| In the last twenty years, nanoscale heat transfer has attracted many attentions and promoted the development of industry. It is extremely significant to build up and improve the theories on nanoscale heat transfer.First, based on the differential bridge method, the thermal conductivity of columned boron nitride nanotubes was measured with the suspended microdevices. The results show that the thermal conductivity increases as the temperature increases and decreases as the diameter increases. In addition, the simulation on heat transfer in a boron nitride nanotube was done with ANSYS Workbench software. The results deduce that the heat transfers in all the layers of boron nitride nanotube.Moreover, the expressions of the elastic restoring force and van der Waals interaction force were built up and the effect of the elastic bending on contact thermal resistance was theoretically analyzed. The ratio of the elastic restoring force of van der Waals force reaches the maximum when the two crossed CNTs have the same suspended length and the included angle is 126.8°, and reduces sharply as the angle deviates from 126.8°. The most maximum percentage change of the contact thermal resistance is 18%.Finally, the thermal conductivities in two directions of bamboo-like boron nitride nanotubes were measured with suspended microdevices. The nearly overlapped curves of thermal conductivity in two directions do not exhibit thermal rectification. The results show that at quasi-equilibrium situation, after the temperatures at the two ends of an asymmetric nanostructure are reversed, the magnitude of heat flux does not change. |
