*2.1. Milling Operation*

Selected raw materials were wet batch milled with the use of a Netzsch LME 1 horizontal bead mill, under air atmosphere. The milling chamber (1.225 L) was loaded to a capacity of 60% (by volume) with 2 mm diameter yttrium stabilised zirconia beads. Cooling water was allowed to circulate through the outer jacket of the milling chamber at a constant inlet temperature of 30 ◦C and flow rate of 525 L·h−1. A water slurry consisting of 10% solids (reactants) was added to the milling chamber and milled for 1 h at 2000 rpm. Samples obtained were divided such that half was filtered and dried at 60 ◦C for 12 h. The remaining half of the sample was subjected to ageing at 80 ◦C for 24 h. The principle of the mill is similar to that of agitator bead mills in which the grinding media is accelerated with the use of an agitator shaft. The energy supplied to the media is then transferred to the solids via collisions and de-acceleration. The vessel is placed in a horizontal position to allow for even grinding activity and activation. Figure 1 depicts a technical schematic of the Netzsch LME 1 horizontal bead mill. The product inlet and outlet to the grinding chamber were sealed to allow for batch milling. Raw materials and grinding media were added to the vessel through the 'bead filling connection'. At the end of every experimental run, the 'tank floor' or front cap of the milling chamber was removed and the sample and beads collected. The grinding media and mill were washed in preparation for the next experimental run. The pump set-up provided by Netzsch was not used.

**Figure 1.** Technical Schematic of Netzsch LME 1 Horizontal Bead Mill as modified from Netzsch.
