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The geometrical properties of metal powders, the main raw material in additive manufacturing processes, can have a significant impact on the quality of the parts produced. Therefore, it is essential to characterise these powders effectively. Nano-computed tomography (Nano-CT) technology, with its high-resolution 3D measurement capability, is ideally suited to measure the geometrical characteristics of tiny powders. However, the current CT testing methods for metal powders has two main drawbacks. Firstly, it does not take into account the effect of particle adhesion. Second, it cannot achieve high-precision measurements of the internal pores of powders. To address these limitations, we propose a novel testing method for metal powders that utilises Nano-CT technology. The method first obtains highly dispersed powder samples through a specially sample preparation technique. Then, an improved U-shape networks with multi-level supervision are proposed to achieve high-precision segmentation of the internal pores of the powder. Ultimately, this paper achieves high-precision 3D characterisation of metal powders. [ABSTRACT FROM AUTHOR]

SiC particles coated with Ti-Si-C layer were prepared by the molten salt synthesis method using NaCl-KCl eutectic mixture as the reaction medium and Ti metal powder as the Ti source. The synthesis was conducted under static argon atmosphere at 900 °C for 1–3 h. The post-synthesis treatment included dissolution of salts in hot water, followed by ultrasonic dispersion and sedimentation procedures. The thickness of the Ti-Si-C layer varied from 0.1 to 0.9 μm as the ratio of Ti to SiC components in the starting mixture changed from 0.05 to 0.4. The layer contained mainly nanocrystalline Ti 5 Si 3 , minor phases were TiC and Ti 3 SiC 2. The as-prepared powders were hot pressed under 30 MPa at 1700 °C. The densification behavior of the samples during hot pressing as well as changes both in phase composition and in microstructure were studied. The flexural strength of the hot-pressed samples increased with an increase in the Ti:SiC molar ratio, giving the value as high as 213 ± 20 MPa for the sample with Ti/SiC = 0.4. [ABSTRACT FROM AUTHOR]

In the present research, it is reported that ball milling technique can be applied to enhance the photocatalytic properties of MnO and ZrO 2 metal oxide powders (MZOx) furthermore the fabricated photocatalyst can be used for the degradation of tetracycline (TTC). XRD analyses revealed that increasing the milling time resulted in the formation of a pure metallic Mn crystal phase, which boosted the antibiotic degradation rate. It was confirmed by SEM technique that the morphological structures of the particles were generally small and uniform. The band gap energy was calculated as 3.70 eV for the hybrid metal oxide. Additionally, the adsorptive and photoluminescence features were illuminated via DRS and PL analyses. The effect of milling time had a major impact on the photodegradation rate of TTC, and the 8 h milling sample (MZOx-8h) exhibited the highest catalytic degradation activity (79.4 %). Low photocatalytic activity was obtained at acidic pHs and increased at alkaline pHs. The presence of H 2 O 2 sharply decreased photocatalytic process time (60 min) and 94.3 % of the TTC was degraded at 7.5 mM H 2 O 2. The photocatalytic degradation process proceeded through superoxide radicals and was supported by holes. The stability of MZOx-8h almost remained constant (70.02 %) even after seven cycles. It was determined that the presence of oxalic acid positively affected the progress of TTC degradation reactions. Further, practical application areas were investigated and MZOx-8h doped on support materials was found to be suitable for such applications in proportion to the doping ratio. Finally, it was demonstrated that MZOx-8h exhibited remarkable performance in photocatalytic reactions of different types of organic pollutants. The synergistic nature of MnO and ZrO 2 with the contribution of ball milling time effect resulted in high photocatalytic activity. • High purity metallic Mn phase was successfully synthesized by ball-milling. • MZOx was used for the first time in TTC photodegradation. • TTC degradation was stable in the seventh cycle. • The different organic pollutants were removed with high efficiency. [ABSTRACT FROM AUTHOR]

Herein, the study reports the first electrochemical nickel‐catalyzed enantioselective hydro‐arylation/alkenylation of enones in an undivided cell with low‐cost electrodes in the absence of external reductants and supporting electrolytes. Aryl bromides/iodides/triflates or alkenyl bromides are employed as electrophiles for the efficient preparation of more than 56 valuable β‐arylated/alkenylated ketones in a simple manner (up to 97% yield, 97% ee). With the advantages of electrochemistry, excellent functional group tolerance and late‐stage modification of complex natural products and pharmaceuticals made the established protocol greener and more economic. Mechanism investigation suggests that a NiI/NiIII cycle may be involved in this electro‐reductive reaction rather than metal reductant driven Ni0/NiII cycle. Overall, the efficient electrochemical activation and turnover of the nickel catalyst avoid the drawbacks posed by the employment of stoichiometric amount of sensitive metal powder reductants. [ABSTRACT FROM AUTHOR]

Superdense phase between graphite and Li metal, C 2 Li, has been significant in the research on both lithium-ion batteries (LIBs) and graphite intercalated compounds (GICs). However, a detailed method for synthesizing C 2 Li remains unknown owing to the limited information regarding C 2 Li and difficulties in distinguishing C 2 Li from C 6 Li. Thus, we performed in situ X-ray diffraction measurements on samples with the nominal composition of C 2 Li under high pressures and temperatures of up to 10 GPa and 400 ∘ C , respectively. We employed two types of C 2 Li samples; one was a mixture of C 6 graphite powder and Li metal (C 6 + 3 Li), and the other was a mixture of C 6 Li and Li metal in which the C 6 Li was prepared by the electrochemical discharge (reduction) reaction that occurs in LIBs. Considering changes in the d-value based on the 001 diffraction peak from C 6 Li or C 2 Li, C 6 Li + 2Li is suitable for synthesizing C 2 Li, although the nonaqueous electrolyte used for the electrochemical reaction should be removed to avoid structural transformations to lower-stage compounds such as C 12 Li and C 18 Li during the heating. These findings pave the way toward a method for synthesizing C 2 Li, which could increase the energy density of LIBs and establish GICs with novel physical and electronic properties. [ABSTRACT FROM AUTHOR]

Printed circuit boards contain gold and palladium. The first step in the recovery of gold and palladium from PCBs is to dissolve them by etching. In this work, a process was developed to recover gold metal and palladium compound from the etching solution containing Al(III), Cu(II), Fe(III), Ni(II), Sn(II) and Zn(II). Gold metal powders with 99.3% purity were recovered from the solutions by chemical reduction with hydrazine at room temperature within 30 mins when the molar ratio of hydrazine to Au(III) was 3. Hydrazine was more effective than sodium borohydride in reducing Au(III). Then Pd(II) could be recovered from the filtrate after separation of Au(III) by either precipitation or oxidative precipitation. When 0.3 M NaI was employed as a precipitant, PdI2 and CuI were co-precipitated from the filtrate, while Pd and Sn ions were co-precipitated during oxidative precipitation by adding 0.54 M NH4Cl as a precipitant and 0.3 M NaClO3 or 0.3 M NaIO3 as an oxidizing agent at room temperature for 30 min and a stirring speed of 500 rpm. It was possible to suppress the co-precipitation of Sn ions by adjusting the concentration of NaIO3. (NH4)2PdCl6 powders with 99.8% purity were recovered within 30 mins from the filtrate by oxidative precipitation with 0.1 M NaIO3 when the molar ratio of NH4Cl to Pd(IV) was 5. The purity of the gold metal and palladium compound thus recovered was verified by measuring the composition of the solution after dissolving them with aqua regia. [ABSTRACT FROM AUTHOR]

