Process for conversion and size reduction of solid particles

A process for the conversion of solid starting particles into solid intermediate particles and the reduction of the median diameter of the intermediate particles to obtain product particles, which process involves the following steps:

• a) flowing a suspension of starting particles through a series of at least two conversion vessels, thereby converting at least part of the starting particles into intermediate particles, which
• i) when the starting particles are amorphous, possess a degree of order, or
• (ii) when the starting particles possess a degree of order, possess a different order, a different degree of order, or no order,
• b) adding a supercritical fluid to one or more of the conversion vessels, thereby forming a supercritical suspension, and
• c) releasing pressure from the supercritical suspension, thereby expanding the suspension and converting the intermediate particles into product particles.