Structural transformations in nanoglobular carbon under the action of pulsed high-energy-density electron beam

Exposure of globular (T-900 technical grade) carbon black to submillisecond pulsed electron beam with an energy density of ??40 J/cm² leads to clearly manifested structural transformations of carbon with the formation of highly ordered graphite-like structure and original morphology, as evidenced by the data of high-resolution transmission electron microscopy.     

Synthesis of metal–carbon nanocomposites containing nanoparticles of transition metals encapsulated in a graphite-like shell

It was shown that methane decomposition on metal–carbon nanocomposites with transition metal (Co, Fe, and Ni) nanoparticles distributed in the bulk of the amorphous carbon matrix leads to carbon deposition with the formation of a graphite-like shell around a metal core. The resulting “core-shell” structures have a diameter of 10–40 nm and contain up to 50 graphene layers with an interlayer distance of 0.34–0.35 nm. For the synthesis of the initial metal–carbon nanocomposites, a method that we proposed earlier was used, which involves low-temperature formation of carbon structures from carbon-chain chloropolymers based on their dehydrochlorination with the formation of polyvinylenes as reactive carbon precursors.     

Structure and composition of aluminum oxide films in contact with the liquid In-Ga eutectic

The oxide layers on the surface of aluminum metal and the aluminum alloys AD-1 and A-5 have been studied by attenuated total reflection infrared spectroscopy. The Al-O and Al-OH surface vibrational modes and A-O modes of the AlO₄ and AlO₆ groups have been identified. The structural inhomogeneity of the surface oxide layers is shown to contribute to their disruption when the sample is brought into contact with the liquid In-Ga eutectic. In situ scanning electron microscopy and X-ray microanalysis have been used to follow the dynamics of oxide layer disruption and the morphological and compositional changes in the eutectic alloy and the surface layer of aluminum.     

Pd/Fiber glass and Pd/5% γ-Al2O3/Fiber glass catalysts by surface self-propagating thermal synthesis

The technique of Surface Self-propagating Thermal Synthesis (SSTS) was used to prepare Pd/??-Al₂O₃/fiber glass (FG) catalysts for selective liquid-phase hydrogenation of acetylene in the presence of CO. The results of XRD SR analysis (in synchrotron radiation) in combination with the technique of arrested combustion shed new light on the dynamic of phase transformations in the systems under study and variation in the size of diffraction-active crystallites. The catalytic performance of synthesized catalysts was found to be close to that of similar conventionally prepared catalysts. The EXAFS and TEM data afforded to estimate the variation in relative amounts of Pd⁰ and PdO in synthesized catalysts. In the course of selective hydrogenation, PdO rapidly (<15 min) reduced to Pd⁰.     

Chemical interaction of the In-Ga eutectic with Al and Al-base alloys

The chemical interaction of the indium-gallium eutectic with Al and Al-base alloys is studied by x-ray diffraction, optical microscopy, and electron microscopy. Experimental data are presented that shed light on the reaction mechanism and the diffusion processes responsible for the subsequent disintegration of the material and its dissolution in water. Mechanical tests show that the activation of aluminum leads to a transition from plastic to brittle fracture.     

Possibilities of Regulating the Texture Parameters of Porous Carbon Materials Obtained by Alkaline Dehydrochlorination of Polyvinyl Chloride with Subsequent Heat Treatment of Forming Polyvinylenes

Protection of Metals and Physical Chemistry of Surfaces - Synthesis of porous carbon materials has been carried out in two ways—by chemical and mechanochemical dehydrochlorination of...     

Transmission electron microscopy application for the analysis of carbon black and metal-carbon nanostructures

Abstract

The article presents the analytical possibilities of the combined use of transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS) methods to study of carbon black and metal-carbon nanostructures. Platinum nanoparticles were shown to be formed on the carbon polyhedral structures and nanocapsules as a result of laser exposure to the carbon black suspensions in H₂PtCl₆ aqueous solution. Phase composition of nickel-carbon and cobalt-carbon core-shell structures was identified.     

Synthesis and study of electrochemical properties of nanocomposites with graphene-like particles integrated into a high-porosity carbon matrix

Carbon–carbon nanocomposite (CCNC) was synthesized by introducing a dispersion of reduced graphite oxide (RGO) into the reaction medium upon the synthesis of polymer with a conjugated bond system (polyvinylene), which is a product of alkaline dehydrochlorination of polyvinylchloride, followed by carbonization of the resulting adduct–RGO-polyvinylene. After activation of CCNC in the CO₂ environment (900°С) a high-porosity material (the specific BET surface is more than 1700 m²/g) with a developed volume of micro- and mesopores was obtained. According to electrochemical investigations, this material possesses a large capacity (100–200 F/g) and high performance, and, therefore, it can be applied in supercapacitor traction systems and for load leveling in electric power lines.     

Synthesis and characterization of massive molybdenum carbides and supported carbide-containing catalysts Mo2C/C prepared through mechanical activation

Procedures for the synthesis of massive molybdenum carbide by the mechanical activation of a mixture of MoO₃, commercial carbon, and Zn in air and the synthesis of the supported carbide-containing catalyst Mo₂C/C by the mechanical activation of commercial carbon impregnated with a 16% aqueous solution of ammonium paramolybdate in an inert atmosphere were developed for the first time. With the use of a set of physicochemical methods, the metal contents, particle sizes, specific surface areas, and phase compositions of the mechanically activated composites were determined. The structure of the carbide-containing supported catalyst was studied by electron microscopy, and its acidic properties were studied by the temperature-programmed desorption of ammonia; catalytic tests in the model reactions of dibenzothiophene (DBT) and alkane aromatization were performed. It was found that the Mo₂C/C catalyst exhibited high activity in these reactions: the conversion of DBT at a contact time of 3–6 h was 80–85%. The conversion of n-heptane at a contact time of 2 h was 31.2%, and 100% toluene was the reaction product. An increase in the contact time to 6 h led to a decrease in the conversion of n-heptane to 1.3%, and to 47% C₆-C₇ cycloalkanes were present in the reaction products. The results of this work are indicative of the high catalytic activity of the Mo₂C/C catalyst obtained by mechanical activation.     

Effect of thermal pretreatment on porous structure of asphalt-based carbon

The effect of thermal pretreatment on the porous structure and adsorption properties of asphalt-based carbons activated with potassium hydroxide was investigated by FTIR, Raman spectroscopy, TEM, N₂ and CO₂ adsorption. Two series of the activated carbons were prepared by a one-stage method using KOH as the activating agent and a two-stage method including pretreatment of asphalt at 450 °C. A cross-effect of the KOH/asphalt ratio and pretreatment conditions on the characteristics of the porous structure of the activated carbons was revealed. The pretreatment of asphalt before activation is demonstrated to be a necessary stage for the effective control of the carbon porous structure by variation the KOH/asphalt ratio from 2 to 4. The porous carbon derived from petroleum asphalt exhibited the high CO₂ adsorption capacity of 3.8 mmol/g at 25 °C and 1 atm and good selectivity for CO₂ over N₂, indicating possible applications in CO₂ capture technology.

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