Evangelia A. Pavlatou

M.-A. Gatou, D.S. Tsoukleris, E.A. Pavlatou

35th International Conference on Environmental Geochemistry and Health (2019), 1-5 July, Manchester Metropolitan University, UK (oral)

Mercury has been reported to be naturally occurring trace contaminant in the oil reservoirs. The chemical nature of mercury in oil reservoirs is of interest for a variety of reasons, but especially because it is important to understand the fate of the various species, as they partition to fuels and waste streams in processing. Practical considerations also exist as mercury affects equipment integrity, catalyst performance, product quality, as well as the health and safety of workers. This study, evaluates the suitability of natural minerals (zeolite and attapulgite) as sorbents of mercury in artificial aqueous solution and crude oil. The tested materials were natural zeolite (clinoptilolite), thermally treated zeolite, silver-loaded zeolite and attapulgite. Mercury sorption experiments were carried out under stable conditions using anartificial aqueous solution, characterized by an Hg concentration of the order of 50 mg dm^-3 , simulating the concentration of mercury in crude oil. In the case of attapulgite and silver-activated zeolite, the sorption efficiency was achieved at a level of above 90%. Under the same experimental conditions testing of commercially available resins took place, in order to be used for further enhancing the absorption capacity of the natural materials, and therefore to present overall higher selectivity in mercury. Additionally, the removal of mercury from real crude oil was investigated. The results for the tested samples indicate a significant increase of the sorption efficiency. Based on these results, a novel, effective and low-cost mercury-selective adsorbent is proposed and therefore, it can be used as a filter during oil production processes.

N. Chronopoulou, A. Karantonis, E.A. Pavlatou

32nd International Conference on Surface Modification Technologies (SMT32)-EAST Forum (2018), 27-29 June, San Sebastian, Spain (poster)

N.Chronopoulou, M. Lekka, E.A.Pavlatou

COST WORKSHOP “Protection against degradation of components by corrosion and corrosion-wear” (2017), 25-27 October, Barcelona, Spain (oral)

E. Rosolymou, S. Spanou, S. Hansal, W. Hansal, E.A. Pavlatou

COST WORKSHOP “Electrochemical processing and corrosion of miniaturized systems” (2016), 12-14 October, Athens (oral)

Copper nanowires were fabricated by filling commercial AAO nanochannels by utilizing Direct and Pulse Current Electrodeposition. Uniform Cu nanowires were produced by using acidic copper baths at room temperature under specific pulse plating conditions. X‐ray diffraction revealed the effect of pulse plating parameters on the crystalline structure of the Cu nanowires and Field Emission Microscopy was used to examine the pore filling of the template.

H. Kazimierczak, P. Ozga, E. Rosolymou, E.A. Pavlatou

COST WORKSHOP “Electrochemical processing and corrosion of miniaturized systems” (2016), 12-14 October, Athens (oral)

The first attempt to fabricate Sn nanowires by using template assisted electrodeposition from citrate electrolytes was conducted. In the first step, the studies of the citrate complexes formation and stability of citrate baths were carried out based on the thermodynamic models of solutions. Next, cyclic voltammetry was used to analyze the kinetics of tin reduction in aqueous citrate electrolytes. Then some trials to electrodeposit Sn nanowires by using direct and pulsed current were performed.

N. Chronopoulou, D.Vozios, E.A. Pavlatou

COST WORKSHOP “Electrochemical processing and corrosion of miniaturized systems” (2016), 12-14 October, Athens (oral)

Ni/graphene coatings are produced using a Watt’s type bath by applying both direct and pulsed current conditions, in presence or absence of additive in the electrolytic bath. The imposed current pulses ranging between 0.1 up to 1000 Hz, while the duty cycle is kept constant and equal to 50%.The surface morphology, the crystallographic orientations, as well as the mechanical properties are investigated.

