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

Laser powder bed fusion (LPBF) processing of aluminum matrix composites (AMC) with blends of AlSi10Mg powder and nanodiamond and graphene additives was investigated. AMC with 0.5 wt% nanodiamonds addition was prepared by mechanical mixing, while AMC with 0.5 wt% of multi-layered graphene was prepared by electrochemical deposition. Initial powders for LPBF were thoroughly characterized and op-timal LPBF parameters were found based on the relative density analysis and optical microscopy. Processing windows of both AMCs moved towards lower energy density possibly due to the increased total absorptivity of the powders. Raman spectroscopy results, SEM and HRTEM studies of samples after LPBF demonstrated the absence of nano-diamond in the structure after processing which is explained by graphitization of the nanodiamond particles during laser melting. In case of AMC with graphene additives, carbon-containing particles remained in the structure with partial in situ formation of Al4C3, along with a noticeable strengthening effect, which increased material's microhardness by more than 40% compared to the initial AlSi10Mg alloy. The strengthening effect is explained by the presence of a network of graphene and Al4C3 particles across the solidified melt-pool promoting the Orowan strengthening mechanism. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Single tracks of Nd2Fe14B powder were obtained by selective laser melting with various process parameters. Initial powder material morphology and elemental composition were controlled. Single tracks were analyzed to study the material's melting features under laser irradiation and determine optimal printing regimes. 950 mm/s scanning speed is a boundary between complete melting and sintering. Single tracks morphology and their cross-sections dimensions and shape were investigated. A selective laser melting process window with a linear energy density of 300-500 J/m with 150-200 W of laser powder and 300-700 mm/s scanning speed was optimal for proper continuous melting of single tracks.

The synthesis features for 3D samples of AlSi10MgCu alloy were investigated. Two types of samples were used: single tracks and cubic samples of 10 mm3 volumes obtained by selective laser melting. 3D printing regimes and samples characteristics were compared for both types of samples. A comprehensive characterization of the initial AlSi10MgCu alloy powder was performed. The morphology, microstructure, and micro-hardness of the obtained single tracks and cubic samples were studied. The mechanism of the porosity formation was discussed in detail. A formation of pores and non–uniform structures was evidently caused by non–equilibrium crystallization during the selective laser melting process, namely 3D samples fast cooling. The lower porosity and the more uniform structure were obtained with higher values of laser power (from 220 to 240 W) Values of laser power had a crucial influence on the morphology and microstructure of the obtained 3D material. Optimal modes for selective laser melting for experimental AlSi10MgCu powder were revealed based on the microstructure and micro-hardness data. The values of the micro-hardness were varied from 115.5 to 151.1 HV. The micro-hardness for samples was increased on average by 20 HV after additional heat treatment. It was caused, most probably, by the separation of the Al2Cu phase.

At present, radiation technologies are most commonly applied for sterilization of medical supplies and irradiation of food products. The results of radiation treatment cannot be fully verified by subsequent non-destructive testing. Therefore, irradiation processes and equipment used for radiation treatment should be subject to mandatory validation and certification. In this paper, we present the results obtained during process validation of radiation-technological installations based on electron accelerators by investigating absorbed dose in irradiated products.

Details and features of the grain structure near the interface region between the AlN ceramic phase and AlSi10Mg matrix after the laser powder bed fusion (LPBF) were investigated. Aluminum nitride particles were obtained through self-propagating high-temperature synthesis and mechanically mixed with aluminum matrix powder. Optimization of the LPBF process parameters resulted in synthesized material free of pores and other defects. Optical microscopy analysis of etched cross-section and more detailed EBSD analysis revealed regions with relatively coarse grains at melting pool boundaries and fine grains in the melt pool core and near the AlN particles. Moreover, a pronounced orientation of fine elongated matrix grains towards the center of the ceramic particle was obtained. The such formed microstructure is attributed to directional heat sink during crystallization due to the higher thermal conductivity of aluminum nitride compared to the AlSi10Mg matrix. On the contrary, poor wettability of AlN by melt partly prevented the formation of such features, thus a combination of these factors determines the final microstructure of the interface in the resulting material.

The graphene synthesis via the electrochemical method and electrochemical deposition of graphene on Al foils and AlSi10MgCu particles were studied. The thickness of deposited graphene layers was varied from 3 to 20 layers and, thus, they were classified as multi-graphene. The chemically pure sucrose C12H22O11 was used as a raw material for graphene synthesis. It was shown that the deposition of graphene layers was affected mainly by the pH values of electrolyte mediums. In the electrochemical reaction at H2SO4 water solution at pH < 7, the graphene was deposited on Al foils and on AlSi10MgCu particles from the electrolyte. The microstructure and composition of graphene formed on Al foils and AlSi10MgCu particles' surface were studied by Raman spectroscopy, SEM, EDX, and TEM methods. The chemical mechanism of graphene formation was defined as follows: the sucrose was recovered via the reaction route C12H22O11 -> C6H12O6 -> C-graphene in acidic aqueous media. An increase in the H2SO4 concentration from 0.05 M to 0.80 M has resulted in the formation of graphene layers with up to 6 mu m thickness on AlSi10MgCu particles.

