The crystallographic orientation relationship between Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and MgAl<Subscript>2</Subscript>O<Subscript>4</Subscript> in the composite material Al<Subscript>2</Subscript>O<Subscript>3</Subscript>/Al–Mg–Si alloy

The formation mechanism of spinels on Al₂O₃ particles in the Al₂O₃/Al–1.0 mass% Mg₂Si alloy composite material has been investigated by transmission electron microscopy (TEM) in order to determine the crystallographic orientation relationship. A thin sample of the Al₂O₃/Al–Mg–Si alloy composite material was obtained by the FIB method, and the orientation relationship between Al₂O₃ and MgAl₂O₄, which was formed on the surface of Al₂O₃ particles, was discovered by the TEM technique as follows:

Determination of standard Gibbs energies of formation of ternary oxides in the system Co-Sb-O by solid electrolyte emf method

An isothermal section of the phase diagram of the system Co-Sb-O at 873 K was established by isothermal equilibration and XRD analyses of quenched samples. The following galvanic cells were designed to measure the Gibbs energies of formation of the three ternary oxides namely CoSb₂O₄, Co₇Sb₂O₁₂ and CoSb₂O₆ present in the system.

Chemical diffusion of (La,Sr)CoO3 and (La,Sr)FeO3

The present work reports equilibration kinetics for (La_0.8,Sr_0.2)CoO₃(LSC) and (La_0.72,Sr_0.18)FeO₃(LSF) in the temperature range 876–1114 K using a gravimetric method. Chemical diffusion determined in this way that depends on oxygen partial pressure, can be expressed by the following temperature dependence at low and high O₂), respectively, for LSC:

Stability and direct conversion of mineral barite crystals in carbonated hydrothermal fluids

The pseudomorphic replacement of mineral barite (BaSO₄) crystals into barium carbonate was investigated in the present work by using carbonated alkaline hydrothermal fluids. Hydrothermal treatments were carried out over the temperature range from 150 up to 250 °C for intervals between 1 and 192 h, with different filling ratios (40–70%), and molar ratios of 1, 5, and 10. The reaction products were characterized by XRD and SEM techniques. The chemical reactivity of mineral barite crystals was markedly limited at temperatures below 200 °C, and only a tiny BaCO₃ layer on the surface of the original BaSO₄ crystal was formed on the crystal treated for 192 h. The rate of the pseudomorphic conversion of BaSO₄ into BaCO₃, was accelerated by increasing the reaction temperature and the molar ratio . Powder X-ray diffraction results showed that under hydrothermal conditions the replacement of ions by ions, in barite crystals was completed at 250 °C with a molar ratio = 10 for an interval of 192 h, resulting in the Witherite structure. The morphology of the completely converted BaCO₃ at 250 °C in a Na₂CO₃ solution for 192 h, showed that the conversion proceed without severe changes of the original shape and dimension of the original crystal, similar to that observed in mineral pseudomorphic replacement process.     

Structural properties of nickel manganite Ni x Mn3−x O4 with 0.5 ⩽x ⩽ 1

Single-phase nickel manganite spinels, Ni _x Mn_3–x O₄, with 0.5 x 1, were prepared by a careful thermal processing of nickel-manganese coprecipitated oxalate precursors. Powder X-ray diffraction analysis of the spinel revealed the presence of cubic single spinel phase with parametera which decreases with nickel content. The lattice parameter variation can be explained in terms of the distribution of Ni²⁺ ions on the octahedral sites. Therefore, a fine analysis of data shows that some Ni²⁺ ions (forx>0.56) are located in tetrahedral sites. The percentage of nickel in A-sites increases with nickel content (x) following the relation % Ni²⁺ in A sites =P = – 82.1x ²+192.4x–81.5 and thus the general formula for cation distribution is

The Distribution of N-Grams

N-grams are generalized words consisting of N consecutive symbols, as they are used in a text. This paper determines the rank-frequency distribution for redundant N-grams. For entire texts this is known to be Zipf's law (i.e., an inverse power law). For N-grams, however, we show that the rank (r)-frequency distribution is

Phase relations in the system Cu-La-O and thermodynamic properties of CuLaO2 and CuLa2O4

