N. G. Chechenin

Impact of high-energy cosmic-ray protons and ions on the elements of spacecraft on-board devices

The radiation environment in space is reviewed in short as an impact factor affecting onboard spacecraft electronics. The mass and energy distributions of the heavy component of space radiation and the contribution of galactic cosmic rays to the general flux are analyzed during a quiet period in solar activity. The nature of the limitations in the concept of linear energy transfer, including the effects of electronic semiconductor component crystallinity, is discussed. Protective measures against upsets in onboard electronics, caused by cosmic ray ions, are considered.

Technological characteristics of the processes of carbon nanostructure production by the methods of plasma-arc and gas-pyrolytic deposition

The techniques of pyrolytic vapor deposition from acetylene and plasma-arc vacuum deposition of graphite are used to prepare carbon nanotubes (CNTs). Graphite electrodes for plasma-arc deposition are premodified with transition metals by electrochemical deposition from aqueous solutions of their salts. It is shown by SEM and AFM that the structure and morphology of the surface of CNT samples depends on the synthesis technique.

FCC/BCC competition and enhancement of saturation magnetization in nanocrystalline Co-Ni-Fe films

The structure, chemical composition, and magnetic properties of electrochemically deposited nanocrystalline Co-Ni-Fe films were investigated using a number of techniques. A high saturation magnetic induction up to Bs = 21 kG was attained. An enhancement of the saturation magnetization compared to the ideal anticipated one was revealed, which correlated with the nonlinear behavior of the structural phase composition and lattice parameters with the change of the composition.

Functionalized carbon nanotubes based filters for chromium removal from aqueous solutions

This investigation examines the filtration efficiency of chromium from aqueous solution using two types of commercial multiwalled carbon nanotubes (MWCNTs) (Taunit-M (TM) and Taunit-MD (TMD)). These MWCNTs were modified using two complementary treatments, purification (using a mixture of hydrochloric acid and hydrogen peroxide) and functionalization (using nitric acid). The effect of these treatments on the morphology of MWCNT Taunit filters was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy to estimate the outer diameter distribution and element content deposited on filters. Effects of different parameters, i.e., carbon nanotube filter mass, concentration of chromium in aqueous solution, and pH of aqueous solution, on removal of this heavy metal were determined. From these investigations, the removal efficiency of chromium could reach 97% for modified TM and 70% for modified TMD at concentration of 10 ppm, suggesting that modified TM is an excellent adsorbent for chromium removal from aqueous solutions and more efficient than modified TMD. A significant increase in chromium removal by modified TM at pH = 2 has been observed compared with higher pH values. It was found that modified TM filters can be reused through many cycles of regeneration with high performance. Modified TM filters may be a promising candidate for heavy metal ion removal from industrial wastewater.

Structure phases of fe nanoparticles in vertically aligned multi-walled carbon nanotubes

Structure and composition of arrays of vertically aligned multi-walled carbon nanotubes grown by continuous injection chemical vapor deposition method were studied using the high resolution transmission electron microscopy combined with energy dispersion spectrometry. A portion of injected Fe catalyst was found in the form of nanosized single crystalline particles with a variety of the structures of α-Fe(C), γ-Fe(C) and orthorhombic Fe3C phases encapsulated in the carbon nanotube channel or incorporated into the carbon nanotube wall. A thorough analysis revealed not only the lattice expansion of the γ-Fe(C) phase due to incorporation of carbon atoms but also a monoclinic distortion of the cubic lattice with orts c > a = b and square base transformed into a rhombic one. The monoclinic lattice distortion was referred to the uniaxial symmetry of the encapsulating tube. No evident coherency was observed in the atomic arrangement at the interface between Fe particle and inner shell of the carbon tube, as well as in the atomic arrangement of neighboring graphene shells of the carbon nanotube wall, meaning that the chirality of the shells is not coherent.

