Investigation Of Phase Composition Research Articles

Microstructure Evolution, Phase Composition, Tensile and Hardness Properties Investigation of CrCuFeNi2Tix-Based High-Entropy Alloys

Microstructure Evolution, Phase Composition, Tensile and Hardness Properties Investigation of CrCuFeNi2Tix-Based High-Entropy Alloys

Application of Mössbauer Spectroscopy to Comprehensive Investigation of Phase Composition, Phase Magnetic State of Mechanically Synthesized Fe-Mn-Ni-C Nanocomposites

Application of Mössbauer Spectroscopy to Comprehensive Investigation of Phase Composition, Phase Magnetic State of Mechanically Synthesized Fe-Mn-Ni-C Nanocomposites

Исследование покрытий на основе системы Ti – Al – C при помощи синхротронного излучения и рентгеновской дифракции

The paper presents results of the phase composition investigations of coatings based on the Ti – Al – C system using an X-ray diffractometer and a synchrotron radiation source. A coating based on the Ti – Al – C system was deposited on molybdenum and titanium samples by cathodic-arc deposition from two single-component titanium and aluminum cathodes in a mixture of acetylene and argon. The results of the study of the phase composition showed that the formation of the Ti2AlC and Ti2C phases depends on the heat treatment mode. Using synchrotron radiation, the phase stability of the coating was studied when the sample was heated to 1500 °C in vacuum. It has been established that the coating after deposition has an amorphous structure, which crystallizes after annealing in vacuum with the formation of Ti2AlC, Ti2C phases and Ti – Al intermetallic compounds.

Facile and highly efficient wet synthesis of nanocrystalline BiFeO3particles by reverse co-precipitation method

In this study a nanocrystalline bismuth ferrite BiFeO3 (BFO) powder was synthesized using a novel, facile and highly efficient reverse co-precipitation method. Proposed method is also highly cost-efficient and environmentally friendly. It was demonstrated that the optimal calcination temperature for the preparation of phase-pure BFO is 400 °C, while at higher temperatures formation of undesirable crystal phases occur. X-Ray diffraction studies were employed for the investigation of crystal structure and phase composition of obtained powders. Scanning electron microscopy (SEM) was used to evaluate the morphology of synthesized powders. For piezoelectric studies, precursors powders were pressed into 12.5 mm diameter pellets and calcined at the same temperatures. Obtained materials show very good piezoelectric properties, as a result of high defects homogeneity and very low crystallite size. Determined piezoelectric coefficient is comparable with praseodymium, samarium or europium doped BiFeO3 ceramic.

Wire arc additive manufacturing Al-5.0 Mg alloy: Microstructures and phase composition

Wire arc additive manufacture is well applied in the fabrication of Al-5.0 Mg products. The investigation of microstructure morphology and phase composition in different regions is not enough. Therefore, the factors of microstructure morphology, dislocations densities and phase composition are worthy to study. Investigations of microstructure morphology demonstrated that the cross-section along the deposition direction has diversified grain size and the diversity increases the dislocation density and decreases the residual stress. The preferred orientation of grain growth analyzed by XRD explained that the decreasing intensity of (200) could improve the homogeneity. EDS results revealed that Al and Al3Mg2 were the main phases. TEM results demonstrated that there was Al2Mg formed inside grains and the irregular shapes of precipitations. The temperature gradient in the two regions is the main factor causing the differences in dislocation density, precipitations formation and microstructure diversity

Investigation of the interface layer phase composition obtained by hot pressing of Cr and Si

The possibility of synthesizing layers of the medium-temperature thermoelectric CrSi2 by hot pressing of the initial components (Cr and Si) has been investigated. The phase composition of samples obtained by hot pressing of Cr and Si before and after annealing in the region of their contact boundary has been investigated by X-ray analysis. It is shown that, under certain conditions, low-temperature synthesis of a CrSi2 layer with a thickness of 50 to 300 μm is possible at the interface between Cr and Si. The synthesis occurs at a temperature significantly lower than that given in the phase diagram, which opens up new technological possibilities for obtaining the CrSi2 compound. Keywords: thermoelectrics, chromium disilicide, phase interface, X-ray phase analysis.

Structure and phase composition of hypereutectic silumin alloy Al – 20Si after compression plasma flows impact

The results of structure and phase composition investigation in hypereutectic silumin alloy with 25 at. % Si content after high-energy pulsed compression plasma flows impact are presented in the work. The compression plasma flows impact with an absorbed energy density 25 – 40 J/cm2 allows to modify the sub-surface layer with a thickness up to 30 – 32 µm due to its melting and high rate solidification. By means of X-ray diffraction method, it was found the formation of two silicon phases with different grain sizes. The high-dispersed structure of silicon is presented in the Al-Si eutectic while the silicon phase with coarse grains exists in the primary crystals. The obtained results are the basis for a new method development for nanostructuring of the surface layers of hypereutectic silumin alloys increasing its wear resistance.

