Phase Composition Of Products Research Articles

Energy-efficient scientific-technological approaches to the processing of plastic waste PET, PE, PP, PS to produce hydrogen-containing gas and titanium carbide powder

The paper considers gaseous products, structure and phase composition of hard products resulting from high-temperature exothermic reactions between Ti–PET–(PE, PP, PS) system components, depending on the content of oxygen-free polymers polyethylene (PE), polypropylene (PP), and polystyrene (PS) in the initial blend. It is found that the addition of PE, PP, PS polymers to the Ti–PET system increases the hydrogen content from 45 to 62 vol% and reduces the carbon monoxide content from 38 to 20 vol% in gaseous products. According to calculations, the adiabatic flame temperature of the synthesized gas in air is very close to that of pure hydrogen. The synthesized gas can therefore be used as ecological fuel for energy sources. On the other hand, oxygen-free polymers presenting in the system provide the formation of substoichiometric carbide TiC0.75. Its hardness is not lower than that of stoichiometric TiC and even exceeds widely used carbides and borides of transition metals. In addition, the agglomerate structure of synthesized TiC0.75 allows to apply it as a promising ecological basis for highly-efficient abrasive pastes, in particular for polishing and finishing fabricated metal products.

Studying the formation of nodules in a Ni-Fe-Cr based superalloy used in fireside corrosion under the impact of creep stress

Creep rupture tests on a Ni-Fe-Cr based superalloy were conducted in a custom-built rig at 750 ℃ under simulated fireside corrosion environment. The impact of creep stress on corrosion was investigated by controlling load level (without loading, loads of 120~195MPa). The phase composition, microstructure, and morphology of surface corrosion products and corrosion-affected area were studied. The mechanism responsible for the production of surface nodules and the observed uniform oxide scale during fireside corrosion are discussed. Results show that the presence of creep stress promotes the development of surface nodules and increases the corrosion-affected area.

Enhancing the high-temperature corrosion resistance of HVOF-sprayed NiCoCrAlY coating in marine environment by Pt modification and pre-oxidation

To prolong the service lifetime of hot-section components used in marine environment at elevated temperatures, it is crucial to explore and develop high-temperature corrosion-resistant coatings. High-velocity oxygen fuel (HVOF) sprayed NiCoCrAlY, Pt-modified NiCoCrAlY and pre-oxidized Pt-modified NiCoCrAlY coatings were prepared and investigated. This study is concerned with the performance of three coatings in a simulated marine environment based on the phase composition of corrosion products and microstructure evolution of coating samples combined with first-principles density functional theory. The results show that the NiCoCrAlY coating was subject to accelerated corrosion and extensive aluminum depletion, leading to premature coating failure. The high-temperature corrosion resistance of Pt-modified NiCoCrAlY coating was found to be better than that of NiCoCrAlY coating. In contrast, the pre-oxidized Pt-modified NiCoCrAlY coating offered long-lasting protection and exhibited the best corrosion resistance, which is attributed to the positive synergistic effect between Pt modification and pre-oxidation.

Құрамында бор бар силикохромды қолдану арқылы төмен көміртекті феррохромды балқыту процесін термодинамикалық модельдеу

The TERRA program for calculating multicomponent heterogeneous systems, based on the principle of maximum entropy, was used to study systems with a complex chemical composition, in which the task of numerical modeling is chemical and phase transformations play an important role. The effect of charge composition and temperature on the chemical and phase composition of melting products was studied, the degree of transition of charge elements into metal was determined, and optimal conditions for obtaining the alloy were found. The thermodynamic analysis of the ferrochromium production process showed that in order to approach the real process of low-carbon ferrochromium smelting, it is necessary to take into account the degree of silicon use by introducing oxygen into the working fluid to oxidize excess silicon according to the calculation. On the basis of the performed thermodynamic analysis, it is also shown that the choice of the process temperature (1750-1800°C and more) is associated with the kinetic conditions of melting, the melting temperature of the formed metal and slag. Therefore, it is expected that the presence of boron oxide, in addition to stabilizing slag from decomposition, will reduce its melting point, and the early appearance of the liquid phase due to low-temperature boron phases will ensure a shift in the reduction reactions of chromium with silicon to the low-temperature region. All these provisions will be implemented during high-temperature experimental work on the development of technological parameters.

