Research on the impact of nano carbon fillers on the morphology of epoxy binder

ABSTRACT: Introduction. When developing a composite material, it is important to understand how the components included in its composition affect its properties. Fillers, by interacting with the matrix, can alter its initial structure, resulting in the composite acquiring characteristics different from the matrix. The high modifying ability of nanofillers is determined by their significant specific surface area. This allows for the total interfacial area between the matrix and the dispersed phase to be covered even with a relatively low concentration of particles, thereby enabling the use of a small amount of filler. Methods and materials. Composite materials with nano carbon fillers were investigated, including fullerenes, nanotubes, and graphene. Fractographic analysis of the tensile fracture surfaces of the samples was chosen to evaluate the structure of the composites, which allows determining the nature of the failure and the ability of the composite to restrain crack propagation. The microstructure of the composite materials, as well as the morphology of the reinforcing nano carbon fillers, were examined with a Tescan MIRA3 scanning electron microscope. Results and discussion. In a graphene composite, crack energy is dissipated through branching and elongation of the crack path. Carbon nanotubes, being embedded in the crack walls, hinder the opening of the crack edges. Crack energy is also consumed in overcoming friction forces during the extraction of nanotubes from the epoxy matrix. Agglomerates of fullerenes act as effective crack front arresters, forcing the crack to circumvent them, thereby creating new areas of fracture surfaces. This leads to an increase in the crack front length and the energy required for material failure. Conclusion. Adding nano-carbon fillers (graphene, CNT and fullerenes) as reinforcing components in the epoxy binder alters the structure. The study defines possible mechanisms for hardening of the composite materials due to adding the nano-carbon fillers

Последовательность действий при визуализации кровоизлияний/гематом мягких тканей у пожилых больных, инфицированных SARS-CoV-2

Aim. To determine ultrasound, computed tomography and angiographic image characteristics for soft tissue hemorrhages/hematomas, the sequence of using imaging methods in patients infected with SARS-CoV-2, to study the morphology of changes in soft tissues, to determine the essence of the concept and to develop treatment tactics for this complication of COVID-19.Material and methods. During 4 months of treatment of elderly patients (+60) infected with SARS-CoV-2, 40 patients were identified with soft tissue hemorrhages/hematomas, of which 26 (65%) patients with large hematomas (>10 cm in size and > 1000 ml in volume). The analysis of clinical and laboratory parameters, methods of instrumental diagnostics (ultrasound – 26 patients, CT – 10 patients, angiography – 9 patients, punctures – 6 patients) was carried out; autopsy material was studied in 11 cases.Results. Image characteristics of hemorrhages/hematomas of soft tissue density were obtained using modern instrumental methods, and the sequence of application of visualization methods was determined. A tactic for managing a patient with stopped and ongoing bleeding has been developed. The morphological substrate of hemorrhagic complications in a new viral infection was studied. All patients were treated with conservative and minimally invasive procedures (embolization, puncture with pressure bandage). 15 patients (57.7%) recovered, 11 patients (42.3%) died from the progression of COVID-19 complications.Conclusion. Comprehensive clinical and laboratory sequential instrumental diagnosis of soft tissue hemorrhages in COVID-19. Treatment should be conservative and significantly invasive. The use of the term “soft tissue hematoma” in SARS-CoV-2 infected patients is not a natural quality of the normal pathological process and should not be observed from our point of view.Цель исследования: определить визуальные ультразвуковые, компьютерно-томографические и ангиографические критерии мягкотканных кровоизлияний/гематом, последовательность использования методов визуализации у больных, инфицированных SARS-CoV-2, изучить морфологию изменений в мягких тканях, определить суть понятия и выработать лечебную тактику при таком осложнении COVID-19.Материал и методы. За 4 мес лечения пожилых больных (+60), инфицированных SARS-CoV-2, выявлено 40 пациентов с мягкотканными кровоизлияниями/гематомами, из них 26 (65%) пациентов с большими гематомами (размер >10 см и объем> 1000 мл). Проведен анализ клинико-лабораторных показателей, методов инструментальной диагностики (УЗИ – 26 пациентов, КТ – 10 пациентов, ангиография – 9 больных, пункции – 6 пациентов), в 11 случаях изучен материал аутопсии.Результаты. Современными инструментальными методами получена визуальная характеристика крово излияний/гематом мягкотканной плотности, определена последовательность применения методов визуализации. Разработана тактика ведения пациента при остановившемся и продолжающемся кровотечении. Изучен морфологический субстрат геморрагического осложнения при новой вирусной инфекции. Все больные пролечены консервативными и минимально инвазивными процедурами (эмболизация, пункция с давящей повязкой). Выздоровели 15 (57,7%) пациентов, умерли от прогрессирования осложнений COVID-19 11 (42,3%) больных.Заключение. Комплексная клинико-лабораторная последовательная инструментальная диагностика мягкотканных кровоизлияний при COVID-19-инфекции позволяет своевременно установить топический диагноз, оценить тяжесть кровопотери, ее остановку или продолжение кровотечения. Лечение должно носить консервативный и минимально инвазивный характер. Использование термина “гематома” мягких тканей у инфицированных SARS-CoV-2 больных не отражает суть происходящего патологического процесса и, с нашей точки зрения, не должно использоваться

On Xenophobia in science fiction

The article deals with how the notion of xenophobia is re-iterated in contemporary science fiction. First, the author provides a brief analysis of xenophobia as a cognitive phenomenon that is, on the one hand, built into the mass culture as an archetypal attitude and, on the other hand, symbolically disguised following the two prototypic scenarios-those of alienation and of appropriation. One of the central arguments of the article is that the quintessential sci-fi “alien” is based on the reinvented image of a Jew in the Western culture, while the narrative of “androids” draws on the historical and emotional experience of black slavery

Identification of fullerenes in iron-carbon alloys structure.

