Scientific Papers in SCI
2023
2023
Nanotecnología en Superficies y Plasma
Structure and Void Connectivity in Nanocolumnar Thin Films Grown by Magnetron Sputtering at Oblique Angles
Alvarez, R; Regodon, G; Acosta-Rivera, H; Rico, V; Alcala, G; Gonzalez-Elipe, AR; Palmero, ACoatings, 13 (2023) 991 DOI: 10.3390/coatings13060991
Abstract
The morphology and void connectivity of thin films grown by a magnetron sputtering deposition technique at oblique geometries were studied in this paper. A well-tested thin film growth model was employed to assess the features of these layers along with experimental data taken from the literature. A strong variation in the film morphology and pore topology was found as a function of the growth conditions, which have been linked to the different collisional transport of sputtered species in the plasma gas. Four different characteristic film morphologies were identified, such as (i) highly dense and compact, (ii) compact with large, tilted mesopores, (iii) nanocolumns separated by large mesopores, and (iv) vertically aligned sponge-like coalescent nanostructures. Attending to the topology and connectivity of the voids in the film, the nanocolumnar morphology was shown to present a high pore volume and area connected with the outside by means of mesopores, with a diameter above 2 nm, while the sponge-like nanostructure presented a high pore volume and area, as well as a dense network connectivity by means of micropores, with a diameter below 2 nm. The obtained results describe the different features of the porous network in these films and explain the different performances as gas or liquid sensors in electrochromic applications or for infiltration with nanoparticles or large molecules.
June, 2023 · DOI: 10.3390/coatings13060991
Reactividad de Sólidos
Effect of thermal treatments below devitrification temperature on the magnetic and magnetocaloric properties in mechanically alloyed Fe70Zr30 powders
Manchon-Gordon, AF; Blazquez, JS; Kowalczyk, M; Ipus, JJ; Kulik, T; Conde, CFJournal of Non-Crystalline Solids, 609 (2023) 122267 DOI: 10.1016/j.jnoncrysol.2023.122267
Abstract
In this work, the relaxation of the amorphous structure of mechanically alloyed Fe70Zr30 powders has been analyzed through interrupted heating ramps below the devitrification temperature. As a result of such thermal treatment, Curie temperature and temperature at maximum magnetic entropy change curves shift to higher temperatures as the temperature of heating treatment increases. This effect can be attributed to both the release of the stress accumulated in the amorphous powder during the milling process and to the initiation of nucleation of alpha-Fe crystallites, as it has been shown by Mo center dot ssbauer spectroscopy.
June, 2023 · DOI: 10.1016/j.jnoncrysol.2023.122267
Nanotecnología en Superficies y Plasma
Strontium/zinc phytate-based self-assembled monolayers on titanium surfaces enhance osteogenesis and antibacterial performance in vitro
Asensio, G; Hernández-Arriaga, AM; Martin-del-Campo, M; Prieto, MA; González-Elipe, AR; Rojo, L; Vázquez-Lasa, BApplied Surface Science, 620 (2023) 156818 DOI: 10.1016/j.apsusc.2023.156818
Abstract
The accumulation of bacteria over implant surfaces is still the first cause of failure, and the development of antimicrobial surfaces constitutes a first line in implant research. Besides, the durability and mechanical performance of implants, in special in the dental area, are mainly determined by their osseointegration capacity into the maxillofacial bone and the appearance of infections. Consequently, implant osseointegration and infection prophylaxis remain as big challenges to attain so a huge investigation is being developed on the production of bioactive surfaces to achieve improvements in these aspects. In this work we propose the functionalization of titanium surfaces (Ti Cp) with self-assembled monolayers (SAMs) of bioactive organophosphate compounds: phytic acid (Ti-PA) and its metallic phytate de- rivatives bearing Sr2+ and/or Zn2+ (Ti-SrPhy, Ti-ZnPhy and Ti-SrPhy/ZnPhy) which exhibited tunable in vitro osteogenic, antimicrobial and antioxidant properties in a previous work. Thus, phytate compounds are chemically anchored onto Ti discs through a simple procedure consisting of a condensation reaction promoted by heat treatment. EDS and XPS spectroscopies confirm the obtaining of the modified surfaces and the topographic properties and wettability analysed by SEM, AFM, profilometry and contact angle measurements, respectively, are explored. Additionally, phytate-SAMs do not release any cytotoxic compound after 14 days and stimulate in vitro adhesion and proliferation of human osteoblast cells after 14 days of culture. The osteogenic ability of the modified surfaces evaluated by the quantification of ALP activity and matrix mineralization degree shows a significant improvement with respect to unmodified surfaces. Furthermore, the antimicrobial activity of phytate-SAMs against Streptococcus mutans cultures is evaluated. The count of viable cells and the quantification of produced biofilm are significantly reduced by all phytate-SAMs groups (p < 0.001). Cell membrane integrity studies by LIVE/DEAD staining and SEM imaging confirm a decreased viability of adhered bacteria when phytate-based surfaces are tested, due to a disruption in the function and permeability of the cell membrane. Therefore, phytate-SAMs exhibit suitable in vitro features suggesting their promising potential as bioactive coatings of dental implants.
May, 2023 · DOI: 10.1016/j.apsusc.2023.156818
Tribología y Protección de Superficies
Tribological Response of delta-Bi2O3 Coatings Deposited by RF Magnetron Sputtering
Rodil, SE; Depablos-Rivera, O; Sanchez-Lopez, JCLubricants, 11 (2023) 207 DOI: 10.3390/lubricants11050207
Abstract
Bismuth oxide (Bi2O3) coatings and composite coatings containing this oxide have been studied due to their potential applications in gas sensing, optoelectronics, photocatalysis, and even tribology. Two parametric models based on chemical features have been proposed with the aim of predicting the lubricity response of oxides. However, such models predict contradictory values of the coefficient of friction (COF) for Bi2O3. In this study, we deposited Bi2O3 coatings, via magnetron sputtering, on AISI D2 steel substrates to evaluate the tribological responses of the coatings and determine which parametric model describes them better. Experimentally, only coatings presenting the cubic defective fluorite-like delta-Bi2O3 phase could be evaluated. We performed pin-on-disk tests at room temperature and progressively increasing temperatures up to 300 degrees C using alumina and steel counter-bodies. Low wear and COFs (0.05 to 0.15) indicated that the delta-phase behaves as a lubricious solid, favoring the validity of one of the models. An alternative explanation is proposed for the low COF of the defective fluorite-like structure since it is well known that it contains 25% of anionic vacancies that can be ordered to form low shear-strength planes, similar to the Magneli phases. Two challenges for future potential applications were observed: one was the low adhesion strength to the substrate, and the other was the thermal stability of this phase.
May, 2023 · DOI: 10.3390/lubricants11050207
Reactividad de Sólidos
Direct comparison of surface crystal growth kinetics in chalcogenide glass measured by microscopy and DSC
Shanelova, J; Honcova, P; Malek, J; Perejon, A; Perez-Maqueda, LAJournal of the American Ceramic Society, 106 (2023) 6051-6061 DOI: 10.1111/jace.19204
Abstract
Surface crystallization in fine powder Se70Te30 chalcogenide glass was studied by differential scanning calorimetry (DSC) and optical microscopy. A complex kinetic analysis of these experimental data reveals that the contracting sphere mechanism (R3 model) is the rate determining step of crystal growth, and the conventional Johnson-Mehl-Avrami-Kolmogorov model cannot be used in this case. Moreover, it is clearly shown that the particle size distribution should be considered in crystallization studies. Actually, when the particle size effect is taken into account, the simulated DSC curves for the R3 model agree very well with the experimental data over the entire temperature range. The crystallization kinetics determined from the nonisothermal DSC data are consistent with previously reported isothermal crystallization data for the same powder fraction. The crystal growth rate calculated from isothermal and nonisothermal DSC data agrees very well with the microscopically measured surface and bulk crystal growth rate.
May, 2023 · DOI: 10.1111/jace.19204
Reactividad de Sólidos
Limits of powder metallurgy to fabricate porous Ti35Nb7Zr5Ta samples for cortical bone replacements
Rodriguez-Albelo, LM; Navarro, P; Gotor, FJ; de la Rosa, JE; Mena, D; Garcia-Garcia, FJ; Beltran, AM; Alcudia, A; Torres, YJournal of Materials Research and Technology-JMR&T, 24 (2023) 6212-6226 DOI: 10.1016/j.jmrt.2023.04.212
Abstract
The use of 13-Titanium alloys to fabricate metal implants with Young's modulus that re-sembles bone tissues is presented as an alternative to commercially pure titanium or a- Titanium alloys, although it is still necessary to introduce proper implant porosity to reach the Young's modulus of cortical bones. In this work, porous samples were fabricated by loose sintering (0 MPa) and compared to samples manufactured at 1000 MPa, both sintered under the same conditions. Raw powders and sintered samples of the 13-Titanium alloy, Ti35Nb7Zr5Ta, were characterized in detail in terms of both physicochemical and micro-structural properties. Moreover, the tribo-mechanical behavior of sintered samples was evaluated by performing ultrasound technique, instrumented micro-indentation (P-h curves), and scratch tests. The bio-functional behavior was studied by impedance spec-troscopy and contact angle measurements. The results allowed the evaluation of the limits of conventional powder metallurgy (percentage of porosity, size, and morphology of pores), as well as the influence of the porosity and chemical composition to achieve a better biomechanical and bio-functional behavior that would guarantee bone requirements. The Ti35Nb7Zr5Ta alloy showed relatively high electrical impedance values compared to commercially pure titanium, indicating an improved bio-corrosion behavior. Furthermore, wettability measurements indicated that porous disks fabricated by loose sintering exhibit higher hydrophilicity, often associated with a better antibacterial response
May, 2023 · DOI: 10.1016/j.jmrt.2023.04.212
Materiales Avanzados
Characterization, thermal and ceramic properties of clays from Alhabia (Almeria, Spain)
Rat, E; Martinez-Martinez, S; Sanchez-Garrido, JA; Perez-Vilargejo, L; Garzon, E; Sanchez-Soto, PJCeramics International, 49 (2023) 14814-14825 DOI: 10.1016/j.ceramint.2022.05.328
Abstract
Clays from Alhabia (Almeria, Spain) have been investigated in this work using several analytical techniques: X-Ray Diffraction (XRD), X-Ray Fluorescence (XRF), thermal analysis (Thermogravimetry, TG, and its first deriv-ative, DTG), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectroscopy (EDS). Texture characteristics (granulometry) and plasticity have been examined. The main ceramic properties (firing shrinkage, water absorption, bulk density, open porosity, flexural strength and thermal conductivity) have been determined using pressed and fired clay samples. Thus, the mineralogical, chemical, textural and ceramic features of these clays have been evidenced for the first time. The mineralogical analysis by XRD indicated that the clay samples are constituted by a mixture of chlorite and illite, as main clay minerals, being quartz and other minerals in lower relative proportion (calcite, gypsum and hematite). This finding is important because the investigations on chlorite-illite-calcitic clays are very scarce. The chemical analysis by XRF showed that silica and alumina are predominant, as expected by the mineralogy, with medium contents of calcium oxide, from calcite, and alkalis, from illite, being-8 and-5%, respectively, besides iron and titanium oxides (-8%). The particle size analysis showed 71.76% of "clay fraction" (<2 mu m) and 21.66% of silt fraction (2-50 mu m). The plasticity index (Atterberg) was 14.3%, with acceptable moulding and extrusion properties. Thermal analysis by TG/DTG indicated a weight loss associated to dehydroxylation of structural water of the clay minerals and decarbonation of calcite by progressive heating. After the characterization of raw clays, the next step was the determination of ceramic properties of mixed and ground clays after firing using pressed bodies. For this purpose, two firing temperatures were selected (900 and 1100 degrees C) for 1 h. The examination of the resultant fired bodies indicated that porous ceramic materials (-36% open porosity and-22% of water absorption capacity) can be obtained by firing at 900 degrees C, with small variations in dimensions (<0.8% at 1100 degrees C). The porosity changed at relatively lower values by firing at 1100 degrees C (-34-35%), being associated to the presence of decomposed calcite. Bulk density was found almost constant from 900 to 1100 degrees C, with a maximum value of-1.67 g/cm3 at 1100 degrees C. Flexural strength reached a maximum value of 34.47 MPa at 1100 degrees C for the ground sample. Finally, thermal conductivity after firing the clay bodies was found almost constant at 900 and 1100 degrees C (0.457 and 0.479 W/mK, respectively). Taking into account these results, the main applications of the Alhabia clays have been evaluated. These clays can be used for the fabrication of porous ceramic supports and tiles by firing at 900 degrees C. Firing the clays at higher temperature (1100 degrees C) is of great interest for the fabrication of ceramic tiles and ceramic bricks of higher flexural strength with variable porosity and practically constant in dimensions. It is economically important although at higher processing costs. Finally, it can be emphasized that this work is a contribution of a better scientific knowledge of chlorite-illite-calcitic clays as ceramic raw materials.