The current study is devoted to laser fusion of aluminum-matrix composites with 3 wt. % of alumina obtained in the vortex layer apparatus. The mixing parameters and the distribution of alumina in the composite structure were studied. Three parameters of laser fusion for plate synthesis were used. The finest results were achieved using a volumetric energy density of 24 J/mm3 with 370 W laser power. The maximum mechanical properties of the samples synthesized by the optimal parameters were: UTS = 384 ± 5 MPa; Ef = 0.54 ± 0.1 %.

This work presents the results revealing the possibility of obtaining a cubic phase of silicon carbide with features of a biomorphic structure. Renewable plant raw materials were used as a source of carbon, in particular, pyrolyzed sawdust, which is a waste of a timber enterprise. Silicon dioxide powder was used as a source of silicon. The synthesis was realized using DC arc discharge plasma initiated in an open air. In this case, the oxidation of the synthesis products was prevented due to the effect of the reaction volume self-shielding from atmospheric oxygen. It was possible due to the generation of protective gaseous medium predominantly consisting of carbon dioxide and monoxide. The dependences of the product phase composition on the supplied energy and composition of initial components were established. The synthesis product was characterized by a significant excess of carbon, which was a caused by the erosion of the electrodes. After removal of chemically unbound carbon from synthesis product by annealing in an atmospheric furnace at 850 °C, obtained powder was sintered by the spark plasma sintering method. In the result, a bulk ceramic sample was obtained in which the only one crystalline phase of silicon carbide with a lattice parameter of 4.359 Å was identified. Graphic Abstract

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.

The paper presents the results of experimental studies on the silicon carbide powder synthesis from charcoal and silicon in plasma of DC low-voltage arc discharge in ambient air. The observed dependencies of the initial mixture composition, arc discharge duration and treatment cycles on the phase composition of synthesized products allow fabrication of the powdery product composed of two phases: graphite and cubic phase of silicon carbide. The powdery product contains crystals that correspond to the morphology of biomorphic wood-derived silicon carbide. The temperature range suitable for synthesis of powdery product with a removal of an excess of free carbon was established by the differential thermal analysis. The synthesis product consists mainly of carbon and silicon, and insignificant amount of impurities contained in the original charcoal. Oxygen is also present in the synthesis product in an amount up to 4.6 at. %, which may indicate the presence of an amorphous silicon oxide layer on the silicon carbide surface. The proposed method finally yielded the silicon carbide based powder with a lattice parameter a = 4.359 angstrom.

Owing to the high hydrogen content, hydrocarbons are considered as an alternative source for hydrogen energy purposes. Complete decomposition of hydrocarbons results in the formation of gaseous hydrogen and solid carbonaceous by-product. The process is complicated by the methane formation reaction when the released hydrogen interacts with the formed carbon deposits. The present study is focused on the effects of the reaction mixture composition. Variations in the inlet hydrogen and methane concentrations were found to influence the carbon product’s morphology and the hydrogen production efficiency. The catalyst containing NiO (82 wt%), CuO (13 wt%), and Al2O3 (5 wt%) was prepared via a mechanochemical activating procedure. Kinetics of the catalytic process of hydrocarbons decomposition was studied using a reactor equipped with McBain balances. The effects of the process parameters were explored in a tubular quartz reactor with chromatographic analysis of the outlet gaseous products. In the latter case, the catalyst was loaded piecemeal. The texture and morphology of the produced carbon deposits were investigated by nitrogen adsorption and electron microscopy techniques.

Aluminum matrix composites (AMC) are of great interest and importance as high-performance materials with enhanced mechanical properties. Al2O3 is a commonly used reinforcement in AMCs fabricated by means of various technological methods, including casting and sintering. Selective laser melting (SLM) is a suitable modern method of the fabrication of net-shape fully dense parts from AMC with alumina. The main results, achievements, and difficulties of SLM applied to AMCs with alumina are discussed in this review and compared with conventional methods. It was shown that the initial powder preparation, namely the particle size distribution, sphericity, and thorough mixing, affected the final microstructure and properties of SLMed materials drastically. The distribution of reinforcing particles tends to consolidate the near-melting pool-edges process because of pushing by the liquid–solid interface during the solidification process that is a common problem of various fabrication methods. The achievement of an homogeneous distribution was shown to be possible through both the thorough mixing of the initial powders and the precise optimization of SLM parameters. The strength of the AMCs fabricated by the SLM method was relatively low compared with materials produced by conventional methods, while for superior relative densities of more than 99%, hardness and tribological properties were obtained, making SLM a promising method for the Al-based matrix composites with Al2O3.

