SiO2-incorporated VO2 film for energy saving smart windows

• Main Author: Lee, Sei Chang
• Other Authors: Long Yi
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: DRNTU::Engineering::Materials::Composite materials
• Online Access: http://hdl.handle.net/10356/76768
• Institution: Nanyang Technological University

In recent times, about 80-90% of working time is spent indoors, with 30-40% of the world’s primary energy being consumed to maintain comfortable indoor temperatures. In tropical countries such as Singapore, most buildings and transportations are air-conditioned to 21-26 ℃ all year long by utilizing energy-consuming air-cooling systems, increase electricity bills and indirectly incurring the hard truth—global warming. There is significant interest in economizing energy usage in buildings through surfaces regularly exposed to the sun such as windows and roofing. In this report, an overview on how optical properties can be changed by mechanical stretching and compressing is given through a composite film consisting of a thin layer of quasi-amorphous array of silica microparticles embedded in bulk elastomeric poly(dimethyl siloxane) PDMS. In addition, the film was further embedded with vanadium dioxide (VO2) nanoparticles that changes its optical properties depending on the amount wavelength of light exposed to it (also known as temperature-stimulated thermochromic effects). Results show that the composite film was highly transparent (>80% transmittance in the visible wavelength) in the initial state and upon mechanical stretching, the transmittance was dramatically reduced to 40% and lower, depending on the amount of particles added; accompanied by a transparency shift from transparent to translucent in appearance. Similar results were also observed when the VO2 embedded film was exposed to varying levels of wavelengths. It was also noted that while the varying the amount of silica microparticles and VO2 NPs embedded in the bulk would affect the range of the transparency shift, they are independent of each other in contributing to the transparency shift and optical response to temperature variations. This allows manufacturers to vary the transparency shift according to the needs of customers.