Seaweeds biorefinery into pigments and carrageenans: Testing a sequential extractions approach Gabriela Gonçalves, Izabel Cristina Freitas Moraes, Bruno Faria, Loic Hilliou Food Hydrocolloids, 2025 This study aims to test a sequential extraction (SE) method for red seaweeds ( Chondrus crispus, Mastocarpus stellatus, Gigartina pistillata ). The tested SE is a preliminary screening step towards the extrusion-based biorefinery (E2B2) of carrageenophytes into various natural products, a concept that still needs to be established. Phycobiliproteins, chlorophyll-a, carotenoids, and hybrid-carrageenans (HK) were isolated with the following sequence: cold-water extraction (CWE), ethanolic extraction (EE), hot water extraction (HWE), and hot alkaline extraction (HAE). HK chemical structures and gelling properties were systematically compared with those of carrageenans isolated from direct extractions (controls). Such comparison, which is critically missing in earlier SE studies, allows to assess the impact of prior extraction sequences on such HK properties. SE effectively separated algal components, facilitating the recovery of HK, particularly with M. stellatus and G. pistillata , with superior gel elasticity and viscosity compared to the controls. HWE yielded less sulphated HK with higher molecular masses and enhanced gelling properties. HAE extracts exhibited lower molecular masses and reduced gelation potential due to the prior HWE sequence. Prolonged extraction generally improved molecular masses and gels elasticity, although a distinct trend was found with C. crispus . The results from this preliminary screening suggest that M. stellatus is not a good candidate for testing in E2B2. • Sequential extractions (SE) separate hybrid carrageenans and pigments from carrageenophytes. • SE produce carrageenans with doubled gel elasticity compared to batch extraction. • Extraction times in each SE step must be optimized for each seaweed. • SE opens the way to the extractive extrusion-based biorefinery (E2B2) of seaweeds.
Reinforcing aluminum nanocomposites with 3D carbon honeycombs: A molecular dynamics study on nanofiller morphology Bruno Faria Materials Today Communications, 2025 Strengthening mechanisms of Al nanocomposites reinforced with 3D carbon honeycomb (CHC) nanofillers of varying aspect ratios were investigated using molecular dynamics. Nanocomposites with CHC nanofillers of increasing aspect ratio were subjected to tensile and compressive loading. Stress-strain curves and key mechanical properties were derived for each nanocomposite. Detailed deformation mechanisms were then compared to those in pure Al. The simulations reveal that the aspect ratio and orientation of the nanofillers significantly influence both the recrystallization process and the formation of a stacking fault network within the unloaded nanocomposites. Low-aspect-ratio nanofillers generate localized stacking faults, while high-aspect-ratio nanofillers promote a network of intersecting stacking faults. Under compressive loading, the nanofillers hinder dislocation motion, delaying the onset of plastic deformation and increasing yield strength. Tensile loading results show the reinforcing effects of the nanofillers are highly dependent on loading direction, with higher aspect ratios demonstrating improved load distribution and stress localization near the nanofiller. Overall, aspect ratio and orientation of the nanofiller relative to loading direction and its interaction with crystallographic imperfections were found to be critical factors in strengthening of the nanocomposites. Valuable insights are provided here into the design of Al-CHCs nanocomposites with tailored mechanical properties for advanced structural applications. • 3D Carbon honeycombs provide anisotropic reinforcement to aluminum nanocomposites. • Elongated nanofillers enhance strength and load distribution along [001] direction. • Long nanofillers create broad stacking fault networks, hampering dislocation motion. • Interlocking stacking planes hinder dislocation motion, increasing stress tolerance • Flattened nanofillers delay plasticity and offer weaker reinforcement.
