Electrochemical study of copper corrosion inhibition in acidic environemnt by 5-(4'-isopropylbenzylidene)-2,4-dioxotetrahydro-1,3-thiazole

Corrosion inhibition properties of the thiazole derivatives, namely (5-(4’-isopropylbenzylidene)-2,4-dioxotetrahydro-1,3-thiazole) (5-IPBDT), as a corrosion inhibitor for copper in acidic sodium sulphate solution 0.1 M have been studied by electrochemical and electro-gravimetrical methods such as potentiodynamic polarization measurements, electrochemical impedance spectroscopy (EIS), electrochemical quartz crystal microbalance (EQCM), and scanning electrochemical microscopy (SECM. The polarization curves showed that the presence of 5-IPBDT successfully reduced the corrosion of copper and this effect increased with increasing the applied concentration. EIS revealed that the presence of inhibitor remarkably increased the impedance of copper electrode over the whole studied frequency range. By obtaining the polarization resistance, the inhibition efficiency of 5-IPBDT as high as 93%, which is in a good agreement with the results obtained by the polarization curves (96%). By using SECM, the formation of the inhibitive film was followed in time. At the open circuit potential, the surface changed gradually from a conductive to an insulating surface in the presence of 5-IPBDT. EQCM studies revealed that the inhibitor shifted the breakdown potential (Eb) of copper electrode to more anodic value, reduced the corrosion current density and hindered the electrode mass loss. Both electrochemical and gravimetric data confirmed that the presence of inhibitor decreases the corrosion rate and thus increases corrosion resistance for copper in 0.1 M Na2SO4 solution

Nanocsövek előállítása, szerkezete és tulajdonságai = Preparation, structure, and properties of nanotubes

A kutatások célja a szén nanocsövek elektrokémiai úton történő előállítása során keletkező termék tulajdonságainak és a technológiai paraméterek közötti összefüggések kimutatása volt. A gyártási paraméterek között a szén katód alapanyagának morfológiája, a só olvadék összetétele, a hőmérséklet, valamint az elektrokémiai művelet paraméterei (áramsűrűség, potenciál, az elektrolízishez szükséges idő) bizonyultak lényegesnek. Az előállítási műveletekkel kapcsolatban megvizsgáltuk az elektrokémiai fémleválasztás kinetikáját is, amely a nanocső szintézis jobb megértését eredményezte. A nanocsöveket tartalmazó termék megtisztítása és az ehhez a lépéshez szükséges eljárások tanulmányozása képezte második feladatot. Tanulmányoztuk azokat a tisztítási módszereket is, amelyek segítségével a nanocsövek felülete módosítható. A nanocsöveket tartalmazó készítményt alagúteffektuson alapuló mikroszkópos vizsgálatoknak vetettük alá, és a pásztázó tűszondás mikroszkóppal meghatároztuk a csövek méretét, alakját, az egyes típusokba sorolt csövek gyakoriságát. A kísérleti eredményeket statisztikai módszerekkel értékeltük ki. A vizsgálatokat elméleti számításokkal egészítettük ki, amelyek célja annak megállapítása volt, hogy a különböző osztályokba sorolható nanocsövek mennyire stabilak. E vizsgálatok céljából több módszerrel is meghatároztuk a csövek aromás jellegét. | The main aim of this research was to determine the correlation between the parameters of the electrolysis and the experimental properties of the carbon nanotubes. The most important parameters, which could affect the quality of the nanotubes were found to be the morphology of the carbon cathode, the composition of the molten salt, the temperature and the parameters of the electrolysis itself (current density, applied potential, and the time period of electrolysis). In connection with these tasks we also studied the mechanism of metal deposition, which yielded new information on the formation of nanotubes. The second object of these investigations was the purification of nanotubes and the necessary steps needed to accomplish this task. Probes containing nanotubes were be investigated by using scanning-tunneling and atomic force microscopes. These investigations revealed the distribution of the various shapes, and thickness of the tubes. The experimental data were evaluated by using statistical methods. Experimental investigations were completed by theoretical calculations. The aim of these investigations was to determine the stability of various types of nanotubes

Acetone alkylation with ethanol over multifunctional catalysts by a borrowing hydrogen strategy

Step by step alkylation of acetone (A) with ethanol (E) in a ratio of 1 : 2 was investigated. A fixed bed flow-through reactor system was used at a total pressure of 21 bar and in the temperature range of 150-350 [degree]C in inert He or a reducing H2 medium. Following the hydrogen borrowing methodology, two types of catalysts were prepared; using neutral activated carbon (AC) and alkaline hydrotalcite (HT) supports, namely 5 wt% Pd/AC in the presence of alkaline additives (10, 20 and 30 wt% KOH or 20% K3PO4); 9 wt% Cu/HT and 5 wt% Pd/HT. The catalysts were activated in a H2 flow at 350 [degree]C. Different yields of mono- or dialkylated ketones were observed. In a hydrogen medium over the same catalyst systems the ketone products could be reduced to alcohols. In this study the Pd/HT catalyst seems to be the most promising for fuel production based on biomass fermentation

The use of nano/micro-layers, self-healing and slow release coatings to prevent corrosion and biofouling

The mitigation of corrosion and biofouling is a challenge. Through application of chemicals and special techniques can slow these undesired processes, an effective resolution requires a multidisciplinary approach involving scientists, engineers, and metallurgists. In order to understand the importance of the use of nano- and microlayers as well as self-healing coatings, the basic concepts of corrosion, corrosion mechanisms, corrosion inhibition and the microbiologically influenced corrosion will be summarised. The preparation, characterization and application of Langmuir-Blodgett and self assembled nanolayers in corrosive and microbial environment will be discussed. Preparation and characterization of microcapsules/ microspheres and their application in coatings will be demonstrated by a number of examples

Enantiomeric discrimination of chiral crown ether ionophores containing phenazine subcyclic unit by ion-selective potentiometry

In this paper the enatiomeric selectivity of two chiral phenazino-18-crown-6 ether hosts ((R,R)-\textbf1 and (R,R)-\textbf2) is quantified. These hosts were incorporated into plasticized PVC membranes and used as recognition elements of ion-selective electrodes. The potentiometric response towards the two enantiomers of 1-phenylethylammonium ions (PEA+) was measured. Potentiometric selectivity coefficients were calculated which reflect the ratio of the stability constants of the diastereomeric complexes. Ligand (R,R)-\textbf1 does not show enantiomeric recognition, while ligand (R,R)-\textbf2 has a slight preference for the (S)-(-) enantiomer over the (R)-(+) enantiomer manifested by a selectivity coefficient of 0.77. The results were compared to enantioselectivity patterns of the ligands towards α -(1-naphthyl)ethyl ammonium perchlorate (NEA+ClO4-) enantiomers measured by circular dichroism and by 1H NMR titrations