Atomic Force Microscopy (AFM) measurements have been performed for Fe doped SrTiO 3 thin films with an Fe concentration of 2 and 5 at%. Thin films with a thickness of about 20 nm were grown by pulsed laser deposition on single crystalline SrTi 0.99 Nb 0.01 O 3 substrates. Low-energy electron diffraction examination showed that the films are single crystalline. The regions treated with the AFM tip (applied dc voltage up to 6V) showed inhomogeneity of the electrical conductivity.
In the current work, we report on the synthesizing of a series of novel nanocomposite materials obtained by functionalizing the SBA-15 silica matrix with anchored iron phosphonate molecules and the following thermal treatment. The obtained results reveal the formation of a unique amorphic layer of Fe-based compounds on the surface of silica walls of SBA-15 channels as a result of the organic groups' decomposition after moderate thermal treatment. Due to their unique structure, represented in an active Fe-containing amorphous coating spread over a large surface area, these materials are of great interest for their potential applications in fields such as catalysis, adsorption, and non-linear optics. The obtained materials remain amorphous, preserving the SBA-15 mesoporous structure up to temperatures of approximately 800 °C, after which the partial melting of the silica backbone is observed with the simultaneous formation of nanocrystals inside the newly-formed glassy mass. All obtained materials were characterized using such techniques as thermogravimetry, transmission and scanning electron microscopy combined with energy dispersive x-ray spectroscopy mapping, Raman spectroscopy, N2sorption analysis, x-ray diffraction, x-ray photoelectron spectroscopy, Mössbauer spectroscopy, and SQUID measurements.
A series of NaNbO 3 : x Mn single crystals had been obtained by flux method. Manganese oxide was introduced to obtain nominal Mn content within 10%mol. Real concentration of Mn dopant was determined as one order lower. It was concluded from valence band analysis that Mn ions built in niobium sublatice mainly. All the samples exhibited discontinuous structural antiferroelectric phase transition proved by DTA test. The phase transition temperature lowers, while the real concentration of Mn increases, with the rate -15 K/%wt (Mn). The X-ray experimental spectrum remains in agreement with the spectrum generated for perovskite NaNbO 3 when orthorhombic Pbcm space group was chosen for simulation. The evolution of lattice constant with Mn concentration was examined.
Graphenic materials have been produced from thermally treated highly metamorphosed carbon material – anthracite using two different methods: (1) the improved Hummers method followed by thermal reduction and (2) cycloaddition of azomethine ylide. Distinct differences were found between both anthracite-derived graphenic materials. The oxidation Hummers process resulted in a wide variety of oxygen functional groups incorporated into the carbon layers, while subsequent thermal reduction caused separation of graphene sheets but reduced the oxygen moieties. The cycloaddition of azometine ylide led to the formation of functionalized graphene sheets containing mostly 3,4-bonded N-methyl-2-(3,4-dihydroxyphenyl)pyrrolidine groups. The first attempts of application of anthracite-derived fillers to epoxy composites showed the improvement of their mechanical and viscoelastic properties, comparable to composites with graphene nanofillers.
The main aim of this work was to use the iron-iron oxide nanochains (Fe NCs) as adsorbents of the carcinogenic cationic crystal violet (CV) and anionic Congo red (CR) dyes from water. The investigated adsorbent was prepared by a magnetic-field-induced reduction reaction, and it revealed a typical core-shell structure. It was composed of an iron core covered by a thin Fe3O4 shell (<4 nm). The adsorption measurements conducted with UV-vis spectroscopy revealed that 15 mg of Fe NCs constituted an efficient dose to be used in the CV and CR treatment. The highest effectiveness of CV and CR removal was found for a contact time of 90 min at pH 7 and 150 min at pH 8, respectively. Kinetic studies indicated that the adsorption followed the pseudo-first-order kinetic model. The adsorption process followed the Temkin model for both dyes taking into account the highest value of the R2 coefficient, whereas in the case of CR, the Redlich-Peterson model could be also considered. The maximal adsorption capacity estimated from the Langmuir isotherms for the CV and CR was 778.47 and 348.46 mg g-1, respectively. Based on the Freundlich model, both dyes adsorbed on the Fe NCs through chemisorption, but Coulombic interactions between the dye and adsorbent cannot be excluded in the case of the CV dye. The obtained results proved that the investigated Fe NCs had an excellent adsorption ability for both dye molecules within five cycles of adsorption/desorption, and therefore, they can be considered as a promising material for water purification and environmental applications.
Synthesis of high-surface-area graphene oxide for application in next-generation devices is still challenging. In this study, we present a simple and green-chemistry procedure for the synthesis of oxygen-enriched graphene materials, having very large surface areas compared with those reported for powdered graphene-related solids. Using the hydrothermal treatment of carbon nanohorns by a green-chemistry H2O2 oxidant under elevated pressure, the progressive creation of a stable carbon nanomaterial, denoted as open-sensu-shaped graphene oxide (OSSGO) by us, is observed. This oxygen-enriched nanographene contains π–π stacked few-layered graphene ribbons curved at the termini derived from the original cone tip. OSSGO is intensively analyzed and cross-characterized by spectroscopy, diffraction, adsorption, and elemental analysis methods. Based on the obtained results, we propose a mechanism of transformation from horns to a structure with several layers of sensu-form stacked graphene oxide. As this transformation process proceeds gradually, one can obtain numerous transition nanoarchitectures of tunable morphology and surface physicochemistry, including materials with an extremely high surface area. As OSSGO bears a fraction of the electron-withdrawing and O–H acidic functionalities, electrochemical studies, especially galvanostatic charge–discharge curves and specific capacitance values (significantly higher than those for other carbon-based materials), show potential applications in next-generation supercapacitors. As a result of the large surface areas, we also predict future applications in programmable adsorbents and catalysts with broad-range activity, while the list of applications is incomplete.
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