Effect of hydrogen on steels in hydrogen sulfide-containing and other environments at gas facilities

The impact of hydrogen sulfide raw materials on steel equipment and pipelines is known and is associated not only with internal corrosion processes, but also with the hydrogenation of carbon and low-alloy steels used. Penetration of hydrogen into steel can lead to the loss of its strength properties and subsequent destruction of gas pipelines operated under high pressure conditions. The manifestations of cracking characteristic of hydrogen sulfide environments, which are a consequence of the penetration of hydrogen into steel, are the most dangerous from the point of view of the safety and reliability of the operation of facilities for the production and transportation of corrosive gas. The effect of H2S on the decrease in ductility of the main types of structural steels was studied based on the results of simulation tests. The formation of blisters (bloatings) and cracks on the surface of steels due to the effect of hydrogen on steel was recorded. The study of the phase composition and properties of corrosion products was carried out in order to assess their possible influence on the processes of steel hydrogenation. The formation of evenly distributed on the surface and the densest corrosion deposits will hinder both the corrosion processes and the penetration of hydrogen into steel. A decrease in the plastic properties of steel is also observed when exposed to hydrogen, which can be transported both separately and together with methane through the main gas pipelines. The main possible means of protecting steels that are unstable to hydrogenation is the use of corrosion inhibitors. It was established that the most effective corrosion inhibitors with rational technologies of application and dosage can protect steels from penetration of hydrogen into them and their destructive effect.

Characteristics of corrosion products of steel bars in modified magnesium oxysulfide cement containing chloride salts

The effects of chlorides on the corrosion of steel bars within a matrix comprising modified magnesium oxysulfide (MMOS) cementitious materials was investigated. The phase composition, morphology and distribution of steel corrosion products (SCPs) were studied. There was basically no corrosion of the steel bars in the MMOS cement without chlorides. A high chloride content and a high water/cement (w/c) ratio in the MMOS matrix had adverse effects on the steel bar corrosion. The primary SCPs in the MMOS mixes were iron oxyhydroxides (FeOOH) and ferric oxide (Fe2O3), while ferrous oxide (FeO) was only observed at low w/c ratios, indicating a lower degree of oxidation. The presence of di-iron nonacarbonyl (Fe2(CO)9) at high w/c ratios suggested a higher degree of oxidation. At lower w/c ratios, rust products readily diffused. Conversely, at higher w/c ratios, these products accumulated close to the steel bars, resulting in a compact structure.

ИЗУЧЕНИЕ ВОЗМОЖНОСТИ ИСПОЛЬЗОВАНИЯ РАЗЛИЧНЫХ КАРБОНАТНЫХ ПОРОД ПРИ СИНТЕЗЕ КАЛЬЦИЕВО-АЛЮМОФЕРРИТОВОГО КЛИНКЕРА

The article considers the possibility of using carbonate rocks of limestone, marl and chalk in the synthesis of calcium-aluminoferrite clinker (CAFC). The analysis of the structure of carbonate rocks, as well as their influence on the physico-chemical processes occurring during the synthesis of calcium-aluminoferrite clinker, is given. Phase formation has been studied in the temperature ranges 900-1000 °C and 1100-1200 °C with an isothermal exposure of 20 minutes. The heat treatment mode has been selected to obtain the basic phase composition of calcium-aluminoferrite clinker. The dynamics of changes in the qualitative phase composition of firing products at various temperatures, ranging from 900 °C to the clinker sintering temperature of 1200 ° C, as well as quantitative characteristics of the intensity of formation of the main clinker phases are presented. It was found that during the firing of CAFC in the temperature range of 900-1000 °C, raw materials mixtures gradually undergo a number of physico–chemical transformations, the main of which are thermal dissociation of CaCO3, the formation of intermediate phases (CS, CF, Al2O3•4SiO2, Al2O3•SiO2), as a result of decomposition of accompanying minerals and solid-phase interactions, as well as the beginning of the formation of clinker compounds CA, C2AS and C2F. It is proposed to use for the limestone-bauxite composition a temperature of 1150 °C with an exposure of 40-60 minutes, marl-bauxite - 1100 °C with an exposure of 30-40 minutes and chalk-bauxite- 1100 °C with an exposure of 30-40 minutes.

