The Experts below are selected from a list of 219 Experts worldwide ranked by ideXlab platform
Yukio Hinatsu - One of the best experts on this subject based on the ideXlab platform.
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Magnetic susceptibilities of YyU1−yO2+x Solid Solutions
Journal of Solid State Chemistry, 1991Co-Authors: Yukio HinatsuAbstract:Abstract Magnetic susceptibilities of CayU1−yO2+x Solid Solutions with fluorite structure were measured from 4.2 K to room temperature. An antiferromagnetic transition was observed for all the Solid Solutions examined in this study (y ɤ 0.33). The Ne´el temperature of the oxygen-hypostoichiometric Solid Solutions (x 0) did not change appreciably with calcium concentrations. From the comparison of the magnetic susceptibility data of the hypostoichiometric Solid Solutions with those of the hyperstoichiometric Solid Solutions, the effect of oxygen vacancies is more significant than that of interstitial oxygens on the decrease of magnetic interactions between uranium ions.
Frank S. Stone - One of the best experts on this subject based on the ideXlab platform.
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Oxide Solid Solutions as catalysts
Advances in Catalysis, 2002Co-Authors: Alessandro Cimino, Frank S. StoneAbstract:Abstract This review traces the development of oxide Solid Solutions as catalysts from their first use in the 1960s to their current application in basic and applied research. Oxide Solid Solutions provide the means to control the properties of catalytically active ions in defined surface environments. When applied to transition metal (TM) ions, interaction with neighbors can be suppressed or progressively developed, depending on the concentration chosen for the active solute and the structure of the insulating matrix selected as solvent oxide. Simple examples are nickel, cobalt and chromium ions in MgO and MgAl 2 O 4 . The successful preparation of Solid Solutions demands a knowledge of the reactivity of Solids and the behavior of crystal defects. This is exemplified in the methods described for preparing Solid Solutions of low and high specific surface area, respectively. Characterization receives detailed attention and the methods specific to oxide Solid Solutions are illustrated. Emphasis is placed on quantitative determination of surface composition for which X-ray photo-electron spectroscopy is the most widely applicable technique. The acidity and basicity of oxide Solid solution surfaces is linked with coordinative unsaturation and this aspect of characterization involves adsorption calorimetry and infra-red spectroscopy. The account of oxide Solid Solutions as catalysts is divided into two parts. The first comprises studies where Solid Solutions have been used as model catalysts to identify and compare the catalytic properties of individual TM ions. For this purpose the catalysis of N 2 0 decomposition, CO oxidation and H 2 D 2 equilibration have long served as prototypical test reactions. These simple reactions enable issues such as the distinctive behavior of isolated ions, pairs and chains to be addressed and matrix effects to be explored. The motivation here is detailed understanding of catalysis on highly characterized microcrystalline oxides. The second catalytic part is broader in scope and focuses to a greater extent on the application of oxide Solid Solutions as catalysts for reactions of industrial interest. Combustion of hydrocarbons is a high-temperature reaction for which perovskite-structured Solid solution catalysts are especially attractive since they accommodate a wide range of TM and main group ions in Solid solution. A second sector covered is selective oxidation of hydrocarbons. Oxide Solid Solutions containing TM ions made an early entry as catalysts for alkene conversion and remained when interest switched to alkanes. The Solid solution approach featured strongly in the search for methane coupling catalysts and currently contributes in a new guise in titanium silicalite. The acidity developed at solute sites is the source of activity for carbenium ion catalysis. SAPOs and McAPOs fall within the Solid solution domain as covalently-bonded counterparts of ionic Solid Solutions. Finally, reduced Solid Solutions with phase-separated transition metal clusters are effective catalysts for reforming of alkanes.
Alessandro Cimino - One of the best experts on this subject based on the ideXlab platform.
