Menú secundario

Artículos SCI



2020


Development of Ti(C,N)-based cermets with (Co,Fe,Ni)-based high entropy alloys as binder phase


de la Obra, AG; Sayagues, MJ; Chicardi, E; Gotor, FJ
Journal of Alloys and Compounds, 814 (2020) 152218
Reactividad de Sólidos

ABSTRACT

High entropy alloys have been proposed as novel binder phases in cemented carbides and cermets. Many aspects related to the stability of these alloys during the liquid phase sintering process are still unclear and were addressed in this work. Consolidated Ti(C,N)-based cermets using four different (Co,Fe,Ni)based high entropy alloys as the binder phase were obtained. The chosen alloys - CoCrCuFeNi, CoCrFeNiV, CoCrFeMnNi and CoFeMnNiV - were previously synthesized through mechanical alloying and a single alloyed solid solution phase with fcc structure and nanometric character was always obtained. The powdered alloys and the consolidated cermets were analyzed by X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectrometry and transmission electron microscopy. Differential thermal analysis was employed to determine the melting point of the four high entropy alloys that ranged between 1310 degrees C and 1375 degrees C. Although a high temperature of 1575 degrees C was required to obtain the highest cermet densification by pressureless sintering, porosity still remained in most of the cermets. Best densification was achieved when CoCrFeNiV was used as the binder phase. During liquid phase sintering, different compositional changes were observed in the ceramic and binder phases. A core-rim microstructure was observed in cermets containing V in the alloys (CoCrFeNiV and CoFeMnNiV), since this element was incorporated to the carbonitride structure during sintering. A slight Cr segregation was detected in cermets containing Cr, leading to CrTi-rich alloys in small binder regions. However, a great Cu segregation was produced when CoCrCuFeNi was used, and the formation of two different fcc alloys -a Cu-rich and a Cu-depleted- was observed. Finally, a loss of Mn was also evidenced in CoCrFeMnNi and CoFeMnNiV, probably due to its sublimation at the sintering temperature. 


Enero, 2020 | DOI: 10.1016/j.jallcom.2019.152218

Preparation and Characterization of Bio-Based PLA/PBAT and Cinnamon Essential Oil Polymer Fibers and Life-Cycle Assessment from Hydrolytic Degradation


Correa-Pacheco, ZN; Black-Solis, JD; Ortega-Gudino, P; Sabino-Gutierrez, MA; Benitez-Jimenez, JJ; Barajas-Cervantes, A; Bautista-Banos, S; Hurtado-Colmenares, LB
Polymers, 12 (2020) 38
Materiales de Diseño para la Energía y Medioambiente

ABSTRACT

Nowadays, the need to reduce the dependence on fuel products and to achieve a sustainable development is of special importance due to environmental concerns. Therefore, new alternatives must be sought. In this work, extruded fibers from poly (lactic acid) (PLA) and poly (butylene adipate-co-terephthalate) (PBAT) added with cinnamon essential oil (CEO) were prepared and characterized, and the hydrolytic degradation was assessed. A two-phase system was observed with spherical particles of PBAT embedded in the PLA matrix. The thermal analysis showed partial miscibility between PLA and PBAT. Mechanically, Young's modulus decreased and the elongation at break increased with the incorporation of PBAT and CEO into the blends. The variation in weight loss for the fibers was below 5% during the period of hydrolytic degradation studied with the most important changes at 37 degrees C and pH 8.50. From microscopy, the formation of cracks in the fiber surface was evidenced, especially for PLA fibers in alkaline medium at 37 degrees C. This study shows the importance of the variables that influence the performance of polyester-cinnamon essential oil-based fibers in agro-industrial applications for horticultural product preservation.


