Synthesis of Hollow Silica Nanospheres by Sacrificial Polystyrene Templates for Thermal Insulation Applications

Linn Ingunn C. Sandberg,Tao Gao,Arild Gustavsen,Bjørn Petter Jelle

doi:10.1155/2013/483651

Abstract

Monodisperse polystyrene (PS) spheres with controllable size have been synthesized by a straight forward and simple procedure. The as-synthesized PS spheres have a typical diameter ranging from~180 nm to~900 nm, where a reduced sphere size is obtained by increasing the polyvinylpyrrolidone (PVP)/styrene weight ratio. The PS spheres function as sacrificial templates for the fabrication of hollow silica nanospheres (HSNSs) for thermal insulation applications. By modifying the silica coating process, HSNSs with different surface roughness are obtained. All resulting HSNSs show typically a thermal conductivity of about 20 mW/(mK), indicating that the surface phonon scattering is probably not significant in these HSNS samples.

Highlights

A substantial amount of the total heat loss of residential buildings passes through the opaque building envelopes, as these components normally account for the largest contact area towards the outside environment
As the demand for energy efficiency in building codes becomes increasingly stringent, it is necessary to reduce the unwanted thermal loss of existing and future building envelopes. This can either be done by increasing the wall thickness when conventional thermal insulation materials such as mineral wool or expanded polystyrene (EPS) is used, or install state-of-theart superinsulating materials such as aerogel blankets/mats or vacuum insulation panels (VIPs)
The size of the polystyrene (PS) templates could be controlled by adjusting the PVP/styrene weight ratio

Summary

Introduction

A substantial amount of the total heat loss of residential buildings passes through the opaque building envelopes, as these components normally account for the largest contact area towards the outside environment. As the demand for energy efficiency in building codes becomes increasingly stringent, it is necessary to reduce the unwanted thermal loss of existing and future building envelopes. This can either be done by increasing the wall thickness when conventional thermal insulation materials such as mineral wool or expanded polystyrene (EPS) is used, or install state-of-theart superinsulating materials such as aerogel blankets/mats or vacuum insulation panels (VIPs). One path which can be followed, is to create nano insulation materials (NIMs), which aim to utilize physical principles such as the Knudsen effect to reduce the thermal conductivity of the material to a minimum [1]. Similar results have been reported for inorganic materials such as hollow silica nanospheres (HSNSs) [2, 4, 5]

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