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1.
Recently, resistivity measurements of some liquid metals and metallic alloys have been obtained using an electrode technique. A marked change of the slope of the resistivity versus temperature has been observed following the history of the alloy in the liquid state and the authors conclude that there are “structural transitions in the melt”. It is of interest to examine such effects and to try to understand their origin. In this work, the resistivities of several liquid metals and metallic alloys were measured as a function of temperature. Particular attention was given to the history of the alloy, including solidification and melting conditions. We also observed “anomalies”. Our experiments lead us to conclude that they must very probably be attributed to the release of gas or vapour bubbles in the liquid alloy at the first heating, resulting from the decomposition of compounds like oxides or hydroxides of the metals, but not from a phase transition in the liquid metallic state involving “breaking” Sn–Sn covalent bands. 相似文献
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Amorphous TiFe, ZrFe and HfFe alloys prepared by low temperature implantation of about 10 at% Fe were found to have superconducting transition temperatures, Tc, enhanced above the values of the pure crystalline elements. In addition, Tc = 2.6 K for TiFe is about 1 K higher than Tc of the equivalent amorphous TiCu alloy. A correlation between the recently observed dband behavior of similar binary transition metal alloys and the forming ability is extended to (Ti,Zr,Hf)-Fe alloys to explain their superconducting properties. 相似文献
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Abstract In comparison with the “regular” binary alloy phase diagrams between “regular” trivalent lanthanide metals, binary intralanthanide alloys of Ce exhibit many irregularities typical for Ce under pressure due to its f electron delocalization. For comparison with the La-Ce and Ce-Pr high pressure phase diagrams also the more regular La-Pr data are presented for the pressure range up to 40GPa. 相似文献
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Neville I. Marzwell 《Journal of magnetism and magnetic materials》1977,5(1):67-77
Magnetic susceptibility and electrical resistivity measurements were performed (Pd100?xCox)80P20 alloys where 15 < x < 50. The magnetic properties show that these alloys undergo a ferromagnetic transition between 272 and 399 K as the cobalt concentration increases from 15 to 50 atomic %. Below 20 atomic % Co the short-range exchange interactions which produce the ferromagnetism are unable to establish a long-range magnetic order and a peak in the magnetization shows up at the lowest temperature range under an applied field of 6.0 kOe. The electrical resistivity of these alloys has been measured from 4.2 K up to the vinicity of the melting point (900 K). The electrical resistivity data could be interpreted by the coexistence fo a Kondo-like minimum and ferromagnetism. The minimum becomes less important as the transition metal concentration increases. The coefficients of In T and T2 become smaller and concentration dependent. The spin ordering in such alloys can be simulated as either the ordering due to an applied “external field” or as an increase in “internal fields”. These are due to an increase in transition metal concentration. The negative magnetoresistivity is a strong indication of the existence of localized moment. 相似文献
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Nguyen V. Hung Dung T. Tran Nguyen C. Toan Barbara Kirchnner 《Central European Journal of Physics》2011,9(1):222-229
A thermodynamic lattice theory has been developed for determination of the melting curves and eutectic points of binary alloys.
Analytical expressions for the melting curves of binary alloys composed of constituent elements with the same structure have
been derived from expressions for the ratio of root mean square fluctuation in atomic positions on the equilibrium lattice
positions and the nearest neighbor distance. This melting curve provides information on Lindemann’s melting temperatures of
binary alloys with respect to any proportion of constituent elements, as well as on their eutectic points. The theory has
been applied to fcc and bcc structure. Numerical results for some binary alloys provide a good correspondence between the
calculated and experimental phase diagrams, where the calculated results for Cu1−x
Ni
x
agree well with the measured ones, and those for the other alloys are found to be in a reasonable agreement with experiment. 相似文献
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The extended X-ray absorption fine structure (EXAFS) associated with the K absorption discontinuity of copper has been studied in the pure metal and in some copper-gallium and copper-germanium alloys, using a bent crystal X-ray spectrograph. The results obtained are discussed in the light of the recent theory of EXAFS proposed by Lytle, Sayers and Stern. It has been shown for the first time that there exists in alloys a correlation between the EXAFS parameter α1 and e/a ratio. This correlation has been used to obtain the value of the lattice parameter “a” for Cu-27 at.% Ge alloy, which is not available in literature. 相似文献
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LU YunBin LIAO ShuZhi XIE Bin CHEN Jia PENG HaoJun ZHANG Chun ZHOU HuiYing XIE HaoWen OUYANG YiFang & ZHANG BangWei Key Laboratory of Low Dimensional Quantum Structures Quantum Control of Ministry of Education 《中国科学:物理学 力学 天文学(英文版)》2011,(5)
Based on the ideal solution approximation, the model for size-dependent melting temperature of pure metal nanoparticles is extended to binary alloy systems. The developed model, free of any adjustable parameter, demonstrates that the melting temperature is related to the size and composition of alloy nanoparticles. The melting temperature of CuNi, PbBi and SnIn binary alloy nanocrystals is found to be consistent with the experiments and molecular dynamics simulations. The research reveals that alloy nanocry... 相似文献
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液态金属和玻璃的若干研究进展 总被引:5,自引:0,他引:5
概述了液态金属和玻璃的的结构和性质研究的一些近期发展,如液态金属的原子间相互作用势和结构的普适性描述,二元液态合金的物理性质的计算和金属--非金属转变的解释,以及玻璃的结构、熔化和弛豫的微观描述。 相似文献
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The volume expansion coefficients (α) of twenty-five glass-forming transition metal alloy liquids, measured using the electrostatic levitation technique, are reported. An inverse correlation between α and the cohesive energy is found. The predicted values of α from this relationship agree reasonably well with the published data for thirty other transition metal and alloy liquids; some disagreement was found for a few alloys containing significant amounts of group III and IV elements. A theoretical argument for this empirical relationship is presented. 相似文献