Metal powder contributes to the environmental burdens of additive manufacturing (AM) substantially. Current life cycle assessments (LCAs) of metal powders present considerable variations of lifecycle environmental inventory due to process divergence, spatial heterogeneity, or temporal fluctuation. Most importantly, the amounts of LCA studies on metal powder are limited and primarily confined to partial material types. To this end, based on the data surveyed from a metal powder supplier, this study conducted an LCA of titanium and nickel alloy produced by electrode-inducted and vacuum-inducted melting gas atomization, respectively. Given that energy consumption dominates the environmental burden of powder production and is influenced by metal materials' physical properties, we proposed a Bayesian stochastic Kriging model to estimate the energy consumption during the gas atomization process. This model considered the inherent uncertainties of training data and adaptively updated the parameters of interest when new environmental data on gas atomization were available. With the predicted energy use information of specific powder, the corresponding lifecycle environmental impacts can be further autonomously estimated in conjunction with the other surveyed powder production stages. Results indicated the environmental impact of titanium alloy powder is slightly higher than that of nickel alloy powder and their lifecycle carbon emissions are around 20 kg CO2 equivalency. The proposed Bayesian stochastic Kriging model showed more accurate predictions of energy consumption compared with conventional Kriging and stochastic Kriging models. This study enables data imputation of energy consumption during gas atomization given the physical properties and producing technique of powder materials. [ABSTRACT FROM AUTHOR]

Systems theory can be used not only to assess the existing state of engineering and technological systems, but also to forecast their development. This approach implies the creation of a generalized model of the object under study taking the existing connections between its individual components into account, along with an analysis of the energetic, material, and informational resources inherent in this object. This allows selection of the most optimal solution for improving the technological system under analysis from a variety of possible options. Creation of high-entropy compounds of various compositions is an intensively developing direction of modern materials science. Due to their specific chemical composition, such materials may exhibit a unique combination of properties, thereby outperforming other types of compounds. In this work, we study structural and functional interactions in a technological system aimed at obtaining coatings by laser cladding of high-entropy materials, which are represented by the starting powders mixed in a certain proportion. The input and output parameters of the laser cladding process are established. This process is represented in the form of sequential phases, resulting in the formation of a coating on the surface of the product. The coating is characterized by both technological and specific properties, depending on the chemical composition of the starting powder components. A structural and functional scheme describing the process of coating formation from a high-entropy material during laser cladding is proposed. Connections between the input and output process parameters are demonstrated. These connections reflect the formation of specific coating properties in the process of laser cladding as a result of interaction of the powder material with the laser beam. It is noted that structural and functional schemes should be used when simulating technological processes based on mathematical models, taking the occurring transformations of substances into account. [ABSTRACT FROM AUTHOR]

In metal additive manufacturing, reusing collected powder from previous builds is a standard practice driven by the substantial cost of metal powder. This approach not only reduces material expenses but also contributes to sustainability by minimizing waste. Despite its benefits, powder reuse introduces challenges related to maintaining the structural integrity of the components, making it a critical area of ongoing research and innovation. The reuse process can significantly alter powder characteristics, including flowability, size distribution, and chemical composition, subsequently affecting the microstructures and mechanical properties of the final components. Achieving repeatable and consistent printing outcomes requires powder particles to maintain specific and consistent physical and chemical properties. Variations in powder characteristics can lead to inconsistencies in the microstructural features of printed components and the formation of process-induced defects, compromising the quality and reliability of the final products. Thus, optimizing the powder recovery and reuse methodology is essential to ensure that cost reduction and sustainability benefits do not compromise product quality and reliability. This study investigated the impact of powder reuse and particle size distribution on the microstructural and mechanical properties of Ti-6Al-4V specimens fabricated using a laser beam directed energy deposition technique. Detailed evaluations were conducted on reused powders with two different size distributions, which were compared with their virgin counterparts. Microstructural features and process-induced defects were examined using scanning electron microscopy and X-ray computed tomography. The findings reveal significant alterations in the elemental composition of reused powder, with distinct trends observed for small and large particles. Additionally, powder reuse substantially influenced the formation of process-induced defects and, consequently, the fatigue performance of the components. [ABSTRACT FROM AUTHOR]

The quality of metal powder is essential in additive manufacturing (AM). The defects and mechanical properties of alloy parts manufactured through AM are significantly influenced by the particle size, sphericity, and flowability of the metal powder. Gas atomization (GA) technology is a widely used method for producing metal powders due to its high efficiency and cost-effectiveness. In this work, a multi-phase numerical model is developed to compute the alloy liquid breaking in the GA process by capturing the gas–liquid interface using the Coupled Level Set and Volume-of-Fluid (CLSVOF) method and the realizable k-ε turbulence model. A GA experiment is carried out, and a statistical comparison between the particle-size distributions obtained from the simulation and GA experiment shows that the relative errors of the cumulative frequency for the particle sizes sampled in two regions of the GA chamber are 5.28% and 5.39%, respectively. The mechanism of powder formation is discussed based on the numerical results. In addition, a discrete element model (DEM) is developed to compute the powder flowability by simulating a Hall flow experiment using the particle-size distribution obtained from the GA experiment. The relative error of the time that finishes the Hall flow in the simulation and experiment is obtained to be 1.9%. [ABSTRACT FROM AUTHOR]

Thermodynamic equilibria in the Al-Ti-C ternary system are considered as applied to synthesizing titanium carbides in an aluminum medium using the CALPHAD method. A set of calculated isothermal sections of the corresponding state diagram is obtained. Using the results of the thermodynamic analysis of the system, a physically substantiated semi-empirical mathematical computer model was developed that describes the kinetics of TiC synthesis processes in the aluminum medium for the Al-TiC two-phase equilibrium region. Based on the simulation results, it was found that with increased aluminum content in the system, the exothermic burst during TiC synthesis is characterized by lower temperatures and becomes more diffuse in time. The dependence of the dispersity of titanium carbide particles on the aluminum content in the mixture is nonlinear. An increase in the aluminum content slows down the growth of TiC particles. It is shown for the Ti-Al-C system that there is a certain threshold value of the aluminum content (about 30-40%), the excess of which leads to a noticeable dispersion of the sizes of the synthesized titanium carbide grains, which makes it possible to obtain submicron TiC particles. The results obtained are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Additive manufacturing from metal powders using selective laser melting technology is gaining increasing interest in various industries. The purpose of this study was to determine the effect of changes in process parameter values on the relative density, microstructure and mechanical properties of Ti-6Al-4V and Ti-6Al-7Nb alloy samples. The experiment was conducted in response to a noticeable gap in the research on the manufacturability of the Ti-6Al-7Nb alloy in SLM technology. This topic is significant given the growing interest in this alloy for biomedical applications. The results of this study indicate that by properly selecting the volumetric energy density (VED), the relative density of the material produced and the surface roughness of the components can be effectively influenced. Microstructural analyses revealed similar patterns in both alloys manufactured under similar conditions, characterized by columnar β phase grains with needle-like α' phases. Increasing the VED increased the tensile strength of the fabricated Ti-6Al-4V alloy components, while the opposite effect was observed for components fabricated from Ti-6Al-7Nb alloy. At the same time, Ti-6Al-7Nb alloy parts featured higher elongation values, which is desirable from the perspective of biomedical applications. [ABSTRACT FROM AUTHOR]

