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Scientific Papers in SCI

2020


Role of Fe(III) in aqueous solution or deposited on ZnO surface in the photoassisted degradation of rhodamine B and caffeine


Tanji, Karim; Navio, J A; Martin-Gomez, A N; Hidalgo, M C; Jaramillo-Paez, C; Naja, Jamal; Hassoune, Hicham; Kherbeche, Abdelhak
Chemosphere, 241 (2020) 125009

ABSTRACT

Iron (III) was incorporated, to the surface of a synthesized ZnO, using two nominal molar percentages of Fe (III): 1% and 5% Fe relative to ZnO. Samples dried and calcined at 200 °C and 400 °C for 2 h, were characterized by XRD, XPS, XRF, N2-adsorption-BET and (UV–vis)-DRS. Photocatalytic activities of the catalysts were assessed based on the degradation of rhodamine B (RhB) and caffeine (CAF) in aqueous solution under two irradiation conditions: UV and visible light illumination. Prior to the photocatalytic tests, the interaction of each one of the substrates with either Fe(III) or Fe(II) was studied in homogeneous medium under UV-illumination and oxygenated environment. It was found that Fe (III) can play an important role in homogeneous media in the photoassisted degradation, both of rhodamine B and caffeine, while Fe (II) does not exert a relevant role in the photoassisted degradation of the referred substrates. Fe–ZnO samples display similar or poorer performance than pure ZnO in the presence of UV light for both studied substrates. The phenomenon can be attributed to the formation of either goethite or ZnFe2O4 at the ZnO surface where the coupled Fe3+/Fe2+ can act as recombination centers for the photogenerated charges. On the contrary, all Fe–ZnO samples showed enhanced photocatalytic activity under visible illumination which seems to be independent of the iron content. In this context, the mechanisms for photoassisted degradation of both the substrates in homogeneous medium and photocatalytic degradation are discussed, as well as the role of Fe in the photodegradation processes.


February, 2020 | DOI: 10.1016/j.chemosphere.2019.125009

2019


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

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.


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

Phyllite clays as raw materials replacing cement in mortars: Properties of new impermeabilizing mortars


Arce, Carolina; Garzon, Eduardo; Sanchez-Soto, Pedro J.
Construction and Building Materials, 224 (2019) 348-358

ABSTRACT

The aim of this investigation was to determine the suitability of phyllite clays as a raw construction material. For that purpose, the cement in mortars was replaced by a phyllite clay (0–90 wt%) making this study the first of its kind to be performed. These materials were prepared with different water proportions according to the water content and water/cement and water/binder (cement plus phyllite clay) relationships. A comparative study of the most important properties of the resulting experimental mortars was carried out, such as apparent density, water retentivity, consistency and mechanical strength (flexural and compressive strength), along with an evaluation of the pozzolanic activity and permeability. The results showed that the increase of phyllite decreases the apparent density, the consistency and mechanical properties of the mortar, while water retentivity fluctuates. Good correlations (R2 > 0.84) were obtained between flexural and compressive strength for the mortars after 28 days of curing. Pozzolanic activity was observed at cement replacement of 80 wt% of phyllite. Moreover, new impermeabilizing mortars constituted by phyllite clay and cement have been obtained according to the low coefficients of permeability. Taking into account the findings of this research, phyllite clays can be applied as raw construction materials with savings derived from replacing cement in mortars and the low energy consumption involved in their production. However, the present study concluded that the use of phyllite clays did not improve the mechanical strength of these new mortars but, in contrast, they can be applied for impermeabilization purposes in Construction and Civil Engineering.


November, 2019 | DOI: 10.1016/j.conbuildmat.2019.07.081

Graphene nanoplatelets for electrically conductive 3YTZP composites densified by pressureless sintering


Lopez-Pernia, C; Gallardo-Lopez, A; Morales-Rodriguez, A; Poyato, R
Journal of the European Ceramic Society, 39 (2015) 4435-4439

ABSTRACT

3 mol% yttria tetragonal zirconia polycrystalline (3YTZP) ceramic composites with 2.5, 5 and 10 vol% graphene nanoplatelets (GNP) were pressureless sintered in argon atmosphere between 1350 and 1450 degrees C. The effects of the GNP content and the sintering temperature on the densification, microstructure and electrical properties of the composites were investigated. An isotropic distribution of GNP surrounding ceramic regions was exhibited regardless the GNP content and sintering temperature used. Electrical conductivity values comparable to the ones of fully dense composites prepared by more complex techniques were obtained, even though full densification was not achieved. While the composite with 5 vol% GNP exhibited electrical anisotropy with a semiconductor-type behaviour, the composite with 10 vol% GNP showed an electrically isotropic metallic-type behaviour.


