Fig. 2. Schematics of thermal rectification behaviors of HI-P and LI-P nanofiber junctions.

a and b HI-P nanofiber junction showing single-direction rectification due to the phase transition of the pristine segment. c and d LI-P nanofiber junction showing dual-mode thermal rectification at different working temperatures. At the high working temperature, the phase transition of the pristine segment induces a rectification behavior like that of the HI-P junction. At the low working temperature, the phase transition of the LI segment gives rise to the rectification in the opposite direction. The pink region in a and c represents the scenario that heat flow in the reverse bias is suppressed and the junction shows positive rectification. The purple region in c represents the scenario of the LI-P nanofiber junction that heat flow in the forward bias is suppressed and the junction shows negative rectification. The solid and open circles in a and c mark different working states under forward or reverse bias.