N.D. Chronopoulou, A.M. Routsi, E. Siranidi, E.A. Pavlatou

7th Pulse Plating Seminar-East Forum (2016), 3-4 March, Baden, Austria (oral)

Electrolytic co-deposition is one of the most widely-used methods for preparing metal/alloy coatings and nanostructured composite coatings. The development of production technology of composite electro-coatings such as metal matrix reinforced with nano-particles, is primarily aimed at improving the mechanical, tribological and corrosion behavior of metal matrix. Conventionally, ceramic powders such as alumina, silicon carbide, and diamond were used as reinforcing materials for Ni-based nanocomposite coatings. Recently, carbon nanotube (CNT) has been applied as a new reinforcing agent for composite coatings due to its excellent mechanical properties and high thermal conductivity. Ni matrix composites reinforced by carbon nanotubes have been studied for both improved mechanical properties and for potential applications as anticathode material in dye sensitized solar cells. This study concerns the electrolytic codeposition of hybrid multi-walled carbon nanotubes (MWCNTs)/Al₂O₃ with nickel by applying both direct and pulsed current conditions, in presence and absence of additive in the bath. The particles were supplied by the group of Prof. Jinbo Bai from the Lab. MSSMat of Ecole Centrale Paris. In this work a Watts type bath, with and without additive was used with a constant pH=3.5 and temperature 50±1°C. The electrodeposition of Ni/ MWCNT-Al₂O₃ composites was carried out on a rotating disk electrode (RDE). Pure Ni deposits were also produced under the same experimental conditions, as reference state for comparison reasons. The surface morphology, the crystallographic orientation and the grain size of nickel matrix were investigated as a function of the type of applied current (e.g. direct or pulse) and the presence of additive. The imposed current pulses ranged between 1 up to 1000 Hz. The surface morphology and structural characteristics of all coatings were investigated by using electron microscopy SEM-EDS, while the predominant crystallographic orientation of crystallites Ni studied by XRD. By utilizing a ball on disc tribometer under dry sliding conditions the wear behavior of the composite coatings were investigated. The roughness of the surface of the coatings as well as of the morphology of wear track was studied by using a laser profilometer. Micro-Raman spectroscopy has been utilized to characterize the composition of the composites, the wear tracks as well as of the crosssectional profile of the coatings. The application of pulse current at high frequencies in combination with the presence of additive, leads to composite coatings with a relatively uniform distribution of MWCNTs-Al₂O₃ particles and coherent structure into the metallic nickel matrix, exhibiting an increased resistance to sliding friction. The simultaneous presence of MWCNT-Al₂O₃ particles in the bath and the application of high current pulses results to the production of nano-structured coatings with a mixed preferred crystalline Ni orientation ([110]+[211]) compared to the pure Ni coatings produced under the same electrolytic conditions that presented a [110] texture.

N. Lymperi, E. Rosolymou, N. Chronopoulou, S. Spanou, E.A. Pavlatou

EastForum 2015-Progress in Functional and sustainable Surface technology (2015), 25-26 June, Lund, Switzerland (oral)

In recent years, nanowire (NW) structures have attracted considerable attention, due to their characteristic chemical and physical properties and their exciting prospects in electronic, photonic and sensors applications. One of the simplest methods to fabricate metal nano-structures, is the so-called template-assisted electroplating which makes use of porous membranes such as anodized aluminium oxide (AAO) disks. Nanoporous alumina is a unique material in several respects. It can easily be prepared by anodic oxidation of aluminium surfaces in polyprotic aqueous media. Using AAO as a template, pore structures with controlled structural properties (pore diameter, modulated pore structure and lengths) can be easily fabricated. We can also achieve uniformity of pore diameters with high pore density (1011 cm^-2), cylindrical pore geometry with high aspect ratio and easy dissolution of AAO template without affecting the fabricated nanostructures (metal NWs) confined inside the nanopores. Generally, anodic aluminium oxide (AAO) films are commonly used as templates for manufacturing micro- and nanostructures as they exhibit material properties in nanopore density, arrangement, mechanical strength and chemical stability. The filling of AAO templates with metals, such as copper and nickel, through the process of electrodeposition, has been the subject of several studies in recent years. For instance, copper nanowires exhibit significant potential for applications in modern electronic technology such as in the field of micro/nanoelectronics industry and, in particular, for interconnection in electronic circuits, while nickel nanowires are potential candidates for magnetic storage devices, nanosensors and biomedical applications. The electrochemical deposition method is one of the most feasible processes for manufacturing nanostructured materials or devices, and is relatively inexpensive and simple. It is possible to produce uniform nanowires of the same diameter, length and with uniform density. Additionally, it is a low temperature process that allows nanostructure fabrication with great precision and control and has the capacity to produce nanowires of better quality in terms of purity due to the selectivity of deposition. In the present work both commercially-available AAO templates (Whatman) and selfordered ones were used in order to produce copper and nickel nanowires with desired characteristics. The anodization of aluminium was carried out using an oxalic acid bath and it was a two-step procedure meaning the change of the voltage at a certain time. The nanowires were prepared by the electrodeposition of the metals, from simple sulfate solutions (NiSO₄, CuSO₄), into the 100nm and 200nm pores of the commerciallyavailable alumina membranes as well as the pores of the self-made templates the diameter of which ranged between 50 nm-80 nm depending on a variety of parameters such as the time of anodization, the type of electrolyte used and the post treatment of the membrane. The electrochemical deposition was carried out under different potential conditions of direct current (DC) and pulse (PED). A detailed analysis of the structural and morphological properties of the Ni and Cu NWs was performed using Field Emission Scanning Electron Microscopy and X-ray Diffraction.