Enero, 2020 | DOI: 10.3390/polym12010038

Effect of Gold Particles Size over Au/C Catalyst Selectivity in HMF Oxidation Reaction


Megias-Sayago, C; Lolli, A; Bonincontro, D; Penkova, A; Albonetti, S; Cavani, F; Odriozola, JA; Ivanova, S
Chemcatchem (2020)
Química de Superficies y Catálisis

ABSTRACT

A series of gold nanoparticles in the 4-40 nm range were prepared, immobilized on activated carbon and further tested, at low base concentration, in the catalytic oxidation of 5-hydroxymethyl furfural (HMF) to 2,5-furandicarboxylic acid (FDCA). Gold particles size variation has no influence on HMF conversion but significantly affects product selectivity and carbon balance. This behavior is ascribed to the thermodynamically favorable oxygen reduction reaction on Au(100) faces. As the gold particle size decreases the Au(100)/Au(111) exposure ratio, estimated by using the van Hardeveld-Hartog model, increases as well as the FDCA selectivity. The smaller the gold particle size the smaller the 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) to FDCA ratio pointing to the gold size dependent behavior of the oxidation of the alcohol function of the HMF molecule.


Enero, 2020 | DOI: 10.1002/cctc.201901742

Processing and properties of Bi0.98R0.02FeO3 (R = La, Sm, Y) ceramics flash sintered at similar to 650 degrees C in <5 s


Gil-Gonzalez, E; Perejon, A; Sanchez-Jimenez, PE; Raj, R; Perez-Maqueda, LA
Journal of the American Ceramic Society, 103 (2020) 136-144
Reactividad de Sólidos

ABSTRACT

We show that flash sintering produces single‐phase, nanograin‐sized polycrystals of isovalent‐substituted multiferroic ceramics of complex compositions. Single‐phase polycrystals of Bi0.98R0.02FeO3 (R = La, Sm, Y) were produced at a furnace temperature of ~650°C in a few seconds by the application of an electric field of 50 V cm−1, with the current limit set to 40 mA mm−2. The dielectric and insulating properties compared favorably with expected values. Impedance spectroscopy suggests electrically homogenous microstructure, except for the sample Bi0.98La0.02FeO3 that shows a small grain boundary contribution to the impedance. These results reinforce the enabling nature of flash sintering for ceramics which pose difficulties in conventional sintering because they contain low melting constituents or develop secondary phases during the sintering protocol.


Enero, 2020 | DOI: 10.1111/jace.16718

Finite Size Effects on Light Propagation throughout Random Media: Relation between Optical Properties and Scattering Event Statistics


Miranda-Munoz, JM; Esteso, V; Jimenez-Solano, A; Lozano, G; Miguez, H
Advanced Optical Materials, 8 (2020) 1901196
Materiales Ópticos Multifuncionales

ABSTRACT

This work introduces a thorough analysis of light transport in thin optically disordered media. The diffusive properties of a turbid material are generally dictated by the transport mean free path, lt. For depths larger than this characteristic length, light propagation can be considered fully randomized. There is however a range of thicknesses for which light becomes only partly randomized, as it only undergoes a single or very few scattering events. The effects of such finitude are experimentally and theoretically studied on the optical properties of the material, such as the angular distribution of scattered light. Simulations provide insight into the phenomena that occur within the optically disordered slab, like the number of scattering events that photons undergo during propagation throughout the material, as a function of the built‐in wavelength dependent scattering mean free path, lsc. This approach provides fundamental information about photon transport in finite optically random media, which can be put into practice to design diffusers with specific requirements in terms of the spectral and angular properties of the scattered light.


Enero, 2020 | DOI: 10.1002/adom.201901196

New waste-based clinkers for the preparation of low-energy cements. A step forward toward circular economy


Martinez-Martinez, S; Perez-Villarejo, L; Eliche-Quesada, D; Sanchez-Soto, PJ; Christogerou, A; Kanellopoulou, DG; Angelopoulos, GN
International Journal of Applied Ceramic Technology, 17 (2020) 12-21
Materiales Avanzados

