Structure Formation Processes Research Articles

CONTROL OF SETTING TIMES OF SLAG-CONTAINING CEMENTS ACTIVATED WITH SODIUM METASILICATE

In global construction practice, theneed for high-strength concrete with intensive earlystrength gain is increasing due to increased requirements for the physical, mechanical and operationalcharacteristics of concrete and the desire to reduceconstruction time. Alkali-activated cements madeusing soluble sodium silicates are capable of rapidstrength development and high standard strength,which is due to the modifying effect of amorphoussilica present in soluble glass. However, the problem with the effective use of such cements is theshort setting time.The purpose of this work is to study the influenceof the method of introducing low-basic sodium silicate into slag-containing compositions, the composition of the compositions and the amount of modifying additive on the setting time. As a result of thework performed, a mechanism for controlling thesetting lines in the “slag + clinker + sodium metasilicate” binder system was developed.The dependence of setting times on the methodof introducing sodium metasilicate into the “slag +clinker” system, on the composition of cement andon the type and quantity of modifier additives hasbeen established. It has been shown that the introduction of sodium metasilicate to cement in theform of an aqueous solution leads to a much greaterintensification of structure-forming processes in theprocess in comparison with the option of usingmetasilicate in the form of a powder with mixingwith water. It has been established that an increasein the clinker content in the slag-clinker mixtureleads to a significant reduction in setting time.A study of the influence of the LSTM additiveshowed the possibility of effectively controlling thesetting lines, subject to an increased amount of useof these additives, namely up to 4%. As a result,technologically acceptable setting times were obtained within the range of 0–38…2–24 hours-min when using LSTM additives in an amount of 2…4%.The results of the study of the structure formation of alkali-activated slag-containing cement confirmed the above conclusions and were in goodcorrelation with the obtained physical and technological results.

Formation of Cellular Concrete Structures Based on Waste Glass and Liquid Glass

The use of waste in the production of building materials is one of the possible ways to solve problems related to the sustainable management of non-degradable waste and difficult-to-recycle secondary resources. In this paper, a method is proposed for the non-autoclave production of an ultra-lightweight cellular concrete based on Portland cement, glass waste and liquid glass. A mixture of sodium hexafluorosilicate and hydroxide is used as a hardening activator, an aluminum powder serves as a gas-forming agent. The setting and hardening of raw mixtures occurs under the action of exothermal heat release due to a complex of chemical reactions occurring in the system, and the resulting material does not require additional heat treatment. It is optimal to use two fractions of glass waste to achieve acceptable material strength: coarse crushed (fineness modulus Fm = 0.945) and finely ground (specific surface Ssp = 450–550 m2/kg) glass. Glass particles of the fine fraction of glass, along with Portland cement, participate in hydrolytic and structure-forming processes, while glass particles of the coarse fraction play the role of reinforcing filler. The influence of the dispersion of glass and the density of liquid glass on the density, porosity, strength, water absorption and water resistance of the resulting cellular material was determined. At an average density of cellular concrete in the dry state of 150–320 kg/m3, the following characteristics can be achieved: a compressive strength up to 2.0 MPa, bending strength up to 0.38 MPa, thermal conductivity coefficient of the material in the range 0.05–0.09 W/(K·m), and a maximum operating temperature of 800 °C. The proposed ultra-lightweight cellular concrete can be used as a non-combustible heat and sound insulation material, as well as a repairing composition; the cellular concrete blocks can be used as filling masonry and for the construction of non-bearing internal walls.

Graphene self-folding: Evolution of free-standing few-layer graphene in plasma synthesis

Substrate and catalyst free gas-phase plasma synthesis of freestanding few-layer graphene (FLG) flakes leads to crumpled FLG structures. In this paper, we elucidate a folding-based mechanism and structure-formation process in accordance with literature on the stability of graphene sheets. Transmission electron microscopy is applied to thermophoretically-sampled FLG at various distances from the plasma zone. Single-layer and few-layer graphene were observed, and a morphology pattern evolution could be discerned. A conceptual model of graphene formation and growth is derived, starting from initial rounded single-layer graphene of a few hundred nanometer in diameter to, eventually, self-folded and strongly crumpled FLG.

