The objective of this research was to assess the effectiveness of a combined remediation strategy - electrokinetic treatment coupled with mechanochemical processes (ultrasound and grinding) and fluid recirculation - for the removal of tributyltin (TBT) from marine sediments. TBT is a persistent and highly toxic compound that resists most conventional remediation methods. The study aimed to validate the synergistic enhancement achieved by integrating these processes and to explore potential relationships between the removal of TBT, heavy metals, and other organic contaminants. A real marine sediment collected from a harbor in Spain was used in the study. The material was muddy (67

Silver tarnishing in museum environments depends on multiple, interacting factors that are not often studied in situ. With the aim of addressing the problem in real-world scenarios, this study presents a one-year assessment at the National Archaeological Museum of Spain, in Madrid, a museum that houses a significant collection of silver objects. Pure Ag coupons were placed in four display cases—two designs with different airtightness—and in an adjacent gallery. Tarnishing was quantified by colorimetry, gravimetry, and galvanostatic reduction, and analyzed in relation to environmental parameters (T/RH) and gaseous pollutants (H2S, SO2, HF, HCl, formic and acetic acids), measured with passive samplers. Coupons showed different degrees of tarnish, with annual corrosion rates ranging from IC1 (very low) to IC2 (low), without a straightforward relation to hydrogen sulfide concentrations. Electrochemical profiles and XPS on representative coupons identified Ag2S as the dominant product, with AgCl and minor Ag2SO4 in the coupons exposed outside the airtight cases, indicating different contributions inside and outside the cases. Findings highlight that sulfide concentration is not the sole driver; case airtightness, internal materials, cleaning products used on adjacent areas, and, possibly, other aspects influence silver tarnishing.

ABSTRACTThis study introduces a novel method for the effective doping of hexagonal molybdenum trioxide (h‐MoO3) microstructures with different contents of nickel, significantly enhancing its electrochemical performance in aluminum‐ion batteries (AIBs). Ni doping does not alter the high crystallinity and phase purity of the pristine oxide but modifies its defective structure and electronic properties. Electrochemical tests, including cyclic voltammograms and charge–discharge cycling, showed improvements in capacity and stability for Ni‐doped samples as compared with undoped ones. Moreover, the incorporation of Ni was found to enhance the structural integrity and electrochemical stability of h‐MoO3, preventing the formation of intermediate phases during cycling and reducing resistance at the electrode–electrolyte interface. The existence of an optimal Ni doping of about 1 at% is evidenced. Samples with this Ni content attain a stabilized specific capacity of 230 mAh g−1 over 100 cycles, doubling that reported in previous works for h‐MoO3 composites with carbon nanotubes. Nickel‐doped h‐MoO3 shows exciting potential for advanced AIB applications, paving the way for further energy storage technology advancements.

A sustainable route to obtain graphene oxide (GO) and reduced graphene oxide (rGO) with highly competitive properties through the utilization of graphite recycled from spent vehicle's lithium-ion batteries is described. As compared with previous works, our precursor material is representative of a larger-scale recycling procedure, involves the processing of both cathodic and anodic materials, and concerns a larger number of batteries operated in diverse conditions. The morphology, chemical features, structure, and conductivity of the samples have been thoroughly investigated. Results obtained from complementary characterization techniques reveal the correct formation of GO and rGO samples from the recycled graphites. Electrical measurements show that the conductivity of our GO and rGO samples are very similar or even larger than those reported for samples obtained from high-purity natural graphite. These results indicate that our strategy is able to produce good-quality GOs and rGOs with potential applications in different fields, contributing to the circular economy and the recyclability of discarded wastes.

