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2021


Nb-C thin films prepared by DC-MS and HiPIMS: Synthesis, structure, and tribomechanical properties


Sala, N; Abad, MD; Sánchez-López, JC; Caro, J; Colominas, C
Surface & Coatings Technology, 422 (2021) 127569
Tribología y Protección de Superficies

ABSTRACT ▼

Nanostructured Nb-C thin films were prepared by direct current magnetron sputtering (DC-MS) and high-power impulse magnetron sputtering (HiPIMS). The films were characterized in depth by X-ray diffraction (XRD), grazing incidence X-ray diffraction, scanning electron microscopy, atomic force microscopy, electron probe microanalysis, and Raman spectroscopy. The mechanical properties were measured by nanoindentation, and the tribological properties were measured by pin-on-disk tests in ambient air. The wear tracks and ball scars were analyzed by Raman spectroscopy to elucidate the tribochemical reactions that occurred at the contact area and to determine the wear mechanism for each specimen type. The thermal stability of the coatings was studied up to 1000 degrees C using Raman spectroscopy and XRD. The samples prepared by DC-MS were very dense, and the phase composition changed from purely nanocrystalline (Nb2C and NbC) to a mixture of NbC crystals embedded in an amorphous carbon-based matrix (NbC/a-C(:H)). However, the samples prepared by HiPIMS developed a marked columnar morphology with a NbC/a-C(:H) nanocomposite structure. The hardness values ranged from 11 to 20 GPa depending on the deposition technique and the amount of the soft a-C(:H) phase present in the sample. The tribological properties of all the coatings were remarkably good when the carbon content was approximately 50 at.%. The formation of a lubricating sp(2)-rich C tribofilm between the ball and coating during the pin-on-disk tests was observed by Raman spectroscopy. The tribofilm formed preferentially on the samples prepared by HiPIMS, which had higher C contents. At 750 degrees C, the degradation of the NbC phases resulted in the formation of an additional a-C phase and niobium oxides.


Septiembre, 2021 | DOI: 10.1016/j.surfcoat.2021.127569

Si sputtering yield amplification: a study of the collisions cascade and species in the sputtering plasma


Cruz, J; Sangines, S; Soto-Valle; Muhl; Sierra, I; De Lucio-Morales, O; Mitrani, A; Calderon-Olvera, RM; Mendoza-Perez, R; Machorro-Mejia, R
Journal of Physics D-Applied Physics, 54 (2021) 375201
Materiales Coloidales

ABSTRACT ▼

The sputtering yield amplification (SYA) is a phenomenon based on doping a sputtering target with atoms of higher atomic mass. This doping changes the depth and the direction of the collision cascade in the target surface promoting a higher ejection of target atoms. In this work, we present a new way of generating the SYA phenomenon without the need of expensive and complex deposition systems. This was accomplished by increasing the working pressure and adding small pieces of W, as dopant element, on the racetrack of a Si target. The physical phenomena necessary to promote the SYA, for our experimental parameters, were analysed in two different deposition chambers and two sizes of sputtering targets. Based on the collisions in the gas phase, a calculation on the number of W atoms returning to the racetrack area was made, considering the number of atoms deposited on the thin films, to determine their effect on the cascade of collisions. In addition, calculations with the simulation of metal transport code were developed to determine the location on the racetrack zone the returning atoms were redeposited. By using reference samples placed on the racetrack of the Si target, we found that the percentage of SYA depends on the number of dopant atoms redeposited as well as the depth distribution these atoms had in the racetrack surface.


