STRUCTURE FORMATION OF DISPERSED-REINFORCED BUILDING COMPOSITES

The results of the study of the mechanism of structure formation of cement compositions reinforced with finely dispersed monofilament are presented in the article. The mechanism of microstructure organization of construction composites was studied on models of dispersed systems, with different qualitative and quantitative composition of linear and dispersed particles. At the same time, restrictions had been placed on particle size – fiber diameter and diameter of dispersed particles are proportional to each other. Study of cracking formation kinetics was carried out on disk-shaped samples made of water-clay and water-cement compositions. Physical and mechanical characteristics of dispersed-reinforced cement stone, including non-reinforced stone, have been defined on prisms-shaped samples of square section with size 40×40×160 mm. The analysis of physical models showed that cluster structures filling with particles of various nature and shape increases structural diversity of entire dispersed system. An inserting of linear particles changes nature of system structure formation. Depending on the characteristics, structural components of the system, substructures are formed, which differ in the periods of their formation and geometric parameters. It has been established that dispersed particles of different nature are structured in different ways into clusters with discrete fibers of different length. Linear particles were more active in the creation of structural aggregates (clusters) comparing to dispersed grains. The impact of highly dispersed fibers on the structure organization of the binder compositions was quantified by the damage coefficient determined on samples of different types. The presence of discrete fibers in the composition of the material leads to modify the qualitative characteristic of compositions cracking formation. Improvement of physical and mechanical properties of the dispersed-reinforced composite confirms the ability of the fiber to change a mechanism of material destruction due to a probable deposition of hydration products on monofilaments, to densify and strengthen the interfacial transitional zone.

STUDY OF THE STRUCTURE AND PROPERTIES OF LEAD-FREE RAPIDLY SOLIDIFIED ZINC-BASED ALLOYS DURING A HEAT TREATMENT

Представлены результаты исследований влияния сверхвысоких скоростей охлаждения расплава, равных не менее 10К/с, на свойства быстрозатвердевших сплавов системы Zn - Sn. Верхняя область фольги, контактирующая с кристаллизатором в процессе затвердевания, имела дисперсные частицы второй фазы, и по мере удаления от верхних слоёв размеры частиц укрупнялись. При комнатной температуре протекает распад пересыщенного твёрдого раствора с выделением дисперсных частиц. Дополнительная термическая обработка приводит к укрупнению частиц второй фазы, и способствует снижению микротвёрдости. Быстрозатвердевшие фольги с максимальной концентрацией цинка характеризуются наличием текстуры (0001), которая по мере увеличения содержания олова в цинке ослабляется, и при легировании выше 20 мас. % Sn происходит перестройка на текстуру (101̅0). Термическая обработка до 160 °С не приводит к изменению текстуры. The results of studies of the effect of ultrahigh melt cooling rates, equal to at least 10 K/s, on the properties of rapidly solidified alloys of the Zn - Sn system are presented. The upper region of the foil, in contact with the crystallizer during solidification, had more dispersed particles of the second phase, and as the distance from the upper layers increased, the particle sizes increased. At room temperature, the decomposition of a supersaturated solid solution proceeds with the release of dispersed particles. Additional heat treatment leads to the coarsening of the particles of the second phase, and helps to reduce the microhardness. Rapidly solidified foils with a maximum zinc concentration are characterized by the presence of a (0001) texture, which weakens as the tin content in zinc increases, and upon alloying up to 30 wt. % Sn is rearranged to (101̅0) texture. Heat treatment up to 160 °C does not change the texture.

Mechanical Properties of Polyester Toughened with Nano-Silica

The fabrication of nanocomposites has played role to the development of the nanotechnology and the technology of advanced composite materials. Thermoset polymers are used in engineering applications widely. Their mechanical properties can be change with adding particles. The mechanism of toughening polymers has been suggested recently by reinforcing well dispersed particles to the plain polymer. Nano-silica particles were added to thermoset polymer of polyester to evaluate their influence on the mechanical properties of the toughened polymer using both experimental and numerical methods. The Representative Volume Element (RVE) approach, which employs finite element models, has been developed to achieve that aim numerically for various types of nano-particle reinforcement ratios. In each case, the stiffness has been calculated with using the equivalent homogeneous material concept. Experimentally, toughened thermoset polymers of polyester reinforced with nano-silica were prepared with different particle content ratio. Several tests were conducted on the nanocomposite, and it was observed increasing nano-silica ratio caused increase in Young’s modulus and decrease in ductility.

