The oxygen potentials corresponding to the YBa2Cu3O6+x phase in the YBaCuO system

Phase relations in the vicinity of the YBa₂Cu₃O_6+x in the CuO-rich part of the YBaCuO system were studied by the equilibration and quenching technique. At 950°C, the system is characterized by the large number of solid four-phase combinations. The oxygen potential as a function of temperature for two four-phase combinations, i.e., YBa₂Cu₃O_6+x + BaCuO₂ + BaCu₂O₂ + Y₂BaCuO₅ and YBa₂Cu₃O_6+x + BaCu₂O₂ + Y₂BaCuO₅ + Cu₂O, were studied by means of solid state EMF measurements. At higher oxygen potentials the pair of YBa₂Cu₃O_6+x and Y₂BaCuO₅ is stable in contact with BaCuO₂. At lower oxygen pressures this pair coexists in equilibrium with BaCu₂O₂ or Cu₂O.     

Hydrothermal reactions in the systems CaCO3SiO2 and MgCO3SiO2

Hydrothermal reactions in the systems calcite-quartz and magnesite-quartz have been studied over the temperature range 200°C to 600°C and the steam pressure range 1.5 to 70 MPa. In the calcite-quartz system, a hydrothermal reaction was found to occur at temperatures in excess of 450°C to form wollastonite. In the magnesite-quartz system, at temperatures above 300°C, formation of talc was observed in all compositions studied, with some formation of serpentine evident at higher magnesite compositions. Above 450°C and at magnesite contents above 80%, talc and forsterite formed. In all cases, the reaction mechanism appears to be the displacement of CO₂ by a mobile silica species. To assess the potential utilization of these reactions in ceramic manufacture, a series of samples was made from carefully graded mixtures and their compressive strengths were measured. Mixtures of calcite and quartz developed a maximum strength of 18±2 MPa at 300°C. In the magnesite-quartz system, the strength was found to increase from 11±2 MPa at 200°C to 31±2 MPa at 300°C and 30±2 MPa at 500°C. The strength rose with time of treatment in each case, reaching a maximum at about forty hours, after which no further increase in strength with time was evident.     

New oxyborates in the MgMnBO system

Two new oxyborate compounds were synthesized during a study of the phase relationships between the pinakiolite-ludwigite series of compounds. The structural topologies of these previously unreported materials have been determined experimentally by comparing calculated with observed electron microscope images. Both of these structures are very similar to each other, and also closely related to pinakiolite which consists of flat walls of edge-sharing octahedra connected to zigzag chains of octahedra by triangular BO₃ groups. The two new structures contain similar infinite walls which are separated by slabs of octahedra that are wider than the zigzag chains found in pinakiolite. A new series of structurally related oxyborate compounds can be envisaged and are described.     

The frequency of the HOH bending fundamental in solids and liquids

A survey has been made of HOH bending frequencies in water-containing solids and liquids, using data from the literature and from the author's laboratory. After the effects of hydrogen bonding and dynamic coupling have been allowed for, HOH bending frequencies are found to be lowered by cation—water interactions. This frequency lowering increases statistically with increasing cation charge and with decreasing cation size.     

Compound and solid-solution formation in the system Li2ONb2O5TiO2

A systematic study of compound and solid-solution formation in the system Li₂ONb₂O₅TiO₂ has been made. Several solid-solution series, based on LiNbO₃, LiNb₃O₈, Li₂Nb₂₈O₇₁, Li₂TiO₃, phase M, Li₂Ti₃O₇, and TiO₂, have been characterized. In all cases, the principal solid-solution mechanism appears to involve stoichiometric formulae with constant overall cation content. One new phase, of approximate formula Li₁₃TiNb₅O₂₁, has been prepared. A subsolidus phase diagram for the ternary system is presented.     

The HfNi and ZrNi systems in the region 65 – 80 at.% Ni

The HfNi and ZrNi systems have been examined in the region 65 – 80 at.% Ni by microscope and X-ray analyses.In the HfNi system the following intermediate phases were observed: Hf₃Ni₇, Hf₈Ni₂₁, HfNi₃(h. t.), HfNi₃(l. t.) and Hf₂Ni₇. Hf₃Ni₇, which is formed peritectically at 1250 ± 20 °C, decomposes eutectoidally at 1016 ± 3 °C into Hf₇Ni₁₀ and HfNi₃(l. t.). Hf₈Ni₂₁ is stable from 1300 ± 20 °C, where it forms peritectically, to 1175 ± 10 °C where it decomposes eutectoidally into Hf₃Ni₇ and HfNi₃(l. t.). HfNi₃(h. t.) is a high temperature phase, forming peritectically at 1350 ± 20 °C and transforming into HfNi₃(l. t.) below 1200 ± 10 °C. Hf₂Ni₇ melts congruently. A eutectic between Hf₇Ni₁₀and Hf₃Ni₇ occurs at 1190 ± 10 °C.In the ZrNi system only one phase forming peritectically exists; this is Zr₈Ni₂₁, which is stable at least down to 800 °C. ZrNi₃ is formed in a reaction between Zr₈Ni₂₁ and Zr₂Ni₇ at 920 ± 10 °C. Crystallographic data for the intermediate phases in the HfNi and ZrNi systems in the region 65–75 at.% Ni are presented.     