Enhancement of magnetic activation on the backfilling performance of coal gangue-based composite materials

ABSTRACT The large accumulation of coal gangue has resulted in significant environmental contamination and detrimental impacts. Utilizing it as a filler material in coal mining operations may successfully address this issue. It may be used to efficiently alleviate this issue by filling up coal mines. The wettability of magnetized solution on the coal gangue surface and the phase composition, microstructure, and pore structure of hydration products of coal gangue-based composite material (CGCM) at different ages were analyzed by means of contact angle (CA), X-ray diffraction (XRD), thermogravimetry (TG/DTG), mercury intrusion (MIP), and scanning electron microscopy (SEM) in order to control the fluidity and mechanical properties of backfilling materials. Simultaneously, an investigation was conducted on the slump expansion, setting time, and compressive strength of composite filler materials derived from magnetized coal gangue. The findings indicate that the application of a magnetic field reduces the interaction force among the molecules in the mixing water. Consequently, this leads to an improvement in the wettability of the coal gangue particle surface. Thus, the fluidity of the backfilling slurry is improved. The permeability and diffusion characteristics of magnetized water surpass those of regular water, The rate of dissolving and hydration reactions of the cementitious active material in the slurry is increased, resulting in a noticeable reduction in the setting time of the slurry. In the backfilling body, magnetized mixing water can encourage the formation of dicalcium silicate (C2S), tricalcium silicate (C3S), and Ca (OH)2. Higher amounts of C-S-H gel and Aft are produced by the pozzolanic action with SiO2, which enhances the pore structure. Thus, the mechanical qualities of the filler body are enhanced. The study findings provide novel insights into the coal gangue backfill mining and offer an environmentally friendly and efficient approach for the large-scale processing and exploitation of coal gangue.

Degradation behavior of zinc-rich epoxy coatings in simulated marine tidal zone

Degradation behaviors of zinc-rich epoxy coatings (ZRCs) were investigated using a simulated tidal apparatus. The steel substrate can be cathodically protected effectively in both immersion and tidal zones. The tidal level has a remarkable influence on the activation rate of zinc pigments in the ZRCs. Both activation degree and consumption of the zinc pigments in the ZRCs decreases with the rise of tidal level. More durable protection offered by zinc pigments can be achieved at the higher tidal level. The encapsulation of corrosion products hinders the sacrifice of zinc pigments, resulting in the high residual of metallic Zn even after the disability of effective cathodic protection of the ZRCs. Moreover, the tidal level affects the phase composition of corrosion products. In addition to the dominant phases including ZnO and Zn5OH8Cl2, Zn5CO32OH6 and Zn4OH6SO4 are formed in outer layers of the ZRCs at the relatively high tidal level.

Synchrotron radiation X-ray diffraction computed tomography (XRDCT): a new tool in cultural heritage and stone conservation for 3D non-destructive probing and phase analysis of inorganic re-treatments.

