*2.2. Ageing Process*

The ageing step was conducted by making use of a bench-top Lasec digital hotplate stirrer. Samples obtained from the milling chamber were divided such that half was immediately filtered and dried and the other half subjected to an ageing step. Samples were placed in a glass beaker and agitated, at 400 rpm, for 24 h. Sample temperature was elevated and kept constant at 80 ◦C. A thin plastic film was placed over the beaker to prevent excessive moisture loss. Experiments were performed without the use of an inert gas under air atmosphere. All samples were filtered and dried at 60 ◦C for 12 h.