ТОПЫРАҚ ТҰРАҚТЫҒЫНА pН ОРТАСЫНЫҢ ӘСЕРІ

Abstract. In world practice, the process of structure formation of mineral dispersions with polymers is one of the effective methods for solving many environmental problems. Patent research over the past 15 years has shown that the developments available in this area relate mainly to the structure formation of soils and soils with salts of low molecular weight substances and polymers. The main disadvantages of modern structure formers are the high salt content in the polycomplex formulation, insufficient water resistance, low aggregation ability and unsatisfactory adhesive properties. Soil particles having a diameter of 12 microns, in the pH range 10.0 - 3.0, the soil suspension should be practically stable, since the value of the energy barrier significantly exceeds the energy of thermal movement of the particles and is 166 kT (pH 10.0), 125 kT (pH 8.0), 63 kT (pH 6.0) and 41kT (pH 5.0). A further decrease in pH leads to a natural decrease in the barrier, which at pH 4.0 is 6 kT, and completely disappears at pH 3.0. Thus, for a fraction of a soil suspension with a diameter less than 12 µm, noticeable coagulation can be observed at pH £ 4.0. It is easy to show that larger soil particles with a diameter of 30-33 microns should be practically aggregatively stable even at pH 3.0, since the energy barrier in this case is 10-15 kT. When interacting with the smallest particles (a = 1 μm), the energy barrier values are: 44 kT (pH 10.0), 28 kT (pH 8.0), 18 kT (pH 6.0), 7 kT (pH 5.0) and 2 kT (pH 4.0) and only for these particles at pH < 4.0 can one expect a noticeable loss of aggregation stability by the dispersion. However, the experiment shows that significant coagulation of particles occurs already at pH 5.0 and continuously increases as the pH decreases. Key words: structure-forming agent; soil; flocculation; coagulation; interaction energy; optical density; potentiometric titration; electrophoretic mobility.

INFLUENCE OF PLASTICIZING AND AIR-ENTRAINING ADMIXTURES ON CONCRETE PROPERTIES

In the modern construction industry of Kazakhstan, to ensure the needs of the market, there is an urgent essential to improve the quality of concrete and expand its functional purpose. To a large extent, this is achieved by designing concrete as composite materials with different structures, quantities and nature of components. The multicomponent composition makes it possible to effectively manage the structure formation processes of the concrete cementing matrix and obtain concretes with the required properties. This article presented the effect of plasticizing and air-entraining admixtures on the properties of heavy concrete. The compositions of concrete mixture with plasticizing and air-entraining admixtures were selected. The results of study of plasticizing and air-entraining admixtures effect on average density, workability, compressive strength of concrete samples are presented. The effectiveness of introduction of a complex admixtures was evaluated in order to further improve operational properties of concrete. The plasticizing effect makes it possible to increase workability of concrete mortar while by reducing water-cement ratio from 0,5 to 0,38. Due to this, density and strength of concrete increased while improving operational characteristics. The combined effect of plasticizing and air-entraining admixtures had a positive effect on mobility of concrete mortar and its strength of concrete samples. The significant strength of 47,2 MPa was achieved with the combined introduction of a plasticizing and air-entraining admixtures in the amount of 1,2% and 0,5% of the cement weight, thereby increasing the strength of concrete samples by 32% compared to the control sample.

