Menú secundario

Artículos SCI



2018


Experimental measurement of the filtration efficiency and pressure drop of wall-flow diesel particulate filters (DPF) made of biomorphic Silicon Carbide using laboratory generated particles


Orihuela, MP; Gomez-Martin, A; Miceli, P; Becerra, JA; Chacartegui, R; Fino, D
Applied Thermal Engineering, 131 (2018) 41-53

ABSTRACT

Biomorphic Silicon Carbide (bioSiC) has been recently introduced in the scope of porous ceramic substrates for hot gas filtration applications, where it has demonstrated to have good thermal and mechanical properties, and a high potential to meet the requirements for current Diesel Particulate Filters (DPF). In this experimental study, a small wall-flow bioSiC diesel filter was characterized using a soot generator, the particle size distribution of which being similar to the one generated by a diesel engine. The bioSiC samples were manufactured from Medium Density Fiberboard (MDF) following a general manufacturing procedure for bioSiC ceramics, but paying special attention in the mechanizing stage to the geometry and optimal design of the honeycomb structure required for diesel engine applications. The samples had a cell density of 57.59 cell/cm(2) (371.6 cpsi), a square cross section of 9.2 x 9.2 mm, and a length of 31 mm. To generate the particle laden stream and perform the filtration tests, a synthetic Soot Generator (SG) was used. Tests were performed under controlled and reproducible conditions, with a fixed gas flow rate of 5 LPM and a soot mass flow rate of 4 mg/h. The filtration efficiency was determined with the aid of a Scanning Mobility Particle Sizer (SMPS) from the measurements of the particle concentration upstream and downstream the filter samples. During the soot loading process, the pressure drop was also monitored. The results show that, in the initial stage (clean filter), bioSiC wall-flow DPFs may have a filtration efficiency between 0.7 and 0.85 and a pressure drop of around 2 kPa for a normalized wall velocity of 0.01 m/s at ambient temperature. The filtration performance of wall-flow bioSiC particle filters showed in this work can help us to better understand their real potential for automotive applications. 


Febrero, 2018 | DOI: 10.1016/j.applthermaleng.2017.11.149

Effect of Basicity on the Hydrolysis of the Bi(III) Aqua Ion in Solution: An Ab Initio Molecular Dynamics Study


Ayala, R; Martinez, JM; Pappalardo, RR; Refson, K; Marcos, ES
Journal of Physical Chemistry A, 122 (2018) 1905-1915

ABSTRACT

Hydrolysis of the Bi(III) aqua ion under a range of solution conditions has been studied by means of ab initio molecular dynamics simulations. While the Bi(III) aqua ion is stable in pure water, there is an increasing degree of hydrolysis with the number of hydroxide anions in the medium. This is accompanied by a monotonic decrease of the total coordination number to an asymptotic value of similar to 6, reached under extreme basicity conditions. Comparison of the simulated Bi(III) hydrolyzed species with the experimental species distribution at different degrees of basicity suggests that, at the PBE/DFT level of theory here employed, liquid water shows an overly acidic character. Predictions of theoretical EXAFS and XANES spectra were generated from the AIMD trajectories for different Bi hydrolyzed species, [Bi(HO)(m)(H2O)(n)](3-m+), m = 0-3 and n = 7-2. Comparison with available experimental spectra is presented. Spectral features joined to the degree of hydrolysis and hydration are analyzed.


