Microscopic image method consists of microscope, CCD camera (or digital camera), graphic acquisition card, computer and other components. Its basic working principle The particle image after magnification of the microscope is transmitted to the computer through the CCD camera and the graphic acquisition card, and the computer performs edge recognition and other processing on these images, calculates the projected area of each particle, and obtains each particle according to the principle of equivalent projected area. The particle size distribution of brown fused alumina oxide and white fused aluminum oxide can be obtained by counting the number of particles in the set particle size range. Since the number of particles detected by this method is small, the same sample can be measured multiple times by changing the field of view to improve the authenticity of the test results. In addition to particle size testing, microscopic imaging is also commonly used to observe and test particle morphology.
In addition to the above-mentioned particle size testing methods for brown fused alumina and white fused alumina powder, scraper method, sedimentation bottle method, ventilation method, ultrasonic method and dynamic light scattering method are also commonly used in production and research fields.
1. Scraper method
Scrape the brown fused alumina oxide and white fused aluminum oxide samples on a flat surface and observe the roughness to evaluate whether the particle size of the samples is qualified.
2. Settling bottle method
Its principle is roughly the same as that of the settlement method before and after. In the test process, a certain amount of sample and liquid are first prepared into a suspension in a 500ml or 1000l graduated cylinder. After fully stirring, a certain amount (such as 20ml) is taken out as the total weight of the sample, and then the settling time of each particle is calculated according to the law, at a fixed time. The same amount of suspension was released respectively to represent the corresponding particle size at this moment. The particle size distribution can be calculated after drying and weighing the suspension obtained at each moment. This method is currently used in industries such as abrasives and river sediment.
3. Breathing method
The ventilation method is also called the Freund method. The sample is loaded into a metal tube and compacted, and the metal tube is installed into a gas circuit to form a closed-loop gas circuit. When the gas flows in the gas path, the gas will pass through the particle gap. If the sample is thicker, the gap between particles will be large, and the gas flow will be less hindered; if the sample is finer, the gap between particles will be small, and the gas flow will be hindered more. The air permeability method is based on such a principle to test the particle size of brown fused alumina oxide and white fused aluminum oxide. This method can only obtain an average particle size value and cannot measure the particle size distribution. This method is mainly used in the magnetic material industry.
4. Ultrasonic method
A method to measure particle size distribution through the principle that particles with different particle sizes have different effects on ultrasonic waves. It can directly test high concentration slurry with solid-liquid ratio up to 70%. This method is a new technology. At present, people at home and abroad are conducting research. It is said that there are already instruments abroad.
5. Dynamic light scattering method
The laser scattering method can be understood as the static light scattering method. When the particles are small to a certain extent, the particles are affected by Brownian motion in the liquid, showing a random motion state, and the moving distance and speed are related to the particle size. The particle size distribution can be obtained by identifying the motion state of these particles through related technologies. Dynamic light scattering is mainly used to measure the particle size distribution of nanomaterials. There are ready-made instruments abroad.