Phase relations in the system Cu-La-O at 1200 K have been determined by equilibrating samples of different average composition at 1200 K, and phase analysis of quenched samples using optical microscopy, XRD, SEM and EDX. The equilibration experiments were conducted in evacuated ampoules, and under flowing inert gas and pure oxygen. There is only one stable binary oxide La₂O₃ along the binary La-O, and two oxides Cu₂O and CuO along the binary Cu-O. The Cu-La alloys were found to be in equilibrium with La₂O₃. Two ternary oxides CuLaO₂ and CuLa₂O₄₊ were found to be stable. The value of varies from close to zero at the dissociation partial pressure of oxygen to 0.12 at 0.1 MPa. The ternary oxide CuLaO₂, with copper in monovalent state, coexisted with Cu, Cu₂O, La₂O₃, and/or CuLa₂O₄₊ in different phase fields. The compound CuLa₂O₄₊, with copper in divalent state, equilibrated with Cu₂O, CuO, CuLaO₂, La₂O₃, and/or O₂ gas under different conditions at 1200 K. Thermodynamic properties of the ternary oxides were determined using three solid-state cells based on yttria-stabilized zirconia as the electrolyte in the temperature range from 875 K to 1250 K. The cells essentially measure the oxygen chemical potential in the three-phase fields, Cu + La₂O₃ + CuLaO₂, Cu₂O + CuLaO₂ + CuLa₂O₄ and La₂O₃ + CuLaO₂ + CuLa₂O₄. Although measurements on two cells were sufficient for deriving thermodynamic properties of the two ternary oxides, the third cell was used for independent verification of the derived data. The Gibbs energy of formation of the ternary oxides from their component binary oxides can be represented as a function of temperature by the equations:

Electrical, magnetic and Mössbauer properties of cadmium - cobalt ferrites prepared by the tartarate precursor method

Six samples of the system Cd_1–x Co _x Fe₂O₄ were prepared by the tartarate precursor method with x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0. The formation of ferrispinels were studied by X-ray powder diffraction, infrared spectroscopy, electrical conductivity, thermoelectric power, magnetic hysteresis, initial magnetic susceptibility and Mössbauer spectroscopy. The data of the temperature variation of the direct current electrical conductivity showed a definite kink (390°C) except x = 0.0 and 0.2, which corresponds to the ferrimagnetic to paramagnetic transitions. Magnetic properties of the samples with x 0.6 showed definite hysteresis loops. The observed low magnetic moment can be explained in terms of the non collinear spin arrangement. A well defined hyperfine Zeeman spectra are observed for samples with x 0.6 at room temperature and resolved into two sextets corresponding to octahedral and tetrahedral sites. The electrical, magnetic and Mössbauer properties suggest that, a canted spin arrangement upto x = 0.8 and Néel's configuration above this composition. The probable ionic configuration for the system is suggested as

Three oxidation states and atomic-scale <Emphasis Type="Italic">p–n</Emphasis> junctions in manganese perovskite oxide from hydrothermal systems

Perovskite oxides have provided magical structural models for superconducting and colossal magnetoresistance, and the search for nano-scale and/or atomic-scale devices with particular property by specific preparations in the same systems has been extensively conducted. We present here the three oxidation states of manganese (Mn³⁺, Mn⁴⁺, Mn⁵⁺) in the perovskite oxide, La_0.66Ca_0.29K_0.05MnO₃, which most interestingly shows the rectifying effect as atomic-scale p–n junctions (namely FY-Junctions) of single crystals and films. The family of cubic perovskite oxides were synthesised by the so-called hydrothermal disproportionation reaction of MnO₂ under the condition of strong alkali media. The new concept of the atomic-scale p–n junctions, based on the ideal rectification characteristic of the p–n junctions in the single crystal, basically originates from the structural linkages of [Mn³⁺–O–Mn⁴⁺–O–Mn⁵⁺], where Mn³⁺ and Mn⁵⁺ in octahedral symmetry serve as a donor and an acceptor, respectively, corresponding to the localized Mn⁴⁺ .     

