Repositório do LNEG
Repositório Científico do Laboratório Nacional de Energia e Geologia
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Inter-equipment ongoing validation of microplastic identification by micro-FTIR using optimal resources
Publication . Fernandes, Rafaela; Miclea, Paul-Tiberiu; ROSSI, Andrea Mario; Giovannozzi, Andrea M.; Putzu, Mara; Morgado, Vanessa; Palma, Carla; Almeida, José Miguel; Pedro, Matilde São; Drago, Claudia; Quendera, Raquel Maria Pina Amaral; Pellegrino, Olivier; Bettencourt da Silva, Ricardo
ABSTRACT: FTIR is widely used for identifying microplastics due to its performance and affordable equipment. However, there is a need for a universal method for the automatic identification of microplastics by FTIR, robust to different spectra collection conditions, and capable of adapting to the diversity of particle spectra. This research presents a method for developing a reliable and simple algorithm for inter-instrumental microplastic identification using micro-FTIR. Spectra collected from different equipments and settings across various laboratories, from microparticles previously confirmed as PET (positive cases) and non-PET (negative cases), were compared with a PET reference using multiple algorithms (match methods) based on six weighted and unweighted correlation coefficients. After excluding low signal-to-noise spectra with a newly developed universal algorithm, the 5th percentile of the match values for positive cases, estimated using a robust bootstrap method, was used as a minimum match (P5 & raquo;P) to ensure a 95% true positive rate (TP). Assuming a normal distribution of the match values for negative cases, the false positive rate (FP) was calculated. The best method identified uses an unweighted correlation of differentiated signals, resulting in a P5 & raquo;P = 0.4140 and FP = 0.0005% for spectra with a minimum signal-to-noise ratio of three. This identification performance, estimated from 117 spectra, is statistically equivalent to that observed from the identification of 405 additional particles using the validated method, at a 99% confidence level set by the Clopper-Pearson method, thereby extending the method's applicability to 522 particles. The developed method for PET identification by FTIR is robust across various acquisition conditions and instruments, was implemented in a user-friendly MS Excel spreadsheet, and can be easily tested with more particles and different instrumental settings. The validity of the identification algorithm and the defined criteria cannot be extrapolated to a different reality with respect to spectral collection conditions and the diversity of negative cases without a prior performance assessment.
A molecular 'LEGO®' approach to high-spin triangular {MnIIILn2} clusters from {MnIII} and {Ln2} metalloligands
Publication . Pantelis, Konstantinos N.; Cunha-Silva, Luís; Saber, Mohamed R.; Dunbar, Kim R.; Alexandropoulos, Dimitris I.; Stamatatos, Theocharis
ABSTRACT: A stepwise "LEGO (R)-brick" strategy has been employed for the targeted assembly of rare low-nuclearity MnIII/LnIII clusters from preformed molecular building units. The mononuclear MnIII metalloligand (Pr2NH2)[MnIII(sacb)2] (1; sacbH2 = N-salicylidene-2-amino-5-chlorobenzoic acid) was combined with newly isolated dinuclear lanthanide complexes [Ln2(sacb)(sacbH)3L(MeOH)] [LnIII = Dy (2), Gd (3); L- = 2-amino-5-chlorobenzoate], affording the trinuclear heterometallic compounds [MnIIILn2(sacb)3(sacbH)2L] [LnIII = Dy (4), Gd (5)]. Single-crystal X-ray diffraction studies revealed that 4 and 5 possess triangular {MnIIILn2(mu-O2CR)3}6+ cores, representing the first structurally characterized triangular {MnIIILn2} complexes and rare examples of triangular {MLn2} (M = any 3d-metal ion) clusters. Magnetic studies have demonstrated that the MnIII-free {Dy2} precursor 2 displays weak field-induced slow relaxation of magnetization, whereas incorporation of the Jahn-Teller active MnIII ion leads to ferromagnetically coupled {MnIIILn2} species. In particular, the {MnIIIGd2} analogue 5 exhibits a high-spin ground state of S = 9, with weak ferromagnetic MnIII & ctdot;GdIII and GdIII & ctdot;GdIII exchange interactions. Although no slow magnetic relaxation was observed for the trinuclear complexes, the results demonstrate that controlled integration of a MnIII metalloligand can promote ferromagnetic exchange in preassembled {Ln2} units and provide a direct route to structurally defined high-spin 3d/4f triangles.
