Thermodynamic description of the interaction processes in the Cu–Ce–O system in the temperature range 1100–1300°C

A thermodynamic simulation and an experimental study of the interaction between cerium and oxygen in liquid copper have been performed. The thermodynamic analysis of the interaction processes in the Cu–Ce–O system is carried out using the technique of constructing the surface of solubility of components in a metal in the temperature range 1100–1300°C. As a result of simulation, data on changes in the Gibbs energy ΔG _T ° and the equilibrium constants of formation of cerium oxides Ce₂O₃ and CeO₂ from the components of a copper-based metallic melt are obtained. The first-order interaction parameters (according to Wagner) of cerium and oxygen dissolved in liquid copper, namely, e _Ce ^Ce, e _O ^Ce, and e _Ce ^O, are evaluated. Experimental studies of the Cu–Ce–O system have been performed. The morphological features, the size, and the composition of nonmetallic inclusions formed as a result of interaction in the Cu–Ce–O system are studied using scanning electron microscopy and electron-probe microanalysis.     

Phase Equilibria in the ZrO2–La2O3–Gd2O3 System at 1600°C

Powder Metallurgy and Metal Ceramics - Phase equilibria and structural transformations in the ternary ZrO2–La2O3–Gd2O3 system at 1600°C were studied by X-ray diffraction,...     

A mass-spectrometric study of the thermodynamics of the Fe−Cu and Fe−Cu−C(sat) systems at 1600°C

The Knudsen cell-mass spectrometer combination has been used to study the Fe?Cu and Fe?Cu?C_(sat) alloys at 1600°C. Activity coefficients in the Fe?Cu system are closely represented by the equations $$\begin{gathered} \ln \gamma _{Fe} = 1.86N_{Cu}^2 + 0.03, (0< N_{Fe}< 0.7) \hfill \\ \ln \gamma _{Cu} = 2.25N_{Fe}^2 - 0.19, (0.7< N_{Fe}< 1.0) \hfill \\ \end{gathered} $$ with an uncertainty in the quadratic terms of about 5 pct. For the iron-rich carbon-saturated alloys, the activity coefficient of copper is given by the equation $$\ln \gamma _{Cu} = 2.45(N'_{Fe} )^2 + 0.3N'_{Fe} + 0.03, (0< N'$$ to within an uncertainty of about 10 pct. N _Fe ^′ represents the fraction N_Fe/(N_Fe+N_Cu), etc. The activity coefficient of iron in this region is found to be essentially constant at 0.69±0.05.     

Structure of surface layers of boron carbide after friction in the temperature range 20–1400°C

Conclusions The experimental results show that, starting from 800°C, friction of the boron carbide is characterized by high ductility associated with the formation of planar defects. The results show that the depth of the deformed layer to temperatures of 800–1000°C is determined by the grain size and in the regions of the coarse-grained material the layer is 10–15 m deep which is 3–5 times greater than in the areas of the fine-grained material. The products of wear do not form a continuous layer on the friction surface of the Bi₄C-B₄C pair and are distributed in the form of individual clusters. Friction of this pair in air at temperatures above 600°C is accompanied by the formation of quasiamorphous oxide films.Translated from Poroshkovaya Metallurgiya, No. 8(284), pp. 93–97, August, 1986.     

Phase Equilibria in the La2O3–Er2O3 System in the Temperature Range 1100–1500°C

Powder Metallurgy and Metal Ceramics - Phase equilibria and structural transformations in the binary La2O3–Er2O3 system at 1100–1500°C have been studied by X-ray diffraction,...     

Phase Equilibria in the ZrO2–La2O3–Sm2O3 System at 1100°C

Powder Metallurgy and Metal Ceramics - Phase equilibria and structural transformations in the ternary ZrO2–La2O3–Sm2O3 system at 1100°C were studied by X-ray diffraction over the...     

The Synthesis of the Fe3O4 Nanoparticles and the Analysis of the Current–Voltage Measurements on Au/Fe3O4/p-Si Schottky Contacts in a Wide Temperature Range

The iron oxide (Fe₃O₄) magnetic nanoparticles were synthesized via the organic solution phase method and used for the fabrication of the Au/Fe₃O₄/p-Si rectifying device. The variation in electrical characteristics of the Au/Fe₃O₄/p-Si Schottky contacts was investigated as a function of temperature using current–voltage (I–V) measurements in the temperature range of 40 K to 370 K (?233 °C to 97 °C). The I–V characteristics of the contacts indicated extremely strong temperature dependence. The double distribution of barrier heights was found in the Fe₃O₄/p-Si Schottky diodes from the I–V-T measurements. The Schottky barrier height (Φ_b) increases with the increasing temperature, while the ideality factor n decreases. The nonlinearity in the activation energy plot was observed, which is attributed to barrier inhomogeneities by assuming a Gaussian distribution of barrier heights at the Fe₃O₄/p-Si interface. The Richardson constant measured from the temperature-dependent I–V characteristics is 2.99 A/K² cm², which is lower than the ideal value.     

Changes in the Properties of Ultrafine Al2O3–ZrO2–Y2O3–CeO2 Powders After Heat Treatment in the Range 400–1450°C

Powder Metallurgy and Metal Ceramics - Ultrafine 90AZK, 80AZK, 70AZK, and 58.5AZK powders in the Al2O3–ZrO2–Y2O3–CeO2 system were produced for the first time by a combined method...     

