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Publication Liquid phases tailored for introducing oxidation-sensitive elements through the master alloy route(Japan Society of Powder and Powder Metallurgy, 2016-04-01) Oro Calderón, Raquel de; Bernardo Quejido, Elena; Campos Gómez, Mónica; Gierl-Mayer, Christian; Danninger, Herbert; Torralba Castelló, José Manuel; European CommissionIntroducing alloying elements through Master Alloy (MA) additions provides the unique opportunity of designing their composition to enhance sintering by forming a liquid phase. However, working with liquid phases poses important challenges like maintaining a proper dimensional control and minimizing the effect of secondary porosity on the final performance of the steel. The critical parameters for designing low melting point compositions are analyzed in this work by combining the use of thermodynamic software tools, wetting angle/infiltration experiments, and advanced thermal analysis techniques. Due to their low ability to dissolve iron, Cu-based liquids present remarkable infiltration properties that provide homogeneous distribution of the alloying elements. Dissolutive liquids, on the other hand, tend to render more heterogeneous microstructures, rapidly solidifying in contact with the matrix. As a consequence of their lower infiltration capacity, dimensional changes upon liquid formation are significantly lowered. When using master alloys with high content in oxidation-sensitive alloying elements, the differences in oxygen affinity cause an oxygen transfer from the surface of the iron base particles to the surface of the master alloys. The change in the surface chemistry modifies the wetting capability of the liquid, and the dimensional stability becomes increasingly sensitive to the processing atmosphere.Publication New nanomaterials for applications in conservation and restoration of stony materials: A review(CSIC, 2017-01-01) Sierra Fernández, A.; Gómez Villalba, Luz Stella; Rabanal Jiménez, María Eugenia; Fort, R.; Comunidad de Madrid; Ministerio de Innovación y Educación (España)In recent times, nanomaterials have been applied in the construction and maintenance of the world's cultural heritage with the aim of improving the consolidation and protection treatments of damaged stone. These nanomaterials include important advantages that could solve many problems found in the traditional interventions. The present paper aims to carry out a review of the state of art on the application of nanotechnology to the conservation and restoration of the stony cultural heritage. We highlight the different types of nanoparticles currently used to produce conservation treatments with enhanced material properties and novel functionalities.Publication Application of thermal analysis in the selection of polymer components used as a binder for metal injection moulding of Co-Cr-Mo alloy powder(2018-10-01) Matula, Grzegorz; Tomiczek, Blazej; Krol, Mariusz; Szatkowska, AleksandraTo produce the polymer-powder slurry for injection moulding the thermoplastic polymers such as polypropylene, high-density polyethylene and ethylene-vinyl acetate were used. Depending on skeletal polymers, in every feedstock paraffin wax (PW) was used in the amount of 50% of binder. Application of PW gives the possibility using solvent debinding or thermal debinding at a lower temperature. Then the open porosity into the injected samples reduces the time of thermal debinding of binder residue. Application of one type of skeletal polymer requires using a long isothermal step. The use of a blend of skeletal polymers enables subsequent thermal degradation which consecutively removes skeletal polymers during the heating to the sintering temperature, to minimise the time of isothermal stops. The rheological properties of blends used as a binder and next feedstocks were investigated during mixing in the twin-screw extruder and capillary rheometer. This results gives the information about the possibility to produce feedstocks and then to their injection moulding. Thermal behaviour of samples was determined by differential scanning calorimetry and thermogravimetric analysis to obtain the information about the temperature of mixing the polymers and to propose the thermal debinding cycle.Publication Experimental and numerical studies of polyamide 11 and 12 surfaces modified by atmospheric pressure plasma treatment(Elsevier, 2022-08) Bahrami, Mohsen; Lavayen Farfan, D.; Martínez Casanova, Miguel Ángel; Abenojar Buendía, JuanaPolyamide 11 and 12 (PA11 and PA12) have been applicable in various industries, including automotive, oil and gas, and sporting goods, over the past 70 years. Although they have good dyeability, their adhesion to other materials is limited due to relatively poor surface properties, which can be promoted by good wettability and high surface energy. This study aims to improve