Yield stress of a copper single crystal containing B2O3 particles

The yield stress of a copper single crystal containing vitreous B₂O₃ particles was measured as a function of temperature (77–1073 K) and strain rate (5.6 × 10^–6–5.6 × 10^–4sec^–1). Although the B₂O₃ particles in the copper matrix are a plastically non-deformable solid at low temperatures, they became liquid-like at high temperatures, above approximately 550 K. The yield stress of the Cu-B₂O₃ alloy at low temperatures was explained by the Orowan mechanism and the modulus-corrected yield stress of the Cu-B₂O₃ alloy at 1073 K was about four-fifths of the values at low temperatures. It was found that the liquid B₂O₃ particles could be the effective hardening centres even at high temperatures. At 873 and 1073 K, the yield stresses of the Cu-B₂O₃ alloy varied with the logarithm of the strain rates.     

Specific Features of Anodic Dissolution of Copper in H2SO4 + H2O and H2SO4 + CuSO4 + H2O Systems

We investigate anodic dissolution of copper in H₂SO₄ + H₂O and H₂SO₄ + H₂O + CuSO₄ systems, which model solutions for the electrochemical production of copper (+2) sulfate. Ultimate densities of anodic current in the temperature range 20–80°C for a voltage up to 8 V were found. We show that a concentration of copper ions ( Cu²⁺) of 1.5–2.0 moles/liter in the anolyte is the limiting one in the electrochemical production of solutions of copper (+2) sulfate.     

Acetone intercalation/de-intercalation processes in the HUP (H3OUO2PO4·3H2O) framework: A model for electrochemical degradation

Intercalation of acetone molecules in the H₃OUO₂PO₄ · 3H₂O framework has been studied by X-ray diffraction, differential scanning calorimetry and IR and Raman spectroscopies. The influence of water traces in acetone is pointed out. Four main phases are observed in the course of the rehydration/de-intercalation process. The nature of proton bonding with the (UO₂PO₄) _n slab and its evolution are discussed (H₃O⁺, PO ₄ ^3– , HPO ₄ ^2– , HPO ₄ ^2– ...). The presence of defects in the sub-stoichiometric HUP is demonstrated. Comparison is made with similar partially dehydrated material obtained under electric field action in electrochemical solid state devices.     

Synthesis of bismuth micro- and nanospheres by a simple refluxing method

Well-separated bismuth micro- and nanospheres were successfully prepared from bismuth citrate and urea by a simple refluxing reaction at 198 °C in ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP). The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX). The larger Brunauer–Emmett–Teller (BET) surface area of these micro- and nanospheres was found to be 17.34 m²/g by the results of N₂ adsorption. It was found that the amount of PVP have an influence on the morphologies of bismuth nanostructure. The possible growth mechanism of bismuth micro- and nanospheres was also discussed.     

Preparation of fatigue-free SrBi2Ta2O9 thin films by r.f. magnetron sputtering and their ferroelectric properties

Fatigue-free bismuth-layered SrBi₂Ta₂O₉ (SBT) films were deposited on Pt/Ti/SiO₂/Si substrates by r.f. magnetron sputtering at room temperature. The variation of structure and electrical properties were studied as a function of annealing temperatures from 750–850 °C. The films annealed at 800 °C had a composition ratio of Sr:Br:Ta = 0.7:2.0:2.0. X-ray photoelectron spectroscopy signals of bismuth show an oxygen-deficient state within the SBT films. The films annealed at 800 °C have a thickness of 200 nm and a relatively dense microstructure. The remanent polarization (2P _r), and the coercive field (2E _c), obtained for the SIBT films, were 9.1 C cm^–2 and 85 kV cm^–1 at an applied voltage of 3 V, respectively. The films showed fatigue-free characteristics up to 10¹⁰ cycles under 5 V bipolar square pulses. The leakage current density was about 7 × 10^–7 A cm^–2 at 150 kV cm^–1. The SBT films prepared by r.f. magnetron sputtering were attractive for application to non-volatile memories.     

