Structural transformations of poly-p-phenylene-1,3,4-oxadiazole during the process of fibre preparation

The possible structural transformations during the sample preparations and the sample observations are important issues in electron microscopy. Several publications of High Resolution Electron Microscopy (HREM) have reported that structural transformations and evaporation of the thin parts of a specimen could happen in the microscope. Diffusion and preferential etchings could also occur during the sample preparation.Here we report a structural transformation of a germanium Σ=13 (510) [001] tilt grain boundary that occurred in a medium-voltage electron microscopy (JEOL 400KV).Among the different (001) tilt grain boundaries whose atomic structures were entirely determined by High Resolution Electron Microscopy (Σ = 5(310), Σ = 13 (320), Σ = 13 (510), Σ = 65 (1130), Σ = 25 (710) and Σ = 41 (910), the Σ = 13 (510) interface is the most interesting. It exhibits two kinds of structures. One of them, the M-structure, has tetracoordinated covalent bonds and is periodic (fig. 1). The other, the U-structure, is also tetracoordinated but is not strictly periodic (fig. 2). It is composed of a periodically repeated constant part that separates variable cores where some atoms can have several stable positions. The M-structure has a mirror glide symmetry. At Scherzer defocus, its HREM images have characteristic groups of three big white dots that are distributed on alternatively facing right and left arcs (fig. 1). The (001) projection of the U-structure has an apparent mirror symmetry, the portions of good coincidence zones (“perfect crystal structure”) regularly separate the variable cores regions (fig. 2).

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INVESTMENT RATING AND STRUCTURAL TRANSFORMATIONS OF AGRICULTURE

Экономика сельского хозяйства России ◽

10.32651/2070-0288-2018-12-2-9 ◽

2018 ◽

pp. 2-9

Author(s):

V.M. Bautin ◽

E.A. Lipchenko

Keyword(s):

Structural Transformations

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FOOD SECURITY IN THE CONTEXT OF STRUCTURAL TRANSFORMATIONS OF THE FOOD SECTOR OF THE ECONOMY

AIC economics management ◽

10.33305/209-4 ◽

2020 ◽

pp. 4-10

Author(s):

E. Lipchenko

Keyword(s):

Food Security ◽

Structural Transformations ◽

Food Sector

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In situ study of structural transformations of the active phase in VMoNbTeO catalysts under reducing conditions

Журнал структурной химии ◽

10.26902/jsc_id47985 ◽

2019 ◽

Keyword(s):

Active Phase ◽

Structural Transformations ◽

In Situ Study ◽

Reducing Conditions

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Study of the structural degradation of steel 15Kh5M upon continuous duty

Industrial laboratory Diagnostics of materials ◽

10.26896/1028-6861-2020-86-1-38-43 ◽

2020 ◽

Vol 86 (1) ◽

pp. 38-43

Author(s):

Vladimir A. Kim ◽

Valeriya V. Lysenko ◽

Anna A. Afanaseva ◽

Khasan I. Turkmenov

Keyword(s):

Grain Boundaries ◽

Structural Changes ◽

Structural Transformations ◽

Structural Degradation ◽

Structural Arrangement ◽

Dispersed Particles ◽

Complex Process ◽

Multifractal Spectra ◽

Steel 15Kh5m ◽

Complex Indicators

Structural degradation of the material upon long-term thermal and force impacts is a complex process which includes migration of the grain boundaries, diffusion of the active elements of the external and technological environment, hydrogen embrittlement, aging, grain boundary corrosion and other mechanisms. Application of the fractal and multifractal formalism to the description of microstructures opens up wide opportunities for quantitative assessment of the structural arrangement of the material, clarifies and reveals new aspects of the known mechanisms of structural transformations. Multifractal parameterization allows us to study the processes of structural degradation from the images of microstructures and identify structural changes that are hardly distinguishable visually. Any quantitative structural indicator can be used to calculate the multifractal spectra of the microstructure, but the most preferable is that provides the maximum range of variation in the numerical values of the multifractal components. The results of studying structural degradation of steel 15Kh5M upon continuous duty are presented. It is shown that structural degradation of steel during operation under high temperatures and stresses is accompanied by enlargement of the microstructural objects, broadening of the grain boundaries and allocation of the dispersed particles which are represented as point objects in the images. The processes of structural degradation lead to an increase in the range of changes in the components of the multifractal spectra. High values of complex indicators of structural arrangement indicate to an increase in heterogeneity and randomness at the micro-scale level, but at the same time, to manifestation of the ordered combinations of individual submicrostructures. Those structural transformations adapt the material to external impacts and provide the highest reliability and fracture resistance of the material.

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