Peculiarities Of Structure Formation Research Articles

Physicochemical processes during solidification and the peculiarities of structure formation in aerated concretes using metallic silicon as a gas generator

Physicochemical processes during solidification and the peculiarities of structure formation in aerated concretes using metallic silicon as a gas generator

Strong Structure Formation of Ceramic Composites Based on Coal Mining Overburden Rocks

Currently, the amount of man-made waste worldwide is steadily increasing. It is, therefore, necessary to constantly look for effective ways of utilization and recycling. It is also necessary to reduce the use of non-renewable resources and reduce the impact on the environment. The use of coal industry waste is currently quite insignificant, amounting to some 10% of the total volume. The work aimed to study the properties of raw materials and study the processes of structure formation during the forming, drying, and firing of composite ceramic produced using overburden rock and additives. The work’s relevance lies in the need to solve environmental, economic, and technological problems related to the utilization of coal mining waste. Experiments of the past prove the possibility of using the waste coal industry as additives in the production of building materials. The article presents the results of studies of the chemical, mineralogical, and granulometric composition of overburden rock in coal mining. Peculiarities of structure formation during the forming, drying, and firing of ceramic composites based on optimal fractional compositions from coal-mine overburden were revealed. Organic and chemical additives were used for the correction of technological properties and improvement of the quality of finished composite products. The physical and mechanical indices of the obtained composite ceramic samples were determined, the analysis of which revealed that the use of highly mineralized carbonaceous rocks as solid additives provided a 2–2.5-fold increase in the strength of the product, 5.6% reduction in water absorption, and an increase in the product frost resistance by 20–25 cycles. The aluminum oxychloride influence on the physical and mechanical indices of the obtained composite articles was reflected in a reduction in their water absorption from 8.2 to 7.0%, a 10–12% increase in strength in compression, and an increase in freeze–thaw resistance by 30–35 cycles. Research results proved that the composition and properties of coal-mine overburden rock are close to those of conventional clays. With special technological preparation, they can be used for the production of composite ceramic products. This will significantly reduce the cost of bricks, to make up for the shortage of high-grade clay raw materials and improve the environmental situation. Nevertheless, further research into the use of coal-mine overburdens in the composite ceramic material technology is warranted.

Effect of vanadium alloying on the phase composition of super duplex steel

The application and advantages of a class of duplex steels (austenitic-ferritic type steels) as a structural material are described. The influence of nitrogen as an alloying element in steels of this class is considered, as well as the peculiarities of structure formation and different types of compounds in the crystallizing melt of the considered compositions of chemical composition. The effect of the concentration of nitrogen, which, when introduced into the steel for alloying, can be in the form of gas filling pores and cracks, the element of introduction in the solid solution based on iron and nitride phases is described. The latter two forms of nitrogen presence in steel are responsible for posi-tive effects on the physicochemical properties, providing in some cases an advantage over traditional stainless steels. Using FactSage software (version 6.4), work was carried out to determine the effect of the main alloying elements of UNS 32750 super duplex steel on its phase composition. As the concentration of the main alloying elements (Cr, Mo, Mn) increased, it was found that in the nitrogen concentration interval of 0.24‒0.35 % (wt.) during melt crystallization there is no zone of existence of purely austenite and ferrite mixture, and the steel cools with formation of metal nitrides in the austenite and ferrite mixture. It can also be noted that this mixture of phases is located at the heat treatment temperatures of this steel 1025‒1125 °C. The proposed composition together increases the temperature existence interval of ferrite during crystallization by an average of 30 °C, which will provide greater nitrogen solubility in the melt. The alloying of this composition with vanadium shifts the formation zone of α + γ + M2N mixture towards less nitrogen concentration, and in the temperature interval below 800 °C an intermetallide phase is formed, which is a compound of CrVN type.

