81 results on '"Miguel Castro"'
Search Results
2. Additive Manufacturing of Functional Ceramics
- Author
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Jesús Canales-Vázquez, Juan Ramón Marín-Rueda, José Fernando Valera-Jiménez, Miguel Castro-García, and Juan Carlos Pérez-Flores
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Materials science ,visual_art ,Metallurgy ,visual_art.visual_art_medium ,Ceramic - Published
- 2021
3. Hybrid material by anchoring a ruthenium(<scp>ii</scp>) imine complex to SiO2: preparation, characterization and DFT studies
- Author
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Luis A. Vargas, Raúl Calixto Flores, Fernando Cuenú, G. Eliad Benitez-Medina, Miguel Castro, Alfonso E. Ramírez, and Pankaj Sharma
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Materials science ,General Chemical Engineering ,Imine ,chemistry.chemical_element ,02 engineering and technology ,General Chemistry ,Electronic structure ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Antibonding molecular orbital ,01 natural sciences ,Acceptor ,0104 chemical sciences ,Ruthenium ,chemistry.chemical_compound ,chemistry ,Physical chemistry ,Deconvolution ,0210 nano-technology ,Hybrid material ,Basis set - Abstract
Ruthenium–silica hybrid material (RuCl2(PR3)2-2-PyCH-AMPTSi/SiO2) was prepared and characterized by various spectroscopic techniques. A deconvolution procedure was applied to the spectroscopic data to deconstruct the overlapped bands. A density functional theoretical approach was applied to get insights into the electronic structure of the ruthenium coordination site and the functional RI-PBE-D3/Def2TZVP basis set was used for the optimization. Relativistic effects were considered using the zero-order regular approximation (ZORA). The anchoring process, evinced for each step of the synthesis of the hybrid material, was tracked by FT-IR analyses. The transitions observed in the FT-IR spectra were verified by DFT analyses, which agree with the experimental data. In the DRS-UV-Vis spectra, three main bands were detected by the deconvolution procedure that correspond to the charge transfer transitions, with the main contributions from ruthenium-chlorine and imine–pyridine fragments. TD-DFT results reveal that ruthenium-chlorine antibonding orbitals act as main charge donors, while pyridine–imine is the main charge acceptor.
- Published
- 2021
4. Corrosion inhibition assessment on API 5L X70 steel by preussomerin G immersed in saline and saline acetic
- Author
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Araceli Espinoza Vazquez, Francisco Javier Rodríguez Gómez, Deyanira Ángeles Beltrán, Alan Miralrio, Miguel Castro, Ignacio A. Figueroa, Mario Figueroa, and Luis Antonio López Reséndiz
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Materials science ,Pyrenochaetopsis sp ,medicine.medical_treatment ,030206 dentistry ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,021001 nanoscience & nanotechnology ,Surfaces, Coatings and Films ,Corrosion ,03 medical and health sciences ,Corrosion inhibitor ,chemistry.chemical_compound ,0302 clinical medicine ,chemistry ,Mechanics of Materials ,Materials Chemistry ,medicine ,0210 nano-technology ,Saline ,Nuclear chemistry - Abstract
The spirodioxynaphthalene preussomerin G, obtained from the fungus Pyrenochaetopsis sp. T1-41 (Plesosporales), was evaluated as a corrosion inhibitor in API 5L X70 steel samples. According to the e...
- Published
- 2020
5. Characterization of Magnetic Series of Iron–Carbon Clusters FenC0,±1 (n ≤ 13)
- Author
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Alan Miralrio, Patricio Limon, and Miguel Castro-Martínez
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Work (thermodynamics) ,Carbon atom ,Materials science ,Series (mathematics) ,Doping ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Characterization (materials science) ,General Energy ,chemistry ,Physical chemistry ,Physical and Theoretical Chemistry ,0210 nano-technology ,Carbon ,Electronic properties - Abstract
The evolution of structural and electronic properties of neutral and charged iron clusters doped with a single carbon atom, FenC0,±1 (n = 1-13) series, is studied in this work; which has been carri...
- Published
- 2020
6. Analysis of Performance Losses and Degradation Mechanism in Porous La2−X NiTiO6−δ:YSZ Electrodes
- Author
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Jesús Canales-Vázquez, Miguel Castro-García, Juan Carlos Pérez-Flores, Flaviano García-Alvarado, Vidal Crespo-Muñoz, and José Fernando Valera-Jiménez
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cathode ,Technology ,Materials science ,020209 energy ,02 engineering and technology ,Article ,law.invention ,law ,0202 electrical engineering, electronic engineering, information engineering ,General Materials Science ,SOFC ,Porosity ,Yttria-stabilized zirconia ,perovskite ,Perovskite (structure) ,degradation ,long-term ,Microscopy ,QC120-168.85 ,Non-blocking I/O ,QH201-278.5 ,021001 nanoscience & nanotechnology ,Engineering (General). Civil engineering (General) ,Cathode ,Dielectric spectroscopy ,TK1-9971 ,Chemical engineering ,Descriptive and experimental mechanics ,Electrode ,Degradation (geology) ,ex-solution ,Electrical engineering. Electronics. Nuclear engineering ,TA1-2040 ,0210 nano-technology - Abstract
The electrode performance and degradation of 1:1 La2−xNiTiO6−δ:YSZ composites (x = 0, 0.2) has been investigated to evaluate their potential use as SOFC cathode materials by combining electrochemical impedance spectroscopy in symmetrical cell configuration under ambient air at 1173 K, XRD, electron microscopy and image processing studies. The polarisation resistance values increase notably, i.e., 0.035 and 0.058 Ωcm2 h−1 for x = 0 and 0.2 samples, respectively, after 300 h under these demanding conditions. Comparing the XRD patterns of the initial samples and after long-term exposure to high temperature, the perovskite structure is retained, although La2Zr2O7 and NiO appear as secondary phases accompanied by peak broadening, suggesting amorphization or reduction of the crystalline domains. SEM and TEM studies confirm the ex-solution of NiO with time in both phases and also prove these phases are prone to disorder. From these results, degradation in La2−xNiTiO6−δ:YSZ electrodes is due to the formation of La2Zr2O7 at the electrode–electrolyte interface and the ex-solution of NiO, which in turn results in the progressive structural amorphization of La18NiTiO6−δ phases. Both secondary phases constitute a non-conductive physical barrier that would hinder the ionic diffusion at the La2−xNiTiO6−δ:YSZ interface and oxygen access to surface active area.
- Published
- 2021
7. Concentrated-plasticity modelling of circular concrete-filled steel tubular members under flexure
- Author
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Yadong Jiang, Luís Macedo, José Miguel Castro, António J. Silva, Tak Ming Chan, and Ricardo Monteiro
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Materials science ,business.industry ,0211 other engineering and technologies ,Stiffness ,020101 civil engineering ,02 engineering and technology ,Building and Construction ,Structural engineering ,Bending ,Plasticity ,0201 civil engineering ,Cracking ,OpenSees ,Buckling ,Flexural strength ,021105 building & construction ,Architecture ,Ultimate tensile strength ,medicine ,medicine.symptom ,Safety, Risk, Reliability and Quality ,business ,Civil and Structural Engineering - Abstract
The research reported herein aims at the proposal of an accurate and efficient simplified numerical modelling approach for circular concrete-filled steel tubular (CFST) members under flexural loading. Experimental tests were carried out to characterize the bending behaviour of CFST members under monotonic and cyclic loading. The observed behaviour was characterized by strength and stiffness deterioration effects, as a result of the development of local buckling of the steel tube and cracking of the concrete core. Numerical simulations of these tests were conducted by resorting to existing modelling approaches, namely through Distributed Plasticity (DP) and Concentrated Plasticity (CP) models. It was found that existing modelling approaches failed to accurately capture the levels of strength deterioration and pinching effects observed in the tests. Thus, a novel CP-based simplified model, designated by matCFSTdet, was implemented in OpenSees. The hysteretic response of the CP model is based on a novel rotational spring model. An advanced calibration framework was introduced with targets to calibrate the accuracy of the model. The validation analyses indicate that the model is able to capture well the deterioration in both strength and stiffness of CFST members under cyclic flexural loading. Furthermore, the elastic stiffness, ultimate strength and the pinching effects of the hysteretic loops were also well simulated. The proposed CP model, coupled with the advanced calibration framework, thus results in a more realistic simulation of the cyclic flexural response of circular CFST members.
