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).

The latest advances in technology and materials science have catalyzed a transformative shift towards the adoption of environmentally conscious and lightweight materials across key sectors such as aeronautics, biomedical, and automotive industries. Noteworthy among these innovations are the magnesium-aluminum (Mg-Al) alloys employed in aeronautical applications, contributing to the overall reduction in aircraft weight and subsequently diminishing fuel consumption and mitigating atmospheric emissions. The present work delves into a study of the anti-corrosive properties inherent in various sol-gel coatings, leveraging a range of environmentally friendly corrosion inhibitors, specifically tailored for samples of the AZ61 alloy. Methodologically, the work involves the synthesis and application of sol-gel coatings on AZ61 alloy containing eco-friendly inhibitors: L-cysteine, N-acetyl-cysteine, curcumin and methylene blue. Subsequently, an accelerated corrosion test in a simulated saline environment is performed. Through microstructural and compositional analyses, the best inhibitors responses are achieved with inhibitors containing S, N heteroatoms and conjugated double bonds in their structure, probably due to the creation of a continuous MgCl2 layer. This research contributes to the ongoing discourse on protective eco-coatings, aligning with the broader paradigm shift towards sustainable and lightweight materials in key industries.

In this study, a two-step surfactant sol-gel strategy is developed to synthesize Co particles with confined sizes in the nanoscale using organic precursors. This approach does not require the use of vacuum techniques or strong reducing atmospheres, making it a simple approach economically attractive. The strategy involves the generation of few-layered graphene shells to provide chemical stability, prevent oxidation and aggregation tendencies. Additionally, the study investigates the use of precursors based on nitrates and acetates, exploring their structural and magnetic properties in densified samples. Remarkably, magnetic properties are competitive for both approaches, with coercivities reaching up to 300Oe and saturation magnetization of ∼60 and ∼80emu/g for samples based on nitrates and acetates prepared at 650 °C, respectively. However, it is observed that smaller and more uniformly sized nanoparticles (around ∼10nm) are obtained with nitrate-based precursors due to an effective ligand decomposition process. Therefore, this chemical approach offers effective nanoscale confinement with intriguing magnetic properties through a cost-effective and reproducible synthesis.

Correction for ‘A feasible pathway to stabilize monoclinic and tetragonal phase coexistence in barium titanate-based ceramics’ by Jallouli Necib et al. , J. Mater. Chem. C , 2022, 10 , 17743–17756, https://doi.org/10.1039/D2TC04265G.

In this study, the effects of Bi and Fe on the optical and electrical qualities of BaTiO3 made with the sol-gel method are examined. On the one hand, UV-visible spectroscopy is used to study the sample's optical behavior. This shows that the band gap energy is lower with Bi and Fe doping than with pure BaTiO3. On the other hand, an impedance spectroscopy investigation is carried out to reveal the conduction processes in the frequency range of 102 to 107 Hz and the temperature range of 450-650 K. This examination is carried out to investigate the conduction mechanisms. The conduction mechanism in the elaborated material is best described by the Overlapping Large Polaron Tunnelling model (OLPT), where the exponent s drops with temperature until reaching a minimal value, at which point it grows again. In addition, the Summerfield scaling method is used to investigate the relationship between conductivity and temperature. When the scaled curves are combined into one master curve, it shows that the time-temperature superposition principle (TTSP) is true and that Koop's concept about how the dielectric constant change with frequency is valid. So, the results give us new information about the optical and dielectric qualities of the functional barium titanate ceramics based on Bi and Fe.

Defective few-layered graphene mesostructures (DFLGMs) are produced from graphite flakes by high-energy milling processes. We obtain an accurate control of the generated mesostructures, as well as of the amount and classification of the structural defects formed, providing a functional material for microwave absorption purposes. Working under far-field conditions, competitive values of minimum reflection loss coefficient (RLmin) = -21.76 dB and EAB = 4.77 dB are achieved when DFLGMs are immersed in paints at a low volume fraction (1.95%). One step forward is developed by combining them with the excellent absorption behavior that offers amorphous Fe73.5Si13.5B9Cu1Nb microwires (MWs), varying their filling contents, which are below 3%. We obtain a RLmin improvement of 47% (-53.08 dB) and an EAB enhancement of 137% (4 dB) compared to those obtained by MW-based paints. Furthermore, a fmin tunability is demonstrated, maintaining similar RLmin and EAB values, irrespective of an ideal matching thickness. In this scenario, the Maxwell-Garnet standard model is valid, and dielectric losses mainly come from multiple reflections, interfacial and dielectric polarizations, which greatly boost the microwave attenuation of MWs. The present concept can remarkably enhance not only the MW attenuation but can also apply to other microwave absorption architectures of technological interest by adding low quantities of DFLGMs.

