AlSi10Mg-based composites were fabricated by laser powder bed fusion (LPBF) technique with the addition of aluminum oxide-carbon nanofiber (Al2O3-CNF) nanocomposite powder. Al2O3-CNF nanocomposite was prepared via a wet impregnation method followed by heat treatment. It consists of aggregated aluminum oxide nanoparticles with an average particle size of 8 nm uniformly distributed among the carbon nanofibers. A planetary ball mill was employed to modify AlSi10Mg powders with 0.1 wt %, 0.25 wt % and 0.5 wt % Al2O3-CNF additions in the AlSi10Mg matrix. The samples obtained with a scanning speed of 1050-1200 mm/s exhibited the highest relative density across all levels of laser power (300-375 W) while the hatch distance and layer thickness were kept constant at 120 and 40 mu m, respectively. A finer sub-cell size was observed only in the AlSi10Mg/Al2O3-CNF samples containing 0.1 wt % and 0.25 wt % of the modified additive. The microhardness of the samples reinforced with 0.1 wt % and 0.25 wt% Al2O3-CNF increased by 27.0 % and 17.5 %, respectively, compared to the values exhibited by AlSi10Mg without the additive. However, samples with higher additive content showed comparable or lower hardness values. A part of CNFs was reacted with aluminum during selective laser melting, transforming into Al4C3. The combination of CNFs, Al2O3 nanoparticles and formed Al4C3 contributed to improvements in the mechanical properties of LPBF fabricated AlSi10Mg/Al2O3-CNF composites through the fine grain strengthening, second phase strengthening and load transfer strengthening.

Over the last decade, laser powder bed fusion (LPBF) received increased attention as a method of producing complex-shaped products from various materials. Recent results indicate the potential of this technology for the production of intermetallic NiTi alloys with shape memory. Several studies have demonstrated a strong influence of the LPBF process conditions on the resulting material properties, i.e., the martensitic phase transformation temperatures, reversible/irreversible strain after cyclic loading, phase composition, chemical composition, etc. However, the mechanisms of functional properties altering during LPBF consolidation remain unexplored in the present state-of-the-art. This study aims to advance the knowledge about tailoring material properties of NiTi under laser influence. In this work, thin-walled samples were manufactured from pre-alloyed NiTi powder via LPBF in a wide window of laser power and scanning speed, excluding hatch spacing by employing a single track-based scanning strategy to reveal the pure effect of the laser’s influence. NiTi samples were characterized by various methods such as differential scanning calorimetry, X-ray diffraction, and mechanical tests. Established relationships between NiTi properties and the LPBF process conditions provide the basis for the development of NiTi production protocols with controlled functional properties.

This paper presents the results of mechanically blending AlSi10Mg micropowder with Co3O4 nanoparticles, resulting in the formation of a nanoparticle coating on the surface of the coarse particles. An automated computer program was developed using Python's OpenCV library to process EDX elemental mapping images and evaluate the homogeneity of a mixture of nano- and micron-sized powders through surface analysis of sample images. The proposed methodology employs Otsu's thresholding technique to segment images into regions of interest and calculates quantitative data on the areas occupied by micron- and nanoscale components, which are key indicators for assessing powder mixture homogeneity. The developed technique is cost-effective and demonstrated its efficacy in measuring the homogeneity distribution of nanoparticles within a micropowder using a set of microscopy images. The only requirement for the method's applicability is a difference in the elemental composition of the powders. In this work, the homogeneity of micron-sized AlSi10Mg powder mixed with varying concentrations of cobalt oxide nanoparticles was analyzed using the processing of elemental mapping images. The results showed that 8 h of blending in a planetary ball mill with grinding balls was sufficient to achieve a homogeneous powder mixture.

Article presents a comparison of surface structure study methods, such as atomic force microscopy, scanning and transition electron microscopy in terms of metallic materials 3D-printed using the laser powder bed fusion technique. The main features, advantages, disadvantages of atomic force microscopy as a research method for the LPBF synthesized samples are discussed in the context of hard magnetic material, specifically Nd-Fe-B. The ability to provide qualitative grain structure analysis with the high-resolution images of atomic force microscopy is comprehensively studied. For confirmation good applicability of the above-mentioned method for LPBF sample analysis images of a magnetic domain structure obtained via atomic force microscopy are presented. Thus, the applicability of atomic force microscopy to the quality microstructural investigation of metallic materials obtained by LPBF is demonstrated.

This paper is devoted to determining the mechanism of reduction of oxygen-containing cobalt compounds obtained by chemical dispersion. Cobalt nanopowders obtained by precipitation of cobalt hydroxide from a solution of salts with alkali and subsequent reduction with hydrogen were used as the object of research. The paper presents the results of thermogravimetric and X-ray phase analysis, the morphology and dispersion of the obtained particles are investigated, the magnetic properties are measured. A mechanism for the reduction of cobalt nanopowder is proposed.

