scholarly journals Ni-Doped Titanium Dioxide Films Obtained by Plasma Electrolytic Oxidation in Refrigerated Electrolytes

Surfaces ◽  
2020 ◽  
Vol 3 (2) ◽  
pp. 168-181 ◽  
Author(s):  
Hamed Arab ◽  
Gian Luca Chiarello ◽  
Elena Selli ◽  
Giacomo Bomboi ◽  
Alberto Calloni ◽  
...  
Keyword(s):  
Plasma Electrolytic Oxidation ◽  
Oxide Films ◽  
Optical Emission ◽  
Threshold Value ◽  
Pure Tio2 ◽  
Emission Spectrometry ◽  
Photoelectrochemical Activity ◽  
Xps Spectra ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

Porous crystalline Ni-doped TiO2 films were produced using DC plasma electrolytic oxidation in refrigerated H2SO4 aqueous solutions containing NiSO4. The crystalline phase structure consisted of a mixture of anatase and rutile, ranging from ~30 to ~80 wt % rutile. The oxide films obtained at low NiSO4 concentration showed the highest photocurrent values under monochromatic irradiation in the UV-vis range, outperforming pure TiO2. By increasing NiSO4 concentration above a threshold value, the photoelectrochemical activity of the films decreased below that of undoped TiO2. Similar results were obtained using cyclic voltammetry upon polychromatic UV-vis irradiation. Glow discharge optical emission spectrometry (GD-OES) analysis evidenced a sulfur signal peaking at the TiO2/Ti interface. XPS spectra revealed that oxidized Ni2+, S4+ and S6+ ions were included in the oxide films. In agreement with photocurrent measurements, photoluminescence (PL) spectra confirmed that less intense PL emission, i.e., a lower electron-hole recombination rate, was observed for Ni-doped samples, though overdoping was detrimental.

scholarly journals Characterisation of porous coatings formed on titanium under AC plasma electrolytic oxidation

2018 ◽  
Vol 178 ◽  
pp. 03008 ◽  
Author(s):  
Krzysztof Rokosz ◽  
Tadeusz Hryniewicz ◽  
Sofia Gaiaschi ◽  
Patrick Chapon ◽  
Steinar Raaen ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Plasma Electrolytic Oxidation ◽  
Optical Emission Spectroscopy ◽  
Optical Emission ◽  
Xps Spectra ◽  
Porous Coatings ◽  
X Ray ◽  
Electrolytic Oxidation ◽  
Voltage Signal ◽  
Plasma Electrolytic

The Plasma Electrolytic Oxidation (PEO) process may be used to fabricate porous coatings on titanium. The ranges of voltages used in case of these plasma treatments are different. It has been found that for DC PEO processing the voltage must be higher than that in the case of AC PEO treatment. In addition, the shape and frequency of the voltage signal have also an influence. In the paper scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and glow discharge optical emission spectroscopy (GDEOS) were used to characterise obtained coatings. It was found that it is possible to obtain the porous coatings enriched with phosphorus and copper by use of AC-PEO at only 200 Vpp, while increasing the PEO voltage results in non-porous and cracked coatings. Based on GDEOS for 200 Vpp three sublayers were used, with ranges of 0-400, and 400-2400, and 2400-3600 seconds of sputtering time for first, and second, and transition sublayers respectively. XPS spectra for sample processed at 200 Vpp indicate in top 10 nm layer presence of titanium as Ti4+ and phosphorous as phosphates (most likely PO43–, HPO42–, H2PO4–, P2O73–).

scholarly journals Exploiting Direct Current Plasma Electrolytic Oxidation to Boost Photoelectrocatalysis

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 325 ◽  
Author(s):  
Silvia Franz ◽  
Hamed Arab ◽  
Andrea Lucotti ◽  
Chiara Castiglioni ◽  
Antonello Vicenzo ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Plasma Electrolytic Oxidation ◽  
Optical Emission ◽  
Tio2 Films ◽  
Photoelectrochemical Activity ◽  
Cell Potential ◽  
X Ray ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic ◽  
Normal Trend

In this study, we report an investigation of the photoelectrochemical activity of TiO2 films formed by DC plasma electrolytic oxidation (PEO) at a variable potential in a sulfuric acid electrolyte at 0 and 25 °C. The surface morphology was mainly determined by the oxide-forming potential. X-Ray Diffraction and Raman analyses showed that the relative amount of the anatase and rutile phases varied from 100% anatase at low potential (110–130 V) to 100% rutile at high potential (180–200 V), while mixed-phase oxide films formed at intermediate potential. Correspondingly, the band gap of the TiO2 films decreased from about 3.20 eV (pure anatase) to 2.94 eV (pure rutile) and was red-shifted about 0.1 eV by reducing the electrolyte temperature from 25 °C to 0 °C. Glow-Discharge Optical Emission Spectroscopy (GD-OES) and X-ray Photoelectron Spectroscopy (XPS) analyses evidenced S-containing species located preferentially close to the TiO2/Ti interface. The photoelectrochemical activity was assessed by measuring the incident photon-to-current efficiency (IPCE) under Ultraviolet C (UV-C) irradiation, which showed a non-gaussian normal trend as a function of the PEO cell potential, with maximum values exceeding 80%. Photoelectrocatalytic activity was assessed by decolorization of model solutions containing methylene blue. Photoanodes having higher IPCE values showed faster decolorization kinetics.