The Role of Carbides in Forming the Steels Structure and Properties under Pulsed Laser Irradiation

Introduction. At present, in scientific publications, there is no unambiguous understanding and reasoned metal physical justification of the role of the carbide phase of irradiated materials in forming the required structure and achieving a given degree of hardening of surface layers of steels during pulsed laser treatment, especially in the zone of laser hardening from a solid (austenitic) state. The solution to this issue is of great importance, since it allows us to reasonably and purposefully design the required structure of surface layers of products of various functional purposes with high performance properties. The complexity and insufficiently detailed study of the process of structure formation in the surface layers of steels under extreme thermal effects of pulsed laser radiation required a series of metal physical experiments to study the fine structure of steels after high-speed high-temperature hardening. The aim of this article was to obtain, quantify and critically analyze the array of results of metal physical studies and to assess the degree of influence of the carbide phase on the formation of structure and properties of surface layers of steels in the process of pulsed laser hardening in different modes, that is, with and without melting the surface of the samples. Materials and Methods. In the work, carbon and alloyed tool steels were subjected to surface laser irradiation at a Kvant 16 installation. The radiation power density was 70–200 MW/m2. Optical, scanning probe and electron microscopy were used in conducting metal physical studies, as well as methods of diffractometric, spectral and durometric analysis of steels before and after laser treatment. Results. It was shown that laser treatment of steels with a radiation power density of 130–200 MW/m2 led to a local change in the chemical composition in the laser-fused areas of the spot, partial or complete dissolution of carbides present in the irradiated metal and an increase in the amount of residual austenite in the fused areas up to 40–60 %. It was found that on P6M5 steel, the maximum possible hardness of the irradiated zones was achieved by dissolving 30 % of carbides, on 9XC, HVG steels — 60–70 %. It was shown that under pulsed laser irradiation with q=70–125 MW/m2, that is, without melting the steel surface, "white zones" formed around carbide inclusions under the influence of thermo-deformation stresses at the boundaries of the "carbide – steel matrix" composition. They had irretrievability, dispersion of the structure and increased hardness (10–12 GPa). It was determined that the maximum hardness of laser-hardened metal in the zones of laser hardening from a solid state was achieved if the "white zones" occupied 40 % of the irradiated area of steel. It was found that the dispersion of carbides in this case was 0.5–1.5 microns. Discussion and Conclusion. The results of the conducted studies indicate that in order to obtain the best combination of hardness and viscosity of the irradiated zones during laser treatment with melting of the surface of steels of different chemical composition, it is necessary to dissolve different amounts of carbides. The dispersed structure of laser-fused steel zones, along with a sufficiently high content of residual austenite, predetermine the possibility of improving the operational characteristics of irradiated materials, especially under conditions of external shock loads. The analysis of the conducted metal physical studies irradiated without melting the surface of steels allows us to conclude that in order to obtain a high degree of hardening, it is necessary and expedient to ensure the presence of a certain volume of dispersed carbides in the structure of the irradiated steel. The structural composition of "white zones" formed during laser treatment without melting the steel surface contributes to obtaining a unique level of operational properties. The results of the performed studies contribute to the theory of steel structure formation under conditions of extreme heat exposure and allow for a rational choice of modes of surface laser processing of products and their operability.

Fabrication and characterization of modified POD membranes with ultra-high tensile strength through hydrogen bonding functioning and copolymerization

A series of modified aromatic oxadiazole polymers were synthesized via condensation reactions of terephthalic dihydrazide (TPH) and varying amounts of Trimesic acid (H3BTC) in polyphosphoric acid (PPA). Pentaerythritol was introduced to construct intermolecular hydrogen bonds among polymeric chains, resulting in a three-dimensional network structure, and correlations between H-bonds and mechanic properties are discussed. Structures and mechanic properties of the polymers were characterized and analyzed. By investigation of molecular structure and membrane formation process of chemically modified and hydrogen bond-regulated polymer membranes, it was found that the modified polymer membranes retain the unique thermal stability, chemical stability, and good hydrophobicity of the POD rigid polymer. Additionally, hydrogen bonds not only significantly improve the overall quality of the membrane, but also play an important role in enhancing the mechanical properties of the membrane, as demonstrated in the highest observed of up to a maximum of 167.19 MPa. Furthermore, impact of H3BCT modification on light absorption and fluorescence performance of T-PODx is also analyzed and discussed in this paper.

