How to Make Carbon Paste Electrode?

Carbon paste electrode is a kind of conductive material used in mineral furnace, calcium carbide furnace and other equipment. It is composed of carbon raw materials and adhesives with unique advantages in environmental monitoring and other fields. It has simple preparation process, low cost, modifiable, flexible adjustment of properties, scientific research and practical application attention.

Preparation of materials

Carbonaceous raw materials

The core carbon materials of معجون القطب الكهربائي are petroleum coke, asphalt coke and graphite. Petroleum coke has high carbon content, less impurities, and lower resistivity after calcination at high temperature. Asphalt coke has high mechanical strength and good electrical conductivity, which can enhance electrode stability. Graphite scrap has excellent electrical and thermal conductivity, which can improve heat transfer and electron transport performance. In fact, according to the use of the electrode paste, the proportion of them is accurately adjusted.

Binder

Coal bitumen is the most commonly used binder. Heated to a certain temperature, it changes from a solid to a liquid, coating the carbon particles evenly and allowing them to bind tightly. The softening point of the coal asphalt determines its softening flow temperature range. And the appropriate softening point enables it to fully infiltrate the raw material when heated. It provides sufficient bonding strength after cooling, and maintains the shape and structure of the electrode paste. The coking value reflects its high temperature coking ability. And the higher coking value helps to improve the mechanical strength and electrical conductivity of the electrode paste at high temperature.

Additives

In order to optimize the performance of the electrode paste, specific additives are sometimes added. Copper powder, aluminum powder and other metal powder due to good electrical conductivity, after addition can significantly improve the electrical conductivity. Fiber materials such as carbon fiber can enhance the mechanical strength. So that the electrode paste is not easy to break when subjected to external forces. Antioxidants can improve the antioxidant capacity at high temperatures and extend the service life. However, the type and amount of additives should be subjected to a large number of experiments and strict tests to prevent affecting other properties.

Carbon paste preparation Step

Weigh the toner and adhesive

Weigh the carbon powder and adhesives according to the carefully designed formula. Use high-precision electronic balance to accurately weigh the carbon raw materials and adhesives. When weighing, strictly control environmental conditions to prevent carbon raw materials from hygroscopicity or deterioration due to temperature and humidity changes. And operate easy hygroscopicity raw materials in a dry environment and processed as soon as possible. Regular calibration of the balance to ensure accurate weighing. Different application scenarios electrode paste performance requirements are different, need to consider the use of environment, performance and cost to determine the best formula.

Mixed grinding

Mix and grind the measured raw materials and adhesives into a high-speed mixer or a strong kneading machine. First, stir at low speed for 10-15 minutes to disperse large particles initially. Then increase the speed and heat up to 150-180 ℃, let the coal pitch soften and wrap the carbon particles. And continue to stir for 30-45 minutes. The fully stirred mixture is also transferred to the ball mill and other equipment for 2-4 hours. To refine the carbon particles, tightly bind the adhesive, and improve the uniformity and stability of the carbon paste.

Carbon paste electrode forming process

Hand filling method

Hand filling method is a simple and direct electrode forming method. First, clean the prepared electrode matrix (such as glass carbon electrode) and dry it with nitrogen. Then, take an appropriate amount of prepared carbon paste. And carefully fill it with carbon paste on the surface of the electrode base or into a specific groove with tweezers or glass rods. When filling, the carbon paste should be evenly distributed as far as possible to avoid holes or uneven thickness. After filling, gently press the carbon paste with your finger or a tool to bind it tightly to the electrode base. This method is easy to operate, no special equipment is required, but the operator’s experience is high. And the electrode consistency after forming is relatively poor.

Mold forming method

The mold forming method can prepare carbon paste electrodes with regular shape, accurate size and good consistency. First, according to the desired electrode shape and size, select or customize the appropriate mold, such as PTFE mold. After the mold is cleaned and dried, evenly apply a layer of release agent on the surface of the mold for subsequent release. Next, fill the carbon paste into the mold cavity, and the tool compacts the carbon paste. To ensure that the carbon paste completely fills the mold and the surface is flat. The mold with the carbon paste is then placed under certain temperature and pressure conditions for curing. (If using a binder that needs to be cured, such as epoxy resin). After curing, carefully open the mold and remove the formed carbon paste electrode. This method is suitable for large-scale preparation and application scenarios requiring high electrode shape and dimensional accuracy.

Carbon paste electrode post-treatment

Surface grinding and polishing

The surface of the formed carbon paste electrode may be uneven or rough. This will affect the electrochemical performance and reproducibility of the electrode. Therefore, it is necessary to grind and polish the electrode surface. First, the surface of the electrode is ground with sandpaper to remove obvious bumps and uneven parts. (From coarse-grained to fine-grained, such as 200 mesh, 400 mesh, 800 mesh, 1200 mesh, etc.) During the grinding process, you should pay attention to keeping the force on the electrode surface uniform. To avoid damaging the carbon paste layer. Then, polish the electrode by using a polishing cloth and polishing paste (such as alumina polishing paste). To achieve a mirror effect on the electrode surface. The polished electrode surface is smoother, which can effectively reduce the background current of the electrode and improve the sensitivity and response stability of the electrode.

Cleaning and activation

Abrasive particles, polishing paste and other impurities may remain on the surface of the electrode after grinding and polishing, and need to be cleaned. Soak the electrodes in anhydrous ethanol for 5-10 minutes ultrasonic cleaning, then rinse with deionized water, and then dry with nitrogen. The cleaned electrode also needs to be activated to improve the electrochemical activity of the electrode. The activation method usually uses electrochemical cyclic voltammetry to scan the electrode several times at a certain scanning rate (such as 50mV/s) in a specific electrolyte. So that a stable active site is formed on the electrode surface, thereby optimizing the electrochemical performance of the electrode.

Quality inspection and performance evaluation

Appearance inspection

Check the appearance of the electrode with the naked eye and microscope. Check with the naked eye whether the overall shape of the electrode is regular. Whether the carbon paste is complete, and whether there are cracks, holes or falls off. You can use the microscope to observe the microscopic structure of carbon paste. Such as whether the distribution of carbon graphite powder is uniform, and the state of adhesive coating. The surface of the high-quality electrode should be smooth and the carbon paste should be tightly combined with the matrix without obvious defects.

Electrochemical performance test

You can use the electrochemical workstation to test the performance of carbon paste electrodes. Common methods include cyclic voltammetry (CV), differential pulse voltammetry (DPV) and AC impedance spectroscopy (EIS). CV studies the REDOX behavior of the electrode, measures the current response at different potentials, determines the REDOX peak potential and current. And it evaluates the catalytic performance of specific substances. DPV has high sensitivity, analyzing current change under pulse potential to detect low concentration substances. EIS studies the electrode/solution interface charge transfer and internal resistance, measures the AC impedance of different frequencies to obtain equivalent circuit parameters. And it evaluates the interface performance and electron transport capability.

الخاتمة

The production of carbon paste electrode has many steps and complex influencing factors. From material selection, preparation, molding, post-treatment and performance evaluation, each link is crucial. Reasonable control of parameters can produce high-quality electrodes, and the future production process will continue to optimize and innovate.