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Kashapov N.F.

Doctor of Engineering Sciences (Advanced Doctor), Professor, Kazan (Volga Region) Federal University, Russia

Experimental studies of the processes of structure formation of composite mixtures with technogenic mechanoactivated silica component

https://doi.org/10.58224/2618-7183-2023-6-2-5-18
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 5-18 p.
Abstract
The paper considers the issues of utilization of technogenic fibrous material – waste of basalt production. The chemical composition of the technogenic fibrous material was studied, it was found that it consists of 44% SiO2. The initial basalt rock, which undergoes changes during high-temperature processing in the process of obtaining basalt fiber, was studied using IR spectroscopy. The grinding of the crowns was carried out for 30 minutes, allowing to reach a specific surface area of 800 m2 / kg. Further grinding does not lead to an increase in the specific surface area, which is associated with the phenomenon of secondary aggregation of fine particles. Research on REM has shown that the “cold shots” before grinding are mostly rounded or oval in shape. The compositions were formed and the strength characteristics of the samples for the 3rd and 28th day were determined. The maximum strength gain of 59 MPa was established at the age of 28 days in samples with the addition of 5% ground “cold shots” . When introducing cold shots in an amount of 10% (composition 5) of the cement mass, an intensive strength gain is noted in the early stages of hardening (7 days) with a strength of 38 MPa, slightly higher than the strength of the control composition. The introduction of 15% ground “cold shots” gives a strength value slightly lower (32 MPa) than the values of the control composition (37 MPa) at all stages of hardening.
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Development of Alkali-activated Binders based on Technogenic Fibrous Materials

https://doi.org/10.58224/2618-7183-2023-6-1-60-73
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 60-73 p.
Abstract
The paper discusses the development of alkali-activated binders based on technogenic fibrous materials. An approach to the secondary use of technogenic fibrous materials as a filler of composite binders is offered. The properties of mineral wool waste have been established. The microstructure of finely ground fibrous particles has been studied. Compositions of alkali-activated binders were de-veloped, when grinding basalt insulation production waste to a specific surface of 300-330 m2 /kg, followed by the formation of a binder according to the first method with rod tamping sealing and, ac-cording to the second, by pressing a raw binder mixture at a pressure of 10 MPa. The developed com-positions of alkali–activated binder by pressing with a compressive strength of 22.8 MPa, and when compacted with subsequent rod tamping – 11.8 MPa.
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Plasma electrolyte production of titanium oxide powder

https://doi.org/10.58224/2618-7183-2022-5-6-75-84
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 75-84 p.
Abstract
The work is devoted to the research of plasma-electrolyte process realized in conditions of cathodic polarity of active metal electrode and its immersion into electrolyte to produce titanium oxide micro- and nanoparticles as well as titanium oxide-coated particles up to 10 μm in size. Two modes of discharge combustion differing in heat generation and concentration of electrolyte solution on particle size distribution were found to influence. Voltage increase can result in discharge combustion in arc mode due to thermal emission of electrons and intensive heating of titanium cathode. This, in its turn, leads to formation of titanium particles up to 10 μm in size, which surface is oxidized. It was found that discharge combustion in the regime with less heat emission leads to formation of titanium oxide particles sized less than 1 µm. These powders can be used in additive manufacturing, powder metal-lurgy and as additives in composite materials.
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Structure and analysis of amorphous silicon dioxide nanoparticles

https://doi.org/10.58224/2618-7183-2022-5-6-85-94
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 85-94 p.
Abstract
One of the most common methods of studying as well as controlling the environment and production products is the method of chromatography. The main working element that separates components into components, in particular, is silicon dioxide powder of nano and micro sizes. At the same time powder materials are widely used and relevant for powder technologies of additive construction. The aim of the work is to study the structure and analysis of obtained nanoparticles of amorphous silicon dioxide, satisfying the characteristics for use in high-performance liquid chromatography columns, as well as in various additive technologies. Studies have shown that the method of introducing water vapor in the plasma chemical reactor of the installation for the production of amorphous silica significantly affects the presence of free hydroxyl groups. In the infrared spectrum of the product, which was caught at a distance of 2 meters the line 3750 cm-1 is absent. At a distance of 1 meter the intensity of the line as a reference with 100% value. When a small amount of NaCl was added to the briquette used in spraying, the intensity dropped by 50%. When removed 1.5 meters away, the intensity is 75%. It follows that in the hotter gas during rapid cooling more OH hydroxyl groups are formed on the surface of the aggregates, when moving away from the reactor i.e. cooling the outgoing gas OH groups are formed less.
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Study of the plasma-electrolyte process for producing titanium oxide nanoparticles