Febrero, 2018 | DOI: 10.1021/acs.jpca.7b12402

Influence of temperature on the biaxial strength of cemented carbides with different microstructures


Chicardi, E; Bermejo, R; Gotor, FJ; Llanes, L; Torres, Y
International Journal of Refractory Metals & Hard Materials, 71 (2018) 82-91

ABSTRACT

The effect of the temperature on the mechanical strength of WC-Co cemented carbides with different microstructures (grain size and binder content) was evaluated. Biaxial flexural tests were performed on three cemented carbide grades at 600 °C using the ball-on-three-balls (B3B) method. Results were interpreted by Weibull statistics and compared to biaxial strength results at room temperature. A detailed fractographic analysis, supported by Linear Elastic Fracture Mechanics, was performed to differentiate the nature and size of critical defects and the mechanism responsible for the fracture. A significant decrease in the mechanical strength (around 30%) was observed at 600 °C for all grades of cemented carbides. This fact was ascribed to the change in the critical flaw population from sub-surface (at room temperature) to surface defects, associated with the selective oxidation of Co. Additionally, an estimation of the fracture toughness at 600 °C was attempted for the three cemented carbides, based upon the B3B strength results, the corresponding number of the tested specimens fragments and the macroscopic area of the B3B fracture surfaces. The fracture toughness was not affected by the temperature, at least up to 600 °C. In addition, the good agreement with the Single Edge Notch Beam toughness data suggests the possibility of employing this approach for fracture toughness evaluation of brittle materials under different testing conditions.


Febrero, 2018 | DOI: 10.1016/j.ijrmhm.2017.11.003

Improving the direct synthesis of hydrogen peroxide from hydrogen and oxygen over Au-Pd/SBA-15 catalysts by selective functionalization


Rodriguez-Gomez, A; Platero, F; Caballero, A; Colon, G
Molecular Catalysis, 445 (2018) 142-151

ABSTRACT

A series of gold-palladium catalysts supported in a mesoporous surface functionalized silica SBA-15 was studied for H2O2 direct synthesis. Support functionalization was performed using different organic groups (namely-SO3H, -NH2 and-SH) while metal was then supported by an ion exchanged method. Different Au-Pd/SBA-15 catalysts were tested in the Direct Synthesis of Hydrogen Peroxide (DSHP). Organic functional groups (-SH, -SO3H and-NH2) with acid-base properties acted as anchoring sites controlling both the dispersion of the metallic active phase and the chemical state of gold and palladium species as Au+ and Pd2+, respectively. Compared to a Au-Pd/SBA-15 system prepared by incipient wetness impregnation over non-functionalized SBA-15, catalytic performance is improved upon functionalization, increasing hydrogen peroxide rate in sulfonic-SBA-15 systems and reducing the hydrogenation/decomposition activity by adding amine groups. The occurrence of amine groups clearly suppresses the support microporosity and probably condition the metal cluster size. The analysis of particle size by TEM showed that sulfonated samples lead to a Pd size compromise which improves the H2O2 production hindering the competitive side reactions, particularly suppressed by the presence of amine groups.


Febrero, 2018 | DOI: 10.1016/j.mcat.2017.10.034

Phase-Contact Engineering in Mono- and Bimetallic Cu-Ni Co-catalysts for Hydrogen Photocatalytic Materials


Munoz-Batista, MJ; Meira, DM; Colon, G; Kubacka, A; Fernandez-Garcia, M
Angewandte Chemie-International Edition, 57 (2018) 1199-1203

ABSTRACT

Understanding how a photocatalyst modulates its oxidation state, size, and structure during a photocatalytic reaction under operando conditions is strongly limited by the mismatch between (catalyst) volume sampled by light and, to date, the physicochemical techniques and probes employed to study them. A synchrotron micro-beam X-ray absorption spectroscopy study together with the computational simulation and analysis (at the X-ray cell) of the light-matter interaction occurring in powdered TiO2-based monometallic Cu, Ni and bimetallic CuNi catalysts for hydrogen production from renewables was carried out. The combined information unveils an unexpected key catalytic role involving the phase contact between the reduced and oxidized non-noble metal phases in all catalysts and, additionally, reveals the source of the synergistic Cu-Ni interaction in the bimetallic material. The experimental method is applicable to operando studies of a wide variety of photocatalytic materials.