This study investigates the efficacy of a combination of chemical, electrical, and mechanical methods for extracting specific metal contaminants from marine dredged sediment. Samples of muddy contaminated sediment from a Spanish harbor were characterized, including the mode of occurrence of heavy metals, using sequential chemical extraction. Desorption tests were conducted using the sediment in its fresh state, in a custom-built cell/reactor filled with an electrolyte—either a solution of 0.25 M citric or acetic acid, or deionized water. Electrical current, ultrasonic energy, and circulating flow were applied in various combinations, and the efficacy of such combinations on the metal desorption was evaluated. After the experiments, the solutions were analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES). X-ray diffraction (XRD) and thermogravimetric analysis/differential thermal analysis (TG/DTA) were performed on the sediment. The sequencial extraction revealed that most metals (excluding Hg, Pb and Zn) were primarily bound to the residual fraction (fraction V), with As and Cu exhibiting the highest concentrations. Cadmium and mercury were preferentially extracted in fraction IV, associated with organic matter. Pb and Zn exhibited their highest percentages in fraction III, bound to Fe–Mn oxides. Regarding desorption, the results indicated that increasing treatment time enhanced metal desorption, with the most significant effect observed during the initial stages. The electrolyte used emerged as the most influential factor. Citric acid proved more effective for As, Cr, and Ni, while acetic acid favored Cu, Pb, and Zn extraction. As, Pb, and Zn exhibited preferential desorption in the presence of ultrasounds, while Cr, Ni, Pb, and Zn desorbed more readily under electrical current. Application of electrolyte circulation had a positive effect on the extraction of all metals. Changes in the electrolyte's chemical composition are the most significant factor influencing metal desorption. In addition to the electrolyte used, the application of some form of energy had a slight positive effect on metal desorption. However, at this stage it seemed that the synergistic effect of both electric field and ultrasounds appears to be only relevant for Cu. Electrolyte circulation had a positive impact on metal desorption for all metals tested. The concentration of recalcitrant and refractory organic matter decreased after all the tests, indicating its degradation into more labile matter.

The urgent need to address the challenges posed by climate change has led to increased research and development efforts aimed at creating lightweight materials to reduce greenhouse gas emissions. This study focuses on corrosion protection of the commercial magnesium alloy AZ61, valued for its wide-ranging applications in engineering and industry, including automotive, aeronautics, and biomedical engineering. Despite its interesting mechanical properties, the AZ61 alloy exhibits poor corrosion resistance in saline aqueous environments, prompting significant research into coatings to enhance its durability. This research aims to design and prepare organic-inorganic hybrid sol-gel coatings for corrosion protection of the AZ61 alloy. The inorganic phase, mainly based on tetramethyl orthosilicate (TMOS), serves as a cross-linking agent, while four organofunctionalized silanes containing hydrolysable methoxy groups and functional organic groups into the same molecule are used as precursors for the organic component of these hybrid coatings. Specifically, the organofunctionalized silanes selected are γ-methacryloxypropyltrimethoxysilane (MAPTMS), γ -glycidoxypropyltrimethoxysilane (GPTMS), γ -aminopropyltrimethoxysilane (AMPTMS), and γ -mercaptopropyltrimethoxysilane (MPTMS). These silanes are chosen for their ability to create organopolysiloxane coatings with sufficient chemical compatibility and flexibility to accommodate other species without phase segregation or cracking. These properties are essential to create a suitable structural environment to encapsulate the selected ecofriendly corrosion inhibitors that are added in later stages of the study, thereby yielding a processable system that serves as a functional phase of active corrosion protection coatings for magnesium alloys. Physicochemical characterization techniques are employed to understand the chemical environment within the hybrid networks and confirm the successful formation of organopolysiloxane networks. Thermogravimetry and differential thermal analysis (TG/DTA), Fourier transform infrared spectroscopy (FTIR), and high-resolution solid-state 13C and 29Si nuclear magnetic resonance spectroscopies are used for these purposes. The performance of coated AZ61 samples is analysed using the aforementioned organic-inorganic hybrid gels. These sol-gel coatings are applied using immersion techniques (dip-coating) on unpolished (as-received) and polished AZ61 samples, to determine the influence of surface conditions on their behaviour during immersion tests in 0.6, 0.06 and 0.006 M NaCl aqueous solutions. Open circuit potential (OCP) measurements and global and localized electrochemical impedance spectroscopies (EIS, LEIS) are applied with this purpose. The microstructure and texture of the coatings, both before and after the corrosion tests, are observed by optical microscopy (OM) and scanning electron microscopy (SEM). Moreover, Energy dispersive X-ray (EDX) microanalyses are performed on several areas of the coated samples after the corrosion tests. In the last phase of the study, modifications to the sol-gel formulations are explored by incorporating environmentally friendly corrosion inhibitors such as cysteine (L-Cys) and benzotriazole (BTA), as well as cross-linking agents like hexamethoxymethylmelamine (HMMM) in presence of an acid catalysts, specifically p-toluenesulfonic acid (p-TSA), to facilitate the cross-linking reaction within the organosilicon network. These modifications aim to enhance the protective properties of the sol-gel coatings. EIS and LEIS are used to assess their effectiveness. Films formulated with HMMM demonstrate robust passive protection against corrosion, while those doped with L-Cys and BTA exhibit self-healing and active protection properties, offering a promising alternative to traditional chemical conversion pretreatments based on hexavalent chromium. Funding Sources This work has been supported by the Project PID2022-139920OB-I00 (Ministry of Science, Innovation and Universities, MICINN, Spain).