The issue of preserving carbonatic stones of cultural heritage (CH) restored in the past that have undergone new decay phenomena is strongly emerging and conservation science has not yet found a reliable solution. In this paper, we propose the application of synchrotron radiation X-ray diffraction computed tomography (XRDCT) to explore the effects of using inorganic-mineral products (ammonium oxalate; ammonium phosphate) in sequence as a novel, compatible and effective re-treatment approach to consolidate decayed carbonatic stones already treated with inorganic-mineral treatments. High-quality XRDCT datasets were used to qualitatively/quantitatively investigate and 3D localize the complex mixture of crystalline phases formed after the conservation re-treatments within a porous carbonatic stone substrate. The XRDCT reconstruction images and the structural refinements of XRD patterns with the Rietveld methods showed that the phase composition of reaction products, their volume distribution, and weight fraction vary as a function of the treatment sequence and penetration depth. The high potential of XRDCT allows (i) assessment of peculiar trends of each treatment/treatment sequence; (ii) exploration of the reaction steps of the sequential treatments and (iii) demonstration of the consolidating effect of inorganic re-treatments, non-destructively and at the micron scale. Above all, our study (i) provides new analytical tools to support the conservation choices, (ii) showcases new analytical possibilities for XRDCT in conservation science, including in investigations of CH materials and decay processes, and (iii) opens up new perspectives in analytical chemistry and material characterisation for the non-destructive and non-invasive analysis of reactions within heterogeneous polycrystalline systems.

Phase Composition of Hydration Products of Portland Cement Mechanically Activated in a Vortex Layer Apparatus with Additives of Various Nature

Phase Composition of Hydration Products of Portland Cement Mechanically Activated in a Vortex Layer Apparatus with Additives of Various Nature

Study on Hot Corrosion of Low-Nickel Cladding Metals Containing Nitrogen in K2SO4-MgSO4 Binary Molten Salt

Molten salt is usually used as the energy storage medium for solar energy heat storage pipes, and 40wt% K2SO4 + 60wt% MgSO4 is very suitable for use as a heat storage material for solar thermal power generation in tower and butterfly parabolic systems. The demand for high-temperature thermal energy storage systems has prompted research on low-cost alloys for use in high-temperature and corrosion-resistant environments. The 44% Ni-24% Cr-0.18N nitrogen-containing low-nickel flux-cored welding wire designed in this article has a corrosion resistance of up to 900 °C after welding repair, which is better than the repair ability of Inconel 625 flux-cored welding wire. Using the high-temperature static immersion corrosion method, the corrosion behavior of two deposited metals immersed in molten salt for 60 h at 900 °C was assessed. The corrosion product phase composition, corrosion morphology, and elemental distribution of the two deposited metals were systematically studied using X-ray diffraction (XRD) and a Gemini SEM 300 (Zeiss thermal field scanning electron microscope). The results showed that the corrosion weight loss of the deposited metals showed the same trend at 900 °C, with corrosion occurring slowly from 0 h to 10 h and increasing after 10 h to 60 h. It was found that 10 h was the boundary point for corrosion behavior, and the corrosion resistance of the low-nickel nitrogen-containing deposited metal is better than that of the Inconel 625 deposited metal. This was because the addition of N energy elements allowed the formation of a stable composite nitride layer to suppress corrosion.

ИССЛЕДОВАНИЕ МИНЕРАЛИЗУЮЩЕГО ЭФФЕКТА КРИОЛИТА И ЕГО ВЛИЯНИЯ НА ПРОЦЕССЫ КЛИНКЕРООБРАЗОВАНИЯ

The article discusses the possibility of using cryolite Na3AlF6, the main fluorine-containing compound of a man-made product of electrolytic aluminum production, as a mineralizing additive when burning clinker. A comparative assessment of the effectiveness of cryolite Na3AlF6, as a mineralizer, and calcium fluoride CaF2, a substance that has the most effective mineralizing effect, is provided. The influence of mineralizer additives on the processes of dissociation of calcium carbonate, assimilation of free calcium oxide with the formation of silicates, aluminates and calcium ferrites, liquid-phase sintering and clinker formation with the synthesis of basic clinker minerals is considered. The physical and chemical processes that occur when heating raw material mixtures without additives and with the addition of mineralizers – CaF2 and Na3AlF6 – to a clinker sintering temperature of 1450ºC are examined in detail. The dynamics of changes in the qualitative phase composition of firing products at various temperatures, ranging from 700ºC to the clinker sintering temperature of 1450ºC, as well as a quantitative characteristic of the intensity of formation of the main clinker minerals are presented. It has been determined that cryolite has a mineralizing effect and can be used as a mineralizer when burning clinker. The effectiveness of cryolite is comparable to the effectiveness of calcium fluoride, and the burning temperature of clinker can be reduced to 1400ºC

