Influence of Metallic Powder Characteristics on Extruded Feedstock Performance for Indirect Additive Manufacturing

Material extrusion (MEX) of metallic powder-based filaments has shown great potential as an additive manufacturing (AM) technology. MEX provides an easy solution as an alternative to direct additive manufacturing technologies (e.g., Selective Laser Melting, Electron Beam Melting, Direct Energy Deposition) for problematic metallic powders such as copper, essential due to its reflectivity and thermal conductivity. MEX, an indirect AM technology, consists of five steps—optimisation of mixing of metal powder, binder, and additives (feedstock); filament production; shaping from strands; debinding; sintering. The great challenge in MEX is, undoubtedly, filament manufacturing for optimal green density, and consequently the best sintered properties. The filament, to be extrudable, must accomplish at optimal powder volume concentration (CPVC) with good rheological performance, flexibility, and stiffness. In this study, a feedstock composition (similar binder, additives, and CPVC; 61 vol. %) of copper powder with three different particle powder characteristics was selected in order to highlight their role in the final product. The quality of the filaments, strands, and 3D objects was analysed by micro-CT, highlighting the influence of the different powder characteristics on the homogeneity and defects of the greens; sintered quality was also analysed regarding microstructure and hardness. The filament based on particles powder with D50 close to 11 µm, and straight distribution of particles size showed the best homogeneity and the lowest defects.

Methane and Carbon Dioxide Hydrate Formation and Dissociation in Presence of a Pure Quartz Porous Framework Impregnated with CuSn12 Metallic Powder: An Experimental Report

Hydrate formation and dissociation processes were carried out in the presence of a pure quartz porous medium impregnated with a metallic powder made with a CuSn12 alloy. Experiments were firstly made in the absence of that powder; then, different concentrations were added to the porous medium: 4.23 wt.%, 18.01 wt.%, and 30.66 wt.%. Then, the hydrate dissociation values were compared with those present in the literature. The porous medium was found to act as an inhibitor in the presence of carbon dioxide, while it did not alter methane hydrate, whose formation proceeded similarly to the ideal trend. The addition of CuSn12 promoted the process significantly. In particular, in concentrations of up to 18.01 wt.%, CO2 hydrate formed at milder conditions until it moved below the ideal equilibrium curve. For methane, the addition of 30.66 wt.% of powder significantly reduced the pressure required to form hydrate, but in every case, dissociation values remained below the ideal equilibrium curve.

Synthesis and characterization of Co3O4 nanoparticles for use as pigments in solar absorbing paints

This aim of this research is to produce Co3O4 oxide by means of one-step solution novel combustion methods using aspatic acid (C4H7NO4); lysine (C6H14N2O2); tris (hydroximethyl) aminomethane (NH2C (CH2OH)3) and ethylene diamine tetra-acetic acid (C10H16N2O8) as fuels. The pigments were characterized using X-ray diffraction, scanning and transmission electron microscopy, infrared spectroscopy with Fourier transform and UV-VIS-IR Spectrophotometry. The paint based on alkyd resin was made from pigments obtained (Co3O4 oxide). In order to make a comparison of the thermal emittance of the paint, two different formulations were prepared and these coating are named "absorbent paint coating": one that included 1% by weight of aluminum in metallic powder and another, with 1% of copper in metallic powder, respectively. The solar absorbance for the Co3O4 powders, plus quartz cuvette, gave a value of 0.9 in all cases. An extraordinary value of absorption on the coatings between 95 and 96% was noted. These results suggested that the synthesis of combustion in solution makes it possible to obtain a Co3O4 absorbent pigment with different fuels. These syntheses have a low environmental impact because they are one-step processes. All use low amounts of reactive ash obtained at a calcination of about 500 °C. These results suggest the possibility of utilizing this oxide in absorbent solar paints.

Influence of Metallic Powder Characteristics On Extruded Feedstock Performance For Indirect Additive Manufacturing

Material Extrusion (MEX) of metallic powder-based filaments has been showing great potential as an additive manufacturing technology. MEX provides an easy solution, as an alternative to direct additive manufacturing technologies (e.g. SLM, EBM, DED) for problematic metallic powder, like copper powder, due to its reflectivity and thermal conductivity. MEX, an indirect technology, consists of 5 steps – optimising metal powder, mixing (feedstock), filament production, shaping, debinding and sintering. The great challenge in MEX is, undoubtedly, filament manufacturing for optimal green density, and consequently the sintered properties. The filament, to be extrudable, must accomplish at optimal powder volume concentration (CPVC) with good rheological performance, flexibility, and stiffness. These have a main role in the quality of the 3D objects after debinding and sintering. In this study, a feedstock composition (similar binder, additives and CPVC - 61% vol.) of copper with three different particle powder characteristics was selected, in order to highlight their role. The quality of the filaments, strands and 3D objects was analyzed by micro-CT highlighting the influence of the different powder characteristics on the homogeneity and defects of the greens. Sintered filaments were also analysed, regarding hardness, microstructure and a comparison between green and sintered defects, using micro-CT. The filament based on particles powder with D50 close to 11 µm and straight distribution of particles size shows the best homogeneity and lower defects.

Optimization of metallic powder filaments for additive manufacturing extrusion (MEX)

Additive manufacturing (AM) of metallic powder particles has been establishing itself as sustainable, whatever the technology selected. Material extrusion (MEX) integrates the ongoing effort to improve AM sustainability, in which low-cost equipment is associated with a decrease of powder waste during manufacturing. MEX has been gaining increasing interest for building 3D functional/structural metallic parts because it incorporates the consolidated knowledge from powder injection moulding/extrusion feedstocks into the AM scope—filament extrusion layer-by-layer. Moreover, MEX as an indirect process can overcome some of the technical limitations of direct AM processes (laser/electron-beam-based) regarding energy-matter interactions. The present study reveals an optimal methodology to produce MEX filament feedstocks (metallic powder, binder, and additives), having in mind to attain the highest metallic powder content. Nevertheless, the main challenges are also to achieve high extrudability and a suitable ratio between stiffness and flexibility. The metallic powder volume content (vol.%) in the feedstocks was evaluated by the critical powder volume concentration (CPVC). Subsequently, the rheology of the feedstocks was established by means of the mixing torque value, which is related to the filament extrudability performance.