nanoparticles from RHs are initially amorphous. Extended
pyrolysis of 0.20 M KNO3 solution treated silica nanoparticle at
800 °C gradually enhanced the sample crystallinity. While the
0.50 M KNO3 solution treated silica nanoparticle exhibited
even higher degree of crystallinity under the same pyrolysis
treatment. More importantly, with increasing crystallinity, the
silica nanoparticles can be processed to form any desirable
shape, and possess sufficient structural integrity (a coin shaped
disk as an example is presented in the inset of Figure 4C).
Thus, they might find wider applications and exhibit superior
performance compared to amorphous porous silica, such as
filtering, etc. While this work focuses on exploring the
possibility to form semicrystalline porous silica framework via
controlled fuse of silica nanoparticles, more detailed research is
underway to fine-tune the pore size and structure using various
dopants and reaction conditions, which will be reported later.
To explain the hierarchical structure of the porous silica
nanoparticles synthesized from RHs, and their melting progress
and porous framework formation, we propose a model as
shown in Figure 6.