M. Fatima Montemor

Layered Ni(OH) 2 -Co(OH) 2 films prepared by electrodeposition as charge storage electrodes for hybrid supercapacitors

Consecutive layers of Ni(OH)2 and Co(OH)2 were electrodeposited on stainless steel current collectors for preparing charge storage electrodes of high specific capacity with potential application in hybrid supercapacitors. Different electrodes were prepared consisting on films of Ni(OH)2, Co(OH)2, Ni1/2Co1/2(OH)2 and layered films of Ni(OH)2 on Co(OH)2 and Co(OH)2 on Ni(OH)2 to highlight the advantages of the new architecture. The microscopy studies revealed the formation of nanosheets in the Co(OH)2 films and of particles agglomerates in the Ni(OH)2 films. Important morphological changes were observed in the double hydroxides films and layered films. Film growth by electrodeposition was governed by instantaneous nucleation mechanism. The new architecture composed of Ni(OH)2 on Co(OH)2 displayed a redox response characterized by the presence of two peaks in the cyclic voltammograms, arising from redox reactions of the metallic species present in the layered film. These electrodes revealed a specific capacity of 762 C g−1 at the specific current of 1 A g−1. The hybrid cell using Ni(OH)2 on Co(OH)2 as positive electrode and carbon nanofoam paper as negative electrode display specific energies of 101.3 W h g−1 and 37.8 W h g−1 at specific powers of 0.2 W g−1 and 2.45 W g−1, respectively.

Structural evolution, magnetic properties and electrochemical response of MnCo2O4 nanosheet films

MnCo2O4 spinel oxide nanosheets were prepared via electrodeposition and post thermal annealing on stainless steel substrates. The structural transformation of an electrodeposited hydroxide phase into a spinel phase was achieved by thermal annealing at different temperatures (250 °C, 350 °C, 450 °C and 650 °C). The surface morphology of the films revealed the presence of a nanosheet percolation network that was converted into nanoplatelets after annealing at 650 °C. The nanosheets are composed of nanocrystals and the crystal size of the MnCo2O4 spinel oxide increased from 10 nm after 250 °C annealing to 100 nm after 650 °C annealing, in which a twinning was observed. The magnetic transition temperature also increased from 101 K to 176 K for the films annealed at 250 °C and 650 °C, respectively. The spinel films displayed specific capacitance values above 400 Fg−1 at 1 Ag−1, making these spinel oxides promising pseudocapacitive materials.

Smart composite coatings for corrosion protection of aluminium alloys in aerospace applications

Abstract Several new concepts to design and fabricate self- healing materials have emerged over the last few years, all presenting advantages and disadvantages. Among these, smart coatings have been considered as extremely promising for several applications, including for corrosion protection purposes. Smart coatings show great potential in what concerns the increased lifetime of metallic structures and reduction of the corrosion-related maintenance costs. This chapter reviews existing self-healing strategies for developing new and more efficient coatings for corrosion protection of aluminium alloys used in aeronautical applications.

γ-FeOOH and amorphous Ni–Mn hydroxide on carbon nanofoam paper electrodes for hybrid supercapacitors

This work reports the preparation of γ-FeOOH and amorphous Ni–Mn hydroxide on carbon nanofoam paper (CNFP) by galvanostatic electrodeposition for application in hybrid FeOOH-CNFP∥Ni–Mn hydroxide-CNFP supercapacitors working in alkaline electrolytes. The γ-FeOOH on CNFP displayed a porous morphology composed of fluffy nanoflakes. It showed an enhanced redox response in the negative working potential range of −1.5–0 V vs. SCE with a storage capacity of 3.48 C cm−2 at 10 mA cm−2 and a response rate of 71% when the current densities increased from 10 mA cm−2 to 50 mA cm−2. The amorphous Ni–Mn hydroxide on CNFP displayed a porous morphology composed of fine nanoflakes. It showed an enhanced redox response in the positive working potential range of 0–0.5 V vs. SCE with a storage capacity of 1.54 C cm−2 at 10 mA cm−2 and a response rate of 73% when the current densities increased from 10 mA cm−2 to 50 mA cm−2. The hybrid FeOOH-CNFP∥Ni–Mn hydroxide-CNFP supercapacitor delivered a high energy density of 1515 mW h cm−2, at a power density of 9 mW cm−2 at a working voltage of 1.8 V and a long cycle life with a capacity retention of 95% after 10 000 charge–discharge cycles. Self-discharge studies revealed the main contribution of the FeOOH-CNFP electrode to the voltage drop of the supercapacitor cell. Activation-controlled processes governed the self-discharge of the FeOOH-CNFP electrode, while mixed activation-controlled and diffusion-controlled processes governed the self-discharge of the Ni–Mn hydroxide-CNFP electrode.

Ag(I) camphorimine complexes with antimicrobial activity towards clinically important bacteria and species of the Candida genus

The present work follows a previous report describing the antibacterial activity of silver camphorimine complexes of general formula [Ag(NO3)L]. The synthesis and demonstration of the antifungal and antibacterial activity of three novel [Ag(NO3)L] complexes (named 1, 2 and 3) is herein demonstrated. This work also shows for the first time that the previously studied complexes (named 4 to 8) also exert antifungal activity. The antibacterial activity of complexes was evaluated against Staphylococcus aureus, Pseudomonas aeruginosa, Burkholderia contaminans and Escherichia coli strains, while antifungal activity was tested against the Candida species C. albicans, C. glabrata, C. parapsilosis and C. tropicalis. The antimicrobial activity of the complexes ranged from very high (complex 4) to moderate (complex 6) or low (complex 8), depending on the structural and electronic characteristics of the camphorimine ligands. Notably, the highest antibacterial and anti-Candida activities do not coincide in the same complex and in some cases they were even opposite, as is the case of complex 4 which exhibits a high anti-bacterial and low antifungal activity. These distinct results suggest that the complexes may have different mechanisms against prokaryotic and eukaryotic cells. The antifungal activity of the Ag(I) camphorimine complexes (in particular of complex 1) was found to be very high (MIC = 2 μg/mL) against C. parapsilosis, being also registered a prominent activity against C. tropicalis and C. glabrata. None of the tested compounds inhibited C. albicans growth, being this attributed to the ability of these yeast cells to mediate the formation of less toxic Ag nanoparticles, as confirmed by Scanning Electron Microscopy images. The high antibacterial and anti-Candida activities of the here studied camphorimine complexes, especially of complexes 1 and 7, suggests a potential therapeutic application for these compounds.