How is the Particle Size of Graphite Electrode Plates Determined?

1. Determination of particle size distribution of graphite electrode plates

There are two methods of measuring the particle size distribution of graphite electrode plate particles of 1 μm or less, electron microscopy and gravity sedimentation.

The advantage of electron microscopy is that in addition to the determination of the particle size distribution, the shape of the particles can also be known. Generally, 10,000 times electron micrographs are used to measure the frequency distribution of graphite particles.

The measuring device of the gravity sedimentation method is an ultracentrifuge. This ultracentrifuge measures the particle size distribution of the graphite electrode plate under the condition of a strong centrifugal force equivalent to 10,000 times the gravity (the maximum centrifugal force of an ordinary laboratory centrifuge is only 2,000 times the gravity).

In current production practice, the sedimentation method is used for particle size determination of graphite particles larger than 1 Hm. First, suspend and disperse the powder sample in pure water, and add a dispersant to prevent particle agglomeration. Dilute the graphite electrode plate to a thin slurry with a graphite concentration of 0.05%, then put it into a container, and measure the particle size of the particles with a gravity sedimentation specific gravity balance. Gravity sedimentation-specific gravity balance is an automatic particle size distribution analyzer with an automatic recording device. This instrument can measure the particle size distribution curve of the sample.

For graphite particles smaller than 1 μm, an automatic particle size determination device by light transmission method is used. The light transmission method is to indirectly measure the particle size distribution by injecting a light beam in the process of changing the concentration of the suspension produced by the powder sedimentation and indirectly measuring the particle size distribution by the light-blocking amount of the powder. The use of the indirect method greatly simplifies the operation procedures. In the micro powder measurement process, the biggest problem is particle agglomeration.

Therefore, when measuring the particle size of micro powder by light transmission method, the best concentration is to make a low-concentration suspension containing 0.05% graphite and add an appropriate amount of dispersant to disperse it.

2. Preparation of the graphite electrode plate test solution used

The dispersion liquid for measuring the particle size of the graphite electrode plate is prepared according to the following method: add a little carboxymethyl cellulose powder in 500 mL of distilled water, stir well to dissolve it completely, and measure the viscosity after standing for 24 hours. The viscosity was adjusted to 0.5~1Pa*s, and the dispersion liquid was prepared.

Take 3g of graphite electrode plate powder, put it in a mortar, add 3g of 3% carboxymethyl cellulose solution, mix it with a glass rod and add a little distilled water to adjust the graphite test solution. Then adjust the concentration of the test concentration. When adjusting, add 100mL of dispersion liquid to a 200mL beaker, drop a drop of graphite test solution, stir evenly and disperse it with an ultrasonic disperser for 3 minutes, and then test the test solution.