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The results obtained from the multi-analytic compositional characterization of ceramic pastes and paints of the Santa María style, from the El Bolsón valley (Belén Department, Catamarca Province, Argentina), are presented here. This... more
The results obtained from the multi-analytic compositional characterization of ceramic pastes and paints of the Santa María style, from the El Bolsón valley (Belén Department, Catamarca Province, Argentina), are presented here. This pottery style had a wide regional distribution in Northwestern Argentina between ca. 1000-1600 AD and is characterized by its complex iconography painted in black, cream and red. The analyses show that the containers correspond to the technical tradition of using grog temper and suggest that its manufacture involved a double firing process. This reveals a new practice for the time.
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Se estudió la síntesis de ferritas de MnZn en tres composiciones diferentes en el sistema MnxZn1-xFe2O4, con x=0,50; 0,65 y 0,85, a partir de las ferritas MnFe2O4 y ZnFe2O4. Con estas espinelas, sintetizadas previamente, se prepararon... more
Se estudió la síntesis de ferritas de MnZn en tres composiciones diferentes en el sistema MnxZn1-xFe2O4, con x=0,50; 0,65 y 0,85, a partir de las ferritas MnFe2O4 y ZnFe2O4. Con estas espinelas, sintetizadas previamente, se prepararon mezclas íntimas que fueron compactadas en forma de pastillas y sometidas a tratamiento térmico a 1100ºC en atmósfera de N2, durante distintos tiempos. Los materiales así obtenidos fueron caracterizados por difracción de rayos x (DRX), análisis térmico diferencial y gravimétrico (ATD/TG), magnetometría de muestra vibrante (VSM) y microscopía electrónica de barrido (SEM). Además se midieron las densidades de las pastillas sinterizadas, para las tres composiciones estudiadas. Se observó la formación de las fases deseadas para cada caso, con densidades entre un 80 y 85% del valor teórico y propiedades magnéticas que superan el 90% de los valores reportados en literatura. Se comparan estos valores con los correspondientes a estas ferritas preparadas por otr...
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ABSTRACT In this study, iron oxide nanoparticles (NPs) were successfully prepared from three different reactive systems by using mechanochemical synthesis. The effect of using iron salts with different oxidation state and the addition of... more
ABSTRACT In this study, iron oxide nanoparticles (NPs) were successfully prepared from three different reactive systems by using mechanochemical synthesis. The effect of using iron salts with different oxidation state and the addition of metallic Fe to the mixture reactive was investigated. The influence of different mechanochemical treatments times on the structural and magnetic properties of the obtained iron oxide NPs was also studied. Composition, crystal structure and morphology of the nanoparticles were analyzed by XRD, Raman spectroscopy, SEM, TEM and DLS techniques. The obtained crystalline NPs exhibited mean sizes of about 8-10 nm and agglomerate in clusters of about 300 nm. Also, magnetic properties as a function of temperature and applied field were determined for the obtained iron oxide NPs, showing high magnetization in the whole temperature range. The results indicated that the presence of metallic Fe in the starting mixture plays a crucial role in the formation of spinel magnetic phases (magnetite/maghemite). Structural and magnetic results are consistent with the formation of maghemite in the studied samples.
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The kinetics of ZnFe{sub 2}O{sub 4} formation starting from mechanochemically activated Zn-Fe{sub 2}O{sub 3} powders are studied. Mixtures of metallic Zn and hematite were activated under air atmosphere in a high energy mill and thermally... more
The kinetics of ZnFe{sub 2}O{sub 4} formation starting from mechanochemically activated Zn-Fe{sub 2}O{sub 3} powders are studied. Mixtures of metallic Zn and hematite were activated under air atmosphere in a high energy mill and thermally treated at temperatures between 500 and 650 deg. C during several holding times. During the activation, morphological and compositional changes were observed, but ZnFe{sub 2}O{sub 4} formation was not detected. The ZnFe{sub 2}O{sub 4} content in heated samples was determined using quantitative X-ray diffraction analysis. The resulting conversion-time curves were fitted using different kinetic models of solid-state reaction, calculating the kinetic parameters of the studied reaction. The comparison with the conventional synthesis method revealed that the mechanochemical treatment provoked a change of the rate-controlling step and a significant decrease of the activation energy, which was more evident for the more activated mixtures.