Hybrid Carrageenans Versus Kappa–Iota-Carrageenan Blends: A Comparative Study of Hydrogel Elastic Properties Maria Alice Freitas Monteiro, Bruno Faria, Izabel Cristina Freitas Moraes, Loic Hilliou Gels, 2025 A comparison between the gel properties of blends of kappa- and iota-carrageenans (K+Is) and hybrid carrageenans (KIs) with equivalent chemical compositions is here presented. The objective is to assess under which conditions hybrid carrageenans are valuable alternative to blends of kappa- and iota-carrageenans for gelling applications and to contribute to the identification of phase-separated structures or co-aggregated helices. Phase states constructed in sodium chloride and in potassium chloride confirm that KIs build gels under a much narrower range of ionic strength and polysaccharide concentration. Hybrid carrageenans displayed salt specificity, forming gels in KCl but not in NaCl, highlighting their limited gelling potential in Na+ environments. A two-step gelation mechanism was found in both systems at lower ionic strengths and when iota carrageenan is the major component. The shear elastic moduli of KI gels are overall smaller than those of blends, but the opposite is observed at lower ionic strengths in KCl and in systems richer in iota-carrageenans. The nonlinear elastic properties of gels do not relate to the use of blends or hybrid carrageenans for their formulation. Instead, larger contents in iota-carrageenans lead to gels able to sustain larger strains before yielding to a fluid state. However, these gels are more prone to strain softening, whereas strain hardening is measured in gels containing more kappa-carrageenan, irrespective of their blend or hybrid structure.
Role of the Molecular Mass on the Elastic Properties of Hybrid Carrageenan Hydrogels Gabriela Gonçalves, Bruno Faria, Izabel Cristina Freitas Moraes, Loic Hilliou Gels, 2025 A set of carrageenans produced in the potassium form and with chemical structures varying from pure iota-carrageenans to nearly pure kappa-carrageenans is submitted to ultrasonication to reduce their molecular masses Mw while maintaining a constant chemical structure and a polydispersity index around 2. The kinetics of ultrasound-induced chain scission are found to be slower for polysaccharides richer in kappa-carrageenan disaccharide units. From the elasticity of samples directly gelled in a rheometer at 1 w/v% in 0.1 M potassium chloride, a critical molecular mass Mc is identified as the mass below which no gel can be formed. Mc is found to be smaller for kappa- and kappa-2-carrageenans of the order of 0.13–0.21 MDa. The presence of more sulphated disaccharide units significantly increases Mc up to 0.28 MDa for iota-carrageenan and 0.57 MDa for a highly sulphated hybrid carrageenan. For the set of Mw and carrageenans tested, no plateau in the Mw dependence of the gels’ elasticities is found.
Structure–Elasticity Relationships in Hybrid-Carrageenan Hydrogels Studied by Image Dynamic Light Scattering, Ultra-Small-Angle Light Scattering and Dynamic Rheometry Amine Ben Yahia, Adel Aschi, Bruno Faria, Loic Hilliou Materials, 2024 Hybrid-carrageenan hydrogels are characterized using novel techniques based on high-resolution speckle imaging, namely image dynamic light scattering (IDLS) and ultra-small-angle light scattering (USALS). These techniques, used to probe the microscopic structure of the system in sol–gel phase separation and at different concentrations in the gel phase, give access to a better understanding of the network’s topology on the basis of fractals in the dense phase. Observations of the architecture and the spatial and the size distributions of gel phase and fractal dimension were performed by USALS. The pair-distance distribution function, P(r), extracted from USALS patterns, is a new methodology of calculus for determining the network’s internal size with precision. All structural features are systematically compared with a linear and non-linear rheological characterization of the gels and structure–elasticity relationships are identified in the framework of fractal colloid gels in the diffusion limit.
Mechanical characterization of polymer-grafted graphene PEG nanocomposites using molecular dynamics Cátia Guarda, Bruno Faria, José N. Canongia Lopes, Nuno Silvestre Composites Science and Technology, 2024 It is known that most polymers exhibit poor interfacial compatibility with graphene sheets. Modification of graphene's surface by functionalization with small polymer chains from the same building blocks as the matrix polymer improves the compatibility of graphene in polymeric materials. In this paper, the mechanical behaviour of polyethylene glycol (PEG) nanocomposites with graphene grafted with polymeric chains under tensile and compression is investigated using molecular dynamics. The influence of the functional groups (-NH2 and –OH) that bond the polymer chain to graphene is analysed. It is found that the system containing the –NH2 functional group showed lower mechanical properties than the system containing the –OH functional group. The mechanical properties of five PEG-nanocomposites are investigated: PEG/G, PEG/GNH-1PEG-S, PEG/GNH-2PEG-L, PEG/GNH-1PEG-S-NH2, PEG/GO-1PEG-S. The radius distribution function values and the variation of interfacial interaction energy are also examined. It is shown that functionalization of the graphene sheet increases the magnitude of the interaction energy, and it also reveals higher adhesion between graphene surface and PEG matrix. It is found that the mechanical properties of PEG are mostly improved in the longitudinal direction (reinforcement up to 43 %). Despite the high interaction between the nanofiller and PEG matrix, the low intrinsic properties of the nanofiller, namely Young's modulus, as well as the rupture of the graphene sheet during the deformation process deteriorated the mechanical properties of the nanocomposite. The presence of polymeric chains grafted to graphene improves the adhesion between the graphene surface and the polymeric matrix but decreases its mechanical properties.