November, 2019 | DOI: 10.1016/j.jeurceramsoc.2019.05.067

Colombian metallurgical coke as catalysts support of the direct coal liquefaction


Rico, D; Agamez, Y; Romero, E; Centeno, MA; Odriozola, JA; Diaz, JD
Fuel, 255 (2019) 115748

ABSTRACT

A Colombian metallurgical coke was modified in its surface chemistry and was used as support of iron sulfide catalysts for direct coal liquefaction. The modification was made by treatments with diluted oxygen and HNO3 at different conditions. Changes in surface chemistry were studied by determining the point of zero charge (PZC), the isoelectric point (IEP), thermogravimetric analysis (TGA), temperature programmed decomposition-mass spectrometry (TPD-MS), Diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS) and nitrogen adsorption at 77 K. The results show that the materials obtained have a wide range of functional groups incorporated in a different proportion and quantity. The textural parameters indicate that treatment with diluted oxygen increases the surface area and incorporates micropores while the samples treated with HNO3 maintain the textural properties of the original material. The catalysts were also characterized by Raman spectroscopy. It was found that impregnation with the iron sulfide precursor does not significantly affect the Raman characteristics of the support. Additionally, XRD analysis shows smaller pyrite crystallites in the coke enriched with oxygenated groups of phenol and lactone indicating better dispersion of the active phase. The amount of oxygen chemisorbed per gram of catalyst shows that both, oxygen and nitric acid treatments, improve the relative dispersion of the active phase. It was found that the presence of the catalysts increases the conversion and yields towards oils and gases with respect to those of the tests without catalysts. Cokes modified by dilute oxygen gaseous treatment contain surface phenol and lactone groups and present the highest yield to oils.


November, 2019 | DOI: 10.1016/j.fuel.2019.115748

The influence of mechanical activation process on the microstructure and mechanical properties of bulk Ti2AlN MAX phase obtained by reactive hot pressing


Salvo, C; Chicardi, E; Garcia-Garrido, C; Jimenez, JA; Aguilar, C; Usuba, J; Mangalaraja, RV
Ceramics International, 45 (2019) 17793-17799

ABSTRACT

The effect of mechanical activation process on the microstructure and mechanical properties of bulk nanostructured Ti2AlN compound has been investigated in this work. The mixture of Ti and AlN powders was prepared in a 2:1 molar ratio, and a part of this powder was subjected to a high-energy milling process under argon atmosphere for 10 h using agate as grinding media. Finally, the densification and formation of the ternary Ti2AlN MAX phase through solid state reaction of both unmilled and milled powders were carried out by hot pressing under 15 or 30 MPa at 1200 degrees C for 2 h. The microstructure of precursor powder mixtures and the consolidated samples was characterized by using X-ray diffraction (XRD) and a scanning electron microscope equipped with an energy dispersive X-ray spectroscopy (SEM/EDS). The X-ray diffraction patterns were fitted using the Rietveld refinement for phase quantification and to determine their most important microstructural parameters. Microstructure and mechanical properties of the consolidated samples were correlated with the load used for the hot pressing process. The substantial increase of hardness, the higher densification and the lower grain sizes observed in the samples prepared from the activated powders were attributed to the formation of second phases like Ti5Si3 and Al2O3.


October, 2019 | DOI: 10.1016/j.ceramint.2019.05.350

Sintering kinetics, defect chemistry and room-temperature mechanical properties of titanium nitride prepared by spark plasma sintering


Chavez, JMM; Moshtaghioun, BM; Hernandez, FLC; Garcia, DG
Journal of Alloys and Compounds, 807 (2019) 151666

ABSTRACT

Fully dense titanium nitride polycrystals have been prepared by spark plasma sintering. The kinetics of the sintering process and the optimized conditions for SPS processing have been put forward. Microstructural analyses of the resulting samples have unambiguously shown the coexistence of titanium as Ti2+, Ti3+ and Ti4+, thus driving the presence of cation vacancies. This fact is a new ingredient which is shown to influence the mechanical properties of this strategic ceramic. 


