Titanium Dioxide (TiO2) Films by Anodic Oxidation in Phosphoric Acid

2012 ◽  
Vol 545 ◽  
pp. 223-228 ◽  
Author(s):  
Hasan Zuhudi Abdullah ◽  
Charles Christopher Sorrell
Keyword(s):  
Phosphoric Acid ◽  
Anodic Oxidation ◽  
Current Density ◽  
Room Temperature ◽  
Single Phase ◽  
Microstructural Characteristics ◽  
Laser Raman ◽  
Acid Bath ◽  
Current Densities ◽  
Electrical Bias

Anodic oxidation is an electrochemical method for the production of an oxide film on a metallic substrate. It involves the application of an electrical bias at relatively low currents while the substrate is immersed in an acid bath. The films can be very dense and stable, with a variety of microstructural characteristics. In the present work, films of the anatase polymorph of TiO2were formed on high-purity Ti foil (50 μm thickness) using phosphoric acid (0.3 M H3PO4). The conditions of oxidation involved the application of potentials (5 to 350 V) and current densities (5 to 60 mA.cm-2) for 10 min at room temperature. The films were characterised using a digital photography, laser Raman microspectroscopy, and field emission scanning electron microscopy. The thicknesses of the oxide films on Ti were measured using a thin film analyser based on optical spectroscopy principles. The colours, thicknesses, and microstructures of the films depended strongly on the applied voltage and current density. At bias more than 15 V, single-phase anatase was observed to form on Ti at low (5 mA.cm-2) and higher (up to 60 mA.cm-2) current density.

scholarly journals The structure of electro-deposited chromium

1943 ◽  
Vol 181 (987) ◽  
pp. 331-344 ◽  
Keyword(s):  
Residual Stress ◽  
Current Density ◽  
Preferred Orientation ◽  
Effect Of Temperature ◽  
X Rays ◽  
Visual Appearance ◽  
Acid Bath ◽  
Current Densities ◽  
Structure Orientation ◽  
Number Of Particles

The visual appearance and crystal structure orientation of electro-deposited chromium have been studied for deposits prepared at current densities from 50 to 3000 amp./sq.ft., and temperatures from 12 to 85° C, using a standard chromic acid bath containing 250 g. CrO 3 per litre, and a ratio of CrO 3 to sulphate ion of 100:1. Some measurements were also made at 95° C. A diagram has been constructed showing the effect of temperature and current density on the appearance and crystal orientation of the deposit. The brightest deposits are characterized by a (111) preferred orientation, and no indication of any other fibre structure has been obtained. If the current densities are plotted against the logarithms of the temperature at which the brightest deposits are formed, a linear relation is obtained. With increasing variation of the conditions of deposition (temperature or current density) from those characteristic of the brightest deposits, two effects are produced: ( a ) an increasing number of particles of purely random orientation are present in the deposit, and ( b ) the perfection of alignment of the particles of preferred orientation becomes less. The residual stress present in electro-deposited chromium has been measured by the method of Stoney. If at a given current density the temperature of deposition is increased, the residual stress, which is contractile at first, rises sharply and may reach values as high as 110 tons/sq.in. This rise continues until the temperature is reached at which particles of preferred orientation first make their appearance. With further rise of temperature, the residual stress falls until it is practically zero at the temperature at which the brightest deposits are formed, and then rises again at higher temperatures. The hardness of electro-deposited chromium has been measured for deposits prepared over the range 25-90° C at current densities of 500, 1000, and 1750 amp./sq.ft. The deposits of completely preferred orientation have the greatest hardness, and this maximum hardness is the same for all three current densities, although the temperatures of deposition at which the maxima occur are of course different. The temperature/hardness curves at different current densities can be almost exactly superposed by a mere shifting o f the temperature scale, and it appears that the hardness is a property depending solely on the structure as revealed by X -rays, and is independent of the exact conditions under which the structure of a given type is produced.

scholarly journals Effect of the Electrolyte Temperature and the Current Density on a Layer Microhardness Generated by the Anodic Aluminium Oxidation

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Emil Spišák ◽  
Miroslav Gombár ◽  
Ján Kmec ◽  
Alena Vagaská ◽  
Erika Fechová ◽  
...  
Keyword(s):  
Growth Rate ◽  
Chemical Composition ◽  
Anodic Oxidation ◽  
Current Density ◽  
Vickers Microhardness ◽  
Surface Current ◽  
Oxidation Time ◽  
Electrolyte Temperature ◽  
Current Densities ◽  
Oxalic Acids

The paper investigates the influence of the chemical composition and temperature of electrolyte, the oxidation time, voltage, and the current density on Vickers microhardness of aluminium oxide layers, at the same time. The layers were generated in the electrolytes with different concentrations of sulphuric and oxalic acids and surface current densities 1 A·dm−2, 3 A·dm−2, and 5 A·dm−2. The electrolyte temperature varied from −1.78°C to 45.78°C. The results have showed that while increasing the electrolyte temperature at the current density of 1 A·dm−2, the increase in the layer microhardness values is approximately by 66%. While simultaneously increasing the molar concentration of H2SO4in the electrolyte, the growth rate of the microhardness value decreases. At the current density of 3 A·dm−2, by increasing the electrolyte temperature, a reduction in the microhardness of the generated layer occurs with the anodic oxidation time less than 25 min. The electrolyte temperature is not significant with the changing values of the layer microhardness at voltages less than 10.5 V.