Liquid steel atomization using close‐coupled nozzles is highly dependent on the relationship between momentum flux ratio, gas–liquid ratio, aspiration pressure, and operating pressure of inert gases. A strong correlation between these parameters and the final powder must be assumed. Understanding these parameters, their influence on the process, and their interactions with each other is indispensable for efficient powder production. In particular, the industrial application of close‐coupled atomization nozzles, which develop a thin pre‐film on the nozzle tip, is not yet fully understood. A model experiment is presented to investigate interactions between the flow conditions of the gaseous and liquid phases, focusing on recirculation phenomena inside the atomization zone. The experiments show the influence of liquid and gas flow conditions on the spray geometry and the liquid core length, as well as the strong dependence of the liquid mass flux on the gas flow. The aspiration pressure below the liquid nozzle is sensitive to gas pressure and has a major influence on the development of the liquid core and the pre‐film, as it increases the liquid mass flux. For practical application, the results confirm an optimal operating point of interacting system parameters, which leads to high‐quality atomization with minimal use of resources. [ABSTRACT FROM AUTHOR]

Quantum‐confined CsPbI3 perovskite nanoplatelets (NPLs) are highly desirable for optoelectronic applications owing to their anisotropic electronic properties that substantially boost the light outcoupling efficiency in light‐emitting diodes (LEDs). However, the structural instability of the emissive CsPbI3 phases makes it degrade rapidly to the non‐emissive δ‐phase under ambient conditions. Here, the study presents a synthetic approach to produce spectrally stable CsPbI3 nanoplatelets (NPLs) through solid‐phase crude reactions with metal iodide powders, MI2 (M2+ = Mn2+ or Zn2+). The synthesized NPLs exhibit narrow and color‐pure red emission with high photoluminescence (PL) quantum yields (QYs, ηPL) of up to 85%. Systematic investigations into the surface chemistry of NPLs reveal that metal iodide treatment stabilizes anisotropic CsPbI3 NPLs via surface passivation with metal and halide ions, substantially hindering from the formation of non‐emissive yellow phase. The anisotropic NPLs display signatures of spontaneous self‐assembly in spin‐casted films, which yield strong emission anisotropy, with up to 82% of the transition dipoles being horizontally oriented with respect to the substrate, as revealed by the back focal plane (BFP) imaging. The results presented here shed light on solid‐phase approaches for the preparation of quantum‐confined nanocrystals (NCs) with desirable geometry, which boost the light outcoupling efficiency in LEDs. [ABSTRACT FROM AUTHOR]

The widespread application of metal additive manufacturing (AM) is limited by the ability to control the complex interactions between the energy source and the feedstock material. Here, we develop a generalizable process to introduce nanoscale grooves to the surface of metal powders which increases the powder absorptivity by up to 70% during laser powder bed fusion. Absorptivity enhancements in copper, copper-silver, and tungsten enable energy-efficient manufacturing, with printing of pure copper at relative densities up to 92% using laser energy densities as low as 83 joules per cubic millimeter. Simulations show that the enhanced powder absorptivity results from plasmon-enabled light concentration in nanoscale grooves combined with multiple scattering events. The approach taken here demonstrates a general method to enhance the absorptivity and printability of reflective and refractory metal powders by changing the surface morphology of the feedstock without altering its composition. [ABSTRACT FROM AUTHOR]

Purpose: Conventional powder bed fusion systems, with their high costs, proprietary nature and restrictive fees, limit research opportunities. This study aims to unveil an affordable, open-source hardware, open-source software laser-based metal powder bed fusion system. Recognizing the distinction between DIY and open-source hardware is crucial for widespread acceptance. Design/methodology/approach: The authors present a comprehensive system architecture using object process methodology for functions and architecture, a design structure matrix to model system dependencies and classical technical drawing exploded views for select subsystems. Modularization enables high adaptability, fostering potential adoption. Findings: The fully open system enables unrestricted research, mirroring common industrial metal laser-based powder bed fusion (L-PBF) systems. While "open" systems are available for purchase, they remain closed-source, lacking source code and technical drawings sharing, hindering contribution and co-development. The authors' is the pioneering and sole open-source metal L-PBF system, boasting 1,500+ print hours. A series of industrial and academic adopters are currently implementing the system. Originality/value: The open system, slicer software and controller offer unique process control, supporting multimaterial printing. The authors shared the design on the OpenAM GitHub page under the CERN-OHL-P v2 Open Source Hardware license. While it is functional for additive manufacturing (e.g. aluminum, tool steel, titanium and stainless steel), the entire process chain is actively evolving, ideal for co-development with the additive manufacturing community. [ABSTRACT FROM AUTHOR]

Based on assumptions and limitations, a mathematical model of the non-stationary thermal state of a composite coating during laser remelting on a metal substrate to obtain an alloy of equimolar or close to equimolar composition has been developed. The model includes the boundary value problem of calculating the nonstationary thermal state of the temperature distribution in the solid, two-phase and liquid regions, considering the heat release of crystallization according to the theory of a quasi-equilibrium two-phase zone in the presence of porosity of a mixture of metal powders. Based on the mathematical model, the computer program "Composite coating thermal state" was created, which allows to determine the non-stationary temperature distribution in the formed coating and substrate, the depth of penetration of the high-entropy coating layer, to evaluate the shrinkage of the molten coating under different technological conditions: laser power, the diameter of its focal spot, as well as the speed of movement along the surface of the processed material. The created program also allows to determine the dynamics of the position of two-dimensional liquidus and solidus lines for each metal included in the mixture. Using the created program, a computer simulation of the process of unsteady heating of a mixture of three metal powders in the same mass fractions: nickel, chromium and iron was carried out. Non-stationary temperature fields in the composite coating are obtained, considering its penetration and heating of the substrate. The depth of penetration of all metals, including the most low-melting one, was determined during laser remelting on a metal substrate in the production of a high-entropy alloy. The practical significance of the developed computer model lies in its use to predict the penetration depth of a composite coating under specified technological modes of laser remelting. At the same time, its adaptation is necessary, based on experimental data on the porosity and thickness of the coating before and after melting of simple metal systems with similar thermophysical properties. [ABSTRACT FROM AUTHOR]

Natural radioactivity and trace elements content of two brands of shaving power that are commonly used by men were determined, in order to evaluate their radiological effect and health risk. The activity concentrations of the radionuclides were measured using gamma spectrometer equipped with calibrated NaI(Tl) detector system while the trace metals were measured using atomic absorption spectrophotometric (AAS) and energy dispersive x-ray fluorescence (ED-XRF) techniques. The averaged activity concentrations of 238U, 232Th and 40K were 2445.97 ± 9.29 Bq kg-1, 315.16 ± 17.72 Bq kg-1 and 50.45 ± 1.79 Bq kg-1 for 40K, 232Th and 238U, respectively. The equivalent dose had a mean value of 2.94 mSv year-1. The results of the trace elements analysis from both AAS and ED-XRF showed that iron had the highest concentration while selenium had the least concentration. ED-XRF showed a better recovery of the trace elements than AAS. The levels of the radionuclides identified were above the normal background for humans and the average concentrations of most of the trace metals were also above the permissible exposure limits, which can constitute health hazard to users of the shaving power. [ABSTRACT FROM AUTHOR]

