Formation Of Composite Structure Research Articles

Combined effect on properties and durability performance of nanomodified basalt fiber blended with bottom ash-based cement concrete: ANOVA evaluation

A control of a cement composite structure formation from modern positions should be carried out taking into account the synergistic effect of its components. The goal of the article is to study the combined effect of nanomodified basalt fiber (NBF) and bottom ash (BA) as structural elements of concrete using a two-factor analysis of variance ANOVA. The tasks for achieving this goal are the development of nanomodified basalt fiber bottom ash-cement concretes, as well as the study of their fresh, physical and mechanical properties (slump, slump flow, average density, compressive and flexural strength, elastic modulus and crack resistance) and durability performances (water, frost, and abrasion resistance). Nanomodified basalt-fiber-reinforced concretes (from 0 to 7 wt % NBF) have been developed, in which the economical Portland cement CEM I 32.5 N is replaced by up to 45 wt % mechanically activated bottom ash (400 m2/kg). Achieving uniform flowability of the compositions (slump 20–22 cm and slump flow 45–52 cm) was carried out by varying the dosage of an economical superplasticizer with a high water-reducing ability (35%). The joint effect of the BA and NBF provides control over the structure formation of cement materials, which ensures the redistribution of internal stresses from shrinkage deformations throughout the entire volume of the composite; during loading, the process of crack formation is retarded, stress concentration near structural defects is reduced, and stresses are redistributed in the microstructure of the cement composite between its components.High values of mechanical properties (compressive strength up to 59.2 MPa, flexural strength up to 17.8 MPa, elastic modulus up to 52.6 GPa, limit stress intensity factor 0.507 MPa m0.5) are explained by the complex effect of bottom ash and nanomodified basalt fibers. For the composition with 30 wt % BA and 5 wt % NBF, W18 water resistance grade, F400 frost resistance grade, and the abrasion resistance of 0.59 g/cm2 were achieved, which characterizes the high durability of the developed materials.

Formation of effective carbon composite structure for improving electrochemical performances of rhombohedral Li3V2(PO4)3 as both cathode and anode materials for lithium ion batteries

Formation of effective carbon composite structure for improving electrochemical performances of rhombohedral Li3V2(PO4)3 as both cathode and anode materials for lithium ion batteries

Structure formation and peculiarities of polymer composites based on the mixture of epoxy and polyethylene oxide oligomers

Structure formation and peculiarities of polymer composites based on the mixture of epoxy and polyethylene oxide oligomers

Особенности формирования структуры спеченных порошковых материалов с использованием отходов металлообработки стальных заготовок

Introduction. Manufacturing processes, to one degree or another, are associated with the metal waste production in the form of metal chips. The development of technologies for recycling of waste from mechanical facilities is a popular solution both from the resource saving and from an environmental points of view. Among many traditional approaches to the problem of recycling metal chips, the most interesting may be the method of using chips as one of the components in a powder material. The aim of this work is to analyze the possibility of using metalworking wastes from steel 45 (metal chips) in powder compositions based on titanium and aluminum not only as a source of iron, but also as a possible source of Fe2O3 oxide. Attention to the oxide was paid in terms of initiating reduction reactions in the powder mixture based on titanium and aluminum with the formation of the Al2O3 oxide phase to obtain a metal matrix composite. Research methods: steel chips after processing workpieces from steel 45 were additionally oxidized in water and crushed in a vibrating mill to an average particle size of 300 μm for use in powder compositions with titanium and aluminum powders. Grinded and oxidized chips were mixed with titanium and aluminum powders in various proportions in order to study its interaction with these powder components. The obtained mixtures were pressed in the form of cylindrical samples and sintered in a vacuum furnace at a temperature of 1,000 °C. The phase composition and microstructure were studied using an XRD-6000 X-ray diffractometer with CuKα – radiation and an AXIOVERT-200MAT optical microscope. Results and discussions. It is shown that after milling without coolant, steel 45 chips did not accumulate a noticeable amount of iron oxides, which required additional oxidizing procedures. The interaction of grinded oxidized chips with the components of powder mixtures is considered, and its effect on volumetric changes in compacts and structure formation of metal-matrix composites is shown. The results of optical metallography and X-ray diffraction analysis (XRD) of sintered powder compositions using oxidized ground chips of steel 45 made it possible to evaluate the ongoing processes of structure formation depending on the combination of interacting components, its mutual influence, and the prospects for obtaining composites with a dispersed oxide phase.

