Microwave synthesis of tungsten oxide and bronze for IR shielding coating

• Main Author: Tan, Wei Jie
• Other Authors: Chen Zhong
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/66827
• Institution: Nanyang Technological University

With regards to the context of tropical climate in Singapore, a simple infrared (IR) shielding coating on windows can provide all year round passive cooling to a room as it reduces the unwanted heat gain from near-infra radiation (NIR). Although such coatings are already commercially available, investigations can still be made in improving the particles and coating properties to enhance its performance. By incorporating small tungsten oxide particles synthesized by microwave hydrothermal synthesis and then heat-treated with forming gas, in silica based coating, the IR shielding performance of this coating has been shown to be better than that of commercially available tungsten oxide nanoparticles. Different heat treatment conditions as well as the use of Na2SO4 as doping salt to increase free electrons were investigated to further improve the IR shielding performance of coatings. In this process, various sodium tungsten bronze nanostructures were synthesized by microwave hydrothermal synthesis at 180 oC. With increasing concentration of Na2SO4, the microstructures of as-synthesized sodium tungsten bronze changed from nanorods to nanosheets. The sodium tungsten bronze nanosheets are approximately 20 nm in thickness and 20 μm in diameter, which has better visible light transmittance and IR shielding properties than that of nanorods in terms of coverage area per weight. From these studies, it could allow retrofitting of the existing buildings with cost efficient IR shielding coating for the windows as a way towards a greener Singapore.