Septiembre, 2021 | DOI: 10.1088/1361-6463/ac0c4e

Persistent luminescent nanoparticles: Challenges and opportunities for a shimmering future


Castaing, V.; Arroyo, E.; Becerro, A.I.; Ocaña, M.; Lozano, G.; Míguez, H.
Journal of Applied Physics, 130 (2021) 080902
Materiales Ópticos Multifuncionales - Materiales Coloidales

ABSTRACT ▼

Persistent phosphors are luminescent sources based on crystalline materials doped with rare-earth or transition metal cations able to produce light after the excitation source vanishes. Although known for centuries, these materials gained renewed interest after the discovery of Eu2+,RE3+ co-doped aluminates and silicates in the late 1990s due to their unprecedented afterglow properties. In contrast, persistent nanophosphors have emerged only recently as a nanoscale alternative to their bulk counterparts, offering exciting opportunities of particular relevance for in vivo imaging, optical data storage, or unconventional light generation. However, taking advantage of the avenues opened by nanoscience demands developing new synthetic strategies that allow precise control of the morphology, surface, and defect chemistry of the nanomaterials, along with a profound understanding of the physical mechanisms occurring in the nanoscale. Besides, advanced physicochemical characterization is required to assess persistent luminescence in a quantitative manner, which allows strict comparison among different persistent nanophosphors, aiming to propel their applicability. Herein, we revisit the main phenomena that determine the emission properties of persistent nanoparticles, discuss the most promising preparation and characterization protocols, highlight recent achievements, and elaborate on the challenges ahead.


Agosto, 2021 | DOI: 10.1063/5.0053283

Study of the Influence of Sintering Atmosphere and Mechanical Activation on the Synthesis of Bulk Ti2AlN MAX Phase Obtained by Spark Plasma Sintering


Salvo, C; Chicardi, E; García-Garrido, C; Poyato, R; Jimenez, JA; Mangalaraja, RV
Materials, 14 (2021) 4574
Reactividad de Sólidos

ABSTRACT ▼

The influence of the mechanical activation process and sintering atmosphere on the microstructure and mechanical properties of bulk Ti2AlN has been investigated. The mixture of Ti and AlN powders was prepared in a 1:2 molar ratio, and a part of this powder mixture was subjected to a mechanical activation process under an argon atmosphere for 10 h using agate jars and balls as milling media. Then, the sintering and production of the Ti2AlN MAX phase were carried out by Spark Plasma Sintering under 30 MPa with vacuum or nitrogen atmospheres and at 1200 degrees C for 10 min. The crystal structure and microstructure of consolidated samples were characterized by X-ray Diffraction, Scanning Electron Microscopy, and Energy Dispersive X-ray Spectroscopy. The X-ray diffraction patterns were fitted using the Rietveld refinement for phase quantification and determined their most critical microstructural parameters. It was determined that by using nitrogen as a sintering atmosphere, Ti4AlN3 MAX phase and TiN were increased at the expense of the Ti2AlN. In the samples prepared from the activated powders, secondary phases like Ti5Si3 and Al2O3 were formed. However, the higher densification level presented in the sample produced by using both nitrogen atmosphere and MAP powder mixture is remarkable. Moreover, the high-purity Ti2AlN zone of the MAX-1200 presented a hardness of 4.3 GPa, and the rest of the samples exhibited slightly smaller hardness values (4.1, 4.0, and 4.2 GPa, respectively) which are matched with the higher porosity observed on the SEM images.


Agosto, 2021 | DOI: 10.3390/ma14164574

Kinetics and cyclability of limestone (CaCO3) in presence of steam during calcination in the CaL scheme for thermochemical energy storage


Arcenegui-Troya, J; Sanchez-Jimenez, PE; Perejon, A; Moreno, V; Valverde, JM; Perez-Maqueda, LA
Chemical Engineering Journal, 417 (2021) 129194
Reactividad de Sólidos

ABSTRACT ▼

In the present work, we explore the use of steam in the CaCO3 calcination step of the Calcium Looping process devised for thermochemical energy storage (CaL-TCES). Steam produces a double benefit: firstly, it fastens calcination, allowing a reduction of the temperature needed to attain full calcination in short residence times, as those required in practice, resulting in energy savings. This behaviour is justified on the basis of a kinetics study results obtained from a non-parametric kinetic analysis, which demonstrate that the presence of steam during calcination can reduce the apparent activation energy from 175 kJ/mol to 142 kJ/mol with a steam's partial pressure of 29%. In addition, the results obtained for multicycle CaL-TCES tests show that steam alleviates the deactivation of the sorbent, which is one of the main limiting factors of this technology. This behaviour is explained in terms of the effect of steam on the microstructure of the regenerated CaO. Importantly, the values of residual conversion attained by calcining in steam are higher than those without steam.