ABSTRACT

This paper describes the use of industrial wastes arising from different production processes of the ceramic and marble industries as raw materials for the design and formulation of new cement clinkers with a high content of dicalcium silicate (Belite). The aim was to reintroduce these wastes in the industrial sector and take advantage of them for a greater environmental benefit, as indicated by the principles of the circular economy. Formulations containing 2.5, 5 and 10 wt% of chamotte and marble sludge, respectively, and a waste-free formulation have been designed to obtain clinkers with a content of dicalcium silicate higher than 60 wt%. The different blends have been studied up to a maximum temperature of 1390 degrees C by Thermal Analysis. Other techniques such as XRD, XRF, Modified Bogue Equation, Quality Indexes (LSF, AM, SM) and Optical Microscopy have been used for the study and characterization of industrial wastes, the raw materials and the high belite-type cement dosages. The results indicate that this type of cements can be designed using different types of wastes and in this way reduce the environmental impacts caused by the extraction of raw materials and the deposition of the wastes in landfills, improving the circular economy of the construction industry.


Enero, 2020 | DOI: 10.1111/ijac.13390

Obituary: Prof. José Manuel Criado


Perez-Maqueda, LA; Real, C; Gotor, FJ; Alcala, MD; Malek, J; Koga, N
Journal of Thermal Analysis and Calorimetry, (2020)
Reactividad de Sólidos

ABSTRACT

Influence of DSC thermal lag on evaluation of crystallization kinetics


Svoboda, R; Maqueda, LP; Podzemna, V; Perejon, A; Svoboda, O
Journal of Non-Crystalline Solids, 528 (2020) 119738
Reactividad de Sólidos

ABSTRACT

Influence of added thermal resistance on crystallization kinetics, as measured by differential scanning calorimetry (DSC), of the Se70Te30 glass was studied. The increase of thermal resistance was achieved by adding polytetrafluorethylene discs of different thicknesses (up to 0.5 mm) in-between the DSC platform and the pan with sample. Increase of the thermal resistance led to an apparent decrease (by more than 30%) in the crystallization enthalpy. Significant change of model-free kinetics occurred: apparent activation energy E of the crystallization process decreased (by more than 20%) due to the DSC data being progressively shifted to higher temperatures with increasing heating rate. The model-based kinetics was changed only slightly; the DSC peaks retained their asymmetry and the choice of the appropriate model was not influenced by the added thermal resistance. The temperature shift caused by added thermal lag was modeled for the low-to-moderate heating rates.


Enero, 2020 | DOI: 10.1016/j.jnoncrysol.2019.119738

Low gas consumption fabrication of He-3 solid targets for nuclear reactions


Fernandez, A; Hufschmidt, D; Colaux, JL; Valiente-Dobon, JJ; Godinho, V; de Haro, MCJ; Feria, D; Gadea, A; Lucas, S
Materials & Design, 186 (2020) 108337
Materiales Nanoestructurados y Microestructura

ABSTRACT

Nanoporous solids that stabilize trapped gas nanobubbles open new possibilities to fabricate solid targets for nuclear reactions. A methodology is described based on the magnetron sputtering (MS) technique operated under quasistatic flux conditions to produce such nanocomposites films with He-3 contents of up to 16 at.% in an amorphous-silicon matrix. In addition to the characteristic low pressure (3-6 Pa) needed for the gas discharge, the method ensures almost complete reduction of the process gas flow during film fabrication. The method could produce similar materials to those obtained under classical dynamic flux conditions for MS. The drastic reduction (>99.5%) of the gas consumption is fundamental for the fabrication of targets with scarce and expensive gases. Si:He-3 and W:He-3 targets are presented together with their microstructural (scanning and transmission electron microscopy, SEM and TEM respectively) and compositional (Ion Beam Analysis, IBA) characterization. The He-3 content achieved was over 1 x 10(18) at/cm(2) for film thicknesses between 1.5 and 3 mu m for both Si and W matrices. First experiments to probe the stability of the targets for nuclear reaction studies in inverse kinematics configurations are presented. 