The effect of the concentration of plastic waste on the formation of reaction products of the Ti–PET system

The paper presents research results of the synthesis, phase composition, and structure of products obtained by highly exothermic reactions between Ti and C10H8O4 mixture components, depending on the plastic waste concentration and Ti powder dispersiveness, density of initial samples, and synthesis medium. The dependence of the phase composition and structure of the synthesis products on the concentration of the polymer (plastic) component in the initial Ti -PET (C10H8O4) system was found. When the plastic waste content is 20 wt% to 25 wt%, synthesis products contain TiC0.5O0.5–TiC0.6–0.75 particle agglomerates. Further growth in the polyethylene terephthalate content from 30 wt% to 45 wt% leads to the formation of synthesis products consisting of titanium carbide (TiC0.6–1.0). The gaseous byproduct composition of the exothermic reaction is investigated for the Ti–C10H8O4 mixture composition. It is found that the gaseous by-product mostly contains hydrogen and carbon monoxide as well as impurities of different hydrocarbons (methane, acetylene, ethane, ethene) and carbon dioxide. The maximum adiabatic temperature of the gas combustion temperature is 2080 oC, which demonstrates the possibility of using gas as a fuel for energy generation devices. Based on the data obtained, it is possible to create a basis for a new plastic waste technology to fabricate carbide-containing materials.

Research on the performance evolution of concrete under the coupling effects of sulfate attack and carbonation

In this study, three coupled modes of coupling effect of sulfate attack and carbonation of concrete were carried out to investigate the change of mass, mechanical properties and apparent morphology. The phase composition, microstructure and morphological characteristics of erosion products were also studied by using environment scanning electron microscope (ESEM-EDS), Fourier infrared spectrometer (FTIR), and X-ray diffraction (XRD). The results indicated that the coupled mode played an obvious effect on the performance and microstructures of specimen due to effects of coupled mode on the deterioration mechanism and erosion products. The surface feature of specimen became worse with carbonation time, and plenty of surface efflorescence and desquamation of products were observed under the coupled mode of carbonation followed by sulfate attack. The relative compressive strength and dynamic elastic modulus of concrete specimen first increased and then decreased with carbonation time, and there existed relationship of a cubic function of single variable between them. The relative mass of concrete specimen increased with the increase of the erosion age of sulfate attack. The difference of the carbonation time per period test played a significant effect on the relative compressive strength and dynamic elastic modulus of concrete specimen, which was due to the dominant effect of carbonation.

Structure–Phase Transitions in the Friction Contact Zone of High-Nitrogen Chromium–Manganese Austenitic Steel

The influence of contact stresses on the phase and concentration composition of thin surface layers and wear products in the tribological contact zone of high-nitrogen FeMn22Cr18N0.83 steel was studied using Mössbauer spectroscopy, X-ray structural analysis, and electron microscopy. It was shown that contact compressive stresses developing under the conditions of dry sliding friction in the surface layers (20–25 microns) resulted in the strain-induced dissolution of cellular precipitation products (nitrides Cr2N) and increased the average content of nitrogen in austenite. Antiferromagnetic ordering in austenite caused by the precipitation of secondary nitrides with low chromium and nitrogen content was observed in tiny external layers (~0.1 microns) of the friction surface and products of steel adhesive wear. The effect of tension stresses in the friction contact zone on the formation of strain-induced martensite and nitrides with α″-Fe16N2 structures was established in the wear products.

