In situ observation of sintering of nickel nanoparticles during nanocasting into mesoporous silica

Hierarchically porous metals are of interest in several application fields, including heterogeneous catalysis. Here, we report the nanocasting of nickel metal into hierarchically porous SBA-15 type monoliths containing ordered arrays of mesopores. Upon removal of the silica template, nickel replicas showed no evidence of an ordered mesopore structure. TEM images and XRD measurements of the nickel-silica composite show that nickel nanoparticles larger than the silica mesopores have formed. In situ heated stage TEM measurements indicate that sintering of nickel nanoparticles occurs, which leads to rapid disruption of the silica template in vacuum. This disruption appears to occur more rapidly in vacuum than under hydrogen atmosphere. (C) 2013 Elsevier B.V. All rights reserved.