Enero, 2020 | DOI: 10.1016/j.matdes.2019.108337

Enhanced Stability of Perovskite Solar Cells Incorporating Dopant-Free Crystalline Spiro-OMeTAD Layers by Vacuum Sublimation


Barranco, A; Lopez-Santos, MC; Idigoras, J; Aparicio, FJ; Obrero-Perez, J; Lopez-Flores, V; Contreras-Bernal, L; Rico, V; Ferrer, J; Espinos, JP; Borras, A; Anta, JA; Sanchez-Valencia, JR
Advanced Energy Materials, (2020) 1901524
Nanotecnología en Superficies y Plasma

ABSTRACT

The main handicap still hindering the eventual exploitation of organometal halide perovskite-based solar cells is their poor stability under prolonged illumination, ambient conditions, and increased temperatures. This article shows for the first time the vacuum processing of the most widely used solid-state hole conductor (SSHC), i.e., the Spiro-OMeTAD [2,2 ',7,7 '-tetrakis (N,N-di-p-methoxyphenyl-amine) 9,9 '-spirobifluorene], and how its dopant-free crystalline formation unprecedently improves perovskite solar cell (PSC) stability under continuous illumination by about two orders of magnitude with respect to the solution-processed reference and after annealing in air up to 200 degrees C. It is demonstrated that the control over the temperature of the samples during the vacuum deposition enhances the crystallinity of the SSHC, obtaining a preferential orientation along the pi-pi stacking direction. These results may represent a milestone toward the full vacuum processing of hybrid organic halide PSCs as well as light-emitting diodes, with promising impacts on the development of durable devices. The microstructure, purity, and crystallinity of the vacuum sublimated Spiro-OMeTAD layers are fully elucidated by applying an unparalleled set of complementary characterization techniques, including scanning electron microscopy, X-ray diffraction, grazing-incidence small-angle X-ray scattering and grazing-incidence wide-angle X-ray scattering, X-ray photoelectron spectroscopy, and Rutherford backscattering spectroscopy.


Enero, 2020 | DOI: 10.1002/aenm.201901524

Bimodal Nd-Doped LuVO4 Nanoprobes Functionalized with Polyacrilic Acid for X-Ray Computed Tomography and NIR Luminescent Imaging


Nuñez, NO; Cusso, F; Cantelar, E; Martin-Gracia, B; de la Fuente, JM; Corral, A; Balcerzyk, M; Ocaña, M
Nanomaterials, 10 (2020) 149
Materiales Coloidales

ABSTRACT

Uniform Nd3+-doped LuVO4 nanophosphors have been synthesized for the first time in literature by using a poliol-based method at 120 degrees C from Nd3+ and vanadate precursors. After optimizing the Nd doping level, these phosphors present intense luminescence in the near-infrared biological windows. The X-ray attenuation capacity of the optimum nanophosphor has been found to be higher than that of a commercial X-ray computed tomography contrast agent. After surface coating with polyacrylic acid, such nanoparticles present high colloidal stability in physiological pH medium and high cell viability. Because of these properties, the developed Nd3+-doped LuVO4 nanoparticles have potential applications as a bimodal probe for NIR luminescent bioimaging and X-ray computed tomography.


Enero, 2020 | DOI: 10.3390/nano10010149

Tribomechanical properties of hard Cr-doped DLC coatings deposited by low-frequency HiPIMS


Santiago, JA; Fernandez-Martinez, I; Sanchez-Lopez, JC; Rojas, TC; Wennberg, A; Bellido-Gonzalez, V; Molina-Aldareguia, JM; Monclus, MA; Gonzalez-Arrabal, R
Surface & Coatings Technology, 382 (2020) 124899
Tribología y Protección de Superficies