Combustion synthesis of Eu2O3 nanomaterials with tunable phase composition and morphology

Combustion reactions in europium nitrate – acetylacetone – 2-methoxyethanol solutions and gels were investigated to produce europium (III) oxide (Eu2O3) nanocrystalline materials and thin films. Thermal analyses of solutions indicated that the 2-methoxyethanol solvent also acts as a fuel in the absence of acetylacetone. Adding acetylacetone increases the overall heat of the reaction. Thermal analysis results revealed that the slow oxidation of unburned hydrocarbon residues follows the primary combustion reaction. Time-temperature profile measurements of the bulk combustion synthesis process in air and nitrogen atmospheres enabled the extraction of the maximum reaction temperature and the heating and cooling rates in the combustion zone. Several direct correlations exist between measured combustion parameters and the phase composition of the products. Combustion in air results in mixed-phase cubic and monoclinic nanocrystalline Eu2O3. Increasing the acetylacetone concentration in solutions increases the synthesis temperature and decreases the quantity of cubic Eu2O3. The reaction of solutions in a nitrogen atmosphere or diluted with Eu2O3 provides control of the product phase composition and reduces the quantity of the monoclinic phase. Transmission electron microscopy imaging shows that the Eu2O3 end products are highly porous aggregates of nanocrystalline particles. Electrospraying of reactive solutions onto different substrates followed by short annealing makes the preparation of Eu2O3 materials with diverse morphologies possible.

Influence of Added Silicon Oxide on Properties of Slag-based Synthetic Stone Casting Products

The study concerned the of obtaining stone-cast products from unmodified blast-furnace slag from Severstal PJSC and its mixture with river sand as a source of silicon dioxide. Mechanical characteristics, surface morphology, cutting microstructure and phase composition of products resulted from blast furnace slag and sand were studied. It was shown that when casting synthetic stone in an electric arc furnace without using a controlled cooling mode, it was possible to obtain a slag casting, the structure of which from chain silicates has a density of 2.9–3.0 g/cm3 and a compressive strength of 44.0–71.4 MPa.

Hydrothermal synthesis and tunable luminescence of YPO4:Eu2+/Eu3+, Tb3+ nanocrystals

The homogeneous and well crystallized rare earth ions RE3+ (RE = Eu, Tb) doped YPO4 and YPO4·0.8H2O nanocrystals (NCs) are synthesized by a simple hydrothermal route. The samples are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The results indicate that the pH value of precursor affects the phase composition and surface morphology of the final product. The results of XPS indicate that both Eu2+ and Eu3+ co-exist in YPO4 NCs, implying that the self-reduction from Eu3+ to Eu2+ takes place with the absence of reducing agents, charge compensation reagents and charge carrier trapping processes. In addition, YPO4:Eu and YPO4·0.8H2O:Eu samples exhibit strong and bright blue and red emission. According to PL spectroscopy, the blue emission is originated from host lattice and Eu2+ ion luminescence and red emission from Eu3+. YPO4:Tb, Eu samples can be effectively excited at 355 nm. An energy transfer phenomenon appears between Tb3+ and Eu3+. It is interesting that by changing the concentration of Tb3+, white phosphor from Y0.90PO4:0.04 Tb, 0.06Eu NCs are successfully obtained. Moreover, the Y0.90PO4:0.04 Tb, 0.06Eu has excellent thermal stability. These results indicate that the combination of defect and rare earth luminescence in YPO4:Tb, Eu NCs can produce tunable luminescence color, which may have potential applications in fields such as solid-state lighting and field emission displays.

Synthesis а compositе containing sialon based on aluminum ferrosilicon and nanosized microsilica in the filtration combustion

A composite containing sialon (β-sialon) and nitride phases (β-Si3N4, Si2N2O) was prepared by self-propagating hightemperature synthesis from a powder mixture of aluminum ferrosilicon and microsilica. The effect of microsilica on the nitriding of aluminum ferrosilicon, the phase composition of nitrided products, and the combustion temperature was studied. The composition of the powder mixture necessary for the efficient synthesis of the sialon phase in the combustion mode has been determined. Ill. 5. Ref. 32.