scholarly journals Plasma electrolytic oxidation of metals

2013 ◽  
Vol 78 (5) ◽  
pp. 713-716 ◽  
Author(s):  
Stevan Stojadinovic
Keyword(s):  
Photoelectron Spectroscopy ◽  
Plasma Electrolytic Oxidation ◽  
Dielectric Breakdown ◽  
Optical Emission ◽  
Active Surface ◽  
Spatial Density ◽  
Oxide Coatings ◽  
X Ray ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

In this lecture results of the investigation of plasma electrolytic oxidation (PEO) process on some metals (aluminum, titanium, tantalum, magnesium, and zirconium) were presented. Whole process involves anodizing metals above the dielectric breakdown voltage where numerous micro-discharges are generated continuously over the coating surface. For the characterization of PEO process optical emission spectroscopy and real-time imaging were used. These investigations enabled the determination of electron temperature, electron number density, spatial density of micro-discharges, the active surface covered by micro-discharges, and dimensional distribution of micro-discharges at various stages of PEO process. Special attention was focused on the results of the study of the morphology, chemical, and phase composition of oxide layers obtained by PEO process on aluminum, tantalum, and titanium in electrolytes containing tungsten. Physicochemical methodes: atomic force microscopy (AFM), scanning electron microscopy (SEM-EDS), x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy served as tools for examining obtained oxide coatings. Also, the application of the obtained oxide coatings, especially the application of TiO2/WO3 coatings in photocatalysis, were discussed.

scholarly journals Discharge Behavior and Dielectric Breakdown of Oxide Films during Single Pulse Anodizing of Aluminum Micro-Electrodes

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2286 ◽  
Author(s):  
Kai Yang ◽  
Haisong Huang ◽  
Jiadui Chen ◽  
Biao Cao
Keyword(s):  
Plasma Electrolytic Oxidation ◽  
Dielectric Breakdown ◽  
Arc Discharge ◽  
Oxide Films ◽  
Single Pulse ◽  
Applied Pulse ◽  
Electrolytic Oxidation ◽  
Capacitive Effect ◽  
Discharge Behavior ◽  
Plasma Electrolytic

Micro-arc discharge events and dielectric breakdown of oxide films play an important role in the formation process of plasma electrolytic oxidation coating. Single pulse anodization of micro-electrodes was employed to study the discharge behavior and dielectric breakdown of oxide films deposited on aluminum in an alkaline silicate electrolyte. Voltage and current waveforms of applied pulses were measured and surface morphology of micro-electrodes was characterized from images obtained using scanning electron microscope (SEM). A feasible identification method for the critical breakdown voltage of oxide film was introduced. Different current transients of voltage pulses were obtained, depending on applied pulse voltage and duration. In addition, the active capacitive effect and complex non-linear nature of plasma electrolytic oxidation process is confirmed using dynamic electrical characteristic curves. A good correlation between the pulse parameters and shape of discharge channels was observed. Circular opened pores were found to close with increasing potential and pulse width. Finally, the characteristic parameters of a single discharge event were estimated.

Influence Characteristics of Al$_2$O$_3$ Oxide Films Grown by Using Plasma Electrolytic Oxidation with Electrolyte Containing Si and P

2013 ◽  
Vol 63 (11) ◽  
pp. 1296-1300
Author(s):  
K. S. MIN ◽  
J. T. KIM ◽  
S. S. LEE ◽  
D. CHA ◽  
S. H. YOON ◽  
...  
Keyword(s):  
Plasma Electrolytic Oxidation ◽  
Oxide Films ◽  
Electrolytic Oxidation ◽  
Plasma Electrolytic

Study on coating growth characteristics during the electrolytic oxidation of a magnesium–lithium alloy by optical emission spectroscopy analysis

RSC Advances ◽  
2015 ◽  
Vol 5 (84) ◽  
pp. 68806-68814 ◽  
Author(s):  
Zhongping Yao ◽  
Qixing Xia ◽  
Han Wei ◽  
Dongqi Li ◽  
Qiu Sun ◽  
...  
Keyword(s):  
Emission Spectroscopy ◽  
Plasma Electrolytic Oxidation ◽  
Optical Emission Spectroscopy ◽  
Optical Emission ◽  
Growth Characteristics ◽  
Spectroscopy Analysis ◽  
Electrolytic Oxidation ◽  
Composition Structure ◽  
Plasma Electrolytic ◽  
Peo Coatings

The aim of this study is to analyze the composition, structure and growth characteristics of plasma electrolytic oxidation (PEO) coatings through optical emission spectroscopy (OES).

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