A. V. Makunin

Nanoparticle process formation in zinc implanted silicon with followed thermal annealing

Results of temperature treatment effect on near surface layer properties of Zn ion implanted Si substrate are presented. Radiation induced point defects and Zn in depth profile was studied by Rutherford back scattering (RBS) method with use of channeling technique. Topology of substrate surface was studied by atomic force microscopy (AFM) and scaning electron microscope (SEM). Phase composition of samples was test by x-ray diffraction in grazing geometry.

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.

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.

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.

Experimental Investigation and Mathematical Modeling of a Coaxial Tubular Apparatus for Steam Methane Conversion

A tubular steam methane conversion apparatus containing a coaxial insert coated with a nickel–chromium catalyst by thermal gas deposition was experimentally studied and mathematically modeled. By solving the inverse problem, the parameters of the kinetic function of the steam–methane reaction were found. The efficiency of the coaxial tubular apparatus was shown to considerably exceed the efficiencies of its modern industrial analogs, namely, the PPR-600 and PPR-1360 furnaces and the Kellog tubular reactor.

Study of silicon implanted with zinc and oxygen ions via Rutherford backscattering spectroscopy

The structural features and dopant profiles of a Si surface layer implanted with Zn+ and O+ ions are studied via Rutherford backscattering spectroscopy based on the analysis of He2+-ion spectra with the use of the channeling technique. The doping-impurity redistribution is analyzed upon the formation of zinc-oxide nanoparticles. The sample surface morphology is examined by means of atomic-force microscopy and scanning electron microscopy under secondary-electron emission conditions. X-ray phase analysis of the implanted layers is carried out.

Formation of Axially Aligned Polydisperse Nanocarbon Structures via Chemical Vapor Deposition from Cyclohexane with Ferrocene

Axial polydisperse carbon microstructures composed of vertically aligned arrays of multiwalled carbon nanotubes (MWCNTs) are synthesized via chemical vapor deposition (CVD) of cyclohexane with ferrocene onto a single-crystal silicon substrate. Their structural peculiarities are examined via scanning electron microscopy on a Tescan Lyra3 FEG system, atomic force microscopy on an Ntegra Spectra NT-MDT probe microscopy, by Raman spectroscopy. The abilities to purify synthesized carbon structures from amorphous carbon through oxidation with atomic oxygen and ozone are studied in order to achieve significant enlargement of specific surface area of nanotubes. The routes of application of polydisperse structures as catalyst supports, solid electrolytes, and chemical sensor supports, as well as absorption techniques of gas and liquid storage, are proposed.