Structure and Inter-Diffusion Coefficients of Liquid Na<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript>K<Subscript>1−<Emphasis Type=Italic>x</Emphasis></Subscript> Alloys

Structure and atomic transport properties of liquid Na-K alloys are reported. Inter-diffusion coefficients of liquid Na _x K_1−x , alloys are calculated using scaling law proposed by Samanta et al. following Dzugutov which express the possible relationship between the excess entropy and diffusion coefficient. The interatomic interactions are described from the individual version of the electron-ion potential proposed by Fiolhais et al. The partial pair distribution functions and structure factors are calculated from the solution of Ornstein-Zernike integral equation with Rogers-Young closure. The evaluation with the composition of static structure and inter-diffusion properties are discussed.     

Formation of ferromagnetism in pseudobinary PrNi<Subscript>5 − <Emphasis Type=Italic>x</Emphasis></Subscript>Cu<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript> (2.5 ≤ <Emphasis Type=Italic>x</Emphasis> ≤ 5) solid solutions

The structure and magnetic properties of the PrNi_{5 − x} Cu _x alloys have been studied in a composition range of 2.5 ≤ x ≤ 5. Single-phase solid solutions with a hexagonal structure of the CaCu₅ type have been shown to be realized within this composition range. It has been found that upon the introduction of nickel into the Van Vleck paramagnet PrCu₅ the ground state of the alloys with x ≤ 4.3 becomes ferromagnetic. All the compositions under study exhibit high magnetocrystalline anisotropy of the “easy-basal-plane” type. With allowance for the literature data available, a complete magnetic phase diagram of the PrNi_{5 − x} Cu _x system was constructed; it is characterized by two maxima in the compositional dependence of the Curie temperature. The earlier suggested model of the effect of local random crystal fields on the magnetic state of Pr³⁺ ions in alloys with low copper contents was shown to be applicable also for the explanation of magnetic properties of alloys with low nickel contents. The results of this study confirm the hypothesis about the determining role of local irregular crystal fields in the formation of the magnetic properties of the pseudobinary PrNi_{5 − x} Cu _x intermetallic compounds.     

Physical Characteristics of Ni<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zr<Subscript>100–<Emphasis Type="Italic">x</Emphasis></Subscript> Alloys Based on Stretching and Heating Processes Using Molecular Dynamics Simulation

The physical characteristics of Ni _x Zr_100–x proportions based on stretching and heating processes were investigated using molecular dynamics (MD) simulation. The physical characteristics included axial stretching, slip vector of dislocation nucleation, radial distribution function, Poisson’s ratio, and internal energy of thermophysical properties of the Ni _x Zr_100–x proportions. The second-moment approximation for tight-binding many-body potential was used for Ni _x Zr_100–x physical characteristics during the MD simulation. Results show that the most Zr atoms of Ni _x Zr_100–x models after axis stretching obviously move and accumulate at the outside of the Ni _x Zr_100–x models due to high-temperature softening behavior and high covalent bond strength. The Poisson’s ratios of the Ni₂₀Zr₈₀, Ni₄₀Zr₆₀, Ni₅₀Zr₅₀ Ni₆₀Zr₄₀, and Ni₈₀Zr₂₀, are 0.401, 0.397, 0.490, 0.437, and 0.385, respectively. The Ni₅₀Zr₅₀ proportion has highest Poisson’s ratio, indicating that the transverse contraction strain to longitudinal extension strain is largest than others proportions. For the thermophysical properties, the atoms of Ni₅₀Zr₅₀ in solids are orientation order.     

Wetting of Sn-Zn-<Emphasis Type=Italic>x</Emphasis>In (<Emphasis Type=Italic>x</Emphasis> = 0.5, 1.0, 1.5 wt%) Alloys on Cu and Ni Substrates

Wetting angles of Sn-8.8Zn and Sn-8.8Zn-xIn alloys (x = 0.5, 1.0, 1.5 wt%) were studied with the sessile drop method. Wetting tests were carried out for 900 s in the presence of ORM0 flux at 493, 523, and 573 K on copper and at 523 K on nickel substrates, respectively. It was found that the addition of In to Sn-8.8Zn alloy improves its wetting on both substrates by reducing the value of apparent wetting angle. Also, with increasing temperature a decrease of wetting angle on copper is observed in the case of 0 and 1.5 wt% of In alloys. Solidified solder-substrate couples were cross-sectioned and examined with scanning electron microscopy coupled with electron dispersive X-ray analysis. Interlayers were found at the interface of solders with copper and nickel, and their compositions are close to Cu₅Zn₈ and Ni₅Zn₂₁ intermetallics, respectively. However, in the case of Sn-8.8Zn-1.5/Ni couple small scallops are observed instead of continuous interlayer.     