Sintering mechanisms in YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7−<Emphasis Type="Italic">x</Emphasis></Subscript> superconducting ceramics

The densification of ceramic compacts of YBa₂Cu₃O_7−x (123) was studied with a vertical dilatometer. The runs effected under isothermal conditions (ISO) covered the 920–970^∘C range and were performed under static air atmosphere. Also, controlled heating rate (CHR) runs, from about 800 to 1050^∘C, were conducted at 5^∘C/min under either flowing oxygen or static air. The ISO data could be satisfactorily fitted by the solution-precipitation (SP) model giving an activation enthalpy of 221 kJ/mol. Furthermore, the CHR data for 920–970^∘C was also fitted with the same model giving 207 kJ/mol as the activation energy. From analysis of CHR data, the initial stage sintering is driven by solid state sintering between 827–894^∘C (823–908^∘C in O₂). Then, in the interval 902–920^∘C (914–934^∘C in O₂) the intermediate stage driven by grain growth (GG), competes with the rearrangement process associated to the presence of a liquid phase. This last process applied because the next sintering stage in the range 922–970^∘C (938–990^∘C in O₂ flow) could be fitted by the SP model with an activation enthalpy of 207 kJ/mol (229 kJ/mol in O₂). In the range 972–995^∘C (990–1014^∘C in O₂), the solid state (GG) intermediate stage mechanism and/or viscous flow competes with the SP process.     

Mass Spectrometric Study of Vapor Composition over Germanium Telluride

The vapor phase over germanium telluride was studied by Knudsen cell mass spectrometric measurements. All of the signals in its mass spectrum were identified for the first time. The GeTe⁺, Te⁺ ₂, Te⁺, Ge⁺, and GeTe⁺ ₂ appearance potentials and temperature-dependent (700–850 K) GeTe and Te₂ partial pressures were refined (for the first time for GeTe₂). Conclusive evidence is presented that germanium telluride sublimes incongruently.     

Behaviour of bismuth during simulated processing of model aluminium capacitor foils

The production of high specification, aluminium-based, electrolytic capacitors requires optimization of material composition and heat and surface treatments in order to maximize the area available for formation of the dielectric, anodic film. Commercial foils contain low additions of copper and lead in order to achieve this goal. The present study examines the effects of heat and surface treatments on aluminium foil containing either 50 or 1000 ppm bismuth, as a replacement for lead, by a combination of Rutherford backscattering spectroscopy and scanning electron microscopy. Heat treatment at 823 K results in segregation of bismuth to the surface regions of the foils, with enrichments in the range 4–8 × 10¹⁴ Bi atoms cm^–2, localized mainly just beneath the thermal oxide, for the selected treatment conditions. The enrichment reduces following alkaline etching, to the range 1–4 × 10¹⁴ Bi atoms cm^–2. This level of enrichment is maintained during subsequent anodizing, with the enrichment partitioned between the metal and the outermost layers of the anodic films. The enrichment of the metal is about 4 × 10¹³ Bi atoms cm^–2. Electropolishing in perchloric acid solution eliminates the enrichment developed during the heat treatment, probably due to activation during the polishing process. The enrichment remains very low or negligible during subsequent anodizing. The general behaviours of bismuth and lead are similar in aluminium foils subject to the selected heat and surface treatments. However, additional studies are needed of tunnel etching to determine the feasibility of substitution of lead by bismuth in commercial foils.     

A comparative study on copper corrosion originated by formic and acetic acid vapours

The copper corrosion rate and products originated by the action of formic and acetic acid vapours at a 100% relative humidity were studied. Copper specimens were exposed to formic and acetic acid vapours for a period of 21 days. Five formic and acetic acid vapour concentrations (10, 50, 100, 200 and 300 ppm) were tested. Copper corrosion rates of up to 1300 mg m^–2 d^–1 (mmd) for formic acid and up to 2300 mmd for acetic acid were measured using a gravimetric method. The corrosion-product layers were characterised using electrochemical, X-ray powder diffraction and scanning electron microscopy techniques. Some of the compounds identified were: cuprite (Cu₂O), for both acids; cupric hydroxide monohydrate (Cu(OH)₂ · H₂O) and copper formate tetrahydrate (Cu(HCOO)₂ · 4H₂O), for formic acid; and copper acetate dihydrate (Cu(CH₃COO)₂ · 2H₂O) and copper hydroxide acetate dihydrate (Cu₄(OH)(CH₃COO)₇ · 2H₂O), for acetic acid.     

