TY - JOUR
T1 - Sintering-Induced Phase Transformation of Nanoparticles
T2 - A Molecular Dynamics Study
AU - Mao, Qian
AU - Ren, Yihua
AU - Luo, Kai H.
AU - Li, Shuiqing
N1 - Publisher Copyright:
© 2015 American Chemical Society.
PY - 2015/12/24
Y1 - 2015/12/24
N2 - Sintering-induced phase transformation of TiO2 nanoparticles is investigated systematically via molecular dynamics simulation. Upon defining a coordination number and bond angle distribution criteria, local phase information is identified for each individual Ti atom originating from amorphous or crystal structure as well as three TiO2 polymorphs, anatase, brookite, and rutile. Size-dependent structures of nanoparticles lead to different dynamics of the sintering-induced phase transformation. Grain boundaries that form between nanoparticles during sintering trigger the nucleation and growth of new phases. During the sintering of two equal-sized core-shell anatase nanoparticles, crystal core regions melt with the temperature increase and the surface energy decrease in the microcanonical (NVE) ensemble. The new phase that develops from the grain boundary spreads into the destroyed core regions in stages, forming a new larger spherical nanoparticle with an ordered atomic arrangement. During the sintering of two unequal-sized nanoparticles (amorphous and core-shell anatase), atoms from the amorphous nanoparticle first nucleate to form crystal anatase in the contact region, and a grain boundary is then developed between the original core region and the newly formed anatase crystal. After that, phase transformation follows much the same route as the equal-sized case from anatase to brookite.
AB - Sintering-induced phase transformation of TiO2 nanoparticles is investigated systematically via molecular dynamics simulation. Upon defining a coordination number and bond angle distribution criteria, local phase information is identified for each individual Ti atom originating from amorphous or crystal structure as well as three TiO2 polymorphs, anatase, brookite, and rutile. Size-dependent structures of nanoparticles lead to different dynamics of the sintering-induced phase transformation. Grain boundaries that form between nanoparticles during sintering trigger the nucleation and growth of new phases. During the sintering of two equal-sized core-shell anatase nanoparticles, crystal core regions melt with the temperature increase and the surface energy decrease in the microcanonical (NVE) ensemble. The new phase that develops from the grain boundary spreads into the destroyed core regions in stages, forming a new larger spherical nanoparticle with an ordered atomic arrangement. During the sintering of two unequal-sized nanoparticles (amorphous and core-shell anatase), atoms from the amorphous nanoparticle first nucleate to form crystal anatase in the contact region, and a grain boundary is then developed between the original core region and the newly formed anatase crystal. After that, phase transformation follows much the same route as the equal-sized case from anatase to brookite.
UR - http://www.scopus.com/inward/record.url?scp=84952942310&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.5b08625
DO - 10.1021/acs.jpcc.5b08625
M3 - Article
AN - SCOPUS:84952942310
SN - 1932-7447
VL - 119
SP - 28631
EP - 28639
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 51
ER -