The Transition from Transient Oxide to Protective Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Scale on Fe–Cr–Al Alloys During Heating to 1000 °C

The transition behavior of an Al-rich amorphous oxide layer to an external Al₂O₃ layer on Fe–(4, 24)Cr–(6, 10)Al (at.%) alloys was investigated during heating to 1000 °C at a heating rate of 50 °C/min, by means of in situ high-temperature X-ray diffraction measurement and TEM observation. In the alloy containing 6Al, internal amorphous Al₂O₃ was initially developed below the Al-rich amorphous surface layer. The amorphous internal precipitates transformed to be crystalline and grew laterally with time. The internal precipitates subsequently connected with each other to form a continuous α-Al₂O₃ scale. In the case of 10Al alloy, an Al-rich amorphous layer transitioned to a crystalline α-Al₂O₃ layer from the interface between transient/amorphous layers during heating. The Al₂O₃ scale developed on high Al alloys contained Fe and Cr with relatively higher contents, but that formed on low Al alloy contained low Fe and Cr. The effect of Cr on promoting an external Al₂O₃ scale formation was found to be weaker for alloys with higher Al content compared to the alloys with lower Al content, if Al₂O₃ scale was directly transitioned from the amorphous layer.     

Magnetic properties and structure of nonstoichiometric rare-earth transition-metal intermetallic compounds TbNi<Subscript>2</Subscript>Mn<Subscript><Emphasis Type=Italic>x</Emphasis></Subscript> (0 ≤ <Emphasis Type=Italic>x</Emphasis> ≤ 1.5)

Crystal structure, magnetization, coercive force, magnetic susceptibility, and anisotropic magnetostriction of nonstoichiometric rare-earth transition-metal intermetallic compounds TbNi₂Mn _x (0 ≤ x ≤ 1.5) have been studied. The samples with x ≤ 1 have an fcc structure, whereas TbNi₂Mn_1.25 has a rhombohedral structure of the PuNi₃ type. It has been found that the magnetic ordering temperature increases sharply when manganese is added. As the Mn concentration grows, the magnetization and the magnetostriction decrease monotonically, while the coercive force increases. The experimental data obtained have been interpreted on the assumption that a partial substitution of manganese for terbium in TbNi₂Mn _x leads to local distortions of the crystal field acting on Tb ions, to the appearance of a local uniaxial random anisotropy, and to the formation of a noncollinear magnetic structure in the terbium sublattice.     

Effect of Si and Y<Subscript>2</Subscript>O<Subscript>3</Subscript> Additions on the Oxidation Behavior of Ni–<Emphasis Type="Italic">x</Emphasis>Al (<Emphasis Type="Italic">x</Emphasis> = 5 or 10 wt%) Alloys at 1150 °C

The effect of Si and Y₂O₃ additions on the oxidation behavior of Ni–xAl (x = 5 or 10 wt%) alloys at 1150 °C was studied. The addition of Y₂O₃ accelerates oxidation rate of alloys, especially growth rate of NiO, but improves adherence of the scale to the substrate. The addition of Si facilitates the selective oxidation of Al, suppresses the formation of NiO and therefore reduces the critical Al content to form continuous layer of alumina scale. Higher Al content decreases the oxidation rate of alloys in binary Ni–Al alloys and increases the oxidation rate of alloys in ternary Ni–Al–Si alloys. The effect of third-element Si is more significant and beneficial than that of Al content in ternary Ni–Al–Si alloys.     

<Emphasis Type=Italic>In Situ</Emphasis> Characterization of Strength and Distortion During Powder Metal Processing

Thermogravimetric analysis and dilatometry are two common in situ measurement techniques used in powder processing to obtain information regarding thermal debinding and sintering. However, these two techniques provide negligible information regarding critical phenomena such as distortion or cracking. This paper discusses newer characterization techniques used to measure in situ strength evolution to help understand defect generation during the thermal debinding process. The information obtained from these in situ measurement techniques assists in intelligent design of optimal thermal cycles and in selection of binders targeted at manufacturing dense sintered components with minimum defects and distortion. The paper discusses examples of applications developed based on the information provided by in situ characterization of strength and distortion.     