Studies on the presence of copper in the galvanized coating on weathering steel and the adherence characteristic of the protective copper complex formed on galvanized weathering steel

Following the hot-dip process for zinc coating on weathering steel, the galvanizing bath was found to have picked up copper. The galvanizing bath was observed to pick up Cu from the weathering steel at an average rate of 1.83×10^–3% s^–1m^–2 at 452±2C. EDAX/SEM studies exhibited a concentration gradient of copper to exist across the thickness of the galvanized coating on weathering steel. XRD studies revealed the formation of a protective copper complex, {Cu[(OH)₂Cu]₃}SO₄, on galvanized coating containing 0.739% Cu, when exposed in marine and industrial atmospheres. The adherence characteristic of the copper complex to the galvanized coating was found to be very satisfactory.     

The structural degradation and lamellar to rod transition in the Bi-Cd eutectic during unidirectional growth

The Bi-Cd eutectic system is a prototype quasi-regular eutectic in which the bismuth-rich phase has a volume fraction of 57%. It shows a high degree of regularity but, clearly, is not a normal (regular) eutectic. Microstructural observations of unidirectionally-grown specimens show that the minor cadmium-rich phase degrades at small temperature gradients and small growth rates. However, the structural refinement resulting from rapid freezing or chemical addition is found to be analogous to that of the F/NF eutectics. A lamellar rod transition has been achieved at intermediate growth rates by adding 2.0 wt % Sn as a modifier to the eutectic alloy. However, this was accompanied by the bismuth phase showing cellular facets of the solid-liquid interface.Nomenclature G _L temperature gradient in the melt ahead of the solid/liquid interface (° C cm^–1) - G _S temperature gradient in the solid behind the solid-liquid interface (° C cm^–1) - R growth rate of solid (cm sec^–1) - S cooling rate (° C sec^–1, ° C h^–1) - K _S thermal conductivity in the solid (W m^–1 K^–1) - K _L thermal conductivity in the melt (W m^–1 K^–1) - L latent heat of fusion (J mol^–1) - T temperature difference, undercooling (° C) - K ₁ constant in Equation 2 - K ₂ constant in Equation 3 - D diffusion coefficient of solute in solid (m² sec^–1) - C solubility in solid (wt %, at %) - M molecular weight (g mol^–1) - density (g cm^–3) - interfacial energy, surface tension (J mm^–2) - R gas constant, 8.314J mol^–1 K^–1 - r radius of curvature (m) - T temperature (K) - t time (sec) - F faceted - NF non-faceted     

Electrochemical Preparation of Arsenic and Its Compounds

Electrochemical processes are used to recover elemental arsenic from NaH₂AsO₃ solutions, oxidize As₂O₃ suspensions to arsenic acid, and reduce arsenic acid to arsine. The electrolysis conditions are optimized for obtaining elemental arsenic: 0.8–0.9 M NaH₂AsO₃, 0.03–0.05 A/cm², 20–25°C. The introduction of tetraalkylammonium salts containing C₉–C₁₂ substituents, e.g., trimethylcetylammonium bromide, is shown to stabilize the current efficiency in terms of As at a level of 45–50%. The current efficiency of copper cathodes attains 89% in 1–2 M H₃AsO₄ solutions at a current density of 0.2 A/cm². In the electrosynthesis of arsenic acid, quantitative substance and current yields are achieved in 2–3 M HCl solutions. Low-waste processes are proposed for preparing arsenic, H₃AsO₄, and As₂O₅ from As₂O₃. The resulting arsenic is suitable for producing high-purity (99.9999%) material. The physicochemical processes underlying arsine generation are examined, and a bench-scale electrochemical arsine generator is described which can be used in the manufacturing of semiconductor materials.     