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Oxide Solid Solutions as catalysts
Advances in Catalysis, 2002Co-Authors: Alessandro Cimino, Frank S. StoneAbstract:Abstract This review traces the development of oxide Solid Solutions as catalysts from their first use in the 1960s to their current application in basic and applied research. Oxide Solid Solutions provide the means to control the properties of catalytically active ions in defined surface environments. When applied to transition metal (TM) ions, interaction with neighbors can be suppressed or progressively developed, depending on the concentration chosen for the active solute and the structure of the insulating matrix selected as solvent oxide. Simple examples are nickel, cobalt and chromium ions in MgO and MgAl 2 O 4 . The successful preparation of Solid Solutions demands a knowledge of the reactivity of Solids and the behavior of crystal defects. This is exemplified in the methods described for preparing Solid Solutions of low and high specific surface area, respectively. Characterization receives detailed attention and the methods specific to oxide Solid Solutions are illustrated. Emphasis is placed on quantitative determination of surface composition for which X-ray photo-electron spectroscopy is the most widely applicable technique. The acidity and basicity of oxide Solid solution surfaces is linked with coordinative unsaturation and this aspect of characterization involves adsorption calorimetry and infra-red spectroscopy. The account of oxide Solid Solutions as catalysts is divided into two parts. The first comprises studies where Solid Solutions have been used as model catalysts to identify and compare the catalytic properties of individual TM ions. For this purpose the catalysis of N 2 0 decomposition, CO oxidation and H 2 D 2 equilibration have long served as prototypical test reactions. These simple reactions enable issues such as the distinctive behavior of isolated ions, pairs and chains to be addressed and matrix effects to be explored. The motivation here is detailed understanding of catalysis on highly characterized microcrystalline oxides. The second catalytic part is broader in scope and focuses to a greater extent on the application of oxide Solid Solutions as catalysts for reactions of industrial interest. Combustion of hydrocarbons is a high-temperature reaction for which perovskite-structured Solid solution catalysts are especially attractive since they accommodate a wide range of TM and main group ions in Solid solution. A second sector covered is selective oxidation of hydrocarbons. Oxide Solid Solutions containing TM ions made an early entry as catalysts for alkene conversion and remained when interest switched to alkanes. The Solid solution approach featured strongly in the search for methane coupling catalysts and currently contributes in a new guise in titanium silicalite. The acidity developed at solute sites is the source of activity for carbenium ion catalysis. SAPOs and McAPOs fall within the Solid solution domain as covalently-bonded counterparts of ionic Solid Solutions. Finally, reduced Solid Solutions with phase-separated transition metal clusters are effective catalysts for reforming of alkanes.
S N Zhevnenko - One of the best experts on this subject based on the ideXlab platform.
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Surface phase transitions in cu-based Solid Solutions
Applied Surface Science, 2017Co-Authors: S N Zhevnenko, S.v. ChernyshikhinAbstract:Abstract We have measured surface energy in two-component Cu-based systems in H2 + Ar gas atmosphere. The experiments on Solid Cu [Ag] and Cu [Co] Solutions show presence of phase transitions on the surfaces. Isotherms of the surface energy have singularities (the minimum in the case of copper Solid Solutions with silver and the maximum in the case of Solid Solutions with cobalt). In both cases, the surface phase transitions cause deficiency of surface miscibility: formation of a monolayer (multilayer) (Cu-Ag) or of nanoscale particles (Cu-Co). At the same time, according to the volume phase diagrams, the concentration and temperature of the surface phase transitions correspond to the Solid solution within the volume. The method permits determining the rate of diffusional creep in addition to the surface energy. The temperature and concentration dependence of the Solid Solutions’ viscosity coefficient supports the fact of the surface phase transitions and provides insights into the diffusion properties of the transforming surfaces.
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diffusional creep in cu fe Solid Solutions
Journal of Alloys and Compounds, 2014Co-Authors: S N ZhevnenkoAbstract:Abstract The activation energy of diffusional creep in copper–iron Solid Solutions was studied. Experiments were performed on foil samples in an atmosphere of dry hydrogen in a temperature range from about 1170–1340 K. The foils had a thickness of 1.8 × 10 −5 m and a length of about 0.15 m. The stress range was from 0 to 300 kPa. The method of the measurements was developed in our previous work and it was based on measuring the time dependence of stress on a sample. The viscosity of the Solid Solutions was higher than that for pure copper. It was shown that there is a gap on temperature dependences of viscosity. The temperature of the gap was about 1295 K. Our previous experiments on the Cu–Co system showed the same feature in the activation energies. As previously shown, two processes are required for describing the diffusional creep. They are the volume diffusion and generation/annihilation of the vacancies. The processes occur in sequence. We assume that only second type processes could lead to the appearance of the gap on the temperature dependence of viscosity in Solid Solutions.