May, 2023 · DOI: 10.1016/j.ceramint.2022.05.328
Materiales y Procesos Catalíticos de Interés Ambiental y Energético
Catalytic performance of cobalt supported onto APTES functionalized TiO2 for Fischer-Tropsch reaction
Platero, F; Caballero, A; Colon, GFuel, 340 (2023) 127528 DOI: 10.1016/j.fuel.2023.127528
Abstract
Cobalt supported TiO2 catalysts have been prepared by wet-impregnation and by immobilization over APTES (3-aminopropyl triethoxysilane) grafted TiO2. Impregnated system showed better catalytic performance after reduction at 260 degrees C but significant deactivation is observed. On the contrary, functionalized catalyst showed better catalytic performance after reduction at 400 degrees C with notable stability. We have stated from CO-DRIFT operando analysis that impregnated system is strongly affected by negative SMSI (strong metal-support inter-action) upon reduction at higher temperature. While immobilization on APTES hinders the loss of metal active sites. The study of spent catalysts denotes that Co is redispersed in the impregnated catalyst while functionalized trends to form agglomerates.
May, 2023 · DOI: 10.1016/j.fuel.2023.127528
Química de Superficies y Catálisis
MIL-100(Fe)-derived catalysts for CO2 conversion via low- and high-temperature reverse water-gas shift reaction
Loe, JG; Pena, AP; Espejo, JLM; Bobadilla, LF; Reina, TR; Pastor-Perez, LHeliyon, 9 (2023) e16070 DOI: 10.1016/j.heliyon.2023.e16070
Abstract
Fe-derived catalysts were synthesized by the pyrolysis of MIL-100 (Fe) metal-organic framework (MOF) and evaluated in the reverse water-gas shift (RWGS) reaction. The addition of Rh as a dopant by in-situ incorporation during the synthesis and wet impregnation was also considered. Our characterization data showed that the main active phase was a mixture of & alpha;-Fe, Fe3C, and Fe3O4 in all the catalysts evaluated. Additionally, small Rh loading leads to a decrease in the particle size in the active phase. Despite all three catalysts showing commendable CO selectivity levels, the C@Fe* catalyst showed the most promising performance at a temperature below 500 degrees C, attributed to the in-situ incorporation of Rh during the synthesis. Overall, this work showcases a strategy for designing novel Fe MOF-derived catalysts for RWGS reaction, opening new research opportunities for CO2 utilization schemes.
May, 2023 · DOI: 10.1016/j.heliyon.2023.e16070
Química de Superficies y Catálisis
Unravelling the CO2 capture and conversion mechanism of a NiRu-Na2O switchable dual-function material in various CO2 utilisation reactions
Merkouri, LP; Martin-Espejo, JL; Bobadilla, LF; Odriozola, JA; Penkova, A; Reina, T; Duyar, MSJournal of Materials Chemistry A, 11 (2023) 13209-13216 DOI: 10.1039/d3ta01892j
Abstract
Time-resolved operando DRIFTS-MS was performed to elucidate the CO2 capture and conversion mechanisms of a NiRuNa/CeAl DFM in CO2 methanation, reverse water-gas shift, and dry reforming of methane. CO2 was captured mainly in the form of carbonyls and bidentate carbonates, and a spillover mechanism occurred to obtain the desired products.
May, 2023 · DOI: 10.1039/d3ta01892j
Materiales Ópticos Multifuncionales
Modeling Weakly Scattering Random Media: A Tool to Resolve the Internal Structure of Nanoporous Materials
Jimenez-Solano, A; Miranda-Munoz, JM; Carretero-Palacios, S; Miguez, HAdvanced Photonics Research, 4 (2023) 5 DOI: 10.1002/adpr.202200267
Abstract
Nanoporous media scatter a small fraction of the light propagating through them, even if pore sizes are significantly smaller than the characteristic visible wavelengths. The disordered spatial modulation of the refractive index at the few or few tens of nanometers length scale, resulting from the presence of randomly distributed air bubbles or solid aggregates within a continuous solid background, gives rise to these weak scattering effects. However, standard theoretical approaches to describe this kind of media use effective medium approximations that do not account for diffuse, ballistic, and specular components. Herein, all spectral components and the angular distribution of the scattered light are captured through optical modeling. A Monte Carlo approach, combining scattering Mie theory and Fresnel equations, implemented within a genetic algorithm, allows us to decode the void and aggregate size distribution and hence the internal structure of a nanocrystalline titania (TiO2) film chosen as a paradigmatic example. The approach allows to generically describe the scattering properties of nanoporous materials which, as shown herein, may be used to decipher their internal structure from the fitting of their far-optical field properties.
May, 2023 · DOI: 10.1002/adpr.202200267
Nanotecnología en Superficies y Plasma
Optical monitoring of detergent pollutants in greywater
Lahoz, F; de Armas-Rillo, S; Hernandez-Rodriguez, C; Gil-Rostra, J; Yubero, FOptics Express, 31 (2023) 15227-15238 DOI: 10.1364/OE.466194
Abstract
Large amount of wastewater is produced by washing machines and dishwashers, which are used in a daily basis. This domestic wastewater generated in households or office buildings (also called greywater) is drained directly to the drainpipes without differentiation from that with fecal contamination from toilets. Detergents are arguably the pollutants most frequently found in greywater from home appliances. Their concentrations vary in the successive stages in a wash cycle, which could be taken into account in a rational design of home appliances wastewater management. Analytical chemistry procedures are commonly used to determine the pollutant content in wastewater. They require collecting samples and their transport to properly equipped laboratories, which hampers real time wastewater management. In this paper, optofluidic devices based on planar Fabry-Perot microresonators operating in transmission mode in the visible and near infrared spectral ranges have been studied to determine the concentration of five brands of soap dissolved in water. It is found that the spectral positions of the optical resonances redshift when the soap concentration increases in the corresponding solutions. Experimental calibration curves of the optofluidic device were used to determine the soap concentration of wastewater from the successive stages of a washing machine wash cycle either loaded with garments or unloaded. Interestingly, the analysis of the optical sensor indicated that the greywater from the last water discharge of the wash cycle could be reused for gardening or agriculture. The integration of this kind of microfluidic devices into the home appliances design could lead to reduce our hydric environmental impact.
May, 2023 · DOI: 10.1364/OE.466194
Química de Superficies y Catálisis
Carbon Capture Enhancement by Water-Based Nanofluids in a Hollow Fiber Membrane Contactor
Yuan, CT; Pan, Z; Wang, Y; Baena-Moreno, FM; Constantinou, A; Zhang, ZEnergy Technology, 11 (2023) 2300254 DOI: 10.1002/ente.202300254
Abstract
Nanoparticles are being used in the CO2 solvents to improve the capture performance. Herein, a 2D model is proposed to study the CO2 capture performance from a gaseous mixture using a hollow fiber membrane contactor (HFMC). Both water-based nanofluids of carbon nanotubes (CNT) and SiO2 are deployed as the carbon absorbents. It is verified that Brownian motion and grazing effect are the major reasons to enhance the mass transfer of nanofluids. The simulation findings show that the modeling data conform well with the experimental studies. The root-mean-square errors for SiO2 nanofluid and CNT nanofluid are 2.37% and 2.56%, respectively. When the amounts of nanoparticles increase between 0.02 and 0.06 wt%, CO2 capture efficiencies of SiO2 and CNT nanofluids increase by 7.92% and 13.17%, respectively. Also, the CNT nanofluid has a better capture performance than the SiO2 nanofluid. Furthermore, research is conducted into how membrane characteristics affect HFMC performance. It is indicated that increasing the membrane porosity and decreasing the membrane tortuosity have a positive impact on the capture efficiency. This work demonstrates the potentials in the use of nanoparticles in CO2 solvents and provides a solid theoretical basis for nanofluids to significantly enhance gas absorption.
May, 2023 · DOI: 10.1002/ente.202300254
Nanotecnología en Superficies y Plasma
Surface Acoustic Waves Equip Materials with Active De-Icing Functionality: Unraveled Glaze Ice De-Icing Mechanisms and Application to Centimeter-Scale Transparent Surfaces
Jacob, S; Pandey, S; Del Moral, J; Karimzadeh, A; Gil-Rostra, J; Gonzalez-Elipe, AR; Borras, A; Winkler, AAdvanced Materials Technologies DOI: 10.1002/admt.202300263
Abstract
Enabling active de-icing functionality on low heat conductive and transparent materials is a requirement for several seminal industries in critical economic sectors. However, developing efficient and environmentally friendly de-icing methods still fails because of compatibility problems with large-scale devices and real-world conditions. In this paper, de-icing several square centimeters covered with thick layers of glaze ice is approached through nanoscale activation by surface acoustic waves (SAWs). De-icing functionality is demonstrated with a self-supported piezoelectric material (LiNbO3) and a piezoelectric film (ZnO) deposited on fused silica, the latter system proving the compatibility of the method with materials of practical relevance. Its applicability to large and transparent substrates is demonstrated by placing the interdigitated electrodes (IDTs) required for activation close to the substrate's edges, leaving most of the surface unaltered. The de-icing mechanism of glaze ice by SAW activation is revealed by simulating the SAW propagation on ice-covered surfaces and by experimental analysis of the ice melting process. This involves a combination of ice mechanical stress activation and heating through the initially formed water/ice front. Possible Joule effects due to ohmic losses in the IDTs have been discarded, monitoring local temperature variations during SAW activation at and out of resonance conditions.
