The thermodynamics of ternary palladium-based solid solutions containing nickel and hydrogen

The solubility of hydrogen in Pd-Ni-H ternary solutions in equilibrium with H gas at atmospheric pressure has been measured in the temperature range 625–1250 K and in Pd-Ni “binary solvents” containing up to 80 at.% of Ni. Concomitant elastic measurements have provided data which enable the partial thermodynamic functions of the H-atoms, deduced from the solubility measurements, to be converted so as to refer to a hypothetical Pd-Ni lattice of constant specific volume. The resulting “volume corrected” functions have been discussed in terms of the cell model for ternary solutions and have been shown to vary with temperature and Ni-concentration in a manner in accord with this mode. The usual linear form of cell interaction energy spectrum has been modified by including supplemental contributions to the cell interaction energy which occur when substitutional solute atoms occupy adjacent sites on the f.c.c. Pd-Ni lattice.     

X-ray studies of cold-worked ternary alloys containing Pd-Ag-Au

The structure of highly deformed filings of the Pd-Ag-Au ternary alloy system has been studied by using the Warren-Averbach X-ray diffraction line profile analysis. The effective particle size and root mean square strain were determined over a range of compositions and were found to be anisotropic. Stacking fault probabilities were obtained from shifts in the peak positions. An extrapolation technique was employed for the determination of the twin fault probabilities which eliminates most of the ambiguity associated with the separation of the overlapping tails between the (111)-(200) peaks. Although a large range in composition was examined, very little variation was observed in the effective particle size, nonuniform microstrain, stacking fault probability, and twin fault probability. Consequently, these quantities are nearly constant except at the corners of the ternary diagram, where the pure elements are approached. Cold working had an appreciable effect on the lattice parameter at certain compositions. For alloys containing all three components both an increase and a decrease in the lattice parameter was observed as the palladium composition was varied. Deformed alloys containing palladium and silver gave lattice parameters which are essentially the same as those reported for the annealed state.     

The leaching behaviour of nickel oxides in acid and in ammoniacal solutions

Leaching studies of nickel(II) oxide and hydroxide, and high valence nickel hydroxide in sulphuric acid and in ammonium carbonate solutions were carried out. The dissolution rate of nickel(II) oxide in both solvents was influenced greatly by the heat treatment given to the oxide prior to leaching and, under the conditions studied, was found to be limited by the rate of the surface chemical reactions.The rates of leaching of nickel(II) and nickel(III) hydroxides on the other hand were very fast. The nickel(III) hydroxide is unstable and decomposes to liberate oxygen in acid solutions and oxidises ammonia to nitrogen and nitrite in ammoniacal solutions.     

Rate of growth of dispersed particles of various oxides in nickel. Part 2

Summary The authors have investigated the influence of the type of oxide on the structural stability of dispersion-hardened nickel over the temperature range 1000–1350°C. Alloys of nickel strengthened with aluminum, silicon, zirconium, and hafnium oxides were studied. It was established that such factors as the density, melting point, energy of formation, etc., of oxides affect their stability. The capacity for growth of the oxides investigated increases in the series: HfO₂2<-Al₂O₃2<-Al₂O₃.Translated from Poroshkovaya Metallurgiya, No. 8(56), pp. 54–59, August, 1967.     

Internal displacement reactions in multicomponent oxides: Part III. Solid solutions of ternary oxide compounds