the surface properties of PA11 and PA12 by employing the advanced method of Atmospheric Pressure Plasma Torch (APPT) treatment. In this regard, the adhesion strengths of four commercially available adhesives were evaluated with the pull-off test on PAs plates before and after APPT treatment. The numerical simulation of this test was carried out in commercial finite element software using a cohesive zone model (CZM) to predict the fracture of adhesively bonded joints. Moreover, the modified PAs were analyzed using XPS, DSC, ATR-FTIR, optical profilometer and surface energy measurement. The results indicated that the surface properties, including wettability, polar surface energy and adhesion bonding, improved by employing the plasma treatment on PAs surfaces. The numerical simulation outcomes showed that the pull-off test might be a viable alternative to determine the CZM laws for fracture mode I.Publication High ampacity carbon nanotube materials(MDPI, 2019-03) Mokry López, Guillermo; Pozuelo de Diego, Javier; Villatela, Juan J.; Sanz Feito, Javier; Baselga Llidó, Juan; Ministerio de Economía y Competitividad (España)Constant evolution of technology is leading to the improvement of electronical devices. Smaller, lighter, faster, are but a few of the properties that have been constantly improved, but these developments come hand in hand with negative downsides. In the case of miniaturization, this shortcoming is found in the inherent property of conducting materials-the limit of current density they can withstand before failure. This property, known as ampacity, is close to reaching its limits at the current scales of use, and the performances of some conductors such as gold or copper suffer severely from it. The need to find alternative conductors with higher ampacity is, therefore, an urgent need, but at the same time, one which requires simultaneous search for decreased density if it is to succeed in an ever-growing electronical world. The uses of these carbon nanotube-based materials, from airplane lightning strike protection systems to the microchip industry, will be evaluated, failure mechanisms at maximum current densities explained, limitations and difficulties in ampacity measurements with different size ranges evaluated, and future lines of research suggested. This review will therefore provide an in-depth view of the rare properties that make carbon nanotubes and their hybrids unique.Publication Improvement of wear resistance of low-cost powder metallurgy beta-titanium alloys for biomedical applications(Elsevier, 2022-03-25) Chirico, C.; Vaz-Romero, Álvaro; Gordo Odériz, Elena; Tsipas, Sophia Alexandra; Comunidad de Madrid; Ministerio de Economía y Competitividad (España)Low wear resistance and the relative high Young's modulus reduce the lifetime of the current biomedical Ti alloys for orthopaedic applications. In this study, two novel low-cost beta-Ti alloys (Ti-5Fe-25Nb and Tisingle bond40Nb in wt%), with reduced elastic modulus, are produced by powder metallurgy route, starting from TiH2 powder. In order to increase their wear resistance, two strategies are proposed: 1) addition of 5 vol% of TiN reinforcement particles and 2) gas nitriding surface treatment to produce a TiN coating. Wear resistance was evaluated by dry sliding reciprocating wear tests against alumina as counter material. Dry sliding tests were performed under unlubricated conditions, applying 10 N and 20 N load. Gas nitrided samples exhibit higher hardness than base alloys, while maintaining low elastic modulus. Both modification techniques improve wear resistance. The highest wear reduction was obtained for gas nitrided samples, reaching a wear rate reduction between 86% and 43%, compared to untreated alloys at 10 N, and between 4% to 15% at 20 N.Publication Effect of small variations in Zr content on the microstructure and properties of ferritic ODS steels consolidated by SPS(MDPI, 2020-03-06) Garcia Junceda Ameigenda, Andrea; Macía Rodríguez, Eric; Garbiec, Dariusz; Serrano, Marta; Torralba Castelló, José Manuel; Campos Gómez, Mónica; Ministerio de Economía y Competitividad (España)Two different zirconium contents (0.45 and 0.60 wt.