Fabrication of hollow silica nanosphere and its application for thermal insulation coating

Abstract

Hollow silica nanospheres (HSNs) were synthesized via sol–gel method followed by calcination, using positively charged polystyrene (PS) as a hard template, and the tetraethoxysilane as precursor. The inner diameter and shell thickness of the HSNs can be expediently controlled by adjusting the particle size of PS and the amount of ammonia, respectively. The average inner diameters of HSNs increased from 153 nm to 255 nm along with the increasing PS particle size from 150 nm to 300 nm. The shell thickness of HSNs decreased from 20 nm to 12 nm with the increasing amount of ammonia from 1.5 mL to 3.0 mL. The structure of HSNs was verified by Fourier-transform infrared, thermogravimetric, scanning electron microscopy, and transmission electron microscopy characterization. The prepared thermal insulation coating comprised of HSNs shows good temperature retention and thermo-insulating properties, which indicate that the as-prepared HSNs are potentially used as an inorganic filler for thermal insulation coating.

A lightweight thermally insulating and moisture-stable composite made of hollow silica particles

“…In all other composites reported to date, the thermal conductivity of the composite is always higher than the thermal conductivity of HSPs. 35–38…”

“…Mixing HSPs in polymer matrices has been extensively explored. 35–37 Ernawati et al showed that mixing HSPs with polyethersulfone polymer results in a composite thin (35 μm) film with a thermal conductivity of ∼0.03 W m −1 K −1 , whereas films made of polyethersulfone alone had a thermal conductivity 0.09 W m −1 K −1 . 37 Nevertheless, mixing HSPs with polymers generally provides composites with thermal conductivities ranging from 0.03 to 0.08 W m −1 K −1 , which are very high compared with other insulation materials and HSPs itself.…”

“…Thus, the original goal of using HSPs as thermal insulation material has become compromised, and HSPs have become only an additive to lower the thermal conductivity of other materials. 35–37…”

Hollow Silica Particles: Recent Progress and Future Perspectives

“…Maximizing the benefit of this characteristic, several types of thermal insulation materials have been developed using HSPs as additives. For example, thermally insulating thin films or coatings have been developed [ 78 , 79 , 80 , 81 , 82 ] by adding HSPs to polymers, such as polyurethane or polyisocyanurate. These films or coatings generally have thermal conductivity that is 50–70% lower than the original polymers used as the matrix.…”

Method for High-Yield Hydrothermal Growth of Silica Shells on Nanoparticles

“…Another innovative application of coating processes is to produce differently shaped hollow structures by removing the core material after the coating process [1][2][3][4] Hollow mesoporous silica structures are used as highly lightweight aerogels and in medical and cosmetic formulations. For example, they can encapsulate active ingredients or bind or absorb molecules, e.g., hollow silica spheres supplying lipids into the skin in daily facial creams [5][6][7].…”