In an internal displacement reaction between a reactive metal A and multicomponent oxide (B,C,D,…)O, the noble cation B in the oxide is selectively displaced by reactive metal A, without changing the crystal structure of the oxide. Concurrently, B is precipitated as an internal metal phase in the oxide matrix. The cations (C,D,…) are inert in terms of exchange reaction. The solid-state displacement reaction occurs by the counterdiffusion of A and B inside the reaction zone. The diffusion of “inert” cations and the concentration profile in the product oxide are dependent on the nature of the oxide: (1) “line” compound of narrow homogeneity range or (2) solid solution of wide composition range. These reactions were discussed in previous articles^[1,2] (Parts I and II) along with specific examples. This article is a continuation of studies in Parts I and II and involves the internal displacement reaction between a metal and a quaternary oxide, which is a solid solution of two ternary line compounds. As a model, the reaction between Fe and an ilmenite solid solution of NiTiO₃-MgTiO₃ was studied at 1273 K as a function of time: In ilmenite solid solution (Ni, Fe, Mg) occupy the same cation sublattice, which is different from the Ti sublattice. During the reaction, only Ni cation in the oxide is displaced Fe; Mg and Ti are “inert” in terms of cation exchange. The reaction products consist of internal “Ni” precipitates (Ni-Fe alloy) in a matrix of (Fe, Mg, Ni)TiO₃ solid solution. In particular, the study focuses on cation flux during the reaction and evolution of product oxide composition profile after time t. The three cations in the product oxide that occupy the same sublattice, (Ni, Fe, Mg), show concentration gradients across the reaction zone, even though Mg is inert for cation displacement. The counterdiffusion of Fe and Ni is consistent with their chemical potential gradients. The diffusion of Mg is in the same direction as that of Fe, indicating that, at constant NMgTiO3, the chemical potential for MgTiO₃ is higher in (Mg, Fe)TiO ₃ solid solution than in (Mg, Ni)TiO₃ solid solution. The concentration of Ti, which occupies a different sublattice, remains constant across the reaction zone (i.e., zero diffusional flux for Ti). The ratio, (Fe+Mg+Ni):Ti=1:1, is consistent with the ilmenite structure of the product oxide. The shape of the cation concentration profiles indicates that terms containing cross-coefficients in the general flux equations contribute significantly to cation diffusion during the reaction.     

X-ray diffractometric analysis of the size distribution of ultradisperse particles of nickel and magnesium oxides

Translated from Poroshkovaya Metallurgiya, No. 12 (360), pp. 82–86, December, 1992.     

Kinetics of the dissolution of cobalt, nickel, and iron oxides in sulfuric acid

The modeling of dissolution of cobalt, nickel, and iron oxides in sulfuric acid shows that the rate-determining step of the dissolution is the passage of oxide complexes formed on the surface of oxide particles to a solution. A system analysis of the dissolution curves (??-??) of the oxides is developed to calculate the kinetic parameters ( $n_{H^ + } $ ,E _a). Cobalt oxide Co₃O₄ dissolves in H₂SO₄ more rapidly than nickel and iron oxides (Ni₂O₃ and Fe₂O₃).     

Critical assessment of activity coefficients of oxides in molten binary and ternary silicates,aluminates and aluminosilicates

Critical assessment is made of the activity coefficients of CaO, MgO, MnO, FeO, Al₂O₃ and SiO₂ in molten silicates, aluminates and aluminosilicates. In this assessment due consideration is given to the consistency of the free energies of formation of the interoxide compounds derived from the oxide activity data, compared with those derived from the compiled thermochemical data. For most oxides, it is found that by using an empirical formulation of the melt composition in ternary systems, the composition dependence of the oxide activity coefficient, γOX, can be represented by a single curve. For example, over a wide composition range in the FeO‐CaO‐SiO₂ system, the log(γCaO) is a single function of the melt composition in mol fraction as (?SiO₂ + 0.3xFeO); this relation being similar to that in the binary CaO‐SiO₂ melts. Therefore, with respect to γCaO, this ternary system is reduced to a pseudo binary system as xCaO ‐ (?SiO₂ + 0.3xFeO). With respect to γCaO, the ternary system CaO‐Al₂O₃‐SiO₂ is reduced to a pseudo binary system as xCaO ‐ (?SiO₂ + 0.4 xAl₂O₃). With γSiO₂, this ternary system is reduced to a pseudo binary system as (?CaO + xAl₂O₃) ‐ xSiO₂.     

Experimental studies on hydrogen solubility in liquid ternary iron-nickel-chromium alloys

The hydrogen solubilities in liquid ternary iron-nickel-chromium alloys have been experimentally determined by Sieverts’ method. The experimental data have been evaluated with the help of regression analysis (Gauß-Jordan) and using own published empirical equations (polynomials). With the help of experimentally determined hydrogen solubilities and the coefficients of the polynomials, the concentration dependencies of hydrogen solubilities, interaction coefficients, enthalpies and entropies of hydrogen solution have been determined. The hydrogen solubility increases with increasing temperature and with an increase in the nickel and chromium concentration. The results have been represented as isothermal planes. The hydrogen solubilities in liquid ternary iron-nickel-chromium alloys (x_Cr ≤ 50%) have been predicted with the help of “Central Atoms” model, assuming the concentration dependencies of the “model parameter λ” and selecting the value of the coordination number (Z’ = 10) for each of the “reference elements” iron or nickel. The comparison between the experimentally determined and the predicted hydrogen solubilities in iron-nickel-chromium alloys confirms that the prediction of hydrogen solubilities in liquid system iron-nickel-chromium can be qualitatively made over a wide range of alloy concentrations (x_Cr = 50%) with the aid of “Central Atoms” model and with the assumption of concentration dependencies of the “model parameter λ”.     

