Cerium-based conversion films developed on LiAl-layered double hydroxide coatings for corrosion protection of AA7075 aluminum alloys

The paper presents several experimental results regarding the influence of various procedures applied to incorporate Ce species in hydrotalcite–type chemical conver­sion coatings on the overall corrosion performance for AA 7075 aluminum alloy as a metallic substrate. Two routes were envisaged: (i) chemical incorporation of Ce by immersion in cerium nitrate solutions and (ii) electrochemical deposition of hydro­phobic Ce - based layer involving ethanolic solutions of stearic acid and cerium nitrate. The chemical route involving immersion in cerium nitrate solutions led to the incorpo­ration of 2.46 – 6.84 wt.% Ce in the composition of the porous conversion layer. The electrochemical process facilitated the formation of a hydrophobic cerium stearate layer on porous hydrotalcite conversion coating showing water contact angles of about 132o and a higher Ce content incorporated of 6.55 – 9.73 wt.%. The corrosion performance of the Ce-based conversion coatings is also discussed

Electrodeposition of Sn–In Alloys Involving Deep Eutectic Solvents

Tin–indium alloys represent attractive lead-free solder candidates. They show lower values of melting point than pure indium, so that they are investigated as materials with significant applications potential in the electronic industry. Electrodeposition is a very convenient route to prepare Sn–In alloys. The paper presents several experimental results regarding the electrodeposition of Sn–In alloy coatings involving deep eutectic solvents (DESs), namely using choline chloride-ethylene glycol eutectic mixtures. The influence of the main operating parameters on the Sn–In alloy composition and characteristics are presented. Adherent and uniform Sn–In alloy deposits containing 10–65 wt % In have been obtained on Cu substrates. The In content was found to increase as both the In:Sn molar concentration ratio of ionic species in the electrolyte and the applied temperature increased. The use of pulsed current allowed the use of higher current densities leading to slightly higher values of In content in the alloy deposit. X-ray diffraction (XRD) analysis revealed the presence of InSn4 and In3Sn phases in agreement with the phase diagram. According to thermogravimetric analysis (TGA) measurements, values of melting points in the range of 118.6 and 127.5 °C were obtained depending on the alloy composition. The solder joints’ behavior and alloy coatings corrosion performance were also discussed

Synthesis and characterization of silver-titania nanocomposites prepared by electrochemical method with enhanced photocatalytic characteristics, antifungal and antimicrobial activity

The paper deals with the synthesis of silver-titania (Ag-TiO2) nanocomposites with enhanced photocatalytic, antifungal and antimicrobial characteristics. Ag nanoparticles have been electrochemically deposited on the commercially available nano-TiO2 powders involving the so-called “sacrificial anode” technique. The obtained nanocomposites were characterized by X-ray diffraction, XPS and Raman spectroscopy to get information on their composition and structure. Particle size distribution and stability of Ag-TiO2 based colloidal solutions have been determined from dynamic light scattering and zeta potential measurements. The recorded UV–vis diffuse reflectance spectra evidenced the presence of an absorption band located in the range of 475–525 nm and the presence of a tail as well, suggesting a better photocatalytic activity. The photoreactivity of the synthesized Ag-TiO2 nanocomposite as well as the influence of Ag content were evaluated for the degradation of Orange II dye under UV irradiation (λ = 365 nm). The heterogeneous photocatalytic degradation rate follows pseudo first order kinetics. Antifungal and antimicrobial efficacy evaluation showed that the synthesized Ag-TiO2 nanocomposites are significantly more active than pure titania. Keywords: Silver-titania nanocomposites, Electrochemical synthesis, Microstructure characterization, Photocatalyst, Antifunga

The Influence of Reflowing Process on Electrodeposited Sn-Cu-Ni Lead-Free Solder Alloy

Sn-Cu-Ni lead-free solder alloy electrodeposited on copper substrate from a deep eutectic solvent (DES)-based electrolyte under direct current (DC) and pulsed current (PC) was subjected to a reflowing process at the industrial company MIBATRON S.R.L. (Otopeni, Romania). The alteration of the alloy’s composition and anti-corrosive properties upon exposure to the reflow process were investigated via Scanning Electron Microscopy (SEM-EDX), X-ray diffraction (XRD), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Corrosion studies conducted in sodium chloride solution revealed that the system obtained under the DC plating mode (Sn-Cu-Ni-DC) exhibited enhanced anti-corrosive properties compared to the system obtained under PC (Sn-Cu-Ni-PC) after reflowing. However, prior to reflowing, the opposite effect was observed, with Sn-Cu-Ni-PC showing improved anti-corrosive properties. These changes in anti-corrosive behavior were attributed to the modification of the alloy’s composition during the reflowing process

Characterization of Carbon Nanomaterials Dispersions: Can Metal Decoration of MWCNTs Improve Their Physicochemical Properties?

A suitable dispersion of carbon materials (e.g., carbon nanotubes (CNTs)) in an appropriate dispersant media, is a prerequisite for many technological applications (e.g., additive purposes, functionalization, mechanical reinforced materials for electrolytes and electrodes for energy storage applications, etc.). Deep eutectic solvents (DES) have been considered as a promising “green” alternative, providing a versatile replacement to volatile organic solvents due to their unique physical-chemical properties, being recognized as low-volatility fluids with great dispersant ability. The present work aims to contribute to appraise the effect of the presence of MWCNTs and Ag-functionalized MWCNTs on the physicochemical properties (viscosity, density, conductivity, surface tension and refractive index) of glyceline (choline chloride and glycerol, 1:2), a Type III DES. To benefit from possible synergetic effects, AgMWCNTs were prepared through pulse reverse electrodeposition of Ag nanoparticles into MWCNTs. Pristine MWCNTs were used as reference material and water as reference dispersant media for comparison purposes. The effect of temperature (20 to 60 °C) and concentration on the physicochemical properties of the carbon dispersions (0.2–1.0 mg cm−3) were assessed. In all assessed physicochemical properties, AgMWCNTs outperformed pristine MWCNTs dispersions. A paradoxical effect was found in the viscosity trend in glyceline media, in which a marked decrease in the viscosity was found for the MWCNTs and AgMWCNTs materials at lower temperatures. All physicochemical parameters were statistically analyzed using a two-way analysis of variance (ANOVA), at a 5% level of significance