- Published
- 2019
8. Activation of MoS2 monolayers by substitutional copper and silver atoms embedded in sulfur vacancies: A theoretical study
- Author
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Miguel Castro, E. Rangel, and Alan Miralrio
- Subjects
inorganic chemicals ,Materials science ,Band gap ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Metal ,chemistry.chemical_compound ,Monolayer ,Molecule ,Reactivity (chemistry) ,Molybdenum disulfide ,Surfaces and Interfaces ,General Chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Copper ,0104 chemical sciences ,Surfaces, Coatings and Films ,Crystallography ,chemistry ,Molybdenum ,visual_art ,visual_art.visual_art_medium ,0210 nano-technology - Abstract
Defective molybdenum disulfide monolayers, with up to three copper and silver atoms substituting sulfur atoms, were studied at a dispersion-corrected DFT level. By the first time, changes produced on electronic properties, reactivity, charge distribution and electrostatic potential by trapping these atoms are widely discussed. Embedded species are expected to remain stable and fixed, since large and favorable metal cluster-vacancy defective monolayer binding energies are obtained, higher than – 2.60 eV in all cases. Several defect states are induced in the forbidden region, being the band gap reduced as more substitutional atoms are added. These states mostly come from molybdenum d and p orbitals from embedded metals. Also, defects reduce the gap up to 0.10 and 0.35 eV, for copper and silver trimers, respectively. Substitutional single atoms and dimers donate charge to molybdenum atoms in the middle layer, whereas trimers tend to accumulate it. However, charge transfer is marginal and the most important rearrangements are produced in atoms neighboring defects. Regions with lower electrostatic potential are produced around the defects. Condensed Fukui indices reveal that systems with defects enhanced the chemical reactivity, towards nucleophilic and nucleophilic attacks, in regions around the embedded species. In contrast to the chemically inert pristine MoS2 monolayer, changes on electronic, energetic properties and reactivity of all defective systems indicate that are promising materials for catalytic purposes and to adsorb other molecules.
- Published
- 2019
9. Experimental assessment of the cyclic behaviour of concrete-filled steel tubular beam-columns with octagonal sections
- Author
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Ray Kai Leung Su, Tak Ming Chan, Junbo Chen, and José Miguel Castro
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Materials science ,0211 other engineering and technologies ,020101 civil engineering ,Flexural rigidity ,02 engineering and technology ,Bending ,Dissipation ,0201 civil engineering ,Cylinder (engine) ,law.invention ,law ,021105 building & construction ,Ultimate tensile strength ,Bending moment ,Composite material ,Ductility ,Beam (structure) ,Civil and Structural Engineering - Abstract
This paper presents an experimental investigation on concrete-filled steel tubular beam-columns with octagonal cross-sections (OCFST) under cyclic lateral loading with or without axial load. A total of nine specimens with different parameters, including the axial load level (n) ranging from 0 to 0.5 and concrete compressive cylinder strength (fc′) varying from 30 MPa to 90 MPa, were tested. The failure modes, ultimate strengths, displacement ductility, effective flexural stiffness and cumulative dissipated energy are presented. The results indicate that OCFST beam-columns exhibit a ductile plastic mode and excellent energy dissipation. With the increase of axial load level, the ductility and the energy dissipation capacity decreases, while the ultimate bending capacity firstly increases then drops. Concrete grades seem to have limited influence on the ultimate strength and energy dissipation capacity. The comparison results of the ultimate bending moments and effective flexural stiffness between predictions using EN 1994-1-1 and AISC 360-16 and test results reveal their applicability to the design of OCFST beam-columns.
- Published
- 2019
10. Optimization and Simulation of a CFR Engine Fueled by Dilute Anode Tail-Gas
- Author
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Geet Padhi, Todd M. Bandhauer, Alexander Balu, Bret Windom, Shane D. Garland, Robert Braun, Daniel B. Olsen, and Miguel Castro
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Thermal efficiency ,chemistry.chemical_compound ,Materials science ,chemistry ,Tail gas ,business.industry ,Nuclear engineering ,Fuel cells ,Computational fluid dynamics ,Combustion ,business ,Methane ,Anode - Abstract
Recent innovations in Metal Supported Solid Oxide Fuel Cells (MS-SOFC) have increased the longevity and reliability of fuel cells. These innovations drive the desire to create power generating systems that combine different ways of extracting power from a fuel to increase overall thermal efficiency. This investigation assesses the feasibility of operating an internal combustion engine with the anode tail-gas, which is a blend of H2, CO, CO2, H2O, and CH4, exhausted by a MS-SOFC. This engine would be used to support fuel cell balance of plant equipment and produce excess electrical power. Four variations of the expected anode tail-gas blends were determined by varying the dewpoint temperature of the fuel. Gas blends are tested by combining separate flows of each constituent, and combustion is tested using a Cooperative Fuel Research (CFR) engine. Compression ratio, spark timing, inlet manifold temperature, and boost pressure were used to obtain optimal operating conditions. Stable engine operation was obtained on all test blends. A combination of computational fluid dynamics (CFD) and analysis of chemical species and reaction mechanisms is used to develop an engine and combustion model. This model allows for further investigation into anode tail-gas combustion characteristics. Response Surface Method Optimization was used to experimentally optimize operating parameters and determine the maximum achievable efficiency utilizing the CFR engine. All test blends with H2O produced power in the engine although the blend with the most water content caused operational problems with the CFR engine test stand, including large amounts of water entering the oil system. Three chemical kinetic mechanisms were investigated that had the correct species for simulating the fuel with a low number of reactions to facilitate low computational time: San Diego (SD), GRI and Gallway 2017 (NUIG) mechanism. Out of these four mechanisms, the NUIG mechanism results fit the CFR engine experimental data best. Response Surface Method Optimization was performed on the most viable test blends, the steam injections blends at 40°C and 90°C fuel dewpoint temperature. During optimization the 40°C dewpoint temperature blend brake efficiency increased from 20% to 21.6%, and the 90°C dewpoint temperature blend brake efficiency increased from 17% to 22.3%.
- Published
- 2020
11. An approach for predicting fatigue life of CFRP retrofitted metallic structural details
- Author
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José Miguel Castro, Rui Calçada, Filippo Berto, Abílio de Jesus, Anis Mohabeddine, P.A. Montenegro, and José A.F.O. Correia
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Materials science ,Mechanical Engineering ,Composite number ,chemistry.chemical_element ,Fatigue damage ,Industrial and Manufacturing Engineering ,Metal ,Stiffness degradation ,chemistry ,Mechanics of Materials ,Aluminium ,Modeling and Simulation ,visual_art ,visual_art.visual_art_medium ,Cyclic loading ,Degradation (geology) ,General Materials Science ,Adhesive ,Composite material - Abstract
This paper presents a new approach to estimate the fatigue life of metallic details retrofitted with bonded CFRP patch. Existing phenomenological and analytical methods to predict the fatigue life of metallic structural details retrofitted with bonded CFRP patch do not consider the cyclic degradation of the composite patch. As for all materials the composite patch (CFRP and adhesive) will experience degradation during fatigue cyclic loading. In this regard, a new approach that takes into account the fatigue cyclic degradation of the composite patch is proposed in this paper by introducing in the fatigue damage accumulation model of the metallic element, a cycle-dependent stiffness degradation parameter of the composite patch. The stiffness degradation parameter is obtained using a fatigue stiffness degradation model calibrated from experimental fatigue data of CFRP adhesively bonded double strap joints. Experimental data available in the literature of central hole aluminium plates bonded with CFRP are utilized for validation of the approach.
- Published
- 2022
12. Electronic properties and enhanced reactivity of MoS2 monolayers with substitutional gold atoms embedded into sulfur vacancies
- Author
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Miguel Castro, Alan Miralrio, and Eduardo Rangel Cortes
- Subjects
Materials science ,Band gap ,Binding energy ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Surfaces and Interfaces ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,01 natural sciences ,Sulfur ,0104 chemical sciences ,Surfaces, Coatings and Films ,Crystallography ,chemistry.chemical_compound ,chemistry ,Molybdenum ,Vacancy defect ,Monolayer ,Atom ,0210 nano-technology ,Molybdenum disulfide - Abstract
The structural and electronic effects produced by several gold atoms embedded into sulfur vacancies of molybdenum disulfide monolayers are assessed theoretically for the first time. These MoS2 defects need less formation energies, of about 3 eV per sulfur vacancy, than those found for other commonly studied bidimensional systems. The defects introduce several new states, mostly from the molybdenum d orbitals, in the band gap. The gap is reduced by means of the sulfur vacancies; which are lowered up to 0.570 eV for the tri-sulfur vacancies. Previously, the inert MoS2 monolayer is activated through sulfur vacancies, which becomes able to trap gold atoms. The gold clusters occupying sulfur sites are energetically favorable, as shown by the estimated binding energies, higher than −2.4 eV per atom. These defects create states in the band gap, which arise from the molybdenum and gold orbitals, gradually reducing the energy up to 0.450 eV. Moreover, the Au atoms receive charges from Mo atoms; being able to transfer it towards other species. That is, the gold atoms may define the catalytic site of the MoS2 monolayer. In fact, those embedded atoms could be suitable for nucleophilic as well as electrophilic attacks according to Fukui indices. Embedded clusters enhanced the reactivity of the whole material which is suggested to act as a catalyst, due to the properties found on it.
