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The deposition of organic phase-change materials (PCMs) on the supporting fibers was shown as a simple and effective way to prepare stable composites with thermoregulating properties, which are feasible as functional additives to dry building mixes. However, the preparation of the composite fibers with optimal morphology to improve their content and thermoregulating performance in the target material still remains challenging. Herein, we report on the stable composite fibers prepared by the deposition of organic PCM eicosane on the biopolymeric fibers of fungal mycelium. The prepared composite had a fibrous morphology with the longitudinal diameter of 1–1.5 μm and the latent heat capacity of 63.2 J/g. The composite was mixed with the dry powder of gypsum plaster with the mass content of 15% and 30%. The electron microscopy revealed a homogeneous distribution of the fibers within the hardened plaster layer. The differential scanning calorimetry confirmed that the addition of the composite to the plaster enhances its thermal performance and brings latent heat storage and release capability with latent heat capacity of 8.2 J/g and 18.2 J/g depending on the composite content. The measurement of the temperature in the volume of the hardened plaster demonstrated that the addition of the thermoregulating fibers effectively reduce the heating rate in the range of 37–39°C and the cooling rate in the range of 38–34°C, corresponding to melting and crystallization of eicosane in the composite structure. [ABSTRACT FROM AUTHOR]

The possibility of using composite fibers with phase change properties as a thermoregulating additive to dry building mixes (mortar mix) with the possibility of accumulating thermal energy under the action of sunlight and a high-frequency alternating magnetic field is studied. Composite fibers were obtained by adsorption of the organic phase-change material eicosane on fibers of microfibrillar cellulose modified with magnetite nanoparticles. The obtained composites demonstrated specific values of stored thermal energy in the range of 129-148 J/g, depending on the content of eicosane in their composition. It is shown that the addition of 10–15% wt. of composite fibers to the dry building mix makes it possible to store and release thermal energy in hardened samples in a temperature range of 27-43°C, corresponding to melting and crystallization of the eicosane in the structure of the composite fibers. It was shown that addition of the composites affects the dynamics of heating under the action of artificial sunlight and subsequent cooling: the samples with added fiber showed more intense heating and slower cooling compared with control samples when the temperature reached 35°C. Samples of the hardened mixture with addition of the composite fibers also exhibited the ability to accumulate thermal energy when exposed to a high-frequency alternating magnetic field with its subsequent sustained removal. [ABSTRACT FROM AUTHOR]

Biopolymeric materials appear as promising eco-friendly and biodegradable matrices for the preparation of composite materials. In this work, G. lucidum, T. hirsuta, P. eryngii, F. velutipes, G. applanatum, L. edodes, and H. erinaceus fungi strains were studied and the fastest-growing fungi strains were revealed. The growth rate and the morphology of formed mycelium were studied depending on the fungi strain type and employed feeding substrate (malt agar, cellulose microcrystals, cellulose microfibrills). It was shown that the mycelium of G. lucidum and T. Hirsuta grown on cellulose microfibrils appears as intertwined hyphae with narrow diameter size distribution and has an optimal morphology as a substrate for the preparation of fibrous composite materials.. [ABSTRACT FROM AUTHOR]

Guar gum is a polymer that is widely used as a gelling agent for technological liquids in the petroleum industry. In this work, we have studied the potential for the environmentally friendly biodegradation of guar gum by enzymes of basidiomycetes for efficient disposal of oil industry wastes. We compared the enzymatic activity against guar gum of seven basidiomycete strains for the first time, namely Trametes hirsute MT-24.24, Lactarius necator, T. hirsute MT-17.24, Schizophyllum commune MT-33.01, Fomes fomentarius MT-4.05, Fomitopsis pinicola MT-5.21, and T. versicolor It-1. This comparison showed that the preparation based on the Fomitopsis pinicola MT-5.21 fungal mycelium at a concentration of 0.05% provides the most efficient decomposition of a hydraulic fracturing fluid containing guar gum. By varying the enzyme concentration in this fluid, it is possible to control the decrease in its viscosity over time. The developed enzyme preparation is an efficient and environmentally friendly guar gum biodegrader and can serve for processing waste fracturing fluids based on polysaccharides in order to reuse water resources. [ABSTRACT FROM AUTHOR]