Enero, 2018 | DOI: 10.1002/anie.201709552

Enhanced photocatalytic removal of phenol from aqueous solutions using ZnO modified with Ag


Vaiano, V.; Matarangolo, M.; Murcia, J.J.; Rojas, H.; Navío, J.A.; Hidalgo, M.C.
Applied Catalysis B-Environmental, 225 (2018) 197-206

ABSTRACT

Different photocatalysts based on commercial ZnO modified by silver photodeposition were prepared in this work. The samples were characterized by X-ray fluorescence spectrometry (XRF), specific surface area (SSA), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and UV–vis diffuse reflectance (UV–vis DRS). XRD and XPS showed that Ag/ZnO samples are composed of metallic Ag (Ag0) and ZnO structure was identified. Furthermore, TEM analysis evidenced that the number of silver particles increased with the Ag content. At last, UV–vis DRS results revealed a reflectance band for Ag/ZnO samples, ascribed to the surface plasmon resonance (SPR) absorption of metal silver particles. Commercial ZnO and Ag/ZnO samples were evaluated in the phenol removal under UV light irradiation. It was observed an enhancement of photocatalytic phenol removal from aqueous solutions by silver addition in comparison to commercial ZnO. In particular, the phenol removal increased with the silver content from 0.14 to 0.88 wt%, after this content (i.e 1.28 wt%) the phenol degradation significantly decreased indicating that the optimal Ag content was equal to 0.88 wt%. The influence of the best photocatalyst dosage and the change of the initial phenol concentration in solution were also investigated in this work and the best photocatalytic performance was obtained by using 50 mg L−1 of phenol initial concentration and 0.15 g L−1 of photocatalyst dosage. Finally, the optimized Ag/ZnO photocatalyst was employed for the treatment of a real drinking wastewater containing phenol in which the almost total phenol removal was achieved after 180 min of UV irradiation time.


Enero, 2018 | DOI: 10.1016/j.apcatb.2017.11.075

Low-cost Ca-based composites synthesized by biotemplate method for thermochemical energy storage of concentrated solar power


Benitez-Guerrero, M; Valverde, JM; Perejon, A; Sanchez-Jimenez, PE; Perez-Maquecla, LA
Applied Energy, 210 (2018) 108-116

ABSTRACT

An ever more environmentally conscious society demands the use of green, sustainable and high-efficiency renewable energy resources. However, large-scale energy storage remains a challenge for a deep penetration of power produced from renewables into the grid. The Calcium-Looping (CaL) process, based on the reversible carbonation/calcination of CaO, is a promising technology for thermochemical energy storage (TCES) in Concentrated Solar Power (CSP) plants. Natural limestone to be used as CaO precursor is cheap, non-toxic and abundant. Nevertheless, recent works have shown that carbonation of CaO derived limestone at optimum conditions for TCES is limited by pore-plugging, which leads to severe deactivation for large enough particles to be employed in practice. In our work, we have synthesized inexpensive CaO/SiO2 composites by means of a biotemplate method using rice husk as support. The morphological and compositional features of the biomorphic materials synthesized help improve the CaO multicycle activity under optimum CSP storage conditions and for particles sufficiently large to be managed in practical processes.


Enero, 2018 | DOI: 10.1016/j.apenergy.2017.10.109

Flexible and Adaptable Light-Emitting Coatings for Arbitrary Metal Surfaces based on Optical Tamm Mode Coupling


Jiménez-Solano, A.; Galisteo-López, J.; Míguez, H.
Advanced Optical Materials, 6 (2018) 1700560

ABSTRACT

This study demonstrates a design that maximizes the power radiated into free space from a monolayer of nanoemitters embedded in a flexible distributed Bragg reflector conformably attached to a metal surface. This is achieved by positioning the light source at the precise depth within the multilayer for which optical Tamm states provide enhanced quantum yield and outcoupling efficiency, which are combined to optimize the luminous power radiated by the surface of the ensemble. This approach, based on the adhesion of flexible multilayer stacks onto metal surfaces with an arbitrary curvature, is versatile and permits the realization of spectrally narrow monodirectional or self-focusing light-emitting surfaces.