- Published
- 2018
13. Probabilistic Fatigue Crack Initiation and Propagation Fields Using the Strain Energy Density
- Author
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A.M.P. De Jesus, F. Bertod, Rui Calçada, José Miguel Castro, José A.F.O. Correia, P.J. Huffman, and Grzegorz Lesiuk
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Materials science ,business.industry ,Probabilistic logic ,Fatigue testing ,020101 civil engineering ,Strain energy density function ,02 engineering and technology ,Structural engineering ,Paris' law ,Pressure vessel ,0201 civil engineering ,Stress (mechanics) ,Equivalent stress ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Mechanics of Materials ,mental disorders ,Solid mechanics ,business - Abstract
The fatigue crack growth (FCG) has been widely studied by the scientific community. There are several proposed FCG models, the best known being the Paris relation. The fatigue crack initiation and propagation have been studied separately, however, researchers have made an effort to study the relationship between these two fatigue phenomena. In this sense, several fatigue crack growth models based on local approaches have been proposed, the UniGrow model being well-known. The fatigue crack growth process is assumed a succession of crack re-initiations considering a certain elementary material size. Recently, Huffman developed a strain energy density based on Walker-like stress life and fatigue crack growth behavior. In this paper, the Huffman model based on local strain energy density is used to predict the fatigue crack initiation and propagation for the P355NL1 pressure vessel steel. This model is combined with the generalized probabilistic fatigue model proposed by Correia aiming the generation of probabilistic fatigue crack initiation and propagation fields. In this study, the local stress and strains at the crack tip were obtained combining linear-elastic and elastoplastic analyses. The probabilistic fatigue crack growth rates fields for several stress R-ratios are estimated considering strain, SWT, and equivalent stress amplitude damage parameters. A comparison between the experimental FCG data and the generated probabilistic FCG fields is made with very satisfactory correlations being found.
- Published
- 2018
14. Experimental Study and Numerical Assessment of the Flexural Behaviour of Square and Rectangular CFST Members under Monotonic and Cyclic Loading
- Author
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Tak Ming Chan, Ricardo Monteiro, José Miguel Castro, Ya Dong Jiang, and Antonio Silva
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Materials science ,business.industry ,Mechanical Engineering ,020101 civil engineering ,Numerical assessment ,Monotonic function ,02 engineering and technology ,Structural engineering ,Square (algebra) ,0201 civil engineering ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Flexural strength ,Mechanics of Materials ,Cyclic loading ,General Materials Science ,business - Abstract
This paper focuses on the characterization of the behaviour of Concrete Filled Steel Tubular (CFST) columns made with Rubberized Concrete (RuC), and on the development of an accurate numerical model for the simulation of CFST columns under monotonic and cyclic bending. The test campaign involves 18 CFST specimens with different configurations, namely the cross-section slenderness, the concrete strength, the axial load level and the lateral loading type. All CFST members tested exhibited good ductility under monotonic loading. The Eurocode 4 design provisions was verified against the test results and the design capacities of the CFST members were validated to be conservative. A comprehensive 3D Finite Element (FE) model was developed and calibrated based on test results. The FE model proved to be reliable in predicting the bending behaviour of CFST member, in terms of local buckling deformation modes, ultimate capacity and ductility of the CFST columns.
- Published
- 2018
15. Fabrication and characterisation of ceramics via low-cost DLP 3D printing
- Author
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Vicente Yagüe-Alcaraz, Jesús Canales-Vázquez, Juan Carlos Ruiz-Morales, Juan José López-López, Juan Ramón Marín-Rueda, Mónica Moral, L. Hernández-Afonso, Miguel Castro-García, and Giftymol Varghese
- Subjects
Ceramics ,Materials science ,Fabrication ,Sintering ,3D printing ,02 engineering and technology ,Photopolymerisation ,01 natural sciences ,Industrial and Manufacturing Engineering ,law.invention ,lcsh:TP785-869 ,law ,0103 physical sciences ,Thermal stability ,Ceramic ,Composite material ,Stereolithography ,010302 applied physics ,business.industry ,Green body ,021001 nanoscience & nanotechnology ,DLP 3D printing ,lcsh:Clay industries. Ceramics. Glass ,Mechanics of Materials ,Photogrammetry ,visual_art ,Ceramics and Composites ,visual_art.visual_art_medium ,Digital Light Processing ,0210 nano-technology ,business - Abstract
A stereolithography-based additive manufacturing technique has been used for the fabrication of advanced ceramics. A customised 3D printer using a Digital Light Processing (DLP) projector as UV source has been built to fabricate green bodies from photosensitive resins loaded with 25–60 wt% of alumina, 3- and 8-YSZ. The 3D-printed bodies were then sintered in the 1200–1500 °C and exhibited thermal stability. As expected, higher ceramic loadings rendered objects with higher density for a given sintering temperature. The limit of solid loading in the resin is approximately 60% and beyond those contents, the extra ceramic appears as powder loosely adhered to the sintered objects. Photogrammetry was used to evaluate the accuracy of the 3D printing process and highlighted a marked deviation between the CAD model and the resulting object, particularly in the top part of the specimens, possibly due to the use of volatile solvents which cause changes in the photoresins used. Nevertheless, that problem may be overcome by thermostatising the printer vat and/or using solvents with higher boiling point. The results obtained suggest the potential application of low cost DLP 3D printing techniques to process ceramics for a number of applications including ceramic fuel cells, piezoelectrics, dental applications, etc.
- Published
- 2018
16. Development of full ceramic electrodes for lithium-ion batteries via desktop-fused filament fabrication and further sintering
- Author
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Jesús Canales-Vázquez, José Fernando Valera-Jiménez, Miguel Castro-García, and Juan Carlos Pérez-Flores
- Subjects
Fabrication ,Materials science ,business.industry ,3D printing ,Sintering ,Fused filament fabrication ,Cathode ,Anode ,law.invention ,law ,visual_art ,Electrode ,visual_art.visual_art_medium ,Optoelectronics ,General Materials Science ,Ceramic ,business - Abstract
The fabrication of energy storage devices and their components via 3D printing involves unquestionable benefits in this field compared to traditional manufacturing processes such as doctor blading or die pressing, providing wide versatility for the development of electrodes with high surface area or the production of devices with geometries that fit specific product designs and maximize the amount of active material within the systems. Among these technologies, fused filament fabrication (FFF) represents a promising and low-cost method to fabricate lithium-ion batteries with tailored geometries. However, the high amount of polymer often included in the electrodes produced via FFF involves important capacity limitations for their use as functional electrodes. In this work, we report for the first time the fabrication of full ceramic LTO anode and LCO cathode electrodes via FFF 3D printing of composite filaments and further sintering, including a thorough study of the micro and macrostructure, phase stability, electrical conductivity, and electrochemical performance of the printed electrodes. With this strategy, 3D printed LTO and LCO electrodes were produced exhibiting similar electrical conductivity values to those of uniaxially pressed ceramic pellets and displayed 168 and 129 mAh g−1, i.e., 96% and 94% of their theoretical capacities, respectively (considering the conventional insertion/deinsertion of 3 Li+ for LTO and 0.5 Li+ for LCO).
- Published
- 2021
17. Monotonic and cyclic flexural behaviour of square/rectangular rubberized concrete-filled steel tubes
- Author
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António J. Silva, Ricardo Monteiro, Yadong Jiang, Nuno Silvestre, and José Miguel Castro
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Materials science ,Aggregate (composite) ,business.industry ,Composite number ,0211 other engineering and technologies ,Metals and Alloys ,020101 civil engineering ,02 engineering and technology ,Building and Construction ,Structural engineering ,Dissipation ,Square (algebra) ,0201 civil engineering ,Flexural strength ,Natural rubber ,Mechanics of Materials ,visual_art ,021105 building & construction ,visual_art.visual_art_medium ,Infill ,Composite material ,Ductility ,business ,Civil and Structural Engineering - Abstract
This paper focuses on the assessment of the behaviour of Concrete Filled Steel Tube (CFST) columns with square/rectangular cross-section, made with Rubberized Concrete (RuC), under flexural loading. The study aims to evaluate the differences between this type of composite members and typical CFST members made with standard concrete (StdC), namely in terms of the influence of the rubber aggregate replacement ratio on member strength, ductility, and energy dissipation capacity. The experimental campaign comprised the testing of 16 square members, 12 RuCFST and 4 StdCFST, and 4 rectangular RuCFSTs. A number of parameters were investigated, namely the cross-section slenderness (i.e., the width-to-thickness ratio of the steel tube), the aggregate replacement ratio (i.e., the percentage of sand aggregate of the concrete mixture that is substituted by rubber particles), axial load level and lateral loading type. The test results are compared with the member capacities obtained with the application of Eurocode 4. The results show a minimal influence of the type of concrete infill on the monotonic and cyclic behaviour of the members and also allow concluding that the European code is conservative in predicting the capacity of the specimens. Furthermore, the results obtained demonstrate that the cross-section slenderness has an important role on the behaviour of these members. Nonetheless, the requirements pertaining this parameter that are currently defined in Eurocodes 4 and 8 can be relaxed.
