ISEL - Engenharia Mecânica
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Browsing ISEL - Engenharia Mecânica by Author "Adan-Mas, Alberto"
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- From bench-scale to prototype: case study on a nickel hydroxide—activated carbon hybrid energy storage devicePublication . Adan-Mas, Alberto; Arévalo-Cid, Pablo; Moura E Silva, Teresa; Crespo, João; MONTEMOR, MARIAHybrid capacitors have been developed to bridge the gap between batteries and ultracapacitors. These devices combine a capacitive electrode and a battery-like material to achieve high energy-density high power-density devices with good cycling stability. In the quest of improved electrochemical responses, several hybrid devices have been proposed. However, they are usually limited to bench-scale prototypes that would likely face severe challenges during a scaling up process. The present case study reports the production of a hybrid prototype consisting of commercial activated carbon and nickel-cobalt hydroxide, obtained by chemical co-precipitation, separated by means of polyolefin-based paper. Developed to power a 12 W LED light, these materials were assembled and characterized in a coin-cell configuration and stacked to increase device voltage. All the processes have been adapted and constrained to scalable conditions to ensure reliable production of a pre-commercial device. Important challenges and limitations of this process, from geometrical constraints to increased resistance, are reported alongside their impact and optimization on the final performance, stability, and metrics of the assembled prototype.
- Nickel-cobalt oxide modified with reduced graphene oxide: Performance and degradation for energy storage applicationsPublication . Adan-Mas, Alberto; Moura E Silva, Teresa; Guerlou-Demourgues, Liliane; Bourgeois, L.; MONTEMOR, FATIMANickel-cobalt oxide is synthesized in combination with electrochemically reduced graphene oxide (Er-GO) by one-step electrodeposition on stainless steel followed by thermal treatment. The presence of reduced graphene oxide leads to enhanced electrochemical response, with a capacity increase from 113 mA h g(-1) to 180 mA h g(-1), and to increased faradaic efficiency and rate capability. Compared to Ni-Co oxide, the addition of reduced graphene oxide increases capacity retention from 58% to 83% after 5000 cycles. The material fade during cycling is studied by means of electrochemical impedance spectroscopy, electron diffraction spectroscopy and scanning electron microscopy. As a result, different degradation mechanisms are identified as source of the capacity decay, such as microstructural cracking, phase transformation and parasitic reactions.
- On the growth and mechanical properties of nanostructured cobalt foams by dynamic hydrogen bubble template electrodepositionPublication . Arévalo-Cid, Pablo; Adan-Mas, Alberto; Moura E Silva, Teresa; Rodrigues, José Alberto; Maçôas, Ermelinda Maria Sengo; Vaz; Montemor, M.F.The growth mechanism of nanostructured cobalt foams prepared by hydrogen bubble template electrodeposition has been studied. To that end, cobalt foams have been synthesized under different electrodeposition times and studied with various characterization techniques, namely scanning electron microscopy (SEM) and confocal microscopy in reflection mode. In addition, the mechanical properties of the resulting foams have been tested by bending and tensile tests. To study the influence of chemical additives in the growth mechanism and final properties of the foams, agar-agar has been added to the electrolytic bath during foam preparation. Results evidence that the addition of agar has successfully modified the microstructure of the final foams, creating a denser porous structure with smaller pore area and reduced growth rate that translates into better mechanical properties. By studying the evolution of the microstructure under different deposition conditions, a growth model of cobalt metallic foams by dynamic hydrogen bubble template is proposed. This easy and scalable route paves the way to produce tailored foams for numerous applications that include, for instance, energy storage and energy conversion.