Electrochemical characterization of copper deposited on plasma and thermally modified titanium surfaces

Thin oxide films were grown at temperatures from 373 to 1073 K in plasma and in air on commercially pure titanium substrates. It was determined that the color, thickness, composition, phase, and polarization behavior in a copper electrolyte varied with operating conditions: temperature, oxygen partial pressure, and plasma composition. High-temperature and high oxygen partial pressure plasma produced a thick oxide film. The surface film structure transformed from TiO₂ (anatase) to TiO₂ (rutile) at a temperature of 600 °C. A lower oxide of the form Ti _n O_2n−1, such as Ti₂O₃ (which may be porous) or possibly Ti₃O₅, was formed on a thermally treated sample (400 °C, 80 mtorr O₂, 3 hours). This sample exhibited the lowest potential for copper nucleation and gave a very uniform, smooth, and hole-free copper foil.     

X-ray diffraction study of the oxidation of Ni3(Al,Ti) alloys

Conclusions A study was made of the phase composition of the scale forming on Ni₃(Al + 15 at.% Ti) and Ni₃(Al + 5 at.%Ti) alloys during atmospheric oxidation at temperatures ranging from 600 to 1000°C. The scale was found to contain the oxides NiO, TiO₂ (rutile),-Al₂O₃, NiO · TiO₂, NiO · Al₂O₃, Ti₃O₅, and Ti₂O₃ together with Ni and a nickel base solid solution (Ni_ss). The character of the distribution of these phase constituents in successive scale layers after oxidation under various conditions is described. A correlation was found between the phase composition of the scale and certain kinetic oxidation characteristics of the alloys.Translated from Poroshkovaya Metallurgiya, No. 7 (151), pp. 70–74, July, 1975.     

Activity of titanium in Fe-Cr melts

The activity of titanium in Fe-Cr melts was measured using a galvanic cell technique. By measuring the activity of oxygen in equilibrium with the molten metal and solid titanium oxide, in conjunction with the analysis of the samples for titanium, the activity coefficient of Ti was measured at 1873 K. Oxygen cells, comprised of a thoria-yttria electrolyte with a Cr-Cr₂O₃ reference electrode and an Al₂O₃ (ZrO₂)-Mo cermet tipped molybdenum lead wire, were used to take the electromotive force (EMF) measurements. The measured values of γ°_Ti and e _Ti ^Cr were 0.018 and 0.1032, respectively.     

Calorimetric and emf studies on liquid Li-Sn alloys

By means of high temperature calorimetry the mixing enthalpies ΔH of liquid Li-Sn alloys have been measured; however, due to experimental problems they were determined only forx _Li = 0.01 to 0.5 andx _Li = 0.87 to 0.99. The range of temperatures studied was 691 to 938 K. High compound forming tendency in Li-Sn is reflected by a triangular-shaped relation for ΔH vs x _Li. The extrapolated maximum of this plot is about −40 kJ mol⁻¹ close to Li₄Sn. Using the concentration cell Bi(l)Li₃Bi(s)| LiF-LiCl|Li-Sn(l) the emf was measured as function of temperature (775 to 906 K) atx _Li = 0.1 to 0.603 enabling calculations of partial thermodynamic data for lithium in liquid Li-Sn solutions. Integral enthalpies calculated from partial enthalpies of lithium correspond well to the calorimetrically obtained integral mixing enthalpies in the concentration range where both emf and calorimetric data were obtained. The extrapolated maximum of ΔH from calorimetric studies and minimum of integral excess entropies from emf measurements correlate well with results of structure measurements and of other structure sensitive properties. All this experimental information indicates a maximum chemical short range order close to the composition Li₄Sn.     

