X.L.Yang1)
,
X.Sun2)
,
C.W. Wang 2)
,
D.Q. Geng2)and C.M. Liu 2) 1)Schoolof Mechanical Engineering and Automation
,
Northeastern University
,
Shenyang 110006
,
China 2)Schoolof Material & Metallurgy
,
Northeastern University
,
Shenyang 110006
,
China
金属学报(英文版)
Thispaperintroducesa valve which useshape memory alloys( SMA) fortemperaturecon trol, which makes useof deformation of SMAcaused by variation oftemperaturetocontrolmechanical parts. Thevalvecan beswitched on or off automatically and hasthe advantages ofsimplestructureand reliable performance.Itcan beusedin adverse workingconditionsor conditions with lower requirementson controlling precision ofthetemperatures. Consequent ly,it hasextensive application prospects.
关键词:
shape memory alloy
,
null
,
null
Journal of Applied Physics
The crystal structure and superconducting properties of RuSr(2-x)Ba(x)GdCu(2)O(8) (0less than or equal toxless than or equal to0.1) have been investigated. X-ray powder diffraction (XRD) patterns show that the solid solution range is 0less than or equal toxless than or equal to0.1. The superconducting transition temperature was raised up to 35 K (zero) and 62 K (onset) for x=0.07, from 16 K (zero) and 45 K (onset) for x=0.0, and then T(C) decreases with x when x>0.07. Rietveld refinement for XRD data of RuSr(2-x)Ba(x)GdCu(2)O(8) show that the apical Cu-O(1) bond length increases with an increase of x, while the Ru-O(1) bond length decreases, This may account for the enhancement of the superconducting transition temperature. (C) 2004 American Institute of Physics.
关键词:
dc magnetization;rusr2gdcu2o8;ferromagnetism;coexistence;gd
Physical Review B
The temperature dependence of the elastic properties of Ni(2+x)Mn(1-x)Ga and Ni(2)Mn(Ga(1-x)Al(x)) (x = 0.0, 0.1, and 0.2) random alloys are investigated by using the first-principles exact muffin-tin orbitals method. At 0 K, the calculated equilibrium parameters in both cubic L2(1) and nonmodulated tetragonal beta'''-Ni(2)MnGa are in good agreement with the available experimental data and other theoretical results. Separating the thermal effects into single electron excitation, volume expansion, phonon smearing, and magnetic terms, we find that phonon smearing gives the dominating positive tetragonal elastic constant (C') versus temperature (T) slope for the cubic phase. For Ni(2+x)Mn(1-x)Ga, the competition between the negative alloying effect (partial derivative C'/partial derivative x < 0) and the positive temperature effect (partial derivative C'/partial derivative T > 0) leads to nearly constant C'[x, T(M)(x)] at the martensitic transition temperature T(M)(x). For Ni(2)Mn(Ga(1-x)Al(x)), where both partial derivative C'/partial derivative x and partial derivative C'/partial derivative T are positive, however, due to the significantly decrease of T(M)(x), the critical C'[x, T(M)(x)] slightly decreases with Al doping. Furthermore, it is demonstrated that both the composition and the temperature dependence of C' are indispensable to get a reasonable theoretical T(M)(x).
关键词:
shape-memory alloys;ni-mn-ga;martensitic phase-transformation;potential model;heusler alloys;ni2mnga alloy;landau theory;approximation;transitions;disorder
Chinese Physics B
X-ray powder diffraction, resistivity and magnetization studies have been performed on polycrystalline Nd(Fe(x)Mn(1-x))(2)Si(2) (0 <= x <= 1) compounds which crystallize in a ThCr(2)Si(2)-type structure with the space group 14/mmm. The field-cooled temperature dependence of the magnetization curves shows that, at low temperatures, NdFe(2)Si(2) is antiferromagnetic, while the other compounds show ferromagnetic behaviour. The substitution of Fe for Mn leads to a decrease in lattice parameters a, c and unit-cell volume V. The Curie temperature of the compounds first increases, reaches a maximum around x = 0.7, then decreases with Fe content. However, the saturation magnetization decreases monotonically with increasing Fe content. This Fe concentration dependent magnetization of Nd(Fe(x)Mn(1-x))(2)Si(2) compounds can be well explained by taking into account the complex effect on magnetic properties due to the substitution of Mn by Fe. The temperature's square dependence on electrical resistivity indicates that the curve of Nd(Fe(0.6)Mn(0.4))(2)Si(2) has a quasi-linear character above its Curie temperature, which is typical of simple metals.
