Raster Microscopy Research Articles

Analysis of the fractional composition of the dust of the working area when drilling composite materials based on carbon fibers

Modern production of unmanned aerial vehicles is characterized by the use of high-tech materials based on carbon fibers, the assembly operations of which are characterized by a large number of mechanical drilling operations, which are performed mainly by hand using a carbide tool with a diamond coating. The paper presents a study of the concentrations and dispersion of the dust composition and the geometric shape of the dust-forming particles in the working space of workers of machining shops during the technological operations of drilling, milling and countersinking of packages of composite materials based on carbon polyacrylonitrile fibers. On the basis of the conducted experiments, the regularities of the distribution of dust of different fractions in the horizontal and vertical planes of the working space at a distance covering the zone of the immediate location of the worker during this type of operation were determined. The obtained data made it possible to record a significant excess of the maximum allowable concentrations of finely dispersed residues of polyacrylonitrile fibers in the working area of the drill, 2.5 and 10 μm in size and elements of the carbon matrix. In order to investigate the possibility of a negative impact of the dust of the working area on the body of the worker, a study of the fractionation and geometric shape of carbon fiber fragments was performed using raster microscopy, based on which it was concluded that the fiber fragments have a spear-shaped, pointed shape, and the carbon matrix forms conglomerates, which are characterized sharp edges and can cause significant damage when they affect the human respiratory system. On the basis of the obtained results, recommendations were given in the work to improve the indicators of the dust load of workers to normalized values with the help of the use of special suction devices and personal protective equipment with special filters.

DEVELOPMENT OF PLASTIC DEFORMATION IN TWO-DIMENSIONAL COPPER POLYCRYSTALS WITH DIFFERENT TWIN STRUCTURE

Experimental studies of regularities of occurrence and development of substructural and orientational heterogeneity of polycrystalline copper foils with different twin structure in the process of their deformation in conditions of active tension have been carried out. It is shown that by selecting the regime of thermal treatment of fine-grained copper foil three types of samples with different twin structure can be obtained. The first type is characterized by the presence of twins, which differ in size, shape and type of boundaries. Samples of the second type contain twins with faceted boundaries. Samples of the third type contain parallel twins with rectilinear boundaries. Such a variety of twin structures not only predetermines the difference of mechanical characteristics for samples of different types but also regularities of substructure and orientation changes accompanying the plastic deformation of samples. The use of a highly sensitive imaging method that allows in situ characterization of substructural and orientational heterogeneity during deformation and other methods (optical and raster microscopy, interferometry) allowed us to detect specific features of the course of relaxation processes in samples of different types.

Study of phase composition and defective state of the gradient structures of borated steels 45 and 5ХНВ

The article reveals methods of electronic diffraction and raster microscopy and a method of X-rays analysis, which study gradient structure of steels 45 and 5ХНВ borated with saturated coatings. The quantitative assessment of the fine structure of steels and phase analysis of distancing from the borated surface are worked out. The classification of the layers of the gradient structure and the mechanism of formation of phases are given in the article.

Some particularities of microscopic investigation of non-metallic objects

Thearticledealswith the comparative application of optical and raster microscopy for non-metallic objects and non-conducting surfaces. It is noted that this issue is not covered much in the special literature. There are practically no publications that compare and describe photos of the structure of materials obtained using fundamentally different microscopes, in particular, metallographic and raster. The causes of image distortion in a raster electron microscope in the study of dielectrics are considered. Comparative images of the oxidized surface, fabrics and natural leather obtained using raster and optical microscopy are presented. The advantages of optical microscopy in the study of non-conducting surfaces are shown.

A Complex Evaluation of the State of the Surface Layer of Austenitic Stainless Steel after Abrasive Impact

The effect of various methods of abrasive impact (filing with standard and impregnated abrasive tools) on the surface layer of 12X18H10T austenitic stainless steel has been investigated, which included the analysis of the interrelation of the measured properties obtained by the methods of direct indentation, Kelvin probe, micro-X-ray spectral analysis, and raster microscopy. The results of the study have demonstrated an interrelation between the obtained values of the electron work function of the studied surfaces and the measured modulus of elasticity and corrosion resistance of the samples after abrasive action. There has been observed significant changes in the properties of the thin surface layer observed after the filing with an impregnated abrasive tool.