Investigation of Microstructural Features, Phase Composition, and Magnetic Characteristics of YBCO-Based Composites and Additives of CuO Non-Superconducting Component Prepared in Low-Pressure Arc Discharge Plasma

A method making it possible to form HTS ceramics of non-superconducting coating consisting of self-organizing CuO crystals, whose sizes are less than the coherence length, i.e., within several tens of nanometers, has been developed. It has been shown that the combination of self-organizing structures in the form of whiskers and nanoparticles which arise as a result of combined sintering of YBa2Cu3O(7–x) powders and electric arc CuO nanopowders results in a significant increase in the current density and appearance of peak effect at high magnetic fields. Very high current density arises from the complex vortex pinning, where whisker defects provide high pinning energy and nanoparticles suppress flux creep. The morphology of such structures can be controlled by a simple change in the concentration of nanodisperse additives. It has been shown that 20 wt % of CuO additive is optimal.

Wetting Behavior of Wear-Resistant WC-Co-Cr Cermet Coatings Produced by HVOF: The Role of Chemical Composition and Surface Roughness

Despite the existence of several methods for production of superhydrophobic coatings from various materials, their application in harsh environments is still a great challenge. In this work, WC-Co-Cr cermet coatings were prepared by means of high velocity oxy-fuel (HVOF) spraying. WC particles dispersed in Co-Cr metallic matrix allowed to form the multi-scale surface roughness and thus to achieve hydrophobicity of the coatings in the as-sprayed state. The additional surface treatment by the silicone oil rendered the coatings superhydrophobic. The WC-Co-Cr coatings were fabricated from three different powder feedstocks: coarse powder with coarse WC particles, coarse powder with ultrafine WC particles, and fine powder with ultrafine WC particles. The investigation of microstructure, phase composition, and surface topography of produced coatings was conducted to study the influence of these factors on the water contact angle and surface free energy, which were obtained by the sessile droplet method. Theoretical models were used to explain the wetting behavior of all the coatings. Finally, preliminary results of the slurry abrasion response test revealed very good robustness of hydrophobicity of the coatings and also pointed to a need for further research on surface modifications for sacrificial applications.

Molecular dynamics simulation of diffusion in Mg-Al system under pressure

The Mg-Al composite material possesses a large potential value in practical application due to its excellent properties. Molecular dynamics with the embedded atomic method potentials is applied to study aluminium-magnesium (Al-Mg) interface bonding during deformation. Study of fabrication techniques to obtain composites with improved mechanical properties, careful investigation of phase composition, dynamics and kinetics are of high importance. The loading scheme used in the present work is the simplification of the scenario, experimentally observed previously to obtain Al/Cu composites. It is shown that shear strain has a crucial role in the diffusion process. The results indicated that the symmetrical diffusion took place in the Mg-Al interface during deformation. Tensile tests showed that fracture took place in the Mg part of the final composite sample, which means that the interlayer region where the mixing of Mg and Al atoms observed is much stronger than the pure Mg part.

Characterization of W-Cr Metal Matrix Composite Coatings Reinforced with WC Particles Produced on Low-Carbon Steel Using Laser Processing of Precoat.

The paper presents the study results of laser processing of precoat applied on C30 steel. The precoat consisted of powder mixtures with a binder in the form of water glass. Tungsten powder, chromium, and tungsten carbide (WC) were used to produce the precoat. The laser processing was carried out using a Yb:YAG disc laser with a rated power of 1 kW. Constant producing parameters (power of laser beam, 600 W; laser beam scanning rate, 400 mm/min) were applied. Chemical composition of the precoat was a variable parameter in coating production. A mixture consisting of 50% W and 50% Cr as a metal matrix was prepared. Subsequently, WC particles in weight ratios of 25%, 50%, and 75% were added to matrix. As a result, W–Cr metal matrix composite coatings reinforced with WC particles were formed. This study focused on investigation of microstructure, microhardness, phase, and chemical composition as well as corrosion and wear resistance, of the newly formed W–Cr/WC coatings. An instrumented nanoindentation test was also used in this study. As a result of laser beam action, the newly formed coatings had an interesting microstructure and good properties which were improved in comparison to substrate material. It is anticipated that the resulting coatings, depending on the treatment parameters (e.g., W–Cr/WC powder mixture) used, can be successfully applied to metal forming or foundry tools.