The sustainability and corrosion protection are two critical factors in the field of materials for mobility. Lightweight alloys, such as the AZ61 magnesium alloy, are gaining recognition for their potential applications in the aerospace, automotive, and marine industries. The use of these alloys not only contributes to weight reduction and consequent fuel and CO2 emission savings, but also opens up new possibilities for innovative design and performance enhancements [1]. In search for sustainable corrosion protection, we have focused our research towards the development of environmentally acceptable sol-gel coatings enriched with green corrosion inhibitors. These coatings not only prolong the lifespan of materials made with the AZ61 magnesium alloy but also align with the commitment to environmental stewardship, offering promising prospects for effective corrosion protection [2]. The sol-gel coatings were synthesized using tetraethyl orthosilicate (TEOS) and 3-(trimethoxysilyl)propyl methacrylate (MAPTMS) as precursors. Four different organic inhibitors - L-cysteine (CYS), N-acetyl-cysteine (N-A-CYS), curcumin (CUR), and methylene blue (MB) - that are environmentally friendly, non-toxic, inexpensive and contain S, N heteroatoms, O and/or OH groups and/or conjugated double bonds - were selected for the study. These compounds were incorporated into the sol as dopants. A set of sols was doped with a common corrosion inhibitor, benzotriazole (BTA), for comparison purposes. The resulting sols were processed and deposited on AZ61 substrates using the dip-coating technique. The thickness of the coatings was determined using the interference fringe method in the ultraviolet-visible and near-infrared ranges [2]. Transmission spectra of coated glass samples were also obtained to determine the wavelength of each coating at 50% transmission. The hydrophilic character of the coatings was characterized by measuring the contact angle. To study the corrosion behaviour of the coated surfaces, weathering tests, based on a variation of the ISO 11130 [3], were conducted. The samples were weighed before and after the corrosion test to examine weight variations. Optical microscopy provided insights into the surface of the samples both before and after the corrosion test. Detailed observations of the surface morphologies of the samples were made using SEM, and EDX analyses were performed to verify the compositions of the compounds found. Confocal Raman microscopy was also employed to provide accurate compositional information at a local microscale level, shedding light on the compounds formed considering the chemical strategies developed in the protective sol-gel coating [4,5]. The study was concluded by applying global and localized electrochemical impedance spectroscopies (EIS, LEIS) to study the corrosion protection behaviour of the sol-gel coatings during immersion tests in 0.006 M and 0.6 M NaCl aqueous solutions. As a concluding remark, it is noteworthy that in several of the tested sol-gel coatings, micro-cracks and defects formed during weathering tests self-seal, thanks to oxy-hydroxides adhering to the Mg alloy substrate. Additionally, in response to the corrosive anions of the aqueous solution, due to the release of the organic inhibitors that were nanoencapsulated in the sol-gel matrix, an active corrosion protection is initiated beneath the coatings. In conclusion, the tested eco-friendly coatings, applicable by dip-coating or spray at room temperature, offer potential for broad industrial use and economic feasibility, suggesting industrial scale-up feasibility. Funding Sources This work has been supported by the Projects PID2022-139920OB-I00, PID2021-126323OA-I00 and TED2021-129688-CT21 (Ministry of Science, Innovation and Universities, MICINN, Spain). The team extends its acknowledgements to Miguel Romero Martín of the ECORR Group for his help with impedance measurements and result analysis. References 1. Kumar, D., Phanden, R.K., Thakur, L. A review on environment friendly and lightweight Magnesium-Based metal matrix composites and alloys. Materials Today: Proceedings, 38, pp. 359-364 (2020). 2. Domínguez-Martínez, J., López-Sánchez, J., García-Galván, F., Serrano, A., Barranco, V., Galván, J.C., Rodríguez de la Fuente, O., Carmona, N. Eco-Friendly Sol-Gel Coatings with Organic Corrosion Inhibitors for Lightweight AZ61 Alloy. Gels 10 (3), art. no. 168 (2024). 3. ISO Standard 11130 ; Corrosion of Metals and Alloys – Alternate Immersion Test in Salt Solution. Available online: https://www.iso.org/standard/71867.html (accessed on 18 April 2023). 4. Aparicio, M., Mosa, J., Rodriguez, G., Guzman, J., Picard, Q., Klein, L.C., Jitianu, A. Consolidated Melting Gel Coatings on AZ31 Magnesium Alloy with Excellent Corrosion Resistance in NaCl Solutions: An Interface Study. ACS Applied Materials and Interfaces 11 (3), pp. 3493-3505 (2019) 5. López-Sánchez, J., Serrano, A., del Campo, A., Muñoz-Noval, Á., Salas-Colera, E., Cabero, M., Varela, M., Abuín, M.,Castro, G.R., Rubio-Zuazo, J., Rodríguez de la Fuente, O., Carmona, N. A combined micro-Raman, X-ray absorption and magnetic study to follow the glycerol-assisted growth of epsilon-iron oxide sol-gel coatings. Journal of Alloys and Compounds 892, art. no. 162061 (2022).