F. Giannopoulos, N. Chronopoulou, E.A. Pavlatou, A. Karantonis

5th Regional Symposium on Electrochemistry South East Europe (2015), 7-11 June, Pravets, Bulgaria (poster)

In principle, nano-composite materials present superior properties than their simple counterparts. Such nano-composites can be fabricated by electrochemical cathodic codeposition. In the present work, the effect of hybrid multi-walled carbon nanotubes/Al₂O₃ particles (MWCNT/Al₂O₃) on the deposition of Ni from Watts solution is studied by Linear Sweep Voltammetry (LSV), Electrochemical Impedance Spectroscopy (EIS) and Scanning Electron Microscopy (SEM). Moreover, the fabrication of a MWCNT electrode is attempted by selective electrodeposition of the nanotubes. The presence of nanotubes enhances the current in comparison to the case of the pure Watts solution. The presence of SDS does not further increase the cathodic current. The increase of the cathodic current may be due to increase of the Ni electrodeposition rate or the increase of the proton reduction rate. The charged transfer resistance in the case of the Watts-MWCNT/Al₂O₃ bath is very small, indicating that Ni electrodeposition is catalyzed by the hybrid nanotubes. Similar conclusions are derived by comparing the LSVs with impedance spectra at various cathodic potentials. In order to achieve selective deposition of MWCNT on a graphite electrode, potentiostatic pulse electrodeposition/electrodissolution was performed. During the cathodic portion of the pulse, co-deposition of Ni and nanotubes was occurring whereas during the anodic portion of the pulse, Ni was dissolved from the composite matrix. This surface morphology is completely different than the morphology of a graphite electrode, indicating that MWCNT actually remained on the electrode surface. This modified electrode has very good capacitative properties, estimated around 9x10^-4 F, for apparent area of 0.07 cm². The capacitative properties of the electrode where evident during Cyclic Voltammetry in K₄Fe(CN)₆, where the redox peaks almost disappeared due to the high value of the capacitance current.

D.S. Tsoukleris, G. Psarellis, M.E. Kassalia, N. Friliggou, E.Α. Pavlatou

Nano & Dispersion Coatings, European Interfinish (2015), 26-27 February,  Politecnico di Milano, Italy (oral)

