Electrode Material Properties describes the material characteristics of a carbon paste, which is used in the manufacture of a Carbon Electrode (CPE). It is important that these properties be maintained to prevent the carbon from breaking away from its binder when heated. This ensures that electrode density is improved, improving both conductivity as well as mechanical strength. A carbon paste that has a low coefficient of thermal expansion can be used for many years at high currents and temperatures without breaking.
Carbon electrodes are primarily made from coal-based materials, like metallurgical coal or anthracite. To optimize the properties, they are combined with other materials containing carbon and then bound with coal-tar pitch. Graphite scrap is also an important raw material because of its low ash content, good electrical conductivity, and low resistance, but it has a low strength. It can be mixed with coal-based products to enhance the strength and durability of electrode pastes and char.
As a binder, coal tar is used to bind granular carbon. A Soderberg traditional electrode contains 70 to 80 percent of calcined ash (calcined char, petroleum slag, graphite or calcined anthracite). As the material heats up, it flows into the steel electrode casing and fills the lower part of it. Once the paste is soft enough to flow, it is called green electrode paste and is then baked in a coal tar pitch carbonization oven to convert it into the final electrode.
Baking changes the chemical makeup of the paste and affects its thermal properties. This is because the volatiles from the coal-tar pitch slowly escape and can impact the quality of sintering as well as the life of the electrode. Carbon pastes have a volatile content that is usually less than 15 percent, though it may vary depending on production processes and binder types.
Carbonized coal tar can then be shaped into blocks and sheets. The sheets are cut into the desired size, and then packaged to be shipped. The volatile content is a key characteristic of carbon paste. It should not exceed 15% in order to avoid breakages when shipping or storing.
A voltammetric study was conducted to examine the potential window of different carbon-based materials, such as glassy carbon (GC), metastable silicon carbide (mS) and carbon nanotubules with nitrogen (CNT-CPE). In a solution of 0.1 mol*L-1 KCL, the anodic maximum potentials were determined for these carbons. This reproducibility was tested by comparing standard deviations between anodic and oxidative peak potential measurements. All carbon types were found to have RSDs of less than 4 % for their anodic peak values. These promising results provide a foundation for future research regarding the use of different carbon materials to make electrode pastes.
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