Synthesis of ((CeO2)0.8(Sm2O3)0.2)@NiO Core-Shell Type Nanostructures and Microextrusion Printing of a Composite Anode Based on Them.

The process of the hydrothermal synthesis of hierarchically organized nanomaterials with the core-shell structure with the composition ((CeO2)0.8(Sm2O3)0.2)@NiO was studied, and the prospects for their application in the formation of planar composite structures using microextrusion printing were shown. The hydrothermal synthesis conditions of the (CeO2)0.8(Sm2O3)0.2 nanospheres were determined, and the approach to their surface modification by growing the NiO shell with the formation of core-shell structures equally distributed between the larger nickel(II) oxide nanosheets was developed. The resulting nanopowder was used as a functional ink component in the microextrusion printing of the corresponding composite coating. The microstructure of the powders and the oxide coating was studied by scanning (SEM) and transmission electron microscopy (TEM), the crystal structure was explored by X-ray diffraction analysis (XRD), the set of functional groups in the powders was studied by Fourier-transform infrared spectroscopy (FTIR) spectroscopy, and their thermal behavior in an air flow by synchronous thermal analysis (TGA/DSC). The electronic state of the chemical elements in the resulting coating was studied using X-ray photoelectron spectroscopy (XPS). The surface topography and local electrophysical properties of the composite coating were studied using atomic force microscopy (AFM) and Kelvin probe force microscopy (KPFM). Using impedance spectroscopy, the temperature dependence of the specific electrical conductivity of the obtained composite coating was estimated.

Fundamentals of technology theory of production, calculation physical and mechanical properties and indicators chemical and biological properties of frame building composites

Energy saving, operational reliability of buildings and structures for various purposes is determined by the durability of building materials and products used in their construction. To date, frame building composites have been developed on the basis of polystructural theory. The frame technology for the manufacture of building products consists in the preliminary manufacture of frames from coarse-pored mixtures, followed by filling voids in the hardened frame with a matrix-plasticized binder, fine-dispersed or fine-grained composition, while the frames and matrix can be formed on various binders. This technology makes it possible to obtain building materials and products with a combination of the most diverse and even incompatible binders with a predetermined set of properties, i.e. opens the way to directional materials science. The paper presents the results of theoretical research and calculation of the technological physical and mechanical properties of frame composite building materials. The regularities of the structure formation of frame composites at the level of the formation of frames and matrices, as well as when they are combined, are revealed. It is established that the process of impregnating the frame with a matrix obeys the laws of motion of freely dispersed or connected dispersed systems. Formulas for calculating structural stresses in hardening frame composites are derived. Analytical dependences for calculating the thermal conductivity coefficient of products are obtained from phenomenological positions. Expressions for the calculation of the modulus of elasticity are obtained for models of ordered aggregates and the kinetics of the processes of destruction of frame composites under their loading is shown. Theoretical dependences for calculating the diffusion coefficient in frame composites on the main structure-forming factors are established.

Structure and phase composition formation of cast aluminum matrix composites during multiple remelting

The lack of understanding as to the nature of interfacial interaction between reinforcing particles and the matrix alloy during repeated remelting of cast composite materials is one of the problems hindering the expansion of their industrial application. This research is aimed at establishing the effect of repeated remelting of AK12 + 10 vol.% SiC aluminum matrix composites on the retention and chemical stability of silicon carbide reinforcing particles. It is shown that an increase in the number of remelting iterations is not accompanied by any new phases appearing at the interfaces between particles and the matrix, which indicates the stability of the SiC reinforcing phase in aluminumsilicon melts under the considered temperature-time and concentration conditions. Repeated remelting of aluminum matrix composites with silicon carbide shifts the particle distribution uniformity towards a more uniform distribution degree (on average 0.81046 at the first remelting iteration, 0.6901 at the second one and 0.5609 at the third one) and slightly reduces their average sizes (from 70.74 μm at the first iteration to 65.76 μm at the second one and 61.21 μm at the third one), apparently due to particle fragmentation that leads to an increase in the quantity of finer particles. At the same time, the share of the area occupied by particles in the section regions under consideration remains practically unchanged (10.9293, 10.9607 and 11.6483 % at the first, second and third remelting iterations, respectively). In the course of repeated remelting of Al–SiC aluminum matrix composites, processes of reinforcing particle redistribution occur that lead to the destruction of agglomerates even without intensive mixing with an impeller. Due to this, the uniformity of particle distribution in the structure of secondary aluminum matrix composite ingots can be significantly improved.

