scholarly journals Bubble Phenomena and Bubble Properties for Horizontal and Vertical Carbon Anode Surfaces in Cryolite Melt Applying a See-Through Cell

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 965
Author(s):  
Nikolina Stanic ◽  
Ana Maria Martinez ◽  
Kristian Etienne Einarsrud ◽  
Espen Sandnes
Keyword(s):  
Current Density ◽  
Bubble Diameter ◽  
Vertical Surface ◽  
Anode Surface ◽  
Large Bubble ◽  
Carbon Anode ◽  
Bubble Behavior ◽  
Coalescence Process ◽  
The Impact ◽  
Bubble Properties

Gas bubble behavior on a carbon anode in a cryolite melt has been studied using a see-through cell. The phenomena studied have been growth, coalescence, detachment, and wetting during electrolysis. The surface orientation affects bubble behavior. Therefore, two different anode designs were tested, an anode with a horizontal downward-facing surface and an anode with a vertical surface. At the horizontal anode, it was found that one large bubble was formed by the growth and coalescence of smaller bubbles, and finally, the large bubble detached periodically. For the vertical anode surface, the detaching bubbles were smaller, and most of them had been going through a coalescence process prior to detachment. The bubbles detached randomly. The coalescence process from the initiation to the final bubble shape at the vertical surface took about 0.016–0.024 s. The current density did not affect the duration of the coalescence. The bubble diameter was decreasing with increasing current density for both anodes. The values were in the range 7.2 to 5.7 mm for the horizontal anode in the current density interval 0.2–1.0 A cm−2 and in the range 3.7 mm to 1.5 mm for the vertical anode in the current density interval 0.1–2.0 A cm−2. The wetting contact angle for the vertical anode stayed more or less constant with an increase in current density, which likely can be attributed to the decreasing bubble size rather than an increase in polarization. In addition to the bubble phenomena described and bubble properties found, the impact of the results for better design of laboratory-scale studies is discussed.

scholarly journals Bubble Behavior on Horizontal and Vertical Carbon Anode Surfaces in Cryolite Melt Applying a See-Through Cell

2021 ◽  
Vol 3 (1) ◽  
pp. 8
Author(s):  
Nikolina Stanic ◽  
Espen Sandnes
Keyword(s):  
Current Density ◽  
Bubble Diameter ◽  
Vertical Surface ◽  
Visual Observation ◽  
Anode Surface ◽  
Large Bubble ◽  
Carbon Anode ◽  
Gas Bubble ◽  
Bubble Behavior

Gas bubble behavior on a carbon anode in a cryolite melt has been studied by visual observation using a see-through cell. The bubble phenomena studied have included growth, coalescence, and detachment during electrolysis. Two different anode designs were tested, an anode with a horizontal facing-downwards surface and an anode with a vertical surface. At the horizontal anode, it was found that one large bubble was formed by the growth and coalescence of smaller bubbles, and finally, the large bubble detached periodically. For the vertical anode surface, many smaller bubbles were formed and detached randomly. The bubble diameter was decreasing with increasing current density for both anodes.

Bubble Breakup Phenomena in a Venturi Tube

2007 ◽  
Author(s):  
A. Fujiwara ◽  
K. Okamoto ◽  
K. Hashiguchi ◽  
J. Peixinho ◽  
S. Takagi ◽  
...  
Keyword(s):  
High Speed ◽  
Bubbly Flow ◽  
Bubble Diameter ◽  
Pressure Change ◽  
Venturi Tube ◽  
Large Bubble ◽  
Breakup Process ◽  
Bubble Behavior ◽  
Bubble Breakup ◽  
Unstable Surface

Microbubble generation techniques have been proposed in former investigations. Here, we study an effective technique using air bubbly flow into a convergent-divergent nozzle (venturi tube). Pressure change in the diverging section induces bubble breakup. The purpose of this study is to clarify the effect of flow velocity at the throat with respect to the bubble breakup process and the bubble behavior in a venturi tube. Relations between generated bubble diameter and bubble breakup process are also described. Using high speed camera for detailed observation of bubble behavior, the following features were obtained. The velocity at the throat is expected to be of the order of the magnitude of the speed of sound of bubbly flow and a drastic bubble expansion and a shrink is induced. Besides, a liquid column appeared after the bubble flowing into the throat, and it grew up to stick to the bubble like in the form of a jet. This jet induced both unstable surface waves and the breakup of a single large bubble into several pieces.

scholarly journals Possible mechanisms of electrochemical processing activation ARMCO-iron

2018 ◽  
Vol 224 ◽  
pp. 01009
Author(s):  
Konstantin Rakhimyanov ◽  
Nadezhda Gaar ◽  
Aleksandr Loktionov
Keyword(s):  
Laser Radiation ◽  
Current Density ◽  
Armco Iron ◽  
Water Solution ◽  
Pulse Repetition Frequency ◽  
Anode Surface ◽  
Potential Range ◽  
Electrochemical Processing ◽  
Stationary Conditions ◽  
The Impact