During the laser-based directed energy deposition (DED-LB) processing, a WC-12Co composite coating with high hardness and strong wear resistance was successfully prepared on a 316L stainless steel substrate by adopting a high-precision coaxial powder feeding system using a spherical WC-12Co composite powder, which showed a large number of dendritic carbides and herringbone planar crystals on the substrate-binding interface. The influences of laser power on microstructural and mechanical properties (e.g., hardness, friction resistance) of WC-12Co composite surfaces were investigated. The results show that laser power has a significant effect on determining the degree of Co phase melting around the WC particles and the adhesion strength between the matrix and the coating. Lower laser power does not meet the melting requirements of WC particles, thus weakening the molding quality of the composite coating. At high laser power, it is possible to dissolve the WC particles and melt the metal powder between the particles, thus improving the material properties. The laser power increased from 700 W to 1000 W and the average hardness of the coating surface gradually increased from 1166.33 HV to 1395.70 HV, which is about 4–5 times higher than the average hardness of the substrate (about 281.76 HV). In addition, the coatings deposited at 1000 W showed better wear resistance. This work shows that the processing parameters during laser-directed energy deposition can be optimized to prepare WC-12Co composite coatings with excellent mechanical properties. [ABSTRACT FROM AUTHOR]

The rapid advancement of additive manufacturing (AM) technologies has provided new avenues for creating three-dimensional (3D) parts with intricate geometries. Fused Deposition Modeling (FDM) is a prominent technology in this domain, involving the layer-by-layer fabrication of objects by extruding a filament comprising a blend of polymer and metal powder. This study focuses on the FDM process using a filament of Copper–Polylactic Acid (Cu-PLA) composite, which capitalizes on the advantageous properties of copper (high electrical and thermal conductivity, corrosion resistance) combined with the easily processable thermoplastic PLA material. The research delves into the impact of FDM process parameters, specifically, infill percentage (IP), infill pattern (P), and layer thickness (LT) on the maximum failure load (N), percentage of elongation at break, and weight of Cu-PLA composite filament-based parts. The study employs the response surface method (RSM) with Design-Expert V11 software. The selected parameters include infill percentage at five levels (10, 20, 30, 40, and 50%), fill patterns at five levels (Grid, Triangle, Tri-Hexagonal, Cubic-Subdivision, and Lines), and layer thickness at five levels (0.1, 0.2, 0.3, 0.4, and 0.5 mm). Also, the optimal factor values were obtained. The findings highlight that layer thickness and infill percentage significantly influence the weight of the samples, with an observed increase as these parameters are raised. Additionally, an increase in layer thickness and infill percentage corresponds to a higher maximum failure load in the specimens. The peak maximum failure load (230 N) is achieved at a 0.5 mm layer thickness and Tri-Hexagonal pattern. As the infill percentage changes from 10% to 50%, the percentage of elongation at break decreases. The maximum percentage of elongation at break is attained with a 20% infill percentage, 0.2 mm layer thickness, and 0.5 Cubic-Subdivision pattern. Using a multi-objective response optimization, the layer thickness of 0.152 mm, an infill percentage of 32.909%, and a Grid infill pattern was found to be the best configuration. [ABSTRACT FROM AUTHOR]

The service performance of chromium-free zinc–aluminum coatings exhibits characteristics from multiple perspectives. Fully considering the physical properties, corrosion resistance, and economic viability of the coatings, this study incorporates the concepts of "domain" and "degree" from extenics theory into the analytic hierarchy process to optimize the formulation of chromium-free zinc–aluminum coatings. The findings reveal that the extension analytic hierarchy process takes into account the diversity of evaluation indicators, enhancing the objectivity and accuracy of the comprehensive evaluation results. Nine formulations were developed using a four-factor, three-level orthogonal experiment to evaluate the effects of metal powder, PEG-400, KH-560, and sodium molybdate on the service performance of chromium-free zinc–aluminum coatings. Utilizing an extensible hierarchical sorting weight system alongside a performance index grading and scoring method, 3# emerged with the highest score, indicating the best overall performance. The research outcomes offer innovative insights and technical support for optimizing the formulations of chromium-free zinc–aluminum coatings and other coatings. [ABSTRACT FROM AUTHOR]

Powder metallurgy is a process for compacting and sintering powders such as metals and ceramics, and has been attracting new attention in recent years. This paper presents research examples in which simulation methods such as molecular dynamics (MD) method, Monte Carlo (MC) method, finite element method (FEM), and discrete element method (DEM) are applied to powder metallurgy. The MD method is used to calculate physical property values such as interfacial energy and diffusion coefficient that change depending on the type of grain boundaries. The MC method is used to calculate the microstructural development due to the sintering and grain growth. The microstructure can be predicted when the sintering process is changed. The FEM is used to calculate deformation and strain. The sintering simulation combined with the MC method can calculate the microstructural changes and deformation simultaneously. In the compaction simulation, density distribution due to the friction with the mold can be analyzed. The DEM is used to calculate the compaction structure. The interaction of the friction and stiffness between particles and particle/mold can be analyzed. As powder metallurgy technology develops, process design that considers the whole process will be important. Supporting technology based on simulation will become increasingly important. [ABSTRACT FROM AUTHOR]

Boron has been considered a promising powdered metal fuel for enhancing composite propellants' energy output due to its high energy density. However, the high ignition temperature and low combustion efficiency limit the application of boron powder due to the high boiling point of the boron oxide layer. Much research is ongoing to overcome these shortcomings, and one potential approach is to introduce a small quantity of metal oxide additives to promote the reaction of boron. This study prepared boron-rich fuels with 10 wt% of eight nano-metal oxide additives by mechanical ball milling. The effect of metal oxides on the thermo-oxidation, ignition, and combustion properties of boron powder was comprehensively studied by the thermogravimetric analysis (TG), the electrically heated filament setup (T-jump), and the laser-induced combustion experiments. TG experiments at 5 K/min found that Bi2O3, MoO3, TiO2, Fe2O3, and CuO can promote thermo-oxidation of boron. Compared to pure boron, Tonset can be reduced from 569 °C to a minimum of 449 °C (B/Bi2O3). Infrared temperature measurement in T-jump tests showed that when heated by an electric heating wire at rates from 1000 K/s to 25000 K/s, the ignition temperatures of B/Bi2O3 are the lowest, even lower than the melting point of boron oxide. Ignition images and SEM for the products further showed that the high heating rate is beneficial to the rapid reaction of boron powder in the single-particle combustion state. Fuels (B/Bi2O3, B/MoO3, and B/CuO) were mixed with the oxidant AP and ignited by laser to study the combustion performance. The results showed that B/CuO/AP has the largest flame area, the highest BO2 characteristic spectral intensity, and the largest burn rate for powder lines. To combine the advantages of CuO and Bi2O3, binary metal oxide (CBO, mass ratio of 3:1) was prepared and the test results showed that CBO can very well improve both ignition and combustion properties of boron. Especially B/CBO/AP has the highest burn rate compared with all fuels containing other additives. It was found that multi-component metal-oxide additive can more synergistically improve the reaction characteristics of boron powder than unary additive. These findings contribute to the development of boron-rich fuels and their application in propellants. [ABSTRACT FROM AUTHOR]

In this work, the influence of powder reuse up to three times on directed energy deposition (DED) with laser processing has been studied. The work was carried out on two different gas atomized powders: a cobalt-based alloy type Stellite® 21, and a super duplex stainless steel type UNS S32750. One of the main findings is the influence of oxygen content of the reused powder particles on the final quality and densification of the deposited material and the powder catch efficiency of the laser deposition process. There is a direct relationship between a higher surface oxidation of the particles and the presence of oxygen content in the particles and in the as-built materials, as well as oxides, balance of phases (in the case of the super duplex alloy), pores and defects at the micro level in the laser-deposited material, as well as a decrease in the amount of material that actually melts, reducing powder catch efficiency (more than 12% in the worst case scenario) and the initial bead geometry (height and width) that was obtained for the same process parameters when the virgin powder was used (without oxidation and with original morphology of the powder particles). This causes some melting faults, oxides and formation of undesired oxide compounds in the microstructure, and un-balance of phases particularly in the super duplex stainless steel material, reducing the amount of ferrite from 50.1% to 37.4%, affecting in turn material soundness and its mechanical properties, particularly the hardness. However, the Stellite® 21 alloy type can be reused up to three times, while the super duplex can be reused only once without any major influence of the particles' surface oxidation on the deposited material quality and hardness. [ABSTRACT FROM AUTHOR]

