scholarly journals An Electrochemical Route for Hot Alkaline Blackening of Steel: A Nitrite Free Approach

Surfaces ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 216-228 ◽  
Author(s):  
Maximilian Eckl ◽  
Steve Zaubitzer ◽  
Carsten Köntje ◽  
Attila Farkas ◽  
Ludwig Kibler ◽  
...  
Keyword(s):  
Linear Sweep Voltammetry ◽  
Bath Temperature ◽  
Alkaline Solutions ◽  
Linear Sweep ◽  
Dc Voltage ◽  
Force Microscopy ◽  
Protective Layers ◽  
Slope Analysis ◽  
Atomic Force ◽  
Steel Surfaces

Blackening belongs to the predominant technological processes in preserving steel surfaces from corrosion by generating a protective magnetite overlayer. In place of the commonly used dipping-procedure into nitrite-containing blackening baths at boiling temperatures that are far above 100 °C, here we describe a more environmentally friendly electrochemical route that operates at temperatures, even below 100 °C. After an investigation of the electrochemical behavior of steel samples in alkaline solutions at various temperatures, the customarily required bath temperature of more than 130 °C could be significantly lowered to about 80 °C by applying a DC voltage that leads to an electrode potential of 0.5−0.6 V vs. Pt. Thus, it was possible to eliminate the use of hazardous sodium nitrite economically and in an optimum way. Electrochemical quantification of the corrosion behavior of steel surfaces that were in contact with 0.1 M KCl solution was carried out by linear sweep voltammetry and by Tafel slope analysis. When comparing these data, even the corrosion rates of conventional blackened surfaces are of the same magnitude as a blank steel surface. This proves that magnetite overlayers represent rather poor protective layers in the absence of additional sealing. Moreover, cyclic voltammetry (CV), atomic force microscopy (AFM), scanning electron microscopy (SEM) and auger electron spectroscopy (AES) characterized the electrochemically blackened steel surfaces.

scholarly journals Development of one-dimensional titania nanomaterials

2014 ◽  
Author(s):  
Ναούμ Βαενάς
Keyword(s):  
Electron Microscopy ◽  
Electrochemical Impedance ◽  
Linear Sweep Voltammetry ◽  
Linear Sweep ◽  
One Dimensional ◽  
Force Microscopy ◽  
Photocurrent Spectroscopy ◽  
Atomic Force ◽  
Transmission Electron ◽  
Dye Solar Cells