Dispersion Stability of MWCNTs Decorated with Ag Nanoparticles through Pulse-Reversed Current Electrodeposition Using a Deep Eutectic Solvent

Carbon nanotubes (CNTs) represent a unique class of nanomaterials with remarkable properties with a wide variety of applications in diverse scientific and technical domains. However, one of the many challenges still requiring improvement is undoubtedly their dispersion stability. The control of the dispersion stability of CNTs is a challenge due to the strong van der Waals forces that lead to their aggregation. Metallic nanoparticles (NPs), such as silver (AgNPs), in the presence of a capping agent, e.g., poly(N-vinyl pyrrolidone) (PVP 10), are recognized as having a key role in the increase of the stability of NP dispersions, and if incorporated in multi-walled CNTs (MWCNTs), may help surpass the MWCNTs’ aggregation problem. The present work reports the enhancement of the stability of MWCNTs upon decoration by AgNPs, using an electrochemical method to generate the silver ions and promote the electrodeposition of silver. To validate the increase in stability of the Ag-decorated MWCNTs, two solvents were used, water and glyceline, a eutectic mixture of choline chloride and glycerol. The time stability of bare MWCNT and AgMWCNT nanofluids was characterized through dynamic light scattering (DLS) and ultraviolet–visible (UV–Vis) spectrophotometry. Compared to commercial MWCNTs, MWCNTs decorated with AgNPs presented a significant stability enhancement, in both water and glyceline. Glyceline also presented higher stability over time, with a retention of UV–Vis absorbance up to 97%, compared to 50% for water media. The DLS and turbidity experiments showed the same trend of MWCNTs’ stability in water and glyceline. In both cases, the use of AgMWCNT materials improved the stability of the dispersions 25× in glyceline and 2.5× in water, when compared to the stability of bare MWCNT dispersions

Renewable Carbon Materials as Electrodes for High-Performance Supercapacitors: From Marine Biowaste to High Specific Surface Area Porous Biocarbons

17 pages, 11 figures, 3 tables.-- Open accessWaste, in particular, biowaste, can be a valuable source of novel carbon materials. Renewable carbon materials, such as biomass-derived carbons, have gained significant attention recently as potential electrode materials for various electrochemical devices, including batteries and supercapacitors. The importance of renewable carbon materials as electrodes can be attributed to their sustainability, low cost, high purity, high surface area, and tailored properties. Fish waste recovered from the fish processing industry can be used for energy applications and prioritizing the circular economy principles. Herein, a method is proposed to prepare a high surface area biocarbon from glycogen extracted from mussel cooking wastewater. The biocarbon materials were characterized using a Brunauer–Emmett–Teller surface area analyzer to determine the specific surface area and pore size and by scanning electron microscopy coupled with energy-dispersive X-ray analysis, Raman analysis, attenuated total reflectance Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The electrochemical characterization was performed using a three-electrode system, utilizing a choline chloride-based deep eutectic solvent (DES) as an eco-friendly and sustainable electrolyte. Optimal time and temperature allowed the preparation of glycogen-based carbon materials, with a specific surface area of 1526 m2 g–1, a pore volume of 0.38 cm3 g–1, and an associated specific capacitance of 657 F g–1 at a current density of 1 A g–1, at 30 °C. The optimal material was scaled up to a two-electrode supercapacitor using a DES-based solid-state electrolyte (SSE@DES). This prototype delivered a maximum capacitance of 703 F g–1 at a 1 A g–1 of current density, showing 75% capacitance retention over 1000 cycles, delivering the highest energy density of 0.335 W h kg–1 and power density of 1341 W kg–1. Marine waste can be a sustainable source for producing nanoporous carbon materials to be incorporated as electrode materials in energy storage devicesThis work was financially supported by the FCT under Research Grants UIDB/00081/2020–CIQUP, LA/P/0056/2020 (IMS), and H2Innovate NORTE-01-0145-FEDER-000076. This work was supported by the Romanian Ministry of Research, Innovation and Digitalization, Romania, under JINR-RO Project no. 91 Code Theme 04–4–1133–2018/2023, grant no. 37/2021, and ECSEL-H2020 projects: PIn3S Contract no. 10/1.1.3H/03.04.2020 Code MySMIS 135127 and BEYOND5 Contract no. 12/1.1.3H/31.07.2020 Code MySMIS 136877. J.A.V. and J.V. thank Xunta de Galicia (Grupos de Potential Crecimiento, IN607B 2021/11) for financial support . A.T.S.C.B. thanks the scholarship awarded by FCT with reference No. 2021.04783.BD and the Schwäbisch Gmünd Scientific Exchange Grant awarded by the European Academy of Surface Technology. R.C. thanks FCT for funding through the program DL 57/2016–Norma transitória (SFRH/BPD/89752/2012)Peer reviewe

From Marine Wastes to Carbon Materials: Optimization of Parameters Enhancing Energy Storage Performance

74th Annual Meeting of the International Society of Electrochemistry, Bridging Scientific Disciplines to Address the World’s Challenges, 3 to 8 September 2023, Lyon, FranceN