May, 2023 · DOI: 10.1002/admt.202300263
Química de Superficies y Catálisis
The Need for Flexible Chemical Synthesis and How Dual-Function Materials Can Pave the Way
Merkouri, LP; Paksoy, AI; Reina, TR; Duyar, MSACS Catalysis, 13 (2023) 7230-7242 DOI: 10.1021/acscatal.3c00880
Abstract
Since climate change keeps escalating, it is imperativethat theincreasing CO2 emissions be combated. Over recent years,research efforts have been aiming for the design and optimizationof materials for CO2 capture and conversion to enable acircular economy. The uncertainties in the energy sector and the variationsin supply and demand place an additional burden on the commercializationand implementation of these carbon capture and utilization technologies.Therefore, the scientific community needs to think out of the boxif it is to find solutions to mitigate the effects of climate change.Flexible chemical synthesis can pave the way for tackling market uncertainties.The materials for flexible chemical synthesis function under a dynamicoperation, and thus, they need to be studied as such. Dual-functionmaterials are an emerging group of dynamic catalytic materials thatintegrate the CO2 capture and conversion steps. Hence,they can be used to allow some flexibility in the production of chemicalsas a response to the changing energy sector. This Perspective highlightsthe necessity of flexible chemical synthesis by focusing on understandingthe catalytic characteristics under a dynamic operation and by discussingthe requirements for the optimization of materials at the nanoscale.
May, 2023 · DOI: 10.1021/acscatal.3c00880
Reactividad de Sólidos
Influence of AC fields and electrical conduction mechanisms on the flash-onset temperature: Electronic (BiFeO3) vs. ionic conductors (8YSZ)
Molina-Molina, S; Perejón, A; Pérez-Maqueda, LA; Sánchez-Jiménez, PECeramics International, 49 (2023) 14834-14843 DOI: 10.1016/j.ceramint.2022.06.242
Abstract
This work aims to clarify the influence of AC (up to 50 kHz) vs DC fields on the flash-onset temperature, emphasizing the role of the electrical conduction mechanism. BiFeO3 (BFO) is used as an example of electronic conductor while 8-mol % Yttria-stabilized zirconia (8YSZ) is used as an example of ionic conductor. For 8YSZ, a frequency dependence of the flash-onset temperature and flash-induced heating is observed. This is consistent with the different contributions found in the total electrical response of 8YSZ as characterized by impedance spectroscopy measurements. Estimations based on the blackbody radiation model suggest that 8YSZ samples attain higher temperatures under AC fields due to a more efficient heating. Moreover, a noticeable decrease in the activation energy for the electrical conduction after the flash is triggered is attributed to electronic conduction. Meanwhile, the lack of frequency response and insensitiveness to the type of electrical field found in the case of BFO can be attributed to its mainly electronic bulk conduction.
May, 2023 · DOI: 10.1016/j.ceramint.2022.06.242
Reactividad de Sólidos
Electrical performance of orthotropic and isotropic 3YTZP composites with graphene fillers
Lopez-Pernia, C; Muñoz-Ferreiro, C; Moriche, R; Morales-Rodriguez, A; Gallardo-Lopez, A; Poyato, RJournal of The European Ceramic Society, 43 (2023) 1605-1612 DOI: 10.1016/j.jeurceramsoc.2022.11.068
Abstract
3 mol% yttria tetragonal zirconia polycrystal (3YTZP) composites with orthotropic or isotropic microstructures were obtained incorporating few layer graphene (FLG) or exfoliated graphene nanoplatelets (e-GNP) as fillers. Electrical conductivity was studied in a wide range of contents in two configurations: perpendicular (sigma(perpendicular to)) and parallel (sigma(//)) to the pressing axis during spark plasma sintering (SPS). Isotropic e-GNP composites presented excellent electrical conductivity for high e-GNP contents (sigma(perpendicular to)similar to 3200 S/m and sigma(//) similar to 1900 S/m for 20 vol% e-GNP), consequence of their misoriented distribution throughout the matrix. Optimum electrical performance was achieved in the highly anisotropic FLG composites, with high electrical conductivity for low contents (sigma(perpendicular to) similar to 680 S/m for 5 vol%), percolation threshold below 2.5 vol% FLG and outstanding electrical conductivity for high contents (sigma(perpendicular to) similar to 4000 S/m for 20 vol%), result of the high aspect ratio and low thickness of FLG.
April, 2023 · DOI: 10.1016/j.jeurceramsoc.2022.11.068
Nanotecnología en Superficies y Plasma
Advanced Cellulose-Nanocarbon Composite Films for High-Performance Triboelectric and Piezoelectric Nanogenerators
Gonzalez, J; Ghaffarinejad, A; Ivanov, M; Ferreira, P; Vilarinho, PM; Borras, A; Amorin, H; Wicklein, BNanomaterials, 13 (2023) 1206 DOI: 10.3390/nano13071206
Abstract
Natural polymers such as cellulose have interesting tribo- and piezoelectric properties for paper-based energy harvesters, but their low performance in providing sufficient output power is still an impediment to a wider deployment for IoT and other low-power applications. In this study, different types of celluloses were combined with nanosized carbon fillers to investigate their effect on the enhancement of the electrical properties in the final nanogenerator devices. Cellulose pulp (CP), microcrystalline cellulose (MCC) and cellulose nanofibers (CNFs) were blended with carbon black (CB), carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs). The microstructure of the nanocomposite films was characterized by scanning electron and probe microscopies, and the electrical properties were measured macroscopically and at the local scale by piezoresponse force microscopy. The highest generated output voltage in triboelectric mode was obtained from MCC films with CNTs and CB, while the highest piezoelectric voltage was produced in CNF-CNT films. The obtained electrical responses were discussed in relation to the material properties. Analysis of the microscopic response shows that pulp has a higher local piezoelectric d(33) coefficient (145 pC/N) than CNF (14 pC/N), while the macroscopic response is greatly influenced by the excitation mode and the effective orientation of the crystals relative to the mechanical stress. The increased electricity produced from cellulose nanocomposites may lead to more efficient and biodegradable nanogenerators.
April, 2023 · DOI: 10.3390/nano13071206
Materiales de Diseño para la Energía y Medioambiente
The Role of Protective Surface Coatings on the Thermal Stability of Delithiated Ni-Rich Layered Oxide Cathode Materials
Reissig, F; Ramirez-Rico, J; Placke, TJ; Winter, M; Schmuch, R; Gomez-Martin, ABatteries-Basel, 9 (2023) 245 DOI: 10.3390/batteries9050245
Abstract
To achieve a broader public acceptance for electric vehicles based on lithium-ion battery (LIB) technology, long driving ranges, low cost, and high safety are needed. A promising pathway to address these key parameters lies in the further improvement of Ni-rich cathode materials for LIB cells. Despite the higher achieved capacities and thus energy densities, there are major drawbacks in terms of capacity retention and thermal stability (of the charged cathode) which are crucial for customer acceptance and can be mitigated by protecting cathode particles. We studied the impact of surface modifications on cycle life and thermal stability of LiNi0.90Co0.05Mn0.05O2 layered oxide cathodes with WO3 by a simple sol-gel coating process. Several advanced analytical techniques such as low-energy ion scattering, differential scanning calorimetry, and high-temperature synchrotron X-ray powder diffraction of delithiated cathode materials, as well as charge/discharge cycling give significant insights into the impact of surface coverage of the coatings on mitigating degradation mechanisms. The results show that successful surface modifications of WO3 with a surface coverage of only 20% can prolong the cycle life of an LIB cell and play a crucial role in improving the thermal stability and, hence, the safety of LIBs.
April, 2023 · DOI: 10.3390/batteries9050245
Química de Superficies y Catálisis
Scalable synthesis of 2D Ti2CTx MXene and molybdenum disulfide composites with excellent microwave absorbing performance
Miao, BJ; Cao, YE; Zhu, QS; Nawaz, MA; Ordiozola, JA; Reina, TR; Bai, ZM; Ren, JN; Wei, FCAdvanced Composites and Hybrid Materials, 6 (2023) 61 DOI: 10.1007/s42114-023-00643-2
Abstract
The signal crosstalk and electromagnetic interference (EMI) problems direly need to be resolved in the rapid development of modern microwave communication technology for a better working frequency and transmission power of electronic systems. Where the new absorbing materials such as molybdenum disulfide (MoS2)/titania (TiO2)/Ti2CTx and MoS2/Ti2CTx composites could meet the requirement of "thin, strong, light weight, and wide band" for excellent absorbing performance. In this work, a lighter Ti2CTx material was selected as the matrix, and MoS2 was in-situ grown on Ti2CTx matrix by traditional hydrothermal method and microwave solvothermal method. The fabricated composite exhibited synergic effect of two-dimensional heterostructural interface and double dielectric elements, where a small amount of TiO2 and a certain proportion of MoS2 jointly improve the impedance matching of the composite material. In here, the extreme reflection loss (RLmin) can reach - 54.70 dB (with a frequency of 7.59 GHz, 3.39 mm thickness), and the maximum effective absorption bandwidth (EAB(max)) can reach 4 GHz. Polyethylene glycol 200 was used as the solvent instead of water to make Ti2CTx less oxidized during the composite process, where the microwave heating would attain fast speed, short time, high efficiency, and uniform product. Since, the MoS2/Ti2CTx composite without oxidizing possessed a wider effective absorption bandwidth (EAB) at a thinner thickness, thus resulting in the excellent microwave absorption performance and confirming the validity and rationality of new microwave absorption materials.
April, 2023 · DOI: 10.1007/s42114-023-00643-2
Materiales y Procesos Catalíticos de Interés Ambiental y Energético
High-Performance Photocatalytic H2 Production Using a Binary Cu/ TiO2/SrTiO3 Heterojunction
Gonzalez-Tejero, M; Villachica-Llamosas, JG; Ruiz-Aguirre, A; Colon, GACS Applied Energy Materials, 6 (2023) 4007-4015 DOI: 10.1021/acsaem.3c00219
Abstract
Cu/TiO2/SrTiO3 hybrid structures have been synthesized by the simple impregnation method from Cu/TiO2 and SrTiO3 systems. The structural and surface characterization stated that Cu/TiO2/SrTiO3 composites form an effective covering of SrTiO3 by Cu/TiO2. The heterostructured catalysts lead to an outstanding improved photoactivity for hydrogen production from methanol photoreforming that would be related with the efficient separation of charge pairs favored by the Cu/ TiO2/SrTiO3 heterojunction. The best photoproduction is attained for the 30 wt % SrTiO3 heterojunction showing 81.7 mmol/g H2 after 6 h (leading to an apparent quantum yield of ca 1%), 1.7 times higher than that of bare Cu/TiO2.
April, 2023 · DOI: 10.1021/acsaem.3c00219
Reactividad de Sólidos
Large-scale oxygen-enriched air (OEA) production from polymeric membranes for partial oxycombustion processes
Garcia-Luna, S; Ortiz, C; Chacartegui, R; Perez-Maqueda, LAEnergy, 268 (2023) 126697 DOI: 10.1016/j.energy.2023.126697
Abstract
Partial oxycombustion using Oxygen-Enriched Air (OEA), produced by air-gas separation with polymeric membranes, combined synergistically with CO2 capture technologies, can reduce the overall energy cost of CO2 capture, and it is a potential alternative to conventional CO2 capture technologies. An exhaustive review of polymeric membranes for this application is presented. The best membranes showed permeability values in the 450-25,100 barrer and selectivities higher than 3.6 for large-scale operations. These membranes can produce OEA with oxygen molar concentrations of up to 40% for retrofitting large-scale power plants (similar to 500 MWe) with partial oxycombustion. For OEA production, the polymeric membrane system is more efficient than cryogenic distillation since the specific power consumption of the former is 35.17 kWh/ton OEA. In comparison, that of the latter is 49.57 kWh/ton OEA. This work proposes that the OEA produced by the membranes feed a partial oxycombustion process integrated with calcium looping within a hybrid CO2 capture system. The power con-sumption of the hybrid CO2 capture system proposed here is 29.05% lower than in the case OEA is produced from cryogenic distillation, which justifies the potential interest in using polymeric membranes for OEA production.
