Scanning electron microscopy is particularly well suited to the observation of nanofibre/cell interaction in the endothelial cells lining the hepatopancreas. (a) Tungsten oxide nanofibres, (b) test ...organism Porcellio scaber and schematic appearance of digestive tubes, (c) digestive tube (hepatopancreas) prepared for SEM investigation, (d) digestive gland cells (C) with nanofibres (NF) embedded in the cell membrane and (e) nanofibres inserted deeply in the cells and damaged nanofibres due to peristalsis.
•Tungsten oxide nanofibres react physically with digestive gland epithelial cells in Porcellio scaber.•Physical peristaltic forces of lead to insertion of nanofibres into the cells.•No toxic responses as measured by conventional toxicity biomarkers were detected.•Physical interactions were observed in a majority of the investigated animals.
We provide data obtained by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) on the interaction of ingested tungsten nanofibers with epithelial cells of the digestive tubes of a test organism Porcellio scaber. Conventional toxicity endpoints including feeding behaviour, weight loss and mortality were also measured in each investigated animal. No toxicity was detected in any of exposed animals after 14 days of feeding on tungsten nanofiber dosed food, but when nanofibers enter the digestive system they can react with epithelial cells of the digestive tubes, becoming physically inserted into the cells. In this way, nanofibers can injure the epithelial cells of digestive gland tubes when they are ingested with food. Our SEM data suggest that peristaltic forces may have an important role, not predicted by in vitro experiments, in the interactions of nanomaterials with digestive intestinal cells.
The investigation was carried out on samples cut from 20-kg as-cast ingots of a Ni alloy. The as-cast microstructures were examined, the intensity of the segregations were determined, and the ...fracture surfaces of the specimens, cooled in liquid nitrogen, were examined. It was found that with slow solidification, carbide particles precipitate on the grain boundaries, diminishing the grain-to-grain cohesion and influencing the morphology of fracture. In the areas of columnar solidification the fracture propagates along the dendrite boundaries.
In this work, the chemically assisted immersion of SiC, Si
3N
4 and Mg
3N
2 particles into a molten aluminum alloy was experimentally investigated for different processing times and temperatures. ...Prior to the introduction of SiC particles into the melt, their surface chemical composition was changed in various ways in order to promote exergonic interfacial reactions between the applied surfactants and the melt. In this way, the activation energy of the overall process of immersion was calculated for each interfacial reaction applied. Si
3N
4 and Mg
3N
2 were introduced into the melt in the as-received condition. The investigation showed that the volume fraction of particles successfully immersed increases linearly with time of immersion and exponentially with the temperature of the molten aluminum alloy. It was also evident that the volume fraction of ceramic reinforcement increases with the lowering of the activation energy of the interfacial chemical reaction. In this way, use of an interfacial reaction with a low activation energy routinely resulted in a composite with more than 20 vol.% of ceramic particles dispersed into the melt. The calculated activation energy for chemically assisted immersion corresponds to the activation energy of the interfacial reaction applied. On this basis, it is likely that the rate-limiting step in the overall process of chemically assisted immersion is probably determined by the kinetics of the applied interfacial reaction. A theoretical explanation of these findings is offered on the basis of the general assumption that there is a contribution from the free energy released by the applied interfacial reaction to wetting behaviour between the ceramic particles and the melt.
During 3 months storing of 50% KOH in a 40-m
3 cistern the content of iron in KOH increased above the allowed limit of 10
mg/l. The analysis of circumstances revealed that the only possible source ...for iron is corrosion of basic material and/or corrosion of welds. Chemical analysis of base material and weld confirmed that both corresponded to declared stainless steel AISI 316 Ti. Metallographic analysis showed the presence of martensite in the outer and inner surface layers with pitting and intercrystalline corrosion. Shotblasting caused plastic deformation and the appearance of deformation induced martensite in both surface layers of the cistern. The presence of martensite diminished corrosion resistance and enabled the start of the corrosion process which increased the content of iron in 50% KOH during the storing period.