%) have been incorporated into a Fe-14Cr-5Al-3W-0.4Ti-0.25Y2O3 oxide dispersion-strengthened (ODS) steel in order to evaluate their effect on the final microstructure and mechanical properties. The powders with the targeted compositions were obtained by mechanical alloying (MA), and subsequently processed by spark plasma sintering (SPS) at two different heating rates: 100 and 400 °C·min-1. Non-textured bimodal microstructures composed of micrometric and ultrafine grains were obtained. The increase in Zr content led to a higher percentage of Zr nano-oxides and larger regions of ultrafine grains. These ultrafine grains also seem to be promoted by higher heating rates. The effective pinning of the dislocations by the Zr dispersoids, and the refining of the microstructure, have significantly increased the strength exhibited by the ODS steels during the small punch tests, even at high temperatures (500 °C)Publication Wire Arc Additive Manufacturing (WAAM) for Aluminum-Lithium Alloys: A Review(MDPI, 2023-02-01) Rodriguez Gonzalez, Paula; Ruiz Navas, Elisa María; Gordo Odériz, Elena; Comunidad de MadridOut of all the metal additive manufacturing (AM) techniques, the directed energy deposition (DED) technique, and particularly the wire-based one, are of great interest due to their rapid production. In addition, they are recognized as being the fastest technique capable of producing fully functional structural parts, near-net-shape products with complex geometry and almost unlimited size. There are several wire-based systems, such as plasma arc welding and laser melting deposition, depending on the heat source. The main drawback is the lack of commercially available wire; for instance, the absence of high-strength aluminum alloy wires. Therefore, this review covers conventional and innovative processes of wire production and includes a summary of the Al-Cu-Li alloys with the most industrial interest in order to foment and promote the selection of the most suitable wire compositions. The role of each alloying element is key for specific wire design in WAAM; this review describes the role of each element (typically strengthening by age hardening, solid solution and grain size reduction) with special attention to lithium. At the same time, the defects in the WAAM part limit its applicability. For this reason, all the defects related to the WAAM process, together with those related to the chemical composition of the alloy, are mentioned. Finally, future developments are summarized, encompassing the most suitable techniques for Al-Cu-Li alloys, such as PMC (pulse multicontrol) and CMT (cold metal transfer).Publication Airbrushed PSF/ZnO composite coatings as a novel approach for the consolidation of historical bones(MDPI, 2023-02-02) Moradienayat, Monireh; González Benito, Francisco Javier; Olmos Díaz, Dania; Comunidad de Madrid; Ministerio de Economía y Competitividad (España); Universidad Carlos III de MadridIn this work, the preparation and characterization of films based on polysulfone (PSF) filled with zinc oxide, ZnO, nanoparticles (NPs) are conducted. The novelty of this research mainly relies on two points: (i) the use of a commercial airbrush to prepare or modify materials, and (ii) the design of new materials (nanocomposites) for the consolidation and restoration of historical bones. To accomplish these objectives, free-standing thin films and ancient bone coatings of PSF/ZnO nanocomposites with different particle contents (0%, 1%, 2%, 5% and 10%, % wt) are prepared using a commercial airbrush. Mechanical characterization is carried out to correlate properties between free-standing thin films and coatings, thus understanding the final performance of the coatings as consolidants for ancient bones. Thin films of PSF/ZnO show that the elastic modulus (E) increases with particle content. The mechanical behavior of the surfaces of the treated and untreated bones is studied locally using Martens hardness measurements. Maximum values of Martens hardness are obtained for the bone samples treated with polysulfone filled with 1% ZnO nanoparticles (HM = 850 N·mm-2) or 2% ZnO (HM = 625 N·mm-2) compared to those treated just with neat PSF (HM = 282 N·mm-2) or untreated bone (HM = 140 N·mm-2), indicating there is a correspondence between rigidity of free-standing films and hardness of the corresponding coatings. In terms of mechanical performance, it is demonstrated the existence of a balance between nanoparticle concentration and probability of nanoparticle aggregation, which allows better material design for ancient bones consolidation.Publication Mechanical performance after high-temperature exposure and Life Cycle Assessment (LCA) according to unit of stored energy of alternative mortars to Portland cement(Elsevier, 2023-02-15) Ramón Álvarez, Irene; Batuecas Fernández, Esperanza; Sánchez Delgado, Sergio; Torres Carrasco, Manuel; Comunidad de Madrid; Ministerio de Ciencia, Innovación y Universidades (España)Decoupling energy demand has led to the importance of energy storage for increasing the capacity of renewable energy power plants. In this field, Portland cement (PC) concrete is proving to be a promising way to store energy as it can be used as sensible thermal energy storage (TES) medium in concentrated solar power (CSP) technology. However, the high energy and water consumption involved in the PC manufacturing process makes it necessary to develop new alternatives. Thus, alkali-activated materials (AAM) and hybrid materials (HM) were manufactured using blast furnace slag and glass waste (GW) to replace the PC and the sand in concretes respectively