Measuring control of construction materials parameters in order to increase reliability of engineering objects

The use of string and string elements find widespread practical application in technology. In the field of measuring technology, there are many devices in which the sensitive elements are elements in the form of strings: strain gauges, accelerometers, crack meters, etc. String sensors are widely used due to its simplicity and low cost. The present paper demonstrates that preliminary studies of structural materials for the parameters of structural materials caused by a group of factors, such as surface properties, chemical composition, processing technology, can be achieved using modern methods of scanning probe, confocal, electron raster microscopy, spectroscopy, and x-ray.

Fore-vacuum plasma-assisted deposition of dielectric coatings and process characterization

The paper aims at imparting electrical insulating properties to conductor surface via deposition of dielectric coatings. The originality of the method consists in the deposition of ceramic coatings as a result of direct electron-beam evaporation of solid dielectric (ceramic) target in the fore-vacuum pressure range (1-100 Pa). As the evaporating material we used alumina ceramics. The spatial distribution (geometrical shape of vapor clouds) of ceramics vapors was also studied using the system of the identical substrates placed at different angles and distances from the target. Raster microscopy have demonstrated that we achieved uniform alumina ceramic coatings with thickness up to 5 µm (measured by a non-contact profile meter), with deposition rate of ≈ 0.3 µm/min and surface resistance up to 140 MOhm (measured by thera ohmmeter).

Electrophysical characteristics of the near-surface layer of semiconductor ceramics for ZnO varistors

Electrophysical properties of near-surface layer of ZnO varistor ceramics forming during high-temperature annealing in oxidizing gaseous atmosphere are studied. Microstructure of near-surface layer and its electrical properties have features which are determined by an increased concentration of oxygen at surface of pressed ceramic billets in comparison with bulk during annealing. From the data of electron raster microscopy of cross-chipping of varistors, it is defined that the average value of thickness of near-surface layer is 40 μm. It is found that the specific resistivity value of near-surface layer is 5.3·1012 Ω·cm. The electrical capacitance of near-surface layer is calculated from capacitance measurement data for varistors containing such layer under two electrodes and without layers. It is shown that the electrical capacitance of near-surface layer exceeds that of varistor by more than an order. Conclusion is made that the near-surface layer gives a weak contribution to dielectric properties of ZnO varistor ceramics. However contribution of this layer to electrical conductivity of ceramics in pre-breakdown region is significant.

Research into biotechnological processes of plant S­nutrition stimulation by the products of phosphogypsum disposal in gas cleaning systems

The rational qualitative and quantitative composition of granules of phosphogypsum that is used as the load for the systems of biochemical cleaning of gas emissions was established. The study of the zones of biotransformation of phosphogypsum component with the use of raster microscopy was performed. The biofilm, formed by sulfur oxidizing bacteria on the surface of granules, and elementary sulfur that is metabolite, deposited during oxidation of hydrogen sulfide, were explored. Physical and chemical properties of biosulfur, produced as a result of biochemical gas cleaning of sulfur-containing gas flows in biofilters with the load from phosphogypsum, were determined. We analyzed the models of metabolic pathways of sulfoxydizing bacteria, providing oxidation of sulfur-containing compounds into the forms that are easily accessible for plants using electronic databases, such as KEGG database, MetaCyc and EzTaxon databases. The biochemical mechanisms of transformation of biosulfur when using it in the process of S-nutrition of plants were determined, which will make it possible to dispose of it in agroecosystems. The combined scheme of the ways of bacterial oxidation of sulfide to sulfate was substantiated. The species structure of ecological and trophic groups of microorganisms, involved in oxidation of sulfur, among which hemolithotrophic bacteria of the genus Thiobacillus are dominant, was assessed.The general technological scheme of the phosphogypsum disposal with the production of biosulfur in the systems of biochemical gas cleaning was developed. Environmental effects from implementation of the proposed technological system were obtained: impurities (hydrogen sulfide, carbon dioxide) were removed from gas emissions; the waste of chemical industry – dump phosphogypsum was disposed of; biosulfur as a product, used to improve S-nutrition in agroecosystems, was produced