Influence of RF Plasma Jet Surface Treatment on Wetting Behavior of Yttria Stabilized Zirconia SPS Coatings

According to the value of water contact angle (WCA), the surfaces can be roughly defined as hydrophilic (with WCA less than 90°) or as hydrophobic (with WCA higher than 90°). Water wetting behavior plays important role and surfaces with special wettability (hydrophobic-superhydrophobic; hydrophilic-superhydrophilic) can be used both in the daily life (solar cells, smartphones, car windows, etc.) and in the industry (corrosion resistance, self-cleaning, anti-icing properties, etc.). Nowadays, the development of hydrophobic surface treatment that may be applied in the industry is very interesting topic. Therefore, it was decided to estimate the influence of radiofrequency (RF) plasma jet in atmosphere on wetting behavior of ceramic plasma sprayed coatings. As the initial material for surface treatment, yttria stabilized zirconia suspension plasma sprayed coatings were used. The influence of RF plasma jet on suspension plasma sprayed coatings was estimated on both hydrophilic and hydrophobic surfaces, and resulted water contact angle and free surface energy of modified samples were measured by sessile droplet method. Microstructure, phase composition and topography investigation were carried out by means of light microscopy, X-ray diffraction techniques and non-contact profilometry.

Ag nanoparticles incorporated tannic acid/nanoapatite composite coating on Ti implant surfaces for enhancement of antibacterial and antioxidant properties

Implant infections caused by bacteria and oxidative stress induced by reactive oxygen species (ROS) would seriously hinder the osseointegration at the interface of bone and titanium (Ti) implant, leading to a failure. Therefore, it is highly desirable to develop an implant surface modification with antibacterial and antioxidant functions. Silver (Ag), which exhibit a broad spectrum of antibacterial properties, was used in this work. Tannic acid (TA) was selected as the reducing agent to realize the generation of Ag nanoparticles, and as an antioxidant to achieve the antioxidative activity of Ti implants. So, a layer of anatase titanium dioxide (TiO2) nanotubes with a diameter of 138.72 ± 14.02 nm was formed on the surface of Ti substrate by anodization and annealing, followed by loading Ag nanoparticles, growing bioactive hydroxyapatite (HA) crystals, and finally forming Ag-HA/TA composite coatings. Morphology and phase composition investigations detected the presence of Ag nanoparticles and HA crystals in the coatings. The results reveal the uniformly distributed Ag particles with a diameter of about 20– 80 nm and needle-like HA crystals with a diameter of about 18– 20 nm. Results of total antioxidant capacity tests indicate that the slow release of TA from the composite coatings leads to a persistent antioxidative activity. The antibacterial and cell compatibility tests in vitro reveal that the Ag-HA/TA coating has high antibacterial activity against both Escherichia coli and Staphylococcus aureus and good cytocompatibility effect with MC3T3-E1 cell lines. This study presents a simple and effective method for the incorporation of antibacterial agents and antioxidant into HA coatings to modify metallic implant surfaces.

Investigation of phase composition and microstructure of foamed cement paste with different supplementary cementing materials

Foamed concrete is highly porous, and the pores inside the material improve the insulation performance. However, the material strength decreases with increasing pores (porosity). To enhance the mechanical properties of the material without reducing porosity, the solid matrix of foamed concrete can be adjusted. For this purpose, several foamed cementitious specimens with various supplementary cementing materials (SCMs) and compositions were produced and investigated to evaluate the effect of SCMs on the microstructures of foamed cement paste. In addition to the specimen with cement only, SCMs such as fly ash and silica fume were used to produce foamed cementitious specimens with increased strength. To compare the effect of the water/binder ratio on the microstructure characteristics, a set of specimens was prepared with varying water/binder ratios. The microstructures of the foamed cementitious specimens with the various SCMs were analyzed using three different approaches: X-ray diffraction, scanning electron microscopy, and X-ray micro-computed tomography. The results from those approaches as complementary tools demonstrated that pozzolanic SCMs can improve the material strength of foamed cement paste by increasing the amount of C–S–H or Si phases. In addition, the microstructural investigation also confirmed that the water/binder ratio affects the degree of hydration.

Molecular dynamics simulation of structural transformations in Cu-Al system under pressure

Aluminium-copper (Al–Cu) compounds are one of the most-studied precipitation-strengthened alloy systems. Mechanical properties of Cu-Al systems considerably dependent on the phase composition. Excellent properties primarily depend on the intrinsic microstructures formed during processing stages, particularly the precipitated phases or the so-called intermetallics, along with various defects and impurity segregation, have important influences on the composite strength. Study of fabrication techniques to obtain composites with improved mechanical properties, careful investigation of phase composition, dynamics and kinetics are of high importance. Molecular dynamics simulation is used to study on the atomistic level the process of formation of Al/Cu composite from two initially separated crystals by severe plastic deformation. The proposed model is the simplification of scenario, experimentally observed previously. However, even in such a simple model, understanding of the mechanisms underlying in the process of composite formation can be obtained.