- Published
- 2017
18. Ductility-Equivalent Viscous Damping Relationships for Beam-to-Column Partial-Strength Steel Joints
- Author
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Carlos Rebelo, Luís Simões da Silva, Hugo Augusto, and José Miguel Castro
- Subjects
021110 strategic, defence & security studies ,Materials science ,business.industry ,0211 other engineering and technologies ,020101 civil engineering ,Monotonic function ,02 engineering and technology ,Building and Construction ,Structural engineering ,Geotechnical Engineering and Engineering Geology ,Finite element method ,Displacement (vector) ,0201 civil engineering ,Seismic analysis ,Linearization ,Dissipative system ,business ,Ductility ,Beam (structure) ,Civil and Structural Engineering - Abstract
This paper seeks to contribute to the development and improvement of displacement-based design procedures, proposing improved ductility-equivalent viscous damping relationships for steel moment-resisting framed structures with dissipative beam-to-column partial-strength joints. These relationships can be used directly in procedures like the Direct Displacement-Based Seismic Design (DDBD) that uses effective stiffness, ductility-equivalent viscous damping relationships and period-displacement relationships in a performance-based design approach. To this end, a finite element model of a steel beam-to-column sub-assemblage, characterized by an extended end-plate, is developed in ABAQUS. The model, which is validated against monotonic and cyclic experimental data obtained in previous research, is employed to carry out non-linear time-history (NLTH) analyses, using real records scaled to target several levels of ductility demand. A procedure is then proposed and applied to determine the ductility-equiv...
- Published
- 2017
19. 08.38: Experimental characterisation of the flexural behaviour of rubberized concrete-filled steel tubular members
- Author
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Yadong Jiang, António J. Silva, José Miguel Castro, and Ricardo Monteiro
- Subjects
Materials science ,Flexural strength ,General Medicine ,Composite material - Published
- 2017
20. 11.12: Derivation of the cyclic behaviour of components in bolted end-plate beam-to-column joints using FEM
- Author
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Luís Simões da Silva, Hugo Augusto, José Miguel Castro, and Carlos Rebelo
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Materials science ,business.industry ,General Medicine ,Structural engineering ,business ,Column (database) ,Finite element method ,Beam (structure) - Published
- 2017
21. 07.07: Numerical study of screw fasteners in built-up CFS chord studs
- Author
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José Miguel Castro, David C. Fratamico, Nouredine Bourahla, Smail Kechidi, and Benjamin W. Schafer
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Materials science ,business.industry ,020101 civil engineering ,02 engineering and technology ,General Medicine ,Structural engineering ,Cold-formed steel ,0201 civil engineering ,law.invention ,020303 mechanical engineering & transports ,0203 mechanical engineering ,law ,Chord (music) ,business - Published
- 2017
22. 08.36: Numerical modelling of circular CFST members and assessment of multi-axial stress state effects
- Author
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António J. Silva, Ricardo Monteiro, Bledar Kalemi, Yadong Jiang, and José Miguel Castro
- Subjects
Stress (mechanics) ,Materials science ,business.industry ,General Medicine ,State (functional analysis) ,Multi axial ,Structural engineering ,business - Published
- 2017
23. Fatigue Damage Analysis of Offshore Structures using Hot-Spot Stress and Notch Strain Approaches
- Author
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José Miguel Castro, Grzegorz Lesiuk, Adriana Valadares Mourão, A.M.P. De Jesus, M. Correia, Rui Calçada, Nicholas Fantuzzi, and José A.F.O. Correia
- Subjects
Stress (mechanics) ,Materials science ,Strain (chemistry) ,Submarine pipeline ,Hot spot (veterinary medicine) ,Fatigue damage ,Composite material - Published
- 2019
24. Fatigue crack growth modelling for cracked small-scale structural details repaired with CFRP
- Author
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Anis Mohabeddine, José Miguel Castro, P.A. Montenegro, and José A.F.O. Correia
- Subjects
Carbon fiber reinforced polymer ,Materials science ,Scale (ratio) ,business.industry ,Mechanical Engineering ,Stiffness ,020101 civil engineering ,02 engineering and technology ,Building and Construction ,Structural engineering ,Paris' law ,0201 civil engineering ,Fatigue crack propagation ,020303 mechanical engineering & transports ,0203 mechanical engineering ,Ultimate tensile strength ,medicine ,medicine.symptom ,business ,Reduction factor ,Civil and Structural Engineering ,Parametric statistics - Abstract
This paper presents an analytical model to predict the mode I fatigue crack growth of steel Central Cracked Tensile (CCT) specimens repaired with Carbon Fiber Reinforced Polymer (CFRP) bonded on the two sides of the plate. A review of the behaviors observed in past experimental tests is provided. The CFRP-steel stiffness ratio, as well as the level of the initial crack length and the location of the CFRP patch, influence the performance of the CFRP crack repair. A total of 69 experimental and 7 numerical results of CFRP repaired specimens were collected from the literature and a database is created. Seventy percent of the data (Experimental only) were used for the development of the model and thirty percent for verification. The fatigue crack propagation of each pair of unrepaired and repaired experimental specimens was calibrated for the development of the model. The effect of the CFRP on the fatigue crack propagation is represented by a SIF reduction factor, β . An analytical law based on nonlinear regression analysis is proposed to evaluate β which depends on the CFRP-steel ratio, level of damage of the steel plate, and patch location. The model is fairly validated with experimental and numerical results. A parametric study is conducted for further verification, the model shows reasonable trends.
- Published
- 2021
25. Finite element modelling of short steel tubes filled with rubberized concrete
- Author
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J. de Brito, Eduardo Júlio, Nuno Silvestre, José Miguel Castro, A.P.C. Duarte, and B.A. Silva
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Materials science ,business.industry ,0211 other engineering and technologies ,020101 civil engineering ,02 engineering and technology ,Structural engineering ,Plasticity ,Finite element method ,0201 civil engineering ,Core (optical fiber) ,Natural rubber ,Energy absorption ,visual_art ,021105 building & construction ,Ceramics and Composites ,visual_art.visual_art_medium ,Dilation (morphology) ,Composite material ,Tube (container) ,business ,Ductility ,Civil and Structural Engineering - Abstract
This paper presents a numerical investigation on the ductility and strength of short steel tubes filled with Rubberized Concrete (RuC), which is a composite material that mixes concrete with rubber particles. This research concerns the enhancement of both ductility and energy absorption of CFST by considering a core of RuC instead of normal concrete (NC). First, a brief literature review on the topic is presented. Then, based on an experimental programme conducted by the authors, numerical models of CFST and RuCFST columns are developed. The results of non-linear analyses (ultimate strengths, load-shortening curves and failure modes) are validated using experimental data, and good agreement is shown. Finally, a numerical study on the properties of confined NC and RuC is conducted. It is concluded that the concrete damaged plasticity model can be used to simulate RuC. The dilation angle plays a key role in RuC and its lower value (compared to that of NC) influences the concrete confinement. Taking into account the RuC dilation angle, steel yield stress and tube local slenderness, a new formula is proposed to predict the concrete core confinement of the studied CFST and RuCFST columns with circular sections.
- Published
- 2016
26. Tests and design of short steel tubes filled with rubberised concrete
- Author
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Nuno Silvestre, Eduardo Júlio, B.A. Silva, J. de Brito, José Miguel Castro, and A.P.C. Duarte
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Materials science ,business.industry ,0211 other engineering and technologies ,020101 civil engineering ,Scrap ,02 engineering and technology ,Structural engineering ,Eurocode ,Dissipation ,0201 civil engineering ,Experimental testing ,021105 building & construction ,Composite material ,business ,Ductility ,Civil and Structural Engineering - Abstract
An experimental investigation on the strength and ductility of short steel tubes filled with rubberised concrete (RuC), sourced from recycled scrap tyres, is presented in this paper. Firstly, a brief literature review on (i) concrete-filled steel tubes (CFST) and (ii) mechanical characterisation of rubberised concrete is presented. Then, the experimental investigation is described and test results are shown and discussed, namely, the assessment of (i) RuC and steel mechanical properties and (ii) RuCFST column structural properties. The influence of various parameters, such as the cross-section shape (square, rectangular, circular), steel grade, and concrete mix (standard concrete versus RuC), on the short column strength and ductility is analysed and discussed. Eurocode 4 is considered (i) to determine the strength of the tested columns and, in particular, (ii) to assess its applicability to RuCFST columns based on a comparison with the experimental results. The main conclusion of this research is that RuCFST short columns present higher ductility than those made of standard concrete, even though they also show lower strength. This improved ductility is noticeable in columns with circular sections, rather than in square and rectangular sections. From a practical viewpoint, this could be a major benefit for structures in seismic areas where energy dissipation is needed.