Preparation technology of Ti-rich material from ilmenite via method of vacuum carbothermal reduction

A route of vacuum carbothermal reduction of Panzhihua ilmenite was introduced to prepare Ti-rich material. The effects of mass ratio of graphite to ilmenite, reduction temperature and vacuum condition on compositions of products and contents of impurities were investigated. Scanning electron microscope images showed that Mg mainly existed in MgSiO₃, MgAl₂O₄ and Mg_nTi_3?nO₅ in ilmenite. Thermodynamic analyses showed that only after TiO₂ was completely reduced to Ti₂O₃, the impurities Mg and Ca could be removed from the products in gaseous state. A Ti-rich material containing 0.39?wt-% Ca and 0.038?wt-% Mg was obtained when Panzhihua ilmenite was reduced with a graphite/ilmenite mass ratio of 0.130:1 at 1773?K for 1?h under the vacuum degree of 10?Pa. X-ray diffraction patterns showed that the final product was mainly composed of Ti₂O₃ and α-Fe.     

Li-Ion Battery with LiFePO<Subscript>4</Subscript> Cathode and Li<Subscript>4</Subscript>Ti<Subscript>5</Subscript>O<Subscript>12</Subscript> Anode for Stationary Energy Storage

Li-ion batteries based on commercially available LiFePO₄ cathode and Li₄Ti₅O₁₂ anode were investigated for potential stationary energy storage applications. The full cell that operated at flat 1.85 V demonstrated stable cycling up to 200 cycles followed by a rapid fade. A Li-ion full cell with Ketjen black modified LiFePO₄ cathode and an unmodified Li₄Ti₅O₁₂ anode exhibited negligible fade after more than 1200 cycles with a capacity of ~130 mAh/g at C/2. The improved stability, along with its cost-effectiveness, environmental benignity, and safety, make the LiFePO₄/Li₄Ti₅O₁₂ combination Li-ion battery a promising option for storing renewable energy.     

Study of Phase Formation Processes in the Systems Li ― N,Si3N4 ― Li3N,Si3N4 ― Li3N ― Y2O3

We have studied phase formation processes in the systems Li N and Si₃N₄ Li₃N. By nitriding lithium powder at temperatures of 400-600°C, we obtained lithium nitride Li₃N with a composition approaching stoichiometric. In the system Si₃N₄ Li₃N in the temperature range 300-1300°C, the ternary compounds Li₈SiN₄ (500°C), Li₅SiN₃, Li₂SiN₂ (900°C), and LiSi₂N₃ (1300°C) are formed. The studied properties of the hot-pressed composite material of the system Si₃N₄ Li₃N Y₂O₃ allow us to provisionally assign it to the class of solid electrolytes.     

Carbothermic reduction of llmenite (FeTiO3) and rutile (TiO2)

The mechanically activated carbothermic reduction mechanism of ilmenite has been examined by a combination of steady-state and dynamic thermal techniques coupled with X-ray diffraction. The reaction was found to proceed via an initial, rapid reduction to elemental iron and rutile, which was followed by a slow reduction of rutile to a series of oxides of the general formula Ti _n O_2n−1 until Ti₃O₅ was formed, which was found to be relatively stable. Iron was probably incorporated into the Ti _n O_2n−1 lattice only for n>3, forming mixed oxides of uncertain composition. The formation of TiC was evident at temperatures as low as 1100 °C, but the rate of reaction was extremely slow, presumably due to a solid-state diffusion limitation. Increasing the temperature gave increasing conversion of TiO₂ to TiC until it was the only confirmed product. The effect of iron on the later stages of reduction was removed by examining the reduction of pure rutile. It was found that the reduction of Ti₃O₅ was enhanced by the presence of iron. The separation of iron from the titanium product proved to be high, with > 90 pct of iron removed after the initial reduction. The iron removal increased slowly to almost 100 pct when elemental iron and titanium carbide were the products.     

Thermodynamic study of Fe2O3-Fe2(SO4)3 equilibrium using an oxyanionic electrolyte (Na2SO4-I)

The emf of the cell, Pt, Ar + O₂ + SO₂ + SO₃/Na₂SO₄-I/Fe₂O₂ + Fe₂(SO₄)₃, Pt, has been measured in the temperature range 800 to 1000 K, using a gas mixture of known input composition as the reference electrode. The equilibrium composition of the reference gas at the measuring temperatures was computed using the thermodynamic data on the gaseous species reported in the literature. A mixture of ferric oxide and sulfate was kept in a closed system to ensure establishment of equilibrium partial pressure at the electrode. The cell was designed to avoid physical contact between Fe₂(SO₄)₃ and Na₂SO₄ electrolyte. Uncertainties arising from the formation of sulfate solid solution were thus eliminated. The Gibbs’ energy of formation of ferric sulfate calculated from the emf is discussed in comparison with data reported in the literature. There is no evidence for the formation of oxysulfates in the Fe-S-0 system. Based on the results obtained in the present study for Fe₂(SO₄)₃ and literature data for other phases, chemical potential diagrams have been constructed for the Fe-S-O system at 900 and 1100 K.     