Laser cladding technology serves as a pivotal technique in industrial production, especially in the realms of additive manufacturing, surface enhancement, coating preparation, and the repair of part surfaces. This study investigates the influence of metal powder composition and processing parameters on laser cladding coatings utilizing the Taguchi orthogonal experimental design method. To optimize the laser cladding parameters, multi-response grey relational analysis (GRA) was employed, aiming to improve both the microhardness and the overall quality of the coatings. The optimal parameter combinations identified through GRA were subsequently validated through experimental tests. The results reveal that the microhardness and quality of the coatings are substantially influenced by several critical factors, including the powder feed rate, laser power, high-entropy alloy (HEA) addition rate, scanning speed, and substrate tilt angle. Specifically, the powder feed rate exerts the most significant effect on the microhardness, dilution rate, and average contact angle. In contrast, laser power primarily impacts the mean contact angle difference. The HEA addition rate notably affects the mean contact angle difference, while the scanning speed affects the microhardness and the substrate tilt angle influences the average contact angle. The results of the validation experiment showed a deviation of only 0.95% from the predicted values, underscoring the efficacy of the grey relational analysis (GRA) in optimizing the laser cladding process parameters. The methodology presented in this paper can be applied to determine the ideal processing parameters for multi-response laser cladding processes, encompassing applications such as surface peening and surface repair. [ABSTRACT FROM AUTHOR]

Previous studies have reported that PLA-Al-based composite-based structures may be used in aerospace, automobiles, and biomedical applications. The present study investigated the fracture, morphological and mechanical characteristics of composite 3D-printed materials comprising polylactic acid (PLA) and aluminum (Al) metal powder. In the first stage, materials extrusion-based printing of PLA-Al composite structures was performed by material extrusion process varying the layer thickness (0.15, 0.20, and 0.25 mm), infill density (60, 80, and 100%) and infill pattern (Grid, Line, Zigzag). In the second stage, investigations have been made on the mechanical and morphological characteristics of the manufactured composite structures. The findings of the tensile study demonstrate that the composite structure prepared using 0.20 mm layer thickness, 80% infill density, and zigzag infill pattern possessed the highest tensile strength (39.13 MPa) and the minimum tensile strength (18.47 MPa) was noticed when it was manufactured using 0.15 mm layer thickness, 60% infill density and grid infill pattern. The results of the morphological analysis showed that the samples had a consistent microstructure with few visible cracks. These results suggest that 3D-printed PLA-Al composites have considerable mechanical and morphological characteristics, with possible applications in a variety of fields, like aviation, automobiles, and healthcare. [ABSTRACT FROM AUTHOR]

Wire electric discharge machining (wire EDM) is a non-traditional material removal method that is commonly used in additive manufacturing (AM) applications to efficiently remove AM metallic parts from their build plates. However, a persistent problem in wire EDM of AM parts is wire breakage which leads to longer machining time, challenges in rethreading wire, and wasted material, decreasing efficiency. This study focuses on the wire EDM strategies to mitigate the two main causes of this issue in AM applications: intermittent workpiece thickness (i.e., support structures) and trapped metal powders. When AM metallic parts are made using a powder bed fusion (PBF) process, pockets of non-fused powder can become trapped in the part and supports. This powder creates a non-uniform cutting path which leads to wire breakage. Additionally, the interrupted cuts and nonuniform support thickness result in interactions between wire and AM support design that is currently not well understood. This study investigates the effects of various AM support structures on EDM wire breakage and overall machining time by understanding the effects of three critical EDM process parameters (voltage, wire feed rate, water flushing rate) on the machinability of 316L SS AM builds. In addition, the effect of heat treatment cycles on wire EDM machinability of AM parts with entrapped powder is investigated. The results of this study show that reducing the wire EDM voltage eliminates wire breaking, and that thicker supports provide steadier cutting conditions for the wire. [ABSTRACT FROM AUTHOR]

High-quality metal and alloy powder feedstock for powder metallurgy (PM) and additive manufacturing (AM) is typically expensive due to stringent physical and chemical requirements. The increasing demand for such powders drives innovation toward more sustainable and cost-effective production methods. In this study, we demonstrate the generation of discrete machining chips (MCs) with controlled characteristics during modulation-assisted drilling of Inconel-718 nickel superalloy. To achieve this, a full factorial experimental design, varying modulation frequency (fm) and amplitude (2A) (two factors: fm and 2A, multi-level: 7 and 5, respectively) was used to define discrete and continuous cutting regimes. Furthermore, the effect of individual modulation (fm and 2A) and machining parameters (drill tool diameter, D, and feed rate, h) on the characteristics of MCs was investigated systematically. The findings reveal direct linear relationships between the investigated parameters, i.e., D, fm, and 2A, on chip characteristics: length, width, and thickness, respectively. Specifically, the average chip length was 10–40% smaller than the length of each cutting edge of the drill tool; the average chip width reduces by 17 % when fm increases from 184 to 251 Hz. Similarly, the average chip thickness increases to 80% when 2A increases from 3.6 to 27.5 μm, confirming the generation of MCs having controllable characteristics. As established using a comprehensive comparative analysis, generated MCs (size range: 100–1200 μm) can be used as feedstock directly in press-and-sinter PM and solid-state friction-stir AM technologies. Additionally, the reusability of these MCs can be further enhanced by converting them into finer powder with a well-defined size distribution via ball milling (average particle size < 100 μm having angular morphology, in the present case), promoting a circular economy by repurposing high-value industrial machining waste into useful products. [ABSTRACT FROM AUTHOR]

Laser powder bed fusion (LPBF) is a metal additive manufacturing (AM) process where a part is created layer-by-layer through the melting and solidification of powder layers. The main challenge in LPBF is quality assurance. An estimation of powder rheology/flowability, as a quality-impacting factor, is therefore necessary prior to printing. To predict powder flowability based on morphological features without cost- and time-inefficient experiments, this study explores using machine learning algorithms (ML). It focuses on a sample set of standard and off-size Ti6Al4V (Ti64) powders, aiming to (1) assess ML regressors and equation fitting for flowability prediction, using the small original dataset and (2) overcome data limitations' impact on regression through data augmentation techniques. Results showed conventional ML regressors like support vector regression (SVR) sufficed for dynamic flowability prediction. Still, more complex targets such as shear flowability and hall flowability required innovative approaches like genetic programming (equation fitting) and synthetic minority over-sampling (SMOTE), respectively, as proposed in this work. [ABSTRACT FROM AUTHOR]

Laser-based metal powder bed fusion (PBF-LB/M) offers great potential for producing complex and filigree sub-millimetre parts with customised shapes, such as patient-specific vascular stents. However, stent fabrication via PBF-LB/M encounters fundamental challenges, including dimensional limitations, poor surface quality, difficult support structure handling and geometrical deviations. This study addresses these challenges by investigating the potential and limitations of a novel hybrid post-processing approach. This technique uses the combination of electrochemical polishing and chemical etching and is investigated from process and design perspectives, to emphasise the interactions between the two. With the systematic application of hybrid post-processing, the strut thickness and the surface roughness were substantially reduced. Moreover, it enabled the successful removal of part-internal support structures. Furthermore, angle and orientation-dependent geometrical deviations could be compensated, highlighting the potential of achieving homogenous strut thicknesses within parts containing variable overhang angles. This study demonstrates that the usage of hybrid (electro)chemical post-processing methods with specifically tailored process parameters is a promising approach for overcoming the design- and process-related challenges in PBF-LB/M manufactured sub-millimetre parts. [ABSTRACT FROM AUTHOR]

