Properties of Mechanochemically Synthesized Famatinite Cu3SbS4 Nanocrystals

In this study, we report the optoelectric and thermoelectric properties of famatinite Cu3SbS4 that was mechanochemically synthesized in a planetary mill from powder elements for 120 min in an inert atmosphere. The tetragonal famatinite Cu3SbS4 was nanocrystalline with a crystallite size of 14 nm, as endorsed by Rietveld refinement. High-resolution transmission electron microscopy showed several crystallites in the range of 20–50 nm. Raman spectroscopy proved the purity of the synthesized famatinite Cu3SbS4 and chemical-state characterization performed by X-ray photoelectron spectroscopy confirmed that the prepared sample was pure. The Cu1+, Sb5+, and S2− oxidation states in Cu3SbS4 sample were approved. The morphology characterization showed homogeneity of the prepared sample. The photoresponse of Cu3SbS4 was confirmed from I–V measurements in the dark and under illumination. The photocurrent increase reached 20% compared to the current in the dark at a voltage of 5 V. The achieved results confirm that synthesized famatinite Cu3SbS4 can be applied as a suitable absorbent material in solar cells. The performed thermoelectric measurements revealed a figure of merit ZT of 0.05 at 600 K

Pressure-less spark plasma sintering of 3D-plotted titanium porous structures

Additive manufacturing of titanium porous structures by direct ink writing involves the removal of the binder needed for powder extrusion and subsequent sintering to consolidate the 3D-plotted body. In this work, pressure-less spark plasma sintering (PL-SPS) was systematically studied for fast consolidation of titanium porous structures. Furthermore, poloxamer 407 was used as the binder and the lowest temperature possible was identified for its thermal elimination. The results show for the first time that PL-SPS generated sintering conditions similar to those generated by conventional pressure-less sintering, producing hierarchical titanium porous structures with equivalent densification, shrinkage, and surface roughness, but with minimal grain growth. The thermal responses of the die and material showed efficient radiation heat transfer, allowing fast heating (100 °C/min) of one sample per run, promoting the formation of sintering necks and powder densification in 10 min, which is much faster than conventional sintering that requires at least 2 h of dwell time. However, the process operates at a sintering temperature 200–300 °C above the conventional sintering temperature, and at the expense of high consumption of electrical energy to achieve such a high heating rate. The mechanical strength of the resulting titanium structures increases with increasing strand densification at nearly constant strand separation, resulting in strong and plastic porous structures