ANALYSIS OF METHODS FOR PREDICTING THE LIMITING NITROGEN CONCENTRATION IN DUPLEX STEELS

The history of origin of the duplex steels (austenitic-ferritic type steels) and improvement of their manufacturing methods in the process of development of metallurgical technologies are described. The influence of nitrogen as an alloying element in steels of this class is considered, as well as the peculiarities of structure formation and different types of compounds in the crystallizing melt of the considered chemical compositions. Influence of limiting nitrogen concentration in the metal as a limiting factor for obtaining defect-free ingots is described. The various methods are given, which makes it possible to predict the nitrogen content in the metal depending on its chemical composition, temperature and atmospheric pressure. These theoretical methods include calculations using the mathematical approach of interaction parameters, calculations using the concept of equivalent concentrations and empirical dependences. A calculation for the specific composition of super duplex steel has been performed and the most promising method for predicting the limiting nitrogen concentration has been established. In order to verify this method of calculation, the work was carried out to obtain experimental samples with different nitrogen contents by smelting pure materials in an open induction furnace. During the experiments, smelting of two compositions of superduplex steel with different nitrogen content was carried out. The results of the macrostructure and chemical composition study of the obtained samples correlate with the results of calculations according to various methods and the conclusion about the possibility of using a specific dependence, using in its basis the mathematical approach of the interaction parameters of the first and second order, when predicting the limiting nitrogen content as an alloying element in obtaining austenite-ferritic steels.

Peculiarities of Structure Formation in Ni–C, Al–C, and Ni–Al–C Systems at High-Temperature Heating

Peculiarities of Structure Formation in Ni–C, Al–C, and Ni–Al–C Systems at High-Temperature Heating

Isolation cementing of oil and gas wells of the Сarpathian region

The problem of reliable isolation cementing of oil wells belonging to non-operating stock is considered. It is shown that the oil and gas fields of the Carpathian region are characterized by unique mining, geological and geographical conditions, as well as a large number of old wells of complex design that require unconventional solutions when performing isolation works. The peculiarities of structure formation, technological properties of insu-lating materials based on oil well cement PCT I-100 and composite mixtures CREA, CREA-LF have been studied. It was found that in the first case, the hydration products are represented by ettringite, hexagonal AFm phases, calcium hydroxide and fibrous hydrosilicates. The following phenomena are characteristic for composite materials: a more uniform distribution of hydrates in the gel mass of hydrosilicates, better ordering of the contact zones of accretion, and an increase in the number of intergrown fibers in blocks of hydrosilicates. All of that ensures the formation of a stone of a denser structure, the closure of a larger number of hydrates surface active centers in contact interactions, controlled synthesis, improvement of the strength characteristics and deformation properties of the cement stone. It is shown that the improvement of the quality of composites is facilitated by the use of modern polyfunctional additives-modifiers applying the technology of manufacturing dry building mixtures. It has been found that to increase the efficiency of krents, it is advisable to use complex additives of multifunctional action, which, complementing each other, make it possible to achieve an additive and sometimes synergistic effect. A new generation plasticizer based on polycarbonates, stabilizing additives and micro-reinforcing fibers is used as a modifier of the CREA and CREA-LF composite mixtures. The ability to microplastic deformation of the composite matrix, reinforced by microreinforcement, causes higher energy consumption for the destruction of the stone. An improved technology for performing insulation works is proposed, taking into account the design features and the state of well support elements, which provides for the use of thermographenite and zeolite tuff in addition to the binder material.

ВЛИЯНИЕ РЕЖИМОВ НАПЛАВКИ НА ХАРАКТЕРИСТИКИ ТЕПЛОМАССОПЕРЕНОСА ЭЛЕКТРОДНОГО МЕТАЛЛА, ФОРМИРОВАНИЕ СТРУКТУРЫ И СВОЙСТВ ПОКРЫТИЙ

The peculiarities of structure formation in coatings deposited under conditions of controlled heat and mass transfer with the pulse change of power parameters of the mode are considered. 
 It is shown that as a result of the pulse control of mode power parameters, in a coating there is observed of structural heterogeneity decrease on a coating section at the expense of the decrease of structural constituent dimensions in it that increases considerably of operation properties of strengthened products operated under conditions of low temperatures of the extreme North. The investigations are carried out with the use of the complex of fast processes of heat and mass transfer that ensured high productivity of the investigation process at lower cost of time and material costs. 
 It is recommended for a wide range of experts in the field of modern physical material science, hydrodynamics, chemistry and mechanics of a deformable solid, reliability and technogenic safety, control of fast processes of the formation of permanent connections modified with pulse high-energy impact.