Towards decarbonizing the carbothermic reduction of iron and steelmaking, which produces around 5% of global CO2 emissions, we herein propose a low-temperature electrolysis (100 °C) with 3D electrically–ionically conductive colloidal Fe2O3 electrodes as a novel and sustainable alternative. With the designed electrodes that offer a 3D conductive network to facilitate the electrochemical reduction of Fe2O3 at such a low temperature, high-purity Fe powder (>95%) can be produced with high current efficiency (>95%) and no direct CO2 emission. In addition to Fe, we also demonstrate the production of metal and alloy powders such as Cu, Ag, and an FeNi alloy using the proposed method. A techno-economic assessment of the process is performed to evaluate industrial feasibility as well as CO2 emission analysis. Altogether, this alternative process is green, environmentally friendly, and energy efficient, showing great potential for revolutionizing the conventional process that has had a significant environmental impact for decades. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: An alkyl radical initiated cyclization/tandem reaction of alkyl bromides and alkyl electrophiles by using potassium metabisulphite (K2S2O5) as a connector is developed for the synthesis of various lactam‐substituted alkyl sulfones. Notably, this process does not require a metal catalyst or metal powder reductant, highlighting its environmentally friendly features. The reaction demonstrates outstanding substrate adaptability and a high tolerance towards diverse functional groups. Furthermore, the biologically active molecules and commercially available drugs with a late‐stage modification are also highly compatible with this transformation. Mechanistic studies revealed that the reaction proceeds through a single‐step process involving intramolecular radical cyclization, "SO2" insertion, and external alkyl incorporation. [ABSTRACT FROM AUTHOR]

Loose powder in metal hydride reactors poses challenges, such as poor thermal conductivity and tube deformation. To address these issues, the metal powder can be encapsulated in a polymer-based matrix to form pellets. This encapsulation helps make the pellets oxygen-impermeable, capable of accommodating the volumetric expansion of metal hydrides, and increases system processability. This study investigates the use of polymer-based pellets containing AB5-based compounds for ambient hydrogen storage. Polymers were selected using ANSYS Granta software, and polyethylene and polymethylmethacrylate were chosen. The AB5 alloy activation in the pellet occurs efficiently after 3 min at 20 °C and 30 bar of hydrogen, facilitated by ball milling-induced reactive surfaces and increased grain boundaries. The optimized pellet, comprising 90 wt% AB5 powder in a PE matrix, exhibits stable hydrogen storage properties, with good mechanical resistance and minimal powder loss (below 3%) over 20 hydrogen sorption cycles in an in-house fabricated single-tube metal hydride reactor. [Display omitted] • Loose metal hydride powder bound in a polymer matrix formed pellets without solvents, simplifying handling and processing. • PE and PMMA were selected via ANSYS Granta as suitable matrix materials for hydride pellets, ensuring effective binding. • 90 wt.% AB5 in a PE matrix demonstrated stable H₂ storage, strong mechanical properties, and less than 3% powder loss. • AB5 alloy in the pellets activated within 3 min at 20°C and 30 bar H₂, enabling rapid and efficient hydrogen storage. • Pellets maintained consistent performance through 20 hydrogen sorption cycles in a custom single-tube reactor. [ABSTRACT FROM AUTHOR]

In this work four metal powder compositions of VZL718 (IN718) alloy are produced, one by vacuum induction melting and gas atomization (VIGA) technology and three by plasma melting and rotating billet centrifugal atomization (PREP) technology. Their particle size distributions, distribution parameters, technological properties, moisture content and gas impurity content of VIGA and PREP initial metal powder compositions are investigated. The differences between VIGA metal powder compositions and PREP metal powder compositions are shown and analyzed, and the differences are explained. Four selective laser melting processes are conducted using the VIGA and PREP metal powder compositions investigated. Particle size distributions, distribution parameters and process characteristics of VIGA metal powder compositions and PREP metal powder compositions after a single application in a selective laser melting process are investigated, and the differences between changes in characteristics and particle size distributions of VIGA and PREP metal powder compositions are revealed. The reasons for the changes identified in VIGA metal powder compositions and PREP metal powder compositions after selective laser melting and the relationships with initial metal powder composition characteristics are explained. Derivations and conclusions about further possibility of reuse of VIGA and PREP metal powder compositions after selective laser melting are made. [ABSTRACT FROM AUTHOR]

Shape Memory Alloys (SMA) are materials used to design smart structures with intrinsic functional properties and improved efficiency. This is a key aspect of aerospace industry and makes SMA good candidates in this field. One of the most widespread SMA is the equiatomic NiTi alloy which, however, has the strong limitation of poor machinability, so only simple shapes can be obtained. Additive Manufacturing processes allow to overcome this limit and to design complex shapes. Compared to other metallic materials, the optimization of the process for NiTi alloy is complicated because, beside mechanical properties and presence of defects, considerable attention needs to be dedicated to the material functionality. The high temperatures involved in the additive process significantly affect the material properties due to possible evaporation of Ni and formation of precipitates that enable a shift of the phase transformation temperatures. This paper is focused on the optimization of the process parameters of the NiTi alloy printed through the Laser Powder Bed Fusion (L-PBF) to ensure optimal pseudo-elastic behaviour, which is essential for the design of structural dampers. This was accomplished starting from simple structures and then designing a damper that couples the pseudoelasticity of NiTi with load support capacity. The L-PBF is a powder-bed technique that selectively melts layers of micrometric metal powder. A pseudoelastic NiTi powder with 50.8 at. % of Ni content was selected and characterized through scanning electron microscope (SEM) and observations connected to an Energy Dispersive X-ray Spectroscopy (EDX) probe. After that, some cubic samples were manufactured, with the dimension of 3 × 3 × 15 mm3. A set of different laser powers and scanning speeds were used to find the set of process parameters that optimize the functional properties of the printed parts. Near fully dense specimens with density higher than 99.5 % were selected for further investigations. Differential scanning calorimetry (DSC) and mechanical tests were performed on as-built and heat-treated samples. Quasi-static mechanical tests were accomplished in compression mode, at different strains, up to 8 %. It was observed that the residual strain for cyclic loading at 4 % is lower than 1 %, so good recovery of the deformation was shown. Moreover, numerical analyses that mimic the pseudoelastic behaviour in compression tests were implemented. Finally, the best set of parameters was selected on the basis of the material's ability to recover deformations and its loss factor. • Optimization of process parameters for functional behaviour of SMA. • Design of damping structure using pseudoelastic effect of Nitinol. • Internal defects observation of manufactured specimens. • Compression tests on as built and thermal treated specimens with strain up to 8 %. • Numerical simulation of compression tests with experimental correlation. [ABSTRACT FROM AUTHOR]