关键词:
Nd(Fe(x)Mn(1-x))(2)Si(2);crystal structure;magnetic properties;resistivity;neutron-diffraction;rmn2ge2 compounds;solid-solution;silicides;0-less-than-or-equal-to-x-less-than-or-equal-to-1;behavior;ndfe2si2
Journal of Alloys and Compounds
Polycrystalline Nd(Mn(1-x)Fe(x))(2)Ge(2) (0 <= x <= 1) compounds have been prepared by arc-melting. X-ray powder diffraction analysis shows that all samples crystallize in the ThCr(2)Si(2)-type structure with the space group 14/mmm. The substitution of Fe for Mn results in decreases of the lattice constants a, c and the unit-cell volume V. Magnetic properties and magnetocaloric effect of the compounds Nd(Mn(0.9)Fe(0.1))(2)Ge(2) and Nd(Mn(0.8)Fe(0.2))(2)Ge(2) have been studied by magnetic measurements. A spin reorientation transition at about 188 K is observed for Nd(Mn(0.9)Fe(0.1))(2)Ge(2). The Nd(Mn(0.8)Fe(0.2))(2)Ge(2) compound shows more complicated magnetic behavior, which is characterized by four magnetic ordering states below room temperature. The maximum values of the magnetic entropy change are 2.35 and 1.84 J kg(-1) K(-1) for x = 0.1 and 0.2, respectively, under the applied field changing from 0 to 5T. The relative cooling powers of Nd(Mn(0.9)Fe(0.1))(2)Ge(2) and Nd(Mn(0.8)Fe(0.2))(2)Ge(2) are 145.9 and 133.8 J kg(-1) under an applied field change of 5T. (C) 2009 Elsevier B.V. All rights reserved.
关键词:
Metals and alloys;Magnetocaloric;X-ray diffraction;room-temperature applications;neutron-diffraction;phase-transitions;crystal-structure;solid-solution;refrigeration;silicides;mn;0-less-than-or-equal-to-x-less-than-or-equal-to-1;mnas1-xsbx
J. Wang
,
W. Jin
金属学报(英文版)
Phase transformation behavior of Ti50-x/2Ni50-x/2Cux (x=2, 5, 15) alloys was investigated using differential scanning calorimetry (DSC). The results show that Ti50-x/2Ni50-x/2Cux alloys undergo a two-stage martensitic transformation on cooling and transform reversely in one stage on heating when treated at 823K for 5 hours. Heat treatment has no effect on the transformation behavior of Ti49Ni49Cu2 alloy but does influence that of Ti47.5Ni47.5Cu5 alloy and Ti42.5Ni42.5Cu15 alloy. Effect of heat treatment is related with precipitation of CuNiTi phase. The maximum recoverable elongation of Ti49Ni49Cu2 wire is about 6%.
关键词:
microstructure
,
null
,
null
,
null
Y.G. Wang
,
F.M Yang
,
C.P. Chen
,
N Tang
,
and Q.D. Wang (State Key Laboratory of Magnetism
,
Institute of Physics
,
Chinese Academy of Sciences
,
P.O. Box 603
,
Beijing 100080
,
China)(Department of Materials Science and Engineering
,
Zheiang University Hangzhou 310027
,
China)
金属学报(英文版)
The magnetic phase diagram (x,T) of the SmMn2(Ge1-xSix)2 system has been studied by susceptibility and magnetization measurement. With increasing silicon concentration the temperature region of ferromagnetic ordering decreases on the phaae diagram.