April, 2023 · DOI: 10.1016/j.energy.2023.126697
Fotocatálisis Heterogénea: Aplicaciones
Photocatalytic treatment based on TiO2 for a coal mining drainage
Murcia-Mesa, JJ; Patino-Castillo, CG; Rojas-Sarmiento, HA; Navio-Santos, A; Hidalgo-Lopez, MD; Angel-Botero, ARevista Facultad de Ingeniería-Universidad de Antioquia, 107 (2023) 88-101 DOI: 10.17533/udea.redin.20211063
Abstract
The aim of the present work was to evaluate the effectiveness of a heterogeneous photocatalyst based on TiO2 in the treatment of coal mining drainage which contains a variety of heavy metals and high concentration sulfates and sulfides. The photocatalytic behavior of the commercial reference Sigma Aldrich and the different materials synthesized using the Sol-gel methodology with surface modifications using sulfation and fluorination processes were analyzed. To find a possible correlation between the physicochemical properties of photocatalysts and their behavior, a characterization was carried out using X-Ray Diffraction (XRD), X-Ray Fluorescence spectrometry (XRF), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflectance Spectra (UV-Vis DRS), N2 physisorption, X-ray photoelectron spectroscopy (XPS), and particle size analysis. Results indicated that the modification of the TiO2 prepared in the laboratory using sulfation and fluorination allowed the successful control of the physicochemical properties of this oxide. However, commercial TiO2 showed the greatest effectiveness in removing metals such as: Fe, Cu, Cr, and As after a photocatalytic reaction for a maximum of 1 hour under continuous nitrogen flow and a light intensity of 120 W/m2.
April, 2023 · DOI: 10.17533/udea.redin.20211063
Química de Superficies y Catálisis
In-situ DRIFTS steady-state study of CO2 and CO methanation over Ni-promoted catalysts
González-Castaño, M; González-Arias, J; Bobadilla, LF; Ruíz-López, E; Odriozola, JA; Arellano-García, HFuel, 338 (2023) 127241 DOI: 10.1016/j.fuel.2022.127241
Abstract
Promoting the performance of catalytic systems by incorporating small amount of alkali has been proved effective for several reactions whilst controversial outcomes are reported for the synthetic natural gas production. This work studies a series of Ni catalysts for CO2 and CO methanation reactions. In-situ DRIFTS spectroscopy evidenced similar reaction intermediates for all evaluated systems and it is proposed a reaction mechanism based on: i) formate decomposition and ii) hydrogenation of lineal carbonyl species to methane. Compared to bare Ni, the enhanced CO2 methanation rates attained by NiFe/Al and NiFeK/Al systems are associated to promoted formates decomposition into lineal carbonyl species. Also for CO methanation, the differences in the catalysts' performances were associated to the relative concentration of lineal carbonyl species. Under CO methanation conditions and opposing the CO2 methanation results where the incorporation of K delivered promoted catalytic behaviours, worsened CO methanation rates were discerned for the NiFeK/Al system.
April, 2023 · DOI: 10.1016/j.fuel.2022.127241
Materiales y Procesos Catalíticos de Interés Ambiental y Energético
Facile Synthesis of Heterogeneous Indium Nanoparticles for Formate Production via CO2 Electroreduction
Perez-Sequera, AC; Diaz-Perez, MA; Angulo, MAL; Holgado, JP; Serrano-Ruiz, JCNanomaterials, 13 (2023) 3052 DOI: 10.3390/nano13081304
Abstract
In this study, a simple and scalable method to obtain heterogeneous indium nanoparticles and carbon-supported indium nanoparticles under mild conditions is described. Physicochemical characterization by X-ray diffraction (XRD), X-ray photoelectron microscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed heterogeneous morphologies for the In nanoparticles in all cases. Apart from In-0, XPS revealed the presence of oxidized In species on the carbon-supported samples, whereas these species were not observed for the unsupported samples. The best-in-class catalyst (In-50/C-50) exhibited a high formate Faradaic efficiency (FE) near the unit (above 97%) at -1.6 V vs. Ag/AgCl, achieving a stable current density around -10 mA center dot cm(geo)(-2), in a common H-cell. While In-0 sites are the main active sites for the reaction, the presence of oxidized In species could play a role in the improved performance of the supported samples.
April, 2023 · DOI: 10.3390/nano13081304
Química de Superficies y Catálisis
Engineering exsolved catalysts for CO2 conversion
Ali, SA; Safi, M; Merkouri, LP; Soodi, S; Iakovidis, A; Duyar, MS; Neagu, D; Reina, TR; Kousi, KFrontiers in Energy Research, 11 (2023) 1150000 DOI: 10.3389/fenrg.2023.1150000
Abstract
Introduction: Innovating technologies to efficiently reduce carbon dioxide (CO2) emission or covert it into useful products has never been more crucial in light of the urgent need to transition to a net-zero economy by 2050. The design of efficient catalysts that can make the above a viable solution is of essence. Many noble metal catalysts already display high activity, but are usually expensive. Thus, alternative methods for their production are necessary to ensure more efficient use of noble metals.Methods: Exsolution has been shown to be an approach to produce strained nanoparticles, stable against agglomeration while displaying enhanced activity. Here we explore the effect of a low level of substitution of Ni into a Rh based A-site deficienttitanate aiming to investigate the formation of more efficient, low loading noblemetal catalysts.Results: We find that with the addition of Ni in a Rh based titanate exsolution is increased by up to similar to 4 times in terms of particle population which in turn results in up to 50% increase in its catalytic activity for CO2 conversion.Discussion: We show that this design principle not only fulfills a major research need in the conversion of CO2 but also provides a step-change advancement in the design and synthesis of tandem catalysts by the formation of distinct catalytically active sites.
March, 2023 · DOI: 10.3389/fenrg.2023.1150000
Materiales Coloidales
Persistent Luminescence Zn2GeO4:Mn2+Nanoparticles Functionalized with Polyacrylic Acid: One-Pot Synthesis and Biosensing Applications
Calderon-Olvera, RM; Arroyo, E; Jankelow, AM; Bashir, R; Valera, E; Ocana, M; Becerro, AIACS Applied Materials & Interfaces, 15 (2023) 20613-20624 DOI: 10.1021/acsami.2c21735
Abstract
Zinc germanate doped with Mn2+ (Zn2GeO4:Mn2+) is known to be a persistent luminescence green phosphor with potential applications in biosensing and bioimaging. Such applications demand nanoparticulated phosphors with a uniform shape and size, good dispersibility in aqueous media, high chemical stability, and surfacefunctionalization. These characteristics could be major bottlenecks and hence limit their practical applications. This work describes a one-pot, microwave-assisted hydrothermal method to synthesize highly uniform Zn2GeO4:Mn2+ nanoparticles (NPs) using polyacrylic acid (PAA) as an additive. A thorough characterization of the NPs showed that the PAA molecules were essential to realizing uniform NPs as they were responsible for the ordered aggregation of their building blocks. In addition, PAA remained attached to the NPs surface, which conferred high colloidal stability to the NPs through electrostatic and steric interactions, and provided carboxylate groups that can act as anchor sites for the eventual conjugation of biomolecules to the surface. In addition, it was demonstrated that the as-synthesized NPs were chemically stable for, at least, 1 week in phosphate buffer saline (pH range = 6.0-7.4). The luminescence properties of Zn2GeO4 NPs doped with different contents of Mn2+ (0.25-3.00 mol %) were evaluated to find the optimum doping level for the highest photoluminescence (2.50% Mn) and the longest persistent luminescence (0.50% Mn). The NPs with the best persistent luminescence properties were photostable for at least 1 week. Finally, taking advantage of such properties and the presence of surface carboxylate groups, the Zn2GeO4:0.50%Mn2+ sample was successfully used to develop a persistent luminescence-based sandwich immunoassay for the autofluorescence-free detection of interleukin-6 in undiluted human serum and undiluted human plasma samples. This study demonstrates that our persistent Mndoped Zn2GeO4 nanophosphors are ideal candidates for biosensing applications.
March, 2023 · DOI: 10.1021/acsami.2c21735
Materiales de Diseño para la Energía y Medioambiente
Effect of Mo and W interlayers on microstructure and mechanical properties of Si3N4-nickel-base superalloy joints
Singh, M; Fernandez, JM; Asthana, R; Ramirez-Rico, J; Valera-Feria, FMInternational Journal of Applied Ceramic Technology, 20(2) (2023) 987-994 DOI: 10.1111/ijac.14266
Abstract
Si3N4/nickel-base superalloy (Inconel-625) and Si3N4/Si3N4 joints with refractory metal (W and Mo) interlayers were vacuum brazed using a Ti-active braze Cu-ABA (92.75Cu-3Si-2Al-2.25Ti) at 1317 K for 30 min with the following interlayered arrangements: Si3N4/Mo/W/Inconel and Si3N4/Mo/W/Si3N4. The joints exhibited Ti segregation at the Si3N4/Cu-ABA interface, elemental interdiffusion across the joint interfaces, and sound metallurgical bonding. Knoop microhardness profiles revealed hardness gradients across the joints that mimicked the interlayered arrangement. The compressive shear strength of Si3N4/Si3N4 joints both with and without W and Mo layers was similar to 142 MPa but the strength of Si3N4/Inconel joints increased from similar to 9 MPa for directly bonded joints without interlayers to 53.5 MPa for joints with Mo and W interlayers.
March, 2023 · DOI: 10.1111/ijac.14266
Materiales Ópticos Multifuncionales - Materiales Coloidales
Oxidation and coordination states assumed by transition metal dopants in an invert ultrabasic silicate glass
Zandona, A; Castaing, V; Shames, AI; Helsch, G; Deubener, J; Becerro, AI; Allix, M; Goldstein, AJournal of Non-Crystalline Solids, 603 (2023) 122094 DOI: 10.1016/j.jnoncrysol.2022.122094
Abstract
An ultrabasic invert silicate glass (46SiO2.11Na2O.21CaO.22BaO, optical basicity index equal to 0.71) was synthesized (O2 atmosphere) and used as host for various transition metal dopants. Optical absorption, emission and electron paramagnetic spectroscopies were used to characterize oxidation and coordination states. Some of the dopants displayed only their maximal oxidation state (Ti4+, V5+, Cr6+, Mo6+ and W6+). Others exhibited mixed valences: (i) Mn3+ was the dominant species, alongside Mn2+ and Mn5+; (ii) stable Fe3+ prevailed, although some Fe2+ was preliminarily suggested by the absorption spectrum; (iii) Co3+ probably accompanied the dominant Co2+ tetrahedral oxide complex; (iv) like in "conventional" silicate glasses, only Ni2+ was detected, though simultaneously located in tetrahedral and octahedral sites (somewhat distorted); (v) Cu+ was surprisingly identified alongside the expected 6-fold coordinated Cu2+. Drastic reduction of the oxygen content in the melting atmosphere led to conversion of Cr6+ to Cr3+, despite the extreme basicity of the host.
