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[EN] This review presents an insight on the advances in the Sol–gel route for preparation of glasses and glass-ceramics, considering the physical and chemical aspects governing the process. An overview of the most important developments and applications including Sol–gel coatings, appearing as the main technique used in optical as well as protective or photocatalytic applications. Biomaterials prepared by Sol–gel are also highlighted.

The purpose of this work was to study the repairing of defect produced by sandstorms on the surface of car windshields and solar panels, by deposition of thin transparent sol-gel layers. Different silica-zirconia films (100-x SiO - x ZrO, x = (10, 15, 20, 25 and 30 mol %) were prepared by the sol–gel process using TEOS and MTES as silica precursors and incorporating two different colloidal suspensions with silica or zirconia nanoparticles. The silica-zirconia sols were deposited by dip coating on soda-lime glass samples previously eroded by sandblasting. Film thickness and homogeneity were evaluated by ellipsometry and AFM, and the optical and mechanical properties were studied by UV–vis spectroscopy, the hardness by microhardness, and the roughness by tactile profilometer. The sol-gel coatings present a good quality and are able to restore the optical and mechanical properties of sandblasted samples thus increasing the service life. The incorporation of zirconia particles to SiO coatings increases the refractive index, from 1.42 to 1.57. Moreover, optical transmission of coated samples increases from 91.4 to 93% for 90SiO–10ZrO coatings, and increases from 80% for eroded samples (Mp = 200 g) coated with SiO–ZrO films up to 91% while micro-hardness is greatly improved from 10.17 GPa for the raw material to 17.62 GPa for 70SiO–30ZrO coated sample., This work was supported by MINECO under projects MAT2017-87035-C2-1-PP

Magnesium alloys such as AZ91D, has been presented as potential material for temporary implant material since it has a mechanical performance suitable with bone tissue and also degrades in time. The fast degradation at early times of AZ91D alloy could be retarded applying bioactive sol-gel glass coatings. In this work, two compositions of known bioactive silica-glasses (58S and 68S) were synthetized by sol-gel method and deposited by dip coating to the magnesium substrates. The glasses were produced without using any nitrate precursor, avoiding the presence of remaining residual in the coatings that could be not beneficial to the body. The coatings presented an excellent bioactive response after immersion in Hanks' balanced salt solution (HBSS) at 37 °C, showing apatite related deposits after 72 h immersion detected by scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Corrosion behaviour has been also analyzed, 58S presented as better protective features after 17 days of immersion. Cell attachment and proliferation tests demonstrate that both 58S and 68S coatings on AZ91D magnesium alloy are suitable as temporary implant materials., Authors would like to acknowledge Dr. Matias Valdes for the help with logistics. This work was supported by CONICET (PUE-073 and PIP 0572), UNMdP Project 15G/509 (Argentina) and Ministerio de Economía y Competitividad (MINECO) MAT2013-42957-R (Spain). This paper is a part of dissemination activities of the project FunGlass. This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 739566.

Transparent glass–ceramics present interesting optical properties for several photonic applications. In particular, compositions based on oxide glass matrices with fluoride crystals embedded inside, known as oxyfluoride glass-ceramics, have gained increasing interest in the last two decades. From 1990s, when these materials were prepared by sol–gel for the first time, many papers appeared in similar topics and literature shows many interesting optical results. However, little innovation on synthesis and processing is found with respect to the pioneering papers published more than 20 years ago. Moreover, most benefits offered by the sol–gel route have not been explored and the majority of papers refer to materials with low active phase content (