- Published
- 2016
27. Experimental study on short rubberized concrete-filled steel tubes under cyclic loading
- Author
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Nuno Silvestre, J. de Brito, Eduardo Júlio, B.A. Silva, José Miguel Castro, and A.P.C. Duarte
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Materials science ,business.industry ,0211 other engineering and technologies ,Test rig ,020101 civil engineering ,Cyclic strength ,02 engineering and technology ,Structural engineering ,Dissipation ,0201 civil engineering ,Natural rubber ,visual_art ,021105 building & construction ,Ceramics and Composites ,visual_art.visual_art_medium ,Axial load ,Cyclic loading ,Composite material ,Envelope (mathematics) ,Ductility ,business ,Civil and Structural Engineering - Abstract
This paper presents an experimental investigation on the cyclic behaviour of short steel tubes filled with rubberized concrete (RuC), a composite material that mixes concrete with rubber particles. A brief literature review on the cyclic behaviour of CFST columns, the mechanical properties of RuC and recent research on RuC-filled steel tubes (RuCFSTs) is presented. Then, the tested specimens are characterized, comprising three cross-section shapes (square, rectangular, circular), three steel grades (S235, S275, S355), three concrete mixes (0%, 5%, 15% of rubber particles content) and two axial load levels (10%, 20% of axial plastic load). After that, the loading protocol, test rig and experimental procedure are described in detail. The experimental results are extensively discussed, focusing on the columns’ cyclic strength, failure modes, hysteretic and envelope curves, as well as on the energy-based ductility factors. Finally, conclusions are drawn regarding all these parameters. The most relevant achievement is that a concrete mix with a low content (5%) of rubber particles leads simultaneously to the lowest decrease (5%) in the cyclic strength and the highest increase (52%) in the ductility of RuCFST columns, thus being the most suitable mix to use in seismic areas, where ductility and energy dissipation requirements are mandatory.
- Published
- 2016
28. Simulation of screw connected built-up cold-formed steel back-to-back lipped channels under axial compression
- Author
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Nouredine Bourahla, David C. Fratamico, Benjamin W. Schafer, José Miguel Castro, and Smail Kechidi
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Chord (geometry) ,business.product_category ,Materials science ,business.industry ,0211 other engineering and technologies ,Stiffness ,020101 civil engineering ,02 engineering and technology ,Structural engineering ,Compression (physics) ,Fastener ,Finite element method ,Cold-formed steel ,0201 civil engineering ,law.invention ,Buckling ,law ,021105 building & construction ,medicine ,Shear wall ,medicine.symptom ,business ,Civil and Structural Engineering - Abstract
The objective of this paper is to validate finite element (FE) modeling protocol for screw connected, back-to-back built-up cold-formed steel (CFS) columns. The protocol is developed and validated using results from previously conducted experiments. The effort is motivated by two applications: (1) to augment experimental findings on built-up CFS columns, particularly for fastener demands and (2) to provide a simulation path for modeling the built-up CFS columns that are used as shear wall chord studs. Shell FE-based models were created in ABAQUS and include monotonic loading, nonlinear geometric and material behavior, geometric imperfections based on laser scanned measurements of tested specimens and a contact model that includes friction. Additionally, the screw fasteners were integrated into the modeling protocol using user-defined element subroutines capable of reproducing strength and stiffness deterioration under monotonic load as well as the pinching that occurs when screw fasteners are subjected to cyclic loads. Monotonic, concentric compression tests on 17 back-to-back CFS columns using two cross-section sizes and varying fastener layouts with sheathing conditions were simulated. Deformations, strength, and collapse mechanisms obtained by the models were in close agreement with the experimental results. An assessment of the loading demand on screw fasteners reveals the conservatism in built-up column fastener layout and design as required by the North American Specification for the Design of Cold-Formed Steel Structural Members (AISI S100-16 Section I1.2). Also, under the tested semi-rigid column end conditions, there is a little boost in axial capacity with the addition of member end fastener groups (EFGs) at the top and bottom of the columns. Numerical models are also used to assess the cyclic performance of axially-loaded columns so that chord stud buckling limit states could be captured in seismic simulations of CFS-framed shear walls in future work.
- Published
- 2020
29. Importance of biomass and binder selection for coking briquette preparation: their effect on coal thermoplastic properties
- Author
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L. Florentino-Madiedo, E. Díaz-Faes, Miguel Castro-Díaz, Carmen Barriocanal, Colin E. Snape, and Research Fund for Coal and Steel
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Briquette ,Thermoplastic ,Materials science ,020209 energy ,General Chemical Engineering ,geology ,Energy Engineering and Power Technology ,Biomass ,02 engineering and technology ,fluidity ,Biomass, coal, binder, briquettes, fluidity ,020401 chemical engineering ,Briquettes ,0202 electrical engineering, electronic engineering, information engineering ,Coal ,0204 chemical engineering ,chemistry.chemical_classification ,Bituminous coal ,Binder ,business.industry ,geology.rock_type ,Pulp and paper industry ,Fuel Technology ,chemistry ,business - Abstract
Blends consisting of a high volatile bituminous coal, biomass, and binder that were used in the preparation of briquettes were analyzed in order to select the best components from the viewpoint of their influence on the coal's thermoplastic properties. The raw materials were studied by means of thermogravimetry, high-temperature rheometry, high-temperature proton nuclear magnetic resonance (H NMR), and Fourier transform infrared (FTIR) spectroscopy. In addition, the fluidity of the blends was determined with the standard Gieseler plastometer test method (ASTM D 2639-74). Various parameters derived from these different techniques were used to explain the effects of biomass and binder on the fluidity of the blends with coal. It was found that the deleterious effect of biomass was mainly related to its physical properties, whereas the effect of the binder was controlled by its chemical composition. Coal tar, coal tar sludge, pine sawdust, and a biocoal derived from hydrothermally treated waste biomass obtained from pruning were the best materials for the preparation of briquettes for cokemaking., The research leading to these results has received funding from the European Union's Research Fund for Coal and Steel (RFCS) research programme under grant agreement No. [RFCR-CT-2014-00006].
- Published
- 2018
30. Seismic performance assessment of conventional steel and steel-concrete composite moment frames using CFST columns
- Author
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Yadong Jiang, Antonio Silva, Ricardo Monteiro, Luís Macedo, and José Miguel Castro
- Subjects
Moment (mathematics) ,Materials science ,business.industry ,Composite number ,Concrete-filled steel tubes ,Seismic performance ,Eurocode 8 ,Structural engineering ,Steel/composite moment frames ,business ,Earthquake-induced losses - Abstract
The research reported in this paper focuses on the assessment of the seismic performance of conventional steel moment-resisting frames (MRFs) and steel-concrete composite moment-resisting frames employing circular Concrete-Filled Steel Tube (CFST) columns. Two comparable archetypes (i.e. one steel MRF, with steel columns and steel beams; and one composite MRF, with circular CFST columns and steel beams) are designed, and used as the basis for comparison between the seismic performance associated with each typology. Both structures are designed against earthquake loads following the recommendations of Eurocode 8. The comparison of the obtained design solutions allows concluding that the amount of steel associated with the main structural members is higher for the steel-only archetype, even though the composite MRF has the higher level of lateral stiffness. This aspect is particularly relevant when one considers that a minimum level of lateral stiffness (associated with the P-Δ inter-storey drift sensitivity coefficient, θ), is imposed by the European code, which may ultimately govern the design process. The two case-studies are then numerically modelled in OpenSees, and their seismic performance is assessed through fragility assessment for a number of relevant limit states, and, finally, earthquake-induced loss estimation. In general, the results obtained clearly indicate that the composite MRF with circular CFST columns exhibits better seismic performance than the equivalent steel-only archetype. This is noticeably shown in the comparison of the fragility curves associated with the collapse limit state, which tend to show substantially higher probabilities of exceedance, at similar levels of 1st-mode spectral acceleration, for the steel-only case. Furthermore, seismic losses at several seismic intensity levels of interest tend to be higher for the steel MRF.
- Published
- 2018
- Full Text
- View/download PDF
31. The Effect of Silver Nanofibers on the Deformation Properties of Blood Vessels: Towards the Development of New Nanotechnologies to Prevent Rupture of Aneurysms
- Author
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Alam Marcelino, Rafael Morales Rodriguez, Miguel Castro, Miguel Gonzalez, Daniel Rivera, and Gabriela Agront
- Subjects
Materials science ,Article Subject ,Nanotechnology ,02 engineering and technology ,Deformation (meteorology) ,010402 general chemistry ,021001 nanoscience & nanotechnology ,medicine.disease ,01 natural sciences ,0104 chemical sciences ,medicine.anatomical_structure ,Blood pressure ,Aneurysm ,Nanofiber ,lcsh:Technology (General) ,cardiovascular system ,medicine ,lcsh:T1-995 ,General Materials Science ,0210 nano-technology ,Blood vessel ,Biomedical engineering - Abstract
An aneurysm is the result of a widening or ballooning of a portion of a blood vessel. The rupture of an aneurysm occurs when the mechanical stress acting on the inner wall exceeds the failure strength of the blood vessel. We propose an innovative approach to prevent the rupture of an aneurysm based on the use of nanotechnology to improve the strength of the blood vessel. We present results on the effect of silver nanofibers on the resistance toward deformation of blood vessels. The silver nanofibers are grown on the surface of the blood vessels. The nanofibers are120±30 nm in diameter and2.7±0.8 μm in length. The deformation per applied force of blood vessels was found to decrease from 0.15 m/N in control blood vessels to 0.003 m/N in blood vessels treated with the nanofibers. This represents an increase in the resistance towards deformation of a factor of 50. The increase in the resistance towards deformation is clinically significant since blood pressure increases by factors slightly larger than one in the human body. Treatment of blood vessels with silver nanofibers is a potential translational clinical tool for preventing rupture of aneurysms in a clinical setting.
