Ultrasound velocity and adiabatic compressibility of GdCl<Subscript>3</Subscript>-<Emphasis Type=Italic>M</Emphasis>Cl (<Emphasis Type=Italic>M</Emphasis> = Na,Cs) melts

The ultrasound velocity in GdCl₃ + MCl (M = Na, Cs) chloride melts is measured over wide temperature and composition ranges, and their adiabatic compressibility is calculated. A correlation is established between the relative deviations of these properties from their values in hypothetic ideal salt mixtures and the reciprocal alkali-metal cation radii. The role of lanthanide compression in the propagation of sound vibrations in the chlorides of cerium group REMs is revealed.     

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.     

<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.     

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.     

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.     

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.     

Interdiffusion behavior of Pt-modified <Emphasis Type="Italic">γ</Emphasis>-Ni + <Emphasis Type="Italic">γ</Emphasis>′-Ni<Subscript>3</Subscript>Al alloys coupled to Ni-Al-based alloys

The effect of platinum addition on the interdiffusion behavior of γ-Ni + γ′-Ni₃Al alloys was studied by using diffusion couples comprised of a Ni-Al-Pt alloy mated to a Ni-Al, Ni-Al-Cr, or Ni-based commercial alloy. The commercial alloys studied were CMSX-4 and CMSX-10. Diffusion annealing was at 1150 °C for up to 100 hours. An Al-enriched γ′-layer often formed in the interdiffusion zone of a given couple during diffusion annealing due to the uphill diffusion of Al. This uphill diffusion was ascribed to Pt addition decreasing the chemical activity of aluminum in the γ + γ′ alloys. For a given diffusion couple end member, the thickening kinetics of the γ′ layer that formed increased with increasing Pt content in the Ni-Al-Pt γ + γ′ alloy. The γ′-layer thickening kinetics in diffusion couples with Cr showed less of a dependence on Pt concentration. Inference of a negative effect of Pt and positive effect of Cr on the Al diffusion in this system enabled explanation of the observed interdiffusion behaviors. There was no or minimal formation of detrimental topologically close-packed (TCP) phases in the interdiffusion zone of the couples with CMSX-4 or CMSX-10. An overlay Pt-modified γ + γ′ coating on CMSX-4 showed excellent oxidation resistance when exposed to air for 1000 hours at 1150 °C. Moreover, the Al content in the coating was maintained at a relatively high level due to Al replenishment from the CMSX-4 substrate.     

Self-propagating high-temperature synthesis of ceramic materials based on the M<Subscript><Emphasis Type="Italic">n</Emphasis> + 1</Subscript>AX<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> phases in the Ti-Cr-Al-C system

Compact ceramic materials based on the M_{n + 1}AX _n phases in the Ti-Cr-Al-C system are produced by forced self-propagating high-temperature synthesis (SHS) compaction. The mechanisms of the structure and phase formation in synthetic products, as well as the combustion macrokinetics of the SHS mixture, are studied. Complex investigations of the structure, phase composition, and physical and mechanical properties of new Ti_{2 ? x} Cr _x AlC ceramic materials synthesized at different charging parameters (x = 0, 0.5, 1, 1.5, and 2) are performed. The highest content (96–98%) of the M_{n + 1}AX _n phase in the composition of synthetic products is found to be in samples where just one of the host elements (titanium (x = 0) or chromium (x = 2)) is present. The produced materials have a high heat resistance, and the increase in the chromium concentration is favorable to an appreciable growth in resistance to high-temperature oxidation.     

Interface stability during displacement reactions between Cu<Subscript>2</Subscript>O and Co<Subscript>1−<Emphasis Type="Italic">X</Emphasis></Subscript>Fe<Subscript><Emphasis Type="Italic">X</Emphasis></Subscript> alloys at 1223 K

The stability of the reactive interface during the solid-state displacement reaction, Cu₂O+Co_1−X Fe _X =2Cu+(Co_1−X Fe _X )O, is studied as a function of Co-Fe alloy composition at 1223 K. For X≤0.03, the reaction zone has a layered structure, and the cation diffusion in (Co, Fe)O is the rate-limiting step. The interface is unstable in the early stages of the reaction; the instability decreases with time as the oxide thickness increases, and the interface becomes planar at long times. The time required for the attainment of interface planarity increases with the value of X. The reaction kinetics are consistent with the available cation-diffusion data in (Co, Fe)O. For X≥0.045, the product zone is a composite of Cu+(Co, Fe)O, and the rate is limited by the oxygen transport in copper. The transition to interface instability occurs when the oxide can support a cation flux that exceeds the maximum possible oxygen flux in copper. During the reaction, composition gradients develop in (Co, Fe)O because of higher diffusion rates for iron than for cobalt.     

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.     

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.     

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.     

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.     

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.     

<Emphasis Type=Italic>Regarding &quot;Sulfide Capacity in Ladle Slag at Steelmaking Temperatures,&quot;</Emphasis><Emphasis Type=Italic>C. Allertz,Du Sichen; MMTB 2015 December</Emphasis>

Allertz and Sichen measured sulfide contents of slags in equilibrium with Cu-S solutions. Results are in very good agreement with calculations by FactSage whose databases were developed by modeling other sets of data obtained under different conditions. However, when results are reported as sulfide capacities, significant errors may result if these are used to calculate sulfide contents at oxygen and sulfur potentials which differ from those of the experiments and/or are fixed by different means.