In this study, the production of novel doped photocatalyst with self-cleaning and antimicrobial properties under visible light irradiation was investigated. TiO₂ is known to possess self-cleaning properties in UV-light, whereas the doping agents were used in order to provide self-cleaning properties under visible light irradiation. For this purpose two different nonmetal dopants were used in order to prepare via sol-gel method nanopowders with band gap lower than 2.5eV. Over the recent years, considerable scientific efforts have been orientated towards improving the photocatalytic action of titanium dioxide. One of the main goals has become the activation of TiO₂ under visible light irradiation. To achieve this objective, several works have been conducted concerning the chemical modification of titania. This is attained by the introduction, “implantation” of various elements such as metal-ions e.g. transition metals: Cu, Co, Ni, Cr, Mn, Mo, Nb, V, Fe, Ru, Au, Ag, Pt, as well as non-metal ions: N, S, C, B, P, I, F. On the other hand, in order to improve the photocatalytic activity under visible light, various doping techniques has been explored including precipitation, sol-gel, hydrolysis, sputtering and chemical vapor deposition (CVD) methods. One of the most prevalent synthetic routes for the production of doped nanostructured titania has become the so called solgel process, widely known as hydrolysis-condensation (SOLution-GELation) which falls into the broad class of wet chemistry methods. In this work emphasis has been given to the study of this specific synthesis route, since it has become the most frequently applied synthetic method providing various advantages. The Sol-Gel synthesis of doped titania nanomaterials comprises various steps. Depending on the desired crystal phase composition, particle size and shape regularly an inorganic TiOSO₄, TiCl₄, or alternatively organic precursor Ti(OR)₄ is used. Particular emphasis is placed on exploring the synthetic routes by altering the experimental parameters. All these key parameters are forecast to affect the stability over time and the sequence of preparing the sol to form the stock solution. An important factor is the choice of conditions during the heat treatment. All these factors were key points that affected the final quality, the physical, chemical, optical and electrical properties of the doped titania particles. 

E. Rosolymou, S. Spanou, A. Karantonis, E.A. Pavlatou

Nano & Dispersion Coatings, European Interfinish (2015), 26-27 February,  Politecnico di Milano, Italy (oral)

Tin-nickel alloys are widely known in industry and microelectronics due to their attractive features, such as resistance to corrosion, ductility and solderability. These alloys are nonallergic to skin. The non-allergic property allows it to replace the electroplated nickel on fasteners for garments. It finds application in replacing chromium in decorative and light engineering industries and in printed circuit boards as an etching resist. Tin-nickel alloys are ideal for fabrication of Li-ion batteries. In particular, the Sn-Ni electrode has high electrochemical capacity and delivers a steady capacity even after 100 charge-discharge cycles. The regulation of alloys structure has a significant practical importance. The possibility to obtain metastable phases by electroplating is well ascertained. In most cases, this fact is related to irreversibility of an alloy phase composition and microstructure. The electroplating is a prospective and economic way of Sn-Ni alloys production but it is rather difficult to obtain films with the desired chemical and phase composition. This work aims to correlate the observed structural characteristics of Sn-Ti coatings reinforced by TiO₂ nanoparticles (i.e. chemical analysis of the alloy, percentage of the embedded nanoparticles in alloy matrix) with the type of applied current and the resulting mechanical and chemical properties. Under this framework, composite coatings of tin-nickel matrix enhanced by titania nano-particles were produced under direct (DC) and pulse current (PC) conditions. The electrodeposition was carried out from a chloride/fluoride electrolytic bath with constant temperature of approximately 70±1^oC and pH 4.4. Additionally, tin-nickel pure coatings were also produced and characterized for comparison reasons. The influence of the variable electrolysis parameters (current density, frequency and duty cycle of pulses, load of particles in the bath) on the surface morphology, structure, mechanical and chemical (anticorrosive) and photocatalytic properties were examined. According to the experimental findings it is proven that the use of low current density in the bath favors increased incorporation percentage of titania nanoparticles and enhanced microhardness values. In general, the overall experimental data reveal that the proper selection of electrodeposition parameters could lead to the production of nano-structured tin-nickel matrix composites exhibiting enhanced mechanical and anticorrosive properties.

N. Chronopoulou, M. Panagopoulou, D.S. Tsoukleris, S. Spanou, E.A. Pavlatou

7th International Conference on Materials Science and Condensed Matter Physics (2014), 16-19 September, Chisinau, Moldova (poster)