Reduction of titanium dioxide in a nonequilibrium hydrogen plasma

Plasma processing offers improved thermodynamics and kinetics over conventional, thermal processing. In the current work, the reduction of TiO₂ was investigated in a moderate-pressure (p<46 torr) nonequilibrium hydrogen plasma at temperatures below 1273 K; the effect of plasma power, plasma pressure, time, and applied voltage on the extent of the reduction was examined. Reduction of powdered TiO₂ at the surface of a packed bed has produced up to 60 pct conversion of TiO₂ to Ti₂O₃ in only 5 minutes of plasma-specimen contact. While the plasma-assisted reduction occurs at the surface, the reduction of TiO₂ to Ti₅₀O₉₉ within the interior of the bed by diatomic hydrogen establishes a value of that leads to the reoxidation of the Ti₂O₃. The continued reduction of the surface material by monatomic hydrogen from the plasma balances this oxidation process, and a steady-state condition is established. When the interior of the bed is completely reduced to Ti₅₀O₉₉, the partial pressure of water vapor declines, and further reduction of Ti₂O₃ at the surface can proceed. It is hypothesized that the reduction process involves the formation of a Magneli-like oxide between Ti₂O₃ and TiO.     

Activities of titanium in molten copper at dilute concentrations measured by solid- state electrochemical cells at 1373 K

In order to obtain the activities of titanium in molten copper at dilute concentrations,i.e., between 5 x 10^-6 and 3.4 x 10^-3 titanium mole fractions, liquid copper was brought into equilibrium with molten {CaCl₂ + Ti₂O₃} slag saturated with Ti₂O₃ (s) at 1373 K and the equilibrium oxygen partial pressures were measured by means of a solid-oxide galvanic cell of the type Mo/Mo + MoO₂/ZrO₂(MgO)/(Cu + Ti)_alloy + Ti₂O₃ + CaCl₂ + Ti₂O_{3 slag}/Mo The free energy change for the dissolution of solid titanium in molten copper at infinite dilution referred to 1 wt pet was determined as Ti (s) = Ti(1 wt pet in Cu) ΔG°/J = -86,100 ± 8900 at 1373 K     

Effect of Crystallization of Li2O-Al2O3-SiO2 Glasses on Luminescence Properties of Nd^3＋ Ions

In the field of solid-state lasers ,it is generallyconsidered that laser action can only be obtained insingle crystals or glasses ,because they ensure lowab-sorption or diffusion of light , which is required toovercome laser threshold . Now, the number of thehost materials has increased withthe addition of a newmaterial group ,glass-ceramics .Transparent glass-ce-ramics may advantageously replace glass lasers in sev-eral applications ranging from microchip lasers andamplifying optical fibers t…     

A solid state emf study of the pyrrhotite-magnetite equilibrium in the temperature interval 850 to 1275 K

The equilibrium 3/(1 −x)Fe_1−x S(s) + (5 − 2x)/(1 −x)O₂(g) Fe₃O₄(s) + 3/(1 −x)SO₂(g) was studied in the temperature interval 850 to 1275 K by measuring oxygen potentials in a galvanic cell containing calcia stabilized zirconia as solid electrolyte. The SO₂ activity was controlled by equilibrating the solid phases pyrrhotite and magnetite with a continuously flowing SO₂-Ar gas mixture of known composition. Formation of S₂ gas was taken into account and a recently published thermodynamic model for the pyrrhotite phase⁴ was used to derive the Gibbs energy change for the pyrrhotite-magnetite equilibrium and for the formation of Fe_1−x S as a function of the variables temperature and pyrrhotite composition.     