The tensile properties of a particulate reinforced al alloy in the temperature range -196–300 °c

The tensile properties of a particulate reinforced Al- Si-Mg alloy were determined in the temperature range — 196–300 °C. Microstructural coarsening of a peak aged (T61) material occurs at the higher temperatures (i.e. 200 and 300 °C), which, together with the test temperature, results in a considerable decrease in flow strength for both the composite and unreinforced alloy. However, the strengthening ratio (i.e. the ratio of composite to matrix strength, σ_c/σ_m actually increases with temperature. This effect is also observed when investigating the influence of test temperature alone (i.e. a stable matrix microstructure over the full temperature range). These results suggest that the primary relaxation mechanisms are damage accumulation and relaxation by plastic deformation of the matrix. There is no evidence of unrelaxed behaviour, even at −196 °C, and the strain rate used during testing is likely to be too high to allow diffusional relaxation to be operative at the higher temperatures     

Preparation of stainless steel master alloy by direct smelting reduction of Fe–Ni–Cr Sinter at 1600°C

Feasibility analysis and experimental studies for the production of a stainless steel master alloy by direct smelting reduction have been investigated in this work, showing that the master alloy with proper compositions and satisfactory metal recoveries can be obtained at 1600°C. When the temperature was increased from 1450 to 1600°C, the grades for Fe, Ni and Cr increased from 50.04, 1.1 and 13.36% up to 73.39, 1.77 and 16.42%, respectively. Experiments were then carried out focusing on the influence of various fluxes on the reduction behaviour, showing that CaO resulted in the increase in the recoveries of Fe, Ni and Cr, SiO₂ improved the recoveries of Fe and Ni, but did not favour the recovery of Cr because of an increase of CrO and Cr₂O₃ within the slag. MgO was not effective as a flux because of the formation of spinel. This increased the effective viscosity of the slag because of the presence of suspended solids, and led to a poor separation between the alloy and slag.     

Processing and performance of Cr2O3–Fe2O3 reference electrode powders prepared by oxide coprecipitation

Abstract

Cr₂O₃–Fe₂O₃ based oxide mixtures for reference electrode powders of oxygen sensors were processed using oxide coprecipitation route. A special method for preparing reference electrode powders has been developed by mixing coarse Cr particles with the oxide mixture in the form of Cr–Fe hydroxide. Morphology and size of the mixed oxide powders were characterised by means of scanning electron microscopy and laser diffraction method. With the coprecipitation process, chemically homogeneous and very fine powders with a mean particle size of 1.53 μm were prepared. This powder mixture adhered and loosely coated to Cr particles. The processed reference electrode powders were tested in low level oxygen concentration measurements of steelmaking process under industrial scale. The reference electrode powders showed excellent results in terms of electromotive force reproducibility, response time and accuracy in soluble aluminium predictions at the oxygen concentration measurements. Most of the particles of the reference electrode powder remained separated after dipping to molten steel.     

Migration and Reaction Mechanism of Barium in BaSO4–CaCO3–Fe2O3 System during Sintering

With the increasingly strict requirements of blast furnaces on the sinter quality, analyzing the phase transition process and reaction mechanism of special elements in the sintering process plays an important role in understanding the sintering process and improving the sinter quality. Herein, the decomposition process of barite during sintering and the influence mechanism on the bonding phase of calcium ferrite are studied by laboratory experiments and thermodynamic calculations. The results show that calcium ferrite and ferric oxide can promote the decomposition of barite and reduce the decomposition temperature in the sintering process. The generated barium enters the calcium ferrite phase and affects the strength and melting point of calcium ferrite. With the increase of barium content, the strength of calcium ferrite sample increases from 1.62 to 2.00 kPa, and the initial melting temperature of calcium ferrite sample stays at 1473 K. However, with the further increase of barium, the sample strength and melting temperature both show a worsening trend. Finally, based on the research results, some suggestions for sintering production are put forward, and the optimal barite content is determined. Results help to better understand the reaction process and action mechanism of barium in the sintering process.     

Study of creep deformation of irradiated zircaloy cladding by isothermal heating of irradiated PHWR fuel pins in temperature range 700°C–900°C

Fuel pins removed from actual irradiated fuel bundles discharged from Pressurised Heavy Water Reactors (PHWRs) have been used for experimental study of high temperature creep deformation as functions of cladding temperature and internal fission gas pressure. Experiment consisted of localized heating of 100 mm long segment of the fuel pins in a furnace in inert atmosphere at temperatures 700°C, 800°C, 850°C and 900°C for 10–15 minutes. The internal pressure and the total void volume in the fuel pins were estimated by puncture test on sibling pins from the same fuel bundle. After the heating experiment the diameter of the pin along the length was measured to obtain the diameter increase due to high temperature creep. Analysis of the experimental data for fuel pins with internal pressure 0.55 ± 0.05 MPa, provided the following empirical correlation for creep rate of the cladding as a function of temperature Creep rate (s^?1) = 2.23 × 10¹⁰ × exp (?305500/RT), for temperatures in the range of 800°C–900°C, where, R is gas constant, 8.314 J/mol K and T is temperature in K. For fuel pins with different internal fission gas pressures, the correlation obtained for the cladding strain as a function of internal pressure (at room temperature) was $$ \begin{gathered} Cladding strain = 118.22 \times 10^{ - 3} exp (0.53P), for temperature = 900^\circ C \hfill \\ where, P is the internal pressure in MPa at room temperature. \hfill \\ \end{gathered} $$ This paper presents the details of the experiment and the results.