Publications

Electrochemically deposited Ni coatings are widely used in the aviation, automotive, telecommunication and electronic industry because of their unique mechanical, protective and decorative properties. These films are commonly deposited from aqueous electrolytes due to the simplicity and cost-effectiveness of the processes. However, the use of water-based baths is related to several issues, i.e. water reduction and hydrogen gas formation that lead to the formation of pores and cracks which result into more brittle coatings. A promising alternative to avoid these problems is to use non-aqueous electrolytes such as Deep Eutectic Solvents (DESs). The feasibility of electroplating Ni and its alloys from choline chloride based DESs has been reported by several research groups [1–3]. In this context, recent studies have been focusing on the use of water as an additive. In most of the cases, just a small addition of water to those non-aqueous electrolytes is beneficial due to a decrease of viscosity and an increase of conductivity [3,4]. However, the electrocatalytic reduction of water during electrodeposition from DESs has also been shown to result into complex chemical and electrochemical processes that have a strong influence in the structure and morphology of the electrodeposited metallic phase [5]. Moreover, industrial electroplating processes are always carried out under forced convection to increase process efficiency and reduce deposition time. The interplay between electrodeposition kinetics and the mass transport of reactants and byproducts of the Ni electrodeposition from DESs has not been evaluated in detail yet. Similarly, the influence of applied potential on the structure and morphology of Ni coatings electrodeposited from DESs, as well as the effect on the electrochemical reduction processes are so far not fully understood. In this presentation, we report on the inter-related effects of water content, applied potential and forced convection in Ni electrodeposition on steel from 1 choline chloride (ChCl): 2 urea (U) DESs. Electrochemical methods such as cyclic voltammetry (CV) and chronoamperommetry (CA) were combined with surface analysis techniques (field emission scanning microscope (FE-SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy) in order to understand the occurring phenomena under both stagnant and forced convection conditions. The influence of mass transport on Ni electrodeposition process was studied by linear sweep voltammetry in combination with a rotating disk electrode (LSV-RDE). The obtained results allowed a better understanding of the complex chemical and electrochemical processes occurring at the electrode surface depending on the mass transport conditions, applied potential and water content, which may result into the formation of NiO-OH and incorporation of DES decomposition by-products in the growing films. [1] A.P. Abbott, A. Ballantyne, R.C. Harris, J.A. Juma, K.S. Ryder, G. Forrest, "A Comparative Study of Nickel Electrodeposition Using Deep Eutectic Solvents and Aqueous Solutions", Electrochim. Acta. 176 (2015) 718–726. [2] L. Anicai, A. Florea, T. Visan, "Studies Regarding the Nickel Electrodeposition from Choline Chloride Based Ionic Liquids", Appl. Ion. Liq. Sci. Technol. (2011) 261–286. [3] V.S. Protsenko, A.A. Kityk, D.A. Shaiderov, F.I. Danilov, "Effect of water content on physicochemical properties and electrochemical behavior of ionic liquids containing choline chloride, ethylene glycol and hydrated nickel chloride", J. Mol. Liq. 212 (2015) 716–722. [4] C. Du, B. Zhao, X.-B. Chen, N. Birbilis, H. Yang, "Effect of water presence on choline chloride-2urea ionic liquid and coating platings from the hydrated ionic liquid", Sci. Rep. 6 (2016) 29225. [5] E.A. Mernissi Cherigui, K. Sentosun, P. Bouckenooge, H. Vanrompay, S. Bals, H. Terryn, J. Ustarroz, "Comprehensive Study of the Electrodeposition of Nickel Nanostructures from Deep Eutectic Solvents: Self-Limiting Growth by Electrolysis of Residual Water", J. Phys. Chem. C. 121 (2017) 9337–9347.

