For ultra-fine calcium carbonate, particle size, specific surface area, crystal form and oil absorption value are the most important technical indicators, which directly affect the application performance of ultra-fine calcium carbonate.
Particle size and specific surface area
How to make the average particle size of ultrafine calcium carbonate primary particles reach 0.02～0.1μm is the basic index of ultrafine calcium carbonate, although it is very important, otherwise it is not called ultrafine calcium carbonate.
But strictly speaking, this has only completed half of the task of producing ultra-fine calcium carbonate. If the surface treatment technology and dispersion technology cannot keep up, the generated primary particles will reunite into large particles of secondary particles with a particle size of up to several hundred nanometers.
Therefore, under the transmission electron microscope (TEM), the photos observed or taken can only reflect the size of the primary particles, and cannot reflect the actual size of the secondary particles after agglomeration Treatment), the ultra-fine calcium carbonate with serious agglomeration, the specific surface area measured by BET is relatively small.
Only by using the combination of transmission electron microscope observation and specific surface area measurement can we obtain a more scientific and comprehensive judgment on the fineness, crystal form, and dispersion of ultrafine calcium carbonate.
The average particle size of ultrafine calcium carbonate is intrinsically related to its specific surface area. Some researchers use sedimentation volume to determine the particle size. As we all know, in addition to the particle size (the quality of limestone, calcined quality of lime, lime digestion, carbonization conditions, etc. will affect the particle size), there are also crystal forms of calcium carbonate which will have effects. The same crystal form is also not very regular geometry, and it is impossible for them to be the same, so the influence of the crystal form on the sedimentation volume is more complicated.
In order to effectively prevent the agglomeration of secondary particles, superfine calcium carbonate generally requires surface modification treatment, because the surface treatment process not only effectively improves the activity of ultrafine calcium carbonate, but also effectively prevents the process of secondary particle agglomeration.

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