M. Montemor | Instituto Superior Técnico (original) (raw)

Papers by M. Montemor

ECS Meeting Abstracts, 2011

not Available.

Journal of Materials Chemistry A, 2018

High energy density, rate performance and long cycle life hybrid γ-FeOOH-carbon nanofoam paper∥am... more High energy density, rate performance and long cycle life hybrid γ-FeOOH-carbon nanofoam paper∥amorphous Ni–Mn hydroxide-carbon nanofoam paper supercapacitors.

Surface and Interface Analysis, 2017

Electrochimica Acta, 2015

Mg alloys are very susceptible to corrosion in physiological media. This behaviour limits its wid... more Mg alloys are very susceptible to corrosion in physiological media. This behaviour limits its widespread use in biomedical applications as bioresorbable implants, but it can be controlled by applying protective coatings. On one hand, coatings must delay and control the degradation process of the bare alloy and, on the other hand, they must be functional and biocompatible. In this study a biocompatible polycaprolactone (PCL) coating was functionalised with nano hydroxyapatite (HA) particles for enhanced biocompatibility and with an antibiotic, cephalexin, for anti-bacterial purposes and applied on the AZ31 alloy. The chemical composition and the surface morphology of the coated samples, before and after the corrosion tests, were studied by scanning electron microscopy (SEM) coupled with energy dispersive x-ray analysis (EDX) and Raman. The results showed that the presence of additives induced the formation of agglomerates and defects in the coating that resulted in the formation of pores during immersion in Hanks' solution. The corrosion resistance of the coated samples was studied in Hank's solution by electrochemical impedance spectroscopy (EIS). The results evidenced that all the coatings can provide corrosion protection of the bare alloy. However, in the presence of the additives, corrosion protection decreased. The wetting behaviour of the coating was evaluated by the static contact angle method and it was found that the presence of both hydroxyapatite and cephalexin increased the hydrophilic behaviour of the surface. The results showed that it is possible to tailor a composite coating that can store an antibiotic and nano hydroxyapatite particles, while allowing to control the in-vitro corrosion degradation of the bioresorbable Mg alloy AZ31.

Applied Surface Science, 2015

This work reports the one-step fabrication of a novel coating on ultra high purity magnesium usin... more This work reports the one-step fabrication of a novel coating on ultra high purity magnesium using a parallel nano assembling process. The multifunctional biodegradable surface was obtained by adding hydroxyapatite nanoparticles (HapNP) plus graphene oxide (GO). The coating was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), micro-Raman spectroscopy. The thin phosphate coating (thickness of 1 m) reveals a uniform coverage with cypress like structures. The incorporation of HapNP and GO promotes the hydrophilic behavior of the coating surface. The results revealed that the proposed coating can be used to tailor the surface properties such as wettability by adjusting the contents of HapNP and GO. The in vitro degradation rate of the coated magnesium suggests that the presence of HapNP and GO/HapNP in the phosphate coating decreased the current density compared to the single phosphate coating and uncoated magnesium. This study also reveals the HapNP/GO/phosphate coating induces apatite formation, showing suitable degradability that makes it a promising coating candidate for enhanced bone regeneration.

Este trabalho teve como objetivo o estudo de armaduras de cilindros de betão armado confinados co... more Este trabalho teve como objetivo o estudo de armaduras de cilindros de betão armado confinados com duas camadas de polímeros reforçados com fibras de vidro (GFRP). Provetes cilíndricos de betão armado com e sem GFRP foram imersos em solução de cloreto de sódio. O estado das armaduras foi avaliado por medições de potencial de circuito aberto e por impedância eletroquímica com sistemas a dois e três eletrodos. Os resultados demostraram que o confinamento de duas camadas de GFRP apresenta baixa permeabilidade e atua como barreira física à penetração de solução. Verificou-se que imperfeições na fase de aplicação do GFRP e sua degradação são de grande importância na eficiência da prevenção de corrosão.

Nanoscale, 2015

This work reports the fabrication, by electrodeposition and post-thermal annealing, of hybrid ele... more This work reports the fabrication, by electrodeposition and post-thermal annealing, of hybrid electrodes for high rate electrochemical energy storage composed of nickel manganese oxide (Ni0.86Mn0.14O) nanosheets over 3D open porous dendritic NiCu foams. The hybrid electrodes are made of two different percolation networks of nanosheets and dendrites, and exhibit a specific capacitance value of 848 F g(-1) at 1 A g(-1). The electrochemical tests revealed that the electrodes display an excellent rate capability, characterized by capacitance retention of approximately 83% when the applied current density increases from 1 A g(-1) to 20 A g(-1). The electrodes also evidenced high charge-discharge cycling stability, which attained 103% after 1000 cycles.

