Solubility of hydrogen (1 atm, 298 K) in some copper/palladium alloys

The solubility of hydrogen (1 atm, 298 K) decreases linearily with copper content in f.c.c. substitutional Cu/Pd alloys to an atom fraction of Cu = 0.20 and thereafter the solubility decreases more abruptly. The fall in solubility at X_Cu > 0.20 is attributed to the inability of alloys with X_Cu > 0.20 to form a second non-stoichiometric hydride phase at 1 atm (298 K). Thermodynamic data are reported for the absorption of hydrogen into the two-phase regions (H-saturated alloy + non-stoichiometric hydride) of these alloys.     

Thermodynamic properties and ordering in liquid NaK alloys

The thermodynamic activities of sodium and potassium were determined by vapour-phase absorption spectrophotometry of atomic resonance lines. Both components exhibit significant positive deviations from ideality. Excess Gibbs energies computed from the activity data were combined with available heat-of-mixing data to yield values for excess entropies. The entropy of mixing which was found to be ideal in the sodium-rich liquid alloys provides no support for the earlier speculations about the existence of Na₂K molecules therein. The partial molar excess entropy of sodium in dilute solution in potassium was found to be surprisingly large and negative for a system of this type. A plausible model, involving sodium-sodium pairing, is proposed to account for the loss of configurational entropy.     

Enthalpies and entropies of solution of first row transition metals in liquid copper

New experimental data for the enthalpies of solution of the first row transition metals in liquid copper are compared with the semiempirical predictions of Miedema et al. For solute metals from vanadium to nickel the enthalpies of solution also are compared with Gibbs energy data to yield excess entropies of solution. For Cr, Mn and Fe in liquid copper it is noted that the observed excess entropies in large measure may arise from the difference between the disordering entropy resulting from the destruction of the quasi-bound magnetic impurity states and the electronic entropy of the pure metal.     

Silver-tracer diffusion in Cu2O

The diffusion of¹¹⁰Ag in Cu₂O has been measured by a serial-sectioning technique as a function of temperature (700–1132°C) and oxygen partial pressure (6 × 10^?6 ?8 × 10^?2 atm). The data are fit to the defect model for Cu₂O developed by the authors in the preceding paper. Silver ions have a larger impurity-vacancy binding free energy and/or a larger jump frequency for the singly charged cation vacancies relative to that for the neutral cation vacancies. The activation enthalpies for the diffusion of copper and silver ions in Cu₂O are nearly equal, but the absolute value of D¹_Ag is about three times larger than D¹_Cu even though the silver ion is 31% larger than the copper ion.     

Hydrogen-vacancy interactions in Ni-H solid solutions

The data for the solubility of hydrogen in nickel in equilibrium with H₂-gas at atmospheric pressure have been analyzed in terms of a model which considers H-vacancy interactions. This model has been shown to be compatible with both the thermodynamic and kinetic data for Ni-H system.     

Defect structure of alumina-rich nonstoichiometric magnesium aluminate spinel

In order to clarify the relation between the dissolution mechanism of hydrogen and the defect structure in alumina-rich nonstoichiometric magnesium aluminate spinels, several compositions of single crystals were grown by the flame fusion method and their compositional dependence of the solubility of hydrogen and that of the mass density were studied by the IR absorption and Archimedes methods, respectively. The solubility of hydrogen increased in proportion to the square root of the water partial pressure and with the increase in the excess amount of alumina. The densities of the single crystals were slightly less than the value calculated based on the reported defect structure. The compositional dependence of the solubility of hydrogen and that of the density can be explained by the model in which the concentration of the oxide ion vacancy increases with the alumina content due to the decrease in the capability of the Mg site to accept the excess Al ion.     

Thermodynamics of ternary Fe-Ni-N-austenites

Measurements, in the range 1140–1548 K, of the temperature variation of the solubility of nitrogen at constant pressure (1.04 × 10⁵ Pa) in Fe-Ni fee solid solutions in equilibrium with N₂ gas, show that the partial molar enthalpy $\text{H}$_i of the nitrogen atoms is invariant to the nickel concentration up to 15 atm % Ni. In the same temperature range the partial molar excess entropy $\text{S}$^xs_i exhibits a slight decrease with increasing nickel concentration.The thermodynamic data are consistent with the cell model for ternary solid solutions in which the nickel atoms create shallow trapping sites for N-atoms, deeper by only 4.9 kJ/mol than interstitial sites in binary Fe-N solutions.The variation in H_i with nickel content due to the distribution of N atoms in energetically differing cells is of about the same size, but opposite in sign, to the contribution to $\text{H}$_i ascribable to the change in specific density of the substitutional lattice with varying Ni content.     

