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.     

Experimental Study of Ferrous Calcium Silicate Slags: Phase Equilibria at {\text{P}}_{{{\text{O}}_{2} }} Between 10?5?atm and 10?7?atm

Ferrous calcium silicate slags, whose principal components are “FeO _x ”-CaO-SiO₂, are widely used in copper smelting and converting operations. In the current study, high-temperature equilibration and rapid quenching techniques were used to study the phase equilibria of the ferrous calcium silicate slags. The compositions of phases in the slags were measured accurately using electron probe X-ray microanalysis (EPMA). The phase equilibria of the system have been characterized at oxygen partial pressures between 10⁻⁵ atm and 10⁻⁷ atm at selected temperatures between 1473 K and 1623 K (1200 °C and 1350 °C). The effects of oxygen partial pressure and temperature on the compositions of phases in the slags are presented.     

Chlorination of hafnium dioxide by gaseous chlorine in the presence of carbon

The thermodynamic simulation of chlorination of hafnium oxide by gaseous chlorine in the presence of carbon at T = 450–1000°C is performed. It is shown that the main reaction products are gaseous hafnium tetrachloride, carbon monoxide, and carbon dioxide; as the temperature increases, the partial pressure of CO increases, while that of CO₂ decreases. In the mentioned temperature range, the variations in the enthalpy, entropy, and the Gibbs energy of chlorination reactions are calculated and the composition of the gas phase under the conditions of thermodynamic equilibrium is determined. In the course of studying the kinetics of chlorination of HfO₂ in the presence of carbon in the range T = 600–950°C, it is established that its limiting stage depends on the process temperature. Below 700°C, its rate is limited by the chemical reaction on the surface of nonporous solid spherical particles of the body with the formation of the volatile product; above 700°C, it is limited by the mass transfer of gaseous substances.     

The activity coefficient of cobalt oxide in silica-saturated iron silicate slags

The solubility of cobalt oxide in silica-saturated iron silicate slags (1.16 to 10.00 wt pct) in equilibrium with cobalt-gold-iron alloys (1.10 to 6.52 wt pct cobalt) and oxygen pressures of 10₋₉ to 10₋₁₀ atm (1 atm = 1.013 x 105 Pa) has been investigated at 1573 K. The activity coefficient of cobalt oxide, γ_CoO, has been calculated relative to pure solid cobalt oxide as standard, namely, γ_CoO = 0.91 ± 0.09 and a relationship derived between weight percent cobalt in slag, Co (wt pct), oxygen pressure, pO₂, and activity of cobalt relative to liquid cobalt,aCo, namely, Co (wt pct) = 1.32 x 10⁶ pO ₂ ^1/2 a_Co ± 10 pct Both errors are calculated at the 95 pct confidence level. Formerly Senior Lecturer in Pyrometallurgy, Murdoch University, Murdoch, Western Australia Formerly Postgraduate Student, Murdoch University, Murdoch, Western Australia     

Dielectric and interface properties of pyrolytic aluminum oxide films on silicon substrates

Aluminum oxide films have been deposited on silicon substrates by thermal decomposition of aluminum-isopropoxide. MOS capacitance and conductance measurements have been made on Al₂O₃-Si structures,and the influence of deposition parameters and silicon surface preparation on interface properties has been examined. The density of interface states varies from 10¹⁰ to 10¹¹ cm^?2(ev)^?1, and the flatband voltage (for ～1000Å oxide) can vary between zero and several volts positive depending upon the deposition parameters and silicon surface preparation. Postdeposition annealing in moist or dry-O₂ at 800°C decreases the flatband voltage. Infrared measurements indicate that this effect is accompanied by the growth of a thin interface SiO₂ film. Only a very thin interface SiO₂ film (～50Å) is required to produce zero flatband voltage. Biastemperature stress increases the flatband voltage value under negative gate bias. Excessive localized conduction and breakdown can be correlated with the occurrence of silicon surface defects. The radiation resistance of Al₂O₃-Si structures is strongly dependent upon the presence of a thin interface SiO₂ film.     