October, 2019 | DOI: 10.1016/j.jallcom.2019.151666

The Calcium-Looping (CaCO3/CaO) process for thermochemical energy storage in Concentrating Solar Power plants


Ortiz, C; Valverde, JM; Chacartegui, R; Perez-Maqueda, LA; Gimenez, P
Renewable & Sustanaible Energy Reviews, 113 (2019) 109252

ABSTRACT

Energy storage based on thermochemical systems is gaining momentum as a potential alternative to molten salts in Concentrating Solar Power (CSP) plants. This work is a detailed review about the promising integration of a CaCO3/CaO based system, the so-called Calcium-Looping (CaL) process, in CSP plants with tower technology. The CaL process relies on low cost, widely available and non-toxic natural materials (such as limestone or dolomite), which are necessary conditions for the commercial expansion of any energy storage technology at large scale. A comprehensive analysis of the advantages and challenges to be faced for the process to reach a commercial scale is carried out. The review includes a deep overview of reaction mechanisms and process integration schemes proposed in the recent literature. Enhancing the multicycle CaO conversion is a major challenge of the CaL process. Many lab-scale analyses carried out show that residual effective CaO conversion is highly dependent on the process conditions and the CaO precursors used, reaching values in a wide range (0.07–0.82). The selection of the optimal operating conditions must be based on materials performance, process integration, technology and economics aspects. Global plant efficiencies over 45% (without considering solar-side losses) show the interest of the technology. Furthermore, the technological maturity and potential of the process is assessed. The direction towards which future works should be headed is discussed.


October, 2019 | DOI: 10.1016/j.rser.2019.109252

Effect of starch as binder in carbon aerogel and carbon xerogel preparation


Rodriguez, N; Agamez-Pertuz, YY; Romero, E; Diaz-Velasquez, JD; Odriozola, JA; Centeno, MA
Journal of Non-Crystalline Solids, 522 (2019) UNSP 119554

ABSTRACT

Carbon aerogels and carbon xerogels were synthesized through resorcinol - formaldehyde polycondensation using Na2CO3 as catalyst. The effect of soluble starch introduction in the organic gel preparation on the porous surface properties of these materials was studied. The role of the drying process of the organic gels on the changes in the surface and structural properties of these materials after the addition of soluble starch is discussed. The presence of starch in the prepared carbon xerogels results in the development of microporosity while maintaining the characteristic mesoporosity of carbon xerogels. The Brunauer - Emmett -Teller (BET) surface area increases from 309 m(2)/g in carbon xerogel without soluble starch until 685 m(2)/g when 10% of soluble starch is added. The R- value and average crystallite lattice parameters, inter-layer spacing, crystallite height, crystallite diameter and the average number of aromatic layers per carbon crystallite are discussed in function of drying step and presence of soluble starch. The surface properties were also studied by Raman and DRIFT spectroscopies.


October, 2019 | DOI: 10.1016/j.jnoncrysol.2019.119554

Highly selective few-ppm NO gas-sensing based on necklace-like nanofibers of ZnO/CdO n-n type I heterojunction


Naderi, H; Hajati, S; Ghaedi, M; Espinos, JP
Sensors and Actuators B-Chemical, 297 (2019) 126774

ABSTRACT

Electrospinning method followed by calcination is applied to synthesize ZnO/CdO nanofibers. Characterization is performed by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and reflection electron energy loss spectroscopy (REELS), which resulted in detailed analysis of the sensing material. For instance, it was found that the ZnO/CdO is n-n type I heterojunction which possesses straddling energy band gap, which could affect the mechanism of gas sensing. An electroless gold-plated interdigitated electrode with spacing 200 mu m is fabricated on alumina substrate to host the designed nanofibers being used as gas sensor. Gas-sensing activity of the heterojunction is investigated against NO, NO2, H2S, CH4, SO2 and CO in addition to VOCs such as ethanol, acetone, ammonia, methanol, and chloroform with high selectivity and response to NO gas by monitoring resistance changes. Detailed discussion on the mechanism of sensing is presented. The ZnO/CdO nanofibers are found to be highly sensitive to very low concentration range of NO gas (1.2-33 ppm) at optimal operating temperature of 215 degrees C. The influence of humidity (20-96%) on the sensor response was found to be ignorable. Additionally, good repeatability and long-term stability (45 days, every 5 days, SD = 0.7) was obtained for this sensor. Typically, short response times of 47 and 35 s are obtained versus 3 and 33 ppm of NO, respectively, making our sensor promisingly applicable for monitoring this toxic gas in polluting industries, metropolises and maybe in exhaled breath.