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Ab initio calculations analyze the properties of the G-type antiferromagnetic Sr2Co2O5 as a high-spin system. The description of the electronic structure is given; all the Co atoms are in a high-spin state with a small unquenched orbital... more
Ab initio calculations analyze the properties of the G-type antiferromagnetic Sr2Co2O5 as a high-spin system. The description of the electronic structure is given; all the Co atoms are in a high-spin state with a small unquenched orbital angular momentum. Thermal analysis on a polycrystalline sample shows a magnetic phase transition at high temperatures.
Research Interests: Condensed Matter Physics, Quantum Physics, Differential scanning calorimetry, First Principles Calculations, High Temperature, and 8 moreElectronic Structure, Thermal Analysis, Enseñanza - Aprendizaje Ciencias Naturales Y Exactas, Ab Initio Calculation, Cobaltates, Ciencias Fisicas, oxygen deficiency, and orbital angular momentum
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Research Interests: Materials Engineering, Mechanical Engineering, Aerospace Engineering, Materials Science, Ingenieria y ciencias de los Materiales, and 10 moreRaw materials, Magnetic Properties, Dielectric Properties, X ray diffraction, Particle Size, Electrical Properties, Epoxy Resin, Elsevier, C. Magnetic Properties, and Polymer Matrix Composite
Research Interests: Engineering, Materials Science, Bioelectromagnetics, Dental Materials, Medicine, and 14 moreBiological Sciences, Humans, Ingenieria y ciencias de los Materiales, Electrical Impedance Spectroscopy, Dentine, Dielectric Properties, Spectrum analysis, Dentin, Enseñanza - Aprendizaje Ciencias Naturales Y Exactas, Psychology and Cognitive Sciences, Restorative Materials, In Vitro Techniques, Ciencias Químicas, and Bicuspid
The physicochemical transformations induced by mechanochemical and thermal treatments of Al–Fe3O4 mixtures under Ar atmosphere have been investigated. This reaction system underwent a self-sustained reaction after 37 min of high-energy... more
The physicochemical transformations induced by mechanochemical and thermal treatments of Al–Fe3O4 mixtures under Ar atmosphere have been investigated. This reaction system underwent a self-sustained reaction after 37 min of high-energy milling, yielding a-Fe and a-Al2O3. The mixtures activated for shorter times showed the same reaction when thermally treated in Ar atmosphere, at approximately 660°C. Depending on the heating conditions, the
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The preparation of ZnFe2O4 from mechanochemically activated reactive mixtures Zn /Fe3O4 is studied. The physicochemical and structural evolution of the system is analyzed by X-ray diffraction, vibrating sample magnetometry, differential... more
The preparation of ZnFe2O4 from mechanochemically activated reactive mixtures Zn /Fe3O4 is studied. The physicochemical and structural evolution of the system is analyzed by X-ray diffraction, vibrating sample magnetometry, differential thermal analysis and scanning electron microscopy. The activated mixtures reacted towards the formation of ZnFe2O4 at lower temperatures than the non-activated ones. In addition, thermal treatments as a function of time revealed a non-expected magnetic behavior of some mixtures. In order to interpret this observation, a qualitative diffusional reaction model is proposed. # 2003 Elsevier B.V. All rights reserved.
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The physicochemical and thermal behavior of mechanochemically activated Al–Fe3O4 mixtures have been studied. The composition and structural changes undergone in the reaction system have been analyzed by DTA and XRD. Experimental evidence... more
The physicochemical and thermal behavior of mechanochemically activated Al–Fe3O4 mixtures have been studied. The composition and structural changes undergone in the reaction system have been analyzed by DTA and XRD. Experimental evidence indicates that the nature of the products was dependent on the conditions of mechanochemical and thermal treatments. Under adequate experimental conditions, a self-sustained reaction was triggered, with the production of α-Fe and α-Al2O3. By varying the treatment parameters, it was possible, through an alternative reaction path, to obtain different products which show interesting properties in their application as functional materials.