Agosto, 2021 | DOI: 10.1016/j.cej.2021.129194

Geopolymers made from metakaolin sources, partially replaced by Spanish clays and biomass bottom ash


Eliche-Quesada, D; Calero-Rodriguez, A; Bonet-Martinez, E;Perez-Villarejo, L; Sanchez-Soto, PJ
Journal of Building Engineering, 40 (2021) 102761
Materiales Avanzados

ABSTRACT ▼

The main objective of this investigation is to study the effect of the substitution of metakaolin (MK) (from calcined industrial kaolin) by four different calcined natural Southern Spain clays traditionally used in the brick and tile sector, as well as by the biomass bottom ash residue (BBA) from the combustion of a mix of olive and pine pruning on the synthesis of geopolymer with physical, mechanical and thermal properties comparable to those of classic construction materials. As alkaline activator, a 8 M solution of sodium hydroxide and sodium silicate have been used. Raw materials, metakaolin; Spanish clays: black clay (BC), yellow clay (YC), white clay (WC), red clay (RC) and BBA were characterized by chemical analysis (XRF), mineralogical analysis (XRD), and particle size analysis. Control geopolymers containing only metakaolin, and batch of geopolymers were formulated containing equal proportions of metakaolin, BBA and each of the four types of clay. After the curing period, at 60 degrees C for 1 day geopolymers were demolded and stored 27 days at room temperature. Geopolymers were characterized using Scanning Electron Microscopy coupled with Energy Dispersive Spectroscopy (SEM-EDS), XRD and Attenuated Total Reflectance-Fourier Transform Infrared Spec troscopy (ATR-FTIR). Their physical, mechanical and thermal properties have also been studied. The addition of BBA and different types of calcined clays to metakaolin gives rise to geopolymers with higher mechanical properties increasing the compressive strength of the control geopolymer containing only MK (24.9 MPa) by more than 50% for the GMK-BBA-WC geopolymers (38.5 MP a). The clays act as fillers and/or promote the precipitation of calcium-rich phases (Ca)-A-S-H-G gel that coexists with the (Na)-A-S-H gel type. The relevant results of physical, mechanical and thermal properties obtained in this research demonstrate the potential of Spanish clays and BBA as binders and substitutes for metakaolin.


Agosto, 2021 | DOI: 10.1016/j.jobe.2021.102761

Calcination under low CO2 pressure enhances the calcium Looping performance of limestone for thermochemical energy storage


Sarrion, B; Perejon, A; Sanchez-Jimenez, PE; Amghar, N; Chacartegui, R; Valverde, JM; Perez-Maqueda, LA
Chemical Engineering Journal, 417 (2021) 127922
Reactividad de Sólidos

ABSTRACT ▼

The Calcium Looping performance of limestone for thermochemical energy storage has been investigated under novel favorable conditions, which involve calcination at moderate temperatures under CO2 at low pressure (0.01 and 0.1 bar) and carbonation at high temperature under CO2 at atmospheric pressure. Calcining at low CO2 pressures allows to substantially reduce the temperature to achieve full calcination in short residence times. Moreover, it notably enhances CaO multicycle conversion. The highest values of conversion are obtained for limestone samples calcined under 0.01 bar CO2 at 765 degrees C. Under these conditions, the residual conversion is increased by a factor of 10 as compared to conditions involving calcination under CO2 at atmospheric pressure. The enhancement of CaO conversion is correlated to the microstructure of the CaO samples obtained after calcination. As seen from SEM, BET surface and XRD analysis, calcination under low CO2 pressure leads to a remarkable decrease of pore volume and CaO crystallite size. Consequently, CaO surface area available for carbonation in the fast reaction-controlled regime and therefore reactivity in short residence times is promoted.


