Ultrasound velocity and adiabatic compressibility of LaCl<Subscript>3</Subscript> + <Emphasis Type=Italic>M</Emphasis>Cl (<Emphasis Type=Italic>M</Emphasis> = Li,Na, K,Rb, and Cs) melts

The ultrasound velocity in binary LaCl₃ + MCl (M = Li, Na, K, Rb, and Cs) melts is measured, and their adiabatic compressibility is calculated as a function of temperature and composition. A relation is established between the relative deviations of these properties from their values for hypothetic ideal salt mixtures, on the one hand, and the ionic potentials of the alkali-metal cations, on the other.     

Thermal conductivity of NdCl<Subscript>3</Subscript>-<Emphasis Type=Italic>M</Emphasis>Cl (<Emphasis Type=Italic>M</Emphasis> = Na,K, Cs) melts

The thermal conductivities of individual NdCl₃, the K₃NdCl₆ chemical compound, an equimolar 0.5NdCl₃-0.5NaCl mixture, and eutectic 0.5NdCl₃-0.5KCl and 0.45NdCl₃-0.55CsCl mixtures are measured. For all melts, the concentration and temperature dependences of the thermal conductivity are found.     

Interaction of strontium oxide with Sr-Cl<Subscript>2</Subscript>-<Emphasis Type=Italic>M</Emphasis>Cl melts

The kinetics of dissolution and the solubility of strontium oxide in melts of KCl, NaCl, CsCl, (3Li-2K)C_leut (eutectic), and LiCl containing 5, 7, and 12 mol % SrCl₂ at 973–1073 K are determined by the isothermal saturation method. The diffusion coefficients of strontium ions in these salt systems are estimated.     

Ultrasound velocity and adiabatic compressibility of molten GdCl<Subscript>3</Subscript> and its solutions in potassium chloride

The ultrasound velocity in the melts of gadolinium chloride and its mixtures with potassium chloride is measured as a function of the temperature and composition, and their adiabatic compressibilities are calculated. A relation is established between the relative deviations of these properties from their values for hypothetic ideal solutions.     

<Emphasis Type=Italic>L</Emphasis><Subscript>3</Subscript>-XANES spectroscopy of the valence-unstable cerium in intermetallic compounds with 3<Emphasis Type=Italic>d</Emphasis> metals

The effective valence of cerium is studied by L ₃-XANES spectroscopy using synchrotron radiation in the following valence-unstable systems with different types of magnetic ordering: a CeNi matrix doped with neodymium, praseodymium, and gadolinium ions in the temperature range 5–300 K and the Ce₂Fe1_{7 − x} Mn _x intermetallic compound. The obtained dependences are discussed in terms of generally accepted models of states with an intermediate valence of rare-earth ions. Possible correlations between the effective valence of cerium and the magnetic properties of the substances are taken into account.     

Anomalous Mixing State in Room-Temperature Ionic Liquid-Water Mixtures: <Emphasis Type=Italic>N,N</Emphasis>-diethyl-<Emphasis Type=Italic>N</Emphasis>-methyl-<Emphasis Type=Italic>N</Emphasis>-(2-methoxyethyl) Ammonium Tetrafluoroborate

The mixing states of room-temperature ionic liquid (RTIL) H₂O mixtures (x = 0.0 mol pct to 99.5 mol pct H₂O) were investigated using wide-angle X-ray scattering (WAXS), small-angle X-ray scattering (SAXS), and optical absorption in an ultraviolet and visible (UV-vis) region. The RTIL is N, N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium tetrafluoroborate, [DEME][BF₄]. In a “prepeak” region of the WAXS, the scattered intensities increased at 85 mol pct to 95 mol pct. A medium-range order (MRO) in the liquid structure as observed in network-forming materials developed markedly. In the SAXS experiments, we can detect nanoscale fluctuations relating to polar and nonpolar regions. At 65 mol pct to 85 mol pct, the SAXS intensity increased unexpectedly. Furthermore, entirely different optical absorption spectra in the UV-vis region were observed as a macroscopic property from 90 mol pct to 95 mol pct. We suppose that these anomalies relate to the MRO of the liquid structure. All anomalies probably are induced by an intrinsic property in [DEME][BF₄]-H₂O mixtures.     

