3.3.2 Effect of calcination dwelling time

The formation of MT at 600°C with 1 h dwelling time was incomplete, with the weight fraction of rutile and periclase that was about 17.2 and 17.4%, respectively, while increasing calcination temperature improves such formation. The effect of calcination dwelling time on the completeness of the MT formation was then examined [29]. It was reported that the formation of MT is significantly improved by prolonged calcination as proven by the MT molar fraction around 65% (equivalent with around 82% by weight) for 1 h to 82% (90% by weight) for 4 h. It was also found that the crystallite size of MT was invariant to dwelling time at values around 76 nm as indicated by insignificant changes on the XRD line.

Therefore, the dissolution method has been successfully implemented to produce high-purity MT nanocrystals. Sub-nanometric MT crystals were achieved from Mg-Ti hydrochloric acid solutions mixing with 6% excessive Mg followed by calcination at 800°C for 1 h. Meanwhile, prolonged calcination at 600°C significantly improved the MT formation up to 82% (molar) and retained its nanometric crystallite size at around 76 nm.