in order to study their feasibility as TES media in parabolic through CSP systems. The viability of these proposed new systems was tested from a mechanical point of view, while taking into account the environmental aspect using Life Cycle Assessment (LCA) methodology to study carbon and water footprints. The new systems were exposed to high temperature (up to 500 °C), showing better performance than the ordinary PC under high temperatures, and their mechanical properties were not affected at all. After thermal treatment the alternatives show improvements of up to 79% compared to the PC reference sample. Furthermore, in terms of LCA analysis, it was concluded that TES systems with partial (HM) or total (AAM) substitution of PC by using by-products improve water use up to 40% when an AAM material includes GW as a recycled aggregate in its composition. Results likewise revealed a more than 100% reduction in the carbon footprint. These results open a new gate for the study of materials as TES since the alternatives to PC are more promising from an operational and environmental point of view.Publication Thermophysical properties of porous Ti2AlC and Ti3SiC2 produced by powder metallurgy(Elsevier, 2021-03-15) Tsipas, Sophia Alexandra; Tabares Lorenzo, Eduardo; Weissgaerber, Thomas; Hutsch, Thomas; Sket, Federico; Velasco Núñez, Beatriz; Comunidad de Madrid; Ministerio de Economía y Competitividad (España)The physicochemical properties of porous Ti2AlC and Ti3SiC2 MAX phase compounds with controlled porosity and grain size obtained by powder metallurgy techniques was studied in depth in order to access their suitability of applications such as catalytic devices on vehicles, heat exchangers or impact resistant structures. The study was performed on isostatic consolidated samples with different amount (20-60 vol%) and size of space holder (250-1000 µm) and in samples without space holder. Oxidation tests were performed at different temperatures for each material depending on their maximum service temperature. In order to understand the oxidation mechanism, oxidation kinetics were analysed to determine the influence of size and amount of porosity in each case. In addition, the microstructure and composition of the oxide layers formed after the tests were analysed by scanning electron microscopy (SEM). Electrical and thermal conductivity where studied at room temperature and at temperature up to 1000 degrees C. The effect of pore size and cell wall thickness is discussed. Permeability of foams was also measured. The effect of micro porosity and macro porosity on permeability is discussed. The coefficient of thermal expiation was also measured for all foams produced. It is established that these porous MAX phases have suitable properties for their use as catalytic substrates, heat exchanges, high temperature filters or volumetric solar receivers.Publication Polyacrylonitrile-b-polystyrene block copolymer-derived hierarchical porous carbon materials for supercapacitor(MDPI, 2022-12-01) Álvarez Gómez, Ainhoa; Yuan, Jiayin; Fernandez Blazquez, Juan P.; San Miguel Arnanz, Verónica; Serrano Prieto, María Bernarda; Ministerio de Ciencia e Innovación (España)The use of block copolymers as a sacrificial template has been demonstrated to be a powerful method for obtaining porous carbons as electrode materials in energy storage devices. In this work, a block copolymer of polystyrene and polyacrylonitrile (PS−b−PAN) has been used as a precursor to produce fibers by electrospinning and powdered carbons, showing high carbon yield (~50%) due to a low sacrificial block content (fPS ≈ 0.16). Both materials have been compared structurally (in addition to comparing their electrochemical behavior). The porous carbon fibers showed superior pore formation capability and exhibited a hierarchical porous structure, with small and large mesopores and a relatively high surface area (~492 m2/g) with a considerable quantity of O/N surface content, which translates into outstanding electrochemical performance with excellent cycle stability (close to 100% capacitance retention after 10,000 cycles) and high capacitance value (254 F/g measured at 1 A/g).Publication Nonwoven mats based on segmented biopolyurethanes filled with MWCNT prepared by solution blow spinning(MDPI, 2022-10-01) Ramos, Pablo; Calvo-Correas, Tamara; Eceiza, Arantxa; González Benito, Francisco Javier; Ministerio de Ciencia, Innovación y Universidades (España); Universidad Carlos III de MadridTo prepare nonwoven mats constituted by submicrometric fibers of thermally responsive biopolyurethanes (TPU) modified with multiwalled carbon nanotubes (MWCNT), solution blow spinning (SBS) was used. The TPU was the product of synthesis using poly(butylene sebacate)diol, PBSD, ethyl ester L-lysine diisocyanate (LDI), and 1,3-propanediol (PD) (PBSe:LDI:PD) as reactants. TPU was modified by adding different amounts of MWCNT (0, 0.5, 1, 2, and 3 wt.