ABSTRACT

Cr-doped diamond-like carbon (Cr-DLC) films with Cr contents ranging from 3 up to 20 at. % were synthesised in a codeposition process with HiPIMS (Cr deposition) and DC-pulsed technology (C deposition). The application of HiPIMS at low frequencies was observed to significantly enhance the energy density during the Cr plasma discharge due to the interaction of Cr-C species. The higher energy bombardment at low HiPIMS frequencies allowed doping with Cr the DLC structure avoiding the graphitization of the carbon structure. EELS spectroscopy was used to evaluate sp(3) content and Raman was used for sp(2) structural characterization of the films. Enhanced mechanical properties (hardness up to 30 GPa) were observed with nanoindentation for Cr-doped DLC at low frequencies. High temperature nanoindentation tests were also performed from room temperature to 425 degrees C in order to evaluate the evolution of hardness and Young Modulus with temperature. The results showed that the mechanical properties at high temperature mainly depend on the initial sp(3)-sp(2) structure. Tribological tests were carried out in air from room temperature to 250 degrees C. Cr-doped DLC coatings deposited by low-frequency HiPIMS showed lower friction and wear compared to undoped DLC.


Enero, 2020 | DOI: 10.1016/j.surfcoat.2019.124899

Dipole reorientation and local density of optical states influence the emission of light-emitting electrochemical cells


Jimenez-Solano, Alberto; Martinez-Sarti, Laura; Pertegas, Antonio; Lozano, Gabriel; Bolink, Henk J; Miguez, Hernan
Physical Chemistry Chemical Physics
Materiales Ópticos Multifuncionales

ABSTRACT

Herein, we analyze the temporal evolution of the electroluminescence of light-emitting electrochemical cells (LECs), a thin-film light-emitting device, in order to maximize the luminous power radiated by these devices. A careful analysis of the spectral and angular distribution of the emission of LECs fabricated under the same experimental conditions allows describing the dynamics of the spatial region from which LECs emit, i.e. the generation zone, as bias is applied. This effect is mediated by dipole reorientation within such an emissive region and its optical environment, since its spatial drift yields a different interplay between the intrinsic emission of the emitters and the local density of optical states of the system. Our results demonstrate that engineering the optical environment in thin-film light-emitting devices is key to maximize their brightness.


Enero, 2020 | DOI: 10.1039/c9cp05505c

Effect of synthesis pH on the physicochemical properties of a synthesized Bi2WO6 and the type of substrate chosen, in assessing its photo-catalytic activities


Jaramillo-Páez, C.; Navío, J.A.; Hidalgo, M.C.
Arabian Journal of Chemistry, 13 (2020) 431-443
Fotocatálisis Heterogénea: Aplicaciones

ABSTRACT

Crystalline orthorhombic Bi2WO6 powders were synthesized by a hydrothermal method from aqueous solutions of Bi(NO3)35H2O and Na2WO42H2O over a range of three selected pH values (2.0, 5.0 and 7.0), using NaOH as precipitating agent. The as-prepared catalysts were characterized by XRD, BET, FE-SEM, TEM, XPS and UV-vis spectroscopy. The effect of pH-synthesis on crystallinity,  morphologies, surface area and optical absorption properties, were investigated.
Although the pH has a marked influence on morphology, the nature of the precipitating agent (NaOH or TEA) also influences the morphology and surface structure composition, as it is observed in the present work. Three different probe molecules were used to evaluate the photocatalytic properties under two illumination conditions (UV and Visible): Methyl Orange and Rhodamine B were chosen as dye substrates and Phenol as a transparent substrate. The photo-catalytic activities are strongly dependent not only on the pH used in the synthesis but also on the nature of the chosen substrate in assessing the photo-catalytic activities. Results were compared with those obtained when using TiO2(P25, Evonik) in the same experimental conditions. The photocatalytic activity of one of the synthesised samples has been evaluated by exposing a mixture of Rhodamine B and Phenol in water, to different illumination conditions. Our results provide new evidences about the issue of whether dyes are suitable substrates to assess the activity of a photo-catalyst.