Enero, 2018 | DOI: 10.1002/adom.201700560

Outstanding performance of rehydrated Mg-Al hydrotalcites as heterogeneous methanolysis catalysts for the synthesis of biodiesel


Navajas, A; Campo, I; Moral, A; Echave, J; Sanz, O; Montes, M; Odriozola, JA; Arzamendi, G; Gandia, LM
Fuel, 211 (2018) 173-181

ABSTRACT

There is still a need for active, selective and stable heterogeneous catalysts for the synthesis of biodiesel. In this work, magnesium-aluminium hydrotalcites with Mg/Al molar ratios within the 1.5-5 range were synthesized by coprecipitation and used as transesterification catalysts for the synthesis of biodiesel. The mixed oxides obtained after calcination recovered the hydrotalcite structure in the form of meixnerite after rehydration in boiling water. The solids were characterized by XRD, TGA, N-2 adsorption-desorption, and SEM. Basic properties were assessed by means of Hammett indicators and CO2-TPD. Rehydrated materials with the highest Mg/Al ratios showed some distinctive features: low surface area, well defined flake-like crystals, high basicity and strong basic sites with H_ values above 11. They were also the most active catalysts allowing to achieve 51-75% sunflower oil methanolysis conversion after 8 h of reaction under mild conditions (60 degrees C, 1 atm), methanol/oil molar ratio of 12 using between 2 and 6 wt% of catalyst. The conversion increased up to 96% (92% fatty acid methyl esters yield) using 2 wt% catalyst and methanol/oil molar ratio of 48. Catalyst leaching was not a serious problem with these solids that could be reutilized maintaining very good activities. A general accordance between solids basic properties and their catalytic performance has been observed. These results are among the best reported in the literature for heterogeneous methanolysis catalysts and have been attributed to the high basicity of the rehydrated solids and the presence of strong and accessible basic sites probably consisting in interlayer hydroxide anions at the edges of the crystals.


Enero, 2018 | DOI: 10.1016/j.fuel.2017.09.061

Microstructural engineering and use of efficient poison resistant Au-doped Ni-GDC ultrathin anodes in methane-fed solid oxide fuel cells


Garcia-Garcia, FJ; Yubero, F; Gonzalez-Elipe, AR; Lambert, RM
International Journal of Refractory Metals & Hard Materials, 43 (2018) 885-893

ABSTRACT

Ultrathin porous solid oxide fuel cell (SOFC) anodes consisting of nickel-gadolinia-dopedceria (Ni-GDC) cermets with a unique porous micro-columnar architecture with intimate contact between the GDC and the Ni phases were made by magnetron sputtering at an oblique deposition angle and characterised in detail by a variety of methods prior to use in hydrogen or methane-fuelled SOFCs. These Ni-GDC anodes exhibited excellent transport properties, were robust under thermal cycling and resistant to delamination from the underlying yttria-stabilised zirconia electrolyte. Similarly prepared Au-doped Ni-GDC anodes exhibited the same morphology, porosity and durability. The gold associated exclusively with the Ni component in which it was present as a surface alloy. Strikingly, whatever their treatment, a substantial amount of Ce3+ persisted in the anodes, even after operation at 800 degrees C under fuel cell conditions. With hydrogen as fuel, the un-doped and Au doped Ni-GDC anodes exhibited identical electrochemical performances, comparable to that of much thicker commercial state-of-the-art Ni-GDC anodes. However, under steam reforming conditions with CH4/H(2)0 mixtures the behaviour of the Au-doped Ni-GDC anodes were far superior, exhibiting retention of good power density and dramatically improved resistance to deactivation by carbon deposition. Thus two distinct beneficial effects contributed to overall performance: persistence of Ce3+ in the working anodes could induce a strong metal-support interaction with Ni that enhanced the catalytic oxidation of methane, while formation of a Ni Au surface alloy that inhibited carbonisation and poisoning of the active nickel surface. 