This study aims to better understand the relationship between the microstructure and magnetic properties of copper ferrite, which is an inverse spinel that present a body-centered tetragonal structure associated with a remarkable Jahn-Teller (JT) effect. For this goal, a sample has been synthesized by the ceramic route from a stoichiometric mixture of high-purity CuO and Fe2O3 powders activated mechanically in a high-energy planetary ball mill. This sample was calcined in air furnace at 1000 degrees C for 6 h. As synthetized sample with a cubic structure was divided into two parts and one of them was annealed at 650 degrees C for 3 h and slowly cooled to room temperature to obtain a pure tetragonal spinel sample. Furthermore, these two samples were subjected to the same processes of severe plastic deformation by milling for up to 70 h and subsequent annealing at temperatures ranging between 300 and 600 degrees C to obtain samples with a mixture of phases in different proportions. For the cubic one, there is no change in its structure due to milling, always remaining 100 % cubic, and the evolution in the saturation magnetization was related to the changes in the density of defects present. On the other hand, copper cations are always found in the octahedral sites of spinel with a tetragonal structure. The small decrease in the degree of inversion to 0.95 induced by milling in this sample is capable of breaking the JT distortion, giving rise to the appearance of a cubic phase. This work demonstrates how the structure, microstructure, defects like stacking faults and deformation twins, and degree of inversion of the different phases are related to changes in magnetic properties.