Properties of optical and photovoltaic cells on the base of In4Se3, In4(Se3)1-х(Te3)х crystals

Theoretical calculations of thin-film interference systems for design of IR-filters on the base of In4(Se3)1-xTe3x solid solution crystals are carried out. Interference-absorptive band-pass filters on In4(Se3)1-xTe3x crystal with different cutting wavelength position depending on the composition x of the solid solution are produced by vacuum evaporation. Spectral transmission characteristics of the filters and dependence of their parameters on structural perfection of substrates and filter films are studied. Photosensitive elements on the base of In4(Se3)1-xTe3x homo-epitaxial heterojunctions are designed and laser correction of their photosensitivity spectral characteristics is carried out. Surface morphology of epitaxial layers is studied by electron raster microscopy. Temperature dependence of In4(Se3)1-xTe3x based photosensitive elements is measured. Mechanical strength and stability of filters and photosensitive elements spectral characteristics under cooling are studied. Laser treatment of photosensitive elements significantly increases photo-response signal of epitaxial structures at optimal operating temperatures.

Inositol 1,4,5-trisphosphate formation, cytoplasmic calcium dynamics, and alpha-amylase secretion of pancreatic acini isolated from aged and chronically alcohol-fed rats.

Three-month-old female Wistar rats were fed with 20% alcohol in their drinking fluid over 6-17 mo using an interrupted feeding regimen. At different times, pancreatic acini were isolated by mild collagenase digestion. The concentrations of inositol-1,4,5-trisphosphate (1,4,5-IP3) were determined by a specific radioreceptor assay, before and at different times after stimulation with varying concentrations of CCK-8. CCK-induced dynamics of cytoplasmic calcium ([Ca2+]c) was investigated in acinar cells by confocal laser raster microscopy. Acinar alpha-amylase (Aml) secretion was measured as enzyme activity in the medium compared to the total activity in the suspension. In 12-13-mo-old rats, the CCK-stimulated 1,4,5-IP3 formation in acini was found to be decreased compared to young rats (age 4 mo). In rats of the same age fed with ethanol from the age of 3 mo on, 1,4,5-IP3 concentrations in acini were higher and reached values comparable to those in young rats. Correspondingly, the CCK-induced [Ca2+]c dynamics in acini isolated from 9-mo-old rats was impaired compared to that of young rats but normal in aged, chronically alcohol-fed rats. Aml secretion under CCK stimulation, however, which was decreased in aged rats, was additionally impaired after alcohol feeding. Chronic alcohol feeding modifies 1,4,5-IP3 formation, the [Ca2+]c dynamics of, and the Aml secretion of rat pancreatic acini in response to CCK stimulation. Obviously, the age-related impairment of 1,4,5-IP3 formation and [Ca2+]c dynamics is improved. In contrast, the decrease in Aml secretion of acini isolated from aged rats is more pronounced after long-term alcohol-feeding.

Spatially-resolved characterization of HTSC-films near T c by laser raster microscopy with thermal excitation

A method (laser raster microscopy with thermal excitation, LRMTE) for characterizing high-Tc thin-film superconductors (HTSC) with microscopic resolution is described. By means of spatially resolved laser excitation and subsequent monitoring of the time dependence of the film resistivity at a base temperature near the transition temperature Tc, spatial variations of the transition temperature (Tc), of the temperature coefficient of the resistivity (dQ/dT), of the heat conductivity and heat capacity of the film and of the heat conductivity between film and substrate can be detected with high spatial resolution (15 μm have been achieved so far).

Study of the behaviour of irradiated polycaprolactam in the living organism

A study was made of the behaviour of surgical polycaprolactam suture in the biological medium of a living organism and the time of complete decomposition determined. By methods of electron raster microscopy and IR spectroscopy a relation was established between the type and degree of decomposition of structures and their structural state determined by the dose of radiation.