Magnetic properties of Ni<Subscript>3</Subscript>Al<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript> alloys

Paramagnetic susceptibility of alloys Ni₃Al _x Mn_{1 − x} in the field of the transition between the ferromagnets described in the band theory (Ni₃Al) and in the spin-localized (Ni₃Mn) model of magnetic moments has been investigated. The concentration dependences of the paramagnetic Curie temperature, effective magnetic moment, and temperature-independent component of magnetic susceptibility have been determined.     

Structure and magnetic properties of mechanically synthesized (Fe<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Ni<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>75</Subscript>C<Subscript>25</Subscript> nanocomposites

X-ray diffraction, Mössbauer spectroscopy, and magnetic measurements have been used to study the phase formation in (Fe_1–xNi_x) (with х = 0–0.20) nanocomposites upon severe plastic deformation in a planetary ball mill and subsequent annealings. It has been shown that the mechanical synthesis results in the formation of mainly a nickel-alloyed nanocrystalline (Fe, Ni)₃C cementite with a distorted crystal lattice and an amorphous Fe–Ni–C phase. During heating above 300°С, the amorphous phase crystallizes with the formation of cementite, which is characterized by a higher Ni content compared to that in mechanically synthesized cementite. The mechanically synthesized samples exhibit low coercive force (equal to several tens ampere per centimeter). In the course of annealing at temperatures of up to 500–550°С, crystal lattice distortions are removed; this results in reliving the magnetic anisotropy constant and high-coercivity state of cementite. At the same time, Ni-rich cementite areas decompose with the formation of γ-(Fe, Ni, C) phase (austenite); as a result, the average nickel content in the cementite substantially decreases. Annealings at higher temperatures cause the complete decomposition of cementite and lead to an abrupt decrease in the coercive force (Н _с) of samples. Alloying with nickel leads to an increase in the Curie temperature of cementite and a decrease in its specific saturation magnetization, coercive force, and thermal stability.     

Ferromagnetic manganites La<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Ca<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>MnO<Subscript>3</Subscript>

A brief review of properties of the ferromagnetic manganites La_{1 − x} Ca _x MnO₃ is given. Lattice properties, magnetic properties, transport phenomena, magnetic resonance, and the results of neutron diffraction and optical studies are considered. Special attention is paid to effects observed near the Curie temperature.     

Hyperfine-interaction parameters and magnetic phase antiferromagnet–ferromagnet transition in Ce(Fe<Subscript>1–<Emphasis Type="Italic">x</Emphasis></Subscript>Si<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript>

Mössbauer spectroscopy study of Ce(Fe_1–x Si _x )₂ compounds with _x = 0 and 0.07 was performed at different temperatures. Easy magnetization axis of the CeFe₂ ferromagnet at 130 K was shown to be in the {110} plane and to deviate from the [001] axis by ～10°. Upon cooling, the Ce(Fe_0.93Si_0.07)₂ compound undergoes the ferromagnet–antiferromagnet phase transition in a temperature range of 120–125 K, which is accompanied by the reduction of the lattice symmetry. The Debye temperature of the Ce(Fe_0.93Si_0.07)₂ compound was estimated using temperature dependences of the integral intensity of Mössbauer spectrum; it is T _D ≈ 310 K. When analyzing the P(H) hyperfine field distributions P(H) derived from the Mössbauer spectra of Ce(Fe_0.93Si_0.07)₂, it was found that in the cubic structure of this compound in the ferromagnetic state there occur local rhomboherdal distortions typical of the antiferromagnetic state.     

Symmetry analysis of the magnetic structures of alloys of the quasi-binary system Fe<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Sn<Subscript>2</Subscript>

To estimate the reliability of the literature data on the magnetic structures of quasi-binary alloys Fe _x Mn_{1 ? x} Sn₂ obtained without using methods of symmetry analysis, we calculated the basic functions of the irreducible representations of the space group D _4h ¹⁸ (I4/mcm) with the stars of wave vectors determined from an analysis of previously published models of these structures. A comparison of these models with the results of calculations has been performed. A conclusion is made that the models of magnetic structures examined are in agreement with the results of the symmetry analysis performed in this work.     