Agosto, 2021 | DOI: 10.1016/j.cej.2020.127922

Mechanochemical synthesis of ternary chalcogenide chalcostibite CuSbS2 and its characterization


Dutkova, E; Sayagues, MJ; Fabian, M; Kovac, J; Kovat, J; Balaz, M; Stahorsky, M
Journal of Materials Science-Materials in Electronics (2021)
Reactividad de Sólidos

ABSTRACT ▼

In this work, the very rapid one-step mechanochemical synthesis of nanocrystalline ternary chalcogenide chalcostibite CuSbS2 prepared from copper, antimony, and sulfur precursors by high-energy milling for only 30 min in a planetary mill is reported. XRD confirmed the orthorhombic crystal structure of CuSbS2. The crystallite size of CuSbS2 calculated by LeBail refinement of the X-ray powder diffraction data was 25 nm. The nanocrystalline chalcostibite CuSbS2 was also confirmed by transmission electron microscopy. The purity of CuSbS2 was verified by Raman spectroscopy. The synthesized chalcostibite exhibits the specific surface area value of 2.4 m(2)g(-1). UV-Vis spectroscopy showed the optical bandgap of CuSbS2 as 1.54 eV with wide range of absorption in visible region. Photoresponse of CuSbS2 was confirmed by I-V measurements under dark and light illumination. The proposed mechanochemical synthesis provides an alternative approach to prepare also other ternary semiconductor nanomaterials. CuSbS2 semiconductor nanocrystals have the potential to be used as light absorbers in photovoltaics.


Agosto, 2021 | DOI: 10.1007/s10854-021-06767-9

One-reactor vacuum and plasma synthesis of transparent conducting oxide nanotubes and nanotrees: from single wire conductivity to ultra-broadband perfect absorbers in the NIR


Castillo-Seoane, J; Gil-Rostra, J; Lopez-Flores, V; Lozano, G; Ferrer, FJ; Espinos, JP; Ostrikov, K; Yubero, F; Gonzalez-Elipe, AR; Barranco, A; Sanchez-Valencia, JR; Borras, A
Nanoscale, 13 (2021) 13882-13895
Nanotecnología en Superficies y Plasma - Materiales Ópticos Multifuncionales

ABSTRACT ▼

The eventual exploitation of one-dimensional nanomaterials needs the development of scalable, high yield, homogeneous and environmentally friendly methods capable of meeting the requirements for fabrication of functional nanomaterials with properties on demand. In this article, we demonstrate a vacuum and plasma one-reactor approach for the synthesis of fundamental common elements in solar energy and optoelectronics, i.e. the transparent conducting electrode but in the form of nanotube and nanotree architectures. Although the process is generic and can be used for a variety of TCOs and wide-bandgap semiconductors, we focus herein on indium doped tin oxide (ITO) as the most previously researched in previous applications. This protocol combines widely applied deposition techniques such as thermal evaporation for the formation of organic nanowires serving as 1D and 3D soft templates, deposition of polycrystalline layers by magnetron sputtering, and removal of the templates by simply annealing under mild vacuum conditions. The process variables are tuned to control the stoichiometry, morphology, and alignment of the ITO nanotubes and nanotrees. Four-probe characterization reveals the improved lateral connectivity of the ITO nanotrees and applied on individual nanotubes shows resistivities as low as 3.5 +/- 0.9 x 10(-4) omega cm, a value comparable to that of single-crystalline counterparts. The assessment of diffuse reflectance and transmittance in the UV-Vis range confirms the viability of the supported ITO nanotubes as random optical media working as strong scattering layers. Their further ability to form ITO nanotrees opens a path for practical applications as ultra-broadband absorbers in the NIR. The demonstrated low resistivity and optical properties of these ITO nanostructures open a way for their use in LEDs, IR shields, energy harvesting, nanosensors, and photoelectrochemical applications.