UV-cured hybrid inorganic-organic polymer electrolyte based on organically modified polysiloxane

Hybrid inorganic-organic polymer electrolyte based on the monomer of organically modified polysiloxane was prepared by UV radiation curing in the presence of liquid electrolyte. The organically modified polysiloxane monomer with acrylate groups at the terminal position was synthesized by hydrolytic condensation of tetramethoxysilane (TMOS) and followed by demethanolation reaction using 2-hydroxyethyl acrylate (2-HEA). The rational formula of the monomer was SiO_1.1436(OH)_0.01606(OCH₃)_1.3394(OCH₂CH₂OCOCH= CH₂)_0.3574 which was determined by proton nuclear magnetic resonance (¹H-NMR) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy and silica analysis. The monomer was polyfunctional with a number average molecular weight of 1185 and a weight average molecular weight of 2292 determined by GPC analysis. The electrochemical properties of the hybrid inorganic-organic polymer electrolyte were determined by ac impedance spectroscopy and cyclic voltammetry. Ionic conductivity was greatly enhanced with increasing amounts of liquid electrolyte. When the polymer electrolyte contained 80 wt% liquid electrolytes, the conductivities were around 3.3 × 10^–3 S cm^–1 at 21°C and 8.0 × 10^–4 S cm^–1 even at –23°C. Interface resistance increased initially and reached a steady value after 2 days. Oxidation stability was up to 5.0 V against the lithium reference electrode and electrochemical plating/stripping of lithium on the stainless steel electrode was reversible.     

Electrochemical lithium insertion in the solid solution Bi2WO6-Sb2WO6 with Aurivillius framework

Following the structural evolution of the Aurivillius crystalline framework in the solid solution Bi₂WO₆-Sb₂WO₆ we have carried out an electrochemical lithium insertion study in this system. A slight loss of the specific capacity of the electrochemical cell was observed as amount of Sb was increased. In general, the different compositions within solid solution Bi_2−xSb_xWO₆ (0.25 ≤ x ≤ 0.75) exhibited a similar behaviour featured mainly by two semiconstant potential regions located at 1.7 and 0.8 V versus Li⁺/Li^o. The oxide Sb₂WO₆ with Autivillius structure but without Bi was tested as cathode too. The maximum amount of lithium inserted, 13.5 lithium atoms per formula, is the same amount inserted in its homologous bismuth oxide Bi₂WO₆.     

Synthesis and thermoelectric characterization of polycrystalline Ni1−x Ca x Co2O4 (x=0–0.05) spinel materials

Ca doped NiCo₂O₄ spinel materials were synthesized by conventional solid state reactions at 900 °C. Thermoelectric properties of polycrystalline products were characterized at high temperature range of 800 °C in air. d.c. conductivity of the prepared polycrystalline 5 mol % Ca doped NiCo₂O₄ was about 60 S m^–1 at 300 °C. The value of d.c. conductivity was increased with the temperature increasing. Thermoelectric voltage of polycrystalline Ni_1–x Ca _x Co₂O₄ (x=0–0.05) was positive at 300–800 °C, this showed p-type thermoelectric properties. The Seebeck coefficient of 5 mol % Ca doped NiCo₂O₄ was ca. 300 V/K at 600 °C. The value of the Seebeck coefficient of Ni_1–x Ca _x Co₂O₄ polycrystalline products decreased with the increasing temperature. Thermal conductivity of 5 mol % Ca doped NiCo₂O₄ was ca. 2.2 W m^–1 K^–1 at 600 °C. The estimated thermoelectric figure-of-merit, Z, of 5 mol % Ca doped NiCo₂O₄ spinel polycrystalline product was about 3.5×10^–5 K^–1 at 600 °C.     

Surface tension and contact angles of molten cadmium telluride

The surface tension and contact angle of molten cadmium telluride (CdTe) were measured as a function of temperature by the sessile drop technique. A FORTRAN code was developed to calculate the surface tension of sessile drops, with the contact angle ranging from O to 180°. The wetting of cadmium telluride melt was studied on different surfaces. The surface tension of cadmium telluride was about 160 ±5 dynes · cm^–1[1.6 m^–1] at the melting point of 1093°C. The contact angle of CdTe melt was about 65° on a quartz optical flat, 75° on commercial fused quartz, and 125° on boron nitride coated quartz.Paper presented at the Tenth Symposium on Thermophysical Properties, June 20–23, 1988, Gaithersburg, Maryland, U.S.A.     