The impact of the presence of TiO2 and SiO2 nanoparticles on the properties of fluorocarbon films synthesized by atmospheric pressure plasma in argon and helium is investigated in this study. The hydrophobicity, chemical composition and roughness of the films are analyzed by Water Contact Angle (WCA), X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and profilometry. As expected, a significant impact of the nanoparticles on the roughness and therefore on the hydrophobicity of the films is observed and so regardless their nature. However, we show that the impact of the nanoparticles is different whether He or Ar are use as plasmagen gas, as He doesn't induce a significant intrinsic roughness, whereas Ar does. We show that the presence of SiO2 nanoparticles underneath the deposited film has no influence on the chemical composition of the films whatever the deposition time, the plasma power and the carrier gas (helium or argon) are. On the contrary, the presence of TiO2 nanoparticles leads to the degradation of the coatings over time. The influence of the plasma power of the discharge and the deposition time is also discussed. Finally, superhydrophobic coatings are synthesized by increasing the concentration of nanoparticles underneath the deposited films.

No abstract is provided for this article.

The current paper considers the interdependency between the current density, the anodic overpotential and the temperature during the porous anodizing of aluminium in a sulphuric acid electrolyte. In contrast to common anodizing experiments, a sequence of increasing current densities is applied to each electrode. As demonstrated, this anodizing approach allows evaluating stationary anodic potentials up to very high current densities without being confronted with anomalous oxide growth. Additionally, anodizing is performed at controlled electrolyte and electrode temperature. Due to its large influence on the electrochemical behaviour, the control of the electrode temperature is important when studying the temperature dependency of the process. Based on the experimental evolutions a macroscopic model is presented, describing the relation between the considered general process parameters. It is demonstrated that a relatively simple expression is capable of well describing the experimental data in the extensive range of temperatures and current densities.

In this paper, different macroscopic electrochemical techniques are applied to study the corrosion inhibitor efficiency, protection mechanism and stability of a calcium aluminum polyphosphate silicate hydrate inhibitor on hot-dip galvanized steel in the time-domain. Potentiodynamic polarization (PP) measurements are applied to study the anodic and cathodic mechanistic behavior as well as inhibitor efficiencies at discrete and single times of exposure. Open circuit potential (OCP) with superimposed linear polarization resistance (LPR) measurements are applied as a faster, non-invasive alternative to PP, characterizing the overall performance of the system in terms of the polarization resistance. Electrochemical impedance spectroscopy (EIS) measurements are applied to detail both the overall performance of the system as well as the corrosion inhibition mechanism related to the electrochemical system's physicochemical representation over time. Electrochemical noise (EN) measurement are used to evaluate the inhibition efficiency as a function of exposure time, represented by the electrochemical noise resistance. Odd random phase electrochemical impedance spectroscopy (ORP-EIS) is selected as the electrochemical tool to study the system's instability, by evaluation of the non-linearities and non-stationarities over time. The non-stationarities present in the inhibitor-containing electrochemical system are shown to cause the overall instability of the system and should be taken into account when interpreting results from the different techniques over time.

In this study, TiO2 films are easily deposited in a single-step process from titanium tetraisopropoxide (TTIP) using a dielectric barrier discharge (DBD) device under atmospheric pressure at room temperature. The surface morphology of the as-deposited TiO2 films is observed by scanning electron microscopy (SEM). The as-deposited TiO2 films exhibit nanometer-sized particles with a lot of agglomerates. The cross section images indicate that the deposition rate of TiO2 films can reach about 70nm·min−1, which is much faster than that of conventional low pressure chemical vapor deposition (CVD) (typically <4nm·min−1). In order to confirm the structure composition and optical properties of the films, glancing incidence X-ray diffraction (GIXRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) are employed. The as-deposited TiO2 films are partly crystalline which show a good photocatalytic activity in the degradation of methylene blue under UV irradiation. After annealing at 673K, the TiO2 films are in the anatase phase and composed by homogeneous nanoparticles. The photocatalytic degradation rate of methylene blue of the TiO2 films after annealing (~0.6h−1) is almost 4 times higher than that of the as-deposited TiO2 films (~0.16h−1). The photocatalytic degradation rate of the TiO2 film after annealing is the same as the one of the commercial anatase TiO2 spin coated film when the error bar is taken into account. The TiO2 films show excellent photocatalytic stability during 3 recycling photocatalytic measurements.

