Diamond micropowder is small, but it also has many shapes

Although the particle size and composition of diamond micropowder are the same, the use effect will be very different due to the difference in particle shape of the micropowder. Manufacturers must classify and manage products according to particle shapes in order to ensure stable product quality.

 

1. Particle shape of diamond powder

Particle shape is the main factor to evaluate the quality of diamond powder. The parameters that characterize the particle shape include particle roundness, particle ellipse, specific surface area, needle-like particles, and flake-like particles. It is generally recommended to use two parameters, particle roundness and plate-like particle number, to characterize the particle shape.

Particle roundness refers to the ratio of the equivalent circumference of the projected area of the particle to the actual projected circumference of the particle, which is a dimensionless number less than 1. Roundness is a comprehensive parameter to characterize the shape of particles, which can not only reflect the circularity of particles, but also reflect the ellipticity of particles, and also reflect the surface roughness of particles.

Flaky particles refer to particles that are very thin and have high light transmittance under the microscope, which are regarded as flaky particles. For the convenience of inspection, the light transmittance is further quantified, and those with a light transmittance greater than 90% are regarded as flake particles.

According to the actual situation of diamond micropowder at present, the proportion of flake particles is between 0-10%. At present, the percentage of the number of flake particles should be less than 10%. The number of flaky particles was previously stipulated to be less than 5%. In fact, even if the flaky particles are greater than 5%, it can still be used, but it affects the use effect. Therefore, this index is relaxed and used as a guiding quality index.

Since the particle roundness and the percentage of flaky particles are guiding indicators, there are no excessive requirements, and the main purpose is to guide production and application.

In the quality inspection of diamond micropowder, needle-rod particles refer to the ratio of the major axis to the minor axis exceeding 3:1. In the micropowder, there should be no needle rod-shaped particles exceeding the maximum particle size, and the needle rod-shaped particles whose length is between the maximum nominal size and the largest particle are not allowed to exceed 3%.

Particle shape will affect particle size detection. It is difficult to obtain products with concentrated particle size when there are many non-spherical particles, and the particle size detection of products with many needle-like particles has large changes and poor consistency. In the application, the particle shape will also affect the grinding efficiency of the product, resulting in many uncertain factors. Usually, when polishing, the particle shape of diamond micropowder is preferably close to spherical and equal-area. However, with the expansion of applications, there are now cases where irregular diamond powders are required.

 

2. Different shapes of micropowders are suitable for different applications

Micropowder with good particle shape and roundness has a better effect in polishing. Blocky, multi-angular, multi-edge, low magnetic and high-strength micropowders have good application effects in diamond electroplating wire saws, and other shapes of micropowders, such as strips, blocks and flakes, are more sharp and are mostly used in resin binders in the grinding wheel.