Ceramic Material and Thermal Switch

Patent metadata

Field	Value
Publication number	US-2016137555-A1
Application number	US-201615001541-A
Country	US
Kind code	A1
Filing date	Jan 20, 2016
Priority date	Sep 2, 2013
Publication date	May 19, 2016
Grant date	—

Abstract

A ceramic material has a characteristic length L a of a micro-structure thereof that satisfies 0.1 L AMFP ≦L a ≦100 L AMFP , and has thermal conductivity that monotonously increases from room temperature to 100° C., where L AMFP denotes apparent mean free path of phonons at room temperature, and is defined as L AMFP =(3×thermal conductivity)/(heat capacity×speed of sound). The characteristic length L a of the micro-structure is an interval between particles of different type of material when the ceramic material includes a composite material in which the different type of material is dispersed in a base material, is an interval between one pore and another pore when the ceramic material includes a porous body, and is the crystalline particle size (interval between one grain boundary and another grain boundary) when the ceramic material includes a polycrystalline body.

First claim

1 . A ceramic material, having a characteristic length L a of a micro-structure thereof that satisfies 0.1 L AMFP ≦L a ≦100 L AMFP , and having thermal conductivity that monotonously increases from room temperature to 100° C., where L AMFP denotes apparent mean free path of phonons at room temperature, and is defined as L AMFP =(3×thermal conductivity)/(heat capacity×speed of sound).

2 . The ceramic material according to claim 1 , wherein thermal conductivity thereof at 100° C. is 1.5 times or more of thermal conductivity at room temperature.

3 . The ceramic material according to claim 1 , wherein thermal conductivity thereof at 200° C. is 2 times or more of thermal conductivity at room temperature.

4 . The ceramic material according to claim 1 , wherein the ceramic material includes a composite material in which a different type of material is dispersed in a base material, and an interval GI between one particle of the different type of material and another particle of the different type of material is the characteristic length L a of the micro-structure.

5 . The ceramic material according to claim 4 , wherein let that the average of the intervals GI between one particle of the different type of material and another particle of the different type of material is GI ave , the interval GI between one particle of the different type of material and another particle of the different type of material is 0.1 GI ave or more and 10 GI ave or less.

6 . The ceramic material according to claim 5 , wherein the base material includes SiC, and the particles of different type material include at least one type selected from the group consisting of O, B, C, N, Al, Si, and Y.

7 . The ceramic material according to claim 5 , wherein the base material includes SiC, and GI ave is from 10 to 500 nm.

8 . The ceramic material according to claim 1 , wherein the ceramic material includes a porous body, and an interval PI between one pore and another pore in the porous body is the characteristic length L a of the micro-structure.

9 . The ceramic material according to claim 8 , wherein let that the average of the intervals PI between one pore and another pore is PI ave the interval PI between one pore and another pore is 0.1 PI ave or more and 10 PI ave or less.

10 . The ceramic material according to claim 9 , wherein the ceramic material is a porous body of SiC, and PI ave is from 10 to 500 nm.

11 . The ceramic material according to claim 1 , wherein the ceramic material includes polycrystal and a particle size d of crystalline particles is the characteristic length L a of the micro-structure.

12 . The ceramic material according to claim 11 , wherein let that the average of the particle size d of crystalline particles is d ave , the particle size d is 0.1 d ave or more and 10 d ave or less.

13 . The ceramic material according to claim 12 , wherein the ceramic material is a polycrystalline body of SiC, and d ave is from 10 to 500 nm.

14 . A thermal switch, comprising the ceramic material according to claim 1 , and having thermal conductivity that changes with temperatures.

Assignees

• Ngk Insulators Ltd

Inventors

• Tomita Takahiro
• Nagai Kenkichi
• Kobayashi Hiroharu

Classifications

• H01H37/32

  Thermally-sensitive members · CPC title

• C04B35/575

  obtained by pressure sintering · CPC title

• C04B2235/5454

  nanometer sized, i.e. below 100 nm · CPC title

• C04B2235/781

  Nanograined materials, i.e. having grain sizes below 100 nm · CPC title

• C04B35/584 Primary

  based on silicon nitride · CPC title