Enero, 2018 | DOI: 10.1016/j.ijhydene.2017.11.020

High temperature creep of 20 vol%. SiC-HfB2 UHTCs up to 2000 degrees C and the effect of La2O3 addition


Zapata-Solvas, E; Gomez-Garcia, D; Dominguez-Rodriguez, A; Lee, WE
Journal of the European Ceramic Society. 38 (2018) 47-56

ABSTRACT

High temperature compressive creep of SiC-HfB2 UHTCs up to 2000 °C has been studied. Microstructural analysis after deformation reveals formation of new phases in the Hf-B-Si and Hf-B-Si-C systems, which are responsible for the poor creep resistance. RE oxide additions have a negative effect reducing the creep resistance of SiC-HfB2 UHTCs. A simplistic analysis for the required creep resistance is described, indicating that only SiC-HfB2 UHTCs could withstand re-entry conditions for 5 min in a single use. However, RE oxide addition to SiC-HfB2UHTCs does not provide the required creep resistance for them to be candidate materials for hypersonic applications.


Enero, 2018 | DOI: 10.1016/j.jeurceramsoc.2017.08.028

Nanostructured hybrid device mimicking bone extracellular matrix as local and sustained antibiotic delivery system


Borrego-Gonzalez, S; Romero-Sanchez, LB; Blazquez, J; Diaz-Cuenca, A
Microporous and Mesoporous Materials, 256 (2018) 165-176

ABSTRACT

A fluidic permeable and stable in wet media, MBG-NfGel, device consisting of a mesoporous ceramic embodied in a nanofibrillar biodegradable polymer has been processed using appropriate thermally induced phase separation (TIPS) processing variables of 5.4% (wt/v) gelatin in 50/50 water/ethanol (v/v) ratio. The device comprises high surface area mesoporous bioactive glass (MBG) microparticles within a fibrous matrix of 170 nm average diameter nanofibers gelatin, forming a meshwork of 0.2-1.6 mu m range voids. Gentamicin sulphate (GS) antibiotic high loading capacity and sustained release ability, as well as in vitro bioactivity and osteoprogenitor cells biocompatibility supports long-term antibacterial and bone growth stimulation properties. Antibiotic local delivery functionality in vitro of this device has been analysed and discussed in relation to other systems previously reported. The presented device properties as well as its industrial scalability potential, in terms of process reliability and absence of toxic chemical agents, low raw material biopolymer cost and immunogenicity, are other important advantages. These advantages rank MBG-NfGel device as a potential candidate to further development for application as local antibiotic device in bone surgery and therapy.


Enero, 2018 | DOI: 10.1016/j.micromeso.2017.08.010

Nickel Particles Selectively Confined in the Mesoporous Channels of SBA-15 Yielding a Very Stable Catalyst for DRM Reaction


Rodriguez-Gomez, A; Pereniguez, R; Caballero, A
Journal of Physical Chemistry B, 122 (2018) 500-510

ABSTRACT

A series of four Ni catalysts supported on SBA-15 and on a high SiO2 surface area have been prepared by modified impregnation (ImU) and deposition-precipitation (DP) methods. The catalysts have been extensively characterized, including in situ XAS (bulk sensitive) and XPS (surface sensitive) techniques, and their catalytic activities evaluated in the dry reforming reaction of methane (DRM). The combined use of XPS and XAS has allowed us to determine the location of nickel particles on each catalyst after reduction at high temperature (750 degrees C). Both Ni/SiO2-DP and Ni/SBA-15-DP catalysts yield well-dispersed and homogeneous metallic phases mainly located in the mesoporosity of both supports. On the contrary, the Ni/SiO2-ImU and Ni/SBA-15-ImU catalysts present a bimodal distribution of the reduced nickel phase, with nickel metallic particles located out and into the mesoporous structure of SiO2 or the SBA-15 channels. The Ni/SBA-15-DP catalyst was found the most stable and performing system, with a very low level of carbon deposition, about an order of magnitude lower than the equivalent ImU catalyst. This outstanding performance comes from the confinement of small and homogeneous nickel particles in the mesoporous channels of SBA-15, which, in strong interaction with the support, are resistant to sintering and coke deposition during the demanding reaction conditions of DRM.