Assessment Possibility of Controlling Structure Formation by Changing the Technological Parameters LPBF Process

Abstract—In this paper, the possibility of creating a controlled structure by varying the parameters of laser powder bed fusion (LPBF) process on the example of austenitic stainless steels is studied. Based on the study of the structure of experimental samples, the influence of a combination of various technological parameters that make up the scanning strategy when preparing a 3D-model for the LPBF process on the processes of structure formation is shown. The possibility of forming elements with different structures within one part during its manufacture by the LPBF method by changing the technological parameters of the process that make up the scanning strategy is shown. It is noted that the use of 3D-models identical in the geometry formed, but different in the strategy of scanning with a laser beam directly in the process of laser fusion, leads to the formation of a fundamentally different structure of the created sample, since the formation of the microstructure is strongly influenced by the conditions of metal crystallization, which directly depend on the scanning strategy.

Кераміка ZrB2 з добавками MoSi2, SiC і B4C: кінетика ущільнення, фазоутворення та опір повзучості

A study was carried out of the processes of compaction, structure formation and mechanical properties of ceramics based on zirconium boride with sintering-activating additives of boron, silicon and chromium carbides, as well as molybdenum silicide, obtained under hot pressing conditions in a CO atmosphere. In ZrB2—18% (vol.) B4C ceramics, the use of the B4C additive reduces the optimal hot pressing temperature to 1940 °C and accelerates the compaction process of the ceramics. The influence of the sample preparation background on high-temperature creep has been established, as a result of which either plastic flow of the material occurs over a wide temperature range, or a high temperature threshold for yield and brittle fracture. In ZrB2—SiC ceramics, during high-temperature plastic deformation both during sintering and in creep tests, a bidisperse structure with a submicrograined component is formed, which is responsible for high creep rates. In ZrB2—B4C ceramics there is no submicrograin component, which provides high creep resistance up to 2000 °C. The phase composition of ZrB2—MoSi2 ceramics changes dramatically during hot pressing; it is represented by a composition of a ZrB2 solid solution with the second phases of SiC and B4C, and in terms of creep resistance it occupies an intermediate position between two other ceramics. Keywords: ultra-high temperature ceramics, zirconium diboride, silicon, boron and chromium carbides, hot pressing in a CO atmosphere, compaction kinetics, structure, creep resistance.

Electrokinetic and Microstructural Peculiarities of the Portland Cement Hydration with Microadditives

AbstractThe results of given studies included a comparison of changes in temperature, redox potential, OH‐ions concentration and pH values in the Portland cement‐water‐additive system depending on the hydration time and features of hydration processes in the microstructure of the cement stone. The studied additives were selected taking into account the prospects for their use in the complex modifiers compositions for cement‐containing building materials. The results of electrokinetic measurements are presented and regularities and features of the influence of each studied additives on the processes of hydration structure and phase formation in Portland cement paste in the early stages of hardening are determined. The microstructure and fracture surfaces of cement stone samples formed during cement paste hardening with the optimal content of additives and features of hydration processes of cement stone were studied. The features of the mutual arrangement of individual phases in crystalline hydrate aggregates of cement stone, as well as the nature of the porosity of its microstructure, were investigated.

Insight into Organization of Gliadin and Glutenin Extracted from Gluten Modified by Phenolic Acids

The changes in the secondary structure of individual gluten protein fractions (gliadin and glutenin) caused by the supplementation of model dough with eight phenolic acids were analysed. Gliadins and glutenins were extracted from gluten samples obtained from overmixed dough. The changes in the gliadin secondary structure depended on the amount of phenolic acid added to the dough. Higher acid concentrations (0.1% and 0.2%) led to a significant reduction in the amount of α-helices and to the formation of aggregates, non-ordered secondary structures, and antiparallel β-sheets. After the addition of acids at a lower concentration (0.05%), the disaggregation of pseudo-β-sheet structures and the formation of β-turns, hydrogen-bonded β-turns, and antiparallel β-sheets were detected. In the case of glutenin, most of the phenolic acids induced the formation of intermolecular hydrogen bonds between the polypeptide chains, leading to glutenin aggregation. When phenolic acids were added at a concentration of 0.05%, the process of protein folding and regular secondary structure formation was also observed. In this system, antiparallel β-sheets and β-turns were created at the expense of pseudo-β-sheets.