Materials such as wood, textiles, or plastics that are part of the exhibition system in museums are known to emit pollutants such as organic acids. Scientific and technical objects that include these materials in their composition can themselves be a potential source of emissions, which, together with inappropriate humidity and temperature conditions, can lead to corrosion of the metallic parts. In this work, we have studied the corrosivity of different locations in two venues of the Spanish National Museum of Science and Technology (MUNCYT). Coupons of the most representative metals from the collection were placed in different showcases and rooms for 9 months. The corrosion of the coupons has been evaluated in terms of the rate of mass gain, colour changes and characterisation of the corrosion products. The results were correlated to the relative humidity and concentration of gaseous pollutants to determine which metals are most susceptible to corrosion. The results show that metal artefacts exposed in showcases have a higher risk of corrosion than those exposed directly in the room, and that some pollutants are emitted by the artefacts. The corrosivity of the museum environment is low for copper, brass, and aluminium in most locations; however, some placements present a higher aggressivity for steel and lead, due to the high humidity and the presence of organic acids.

The use of magnesium and its alloys has increased in recent years due to their low weight, high strength, excellent machinability, and high dimensional durability. Therefore, they have found application in communications, automotive and aerospace industries, among others. However, their high negative reduction potentials, low chemical stability, and the unstable native oxide films have limited their use, particularly in applications that require high corrosion resistance.1 -3 The application of sol-gel coatings has shown to be an effective method to overcome this problem. In this context, the aim of this study was to develop sol-gel thin-films doped with ecological corrosion inhibitors for corrosion protection of AZ61 alloy surfaces. The objective was to determine whether these new systems could provide an alternative to the replacement of chromates, surface pre-treatments and chemical conversion coatings that contain conventional corrosion inhibitors, which are currently being questioned for their harmfulness to health and the environment.4 Methyltriethoxysilane (MTEOS) and tetraethylorthosilicate (TEOS) were used as precursors to produce sols, which were then modified with active corrosion protection dopants. Eco-benign corrosion inhibitors, such as L-cysteine (L-Cys), lanthanum (III) acetate hydrate, and lanthanum (III) isopropoxide were incorporated in the sol-gel matrix as dopants. A set of sol-gel coatings was modified with a common dopant, benzotriazole (BTA), for comparison purposes, as it is a well-known effective corrosion inhibitor. However, this chemical compound is known to be carcinogenic and toxic to flora and fauna, and its use is currently being restricted today in compliance with environmental protection regulations.5,6 The resulting sols were processed and deposited on AZ61 substrates by dip-coating technique, producing transparent sol-gel thin-films. The thickness of the films was evaluated by interference of reflection spectra. Their chemical composition was characterized by X-ray fluorescence (XRF), while surface chemical composition and oxidation state of elements present at the outermost surface nanolayers was also analysed by X-ray photoelectron spectroscopy (XPS). The structural and thermal characterization of the doped thin-films were respectively analysed by Fourier transformed infrared spectroscopy (FTIR) and thermogravimetry and differential thermal analysis (TG/DTA). The corrosion protection behaviour of the sol-gel coatings during immersion tests in 0.006 M and 0.6 M NaCl aqueous solutions was studied using a multiscale electrochemical approach. Global electrochemical impedance spectroscopy (EIS) was used for macroscopic scale characterisation. Localised electrochemical impedance spectroscopy (LEIS and LEIM) was used for the characterisation at micro- and sub-microscopic scales using an electrochemical minicell system and a scanning electrochemical workstation. The texture and microstructure of coated samples before and after corrosion tests were observed by optical and scanning electron microscopies (OM and SEM), while topography and coating roughness were analysed by atomic force microscopy (AFM). In terms of corrosion resistance, similar results were obtained with sol-gel thin-films doped with lanthanum acetate or lanthanum isopropoxide. The synthesis method of the acetate-doped gels is much simpler and cheaper, so from a practical standpoint, these sol-gel thin-films could be more interesting. On the other hand, highly satisfactory results were obtained with gels doped with non-toxic L-Cys compared with those doped with BTA. Finally, it is noteworthy that an interesting synergistic effect was observed in the corrosion protection of the AZ61 alloy in sol-gel coatings that were doped with metal-organic inhibitors and loaded with organic inhibitors (L-Cys or BTA). As a concluding remark, this study has provided an effective and environmentally friendly solution for the active corrosion protection of the AZ61 alloy. Sol-gel thin-films doped with eco-friendly corrosion inhibitors have showed promising results in extending the durability of AZ61 alloy while being sustainable. The multiscale electrochemical approach used has provided a comprehensive understanding of the active corrosion protection behaviour and the self-healing properties of sol-gel coatings, which can be extended to other materials and systems. Funding Sources This work has been supported by the Ministry of Science and Innovation (MCINN, Spain) through the Project PID2019-104717RB-I00. References Feliu Jr., S., Maffiotte, C., Samaniego, A., Galván, J.C., Barranco, V. Acta, 56 (12) (2011) 4554-4565 Stojadinović, S., Vasilić, R., Radić-Perić, J., Perić, M. Coat. Technol., 273 (1) (2015), pp. 1-11 Toorani, M., Aliofkhazraei, M., Naderi, R., Golabadi, M., Sabour Rouhaghdam, A. Ind. Eng. Chem., 53, (2017) pp. 213-227 Vaghefinazari, B., Wierzbicka, E., Visser, P., Posner, R., Arrabal, R., Matykina, E., Mohedano, M., Blawert, C., Zheludkevich, M., Lamaka, S. Materials, 15 (23) (2022), art. no. 8676 Albini, M., Letardi, P., Mathys, L., Brambilla, L., Schröter, J., Junier, P., Joseph, E. Corrosion Sci., 143 (2018), pp. 84-92 Tan, L., Sun, Y., Li, J., Han, S., Zhou, X., Tang, Y., Zeng, X. Langmuir, 39 (2023), 2579-2588