Microstructure and phase formation of mullite-Pr6O11 composite prepared by spark plasma sintering

The present work investigates the effect of high praseodymium oxide(Pr₆O₁₁) content on the microstructure and phase formation of mullite(3Al₂O₃·2SiO₂) precursor by means of the spark plasma sintering process.30 wt% Pr₆O₁₁ was added to a mullite precursor consisting of aluminum nitrate nonahydrate and tetraethyl orthosilicate through a high energy mixer mill in ethanol media.The spark plasma sintering was performed at a ...     

The separation of zirconium and hafnium in a molten salt-molten zinc system

The commercial separation of zirconium and hafniumvia aqueous/organic extraction procedures is both difficult and expensive. The principal objective of the present work was to study an alternative procedure involving the oxidation-reduction equilibria of zir-conium and hafnium between a molten salt phase and molten zincvia the displacement reaction: Zr(IV)_{molten salt} + Hf_{molten zink} ⇌ Hf(IV)_{molten salt} + Zr_{molten zink} The reaction goes strongly to the right with an equilibrium constant: logK =0.432 ×10⁴/T - 1.565 for Na₂Zr(Hf)F₆ dissolved in NaKCl₂ solvent, thus showing promise as the basis for an anhydrous process for separating zirconium and hafnium. The rate of approach to chemi-cal equilibrium was studied in a baffled stirred reactor. The equilibration rate was found to be controlled by the hafnium mass transfer rate from the molten zinc to the metal-salt interface. The mass transfer rate could be estimated from the physical properties of the molten metal and the salt phases, using the Mayer correlation. Formerly with the Teledyne Wah Chang Cor-poration, Albany, OR.     

Lattice misfits in four binary Ni-Base γ/γ1 alloys at ambient and elevated temperatures

High-temperature X-ray diffractometry was used to determine thein situlattice parameters,a _γ anda _γ′, and lattice misfits, δ = (a _γ′, -a _γ)/a _γ, of the matrix (γ) and dispersed γ′-type (Ni₃X) phases in polycrystalline binary Ni-Al, Ni-Ga, Ni-Ge, and Ni-Si alloys as functions of temperature, up to about 680 °C. Concentrated alloys containing large volume fractions of theγ′ phase (∼0.40 to 0.50) were aged at 700 °C to produce large, elastically unconstrained precipitates. The room-temperature misfits are 0.00474 (Ni-Al), 0.01005 (Ni-Ga), 0.00626 (Ni-Ge), and -0.00226 (Ni-Si), with an estimated error of ± 4 pct. The absolute values of the lattice constants of theγ andγ′ phases, at compositions corresponding to thermodynamic equilibrium at about 700 °C, are in excellent agreement with data from the literature, with the exception of Ni₃Ga, the lattice constant of which is much larger than expected. In Ni-Ge alloys, δ decreases to 0.00612 at 679 °C, and in Ni-Ga alloys, the decrease is to 0.0097. In Ni-Si and Ni-Al alloys, δ exhibits a stronger temperature dependence, changing to-0.00285 at 683 °C (Ni-Si) and to 0.00424 at 680 °C (Ni-Al). Since the times required to complete the high-temperature X-ray diffraction (XRD) scans were relatively short (2.5 hours at most), we believe that the changes in δ observed are attributable to differences between the thermal expansion coefficients of theγ andγ′ phases, because the compositions of the phases in question reflect the equilibrium compositions at 700 δC. Empirical equations are presented that accurately describe the temperature dependences ofa _γ,a _γ′, and δ over the range of temperatures of this investigation.     

Growth and interface of amorphous La2Hf2O7/Si thin film

Amorphous La2Hf2O7 thin films were deposited on Si(100) substrate by pulsed laser deposition (PLD) method under different con-ditions. The interfacial states of the La2Hf2O7/Si films were studied by synchrotron X-ray reflectivity (XRR) and X-ray photoelectron spec-troscopy (XPS). When grown under vacuum condition, silicate, silicide and few SiOx were formed in the interface layer. However, the Hf-silicide formation could be effectively eliminated by the ambient oxygen pressure during film growth. The result revealed that the La2Hf2O7/Si interlayer was intimately related with growth condition. Insufficient supply of oxygen would cause Hf-silicide formation at the interface and it could be most effectively controlled by the ambient oxygen pressure during film growth.     