Enero, 2020 | DOI: 10.1016/j.arabjc.2017.05.014



2019


Porous Graphene-like Carbon from Fast Catalytic Decomposition of Biomass for Energy Storage Applications


Gomez-Martin, A; Martinez-Fernandez, J; Ruttert, M; Winter, M; Placke, T; Ramirez-Rico, J
ACS Omega, 4 (2019) 21446-21458
Materiales de Diseño para la Energía y Medioambiente

ABSTRACT

A novel carbon material made of porous graphene-like nanosheets was synthesized from biomass resources by a simple catalytic graphitization process using nickel as a catalyst for applications in electrodes for energy storage devices. A recycled fiberboard precursor was impregnated with saturated nickel nitrate followed by high-temperature pyrolysis. The highly exothermic combustion of in situ formed nitrocellulose produces the expansion of the cellulose fibers and the reorganization of the carbon structure into a three-dimensional (3D) porous assembly of thin carbon nanosheets. After acid washing, nickel particles are fully removed, leaving nanosized holes in the wrinkled graphene-like sheets. These nanoholes confer the resulting carbon material with approximate to 75% capacitance retention, when applied as a supercapacitor electrode in aqueous media at a specific current of 100 A.g(-1) compared to the capacitance reached at 20 mA.g(-1), and approximate to 35% capacity retention, when applied as a negative electrode for lithium-ion battery cells at a specific current of 3720 mA.g(-1) compared to the specific capacity at 37.2 mA.g(-1). These findings suggest a novel way for synthesizing 3D nanocarbon networks from a cellulosic precursor requiring low temperatures and being amenable to large-scale production while using a sustainable starting precursor such as recycled fiberwood.


Diciembre, 2019 | DOI: 10.1021/acsomega.9b03142

Dry Reforming of Ethanol and Glycerol: Mini-Review


Yu, J; Odriozola, JA; Reina, TR
Catalysts, 9 (2019) art. 1015
Química de Superficies y Catálisis

ABSTRACT

Dry reforming of ethanol and glycerol using CO2 are promising technologies for H-2 production while mitigating CO2 emission. Current studies mainly focused on steam reforming technology, while dry reforming has been typically less studied. Nevertheless, the urgent problem of CO2 emissions directly linked to global warming has sparked a renewed interest on the catalysis community to pursue dry reforming routes. Indeed, dry reforming represents a straightforward route to utilize CO2 while producing added value products such as syngas or hydrogen. In the absence of catalysts, the direct decomposition for H-2 production is less efficient. In this mini-review, ethanol and glycerol dry reforming processes have been discussed including their mechanistic aspects and strategies for catalysts successful design. The effect of support and promoters is addressed for better elucidating the catalytic mechanism of dry reforming of ethanol and glycerol. Activity and stability of state-of-the-art catalysts are comprehensively discussed in this review along with challenges and future opportunities to further develop the dry reforming routes as viable CO2 utilization alternatives.


Diciembre, 2019 | DOI: 10.3390/catal9121015

Silver effect on the tribological and antibacterial properties of a-C:Ag coatings


Dominguez-Meister, S; Rojas, TC; Frias, JE; Sanchez-Lopez, JC
Tribology International, 140 (2019) UNSP 105837
Tribología y Protección de Superficies

ABSTRACT

a-C:Ag coatings (1.2-23.4 at.% of Ag) were deposited using magnetron sputtering. Ag nanoparticles appear embedded in the carbon matrix or segregated to the column boundaries or surface. The silver doping has not promoted significant changes of the sp(2)/sp(3) ratio although a decrease of the hardness is observed (from 17 to 7 GPa). The tribological behavior did not show a clear dependence on the silver concentration in unlubricated or lubricated conditions (fetal bovinum serum) against alumina or UHMWPE balls. Ag nanoparticle dispersion enhanced the bactericide behavior as determined by the released Ag+ ion in the fluid media. There is no clear effect of friction rubbing on the released silver indicating that diffusion and top segregation are prevalent mechanisms for its dissolution.


