Macroalgae Ulva lactuca, has been employed as a natural source for the production of extracts with potent bioactivity. The biochemical characterization showed that the macroalgae biomass contains a remarkable amount of the polysaccharide Ulvan (49.9 wt%) which is a valuable chemical compound well known for its benefits in human health. Four nontoxic solvents, water, ethyl acetate, ethanol, and an ethanol/water mixture (70:30 v/v) were examined for their recovery efficiency of total carotenoid and phenolic contents. Experimental results showed that the aqueous mixture of ethanol was the most efficient solvent in the recovery of bioactive compounds with extraction yield of 10–15% dw. The effect of extraction parameters, namely time, temperature, and the ratio of biomass to solvent, on the carotenoid and phenolic compounds’ content, antioxidant activity, and extraction yield, was investigated, using the ethanol/water mixture as a solvent. The extract obtained under 60 °C, 3 h of extraction time and 1:10 biomass to solvent mass ratio showed the highest antioxidant activity. This extract maintained its antioxidant capacity almost stable for five days of storage under cool and dark conditions. Finally, specific phenolic and carotenoid compounds in the U. lactuca extracts were identified using the High-Performance Liquid Chromatography (HPLC) technique.

C. vulgaris microalgae biomass was employed for the extraction of valuable bioactive compounds with deep eutectic-based solvents (DESs). Particularly, the Choline Chloride (ChCl) based DESs, ChCl:1,2 butanediol (1:4), ChCl:ethylene glycol (1:2), and ChCl:glycerol (1:2) mixed with water at 70/30 w/w ratio were used for that purpose. The extracts’ total carotenoid (TCC) and phenolic contents (TPC), as well as their antioxidant activity (IC50), were determined within the process of identification of the most efficient solvent. This screening procedure revealed ChCl:1,2 butanediol (1:4)/H₂O 70/30 w/w as the most compelling solvent; thus, it was employed thereafter for the extraction process optimization. Three extraction parameters, i.e., solvent-to-biomass ratio, temperature, and time were studied regarding their impact on the extract’s TCC, TPC, and IC50. For the experimental design and process optimization, the statistical tool Response Surface Methodology was used. The resulting models’ predictive capacity was confirmed experimentally by carrying out two additional extractions under conditions different from the experimental design.

Harvesting of microalgae is a crucial step in microalgae-based mass production of different high value-added products. In the present work, magnetic harvesting of Chlorella vulgaris was investigated using microwave-synthesized naked magnetite (Fe₃O₄) particles with an average crystallite diameter of 20 nm. Optimization of the most important parameters of the magnetic harvesting process, namely pH, mass ratio (m_r) of magnetite particles to biomass (g/g), and agitation speed (rpm) of the C. vulgaris biomass–Fe₃O₄ particles mixture, was performed using the response surface methodology (RSM) statistical tool. Harvesting efficiencies higher than 99% were obtained for pH 3.0 and mixing speed greater or equal to 350 rpm. Recovery of magnetic particles via detachment was shown to be feasible and the recovery particles could be reused at least five times with high harvesting efficiency. Consequently, the described harvesting approach of C. vulgaris cells leads to an efficient, simple, and quick process, that does not impair the quality of the harvested biomass.

Tailor-made materials used for advanced applications are nowadays of great research interest in various industrial and technological fields, ranging from aerospace and automotive applications to consumer goods and biomedical components. In the present research, Inconel 718 superalloy specimens were fabricated by the selective laser melting (SLM) technique. Structural characterization of the 3D-printed samples showed that they consisted of γ solid solution along with spherical carbide particles. To explore the applicability of these materials in abrasive tribological applications, reciprocating sliding tests were performed under dry conditions versus an Al₂O₃ counter-body. A 3D representation (triboscopy) of the tangential force during each sliding cycle was carried out in order to obtain better insight on the evolution of friction and to visualize localized tribological phenomena. Quantification of wear was performed with confocal microscopy and the wear mechanisms were analyzed with SEM and EDS techniques. Furthermore, the effect of surface finishing (as-printed and polished) on friction and wear were also investigated, and a comparison with other industrial materials is also included to evaluate the applicability of these alloys. The results indicated that surface finishing had an effect on friction during the run-in stage, whereas in steady-state conditions, no significant differences were observed between the as-printed and polished specimens. In all cases, the main wear mechanisms observed were a mixture of two-body and three-body abrasion, along with oxidative wear (indicated by the formation of an oxide-based tribo-layer).

Novel hybrid semiconducting thin films comprising CdSe with the addition of nitrogen-doped carbon dots (NCDs) were developed onto titanium substrates using a one-step electrocodeposition technique. The deposition took place using an acidic aqueous electrolytic bath containing hydrothermally produced ΝCDs under direct and pulse current regime. The specimens were studied using XRD, SEM-EDS, and UV-Vis spectroscopy techniques to determine their microstructural characteristics, surface morphology and composition and the energy gap, respectively. Their photochemical behavior was studied utilizing a photoelectrochemical cell (PEC). Variations in physical properties, along with significantly improved photoelectrochemical responses, were observed for the NCD-infused semiconductive thin films compared to their plain CdSe counterparts. These variations were highly affected by the incorporation rate of the NCDs in each thin film, as well as the imposed electrolysis conditions.