The structure of the digestive gland epithelium of a terrestrial isopod Porcellio scaber has been investigated by conventional scanning electron microscopy (SEM), focused ion beam-scanning electron ...microscopy (FIB/SEM), and light microscopy in order to provide evidence on morphology of the gland epithelial surface in animals from a stock culture. We investigated the shape of cells, extrusion of lipid droplets, shape and distribution of microvilli, and the presence of bacteria on the cell surface. A total of 22 animals were investigated and we found some variability in the appearance of the gland epithelial surface. Seventeen of the animals had dome-shaped digestive gland “normal” epithelial cells, which were densely and homogeneously covered by microvilli and varying proportions of which extruded lipid droplets. On the surface of microvilli we routinely observed sparsely distributed bacteria of different shapes. Five of the 22 animals had “abnormal” epithelial cells with a significantly altered shape. In three of these animals, the cells were much smaller, partly or completely flat or sometimes pyramid-like. A thick layer of bacteria was detected on the microvillous border, and in places, the shape and size of microvilli were altered. In two animals, hypertrophic cells containing large vacuoles were observed indicating a characteristic intracellular infection. The potential of SEM in morphological investigations of epithelial surfaces is discussed.
Evolution of the microstructure at the Rheo-light process bases on fact that rapid cooling of the melt enables formation of numerous nucleus in the melt and further slower cooling rate enables the ...growth of globulitic primary phase and prevents the formation of dendritic microstructure. Hot working of material starts at presence of 20 % to 30 % of liquid eutectic phase that enables good filling of the tool cavity. Presented are conditions for formation of globulitic microstructure and typical microstructure of the component, processed by rheo-light process.
In our previous papers, the Self-Propagating High-Temperature Synthesis (SHS) of aluminium and titanium nitrides was studied. In this paper the synthesis of the complex nitrides of intermetallics, ...based on titanium, aluminium and nickel, was carried out. The samples were produced by the direct SHS of nickel–aluminium and titanium–aluminium mixtures in a nitrogen atmosphere, as well as by the SHS synthesis of nickel–aluminium and titanium–aluminium intermetallics followed by pulsed plasma ion nitriding. Composition of products was studied by chemical analysis, as well as by X-ray diffraction and X-ray photoelectron spectroscopy. Experiments revealed that the highest extent of nitridation was achieved during direct one-stage SHS synthesis of the complex intermetallic nitrides.
The changeover to cast Al strip for foil production has been defined by the management of Impol as the key part of its strategy for the plant's development and the restructuring of roll-casting ...technology. In comparison with hot-rolled strip, continuous cast strip is a cost-effective raw material for foil production, but different in terms of microstructure, phase composition, formability and other technological characteristics. Due to the very rapid solidification of molten metal in continuous thin strip, the microstructure consists of a strongly supersaturated aluminium solid solution and an increased fraction of fine particles of intermetallic phases, precipitated in Al crystal grains. This has a negative effect on cast-strip formability, and moreover, the cast strip's surface is oxidized and contaminated with graphite. For the purpose of producing strip from technical aluminium (group AA 1xxx) and alloys of the Al-Fe type (group AA8xxx) it was necessary to change the casting parameters as well as the parameters for further strip processing, which differ from conventional roll-casting procedures. Continuous cast strip is primarily intended for insulation, converter and household foils of different widths. The principal foil characteristics, prescribed by EN standards, are the mechanical characteristics, surface quality, porosity and the thermostability. The research work was focused on achieving the listed characteristics by changing the alloy composition and the conditions of transformation of continuous cast strip into foil. A suitable thermomechanical treatment changes the distribution of alloy elements in the existing microstructural phases and thereby also their effect on static recrystallisation, thereby affecting the surface quality and the mechanical characteristics of the foil. In this study the optimum composition and the process parameters of continuous casting that make it possible to use the strip as raw material for producing sheets and insulation, converter and household foils of standard quality are presented.
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