For a considerable number of practical applications, TiO₂ and related semiconducting materials have been widely used as photocatalysts in order to decompose liquid industrial pollutants. The photocatalyst, usually is immobilized in the form of a thin film on an inert substrate1. In this framework, this work describes the synthesis of efficient Ni-P titania photocatalysts which have a high stability, an excellent corrosion resistance and a photocatalytic action against liquid pollutants. Nano-structured composite coatings were obtained by electrochemical codeposition of TiO₂ nano-particles (mean diameter 21 nm, Degussa P25) with NiP matrix, from an additive-free Watts type bath, under both direct and pulse current conditions. The impact of pulse plating parameters, such as frequency of applied current pulses over a wide range of values, as well as the load of the particles in the electrolyte, on the composition, microstructure, morphology and microhardness of the Ni–P TiO₂ composite coatings were examined. The aim of the study was to correlate the observed structural characteristics of the coatings with the resulting mechanical (microhardness), wear and photocalaytic behavior. The surface morphology and the structure of composites were investigated, along with the distribution and the percentage of the embedded nano-particles in nickel based matrices. The data revealed that enhanced codeposition percentages of titania nanoparticles in the alloy matrix were obtained under high pulse frequencies and relatively high load of particles in the bath. Moreover, thermal treatment of the coatings was found to be beneficial for enhancing microhardness values, and improving wear and photo-induced properties. The wear behavior of the coatings was investigated by using a Ball-on-Disc tribometer under dry uni-directional sliding conditions, and the results showed that the presence of the reinforcing TiO₂ nanoparticles increased the wear resistance of the composite coatings compared to the pure NiP ones. For the majority of the composites, the sliding wear took place by abrasive and adhesive mechanisms. The photo-induced properties of the Ni–P TiO₂ composite coatings were investigated by means of photocatalytic degradation of methyl-orange under UV irradiation (350 nm) as well as by contact angle measurements. The best photo-induced properties were observed for composites thermally treated and exhibiting the highest TiO₂ codeposition percentage in the alloy.

D.S. Tsoukleris, E.A. Pavlatou, S. Spanou, C. Zanella, P. Leisner

65th Annual Meeting of the International Society of Electrochemistry (2014), 31 August-5 September, Lausanne Switzerland (poster)

Hygiene/antimicrobial issues in public places eg. hospitals, schools, hotels, public transportation etc. are of crucial importance as inattention could lead to spread of viral diseases or epidemics and consequently to deaths. It is estimated that 15% of these infections is due to transmission through inanimate objects. Although sanitization and disinfection of surfaces using chemical liquids as chlorine or alcohol is a common practice to prevent transmission of diseases, many times such procedures are skipped, skimped or in the case of public transportation not practically feasible. Specifically, the present work focuses on investigating the efficient immobilization of TiO₂ doped nanoparticles in a Sn-Ni metal matrix for the development of hygienic and antibacterial nanostructured coatings being activated indoors, with improved wear and corrosion resistance. This work is part of the SelfClean ongoing EU project, targeting in self-cleaning, antibacterial electrolytic coatings of high aesthetics and durability. Of crucial importance is the percentage of the incorporated nanoparticles. In order to increase the codeposition rate and consequently the photocatalytic activity, pulse current plating has been utilized. With this method higher codeposition rate of nanoparticles can be achieved compared to the conventional direct current plating. These kind of coating will be able to operate under indoor light irradiation and can be applied to common touched objects (knobs, taps, handles) reducing the risk of infection’s transmission by 50-100%. The SelfClean project is on track to achieve the expected results from individual research work packages. One of the first achievements of the project is the mass production of doped TiO₂ particulates exhibiting a band gap less than 2.3 eV, able to be activated by indoor light irradiation. The production steps of the electrochemical industrial processes followed in this project, towards the efficient fabrication of the added value composite electrocoatings, as well as the interesting trouble shooting during electroplating will be described in this paper. Finally, the tribological and corrosion characterization of the produced composites will be presented.

D.S. Tsoukleris, E.A. Pavlatou, N. Chronopoulou, A. Karantonis, C. Sarafoglou, D.I. Pantelis

65th Annual Meeting of the International Society of Electrochemistry (2014), 31 August-5 September, Lausanne Switzerland (poster)