Novel transparent oxyfluoride nano-glass-ceramics containing undoped and 0.5 Eu (mol%) doped NaGdF nanocrystals (NCs), were obtained by sol-gel for the first time. X-ray diffraction (XRD) confirms the precipitation of α- and β-NaGdF NCs with a size ranging between 5 and 24 nm. When the Na:Gd ratio, temperature and heating time are fixed to 0.95:1, 550–600 °C and 1–8 h, respectively, only the β-NaGdF phase precipitates. These results are confirmed by high-resolution transmission electron microscopy (HRTEM). The decomposition of trifluoroacetic acid (TFA) and the formation of fluoride lattice bonds were studied by Fourier transform infrared spectroscopy (FTIR). Thus, the sol-gel route permits NaGdF glass-ceramics to be obtained through the control of Na:Gd ratio, temperature and heating time. The incorporation of dopant ions in the NaGdF NCs was confirmed by photoluminescence measurements which show narrow and well-resolved Eu emission and excitation spectra in GCs. Moreover, the low asymmetry ratio values between the electric dipole (D → F) to the magnetic dipole (D → F) transitions indicate that Eu ions are incorporated in the NaGdF NCs. Furthermore, efficient Gd→ Eu energy transfer results in an enhancement of the reddish Eu emissions, further supported by fluorescence decay lifetimes., This work was supported by MINECO under Projects N° MAT2013-48246-C2-1-P/2-P and MAT2017-87035-C2-1-P/-2-P (AEI/FEDER, UE),and Basque Country University PPG17/07 and GIU17/014. This paperis a part of dissemination activities of the project FunGlass. This projecthas received funding from the European Union's Horizon 2020 researchand innovation programme under grant agreement No 739566

In this work, the process parameters involved in the electrophoretic deposition (EPD) to obtain thin TiN films was studied and optimised. The stability of commercial TiN nanopowder in isopropyl alcohol adding a cationic polymer (polyethylenimine) as dispersant, with different molecular weights, was investigated to determine the kinetics of the deposition and to reach the most efficient EPD process. Cathodic EPD was performed over electro-polished stainless steel substrates. It was found that the provided dispersion when the PEI with the highest molecular weight was added to the suspension, leads to the best deposition behaviour for short times. New flocculation phenomena were described which affect to the sticking factor, and thus to the evolution of the EPD kinetics. As a result of the designed stabilization system, a reliable and versatile EPD method to produce well consolidated nano-TiN coatings at 1200 ◦C in vacuum atmosphere was described. This work has been supported by the Spanish Ministry of Economy and Competitiveness (MINECO) under contract MAT2012-38650-C02-01 and Community of Madrid (CAM) for MULTIMATChallenge Project (S2013/MIT-2862). Acknowledges to MINECO through the grant PTQ-13-05985. Publicado

Here we describe the development of novel nanostructured coating systems with improved photocatalytic and antibacterial activities. These systems comprise a layer of SiO2 followed by a layer of mesoporous or dense TiO2-anatase, and doping with silver nanoparticles (Ag NPs). The coatings were synthesized via a sol–gel technique by combining colloidal Ag NPs with TiO2 and SiO2 sols. The photocatalytic activity was studied through methyl orange decomposition under UV light. Results showed a great increase of photocatalytic activity by Ag NPs doping. The most active photocatalyst corresponded to the Ag–SiO2/TiO2 mesoporous system, associated with the porosity of the coatings and with the decrease of e–h recombination for the presence of Ag NPs. All the TiO2 coatings showed a strong bactericidal activity against planktonic forms of Gram-negative (enterohemorrhagic Escherichia coli) and Gram-positive (Listeria monocytogenes) pathogens, as well as a strong germicidal effect against deadly spores of human gas gangrene- and anthrax-producing bacteria (Clostridium perfringens and Bacillus anthracis, respectively). The bactericidal and sporocidal activity was improved by doping the coatings with Ag NPs, even more when nanoparticles were in the outer layer of TiO2, because they are more accessible to the environment. The mechanisms responsible for the increase of photocatalytic and bactericidal behaviors related to Ag NP doping were studied by spectroscopic ellipsometry, UV–vis spectroscopy, photoluminescence and anodic stripping voltammetry. It was found that the separation of the electron–hole pair contributed to the enhancement of photocatalysis, whereas the effect of the local electric field reinforcement was probably present. A possible involvement of a decrease of band-gap energy and dispersion by silver nanoparticles is ruled out. bactericidal efficacy was increased by Ag+ ion release. Overall, the results included in this article show that the architecture of the films may tune photocatalytic and bactericidal properties. Fil: Roldan, Maria Virginia. Universidad Nacional de Rosario. Facultad de Cs.exactas Ingeniería y Agrimensura. No Declara. Laboratorio de Materiales Ceramicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina Fil: de Oña, Paula. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina Fil: Castro, Yolanda. Instituto de Ceramica y Vidrio de Madrid; España Fil: Duran, Alicia. Instituto de Ceramica y Vidrio de Madrid; España Fil: Faccendini, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Química Rosario; Argentina Fil: Lagier, Claudia Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Rosario. Instituto de Química Rosario; Argentina Fil: Grau, Roberto Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; Argentina Fil: Pellegri, Nora Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; Argentina. Universidad Nacional de Rosario. Facultad de Ciencias Exactas, Ingeniería y Agrimensura; Argentina

