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Saltarelli L, Gupta K, Rasi S, Kethamkuzhi A, Queraltó A, Garcia D, Gutierrez J, Farjas J, Roura-Grabulosa P, Ricart S, Obradors X, Puig T. Chemical and Microstructural Nanoscale Homogeneity in Superconducting YBa 2Cu 3O 7-x Films Derived from Metal-Propionate Fluorine-free Solutions. ACS Appl Mater Interfaces 2022; 14:48582-48597. [PMID: 36269760 PMCID: PMC9634695 DOI: 10.1021/acsami.2c11414] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Accepted: 10/07/2022] [Indexed: 06/16/2023]
Abstract
Research involved in developing alternative energy sources has become a necessity to face global warming. In this context, superconductivity is an appealing solution to enhance clean electrical energy provided that lower production costs can be attained. By implementation of chemical solution deposition techniques and high-throughput growth methods, low-cost nanostructured epitaxial cuprate superconductors are timely candidates. Here, we present a versatile and tunable solution method suitable for the preparation of high-performance epitaxial cuprate superconducting films. Disregarding the renowned trifluoroacetate route, we center our focus on the transient liquid-assisted growth (TLAG) that meets the requirement of being a greener chemical process together with ultrafast growth rates beyond 100 nm/s. We developed a facile, fast, and cost-effective method, starting from the synthesis of metal-propionate powders of Y, Ba, and Cu of high purity and high yields, being the precursors of the fluorine-free solutions, which enable the chemical and microstructural nanoscale homogeneity of YBa2Cu3O7-x (YBCO) precursor films. These solutions present endured stability and enable precise tunability of the composition, concentration, porosity, and film thickness. Homogeneous precursor films up to thicknesses of 2.7 μm through eight layer multidepositions are demonstrated, thus establishing the correct basis for epitaxial growth using the fast kinetics of the TLAG process. YBCO films of 500 nm thickness with a critical current density of 2.6 MA/cm2 at 77 K were obtained, showing the correlation of precursor film homogeneity to the final YBCO physical properties.
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Affiliation(s)
- Lavinia Saltarelli
- Institut
de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Kapil Gupta
- Institut
de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Silvia Rasi
- Institut
de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Aiswarya Kethamkuzhi
- Institut
de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Albert Queraltó
- Institut
de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Diana Garcia
- Institut
de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Joffre Gutierrez
- Institut
de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Jordi Farjas
- GRMT,
Department of Physics, University of Girona, E17071 Girona, Catalonia, Spain
| | - Pere Roura-Grabulosa
- GRMT,
Department of Physics, University of Girona, E17071 Girona, Catalonia, Spain
| | - Susagna Ricart
- Institut
de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Xavier Obradors
- Institut
de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
| | - Teresa Puig
- Institut
de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus de la UAB, 08193 Bellaterra, Catalonia, Spain
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2
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Rasi S, Queraltó A, Banchewski J, Saltarelli L, Garcia D, Pacheco A, Gupta K, Kethamkuzhi A, Soler L, Jareño J, Ricart S, Farjas J, Roura‐Grabulosa P, Mocuta C, Obradors X, Puig T. Kinetic Control of Ultrafast Transient Liquid Assisted Growth of Solution-Derived YBa 2 Cu 3 O 7 -x Superconducting Films. Adv Sci (Weinh) 2022; 9:e2203834. [PMID: 36116124 PMCID: PMC9661858 DOI: 10.1002/advs.202203834] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Revised: 08/13/2022] [Indexed: 06/15/2023]
Abstract
Transient liquid assisted growth (TLAG) is an ultrafast non-equilibrium growth process mainly governed by kinetic parameters, which are only accessible through fast in situ characterizations. In situ synchrotron X-ray diffraction (XRD) analysis and in situ electrical resistivity measurements are used to derive kinetic diagrams of YBa2 Cu3 O7- x (YBCO) superconducting films prepared via TLAG and to reveal the unique peculiarities of the process. In particular, diagrams for the phase evolution and the YBCO growth rates have been built for the two TLAG routes. It is shown that TLAG transient liquids can be obtained upon the melting of two barium cuprate phases (and not just one), differentiated by their copper oxidation state. This knowledge serves as a guide to determine the processing conditions to reach high performance films at high growth rates. With proper control of these kinetic parameters, films with critical current densities of 2-2.6 MA cm-2 at 77 K and growth rates between 100-2000 nm s-1 are reached. These growth rates are 1.5-3 orders of magnitude higher than those of conventional methods.