Enero, 2018 | DOI: 10.1021/acs.jpcb.7b03835

Packing Defects in Fatty Amine Self-Assembled Monolayers on Mica as Revealed from AFM Techniques


Benitez, JJ; Heredia-Guerrero, JA; San-Miguel, MA; Galloway, HC
Journal of Physical Chemistry B, 122 (2018) 493-499

ABSTRACT

Self-assembled monolayers of n-octadecylamine (ODA-SAMs) on mica have been prepared and studied by contact and jumping mode atomic force microscopy (AFM). Adhesion and friction data show that the compactness of the monolayers spontaneously increases as they are allowed to ripen. Molecular packing can also be induced by the controlled mechanical perturbation exerted by the probe when getting into and out of contact intermittently. Under these conditions, defects and vacancies aggregate giving rise to detectable pinholes uniformly distributed in AFM images. Created pinhole density was found to decrease with ripening time, thus confirming the proposed spontaneous self-healing mechanism. Pinhole density is also suggested as a parameter characterizing the packing degree of ODA-SAMs, and it has been related to their tribological properties. Additionally, molecular dynamics simulations were used to corroborate the compatibility between the packing degree and the observed topography of ODA-SAMs on mica.


Enero, 2018 | DOI: 10.1021/acs.jpcb.7b03603

A new combustion route for synthesis of TaB2 nanoparticles


Jalaly, M; Gotor, FJ
Ceramics International, 44 (2018) 1142-1146

ABSTRACT

Tantalum diboride (TaB2) nanoparticles were synthesized through a mechanically induced self-sustaining reaction (MSR). In this method, the ternary system of Mg/Ta2O5/B was employed in which, magnesium was used as a reducing agent for reduction of tantalum oxides in a combustive regime. The processing route of TaB2 by the solid-state combustion was very short-term and the product purification was extremely easy and rapid. The synthesis mechanism was studied and revealed that magnesiothermic reduction of tantalum oxide is the initiator of the total reaction, while borothermic reduction of the oxide may occur in parallel.


Enero, 2018 | DOI: 10.1016/j.ceramint.2017.10.074

A facile shape-controlled synthesis of highly photoactive fluorine containing TiO2 nanosheets with high {001} facet exposure


Lara, M. A.; Sayagues, M. J.; Navio, J. A.; Hidalgo, M. C.
Journal of Materials Science, 53 (2018) 435-446

ABSTRACT

Surface-fluorinated TiO2 materials with high {001} facet exposure were prepared by a simple and high-yield preparation procedure. Faceted/fluorinated samples showed a high photocatalytic performance not only in oxidation processes, tested in phenol and methyl orange degradation, but also in a reduction process as Cr(VI) photoreduction. Reaction rates for these materials greatly exceeded the ones obtained for materials prepared without fluorine addition and for commercial TiO2 Degussa (Evonik) P25 used as reference photocatalyst. A broad characterisation of the samples allowed us to estimate the percentages of different facets and the amount and form in which the fluorine is found on the surfaces. Good photocatalytic behaviour can be ascribed to both high {001} facet exposure and adsorbed fluorine on the photocatalysts surfaces.


Enero, 2018 | DOI: 10.1007/s10853-017-1515-6

Corrigendum to “Dense graphene nanoplatelet/yttria tetragonal zirconia composites: Processing, hardness and electrical conductivity” [Ceram. Int. 43 (2017) 11743–11752]


Gallardo-Lopez, A; Marquez-Abril, I; Morales-Rodriguez, A; Munoz, A; Poyato, R
Ceramics International, 44 (2018) 1225-1225

ABSTRACT

Development of a novel fcc structure for an amorphous-nanocrystalline Ti-33Nb-4Mn (at.%) ternary alloy