Porous TiO2-anatase thin films were prepared by the sol-gel route and used for the study of the influence of structural properties in their photocatalytic activity. Sols were prepared by using titanium isopropoxide with two types of modifier ligands, namely acetic acid and acetyl acetone, and pore generating agents such as polyethylene glycol, pluronic F-127 and polyethylene glycol hexadecyl ether (Brij 58). The photocatalytic activity for the degradation of trichloroethylene in air was evaluated under ultraviolet irradiation at different gas flows and water vapour contents. The photocatalytic activity depends on the nature of the pore generating agent which influences the TiO2 crystallite size and the textural properties of the final material. The samples obtained by using acetic acid as the modifier ligand and either Brij 58 or PEG as pore the generating agent exhibited the best photocatalytic behaviour even in the presence of high quantities of water vapour. The direct trichloroethylene oxidation pathway to CO2 is favoured at low water vapour contents, but an important generation of COCl2 is observed even at low water partial pressures, The authors are grateful to Community of Madrid (CM, Spain) for its financial support (DETOX- H2S P-AMB-000406-0505) and the concession of a CM contract (CPI/0565/2007). They are also grateful to the Spanish Ministry of Science and Innovation (former Ministry of Science and Technology) for financial support (CTM2008-06876-C02-01 and Ramón y Cajal program).

This work reports the preparation of glass-like, environmentally-friendly, cerium-based coatings for active corrosion protection of aluminiumandmagnesiumalloys. It describes the production of ceriumsol–gel sols from ceriumnitrate and their deposition by immersion and automatic spray onto aluminiumandmagnesiumalloys to produce uniform coatings with amorphous (glass-like) structures (CexOy). The coatings have been characterised by profilometry, scanning electron microscopy (SEM), spectral ellipsometry and UV–visible, in order to analyse the structure and density of the glass-like ceriumcoatings aswell as their redox ratio Ce4+/Ce3+ as a function of pH and sintering temperature. Finally, electrochemical measurements (EIS) and standard corrosion tests (neutral salt spray, filiform corrosion, immersion–emersion test and adhesion on embossing and T-bend test) have been performed to study the corrosion behaviour of the cerium glass-like coatings on aluminium and magnesium alloys. EIS measurements confirm the healing or blocking of the defects by the corrosion inhibiting species. Excellent corrosion protection is provided by cerium glass-like coatings, satisfying the most demanding industrial requirements.

5 páginas, 5 figuras, 2 tablas., Inorganic and hybrid planar waveguides with different compositions (silica–titania, methacrylate–silica– cerium oxide, zirconia–cerium oxide and silica–zirconia) have been obtained by sol–gel synthesis followed by dip-coating. Soda-lime glass slides and conventional commercial window glass were used as substrates. The thickness and refractive index of the coatings were determined by profilometry and Spectroscopic Ellipsometry. Waveguide efficiency was measured at ca. 70.8% with a He–Ne laser beam, coupled with an optical microscope objective into and out of the waveguiding layer via a double prism configuration. Thicknesses between 150 and 2000 nm, along with refractive index values ranging between 1.45 and ~1.99 (λ=633 nm) were obtained depending on the sol composition and the dip-coating conditions. This wide range of values allows designing multilayered guides that can be used in a variety of applications, The authors acknowledge funding from MICINN (TEC2006-10469, CEN 2007–2014 and SURFALUX SOL-00030930), from DGA (Group of Excellence in Laser Material Processing and Characterisation) and XUNTA DE GALICIA/FEDER (INCITE08PXIB206013PR).