Σκοπός αυτής της διδακτορικής διατριβής είναι η ανάπτυξη μονοδιάστατων νανοδομών τιτανίας και εν συνεχεία η εφαρμογή τους στην κατασκευή ευαισθητοποιημένων ηλιακών κελιών (Dye Solar Cells - DSCs). Οι νανοσωλήνες τιτανίας αποτελούν την ιδανική επιλογή για τους στόχους αυτής της έρευνας καθώς: α) μπορούν να προετοιμαστούν εύκολα από την ανοδική οξείδωση ενός φύλλου τιτανίου, β) επιτρέπουν τον εύκολο έλεγχο της μορφολογίας τους μέσω της ηλεκτροχημικής νάνο-μηχανικής, γ) εξασφαλίζουν εξαιρετικές ηλεκτρικές ιδιότητες, όπως κατευθυνόμενη κίνηση των ηλεκτρονίων. Οι νανοσωλήνες τιτανίας χρησιμοποιήθηκαν ως ηλεκτρόδια εργασίας (photo-anodes) στα ευαισθητοποιημένα ηλιακά κελιά που κατασκευάστηκαν στη συνέχεια.Τα μορφολογικά και δομικά χαρακτηριστικά των νανοσωλήνων μελετήθηκαν με τις τεχνικές, της μικροσκοπίας ατομικών δυνάμεων (Atomic Force Microscopy - AFM), της μικροσκοπίας ηλεκτρονικής σάρωσης (Scanning Electron Microscopy - SEM), της μικροσκοπίας ηλεκτρονικής διελεύσεως (Transmission Electron Microscopy - TEM), της φασματοσκοπίας υπεριώδους/ορατού (Ultraviolet–Visible - UV-Vis) και της φασματοσκοπίας Ράμαν (Raman spectroscopy). Επιπλέον η αξιολόγηση και ο χαρακτηρισμός των ηλιακών κελιών πραγματοποιήθηκε με τις μεθόδους, της φασματοσκοπίας ηλεκτροχημικής εμπέδησης (Electrochemical Impedance Spectroscopy - EIS), της φασματοσκοπίας φωτοδυναμικού/φωτορεύματος περιοδικά μεταβαλλόμενης έντασης φωτισμού (Intensity Modulated Photovoltage/ Photocurrent Spectroscopy - IMVS/IMPS) και τελικά οι αποδόσεις των φωτοβολταϊκών εξάχθηκαν από την βολταμετρία φωτορεύματος (Linear Sweep Voltammetry - LSV). Κίνητρα για αυτήν την μελέτη αποτέλεσαν η ανάγκη κατανόησης, των βασικών μηχανισμών ανάπτυξης των νανοσωλήνων τιτανίας καθώς και των αρχών λειτουργίας που διέπουν τα ευαισθητοποιημένα ηλιακά κελιά. Στο πρώτο μέρος αυτής της έρευνας πραγματοποιήθηκαν μερικά προκαταρτικά πειράματα, με σκοπό την βελτίωση της μορφολογίας του χρησιμοποιούμενου υποστρώματος τιτανίου, όπως και των νανοσωλήνων τιτανίας που προέκυψαν. Μόλις οι συνθήκες ανοδίωσης σταθεροποιήθηκαν, υψηλής ομοιογένειας και ποιότητας νανοσωλήνες προετοιμάστηκαν και χρησιμοποιήθηκαν σε ευαισθητοποιημένα ηλιακά κελιά με ικανοποιητική απόδοση. Στην δεύτερη φάση αυτού του έργου, οι δομικές ιδιότητες των νανοσωλήνων μελετήθηκαν , με σκοπό να εξασφαλιστεί η ανεμπόδιστη μεταφορά των ηλεκτρονίων. Συγκεκριμένα η επίδραση της διαδικασίας απόπτυσης των νανοσωλήνων διερευνήθηκε συνάρτηση των ηλεκτρικών χαρακτηριστικών των φωτοβολταϊκών συσκευών που τελικά παράχθηκαν. Στο τρίτο στάδιο της διατριβής, προηγμένες δομές νανοσωλήνων προετοιμάσθηκαν μέσω σύνθετων τρόπων ανοδίωσης. Η ποτενσιοστατική και γαλβανοστατική ανοδίωση συνδυάστηκαν για πρώτη φορά στην βιβλιογραφία και οδήγησαν στην εξέλιξη της μεθόδου της ανοδίωσης. Το τελευταίο μέρος της δουλειάς αφιερώθηκε αποκλείστηκα στην αύξηση της απόδοσης των φωτοβολταϊκών που ενσωμάτωναν φωτοηλεκτροδία νανοσωλήνων, μέσω της χρήσης των πιο σύγχρονων ηλεκτρολυτών και χρωστικών. Το οξειδοαναγωγικό ζεύγος κοβαλτίου διαχύθηκε με ευκολία στους πορώδους νανοσωλήνες και σε συνδυασμό με την οργανική χρωστική D35, οδήγησε σε υψηλές φωτοτάσεις και αποδόσεις.

Effect of cetyltrimethylammonium bromide on the electrochemiluminiscence and electrooxidation of luminol

1983 ◽  
Vol 48 (2) ◽  
pp. 477-483 ◽  
Author(s):  
Jan Lasovský ◽  
František Grambal
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Linear Sweep Voltammetry ◽  
Critical Micellar Concentration ◽  
Peak Height ◽  
Anodic Peak ◽  
Alkaline Solutions ◽  
Platinum Electrodes ◽  
Micellar Solutions ◽  
Linear Sweep ◽  
Low Concentrations

The electrooxidation of luminol in alkaline solutions in the presence of cetyltrimethylammonium bromide (I) was studied by linear sweep voltammetry on fixed and vibrating platinum electrodes. The presence of I in low concentrations (below the critical micellar concentration) brings about aggregation of the luminol, which is manifested by an increase in the anodic peak height and its shift towards lower potentials. In micellar solutions the peak height decreases owing to the slower diffusion of the bulkier micelles, the shift to lower potentials being preserved. The light-voltage curves correspond with the voltammetric curves, exhibiting identical shifts of the peak potentials in dependence on the concentration of the surfactant.