Agosto, 2021 | DOI: 10.1039/d1nr01937f

Laser-induced scanning transfer deposition of silver electrodes on glass surfaces: A green and scalable technology


Molina, R; Ertugrul, M; Larrea, A; Navarro, R; Rico, V; Yubero, F; Gonzalez-Elipe, AR: De la Fuente, GF; Angurel, LA
Applied Surface Science, 556 (2021) 149673
Nanotecnología en Superficies y Plasma

ABSTRACT ▼

A pulsed laser ablation backwriting technique with high repetitive rates is implemented for the fabrication of silver coatings on glass surfaces. This method enables geometrical constraint-free deposition of metallic coatings. These exhibit sufficiently low electrical resistance to be used as electrodes in dielectric barrier discharge (DBD) plasma elements. Ambient air deposition of metallic silver electrodes on standard glass slides is explored using a sub-ns UV laser source, combined with hybrid beam scanning methods. The green nature of the overall deposition process includes a preliminary irradiation scan to homogenise the target surface before the subsequent backwriting step. Metal transfer is achieved by combining two phenomena within a simple beam scanning process: LIRT (laserinduced reverse transfer) of silver from the target to the glass, with a partial and secondary LIFT (Laser-Induced Forward Transfer) of silver from the glass to the target. Appropriate selection of pulse energy and pulse repetition rates, beam scanning velocities and target motion enable the growth of sufficiently thick Ag deposits on glass with the required low electrical resistivity and nearly 2D constraint-free geometry. This method avoids the use of vacuum and liquids, resulting in a cheap, facile and green methodology for the deposition of silver electrodes onto transparent substrate surfaces.


Agosto, 2021 | DOI: 10.1016/j.apsusc.2021.149673

ZnO/Ag3PO4 and ZnO–Malachite as Effective Photocatalysts for the Removal of Enteropathogenic Bacteria, Dyestuffs, and Heavy Metals from Municipal and Industrial Wastewater


Murcia, JJ; Hernández Miño, JS; Rojas, H; Brijaldo, MH; Martin-Gómez, AN; Sánchez-Cid, P; Navío, JA; Hidalgo, MC; Jaramillo-Pérez, C
Water, 13 (2021) 2264
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT ▼

Different composites based on ZnO/Ag3PO4 and ZnO–malachite (Cu2(OH)2CO3) were synthesized in order to determine their effectiveness in the treatment of municipal and industrial wastewaters (mainly polluted by enteropathogenic bacteria, dyes, and heavy metals). The addition of Ag3PO4 and malachite did not significantly modify the physicochemical properties of ZnO; however, the optical properties of this oxide were modified as a result of its coupling with the modifiers. The modification of ZnO led to an improvement in its effectiveness in the treatment of municipal and industrial wastewater. In general, the amount of malachite or silver phosphate and the effluent to be treated were the determining factors in the effectiveness of the wastewater treatment. The highest degree of elimination of bacteria from municipal wastewater and discoloration of textile staining wastewater were achieved by using ZnO/Ag3PO4 (5%), but an increase in the phosphate content had a detrimental effect on the treatment. Likewise, the highest Fe and Cu photoreduction from coal mining wastewater was observed by using ZnO–malachite (2.5%) and ZnO/Ag3PO4 (10%), respectively. Some of the results of this work were presented at the fourth Congreso Colombiano de Procesos Avanzados de Oxidación (4CCPAOx).