Composite Porous Structure Formation by Platinum-Particle-Assisted Etching of a Highly-Doped p-Type Silicon: Evaluation of Charge Flow in Silicon

Electroless deposition of metal particles on silicon (Si) followed by the metal-assisted etching (metal-assisted chemical etching) is a simple way to fabricate Si nanostructures. A composite porous structure consisting of straight macropores and a mesoporous layer can be created by platinum (Pt)-particle-assisted etching. In this work, we studied the composite structure formation on a highly-doped p-Si (ca. 5 × 1018 cm−3) in comparison with a moderately-doped p-Si (ca. 1 × 1015 cm−3). The composite structure drastically changed: the ratio of mesoporous layer thickness to macropore depth increased to 1.1 from 0.16 by using the highly-doped Si instead of the moderately-doped Si. The open circuit potential of Si in the etching solution shifted to the positive direction by the Pt deposition. The potential shift of highly-doped Si was smaller than that of moderately-doped Si, which can be explained by the polarization characteristics. We calculated the band bending in Si by using a device simulator that reproduced the conditions of Pt-particle-assisted etching. The results indicated that, in the case of highly-doped Si, the consumption rate of positive holes at the Si surface away from the Pt particles increases due to the tunneling effect, which is consistent with the thick mesoporous layer formation.

Основные результаты и направления дальнейших исследований по низкотемпературному плазменному формированию композитных структур на рабочих поверхностях геометрически сложных металлических изделий

The attained results and valid directions of further research on improving the efficiency of low-temperature plasma for-mation of composite structures on the functional surfaces of geometrically complicated metal products (in particular, metal-cutting tools) are conducive to improving their durability and expanding areas of application

Influence of Parameters of Melt Processing by Nanosecond Electromagnetic Pulses on the Structure Formation of Cast Aluminum Matrix Composites

Influence of Parameters of Melt Processing by Nanosecond Electromagnetic Pulses on the Structure Formation of Cast Aluminum Matrix Composites

A Study of the Peculiarities of Molding and Structure Formation of Compacted Multicomponent Silicide Composites

A Study of the Peculiarities of Molding and Structure Formation of Compacted Multicomponent Silicide Composites

Investigation of the effect of a multicomponent additive on the structure formation and hardening of cement composites

The development and application of multicomponent multifunctional additives for cement composites is an important research area since the use of such additives allows controlling both the rheological properties of the freshly prepared mixture and the physical and mechanical characteristics of the finished composite. This work proposes to use a multicomponent multifunctional additive with the composition of “SiO2 nanoparticle - superplasticiser - polypropylene fibre” for the modification of cement composite materials based on sand and chalky flour. We studied the peculiarities of the influence of this additive on the technological characteristics of mixtures (plasticity and form stability) and the processes of setting-up, hydration, structure formation, and strength gain of the composite materials. It was shown that the introduction of this additive allows increasing the plasticity limit and structural strength and reducing relative plastic deformations of the cement mixture at the manufacturing stage. At the same time, this additive accelerates the processes of setting-up, hydration, and strength gain of cement composites. It was proved that the increase in strength is due to the formation of a dense structure of hydrated new growths of the cement substance formed by phases of low and highly basic calcium silicate hydrates of various compositions and morphologies, as well as the absence of a portlanditephase.

Formation of composite structure of Fe—Cr—C + TiC system during arc surfacing using filler flux-cored wire

Arc surfacing using filler flux-cored wire contained titanium carbides with a size of 900...2390 µm is considered. It is shown that titanium carbide is partially preserved in the deposited metal, but is characterized by an uneven distribution. Dissolved titanium carbide is formed in the structure by uniformly distributed finely dispersed phases ranging in size from 4 to 33 µm. It is shown that it is more expedient to use a scheme with the supply of filler material from the head side of the weld pool.