The last decades carbon nanotubes (CNTs) have drawn considerable attention in material sciences. CNTs are a kind of allotrope of carbon materials featured with a seamless tubular structure formed by curling-up graphene sheets, which are classified into single-walled CNTs (SWCNTs) and multi-walled CNTs (MWCNTs) according to their layers of graphene sheets. Multi-walled CNTs form 3D networks and are frequently used as thin films in applications such as capacitors, actuators and displays. Nanocomposites of CNT and Ni species are promising for applications in capacitors, hydrogen storage and hydrogenation catalysis. CNT/Ni-species (including Ni, NiO, Ni(OH)₂) nanocomposites may be effectively fabricated by electroless plating, electroplating, impregnation and other processes. Pulsed electrodeposition, in which the applied potential is oscillated at high frequencies during deposition of metals, is another strategy to fabricate nanostructured Ni coatings. In this work composite coatings were obtained by electrolytic codeposition of hydride MWCNTs-Al₂O₃ with Ni matrix from an additive-free Watts type bath, under both direct (DC) and pulse current (PC) conditions. Pure Ni deposits were produced under the same experimental conditions for comparison reasons. The electrodeposition of all deposits was carried out on a rotating disk electrode. The surface morphology and structural characteristics of all coatings were investigated, along with the optimum electroplating conditions concerning the distribution of the embedded hydride particles in the nickel matrix. By utilizing a ball on disc tribometer under dry sliding conditions, wear resistance were studied and correlated with the above mentioned structural characteristics. The corrosion resistance of different deposits was determined in 0.6M NaCl solution by the Tafel method and electrochemical impedance spectroscopy. It was found that the application of high frequency pulse current conditions in combination with low concentrations of MWCNTs in the bath was beneficial for the homogeneous distribution of the hydride MWCNTs in the Ni matrix, both exhibiting a positive effect on the tribological behaviour of the deposits, additionally presenting relatively low corrosion rates. High pulse current frequencies in presence of the hydride particulates resulted in the predominance of a mixed [110+211] orientation for the composites, compared to the pure Ni coatings prepared under the same conditions oriented through the [110] axis.

S. Spanou, D. Tsoukleris, E. Rosolymou, N. Chronopoulou, A. Zoikis-Karathanasis, E.A. Pavlatou

2nd International Surface Treatment Symposium (2014), 25-27 June, Istanbul Technical University, Turkey (oral)

D.S. Tsoukleris, V. Binas, G. Kiriakidis, A. Zachopoulos, E.Α. Pavlatou

SPEA8-8th European Meeting on Solar Chemistry and Photocatalysis, Environmental Applications (2014), 25-28 June, Thessaloniki, Greece (poster)

In this work, the efficiency of solar photocatalytic process to remove acetaldehyde under visible light irradiation was investigated. For this purpose four different types of doped TiO₂ photocatalysts were prepared via sol-gel method and immobilized onto appropriate glass spherules substrate by means of a leave coating technique. The effect of various operating parameters, such as the immobilized catalyst amount, the thermal treatment process and the presence of other organic substances on process efficiency were investigated.

D.S. Tsoukleris, C. Fratti, C. Barholm-Hansen, A.A. Rasmussen, E.Α. Pavlatou

SPEA8-8th European Meeting on Solar Chemistry and Photocatalysis, Environmental Applications (2014), 25-28 June, Thessaloniki, Greece (poster)

In this study, the production of novel doped nanopowders with photocatalytic and antimicrobial properties under UV and visible light irradiation was investigated. TiO₂ is known to possess self-cleaning properties in UV-light, whereas the doping agents were used in order to provide self-cleaning properties under visible light irradiation. For this purpose two different non-metal dopants were used in order to prepare via sol-gel method nanopowders with band gap lower than 2.5eV.

E.Α. Pavlatou

6th Pulse Plating Seminar (2014), 7th March, Baden, Austria (oral)

E.Α. Pavlatou, N. Chronopoulou, A. Karantonis, C. Sarafoglou, D.I. Pantelis

Nanocoatings-International Conference on Functional Nanocoatings (2013), 8-9 July, Politecnico of Milano, Milano, Italy (oral)

