Pitch-based carbon foam heat sink with phase change material

Abstract

A process for producing a carbon foam heat sink is disclosed which obviates the need for conventional oxidative stabilization. The process employs mesophase or isotropic pitch and a simplified process using a single mold. The foam has a relatively uniform distribution of pore sizes and a highly aligned graphic structure in the struts. The foam material can be made into a composite which is useful in high temperature sandwich panels for both thermal and structural applications. The foam is encased and filled with a phase change material to provide a very efficient heat sink device.

What is claimed is:  
     
         1 . A process of producing a carbon foam heat sink comprising: 
 selecting an appropriate mold shape;    introducing pitch to an appropriate level in said mold;    purging air from said mold to form a vacuum;    heating said pitch to a temperature sufficient to coalesce said pitch into a liquid;    releasing said vacuum and backfilling an inert fluid at a static pressure up to about 1000 psi;    heating said pitch to a temperature sufficient to cause gases to evolve and form a carbon foam;    heating said carbon foam to a temperature sufficient to coke the pitch;    cooling said carbon foam to room temperature and simultaneously releasing said inert fluid;    at least partially encasing said carbon foam; and    at least partially filling porous regions of said carbon foam with a phase change material.    
     
     
         2 . The process of  claim 1  wherein said pitch is introduced as granulated pitch.  
     
     
         3 . The process of  claim 1  wherein said pitch is introduced as powdered pitch.  
     
     
         4 . The process of  claim 1  wherein said pitch is introduced as pelletized pitch.  
     
     
         5 . The process of  claim 1  wherein said pitch is a synthetic mesophase or isotropic pitch.  
     
     
         6 . The process of  claim 1  wherein said pitch is a petroleum derived mesophase or isotropic pitch.  
     
     
         7 . The process of  claim 1  wherein said pitch is a coal-derived mesophase or isotropic pitch.  
     
     
         8 . The process of  claim 1  wherein said pitch is a blend of pitches selected from the group consisting of synthetic mesophase or isotropic pitch, petroleum derived mesophase or isotropic pitch, and coal derived mesophase or isotropic pitch.  
     
     
         9 . The process of  claim 1  wherein said pitch is a solvated pitch.  
     
     
         10 . The process of  claim 1  wherein said purging is effected by a vacuum step.  
     
     
         11 . The process of  claim 1  wherein said purging is effected by an inert fluid.  
     
     
         12 . The process of  claim 1  wherein said vacuum is applied at less than 1 torr.  
     
     
         13 . The process of  claim 1  wherein nitrogen is introduced as the inert fluid.  
     
     
         14 . The process of  claim 1  wherein said pitch is heated to a temperature in the range of about 500° C. to about 1000° C. to coke said pitch.  
     
     
         15 . The process of  claim 1  wherein said pitch is heated to a temperature of about 800° C. to coke said pitch.  
     
     
         16 . The process of  claim 1  wherein the temperature to coke said pitch is raised at a rate of no greater than 5° C. per minute.  
     
     
         17 . The process of  claim 1  wherein said pitch is soaked at the coking temperature for at least 1  5  minutes to effect said coking.  
     
     
         18 . The process of  claim 1  wherein said pitch is heated to a temperature of about  630 ° C to coke said pitch.  
     
     
         19 . The process of  claim 1  wherein said pitch is heated to a temperature of about 50° C. to about 100° C. to coalesce said pitch.  
     
     
         20 . The process of  claim 1  where said foam is cooled at a rate of approximately 1.5° C./min with the release of pressure at a rate of approximately 2 psi/mn.  
     
     
         21 . The process of  claim 1  further including step of densifying said foam.  
     
     
         22 . The process of  claim 1  wherein said phase change material is acetic acid.  
     
     
         23 . The process of  claim 1  wherein said phase change material is a paraffin wax.  
     
     
         24 . The process of  claim 1  wherein said phase change material is germanium.  
     
     
         25 . The process of  claim 1  wherein said encasement material is polyethylene.  
     
     
         26 . The process of  claim 1  wherein said encasement material is aluminum.  
     