Experimental Study of Ferrous Calcium Silicate Slags: Phase Equilibria at {\text{P}}_{{{\text{O}}_{2} }} Between 10–8?atm and 10–9?atm

The phase equilibria of ferrous calcium silicate slags (“FeO _x ”-CaO-SiO₂) have been investigated at an oxygen partial pressure of 10^–8 atm at temperatures between 1423 K and 1623 K (1150 °C and 1350 °C), and at an oxygen partial pressure of 10^–9 atm at temperatures of 1473 K and 1573 K (1200 °C and 1300 °C). High-temperature equilibration/quenching/electron probe X-ray microanalysis (EPMA) techniques were applied to acquire accurate information on the phase equilibria of the system. Phase diagrams showing the liquidus isotherms of the systems at the selected oxygen partial pressures are provided. The solubilities of components in the solids of primary phases are presented. The system and conditions selected are relevant to industrial copper smelting.     

Epitaxial growth and characterization of Gd2O3-doped HfO2 film on Ge （001） substrates with zero interface layer

The GHO （Gd2O3-doped HfO2） films were epitaxially grown on Ge （001） substrates adopting cube-on-cube mode with zero interface layer using pulsed laser deposition （PLD）. Reflection high-energy electron diffraction （RHEED） and high-resolution transmission electron microscopy （HRTEM） observation revealed a sharp interface of GHO/Ge and orientation relationship corre-sponding to （001）GHO//（001）Ge and [011] GHO//[011]Ge. The band offset for GHO/Ge stack was evaluated to be 3.92 eV for va-lence band and 1.38 eV for conduction band by X-ray photoelectron spectrum. Small equivalent oxide thickness （0.49 nm） and inter-face state density （7×1011 cm-2） were achieved from Au/Ti/GHO/Ge/Al capacitors.     

Thermodynamic modeling of the interaction of Y2O3 with Nb-Si-based melts

Thermodynamic modeling of the interaction of the yttrium ceramics with Nb-Si-based melts alloyed with Ti, Cr, Hf, and Al is performed. It is shown that the result of their chemical interaction is the formation of a solid solution of hafnium oxide (HfO₂), while other elements almost do not participate in the interaction. It is revealed in the course of modeling that the main interaction mechanism is the reduction of yttrium oxide upon its dissolution from ceramics into the metallic solution, in which the Y content depends on the temperature, composition, and amount of the metallic phase.     

Healing of Double-Oxide Film Defects in Commercial Purity Aluminum Melt

The possibility of the formation of bonding between the two layers of a double-oxide film defect when held in a commercial purity liquid Al alloy was investigated. The defect was modeled experimentally by maintaining two aluminum oxide layers in contact with one another in a commercial purity Al melt at 1023 K (750 °C) for times ranging from 7 minutes to 48 hours. Any changes in the composition and morphology of these layers were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results showed that the oxide layers started to bond to one another after approximately 5 hours, and the extent of the bonding increased gradually by the holding time. The bonding is suggested to form because of the transformation of γ- to α-Al₂O₃. A complete bonding formed between the layers only when the oxygen and nitrogen trapped between the two layers were consumed, after approximately 13 hours. The results also confirmed that the nitrogen within the atmosphere of an oxide film defect reacts with the surrounding Al melt to form AlN at the interface of the defect and the melt.     

Dissolution and Interface Reactions between Palladium and Tin(Sn)-Based Solders: Part II. 63Sn-37Pb Alloy

