Selective laser melting (SLM) allows for manufacturing intricate and accurate component designs that are challenging, expensive, or impossible to achieve using traditional methods. To achieve a high-quality final product with SLM, it is necessary to optimize the process parameters carefully. This optimization helps to minimize internal structural defects and control the microstructure. In this study, the optimum production parameters of Ti6Al4V alloy were determined using the Response Surface Method (RSM). The micro-CT analysis was utilized to calculate the relative densities of the samples fabricated using different production parameters. Furthermore, the influence of heat treatment, conducted below and above the β transformation temperature, on the mechanical properties was examined. The results were analyzed by considering the microstructure images obtained from Scanning Electron Microscope (SEM) and X-ray Diffraction (XRD) analysis. The optimum production parameters for the SLM method were found to be 80W laser power, 1125 mm/s scanning speed, 25 μm layer thickness, and 45 μm hatch distance. Samples created with these optimized parameters achieved 99.919% relative density, 1050 MPa ultimate tensile stress, and 13.8% elongation, surpassing the minimum standards outlined in ASTM F3001-14. Additionally, the systematic parameter reduction approach used in the study led to savings in both powder consumption and time in SLM, a method that could be applied to various metallic materials. 

Effects of process parameters on selective laser melting of Ti6Al4V-ELI alloy and parameter optimization via response surface method

In this study, a Discrete Element Method (DEM)-based model was developed to simulate the powder spreading process in Powder bed Fusion (PBF) for Polyamide 6 (PA6) powder, which considered the spreading speed (3 mm/s and 30 mm/s) and temperature (25 °C and 110 °C) as parameters affecting the final spreading powder layer quality. The particle horizontal and vertical velocities were analysed in regions near the spreading blade, where at the lower spreading speed, particle velocities are far less compared to the higher spreading speed. The lower particle velocities lead to gently settling down and rearranging particles during spreading on the bed, allowing a uniform powder layer to form. Increasing the spreading speed led to an increase in shear stress and inertia number. At higher temperatures, shear stresses also rise while the inertia number is slightly reduced due to the greater cohesion between particles. The generated powder layer by the DEM model was analysed using the wavelet analysis technique and compared to experiments. The spreadability index of experiments can be estimated with less than 5% error using DEM simulations, though in an approximately consistent manner that captures the experimental trends of spreading speed and temperature. The packing fraction of simulated powder layers was investigated in the spreading direction. The DEM simulations show that packing fraction decreases as temperature or spreading speed are increased, with its variation across the bed increasing for higher spreading speeds. Increasing the spreading speed leads to greater motion and inertia number of particles and, consequently, it intensifies the particle ejection and results in many unfilled areas in the spread powder layer. Increasing temperature leads to an increase in cohesivity between particles, resulting in aggregates forming on the spread powder layer. 

Investigating the effect of temperature on powder spreading behaviour in powder bed fusion additive manufacturing process by Discrete Element Method

The spinal ferrites are regarded as promising for renewable energy application like hydrogen production from sodium borohydride (NaBH4) since they have superior catalytic activity. The current work considers the preparation of Cu1-xZnxFe2O4 (x = 0.0, 0.2, 0.4, 0.6 and 0.8) nanoparticles via the low temperature sol-gel method. The cubic crystal structure of nanoparticles was identified by XRD spectra analysis. The average crystal size was provided concerning the full width at half maximum to be 10.0 nm according to Scherer formula. FTIR spectra of synthesized ferrite nanoparticles showed the vibrational bands of Cu1-xZnxFe2O4. The images showed a cross-linked porous surface morphology. The TEM images of the CuFe2O4 and Cu0.6Zn0.4Fe2O4 samples showed spherical nanoparticles with an average size of 10 nm. The surface area BET at 0.0, 0.2, 0.4, 0.6 and 0.8 content of zinc were 95, 66, 46, 49 and 41 m2/g. The values of direct band gaps for nanocrystalline Cu1-xZnxFe2O3 were 52.25, 2.0, 2.16, 1.9 and 2.11 eV at x = 0.0, 0.2, 0.4, 0.6, and 0.8. The hydrogen catalytic effect of Cu1-xZnxFe2O4 nanoparticles is accelerated, especially the sample CuFe2O4. The nanoparticles show high generation rates but the sample CuFe2O4 is the highest catalytic material (1810 mL/gmin). 

