Metal Carbon Nanoparticles Research Articles

A Composite Magnetosensitive Sorbent Based on the Expanded Graphite for the Clean-Up of Oil Spills: Synthesis and Structural Properties

Oil spills necessitate the development of effective methods for preventing their damaging effects on the environment. A number of physical, chemical, thermal, and biological methods are used to combat oil spills. Among them, sorption is considered to be efficient in removing thin oil films from water surfaces. Currently, there is an urgent need for simple methods of obtaining oil sorbents that include a magnetosensitive component to optimize the process of removing oil from the water surface. The purpose of the work is to obtain and research oil sorbents resistant to destruction, with increased bulk density and complex magnetosensitivity, based on thermally expanded graphite (TEG) with the inclusion of micro- and nano-particles of iron and its oxides. The structure and composition of the new composite material was characterized using scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffractometry, thermogravimetric analysis, and laser diffraction particle sizing. The composite sorbent comprised TEG with the inclusion of iron-containing magnetosensitive particles. Metal-carbon nanoparticles (MCN) were used as the magnetosensitive component; they had a magnetosensitive iron core covered with a carbon shell. We used two methods of synthesis, namely (i) mechanical mixing of the TEG flakes and MCN particles, and (ii) applying a thermal shock (microwave processing) to the mixture of graphite intercalated with sulphuric acid and micro- and nanoparticles of iron and iron oxides. In the first case, MCN particles were fixed on the faces, edges, and other surface defects of the TEG flakes due to intermolecular forces, coordinate bonds, and electrostatic interaction. The strong adhesion of magnetosensitive iron/iron oxide and TEG particles in the second case was due to the mutual dissolution of iron and carbon components during the thermal shock, which formed an interfacial layer in which iron carbide is present. The presence of magnetosensitive components in the structure of the proposed oil sorbents allows the use of magnetic separation for the localization and removal of oil spills, increases the density of sorbents, and, accordingly, leads to a decrease in windage while retaining the advantageous properties of thermally expanded graphite. According to the results of laboratory studies, the efficiency of removing oil from the water surface is not lower than 95–96%.

Catalytic Growth of a Graphite-Like Shell on Transition Metal Nanoparticles with the Formation of Core–Shell Structures

Methods for the production of metal–carbon nanoparticles of the core–shell type based on the formation of transition metal nanoparticles and a graphite-like shell on their surface containing to 50 graphene layers are considered. Various types of high-energy impacts or thermal transformations under exposure in a temperature range of 600–850°С were used for the synthesis of metal–carbon nanoparticles from initial metal- and carbon-containing components. Due to their unique properties, nanoparticles of this kind can be of interest as highly efficient catalysts, targeted drug carriers, contrasts in MRI diagnostics, and an element base of electronic and magnetic devices.

Obtaining of composite metal-carbon nanoparticles by magnetron sputtering

Nanocomposites represent a new generation of new materials that are formed by mixing one or more dissimilar materials at the nanoscale to control and develop new and improved structures, as well as properties. In this work, metal-carbon nanoparticles were synthesized by magnetron sputtering at different direct current values. During the experimental work, the working gas pressure varied from 0.5 to 1.5 torr, and the gas discharge current from 0.2 to 0.6 A. The dependence of the size of the synthesized nanoparticles on the gas pressure in the volume was also experimentally determined. It was found that with a change in gas pressure and gas flow, the size of the nanoparticles and their concentration changes. An SEM image and the chemical composition of the samples were obtained, and a particle size distribution was constructed. The SEM image shows that the sizes of carbon-copper nanoparticles obtained at various parameters of the magnetron discharge vary in the range of 36–250 nm.

Obtaining of composite metal-carbon nanoparticles in complex plasma

Composite metal-carbon nanoparticles attract great attention as a subject of research because of their well-known properties, such as good conductivity, antibacterial and catalytic effects, etc. There are various methods for obtaining composite metal-carbon nanoparticles, chemical, electrochemical, sonochemical, etc. In this work, a combined RF and magnetron discharge was used to obtain composite metal-carbon nanoparticles. According to the results of the experiments, it was found that an increase in the discharge current of the magnetron leads to an increase in the size of carbon-copper composite nanoparticles, as well as an increase in the thickness of nanostructured films. For the synthesis of composite carbon-copper nanoparticles, an argon-methane gas mixture (10%) was used. It was determined that increasing the gas pressure in the volume leads to a decrease in the size of the nanoparticles.