The interface microstructures and dissolution behavior were studied, which occur between 99.9 pct Pd substrates and molten 95.5Sn-3.9Ag-0.6Cu (wt pct, Sn-Ag-Cu) solder. The solder bath temperatures were 513 K to 623 K (240 °C to 350 °C). The immersion times were 5 to 240 seconds. The IMC layer composition exhibited the (Pd, Cu)Sn₄ (Cu, 0 to 2 at. pct) and (Pd, Sn) solid-solution phases for all test conditions. The phases PdSn and PdSn₂ were observed only for the 623 K (350 °C), 60 seconds test conditions. The metastable phase, Pd₁₁Sn₉, occurred consistently for the 623 K (350 °C), 240 seconds conditions. Palladium-tin needles appeared in the Sn-Ag-Cu solder, but only at temperatures of 563 K (290 °C ) or higher, and had a (Pd, Cu)Sn₄ stoichiometry. Palladium dissolution increased monotonically with both solder bath temperature and exposure time. The rate kinetics of dissolution were represented by the expression At ⁿ exp(∆H/RT), where the time exponent (n) was 0.52 ± 0.10 and the apparent activation energy (∆H) was 44 ± 9 kJ/mol. The IMC layer thickness increased between 513 K and 563 K (240 °C and 290 °C) to approximately 3 to 5 μm, but then was less than 3 μm at 593 K and 623 K (320 °C and 350 °C). The thickness values exhibited no significant time dependence. As a protective finish in electronics assembly applications, Pd would be relatively slow to dissolve into molten Sn-Ag-Cu solder. The Pd-Sn IMC layer would remain sufficiently thin and adherent to a residual Pd layer so as to pose a minimal reliability concern for Sn-Ag-Cu solder interconnections.     

Modeling Viscosities of CaO-MgO-FeO-MnO-SiO2 Molten Slags

A model for estimating the viscosity of silicate melts is proposed in this article. The structural characteristics of a silicate slag can be described by the numbers of the bridging oxygen, nonbridging oxygen, and free oxygen present in the slag. A method of calculating the numbers of the different types of oxygen ions is presented in this article, which involves a simple approximation of “complete bridge breaking.” With just a few parameters, the model provides both the temperature and composition dependencies of viscosity for the pure component: SiO₂; the binary systems: MgO-SiO₂, CaO-SiO₂, FeO-SiO₂, and MnO-SiO₂; the ternary systems: CaO-MgO-SiO₂, CaO-FeO-SiO₂, MgO-FeO-SiO₂, and CaO-MnO-SiO₂; and the quaternary systems: CaO-MgO-MnO-SiO₂ and CaO-FeO-MnO-SiO₂. It was found that the ability of different basic metal oxides to decrease viscosity varies and is in the following hierarchy: FeO > MnO > CaO > MgO. Two factors influence the viscosity: The first is related to the mutual interaction among different ions, and the stronger the interaction, the higher the viscosity. The second factor is the size (radius) of basic oxide cation, with viscous flow becoming increasingly more difficult (i.e., viscosity increases) as the cation size increases. However, there is a paradox in the effect of cation radius (of the basic oxide) on the two factors. Thus, varying cation size causes competitive effects; smaller cationic radii give stronger interactions among ions but less hindrance to viscous flow (and vice versa for large cation radii).     

Novel self-assembled films of La-based phosphonate 3-aminopropyltriethoxysilane

Silane coupling reagent (3-aminopropyltriethoxysilane (APTES)) was prepared on single-crystal silicon substrates to form two-dimensional self-assembled monolayer (SAM). The terminal-NH2 groups in the film were in situ phosphorylated to-PO(OH)2 group to endow the film with good chemisorption ability. Then La-based thin films were deposited on phosphorylated APTES-SAM in order to make good use of the chemisorption ability of-PO(OH)2 groups. The thickness of the film was determined with ellipsometer, while phase trans-formation and surface morphology, surface energy, phase composition were analyzed by means of atomic force microscope (AFM), contact angle measurements and X-ray photoelectron spectroscopy (XPS). The results indicated that the terminal -NH2 groups could be completely transformed into desirable-PO(OH)2 groups after phosphorylation of APTES-SAM. Detailed XPS analysis of the La3+ peaks revealed that lanthanum element existed in the films in different states. As a result, conclusion could be made that lanthanum reacted with-PO(OH)2 groups on the surface of the substrate by chemical bond which would improve the bonding strength between the film and silicon substrate.Since the La-based thin films were well adhered to the silicon substrate, it might find promising application in the surface-modification of single-crystal Si and SiC in microelectromechanical systems (MEMS).