Agosto, 2021 | DOI: 10.3390/w13162264

Light-Harvesting Properties of a Subphthalocyanine Solar Absorber Coupled to an Optical Cavity


Esteso, V; Calio, L; Espinos, H; Lavarda, G; Torres, T; Feist, J; Garcia-Vidal, FJ; Bottari, G; Míguez, H
SOLAR RRL, (2021) 2100308
Materiales Ópticos Multifuncionales

ABSTRACT ▼

Herein, both from the experimental and theoretical point of view, the optical absorption properties of a subphthalocyanine (SubPc), an organic macrocycle commonly used as a sunlight harvester, coupled to metallic optical cavities are analyzed. How different electronic transitions characteristic of this compound and specifically those that give rise to excitonic (Q band) and charge transfer (CT band) transitions couple to optical cavity modes is investigated. It is observed that whereas the CT band couples weakly to the cavity, the Q band transitions show evidence of hybridization with the photon eigenstates of the resonator, a distinctive trait of the strong coupling regime. As a result of the different coupling regimes of the two electronic transitions, very different spectral and directional light-harvesting features are observed, which for the weakly coupled CT transitions are mainly determined by the highly dispersive cavity modes and for the strongly coupled Q band by the less angle-dependent exciton-polariton bands. Modeling also allows discriminating parasitic from productive absorption in each case, enabling the estimation of the expected losses in a solar cell acting as an optical resonator.


Julio, 2021 | DOI: 10.1002/solr.202100308

Mechanistic Considerations on the H-2 Production by Methanol Thermal-assisted Photocatalytic Reforming over Cu/TiO2 Catalyst


Platero, F; Lopez-Martin, A; Caballero, A; Colon, G
CHEMCATCHEM, 13 (2021) 3878-3888
Materiales y Procesos Catalíticos de Interés Ambiental y Energético

ABSTRACT ▼

We have studied the gas phase H-2 production by methanol thermo-photoreforming using Cu-modified TiO2. Metal co-catalyst has been deposited by means of photodeposition method. The concentration of methanol in the steam was also considered. It appears that H-2 production is notably higher as temperature increases. Moreover, the optimum H-2 yield is achieved using methanol concentration of 10 % v/v. CO and CO2 were monitored as side products of the overall reaction. It has been stated that CO evolution is significant at lower temperatures. As temperature increases, CO evolution is hindered and H-2 appeared boosted. We have demonstrated that other reactions such water-gas-shift or formate dehydration would participate in the overall process. On this basis, optimal operational condition for H-2 production is attained for thermo-photocatalytic reforming of methanol solution 10 % v/v at 200 degrees C.


Julio, 2021 | DOI: 10.1002/cctc.202100680

Ligand-Free MAPbI(3) Quantum Dot Solar Cells Based on Nanostructured Insulating Matrices


Rubino, A; Calio, L; Calvo, ME; Miguez, H
SOLAR RRL (2021) 2100204
Materiales Ópticos Multifuncionales

ABSTRACT ▼

The stability, either chemical or thermal, and performance of colloidal quantum dot (CQD) devices are typically limited by the presence of surface-bonded organic ligands required to stabilize the nanocrystals. In addition, optimization of charge transport implies lengthy ligand exchange processing. Herein, evidence of efficient charge transport through a network of ligand-free perovskite quantum dots (PQDs) embedded in an insulating porous matrix made of monodisperse SiO2 nanoparticles is shown. Methylammonium lead iodide (CH3NH3PbI3 or MAPbI(3)) QDs are prepared in situ by infiltration of precursors within the matrix pores, which act both as nanoreactors for the synthetic reaction and as supporting scaffolds, hence reducing the number of synthetic and postprocessing steps usually required in CQD solar cells. Above a certain nanocrystal load, charge percolation is reached and dot-to-dot transport achieved without compromising quantum confinement effects. Solar cells based on MAPbI(3) QDs prepared in this way present a 9.3% efficiency, the highest reported for a scaffold-supported PQD solar cell, and significantly improved stability under solar illumination with respect to their bulk counterparts. Therefore, adequately designed networks of ligand-free PQDs can be used as both light harvesters and photocarrier conductors, in an alternative configuration to that used in previously developed QD solar cells.