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Affiliation(s)
- Silvia Rasi
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Albert Queraltó
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Juri Banchewski
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Lavinia Saltarelli
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Diana Garcia
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
- Departament de QuímicaUniversitat Autònoma de BarcelonaBellaterraCatalonia08193Spain
| | - Adrià Pacheco
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Kapil Gupta
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Aiswarya Kethamkuzhi
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Laia Soler
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Julia Jareño
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Susagna Ricart
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Jordi Farjas
- GRMTDepartment of PhysicsUniversitat de GironaCampus Montilivi, Edif. PIIGironaCataloniaE17003Spain
| | - Pere Roura‐Grabulosa
- GRMTDepartment of PhysicsUniversitat de GironaCampus Montilivi, Edif. PIIGironaCataloniaE17003Spain
| | - Cristian Mocuta
- Synchrotron SOLEILL'Orme des Merisiers Saint‐Aubin BP 48Gif‐sur‐Yvette91192France
| | - Xavier Obradors
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
| | - Teresa Puig
- Institut de Ciència de Materials de BarcelonaICMAB‐CSICCampus UABBellaterraCatalonia08193Spain
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3
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Herrero R, Farjas J, Pi F, Orriols G. Nonlinear complexification of periodic orbits in the generalized Landau scenario. Chaos 2022; 32:023116. [PMID: 35232025 DOI: 10.1063/5.0069878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 01/24/2022] [Indexed: 06/14/2023]
Abstract
We have found a way for penetrating the space of the dynamical systems toward systems of arbitrary dimension exhibiting the nonlinear mixing of a large number of oscillation modes through which extraordinarily complex time evolutions may arise. The system design is based on assuring the occurrence of a number of Hopf bifurcations in a set of fixed points of a relatively generic system of ordinary differential equations, in which the main peculiarity is that the nonlinearities appear through functions of a linear combination of the system variables. The paper outlines the design procedure and presents a selection of numerical simulations with a variety of designed systems whose dynamical behaviors are really rich and full of unknown features. For concreteness, the presentation is focused on illustrating the oscillatory mixing effects on the periodic orbits, through which the harmonic oscillation born in a Hopf bifurcation becomes successively enriched with the intermittent incorporation of other oscillation modes of higher frequencies while the orbit remains periodic and without the necessity of bifurcating instabilities. Even in the absence of a proper mathematical theory covering the nonlinear mixing mechanisms, we find enough evidence to expect that the oscillatory scenario be truly scalable concerning the phase-space dimension, the multiplicity of involved fixed points, and the range of time scales so that extremely complex but ordered dynamical behaviors could be sustained through it.
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Affiliation(s)
- R Herrero
- Departament de Física, Universitat Politècnica de Catalunya, 08222 Terrassa, Spain
| | - J Farjas
- Departament de Física, Campus Montilivi, Universitat de Girona, 17003 Girona, Spain
| | - F Pi
- Departament de Física, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
| | - G Orriols
- Departament de Física, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
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Soler L, Jareño J, Banchewski J, Rasi S, Chamorro N, Guzman R, Yáñez R, Mocuta C, Ricart S, Farjas J, Roura-Grabulosa P, Obradors X, Puig T. Ultrafast transient liquid assisted growth of high current density superconducting films. Nat Commun 2020; 11:344. [PMID: 31953396 PMCID: PMC6969047 DOI: 10.1038/s41467-019-13791-1] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Accepted: 11/29/2019] [Indexed: 11/10/2022] Open
Abstract
The achievement of high growth rates in YBa2Cu3O7 epitaxial high-temperature superconducting films has become strategic to enable high-throughput manufacturing of long length coated conductors for energy and large magnet applications. We report on a transient liquid assisted growth process capable of achieving ultrafast growth rates (100 nm s−1) and high critical current densities (5 MA cm−2 at 77 K). This is based on the kinetic preference of Ba-Cu-O to form transient liquids prior to crystalline thermodynamic equilibrium phases, and as such is a non-equilibrium approach. The transient liquid-assisted growth process is combined with chemical solution deposition, proposing a scalable method for superconducting tapes manufacturing. Additionally, using colloidal solutions, the growth process is extended towards fabrication of nanocomposite films for enhanced superconducting properties at high magnetic fields. Fast acquisition in situ synchrotron X-ray diffraction and high resolution scanning transmission electron microscopy (STEM) become crucial measurements in disentangling key aspects of the growth process. High throughput manufacturing of long length coated conductors requires fast epitaxial growth of high-temperature superconducting films. Here, Soler et al. report an ultrafast growth rates and high critical current densities of YBa2Cu3O7 films using a transient liquid-assisted growth method.