Phase composition investigation of titanium oxide nanostructures obtained by the local anodic oxidation

The paper presents the results of a phase composition study of titanium oxide nanostructures obtained by local anodic oxidation. A mathematical model was presented, which made it possible to calculate the distribution of oxide phases in the nanostructure volume. The results of the X-ray photoelectron spectroscopy (XPS) spectrum analysis are presented, which are consistent with theoretical calculations.

Investigation of thermal stability, optical properties, phase and chemical composition of transparent conductive tin oxide films deposited by pyrolytic method on silica float glass

The object of research is transparent conductive coating based on fluorine doped tin oxide deposited on silica float glass by the pyrolytic method. However, both in the manufacturing process of such a coating and in the process of its operation, degradation of its electrically conductive properties is observed. This may be due to changes in the structure of the coating under the influence of certain technological and operational factors, namely: process temperature, holding time, gas environment during the application and operation of a transparent electrically conductive coating. Studies have confirmed a significant increase in electrical conductivity. They also found a slight decrease in the transmittance of transparent oxide-tin films obtained with the introduction of ammonium fluoride as a dopant during the pyrolysis of 1M alcohol solutions of Sn2+ and Sn4+chlorides and are widely used as precursors for the content of such coatings. So, with a ratio of Sn4+/F=10 in working solutions, a minimum of specific surface resistance was fixed at 32 Ohm/m2. At the same time, a decrease in the value of the averaged transmittance in the optical wavelength range of 0.2-6.0 μm by 51 %, and in its visible part (0.4-0.8 μm) by 11 %. It is shown that thermal degradation of the coating is a significant factor in increasing the resistance values both in the technological process and during operational impacts. The results obtained indicate that reheating to temperatures above 450 °C leads to the appearance of the phenomenon of thermal degradation of the electrically conductive properties of the coating. So, during a 1-hour exposure at a temperature of 550 °C, the increase in specific surface resistance increases by 2 times and is fixed at 68 Ohm/m2 after complete cooling. Repeated heating cycles with the indicated parameters lead to a significantly lesser effect, which may indicate stabilization of the processes that occur during thermal destruction of the electrically conductive coating.

Bioactive Coating on Ti Alloy with High Osseointegration and Antibacterial Ag Nanoparticles.

Titanium alloys have advanced mechanical properties jointly with high biocompatibility that make them eminently suitable for biomedical applications such as dental and orthopedic implants. Improvement in their osseointegration with human bone can be achieved by the development of hydroxyapatite (HAp) on a Ti alloy surface using different methods of deposition. However, plasma electrolytic oxidation (PEO) treatment has been found to be one of the most promising techniques, due to the formation of high bonding between the bone and the Ti surface. Along with this high bonding, an antibacterial ability of the surface to prevent bacterial infection is also essential. Silver, which is a widely applicable antibacterial agent, was used in this work. First, a titanium oxide coating containing calcium and phosphorus and Ag nanoparticles was formed by PEO treatment. Then, Ti alloy was subjected to hydrothermal treatment to ensure a crystalline formation of HAp. Morphology and phase composition investigations detected the presence of HAp crystals in the coating along with antibacterial agents of silver nanoparticles. The biocompatibility and bioactivity of the created coating were examined by contact angle (CS) measurement and electrochemical impedance spectroscopy (EIS). It was shown that the coating was extensively grown after exposure of the alloy to simulated body fluid (SBF) solution for 7 days with no effect on the Ag nanoparticles. An antibacterial test using Staphylococcus aureus and Escherichia coli revealed that the coating containing Ag nanoparticles has more significant antibacterial effectiveness compared to a coating that does not contain silver.

The influence of manganese oxide on the sintering and properties of the eutectic ceramics ZrO2-Al2O3-SiO2 system

The results of investigation of sintering, microstructure and phase composition of the system ZrO2-Al2O3-SiO2 with MnO admixture are shown. It was approved that the usage of MnO admixture promoted sintering temperature decrease up to 1250-1350 °C. The product obtained is characterized by a high content of tetragonal phase as well as high strength while bending.

Microstructure and wear of thermal sprayed composite NiAl-based coatings

In present paper, the NiAl intermetallic was used as a matrix for elaboration of new composite coatings with hard additives like CrB2 and ZrB2 borides. The composite materials of NiAl-CrB2 and NiAl-ZrB2 systems were obtained by sintering of initial powders in vacuum. The composite powders were deposited by atmospheric plasma spray (APS) and detonation (D-gun) methods. Investigation of phase composition of developed composite materials as well as coatings obtained from them, the XRD analyses were performed. The microstructure of composite coatings has been investigated using SEM and TEM methods.