Samples with inversion parameter values (delta) ranging from 0.27 to 0.14 while maintaining the crystallite size value have been successfully fabricated from commercially available powders by mechanical grinding and thermal annealing treatments at temperatures ranging between 400 and 600 degrees C. Detailed characterization studies of these samples using X-ray, neutron diffraction and magnetic measurements have confirmed for the first time the simultaneous coexistence at 2 K of short range antiferromagnetic and ferrimagnetic ordering for a wide range of the inversion parameter. The magnetic phase diagram obtained is different from the one previously reported, which shows at 2 K the coexistence of long range antiferromagnetic order and short range order for values of inversion parameters less than 0.1 and the presence of a ferrimagnetic order only for values of delta > 0.2. At room temperature, the Rietveld analysis of NPD patterns and the magnetization curves showed a paramagnetic behavior in the samples with delta <= 0.1. For the samples with higher cationic inversion, typical hysteresis curves of ferrimagnetic materials were observed and the saturation magnetization values obtained agree quite well with the net magnetic moment obtained from the Rietveld refinement of the neutron diffraction patterns.

Weathering steels are widely used in civil engineering, architecture and contemporary art due to their mechanical properties, their enhanced resistance to atmospheric corrosion as well as their aesthetic properties. Artists and blacksmiths often apply chemical treatments to obtain the appealing colors of a patina in a shorter period of time. However, the development of an accelerated patina may have an effect on the final appearance and color of the surface. With the aim of evaluating differences in color and studying the evolution of the surface, eight accelerated patinas were made and exposed to the atmosphere for periods of time of up to 24 months and were compared to a natural patina. The characterization studies showed the presence of lepidocrocite on the surface. A close inspection of the X-ray diffraction patterns showed the displacement of the (020) lepidocrocite reflection and asymmetric broadening of selective lines of this phase that were associated to stacking and twins faults, respectively. These faults decrease with the exposure time and are related to a maximum at 630 nm in the reflectance spectrum and the stabilization of the b* coordinate (yellow color). The colors of the accelerated patinas differ from the natural patina at short exposure times. However, they tend to converge at longer exposure times.