October, 2019 | DOI: 10.1016/j.snb.2019.126774

From structure to luminescence investigation of oxyfluoride transparent glasses and glass-ceramics doped with Eu3+/Dy3+ ions


Walas, M; Lisowska, M; Lewandowski, T; Becerro, AI; Lapinski, M; Synak, A; Sadowski, W; Koscielska, B
Journal of Alloys and Compounds, 896 (2019) 1410-1418

ABSTRACT

Glasses and glass-ceramics with nominal composition 73 TeO2- 4BaO-3Bi(2)O(3)-18SrF(2)-2RE(2)O(3) (where RE = Eu, Dy) have been synthesized by conventional melt-quenching technique and subsequent heat treatment at 370 degrees C for 24 h in air atmosphere. Various Eu3+ to Dy3+ molar ratio have been applied to investigate luminescence properties in both glass and glass-ceramic matrices. Especially, white light emission through simultaneous excitation of Eu3+ and Dy3+ has been studied in detail. Influence of crystalline SrF2 phase on luminescence kinetics has been determined by luminescence decay time measurements. Presence of crystalline SrF2 phase has been confirmed by X-ray diffraction technique XRD and transmission electron microscopy TEM. X-ray photoelectron spectroscopy XPS and Fourier-transform infrared spectroscopy FTIR have been applied to get further insight into structural properties of glass and glass-ceramic materials. Color tunable white light emission has been obtained using UV excitation. Influence of the SrF2 crystallization on luminescence properties of prepared materials have been described in detail. Moreover, luminescence properties and especially emission color dependence on the Eu3+ to Dy3+ molar ratio have been exhaustively studied. Color-tunable white light emission has been observed as a result of simultaneous radiative transition of both, Eu3+ and Dy3+ ions when applying UV excitation. Judd - Ofelt and other optical parameters have been calculated based on luminescence emission spectra. Achieved results confirm that tellurite glass-ceramics containing SrF2 nanocrystals are good hosts for RE3+ ions and they can be considered as new phosphors for white light emitting diodes WLEDs.


October, 2019 | DOI: 10.1016/j.jallcom.2019.07.017

Sodium ion storage performance of magnetron sputtered WO3 thin films


Garcia-Garcia, FJ; Mosa, J; Gonzalez-Elipe, AR; Aparicio, M
Electrochimica Acta, 321 (2019) 134669

ABSTRACT

WO3 thin film electrodes were successfully prepared by magnetron sputtering (MS) deposition under an oblique angle configuration (OAD). Intercalation of Na ions in the tungsten oxide layers has been studied using electrochemical techniques. Sample characterization before and after sodium intercalation has been carried out by Raman, XPS and XRD measurements. ToF-SIMS analysis has been also performed in order to analyze the element depth profiles along the electrode thickness. Electron microscopy evaluation of the cross section confirms the porous structure of the coatings. Batteries integrating these WO3 electrodes have a discharge capacity of 120 mA h g(-1) at the initial cycles and show an adequate capacity retention upon 300 cycles. The WO3-OAD thin-films are proposed as promising electrodes for Na-ion batteries.


October, 2019 | DOI: 10.1016/j.electacta.2019.134669

Synthesis, functionalization and properties of uniform europium-doped sodium lanthanum tungstate and molybdate (NaLa(XO4)(2), X = Mo,W) probes for luminescent and X-ray computed tomography bioimaging


Laguna, M; Nunez, NO; Becerro, AI; Lozano, G; Moros, M; de la Fuente, JM; Corral, A; Balcerzyk, M; Ocana, M
Journal of Colloid and Interface Science, 554 (2019) 520-530

ABSTRACT

A one-pot simple procedure for the synthesis of uniform, ellipsoidal Eu3+-doped sodium lanthanum tungstate and molybdate (NaLa(XO4)(2), X = W, Mo) nanophosphors, functionalized with carboxylate groups, is described. The method is based on a homogeneous precipitation process at 120 degrees C from appropriate Na+ Ln(3+) and tungstate or molybdate precursors dissolved in ethylene glycol/water mixtures containing poly acrylic acid. A comparative study of the luminescent properties of both luminescent materials as a function of the Eu3+ doping level has been performed to find the optimum nanophosphor, whose efficiency as X-ray computed tomography contrast agent is also evaluated and compared with that of a commercial probe. Finally, the cell viability and colloidal stability in physiological pH medium of the optimum samples have also been studied to assess their suitability for biomedical applications.