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Affiliation(s)
- L Soler
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193, Bellaterra, Catalonia, Spain
| | - J Jareño
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193, Bellaterra, Catalonia, Spain
| | - J Banchewski
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193, Bellaterra, Catalonia, Spain
| | - S Rasi
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193, Bellaterra, Catalonia, Spain.,GRMT, Department of Physics, Universitat de Girona, Campus Montilivi, Edif. PII, E17003, Girona, Catalonia, Spain
| | - N Chamorro
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193, Bellaterra, Catalonia, Spain.,Departament de Química, Universitat Autònoma de Barcelona, 08193, Bellaterra, Catalonia, Spain
| | - R Guzman
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193, Bellaterra, Catalonia, Spain
| | - R Yáñez
- Departament de Química, Universitat Autònoma de Barcelona, 08193, Bellaterra, Catalonia, Spain
| | - C Mocuta
- Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin BP 48, 91192, Gif-sur-Yvette, France
| | - S Ricart
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193, Bellaterra, Catalonia, Spain
| | - J Farjas
- GRMT, Department of Physics, Universitat de Girona, Campus Montilivi, Edif. PII, E17003, Girona, Catalonia, Spain
| | - P Roura-Grabulosa
- GRMT, Department of Physics, Universitat de Girona, Campus Montilivi, Edif. PII, E17003, Girona, Catalonia, Spain
| | - X Obradors
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193, Bellaterra, Catalonia, Spain
| | - T Puig
- Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193, Bellaterra, Catalonia, Spain.
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5
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Martínez-Esaín J, Puig T, Obradors X, Ros J, Farjas J, Roura-Grabulosa P, Faraudo J, Yáñez R, Ricart S. Using evolved gas analysis - mass spectrometry to characterize adsorption on a nanoparticle surface. Nanoscale Adv 2019; 1:2740-2747. [PMID: 36132724 PMCID: PMC9417425 DOI: 10.1039/c9na00098d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 06/03/2019] [Indexed: 06/16/2023]
Abstract
The surface chemistry of nanoparticles is the key factor to control and predict their interactions with molecules, ions, other particles, other materials, or substrates, determining key properties such as nanoparticle stability or biocompatibility. In consequence, the development of new techniques or modification of classical techniques to characterize nanoparticle surfaces is of utmost importance. Here, a classical analysis technique, thermally evolved gas analysis - mass spectrometry (EGA-MS), is employed to obtain an image of the nanoparticle-solvent interface, unraveling the molecules present on the surface. As the use of complementary techniques is urged, the validity of EGA-MS characterization is corroborated by comparison with a previously reported surface characterization method. Previous studies were based on several experimental techniques and MD simulations using YF3 nano/supraparticles and LaF3 nanoparticles as model systems. We demonstrate the applicability of this technique in two differently sized systems and two systems composed of the same ions on their surface but with a different inorganic core (e.g. LaF3 and YF3 nanoparticles). The results described in this paper agree well with our previous results combining experimental techniques and MD simulations. EGA-MS not only revealed the ions attached to the nanoparticle surface but also shed light on their coordination (e.g. citrate attached to one or two carboxylate moieties). Thus, we show that EGA-MS is a useful and efficient technique to characterize the surface chemistry of nanoparticles and to control and predict their final properties.