Thermodynamic analysis of the dominant phase equilibria in <Emphasis Type=Italic>M</Emphasis>(Si,Cr, Al)-O-C systems

Various approaches are proposed for developing thermodynamic models of dominant phase equilibria. It is noted that, as a thermodynamic analysis of the phase equilibria in M(Si, Cr, Al)-O-C systems is performed, the equilibrium concentrations and the stability of the phases should be calculated by minimizing the Gibbs energy for the systems at a given temperature and pressure.     

Crystallization of Co<Subscript>100-<Emphasis Type="Italic">x</Emphasis></Subscript>Pt<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>B<Subscript>10</Subscript>Si<Subscript>12</Subscript> amorphous metallic alloys

Alloys of Co_78-x Pt _x B₁₀Si₁₂ were produced using the melt-spin process in order to study the crystallization behavior and ensuing magnetic properties of the Co-Pt amorphous alloys as a function of the Pt content. We showed that when x>15, well below its stoichiometric composition, CoPt intermetallic compound crystallized in the amorphous alloy. Below this composition, the main crystallization product was Co with Pt dissolved in its lattice. The nucleation of CoPt greatly altered the crystallized microstructures and magnetic properties of the Co-Pt amorphous alloys during annealing. In spite of the nucleation of CoPt with its high magnetic anisotropy, the highest coercivity was obtained when x was 15, free of the CoPt grains. It was also concluded that the Pt addition, in general, triggered crystallization to occur at a progressively lower temperature.     

A Derivation of a Quadratic Activity Coefficient <Emphasis Type=Italic>vs</Emphasis> Composition Relationship in a Quaternary System, <Emphasis Type=Italic>A-B-C-D</Emphasis>

In the literature, no direct derivation exists of the quadratic activity coefficient vs composition relationships for a quaternary system with high solute concentrations. Such relations for a ternary system (1-2-3) were derived by Darken by extending the results of a binary system (1-2), introducing a new concept of “hypothetical system” (2-3). To present a better scheme to find the activity coefficient-composition relations for multicomponent systems, derivations are made for a quaternary system A-B-C-D in the current work. Using a MacLaurin series expansion, the (Raoultian) activity coefficient, ln γ _i , of each component is equated with a quadratic expression of mole fractions (x), involving the activity coefficient at zero concentration ( g_i⁰ ) left( {gamma_{i}^{0} } right) and nine interaction coefficients (ε). Subsequently, with the help of a Gibbs–Duhem equation, followed by a comparison of coefficients, most preceding 9 × 4, i.e., 36 interaction coefficients are eliminated, leaving behind only three self- and three ternary interaction coefficients, which are enough to express the activity coefficient vs composition relationships for the solutes B, C, and D, as well as for the solvent A. Setting the mole fraction x _D  = 0, the preceding expressions establish the same relations as proposed by Darken for the ternary system A-B-C. The derivation also clarifies how the quadratic concentration terms accompany the first-order interaction coefficients, not the second-order ones. Applications of the derived relations to determine simultaneously the activity coefficients g_i⁰ gamma_{i}^{0} and the interaction coefficients ε in a new way in some iron- and steelmaking systems are presented. A new data on interaction coefficients in liquid iron at 1873 K (1600 °C), e_textV^textV = - 6. 1, varepsilon_{text{V}}^{text{V}} = - 6. 1, has been generated through such an application.     

Processing,microstructure, and mechanical properties of cast <Emphasis Type="Italic">in-Situ</Emphasis> Al(Mg,Mn)-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>(MnO<Subscript>2</Subscript>) composite

