O. V. Voitenko

Colloid stable sorbents for cesium removal: Preparation and application of latex particles functionalized with transition metals ferrocyanides

In this paper we suggest a principally new approach to preparation of colloid stable selective sorbents for cesium uptake using immobilization of transition metals (cobalt, nickel, and copper) ferrocyanides in nanosized carboxylic latex emulsions. The effects of ferrocyanide composition, pH, and media salinity on the sorption properties of the colloid stable sorbents toward cesium ions were studied in solutions containing up to 200 g/L of sodium nitrate or potassium chloride. The sorption capacities of the colloid sorbents based on mixed potassium/transition metals ferrocyanides were in the range 1.3-1.5 mol Cs/mol ferrocyanide with the highest value found for the copper ferrocyanide. It was shown that the obtained colloid-stable sorbents were capable to penetrate through bulk materials without filtration that made them applicable for decontamination of solids, e.g. soils, zeolites, spent ion-exchange resins contaminated with cesium radionuclides. After decontamination of liquid or solid radioactive wastes the colloid-stable sorbents can be easily separated from solutions by precipitation with cationic flocculants providing localization of radionuclides in a small volume of the precipitates formed.

Graphics processors in problems of electron tomography

Algorithms were developed for the tomographic reconstruction of structure from microscopic images using graphics processors of general application. The effect of noise and the choice of reconstruction filters for tomographic problems in materials science is investigated. It is shown that the use of ρ-filtration in reconstruction allows one to estimate the geometrical characteristics of three-dimensional microstructures in amorphous metal alloys.

HAADF-STEM investigation of the structures of electrolytically deposited CoP and CoNiP alloys

The structure and chemical composition of electrolytically deposited films of CoP and CoNiP amorphous alloys are studied by means of high-angle annular dark-field scanning transmission electron microscopy in the z-contrast mode, and via EELS and EDS spectroscopy with high locality. It is shown that variations in chemical composition correlate with heterogeneities in film structure.

Electron tomography and STEM investigations of the structure of multilayer amorphous and nanocrystalline alloys of CoP-CoNiP, CoW-CoNiW systems under external action

The structure of amorphous and nanocrystalline alloys of the CoP-CoNiP and CoW-CoNiW systems under the external action is investigated by means of high-resolution transmission electron microscopy and electron tomography. It is revealed that the crystalline phase is predominantly nucleated in the regions with the maximum density gradient. Algorithms for image filtering and reconstruction for a graphical processor unit are implemented.

Investigating the structure of electrolytically deposited alloys of the CoP-CoNiP system under thermal action

The problems of structural relaxation and crystallization of electrolytically deposited amorphous metal alloys of the CoP-CoNiP system are investigated. The onset of the structural relaxation and crystallization is found to occur through the nucleation of nanocrystalline particles of an unrecognized CoxNiyP1−x−y phase. An increase in the concentration of Ni is shown to yield a substantial thickening of the amorphous structure and to increase the temperature of the onset of structural relaxation and crystallization by 50–70°C.

Electron tomography algorithms in scanning transmission electron microscopy

Different weighting filters used in tomographic algorithms are investigated. Algorithms for the recovery of tomographic structures are produced for general application in graphic processors. Software for a Carl Zeiss Libra 200FE microscope that enables us to record a series of projections in the STEM mode is developed. Calculation experiments show the improvement in tomogram quality when using cosine and 1/z2 filters instead of a linear filter at high noise levels for objects larger than 25 points.

Electron tomography and morphological analysis of the structure of multicomponent amorphous and nanocrystalline alloys

The structure of amorphous and nanocrystalline alloys of the CoP-CoNiP and CoW-CoNiW systems is investigated by means of electron tomography. The systems’ morphometric characteristics are obtained, and the results from two-dimensional imaging and three-dimensional reconstructions are compared.

In-situ investigation of the structure of electrolitically deposited cobalt-phosporous alloy upon heating

The effects of heating on the structure of deposited CoP alloy is investigated by means of transmission electron microscopy and electron diffraction. A series of electron diffraction patterns of the in situ annealing process are obtained. Methods for analyzing diffraction patterns and intensity profiles are examined. Custom software is developed to automate the analysis of electron diffraction patterns and the detection of peaks in intensity profiles, along with their parameterization.

TEM and STEM Electron Tomography Analysis of Amorphous Alloys CoP-CoNiP System

This paper covers the analysis of amorphous alloys CoP-CoNiP system by means of high-resolution transmission electron microscopy (HRTEM), scanning transmission electron microscopy and electron tomography. The last years have seen a sufficient progress in the analysis of nanomaterials structure with the help of high resolution tomography. This progress was motivated by the development of microscopes equipped with aberration correctors and specialized sample holders which allow reaching the tilts angles up to ±80°. The opportunities delivered by the method of electron tomography sufficiently grow when producing high resolution images and using chemical analysis, such as X-Ray energy-dispersive microanalysis and electron energy loss spectroscopy (EELS).

Characterizing the structure of Co/Cu and NiFe/Cu multilayered magnetic nanowires

Multilayered magnetic Co/Cu and NiFe/Cu nanowires were grown via template-assisted electrodeposition. Structures were described by means of focused ion beam/scanning electron microscopy and energy dispersive X-ray spectroscopy.