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Affiliation(s)
- Jordi Martínez-Esaín
- Departament de Química, Universitat Autònoma de Barcelona 08193 Bellaterra Spain
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) 08193 Bellaterra Spain
| | - Teresa Puig
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) 08193 Bellaterra Spain
| | - Xavier Obradors
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) 08193 Bellaterra Spain
| | - Josep Ros
- Departament de Química, Universitat Autònoma de Barcelona 08193 Bellaterra Spain
| | - Jordi Farjas
- University of Girona Campus Montilivi, Edif. PII E17071 Girona Spain
| | | | - Jordi Faraudo
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) 08193 Bellaterra Spain
| | - Ramón Yáñez
- Departament de Química, Universitat Autònoma de Barcelona 08193 Bellaterra Spain
| | - Susagna Ricart
- Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) 08193 Bellaterra Spain
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6
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Abstract
We present a set of phase-space portraits illustrating the extraordinary oscillatory possibilities of the dynamical systems through the so-called generalized Landau scenario. In its simplest form the scenario develops in N dimensions around a saddle-node pair of fixed points experiencing successive Hopf bifurcations up to exhausting their stable manifolds and generating N-1 different limit cycles. The oscillation modes associated with these cycles extend over a wide phase-space region by mixing ones within the others and by affecting both the transient trajectories and the periodic orbits themselves. A mathematical theory covering the mode-mixing mechanisms is lacking, and our aim is to provide an overview of their main qualitative features in order to stimulate research on it.
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Affiliation(s)
- R Herrero
- Departament de Física i Enginyeria Nuclear, Universitat Politècnica de Catalunya, 08222 Terrassa, Spain
| | - J Farjas
- Departament de Física, Campus Montilivi, Universitat de Girona, 17003 Girona, Spain
| | - F Pi
- Departament de Física, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
| | - G Orriols
- Departament de Física, Universitat Autònoma de Barcelona, 08193 Cerdanyola del Vallès, Spain
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7
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Farjas J, López-Olmedo JP, Roura P. Model-free isoconversional method applied to polymer crystallization governed by the Hoffman-Lauritzen kinetics. POLYMER 2017. [DOI: 10.1016/j.polymer.2017.05.053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Affiliation(s)
| | - Jordi Farjas
- University of Girona, Physics Dept., Campus MontiliviEdif. PIIGirona CataloniaE17071 Spain
| | - Pere Roura
- University of Girona, Physics Dept., Campus MontiliviEdif. PIIGirona CataloniaE17071 Spain
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9
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Calleja A, Mos RB, Roura P, Farjas J, Arbiol J, Ciontea L, Obradors X, Puig T. Growth of epitaxial CeO2 buffer layers by polymer assisted deposition. ACTA ACUST UNITED AC 2012. [DOI: 10.1557/opl.2012.1250] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTPolymer assisted deposition (PAD) has been reported as a novel CSD approach for thin film growth with improved homogeneity and long stability by forming a metal polymer species. It also offers the interesting possibility of having a library of PAD solutions for each precursor metal and obtaining the required composition by simple mixing. Another potential advantage is the increase in thickness since mechanical stresses are expected to be alleviated during shrinkage in the metalorganic decomposition by the metal-polymer network.Cerium oxide films on YSZ single crystals were grown from water-based solutions containing cerium nitrate, polyethyleneimine and complexing EDTA, in order to explore the benefits of using the PAD approach for growing buffer layers in coated conductors. An ultrafiltration step was performed to remove the non-coordinated species in solution. The degree of purification and efficiency in the cerium recovery was investigated by different techniques. TGA-DTA analysis was used to provide guidance to the best thermal profiles in different atmospheres and specially to diminish the adverse effects of exothermic events during decomposition. Microstructural evolution was tracked by AFM and TEM, while epitaxial fraction was followed by X-ray diffraction. The results show the high importance of choosing the proper atmosphere and the need for tuning of heating ramps to obtain dense, flat and epitaxial ceria films by PAD.
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Farjas J, Sanchez-Rodriguez D, Eloussifi H, Hidalgo RC, Roura P, Ricart S, Puig T, Obradors X. Can We Trust on the Thermal Analysis of Metal Organic Powders for thin film preparation? ACTA ACUST UNITED AC 2012. [DOI: 10.1557/opl.2012.919] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTThermal analysis techniques are routinely applied to characterize the thermal behavior of metal organic precursors used for oxide film preparation. Since the mass of films is very low, researchers do their thermal analyses on powders and consider that the results are representative of films. We will show here that, in general, this assumption is not true. Several examples involving precursors of YBa2Cu3O7-x (Ba and Y trifluoroacetates and Ba propionate) will serve to appreciate that films can behave very differently than powders due to their enhanced heat and mass transport paths. Ultimately, we will demonstrate that, in some cases, relying on powders thermal analysis may lead to erroneous conclusions.