- Published
- 2014
32. Small binary iron‐carbon clusters with persistent high magnetic moments. A theoretical characterization
- Author
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Miguel Castro, Patricio Limon, and Alan Miralrio
- Subjects
Materials science ,Magnetic moment ,Binary number ,chemistry.chemical_element ,Electronic structure ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Characterization (materials science) ,chemistry ,Chemical physics ,Density functional theory ,Binary clusters ,Physical and Theoretical Chemistry ,Carbon - Published
- 2019
33. Structural and Electronic Properties of the Graphene-Like Carbon Nitride Nanosheets
- Author
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H. Hernández Cocoletzi, E. Chigo Anota, and Miguel Castro
- Subjects
Materials science ,Graphene ,Nanotechnology ,General Chemistry ,Condensed Matter Physics ,law.invention ,Computational Mathematics ,chemistry.chemical_compound ,chemistry ,law ,General Materials Science ,Electrical and Electronic Engineering ,Carbon nitride ,Electronic properties - Published
- 2013
34. An investigation into the effect of fast heating on fluidity development and coke quality for blends of coal and biomass
- Author
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Sylvia Kokonya, Colin E. Snape, Carmen Barriocanal, and Miguel Castro-Díaz
- Subjects
Materials science ,Renewable Energy, Sustainability and the Environment ,Carbonization ,business.industry ,Biomass ,Forestry ,Coke ,Torrefaction ,Pulp and paper industry ,Biofuel ,Pellet ,Botany ,Coal ,business ,Waste Management and Disposal ,Agronomy and Crop Science ,Mass fraction - Abstract
The addition of biomass to coking coals can reduce operational costs and carbon emissions but also reduces fluidity development. The use of heating rates up to 20 °C min−1 in the softening stage of coal has been investigated using high-temperature small-amplitude oscillatory-shear (SAOS) rheometry to improve the fluid characteristics of binary blends of two coking coals with Scots pine. The effects of biomass concentration and particle size, biomass torrefaction, pellet mass and thermal pre-treatment of the blend on fluidity development and semicoke strength have also been studied. Fluidity increased with an increase in heating rate and an increase in the final temperature for fast heating. Relationships were found between the minimum complex viscosity of the blend, the heating rate and the concentration of biomass, which have been used to propose an equation to calculate the heating rate necessary to achieve optimum fluidity for a particular blend with biomass. The fluid characteristics of the blend were not affected to a great extent by the particle sizes of the biomass studied ( 500 μm) or the torrefaction of the biomass (250 °C for 1 h in N2), were increased by an increase in pellet mass, and were destroyed by blend pre-heating. The semicoke strength of the blend with a mass fraction of 10% Scots pine and fast heating (10 °C min−1) proved to be higher than that of the coal alone with slow heating (3 °C min−1) and resulted in a 3% reduction in non-renewable carbon emissions.
- Published
- 2013
35. Density Functional Theory Studies of the Structural and Electronic Properties of Germanium Nanosheets
- Author
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A. Bautista Hernández, Miguel Castro, E. Chigo Anota, and Gregorio H. Cocoletzi
- Subjects
Materials science ,Condensed matter physics ,Silicene ,Polarity (physics) ,Graphene ,Doping ,chemistry.chemical_element ,Ionic bonding ,Germanium ,General Chemistry ,Condensed Matter Physics ,Semimetal ,law.invention ,Computational Mathematics ,chemistry ,Computational chemistry ,law ,General Materials Science ,Density functional theory ,Electrical and Electronic Engineering - Abstract
Ab-initio calculations, based on the density functional theory, have been performed to investigate the electronic and atomic structures of defects free hexagonal germanium (h-Ge) and germanium (d-Ge) nanosheets with Stone-Wales defects type. The exchange-correlation energies are treated according to the Perdew-Wang (PW) and Perdew–Burke–Ernzerhof (PBE) functionals. Nanosheets are represented by CnHm clusters in the armchair configuration. We investigate the doping effects when a Ga replaces a Ge. The atomic structure of both d-Ge doped free and doped sheets displayed corrugation with a concavity similar to that exhibited by silicene and graphene. In addition systems are ionic with semimetal electronic behavior. It is worthwhile mentioning that the modified by doping sheets show changes in the polarity, nevertheless the semimetal behavior remains.
- Published
- 2013
36. Theoretical Investigation of the Influence of Point Defects on the Electronic Properties of Graphanol
- Author
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E. Chigo-Anota, Gregorio H. Cocoletzi, and Miguel Castro
- Subjects
Computational Mathematics ,Materials science ,Condensed matter physics ,Doping ,General Materials Science ,General Chemistry ,Electrical and Electronic Engineering ,Condensed Matter Physics ,Crystallographic defect ,Electronic properties - Published
- 2013
37. Biosynthesis of gold nanoparticles by extracellular molecules produced by the phytopathogenic fungus Botrytis cinerea
- Author
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Miguel Castro, Luis Cottet, and Antonio Castillo
- Subjects
Materials science ,biology ,Mechanical Engineering ,Reductase ,Condensed Matter Physics ,biology.organism_classification ,Absorbance ,chemistry.chemical_compound ,chemistry ,Biochemistry ,Mechanics of Materials ,Colloidal gold ,Chloroauric acid ,Extracellular ,Biophysics ,General Materials Science ,Denaturation (biochemistry) ,Surface plasmon resonance ,Botrytis cinerea - Abstract
The biosynthesis of gold nanoparticles (AuNPs) by extracellular components of the phytopathogenic fungus Botrytis cinerea was observed. Chloroauric acid (HAuCl 4 ) reduction and the formation of AuNPs were evidenced by a color change in the free-mycelium culture filtrate, from a pale yellow to a dark purple, and through an absorbance peak of 540 nm due to surface plasmon resonance of AuNPs. Characterization of the AuNPs showed triangular, hexagonal, spherical, decahedral, and pyramidal shapes of approximate sizes ranging from 1 to 100 nm. The experimental data presented in this study demonstrates that extracellular putative NADH-dependent reductase activity participates in reduction of HAuCl 4 and in the subsequent formation of AuNPs. However, this reductase is not the only active component secreted by the fungus in this process as the formation of AuNPs also occurs in conditions of high denaturation. The present study is the first to report on a rapid and eco-friendly method for the production of AuNPs by B. cinerea .
- Published
- 2014
38. Adsorption of molecular gases on porous materials in the SAFT-VR approximation
- Author
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Haret Codratian Rosu, Alejandro Martínez, Miguel Castro, and R. Martinez
- Subjects
Chemical Physics (physics.chem-ph) ,Statistics and Probability ,Real gas ,Materials science ,Silica gel ,FOS: Physical sciences ,Thermodynamics ,Computational Physics (physics.comp-ph) ,Condensed Matter Physics ,chemistry.chemical_compound ,symbols.namesake ,Adsorption ,chemistry ,Propane ,Physics - Chemical Physics ,Helmholtz free energy ,medicine ,symbols ,Molecule ,Porous medium ,Physics - Computational Physics ,Activated carbon ,medicine.drug - Abstract
A simple molecular thermodynamic approach is applied to the study of the adsorption of gases of chain molecules on solid surfaces. We use a model based on the Statistical Associating Fluid Theory for Variable Range (SAFT-VR) potentials [A. Gil-Villegas, A. Galindo, P. J. Whitehead, S. J. Mills, G. Jackson, A. N. Burgess, J. Chem. Phys. 106 (1997) 4168] that we extend by including a quasi-two-dimensional approximation to describe the adsorption properties of this type of real gases [A. Martinez, M. Castro, C. McCabe, A. Gil-Villegas, J. Chem. Phys. 126 (2007) 074707]. The model is applied to ethane, ethylene, propane, and carbon dioxide adsorbed on activated carbon and silica gel, which are porous media of significant industrial interest. We show that the adsorption isotherms obtained by means of the present SAFT-VR modeling are in fair agreement with the experimental results provided in the literature, Comment: 9 pages, 12 eps figures
- Published
- 2010
39. Use of small-amplitude oscillatory shear rheometry to study the flow properties of pure and potassium-doped Li2ZrO3 sorbents during the sorption of CO2 at high temperatures
- Author
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Miguel Castro-Díaz, Mara Olivares-Marín, M. Mercedes Maroto-Valer, and Trevor C. Drage
- Subjects
Materials science ,Rheometry ,Potassium ,chemistry.chemical_element ,Mineralogy ,Filtration and Separation ,Sorption ,Dynamic mechanical analysis ,Analytical Chemistry ,chemistry.chemical_compound ,chemistry ,Chemical engineering ,Rheology ,Dynamic modulus ,Carbonate ,Eutectic system - Abstract
It has been previously recognized that the addition of lithium/potassium carbonates salts to pure Li2ZrO3 improves significantly the diffusion of CO2 uptake and, consequently, the CO2 sorption capacity. This effect has been associated with the formation of a eutectic molten carbonate layer on the outer surface of the reactant Li2ZrO3 particles. The present work proposes for the first time the use of small-amplitude oscillatory shear (SAOS) rheometry to determine the rheological properties of pure Li2ZrO3 and K-doped Li2ZrO3 under CO2 atmosphere and understand the interplay between these properties and the CO2 absorbed. The results have shown that the rheological parameters (storage modulus, G′; loss modulus, G″; and phase angle, δ) of the samples depend on the type of carbonate mixture and the extent of diffusion and sorption of CO2.