The Investigation of Thin Protecting Layers on Roughened Galvanized Steel Surfaces Produced by Different Coating Methods

2008 ◽  
Vol 589 ◽  
pp. 433-438 ◽  
Author(s):  
Péter Németh ◽  
Ágnes Csanády ◽  
Katalin Papp ◽  
Anna C. Pintér ◽  
László Szabó ◽  
...  
Keyword(s):  
Thickness Distribution ◽  
Thin Layers ◽  
Galvanized Steel ◽  
Photoemission Spectroscopy ◽  
Force Microscopy ◽  
Atomic Force ◽  
Coating Methods ◽  
Chemical States ◽  
Steel Surfaces ◽  
Thickness Variations

Protective, chromate substitute thin layers on roughened galvanized surfaces produced at OCAS (Arcelor, Belgium) were characterized and compared using Scanning Electron Microscopy (SEM+EDS), Atomic Force Microscopy (AFM), Nanoindentation and X-ray Photoemission Spectroscopy (XPS). EDX maps, line scans and point analyses obtained at various places of the surfaces have shown differences between the CVD and silane nanolayers in the matter of thickness distribution and composition. At cross-section specimens the thickness of the layers could be shown. The hardness differences caused by layer thickness variations are hard to follow by nanoindentation as the penetration depth of the indenter is much larger than the thickness of the coatings. XPS measurements can distinguish between the chemical states of silicon in CVD and silane coatings.

Effect of Molarity on Structural and Optical Properties of Chemically Deposited Nanocrystalline PbS Thin Film

2017 ◽  
Vol 74 ◽  
pp. 22-35 ◽  
Author(s):  
Manash Pratim Sarma ◽  
G. Wary
Keyword(s):  
Thin Films ◽  
Ph Value ◽  
Bath Temperature ◽  
Ion Source ◽  
Complexing Agent ◽  
X Ray ◽  
Force Microscopy ◽  
Nanocrystallite Size ◽  
Atomic Force ◽  
Cbd Method

Thin films of PbS were deposited by chemical bath deposition (CBD) method under various molarities using lead acetate as Pb2+ ion source, thiourea as S2- ion source and ammonia as complexing agent at a fixed pH value of 9 under bath temperature of 333 K. Four different molarities of PbS thin films were prepared. The as-prepared films were characterized by using X-ray diffraction (XRD), X-ray fluorescence (XRF), EDX, field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). Parameters like crystallite size, lattice constant, microstrain, dislocation density were calculated. Optical constants such as extinction coefficient, absorption coefficient were measured from absorption spectra. Studies show that average nanocrystallite size increases from14.2 nm to 18.1 nm as the molarity of the film increases. Optical studies reveal the decrease of band gap from 1.75 eV to 1.44 eV with increasing molarity of the film indicating higher electrical conductivity of the films.

scholarly journals Pt-Rh Alloy Catalysts for Hydrogen Generation developed by Direct Current/Pulse Method

2021 ◽  
Author(s):  
praveen bm ◽  
Bharath K Devendra ◽  
Tripathi V S ◽  
Nagaraju DH ◽  
Nayana K O
Keyword(s):  
Direct Current ◽  
Hydrogen Generation ◽  
Linear Sweep Voltammetry ◽  
Pulse Method ◽  
Force Microscopy ◽  
Highly Active ◽  
Atomic Force ◽  
Alloy Catalysts ◽  
Alloy Catalyst ◽  
Pc Method

Abstract Highly active Pt-Rh alloy catalyst coatings were developed by direct current (DC) and pulse current (PC) electrodeposition method for efficient hydrogen evolution reaction (HER) catalysts. The coatings were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) linear sweep voltammetry (LSV) studies. Pt-Rh alloy catalyst coatings showed almost similar behavior as pure platinum metal.The Pt-Rh coating were obtained by PC method showed low over potentialfor HER. Very low slope of 41.2 mV/dec is obtained represents the Volmer-Tafel mechanistic path way for HER process. Chronopotentiometry was conducted and amount of hydrogen collected during these experiments was 24 ml for PC method 75% duty cycle sample.