Steels of various purposes are used in the construction industry, for example, as the reinforcement material in reinforced concrete structures. In the oil and gas industry, steel structures are used for storage and transportation of explosive toxic media. In this case the catastrophic damages might take place, that points at insufficiently deep knowledge about the processes running in structural materials when load is applied. Recent studies show that many properties of steel are set at the nanoscale level during crystallization from the molten metal and thermal treatment. To detect and identify fullerenes С60 and С70, which are independent nanoscale objects in steel structure, by various methods requires studying of how these objects influence on formation of steel properties. Iron atoms can serve as a catalyst and, interacting with large aromatic structures or fragments of the graphite planes, they form voluminous fullerene-type structures. The inverse phenomenon, i.e. influence of the formed nanoscale objects on structuring of the iron atoms, is also possible, as fullerene size is comparable with the size of the stable nucleus of the iron crystalline phase. The article discusses the issue of mechanisms of fullerenes formation in steels and cast irons. The most complicated issue in the study is the fullerenes identification by spectral methods as the quantity of released molecules is small. In order to increase the sensitivity of the fullerenes IR-spectrometry method, potassium bromide has been proposed to use. Dried and reduced sediment obtained as a result of dissolving iron matrix in steels is mixed with potassium bromide, the mixture becomes bright-orange. This fact points to presence of bromic fullerenes and to presence of fullerenes in the studied specimens. It is shown that the offered specimen preparation algorithm significantly increases sensitivity of the method

The evolution of the welded joints structure at low cycle fatigue

The effect of cyclic damage on the structure evolution and the change in the micro stresses of the crystal cell in characteristic zones of dissimilar welded joints of steels strength classes X60 and X70 is estimated. It is shown, that with increase in the number of loading cycles in less strong metal of the welded joint, relaxation of internal stresses, realized by splitting individual ambits of ferrite grain or by the initiation of micro cracks, is observed. The results of fractographic analysis of a less reliable weld zone at different levels of samples fractures of accumulated damage are presented

The evolution of the welded joints structure at low cycle fatigue

The effect of cyclic damage on the structure evolution and the change in the micro stresses of the crystal cell in characteristic zones of dissimilar welded joints of steels strength classes X60 and X70 is estimated. It is shown, that with increase in the number of loading cycles in less strong metal of the welded joint, relaxation of internal stresses, realized by splitting individual ambits of ferrite grain or by the initiation of micro cracks, is observed. The results of fractographic analysis of a less reliable weld zone at different levels of samples fractures of accumulated damage are presented

Regularities of welded joint surface relief morphology change of oil and gas equipment under operating conditions

Methods that are used to study the fine structure of constructional materials are becoming more popular. Interdisciplinary approaches are important for explaining the relation between macrolevel processes and higher levels of metal destruction mechanisms research. Synergetics properly reflects the essence of natural processes, in particular the plastic deformation of metals. It is known when energy is supplied from outside, the open system organizes itself, striving to produce minimum of entropy. In this case when the accommodative mechanism is exhausted, the system passes to another dissipative structure with a dramatic change in properties. The authors studied deformation processes of outer layers and internal subsurface volumes of a metal when welded joints are deformed. It is shown that the zone of thermal influence in a welded joint is the area of discharge of the supplied energy and the zone of accommodation of the plastic deformation of the welded joint. The deformations of a new and embrittled metal after theoperation run in different ways. This difference is taken as the basis for the assumption about the welded joint continuity preservation mechanisms under deformation. The microrelief of the welded joint on the surface and in the internal subsurface volumes zones has been investigated: welded seam, zone of influence, base metal. The relief parameters on micro-, nanolevel have been quantitatively evaluated: dispersion Rа and asymmetry Rsk according to GOST R ISO 4287-2014. It is shown that all parameters increase in the zone of thermal influence and are sensitive to discontinuities in the form of microcracks. One should note that the deformation relief is self-similar at various hierarchical levels. Fractal analysis of welded joint zones has been performed. It is shown that under deformation fractality increases in the zone of thermal influence

Assessment of mechanical characteristics of steel subject to cyclic loads effect on non-standard compact specimens

It is showed by experiments that the use of compact specimens for determination of fracture work of steel that undertook cyclic deformations enables to identify metal with a number of cumulative fatigue damages. The yield limit determined in the first series of experiments was used for cycling parameters determination: 0.9 from the yield limit was set for damage accumulation in the elastoplastic stress range. At the same time an average cycle load was 8.9 kN, and an amplitude was 8.6 kN. It is demonstrated that specific fracture work increases upon the increase of compact specimens’ thickness. The tendency of specific fracture work decrease is observed upon fatigue damage accumulation. Thin specimens are particularly sensitive to damage accumulation. The results of the experiments indirectly support the hypothesis of fractional-dimensional surface layer existence