In this study, we investigated the atmospheric plasma polymerization of allyl methacrylate (AMA), n-propyl methacrylate (nPMA), and propyl isobutyrate (PiB), whose chemistry mainly differs by their number of unsaturations. The resulting material is characterized using X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRRAS) while the thickness of the coatings is determined by visible spectroscopic ellipsometry (Vis-SE). The results show that the concentration of ester groups at the surface of the plasma polymers, as well as their deposition rate strongly depends on the surrounding unsaturations present in the precursor. A stabilization of the ester groups and an increase in the deposition rate due to the carbon–carbon double bonds is suggested.

The visual appearance of gold and gilding can be influenced in many ways, such as by changing the composition of the gold alloy or the nature of the gilded substrate. A less known medieval technique, reported in historical treatises, is the chemical treatment of the gilded surface itself, after application and burnishing of the gilding. We reporte here results regarding the study of the Holy Lady Shrine of Huy (13th c AD Mosan, Belgium) on which a possible artificial colouration of the gildings was detected. This led to many questions regarding applicable conservation-restoration treatments. Here is an overview of the results obtained, along with a discussion of the methodology that was developed to study this colouration process, also highlighting the necessary complementarity between laboratory and synchrotron-based analytical approaches. The 3-steps methodology proposed in this paper is generic for most cultural heritage problems where the application of ancient surface modification recipes is suspected but where the scarcity of the historical samples does not allow a direct study of such samples.

We report on a study wherein we synthesized TMOS-based silica monolithic skeletons in capillaries with an i.d. of 5 and 10 μm to produce skeleton structures with very low capillary-to-domain size aspect-ratios. These structures include the absolute minimal aspect-ratio case of a monolithic structure whose cross-section only contains a single node point. With domain-sized based reduced plate heights running as low as hmin = 1.3–1.5 for retained coumarin dyes providing a retention factor of k = 0.6–1.0, the study confirms the classic observation that ultralow aspect ratio columns generate a markedly lower dispersion than columns with a larger aspect ratio made in the past by Knox, Jorgenson, and Kennedy for the packed bed of spheres, but now for silica monoliths. The course of the reduced van Deemter curves, and more specifically the ratio of A-term versus C-term band broadening, could be interpreted in terms of the width and persistence length of the velocity bias zones in the columns. Considering the overall kinetic performance, it is found that the two best performing structures are also the structures with the lowest number of domains or node points, that is, with the lowest capillary-to-domain size aspect-ratio and, hence, resembling closest to the open-tubular format, which remains confirmed as the column format with the best kinetic performance. This is quantified by the fact that the minimal impedance values (order of Emin = 100) of the best performing ultralow aspect ratio monolithic columns are still significantly larger than the Emin values for the reference open-tubular columns (order of Emin = 15–20).

The Devanathan-Stachurski-cell is the most commonly used electrochemical technique for the investigation of the hydrogen trapping properties of a material. In this set-up, a flux of hydrogen atoms diffuses through a metal membrane under study. The atoms are subjected to the heterogeneities naturally present in the lattice of the metal, acting as traps. This matter influences the diffusion of hydrogen, which is strongly microstructure related. In this paper, we apply a numerical model to different iron-alloys to determine the hydrogen trapping parameters characterizing the materials. We highlight the complexity of the hydrogen trapping mechanism which needs to be further investigated.

The effect of zirconium-based conversion of thermally vaporized zinc, aluminium and magnesium on the chemisorption of dimethylsuccinate was studied using attenuated total reflection – Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS) analysis. Two competing chemisorption mechanisms contribute to interfacial bond formation. Hydrogen interactions on one hand were shown to occur between metal hydroxides and non-hydrolysed ester-groups of the molecule. On the other hand, both native and zirconium-treated substrates were shown to form interfacial carboxylate bonds with dimethylsuccinate, evidencing their capability of hydrolysing ester groups towards more reactive acid groups. Both interactions were shown to correlate to the metal oxide acid-base properties.