Owing to the quality issues of highly filled compounds used in metal injection molding, the current research is focused on intercepting flow-induced inhomogeneities in multiphase compounds resulting from the segregation of metal powder particles from (typically) three/four-component polymer binders, resulting in an unacceptable porosity of the final sintered metal parts. A recently developed nondestructive approach for quantifying the extent of these flow-induced defects was employed to study the effect of the size and shape of water- and gas-atomized 17-4PH stainless steel powders on segregation. This method combines scanning electron microscopy/energy dispersive x-ray spectroscopy with an in-house analytical tool. The results show a higher tendency of coarser particles (D50 of 20 μm) for flow-induced defects, while an irregular shape (water-atomized particles) reduces this unwanted phenomenon. [ABSTRACT FROM AUTHOR]

Spent lithium-ion batteries (LIBs) contain some valuable metals. Smelting reduction of spent LIBs produces metallic alloys containing Co, Cu, Fe, Mn, and Ni. Leaching of the metallic alloys with inorganic acid solutions and subsequent separation of Cu(II), Fe(III) and Mn(II) results in a solution containing Co(II) and Ni(II). In this work, solvent extraction and chemical reduction experiments were performed to recover pure metals from this solution. Cobalt(II) was first separated from Ni(II) by solvent extraction with saponified Cyanex 272. Batch simulation experiments based on the McCabe-Thiele diagram for the extraction of Co(II) verified the complete separation of Co(II) from Ni(II). Hydrazine was then employed as a reducing agent for Co(II) and Ni(II) from the stripping solution and the raffinate, respectively. The effect of several variables on the reduction such as the molar ratio of hydrazine to metal ion, reaction time, temperature, and solution pH was investigated. It was found that the reduced metals could be dissolved owing to the oxidizing action of hydrazonium in acidic solution. Addition of NH4Cl was effective in suppressing the dissolution of the reduced metals. Especially, there was an optimum molar ratio of NH4Cl at which maximum reduction of Co(II) was obtained. The recovery percentages of Co and Ni powder were higher than 99.1% and 99.9%, respectively, and the purity of the reduced metals was higher than 99.9%. [ABSTRACT FROM AUTHOR]

Laser-based powder bed fusion of metals (PBF-LB/M) is the most used additive manufacturing (AM) technology for metal parts. Nevertheless, challenges persist in effectively managing metal powder, particularly in blending methodologies in the choice of blenders as well as in the verification of blend results. In this study, a bespoke laboratory-scale AM blender is developed, tailored to address these challenges, prioritizing low-impact blending to mitigate powder degradation. As a blending type, a V-shape tumbling geometry meeting the requirements for laboratory AM usage is chosen based on a literature assessment. The implementation of thermal oxidation as a powder marking technique enables particle tracing. Blending validation is achieved using light microscopy for area measurement based on binary image processing. The powder size and shape remain unaffected after marking and blending. Only a small narrowing of the particle size distribution is detected after 180 min of blending. The V-shape tumbling blender efficiently yields a completely random state in under 10 min for rotational speeds of 20, 40, and 60 rounds per minute. In conclusion, this research underscores the critical role of blender selection in AM and advocates for continued exploration to refine powder blending practices, with the aim of advancing the capabilities and competitiveness of AM technologies. [ABSTRACT FROM AUTHOR]

Numerous efforts in the additive manufacturing literature have been made toward in-situ defect prediction for process control and optimization. However, the current work in the literature is limited by the need for multi-sensory data in appropriate resolution and scale to capture defects reliably and the need for systematic experimental and data-driven modeling validation to prove utility. For the first time in literature, we propose a data-driven neural network framework capable of in-situ micro-porosity localization for laser powder bed fusion via exclusively within hatch strip of sensory data, as opposed to a three-dimensional neighborhood of sensory data. We further propose using prior-guided neural networks to utilize the often-abundant nominal data in the form of a prior loss, enabling the machine learning structure to comply more with process physics. The proposed methods are validated via rigorous experimental data sets of high-strength aluminum A205 parts, repeated k-fold cross-validation, and prior-guided validation. Using exclusively within hatch stripe data, we detect and localize porosity with a spherical equivalent diameter (SED) smaller than 50.00 μ m with a classification accuracy of 73.13 ± 1.57 % This is the first work in the literature demonstrating in-situ localization of porosities as small as 38.12 μ m SED and is more than a five-fold improvement on the smallest SED porosity localization via spectral emissions sensory data in the literature. In-situ localizing micro-porosity using exclusively within hatch-stripe data is a significant step towards within-layer defect mitigation, advanced process feedback control, and compliance with the reliability certification requirements of industries such as the aerospace industry. [ABSTRACT FROM AUTHOR]

Arsenic containing non-ferrous metal and precious metal sulfide ore will produce acidic high concentration arsenic solution in the smelting process, which has the characteristics of high arsenic concentration, complex composition, large changes, strong toxicity and difficult to store, such as direct discharge without treatment, will have a great impact on the environment and human health. In this paper, the principles, advantages and disadvantages of chemical precipitation method, evaporation enrichment method and metal powder method are reviewed, as well as the research progress of each method, so as to provide reference for the development of arsenic removal technology. [ABSTRACT FROM AUTHOR]

Nickel silicides are crucial in advanced technology applications ranging from semiconductor devices to high-temperature materials. Gas atomization is a process that involves the formation of fine liquid droplets and their rapid cooling and solidification to make powder particles. The final microstructure and the properties of the particles are highly sensitive to the gas atomization process parameters. In the present study, gas atomization of NiSi12-wt% was performed at three different pressures (35, 40, and 45 bars) to optimize the particle size distribution for additive manufacturing applications. A comprehensive range of characterization techniques, including scanning electron microscopy, X-ray diffraction, particle size distribution measurements, light optical microscopy, and density measurements, was used to evaluate the microstructural features, phase composition, and density of the produced NiSi12-wt% powders. Higher atomizing gas pressures resulted in a finer particle size distribution due to improved molten droplet breakup, increased satellite formation, and a well-suited particle size distribution for additive manufacturing applications. [ABSTRACT FROM AUTHOR]

This review explores the critical role of powder quality in metal 3D printing and the importance of effective powder recycling strategies. It covers various metal 3D printing technologies, in particular Selective Laser Melting, Electron Beam Melting, Direct Energy Deposition, and Binder Jetting, and analyzes the impact of powder characteristics on the final part properties. This review highlights key challenges associated with powder recycling, including maintaining consistent particle size and shape, managing contamination, and mitigating degradation effects from repeated use, such as wear, fragmentation, and oxidation. Furthermore, it explores various recycling techniques, such as sieving, blending, plasma spheroidization, and powder conditioning, emphasizing their role in restoring powder quality and enabling reuse. [ABSTRACT FROM AUTHOR]

Pb(Mg 0. 5 W 0. 5 )O3–Pb(Ni 1 ∕ 3 Nb 2 ∕ 3 )O3–Pb(Zr 0. 5 Ti 0. 5 )O3 (PNN–PMW–PZT) piezoceramics were sintered at a low temperature of 900∘C by the mixed metal oxide powder solid-state reaction route. CaCO3 and Li2CO3 as sintering aids and Yb2O3 as a dopant were added into the PNN–PMW–PZT ceramic system for low-temperature sintering and enhancement of electrical properties, respectively. The effects of different Yb2O3 doping amounts on the microstructure, dielectric, piezoelectric and ferroelectric properties of the samples were systematically investigated. The piezoceramics doped with 0.1 mol% Yb2O3 have optimal electrical properties ( d 3 3 = 5 6 3 pC/N, k p = 0. 6 6 , ε r = 2 7 2 8 (1 kHz), tan δ = 0. 0 1 7 6 (1 kHz), and T C = 3 0 1 ∘ C). While the piezoceramics doped with 0.3 mol% Yb2O3 have optimal energy conversion properties: the piezoelectric voltage coefficient g 3 3 = 2 6. 7 × 1 0 − 3 Vm/N and the effective piezoelectric energy conversion coefficient d 3 3 × g 3 3 = 1 4 3 6 6 × 1 0 − 1 5 m2/N. [ABSTRACT FROM AUTHOR]