Electrodeposition is one of the most widely-used methods for preparing metal/alloy coatings and nanostructured composite coatings. Among various process technologies, electrodeposition has advantages such as cost-effectiveness relative to other techniques like spray and sputtering processes. The development of production technology of composite electrocoatings, such as metal matrix reinforced with nano-particles, is primarily aimed at improving the mechanical, tribological and corrosion behavior of metal matrix. Conventionally, ceramic powders such as alumina, silicon carbide, and diamond were used as reinforcing materials for Ni-based nanocomposite coatings. Recently, carbon nanotube (CNT) has been applied as a new reinforcing agent for composite coatings due to its excellent mechanical properties and high thermal conductivity. As Ni exhibits high wear resistance, good ductility, and ferromagnetism, Ni-CNT composite coatings have potential applications not only for wear-resistance coatings and microelectromechanical systems (MEMS), but also for corrosion-resistance coatings. Moreover, Ni matrix composites reinforced by carbon nanotubes have been studied for both improved mechanical properties and for potential applications as anticathode material in dye-sensitized solar cells. This study concerns the electrolytic co-deposition of hybrid structures composed by multiwalled carbon nanotubes (MWCNTs) and Al₂O₃ microparticles with nickel by applying both direct and pulsed current conditions. In this work a Watts type bath in absence of additives was used with a constant pH=3.5 and temperature 50±1°C. The electrodeposition of Ni/CNT-Al₂O₃ composites was carried out on a rotating disk electrode (RDE) by using various velocities in the range of 200 up to 1200 rpm. Pure Ni deposits were also produced under the same experimental conditions, as reference state for comparison reasons. The surface morphology, the crystallographic orientation and the grain size of nickel matrix were investigated as a function of the concentration of CNT-Al₂O₃ nanoparticles in the bath as well as of the type of applied current (e.g. direct or pulse). The imposed current pulses exhibited frequency of 0.01 up to 1000 Hz, while the duty cycle was kept constant and equal to 50%. The corrosion resistance of composite coatings was studied by conducting potentiodynamic tests and applying electrochemical impedance technique. The results of this work demonstrated that the imposition of pulse current conditions at high frequencies and reduced amounts of hybrid particles in the bath results to the production of composite coatings with enhanced wear resistance and relatively low corrosion rates. The simultaneous presence of CNT-Al₂O₃ particles in the bath and the application of high current pulses results to the production of nano-structured coatings with a mixed preferred crystalline Ni orientation ([110] +[211]) compared to the pure Ni coatings that presented a [110] texture.

A.Tzani, A. Douka, A. Papadopoulos, T. Kosanovic, E.Α. Pavlatou, E. Voutsas, A. Detsi

3rd International Symposium on Green Chemistry for Environment, Health and Development (2012), October 3-5, Skiathos Island-Greece (oral)

Green chemistry possesses the spirit of sustainable development and is attracting increasing interest in the 21st century. In the chemical world, strategies for increasing sustainability often require the redesign of reactions and modifications of existing chemical processes aiming, among other things, at the reduction of chemicals used as solvents in a wide range of industrial applications. In this context, ionic liquids (ILs) have recently emerged as a potential replacement for toxic, hazardous flammable and highly volatile organic solvents (VOCs) owing mainly to their negligible volatility, excellent thermal stability, and the variety of structures available. However in order to confidently label this class of solvents as ‘‘green’’, their effect on the environment must be thoroughly examined through biodegradation studies. ILs have been increasingly exploited in the pharmaceutical industry in various applications, such as drug formulations, solvents for the solubilization of drugs and for the synthesis of active pharmaceutical ingredients. In the frame of a research which examines the possibility of using task-specific ILs for developing green methodologies towards novel bioactive compounds, we present here preliminary results from the synthesis of ILs derived from ethanolamine and organic carboxylic acids and their application in the synthesis of 4-hydroxy-bis-coumarins possessing antioxidant activity. Three ILs were synthesized namely N-hydroxyethylammonium formate, acetate and trifluoroacetate and were used as solvents for the reaction between 4-hydroxy-coumarin and various benzaldehydes. Optimization studies were conducted regarding the most important reaction parameters such as reaction time, temperature and the molar ratio of reactants. It was ascertained that the reaction proceeded smoothly in 40^oC in 3h, providing the desired 4-hydroxy-bis-coumarins in almost quantitative yields and high purity after simple aqueous work-up. The ILs could be recycled and re-used for three times without decrease in the yield. In addition, the physicochemical properties of the synthesized ILs were determined and their biodegradability level has been investigated applying the Biological Oxygen Demand (BOD-5) closed-bottle test. The first results indicated that the three ILs present satisfactory biodegradability potential, higher than 62%.