Regularities in the Formation of Metal-Carbon Nanoparticles during Pyrolysis and Photolysis of Gaseous Compaunds

Regularities in the Formation of Metal-Carbon Nanoparticles during Pyrolysis and Photolysis of Gaseous Compaunds

UV laser synthesis of nanoparticles in the gas phase

This review deals with the UV laser photodissociation of metal carbonyls, ferrocene, carbon suboxide, and other precursors. The formation of supersaturated atomic vapors followed by the formation of carbon, metal, and metal–carbon nanoparticles is discussed. Application of UV laser synthesis to preparation of catalytic nanomaterials is considered.

Electronic structure and stability of metal–carbon nanoparticles with Cr, Mn, Fe and W impurities

Theoretical modeling of the effect of Cr, Mn and W atoms substituting iron sites on the electronic structure of the most stable isomers of some FexCy clusters as well as of the fragments of Fe3C and M23C6 (M=Cr, Mn, Fe, W) crystal carbides lattice was carried out using the DFT based Dmol3 method. Our calculations predict the most preferable impurity positions, magnetic moments on metal atoms as well as the stability of binary and ternary clusters. We demonstrated that in the cases of systems containing 3d-atoms the interactions between M4s, 4p and C2p orbitals correlate with the variation of stability, whereas for the W–C bonding this correlation was obtained for the interaction between W5d and C2p states.

Synthesis of metal-carbon nanoparticles in pulsed UV-photolysis of Fe(CO)5-CCl4 mixtures at room temperature

Synthesis of iron-carbon nanoparticles in joint photolysis of iron pentacarbonyl (Fe(CO)5) and carbon tetrachloride (CCl4) has been studied. When mixtures containing iron pentacarbonyl and CCl4 are exposed to UV light, Fe(CO)5 molecules decompose to yield an atomic vapor of iron with well-known and easily controlled parameters, whereas CCl4 molecules decompose to give CCl3 radicals. A pulsed Nd:YAG laser (fourth harmonic, 266 nm) served as a source of light. The growth process of nanoparticles in condensation of supersaturated vapors was monitored by the laser extinction method; nanoparticle samples were examined with an atomic-force microscope. It was found that the concentration of the CCl4 additive affects the manner in which the optical properties of nanoparticles synthesized in a binary mixture change relative to the properties of nanoparticles synthesized in photolysis of pure Fe(CO)5, which indicates that a carbon shell grows on the surface of iron nanoparticles.

The influence of Fe, Cu, SiO2, TiO2, and Al2O3 nanoparticles in aqueous solution on proton relaxation times

Measurements of proton nuclear spin-spin and spin-lattice relaxation times are applied for determining the concentration of solid-phase nanoparticles in nanofluids. This approach is tested for metal oxides SiO2, TiO2, Al2O3 and metal-carbon nanoparticles of 3d-metals Fe and Cu. It is shown that the sensitivity of the method for determining concentrations of 3d-metals is much higher than for oxides (by 2–4 orders of magnitude). It is revealed that measurement of the proton spin-spin relaxation time allows one to determine the concentration of Cu nanoparticles to 0.0001 mg/ml and that of Fe nanoparticles to 0.00001 mg/ml.

Electronic Structure, Chemical Bonding, and Properties of Binary Carbides M x M′ y C z in the Crystalline and Molecular States: XES, XPS, and Quantum-Chemical Studies

This paper reviews the results of electronic structure studies and investigations of the nature of chemical bonding and properties of binary d-metal carbides in the crystalline and molecular states. X-ray emission and X-ray photoelectron spectroscopy as well as quantum-chemical data are analyzed, and variations of the electronic properties and interatomic interactions are discussed for carbides of high-melting metals doped on the metal sublattice and a series of their reciprocal solid solutions: NbC–TaC, TiC–VC0.87, TiC–NbC, and NbC–MoC0.67 over a wide range of compositions. Prospects are discussed for application of quantum-chemical methods to structure and property modeling and forecasting for a new class of molecular clusters — binary metallocarbohedrenes M8-n M′n C12 and related metal–carbon nanoparticles of “mixed” composition.