Peculiarities of Structure Formation in Copper/Steel Bimetal Fabricated by Electron-Beam Additive Technology

In the present paper, the microstructure of heterogeneous material bimetal compound fabricated by wire-feed electron-beam additive technology from CrNiTi stainless steel and С11000 copper has been investigated. The bimetallic compound is characterized by the well-defined interface between the two materials and possesses two-phase transition areas on both sides of the interface. The heterogeneity of strength properties (microhardness) in the transition zones is associated with a solid solution hardening of the bimetal basis components and formation of composite structures in the transition zone of the bimetal: spherical inclusions of steel in the copper part and copper inclusions in the steel section. In the copper part of the bimetal sample, a heterogeneous grain structure is formed – areas with macroscale non-equiaxed grain structure and zones with spherical grains were observed. The heterogeneity of grain structure does not have significant influence on the yield strength, but affects the macroscopic deformation pattern of the bimetal copper part, as has been revealed by microstructural analysis of slip traces and grain structure calculated using the Hall–Petch relationship.

Peculiarities of structure formation and the properties of silver-containing polymer composites based on chemically modified melamine-formaldehyde polymer

Peculiarities of structure formation and the properties of silver-containing polymer composites based on chemically modified melamine-formaldehyde polymer

Investigation into the Peculiarities of Structure Formation and Properties of Copper-Based Powder Pseudoalloys Modified by ZnO and TiN Nanoparticle Additives

Comprehensive investigations into Cu–ZnO (nano) and Cu–TiN (nano) copper-based materials by standard methods in combination with metallographic and electron microscopy investigations using energy-dispersive and thermal analyses make it possible to identify stable correlation relations between the content of nanoparticle additives, microstructural parameters, and mechanical-and-physical properties of pseudoalloys. Process procedures of increasing the distribution uniformity of modifying additives of ZnO and TiN nanoparticles over the pseudoalloy bulk excluding their conglomeration are developed and substantiated. Novel original methods of nanoparticle introducing into a matrix material in the form of a master alloy made of Cu–Al–ZnO or copper powders coated with TiN nanoparticles are proposed. A high specific surface and reactivity of nanopowders make it possible to lower the ceramic phase in electrocontact materials (down to 2.0–3.0% instead of 10–15% when compared with known commercial brands). This results in the conservation of the main properties characteristic of the matrix material (copper) such as thermal and electrical conductivity at a rather high level, while the general level of physicomechanical characteristics (hardness, strength, and wear resistance) and operational properties of composite pseudoalloys simultaneously increases. The main characteristics of copper-based composite materials are as follows: electrical resistance (ρ = 0.025 μΩ m), bonding strength to the contact support material (σ ~ 2 MPa), and dispersed ceramic phase inclusions. They reduce the electroerosive wear (up to a factor of 2.5) when compared with conventional materials.

Особенности формирования структуры изделий, получаемых на электронно-лучевом 3D принтере с использованием проволоки из титанового сплава

Особенности формирования структуры изделий, получаемых на электронно-лучевом 3D принтере с использованием проволоки из титанового сплава

Peculiarities of structure formation of steel carbon wire of perlite class after a combined deformation processing

Creation of methods of metals and alloys deformation nanostructuring, which could be adapted into existing industrial plant by their technological parameters and productivity, is one of actual problems to be solved at present by researchers.Description of a wire combined deformation processing bydrawing with bending and twisting presented. Results of metallographic study of high-carbon wire of Stal 70 grade steel indicated specific peculiarities of influence of different kinds of plastic deformation combining on the steel structure. Mechanical tests of the wire after different kinds of combined processing showed, that such a processing provides combination of strength and ductility, typical for a steel with ultrafine grain structure. Using a method of differential scanning calorimetry, the stored energy value and calorimetric peak temperature value of deformed wire made of high-carbon Stal 70 steel determined. It was shown, that the stored energy value and calorimetric peak temperature value are sensitive to technological parameters of combined deformation processing change.