Oxidation of cobalt, nickel, molybdenum and tungsten nanoparticles under prolonged exposure in the air was studied. Nanoparticles were obtained by chemical dispersion with the following reduction temperatures: 200-400 degrees C for cobalt; 200-400 degrees C for nickel; 700-800 degrees C for molybdenum and 750-850 degrees C for tungsten. Scanning electron microscopy, transmission electron microscopy, XRD and thermogravimetric analysis were used for nanoparticles characterisation. The average size of nanoparticles, specific surface area and the coherent scattering area were determined. The method for oxide film thickness calculation on the surface of the nanoparticles was proposed and confirmed its adequacy. Based on experimental data, the growth law of the oxide film on the studied nanoparticles was determined. The obtained results can be used in the certification of nanoparticles and evaluation of a highly dispersed metal powders shelf life.

Synthesis of in-situ composite CNTs/nAl(2)O(3) was studied. CNTs/(5-15 wt. %)nAl(2)O(3) composite was obtained varying the initial Al-contained materials with or without calcination at 700 ?C. The CNTs/nAl(2)O(3) nanopowders were comprehensively characterized by XRD, TEM, SEM, EDX, and electron diffraction methods. The morphology of the in-situ synthesized composite CNTs/nAl(2)O(3) was found as a net-shaped structure of nAl(2)O(3) nanofibers uniformly distributed in CNTs with the particle size of less than 30 nm. The synthesized composite CNTs/nAl(2)O(3) is an attractive candidate modifier material for 3D printed silumin.

Additive manufacturing (AM) processes have attracted a great interest in the scientific community during the last five years. This paper presents the 3D printing of a hypoeutectic Al alloy obtained by the Selective Laser Melting (SLM) technique. The initially printed material presented a cellular Al matrix microstructure with interconnected Si networks. Different tensile behaviors were found depending on the orientation of the specimens for both the initial material and after the annealing heat treatment. The specimens cut in the printing direction recorded lower ductility values, while those from the perpendicular plane and in the radial direction showed higher ductility and strength values.

Composite energetic materials such as solid propellants are characterized by a solid fuel, typically a polymeric binder matrix, containing solid oxidizer particles. The energetic performance of solid propellants is inferior to that of liquid or hybrid propellants. The main reason is that the available practical solid oxidizers are less energetic than the available liquid oxidizers. This article presents and studies the novel concept of an energetic material consisting of a solid fuel matrix containing liquid oxidizer units. The oxidizer units may be capsules filled with a liquid oxidizer. The size of the capsules may be similar to that of typical solid oxidizer particles. In this way, one maintains the structural characteristics of a solid material (e.g., solid propellant), yet benefiting from the superior energy of a liquid oxidizer. The study reveals the theoretical energetic performance (specific impulse) of solid propellants containing different liquid oxidizers compared to standard solid propellants consisting of ammonium perchlorate (AP) oxidizer. It is shown that the combination of certain liquid oxidizers such as hydrogen peroxide or nitrogen tetroxide with a hydroxyl-terminated polybutadiene (HTPB) matrix can increase the overall energy by about 20%, implying about 12% increase in the specific impulse. The combustion processes are discussed as well.

In this investigation, a hypoeutectic AlSi11Cu alloy was printed. This alloy was obtained in powder form with an average particle size of 40 μm. Bars 20 mm in diameter and 100 mm in length were printed with the building direction parallel to the bars' longitudinal direction. The microstructural characterization demonstrated an Al matrix surrounded by a Si network forming a coral-like pattern. The microstructure of the alloy showed a heterogeneous behavior with a mixture of columnar and equiaxed grains. Likewise, the texture indicated that the columnar grains were preferentially oriented towards the building direction, while the equiaxed followed a texture dominated by the cube component. On the other hand, the as-printed material strength showed higher values than those obtained in the same alloy using conventional processes such as casting. In addition, strength and ductility differences were found in the printed material, depending on the measurement direction. The highest values were obtained in the radial direction (565 MPa maximum strength and 4.8% elongation to failure). The lowest values corresponded to the transverse direction (508 MPa maximum strength and 3.2 elongation to failure), which corroborate the material anisotropy. Keywords—Additive manufacturing, aluminium alloy, melting pools, tensile test.