关键词:
magnetic phase diagram
,
null
,
null
,
null
Physical Review B
The magnetic transitions and magnetic and magnetostrictive properties of Tb(x)Dy(1-x)(Fe(0.8)Co(0.2))(2) (0.20 <= x <= 0.40) compounds have been investigated. The spin-reorientation temperature T(SR) decreases from above to below room temperature, when x is increased from 0.25 to 0.40. The easy magnetization direction at room temperature of the Laves phase lies along the < 100 > axis in compounds with 0.20 <= x <= 0.27, while it lies along the < 111 > axis as 0.30 <= x <= 0.40. The magnetocrystalline anisotropy constant K(1) at room temperature reaches a minimum value at x=0.30, indicating it is near the composition for anisotropy compensation. The large polycrystalline saturation magnetostriction lambda(s)approximate to 980 ppm is observed for x=0.30, which can be ascribed to the large magnetostriction coefficients lambda(111) and lambda(100). lambda(100) has a value larger than 600 ppm for the compounds with 0.30 <= x <= 0.35, which can be attributed to the change of the filling of the 3d band due to Co substitution for Fe. Tb(0.30)Dy(0.70)(Fe(0.8)Co(0.2))(2) with a high magnetostriction and a low anisotropy is found to be a good candidate material for magnetostriction applications. A detailed spin configuration diagram for Tb(x)Dy(1-x)(Fe(0.8)Co(0.2))(2) Laves phase around the composition for the anisotropy compensation is given, which should be a guide to develop novel magnetostrictive materials for applications in this series.
关键词:
anisotropy compensation;laves phase;intermetallics;substitution;tbfe2;tb0.27dy0.73fe2;compound;alloys
Applied Physics Letters
A series of polycrystalline Ca(3)Co(2-x)Mn(x)O(6) with 0.93 < x < 1.07 are prepared in order to investigate the effect of Co:Mn ratio around x similar to 1.0 on the multiferroicity. It is found that the ferroelectric polarization P at low temperature shows significant dependence on the Co:Mn ratio, forming a V-shaped pattern with the lowest point at x similar to 0.99. It is proposed that the suppression of P with the Co:Mn ratio approaching to the best Co/Mn order originates from the disruption of the long range spin order. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3464289]
关键词:
calcium compounds;ferroelectric materials;multiferroics;one-dimensional oxides;ca3co1+xmn1-xo6
International Journal of Hydrogen Energy
The La(2-x)Ti(x)MgNi(9) (x = 0.1, 0.2, 0.3, 0.4) alloys were prepared by magnetic levitation melting under Ar atmosphere. The effects of partial substitution Ti for La on the phase structures, hydrogen-storage proper-ties and electrochemical characteristics of the alloys were investigated systematically. For La(2-x)Ti(x)MgNi(9) (x = 0.1, 0.2, 0.3, 0.4) alloys, LaNi(5), LaNi(3) and LaMg(2)Ni(9) are the main phases, the maximum hydrogen-storage capacity is 1.51, 1.36, 1.35 and 1.22 wt%, respectively. The absorption-desorption plateau pressure of the alloys first decreases and then increases with increase of Ti content, and the La(1.8)MgTi(0.2)Ni(9) alloy has the lowest absorption-desorption plateau pressure. The discharge voltage of the alloy electrodes rises with increasing the amount of Ti content. The La(1.8)Ti(0.2)MgNi(9) alloy electrode presents good electrochemical performance. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.
关键词:
Hydrogen-storage alloy;Hydrogen-storage property;Electrochemical;characteristic;electrochemical properties;electrode alloys;substitution;mn;la;ni;co;zr;al;microstructures