Synthesis and characterization of copper ink and direct printing of copper patterns by inkjet printing for electronic devices

Among the conventional metallic inks used in the printing process, silver exhibits high conductivity and thermal stability. Nevertheless, due to the high cost of silver, it cannot be extensively used for the fabrication of inks. As a competitive alternative, copper can be considered as a substitute for silver; however, copper ink oxidizes under certain atmospheric conditions. To meet these shortcomings, a cost effective, highly conductive, and oxidation-free copper-based ink has been synthesized in this study, wherein, oxidation of the copper particles in the copper-based ink was prevented by using copper complexes. The copper ink thus fabricated was printed on chemically treated Si/SiO₂ substrates followed by the characterization of the printed copper films. The results of this study confirmed that the synthesized copper ink exhibited properties suitable for its use in the inkjet printing process for fabrication of various electronic devices.     

Methanol decomposition on platinum (111)

The interaction of methanol with clean and oxygen-covered Pt(111) surfaces has been examined with high resolution electron loss spectroscopy (EELS) and thermal desorption spectroscopy (TDS). On the clean Pt(111) surface, methanol dehydrogenated above 140 K to form adsorbed carbon monoxide and hydrogen. On a Pt(111)-p(2 × 2)O surface, methanol formed a methoxy species (CH₃O) and adsorbed water. The methoxy species was unstable above 170 K and decomposed to form adsorbed CO and hydrogen. Above room temperature, hydrogen and carbon monoxide desorbed near 360 and 470 K, respectively. The instability of methanol and methoxy groups on the Pt surface is in agreement with the dehydrogenation reaction observed on W, Ru, Pd and Ni surfaces at low pressures. This is in contrast with the higher stability of methoxy groups on silver and copper surfaces, where decomposition to formaldehyde and hydrogen occurs. The hypothesis is proposed that metals with low heats of adsorption of CO and H₂ (Ag, Cu) may selectively form formaldehyde via the methoxy intermediate, whereas other metals with high CO and H₂ chemisorption heats rapidly dehydrogenate methoxy species below room temperature.     

Effect of nickel,iron, and manganese on the solubility of copper in the alloy Al−10% Si

A study has been made of the effect of nickel, iron, and manganese on the solubility of copper in solid silicon-aluminum alloys. Nickel leads to solid solutions having the least copper. Iron has essentially no effect on the solubility of copper in the solid solution. Manganese, which binds copper in the ternary compound Al₁₂Mn₂Cu, partially replaces it in solid solution.Translated from Izvestiya VUZ. Fizika, No. 3, pp. 92–95, March, 1970.     

On the iron-vacancy-hydrogen system

The solubility of hydrogen in equilibrium with H₂-gas at atmospheric pressure exhibits a temperature variation, in the BCC phase range, which is incompatible with the simple quasi-regular statistics expected for a dilute interstitial solid solution. This behavior has been analyzed in term of a statistical model that includes the interactions between interstitial H-atoms and lattice vacancies. Good agreement is found between the model and the experimental data.     

Spontaneous nuclear magnetic ordering in copper and silver at nano- and picokelvin temperatures

Owing to the weak mutual interactions, spontaneous nuclear magnetic ordering in metallic copper and silver occurs at 60 nK and 560 pK, respectively. These extremely low spin temperatures can be reached by two-stage adiabatic nuclear demagnetization. Spin ordering has been investigated by employing magnetic susceptibility measurements on copper and silver and by using neutron diffraction techniques on copper. Three antiferromagnetic phases in the field-entropy plane have been discovered in copper, caused by competition between the dipolar and Ruderman-Kittel exchange interactions; only one ordered state has been found in silver. Negative spin temperatures have been produced in silver as well, and a clear ferromagnetic tendency was observed when T < 0. The theoretically calculated spin-spin interactions, ordering temperatures, magnetic phase diagrams and ordered spin structures are in good overall agreement with experimental data for these two metals.     

A molecular-beam investigation of the reaction H2 + 12O2 → H2O on Pd(111)

Using molecular-beam relaxation techniques and isotopic exchange experiments, the water-formation reaction on Pd(111) has been shown to proceed via a Langmuir-Hinshelwood mechanism. The reaction product H₂O is emitted from the surface with a cosine distribution. The rate-determining step is the formation of OH_ad in the reaction O_ad + H_ad → OH_ad. The activation energy for this step is 7 kcal/mole with a pre-exponential factor, v, of 4 × 10^?8 cm² atom^?1 sec^?1. This value for v lies well below that observed for simple second-order desorption of dissociatively adsorbed diatomic gases, but is roughly of the order of that obtained for the oxidation of CO on Pd(111). The formation of H₂O proceeds differently under conditions of excess O₂ or H₂. In an excess of H₂, the kinetics is dominated by the transport of atomic hydrogen between the bulk and the surface as was found for the H?D exchange reaction on Pd(111). In an excess of O₂, diffusion of hydrogen into the bulk is blocked by adsorbed oxygen and the hydrogen reservoir available for reaction at the surface is decreased by several orders of magnitude. This results in a drastic reduction of the reaction rate which can be reversed by increasing the partial pressure of H₂.     

