Materials Science Forum Vol. 1165

Abstract: In this work, it is proposed that the thermophysical properties of the composite material can be improved by modifying the binder with nanoscale additives. It is proved that the introduction of nanoparticles into oligomers at concentrations around 1% increases the thermal conductivity by 1.3–1.6 times. Macrosized particles were also used for comparison. It was found that this effect is achieved due to a decrease in thermal resistance at the interface in result of the formation of outer surface layers. Such modified binders are effective for creating various materials and coatings based on them with a wide range of characteristics.

Abstract: In the production of layered steel-based composite materials by the liquid-phase method, an importance is attached to preserving the structural and physical-mechanical characteristics of the steel sheet serving as the middle layer. The temperature field in such a steel layer contacting with aluminum melt at a temperature of ~700°C in a roller-crystallizer is analyzed. A formula is obtained that can be used to determine the temperature distribution in the middle layer of steel at the initial stage of the technological process. A comparison of the theoretical results with experimental studies of the thermal modes of obtaining a layered steel–aluminum composite by the liquid-phase method is carried out.

Abstract: Nanoclays in 2D layered silicate materials are versatile and dynamic materials with tremendous potential for advanced functional applications. Small particle size, large surface area, and high porosity are the prominent factors that support the use of nanoclays in many different industrial applications. Apart from these well-known features, with their development capabilities such as mechanical strength, thermal and dimension stability, and permeability, nowadays, nanoclays are the most desired material especially in the production of composite materials and products due to their performance-enhancing effects. This paper provides an overview of the latest applications and improvements of polymer/nanoclay composites. Structures, chemical compositions, surface modification methods before use, synthesis techniques of nanoclay composites, and their usage for innovative applications in various fields regarding the latest developments are briefly summarized.

Abstract: Increasing the operational reliability and durability of parts and mechanisms used to operate under conditions of intense wear, loads, high pressure and temperatures requires the protection of working surfaces with functional coatings. The E.O. Paton Institute of Electric Welding of the National Academy of Sciences of Ukraine has developed a technology and equipment for multichamber detonation spraying (MCDS) of these coatings. This paper summarizes the data of experimental studies of the structure of composite coatings of various systems (Ni–Cr–Fe–B–Si, Cr₃C₂–NiCr, WC–Co–Cr, ZrSiO₄, and Al₂O₃) for different materials. Research has established the influence of technological modes of spraying on structural and phase changes in the coating materials obtained by detonation spraying. Under different processing modes, the materials change volume fraction of phase components, microhardness, (sub)grain structure parameters, size of dispersed phases, and nature and distribution of dislocation density. The peculiarity of the structure of coatings obtained by the MCDS method is the formation of a dispersed structure, the presence of a nanoscale substructure and nanoparticles of hardening phases with a size of 10–100 nm. The formation of a nanostructural state contributes to an increase in the strength, fracture toughness, and crack resistance of coatings obtained by the MCDS method.

Abstract: The work aimed to obtain zirconium diboride ZrB₂ and silicon carbide SiC based ultra-high temperature ceramics, which have improved properties due to the unique morphology of starting ultrafine homogeneous composite powders. Such properties make it possible to use the product as thermal protection materials of hypersonic aircraft. The novelty of the research is the use of methods that lead to relevant selection of sintering additives/dopants and obtaining a fine microstructure, as well as the combined effect of these factors. Boron carbide B₄C, graphite powder, carbon black, and graphene structures are used as sintering additives. ZrB₂ nano powders with different stoichiometry and graphene nanostructural inclusions are produced and then their nanopowder ceramic composites with SiC are made by vacuum hot-pressing method at 1700–1750°C. The following key properties of powders and ceramics were determined: morphology, elemental and phase compositions, particle size distribution, relative density, hardness, and flexural strength and modulus.