%). The effect of the presence and amount of MWCNT on the morphology and structure of the materials was studied using field-emission scanning electron microscopy (FESEM) and Fourier-transform infrared spectroscopy (FTIR), respectively, while their influence on the thermal and electric behaviors was studied using differential scanning calorimetry (DSC) and capacitance measurements, respectively. The addition of MWCNT by SBS induced morphological changes in the fibrous materials, affecting the relative amount and size of submicrometric fibers and, therefore, the porosity. As the MWCNT content increased, the diameter of the fibers increased and their relative amount with respect to all morphological microfeatures increased, leading to a more compact microstructure with lower porosity. The highly porous fibrous morphology of TPU-based materials achieved by SBS allowed turning a hydrophilic material to a highly hydrophobic one. Percolation of MWCNT was attained between 2 and 3 wt.%, affecting not only the electric properties of the materials but also their thermal behavior.Publication Sliding wear behavior of intermetallic Ti-45Al-2Nb-2Mn-(at%)-0.8vol%TiB2 processed by centrifugal casting and hot isostatic pressure: Influence of microstructure(MDPI, 2022-11-02) Shagñay Pucha, Segundo Manuel; Cornide Arce, Juan; Ruiz Navas, Elisa MaríaIntermetallic alloys such as titanium aluminides (TiAl) are potential materials for aerospace applications at elevated temperatures. TiAl intermetallics have low weight and improved efficiency under aggressive environments. However, there is limited information about wear behavior of these alloys and their microstructure. The present work aims to study the influence of the microstructure in the tribological behavior of TiAl intermetallic alloy (45Al-2Mn-2Nb(at%)-0.8 vol%TiB2). Wear tests were performed on samples manufactured by centrifugal casting (CC) and hot isostatic pressure (HIP). Reciprocating sliding wear test was carried out for TiAl, it was combined with different loads and frequencies. Wear tracks were analyzed through opto-digital microscopy and electron microscopy (SEM). The results obtained reveal that CC intermetallics present the lowest volume wear lost, approximately 20% less than HIP intermetallics. This good behavior could be related to the high hardness material, associated with the main microstructure where CC intermetallic has nearly lamellar microstructure and HIP intermetallics present duplex microstructure.Publication Norbornene as key for a possible efficient chemical recycling in structures based on ethylene(MDPI, 2022-11-02) Calles Valero, Antonio F.; García Peñas, Alberto; Cerrada, María L.; Gómez Elvira, José M.; Comunidad de Madrid; Ministerio de Ciencia e Innovación (España)Different circular strategies attempt to increase the energy efficiency or reduce the accumulation of plastic in landfills through the development of circular polymers. Chemical recycling is essential to recover the initial monomers from plastic residues for obtaining new goods showing the same properties as those using virgin monomers from the initial feedstocks. This work addresses the preparation of poly(ethylene-co-norbornene) copolymers for a promising generation of materials for energy applications that could be treated by chemical recycling. The thermal and thermo-oxidative stability for these copolymers with norbornene is higher than for the neat PE, while their degradation exhibits an activation energy lower than that observed in PE, pointing out that chemical recycling would require a lower energy consumption.Publication Water-soluble and-insoluble polymers and biopolymers for biomedical, environmental, and biological applications [Editorial](MDPI, 2022-06-02) Stadler, Florian J.; García Peñas, AlbertoPublication Gum acacia-crosslinked-poly(acrylamide) hydrogel supported C3N4/BiOI heterostructure for remediation of noxious crystal violet dye(MDPI, 2022-04-01) Sharma, Gaurav; Kumar, Amit; Naushad, Mu.; Dhiman, Pooja; Thakur, Bharti; García Peñas, Alberto; Stadler, Florian J.Herein, we report the designing of a C3N4/BiOI heterostructure that is supported on gum acacia-crosslinked-poly(acrylamide) hydrogel to fabricate a novel nanocomposite hydrogel. The potential application of the obtained nanocomposite hydrogel to remediate crystal violet dye (CVD) in an aqueous solution was explored. The structural and functional analysis of the nanocomposite hydrogel was performed by FTIR (Fourier transform infrared spectroscopy), X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The different reaction parameters, such as CVD concentration, nanocomposite hydrogel dosage, and working pH, were optimized. The C3N4/BiOI heterostructure of the nanocomposite hydrogel depicts Z-scheme as the potential photocatalytic mechanism for the photodegradation of CVD. The degradation