Void probability function inside cosmic voids: evidence for hierarchical scaling of high-order correlations in real space

ABSTRACT We compare the reduced void probability function (VPF) inside and outside of cosmic voids in the TNG300-1 simulation, both in real and simulated redshift space. The VPF is a special case of the Counts-in-Cells approach for extracting information of high-order clustering that is crucial for a full understanding of the distribution of galaxies. Previous studies have validated the hierarchical scaling paradigm of galaxy clustering moments, in good agreement with the ‘negative binomial’ model, in redshift surveys but have also reported that this paradigm is not valid in real space. However, in this work, we find that hierarchical scaling can indeed be found in real space inside cosmic voids. This is well fitted by the negative binomial model. We find this result to be robust against changes in void identification, galaxy mass, random dilutions, and redshift. We also obtain that the VPF in real space at high redshift approaches the negative binomial model, and, therefore, it is similar to the VPF inside voids at the present time. This study points, for the first time, towards evidence of hierarchical scaling of high-order clustering of galaxies in real space inside voids, preserving the pristine structure formation processes of the Universe.

SECONDARY RESOURCES IN PRODUCTION OF COMPOSITE BUILDING MATERIALS BASED ON CEMENT

Link for citation: Kopanitsa N.O., Demyanenko O.V., Kulikova A.A., Tkach E.V., Shestakov N.I., Stepina I.V. Secondary resources in production of composite building materials based on cement. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 10, рр. 49-60. In Rus. The relevance of the research is caused by the importance of the problem of rational use of natural resources in production of composite building materials. The possibility of partial replacement of natural non-renewable raw materials used in the production of multi-ton concrete and mortar mixtures based on cement with secondary products from the production of various industries will solve the problems of: resource saving, energy consumption and ecology. The construction industry is the largest consumer of by-products of mining enterprises: overburden and waste from mining and processing enterprises, which is hundreds of millions of tons per year. The most studied are the issues related to their use as fine and coarse aggregates in concrete and mortar mixtures for various purposes. The expansion of the possibility of using secondary products of mining enterprises in the production of composite building materials is associated with the production of active mineral additives, fillers in concrete and mortar mixtures, as well as energetically active nanomodifiers. The use of by-products of different chemical composition and dispersion makes it possible to control the processes of structure formation and hardening of composite materials based on cement and to obtain composite materials with the required performance properties. The main goal of the research is to scientifically substantiate and investigate the possibility of using waste from mining enterprises as components in concrete and mortar mixtures based on cement. Objects: modifying additives based on secondary products; composite materials with enhanced performance properties. Methods: determination of the mobility of mixtures, normal density, hardening time, flexural and compressive strength according to SS; thermal analysis; electron microscopy, x-ray phase analysis, colorimetry. Results. The paper introduces the results of studies necessary for the scientific substantiation, development and implementation in the construction industry of the technology for production of building mortar mixtures obtained using secondary products of mining enterprises as well as the comparative results of studies on the effect of a complex additive of microcalcite and nano-SiO2 on the properties of cement systems. It is shown that the introduction of a complex additive increases the compressive strength of cement stone, reduces the consumption of cement without reducing its standard characteristics and improves the performance properties of concrete.

Investigation of the Processes of Structure Formation during Explosion Welding of Copper and Molybdenum

This article examines the processes of structure formation occurring during joint plastic deformation by the explosion of copper and molybdenum. These components are dissimilar metals with very limited mutual solubility under normal conditions, and the circumstances allowing for their interaction, as well as the products of the mechanochemical reactions of such interactions, have not been sufficiently studied and require new approaches. A cluster approach was used to describe the processes of structure formation, which describes phase formation as the process transitioning of the polyhedron of the initial phase into the polyhedron of the final phase. This work shows that under the conditions under consideration, not only is the formation of solid solutions in the contact zone with smooth concentration transitions from one component to another possible, but also the formation of new structural states, which can be represented as localized icosahedral atomic configurations (amorphous metal clusters). Such a structure is capable of locally strengthening the composite, which is confirmed by microhardness studies.