Formation and growth of iron,nickel and copper nuclei during gaseous reduction of their oxides

Compacts of the oxides of the fcc metals gamma-iron, nickel and copper were partially reduced at elevated temperatures in hydrogen and observed under scanning electron microscope to study the formation and growth pattern of metal nuclei during the very early stages of reduction. A characteristic but common feature of the nuclei growth pattern in the form of tetrahedral based pyramid was observed in all three metals. The habit plane for the growth of the metal nuclei is (111) while the growth planes are of (100) and (011) type. Although the initial shape of nuclei is of the form of a disc, it slowly transforms to tetrahedral based pyramid. This is explained in terms of mixed control mechanism of metal ion diffusion and oxygen removal from the surface. The sizes of nuclei are predicted and compared with the experimentally observed values.     

Molecular modeling studies of the DNA-topoisomerase I ternary cleavable complex with camptothecin

The present studies provide a three-dimensional model for the postulated ternary cleavable complex of topoisomerase I (top1), DNA, and camptothecin (CPT). Molecular simulations were done using the AMBER force field. The results suggest that a ternary cleavable complex might be stabilized by several hydrogen bonds in the binding site. In this proposed "drug-stacking" model, CPT is pseudointercalated in the top1-linked DNA cleavage site and interacts with the protein near its catalytic tyrosine through hydrogen bonding and stacking. The structural model is consistent with the following experimental observations: (i) the N3 position of the 5' terminal purine of the cleaved DNA strand is readily alkylated by 7-chloromethyl 10,11-methylenedioxy CPT; (ii) CPT generally tolerates substituents at positions 7, 9, and 10 but is inactivated by additions at position 12; (iii) 10,11-methylenedioxy (MDO) CPT is much more potent than 10,11-dimethoxy (DMO) CPT; (iv) the lactone portion of CPT is essential for top1 inhibitory activity; (v) 20S derivatives of CPT are much more potent than the 20R analogues; (vi) a catalytic tyrosine hydroxyl in top1 covalently links to the 3' terminal base, T, of the cleaved DNA strand; and (vii) top1 mutation Asn722Ser leads to CPT resistance. A total of 18 camptothecin derivatives with different DNA cleavage potencies were docked into the hypothetical cleavable complex binding site to test and refine the model. These studies provide insight into a possible mechanism of top1 inhibition by CPT derivatives and suggest rational approaches for the design of new CPT derivatives.     

Identification of zero-flux planes and flux reversals in several studies of ternary diffusion

Several past studies of isothermal diffusion in ternary systems have been examined for the identification of zero-flux planes (ZFP) and flux reversals of the individual components. The phenomenon of ZFP initially recognized in the Cu-Ni-Zn diffusion couples has now been identified in several ternary systems including Cu-Ag-Au, Cu-Zn-Sn, Fe-Ni-Co, Fe-Ni-Al, and Co-Ni-Cr. The development of ZFP is dictated by the terminal alloys of the diffusion couples and can occur in both single phase and multiphase assemblies. Discontinuous flux reversals can also occur at interfaces in multiphase systems. The compositions of ZFP’s developed for a couple correspond to the intersections of its diffusion path and the isoactivity lines for the components drawn through the terminal alloy compositions on a ternary isotherm.     

Polarized appraisals of out-group members.

Developed and tested a model that assumes that people have a more complex schema regarding in-groups than out-groups and consequently, that appraisals of out-group members will be more extreme or polarized than appraisals of in-group members. Four experiments with 415 White male and female undergraduates tested this model, as well as predictions derived from attribution principles. In Exp I, Ss read and evaluated a law school application containing incidental information about the applicant's race and gender. A Black applicant with strong credentials was judged more favorably than an identical White applicant, supporting a prediction derived from the augmentation principle. In Exp II, an applicant with weak credentials was included in the design. Results support the prediction that out-group members would be evaluated more extremely: When the application credentials were positive, the out-group member (a Black or opposite-sex applicant) was evaluated more favorably than the in-group member (a White or same-sex applicant). When the application credentials were weak, the out-group member was evaluated more negatively. Exp III and IV provided support for the 2 assumptions underlying the complexity–extremity hypothesis: First, White Ss demonstrated greater complexity regarding Whites than Blacks. Second, greater complexity resulted in evaluative moderation. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)