Diciembre, 2019 | DOI: 10.1016/j.triboint.2019.06.030

3D Organic Nanofabrics: Plasma-Assisted Synthesis and Antifreezing Behavior of Superhydrophobic and Lubricant-Infused Slippery Surfaces


Alcaire, M; Lopez-Santos, C; Aparicio, FJ; Sanchez-Valencia, JR; Obrero, JM; Saghi, Z; Rico, VJ; de la Fuente, G; Gonzalez-Elipe, AR; Barranco, A; Borras, A
Langmuir, 35 (2019) 16876-16885
Nanotecnología en Superficies y Plasma

ABSTRACT

Herein, we present the development of supported organic nanofabrics formed by a conformal polymer-like interconnection of small-molecule organic nanowires and nanotrees. These organic nanostructures are fabricated by a combination of vacuum and plasma-assisted deposition techniques to generate step by step, single-crystalline organic nanowires forming one-dimensional building blocks, organic nanotrees applied as three-dimensional templates, and the polymer-like shell that produces the final fabric. The complete procedure is carried out at low temperatures and is compatible with an ample variety of substrates (polymers, metal, ceramics; either planar or in the form of meshes) yielding flexible and low solid-fraction three-dimensional nanostructures. The systematic investigation of this progressively complex organic nanomaterial delivers key clues relating their wetting, nonwetting, and anti-icing properties with their specific morphology and outer surface composition. Water contact angles higher than 150° are attainable as a function of the nanofabric shell thickness with outstanding freezing-delay times (FDT) longer than 2 h at −5 °C. The role of the extremely low roughness of the shell surface is settled as a critical feature for such an achievement. In addition, the characteristic interconnected microstructure of the nanofabrics is demonstrated as ideal for the fabrication of slippery liquid-infused porous surfaces (SLIPS). We present the straightforward deposition of the nanofabric on laser patterns and the knowledge of how this approach provides SLIPS with FDTs longer than 5 h at −5 °C and 1 h at −15 °C.


Diciembre, 2019 | DOI: 10.1021/acs.langmuir.9b03116

Design swelling micas: Insights on heavy metals cation exchange reaction


Osuna, FJ; Pavon, E; Alba, MD
Applied Clay Science, 182 (2019) 105298
Materiales de Diseño para la Energía y Medioambiente

ABSTRACT

Heavy metal pollution has become one of the most serious environmental problems, demanding specialized remediation mechanisms. Among the studied treatments, ion-exchange processes have been widely used due to their high remediation capacity, efficiency and fast kinetic. Here, the potential use of a new family of design micas as cation exchanger has been analysed. Micas with a layer charge in the range of brittle micas have been synthesized and their heavy metals cation exchange capacity analysed as a function of the nature of the heavy metal cations (Pb2+, Cd2+ or Hg2+), the nature of the counterions (Cl− or NO3−), concentration of the solutions and the micas layer charge. A cation exchange ratio between 35% and 154% of their cation exchange capacity (CEC) was achieved, being more efficient when mica layer charge diminished. In general, the maximum adsorption capacity followed the trend: Hg2+ > Pb2+ > Cd2+. The efficiency of the cation exchange and adsorption mechanism of the synthetic micas depended on the experimental conditions and they were more efficient than raw and modified natural clay minerals.


Diciembre, 2019 | DOI: 10.1016/j.clay.2019.105298

Understanding segregation processes in SAMs formed by mixtures of hydroxylated and non-hydroxylated fatty acids


Bueno, OVM; Benitez, JJ; San-Miguel, MA
RSC Advances, 9 (2019) 39252-39263
Materiales de Diseño para la Energía y Medioambiente

ABSTRACT

In this paper, we focus on the segregation processes emerging when preparing mixtures with different compositions of aleuritic (9,10,16 trihydroxyhexadecanoic) (ALE) and palmitic (hexadecanoic) (PAL) acids. The combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations enabled us to prove the role of the functional groups in the formation of self-assembled monolayers (SAMs) on muscovite mica surfaces. MD simulations indicate that segregation processes are favored in high ALE composition mixtures in agreement with the experimental evidence, whereas low ALE compositions promote the co-existence between segregated and dispersed systems. The secondary hydroxyl groups play a central role in the self-assembling mechanism because they control the formation of hydrogen bonding networks guarantying system stability.


Diciembre, 2019 | DOI: 10.1039/c9ra06799j

Páginas

icms