Thermoelectric properties of porous n-type {\text{Fe}}_{{\text{0}}{\text{.94}}} {\text{Co}}_{{\text{0}}{\text{.06}}} {\text{Si}}_{\text{2}} compounds prepared by pressureless sintering

The effects of bulk porosity on the thermoelectric properties of porous n-type ${\text{Fe}}_{{\text{0}}{\text{.94}}} {\text{Co}}_{{\text{0}}{\text{.06}}} {\text{Si}}_{\text{2}} $ compounds prepared by pressureless sintering were examined. A small amount of metallic phase ?-FeSi remained after annealing at 800 °C for 100 h. As the sintering temperature increased from 1150 to 1175 °C, the phase transition to β-FeSi₂ during annealing occurred more rapidly. The porous specimen, sintered at 1150 °C for 2 h with coarse powders (<45 μm) and then annealed at 800 °C for 100 h, showed the highest Seebeck coefficient of $ - 363_{\mu } {VK}^{ - {1}} $ at 400 °C and the highest power factor of ${\text{1}}{\text{.57}} \times 10^{ - 3} {\text{Wm}}^{ - 1} {\text{K}}^{ - 2} $ at 400 °C.     

Thermodynamics of the System InCl3–HCl–H2O at 25° C

A comprehensive equation for the thermodynamic properties of the system at 25°C in the ion-interaction (Pitzer) equation form is generated on the basis of a very recent and comprehensive array of electrochemical-cell measurements of the HCl activity, together with older published measurements of the activity of InCl₃ in mixtures with 0.02 molal HCl. Alternate equations with and without explicit consideration of the ion pair InCl²⁺ as a separate species are tested. Excellent agreement is obtained on either formulation between calculated and measured activities, although considerable uncertainty remains concerning the standard potential for the in electrode.     

Oxidation Behavior of C/SiC Composite with CVD SiC-B4C Coating in a Wet Oxygen Environment

A two-layered self healing coating with a B₄C internal layer and a SiC external layer is prepared on C/SiC composite by chemical vapor deposition (CVD). Microstructure and component of the coating was analyzed by SEM, EDS, and XRD. Oxidation behavior of SiC-B₄C coated C/SiC composite was compared with SiC-SiC coated C/SiC in an environment of at 700°C, 1,000°C and 1,200°C for 100 h, respectively. It is demonstrated that the SiC-B₄C coating is more efficient to protect the composite from oxidation than SiC-SiC coating below 1,000°C due to the self healing behavior. After oxidized at 700°C for 100 h, the residual flexural strength of SiC-B₄C coated C/SiC is about 86%, and that of SiC-SiC coated is about 64%. While after oxidized at 1,200°C, the former is about 86% and the later is about 89%. This is due to the enhanced evaporation of B₂O₃ at higher temperature.     

Defect structure of acceptor-doped calcium titanate at elevated temperatures

The defect structure of acceptor (Al or Cr)-doped polycrystalline calcium titanate was investigated by measuring the oxygen partial pressure dependence (at 10° to 10–18 atm) of the electrical conductivity at 1000 and 1050° C. The observed electrical conductivity data were proportional to for the oxygen pressure range < 10^–10 atm and proportional to for the oxygen pressure range ( 10^–7 atm. The conductivity values were observed to increase with the acceptor concentration in the p-type region with the shift in the conductivity minima towards lower oxygen partial pressure. The absolute value of the electrical conductivity in the acceptor-doped samples were lower in the n-type region compared to the values in the undoped CaTiO₃. Aluminium and chromium were found to be equally effective in acting as acceptor impurities in CaTiO₃. The defect chemistry of CaTiO₃ is dominated by the added acceptor impurities for the entire oxygen partial pressure range used in this investigation.     

Surface and grain-boundary energies of cubic zirconia

Using the multiphase equilibration technique for the measurement of contact angles, the surface and grain-boundary energies of polycrystalline cubic ZrO₂ in the temperature range of 1173 to 1523 K were determined. The temperature coefficients of the linear temperature function obtained, are expressed as $$\frac{{{\text{d}}\gamma }}{{{\text{d}}T}}({\text{ZrO}}_{\text{2}} ){\text{ }} = {\text{ }} - 0.431{\text{ }} \times {\text{ }}10^{ - 3} {\text{ }} \pm {\text{ }}0.004{\text{ }} \times {\text{ }}10^{ - 3} {\text{ Jm}}^{ - {\text{2}}} {\text{ K}}^{ - {\text{1}}} $$ and $$\frac{{{\text{d}}\gamma }}{{{\text{d}}T}}({\text{ZrO}}_{\text{2}} - {\text{ZrO}}_{\text{2}} ){\text{ }} = {\text{ }} - 0.392{\text{ }} \times {\text{ }}10^{ - 3} {\text{ }} \pm {\text{ }}0.126{\text{ }} \times {\text{ }}10^{ - 3} {\text{ Jm}}^{ - {\text{2}}} {\text{ K}}^{ - {\text{1}}} $$ respectively. The surface fracture energy obtained with a Vickers microhardness indenter at room temperature is found to be γ _F=3.1 J m^?2.     