The mechanism of H2S elimination in gas phase by means of heterogeneous photocatalysis was investigated. The main drawbacks for a real application were identified to be related to the nature of the reaction products: SO2 is toxic, corrosive and malodorous, and SO4 2− accumulates on the photocatalyst surface leading to deactivation. In order to face this challenge, supported photocatalysts with different properties were synthesised to investigate several strategies according to the photocatalyst selectivity. On one hand, two different approaches for coupling adsorption and photocatalysis have been proposed to solve the problem of SO2 release and prolong the catalyst lifetime. First, porous and SO2-selective photocatalysts were synthesised by sol–gel with the help of surfactants. These materials presented good conversion values and suffered slower deactivation; an external adsorption unit might retain the SO2 produced. Alternatively, improved adsorption capability of the photocatalyst was obtained through the synthesis of coated and incorporated hybrid TiO2–SiMgOx composites, whereby SO2 release was avoided and the lifetime of the photocatalyst prolonged. The combination in a hybrid material of an efficient photocatalyst and an adsorbent that may act as support constitutes a promising alternative for H2S elimination due to the coupling of photocatalytic and adsorptive properties. On the other hand, photocatalyst regeneration was achieved by rising with water, which recovered the active sites. Moreover, when a 1M KOH solution was used in the process, the creation of new basic active sites resulted in an increase of the photocatalytic activity, even higher than for the fresh material., The authors would like to acknowledge to Comunidad de Madrid for financing the programme DETOX-H2S S-0505/AMB/0406 and Miguel Sánchez for ion chromatography analysis., Comunidad de Madrid for financing the programme DETOX-H2S S-0505/AMB/0406

Porous TiO2-anatase thin films were obtained by sol–gel method using dip-coating procedure onto glassslides and silicon wafers in order to study the effect of the porous structure on the photocatalytic properties. Titania sols were synthesized using titanium isopropoxide (TISP) with two types of complexant molecules (acetyl-acetone (AcAc) or acetic acid (AcOH)) and different types of pore-generating agents as: Pluronic F127 (F127), cetyl trimethyl ammonium bromide (CTAB), sodium dodecyl sulfate (SDS), polyethylene glycol hexadecyl ether (Brij56, Brij58). The coatings were characterised by different techniques as grazing X-ray diffraction (GXRD), spectral ellipsometry, Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Maximum thickness around 280 nm, and refractive index as low as 1.68 were obtained, indicating that the surfactants allow obtaining porous films. GXRD and TEM analysis confirm the presence of a porous structure but not ordered. TiO2 films obtained from AcAc or AcOH with Brij58 and F127 sols present specific surface areas between 28 and 68m2/g. Photocatalytic activity was studied through the degradation of methyl orange in aqueous solution under UV light exposure. Methyl orange degradation increases with the film thickness up to a maximum value of 470 nm, beyond which the efficiency does not further increase. The photocatalytic activity depends on different parameters, such as porosity, film thickness and total surface exposed to illumination.

Hybrid sol–gel coatings provide an approach as protective layers on metals. In this work, corrosion protection of aluminium and magnesium alloys by SiO2-methacrylate coatings doped with TiO2–CeO2 nanoparticles was studied. The films show an improvement of the barrier properties at initial immersion. The reactivity of both alloys produces a deterioration of the protection with longer immersion, although TiO2– CeO2 nanoparticles let to observe signals of self-healing effect. Aluminium oxide/sol–gel interface was found to be stable. In combination with excellent paint adhesion on sol–gel films, these coatings can be a promising alternative pre-treatment for high strength aluminium alloys prior to painting.