Variation of algal viability during electrochemical disinfection using Ti/RuO2 electrodes

2011 ◽  
Vol 64 (1) ◽  
pp. 162-170 ◽  
Author(s):  
Wenyan Liang ◽  
Ke Wang ◽  
Li Chen ◽  
Lingling Ruan ◽  
Lili Sui
Keyword(s):  
Microcystis Aeruginosa ◽  
Current Density ◽  
Room Temperature ◽  
Neutral Red ◽  
Operating Conditions ◽  
Oh Radicals ◽  
Electrochemical Disinfection ◽  
Blue Green Algae ◽  
Current Densities ◽  
Inactivation Effect

This paper studied the influence of the operating conditions, e.g. current density, electrolyte and exposure time, on the variation of the algal viability during electrochemical disinfection processes. An electrochemical tube employing Ti/RuO2 as anodes was constructed for inactivation of cyanobacteria (often called blue-green algae) Microcystis aeruginosa. Viability of algal cells was determined by 2,3,5-triphenyl-tetrazoliumchloride (TTC) dehydrogenase activity assay and neutral red (NR) staining assay. Algal suspensions with cell density of 5–7 × 109 L−1 were exposed to current densities from 1 to 8 mA cm−2 at room temperature (25–30 °C) for 30 min. The results showed that the cell viability decreased obviously with the increase of current density. After exposure to 4 mA cm−2 for more than 7 min, Microcystis aeruginosa didn't have the ability to resume growth. Comparative disinfection tests with different electrolytes were conducted, including chlorides, sulfates, nitrates and phosphates. Microcystis aeruginosa appeared to be sensitive to electro-generated chlorine oxidants. The inactivation effect was also demonstrated to occur in chlorine-free electrolytes. However, decrease of the inactivation effect by adding ascorbic acid as an oxidant scavenger indicated that the reactive oxygen species, especially •OH radicals, played an important role for chlorine-free electrolytes.

scholarly journals Effect of Current Density on Thermodynamic Properties of Nanocrystalline Palladium Capped Samarium Hydride Thin Film Switchable Mirrors

2007 ◽  
Vol 2007 ◽  
pp. 1-7 ◽  
Author(s):  
Pushpendra Kumar ◽  
L. K. Malhotra
Keyword(s):  
Thermodynamic Properties ◽  
Current Density ◽  
Diffusion Coefficients ◽  
Room Temperature ◽  
Hexagonal Phase ◽  
Ex Situ ◽  
Applied Current ◽  
Applied Current Density ◽  
Current Densities ◽  
Fcc Phase

A 55 nm samarium film capped with a 10 nm palladium overlayer switched from a metallic reflecting to a semiconducting, transparent in visible state during ex-situ hydrogen loading via electrochemical means in 1 M KOH electrolytic aqueous solution at room temperature. The switching between metal to semiconductor was accompanied by measurement of transmittance during hydrogen loading/unloading. The effect of current density on switching and thermodynamic properties was studied between dihydride state (FCC phase) and trihydride state (hexagonal phase). From the plateau of partial pressure of hydrogen atx=2.6, enthalpy of formation was calculated at different current densities. The diffusion coefficients and switching kinetics are shown to depend on applied current density.

Facet Topography and Dislocation Structure as a Possible Source for Electrical Heterogeneity in [001] TILT Bicrystals of YBa2Cu3O7-δ

1996 ◽  
Vol 54 ◽  
pp. 338-339
Author(s):  
I-Fei Tsu ◽  
D.L. Kaiser ◽  
S.E. Babcock
Keyword(s):  
Grain Boundary ◽  
Critical Current Density ◽  
Critical Current ◽  
Current Density ◽  
Electromagnetic Properties ◽  
Length Scale ◽  
Density Values ◽  
Current Densities ◽  
Applied Fields ◽  
A Current

A current theme in the study of the critical current density behavior of YBa2Cu3O7-δ (YBCO) grain boundaries is that their electromagnetic properties are heterogeneous on various length scales ranging from 10s of microns to ˜ 1 Å. Recently, combined electromagnetic and TEM studies on four flux-grown bicrystals have demonstrated a direct correlation between the length scale of the boundaries’ saw-tooth facet configurations and the apparent length scale of the electrical heterogeneity. In that work, enhanced critical current densities are observed at applied fields where the facet period is commensurate with the spacing of the Abrikosov flux vortices which must be pinned if higher critical current density values are recorded. To understand the microstructural origin of the flux pinning, the grain boundary topography and grain boundary dislocation (GBD) network structure of [001] tilt YBCO bicrystals were studied by TEM and HRTEM.