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The influence of mechanochemical treatment on the synthesis and properties of YxLa1−xFeO3 (0≤x≤1) orthoferrites is studied. Solid mixtures of the corresponding metal oxides were treated in a high-energy ball-mill. X-ray diffraction... more
The influence of mechanochemical treatment on the synthesis and properties of YxLa1−xFeO3 (0≤x≤1) orthoferrites is studied. Solid mixtures of the corresponding metal oxides were treated in a high-energy ball-mill. X-ray diffraction revealed that during the milling the disappearance of the reactants and a fast conversion to orthoferrite phase take place. Magnetic measurements showed a weak ferromagnetic behavior of the obtained
The solid state reaction between Al and Fe3O4 (magnetite) using mechanochemical activation of powder mixtures under Ar atmosphere is studied. The phase evolution during the reaction is analyzed by X-ray diffraction (XRD), vibrating sample... more
The solid state reaction between Al and Fe3O4 (magnetite) using mechanochemical activation of powder mixtures under Ar atmosphere is studied. The phase evolution during the reaction is analyzed by X-ray diffraction (XRD), vibrating sample magnetometry (VSM), differential thermal analysis (DTA) and scanning electron microscopy (SEM). At 37 minutes of high-energy ball-milling the disappearance of reactive phases and the production of
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The synthesis of the orthoferrite LaFeO3 using high-energy ball-milling of La2O3 and Fe3O4 or α-Fe2O3 oxides and subsequent thermal treatments of resulting powders was studied. The phase evolution during the mechanical treatment was... more
The synthesis of the orthoferrite LaFeO3 using high-energy ball-milling of La2O3 and Fe3O4 or α-Fe2O3 oxides and subsequent thermal treatments of resulting powders was studied. The phase evolution during the mechanical treatment was analyzed by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM). Also, magnetic properties of the obtained materials were measured at room temperature by
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The mechanochemical effects on the reactivity and properties of a titanium/hematite powder mixture with molar ratio of 1/2 are investigated. Crystalline-phase structure, composition, hyperfine and magnetic behaviors were analyzed as a... more
The mechanochemical effects on the reactivity and properties of a titanium/hematite powder mixture with molar ratio of 1/2 are investigated. Crystalline-phase structure, composition, hyperfine and magnetic behaviors were analyzed as a function of activation time by means of X-ray diffraction, scanning electron microscopy, Mössbauer spectroscopy and vibrating sample magnetometry. The results showed that at relatively short activation times metallic Ti
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The dielectric response of polycrystalline La0.5Ca0.5MnO3 as a function of frequency and temperature was studied. The semiconducting nature of this oxide gave rise to very high dielectric constant values, which were mainly attributed to... more
The dielectric response of polycrystalline La0.5Ca0.5MnO3 as a function of frequency and temperature was studied. The semiconducting nature of this oxide gave rise to very high dielectric constant values, which were mainly attributed to interfacial polarization (grain boundaries and contacts sample-electrode). However, an increase of the permittivity at temperatures close to a magnetic phase transition suggests the contribution of intrinsic
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Polycrystalline Y0.5La0.5FeO3 powder was synthesized by mechanochemical activation of Fe3O4–La2O3–Y2O3 reactive mixtures. X-ray diffraction was used to follow the evolution of the formation of this orthoferrite. Peaks corresponding to... more
Polycrystalline Y0.5La0.5FeO3 powder was synthesized by mechanochemical activation of Fe3O4–La2O3–Y2O3 reactive mixtures. X-ray diffraction was used to follow the evolution of the formation of this orthoferrite. Peaks corresponding to reactants were no longer observed after 3h of activation, showing the completion of the reaction after this time. Magnetic hysteresis loops measured at room temperature revealed a gradual decrease of saturation