October, 2019 | DOI: 10.1016/j.jcis.2019.07.031

Extraordinary visible photocatalytic activity of a Co0.2Zn0.8O system studied in the Remazol BB oxidation


KarimTanji; J.A.Navio; Jamal Naja; M.C.Hidalgo; Abdellah Chaqroune; C.Jaramillo-Páez; Abdelhak Kherbeche
Journal of Photochemistry and Photobiology A: Chemistry, 382 (2019) 111877

ABSTRACT

Nanoparticles of CoxZn1-xO system with a nominal composition of x=0.2 were synthesized by the Solution Combustion Method (SCM). Structural and morphological studies as well as the chemical composition of the material were widely investigated by different techniques. Photocatalytic activity under UV and Visible illumination was studied by means of the Remazol Brilliant Blue dye (RBB) oxidation reaction. The effect of different experimental parameters, such as the initial dye concentration, photocatalyst mass, pH or hydrogen peroxide concentration on the RBB discoloration under UV irradiation was studied. Optimal experimental conditions were found to be a photocatalyst mass of 1 g.L-1, dye concentration of 20 mg.L-1 and solution pH of 11. Hydrogen peroxide addition was found to have no effect in the photocatalytic behavior of the material in the range of concentration studied (0 to 6•10-4 M). The optimal parameters were chosen to investigate the degradation of RBB under UV-illumination and just visible illumination. It was observed that the UV-photocatalytic property of pristine ZnO for the RBB removal was scarcely improved after cobalt-incorporation, whereas the effect of cobalt incorporation into ZnO greatly enhanced the RBB conversion under visible illumination. Even more interesting is that, under same experimental conditions, the visible efficiency of the Co-ZnO system is the same that the one showed under UV illumination, i.e. the system does not loose efficiency when illuminated only with visible light.


September, 2019 | DOI: 10.1016/j.jphotochem.2019.111877

Insoluble and Thermostable Polyhydroxyesters From a Renewable Natural Occurring Polyhydroxylated Fatty Acid


Benitez, JJ; Guzman-Puyol, S; Cruz-Carrillo, MA; Ceseracciu, L; Moreno, AG; Heredia, A; Heredia-Guerrero, JA
Frontiers in Chemistry, 7 (2019) art. 643

ABSTRACT

To explore the potential of long chain polyhydroxyalkanoates as non-toxic food packaging materials, the characterization of polyesters prepared from a natural occurring polyhydroxylated C16 carboxylic acid (9,10,16-trihydroxyhexadecanoic or aleuritic acid) has been addressed. Such monomer has been selected to elucidate the reactivity of primary and secondary hydroxyl groups and their contribution to the structure and properties of the polyester. Resulting polyaleuritate films have been produced using an open mold in one-step, solvent-free self-polycondensation in melt state and directly in air to evaluate the effect of oxygen in their final physical and chemical properties. These polymers are amorphous, insoluble, and thermostable, being therefore suitable for solvent, and heat resistant barrier materials. Structurally, most of primary hydroxyls are involved in ester bonds, but there is some branching arising from the partial participation of secondary O-H groups. The oxidative cleavage of the vicinal diol moiety and a subsequent secondary esterification had a noticeable effect on the amorphization and stiffening of the polyester by branching and densification of the ester bond network. A derivation of such structural modification was the surface compaction and the reduction of permeability to water molecules. The addition of Ti(OiPr)(4) as a catalyst had a moderate effect, likely because of a poor diffusion within the melt, but noticeably accelerated both the secondary esterification and the oxidative processes. Primary esterification was a high conversion bulk reaction while oxidation and secondary esterification was restricted to nearby regions of the air exposed side of cast films. The reason was a progressive hindering of oxygen diffusion as the reaction progresses and a self-regulation of the altered layer growth. Despite such a reduced extent, the oxidized layer noticeably increased the UV-vis light blockage capacity. In general, characterized physical properties suggest a high potential of these polyaleuritate polyesters as food preserving materials.


September, 2019 | DOI: 10.3389/fchem.2019.00643

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, (2019)

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.