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Edward Siegel 《Journal of magnetism and magnetic materials》1980,22(1):41-57
The Yonezawa-Watabe (YW) study of the metal-nonmetal transitions in nondegenerate, s-electron disordered binary systems: doped semiconductors, metal-ammonia solutions, liquid metals and mixed crystals (alloys), is generalized to include ten-fold d-electron (hole) degeneracy. Such degeneracy automatically includes Hund's rule d-electron coupling and intra-site enhanced Coulomb and exchange interactions. Such a calculation is specifically relevant only to transition metal alloys, transition metal oxides and mixed transition metal oxides. It is seen that potential fluctuations exist in these systems and the possibility of Anderson localization in these disordered degenerate binary transition metal systems is explored. The YW CPA treatment of the effect of substitutional disorder (alloying) upon the mobility gap and quasiparticle states of the density of states at the extreme band edges and localization due to random spin configuration are generalized to these degenerate d-electron systems and it is shown that the disappearance of the mobility gap, not the density of states gap, causes the metal-nonmetal transition for degenerate d-electrons. 相似文献
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The effect of dynamical electron-electron correlations on the electronic structure of the paramagnetic disordered binary alloy of the transition and simple metals is studied for the Anderson model extended to arbitrary concentration of the transition metal impurities. We use the terminal-point approximation for the many-body quantities, which allows us to solve the random part of the problem within the single-site approximation. The many-body part of the problem is treated within the selfconsistent T-matrix approximation, valid for low, but finite concentration of particles ( ? 0.3/atom/spin). For low concentration of the transition metal impurities we obtain results identical with those for the Anderson model. The theory is illustrated numerically for a simple bandstructure model. 相似文献
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Thermal neutron scattering experiments have provided detailed information on the distributions of magnetic moment in a number of disordered ferromagnet binary alloys. The general features of these distributions together with saturation magnetization data are discussed and compared with various simple theories. Attention is focused on dilute alloy systems. After an introduction the paper is divided into four sections, the first of which deals with alloys which tend to follow the Slater-Pauling curve. Here a simple Thomas-Fermi treatment due to Friedel suggests that magnetic moment changes, largely confined to the minor constituent (solute) sites, should occur with a sign dependent on the nature of the density of states at the Fermi level in the pure major constituent (solvent). Comparison with experiment shows qualitative agreement except in the case of Fe-based alloys containing transition element solutes from the right of Fe in the periodic table. This discrepancy is examined and an explanation put forward. The next section outlines a discussion of the electronic structure of alloys of transition elements with non-transition metal solutes. The view is taken that the electronic configuration of a solute atom is roughly similar to the configuration found in the pure non-transition metal: it follows that no partially filled d orbitals are expected at solute sites. Use of a simple Thomas-Fermi model based on this assumption indicates that some of the electric screening associated with a non-transition metal solute takes place in the surrounding transition metal slovent. Additional electrons introduced in this way into the solvent occupy mainly d states and cause a reduction in magnetic properties. This reduction together with the total loss of d-state effects from the solute sites themselves can account qualitatively for the changes observed in Ni, Pd and Fe-based alloys with non-transition elements. The fourth section deals with the transition metal alloys which show marked departures from Slater-Pauling behaviour, e.g. NiCr. An explanation for these alloys has been provided by Friedel's bound impurity state model and the mechanism suggested by Comly, Holden and Low to account for the similarity in shape of the magnetic disturbances observed in different systems. The final section discusses ferromagnetic alloys of PdFe and PdCo. The giant moments associated with the Fe and Co solutes result from a widespread polarization of the Pd solvent contiguous to the solute atoms. This polarization can be interpreted with the use of a non-local exchange-enhanced susceptibility function for the Pd host. With increasing solute content this function becomes modified to an extent dependent on the shift of d holes from one spin direction to the other, i.e. on the mean polarization of the Pd. 相似文献
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It is shown, starting from a nearly-free electron approximation, how correlations can occur in the atomic positions of binary liquid and glassy alloys. In particular, it follows from energy considerations that for an alloy of a transition metal with a metalloid there is a concentration region where there should be no metalloid-metalloid nearest neighbors. This concentration region is just the same as that where glass formation is often observed in these systems. 相似文献
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Chepkasov I. V. Gafner Yu. Ya. Vysotin M. A. Redel’ L. V. 《Physics of the Solid State》2017,59(10):2076-2081
The melting processes of various Pt–Pd nanoparticles (binary alloy, core–shell, D ≤ 4.0 nm) with different percent platinum atom content are investigated via the molecular dynamics using the embedded atom method potential in order to establish the thermal stability of simulated particle structure. In accordance with the data obtained, the most thermally stable are Pt–Pd nanoalloys with a diameter above 2.0 nm and core–shell Pd@Pt particles. As is shown, heating of binary Pt–Pd cluster alloys with the particle diameters less than 2.0 nm may cause the transition to pentagonal symmetry structures and core–shell-like complex formations.
相似文献20.
It is shown that the ordered structures occurring in binary substitutional transition metal alloys on simple lattices (f.c.c., b.c.c.) can systematically be obtained from the electronic structure of the disordered alloys. Generalized structural maps are introduced; their physical meaning and their relation to the phenomenological structural maps used previously by other authors are discussed. 相似文献