures of water and deuterium oxide as the liquid phase, were used to match the density of charged colloidal particles. Kossel diffraction method was used to detect the crystal structures. The experiments und...Liquid mixtures of water and deuterium oxide as the liquid phase, were used to match the density of charged colloidal particles. Kossel diffraction method was used to detect the crystal structures. The experiments under the density-matched （g=0） and unmatched （g=1） conditions are compared to examine the influence of gravity on the crystal structures formed by self-assembly of 110 nm （in diameter） polystyrene microspheres. The result shows that the gravity tends to make the lattice constants of colloidal crystals smaller at lower positions, which indicates that the effect of gravity should be taken into account in the study of the colloidal crystals.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
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 National Key Research and Development Program of China(2023YFB4005401)the National Natural Science Foundation of China(52425401,52204386)the Natural Science Foundation of Heilongjiang Province(JQ2023E003).
文摘Ti-V-based alloys are proved of huge potential in storing hydrogen,but the incomplete reversible hydrogen storage capacity caused by overstability of V hydride has limited the large-scale application.In this study,Ti_(32)V_(40+x)Fe_(23-x)Mn_(5)(x=0,4,8,12,at.%)alloys were designed,and the effects of V/Fe ratio on phase constitution and hydrogen storage properties were investigated.The main phase of the alloys is body-centered cubic(BCC)phase,and the lattice constants of the BCC phase decrease with the decrease of V/Fe ratio.Moreover,C14 Laves phase exists in alloys with a Fe content of 19at.%to 23at.%.For hydrogenation,the C14 Laves phase can accelerate the hydrogen absorption rate,but the hydrogen absorption capacity is reduced.With the decrease of V/Fe ratio,the hydride gradually destabilizes.Owing to its large lattice constant and high hydrogen absorption phase content,the Ti_(32)V_(52)Fe_(11)Mn_(5)alloy shows the most enhanced hydrogen storage properties with hydrogenation and dehydrogenation capacities of 3.588wt.%at 298 K and 1.688wt.%at 343 K,respectively.The hydrogen absorption capacity of this alloy can be reserved to 3.574wt.%after 20 cycles of hydrogen absorption and desorption.
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Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education(20040610024)
文摘AgGa_(1-x)In_(x)Se_(2)polycrystals were synthesized by the method of mechanical oscillation and temperature oscillation.X-ray diffraction spectra of polycrystal powder are conformable with the JCPDS cards.Lattice constants a and c calculated from the XRD were found to obey Vegard's law.The melting point of AgGa_(0.8)In_(0.2)Se_(2)obtained by means of differential scanning calorimetry(DSC)is 796.53℃.The DSC curve also show that there are no other transformation points below the melting point.The results indicate that polycrystalline materials synthesized by the method mentioned above are high-quality and can be used to grow single crystals by the vertical Bridgman technology.
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 the Beijing Natural Science Foundation (No. 1112005)the National Major Fundamental Research Program of China,Ministry of Science and Technology China (No. 2010CB833100)
文摘Bulk Mn_(1.2)Fe_(0.8)P_(0.76)Ge_(0.24) alloy was prepared by mechanical milling and subsequent spark plasma sintering technique.Effect of annealing on the structure and magneto-caloric properties of the alloy was investigated.XRD results show that both sintered and annealed samples possess a hexagonal Fe_2P-type crystal structure.After annealing,ferromagnetic impurity Fe_3Mn_4Ge_6,which exists in the sintered sample,was eliminated from the alloy.Furthermore,the lattice constants a and c change noticeably,leading to a decrease in c/a ratio,while the cell volume almost remains invariable.As a result,the Curie temperature of the alloy increases from 253 K to 298 K,but the maximum magnetic entropy change decreases from 37.5 to 11.7 J·kg·K^(-1) for 2 T magnetic field change.On the other hand,the thermal hysteresis of M-T curves around T_C upon heating and cooling is 14 and 8 K for the as-sintered and the annealed sample,respectively,showing evident change.
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.
文摘Using the plane-wave expansion (PWE)method , the band gaps of the two-dimension phononic crystals composed of square, triangle and honeycomb arrays aluminum cylinders in the air are calculated numerically. The band structures of three lattices were compared and analyzed. It is concluded that the band-gap of honeycomb lattices is located at lower frequency fields, compared with square and triangle lattices. When the filling fraction is between 0.091 and 0.6046, the honeycomb lattices have larger band gaps and gain an advantage over square and triangle lattices. In addition, the gap map is introduced to illustrate the influences of filling fraction on the number, the relative width and the limit frequency of the band-gap.
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 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.
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Al-1.1%Sc and A1-2%Sc （mass fraction） alloys were prepared using gas atomized alloy particles. Samples from consolidated alloys were analyzed by XRD for the determination of lattice parameters. Using these lattice parameters, the mechanical properties of the alloys were calculated theoretically with WIEN2k and EMTO programs, respectively. The elasticity moduli of the experimentally produced alloys were compared with the theoretical calculation results. The calculated mechanical properties of A13Sc phase and A1-Sc alloys were discussed to determine the optimum Sc content of Al-Sc alloys. It may be concluded that the Sc content should be the maximum about 1.0%, much more Sc addition could not improve the mechanical properties of the alloys.
基金ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.20473108, No.10672173, and No.10432060） and the ＂Chuang-xin Project＂ of the Chinese Academy of Sciences.
文摘Liquid mixtures of water and deuterium oxide as the liquid phase, were used to match the density of charged colloidal particles. Kossel diffraction method was used to detect the crystal structures. The experiments under the density-matched （g=0） and unmatched （g=1） conditions are compared to examine the influence of gravity on the crystal structures formed by self-assembly of 110 nm （in diameter） polystyrene microspheres. The result shows that the gravity tends to make the lattice constants of colloidal crystals smaller at lower positions, which indicates that the effect of gravity should be taken into account in the study of the colloidal crystals.
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.
