Conduction heat transfer switching using magnetic Fe _x O _y -decorated carbon-based nanomaterials

Smart windows are used to minimize overall indoor energy consumption for thermal regulation through the modulation of radiant and conducted heat. While the control of thermal radiation can be done effectively by various technologies such as electrochromic, thermochromic, photochromic, etc., the modulation of heat conduction through smart windows remains a very challenging problem to be solved. The main obstacles are the lack of an effective conduction pathway within a double-glazed window and the need for a reliable active thermal switching mechanism. In this work, we introduce a novel idea for modulating heat conduction through a smart window by building thermally conductive pathways via coatings together with a heat transfer switching channel. The thermal switch uses various Fe_xO_y-decorated carbon-based nanomaterials that can be turned ‘ON’ or ‘OFF’, thus modulating heat conduction through a window. By applying an external magnetic force, such carbon-based magnetic nanomaterials can be easily moved or aligned within the switching channel to modulate thermal conduction. In this work, Fe_xO_y-decorated carbon nanotubes (CNTs) and graphene are developed as a thermal conduction pathway, and a thermal heat switching mechanism is developed and proposed. The Fe_xO_y-decorated carbon nanotubes (CNTs) and graphene show excellent heat diffusivity as a thermal conduction pathway coating, through a 2 mm channel gap with a 40 mm distance from the heat source, whilst the thermal conduction switch proposed is shown to effectively modulate thermal conduction through it.