The aim of this work is the characterisation of the corrosion behaviour of stainless steel (AISI 304) substrates coated by dipping and electrophoretic deposition (EPD) from a sol–gel basic sol. Particulate silica sols (labelled NaSi)were prepared by basic catalysis from ethyltriethoxysilane (TEOS), methyltriethoxysilane (MTES) and sodium hydroxide. Coatings between 2 and 10 mwere prepared by using concentrated and diluted sols by dipping and EPD process and the corrosion behaviour of the coated substrates were studied through potentiodynamic and impedance spectroscopy measurements (EIS). Potentiodynamic studies of coatings produced by dipping reveal a strong dependence of the protective properties with the concentration of the sol. This behaviour was confirmed by EIS showing that only the coatings obtained from concentrated sol present enough protective properties. On the contrary, EPD coatings prepared from diluted NaSi sol showed an excellent corrosion resistance, maintaining a pure capacitive behaviour for long periods of immersion. EPD deposition is thus proposed as a good alternative method for obtaining thicker and denser coatings with good protective properties from dilute and stable sols.

Porous TiO2-anatase films were prepared by sol–gel route showing higher photocatalytic activity in degradation of trichloroethylene (TCE) in air compared to dense titania films. Titania sols were synthesized with andwithout a pore generating agent, polyethylene glycol (PEG), to evaluate the effect of porosity in the photocatalytic activity of the coatings. The films were deposited by dipping and sintered at different temperature and time. The characterisation was performed by profilometry, Fourier transform infrared spectroscopy (FTIR), grazing X-ray diffraction (GXRD) and field emision scan electron microscopy (FE-SEM), observing that anatase phase is obtained at temperatures as low as 350 8C. The maximum specific surface area (Ss = 43m2/g)wasobtained for coatings prepared fromTiO2 sol with PEGand sintered at 400 8C. Porous TiO2-anatase films present TCE conversion around 20% higher than that of dense films. Porous volume, surface area and thickness of the coating play a key role in the photocatalytic activity. On the other side, variation in particle size seems not to be a critical parameter in the studied range.

Sol–gel technology allows the production of hybrid coatings on metals using low temperatures for densification, but has an important limitation related with the maximum coating thickness attainable, typically lower than 2 mm. The incorporation of nano-particles to the sol can make it possible to increase the coating thickness, without increasing the sintering temperature. This work deals with the preparation of thick sol–gel coating by electrophoretic deposition (EPD). Commercial SiO2 nanoparticles are suspended in an acid-catalysed SiO2 sol, whose stability is largely increased by adding tetramethylammonium hydroxide (TMAH) up to pH 6. Coatings are formed by dipping and by EPD on AISI 304 stainless steel substrates. The protective behaviour against corrosion in aggressive media (i.e. marine water) of the produced films is studied. EPD leads to coatings as thick as 5 mm with good corrosion resistance, while the suspension stability is increased by 15 times compared with that of the starting acid suspension.

Hybrid sols were prepared from tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and 3-(methacryloxypropyl) trimethoxysilane (c-MPS) in an acid medium at different TEOS/MTES and TEOS/c-MPS ratios. An organic monomer, 2-hydroxyethyl methacrylate (HEMA), was free-radical co-polymerized with c-MPS, with 2,20-azobis(isobutyronitrile) (AIBN) as initiator. We report the preparation of coatings from different sols on amber beer bottles and soda-lime glass rods and slides by a dipping process. Various withdrawal rates and heat treatments (from 150 to 500 C) were used to prepare the coats in order to determine the best conditions as a function of composition. In all cases, transparent and crack-free coatings with good adhesion were obtained. Rods and slides of soda-lime glass were mechanically tested using four-point flexure and ring-on-ring tests. The results indicate that the TEOS/c-MPS coated rods and slides treated at 150 C show the best behavior. The scale factor was increased by 26.5% and 22.8% in rods and slides, respectively. In the case of beer bottles, two different types of container were used: untreated and protected bottles with a hot-end SnO2 coating. The bottles were tested using the normal standards of hollow glass: scratch resistance, sliding angle, and internal pressure. Mechanical properties of the coated bottles were analyzed for possible industrial application. The internal pressure of TEOS/c-MPS coatings is similar to standard values, while especially good scratch resistance was observed for TEOS/c-MPS/HEMA/PEG coatings, more than 15 cycles at 294N.