Chicardi, E; Garcia-Garrido, C; Sayagues, MJ; Torres, Y; Amigo, V; Aguilar, C
Materials Characterization, 135 (2018) 46-56

ABSTRACT

In this work, a novel amorphous-nanocrystalline titanium-niobium-manganese solid solution ternary alloy with a Ti-33Nb-4Mn (at.%) nominal composition was developed by a High-Energy Mechanical Alloying. Nb and Mn were added to the elemental Ti as a beta-phase (bcc) stabilizer and an amorphization promoter, respectively. The system evolved from the elemental Ti, Nb and Mn raw materials to a body centred cubic (bcc) TiNbMn alloy and, finally, to the formation of an original and stable face centred cubic (fcc) nanocrystalline TiNbMn alloy, not reported until now, at short milling time (20 h). This alloy remains invariant until 120 h. In turn, the partial amorphization of the system occurs and increases until at intermediate milling time (80 h). The production of both original fcc and the amorphous TiNbMn alloy may be beneficial for reducing the Young's modulus and improving the mechanical strength pursued for the Ti alloy. The optimal milling time respect to the amorphization, nanocrystalline size and Fe mount from milling media was 60 h and 80 h (TiNbMn60h and TiNbMn80h), with > 50 wt% of an amorphous phase and a crystalline domain size of approximately 5 nm.


Enero, 2018 | DOI: 10.1016/j.matchar.2017.11.021

Nickel/Copper Bilayer-modified Screen Printed Electrode for Glucose Determination in Flow Injection Analysis


Salazar, P.; Rico, V.; Gonzalez-Elipe, Agustin R.
Electroanalysis, 30 (2018) 187-193

ABSTRACT

This work reports about the performance of a Ni/Cu-modified screen printed electrodes (SPE/Ni/Cu), prepared by physical vapor deposition (PVD) in an oblique angle configuration (OAD), for non-enzymatic glucose sensing applications. SPE/Ni/Cu electrodes showed an excellent reversibility and a catalytic behavior for detection of glucose that were controlled by the diffusion of reactants up to the active sites at the electrode surface. The study with a flow injection analysis (FIA) setup of the main experimental variables affecting the detection process has shown that the developed electrode system had an excellent glucose sensitivity of 1.04AM(-1)cm(-2) (R-2:0.999), a linear response up to 1mM, a limit of detection of 0.33M and a time of analysis of ca. 30s per sample. The selectivity of the sensor was checked against various interferences, including ascorbic acid, uric acid, acetaminophen and other sugars, in all cases with excellent results. The feasibility of using this sensor for practical applications was successfully confirmed by determining the glucose concentration in different commercial beverages.


Enero, 2018 | DOI: 10.1002/elan.201700592

Core-rim structure formation in TiC-Ni based cermets fabricated by a combined thermal explosion/hot-pressing process


Lemboub, S; Boudebane, S; Gotor, FJ; Haouli, S; Mezrag, S; Bouhedja, S; Hesser, G; Chadli, H; Chouchane, T
International Journal of Refractory Metals & Hard Materials, 70 (2018) 84-92

ABSTRACT

TiC-Ni-based cermets were obtained by thermal explosion from different elemental mixtures (Ti, C, Ni and X, where X = Cr, Mo or W) and subsequently densified by hot-pressing under a cyclic load. The whole process was performed in a single stage in the same experimental device according to the following thermal and pressure procedure: a heating rate ramp up to 1573 K without applying any load followed by an isothermal dwelling under a compressive cyclic load of 32 MPa. The thermal explosion synthesis occurred during the heating ramp at a temperature close to 1273 K that was practically independent of the starting nominal composition. The influence of different refractory elements on the chemical composition and microstructure of cermets was studied. SEM characterization showed that only with Mo and W, the cermets developed the characteristic core-rim structure. A high densification was achieved, but decreased when the refractory elements were added. Nevertheless, in these cases higher hardness values were obtained.


Enero, 2018 | DOI: 10.1016/j.ijrmhm.2017.09.014

Páginas

icms