Page 109 - Book Hosokawa Nanoparticle Technology Handbook

2.4 COMPOSITE STRUCTURE FUNDAMENTALS

(b)
(b)
(a)
(a)

Nanocoating
Nanocoating

Figure 2.4.13
SEM images for VO –SiO hybrid nanoparticles.
2 2

nanoparticles with well-controlled particle size can be VO
prepared by the Stöber method. However, it was diffi- Annealing at 600 °C 2
cult to prepare the monodispersed silica nanospheres N
with smaller size less than 100 nm by the Stöber 2
method. Then, the two stages for the nucleation and In-situ combustion
the growth of the particles were effectively separated at 200 °C
to prepare the monodispersed particles of 10 nm in
diameter [6]. Intensity(a.u.)
In this section, a nanocoating method on the surface
of monodispersed silica nanoparticles was described
including the applications to cost-effective smart win-
dows by dispersing the VO –SiO hybrid nanoparti-
2
2
cles into the transparent biodegradable polylactic acid
(PLA) [7–9].
The actual preparation procedure is as follows;
For the water removal, the monodispersed SiO 2 10 20 30 2θ(deg.) 40 50 60
nanoparticle sol (solvent was ethanol including
small amount of residual water) was substituted for Figure 2.4.14
solvent by 1-butanol. Vanadium precursor solution X-ray diffraction patterns for VO –SiO hybrid nanoparticles.
was prepared by dissolving VO(O-i-Pr) in the mixed 2 2
3
solvent of 2-propanol and 2-methoxy ethanol or 2-
propanol solvent. Acetic acid was added to the vana-
dium precursor solutions to form the chemically dissolved PLA followed by casting it on a glass plate
modified vanadium alkoxide by the chelation that at 110°C to solidify.
controls the following hydrolysis and condensation on The scanning electron microscope (SEM) image
the surface of the monodispersed silica nanospheres and XRD patterns of the resultant VO –SiO hybrid
2
2
(nanocoating). The resulting hybrid nanoparticle sol nanoparticles are shown in Figs. 2.4.13 and 2.4.14,
was filtrated by suction to obtain the VO –SiO hybrid respectively to exhibit the particle size distribution
2
2
precursor nanoparticles. This precursor nanoparticles and crystalline phase. The well-crystallized VO –SiO 2
2
were oxidized for the crystallization and then reduced hybrid nanoparticles were successfully prepared by
or were crystallized by the in-situ combustion method the reaction control of the precursor alkoxide using
of the chemically modified hybrid precursor to form controlled chemical modification method. As shown
the VO –SiO hybrid nanoparticles. Crystallinity of in the SEM photograph, the hybrid nanoparticles
2
2
the as-prepared VO –SiO hybrid nanoparticles by the maintain the shape of the original monodispersed
2
2
in-situ combustion method was not so good that the silica nanospheres to show the achievement of the
further annealing at 600°C for 1 h was conducted in nanocoating (Fig. 2.4.15).
N atmosphere to increase the crystallinity. The smart For the molecular designing of alkoxide-derived
2
film consisting of the VO –SiO hybrid nanoparticles precursors, deep knowledge on the organic chemistry
2
2
and PLA was prepared by dissolving PLA and dis- is essential. The controlled chemical modification
persing the VO –SiO hybrid nanoparticles into the method enables the partial hydrolysis of the precursor
2
2
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