Low temperature sol-gel synthesis of copper zinc ferrite for hydrogen catalytic hydrolysis of sodium borohydride

Metal powder feedstock evaluation and management for powder bed fusion: a review of literature, standards, and practical guidelines

In this work, a novel catalyst for the hydrolysis reaction of sodium borohydride to produce hydrogen—graphene oxide modified perlite supported cobalt—was produced. After being exposed to 98% H2SO4, the natural mineral perlite was calcined and then mixed with graphene oxide. To create the Co@Perlite-GO catalyst, the synthesized Perlite-GO was added to the cobalt catalyst as a supporting material. The morphological layout and nature of the sample were evaluated using different spectroscopic techniques. Comparative analysis was carried out to investigate the catalytic effects of Co@Perlite-GO and Co@Perlite catalysts on the sodium borohydride (SBH) hydrolysis reaction. When the Co@Perlite-GO catalyst containing 4 mg Co was utilized, the hydrogen production rate was 12401 ml g-1 min-1 as a consequence of the optimization procedures carried out at 298 K. Under room conditions, the reaction occurred as catalyst control (0th degree), and the standard turnover frequency (TOF) was measured to be 8615 s-1. The activation energy, enthalpy, and entropy of the reaction were measured as 53.35 kJ mol-1, 50.77 kJ mol-1, and -58 J/(mol.K) respectively. It was found that the catalyst maintained 100% efficiency even after being used six times. 

Synthesis of a cobalt catalyst supported by graphene oxide modified perlite and its application on the hydrolysis of sodium borohydride

Powder spreadability is critical to particle spread layer and thus the quality of final product in powder-based additive manufacturing, but the metrics and the underlying mechanics have not yet been well acknowledged. In this work, the metrics of spreadability are examined for powder with different size classes, and the factors affecting powder spreadability are analysed, in which both the cohesion and interlocking of particles are included. The simulation results are validated by comparing the total particle volume of spread layer against the experimental and numerical data in previous work. The results show that relative powder spreadability should be compared at the same ratio of the gap height to particle size, especially for the powders with different particle size classes. Powder spreadability is mainly controlled by the shear action of the blade on the heap, the stagnation effect due to rough surface of substrate, particle jamming around the gap region, and the effect of powder flowability on the movement of particles within the heap. Jamming makes powder spreadability different from powder flowability. As particle jamming is more prone for the particles with strong interlocking, powder spreadability is more sensitive to the rolling friction than the cohesion of particles, especially for the substrate surface with small roughness, although the rheological behaviour of bulk particles is similar in front of the gap. A physical model is proposed to predict the maximum fraction of spread layer at the specified gap height. 

Analysis of the metrics and mechanism of powder spreadability in powder-based additive manufacturing

One-pot synthesis of magnetic copper ferrite nanocubes for hydrogen production by hydrolysis of sodium borohydride

The microspheres prepared by the microfluidic-assisted internal gelation process are still challenging to reach the millimeter size due to the large gravity. The gravity would affect the sphericity and size uniformity of microspheres. The improved microfluidic-assisted internal gelation process is designed and optimized to produce large-sized monodisperse ceramic microspheres with good sphericity. The movement mechanism of millimeter-sized sol droplets and gel microspheres in the microchannel is summarized and the state of the dispersed phase entering the measuring cylinder is controlled. The friction between the gel microspheres and the tubing wall is reduced as much as possible, and ZrO2 ceramic microspheres of 500 ± 5 μm with good sphericity are prepared with the broth at room temperature. The mechanism of sol droplets entering the oil surface is explored to demonstrate the superiority of the improved microfluidic-assisted internal gelation process. The improved microfluidic-assisted internal gelation process could be directly extended to preparing other millimeter-sized monodisperse ceramic microspheres. 

An improvement of microfluidic assisted internal gelation in the preparation of millimeter‐sized ceramic microspheres

A new approach for impregnation of Cs into zirconia microsphere matrix

Enhanced mechanical properties of YSZ ceramic microspheres via urea solution-modified external gelation process

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