In this work, we synthesized samples of carboxylated nanofibrillar cellulose (NFC) and a derivative that is a product of chemical crosslinking of carboxylated NFC with ethylenediamine. The results of transmission electron microscopy revealed that crosslinking does not lead to noticeable morphological changes in the NFC structure. The chemical modification of the carboxylated NFC was confirmed by FTIR spectroscopy. It was found that chemical crosslinking of carboxylated NFC with ethylenediamine leads to an increase in the colloidal stability of aqueous suspensions, water retention capacity, and dynamic viscosity of gels. The study of the rheological characteristics showed that the aqueous dispersions of the obtained samples are pseudoplastic liquids and have thixotropic properties. [ABSTRACT FROM AUTHOR]

Abstract: A process has been described for obtaining polymer (polyelectrolyte) microcapsules and polyelectrolyte/magnetite composite microcapsules, as well as silica-based hybrid capsules via silane-type precursor hydrolysis, which gives rise to the formation of silica nanoparticles in the structures of shells containing different numbers of polymer layers. The polymer and nanocomposite microcapsules have been formed by successive adsorption of oppositely charged polyelectrolytes and/or nanoparticles on the surface of microparticles of vaterite, which is a polymorphous modification of calcium carbonate. The obtained shells of microcapsules of all types have been studied by atomic force microscopy, confocal fluorescence microscopy, and scanning electron microscopy before and after sonication. The effect of high-intensity focused ultrasound on the obtained samples of microcapsules has been investigated and the sonication parameters that ensure efficient disruption of their shells in an aqueous medium have been determined. It has been found that composite microcapsules containing magnetite nanoparticles in their shells are most sensitive to sonication. The obtained composite microcapsules are promising for developing new systems for delivery of biologically active substances and multifunctional coatings. [ABSTRACT FROM AUTHOR]

The Navier-Stokes equations were used to carry out the numerical modeling of chemically reactive gas flow in an annular flow chamber. The model was based on laws of conservation of mass, momentum, and energy for nonstationary two-dimensional compressible gas flow in the case of axial symmetry with a tangential component of the gas velocity. Viscosity, thermal conductivity, and turbulence were taken into account. Fuel and oxidizer were fed into the chamber separately, and heat release in the chemical reaction zone was largely determined by the rate of turbulent mixing of the gas components. The possibility of burning out of the mixture in the chamber was demonstrated numerically. Detonation failure can occur if reagents temporarily cease to be fed into the chamber, which can be caused by high pressure in the reaction zone. With short combustion chamber lengths, there are the underburning of fuel and the release of unreacted hydrogen into the atmosphere. [ABSTRACT FROM AUTHOR]

We describe the preparation of multilayer composite coating comprising nanoparticles of magnetite on metal substrates previously modified by sonication. Using the Brillouin light-scattering method, we have investigated the spectral characteristics of thermal magnons in these films as a function of the number of layers and the external magnetic-field strength. [ABSTRACT FROM AUTHOR]

The problem of the passage of acoustic waves in the neighborhood of a gas bubble in a tube is formulated and solved numerically. The main parameters determining the bubble dynamics in a non-stationary field are determined. The mechanism of jet deformation of the bubble followed by jet fragmentation and formation of a secondary small-size bubble fraction is studied. A possible explanation of the nature of local sonoluminiscence is proposed. [ABSTRACT FROM AUTHOR]

Wave interaction of bubbles in a cavitation cluster is studied theoretically and experimentally. It is found that two groups of bubbles with different phases of oscillations and collapse time are formed at the early stage of bubble‐cluster formation. It is shown that small bubbles accumulating energy in the initial pulsed acoustic wave collapse in the field of internal positive pressure of the cluster. A secondary compression wave generated by inertial expansion of large bubbles is determined by means of numerical simulation and registered experimentally. The amplitude of this wave is comparable to the amplitude of the initial pulse. A decrease in the oscillation period and strengthening of the microbubble collapse are observed in the cluster under pulsed compression. [ABSTRACT FROM AUTHOR]

The existence of solutions of the traveling–wave type is studied for a system of equations that describes a one–dimensional motion of a suspension of evaporating particles in a viscous and heat–conducting chemically reacting gas. Using topological methods, it is shown that solutions corresponding to weak, strong, and Chapman—Jouguet detonation exist under certain restrictions on energy release and mass transfer. [ABSTRACT FROM AUTHOR]