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

Today's environmental needs require the reduction of the weight of vehicles, thus reducing fuel consumption and associated emissions. For this reason, the use of light alloys is being studied, which, due to their reactivity, must be protected before use. In this work, the effectiveness of a hybrid sol-gel coating doped with various organic environmentally friendly corrosion inhibitors applied to an AA2024 lightweight aluminium alloy is evaluated. Some of the inhibitors tested are pH indicators, acting as both corrosion inhibitors and optical sensors for the surface of the alloy. Samples are subjected to a corrosion test in a simulated saline environment and characterised before and after the test. The experimental results regarding their best inhibitor performance for their potential application in the transport industry are evaluated.

We present a simple and optimized approach for obtaining magnetic carbon-nanoparticle composites by a novel one-pot sol-gel method. The route explores the combination of different metal cations ratios of Fe3+ and Co2+ for the synthesis of core/shell nanoparticles with tailored magnetic properties. The ratio of Fe:Co is a critical parameter that governs the emergence of different crystalline phases. The smallest introduction of Co into the synthesis (19:1) provides an abrupt emergence of the body-centered cubic (bcc) Fe-Co alloy, suppressing the Fe3C formation (1:0). The high-resolution scanning transmission electron microscopy, combined with electron energy-loss spectroscopy, and the Rietveld analysis of the Synchrotron X-ray diffractograms, reveal for several Fe:Co ratios evaluated a distribution of core/shell sphere-like Fe-Co alloy/Co-ferrite nanoparticles embedded in carbon matrix. The nanoparticles range in size from ~10-45 nm and have a spinel crystallographic structure for the shells of 2-3 nm of thickness. In addition, X-ray absorption spectroscopy unveils that the oxidation state of Fe and Co cations is close to 0, demonstrating the main metallic character of the nanoparticles. The magnetic properties can be modulated through a precise control of the alloy composition by varying the Co content, displaying saturation magnetization values close to ~138 emu/g. The nanoparticles are mainly single magnetic domain with a coercive field of ~485 Oe. We conclude that the semi-hard magnetic character along with higher coercive fields than those reported in the literature, are due to a notable spring exchange effect emerged by passivating the surface of Fe-Co-bcc cores with the Co-ferrite like shell.

Physiological human fluid is a natural corrosive environment and can lead to serious corrosion and mechanical damages to light Mg–Al alloys used in prosthetics for biomedical applications. In this work, organic–inorganic hybrid coatings doped with various environmentally friendly and non-toxic corrosion inhibitors have been prepared by the sol-gel process for the corrosion protection of AZ61 magnesium alloys. Effectiveness has been evaluated by pH measurements, optical microscopy, and SEM during a standard corrosion test in a Hanks’ Balanced Salt Solution. The results showed that the addition of an inhibitor to the sol-gel coating can improve significantly the corrosion performance, being an excellent barrier for the L-cysteine-doped hybrid sol-gel films. The incorporation of TiO2 nanoparticles, 2-Aminopyridine and quinine organic molecules slowed down the corrosion rate of the Mg–Al alloy. Graphene oxide seemed to have the same response to corrosion as the hybrid sol-gel coating without inhibitors.

A temperature-dependent Raman experiment between 80 and 600 K was performed in a nanoparticulated coating of single-phase hematite grown on a silica substrate. In that range, a thermal Raman shift hysteresis was identified in the vibrational modes that accompanies the Morin transition, observing large effects in the two-magnon Raman frequency position and in its relative intensity. Interestingly, no decrease in coercivity occurs when the hematite crosses the Morin transition below 230 K. The spin-flop processes produced in the coating leads to a strong decompensation of the surface spins, generating a ferromagnetic component over the whole temperature range studied. Such unusual effects might be promoted by a certain degree of structural disorder and the stresses produced by the nanoparticulation growth approach of the hematite coating. As a result, a high stability of the two-magnon excitation is obtained over a wide temperature range and considerable advances are made for the development of spintronic devices based on semiconductor antiferromagnetic materials.

Multiphase coexistence has attracted significant interest in recent years because its control has entailed a significant breakthrough for the piezoelectric activity enhancement of lead-free piezoelectric oxides.

Epsilon iron oxide (epsilon-Fe2O3) coatings on Si(100) substrates are obtained by an easy one-pot sol-gel recipe assisted by glycerol in an acid medium. Glycerol, given its small dimensions, enables the formation of epsilon-Fe2O3 nanoparticles with a size of a few nanometers and the highest purity is reached in coatings after a densification treatment at 960 degrees C. The structural and compositional evolution up to 1200 degrees C is studied by confocal Raman microscopy and X-ray absorption spectroscopy techniques, correlating the existing magnetic properties. We report a novel characterization method, which allows monitoring the evolution of the precursor micelles as well as the intermediate and final phases formed. Furthermore, the inherent industrial technology transfer of the sol-gel process is also demonstrated with the epsilon-Fe2O3 polymorph, impelling its application in the coatings form. (C) 2021 The Author(s). Published by Elsevier B.V.CC_BY_NC_ND_4.0

Few-layered mesoporous graphene (FLMG) is employed as a sensing material to develop an innovative and high-sensitivity room temperature NO2 sensor through a simple manufacturing process. For this purpose, sensing material is optimized at 100 min by a high-energy milling process where natural graphite is used as a precursor: it is an inexpensive, sustainable and suitable active material. The large number of defects created and the enhanced degree of mesoporosity produced during the milling process determine the physical principles of operation of the designed device. NO2 gas sensing tests reveal an improved and selective performance with a change in resistance of similar to 16 % at 0.5 ppm under ultraviolet photo-activation, establishing a detection limit around similar to 25 ppb. Interestingly, the response of the developed sensor to humidity is independent in the measured range (0-33 % relative humidity at 25 degrees C) and the dependency to the presence of NH3 is rather poor as well (similar to 1.5 % at 50 ppm).