- Published
- 2010
40. Patient-specific simulation of guidewire deformation during transcatheter aortic valve implantation
- Author
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Vincent Auffret, Miguel Castro, Stéphane Avril, Phuoc Vy, Pierre Badel, Michel Rochette, Pascal Haigron, Biologie intégrative du tissu osseux, Université Jean Monnet [Saint-Étienne] (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM), Laboratoire Traitement du Signal et de l'Image (LTSI), Université de Rennes 1 (UR1), Université de Rennes (UNIV-RENNES)-Université de Rennes (UNIV-RENNES)-Institut National de la Santé et de la Recherche Médicale (INSERM), INSERM U1059, SAINBIOSE - Santé, Ingénierie, Biologie, Saint-Etienne (SAINBIOSE-ENSMSE), Université Jean Monnet [Saint-Étienne] (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre Ingénierie et Santé (CIS-ENSMSE), École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-École des Mines de Saint-Étienne (Mines Saint-Étienne MSE), Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT), ANSYS, Europe FEDER, French ANR within the Investissements d'Avenir program (Labex CAMI) [ANR-11-LABX-0004], ANR-11-LABX-0004,CAMI,Gestes Médico-Chirurgicaux Assistés par Ordinateur(2011), Biologie Intégrative du Tissu Osseux (LBTO), Université Jean Monnet - Saint-Étienne (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM), Université de Rennes (UR)-Institut National de la Santé et de la Recherche Médicale (INSERM), Santé Ingénierie Biologie Saint-Etienne (SAINBIOSE), Centre Ingénierie et Santé (CIS-ENSMSE), and Institut Mines-Télécom [Paris] (IMT)-Institut Mines-Télécom [Paris] (IMT)-Université Jean Monnet - Saint-Étienne (UJM)-Institut National de la Santé et de la Recherche Médicale (INSERM)
- Subjects
Male ,Aortic valve ,Materials science ,medicine.medical_treatment ,0206 medical engineering ,Biomedical Engineering ,02 engineering and technology ,030204 cardiovascular system & hematology ,Deformation (meteorology) ,Curvature ,Prosthesis ,Transcatheter Aortic Valve Replacement ,03 medical and health sciences ,0302 clinical medicine ,medicine.artery ,medicine ,Humans ,Molecular Biology ,Aorta ,Applied Mathematics ,Models, Cardiovascular ,Stiffness ,020601 biomedical engineering ,Finite element method ,medicine.anatomical_structure ,Computational Theory and Mathematics ,Aortic Valve ,Heart Valve Prosthesis ,Modeling and Simulation ,Female ,[SDV.IB]Life Sciences [q-bio]/Bioengineering ,Implant ,medicine.symptom ,[SPI.SIGNAL]Engineering Sciences [physics]/Signal and Image processing ,Software ,Biomedical engineering - Abstract
International audience; Transcatheter aortic valve implantation is a recent mini-invasive procedure to implant an aortic valve prosthesis. Prosthesis positioning in transcatheter aortic valve implantation appears as an important aspect for the success of the intervention. Accordingly, we developed a patient-specific finite element framework to predict the insertion of the stiff guidewire, used to position the aortic valve. We simulated the guidewire insertion for 2 patients based on their pre-operative CT scans. The model was designed to primarily predict the position and the angle of the guidewires in the aortic valve, and the results were successfully compared with intraoperative images. The present paper describes extensively the numerical model, which was solved by using the ANSYS software with an implicit resolution scheme, as well as the stabilization techniques which were used to overcome numerical instabilities. We performed sensitivity analysis on the properties of the guidewire (curvature angle, curvature radius, and stiffness) and the conditions of insertion (insertion force and orientation). We also explored the influence of the model parameters. The accuracy of the model was quantitatively evaluated as the distance and the angle difference between the simulated guidewires and the intraoperative ones. A good agreement was obtained between the model predictions and intraoperative views available for 2 patient cases. In conclusion, we showed that the shape of the guidewire in the aortic valve was mainly determined by the geometry of the patient's aorta and by the conditions of insertion (insertion force and orientation).
- Published
- 2018
41. Use of Oscillatory Shear Rheometry and Thermogravimetric Analysis To Examine the Microstructural Changes during Coal Pyrolysis/Carbonization for the Prediction of IRSID Strength Indices
- Author
-
Karen M. Steel, Miguel Castro Diaz, John J. Duffy, and Colin E. Snape
- Subjects
Thermogravimetric analysis ,Fuel Technology ,Materials science ,Rheology ,Rheometry ,Carbonization ,General Chemical Engineering ,Energy Engineering and Power Technology ,Coke ,Dynamic mechanical analysis ,Composite material ,Pyrolysis ,Viscoelasticity - Abstract
During pyrolysis and carbonization of coal, the viscoelastic properties vary across a wide range, with complex viscosity (eta*) decreasing to as low as 100 Pa s before increasing to approximately 10(8) Pa s and phase angle (delta) varying from close to 90 degrees (Newtonian liquid) down to 0 degrees (Hookean solid). A new rheometry method has been developed that combines tests using 25 and 8 mm plates to enable measurements of the entire resolidification process. When combined with thermogravimetric analysis, the method has provided new insights into the mechanisms leading to high and low IRSID, I40 strength indices. Although coals with very different volatile matter contents have similar rates of volatile release above 475 degrees C, viscoelastic properties above this temperature are highly variable. From a study of 13 coals, all coals for which delta 65 degrees at 475 degrees C had an I40 index > 44%. It is thought that, when delta 65 degrees and stays high until higher temperatures, the material is able to contract as volatiles are released without fissuring, ultimately leading to a higher I40 index. A relationship between the final storage modulus (G') of the material and the I10 index was also found, whereby a low G' corresponded to a high I10 index. Greater understanding of the relationships between viscoclasticity and pore/fissure network development could enable more precise relationships to be developed, ultimately leading to improved methods for predicting coke quality and devising strategies to make high-quality coke from various sources.
- Published
- 2009
42. Quantum (5 5 12)Si Nanowire 300K MOSFET
- Author
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Michael Kendall, Miguel Castro-L, Francisco J. De la Hidalga-W, W. Calleja-A, A. Torres-J, Roberto Murphy-A, Don L. Kendall, Ramiro Rodríguez-M, Ignacio Juárez-R, C. Zuniga-I, Elizabeth Meza Prieto, Netzahualcoyotl Carlos-R, and Mauro Landa-V
- Subjects
Materials science ,business.industry ,MOSFET ,Nanowire ,Optoelectronics ,business ,Quantum - Abstract
A nanowire (NW) device in parallel with a normal nMOSFET is fabricated with a poly-Si planar CMOS process on (5 5 12)Si. With a unit cell of 5.35 nm, this plane has the largest stable atomically flat Si surface. When output current Isd flows from source S to drain D along , the device has 15 positive spikes at integer multiples of 154 mV, all at 300K and zero magnetic field. Ids has only 9 positive and 2 negative spikes. The positive spikes in Isd and Ids are due to parabolic confinement of elongated q-dots in the NWs near D. Both Isd and Ids show missing spikes and one-dimensional artificial atom behavior. The negative spikes appear to be Kronig-Penney effects on the NWs. The NWs and q-dots have estimated widths near 2 nm and Line Edge Roughness (LER) less than 0.1 nm due to the crystal-lattice precision of the surface.