Electrical conductivity,TEP and dielectric studies on mol% 66.6 Agl-22.2 Ag2O-11.1 (0.8 V2O5-0.2 P2O5) electrolyte material for solid state batteries

In the superionic conducting quarternary system Agl-Ag₂O-V₂O₅-P₂O₅, the best ionic conductivity was obtained for the composition 66.6% Agl-33.3% (2Ag₂O-1 (V₂O₅-P₂O₅)), when the GF/GM ratio was varied from 0.20 to 5.0. Then fixing the GF/GM ratio at 0.50, the ratio of the glass formers V₂O₅ and P₂O₅ were varied and the highest conducting composition was obtained as 66.6% Agl-22.2 Ag₂O-11.1% (0.8 V₂O₅-0.2 P₂O₅). A preliminary investigation using this material in the form of an electrolyte in a solid state electrochemical cell is reported. The polycrystalline and amorphous compounds were prepared from the same melt, by open air crucible melting and the rapid quenching technique. The ionic conductivity for the best conducting polycrystalline (hence referred as 66VP82P) and amorphous (66VP82G) samples was obtained as 8.3 × 10^–3 and 4.2 × 10^{–2 –1} cm^–1 respectively. The electronic conductivity of the order 10^{–10 –1} cm^–1 was observed for 66VP82G and 10^{–8 –1} cm^–1 for 66VP82P samples. Thermoelectric power studies revealed that the charge carriers are the Ag⁺ ions, with an activation energy of 0.288eV for 66VP82G, which correlated well with the activation energy obtained from the conductivity measurements. The dielectric constant, dielectric loss and the loss tangent were calculated for both polycrystalline and glassy 66VP82 material. It was observed that the dielectric loss is more for the glassy material than the polycrystalline material. Solid state galvanic cells with 66.6% Agl-22.2% Ag₂O-11.1% V₂O₅, 66.6% Agl-22.2%-Ag₂O-11.1% P₂O₅ and 66.6% Agl-22.2% Ag₂O-11.1% (0.8 V₂O₅-0.2 P₂O₅) (coded as 66V, 66P and 66VP82 respectively) electrolytes were constructed. Both polycrystalline and amorphous electrolyte cells were fabricated for a comparative study and the polarization effects were observed to be negligible in amorphous cells. The variation of open circuit voltage with temperature was reported and the current discharge curves indicate that the 66VP82 material has higher current capacity with high current drain when compared to 66V and 66P cells.     

NMR studies of the orientational ordering in dilute solid N2-Ar mixtures

We report the results of NMR studies of the orientational ordering of¹⁵N₂ molecules in solid N₂-Ar mixtures for N₂ concentrations in the 40–50% range. For samples with 50%¹⁵N₂ a new phase distinct from the quadrupolar glass phase for the hcp structure has been observed. In this new phase, the local orientational order parameters were found to have very closely the same value at each site in contrast to the very broad distribution of order parameters observed in the quadrupolar glass state for the hcp lattice at higher concentrations (57–77%).     

Structural Stability of SrCo<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Fe<Subscript>x</Subscript>O<Subscript>3 − δ</Subscript> Solid Solutions

SrCo_{1 − x} Fe_xO_{3 − δ} solid solutions with 0.3 ≤ x ≤ 0.9 are shown to have the cubic perovskite structure. The unit-cell parameter and volume of the solid solutions are nonmonotonic functions of Fe content, with a minimum at x = 0.4. Dilatometric data are used to determine the thermal expansion coefficients of the solid solutions. At low oxygen partial pressures ( ≤ 40 Pa), the high-temperature, disordered perovskite phase exists between 850 and 1000°C, which is the optimal temperature range for the effective use of SrCo_{1 − x} F_xO_{3 − δ} ceramics as oxygen membranes in oxygen partial pressure gradients of 10⁴–10⁵/10–100 Pa.__________Translated from Neorganicheskie Materialy, Vol. 41, No. 8, 2005, pp. 998–1004.Original Russian Text Copyright © 2005 by Kokhanovskii, Zonov, Ol’shevskaya, Pan’kov.     

Thermal and magnetic properties of copper potassium tutton salt below 0.15 K

The specific heat and the ac susceptibility of copper potassium tutton salt have been measured between 0.01 and 0.15 K. The magnetic phase transition from the paramagnetic to the canted ferromagnetic state was observed at 29.5 mK in zero field. From the obtained electronic entropy curve this salt is considered to be a Heisenberg-type ferromagnet. The copper nuclear specific heat of the hyperfine splitting is estimated to beC _N =1.1×10^–5 R/ (T ²/[K²]), which is one order smaller than the value calculated from previous results of the paramagnetic resonance.