Improvements in durable lubrication together with minimized wear are essential for obtaining long-term, functioning metallic joint prostheses. To achieve this objective, CoCr surface was functionalized with Graphene Oxide (GO) and characterized by FTIR and XPS. CoCr alloy was subjected to alkalinization in order to generate high hydroxyl content on the surface. FTIR and XPS revealed reactive OH groups, enabling intermediate coupling via (3-aminopropyl) triethoxysilane (APTES), which was cured at 45 ?C and 75 ?C for 24 h and 30 min, respectively. FTIR revealed cross-linked films (Si-O-Si), inferring condensation and self-assembly of silane layers, while XPS revealed the presence of NH2, enabling chemical binding of GO. Silane-coated CoCr disks were immersed in GO solution at 60 ?C for 12h and 24h, respectively. FTIR displayed C= C band confirming the assembly of GO on silane-coated CoCr surfaces. XPS revealed three possible surface mechanisms: (1) reaction between primary amines of APTES and epoxy groups of GO; (2) free -OH groups in APTES and carboxyl groups in GO; and (3) reaction between APTES primary amines and -OH from carboxyl groups of GO. Overall, the multilayer system CoCr-OH-Si45-GO24h showed covalent functionalization of metal substrate with GO to a large extension of surface area among all the multilayer systems studied.

Different studies carried out in the last three decades on the magnetic susceptibility of the spinel ZnFe2O4 ferrite have revealed the positive character of its Curie–Weiss temperature, contradicting its observed antiferromagnetic behavior which is characterized by a well-defined susceptibility peak centered around the Neel temperature (10 K). Some approaches based on ab initio calculations and mixture of interactions have been attempted to explain this anomaly. This work shows how for very low values of the inversion parameter, the small percentage of Fe atoms located in tetrahedral sites gives rise to the appearance of ferrimagnetic clusters around them. Superparamagnetism of these clusters is the main cause of the anomalous Curie–Weiss behavior. This finding is supported experimentally from the thermal dependence of the inverse susceptibility and its evolution with the degree of inversion.

The antiferromagnetic (AFM) transition of the normal ZnFe2O4 has been intensively investigated with results showing a lack of long-range order, spin frustrations, and a “hidden” entropy in the calorimetric properties for inversion degrees δ ≈ 0 or δ = 0. As δ drastically impacts the magnetic properties, it is logical to question how a δ value slightly different from zero can affect the magnetic properties. In this work, (Zn1-δFeδ)[ZnδFe2-δ]O4 with δ = 0.05 and δ = 0.27 have been investigated with calorimetry at different applied fields. It is shown that a δ value as small as 0.05 may affect 40% of the unit cells, which become locally ferrimagnetic (FiM) and coexists with AFM and spin disordered regions. The spin disorder disappears under an applied field of 1 T. Mossbauer spectroscopy confirms the presence of a volume fraction with a low hyperfine field that can be ascribed to these spin disordered regions. The volume fractions of the three magnetic phases estimated from entropy and hyperfine measurements are roughly coincident and correspond to approximately 1/3 for each of them. The “hidden” entropy is the zero point entropy different from 0. Consequently, the so-called “hidden” entropy can be ascribed to the frustrations of the spins at the interphase between the AFM-FiM phases due to having δ ≈ 0 instead of ideal δ = 0.

The effect of laser surface melting on the corrosion resistance of AZ31 Mg alloy in 0.1 M NaCl solution was investigated using different laser processing conditions (energy densities of 14 and 17 J cm−2). Laser treatment induced rough surfaces primarily composed of oxidized species of Mg. XPS analysis revealed that the surface concentration of Al increased significantly as a consequence of LSM. Electrochemical impedance spectroscopy showed that the laser treatment remarkably increased the polarization resistance of the AZ31 Mg alloy and induced a passive-like region of about 100 mV, as determined by potentiodynamic polarization. Analysis of the results obtained provide solid evidence that within the immersion times used in this study, LSM treatment increased the corrosion resistance of AZ31 Mg alloy under open circuit conditions and anodic polarization.