     
         27 . The process of  claim 1  wherein said encasement material is a carbon/carbon composite.  
     
     
         28 . A carbon foam heat sink product as produced by the process of  claim 1 .  
     
     
         29 . A process of producing a carbon foam heat sink comprising: 
 selecting an appropriate mold shape and a mold composed of a material that the molten pitch does not wet;    introducing said pitch to an appropriate level in the mold;    purging the air from said mold to form a vacuum;    heating said pitch to a temperature sufficient to coalesce said pitch into a liquid;    releasing said vacuum and backfilling an inert fluid at a static pressure up to about 1000 psi;    heating said pitch to a temperature sufficient to coke the pitch; and    cooling said foam to room temperature and simultaneously releasing said inert fluid;    at Least partially encasing said foam; and    at least partially filling porous regions of said foam with a phase change material.    
     
     
         30 . The process of  claim 29  wherein said pitch is introduced as granulated pitch.  
     
     
         31 . The process of  claim 29  wherein said pitch is introduced as powdered pitch.  
     
     
         32 . The process of  claim 29  wherein said pitch is introduced as pelletized pitch.  
     
     
         33 . The process of  claim 29  wherein said pitch is a synthetic mesophase or isotropic pitch.  
     
     
         34 . The process of  claim 29  wherein said pitch is a petroleum-derived mesophase pitch.  
     
     
         35 . The process of  claim 29  wherein said pitch is a coal-derived mesophase pitch.  
     
     
         36 . The process of  claim 29  wherein said mold is pureed by a vacuum applied at less than 1 torr.  
     
     
         37 . The process of  claim 29  wherein said mold is purged by an inert fluid before heating.  
     
     
         38 . The process of  claim 29  wherein said phase change material is acetic acid.  
     
     
         39 . The process of  claim 29  wherein said phase change material is a paraffin wax.  
     
     
         40 . The process of  claim 29  wherein said phase change material is germanium.  
     
     
         41 . The process of clam  29  wherein said encasement material is polyethylene.  
     
     
         42 . The process of  claim 29  wherein said encasement material is aluminum.  
     
     
         43 . The process of  claim 29  wherein said encasement material is a carbon/carbon composite.  
     
     
         44 . A carbon foam heat sink product as produced by the process of  claim 29 .  
     
     
         45 . A process of producing a carbon foam heat sink comprising: 
 selecting an appropriate mold shape;    introducing pitch to an appropriate level in said mold;    purging air from said mold to form vacuum;    heating said pitch to a temperature sufficient to coalesce said pitch into a liquid;    releasing said vacuum and backfilling an inert fluid at a static pressure up to about 1000 psi;    heating said pitch to a temperature sufficient to cause gases to evolve and form carbon foam;    heating said carbon foam to a temperature sufficient to coke the pitch;    cooling said carbon foam to room temperature and simultaneously releasing said inert fluid;    placing facesheets on the opposite sides of said carbon foam, adhering the facesheets to said carbon foam;    at least partially encasing said carbon foam and facesheets; and    at least partially filling porous regions of said carbon foam with a phase change material.    
     
     
         46 . The process of  claim 45  wherein the adhering of the facesheets to the carbon foam is effected by a molding step.  
     
     
         47 . The process of  claim 45  wherein the adhering of the facesheets to the carbon foam is effected by a coating material.  
     
     
         48 . The process of  claim 45  wherein said phase change material is acetic acid.  
     
     
         49 . The process of  claim 45  wherein said phase change material is a paraffin wax.  
     
     
         50 . The process of  claim 45  wherein said phase change material is germanium.  
     
     
         51 . The process of  claim 45  wherein said encasement material is polyethylene.  
     
     
         52 . The process of  claim 45  wherein said encasement material is aluminum.  
     
     
         53 . The process of  claim 45  wherein said encasement material is a carbon-carbon composite.  
     
     
         54 . The process of  claim 45  wherein said facesheets material is a carbon-carbon composite.  
     
     
         55 . A composite carbon foam heat sink product produced by the process of  claim 45