of CVD was also specified in terms of COD and HR-MS analysis was carried to demonstrate the major degradation pathways.Publication Magnetic cork particles as reinforcement in an epoxy resin: effect of size and amount on thermal properties(Springer, 2023-03) Abenojar Buendía, Juana; López de Armentia, Sara; Barbosa, A. Q.; Martínez Casanova, Miguel Ángel; Del Real, J. C.; Da Silva, L. F. M.; Velasco López, Francisco JavierNatural brightness of epoxy adhesives can be reduced by adding cork. Besides, when cork was magnetized, it was possible to move them depending on the properties required in each section of the adhesive bond (PAT354/2019). The main objective of this work was to study possible changes in the thermal properties of the adhesive due to the addition of magnetic cork particles. If changes were significant, the use of magnetic cork particles would be compromised. To this end, natural cork particles and magnetic cork particles, with two different particle size (53–38 and 250–125 μm) and percentage (1 and 5 v/v%), were compared as reinforcement material. Magnetic cork was obtained by co-precipitated coating, according to patent number WO2019025651. The thermal properties studied by Differential Scanning Calorimetry were activation energy of curing reaction, glass transition temperature (Tg) and thermal conductivity. Two different hardeners were studied and a factorial design (2k with k = 4) was carried out. It allowed to determine which variable or combination of variables had most impact on thermal properties. Results showed that the main parameter affecting thermal properties was the hardener, regardless of the kind of particle used. However, the presence of magnetic cork highlights further the differences found between hardeners. The conclusion of this study was that magnetic cork particles can be used as fillers in epoxy resin to make graded joints, since they do not affect the thermal properties of the resin.Publication Polymerization kinetics of acrylic photopolymer loaded with graphene-based nanomaterials for additive manufacturing(MDPI, 2022-12-02) Lopez de Armentia, Sara; Abenojar Buendía, Juana; Ballesteros, Yolanda; Del Real, Juan Carlos; Dunne, Nicholas; Paz, EvaGraphene-based nanomaterials (GBN) can provide attractive properties to photocurable resins used in 3D printing technologies such as improved mechanical properties, electrical and thermal conductivity, and biological capabilities. However, the presence of GBN can affect the printing process (e.g., polymerization, dimensional stability, or accuracy), as well as compromising the quality of structures. In this study an acrylic photocurable resin was reinforced with GBN, using methyl methacrylate (MMA) to favor homogenous dispersion of the nanomaterials. The objective was to investigate the influence that the incorporation of GBN and MMA has on polymerization kinetics by Differential Scanning Calorimetry using Model Free Kinetics, ultra-violet (UV) and thermal triggered polymerization. It was found that MMA catalyzed polymerization reaction by increasing the chain's mobility. In the case of GBNs, graphene demonstrated to inhibit both, thermally and UV triggered polymerization, whilst graphene oxide showed a double effect: it chemically inhibited the polymerization reaction during the initialization stage, but during the propagation stage it promoted the reaction. This study demonstrated that MMA can be used to achieve photocurable nanocomposites with homogenously dispersed GBN, and that the presence of GBN significantly modified the polymerization mechanism while an adaptation of the printing parameters is necessary in order to allow the printability of these nanocomposites.Publication Tuning the electromagnetic shielding mechanism with nitrogen-doped graphene aerogels(Wiley, 2023-01) Pozuelo de Diego, Javier; Baselga Llidó, Juan; Álvarez Robledo, Marcos; Ministerio de Ciencia e Innovación (España)The electromagnetic shielding efficiency of a given material can be quantified as the sum of three contributions: reflection, absorption, and multiple reflections, which under certain conditions can be reduced to the first two, which are the main shielding processes decisive for its further application. A simple process to prepare nitrogen-doped graphene aerogels followed by subsequent thermal treatments is proposed to adapt and control the shielding mechanisms that take place to the possible requirements of the system. Nitrogen-doped aerogels are prepared by the addition of urea in the hydrothermal synthesis and subsequent heat treatments at 500 and 1000 °C. Reflection/absorption power ratio values of unity down to values as low as 0.2 are obtained. This study represents an advance in electromagnetic shielding materials and the adaptation of these to the needs of different applications, reducing the traditional negative environmental impact of these devices.