Electroplated CuO Thin Films from High Alkaline Solutions

2011 ◽  
Vol 15 (1) ◽  
pp. 49-55
Author(s):  
V. Dhanasekaran ◽  
T. Mahalingam ◽  
S. Rajendran ◽  
Jin Koo Rhee ◽  
D. Eapen
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Film Thickness ◽  
Structural Characteristics ◽  
Band Gap Energy ◽  
Alkaline Solutions ◽  
X Ray Diffraction ◽  
Force Microscopy ◽  
Microstructural Parameters ◽  
Atomic Force

CuO thin films were coated on ITO substrates by an electrodeposition route through potentiostatic mode. The electrodeposited CuO thin films were characterized and the role of copper sulphate concentration on the structural, morphological and optical properties of the CuO films was studied. Film thickness was measured by a stylus profilometer and found to be in the range between 800 and 1400 nm. The structural characteristics studies were carried out using X-ray diffraction and found that the films are polycrystalline in nature with a cubic structure. The preferential orientation of CuO thin films is found to be along (111) plane. The estimated microstructural parameters revealed that the crystallite size increases whereas the number of crystallites per unit area decreases with increasing film thickness. SEM studies show that the grain sizes of CuO thin films vary between 100 and 150 nm and also morphologies revealed that the electrodeposited CuO exhibits uniformity in size and shape. The surface roughness is estimated 15 nm of the CuO film were studied by atomic force microscopy. Optical properties of the films were analyzed from absorption and transmittance studies. The optical band gap energy was determined to be 1.5 eV from absorption coefficient. The variation of refractive index (n), extinction coefficient (k), with wavelength was studied and the results are discussed.

scholarly journals Membranes for Cation Transport Based on Dendronized Poly(Epichlorohydrin-Co-Ethylene Oxide). Part 2: Membrane Characterization and Transport Properties

Polymers ◽  
2021 ◽  
Vol 13 (22) ◽  
pp. 3915
Author(s):  
Alireza Zare ◽  
Xavier Montané ◽  
José Antonio Reina ◽  
Marta Giamberini
Keyword(s):  
Transport Properties ◽  
Liquid Crystalline ◽  
Linear Sweep Voltammetry ◽  
Cation Transport ◽  
Side Chain ◽  
Force Microscopy ◽  
Atomic Force ◽  
Membrane Characterization ◽  
Alkaline Cations

In this paper, we report on the preparation and characterization of membranes out of two side-chain liquid crystalline copolymers, dendronized at two different extents (20 and 40%, CP20 and CP40, respectively). The membranes were characterized by atomic force microscopy (AFM), field-emission scanning electron microscopy (FESEM), contact angle (CA) analysis, and water uptake. Moreover, transport properties were studied by methanol and proton conductivity experiment and by linear sweep voltammetry (LSV). For the sake of comparison, the behavior of the grafted copolymers was compared with the unmodified copolyether CP0 and with Nafion 117. Results demonstrated that in CP20 and CP40, cation transport depends on the presence of defined cationic channels, not affected by water presence; the comparison between LSV experiments performed with different alkaline cations suggests that CP40 possesses channels with larger diameters and better-defined inner structures.

scholarly journals Effect of Stabilizer on Gold Leaching with Thiourea in Alkaline Solutions

Minerals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 89
Author(s):  
Wenjuan Li ◽  
He Shang ◽  
He Zhou ◽  
Yongsheng Song ◽  
Shuilin Zheng ◽  
...  
Keyword(s):  
Activation Energy ◽  
Sodium Silicate ◽  
Cyclic Voltammetry Curve ◽  
Sodium Sulfite ◽  
Alkaline Solutions ◽  
Gold Leaching ◽  
Force Microscopy ◽  
Atomic Force ◽  
Alkaline Thiourea ◽  
The Stability

The present work investigated the comparison of the effects of Na2SO3 and Na2SiO3 on thiourea stabilization, and a systematic study was undertaken to establish the effects of these stabilizers on the stability of alkaline thiourea, both qualitatively and quantitatively. The effects of these stabilizers on the activation energy of alkaline thiourea gold leaching was also studied. The results showed that sodium silicate was more suitable as a stabilizer in this system than sodium sulfite because the peak current of gold dissolution with sodium sulfite was higher than that with sodium silicate, but the inhibition of thiourea decomposition by the former was less obvious than that of sodium silicate in the cyclic voltammetry curve. The quartz crystal microbalance results showed that the quality decreased to about 100 ng cm2 in the presence of a stabilizer, while it increased to 300 ng cm2 in the absence of the stabilizer. It is inferred that gold can be dissolved by alkaline thiourea in the presence of a stabilizer, while it cannot without a stabilizer because of the decomposition of thiourea. This assumption was confirmed by atomic force microscopy measurements. The surface activation energy of Au dissolution decreased from 183.76 to 98.07 kJ/moL with the addition of sodium silicate, indicating that Au dissolution was promoted with the chemical.

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