The growth of nickel oxide films has attracted much attention over the years, and various diffusion mechanisms have been proposed to model the process. The popular techniques used to study the mass transport mechanism...
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The growth of nickel oxide films has attracted much attention over the years, and various diffusion mechanisms have been proposed to model the process. The popular techniques used to study the mass transport mechanisms have been Auger electron spectroscopy and secondary ion mass spectroscopy (SIMS). Another approach that has been suggested is the study of isotope separation during thin film growth. This type of analysis can give the mechanism of reaction during the film growth and is the technique used in this study. A normal isotope separation implies either grain boundary or lattice diffusion, whereas a reverse separation explicity implies grain boundary diffusion. This study looks at nickel oxides grown on polycrystalline nickel at 400, 600 and 800°C, and which range from 1.5 to 18 μm in thickness. Oxides were grown under atmospheric oxygen partial pressure conditions. X-ray diffraction was used to determine the nature of the oxide, and SIMS, in conjunction with Auger spectroscopy and argon ion sputtering, was used to determine the isotope separation if any. It was found that the oxide grown at 800°C exhibited reverse isotope separation, whereas the oxides grown at lower temperatures showed normal separation. Simplified calculations of the chemical diffusion coefficients of nickel in nickel oxide have also been made at the temperatures of interest, and activation energies ranging from 55.2 to 190.4 kJ mol -1 were obtained.
A shear transformation has previously been shown to account for the discontinuities or jumps in the crystallographic thermal expansion coefficients across the normal to superconducting transition temperature. The crys...
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A shear transformation has previously been shown to account for the discontinuities or jumps in the crystallographic thermal expansion coefficients across the normal to superconducting transition temperature. The crystallographic stress dependence of the superconducting transition temperature is shown here to also support a shear transformation;dT(c)/dtau = 4 K/GPa. The shear motion of the lattice restricts the elastic compliances involved in superconductivity to tetragonal symmetry while considering all nine elastic interactions with the orthorhombic super-conducting crystal. The shear transformation has isothermal elastic interactions with the lattice through the orthorhombic shear compliance changes of (DELTAs11 + DELTAs22 - 2DELTAs12). The onset of superconductivity restricts to a higher symmetry the shear motion of the orthorhombic lattice with DELTAs11 = DELTAs22 and DELTAs23 = DELTAs13 across the superconducting phase boundary. Crystallographic second order thermodynamics predicts that isothermally DELTAs11 = -DELTAs12 = 1.7 X 10(-15)/Pa. It is shown that the jumps in the elastic compliance matrix are unique functions of the thermal expansion matrix jumps and the heat capacity jumps for any second order phase transition.
The electrochemical behavior of iron has been characterized in aqueous ammoniacal ammonium carbonate solution. Pure iron anodically polarized in He‐ or solutions exhibits both stable active (, SHE) and passive region...
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The electrochemical behavior of iron has been characterized in aqueous ammoniacal ammonium carbonate solution. Pure iron anodically polarized in He‐ or solutions exhibits both stable active (, SHE) and passive regions. A cathodic loop was observed in the potential range of −380 to 100 mV. It is suggested, on the basis of cathodic polarization curves of a graphite electrode in various concentrations of ammoniacal solution, that the cathodic loop is due to oxygen discharge. The addition of to the ammoniacal solution has the same effect as oxygen in that it increases the cathodic current and potential range of the cathodic loop and, as such, functions as a strong oxidant.
A framework is established for the analysis of the defect chemistry of the entire (Pb1?x Sn x )1?y Te y system based upon statistical thermodynamic calculations and experimentally measured carrier-concentration and t...
