Thermal Diode

Abstract

The thermal diode is formed of a first material as a ceramic material exhibiting thermal conductivity that increases in a certain temperature range of −200° C. or higher but 1000° C. or lower and a second material exhibiting the thermal conductivity that decreases in the temperature range, the first material and the second material being bonded together. The first material has preferably a microstructure having a characteristic length L a of 1 nm to 10 μm.

1 . A thermal diode comprising:
 a first material as a ceramic material exhibiting thermal conductivity that increases in a certain temperature range of −200° C. or higher but 1000° C. or lower; and   a second material exhibiting the thermal conductivity that decreases in the temperature range,   wherein the first material and the second material are bonded together.   
     
     
         2 . The thermal diode according to  claim 1 , wherein the first material has a microstructure having a characteristic length L a  of 1 nm to 10 μm. 
     
     
         3 . The thermal diode according to  claim 2 , wherein the first material is configured by a composite material in which a dissimilar material is dispersed in a base material, a gap GI between particles of the dissimilar material represents the characteristic length L a  of the microstructure, and the particles of the dissimilar material have a particle diameter of 1 nm to 1000 nm. 
     
     
         4 . The thermal diode according to  claim 3 , wherein when an average value of gaps GI between the particles of the dissimilar material of the first material is defined as GI ave , the gaps GI between the particles of the dissimilar material are 0.1GI ave  or more but 50GI ave  or less. 
     
     
         5 . The thermal diode according to  claim 2 , wherein the first material is configured by a porous body, a gap PI between pores in the porous body represents the characteristic length L a  of the microstructure, and a pore diameter is 1 nm to 1000 nm. 
     
     
         6 . The thermal diode according to  claim 5 , wherein when an average value of gaps PI between the pores of the first material is defined as PI ave , the gaps PI between the pores are 0.1PI ave  or more but 50PI ave  or less. 
     
     
         7 . The thermal diode according to  claim 2 , wherein the first material is configured by a polycrystal, a particle diameter “d” of crystal particles represents the characteristic length L a  of the microstructure, and the particle diameter “d” is 1 nm to 1000 nm. 
     
     
         8 . The thermal diode according to  claim 7 , wherein when an average value of particle diameters “d” of the crystal particles of the first material is defined as d ave , the particle diameters “d” are 0.1d ave  or more but 50d ave  or less.