Effect of the partial covalency on the solubility of AgBr In α-AgI

The internal energy and free energy of α-AgI-type solid solution have been calculated. On the basis of this calculation, the solubility limit of AgBr in α-AgI has been discussed. The difference of the solubility of AgBr in β-AgI and of β-AgI in AgBr has been interpreted due to the variation of the vibrational entropy depending on the mean value of anion mass. The partial ionicity in these solid solutions has also been discussed.     

The influence of surface roughness on the Raman scattering of pyridine on copper and silver surfaces

The surface enhanced Raman scattering (SERS) has been measured of pyridine adsorbed on silver or copper with various surface roughness. The surface has been controlled by electron microscopy. In addition the incident laser wavelength has been varied. By taking into account the dielectric constants of silver and copper the maximum enhancement factors for an average roughness of 1000 Å and 500 Å for silver and copper, respectively, could be quantitatively accounted for by the antenna resonator model.     

Atomic dynamics of the α-(Al,Si)CuFe alloy: A crystalline approximant of a quasicrystal...

The atomic dynamics of the Al_0.550Si_0.070Cu_0.255Fe_0.125 alloy with the structure that approximates the structure of an icosahedral quasicrystal with a similar chemical composition has been investigated using inelastic neutron scattering. The partial vibrational spectra of copper, iron, and aluminum atoms and the total spectrum of thermal vibrations of the compound have been directly reconstructed from the experimental data for the first time. A combined analysis of the results obtained and the data on the atomic dynamics of the i-AlCuFe icosahedral quasicrystal has been performed.     

The scattering of hydrogen,deuterium, and the rare gases from silver (111) single crystals

The scattering of hydrogen, deuterium, and the rare gases from the (111) face of silver has been studied at ultrahigh vacuum. The surfaces were prepared by argon ion bombardment and high temperature annealing. Incident angles between 20° and 65° and surface temperatures between room temperature and 573°K have been investigated. The scattering data exhibit quasi-elastic scattering (He, H₂, D₂), inelastic scattering (Ne, Ar, Kr), and trapping dominated scattering (Xe). Identification of these scattering regimes correlates with D/kT_g and is consistent with similar data from Pt(111) and W(110). The separate effects of microscopic surface roughness and thermal roughening have been identified and thermal attenuation in the elastic regime correlated with dynamical interactions rather than thermal roughening. Trapping and rotational coupling are discussed. Comparison of the data with scattering from epitaxial (111) silver indicates that the epitaxial surfaces are significantly more disordered than the single crystal surfaces.     

Presence of Jahn-Teller distortions in a novel six-coordinate Ag(II) complex: temperature dependent EPR,optical and magnetic susceptibility measurements

Single-crystal variable temperature EPR, optical and polycrystalline magnetic susceptibility studies have been made on a novel six-coordinate Ag(II) complex. Temperature dependent EPR studies on pure single crystals of this compound reveal that dynamic Jahn-Teller distortion operates above 230 K, between 230 K and 120K static Jahn-Teller distortion sets in and below 110 K there is evidence of exchange interaction. Crystal g values were obtained by least-squares fitting with the data obtained from the orientation dependent EPR spectra of the undiluted single crystal of this complex at 300 K and 77 K. From an optical study the Jahn-Teller stabilization energy is found to be ～2250cm^?1. Comparison of Abs_max values for other silver(II) compounds enables us to conclude that the formal geometry of this complex is a tetragonally distorted octahedral. Infrared spectra of this complex were also recorded over a wide range of temperature. Magnetic susceptibility measurements over a wide range of temperature on the powder sample of this compound reveal that the complex is antiferromagnetically coupled in the temperature range 5–40 K with 2J = 0.906cm^?1, and above 40K it is ferromagnetically coupled with 2J = +7.4cm^?1. The effective magnetic moment (μ_eff) of this complex has been compared with that of a series of other silver(II) complexes available in the literature. Finally, the spectral and magnetic data of this complex have been compared with those of a corresponding isostructural and isomorphous copper(II) complex.     

Stability of the H2–(He,Ne, Ar) fluid mixtures

A theory of mixtures based on a statistical mechanical perturbation scheme is used to compute the excess free energy of mixing, the excess entropy of mixing and the concentration fluctuations in the long wavelength limit as functions of composition (c) over a wide range of temperature (T = 150 to 350 K) and pressure (p = 10 MPa to 10 GPa). This has been utilized to investigate the effects of c, T and p on the solubility of H₂ (the first element of the periodic table) to He, Ne and Ar (the first three elements of the last group) and the thermodynamic stability of the mixture. The long-range correlations among the constituent species are included through the double Yukawa potential which acts as a perturbation to the hard sphere reference mixture. The non-additivity of the potentials of the constituent species is linked to the second virial coefficients which can be determined from the experimental data. Necessary corrections to the equation of state for dimerisation of H₂ molecule and quantum effects are included. At a given T = 150 K and p = 100 MPa, H₂–Ar mixture exhibits greater thermodynamic stability than H₂–Ne and H₂–Ar.