September, 2019 | DOI: 10.1111/ijac.13390

Correlation of Structure and Performance of Hard Carbons as Anodes for Sodium Ion Batteries


Gomez-Martin, A; Martinez-Fernandez, J; Ruttert, M; Winter, M; Placke, T; Ramirez-Rico, J
Chemistry of Materials, 31 (2019) 7288-7299

ABSTRACT

Hard carbons are the material of choice as negative electrode in sodium ion batteries. Despite being extensively studied, there is still debate regarding the mechanisms responsible for storage in low- and high-potential regions. This work presents a comprehensive approach to elucidate the involved storage mechanisms when Na ions insert into such disordered structures. Synchrotron X-ray total scattering experiments were performed to access quantitative information on atomic ordering in these materials at the nanoscale. Results prove that hard carbons undergo an atomic rearrangement as the graphene layers cross-link at intermediate temperatures (1200-1600 degrees C), resulting in an increase of the average interplanar distance up to 1400 degrees C, followed by a progressive decrease. This increase correlates with the positive trend in the reversible capacity of biomass-derived carbons when processed up to 1200-1600 degrees C due to an increased capacity at low potential (<= 0.1 V vs Na/Na+). A decrease in achievable sloping capacity with increasing heat-treatment temperature arises from larger crystalline domains and a lower concentration of defects. The observed correlation between structural parameters and electrochemical properties clearly supports that the main storage of Na ions into a hard-carbon structure is based on an adsorption-intercalation mechanism.


September, 2019 | DOI: 10.1021/acs.chemmater.9b01768

Antibacterial Nanostructured Ti Coatings by Magnetron Sputtering: From Laboratory Scales to Industrial Reactors


Alvarez, R; Munoz-Pina, S; Gonzalez, MU; Izquierdo-Barba, I; Fernandez-Martinez, I; Rico, V; Arcos, D; Garcia-Valenzuela, A; Palmero, A; Vallet-Regi, M; Gonzalez-Elipe, AR; Garcia-Martin, JM
Nanomaterials, 9 (2019) art. 1217

ABSTRACT

Based on an already tested laboratory procedure, a new magnetron sputtering methodology to simultaneously coat two-sides of large area implants (up to similar to 15 cm(2)) with Ti nanocolumns in industrial reactors has been developed. By analyzing the required growth conditions in a laboratory setup, a new geometry and methodology have been proposed and tested in a semi-industrial scale reactor. A bone plate (DePuy Synthes) and a pseudo-rectangular bone plate extracted from a patient were coated following the new methodology, obtaining that their osteoblast proliferation efficiency and antibacterial functionality were equivalent to the coatings grown in the laboratory reactor on small areas. In particular, two kinds of experiments were performed: Analysis of bacterial adhesion and biofilm formation, and osteoblasts-bacteria competitive in vitro growth scenarios. In all these cases, the coatings show an opposite behavior toward osteoblast and bacterial proliferation, demonstrating that the proposed methodology represents a valid approach for industrial production and practical application of nanostructured titanium coatings.


September, 2019 | DOI: 10.3390/nano9091217

2018


A QTAIM and DFT study of the dizinc bond in non-symmetric [CpZn2Ln] complexes


Ayala, R; Galindo, A
Journal of Organometallic Chemistry, 898 (2019) UNSP 120878

ABSTRACT

Several [Zn2L2] and [CpZn2Ln] dizinc compounds have been studied by density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) in order to compare the nature and topology of the Zn-Zn bond in symmetrical and non-symmetrical complexes. The stability of these complexes have been evaluated on the basis of the formation energies. The disproportionation reaction has also been analysed indicating that symmetric complexes are less stable than non-symmetric ones. To certain extent, the properties of the [CpZn2Ln] complexes are between those of the [Zn2L2] and [Zn2Cp2] compounds. The asymmetry of the [CpZn2Ln] compounds is illustrated in terms of the topological properties, especially in the Source Function (SF) and Natural Bond Orbital (NBO) analysis. 


October, 2019 | DOI: 10.1016/j.jorganchem.2019.120878

Elusive super-hard B6C accessible through the laser-floating zone method


Moshtaghioun, BM; Cumbrera, FL; Gomez-Garcia, D; Pena, JI
Scientific Reports, 9 (2019) art. 13340

ABSTRACT

Boron carbide is among the most promising ceramic materials nowadays: their mechanical properties are outstanding, and they open potential critical applications in near future. Since sinterability is the most critical drawback to this goal, innovative and competitive sintering procedures are attractive research topics in the science and technology of this carbide. This work reports the pioneer use of the laser-floating zone technique with this carbide. Crystallographic, microstructural and mechanical characterization of the so-prepared samples is carefully analysed. One unexpected output is the fabrication of a B6C composite when critical conditions of growth rate are adopted. Since this is one of the hardest materials in Nature and it is achievable only under extremely high pressures and temperatures in hot-pressing, the use of this technique offers a promising alternative for the fabrication. Hardness and elastic modulus of this material reached to 52 GPa and 600 GPa respectively, which is close to theoretical predictions reported in literature.


September, 2019 | DOI: 10.1038/s41598-019-49985-2

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