- Published
- 2008
43. Determination of the Effects Caused by Different Polymers on Coal Fluidity during Carbonization Using High-Temperature 1H NMR and Rheometry
- Author
-
Karen M. Steel, Miguel Castro Diaz, John W. Patrick, Lucky Edecki, and Colin E. Snape
- Subjects
Bituminous coal ,Materials science ,Rheometry ,Carbonization ,business.industry ,General Chemical Engineering ,geology.rock_type ,technology, industry, and agriculture ,geology ,Energy Engineering and Power Technology ,Coke ,Polyethylene ,complex mixtures ,respiratory tract diseases ,chemistry.chemical_compound ,Fuel Technology ,chemistry ,Rheology ,Chemical engineering ,Coal ,business ,Pyrolysis - Abstract
The effects of blending polyethylene (PE), polystyrene (PS), poly(ethyleneterephthalate) (PET), a flexible polyurethane (FPU), and a car shredded fluff waste (CSF) on fluidity development of a bituminous coal during carbonization have been studied by means of high-torque, small-amplitude controlled-strain rheometry and in situ high-temperature H-1 NMR spectroscopy. The most detrimental effects were caused by PET and PS, which completely destroyed the fluidity of the coal. The CSF had a deleterious effect on coal fluidity similar to that of PET, although the deleterious effect on the viscoelastic properties of the coal were less pronounced than those of PET and PS. On the contrary, the addition of 10 wt % PE caused a slight reduction in the concentration of fluid hydrogen and an increase in the minimum complex viscosity, and the addition of 10 wt % FPU reduced the concentration of fluid hydrogen without changing the viscoelastic properties of the coal. Although these results suggest that these two plastics could potentially be used as additives in coking blends without compromising coke porosity, it was found that the semicoke strengths were reduced by adding 2 wt % FPU and 5 wt % PE. Therefore, it is unlikely that more than 2 wt % of a plastic waste could be added to a coal blend without deterioration in coke quality.
- Published
- 2007
44. Preparação dos dados para análise
- Author
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Márcia Miguel Castro Ferreira
- Subjects
Materials science - Published
- 2015
45. Pulsed-laser switching in the bistability domain of a cooperative spin crossover compound: a critical study through calorimetry
- Author
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José Antonio Real, Olivier Roubeau, Miguel Castro, Lucía Piñeiro-López, José Alberto Rodríguez-Velamazán, Ministerio de Economía y Competitividad (España), European Commission, Gobierno de Aragón, Consejo Superior de Investigaciones Científicas (España), and Generalitat Valenciana
- Subjects
Materials science ,Bistability ,Pyrazine ,Pulse (signal processing) ,Calorimetry ,Laser ,Molecular physics ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,law.invention ,chemistry.chemical_compound ,General Energy ,chemistry ,Spin crossover ,law ,Physical and Theoretical Chemistry ,Spectroscopy ,Spin-½ - Abstract
The photoswitching from the low spin (LS) to high spin (HS) state and the reverse process in the bistability domain of spin crossover (SCO) compounds is a promising function to be used in molecular electronic devices, and evidenced mainly through spectroscopy. The phenomenon, and in particular its mechanism, is however still under debate since some controversial experimental results have been reported. Here we present a calorimetric experimental study of the photoswitching of the [Fe(pyrazine)Pt(CN)4] SCO material by a nanosecond-pulsed green laser. Our results confirm that the single laser pulse of varying energies results in significant LS to HS transformations and show that calorimetry provides an accurate quantification of the overall conversion. Successive pulses allow increasing the conversion, achieving a maximum of 60% under our experimental conditions. The HS to LS transformation is on the other hand not induced at any laser fluences contrary to previous reports. The results are compared with those reported with Raman spectroscopy and critically discussed in terms of efficiency of the transformation and potential thermal effects., This work has been supported by the Spanish MINECO and European Commission FEDER under projects MAT2011-24284, MAT2011-27233-C02-02, CTQ2011-23862-C02-01, CSD2007-00010, and CTQ2013-46275-P, by the Gobierno de Aragón through grants E98-“MOLCHIP” and E100-“Propiedades Termicas de Materiales”, and by the Generalitat Valenciana through PROMETEO/2012/049. L.P.L. thanks the Generalitat Valenciana for a predoctoral fellowship in the frame of the project PROMETEO/2012/049. JARV acknowledges CSIC for a JAE-doc contract.
- Published
- 2015
46. Comparative study of the electronic structure of alkaline-earth borides (MeB2; Me=Mg, Al, Zr, Nb, and Ta) and their normal-state conductivity
- Author
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Miguel Castro, Pablo de la Mora, and Gustavo Tavizon
- Subjects
Materials science ,Condensed matter physics ,Condensed Matter - Superconductivity ,FOS: Physical sciences ,Electronic structure ,Conductivity ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,Superconductivity (cond-mat.supr-con) ,Inorganic Chemistry ,Electrical resistivity and conductivity ,Condensed Matter::Superconductivity ,Materials Chemistry ,Ceramics and Composites ,Density of states ,Density functional theory ,Physical and Theoretical Chemistry ,Anisotropy ,Electronic band structure ,Electronic density - Abstract
By means of density functional theory the electronic structure of the MgB2 superconductor was characterised and compared with that of the related iso-structural systems: AlB2, ZrB2, NbB2, and TaB2. Using the full-potential linearized augmented plane waves (FP-LAPW) method and the generalised gradient approximation, the electronic density distribution, density of states, and band structures were obtained for these compounds. The electrical conductivity, which cannot be easily measured in the c-direction, was calculated, in the relaxation time approximation using band structure results. It was found that the two-dimensional (2D) crystal structure character of these metallic diborides is also reflected in the electronic charge distribution. This 2D pattern is not completely seen in the electrical conductivity as it is, for instance, in the superconductor high Tc cuprates. Indeed, it was found that, by the electrical conductivity calculations, all these compounds have a bulk, yet anisotropic, conductivity., 12 pages, 5 figures and 2 tables
- Published
- 2002
47. Panel discussion: on ?The status of the theory of chemical reactions,? Third CISTCP, Mexico City, November 8-13, 1999
- Author
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Miguel Castro
- Subjects
Materials science ,Economy ,Mexico city ,Physical and Theoretical Chemistry ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Panel discussion - Published
- 2000
48. Theoretical study of neutral and charged Sc n≤2–(benzene) m≤3 clusters
- Author
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Miguel Castro and Miguel Ángel Maynez-Rojas
- Subjects
Materials science ,Bioengineering ,General Chemistry ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Hybrid functional ,Bond length ,Delocalized electron ,Crystallography ,Modeling and Simulation ,Atom ,Molecule ,General Materials Science ,Density functional theory ,Atomic physics ,Ionization energy ,Valence electron - Abstract
Interactions of benzene molecules with scandium atoms, Scn≤2–(C6H6)m≤3, in the gas phase were studied by means of density functional theory. All-electron calculations were performed using the B3LYP hybrid functional in concert with 6-311+G(d,p) orbital basis sets for the Sc, C, and H atoms. Multiple-decker sandwich (MDS) structures are identified as the ground states for Scn≤2–(C6H6)m≤3, where the ligands are attached to the metal through Sc–C bonding, formed between the 3d electrons and the π-clouds of the benzene rings. Significant distortion is produced on the absorbed benzene molecules by the metal–ligand bonding. Rice ball structures also appeared, but they were found at higher energies, in such a way that essentially MDS isomers may emerge in the molecular beams. Even the low number of valence electrons (3d24s1) of the Sc atom; sextuple coordinations are formed, but they show different Sc–C bond lengths, diminishing the symmetry of neutral and charged clusters. The estimated ionization energies, in near agreement with experimental data, and electron affinities, suggest delocalization of the valence electrons through the network of 3d–π bonds of Sc1,2–(C6H6)m≤3. The binding energies decrease with the absorption of more benzene molecules, and in some cases increase as more metal atoms are added to the cluster.
- Published
- 2012
49. Dielectric relaxation processes in an antiferroelectric liquid crystal
- Author
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M. Rosario de la Fuente, Santos Merino, Miguel Castro, Blanca Ros, Miguel Angel Perez Jubindo, José Antonio Puértolas, and Yolanda González
- Subjects
Permittivity ,Nuclear magnetic resonance ,Materials science ,Condensed matter physics ,Mechanics of Materials ,Liquid crystal ,Mechanical Engineering ,Antiferroelectricity ,Relaxation (physics) ,General Materials Science ,Dielectric - Published
- 1995
50. Anomalous Dielectric Behaviour in Orthopalladated Ferroelectric Liquid Crystals
- Author
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Blanca Ros, José Antonio Puértolas, Maria de la Fuente, Miguel Angel Perez Jubindo, José Luis Serrano, and Miguel Castro
- Subjects
Permittivity ,Crystallography ,Materials science ,Liquid crystal ,law ,Dielectric ,Crystallization ,Atmospheric temperature range ,Condensed Matter Physics ,Polarization (electrochemistry) ,Ferroelectricity ,Heat capacity ,law.invention - Abstract
A ferroelectric ortho-palladated dimer derived from chiral imines with two chiral terminal chains in the aromatic ring has been characterized by dielecctric permittivity, polarization, X ray and heat capacity measurements. An anomalous behaviour has been detected in the low temperature range of the SmC* phase. A new molecular arrangement has been found on cooling prior to the crystallization not detected before by DSC experiments.
- Published
- 1995
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