March, 2023 · DOI: 10.1016/j.jnoncrysol.2022.122094
Química de Superficies y Catálisis
Functionalized Biochars as Supports for Ru/C Catalysts: Tunable and Efficient Materials for γ-Valerolactone Production
Bounoukta, CE; Megias-Sayago, C; Navarro, JC; Ammari, F; Ivanova, S; Centeno, MANanomaterials, 13 (2023) 1129 DOI: 10.3390/nano13061129
Abstract
Cotton stalks-based biochars were prepared and used to synthetize Ru-supported catalysts for selective production of gamma-valerolactone from levulinic acid in aqueous media. Different biochars' pre-treatments (HNO3, ZnCl2, CO2 or a combination of them) were carried out to activate the final carbonaceous support. Nitric acid treatment resulted in microporous biochars with high surface area, whereas the chemical activation with ZnCl2 substantially increases the mesoporous surface. The combination of both treatments led to a support with exceptional textural properties allowing the preparation of Ru/C catalyst with 1422 m(2)/g surface area, 1210 m(2)/g of it being a mesoporous surface. The impact of the biochars' pre-treatments on the catalytic performance of Ru-based catalysts is fully discussed.
March, 2023 · DOI: 10.3390/nano13061129
Nanotecnología en Superficies y Plasma
Microstructural Characterization and Self-Propagation Properties of Reactive Al/Ni Multilayers Deposited onto Wavelike Surface Morphologies: Influence on the Propagation Front Velocity
Camposano, YHS; Bartsch, H; Matthes, S; Oliva-Ramirez, M; Jaekel, K; Schaaf, PPhysica Status Solidi A-Applications and Materials Science (2023) 2200765 DOI: 10.1002/pssa.202200765
Abstract
Reactive multilayer systems are nanostructures of great interest for various technological applications because of their high energy release rate during the self-propagating reaction of their components. Therefore, many efforts are aimed at controlling the propagation velocity of these reactions. Herein, reactive multilayer systems of Al/Ni in the shape of free-standing foils with a wavelike surface morphology prepared by using sacrificial substrates with well-aligned waves are presented and the propagation of the reaction along different directions of the reproduced waves is analyzed. During the ignition test, the propagation front is recorded with a high-speed camera, and the maximum temperature is measured using a pyrometer. The propagation of the reaction is favored in the direction of the waves, which points out the influence of the anisotropy generated by this morphology and how it affects the propagation dynamics and the resulting microstructure. Furthermore, compared to their counterparts fabricated on flat substrates, these reactive multilayers with wavelike morphology exhibit a remarkable reduction in the propagation velocity of the reaction of about 50%, without significantly affecting the maximum temperature registered during the reaction.
March, 2023 · DOI: 10.1002/pssa.202200765
Materiales y Procesos Catalíticos de Interés Ambiental y Energético
Revealing the Impact of Different Iron-Based Precursors on the ‘Catalytic’ Graphitization for Synthesis of Anode Materials for Lithium Ion Batteries
Frankenstein, L; Glomb, P; Ramirez-Rico, J; Winter, M; Placke, T; Gomez-Martin, AChemelectrochem, 10 (2023) e202201073 DOI: 10.1002/celc.202201073
Abstract
Low cost and environmentally friendly production of graphite anodes from naturally available biomass resources is of great importance to satisfy the increasing material demand for lithium ion batteries. Herein, graphitization of coffee ground was performed using four different iron-based activating additives, including iron (III) chloride, iron (III) nitrate, iron (III) oxide and pure iron, following either a wet or a dry mixing approach. The structural development regarding the type of activator used and the impact on the corresponding electrochemical performance are systematically investigated. A maximum degree of graphitization between 55 and 74 % (as determined by Raman spectroscopy) is attained using iron (III) chloride and iron powder, respectively. The graphitic anode material synthesized using iron powder reached a maximum reversible capacity of approximate to 320 mAh g(-1) at a rate of 0.1 C. This study provides significant insights into the impact of activators on the design of synthetic graphite from renewable sources.
March, 2023 · DOI: 10.1002/celc.202201073
Nanotecnología en Superficies y Plasma
Improved strain engineering of 2D materials by adamantane plasma polymer encapsulation
Carrascoso, F; Li, H; Obrero-Perez, JM; Aparicio, FJ; Borras, A; Island, JO; Barranco, A; Castellanos-Gómez, ANPJ 2D Materials and Applications, 7 (2023) 24 DOI: 10.1038/s41699-023-00393-1
Abstract
Two-dimensional materials present exceptional crystal elasticity and provide an ideal platform to tune electrical and optical properties through the application of strain. Here we extend recent research on strain engineering in monolayer molybdenum disulfide using an adamantane plasma polymer pinning layer to achieve unprecedented crystal strains of 2.8%. Using micro-reflectance spectroscopy, we report maximum strain gauge factors of -99.5 meV/% and -63.5 meV/% for the A and B exciton of monolayer MoS2, respectively, with a 50 nm adamantane capping layer. These results are corroborated with photoluminescence and Raman measurements on the same samples. Taken together, our results indicate that adamantane polymer is an exceptional capping layer to transfer substrate-induced strain to a 2D layer and achieve higher levels of crystal strain.
March, 2023 · DOI: 10.1038/s41699-023-00393-1
Materiales Ópticos Multifuncionales
Origin of anomalously stabilizing ice layers on methane gas hydrates near rock surface
Li, Y; Corkery, RW; Carretero-Palacios, S; Berland, K; Esteso, V; Fiedler, J; Milton, KA; Brevik, I; Bostrom, MPhysical Chemistry Chemical Physics, 25 (2023) 6636-6652 DOI: 10.1039/d2cp04883c
Abstract
Gas hydrates (GHs) in water close to freezing temperatures can be stabilised via the formation of ice layers. In a recent work [Bostrom et al., Astron. Astrophys., A54, 650, 2021], it was found that a surface region with partial gas dilution could be essential for obtaining nano- to micron-sized anomalously stabilizing ice layers. In this paper, it is demonstrated that the Casimir-Lifshitz free energy in multi-layer systems could induce thinner, but more stable, ice layers in cavities than those found for gas hydrates in a large reservoir of cold water. The thickness and stability of such ice layers in a pore filled with cold water could influence the leakage of gas molecules. Additional contributions, e.g. from salt-induced stresses, can also be of importance, and are briefly discussed.
March, 2023 · DOI: 10.1039/d2cp04883c
Fotocatálisis Heterogénea: Aplicaciones
Boosting the photocatalytic properties of NaTaO3 by coupling with AgBr
Puga, F; Navío, JA; Hidalgo, MCPhotochemical & Photobiological Sciences, 22 (2023) 549-566 DOI: 10.1007/s43630-022-00334-9
Abstract
AgBr/NaTaO3 composites, with different molar % of NaTaO3 (Br/NTO(X%)), have been synthesized by simple precipitation methods; bare NaTaO3 was synthesized by hydrothermal procedure, while AgBr was synthesized by a precipitation procedure using cetyl-tri-methyl-ammonium bromide (CTAB) and AgNO3. Samples have been characterized by X-ray diffraction (XRD), N2 adsorption, UV–vis diffuse reflectance spectroscopy (DRS), Fourier-transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Photocatalytic activity of the as-prepared photo-catalysts was evaluated through photocatalytic degradation of rhodamine B (RhB), methyl orange (MO) and caffeic acid (CAFA) under UV and visible illumination. Single AgBr material and Br/NTO(X%) composites displayed the ability to absorb light in the visible region, while NaTaO3 is only photoactive under UV irradiation. Based on the position of conduction and valence bands of AgBr and NaTaO3, the heterojunction between these two photo-catalysts corresponds to a type II junction. In the case of photocatalytic degradation of RhB and CAFA, Br/NTO(x%) composites have highest photocatalytic activity than that obtained by both parental materials under the same operational conditions. AgBr and Br/NTO(x%) composites achieve a fast degradation of MO, together with a considerable adsorption capacity, attributed to the presence of a remaining amount of residual CTAB on the AgBr surface. In summary, coupling AgBr with NaTaO3 improves the photocatalytic activity under both UV and visible illumination with respect to the parental components, but the performance of the composites is highly dependent on the type of substrate to be degraded and the illumination conditions.
March, 2023 · DOI: 10.1007/s43630-022-00334-9
Materiales de Diseño para la Energía y Medioambiente
Bio-based lacquers from industrially processed tomato pomace for sustainable metal food packaging
Benitez, JJ; Ramirez-Pozo, MC; Duran-Barrantes, MM; Heredia, A; Tedeschi, G; Ceseracciu, L; Guzman-Puyol, S; Marrero-López, D; Becci, A; Amato, A; Heredia-Guerrero, JAJournal of Cleaner Production, 386 (2023) 1356836 DOI: 10.1016/j.jclepro.2022.135836
Abstract
Bio-based lacquers prepared from an underutilized tomato processing residue such as pomace have been investigated as sustainable alternatives to bisphenol A (BPA)-based coatings for metal food packaging. The fabrication methodology consisted of a two-step process: spray-coating of a paste of the lipid fraction of tomato pomace with a mixture ethanol:H2O (3:1, v:v) on common metal substrates, used for food canning, such as aluminum (Al), chromium-coated tin-free steel (TFS), and electrochemically tin-plated steel (ETP), followed by the self melt-polycondensation of such lipid fraction. The polymerization reaction was conducted at 200 degrees C for different times (10, 20, 30, 40, 50, and 60 min) and was monitored by specular infrared spectroscopy, resulting in maximum degrees of esterification of-92% for Al and-85% for TFS and ETP substrates. The anticorrosion performance of the coatings was studied by electrochemical impedance spectroscopy at different immersion times (time intervals of 2-5 h during an overall stability test up to 170 h) in an aqueous solution of 1 wt% NaCl. The degree of polymerization and the physical properties of the coatings showed a strong dependence on the metal substrate used. In general, the best results were found for tomato pomace-based lacquers applied on aluminum, achieving higher mechanical strength (critical load of 1739 +/- 198 mN for Al, 1078 +/- 31 mN for ETP, and 852 +/- 206 mN for TFS), hydrophobicity (water contact angle-95 degrees for Al,-91 degrees for ETP, and-88 degrees for TFS), and improved anticorrosion performance (coating resistance of 0.7 M omega cm2 after 170 h of immersion for Al, 0.7 M omega cm2 after 70 h of immersion for TFS, and negligible coating resistance for ETP). In view of the technical innovation proposed in the present paper, the estimation of the environmental sustainability of the process has been considered relevant to fit the circular economy target. For this purpose, a life cycle analysis (LCA) was applied to the overall process, revealing multiple advantages for both the environment and human health.
February, 2023 · DOI: 10.1016/j.jclepro.2022.135836
Reactividad de Sólidos
Structural, Vibrational, and Magnetic Characterization of Orthoferrite LaFeO3 Ceramic Prepared by Reaction Flash Sintering
Manchon-Gordon, AF; Sanchez-Jimenez, PE; Blazquez, JS; Perejon, A; Perez-Maqueda, LAMaterials, 16 (2023) 1019 DOI: 10.3390/ma16031019
Abstract
LaFeO3 perovskite ceramics have been prepared via reaction flash technique using Fe2O3 and La2O3 as precursors. The obtained pellets have been investigated using several techniques. The formation of LaFeO3 has been clearly confirmed by X-ray diffraction. The scanning electron microscopy micrographs have shown the microporous character of the obtained pellets due to the low temperature and dwell time used in the synthesis process (10 min at 1173 K). The orthorhombic-rhombohedral phase transition has been observed at approximately 1273 K in differential thermal analysis measurements, which also allows us to determine the Neel temperature at 742 K. The fitted Mossbauer spectra exposed the presence of a single sextet ascribed to the Fe+3 ions in the tetrahedral site. Finally, magnetic measurements at room temperature indicate the antiferromagnetic character of the sample.