Transport properties of solid solutions of <Emphasis Type="Italic">х</Emphasis>KYF<Subscript>4</Subscript>–(1–<Emphasis Type="Italic">х</Emphasis>)PbF<Subscript>2</Subscript> system

In the system (1–x)PbF_2–x YF_3–x KF, solid solutions of aliovalent substitution with fluorite structure at 0.47 < x < 0.69 are formed, in which the fluorine ions are found to be in three structurally nonequivalent positions that differ in the local environment and mobility. There are immobile, locally mobile, and highly mobile anions. The conductivity of the synthesized polycrystalline samples is ensured by highly mobile interstitial fluoride ions, whose concentration and hence electrical conductivity increase on heating. The contribution of the surface conductivity of crystallites is not detected. The electronic component is two orders of magnitude lower than the ionic one.     

Photodecomposition of H<Subscript>2</Subscript>S to H<Subscript>2</Subscript> over Cd<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Zn<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>S composite photocatalysts

A series of Cd _x Zn_1−x S (x = 0.1–0.9) photocatalysts were prepared by coprecipitation. They could form solid solution semiconductors with hexagonal phase in agreement with pure CdS by characterization of XRD. The photophysical properties of Cd _x Zn_1−x S photocatalysts were measured by UV-Vis diffuse reflectance spectrum and surface photovoltage spectroscopy (SPS). The band gap energy gradually reduced with the increasing of x value in CdxZn_1−x S, and when x = 0.7, the Cd_0.7Zn_0.3S photocatalyst had the strongest surface photovoltage. Cd _x Zn_1−x S photocatalysts were used in the photodecomposition of H₂S to H₂. The evolution rate of H₂ over the Cd_0.7Zn_0.3S photocatalyst was also the highest among Cd _x Zn_1−x S photocatalysts. And the effect of calcination temperature on the evolution rate of H₂ was investigated and the optimum temperature was 650°C.     

Photovoltaic structures ITO/SiO<Subscript> <Emphasis Type="Italic">х</Emphasis> </Subscript>/<Emphasis Type="Italic">n</Emphasis>-Si of increased efficiency

Structures ITO/SiO_х/n-Si are fabricated by pulverization of solutions of indium and tin chlorides on the (100) surface of silicon wafers with resistivity 4.5 Ω cm. The influence of the state of the Si surface on the efficiency of structures as photoelectric converters is investigated. It is shown that structures with an unetched surface of silicon wafers are the most efficient. Solar cells based on studied ITO/SiO_х/n-Si structures with an inverse layer demonstrate an efficiency close to 16% in AM 1.5 conditions.     

Electrodeposition Process and Performance of CuIn(Se<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>S<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>2</Subscript> Film for Absorption Layer of Thin-Film Solar Cells

CuIn(Se _x S_1?x )₂ thin film is prepared by the electrodeposition method for the absorption layer of the solar cell. The CuIn(Se _x S_1?x )₂ films are characterized by cyclic voltammetry measurement for the reduction of copper, indium, selenium and sulfur in selenium and sulfur in aqueous solutions with sodium citrate and without sodium citrate. In the four cases, the defined reduction process for every single element is obtained and it is observed that sodium citrate changes the reduction potentials. A linear relationship between the current density of the reduction peak and (scan rate v)^1/2 for copper and indium is achieved, indicating that the process is diffusion controlled. The diffusion coefficients of copper and indium ions are calculated. The diffusional coefficient D value of copper is higher than that of indium, and this is the reason why the deposition rate of copper is higher. When four elements are co-deposited in the aqueous solution with sodium citrate, the quaternary compound of CuIn(Se _x S_1?x )₂ is deposited together with Cu₃Se₂ impure phases after annealing, as found by XRD spectra. Morphology is observed by SEM and AFM. The chemical state of the films components is analyzed by XPS. The UV-Visible spectrophotometer and electrochemistry workstation are employed to measure the photoelectric properties. The results show that the smooth, uniform and compact CuIn(Se _x S_1?x )₂ film is a semiconductor with a band gap of 1.49 eV and a photovoltaic conversion efficiency of 0.45%.