Chemical and thermal properties of VO 2 mechanochemically derived from V 2 O 5 by co-milling with paraffin wax

• Published in: RSC advances 2018-06, Vol.8 (38), p.21306-21315
• Main Authors: Takai, Chika, Senna, Mamoru, Hoshino, Satoshi, Razavi-Khosroshahi, Hadi, Fuji, Masayoshi
• Format: Article
• Language: English
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C8RA02159G

A novel mechanochemical reduction process of V O to VO was established by milling with paraffin wax (PW, average molecular weight 254-646), serving as a reductant. The reduction progressed with increasing milling time and mass ratio V O  : PW (MRVP). The mechanochemically derived VO became phase pure after milling for 3 h with an MRVP of 30 : 1 and exhibited a reversible polymorphic transformation between tetragonal and monoclinic phases at around 53-60 °C and 67-79 °C during heating and cooling, respectively. The latent heat was above 20 J g in both processes, being superior to those of commercial VO . Doping of starting V O with Cr, Mo or W at 1 at% in the form of oxide did not increase the latent heat. This is another difference from the conventionally prepared doped VO . These anomalous heat storage properties of mechanochemically derived VO were discussed mainly on the basis of X-ray photoelectron spectroscopy V peaks combined with ion etching. The observed relatively high heat storage capacity of undoped VO is primarily ascribed to the abundance of V ionic states introduced during milling with PW, which were stabilized with simultaneously introduced structural degradation throughout the entire particles. The possible role of a remaining small amount of PW was also discussed.