Low performance is considered one of the main drawbacks of laser powder bed fusion (LPBF) technology. In the present work, the effect of the AlSi10Mg powder layer thickness on the laser melting process was investigated to improve the LPBF building rate. A high-fidelity simulation of the melt pool formation was performed for different thicknesses of the powder bed using the Kintech Simulation Software for Additive Manufacturing (KiSSAM, version cd8e01d) developed by the authors. The powder bed after the recoating operation was obtained by the discrete element method. The laser energy deposition on the powder particles and the substrate was simulated by ray tracing. For the validation of the model, an experimental analysis of single tracks was performed on two types of substrates. The first substrate was manufactured directly with LPBF technology, while the second was cast. The simulation was carried out for various combinations of process parameters, predominantly with a high energy input, which provided a sufficient remelting depth. The calculations revealed the unstable keyhole mode appearance associated with the low absorptivity of the aluminum alloy at a scanning speed of 300 mm/s for all levels of the laser power (325–375 W). The results allowed formulating the criteria for the lack of fusion emerging during LPBF with an increased layer thickness. This work is expected to provide a scientific basis for the analysis of the maximum layer thickness via simulation to increase the performance of the technology.

A new low-alloyed Al–Ce–Fe alloy was consolidated by laser power bed fusion (LPBF) method. The process conditions that ensure the production of samples with minimal porosity (0.2

Fe-Co alloy nanoparticles with different sizes, supported by carbon derived from several polymers, namely polyacrylonitrile, polyvinyl alcohol and chitosan, have been synthesized by a one-pot method involving simultaneous metal nanoparticle formation and polymer carbonization. The method involves the joint dissolution of metal salts and a polymer, followed by annealing of the resulting dried film. Detailed XRD analysis confirmed the formation of Fe-Co alloy nanoparticles in each sample, regardless of the initial polymer used. Transmission electron microscopy images showed that the Fe-Co nanoparticles were all spherical, were homogeneously distributed within the carbon support and varied by size depending on the initial polymer nature and synthesis temperature. Fe-Co nanoparticles supported by polyacrylonitrile-derived carbon exhibited the smallest size (6–12 nm), whereas nanoparticles on chitosan-derived carbon support were characterized by the largest particle size (13–38 nm). The size dependence of magnetic properties were studied by a vibrating sample magnetometer at room temperature. For the first time, the critical particle size of Fe-Co alloy nanoparticles with equiatomic composition has been experimentally determined as 13 nm, indicating the transition of magnetic properties from ferromagnetic to superparamagnetic.

The processes of phase formation of aluminum oxide nanopowder during the thermal decomposition of chemically precipitated aluminum hydroxide are considered in detail. It is shown that precipitated aluminum hydroxide has a flake morphology with an average particle diameter of 5.5 nm and is characterized by a complex phase composition. According to the results of differential thermal analysis, it is found that freshly precipitated aluminum hydroxide consists of two phases, bayerite α-Al(OH)3 and aluminum oxyhydroxide AlOOH, the thermal decomposition of which leads to the formation of γ-Al2O3 with an equiaxed particle shape and an average size of 7 nm.

A method for conversion of polyethylene terephthalate (PET) waste into cobalt-carbon nanocomposites is proposed. The main feature of the procedure is the simultaneous formation of highly porous PET-derived carbon support and cobalt nanoparticles. Pyrolysis of a joint precursor obtained by mixing the three main components (PET, cobalt nitrate and KOH) in dimethyl sulfoxide results in the formation of a metal-carbon nanocomposite. The effect of the amount of KOH introduced on the structural properties of nanocomposites has been studied. It was shown that the weight ratio of PET:KOH affects both the porous characteristics of the material and the size of the cobalt nanoparticles. Also, the amount of alkali affects the yield of nanocomposite, both the yield of carbon residue, increasing it from 11.6 to 20.7 wt%, and the content of metal in the composite, which was in the range of 18.5-28.4 wt%.

Carbon-supported bimetallic Fe-Co nanocatalysts with different particle sizes have been synthesized by one-pot method involving simultaneous metal nanoparticles formation and chitosan carbonization. The Fe-Co particle size has been found to vary from 5 to 14 nm depending on the amount of metal loaded in the polymer precursor. For the first time, the size effect of Fe-Co alloy nanoparticles on the specific catalyst activity, yield and selectivity of the products of the Fischer-Tropsch synthesis has been studied. It has been revealed that smaller size of the Fe Co nanoparticles allows to achieve the maximum selectivity towards C5+ hydrocarbons at lower reaction temperature. The catalyst with the Fe-Co average particle size of 10 nm has been demonstrated the highest specific activity (per unit mass) of 126 mu molCO/(g(Fe-Co)center dot s). The structure of the Fe-Co bimetallic nanoparticles formed in the composites with different initial metal loading was studied and reviewed for details by XRD analysis.