Abstract: An optimized method for assessing the fire protection efficiency of intumescent coatings has been proposed, which can be applied during the development and research of new formulations of fire retardant compositions. To achieve this goal, a critical analysis of existing methods for evaluating the fire protection efficiency of intumescent fire retardant coatings has been conducted, both those approved by regulatory documents and those used by researchers for the fire protection agents effectiveness rapid assessments. Based on the analysis of the studied methods advantages and disadvantages, an optimized method for evaluating the intumescent fire-resistant coatings efficiency has been proposed to reduce the time for preparing and processing experimental results. The proposed optimized method involves the use of an electrical furnace with an insulated test chamber for heat accumulation as a source of thermal radiation, which allows obtaining temperatures on the reverse side of the metal plate exceeding 950 °C. As a criterion for fire protection efficiency, it is proposed to use the comparison of the time to reach the critical temperature (500 °C) on the outer side of metal plates protected by fire retardant coatings. The efficiency of fire protection of the metal plate has been investigated using the proposed method for three samples of intumescent fire protection agents: a coating based on epoxy oligomer, ammonium polyphosphate, aluminum hydroxide, and intercalated graphite, a coating on a styrene-acrylic basis of industrial production, and a well-known coating based on epoxy oligomer filled with monoammonium phosphate and intercalated graphite. The results of the experiment allowed a comparative assessment of the studied coatings fire protection efficiency. The use of the optimized method significantly simplifies the experiment and reduces the time spent on sample preparation and processing of its results.

Abstract: This study presents the possibilities of using a fire extinguishing agent based on a water-soluble polymer for extinguishing fires at facilities where the fire load is formed by liquid combustible materials. It has been theoretically and experimentally shown that by changing the concentration of gelling additives, the viscosity can be varied, which, in turn, directly affects the characteristics of the protective layer created by applying the gel fire extinguishing agent to the surface of the combustible liquid.. The results of an experimental study of the effectiveness of gel fire extinguishing agents based on a polymer of the ECOFLOC A-18 type are presented. A method for preparing liquid solutions of concentrates of aqueous fire extinguishing agents with a gelling agent concentration of up to 10 %, which are easy to dissolve in water or in a foaming agent, is proposed. It is noted that their concentration should be such that when creating a working solution, the amount of gelling agent in it is not less than 0.05 % for the use of the solution in extinguishing fires.

Abstract: To extinguish flammable polar liquids, it is proposed to use a multicomponent fire extinguishing system consisting of one or two layers of wetted lightweight bulk materials. It has been established that wetting bulk materials leads to a significant increase in the following components of fire extinguishing action: cooling, insulation, and dilution. In addition, the introduction of water into the fire extinguishing system leads to a decrease in the concentration of vapors of polar flammable liquids above the fire extinguishing layer of bulk materials due to their absorption by water. Crushed foam glass with a granule size of 10-15 mm was selected as a bulk material for the formation of the base layer of the fire extinguishing system. To improve the insulating properties of the base layer, it is proposed to apply swollen perlite with a granule size of 1.0-1.4 mm or swollen lamellar vermiculite with a scale size of 1 × 2.5 mm to its surface. Such sizes of perlite and vermiculite particles enable them to fill the cavities between the granules of the foam glass base layer, which leads to an increase in the insulating properties of the fire extinguishing system. The following were experimentally determined: bulk density, buoyancy in methanol, ethanol, propanol-2, and acetone, moisture retention of bulk materials, and the fraction of material that spilled through the foam glass layer. The fire extinguishing capacity of the proposed fire extinguishing systems based on bulk materials in the case of extinguishing polar flammable liquids was experimentally determined. The systems based on bulk materials have a combined fire extinguishing effect by the following mechanisms of combustion termination: cooling, insulation, and dilution. It is concluded that the advantages of the proposed system in comparison with existing fire extinguishing agents for polar flammable liquids are substantiated.

Abstract: The paper presents research of the possibility of using potassium carbonate and bicarbonate as inhibitors in the compositions of aqueous fire-extinguishing substances for the elimination of fires associated with the burning of solid and liquid combustible materials. It has been shown theoretically and experimentally that both potassium carbonate and bicarbonate are highly effective in inhibition of chain reactions in the gas phase of flame combustion. Recommendations on the selection of the inhibitory component when creating compositions of aqueous fire extinguishing substances are given.