The Peculiarities of Structure Formation Upon Sintering of TiH2+TiВ2 Powder Blends

The investigation results on peculiarities of phase and structure formation as well as sintering kinetic of compacted TiH2 - TiВ2 powder blends. It was shown, the most intensive shrinkage upon heating took place within temperature range of TiH2 dehydrogenation (400 ÷ 650 0С). Heating of powder blend up to sintering temperature (1350 0С) resulted in formation of acicular TiB particles in titanium matrix, the amount of particles is increased with increase in exposure to 20 min. The longer duration of isothermal exposure did not lead to increase in amount and size growing of TiB particles. X-ray analysis of sintered TiН2+TiВ2 powder blend demonstrated the presence of titanium matrix phase, orthorhombic TiВ phase, and traces of Ti-B compounds of different concentrations (Ті3В4 and Ті2В5). The dilatometric investigations proved that addition of boride compounds and increase in boride content in powder blend led to decrease in shrinkage upon sintering as compared to shrinkage of single TiH2 powder compacts.

Peculiarities of structure formation of epoxy-amine polymers upon curing of diglycidyl ester of diphenylolpropane with adamantane diamines

The peculiarities of structure formation of epoxy-amine polymers upon curing of diglycidyl ester of diphenylolpropane with adamantane diamines are discussed. It is shown that, at the initial stage of polycondensation, deceleration of the curing process takes place that is caused by glass transition of the polycondensation products. It is found that complete consumption of all functional groups is impossible without additional postcuring.

Особливості структуроутворення нефритованої глазурі

The results of the development of new formulations raw glazes for sanitaryware, which enhances whitness and coating microhardness products, is shown. The peculiarities of structure formation in the glaze during the firing process is noted

Effect of factors governing dry friction on structure formation for the tribological synthesis zone in composites based on copper

Features and peculiarities of structure formation for the friction zone in highly effective composite materials based on copper for prescribed experimental conditions (high contact loads and sliding rates, absence of a lubricant, operation in a high vacuum or in air) are considered. It is shown that reliable efficiency for a tribological system under friction conditions with action of high compressive forces and sliding rates is provided by material adaptation that is achieved via the tribological synthesis at the contact surfaces of a lubricating layer different in composition and structure from the original composite.

Peculiarities of structure formation during casting of hypereutectic silumin with inverted structure

Peculiarities of structure formation during casting of hypereutectic silumin with inverted structure

Structural parameters of concentrated aqueous solutions of LiCl under extreme conditions, as calculated by the method of integral equations. Effect of temperature

Peculiarities of structure formation of aqueous LiCl solutions at different salt : water molar ratios (LiCl : n H2O, n = 3.15, 8.05, 14.90) under conditions of isobaric heating (p = 100 bar, T = 298, 323—523 K, ΔT = 50 K) were studied by the method of integral equations. Heating of LiCl : 14.90H2O solution was found to lead to disappearance of tetrahedral ordering of solvent molecules, appreciable weakening of the coordination abilities of both ions, and to an increase of the number of contact ion pairs and a decrease of the number of solvent-separated ion pairs. For the LiCl : 8.05H2O system, the tetrahedral structure of the solvent disappears at a lower temperature and heating has a less pronounced effect on the coordination and associative abilities of the ions. In the LiCl : 3.15H2O solution, tetrahedral ordering of the solvent molecules disappears at 298 K and the number of contact ion pairs decreases as temperature increases. Other structural changes in this system upon heating are similar to those found for the LiCl : 14.90H2O and LiCl : 8.05H2O solutions.

The Influence of Directed Alloying and Thermomechanical Treatment on the Structure and Mechanical Properties of High-Purity Chromium, Molybdenum and Tungsten

The possibilities of directed alloying as well as thermomechanical treatment for improvement of the mechanical properties of high-purity chromium, molybdenum and tungsten are considered. Classification of methods of directed alloying is given. The conditions are considered of hot, warm and cold metal working as well as the peculiarities of structure formation in each temperature range.

The Influence of Mesomorphic State on the Durability of Polymer Coatings

Abstract The laws governing the destruction of polymer coatings during their use are partly defined by the fact that the rate and other specific features of their destruction are influenced by internal stresses occurring as a result of incomplete relaxation processes due to peculiarities of structure formation.1 This paper deals with an investigation carried out with the help of the NMR method of higher resolution, electron microscopy and physicochemical methods to study the effect of the oligomeric block structure, length and flexibility of a number of oligoester acrylates on peculiarities of oligomer structure formation as well as coatings structure and properties and their durability in the conditions of aging under ultraviolet radiation. It's been shown that coatings set through the intermediacy of mesomorphic structure formation have increased durability of 2-2.5 times, during aging under ultraviolet light radiation. Of all the studied systems those with a globular structure tend to have the lowest d...