Journal of Electroanalytical Chemistry, 2015

Copper-iron (Cu-Fe) 3D porous foams for supercapacitor electrodes were electrodeposited in the ca... more Copper-iron (Cu-Fe) 3D porous foams for supercapacitor electrodes were electrodeposited in the cathodic regime, on stainless steel current collectors, using hydrogen bubbling dynamic template. The foams were prepared at different current densities and deposition times. The foams were submitted to thermal conditioning at temperatures of 150 and 250 °C. The morphology, composition and structure of the formed films were studied by SEM, EDS and XRD, respectively. The electrochemical behaviour was studied by cyclic voltammetry, electrochemical impedance spectroscopy and chronopotentiometry. The morphology of the 3D Cu-Fe foams is sensitive to the electrodeposition current and time. The increase of the current density produces a denser, larger and more ramified dendritic structure. Thermal conditioning at high temperature induces a coarser grain structure and the formation of copper oxides, which affect the electrochemical behaviour. The electrochemical response reveals the presence of various redox peaks assigned to the oxidation and reduction of Cu and Fe oxides and hydroxides in the foams. The specific capacitance of the 3D Cu-Fe foams was significantly enhanced by thermal conditioning at 150 °C. The highest specific capacitance values attained 297 Fg-1 which are much above the ones typically observed for single Cu or Fe oxides and hydroxides. These values highlight a synergistic behaviour resulting from the combination of Cu and Fe in the form of nanostructured metallic foams. Moreover, the capacitance

Materials Science Forum, 1995

Page 1. Materials Science Forum Vols. 192-194 (1995) pp 867-876 © (1995) Trans Tech Publications,... more Page 1. Materials Science Forum Vols. 192-194 (1995) pp 867-876 © (1995) Trans Tech Publications, Switzerland doi: 10.4028/www. scientific. net/MSF. 192-194.86 7 Carbonation of Flyash-Containing Concrete: Electrochemical ...

Progress in Organic Coatings, 2004

The present work aims at correlating the evolution of the analytical composition of bis-1,2-(trie... more The present work aims at correlating the evolution of the analytical composition of bis-1,2-(triethoxysilyl)ethane films formed on hot dip galvanised steel substrate during immersion in NaCl solution with the corrosion performance of the pre-treated substrates. The electrochemical tests were carried out by electrochemical impedance spectroscopy and the analytical characterisation was performed by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and infrared spectroscopy (FT-IR). The electrochemical results show that the functional silane provides temporary corrosion protection for hot dip galvanised steel during immersion in NaCl-containing solutions. The analytical results show that the chemical composition of the silane film changes during immersion in the aggressive solution. During the first days of immersion these changes improve the corrosion resistance of the pre-treated substrate.

Materials Science Forum, 1998

Page 1. Materials Science Forum Vols. 289-292 (1998) pp 1139-1150 © (1998) Trans Tech Publication... more Page 1. Materials Science Forum Vols. 289-292 (1998) pp 1139-1150 © (1998) Trans Tech Publications, Switzerland doi: 10.4028/www. scientific. net/MSF. 289-292.1139 Effect of Mo on the Composition and Electronic Properties ...

Materials science & engineering. C, Materials for biological applications, 2015

In this work a biofunctional composite coating architecture for controlled corrosion activity and... more In this work a biofunctional composite coating architecture for controlled corrosion activity and enhanced cellular adhesion of AZ31 Mg alloys is proposed. The composite coating consists of a polycaprolactone (PCL) matrix modified with nanohydroxyapatite (HA) applied over a nanometric layer of polyetherimide (PEI). The protective properties of the coating were studied by electrochemical impedance spectroscopy (EIS), a non-disturbing technique, and the coating morphology was investigated by field emission scanning electron microscopy (FE-SEM). The results show that the composite coating protects the AZ31 substrate. The barrier properties of the coating can be optimized by changing the PCL concentration. The presence of nanohydroxyapatite particles influences the coating morphology and decreases the corrosion resistance. The biocompatibility was assessed by studying the response of osteoblastic cells on coated samples through resazurin assay, confocal laser scanning microscopy (CLSM) ...