Features of structure formation in antifriction composite powder infiltered with copper alloy material based on iron (pseudo-alloy) under high-temperature thermomechanical treatment

The results of studies of the structure formation process in an iron-based antifriction composite powder material infiltrated with a copper alloy (pseudo-alloy) during thermal and high-temperature thermomechanical treatment (HTMT) are presented. It is shown that after infiltration the structure of the pseudo-alloy consists of sections of the steel skeleton with a perlite structure almost homogeneous in carbon and a small amount of cementite, sections of the copper phase located along the boundaries and at the joints of the particles of the steel skeleton, sulfide inclusions mainly in the copper phase. In the process of hardening, carbon is redistributed in the particles of the steel skeleton; a layer 2–5 µm thick with an increased carbon content is formed at the boundary with the copper phase. During HTMT, the structure is refined, a macrotexture is formed, and the thickness of the copper phase interlayers decreases, depending on the degree of deformation. The degree of deformation also affects the structure of the steel skeleton. After HTMT with a degree of deformation of 30 %, the structure consists of structureless martensite, troosto-martensite and residual austenite, and in the areas adjacent to the copper phase the carbon content is slightly lower, with a degree of deformation of 50 % – structureless martensite, 25 % more austenite content, more uniform distribution of carbon. It has been established that, due to the activation of diffusion processes during deformation during HTMT, molybdenum sulfides decompose and form iron and copper sulfides of various compositions; molybdenum alloys the iron base or forms carbide. The investigation results can be used in the development of high-strength antifriction materials for heavily loaded friction units.

Pressure oscillation and vortex in an asymmetric T-junction

The T-junction structure with one inlet and two outlets is ubiquitous in natural and aerospace systems. However, previous research has mainly focused on vortex breakdown under steady-state flow in symmetrical structures. Limited research has been conducted on vortex breakdown in asymmetric structures, where the radii of the two channels differ. This creates a flow rate difference between the outlets, and the ratio of mass flow rate in the small channel to the large channel is defined as the splitting ratio. To study the appearance of vortex structures in the outlet channel under different flow rates and splitting ratios, a split-type asymmetrical circular cross-section pipeline experimental system that can be flexibly disassembled was designed and built. Pressure signals of each channel using pressure sensors were measured and analyzed. It is worth noting that a string tracing technology combined with particle image velocimetry (PIV) technology to monitor the outlet channel was adapted to visualize the flow. Results show that the pressure oscillations in the channels of the T-junction are related to the splitting ratio. Besides, asymmetric T-junction structure exhibits different large vortex structure formation and breakup processes in the two outlet channels, and these processes are influenced by the splitting ratio.

Microstructural characterization and mechanical behavior of Aba Panu meteorite by correlative microscopy and nanoindentation

Meteorite samples that land on earth can provide important information about asteroid and meteors found in space. Thorough, multimodal, and multiscale microstructural analysis is necessary to provide clues about the formation history of these materials. Both 3D x-ray tomography and scanning electron microscopy, along with energy dispersive spectroscopy, were used to obtain detailed structural information from the Aba Panu meteorite. EDS was utilized to obtain elemental composition and identify existing minerals in the meteorite. The microstructural analysis enabled a proposed hypothesis of potential local structure formation processes supported by phase diagrams of the existing minerals. Mechanical properties of identified phases were measured using nanoindentation and Vickers hardness testing. By combining structural, compositional, and mechanical results, a comprehensive characterization and discussion of meteorite Aba Panu was obtained.

