Chemically assisted comminution, in which chemical and/or physicochemical actions are introduced into powders to be ground, was conducted under dry conditions. The comminution method is called “chemically assisted dry comminution” (CADC). In the CADC sericite powder, a kind of mica, was first mixed with a nitrate, and the mixed powder was comminuted under a dry condition, followed by obtaining finely ground sericite after removing the nitrate by water cleaning. Lithium, sodium, potassium and rubdium nitrate were used as the nitrates.
The sericite powder obtained by every CADC had a much larger specific surface area and a smaller amount of impurity than that obtained by an ordinary dry comminution. On the other hand, the median diameters of sericite by CADC were slightly smaller than those by an ordinary dry comminution.
Potassium ions in sericite decreased only in the case of the CADC, which suggested that potassium ions were exchanged with alkali ions in the nitrate during the CADC. There was a correlation between the amount of exchanged potassium ions and the specific surface area of the sericite by the CADC. Stabilisation of the nascent surface and the prevention of agglomeration of the sericite by nitrate during comminution was considered to be another reason for the enhanced grindability by CADC.