Search results for "dynamic condition"
showing 10 items of 16 documents
Photoelectrochemical characterization of anatase-rutile mixed TiO2 nanosponges
2016
This work studies the influence of using hydrodynamic conditions during anodization on the morphology and electrochemical properties of anatase/rutile mixed TiO2 nanotubes (Reynolds number, Re = 0) and nanosponges (Re > 0). To this purpose different techniques were used, such as: microscopy techniques (Field-Emission Scanning Electron Microscope, FE-SEM, and Confocal Laser-Raman Spectroscopy), Electrochemical Impedance Spectroscopy (EIS), Mott Schottky (MS) analysis and photoelectrochemical water splitting tests. This investigation demonstrates that the morphology of TiO2 nanostructures may be greatly affected due to the hydrodynamic conditions and it can be adjusted in order to increase th…
Effect of Reynolds number and lithium cation insertion on titanium anodization
2016
This work studies the influence of using hydrodynamic conditions (Reynolds number, Re = 0 to Re = 600) during Ti anodization and Li+ intercalation on anatase TiO2 nanotubes. The synthesized photocatalysts were characterized by using Field Emission Scanning Electron Microscope (FE-SEM), Raman Confocal Laser Microscopy, Electrochemical Impedance Spectroscopy (EIS), Mott-Schottky analysis (M-S), photoelectrochemical hydrogen production and resistance to photocorrosion tests. The obtained results showed that the conductivity of the NTs increases with Li+ intercalation and Re. The latter is due to the fact that the hydrodynamic conditions eliminate part of the initiation layer formed over the tu…
Influence of annealing atmosphere on photoelectrochemical response of TiO2 nanotubes anodized under controlled hydrodynamic conditions
2021
[EN] The influence of three annealing atmospheres (air, nitrogen and argon) and the use of controlled hydrodynamic conditions (from 0 to 5000 rpm) on morphological, structural, chemical and photoelectrochemical properties of TiO2 nanotubes have been evaluated. For this purpose, different characterization techniques have been used: Field Emission Scanning Electron Microscopy, Raman Confocal Laser Spectroscopy, X-Ray Diffraction, X-Ray Photoelectron Spectroscopy, Incident Photon-to-electron Conversion Efficiency measurements, ultraviolet-visible absorption spectra, Mott-Schottky analysis and photoelectrochemical water splitting tests. According to the results, it can be concluded that both hy…
Keep the faith in banking : New evidence for the effects of negative interest rates based on the case of Finnish cooperative banks
2021
This paper analyses the profitability of Finnish cooperative banks during the period of negative nominal interest rates. Contrary to expectations, the continuous decline in money market interest rates between 2009 and 2014, and the following negative rate era, did not have adverse effects on the profitability of banks at the beginning of negative interest rate period. Based on especially using a risk-adjusted measure for bank profitability, these results contrast with previous findings. In our findings, the increasing wholesale funding (WSF) ratio seems to be an important factor. However, after 2017 the banks have not been able to improve especially their risk-adjusted profitability so stro…
Bitcoin and stock market indices: analysis of volatility’s clusters during the bitcoin bubble based on the dynamic conditional correlation model
2019
The market of virtual currencies, called cryptocurrency, has grown immensely since 2008 in terms of market capitalisation and the numbers of new currencies. Bitcoin is one of the most famous cryptocurrency with an estimated market capitalisation of nearly $ 69 billion. The fact that Bitcoin prices have fallen about 70% from their peak value and most indices were down double-digit year to date (2018) with a high daily volatility create the appearance that there has to be a correlation. The purpose of this paper is to investigate the contagion effect between Bitcoin prices and the leading American, European and Asian equity markets using the dynamic conditional correlation (DCC) model propose…
Timescale-dependent stock market comovement: BRICs vs. developed markets
2014
This paper examines the differences in the asset return comovement of the BRIC countries (Brazil, Russia, India and China), the other developed economies in their regions (Canada, Hong Kong and Australia) and the major industrialized economies (the U.K., Germany and Japan) with respect to the U.S. for different return periods. The novelty of the paper is that the stock return indices are decomposed to several timescales using wavelet analysis and that the results are further used as inputs for the dynamic conditional correlation (DCC) framework, which is used as a measure of comovement. The results propose that the level of stock market comovement depends on regional aspects, the level of d…
ZnO/ZnS heterostructures for hydrogen production by photoelectrochemical water splitting
2016
This work studies the photoelectrochemical behavior of novel ZnO/ZnS heterostructures obtained by means of anodization in water and glycerol/water/NH4F electrolytes with different Na2S additions under controlled hydrodynamic conditions. For this purpose different techniques such as Field Emission Scanning Electronic Microscopy (FE-SEM) with EDX, Raman spectroscopy and photoelectrochemical water splitting tests under standard AM 1.5 conditions have been carried out. The obtained results showed that the hydrodynamic conditions promoted an ordered nanotubular morphology which facilitates electron-hole separation and consequently, the photoelectrochemical activity for water splitting is enhance…
Novel tree-like WO3 nanoplatelets with very high surface area synthesized by anodization under controlled hydrodynamic conditions
2016
In the present work, a new WO3 nanostructure has been obtained by anodization in a H2SO4/NaF electrolyte under controlled hydrodynamic conditions using a Rotating Disk Electrode (RDE) configuration. Anodized samples were analyzed by means of Field Emission Scanning Electronic Microscopy (FESEM), Confocal Raman Microscopy and photoelectrochemical measurements. The new nanostructure, which consists of nanoplatelets clusters growing in a tree-like manner, presents a very high surface area exposed to the electrolyte, leading to an outstanding enhancement of its photoelectrochemical activity. Obtained results show that the size of nanostructures and the percentage of electrode surface covered by…
Formation of ZnO nanowires by anodization under hydrodynamic conditions for photoelectrochemical water splitting
2020
[EN] The present work studies the influence of hydrodynamic conditions (from 0 to 5000 rpm) during Zn anodization process on the morphology, structure and photoelectrocatalytic behavior of ZnO nanostructures. For this purpose, analysis with Confocal Laser-Raman Spectroscopy, Field Emission Scanning Electron Microscope (FE-SEM) and photoelectrochemical water splitting tests were performed. This investigation reveals that hydrodynamic conditions during anodization promoted the formation of ordered ZnO nanowires along the surface that greatly enhance its stability and increases the photocurrent density response for water splitting in a 159% at the 5000 rpm electrode rotation speed.
Controlled hydrodynamic conditions on the formation of iron oxide nanostructures synthesized by electrochemical anodization: Effect of the electrode …
2017
[EN] Iron oxide nanostructures are of particular interest because they can be used as photocatalysts in water splitting due to their advantageous properties. Electrochemical anodization is one of the best techniques to synthesize nanostructures directly on the metal substrate (direct back contact). In the present study, a novel methodology consisting of the anodization of iron under hydrodynamic conditions is carried out in order to obtain mainly hematite (alpha-Fe2O3) nanostructures to be used as photocatalysts for photoelectrochemical water splitting applications. Different rotation speeds were studied with the aim of evaluating the obtained nanostructures and determining the most attract…