February, 2023 · DOI: 10.3390/ma16031019
Nanotecnología en Superficies y Plasma
Photoelectrochemical Water Splitting with ITO/WO3/BiVO4/CoPi Multishell Nanotubes Enabled by a Vacuum and Plasma Soft- Template Synthesis
Gil-Rostra, J; Castillo-Seoane, J; Guo, Q; Sobrido, ABJ; Gonzalez-Elipe, AR; Borras, AACS Applied Materials & Interfaces, 15 (2023) 9250-9262 DOI: 10.1021/acsami.2c19868
Abstract
A common approach for the photoelectrochemical (PEC) splitting of water relies on the application of WO3 porous electrodes sensitized with BiVO4 acting as a visible photoanode semiconductor. In this work, we propose a new architecture of photoelectrodes consisting of supported multishell nanotubes (NTs) fabricated by a soft-template approach. These NTs are formed by a concentric layered structure of indium tin oxide (ITO), WO3, and BiVO4, together with a final thin layer of cobalt phosphate (CoPi) co-catalyst. The photoelectrode manufacturing procedure is easily implementable at a large scale and successively combines the thermal evaporation of single crystalline organic nanowires (ONWs), the magnetron sputtering deposition of ITO and WO3, and the solution dripping and electrochemical deposition of, respectively, BiVO4 and CoPi, plus the annealing in air under mild conditions. The obtained NT electrodes depict a large electrochemically active surface and outperform the efficiency of equivalent planar-layered electrodes by more than one order of magnitude. A thorough electrochemical analysis of the electrodes illuminated with blue and solar lights demonstrates that the characteristics of the WO3/BiVO4 Schottky barrier heterojunction control the NT electrode efficiency, which depended on the BiVO4 outer layer thickness and the incorporation of the CoPi electrocatalyst. These results support the high potential of the proposed soft-template methodology for the large-area fabrication of highly efficient multishell ITO/WO3/BiVO4/CoPi NT electrodes for the PEC splitting of water.
February, 2023 · DOI: 10.1021/acsami.2c19868
Materiales Semiconductores para la Sostenibilidad
Non-sticky interactions
Esteso, VNature Physics, 19 (2023) 161-162 DOI: 10.1038/s41567-022-01935-y
Abstract
Quantum mechanical fluctuations of the electromagnetic field in a vacuum between two close together objects result in an attractive force. Now, it has been experimentally shown that by exploiting a similar repulsive interaction, attraction between objects can be modulated simply by tuning temperature.
February, 2023 · DOI: 10.1038/s41567-022-01935-y
Materiales Avanzados
Effect of L-Glutamic Acid on the Composition and Morphology of Nanostructured Calcium Phosphate as Biomaterial
Takabait, F; Martinez-Martinez, S; Mahtout, L; Graba, Z; Sanchez-Soto, PJ; Perez-Villarejo, LMaterials, 16 (2023) 1262 DOI: 10.3390/ma16031262
Abstract
Calcium phosphate (CaP) with several chemical compositions and morphologies was prepared by precipitation using aqueous solutions of L-Glutamic acid (H(2)G) and calcium hydroxide, both mixed together with an aqueous solution (0.15 M) of phosphoric acid. Plate-shaped dicalcium phosphate dihydrate (brushite) particles were obtained and identified at a lower concentration of the solution of the reactants. The Ca/P ratio deduced by EDS was similar to 1, as expected. The nanoscale dimension of carbonate apatite and amorphous calcium phosphate, with variable Ca/P ratios, were revealed by X-ray diffraction (XRD) and scanning electron microscopy and energy dispersive X-ray spectroscopy analysis (SEM-EDS). They were characterized in medium and high concentrations of calcium hydroxide (0.15 M and 0.20 M). The equilibria involved in all the reactions in aqueous solution were determined. The thermodynamic calculations showed a decrease in the amount of chelate complexes with an increase in pH, being the opposite of [CaPO4-] and [CaHG(+)]. This fluctuation showed an evident influence on the morphology and polymorphism of CaP particles obtained under the present experimental conditions, with potential use as a biomaterial.
February, 2023 · DOI: 10.3390/ma16031262
Materiales Ópticos Multifuncionales
Determination of the optical constants of ligand-free organic lead halide perovskite quantum dots
Rubino, A; Lozano, G; Calvo, ME; Miguez, HNanoscale, 15 (2023) 2553-2560 DOI: 10.1039/d2nr05109e
Abstract
Precise knowledge of the optical constants of perovskite lead halide quantum dots (QDs) is required to both understand their interaction with light and to rationally design and optimize the devices based on them. However, their determination from colloidal nanocrystal suspensions, or films made out of them, remains elusive, as a result of the difficulty in disentangling the optical constants of the organic capping ligands and those of the semiconductor itself. In this work, we extract the refractive index and extinction coefficient of ligand-free methylammonium lead iodide (MAPbI(3)) and bromide (MAPbBr(3)) nanocrystals. In order to prevent the use of organic ligands in the preparation, we follow a scaffold assisted synthetic procedure, which yields a composite film of high optical quality that can be independently and precisely characterized and modelled. In this way, the contribution of the guest nanocrystals can be successfully discriminated from that of the host matrix. Using a Kramers-Kronig consistent dispersion model along with an effective medium approximation, it is possible to derive the optical constants of the QDs by fitting the spectral dependence of light transmitted and reflected at different angles and polarizations. Our results indicate a strong dependence of the optical constants on the QD size. Small nanocrystals show remarkably large values of the extinction coefficient compared to their bulk counterparts. This analysis opens the door to the rigorous modelling of solar cells and light-emitting diodes with active layers based on perovskite QDs.
February, 2023 · DOI: 10.1039/d2nr05109e
Materiales Coloidales
Europium doped-double sodium bismuth molybdate nanoparticles as contrast agents for luminescence bioimaging and X-ray computed tomography
Calderon-Olvera, RM; Nunez, NO; Gonzalez-Mancebo, D; Monje-Moreno, JM; Munoz-Rui, MJ; Gomez-Gonzalez, E; Arroyo, E; Torres-Herrero, B; De la Fuente, JM; Ocaña, MInorganic Chemistry Frontiers, 10(11) (2023) 3202 DOI: 10.1039/D2QI02664C
Abstract
A one-pot method for the synthesis of uniform Eu3+-doped NaBi(MoO4)2 nanoparticles with an ellipsoidal shape and tetragonal crystal structure functionalized with polyacrylic acid is reported for the first time in the literature. The method is based on a homogeneous precipitation reaction from solutions in an ethylene glycol/water medium containing appropriate bismuth, sodium, and molybdate precursors and polyacrylic acid. The luminescence properties (excitation and emission spectra and luminescence lifetime) of such nanoparticles are evaluated for different Eu3+ doping levels, finding an intense red emission for all synthesized samples. The X-ray attenuation properties of the nanoparticles have been also analyzed, which were found to be better than those of a commercially computed tomography contrast agent (iohexol). The dispersibility of the nanoparticles in a physiological medium was also analyzed, finding that they could be well dispersed in a 2-N-morpholinoethanesulfonic acid monohydrate medium (pH = 6.5). Finally, the cell viability of such a phosphor has been analyzed using MIA-PaCa-2 cells and its in vivo toxicity has been evaluated using the nematode Caenorhabditis elegans model finding no significant toxicity in both cases up to a nanoparticle concentration of 100 μg mL−1, which is within the range required for most in vivo applications. The developed Eu3+-doped NaBi(MoO4)2 nanoparticles are, therefore, excellent candidates for their use as bimodal probes for luminescence imaging and X-ray computed tomography.
February, 2023 · DOI: 10.1039/D2QI02664C
Reactividad de Sólidos
Determination of the activation energy under isothermal conditions: revisited
Arcenegui-Troya, J; Sanchez-Jimenez, PE; Perejon, A; Perez-Maqueda, LAJournal of Thermal Analysis and Calorimetry, 148 (2023) 1679-1686 DOI: 10.1007/s10973-022-11728-3
Abstract
The kinetic analysis of solid-state processes aims at obtaining fundamental information that can be used for predicting the time evolution of a process within a wide range of conditions. It is an extended belief that the determination of the kinetic parameters from the analysis of curves recorded under isothermal conditions is strongly conditioned by the kinetic model used to fit the experimental data. Thus, much effort is devoted to finding the model that truly describes a process in order to calculate the kinetic parameters with accuracy. In this work, we demonstrate that the value of activation energy determined from kinetic analysis of isothermal curves is independent of the kinetic model used to fit the experimental data and, taking advantage of the underlying reason for this, a method for determining the activation energy with two isothermal curves is proposed.
February, 2023 · DOI: 10.1007/s10973-022-11728-3
Nanotecnología en Superficies y Plasma
Incorporation of a Metal Catalyst for the Ammonia Synthesis in a Ferroelectric Packed-Bed Plasma Reactor: Does It Really Matter?
Navascues, P; Garrido-Garcia, J; Cotrino, J; Gonzalez-Elipe, AR; Gomez-Ramirez, AACS Sustainable Chemistry & Engineering, 11 (2023) 3621-3632 DOI: 10.1021/acssuschemeng.2c05877
Abstract
Plasma-catalysis has been proposed as a potential alternative for the synthesis of ammonia. Studies in this area focus on the reaction mechanisms and the apparent synergy existing between processes occurring in the plasma phase and on the surface of the catalytic material. In the present study, we approach this problem using a parallel-plate packed-bed reactor with the gap between the electrodes filled with pellets of lead zirconate titanate (PZT), with this ferroelectric material modified with a coating layer of alumina (i.e., Al2O3/PZT) and the same alumina layer incorporating ruthenium nanoparticles (i.e., Ru-Al2O3/PZT). At ambient temperature, the electrical behavior of the ferroelectric packed-bed reactor differed for these three types of barriers, with the plasma current reaching a maximum when using Ru-Al2O3/PZT pellets. A systematic analysis of the reaction yield and energy efficiency for the ammonia synthesis reaction, at ambient temperature and at 190 °C and various electrical operating conditions, has demonstrated that the yield and the energy efficiency for the ammonia synthesis do not significantly improve when including ruthenium particles, even at temperatures at which an incipient catalytic activity could be inferred. Besides disregarding a net plasma-catalysis effect, reaction results highlight the positive role of the ferroelectric PZT as moderator of the discharge, that of Ru particles as plasma hot points, and that of the Al2O3 coating as a plasma cooling dielectric layer.
February, 2023 · DOI: 10.1021/acssuschemeng.2c05877
Química de Superficies y Catálisis
Flexible NiRu Systems for CO2 Methanation: From Efficient Catalysts to Advanced Dual-Function Materials
Merkouri, LP; Martin-Espejo, JL; Bobadilla, LF; Odriozola, JA; Duyar, MS; Reina, TRNanomaterials, 13 (2023) 506 DOI: 10.3390/nano13030506
Abstract
CO2 emissions in the atmosphere have been increasing rapidly in recent years, causing global warming. CO2 methanation reaction is deemed to be a way to combat these emissions by converting CO2 into synthetic natural gas, i.e., CH4. NiRu/CeAl and NiRu/CeZr both demonstrated favourable activity for CO2 methanation, with NiRu/CeAl approaching equilibrium conversion at 350 degrees C with 100% CH4 selectivity. Its stability under high space velocity (400 L center dot g(-1)center dot h(-1)) was also commendable. By adding an adsorbent, potassium, the CO2 adsorption capability of NiRu/CeAl was boosted, allowing it to function as a dual-function material (DFM) for integrated CO2 capture and utilisation, producing 0.264 mol of CH4/kg of sample from captured CO2. Furthermore, time-resolved operando DRIFTS-MS measurements were performed to gain insights into the process mechanism. The obtained results demonstrate that CO2 was captured on basic sites and was also dissociated on metallic sites in such a way that during the reduction step, methane was produced by two different pathways. This study reveals that by adding an adsorbent to the formulation of an effective NiRu methanation catalyst, advanced dual-function materials can be designed.