We show the efficiency in the preparation of >95 % dense ZnO ceramics by cold sintering process through the incorporation of ZnO nanoparticles in the 1−10 wt% range at temperatures of 170 °C, pressures of 750 MPa and a pellet height/diameter ratio of 0.38. Morphological, structural and physical properties are dependent on the amount of ZnO nanoparticles incorporated into the system. After the densification by cold sintering process, ZnO ceramics show a reduction of the average valence indicating the deficiency of oxygen, similar to ceramics sintered by the conventional route. Besides, the generation of structural disorder and modifications into the ZnO lattice are identified in sintered ceramics, inducing intrinsic defects related to the loss of oxygen ions, the diffusion of zinc and zinc vacancies, which depend on the sintering process and the starting powders. These characteristics influence the final functional properties of the sintered ZnO ceramics, such as the visible photoluminescence signal.

The occurrence of epsilon-Fe2O3 in archaeological samples that have been subjected to high temperatures is gradually being detected by the use of micrometric structural characterization techniques. This work provides new information by revealing that the epsilon-Fe2O3 is formed as a response to temperature, the aggregation state and the position within the baked clay with respect to the nearest heat source. In addition, depending mainly on the atmospheric environment, the temperature reached by the combustion structure, the distance from the heating source and the particle aggregation, other iron oxide magnetic phases are produced. In the baked clay studied here, hematite is found over the whole range of samples studied but its magnetic contribution is negligible. Magnetite is observed at the sample surface, probably due to local atmospheric environment closest to the combustion source. Maghemite is found at all depths up to 6 cm below the sample surface. epsilon-Fe2O3 has a limited distribution, found within 2-3 cm of the sample surface. Furthermore, the viability of this compound as a palaeofield marker has been evaluated in both archaeological and synthetic samples. The results indicate that epsilon-Fe2O3 is able to register the direction of the magnetic field. Linear palaeointensity plots have been obtained in synthetic samples, although the value of the palaeofield could be, sometimes, overestimated.

In the present study, a coating with icephobic properties has been developed based on an easy two-step fabrication process. The coating is free from fluorides and nanoparticles. The procedure is easy, adequate for large scale applications and uses environmentally friendly low-cost raw materials. It has been applied on carbon fiber/epoxy resin composite panels, but it could be extended to other kind of surfaces. The structure of the coating has been prepared by the modification with PDMS of a commercial polyurethane paint as a first step. The second step involves the preparation of a hybrid sol-gel that is deposited on the polyurethane paint modified with PDMS forming a heterogeneous film of isolated solid droplets. The results show a reduction of the adhesion force of the ice up to 80 %. Properties like roughness, water contact angle and ice adhesion tests have been measured for more than 100 shear-off/freezing ice cycles. The evolution of the surface during the cycles has been monitored and it shows a modification process reported in the manuscript. This icephobic coating is a promising candidate to protect surfaces in different industrial sectors where other systems against ice accumulation cannot be easily employed.

•Novel method to produce large superhydrophobic surfaces.•Rheologic study of particle embedding process via spray.•Measurements of water contact angle over time to study the pinning of the water droplets.

The purpose of this work is to fabricate self-assembled microstructures by the sol-gel method and study the morphological, structural and compositional dependence of epsilon-Fe2O3 nanoparticles embedded in silica when glycerol (GLY) and cetyl-trimethylammonium bromide (CTAB) are added as steric agents simultaneously. The combined action of a polyalcohol and a surfactant significantly modifies the morphology of the sample giving rise to a different microstructure in each of the studied cases (1, 3 and 7 days of magnetic stirring time). This is due to the fact that the addition of these two compounds leads to a considerable increase in gelation time as GLY can interact with the alkoxide group on the surface of the iron oxide precursor micelle and/or be incorporated into the hydrophilic chains of CTAB. This last effect causes the iron oxide precursor micelles to be interconnected forming aggregates whose size and structure depend on the magnetic stirring time of the sol-gel synthetic route. In this paper, crystalline structure, composition, purity and morphology of the sol-gel coatings densified at 960 degrees C are examined. Emphasis is placed on the nominal percentage of the different iron oxides found in the samples and on the morphological and structural differences. This work implies the possibility of patterning epsilon-Fe2O3 nanoparticles in coatings and controlling their purity by an easy one-pot sol-gel method.