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A framework is established for the analysis of the defect chemistry of the entire (Pb1?x Sn x )1?y Te y system based upon statistical thermodynamic calculations and experimentally measured carrier-concentration and tellurium partial-pressure data. The energy-band structure, in which inversion of light-mass, non-parabolic, direct-gap bands occurs and a second, parabolic valence band is present, is explicity incorporated into the analysis for the first time and the usual non-degeneracy assumption is abandoned. The densities of states of the non-ellipsoidal bands and the Fermi levels are calculated numerically. The remaining intrinsic material parameters (the partial pressure of tellurium over intrinsic, pure material and the Schottky constant for doubly-ionized vacancies) are then determined by the fit to the carrier concentration-partial pressure-temperature data. The model established is applied to only PbTe and SnTe because of the lack of partial-pressure data for the ternary solid solutions and satisfactory fits are obtained. The Fermi level lies in the light-mass valence band of SnTe for all of the observed carrier concentrations so that previous analyses of SnTe, which assumed that the hole distribution is non-degenerate, were in error. The 1 at. % wide homogeneity range of SnTe is wide enough that a compositional variation in the sum of the chemical potentials of tin and tellurium has been detected experimentally. This variation is theoretically zero in the usual models for narrow homogeneity-range compounds, but is accounted for in this analysis. Quantitatively satisfactory fits are obtained for PbTe using 0.85mo for the density-of-states effective mass which characterizes the second, parabolic valence band extrema. Only slightly poorer fits are obtained with the roughly established value of 1.0m o. To obta
The discontinuities or jumps in the crystallographic thermal expansion coefficients across the superconducting to normal phase boundary have been reported to contain opposite signs and nearly equal magnitudes between ...
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The discontinuities or jumps in the crystallographic thermal expansion coefficients across the superconducting to normal phase boundary have been reported to contain opposite signs and nearly equal magnitudes between the a and b crystal axes. A shear transformation is shown to account for almost all of the thermal expansion jumps in a coordinate system that is rotated by pi/4 about the c axis. The heat capacity, the shear ther-mal expansion coefficient and the elastic compliance matrix jumps in this rotated coordinate are related using second order phase transformation thermodynamics for a solid. The lattice motion for the shear transformation involves a single coupled displacement. A shear stress that gives a pure shear strain displacement will change T(c) in this crystal. The thermal expansion jumps when restricted to contain no volume terms have been emphasized in this paper. This shear thermal expansion is found to interact with the lattice through the orthorhombic shear compliance Of (S11 + S22 - 2s12).
Al matrix composites reinforced with micro-composite Al2O3/Al particles were synthesized by reactive infiltration of molten Al into preforms of particulate SiO2 or Mg + SiO2 mixtures at 1075 degrees C. Displacement re...
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Al matrix composites reinforced with micro-composite Al2O3/Al particles were synthesized by reactive infiltration of molten Al into preforms of particulate SiO2 or Mg + SiO2 mixtures at 1075 degrees C. Displacement reactions between silica and magnesium containing oxides lead to in-situ formation of the reinforcements and also aid the infiltration of the melt. In the presence of Mg, it was found that the consistency of infiltration was better and that the transformation of silica to alumina involved intermediate displacement reactions unlike the single step reaction without Mg in the preform. It was observed that the morphology and size scale of the micro-composite Al2O3/Al particles were affected by the presence of Mg. Without Mg a finer scale Al2O3/Al microstructure with a tendency to be elongated in the growth direction formed, while a coarser morphology with interconnectivity in both phases developed from Mg + SiO2 preforms. Potential for such microstructural variations of the reinforcements permits control of the overall mechanical properties of the composite. (C) 1997 Acta Metallurgica Inc.
We fabricated sulfur and nitrogen codoped cyanoethyl cellulose-derived carbons(SNCCs)with state-of-the-art electrochemical performance for potassium ion battery(PIB)and potassium ion capacitor(PIC)*** 0.2,0.5,1,2,5,an...
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We fabricated sulfur and nitrogen codoped cyanoethyl cellulose-derived carbons(SNCCs)with state-of-the-art electrochemical performance for potassium ion battery(PIB)and potassium ion capacitor(PIC)*** 0.2,0.5,1,2,5,and 10 A g−1,the SNCC shows reversible capacities of 369,328,249,208,150,and 121 mA h g−1,*** to a high packing density of 1.01 g cm^(−3),the volumetric capacities are also uniquely favorable,being 373,331,251,210,151,and 122 mA h cm^(−3)at these currents,*** also shows promising initial Coulombic efficiency of 69.0%and extended cycling stability with 99.8%capacity retention after 1000 *** proof of principle,an SNCC-based PIC is fabricated and tested,achieving 94.3Wh kg^(−1)at 237.5Wkg^(−1)and sustaining over 6000 cycles at 30 A g−1 with 84.5%*** internal structure of S and N codoped SNCC is based on highly dilated and defective graphene sheets arranged into nanometer-scale *** a baseline S-free carbon for comparison(termed NCC),the role of S doping and the resultant dilated structure was *** to galvanostatic intermittent titration technique and electrochemical impedance spectroscopy analyses,as well as COMSOL simulations,this structure promotes rapid solid-state diffusion of potassium ions and a solid electrolyte interphase that is stable during cycling.X-ray diffraction was used to probe the ion storage mechanisms in SNCC,establishing the role of reversible potassium intercalation and the presence of KC36,KC24,and KC8 phases at low voltages.