Aqueous Electrolytes at Near-Critical and Supercritical Temperatures

The aqueous electrolyte systems are of great interest both geologically and industrially. Equations of state were developed recently for these systems; they are based on theoretical modeling for mixtures of hard spheres with appropriate diameters and dipole moments for H₂O, NaCl, and KCl and with a quadrupole moment for CaCl₂. Empirical terms are added as required to fit the available experimental data. The fit to the compositions and densities at equilibrium of the saturated vapor and liquid constitutes a severe test, in addition to properties in the single-phase regions. Temperatures range upward from 300°C for NaCl and KCl and from 250°C for CaCl₂ for these equations. Complications from hydrolysis and alternate equations valid at lower temperatures are discussed briefly. In addition, there is a very important theoretical aspect relating to the general phase diagrams. With the high ratio of critical temperatures of the salts to that of water, complex diagrams involving liquid–liquid phase separation near the critical point of water are expected. But no such effect is observed experimentally; instead, one finds simple type I phase diagrams. This is particularly clear in the case of , where the database is very accurate and extends above 1000 K.     

EPR and magnetic susceptibility studies on V2 O5-P2O5-PbO glasses

EPR and magnetic susceptibility investigations on the glass system with 04+ ion content are explained using a simulation program on the assumption of the superposition of two signals, one with hyperfine structure (hfs) typical for isolated ions and another one consisting of a broad line without hfs characteristic for clustered ions. The hfs is not shown for x<3mol%V₂O₅. The EPR data show the presence of V₄₊ ions in a square-pyramidal co-ordination (C_4V) for 3x20mol%V₂O₅. The progressive disappearance of hfs for high V²O⁵ content (>20 mol %) suggests the increase of the associated ion number coupled by superexchange interactions. This result is consistent with magnetic susceptibility data for >3 mol % where the temperature dependence of magnetic susceptibility is described by the Curie–Weiss type law with a negative paramagnetic Curie temperature. The magnetic susceptibility results allowed the estimation of the V⁴⁺/V⁴⁺ + V⁵⁺ ratio in the sample studied.     

The thermal behaviour of copper diphosphates made by wet process

Copper diphosphates (Cu₂P₂O₇ · 5H₂O, Cu_1.6K_0.8P₂O₇ · 1.7H₂O, and Cu_1.5K_1.0P₂O₇ · 2.8H₂O) were made by mixing aqueous solutions of tetrapotassium diphosphate and copper dichloride. When the diphosphates were heated, the decomposition of the diphosphates to orthophosphate was observed at a temperature lower than 150° C. The orthophosphate was polymerized by condensation to polyphosphates in the temperature range of about 150 to 450° C. The polyphosphates reorganized to diphosphate at 450 to 550° C according to the following reaction:

Thermodynamics of the System MgCl2–NaCl–H2O to 573 K: New Measurements of Heat of Mixing and Heat of Dilution

Heats of mixing of NaCl(aq) with MgCl₂(aq) at 373.15, 423.15, 473.15, 523.15, and 573.15 K for ionic strengths of 0.5 to 3.8 mol·kg^–1, and heats of dilution of MgCl₂(aq) at 523.15 and 573.15 K for ionic strengths of 0.3 to 4.6 mol·kg^–1, have been measured at 20.5 MPa. These experimental data are combined with published heat of mixing data at 298 and 373 K to provide a comprehensive Pitzer ion-interaction treatment for the thermodynamic properties of the system to 573 K. The treatment includes a general equation valid to 523 K, incorporating the published equations for NaCl(aq) and MgCl₂(aq), and equations for MgCl₂(aq) and the mixed system valid at 573 K.     

Study on the behavior of elastic-plastic fracture under mixed I+II mode loading in aluminum alloy Ly12-J-integral analysis

The elastic-plastic fracture behavior of aluminum alloy Ly12 under mixed I+II mode loading was studied by finite element method and fracture test. A mixed mode elastic-plastic fracture criterion of J-integral was proposed by using the J-resistance curve, and the maximum fracture effective plastic strain _p max of different mixed ratios at crack tip were also calculated. The results show that(1) the initiation J-integral values of different mixed ratios have the equation