February, 2023 · DOI: 10.3390/nano13030506
Reactividad de Sólidos
Flexible Kinetic Model Determination of Reactions in Materials under Isothermal Conditions
Arcenegui-Troya, J; Perejón, A; Sánchez-Jiménez, PE; Pérez-Maqueda, LAMaterials, 16 (2023) 1851 DOI: 10.3390/ma16051851
Abstract
Kinetic analysis remains a powerful tool for studying a large variety of reactions, which lies at the core of material science and industry. It aims at obtaining the kinetic parameters and model that best describe a given process and using that information to make reliable predictions in a wide range of conditions. Nonetheless, kinetic analysis often relies on mathematical models derived assuming ideal conditions that are not necessarily met in real processes. The existence of nonideal conditions causes large modifications to the functional form of kinetic models. Therefore, in many cases, experimental data hardly obey any of these ideal models. In this work, we present a novel method for the analysis of integral data obtained under isothermal conditions without any type of assumption about the kinetic model. The method is valid both for processes that follow and for those that do not follow ideal kinetic models. It consists of using a general kinetic equation to find the functional form of the kinetic model via numerical integration and optimization. The procedure has been tested both with simulated data affected by nonuniform particle size and experimental data corresponding to the pyrolysis of ethylene-propylene-diene.
February, 2023 · DOI: 10.3390/ma16051851
Fotocatálisis Heterogénea: Aplicaciones
CO2 Methanation over Nickel Catalysts: Support Effects Investigated through Specific Activity and Operando IR Spectroscopy Measurements
Gonzalez-Rangulan, VV; Reyero, I; Bimbela, F; Romero-Sarria, F; Daturi, M; Gandia, LMCatalysts, 13 (2023) 448 DOI: 10.3390/catal13020448
Abstract
Renewed interest in CO2 methanation is due to its role within the framework of the Power-to-Methane processes. While the use of nickel-based catalysts for CO2 methanation is well stablished, the support is being subjected to thorough research due to its complex effects. The objective of this work was the study of the influence of the support with a series of catalysts supported on alumina, ceria, ceria-zirconia, and titania. Catalysts' performance has been kinetically and spectroscopically evaluated over a wide range of temperatures (150-500 degrees C). The main results have shown remarkable differences among the catalysts as concerns Ni dispersion, metallic precursor reducibility, basic properties, and catalytic activity. Operando infrared spectroscopy measurements have evidenced the presence of almost the same type of adsorbed species during the course of the reaction, but with different relative intensities. The results indicate that using as support of Ni a reducible metal oxide that is capable of developing the basicity associated with medium-strength basic sites and a suitable balance between metallic sites and centers linked to the support leads to high CO2 methanation activity. In addition, the results obtained by operando FTIR spectroscopy suggest that CO2 methanation follows the formate pathway over the catalysts under consideration.
February, 2023 · DOI: 10.3390/catal13020448
Materiales de Diseño para la Energía y Medioambiente
Improved stability of design clay minerals at high temperature: A comparison study with natural ones
Osuna, FJ; Chaparro, JR; Pavon, E; Alba, MDCeramics International, 49 (2023) 5279-5291 DOI: 10.1016/j.ceramint.2022.10.046
Abstract
Clay minerals are ceramics materials that are involved in a wide range of economic uses. But, their structure and composition are modified by heating and, consequently, compromise their final applications. The actual tem-peratures at which changes occur vary greatly from one group to another group and even for different specimens within a given group. The aim of this research has been to evaluate the thermal behaviour of a set of design swelling micas, Na-Mica -n (Mn) and compare them with a set of natural smectites. All samples were heated in the range 200 degrees C to 1000 degrees C; afterwards, they were rehydrated thorough water suspension (0.4% wt). The results have shown that swelling micas have better property of hydration/dehydration than natural clay minerals and those with higher layer charge exhibited higher rehydration ability and dehydration temperature.
February, 2023 · DOI: 10.1016/j.ceramint.2022.10.046
Química de Superficies y Catálisis
Low CO2 hydrogen streams production from formic acid through control of the reaction pH
Santos, JL; Lopez, ER; Ivanova, S; Monzon, A; Centeno, MA; Odriozola, JAChemical Engineering Journal, 455 (2023) 140645 DOI: 10.1016/j.cej.2022.140645
Abstract
There are multiple factors that influence the catalyst performance in the reaction of formic acid dehydrogena-tion: the nature of catalyst and/or support, the used solvent and reaction variables such as temperature, time, formic acid concentration, presence/absence of formates and pH of the solution. This work evaluates a series of important parameters like the influence of the pH by itself, the influence of the nature of used alkali agents and the effect of direct formate addition as reactive on hydrogen production via formic acid dehydrogenation over a commercially available catalyst. The catalytic performance appears to depend on the ionic radius of the cations of the used base which reflects consequently on the hydrogen selectivity. The best base to be used must have lower hydrated cationic radii and a starting pH around 4 to achieve important hydrogen selectivity for medium term formic acid conversion.
February, 2023 · DOI: 10.1016/j.cej.2022.140645
Química de Superficies y Catálisis
Spinel ferrite catalysts for CO2 reduction via reverse water gas shift reaction
Navarro, JC; Hurtado, C; Gonzalez-Castano, M; Bobadilla, LF; Ivanova, S; Cumbrera, FL; Centeno, MA; Odriozola, JAJournal of CO2 Utilization, 68 (2023) 102356 DOI: 10.1016/j.jcou.2022.102356
Abstract
The production of CO via Reverse Water Gas Shift (RWGS) reaction is a suitable route for CO2 valorization. In this study a series of modified spinels AB2O4 (A site symbolscript Ni, Zn and Cu and B symbolscript are investigated as RWGS catalysts and their structure-to-function relationships derived from the changes on the A-site cation are ratio-nalized. For all ferrite systems, the RWGS reaction the process main activity and selectivity is governed by the B -site cation, but the variations on the A-site metals determines catalysts' structural features and stability in the reaction. Among the catalyst series, superior RWGS performance displayed the ferrites modified with Cu and Ni associated to the greater oxygen vacancy population for those spinels enabled by the partial allocation on symbolscript cations into the tetrahedral sites.
February, 2023 · DOI: 10.1016/j.jcou.2022.102356
Fotocatálisis Heterogénea: Aplicaciones
Effect of phenol concentration on the photocatalytic performance of ZnO nanoparticles
Gonzalez, RL; De la Fuente, O; Garcia, RL; Lopez, MDU; Owen, PQ; Lopez, MCH; Lemus, MAAJournal of Chemical Technology and Biotechnology, 98(8) (2023) 1826-1836 DOI: 10.1002/jctb.7334
Abstract
BACKGROUND: Phenol and its derivatives are considered toxic compounds, even at low concentrations. Their accumulation in water effluents has become a serious problem that could be resolved by using zinc oxide (ZnO)-based photocatalysts.RESULTS: ZnO nanoparticles were synthesized through the precipitation method, using zinc nitrate and sodium carbonate as reagents. The as-synthesized powder was calcined for 4 h at 500 degrees C (2 degrees C min(-1)). X-Ray diffraction analysis confirmed a hexag-onal crystalline phase (wurtzite) with an average crystallite size of 38 nm. The Kubelka-Munk method was used to determine a band gap of 3.27 eV through UV-Vis diffuse reflectance spectrum and a Brunauer-Emmett-Teller (BET) specific area of 12 m(2) g(-1) was obtained from N2 adsorption analysis. The photocatalytic activity of ZnO was evaluated under visible light (300 W) lamp, with 1 mg mL(-1) of photocatalyst and using phenol solutions at different concentrations of 5,10, 25, and 50 ppm; the obtained degradation percentages were 98%, 97%, 94%, and 71%, respectively. Three cycles were performed with the ZnO used in the reactions with phenol at 5 and 50 ppm, decreasing the degraded percentages to 87% and 65%, respectively. The generation of hydroxyl radicals was estimated for the ZnO and ZnO samples after three cycles by means of fluorescence spectroscopy analy-sis. It was observed that the first-used ZnO material generated a significant amount of hydroxyl radicals.CONCLUSION: When compared to ZnO after three cycles of reaction, the amount of generated hydroxyl radicals decreased. It was observed that the higher the amount of phenol, the lower the generation of hydroxyl radicals after reuse; this was probably due to the presence of some adsorbed by-products of the photocatalytic reaction on the surface of ZnO, as the FTIR spectrum of the post-reaction sample showed.
February, 2023 · DOI: 10.1002/jctb.7334
Materiales Avanzados
Sintering behaviour of a clay containing pyrophyllite, sericite and kaolinite as ceramic raw materials: Looking for the optimum firing conditions
Sanchez-Soto, PJ; Garzon, E; Perez-Villarejo, L; Eliche-Quesada, DBoletin de la Sociedad Española de Ceramica y Vidrio, 62 (2023) 26-39 DOI: 10.1016/j.bsecv.2021.09.001
Abstract
The sintering behaviour of a pyrophyllite clay has been investigated. The mineralogical composition by X-ray diffraction (XRD) of this sample was -35 wt.% pyrophyllite, -25 wt.% sericite/illite, -15 wt.% kaolinite and -20 wt.% quartz. The chemical composition was consistent with these results, with a total flux content of 4.18 wt.%. Prismatic bars were prepared by dry pressing using this sample and fired in the range 800-1500 degrees C with 0.5-5 h of soaking times. Sintering diagrams were obtained using the results of linear firing shrinkage, water absorption capacity, bulk density and apparent porosity determined in the ceramic bodies as a function of firing temperatures. It was found a trend of slight variations of bulk density values firing in the range 1000-1150 degrees C, with marked decreases of these values for these bodies fired at 1200 degrees C and 1300 degrees C. The temperature of maximum bulk density was determined as -1200 degrees C and the vitrification temperature was -1300 degrees C where the apparent porosity becomes almost zero. The vitrification process of the pyrophyllite clay sample was investigated using a method previously described in the literature, which considered an Arrhenius approach under isothermal conditions and a first order kinetic. It was determined an activation energy (Ea) of -45 kJ/mol with a linear correlation coefficient of 0.998. The relative rates of vitrification were calculated. It was found that the contribution of vitrification due to the heating was relatively small compared to the vitrification during soaking. Mullite and quartz are forming the ceramic bodies besides a vitreous or glassy phase. The thermally treated pyrophyllite clay showed a dense network of rod-shaped and elongated needle-like crystals, being characteristic features of mullite as a dense felt. The vitrification rate equation, as deduced in this study by first time, can be a useful tool to estimate the optimum firing conditions of the pyrophyllite clays applied as ceramic raw materials.