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Kail F, Molera J, Farjas J, Roura P, Secouard C, Roca i Cabarrocas P. Can the crystallization rate be independent from the crystallization enthalpy? The case of amorphous silicon. J Phys Condens Matter 2012; 24:095401. [PMID: 22316607 DOI: 10.1088/0953-8984/24/9/095401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The crystallization enthalpy measured in a large series of amorphous silicon (a-Si) materials varies within a factor of 2 from sample to sample (Kail et al 2011 Phys. Status Solidi RRL 5 361). According to the classical theory of nucleation, this variation should produce large differences in the crystallization kinetics leading to crystallization temperatures and activation energies exceeding 550 °C and 1.7 eV, respectively, the 'standard' values measured for a-Si obtained by self-implantation. In contrast, the observed crystallization kinetics is very similar for all the samples studied and has no correlation with the crystallization enthalpy. This discrepancy has led us to propose that crystallization in a-Si begins in microscopic domains that are almost identical in all samples, independently of their crystallization enthalpy. Probably the existence of microscopic inhomogeneities also plays a crucial role in the crystallization kinetics of other amorphous materials and glasses.
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Affiliation(s)
- F Kail
- GRMT, Department of Physics, University of Girona, Montilivi Campus, E17071-Girona, Catalonia, Spain
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12
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González I, Pla-Quintana A, Roglans A, Dachs A, Solà M, Parella T, Farjas J, Roura P, Lloveras V, Vidal-Gancedo J. Ene reactions between two alkynes? Doors open to thermally induced cycloisomerization of macrocyclic triynes and enediynes. Chem Commun (Camb) 2010; 46:2944-6. [PMID: 20386831 DOI: 10.1039/b926497c] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Iván González
- Dept. de Química, Universitat de Girona (UdG), Campus de Montilivi, s/n, E-17071-Girona, Spain
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13
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Roura P, Farjas J. Comment on "relaxation kinetics of nanoscale indents in a polymer glass". Phys Rev Lett 2009; 103:119801-119802. [PMID: 19792412 DOI: 10.1103/physrevlett.103.119801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2009] [Indexed: 05/28/2023]
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14
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Roura P, Farjas J, Roca i Cabarrocas P. Restricted epitaxial growth of crystallites in hydrogenated nanocrystalline silicon during thermal crystallization experiments. J Nanosci Nanotechnol 2009; 9:3700-3707. [PMID: 19504906 DOI: 10.1166/jnn.2009.ns54] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Thermal crystallization experiments have been carried out on nanocrystalline silicon films. From the thermal activation of the process, it is concluded that the amorphous phase crystallizes by solid phase epitaxy around the preexisting crystallites. However, and in contrast with the usual epitaxial crystallization of wafers partially amorphized by ion implantation or ball-milled powders, the epitaxial growth is inhibited for most of the amorphous-crystalline interface. Our analysis indicates that a small fraction of the interface contributes to the epitaxial growth. Although the influence of oxidation and of Si-H groups located at the interface cannot be completely excluded, this behavior is explained in terms of a high density of microvoids located at the a-c interface. This result has implications for the models of electrical conduction of nc-Si:H.
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Affiliation(s)
- P Roura
- GRMT, Department of Physics, University of Girona, Campus Montilivi, E17071-Girona, Catalonia, Spain
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15
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Dachs A, Masllorens J, Pla-Quintana A, Roglans A, Farjas J, Parella T. Structural Differences between Open-Chain and Macrocyclic Triene Ligands for Palladium(0): Influence on the Stability and Catalytical Properties. Organometallics 2008. [DOI: 10.1021/om800544h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Anna Dachs
- Department of Chemistry, Universitat de Girona, Campus de Montilivi, s/n. E-17071-Girona, Spain
| | - Judit Masllorens
- Department of Chemistry, Universitat de Girona, Campus de Montilivi, s/n. E-17071-Girona, Spain
| | - Anna Pla-Quintana
- Department of Chemistry, Universitat de Girona, Campus de Montilivi, s/n. E-17071-Girona, Spain
| | - Anna Roglans
- Department of Chemistry, Universitat de Girona, Campus de Montilivi, s/n. E-17071-Girona, Spain
| | - Jordi Farjas
- Department of Physics, Universitat de Girona, Campus de Montilivi, s/n. E-17071-Girona, Spain
| | - Teodor Parella
- Servei de RMN, Universitat Autònoma de Barcelona, Cerdanyola, E-08193-Barcelona, Spain
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17