The Application of Organic Phosphate Nucleating Agents in Polypropylene with Different Molecular Weights

Two kinds of organic phosphate nucleating agent (NA-11 and NA-21) were used in PP with different molecular weights through the melt extrusion method. The dispersibility of the nucleating agents in PP, and the effect of the nucleating agents on the molecular weight, rheological behavior and crystallization behavior of PP were investigated. SEM and TEM analysis showed that the average radius of the dispersed particles (nucleating agents) was larger in LPP than that in HPP. The good dispersion of NA-21 also created more nucleation embryos for the adsorption of polypropylene molecules than the agglomerated NA-11. The gel permeation chromatography (GPC) analysis showed that the average molecular weight of HPP and LPP both decreased with the addition of a nucleating agent. The rotational rheometer and capillary rheometer analysis showed that the effect of NA-21 on reducing intermolecular entanglement was more significant, whether in HPP or LPP. The addition of NA-21 had less elastic energy storage and better flow stability, and could be processed at a higher speed. Simultaneously, the relaxation time in the blends with LPP was shorter than that with HPP. It was found that the crystallinity and nucleation efficiency of HPP/nucleating agent blends increased remarkably, while there was a barely perceptible increase in LPP/nucleating agent blends.

Cleaning Air Streams from Fine Particles in Paint Booths

To solve the problem of increasing the efficiency of cleaning the exhaust air of painting chambers from fine particles, a separation device with elements of a square and rectangular shape has been developed and described by the principles of its operation. A method for calculating the design dimensions of the developed separation device is presented. Different versions of the height of the separation zone are considered, depending on the size of dispersed particles. It is shown that the device is able to capture particles smaller than 10 microns with an efficiency close to 100 %, provided they adhere to the walls. The peculiarity of the design of the separation device is that a set of small-diameter vortices is created, in which the flow regime is close to laminar, and to achieve large values of centrifugal force, it is not necessary to create high speeds in the crevices.

Ultra-dispersed particles of water-soluble and water-insoluble substances formed from gas-droplet flows

The work is devoted to the experimental study of the ultra dispersed particles formation process, which is essentially a fundamental problem of heat and mass transfer in gas-droplet flows under phase transformation conditions. Various methods of generating and controlling the gas-droplet flow parameters are considered. The description of the created equipment and diagnostic methods for studying gas-droplet flows is given. The particle size distribution functions are obtained using an aerosol particle spectrometer. The possibility of controlling the parameters of ultrafine particles of water-soluble and water-insoluble substances (medications) formed under evaporation of microdroplets of solutions and suspensions is shown experimentally. An attempt to reconstruct the distribution functions of microdroplets and their average dimension from measurements of the parameters of ultrafine particles formed after complete evaporation of the droplets is made.

Study on the improvement the quality of drinking water via electrochemical pulse treatment

This article provides information on the ongoing research on the provision of clean and high-quality drinking water, comprehensive development and modernization of drinking water supply and sewerage systems, quality characteristics, physical and chemical composition, and water treatment methods. Initial electrochemical pulse treatment for drinking water is proposed. When water is treated with an electrochemical pulse, the substances become dispersed particles and, due to improved oxidation, reduce the amount of dry matter in the water by 28%, and the oxidation rate increase by 33%, and the hydrogen peroxide ratio by 30%.

Nanocarbon mesh in the flame of aromatic compounds

The soot in the flame of the pyrotechnic composition is presented in a variety of shapes and structures. Part of the dispersed particles consists entirely of carbon. The sizes of such particles are in the submicron range. Another part of the particles contains carbon in the form of nanostructures - needles and tubes. A detailed study of the morphology and chemical composition of dispersed particles on optical and scanning electron microscopes showed the existence of yet another unidentified species of particles - tuba. The resulting formations are micron-sized and retain the properties of nanostructures.