January, 2023 · DOI: 10.1016/j.bsecv.2021.09.001
Reactividad de Sólidos
A novel, green, cost-effective and fluidizable SiO2-decorated calcium-based adsorbent recovered from eggshell waste for the CO2 capture process
Imani, M; Tahmasebpoor, M; Sanchez-Jim, P; Valverde, J; Garcia, VMSeparation and Purification Technology, 305 (2023) 122523 DOI: 10.1016/j.seppur.2022.122523
Abstract
The reduction, storage, and reuse of greenhouse gas carbon dioxide (CO2) is a crucial concern in modern society. Bio-waste adsorbents have recently aroused the investigator's attention as auspicious materials for CO2 capture. However, the adsorption capacity decaying and poor fluidizability during carbonation/calcination cycles of all natural adsorbents used in the calcium-looping process (CaL) are important challenges. The current study ex-plores the performance of a novel SiO2-decorated calcium-based adsorbent recovered from eggshell waste in terms of both CO2 capture capacity and fluidity. Two preparation methods of hydration and sol-gel were used to obtain Ca-based adsorbents with different pore configurations and volumes. Modification of the adsorbents was applied by dry physically mixing with different weight percentages of hydrophobic SiO2 nanoparticles (NPs), in order to maintain stability and fluidity. The adsorbent prepared by the sol-gel method exhibited a fluffier structure with smaller grain sizes and higher porosity than that of prepared by the hydration method, leading to a 6.9 % increase in conversion at the end of the 20th cycle. Also, with the optimal amount of SiO2 nanoparticles, i. e. 7.5 wt%, the amount of CaO conversion obtained by sol-gel derived adsorbent was 27.59 % higher than that by pristine eggshell at the end of the 20th carbonation/calcination cycles. The fluidizability tests showed that the highest bed expansion ratio (2.29) was achieved for sol-gel derived adsorbent in the presence of 7.5 wt% silica nanoparticles which was considerably higher than the amount of 1.8 and 1.6 belonged to sol-gel derived adsorbent and pristine eggshell without silica at the gas velocity of approximate to 6.5 cm/s, respectively. The high adsorption capacity and proper fluidity of this novel and green calcium-based adsorbent promise its wide application.
January, 2023 · DOI: 10.1016/j.seppur.2022.122523
Reactividad de Sólidos
Thermal arrest analysis of the reverse martensitic transformation in a Ni55Fe19Ga26 Heusler alloy obtained by melt-spinning
Vidal-Crespo, A; Manchon-Gordon, AF; Blazquez, JS; Ipus, JJ; Svec, P; Conde, CFJournal of Thermal Analysis and Calorimetry, (2023) DOI: 10.1007/s10973-022-11889-1
Abstract
Ni55Fe19Ga26 ribbons obtained by melt-spinning technique exhibit a martensitic transformation from L2(1) cubic austenite phase to 14 M martensite phase above room temperature. We have taken advantage of the existence of thermal hysteresis of the martensitic phase transition (similar to 11 K) to analyze the effect of isothermal treatments on the reverse martensitic transformation, which has been analyzed by means of interrupted heating using differential scanning calorimetry. The experimental findings clearly indicate a time-depending effect in the martensitic transformation at temperatures between the austenite start and finish temperatures. Moreover, it has been observed that two successive martensitic transformations take place after the isothermal arrest was performed.
January, 2023 · DOI: 10.1007/s10973-022-11889-1
Química de Superficies y Catálisis
Engineering morphologies of yttrium oxide supported nickel catalysts for hydrogen production
Zhang, RB; Tu, ZA; Meng, S; Feng, G; Lu, ZH; Yu, YZ; Reina, TR; Hu, FY; Chen, XH; Ye, RPRare Metals, 42 (2023) 176-188 DOI: 10.1007/s12598-022-02136-5
Abstract
The catalytic performance is highly related to the catalyst structure. Herein, a series of Ni nanoparticles supported on Y2O3 with different morphologies were successfully synthesized via hydrothermal process screening different pH environments. These Ni/Y2O3 catalysts were applied to efficiently produce COx-free H-2 through ammonia decomposition. We identify a significant impact of Y2O3 supports on nickel nanoclusters sizes and dispersion. The experimental results show that Ni/Y11 catalyst achieves 100% ammonia decomposition conversion under a gas hour space velocity (GHSV) of 12,000 ml.h(-1).g(cat)(-1) and temperature of 650 degrees C. Such a high level of activity over Ni/Y11 catalyst was attributed to a large specific surface area, appropriate alkalinity, and small Ni nanoparticles diameter with high dispersion.
January, 2023 · DOI: 10.1007/s12598-022-02136-5
Nanotecnología en Superficies y Plasma
Determination of the Primary Excitation Spectra in XPS and AES
Pauly, N; Yubero, F; Tougaard, SNanomaterials, 13 (2023) 339 DOI: 10.3390/nano13020339
Abstract
This paper reviews a procedure that allows for extracting primary photoelectron or Auger electron emissions from homogeneous isotropic samples. It is based on a quantitative dielectric description of the energy losses of swift electrons travelling nearby surfaces in presence of stationary positive charges. The theory behind the modeling of the electron energy losses, implemented in a freely available QUEELS-XPS software package, takes into account intrinsic and extrinsic effects affecting the electron transport. The procedure allows for interpretation of shake-up and multiplet structures on a quantitative basis. We outline the basic theory behind it and illustrate its capabilities with several case examples. Thus, we report on the angular dependence of the intrinsic and extrinsic Al 2s photoelectron emission from aluminum, the shake-up structure of the Ag 3d, Cu 2p, and Ce 3d photoelectron emission from silver, CuO and CeO2, respectively, and the quantification of the two-hole final states contributing to the L3M45M45 Auger electron emission of copper. These examples illustrate the procedure, that can be applied to any homogeneous isotropic material.
January, 2023 · DOI: 10.3390/nano13020339
Química de Superficies y Catálisis
Is the RWGS a viable route for CO2 conversion to added value products? A techno-economic study to understand the optimal RWGS conditions
Portillo, E; Gandara-Loe, J; Reina, TR; Pastor-Perez, LScience of the Total Environment, 857 (2023) 159394 DOI: 10.1016/j.scitotenv.2022.159394
Abstract
Understanding the viability of the RWGS from a thermodynamic and techno-economic angle opens new horizons within CO2 conversion technologies. Unfortunately, profitability studies of this technology are scarce in literature and mainly focused on overall conversion and selectivity trends with tangential remarks on energy demands and pro-cess costs. To address this research gap, herein we present a comprehensive techno-economic study of the RWGS reac-tion when coupling with Fischer-Tropsch synthesis is envisaged to produced fuels and chemicals using CO2 as building block. We showcase a remarkable impact of operating conditions in the final syngas product and both CAPEX and OPEX. From a capital investment perspective, optimal situations involve RWGS unit running at low temperatures and high pressures as evidenced by our results. However, from the running cost angle, operating at 4 bar is the most favorable alternative within the studied scenarios. Our findings showcase that, no matter the selected temperature the RWGS unit should be preferentially run at intermediate pressures. Ultimately, our work maps out multiple operat-ing scenarios in terms of energy demand and process cost serving as guideline to set optimal reaction conditions to un-lock the potential of the RWGS for chemical CO2 recycling.
January, 2023 · DOI: 10.1016/j.scitotenv.2022.159394
Reactividad de Sólidos
Low Temperature Magnetic Transition of BiFeO3 Ceramics Sintered by Electric Field-Assisted Methods: Flash and Spark Plasma Sintering
Manchon-Gordon, AF; Perejon, A; Gil-Gonzalez, E; Kowalczyk, M; Sanchez-Jimenez, PE; Perez-Maqueda, LAMaterials, 16 (2023) 189 DOI: 10.3390/ma16010189
Abstract
Low temperature magnetic properties of BiFeO3 powders sintered by flash and spark plasma sintering were studied. An anomaly observed in the magnetic measurements at 250 K proves the clear existence of a phase transition. This transformation, which becomes less well-defined as the grain sizes are reduced to nanometer scale, was described with regard to a magneto-elastic coupling. Furthermore, the samples exhibited enhanced ferromagnetic properties as compared with those of a pellet prepared by the conventional solid-state technique, with both a higher coercivity field and remnant magnetization, reaching a maximum value of 1.17 kOe and 8.5 10(-3) emu/g, respectively, for the specimen sintered by flash sintering, which possesses the smallest grains. The specimens also show more significant exchange bias, from 22 to 177 Oe for the specimen prepared by the solid-state method and flash sintering technique, respectively. The observed increase in this parameter is explained in terms of a stronger exchange interaction between ferromagnetic and antiferromagnetic grains in the case of the pellet sintered by flash sintering.
January, 2023 · DOI: 10.3390/ma16010189
Nanotecnología en Superficies y Plasma
A Holistic Solution to Icing by Acoustic Waves: De-Icing, Active Anti-Icing, Sensing with Piezoelectric Crystals, and Synergy with Thin Film Passive Anti-Icing Solutions
Del Moral, J; Montes, L; Rico-Gavira, VJ; Lopez-Santos, C; Jacob, S; Oliva-Ramirez, M; Gil-Rostra, J; Fakhfouri, A; Pandey, S; Del Val, MG; Mora, J; García-Gallego, P; Ibanez-Ibanez, PF; Rodríguez Valverde, MA; Winkler, A; Borras, A; Gonzalez-Elipe, ARAdvanced Functional Materials, 33 (2023) 2209421 DOI: 10.1002/adfm.202209421
Abstract
Icing has become a hot topic both in academia and in the industry given its implications in transport, wind turbines, photovoltaics, and telecommunications. Recently proposed de-icing solutions involving the propagation of acoustic waves (AWs) at suitable substrates may open the path for a sustainable alternative to standard de-icing or anti-icing procedures. Herein, the fundamental interactions are unraveled that contribute to the de-icing and/or hinder the icing on AW-activated substrates. The response toward icing of a reliable model system consisting of a piezoelectric plate activated by extended electrodes is characterized at a laboratory scale and in an icing wind tunnel under realistic conditions. Experiments show that surface modification with anti-icing functionalities provides a synergistic response when activated with AWs. A thoughtful analysis of the resonance frequency dependence on experimental variables such as temperature, ice formation, or wind velocity demonstrates the application of AW devices for real-time monitoring of icing processes.
January, 2023 · DOI: 10.1002/adfm.202209421
Reactividad de Sólidos
Nanocrystalline Skinnerite (Cu3SbS3) Prepared by High-Energy Milling in a Laboratory and an Industrial Mill and Its Optical and Optoelectrical Properties
Dutkova, E; Sayagues, MJ; Fabian, M; Balaz, M; Kovac, J; Kovac, J; Stahorsky, M; Achimovicova, M; Bujnakova, ZLMolecules, 28 (2023) 1 DOI: 10.3390/molecules28010326
Abstract
Copper, antimony and sulfur in elemental form were applied for one-pot solid-state mechanochemical synthesis of skinnerite (Cu3SbS3) in a laboratory mill and an industrial mill. This synthesis was completed after 30 min of milling in the laboratory mill and 120 min in the industrial mill, as corroborated by X-ray diffraction. XRD analysis confirmed the presence of pure monoclinic skinnerite prepared in the laboratory mill and around 76% monoclinic skinnerite, with the secondary phases famatinite (Cu3SbS4; 15%), and tetrahedrite (Cu11.4Sb4S13; 8%), synthesized in the industrial mill. The nanocrystals were agglomerated into micrometer-sized grains in both cases. Both samples were nanocrystalline, as was confirmed with HRTEM. The optical band gap of the Cu3SbS3 prepared in the laboratory mill was determined to be 1.7 eV with UV-Vis spectroscopy. Photocurrent responses verified with I-V measurements under dark and light illumination and Cu3SbS3 nanocrystals showed similar to 45% enhancement of the photoresponsive current at a forward voltage of 0.6 V. The optical and optoelectrical properties of the skinnerite (Cu3SbS3) prepared via laboratory milling are interesting for photovoltaic applications.
January, 2023 · DOI: 10.3390/molecules28010326
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