X-ray diffraction of concrete composites of high structural strength and density

Аn analysis of the structure formation of concrete composites, compressive strength of which exceeds 120 MPa and a quantitative analysis of their qualitative composition and hydration products by X-ray diffraction, x-ray spectral analysis. The main factors affecting the physicomechanical parameters of the complex of various nanofillers and the formation of a denser cement stone structure, which mainly includes calcium hydrosilicates, calcium silicate hydroaluminates and hydroaluminates of various basicity, are studied.

Strength equation of composite materials and fractal dimension of cracks

The paper presents the derivation of a strength equation of composite materials that can be represented in the form of polydisperse systems. The theoretical analysis shows that the process of composite material structure formation is anti-persistent. A structural transition was revealed at a volume defect concentration of 0.65, which leads to a sharp decrease in the relative material strength. The dependence for calculating the crack system fractal dimension based on the experimental dependences of the material strength and porosity is justified.

Electrochemical Investigation of the Effect of Hydrogen Peroxide Concentration on Platinum-Particle-Assisted Etching of p-Type Silicon in a Hydrofluoric Acid Solution

Metal-assisted etching (metal-assisted chemical etching) has attracted increasing attention as a low-cost and versatile microfabrication technique of semiconductors. In platinum (Pt)-particle-assisted etching of silicon (Si), a composite structure of straight macropores and a mesoporous layer can be produced, but the mechanism of the structure formation is still open to discussion. We employed an electrochemical approach to investigate the composite structure formation by the Pt-assisted etching. Polarization curves of Pt-deposited Si and bare Si were measured in hydrofluoric acid (HF) solutions containing different concentrations of hydrogen peroxide (H2O2). The open circuit potential during the Pt-assisted etching was more positive than that of the bare Si and it shifted in the positive direction with increasing the H2O2 concentration as a consequence of the enhancement of the H2O2 reduction reaction. For the structure observation, both the macropore depth and the mesoporous layer thickness increased with increasing the H2O2 concentration, while the ratio between them changed. We discussed the structure change on the basis of the polarization characteristics. The mesoporous layer formation can be explained by the hole consumption at the Si surface under the positive potential which is determined by mixed potential theory.

Revealing specific features of structure formation in composites based on nanopowders of synthesized zirconium dioxide

Peculiarities of formation of microstructure in composites based on chemically synthesized zirconium nanopowders obtained by the method of decomposition from fluoride salts were considered. Hydrofluoric acid, concentrated nitric acid, aqueous ammonia solution, metallic zirconium, and polyvinyl alcohol were used. It was established that the reduction of porosity in nanopowders in the sintering process is the main problem in the formation of high-density materials. Analysis of various initial nanopowders, their morphology, and features of sintering by the method of hot pressing with direct transmission of electric current was made. Peculiarities of obtaining the composites based on them with the addition of Al2O3 nanopowders applying the electric sintering method were considered. It was shown that the increase in the content of alumina nano additives leads to an increase in strength and crack resistance of the samples due to simultaneous inhibition of abnormal grain growth and formation of a finer structure with a high content of tetragonal phase. The influence of sintering modes on the formation of the microstructure of zirconium nanopowders has been studied for different contents of alumina additives. Electric current promotes the surface activity of nanopowders and its variable value promotes partial fragmentation of agglomerated grains thus affecting the composite structure. Physical-mechanical properties of the obtained samples, optimal compositions of mixtures, and possibilities of improving some parameters were determined. It was found that nanopowders of zirconium dioxide obtained by the method of decomposition from fluoride salts are quite suitable for the production of composite materials with high physical and mechanical properties. They can compete with imported analogs and enable obtaining of crack resistance of 7.8 MPa·m1/2 and strength of 820 MPa.