On hydrolysis of Ba–Bi–O and K–Ba–Bi–O oxide systems

Fundamentally different behavior of Ba–Bi–O (Ba : Bi = 11 : 4, 1 : 1, 2: 3, and 1 : 5 mol/mol) and K_nBa_mBi_m+nO_y (m = n = 1, 2,...; exhibiting superconducting properties with T_c = 28–32 K) oxides and BaO₂ in hydrolysis reactions has been revealed by means of potentiometry and chemical analysis. Products of the oxides treatment with water do not contain H₂O₂, evidencing the absence of peroxide ions in their structure. The perovskite-type barium-bismuth(III) oxides are completely hydrolyzed into Ba(OH)₂ and Bi₂O₃ at room temperature.     

Phase diagram for the system Bi2O3CaOSrOCuO in the SrO-rich region

It has been found experimentally that phase diagram for the system Bi₂O₃CaOSrOCuO in SrO-rich region at 850°C in the open air includes three elementary tetrahedra: CaOSrOSr₆Bi₂O₁₁Sr₂CuO₃, CaOSr₂CuO₃Sr₆Bi₂O₁₁Sr_3,5Ca_0,5Bi₂O₇ and Sr₃Bi₂O₆Sr₆Bi₂O₁₁Sr_3,5Ca_0,5Bi₂O₇ Sr₂CuO₃. In the considered interval of corresponding oxide concentrations quaternary oxides are not formed under the above conditions.     

Thermodynamic and sintering studies in the CoWC system

Sintering studies of WC-11%Co samples have been performed in a dilatometer. The temperature dependence of the shrinkage and the shrinkage rate during heating and isothermal treatment has been determined using computer evaluation. The relative magnitude of the densification in the solid and liquid states, respectively, has been determined and correlated to the CoWC phase diagram. Furthermore, some structural changes occurring under decarburizing conditions have been explained. Mechanisms for solid and liquid state sintering are presented.     

Fluorination behaviors of the complexes of RbFUF4 and CsFUF4 systems

The reaction behaviors between some complex fluorides of MFUF₄ system (M = Rb or Cs) and fluorine were investigated. In all the cases, uranium was oxidized to hexa-valent state at the temperatures between 300 and 500°C and M₂UF₈ type complex was formed, except for the cases of 3MF·UF₄ type complexes. In the fluorinations of 3MF·UF₄, products with the composition of M₃UF₉ were formed. A change in the stability of RbFUF₆ systems with RbF/UF₆ ratio was also investigated.     

Importance of axial ligand in meso-tetraphenylporphinatoiron(III) promoted NO and OO bonds cleavages

Amines, especially imidazole, were found to be essential in the meso-tetraphenylporphinatoiron (III) promoted demethylation of N, N-dimethylaniline N-oxide through the Polonovski type reaction and in the cumene hydroperoxide dependent oxidative demethylation of N, N-dimethylaniline in dichloromethane. When benzenethoil was used instead of these amines, deoxygenation of N, N-dimethylaniline N-oxide took place very readily     

Phase equilibria in the CsUO system in the temperature range from 873 to 1273 K

Portions of the cesium-uranium-oxygen system have been investigated between 873 and 1273 K and a phase diagram has been constructed using our data and the data of other workers in the field. A consistent set of measured and estimated thermodynamic data for cesium uranates has been used to calculate the equilibrium cesium partial pressure and the equilibrium oxygen partial pressure over two and three phase regions in the CsUO system. For a given temperature, the equilibrium cesium partial pressure in a two phase region decreases as the equilibrium oxygen partial pressure increases.     

Analysis of the interaction energy in the Cu+-H2O and Cl−-H2O systems,with CP corrections to the BSSE of the separate terms,and MC simulations of the aqueous systems with and without CP corrections

The interaction energyE of the systems Cu⁺-H₂O and Cl^–-H₂O has been computed over a wide range of distances and orientations with the MINI-1 basis set in the SCF approximation. The interaction energy has been decomposed according to the Kitaura-Morokuma scheme, with and without counterpoise (CP) corrections to the basis set superposition error. The importance of this correction is analysed by its effect upon Monte Carlo calculations of the Cu⁺-water and Cl^–-water systems, using two-body potentials without and with CP corrections. The effect of CP corrections on theE analysis is similar to that found in other systems of analogous composition (of the general type ion plus neutral ligands), but with significant differences in the details. The effect of the CP corrections to the interaction potential, and then on the results of the Monte Carlo simulations, is small for the Cu⁺ ion, but remarkable for the Cl^– ion.     

Subsolidus phase relationships in the system BaOCaOFe2 O3

The phase relationships at 1100°C among the reaction products of BaO, CaO and Fe₂O₃ were determined by the air quenching technique. Two binary solid solutions are formed, one between barium hexaferrite and a hypothetical calcium tetraferrite and another pseudobinary one adjacent to 2BaO·Fe₂O₃. Based on experimental results obtained by x-ray diffraction, optical microscopy and titrimetric determination of Fe⁺⁴, the 1100°C isothermal section for the system BaOCaOFe₂O₃ was derived.