Thermal insulator and method of manufacturing the same

Abstract

A thermal insulator with both excellent heat insulation and strength and a method of manufacturing the thermal insulator are provided. A thermal insulator according to the present invention includes metal oxide fine particles with an average particle diameter equal to or smaller than 50 nm and a reinforcing fiber, wherein the thermal insulator has a bridge structure between the metal oxide fine particles which is formed by elution of part of the metal oxide fine particles. A method of manufacturing a thermal insulator according to the present invention includes a curing step of curing a dry pressed compact including metal oxide fine particles with an average particle diameter equal to or smaller than 50 nm and a reinforcing fiber under a pressurized vapor saturated atmosphere at a temperature equal to or higher than 100° C. for four hours and a drying step of drying the cured dry pressed compact.

1 . A thermal insulator comprising a dry pressed compact including metal oxide fine particles with an average particle diameter equal to or smaller than 50 nm and a reinforcing fiber, wherein
 the thermal insulator has a bridge structure between the metal oxide fine particles which is formed by elution of part of the metal oxide fine particles.   
     
     
         2 . The thermal insulator according to  claim 1 , wherein
 the metal oxide fine particles include silica fine particles.   
     
     
         3 . The thermal insulator according to  claim 1 , wherein
 the thermal insulator has a bulk density and a compressive strength of the following (a) or (b):   (a) the bulk density is equal to or larger than 180 kg/m 3  and equal to or smaller than 300 kg/m 3  and the compressive strength is equal to or larger than 0.6 MPa; or   (b) the bulk density exceeds 300 kg/m 3  and equal to or smaller than 500 kg/m 3  and the compressive strength is equal to or larger than 0.8 MPa.   
     
     
         4 . The thermal insulator according to  claim 1 , wherein
 the metal oxide fine particles include alumina fine particles.   
     
     
         5 . The thermal insulator according to  claim 4 , wherein
 the thermal insulator has a hot-wire shrinkage ratio at 1000° C. equal to or smaller than 3%.   
     
     
         6 . The thermal insulator according to  claim 1 , wherein
 the thermal insulator includes 50 to 98 mass % of the metal oxide fine particles and 2 to 20 mass % of the reinforcing fiber.   
     
     
         7 . The thermal insulator according to  claim 1 , wherein
 the thermal insulator does not comprise a binder.   
     
     
         8 . A method of manufacturing a thermal insulator comprising:
 a curing step of curing a dry pressed compact including metal oxide fine particles with an average particle diameter equal to or smaller than 50 nm and a reinforcing fiber under a pressurized vapor saturated atmosphere at a temperature equal to or higher than 100° C.; and   a drying step of drying the cured dry pressed compact.   
     
     
         9 . The method of manufacturing a thermal insulator according to  claim 8 , wherein
 in the curing step, part of the metal oxide fine particles is eluted between the metal oxide fine particles to form a liquid bridge structure, and   in the drying step, the bridge structure is solidified.   
     
     
         10 . The method of manufacturing a thermal insulator according to  claim 8 , wherein
 the metal oxide fine particles include silica fine particles.   
     
     
         11 . The method of manufacturing a thermal insulator according to  claim 8 , wherein
 the metal oxide fine particles include alumina fine particles.   
     
     
         12 . The method of manufacturing a thermal insulator according to  claim 8 , wherein
 the dry pressed compact includes 50 to 98 mass % of the metal oxide fine particles and 2 to 20 mass % of the reinforcing fiber.   
     
     
         13 . The method of manufacturing a thermal insulator according to  claim 8 , wherein
 the dry pressed compact does not comprise a binder.   
     
     
         14 . (canceled)