Calcination causes phase transformation of TiO2 from anatase to rutile at 700 oC but generally calcination in imprignation is done in between 400-600 oC. Bond formation can happen in hydrothermal synthesis(generally in between 140-180 oC) but at high tempratures (in hydrothermal synthesis) Ti-O-Ti is more preferable rather than Ti-C bond. Few papers have reported vague information about formation of Ti-C bond due to calcination. So, is calcination being done for bond formation or just to vaporize precursors from the TiO2/ACF felt.
https://doi.org/10.1016/j.jcis.2012.08.038
https://doi.org/10.1016/j.partic.2013.04.006
http://pubs.rsc.org/en/Content/ArticlePDF/2014/NJ/c4nj00962b
https://doi.org/10.1016/j.matlet.2013.10.097
Sir,
The calcining step volatilizes the water and decomposes and volatilizes the organic materials. The calcining step, therefore, causes shrinkage of fibres of about 50 –60 wt.%
without any change in shape. There are defects that occur during calcination are hollow fibres, core and sheath structures and cracking and splitting of fibres. Crackng of fibres can be caused by improperc ontrol over removal of organics and water especially during initial stages of calcination.
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