Electron-beam damage of oxides at high current densities

1989 ◽  
Vol 47 ◽  
pp. 634-635
Author(s):  
M. R. McCartney ◽  
J. K. Weiss ◽  
David J. Smith
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Current Density ◽  
Transition Metal Oxides ◽  
Time Resolved ◽  
Rapid Acquisition ◽  
Resolution Electron ◽  
Current Densities ◽  
Electron Stimulated Desorption ◽  
Channel Analyzer

It is well-known that electron-beam irradiation within the electron microscope can induce a variety of surface reactions. In the particular case of maximally-valent transition-metal oxides (TMO), which are susceptible to electron-stimulated desorption (ESD) of oxygen, it is apparent that the final reduced product depends, amongst other things, upon the ionicity of the original oxide, the energy and current density of the incident electrons, and the residual microscope vacuum. For example, when TMO are irradiated in a high-resolution electron microscope (HREM) at current densities of 5-50 A/cm2, epitaxial layers of the monoxide phase are found. In contrast, when these oxides are exposed to the extreme current density probe of an EM equipped with a field emission gun (FEG), the irradiated area has been reported to develop either holes or regions almost completely depleted of oxygen. ’ In this paper, we describe the responses of three TMO (WO3, V2O5 and TiO2) when irradiated by the focussed probe of a Philips 400ST FEG TEM, also equipped with a Gatan 666 Parallel Electron Energy Loss Spectrometer (P-EELS). The multi-channel analyzer of the spectrometer was modified to take advantage of the extremely rapid acquisition capabilities of the P-EELS to obtain time-resolved spectra of the oxides during the irradiation period. After irradiation, the specimens were immediately removed to a JEM-4000EX HREM for imaging of the damaged regions.

scholarly journals Effect of Plating Current Density on the Ball-On-Disc Wear of Sn-Plated Ni Coatings on Cu Foils

Coatings ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 56
Author(s):  
Ashutosh Sharma ◽  
Byungmin Ahn
Keyword(s):  
Current Density ◽  
Wear Loss ◽  
Wear Properties ◽  
Friction Behavior ◽  
Track Geometry ◽  
Cu Substrates ◽  
Current Densities ◽  
The Impact ◽  
Sliding Distance ◽  
Ball On Disc

Metallic and alloyed coatings are used widely in several decorative and technology-based applications. In this work, we selected Sn coatings plated on Cu substrates for joining applications. We employed two different plating baths for the fabrication of Sn and Ni coatings: acidic stannous sulfate for Sn and Watts bath for Ni layer. The plating current densities were varied from 100–500 mA/cm2. Further, the wear and friction behavior of the coatings were studied using a ball-on-disc apparatus under dry sliding conditions. The impact of current density was studied on the morphology, wear, and coefficient of friction (COF) of the resultant coatings. The wear experiments were done at various loads from 2–10 N. The sliding distance was fixed to 7 m. The wear loss was quantified in terms of the volume of the track geometry (width and depth of the tracks). The results indicate that current density has an important role in tailoring the composition and morphology of coatings, which affects the wear properties. At higher loads (8–10 N), Sn coatings on Ni/Cu had higher volume loss with a stable COF due to a mixed adhesive and oxidative type of wear mechanism.

Strengthening Mechanism of TiB2-TiC Complex Phases Coated Electrode

2012 ◽  
Vol 433-440 ◽  
pp. 251-255 ◽  
Author(s):  
Ping Luo ◽  
Shi Jie Dong ◽  
Zhang Qiang Mei ◽  
Zhi Xiong Xie
Keyword(s):  
Failure Mechanism ◽  
Current Density ◽  
Spot Welding ◽  
Single Phase ◽  
Welding Process ◽  
Strengthening Mechanism ◽  
Galvanized Steel ◽  
Steel Weld ◽  
Galvanized Steels ◽  
Coated Electrode

TiB2-TiC complex phases coating deposited onto the surface of electrodes by electro-spark deposition (ESD) in order to prolong the life of single phase coated electrode (TiB2 or TiC) during resistance welding of galvanized steels. The microstructures and TiB2-TiC complex phases coatings were characterized by SEM and XRD. The results indicate that life of TiB2-TiC complex phases coated electrode is prolonged significantly than life of single-phase coated electrode （TiB2 or TiC ）, failure mechanism of TiB2-TiC complex phases coated electrode is mainly wear to cause diameter increase on electrode tip, which results in lower current density during welding process, and then nugget size cannot satisfy the requirement of resistance spot welding. The failure mechanism of TiB2-TiC complex phases coated electrode is obviously different from uncoated electrode, the failure mechanism of uncoated electrode is wear and alloying between electrode tip surface and molten Zn on galvanized steel weld surface.

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