E. V. Pustovalov

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 as a tool for studying the structures of amorphous alloys

Structural defects in amorphous and nanocrystalline alloys of the CoP–CoNiP–NiP and CoW‒CoNiW–NiW systems are studied by means of electron tomography. An algorithm and software are developed to optimize the level of binarization of tomographic models used to select objects. Computer simulations show that the distribution of the volume of material density fluctuations is a Pareto distribution. It is established that a modified Pareto distribution describes the experimental distribution of volumes with a smaller error.

Gibbs distribution-based Bayesian segmentation of electron microscopy nanostructure images

The use of Gibbs distribution-based Bayesian segmentation of electron microscopy images for visualizing nanostructures is investigated. Bayesian segmentation involves dividing an image into nonoverlapping areas that correspond as closely as possible to the observed image. A quantitative characteristic of this correspondence is the a posteriori probability of one variant of division or another. The most likely version is always the division with the greatest a posteriori probability. The Metropolis algorithm for stochastic relaxation is used to obtain Bayesian estimates of the a posteriori probability of a division. Our study of Bayesian segmentation requires visualization of nanostructures on an electron microscopy image of a film made of NiW nanocrystalline alloy.

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.

Simulation and analysis of images using spectral characteristics

Methods intended for the analysis and simulation of microstructure images using integral spectral characteristics of orthogonal transformations are proposed. The described methods, algorithms, and software tools allow the primary processing of such images, along with identifying the correlation spectrum characteristics of microstructures and eliminating distortions related to smearing, blurring, and defocusing.