Julio, 2021 | DOI: 10.1002/solr.202100204

Bimetallic Ni-Ru and Ni-Re Catalysts for Dry Reforming of Methane: Understanding the Synergies of the Selected Promoters


Moreno, AA; Ramirez-Reina, T; Ivanova, S; Roger, AC; Centeno, MA; Odriozola, JA
Frontiers in Chemistry, 9 (2021) 694976
Química de Superficies y Catálisis

ABSTRACT ▼

Designing an economically viable catalyst that maintains high catalytic activity and stability is the key to unlock dry reforming of methane (DRM) as a primary strategy for biogas valorization. Ni/Al2O3 catalysts have been widely used for this purpose; however, several modifications have been reported in the last years in order to prevent coke deposition and deactivation of the samples. Modification of the acidity of the support and the addition of noble metal promoters are between the most reported strategies. Nevertheless, in the task of designing an active and stable catalyst for DRM, the selection of an appropriate noble metal promoter is turning more challenging owing to the lack of homogeneity of the different studies. Therefore, this research aims to compare Ru (0.50 and 2.0%) and Re (0.50 and 2.0%) as noble metal promoters for a Ni/MgAl2O4 catalyst under the same synthesis and reaction conditions. Catalysts were characterized by XRF, BET, XRD, TPR, hydrogen chemisorption (H2-TPD), and dry reforming reaction tests. Results show that both promoters increase Ni reducibility and dispersion. However, Ru seems a better promoter for DRM since 0.50% of Ru increases the catalytic activity in 10% and leads to less coke deposition.


Julio, 2021 | DOI: 10.3389/fchem.2021.694976

Current scenario and prospects in manufacture strategies for glass, quartz, polymers and metallic microreactors: A comprehensive review


Dominguez, MI; Centeno, MA; Martinez, TM; Bobadilla, LF; Laguna, OH; Odriozola, JA
Chemical Engineering Research & Design, 171 (2021) 13-35
Química de Superficies y Catálisis

ABSTRACT ▼

One of the most remarkable benefits of the microreactors is the achievement of more efficient processes by enhancing the heat and mass transfer phenomena, which is the key factor for processes intensification in chemical reactions, resulting in higher conversion, selectivity and yield towards desired products. Currently, the entire scenario of microreaction approach is an emergent technology and further advances are ongoing. Several strategies have been successfully applied for structuring processes that imply the fixation of the catalysts on the microreactors. However, there are features such as the physicochemical stability of the coatings under reaction conditions that must be improved, motivating the search for new protocols. This review provides a general overview of the most important methodologies applied for glass, quartz, polymers and metals microreactors manufacture and for their coating, analyzing the advantages and drawbacks of every procedure. Furthermore, an outline of the novel insights based on additive manufacturing techniques are described.


Julio, 2021 | DOI: 10.1016/j.cherd.2021.05.001

Characterizing the physicochemical and mechanical properties of ZrN thin films deposited on Zr substrates by pulsed laser technique


Ghemras, I; Abdelli-Messaci, S; Alili, B; Gonzalez-Elipe, AR; Rico, VJ; Izerrouken, M; Khereddine, AY; Hadj-Larbi, F
European Physical Journal-Applied Physics, 95 (2021) 10301
Nanotecnología en Superficies y Plasma

ABSTRACT ▼

Due to their outstanding physical and mechanical features, ZrN thin films are increasingly used as coatings to protect materials intended for nuclear applications such as Zirconium. To our knowledge, there is no report of pulsed laser deposition (PLD) of ZrN thin films on a Zr substrate. In this work, we have successfully prepared ZrN thin films on Zr substrates using the PLD technique with a KrF excimer laser, in a N-2 environment at 2 Pa pressure and a fixed substrate temperature of 500 degrees C. The deposited 200 nm ZrN thin films exhibited a homogeneous surface and showed a face-centered cubic polycrystalline structure. The surface roughness was 3.69 nm. X-ray diffraction, Raman and X-ray photoelectron spectroscopy measurements confirmed the presence of ZrN. The coated sample's mean value of hardness (11.6 GP) doubled that of the uncoated sample.