T. G. Aminov - One of the best experts on this subject based on the ideXlab platform.
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Paramagnetism of Fe_x(Cu_0.5In_0.5)_1_– xCr_2S_4 Solid Solutions
Inorganic Materials, 2020Co-Authors: T. G. Aminov, G. G. Shabunina, E. V. Busheva, N. N. EfimovAbstract:— We have synthesized Fe_ x (Cu_0.5In_0.5)_1 _ – x Cr_2S_4 Solid Solutions and measured their magnetic properties in the temperature range 4.2–300 K in a static magnetic field of 0.1 and 45 kOe. The main magnetostatic parameters of the synthesized materials have been determined: saturation magnetization, effective and spin magnetic moments, Curie and Néel temperatures, Curie constants, and Curie–Weiss constants. The results thus obtained, including the properties of magnetic clusters and the composition dependence of the asymptotic Curie temperature, have been interpreted using a previously reported magnetic phase diagram of the Fe_ x (Cu_0.5In_0.5)_1 _ – x Cr_2S_4 Solid Solutions, which provides insight into the nature of the phase transformations involved.
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Magnetic phase diagram of Solid Solutions in the CoCr2S4–Cu0.5In0.5Cr2S4 system
Inorganic Materials, 2016Co-Authors: T. G. Aminov, G. G. Shabunina, E. V. Busheva, Vladimir M. NovotortsevAbstract:The magnetic properties of CoCr2S4–Cu0.5In0.5Cr2S4 Solid Solutions have been studied in the temperature range 5–300 K at different ac magnetic field frequencies (100, 500, and 1000 Hz) and an amplitude of 79.6 A/m. We have determined the temperatures of the magnetic transformations in the system, identified their nature, and constructed the magnetic phase diagram of the Solid Solutions.
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Magnetic properties of Cu_0.5Fe_0.5Cr_2S_4-based Solid Solutions
Inorganic Materials, 2012Co-Authors: T. G. Aminov, G. G. Shabunina, D. I. Kirdyankin, Vladimir M. NovotortsevAbstract:Different models are used to analyze the magnetic properties of Solid Solutions of the Cu_0.5Fe_0.5Cr_2S_4 ferrimagnet in the ZnCr_2S_4, Cu_0.5In_0.5Cr_2S_4, and Cu_0.5Ga_0.5Cr_2S_4 antiferromagnets. The composition dependences of the saturation magnetic moment and Curie temperature for the Solid Solutions are determined.
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Magnetic properties of Cu0.5Fe0.5Cr2S4-based Solid Solutions
Inorganic Materials, 2012Co-Authors: T. G. Aminov, G. G. Shabunina, D. I. Kirdyankin, Vladimir M. NovotortsevAbstract:Different models are used to analyze the magnetic properties of Solid Solutions of the Cu0.5Fe0.5Cr2S4 ferrimagnet in the ZnCr2S4, Cu0.5In0.5Cr2S4, and Cu0.5Ga0.5Cr2S4 antiferromagnets. The composition dependences of the saturation magnetic moment and Curie temperature for the Solid Solutions are determined.
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CuCr2-xSbxS4 and Cu1-ySbyCr2S4 Solid Solutions
Inorganic Materials, 2000Co-Authors: T. G. Aminov, E. V. Busheva, T. I. Arbuzova, G. G. ShabuninaAbstract:CuCr2–ySbxS4 and Cu1–ySbyCr2S4 Solid Solutions with the spinel structure were synthesized, and their magnetic and electrical properties were studied. The limits of Solid Solutions in these systems were found to bex = 0.5 andy = 0.22. Models of the cation distributions in the Solid Solutions are proposed. The CuCr2-xSbxS4 Solid Solutions with 0.10