Cast particulate composites, containing in-situ generated reinforcing particles of alumina, have been developed by solidification of slurry obtained by dispersion of externally added manganese dioxide particles (MnO₂) in molten aluminum, and alumina is formed by reaction of manganese dioxide with molten aluminum. The chemical reaction also releases manganese into molten aluminum. Magnesium is added to the melt in order to help wetting of alumina particles by molten aluminum and to retain the particles inside the melt. The present work aims to understand the influence of key parameters such as processing temperature, time, and the amount of MnO₂ particles added on the microstructure and mechanical properties of the resulting cast in-situ composites. The sequence of addition of MnO₂ particles and magnesium has significant influence on the microstructure and mechanical properties. Increasing processing temperature and time increases the extent of reduction of MnO₂ particles, generating more alumina particles as well as releasing more manganese to the matrix alloy. Alumina helps to nucleate finer and sometimes blocky MnAl₆ in the matrix of the composite and thereby results in relatively higher ductility and increased strength in the composite as compared to the base alloy of similar composition. Even in the presence of relatively higher porosity of 8 to 9 vol pct, one observes a percent elongation not below 7 to 8 pct, which is considerably higher than those observed in cast Al(Mg)-Al₂O₃ composite synthesized by externally added alumina particles.     

Isothermal compressibility,isochoric heat capacity,and intrinsic pressure of KCl-NdCl<Subscript>3</Subscript> melts

The temperature dependences of the isothermal compressibility, isochoric heat capacity, intrinsic pressure, expansion work, number of vibrational degrees of freedom, and parameter a of KCl-NdCl₃ melts are calculated from experimental data on the ultrasound velocity, density, and heat capacity of these melts.     

Raman spectra of crystalline and molten GdCl<Subscript>3</Subscript>

The Raman spectra of crystalline (over a wide temperature range) and molten GdCl₃ are mea- sured. The hexagonal structure C ² _6h (UClC26h₃ type) of crystalline GdCl₃ is found to change weakly over the entire temperature range under study. The temperature dependences of the characteristic frequencies change in the premelting range.     

Prediction of the types of crystal structure for <Emphasis Type="Italic">ABX</Emphasis><Subscript>2</Subscript> (<Emphasis Type="Italic">X</Emphasis> = Fe,Co, Ni) intermetallics

A software package is developed to predict the types of crystal structures for ternary ABX ₂ (A, B are metals; X = Fe, Co, Ni) intermetallics under normal conditions. These compounds are shown to be characterized by a Heusler-phase-type cubic structure. New ABFe₂ Heusler phases are predicted for the first time.     

Reactive synthesis of <Emphasis Type="Italic">in-situ</Emphasis> ZrAl<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al composites

In this work, a reactive synthesis process is proposed to obtain ZrAl₃-Al₂O₃ particulate-reinforced aluminum matrix composites. The process involves the in-situ formation of Al₂O₃ and ZrAl₃ from Al-ZrO₂ green compacts. Upon compact heating, it is found that reduction of ZrO₂ by molten aluminum occurs at temperatures above 750 °C, leading to the development of ZrAl₃ and Al₂O₃ phases. Thermodynamically, it is found that the reduction of zirconium oxide is driven mainly by the dissolution of Zr in molten aluminum. Because the solubility of Zr in liquid aluminum is extremely small, the formation of ZrAl₃ is favored after relatively small Zr dissolutions. The first Zr-Al intermetallics to form at the lowest temperatures seem to be metastable, as infered from the measured atom ratios for Al : Zr of 2.83 : 1. At increasing temperatures, the reaction comes into completion, resulting in the formation of equilibrium intermetallic ZrAl₃ phases. The results obtained from differential scanning calorimetry (DSC) indicate that by increasing the scanning rates, both the reaction temperature and the exothermic peak intensity also increase. Alternatively, it is found that by reducing the amount of ZrO₂ in the green compact, the in-situ reaction temperatures also shift toward higher values.     

Standard enthalpy of formation of crystalline titanomagnetites (FeO)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> · TiO<Subscript>2</Subscript>

A mathematical model developed previously is used to obtain equations for the calculation of the standard enthalpies of formation of some stoichiometric oxides and complex oxides of a variable composition in the Fe-O-Ti system. These entropies have been determined.     

Mechanochemical preparation of Ni<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Al<Subscript><Emphasis Type="Italic">y</Emphasis></Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanocomposites

The mechanochemical preparation of nickel aluminide/corundum (Ni _x Al _y /Al₂O₃) powder nanocomposites is shown to be possible during the mechanochemical aluminum reduction of nickel oxide at various weight proportions of the components.