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Rius J, Figueras M, Herrero R, Farjas J, Pi F, Orriols G. N-dimensional dynamical systems exploiting instabilities in full. Chaos 2000; 10:760-770. [PMID: 12779426 DOI: 10.1063/1.1324650] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We report experimental and numerical results showing how certain N-dimensional dynamical systems are able to exhibit complex time evolutions based on the nonlinear combination of N-1 oscillation modes. The experiments have been done with a family of thermo-optical systems of effective dynamical dimension varying from 1 to 6. The corresponding mathematical model is an N-dimensional vector field based on a scalar-valued nonlinear function of a single variable that is a linear combination of all the dynamic variables. We show how the complex evolutions appear associated with the occurrence of successive Hopf bifurcations in a saddle-node pair of fixed points up to exhaust their instability capabilities in N dimensions. For this reason the observed phenomenon is denoted as the full instability behavior of the dynamical system. The process through which the attractor responsible for the observed time evolution is formed may be rather complex and difficult to characterize. Nevertheless, the well-organized structure of the time signals suggests some generic mechanism of nonlinear mode mixing that we associate with the cluster of invariant sets emerging from the pair of fixed points and with the influence of the neighboring saddle sets on the flow nearby the attractor. The generation of invariant tori is likely during the full instability development and the global process may be considered as a generalized Landau scenario for the emergence of irregular and complex behavior through the nonlinear superposition of oscillatory motions. (c) 2000 American Institute of Physics.
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Affiliation(s)
- J. Rius
- Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Spain
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Rius J, Figueras M, Herrero R, Pi F, Farjas J, Orriols G. Full instability behavior of N-dimensional dynamical systems with a one-directional nonlinear vector field. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 2000; 62:333-48. [PMID: 11088468 DOI: 10.1103/physreve.62.333] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/1999] [Revised: 02/11/2000] [Indexed: 11/07/2022]
Abstract
We show how certain N-dimensional dynamical systems are able to exploit the full instability capabilities of their fixed points to do Hopf bifurcations and how such a behavior produces complex time evolutions based on the nonlinear combination of the oscillation modes that emerged from these bifurcations. For really different oscillation frequencies, the evolutions describe robust wave form structures, usually periodic, in which self-similarity with respect to both the time scale and system dimension is clearly appreciated. For closer frequencies, the evolution signals usually appear irregular but are still based on the repetition of complex wave form structures. The study is developed by considering vector fields with a scalar-valued nonlinear function of a single variable that is a linear combination of the N dynamical variables. In this case, the linear stability analysis can be used to design N-dimensional systems in which the fixed points of a saddle-node pair experience up to N-1 Hopf bifurcations with preselected oscillation frequencies. The secondary processes occurring in the phase region where the variety of limit cycles appear may be rather complex and difficult to characterize, but they produce the nonlinear mixing of oscillation modes with relatively generic features.
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Affiliation(s)
- J Rius
- Departament de Fisica, Universitat Autonoma de Barcelona, 08193 Bellaterra, Spain
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Méndez V, Fort J, Farjas J. Speed of wave-front solutions to hyperbolic reaction-diffusion equations. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1999; 60:5231-43. [PMID: 11970393 DOI: 10.1103/physreve.60.5231] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/1999] [Revised: 07/21/1999] [Indexed: 04/18/2023]
Abstract
The asymptotic speed problem of front solutions to hyperbolic reaction-diffusion (HRD) equations is studied in detail. We perform linear and variational analyses to obtain bounds for the speed. In contrast to what has been done in previous work, here we derive upper bounds in addition to lower ones in such a way that we can obtain improved bounds. For some functions it is possible to determine the speed without any uncertainty. This is also achieved for some systems of HRD (i.e., time-delayed Lotka-Volterra) equations that take into account the interaction among different species. An analytical analysis is performed for several systems of biological interest, and we find good agreement with the results of numerical simulations as well as with available observations for a system discussed recently.
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Affiliation(s)
- V Méndez
- Facultat de Ciències de la Salut, Universitat Internacional de Catalunya, Gomera s/n, 08190 Sant Cugat del Vallès, Barcelona, Catalonia, Spain
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Herrero R, Pons R, Farjas J, Pi F, Orriols G. Homoclinic dynamics in experimental Shil'nikov attractors. Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics 1996; 53:5627-5636. [PMID: 9964919 DOI: 10.1103/physreve.53.5627] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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