Progress in Organic Coatings, 2002

The corrosion performance and the composition of galvanised steel treated by immersion in nitrate... more The corrosion performance and the composition of galvanised steel treated by immersion in nitrate solutions of rare-earth metals (cerium, yttrium and lanthanum) were evaluated by electrochemical techniques and surface analysis. The surface film consists of a mixture of rare-earth oxides/hydroxides, which hinders the corrosion reactions of the substrate by reducing the rate of both the cathodic and the anodic reactions.

Progress in Organic Coatings, 2005

... The results show that the pre-treatments based on silanes provide good corrosion protection b... more ... The results show that the pre-treatments based on silanes provide good corrosion protection both on painted and ... Table 1. Classification of adhesion tests results [20 ... AA2024-T3, and AA2024-T3 pre-treated with chromate and AA2024-T3 pre-treated with the silanes under study. ...

Electrochimica Acta, 2011

In this work, the corrosion behaviour of magnesium alloys ZK31, EZ33 and WE54 was studied in sodi... more In this work, the corrosion behaviour of magnesium alloys ZK31, EZ33 and WE54 was studied in sodium borate buffer solution at pH 9.2. The electrochemical processes were studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The composition and morphology of the alloys and corrosion products formed were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The experimental findings highlighted the differences in the corrosion mechanisms of the different alloys tested. The results showed that the presence of rare-earth elements (RE) only increases the corrosion resistance when present in solid solution, as is the case of the WE54 alloy. At pH 9.2, an amorphous yttrium oxide/hydroxide thick film was formed, which possesses greater stability when compared to magnesium oxide/hydroxide. The role of RE in the corrosion mechanism was discussed.

Electrochimica Acta, 2010

The passive behavior of magnesium alloys ZK31, EZ33 and WE54 was studied in alkaline media (NaOH-... more The passive behavior of magnesium alloys ZK31, EZ33 and WE54 was studied in alkaline media (NaOH-pH 13) in the presence and absence of chloride ions. The electrochemical properties were investigated by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and capacitance measurements. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed for the study of the chemical composition and surface morphology of the surface films, respectively. The electrochemical impedance results revealed that the film formed on the surface of the three alloys is characterized by an increasing resistance, which stabilized with time. In the absence of chloride the film resistance was identical for all the three alloys. However, in the presence of chloride, the resistance of the film formed on the EZ33 alloy dropped nearly one order of magnitude comparatively to the other alloys. Generally, in the presence of chloride there was a decrease of the conductive character of the film. The films are homogeneous and, according to the XPS results, the outer layer seemed mainly composed of Mg(OH) 2 and the internal layer composed of MgO, independently of the presence of chloride. The AFM study revealed that the presence of chloride affected film morphology, namely nano-crystallites dimensions and aggregates size that increased.

Electrochimica Acta, 2007

The inhibiting effect of several organic compounds on the corrosion of 2024 aluminium alloy in ne... more The inhibiting effect of several organic compounds on the corrosion of 2024 aluminium alloy in neutral chloride solution was investigated in the present work. The candidates were selected based on the assumption that effective inhibitors should form highly insoluble complexes with components of AA2024. Along with organic complexing agents, the salts of rare-earth elements were included into screening electrochemical impedance spectroscopy (EIS) test for getting comparative data. Results of EIS analysis revealed three most effective organic inhibitors: salicylaldoxime, 8-hydroxyquinoline and quinaldic acid. Their anti-corrosion performance was additionally investigated via dc polarization, as well as localized techniques: scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy coupled with scanning Kelvin probe (SKPFM). Localized measurements at exactly the same microdimensional zones of the alloy before and after immersion into 0.05 M sodium chloride solution allowed tracing the evolution of the Volta potential, chemical composition, surface topography and formation of corrosion products on the surface and intermetallic inclusions during the corrosion tests. The results show that the quinaldic acid, salicylaldoxime and 8-hydroxyquinoline provide anti-corrosion protection for AA2024 forming a thin organic layer of insoluble complexes on the surface of the alloy. Inhibiting action is the consequence of suppression of dissolution of Mg, Al and Cu from the corrosion active intermetallic zones.

Electrochemistry Communications, 2005

... References. [1] JH Osborne, Prog. Org. Coat. 41 (2001), p. 280. ... 33 (1998), p. 91. Article... more ... References. [1] JH Osborne, Prog. Org. Coat. 41 (2001), p. 280. ... 33 (1998), p. 91. Article | PDF (144 K) | View Record in Scopus | Cited By in Scopus (135). [3] JH Osborne, KY Blohowiak, SR Taylor, C. Hunter, G. Bierwagon, B. Carlson, D. Bernard and MS Donley, Prog. Org. Coat. ...