A method for the synthesis of nanoparticles of the Cu-Fe bimetallic system with limited mutual solubility of the components is proposed. The synthesis method consists of a one-stage process of IR pyrolysis of precursors in the form of films obtained from a joint solution of polyacrylonitrile and hydrates-nitrates of iron and copper. The effect of the synthesis temperature on the structure formation of the nanocomposites and the phase composition of bimetallic Cu-Fe nanoparticles dispersed in the carbon matrix was studied. The analysis showed a simultaneous presence of Fe and Cu phases in nanocomposites, presumably with a low solubility of the components. The average particle size is 14-17 nm and changes insignificantly with an increase in the synthesis temperature from 400 to 700°C. An increase in the synthesis temperature to 800°C led to a broadening of the particle size distribution and the increase in the average size. The formation of complex carbon nanostructures on Cu-Fe nanoparticles is found.

An approach to the synthesis of metal-carbon nanocomposites, comprising iron-containing nanoparticles distributed in a highly porous carbon support based on pyrolyzed polyacrylonitrile, has been developed. It is shown that metal nanoparticles form in situ during pyrolysis of the polymer and the formation of a porous carbon matrix. Features of the formation of iron-containing particles are investigated, depending on the temperature of preliminary treatment (200, 500, and 800°C) and on the final temperature of synthesis, which varied from 500 to 900°C. The change in the specific surface area of the carbon support is shown, depending on the conditions of preparation. The formation of phases α-Fe, γ-Fe, and KFeO2 is observed in addition to that of iron carbide nanoparticles.

In this study, metal-carbon nanocomposites have been synthesized via the method of simultaneous formation of bimetallic Fe–Co nanoparticles and carbon support based on pyrolyzed chitosan under the IR irradiation. The XRD structural characteristics as well as morphology and dispersity of Fe–Co nanoparticles depending on the loading of metals in the nanocomposites have been studied. It has been shown that the increase in the metal salts loading in the precursor leads to the formation of metal nanoparticles of larger size and more homogeneous composition of the Fe–Co solid solution. Detailed analysis of the XRD peaks of the obtained Fe–Co phase has allowed to distinguish them into several phases of a solid solution based on body-centered cubic and face-centered cubic lattices.

This study is devoted to the investigation of the energetic properties of two types of aluminized solid propellants with inert and active binders modified by additives of six different metal nanopowders. The substitution of an inert binder for the active one resulted in significant improvement of energetic properties. However, burning rate regulation become more complicated because the pressure exponent in burning rate law was increased as well. The DSC analysis revealed that the most significant catalytic effects were observed while using Zn, Cu, and Mo powders. Combustion of compositions based on an inert combustible binder and ammonium nitrate was studied in the pressure range 0.1-10.0 MPa. Due to the low combustion rate, no dispersion of burning aluminum particles was observed. During combustion, a single agglomerate of aluminum particles was formed, the mass of which was about 96 % of the initial aluminum mass in the formulation. A comparative analysis of nanosized metal additive effect on the propellant's combustion process was performed. It had been found that the activity of the metal nanopowders depends on the propellant formulation. It had been shown that Al and Zn did not affect the combustion rate of propellant with inert binder but they were effective in compositions with an active binder. Cu and Ni were found to be a good catalyst for the ammonium nitrate and active binder decomposition.

The article presents a detailed study and characterization of the oxide layers on the surface of iron particles of various sizes. Ten iron samples with a size range from a few nm to 50 µm were studied in detail using SEM, TEM, XRD, and TGA analysis. The composition of the multiphase oxide layers on the powder surface was investigated. The main components of the oxide layer were FeO, Fe3O4, and Fe2O3. By the obtained data, a model for the calculation of a multiphase oxide layer thickness on the surface of iron particles was proposed. The proposed model was validated and can be used for the characterization and certification of micro– and nanoscale iron particles.

Metal-carbon nanocomposites, the structure of which is a carbon matrix with nanoparticles of a Fe–Co solid solution uniformly distributed in it, are synthesized by pyrolysis of a precursor based on chitosan and iron and cobalt nitrates under the action of infrared radiation in the temperature range 500–700°С. The features of the formation of nanoparticles of an Fe–Co solid solution are studied by X-ray diffraction depending on the synthesis conditions and the ratio of the metals in the system. The experimentally determined values of the lattice parameters are used to estimate the composition of the forming bimetallic Fe–Co nanoparticles. The morphology and dispersion of metal nanoparticles are studied by transmission electron microscopy. Elemental analysis of the samples under study is carried out by the methods of X-ray fluorescence analysis and X-ray photoelectron spectroscopy.

The study is devoted to X-ray fluorescence spectroscopy (XRF) features of micro- and nanosized powder mixtures of copper and nickel. XRF is a high accuracy method that allows for both qualitative and quantitative analysis. However, the XRF measurement error due to the size of the studied particles is not usually taken into account, which limits the use of the method in some cases, such as analysis of Ni-Cu mixtures and coatings. In this paper, a method for obtaining copper and nickel nanoparticles was investigated, and the XRF of powder compositions was considered in detail. The initial micro- and nanoparticles of copper and nickel were studied in detail using SEM, TEM, XRD, and EDX. Based on experimental data, calibration curves for copper-nickel powder compositions of various sizes were developed. According to the results, it was experimentally established that the calibration curves constructed for nanoscale and microscale powders differ significantly. The presented approach can be expanded for other metals and particle sizes.