1,720,979 research outputs found
Methods and Instruments | Transmission Electron Microscopy
No full textTransmission Electron Microscope (TEM) and related techniques, such as High-Resolution Transmission Electron Microscopy (HRTEM), Scanning Transmission Electron Microscopy (STEM), principles and applications in the field of electrochemical power sources are briefly described. Instrumentation and operation are introduced together with the basis of electron scattering phenomena that generate contrast both in the real (imaging mode) and reciprocal space (diffraction mode). Applications of TEM to the study of materials in electrochemical devices are discussed demonstrating the capability of this technique in the characterization of electrochemically active materials down to the atomic scale, also by the mean of innovative methods such as operando- and cryo-STEM
Methods and Instruments | Scanning Electronic Microscopy
No full textScanning Electron Microscopy (SEM) principles are introduced and some applications to the characterization of electrochemical power sources are presented. The general features of a SEM microscope are briefly described with particular attention to: (i) generation and focusing of the electron beam over the samples; (ii) interactions between electrons and atoms in the sample producing the analytical signals; (iii) detection and recording of secondary or backscattered electrons for image reconstruction; (iv) detector of X-rays and electron probe microanalysis. Some applications of the technique in the field of electrochemical storage devices are summarized, with the aim of shedding light onto the relationships between morphology/composition and electrochemical behavior of electrodes. Finally, an outlook on recent methodologies is given,
such as environmental SEM which, operating under moderate pressures, allows in situ monitoring of chemical and morphological transformations related to electrochemical power sources
An extensive model for renewable energy electrochemical storage with Solid Oxide Cells based on a comprehensive analysis of impedance deconvolution
No full textSolid Oxide Cells are potentially one of the most efficient energy conversion systems, yet unfavourable operating conditions may cause a performance drop. These electrochemical devices can be operated in reversible mode (fuel cell /electrolysers); therefore, they are suitable in chemical storage applications. However, reversible operation and inversion cycles further jeopardise performance stability. Advanced processing of experimental data such as Distribution of Relaxation Times (DRT) on Electrochemical Impedance Spectroscopy (EIS) mea- surements is a powerful tool to investigate physicochemical processes occurring in Solid Oxide Cells and to analyse ageing mechanisms.
This paper presents a method to identify the main processes behind polarisation losses in order to build an equivalent circuit model (ECM) suitable for real-time diagnosis based on EIS. The fuel cell operation is chosen as a reference for degradation detection and diagnosis. A comprehensive experimental campaign was executed on a commercial cell operated in fuel cell mode in a laboratory test apparatus by systematically varying operating temperature, current density, fuel flow and its composition. DRT deconvolution highlights five main processes, namely: oxygen transport and charge transfer in the anode, anodic diffusion, charge transfer at the cathode and cathodic diffusion. Therefore, the proposed ECM for the cell can be schematised as LR0(Ra1Qa1)(Ra2Qa2)WFLWaG (Rc1Qc1). Beyond determining the model, a complete look-up table for the circuital elements is built thanks to EIS measurements fit. This is a rich database for solid oxide fuel cell electrochemical performance simulation, and it allows the future implementation of the model in a useful diagnostic tool, even in the broader case of reversible operation in energy storage systems
Characteristics and performance of old plasters from the 16° to the beginning of the 19° century.
No full textAn extensive model for renewable energy electrochemical storage with Solid Oxide Cells based on a comprehensive analysis of impedance deconvolution
No full textSolid Oxide Cells are potentially one of the most efficient energy conversion systems, yet unfavourable operating conditions may cause a performance drop. These electrochemical devices can be operated in reversible mode (fuel cell /electrolysers); therefore, they are suitable in chemical storage applications. However, reversible operation and inversion cycles further jeopardise performance stability. Advanced processing of experimental data such as Distribution of Relaxation Times (DRT) on Electrochemical Impedance Spectroscopy (EIS) measurements is a powerful tool to investigate physicochemical processes occurring in Solid Oxide Cells and to analyse ageing mechanisms. This paper presents a method to identify the main processes behind polarisation losses in order to build an equivalent circuit model (ECM) suitable for real-time diagnosis based on EIS. The fuel cell operation is chosen as a reference for degradation detection and diagnosis. A comprehensive experimental campaign was executed on a commercial cell operated in fuel cell mode in a laboratory test apparatus by systematically varying operating temperature, current density, fuel flow and its composition. DRT deconvolution highlights five main processes, namely: oxygen transport and charge transfer in the anode, anodic diffusion, charge transfer at the cathode and cathodic diffusion. Therefore, the proposed ECM for the cell can be schematised as LR0(Ra1Qa1)(Ra2Qa2)WFLWaG(Rc1Qc1). Beyond determining the model, a complete look-up table for the circuital elements is built thanks to EIS measurements fit. This is a rich database for solid oxide fuel cell electrochemical performance simulation, and it allows the future implementation of the model in a useful diagnostic tool, even in the broader case of reversible operation in energy storage systems
Evaluation of Silicon-Rich Anodes for Low-Temperature Applications
No full textSilicon-rich anodes were investigated as promising alternatives to graphite for lithium-ion batteries operating at sub-zero temperatures. Micro-sized silicon particles were employed with a capacity-limitation strategy (1000 mAh g−1) to mitigate mechanical stress and volume expansion during cycling. Electrochemical performance was assessed in three-electrode half-cells and bi-layer pouch full-cells (Si - NMC811) at temperatures ranging from 25 °C down to −25 °C. Despite the increased polarization and hysteresis observed in the galvanostatic charge/discharge profiles at low temperatures, micro-Si anodes retained a reversible lithiation/delithiation behaviour and high coulombic efficiency. Full-cell response was mainly affected by the NMC cathode, while the Si anode exhibited good capacity retention. These results demonstrate that capacity-limited micro-silicon anodes enable stable and efficient operation under cold conditions, providing a scalable, safe, and cost-effective route toward next-generation lithium-ion batteries and reducing reliance on graphite now listed as a critical raw material in the E
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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