A quantitatively good overall fit is obtained to the phase diagram and thermodynamic data in the system. In the binaries the partial pressures along the three‐phase curves are fit in addition to the liquidus points. ...
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A quantitatively good overall fit is obtained to the phase diagram and thermodynamic data in the system. In the binaries the partial pressures along the three‐phase curves are fit in addition to the liquidus points. Moreover, the liquid phase parameters are constrained so that the enthalpy and entropy of mixing of the stoichiometric binary melts are properly related to the enthalpy and entropy of formation of the binary compounds. Also included in the fit are the pseudobinary liquidus and solidus points, the partial pressure of Hg in the pseudobinary melt, and the partial pressures of Hg, Cd, and for the Te‐saturated pseudobinary solid, . Finally, a choice is made for the most reliable ternary liquidus points and these are included. Portions of the phase diagram, as yet unmeasured, are then calculated and presented. The liquid phase is described by a simple extension of the regular associated solution model of Jordan and Szapiro in which the interaction coefficients and dissociation constants are allowed to depend upon temperature. The partial molar quantities for the liquid phase components are derived and used in liquidus equations that are more exact than the commonly used version of the Vieland equation. Errors in some previous studies are discussed in the appendix. It is concluded that the model cannot provide a satisfactory fit to the entire Hg‐Cd‐Te system. Neither can it fit analogous systems in which the liquidus lines of the binary compounds are asymmetric.
Recent measurements of the discontinuity of the volume expansivity of Y//1Ba//2Cu//3O//7// minus // delta across the superconducting transition have been shown to be self-consistent with the measured pressure dependen...
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Recent measurements of the discontinuity of the volume expansivity of Y//1Ba//2Cu//3O//7// minus // delta across the superconducting transition have been shown to be self-consistent with the measured pressure dependence of the superconducting transition temperature. Ehrenfest second-order transitions have jumps in specific heat, bulk modulus and thermal expansivity. Supercondutivity is generally considered to occur as an Ehrenfest second-order phase transition. The jump in thermal expansivity has been found by measuring the crystallographic cell volume by high resolution neutron diffraction at selected temperatures and assuming that the volume was continuous across the superconducting transition. This data was curve fit above and below the transition temperature. The thermal expansion coefficient jump of normal less superconducting values deduced using this curve fit data is DELTA a equals minus 6. 4 plus or minus 9. 3 multiplied by 10** minus **7/K. In this paper it is shown that this value is consistent with other thermodynamic data while reducing the large error bars on the data. This also suggests that the lattice has only a minor role in the transition. 11 Refs.
In this paper we explore the crystallization kinetics of poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and miscible blends of PBT with a polyarylate based on Bisphenol A and a 75/25 mole rati...
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In this paper we explore the crystallization kinetics of poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and miscible blends of PBT with a polyarylate based on Bisphenol A and a 75/25 mole ratio of isophthalic and terephthalic acids. For PBT, a regime II --> III transition is indicated near 210-degrees-C (DELTA-T approximately 30-degrees-C) and the fold surface free energy (sigma(e)) was found to be in the range of 57-75 erg/cm2. This leads to a work of chain folding (q) of approximately 3-5 kcal/mol folds. Analysis of the crystallization data of van Antwerpen and van Krevelen for PET shows that crystallization occurs in regime II across a wide range of T(c). Sigma(e) was estimated to be approximately 140 erg/cm2 and q approximately 10 kcal/mol from their data. These values are roughly twice that of PBT, consistent with the longer flexible segments in the PBT repeat unit. Crystallization data for three PBT/PAr blends was analyzed using a modified Lauritzen-Hoffman method and compared to that of pure PBT.
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