Simulation of the geometry and internal grain size changes of laser cladding has been extensively studied, with the majority of such simulations focusing on pure metal powders. However, there are fewer simulations for aluminum-based composite coatings by laser cladding. In this paper, a new three-dimensional model of laser cladding composite coatings is proposed, which can accurately determine the geometrical size of the AlSiTiNiCo-WC cladding layer and the internal grain morphology and grain size changes of the cladding layer. The temperature-selective judgment mechanism and material thermal property calculation ensure the calculation accuracy of the composite coating, while the model accurately and intuitively determines the state changes of the composite coating in the process of laser cladding. Furthermore, the model verifies the feasibility of the exponential decay laser source in the simulation of composite cladding, and temperature field analysis accurately predicts the trends of grain morphology and grain size inside the cladding. The simulation results show that the variation of the laser scanning speed has a more pronounced effect on the depth of the cladding layer. The high-temperature gradient at the top of the molten pool is more likely to form fine grains, and the bottom of the cladding layer tends to form coarse columnar crystals with the increase in the internal temperature gradient at the depth. The simulation results were compared with experimental results to validate the accuracy of the simulation process. [ABSTRACT FROM AUTHOR]

To understand the mechanism of powder transportation in a coaxial feeding system, computational fluid dynamics and the discrete element method are coupled to simulate the gas flow and metal powder transportation characteristics in a directed energy deposition feeding system. Results indicate that powder diversion occurs in the bending region of powder transportation pipes. In a conveying pipe containing powders with a particle size of 53–85 μm, powder aggregation occurs at concentrations of 5.63 and 6.26 kg/m3 in bending curvatures of 11.13 and 13.33 m−1, respectively. The ratio of the particles in the three conveying pipes transported into the mixture region is 92.8% for particles with diameters of 53–85 μm, 95.0% for particles with diameters of 85–117 μm, and 96.7% for particles with diameters of 117–150 μm. This is the reason for the smaller average size of particles in the mixture region. [ABSTRACT FROM AUTHOR]

A new method to assess the quality of additive manufacturing (AM) metal powders using the triboelectric charging concept is demonstrated using CpTi, Ti6Al4V, AlSi10Mg, IN 738, and SS 316L powders. For each powder tested, the surface chemical composition was first analyzed using X-ray photoelectron spectroscopy (XPS) to determine the composition of the passivation layer. Some modifications to the current GranuCharge™ setup, developed by GranuTools™, were then performed by incorporating a flow rate measuring tool to assess how tribocharging is affected as a function of flow rate. Variations in the tribocharging response have been found with the flow rate of CpTi, AlSi10Mg and SS 316L powders. Moreover, results suggest that the tribocharging behavior might not be the same even with powders fabricated with the same passivation process. Finally, the compressed exponential model of Trachenko and Zaccone was used to reproduce the tribocharging behavior of the powders. The models were found to work best when the stretch constant β = 1.5, which is identical to the value found in other systems such as structural glasses, colloidal gels, entangled polymers, and supercooled liquids, which experience jamming when motion of individual particles become restricted, causing their motion to slow down. [ABSTRACT FROM AUTHOR]

Electron beam selective melting is a metal powder bed fusion additive manufacturing technology. In order to study the temperature field and melt pool changes of high Nb-TiAl electron beam selective melting on a single scan line and multi-scan lines. In this paper, two three-dimensional thermal-fluid models are established to simulate the evolution of the melt pool and temperature field at different electron beam scanning speeds under a single scan line and the evolution of the temperature field under multi-scan lines. The simulation results of a single scan line show that the length of the bath increases with the increase in the electron beam scanning speed, while the width and depth of the bath decrease with the increase in the speed. The scanning speed has a significant impact on the length and depth of the micro-bath, but the impact on the width is relatively small. The simulation results of multi-scan lines show that the preheating temperature has a greater influence on the melting temperature field, while the size of the scanning current has a smaller influence on the temperature field. The conclusion drawn from the results obtained through simulation is that the temperature during the preheating process must be strictly controlled, and the melting process speed must be appropriately set in order to obtain high-quality samples. [ABSTRACT FROM AUTHOR]

FFF (fused filament fabrication) is a type of 3D printing that utilizes filament for part creation. This study proposes using by-products or waste to replace part of the plastic in FFF filament, reducing environmental impact. The aim is to maintain a simple manufacturing process involving extrusion on a single-screw desktop machine followed by printing. The plastic matrix comprises polylactic acid (PLA) and polyethylene glycol (PETG), with added powdered by-products: seashells, car glass and mill scale (metal). Additives will be incorporated at 10% and 20% by weight, with two grain sizes: up to 0.09 mm and up to 0.018 mm. Mechanical tests (tensile, flexural and hardness) and thermal characterization tests will be conducted. Findings suggest adding 10%w powder of any variety to PETG increases tensile strength up to 48%, with metal powder (mill scale) showing the highest enhancement, even at 20%w, resulting in a 41% increase. Conversely, adding powder to PLA worsens mechanical properties without stiffening the material; instead, the elastic modulus decreases. Metal grain size has minimal impact, with grain sizes lower than 0.09 mm optimal for PLA. Thermal conductivity in polymers blended with powder additives is lower than in virgin polymers, likely due to air void formation, supported by density and microscopic evaluations. This research underscores the potential of utilizing waste materials with a simple FFF filament production to enhance sustainability in 3D printing practices. [ABSTRACT FROM AUTHOR]

In this industry 4.0 era, additive manufacturing is proving to be a key manufacturing technology with great potential. Laser additive manufacturing-directed energy deposition, the directed energy deposition variant that utilizes metal powder, is ideal for metallic part repair and coating. It is also referred to as powder-blown laser cladding. Relatively, it is a newer additive technology that is currently attracting a lot of research. This paper uses in-situ monitoring and statistical analysis to characterize the multi-track height powder-blown laser cladding functional coating. This study investigates the effect of laser scanning speed, laser power, and shield gas flow rates on the melt pool temperature and image area. Multi-track functional coating samples are built of one layer under different shield gas flow rates and laser scanning speed levels. The powder flow rate is kept constant at its ideal level (16.2 g/min). The sensor signals, alternatively called process signatures, such as melt pool temperature and melt pool image, are gathered and used in the conducted statistical analysis to predict the process response. Multi-track height is measured after sectioning the samples. Most related work focuses on the three major process parameters: laser power, laser beam scanning speed, and powder feeding rate. A dearth of the literature considers shield gas flow rate even though it is proving significant, especially in cases with a sudden geometry change. Even though there is a shortage in functional coating (multi-track cladding) characterization, non-commercial-like scenarios such as single bead (single track) are well studied by other researchers. In-situ monitoring of the process and incorporation of sensor signals are hardly addressed for multi-track cladding. The analysis conducted in this research revealed that the shield gas flow rate, laser scanning speed, and their interaction significantly affect the functional coating's multi-track height, melt pool image area, and melt pool temperature. Moreover, a separate experiment has been conducted to identify how the laser scanning speed and laser power affect the heating adequacy and how that relates, in turn, to the quality of the multi-track coating produced. This study paves the way for the integration of in-situ monitoring, which is rarely used in standardized commercial systems, exploring the use of process signatures in predicting the process response. [ABSTRACT FROM AUTHOR]