Processing of ilmenite into synthetic rutile using ball milling induced sulphurisation and carbothermic reduction

Sri Lanka is a major global producer of raw material-heavy minerals from beach placer deposits. This study focusses on upgrading Sri Lankan ilmenite sands to synthetic rutile via a mechanochemical method. Ball milling-induced sulphurisation and carbothermic reductions were examined using several geochemical techniques. Raw ilmenite concentrate contained over 95 wt% FeTiO3, ∼2 wt% SiO2, and ∼ 1 wt% Al2O3. Ilmenite was mixed with additives (i.e. sulphur, vein graphite, and a 1:1 mix of sulphur and vein graphite), separately in three ratios by weight, namely 1:1, 2:1 and 4:1, respectively. Each mixture was milled for 4 and 6 h. A high percentage of ilmenite/sulphur + graphite (ISG) was converted to nanoparticles (average particle size = 124 nm) in samples milled for 6 h. X-ray diffraction (XRD) spectra indicate that the intensities of sulphur and graphite peaks decrease after ball milling. This suggests possible dissolution of sulphur and graphite into the ilmenite structure, with the formation of mixed composite structures. The optimum ilmenite to additives ratio for ilmenite to rutile conversion was found to be 4:1. The occurrence of pyrite and pseudorutile peaks in XRD spectra of milled samples indicates that ilmenite reduction was initiated during ball milling. Fourier-transform infrared (FTIR) spectra of milled samples confirm the octahedral metal-ion stretching vibrations of carbon-incorporated ilmenite structures. The ilmenite-additive mixtures containing both sulphur and graphite (ISG) showed the best results. Consequently, ISG samples (mixing ratio of 4:0.5:0.5, and milled for 6 h) were isothermally annealed at 800 °C, 1000 °C and 1200 °C, respectively. Sharpening of rutile peaks and disappearance of pyrrhotite peaks in the annealed samples indicated the completion of the mechanochemical reactions that were initiated during ball milling. The optimum temperature for ilmenite reduction was determined to be 1000 °C. At that temperature pseudorutile peaks had disappeared from the XRD spectra of the annealed samples, whereas brookite and rutile peaks appeared. The method introduced in this study thus can be utilised to convert ilmenite to synthetic rutile.

Усиление внутреннего слоя многослойного композита базальтопластиком в виде сотовой структуры

In our studies we present a multilayer structure consisting of outer layers of two-ply basalt composed of basalt fabric impregnated with an epoxy compound and an inner layer of polyurethane reinforced with basalt, having the same composition, formed in conjugate hexagonal prisms, and forming a cellular framework. The main part describes the technological sequence of obtaining basalt face layers, basalt hexagonal cellular frame, and filling it with a liquid reaction mass of rigid polyurethane system. The formation of a single multilayer composite structure is shown. We also present the results of the experimental research of strength of a laminated composite and its inner layer without facing layers when tested for static bending with concentrated load increasing at a constant rate and compression testing up to 10% of relative deformation. It describes the effect of the size of hexagonal prismatic cells of the frame on the physical and mechanical characteristics of the middle layer. The reduction of the cell size results in the increase of the composite strength. The dependence of the composite density on the size of the cells of the basalt frame has been studied.

The Network Structure Formation of Cu-CNTs Composites During Multi-Directional Forging Process and its Mechanical Properties

Cu–[Formula: see text] CNTs composites ([Formula: see text], 1, 2, 3 vol.%) were successfully prepared using a combination of pre-treatment, powder metallurgy and multi-directional forging processes, which provides a solution for the industrial manufacture of the composites with network CNTs structures. During the multi-directional forging process, the CNTs in the composites were distributed in a network under the synergy of metal flow and copper particle squeeze. Compared with other structure modes, the network CNTs can effectively carry and transfer loads resulting in the promotion of mechanical properties (such as, the tensile strength approximately 1.5 times higher than those of composites with the same volume fraction without network structure). The composite with 2 vol.% CNTs had the highest elongation in this experiment (41%), which is about 5 times higher than the composites with other CNTs distribution patterns. At a low CNTs content level (1[Formula: see text]vol.%), a complete load transfer network cannot be formed, resulting in a relatively insufficient mechanical properties of the composites. As the content level is exceeded (3vol.%), it caused significant agglomeration of the CNTs, which lead to fracture in the agglomerated CNTs and elongation degradation of the composites.