Julio, 2021 | DOI: 10.1051/epjap/2021210064

How a small modification in the imidazolium-based SDA can determine the zeolite structure? MFI vs. TON


Megias-Sayago, C; Blanes, JMM; Szyja, BM; Odriozola, JA; Ivanova, S
Microporous and Mesoporous Materials, 322 (2021) 111160
Química de Superficies y Catálisis

ABSTRACT ▼

The present study proposes an important contribution to the understanding of ionic liquid role as structure directing agent for zeolite synthesis. A series of imidazolium based ionic liquids are used for this purpose. While the anionic counterpart influences the micellar organization during the synthesis, the imidazolium cation clearly directs the structure to one or another zeolite family as a function of its substituents and their interaction with the zeolite framework. The experimental observations are contrasted with molecular modeling explaining the distinct zeolite families obtained on the basis of different preferential orientation of the ionic liquids to the Si33 precursor.


Julio, 2021 | DOI: 10.1016/j.micromeso.2021.111160

Tuning the excitation wavelength of luminescent Mn2+-doped ZnSxSe1-x obtained by mechanically induced self-sustaining reaction


Aviles, MA; Gotor, FJ
Optical Materials, 117 (2021) 111121
Reactividad de Sólidos

ABSTRACT ▼

Mn2+-doped ZnSxSe1-x solid solution samples (Mn:ZnSxSe1-x) were synthesized by the mechanochemical process denoted as mechanically-induced self-sustaining reaction from Mn/Zn/S/Se powder elemental mixtures. The samples were characterized by X-ray diffraction, scanning electron microscopy, diffuse reflectance UV-Vis spectroscopy and emission and excitation photoluminescence measurements. The band-gap energy of samples was controlled by changing the stoichiometry, x, of the solid solution. All samples showed the characteristic Mn2+ 4T1-6A1 emission at -588 nm when exciting the host material, so it was possible to tune the excitation wavelength from 349 nm to 467 nm. However, an efficiency loss was observed with increasing Se content, probably due to the overlap between the absorption and emission spectra that induced self-absorption and emission quenching.


Julio, 2021 | DOI: 10.1016/j.optmat.2021.111121

Archeometric characterization (physical-chemical and microstructural) of tiles in the Mudejar Palace of the Royal Alcazar of Seville using non-invasive quantitative chemical methods


Perez-Rodriguez, JL; Robador, MD; Castaing, J; de Viguerie, L; Garrote, MA; Pleguezuelo, A
Boletin de la Sociedad Española de Ceramica y Vidrio, 60 (2021) 211-228

ABSTRACT ▼

The Palaces in the Alcazar of Seville, Spain, are famous for their ceramic decoration. The technique of tessellation was used extensively in all rooms in the Mudejar Palace, dated in the fourteenth century. These glazed ceramics have been analysed in situ using noninvasive quantitative chemical methods of X-ray fluorescence and diffraction (XRF and XRD). Micro-samples were taken to prepare cross-sections and analysed by optical and electronic microscopy. The composition of these ceramics, their manufacturing technique and the time of application in the different areas of the Palace have been characterized in this work. Five colours have been found in the glazed ceramics: green, black, molasses, white and blue. Fe, Co, Cu, Mn and Sn are the main chemical elements responsible for the colour of the glass phase of these ceramics. Wollastonite, quartz, bustamite and feldspars inclusions have been found in the glass phase. Casiterite and Malayaite have been also characterized by XRD. The ceramic paste used for manufacturing was calcic and was heated at about 900 degrees C. Thenardite, gypsum, sodium chloride and nitrogen compounds have been characterized in the ceramic and are responsible for their alteration. The information obtained in the 24 zones studied shows that there is no homogeneity in the ceramics due to the different times in which the tiles were placed and the restorations carried out over time. There are 3 main groups of ceramics: a) probably from 14th century, b), probably from 15-16th centuries and c) from 19-20th centuries and recent restorations. 


Julio, 2021 | DOI: 10.1016/j.bsecv.2020.03.001

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