The peculiarities of the electrochemical dissolving of ARMCO-iron in the 15% water solution of the sodium chloride during electrochemical dissolving the material and under the impact of laser radiation with a wavelength of 1.06 micrometer are considered. The investigations were conducted at a special installation by the potentiodynamic method. It is established that the material passivation at a potential range of 1.26 – 2.6 V is observed during electrochemical dissolving the material in the stationary conditions. The increase in the value of the current density by 45 times occurs in introducing the laser radiation in the process of anode dissolving and the passivation areas are not observed. The dissolution process takes place actively in the whole range of potentials from 0 to 5 V. It is shown that the main mechanisms of laser activation of electrochemical dissolving the materials is the depassivation of the anode surface and the acceleration of electrochemical reactions. It is determined that the maximum current density is achieved during laser-electrochemical processing of ARMCO-iron at a pulse repetition frequency of laser radiation equal to 3 kHz.

scholarly journals The Effect of Brush Plate Structure and Operating Parameters on the Energy Consumption of Electrolytic Cells

Processes ◽  
2021 ◽  
Vol 9 (12) ◽  
pp. 2186
Author(s):  
Shengxian Yi ◽  
Zhongjiong Yang ◽  
Liqiang Zhou ◽  
Gaofeng Zhang
Keyword(s):  
Energy Consumption ◽  
Density Distribution ◽  
Current Density ◽  
Current Density Distribution ◽  
Electrolytic Cell ◽  
Anode Surface ◽  
Operating Parameters ◽  
Additional Energy ◽  
Impact Time ◽  
The Impact

The nickel powder brush plate is a core component of the direct contact between the cleaning machine and cathode plate of an electrolyzer, and its movement in the electrolytic cell will affect the energy consumption of the electrolyzer. In order to optimize the structure of the brush plate, a cleaning trolley brush plate was taken as the research object, a mathematical model of its electrolyzer was established, and the reliability was subsequently verified. The influence of the structural and operating parameters of the brush plate on the energy consumption of the electrolytic cell was studied. The research results show that additional energy consumption is the lowest in the process of cleaning a return grooved brush plate. Brush plates with a large slotting area have less impact on the energy consumption of the electrolyzer. The slotting method, where the anodes are arranged directly opposite each other and relatively concentrated, can be adapted to render a more uniform current density distribution on the anode surface, with lower energy consumption and less variation in voltage and current. With the increasing number of slots from one to three, the current density distribution on the anode surface became more uniform, with a reduction in the variation range of the slot voltage and current in the branch where the cathode plate was cleaned and a decreased energy consumption. With the linear increase in brush cleaning speed, the impact time of the brush plate on the electrolyzer decreased nonlinearly, and as the extent of this decrease gradually diminished, the additional energy consumption showed the same trend. These research results were then used as a basis for optimizing the existing commonly used empirical C-brush plates. Following optimization, the current density distribution on the anode surface was found to be more uniform, the variation amplitude of tank voltage was reduced by 34%, the current drop amplitude of the branch circuit where the brushed cathode plate was located was reduced by 39%, the impact time on the current field of the electrolytic tank was reduced by 40%, and the additional energy consumption was reduced by 50.9%. These results can be served as a reference for further theoretical research related to brush plates.

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.

scholarly journals Electrochemical synthesis of biobased polymers and polymer building blocks from vanillin

RSC Advances ◽  
2021 ◽  
Vol 11 (15) ◽  
pp. 8970-8985
Author(s):  
Robin Kunkel ◽  
Volkmar M. Schmidt ◽  
Carsten Cremers ◽  
Dominik Müller ◽  
Detlef Schmiedl ◽  
...  
Keyword(s):  
Process Parameters ◽  
Current Density ◽  
Electrode Material ◽  
Electrochemical Synthesis ◽  
Building Blocks ◽  
Biobased Polymers ◽  
The Impact

Hydrovanilloin and polyvanillin were synthesized electrochemically investigating the impact of process parameters such as electrode material, charge and current density.

scholarly journals Development of Bubble Characteristics on Chute Spillway Bottom

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1129
Author(s):  
Ruidi Bai ◽  
Chang Liu ◽  
Bingyang Feng ◽  
Shanjun Liu ◽  
Faxing Zhang
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Dissipation Rate ◽  
Bubble Diameter ◽  
Bubble Size Distribution ◽  
Impact Zone ◽  
Air Bubble ◽  
Air Supply ◽  
Bubble Characteristics ◽  
The Impact

Chute aerators introduce a large air discharge through air supply ducts to prevent cavitation erosion on spillways. There is not much information on the microcosmic air bubble characteristics near the chute bottom. This study was focused on examining the bottom air-water flow properties by performing a series of model tests that eliminated the upper aeration and illustrated the potential for bubble variation processes on the chute bottom. In comparison with the strong air detrainment in the impact zone, the bottom air bubble frequency decreased slightly. Observations showed that range of probability of the bubble chord length tended to decrease sharply in the impact zone and by a lesser extent in the equilibrium zone. A distinct mechanism to control the bubble size distribution, depending on bubble diameter, was proposed. For bubbles larger than about 1–2 mm, the bubble size distribution followed a—5/3 power-law scaling with diameter. Using the relationship between the local dissipation rate and bubble size, the bottom dissipation rate was found to increase along the chute bottom, and the corresponding Hinze scale showed a good agreement with the observations.