On the synthesis and thermal conductivity of nanocomposites with multiwalled carbon nanotubes

A method for growing arrays of vertically aligned carbon nanotubes and synthesizing a polymer composite based on vertically aligned, horizontally aligned, and unaligned carbon nanotubes is described. The thermal conductivity of polymer composites is studied by the laser-flash method. It is found that filling of the polymer with vertically aligned carbon nanotubes leads to an increase in the thermal conductivity coefficient of the epoxy resin by a factor of 10 and more.

Morphological and structural modifications of multiwalled carbon nanotubes by electron beam irradiation

Effects of electron beam irradiation on a morphology and structure of multiwalled carbon nanotubes sample in a normal imaging regime of a scanning electron microscope (SEM) were investigated. Direct SEM observations give evidence that irradiation by electron beam in SEM eliminates morphological unevenness, in the form of round spots of white contrast, on the surface of carbon nanotubes (CNTs) and makes the tubes thinner. Electron dispersive analysis and Raman spectroscopy are used to explore the origin and nature of these spots. From this analysis we found that e-beam irradiation improves the CNTs graphitization. The synergy of thermal heating and ionization produced by the irradiation are discussed as possible mechanisms of the observed effects.

Erosion of carbon nanotube-based polymer nanocomposites exposed to oxygen plasma

We present the results of the simulation tests of samples of polymer nanocomposites based on carbon nanotubes for resistance to oxygen plasma in the Earth’s upper atmosphere. Data on the weight loss of the samples, the results of analysis of their surface structure after irradiation, and data on arrays of carbon nanotubes damaged under the effect of oxygen plasma are given. Possible mechanisms of destruction of the nanotubes are discussed.

High efficiency of multiwalled carbon nanotubes filters for benzene removal from aqueous solutions: quantitative analysis using Raman spectroscopy

High Efficiency of Multiwalled Carbon Nanotubes Filters for Benzene Removal from Aqueous Solutions: Quantitative Analysis using Raman Spectroscopy The environmental application of multiwalled carbon nanotubes (MWCNTs) as a new type of filters to remove benzene from aqueous solutions was investigated. The surface functionalization of MWCNTs enhances their performance for this application. Arrays of MWCNTs were synthesized via chemical vapor deposition (CVD) by spray-pyrolysis method. An aliquot of these MWCNTs array was oxidized by concentrated nitric acid. The Fourier transform infrared analysis showed that the peaks corresponded to the hydroxyl and carboxylic acid groups in oxidized MWCNTs (O-MWCNTs) are more intense than that in raw MWCNTs (R-MWCNTs). The images of scanning electron microscopy indicated that the O-MWCNTs have a lower degree of entanglement and decreased nanotubes diameters. Energy dispersive X-ray spectroscopy showed high oxygen content for O-MWCNTs compared to R-MWCNTs. In order to estimate the removal efficiency of MWCNTs filters, Raman spectroscopy as a quantitative technique to make concentration measurements of benzene in water solutions was conducted and used to estimate the purification efficiency. The removal efficiency of benzene by O-MWCNTs was found to reach 99% for concentration of 500 ppm, indicating the existence of specific π-π electronic interactions between benzene molecules and the surface of O-MWCNTs. Functionalized MWCNTs possess good potential applications to water and wastewater treatment, maintaining a high qualityof water, and could be used for cleaning up environmental pollution.

Ion-Beam Analysis of the Structure and Composition of Nanocomposite nc-TiC/a-C: H Coatings

The structure and composition of nanocomposite nc-TiC/a-C:H thin films prepared by closed-field unbalanced reactive magnetron sputtering in an argon-acetylene atmosphere have been investigated. The concentrations of carbon and heavier elements have been obtained by Rutherford backscattering and nuclear backscattering. The hydrogen concentration in the films has been determined by elastic recoil detection analysis. Based on the data obtained, a scheme has been proposed to evaluate the C:H matrix mass density and the sp3 and sp2 fractions in the matrix.