Mapping the Pan-African inventory of Critical Raw Material deposits and processing capacities
Publication . Fortes, Carla; de Oliveira, Daniel Pipa Soares; Guillaneau, Jean-Claude; Marques Prazeres, Cátia
ABSTRACT: The AfricaMaVal project (2022–2025) supported the European Union’s objective of securing responsible and sustainable access to Extended Critical Raw Materials (ECRM) through strengthened cooperation with African countries. This study presents the development of two harmonised pan-African inventories: an ECRM mineral deposit database and a database of existing ore processing and refining capacities. Using the Minerals4EU data model within an INSPIRE compliant framework, heterogeneous datasets were integrated and validated through commercial and consortium sources. The resulting inventories document more than 20.000 mineral occurrences and 219 processing facilities, classified as plants, smelters, refineries and concentrators. The analysis reveals a strong geographical concentration, with South Africa and the Democratic Republic of Congo hosting over half of all facilities, and processing activities largely centred on copper and cobalt. These findings highlight regional disparities and priority areas for investment. Overall, the inventories provide a robust knowledge base to support a resilient EU raw materials strategy and guide future EU–Africa partnerships.
(CrVW)(1-x)(TaTi)x, (x=10 and 20 at.%), high entropy alloys as thermal barriers for nuclear fusion reactors
Publication . Martins, Ricardo; Lara, S. de; Neves, Filipe; Sá, Ana; Luz, Paulo P. da; Pereira Gonçalves, Antonio; Galatanu, Andrei; Sobieraj, Damian; Nguyen-Manh, D.; Dias, Marta
ABSTRACT: Due to the extreme operating temperatures in nuclear fusion reactors, current divertor monoblock materials, tungsten (plasma-facing material) and CuCrZr (heat sink), exhibit a substantial mismatch in mechanical and thermal properties. Therefore, a thermal barrier interlayer is required to guarantee continuous operation. In this work, (CrVW)(1-x)(TaTi)x alloys (x = 10 and 20 at.%) were studied for application as interlayers in nuclear fusion reactors. Atomistic modeling using Monte Carlo simulations combined with a first-principles-based Cluster Expansion Hamiltonian has been performed as a function of temperature to predict the order-disorder transitions in the investigated high-entropy alloys. Moreover, the experimental alloys were prepared by mechanical alloying followed by spark plasma sintering. Both alloy compositions display strong negative average chemical shortrange ordering below 1500 K for the W-Ta and W-Ti chemical pairs, with an estimated transition temperature around 1300 K. Atomic structures obtained from Monte Carlo simulations for (CrWV)80(TaTi)20 indicate that the ordering observed in this composition is stronger than that for (CrWV)90(TaTi)10. Moreover, both systems exhibit a bcc structure, and heat treated samples show phase growth and a four phase microstructure. The thermal diffusivity increases with temperature, reaching lower values than those of pure W and CuCrZr.
Acid-Based Deep Eutectic Solvents for Structural Modification of Sulphite Pulp Cellulose: A Potential Route Toward Advanced Materials
Publication . Moran, Guadalupe; Costa Trigo, Iván; Domínguez, José Manuel; Vilaseca, Fabiola
ABSTRACT: The transition toward renewable and environmentally responsible materials has intensified interest in cellulose-based systems for use in sustainable packaging applications. Although cellulose offers biocompatibility, structural versatility, and tuneable physicochemical properties, conventional modification routes rely on harsh chemicals and generate environmentally burdensome effluents. In this study, an efficient and a potentially green strategy for cellulose modification was developed using acid-based deep eutectic solvents (DES) composed of choline chloride and lactic, acetic, or citric acid at different molar ratios. Under mild conditions (110 degrees C, 4 h), DES pretreatment reduced glucan content in sulphite pulp from 99% to 79-93%, depending on the hydrogen bond donor (HBD), while suggesting an apparent increase in relative crystallinity, from approximately 82% to 90%, as estimated by the Segal method. FTIR, XRD, and morphological analyses revealed the disruption of the hydrogen bonding network, enhanced fibrillation, and residual DES-derived functional groups detectable by FTIR. Although DES pretreatment increased structural order, it also reduced enzymatic digestibility due to the higher proportion of crystalline domains. Overall, the results demonstrate that acidic DES constitutes a sustainable and recyclable medium capable of modulating cellulose structure and generating materials with enhanced physicochemical properties. These findings suggest that DES-modified cellulose could serve as a potential reinforcement platform for future biodegradable packaging and bioplastic formulations, enabling the development of high-performance, renewable, and environmentally compliant packaging materials.