https://doi.org/10.58224/2618-7183-2022-5-5-70-79
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 70-79 p.
Abstract
The work is devoted to the investigation of the process of obtaining titanium oxide nanoparticles by burning high voltage DC gas discharge in an argon atmosphere when an aqueous solution is used as one of the electrodes. It was found that using an aqueous glycine solution in an inert gas medium, the plasma-electrolyte process using a streamer discharge is well suited for producing titanium oxide nanoparticles. An important regularity of particle size decrease with the increase of argon pressure in the chamber was revealed. Thus, when the pressure is increased from 1 MPa to 3 MPa, a sharp decrease in the average particle size from 62 nm to 16 nm is observed, while the changes in the aver-age particle size are not cardinal already in the process of pressure increase up to 5 MPa. A narrowing of the dispersion composition scatter with increasing pressure for 1 MPa - ± 40 nm, 3 MPa - ± 20 nm and 5 MPa - ± 8 nm was determined. The presence of titanium oxide particles was confirmed on the basis of plasmon resonance detection at 224, 230 and 235 nm.
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Development of a plasma-chemical method for producing amorphous silicon dioxide nanoparticles

https://doi.org/10.58224/2618-7183-2022-5-5-80-90
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 80-90 p.
Abstract
One of the most promising areas of production is additive technologies of building, in particular powder 3D printing. The aim of the work is to create a plasma-chemical method of obtaining amorphous silicon dioxide, satisfying the characteristics for the use of additive technologies of build-ing products, as well as in columns used in high performance liquid chromatography - one of the most common methods of study, as well as control of the environment and production products. One of the main requirements for particles is a porous structure with a surface that has a chemically bonded or physically coated active phase used for separation. Experimental installation for obtaining amorphous silica was developed, the feature of which was the possibility of rapid and continuous supply of pressed briquettes, rather than powdered material as it was previously. Studies have shown that the developed plasma-chemical process implemented in the condition of evaporation of briquettes consist-ing of 70% sand and 30% coke is effective enough to produce silicon oxide nanoparticles smaller than 200 nm. The developed method of obtaining nanoparticles should be further investigated on the ability to obtain nanoparticles smaller than 20 nm, it is so necessary to obtain the specific surface area of 200 m2/g, which will make it possible to produce from this raw material particles of the fixed phase carrier column of high-performance liquid chromatography.
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THE RELIABILITY COEFFICIENT FOR FIBRE CONCRETE MATERIAL

https://doi.org/10.58224/2618-7183-2022-5-2-51-58
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 51-58 p.
Abstract
One of the main parameters of the method for calculating building structures made of concrete and fibre concrete by limiting states is the reliability coefficient for the material, which characterizes the heterogeneity of the physical and mechanical properties of the material. In national and foreign standards, it takes a constant value of 1.3 (obtained on the basis of direct tests), or 1.5 (obtained on the basis of indirect tests and the use of graduated dependencies). The concrete matrix for the formation of the structure of fibre concrete is most often fine-grained concrete with special additives, which has greater uniformity in comparison with heavy concrete, which cannot but affect the reliability of the composite material in question as a whole: the stock coefficients for fibre concrete should be lower than for normal concrete, which has not been reflected in modern standards for design yet. Starting from interval estimates of the average strength value, a new approach to determining the reliability coefficient for the material, differentiated by the 1st and 2nd groups of limit states, is proposed. The results of calculations according to the proposed formulas for previously conducted tests of steel- and glass-fiber concrete images allowed us to conclude: the introduction of fiber into the concrete matrix of the proposed effective composite composition increases the uniformity of the strength properties of the material, which leads to an increase in the reliability of its use in building structures, a decrease in the value of the reliability coefficient (margin) for the material to 1.164...1.235 for central axial compression and up to 1.172...1.272 – for central axial stretching. The obtained actual coefficients in strength calculations will allow to reveal the supplemented reserves of the bearing capacity of structures made of this material up to 22.4%.
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