The dramatic texture and microstructural changes observed in 6061Al-20vol%SiCw metal matrix composite undergoing severe thermal cycles, under the absence and the simultaneous action of an external tensile stress, are studied. Under only thermal cycles (100-450 degrees C) homogenization and disorientation of the SiC whisker rein-forcement and crystallographic texture randomization occurs. However, when a simultaneous tensile stress is applied, the whiskers rotate so that their long direction aligns with the tensile axes. Furthermore, a strong texture and large deformations (superplasticity), higher than 1000%, are achieved. These results are explained on the basis of the microscopic stress fields generated at the different microstructural scales (stresses of type II and type III) and well-known observation of dislocation generation at the SiC-metal interface during the cooling period of the cycles. We propose that moving dislocations (responsible of type III stresses) operate differently under the absence or the presence of the external stress. Under no stress, dislocation motion (occurring mainly during the heating period) is driven only by the type II internal stress. However, dislocation motion is improved when an external stress is applied, leading to texture changes and large elongations. Despite that a low external stress is applied, it overcomes the effect of the internal stresses for dislocation motion.

High-Mn twinning-induced plasticity (TWIP) steels have been proposed to meet higher passenger safety and crash-safe vehicle frame requirements demanded by the automotive industry. The corrosion behaviour of welded Fe-30Mn-5Al-0.5C-6Cr TWIP steel using the resistance-spot-welding (RSW) technique was studied. Welds showed a microstructure consisting of primary austenite dendrites and interdendritic delta-ferrite in both fusion zone (FZ) and base metal (BM), which is in agreement with an austenitic-ferritic (AF) solidification mode. The results reveal that the refinement of the microstructure in the weld region does not significantly affect the corrosion resistance of this region, having a low corrosion current density of the order of 1 mu A cm(-2). It was concluded that Cr-rich second phase particles along the austenite/delta-ferrite interface can lead to Cr-depleted zones, increasing pitting corrosion susceptibility. It was found that the minimum Cr content at the Cr-depleted zones is nearly independent of the delta-ferrite volume fraction.

We study the light emission of plasmonicluminescent hybrid nanostructures consisting of Ag nanoparticles (NPs) embedded in europium oxide (EuOx). The Ag NPs present a bidimensional organization in the nanostructures and they optically behave as oblate spheroids. The photoluminescence (PL) spectral response of the nanostructures evolves from a narrow red emission characteristic of Eu3+ ions in absence of Ag NPs to a broad blue-green emission band associated with Eu2+ ions when the layer of Ag NPs is present. This behavior is not related to a change in the Eu2+/Eu3+ ratio, which is verified by compositional analysis. Instead, a detailed investigation of the PL emission of the nanostructures suggests that the coupling of the Ag NPs to the Eu2+ ions present in the EuOx layer, which manifests itself in an efficient sensitization of these ions, enhances their broad visible emission. In particular, the longitudinal mode of the Ag NPs surface plasmon is considered to be responsible for the efficient energy transfer for the non-normal incidence excitation PL configuration used. Finally, the use of a capping amorphous Al2O3 layer allows improving the robustness of hybrid nanostructures and further enhances their PL emission. These findings provide a new path to actively control the selective excitation of Eu2+ and Eu3+ ions via a controlled coupling with the surface plasmon resonance modes of the Ag NPs and points to these nanostructures as promising building blocks for the development of integrable white light sources.

The correct identification of the materials of assets that make up the movable scientific and technical heritage and the interactions between them is essential to establish effective conservation strategies with adapted intervention criteria. In this work, a study of the conservation condition, materials and pathologies of the collection of fire extinguishers of the National Museum of Science and Technology is presented. A database has been created with 56 fire extinguishers from the museum, documenting each object, typology and conservation condition. The analyses carried out on some of them (by X-ray fluorescence and X-ray diffraction) have made it possible to identify the materials of the fire extinguishers, in some cases their contents, and to establish degradation mechanisms. In the case of foam and water fire extinguishers, it has been shown that the extinguishing agent is highly corrosive and has caused severe damage to the objetct. In these cases, it is advisable to eliminate the content if correct conservation of the fire extinguishers is to be ensured.