Tensile and Compressive Behavior of CHC-Reinforced Copper using Molecular Dynamics Bruno Faria, Nuno Silvestre, José N. Canongia Lopes Advanced Engineering Materials, 2023 Graphene has been extensively studied as nanofiller to produce ultra‐strong and ductile metal nanocomposites but challenges such as poor adhesion at the metal–carbon interface have yet to be met. Carbon honeycombs (CHCs) are highly porous 3D graphene networks that possess a very large surface area‐to‐volume ratio, an outstanding physical absorption capacity and notable mechanical properties. Herein, these recently synthetized 3D CHCs are introduced in copper as nanofillers, and the mechanical properties of the nanocomposites, such as elastic modulus, tensile strength, failure strain, compressive strength, and critical strain, are obtained using molecular dynamics simulations. Three CHC lattice types are studied, and the metal–carbon interface is accurately modeled by using melting and recrystallization of the copper matrix around the nanofiller. Gains between 28% and 50% are obtained for the Young's modulus, while the tensile strength improved between 43% and 49%. Pullout tests reveal that the copper nanopillars that form by the filling of the honeycomb cells of CHC by copper atoms considerably increase the pullout force and are responsible for improvements in adhesion and in loading stress transfer.
Influence of matrix recrystallization and nanofiller porosity on the interfacial properties of holey graphene-aluminium nanocomposites Cátia Guarda, Bruno Faria, Nuno Silvestre, José N. Canongia Lopes Composite Structures, 2023 Due to their excellent properties, graphene-like 2D structures have been widely used to reinforce aluminium nanocomposites. However, the interfacial behaviour presented by different types of holey graphenes and their reinforcing effect on the mechanical properties of the nanocomposites are still not completely clear. In this work, Molecular Dynamics simulations are used to investigate the interfacial behaviour between five different graphenes and an aluminium matrix (Al-graphene, Al-Phagraphene, Al-haeckelite, Al-N-holey-graphene (hG) and Al-B-hG). Using pull-out loading test, the influence of the 2D nanofillers porosity on the mechanical properties of the nanocomposites is assessed. Additionally, and regarding the aluminium matrix, two different cases were studied: (i) the aluminium matrix was not recrystallized and (ii) the aluminium matrix was melted and then recrystallized. It was found that the introduction of porous graphene improves the interfacial adhesion in the nanocomposites while the pull-out force and interfacial shear strength of the nanocomposites are significantly higher when the aluminium matrix is previously melted and then recrystallized.
Mechanical properties of phenine nanotubes Bruno Faria, Nuno Silvestre Extreme Mechanics Letters, 2022 Phenine Nanotubes (PhNT) are cylinder-shaped molecules synthetized from 1,3,5-trisubstituted benzene ring building blocks that can form tubular segments of different sizes. Small nanotube segments have been recently synthetized, and efforts are being made to increase the nanotubes’ length by adding more “phenine” units. To the authors’ best knowledge, a complete characterization of the mechanical properties of these nanotubes has not yet been accomplished. In this work, Reax and AIREBO forcefields were used to model armchair and zigzag PhNTs and Molecular Dynamics simulations were employed to determine their mechanical properties for tensile, compressive, bending and twisting loadings. It was found that PhNTs have a much lower Young’s modulus (about 30%) and tensile strengths (about 45%) than carbon nanotubes (CNTs), but can endure longer tensile strains without breaking apart. Although possessing a lower bending and twisting stiffness than CNTs, PhNT have highly flexible sidewalls due to their superior porosity, and therefore can withstand higher angles of twist and angles of bend without breaking bonds. This extra flexibility; extended porosity; possibility for heteroatom doping and reasonable strength, make PhNTs very promising candidates for a wide range of applications, such as sensing, ionic transistors or molecular sieving. Finally, a brief study on the application of elastic continuum shell formulas to predict the critical stress (compression), critical moment (bending) and critical torque (twisting) is also presented.
