The Role of Transition Metals in Crystallization of Amorphous Al–Ni–Co–Yb Alloys

Technical Physics - Al86Ni4Co4Yb6 and Al86Ni6Co2Yb6 metallic ribbons have been obtained by a standard planar flow method. According to X-ray diffraction data, the ribbons are amorphous. Their...     

Role of Magnetism in the Decomposition of α-Fe–Cu Alloy

Recent ab initio studies of the role of magnetism in the decomposition of α-Fe–Cu alloy are analyzed. It is shown that the calculations based on effective pair potentials obtained earlier in the framework of the partial disordered-local moment model strongly overestimate the magnetic contribution. A simple model with the ab initio parametrization is formulated. It allows us to calculate the solubility limits for the bcc and fcc copper precipitates in α-Fe, which are in good qualitative agreement with the experimental data.     

Superconductivity of the Bi–Sn Eutectic Alloy

Physics of the Solid State - We report on the results of investigations of superconductivity in the Bi–Sn binary alloy with a eutectic concentration of 57 wt % of Bi and 43 wt % of Sn. The...     

The Effect of Transition Metals on the Dielectric Properties of Diamond-Like Silicon–Carbon Films

Physics of the Solid State - Studies of the effect of transition metals on the phase composition and electric and dielectric properties of diamond-like silicon–carbon films fabricated by...     

Dynamical Transition of Myoglobin and Cu／Zn Superoxide Dismutase Revealed by Molecular Dynamics Simulation

We have carried out parallel moecular dynamics simulations of solvated and non-solvated myoglobin and solvated Cu/Zn superoxide dismutase at different temperatures.By analysis of several methods,the simulati8ons reproduce the quasielastic neutron scattering experimental reults.Below 200K these two proteins behave as harmonic solids with essentially only vibrational motion,while above this temperature,there is a striking dynamic transition into anharmonic motion.Moreover,the simulations further show that water molecules play an important role for this dynamical transition.There is no such sharp dynamical transition in non-solvated proteins and the higher the solvate density is ,the steeper at transition point the curve of mean square displacement versus temperature will be.The simulations also display that the dynamical transition is a general propoerty for globular protein and this transition temperature is a demarcation of enzyme activity.     

Electrochemical Emission during the Straining and Destruction of an Aluminum–Magnesium Alloy in an Aqueous Medium

Technical Physics - The spatiotemporal structures of Portevin–Le Chatelier deformation bands at the stage of neck formation and fracture of an aluminum–magnesium alloy deformed in an...     

The structure and composition of novel electrodeposited Sn–Fe and Sn–Co–Fe alloys from a flow circulation cell system

This study involved the use of a flow circulation cell, using varying circulation rates as a room temperature process (20°C). Mössbauer and XRD analysis were conducted to ascertain whether amorphous or microcrystalline structures could be obtained at 20°C using a range of current densities. Amorphous or microcrystalline structures of Sn–Fe and Sn–Co–Fe have potentially important industrial applications for energy efficient cells, for use as high performance electrodes in lithium batteries, as environmentally acceptable corrosion resistant materials and are derived from an energy efficient environmentally friendly electrolyte process which would be acceptable as an industrial process. $^{\it 57}Fe$ and $^{\it 119}Sn$ Mössbauer investigations supported by XRD analysis confirmed that the room temperature flow circulation cell gave rise to previously unknown non-equilibrium amorphous structures which do not occur in the corresponding thermally prepared alloys as shown in the thermal equilibrium diagrams. Mössbauer analysis shows these alloys to be both amorphous and ferromagnetic. It is shown that the flow circulation cell used at 20°C based on the environmentally friendly gluconate bath reported gives amorphous based Sn–Fe and Sn–Co–Fe alloys over a useful range of current densities facilitated by using a range of circulation rates.     

Influence of the Order-Disorder Phase Transition on the Grain Structure of Iron–Palladium Alloy

Transmission diffraction electron microscopy and optical metallography are used to investigate the grain structure and the crystallographic parameters of grain boundaries in Pd₃Fe alloy with short- and long-range atomic orders having the superstructure L1₂. It has been found that ordering annealing of the Pd₃Fe alloy with the ordering temperature T _K lower than the recrystallization temperature is accompanied by changes in the grain structure. The average distance between the nearest boundaries and the average grain size decrease. The fraction of twinning boundaries for which the inverse density of coinciding lattice sites () is equal to 3 increases. This results in a decrease of the twinning boundary energy. A comparative analysis of changes in the grain structure of Ni₃Fe and Pd₃Fe alloys at the A1 L1₂ phase transition is performed. The mechanisms of changes of the grain structure during ordering annealing are discussed.     

Hyperfine Field and Isomer Shift Evolution in Hydrogenated Nd–Fe–B Alloy

RE₂Fe₁₄B (RE=rare earth) materials are capable of absorbing hydrogen to form a stable solid solution at room temperature. Hydrogenation produces a number of significant changes in the hyperfine interactions. In this work, ⁵⁷Fe Mössbauer effect spectroscopy and X-ray diffraction measurements were performed on Nd_14.01Hf_0.08Fe_78.91B_7.00 alloys submitted to thermal treatment in hydrogen atmosphere. A non-linear increase of the hyperfine fields and isomer shifts with hydrogen concentration was observed. The hyperfine parameters of the 8j₁ site exhibit a rather different evolution than those experienced by the other major sites (8j₂, 16k₁, 16k₂). The origin of the hyperfine field enhancement is analyzed in terms of volume expansion and H nearest neighbors to the Fe sites. A linear expression on these two effects to give account of isomer shift evolution for 8j₁ site is given.     