On the Application of Lithium Additives in the Electrolytic Production of Primary Aluminum

The behavior of carbon–graphite subjected to treatment in the lithium carbonate Li₂CO₃ melt without cryolite and alkali-metal fluorides is studied to reliably estimate the influence of lithium on the surface layers of a carbon-containing cathode lining. The chemical composition and the structure of the carbon–graphite material after its interaction with lithium in the Li₂CO₃ melt have been studied. The high-temperature interaction of the system components in the melt is found to be accompanied by fracture of the operating surface of the carbon–graphite material, while the carbon–graphite surface does not failed upon interacting with lithium vapors. Based on the obtained data, a model for the formation of lithium ions during the reduction of lithium and its interaction with a carbon–graphite sample during the electrolysis of lithium carbonate is proposed.     

Rapid Quenching Setup: Design, Development and Applications in Solid State Ionics

Quenching rate of the order of 10⁵ K/s has been achieved using a home-built twin-roller rapid quenching setup which is two orders of magnitude higher as compared to the rate possible through conventional quenching methods. The glass forming limit for the two ternary glassy electrolytes Li₂O–B₂O₃–P₂O₅ and Li₂O–Nb₂O₅–P₂O₅ has been extended using the twin roller setup by incorporating mol% 66.7 and 50 of the glass modifier (Li₂O) in the above glass systems. Further, the effect of mixed glass formers B₂O₃–P₂O₅ and Nb₂O₅–P₂O₅, investigated in the above extended glassy systems, reveal an initial increase in the glass transition temperature (T_g) and ionic conductivity (σ_dc), as one glass former replaces the other. The T_g and σ_dc show maximum values for the compositions mol% 66.7Li₂O–33.3[0.6B₂O₃–0.4P₂O₅] and mol% 50Li₂O–50[0.6Nb₂O₅–0.4 P₂O₅], indicating the “mixed glass former effect”. The composition mol% 66.7Li₂O–33.3[0.6B₂O₃–0.4P₂O₅], showing good thermal stability as well as conductivity, is a potential electrolyte material for device applications.     

Thermodynamics of molten Li-Sn alloys

The activity of Li in molten Li-Sn alloys was continuously varied and monitored electrochemically in cells of the type Al-LiAl/glass electrolyte/Sn/glass electrolyte/Al-LiAl. The temperature (320 to 380 °C) and compositional dependence of the Li activity coefficient, γ_Li, was found to follow a quadratic expression of the form In γ_Li = A + B(1 − X_Li)² up to 30 mole pct lithium. Further, the liquidus temperature, T_L, was found to follow TL(°C) = 642 X_Li + 188 for 0.20 X_Li 0.44 over the temperature range 320 to 470 °C. The partial and integral molar heats of solution were calculated and the results indicate that strong attractive forces exist between Sn and Li. These forces are strong enough to induce substantial ordering in the melt to an extent that the integral molar entropy of mixing at high Li contents (36 mole pct) is negative.     

Properties investigation of CaO–Al2O3–SiO2–Li2O–B2O3–Ce2O3 mould flux with different w(CaO)/w(Al2O3) for heat-resistant steel continuous casting

The new CaO–Al₂O₃–SiO₂–Li₂O–B₂O₃–Ce₂O₃ mould flux was devised to realise smooth continuous casting of Ce-bearing heat-resistant steel. The new devised mould flux was based on calcium-aluminate system, so the w(CaO)/w(Al₂O₃) has great influence on the properties of the slag, which is similar to the basicity in the silicate system. The melting temperature, viscous properties, slag structure and crystalline phases with different w(CaO)/w(Al₂O₃) were investigated. The melting temperature of the mould flux could remain relatively steady with w(CaO)/w(Al₂O₃) in the range of 1.0–1.82. The main network former in the new slag was [AlO₄]-tetrahedron. The network formed by [AlO₄]-tetrahedron was destroyed by increasing w(CaO)/w(Al₂O₃), the viscosity decreased consequently. The mould flux show weaker crystallisation tendency with increasing w(CaO)/w(Al₂O₃). When the temperature decreased to 1100°C, the change of the fully crystallised phases with increasing w(CaO)/w(Al₂O₃) was as follows: Li₂O·Al₂O_3?+?2CaO·Al₂O₃·SiO_2?→?Li₂O·Al₂O_3?→?Li₂O·Al₂O_3?+?3CaO·Al₂O_3?+?CaCeAlO₄.     

