What does 'comminution' refer to in materials processing?

Comminution refers specifically to the process of reducing the size of particles in materials processing, which involves crushing and grinding operations to break down larger materials into smaller, more manageable particles. This process is essential in various industries, including mining and mineral processing, where ore is reduced to fine sizes to facilitate subsequent operations such as separation and extraction. The reduction in particle size increases the surface area of the materials, enhancing their reactivity and making them easier to work with during subsequent processing steps.

The other options describe different processes: shaping materials refers to techniques like molding or forming, coating surfaces involves applying a layer on a material for protection or enhancement, and alloying metals is the mixing of different metals to create a composite material with desired properties. Each of these processes serves a distinct purpose in materials engineering, but none relate to the specific function of comminution, which is exclusively about size reduction.