Nonstationary Electrochemical Response to the Intermittent Portevin–Le Chatelier Deformation in an Aluminum–Magnesium Alloy

Physics of the Solid State - It has been established that the Portevin–Le Chatelier effect in the AlMg6 aluminum–magnesium alloy deformed in an aqueous medium is accompanied by an...     

Role of heterogeneities in Staebler–Wronski effect

The effect of light soaking (LS) on the properties of hydrogenated amorphous silicon (a-Si:H) presents many challenging puzzles. We look at some of them, along with their present understanding. In particular, the role of the heterogeneities in LS is examined. We find that for most of the solved as well as unsolved puzzles, the long-range potential fluctuations arising from the heterogeneities in the films, afford an alternative view which looks quite plausible. The implications of such considerations are used to speculate on the possibility of making stable a-Si:H solar cells.     

The Model of Decomposition of a Fe–Cu Alloy with Concentration-Depending Interatomic Interactions

Physics of the Solid State - The thermodynamics and kinetics of decomposition of a Fe–Cu alloy are investigated in the context of a simple ab initio parameterization model taking into account...     

Effect of Annealing in a Ferromagnetic State on the Structure of an Fe–18 at % Ga Alloy

Physics of the Solid State - The atomic structure of the iron–gallium alloy containing 18 at % Ga has been studied by X-ray diffraction. The samples were annealed in the paramagnetic (T...     

Discontinuous Structural Phase Transition Behaviour in Multiple Component Alloy Melts

Discontinuous structural phase transition behaviour in seven kinds of liquid multiple component alloys are found by using a torsional oscillation viscometer. There are different phases existing in the system and the number of phases is discussed using the equilibrium thermodynamics phase rule. The phase parameters （ηo,ε） and order parameter dI in different phase regions are calculated based on the researched results. It is found that the parameters （ηo,ε, df） change at the structural transition point. The diameter of the fluid clusters, di, is stable in each phase region, which indicates that the structure is uniform.     

Role of glueballs in non-perturbative quark–gluon plasma

Discussed is how non-perturbative properties of quark gluon plasma, recently discovered in RHIC experiment, can be related to the change of properties of scalar and pseudoscalar glueballs. We set up a model with the Cornwall–Soni's glueball–gluon interaction, which shows that the pseudoscalar glueball becomes massless above the critical temperature of deconfinement phase transition. This change of properties gives rise to the change of sign of the gluon condensate at T>Tc$T>T_c$. We discuss the other physical consequences resulting from the drastic change of the pseudoscalar glueball mass above the critical temperature.     

Study of defects in Fe–Re and Fe–Mo alloys by the Mössbauer and positron annihilation spectroscopies

The room temperature positron annihilation lifetime spectra and ⁵⁷Fe Mössbauer spectra were measured for pure Fe as well as for iron-based Fe_1?xRe_x and Fe_1?xMo_x solid solutions with x in the range 0.01≤x≤0.05. The measurements were performed in order to learn more about creation of structural defects during formation and further mechanical processing of the iron systems under consideration. The spectra were collected at least twice for each studied sample synthesized in an arc furnace—after cold rolling to the thickness of about 40 μm as well as after subsequent annealing at 1270 K for 2 h. It was found that in the annealed samples positrons live much shorter than in the not annealed ones which suggest that the latter samples are more defected as it could be expected. Moreover simultaneous analysis of the positron and Mössbauer data shows that cold rolling leads to creation of two types of defects. It seems that they are dislocations and vacancies. Finally from the Mössbauer data it follows that vacancies are located mainly in the vicinity of non-iron atoms, Re or Mo. This speaks in favour of the suggestion that in iron matrix the impurities mentioned above and vacancies interact attractively which supports the known from the literature, theoretical calculations on the Mo-vacancy interaction in iron.     

Role of electrolyte pH on structural and magnetic properties of Co–Fe films

Co–Fe films were electrodeposited on polycrystalline Titanium substrates from the electrolytes with different pH levels. X-ray diffraction (XRD) was used to study the crystal structure of the films. The XRD patterns showed that the films grown at the pH levels of 3.70 and 3.30 have a mixed phase consisting of face-centred cubic (fcc) and body-centred cubic, while those grown at pH=2.90 have only fcc structure. It was observed that the film composition, by energy dispersive x-ray spectroscopy, contain around 88 at% Co and 12 at% Fe for all films investigated in this study. Morphological observations indicated that all films have grainy structure with the slight change of grain size depending on the electrolyte pH. Magnetoresistance measurements, made at room temperature, showed that all films exhibited anisotropic magnetoresistance, which is affected by the electrolyte pH. From the magnetic measurements made by vibrating sample magnetometer, the saturation magnetization increases as the electrolyte pH decreases. Furthermore, all films have in-plane easy-axis direction of magnetization.     

Propagation Ultrasound Velocity at Plastic Deformation of Fe–Cr–Ni Alloy within 180–318 K

Russian Physics Journal - The paper studies the mechanical properties of the Fe–Ni–Cr alloy and the ultrasound propagation velocity (Rayleigh waves) during its plastic deformation...     

Kinetics of Early Decomposition Stages in Diluted bcc Fe–Сu–Ni–Al Alloy: MC+MD Simulation

Physics of the Solid State - A combined approach including the Monte Carlo and molecular-dynamics simulation, decomposition kinetics and segregation formation in the multicomponent low-alloy...