Phase relations and gibbs energies in the system Mn-Rh-O

Phase relations in the system Mn-Rh-O are established at 1273 K by equilibrating different compositions either in evacuated quartz ampules or in pure oxygen at a pressure of 1.01 × 10⁵ Pa. The quenched samples are examined by optical microscopy, X-ray diffraction, and energy-dispersive X-ray analysis (EDAX). The alloys and intermetallics in the binary Mn-Rh system are found to be in equilibrium with MnO. There is only one ternary compound, MnRh₂O₄, with normal spinel structure in the system. The compound Mn₃O₄ has a tetragonal structure at 1273 K. A solid solution is formed between MnRh₂O₄ and Mn₃O₄. The solid solution has the cubic structure over a large range of composition and coexists with metallic rhodium. The partial pressure of oxygen corresponding to this two-phase equilibrium is measured as a function of the composition of the spinel solid solution and temperature. A new solid-state cell, with three separate electrode compartments, is designed to measure accurately the chemical potential of oxygen in the two-phase mixture, Rh + Mn_3−2xRh_2xO₄, which has 1 degree of freedom at constant temperature. From the electromotive force (emf), thermodynamic mixing properties of the Mn₃O₄-MnRh₂O₄ solid solution and Gibbs energy of formation of MnRh₂O₄ are deduced. The activities exhibit negative deviations from Raoult’s law for most of the composition range, except near Mn₃O₄, where a two-phase region exists. In the cubic phase, the entropy of mixing of the two Rh³⁺ and Mn³⁺ ions on the octahedral site of the spinel is ideal, and the enthalpy of mixing is positive and symmetric with respect to composition. For the formation of the spinel (sp) from component oxides with rock salt (rs) and orthorhombic (orth) structures according to the reaction, MnO (rs) + Rh₂O₃ (orth) → MnRh₂O₄ (sp),ΔG° = -49,680 + 1.56T (±500)J mol⁻¹ The oxygen potentials corresponding to MnO + Mn₃O₄ and Rh + Rh₂O₃ equilibria are also obtained from potentiometric measurements on galvanic cells incorporating yttria-stabilized zirconia as the solid electrolyte. From these results, an oxygen potential diagram for the ternary system is developed.     

Study on Ferroelectric and Dielectric Properties of La-Doped CaBi4Ti4O15-Based Ceramics

Research on bismuthlayer structuredferroelectricceramics as piezoelectric material with high Curie tem-perature ,strong anisotropic characters ,lowdielectricdissipationfactor and lowaging rate has attracted in-creasing interest[1,2].It can be used to manu…     

Influence of Li2O on the carbonate capacity of CaO- CaFv2- AI2O3 Melts

The influence of Li₂O on the carbonate capacity of CaO-CaF₂-Al₂O₃-based fluxes is examined by a thermogravimetric technique over the temperature range 1250 °C to 1350 °C. The values of the carbonate capacities (Cc = wt pct CO₂/P_CO2) were calculated by the solubility and the partial pressure of carbon dioxide. The replacement of CaO by Li₂O resulted in a decrease of the carbonate capacity. The addition of Li₂O, from 0.4 to 2.0 pct, to the CaO-CaF₂-Al₂O₃ increases the carbonate capacity at 1300 °C by 50 pct. At 0.4 pct Li₂O,Cc is 1.2, and at 2.1 pct Li₂O,Cc is 2.1. The replacement of CaF₂ by Al₂O₃ was found to have no significant influence on the carbonate capacity of the investigated ternary system. SIMEON SIMEONOV, formerly Visiting Research Fellow, Institute of Industrial Science, University of Tokyo. KOJI FUKTTA, formerly with the Institute of Industrial Science, University of Tokyo.