RIB/Channel Effect on Cell Performance Under High Current Density Operation

2010 ◽  
Author(s):  
Yuichiro Tabuchi ◽  
Takeshi Shiomi ◽  
Osamu Aoki ◽  
Norio Kubo ◽  
Kazuhiko Shinohara
Keyword(s):  
Water Transport ◽  
Current Density ◽  
Liquid Water ◽  
Water Distribution ◽  
Numerical Study ◽  
High Current Density ◽  
Cell Performance ◽  
High Current ◽  
Numerical Validation ◽  
The Impact

Heat and water transport in polymer electrolyte membrane fuel cell (PEMFC) has considerable impacts on cell performance under high current density which is desired in PEMFC for automobiles. In this study, the impact of rib/channel, heat and water transport on cell performance under high current density was investigated by experimental evaluation of liquid water distribution and numerical validation. Liquid water distribution between rib and channel is evaluated by Neutron Radiography. In order to neglect the effect of liquid water in channel and the distribution of oxygen and hydrogen concentration distribution along with channel length, the differential cell was used in this study. Experimental results show that liquid water under channel was dramatically changed with Rib/Channel width. From numerical study, it is found that the change of liquid water distribution was strongly affected by temperature distribution between rib and channel. In addition, not only heat transport but also water transport through membrane also significantly affected cell performance under high current density operation. From numerical validation, it is concluded that this effect on cell performance under high current density could be due to the enhancement of back-diffusion of water through membrane.

Bubble Formation From Porous Plates in Liquid Cross-Flow

2018 ◽  
Author(s):  
Thomas Shepard ◽  
Eric Ruud ◽  
Henry Kinane ◽  
Deify Law ◽  
Kohl Ordahl
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Bubble Diameter ◽  
Bubble Formation ◽  
Cross Flow ◽  
Rectangular Channels ◽  
Gas Liquid Flow ◽  
Liquid Flows ◽  
Processing Techniques ◽  
The Impact

Controlling bubble diameter and bubble size distribution is important for a variety of applications and active fields of research. In this study the formation of bubbles from porous plates in a liquid cross-flow is examined experimentally. By injecting air through porous plates of various media grades (0.2 to 100) into liquid flows in rectangular channels of varying aspect ratio (1–10) and gas/liquid flow rates the impact of the various factors is presented. Image processing techniques were used to measure bubble diameters and capture their formation from the porous plates. Mean bubble diameters ranged from 0.06–1.21 mm. The present work expands upon the work of [1] and further identifies the relative importance of wall shear stress, air injector pore size and gas to liquid mass flow ratio on bubble size and size distribution.

High dielectric 3D scaffold to suppress Li-dendrites and increase the reversibility of anode-less Li-metal anodes

2021 ◽  
Author(s):  
Chao Wang ◽  
Ming Liu ◽  
Michel Thijs ◽  
Frans Ooms ◽  
Swapna Ganapathy ◽  
...  
Keyword(s):  
Porous Scaffold ◽  
Specific Capacity ◽  
Anode Surface ◽  
3D Scaffold ◽  
Metal Anode ◽  
Metal Plating ◽  
Lithium Metal Anode ◽  
High Dielectric ◽  
Battery Energy ◽  
The Impact

Abstract The lithium metal anode is intensively investigated because it considerably increases Li-battery energy density. However, the formation of dendritic/mossy Li-metal microstructures amplifies electrolyte decomposition and Li deactivation. Here we investigate the impact of a high-dielectric porous scaffold, aiming to eliminate the fundamental driver for dendritic/mossy Li-metal growth, the large electrical field gradients at inhomogeneities at the anode surface. In an anode-less (Li-metal free) high-dielectric porous scaffold, this promotes dense plating as observed by operando solid-state NMR. Even in a simple carbonate electrolyte, 1M LiPF6 in EC/DMC, the high-dielectric scaffold improves the plating/stripping efficiency up to 99.82%, extending the cycle life, indicating that electrolyte decomposition is minimized by the induced compact Li-metal plating. The large porosity of the scaffolds, non-optimized and easy to prepare, enables a specific capacity beyond 2000 mA h g-1, presenting a facile approach to promote compact Li-metal plating to improve Li-metal anode efficiency and safety.

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