INVESTIGATION OF THE PHASE FORMATION PROCESS
 DURING THE SYNTHESIS OF CERAMIC MATERIALS
 BASED ON MODIFIED YTTRIUM MANGANITE

The aim of this work is to establish the nature and sequence of phase formation processes in the synthesis of ceramic
 materials based on yttrium manganite using different manganese oxides and structure modifiers. Differential scanning calorimetry,
 X-ray phase analysis, and scanning electron microscopy were used as research methods in the work. The physicochemical
 and electrophysical properties of the obtained samples were determined. Samples of modified yttrium manganite
 were obtained by solid-phase sintering of the initial components at various temperature-time parameters of heat treatment.
 The influence of Bi2O3, CoO and TeO2 additives on the physicochemical and electrophysical properties of prototypes was
 studied. Regularities of the structure formation processes and phase composition of ceramic materials are established in
 relation to the composition of raw materials and the technological parameters of the synthesis of modified yttrium manganite.
 It has been established that the addition of oxides of the RO type contributes to a decrease in the degree of crystallization
 of the samples, as evidenced by a decrease in the intensity of the diffraction peaks of the crystalline phases. In this case,
 the qualitative composition of the phases practically does not change, but the proportion of the amorphous component in the
 structure of the material increases. Bi2O3 has the most effective modifying effect in the synthesis of yttrium manganite.
 Its addition into the composition of the raw mixture intensifies the process of formation of the yttrium manganite phase with
 a crystal size of 2–4 μm, which is confirmed by the results of DSC, XRD, and electron microscopy. The intensification of the
 crystallization process due to the addition of bismuth oxide is explained by the developed mechanism of liquid-phase sintering
 and the formation of a significant number of crystallization centers. The developed ceramic materials based on modified
 yttrium manganite have a set of electrophysical characteristics that make it possible to recommend them for the manufacture
 of various elements of electronic technology.

Mechanical activation of aqueous solutions as a way to improve mixing and structure formation in dispersed systems

The process of dough preparation is one of the most complex in bread production technology. Stirring of flour with liquid components (water, aqueous solutions) is a complex process of surface interaction associated with overcoming the surface energy at the interface between phases. The intensity of formation of a homogeneous mixture of flour and liquid components, subsequently transformed into dough, determines its structural and mechanical properties. The aim of the work is theoretical substantiation and experimental confirmation of the influence of preliminary mechanical treatment of liquid components on the process of dough mixing and structure formation of water disperse system. Theoretical analysis of the process of adhesive interaction of bulk material with liquid has been carried out. It is shown that the surface energy at the boundary of interaction with phases should be reduced. It is experimentally established that mechanical action on water and aqueous solutions reduces surface tension by 20-30 %. It is established that at mixing of flour and liquid components of dough the preliminary mechanical treatment gives the effect of improvement of wetting, increase of elasticity and reduction of time of structure formation in dough. The specific power during kneading is reduced by 15-20 %. With the help of rheometry means ("Rheotest", Structurometer ST 2, conical Rebinder plastometer) improvement of structural and mechanical properties of the dough is shown: increase of ultimate shear stress by 20-25 %, decrease of adhesion by 30-40 %, increase of elastic properties after kneading up to 10 %, increase of water-binding capacity. The studies were carried out on laboratory equipment and in production conditions at the enterprises of JSC "Kemerovokhleb".

Concentration dependence of microstructural evolution of Zr-Pt liquid alloys: A molecular dynamics study

The concentration dependence of the atomic structure and glass formation process of Zr100-xPtx (10 ≤ x ≤ 60) alloys were investigated by molecular dynamics simulations in this study. The agreement between the structural functions and the experimental data showed that the local order is reliably predicted. It was observed that the Zr40Pt60 alloy has the highest glass transition temperature and the fraction of crystal-like clusters. Common neighbor analysis revealed that the icosahedra and icosahedra-like clusters are more frequent for x < 50 concentrations, while bcc-like clusters are effective for x ≥ 50. It was seen that the local environment around Pt atoms would be more flexible, while Zr atoms would more easily adopt a preferential local packing according to their preferences. Present findings suggest that the strong chemical affinity between Zr and Pt plays an influential role in the nucleation of local structure in the system, and the addition of Pt weakens the icosahedra short-range order.