Expanded graphite and products produced therefrom

Abstract

Graphite nanoplatelets of expanded graphite and composites and products produced therefrom are described. The preferred method of expanding the graphite is by microwaves or other radiofrequency wave treatment of intercalated graphite. The expanded graphite is preferably then crushed to nanometer (substantially all 200 microns or less). The expanded graphite is used in polymer composites. The expanded graphite is particularly useful for batteries, anodes and fuel cells.

We claim:  
     
         1 . A composite material which comprises: 
 (a) finely divided expanded graphite consisting essentially of single platelets which are less than 200 microns in length; and    (b) a polymer having the expanded graphite dispersed therein.    
     
     
         2 . A composite material which comprises: 
 (a) finely divided expanded graphite having single platelets with a length less than about 200 microns and a thickness of less than about 0.1 microns; and    (b) a polymer having the expanded graphite particles dispersed therein, wherein the composite material contains up to about 50% by volume of the graphite.    
     
     
         3 . The composite material of  claim 2  wherein the graphite platelets are present in an amount so that composite material is conductive.  
     
     
         4 . The composite material of any one of claims  1 ,  2  or  3  wherein the polymer is a thermoplastic or thermoset polymer.  
     
     
         5 . The composite material of any one of claims  1 ,  2  or  3  wherein a graphite precursor contained a chemical which was vaporized at least in part by heat to form the expanded graphite.  
     
     
         6 . The composite material of any one of claims  1 ,  2  or  3  wherein the expanded graphite has been formed in a radiofrequency wave applicator by heating a graphite precursor with the radiofrequency waves.  
     
     
         7 . The composite material of any one of claims  1 ,  2  or  3  wherein the polymer and the expanded graphite have been heated together with a radiofrequency wave applicator.  
     
     
         8 . The composite material of any one of claims  1 ,  2 , or  3  wherein the polymer is an epoxy resin.  
     
     
         9 . The composite material of any one of claims  1 ,  2  or  3  wherein a precursor graphite has been treated with a fuming oxy acid and heated to form the expanded graphite.  
     
     
         10 . The composite material of any one of claims  1 ,  2  or  3  wherein the polymer is thermoplastic and is selected from the group consisting of polyamides, proteins, polyesters, polyethers, polyurethanes, polysiloxanes, phenol-formaldehydes, urea-formaldehydes, melamine-formaldehydes, celluloses, polysulfides, polyacetals, polyethylene oxides, polycaprolactams, polycaprolactons, polylactides, polyimides, and polyolefins.  
     
     
         11 . The composite material of any one of claims  1 ,  2  or  3  which contains less than about 8% by weight of the expanded graphite.  
     
     
         12 . A method for preparing a shaped composite which comprises: 
 (a) providing a mixture of a finely divided expanded graphite consisting essentially of single platelets which are essentially less than 200 microns in length and with a polymer with the expanded dispersed therein; and    (b) forming the shaped composite material from the mixture.    
     
     
         13 . A method for preparing a shaped composite material which comprises: 
 (a) providing a mixture of an expanded graphite having single platelets with a length less than about 200 microns and a thickness of less than about 0.1 microns and a polymer with the expanded graphite dispersed therein, wherein the composite material contains up to about 50% by volume of the expanded graphite platelets;    (b) forming the shaped composite material from the mixture.    
     
     
         14 . The method of claims  12  or  13  wherein the expanded graphite is provided in the polymer in an amount sufficient to render the shaped composite conductive.  
     
     
         15 . The method of claims  12  or  13  wherein the polymer is a thermoplastic or thermoset polymer.  
     
     
         16 . The method of claims  12  or  13  wherein a graphite precursor of the expanded graphite platelets contain an expanding chemical which is at least in part evaporated to form the expanded graphite.  
     
     
         17 . The method of claims  12  or  13  wherein the expanded graphite is formed in a radiofrequency wave applicator by heating the graphite precursor with radiofrequency waves.  
     
     
         18 . The method of claims  12  or  13  wherein an graphite precursor is treated with a fuming oxy acid and heated to provide the expanded graphite.  
     
     
         19 . The method of any one of claims  12  or  13  wherein the polymer is a curable thermoset resin which is mixed with the expanded graphite and cured.  
     
     
         20 . The method of claims  12  or  13  wherein the shaped composite material contains less than 8% by weight of the expanded graphite.  
     
     
         21 . In a battery containing ions the improvement in the anode which comprises a finely divided microwave or RF expanded graphite having single platelets with a length less than about 200 microns and a thickness of less than about 0.1 microns.  
     
     
         22 . In a catalytic conversion of an organic compound to hydrogen with a catalytic material deposited on a substrate the improvement in the substrate which comprises a finely divided microwave or RF expanded graphite having single particles with a length less than about 200 microns and a thickness of less than about 0.1 microns.  
     
     
         23 . A process for producing platelets of expanded graphite which comprises: 
 (a) expanding graphite intercalated with a chemical which expands upon heating to produce expanded graphite platelets; and    (b) reducing the expanded graphite platelets so that essentially all of the individual platelets are less than 200 microns in length, 0.1 micron in thickness.    
     
     
         24 . The process of  claim 23  wherein the chemical agent is an inorganic oxy acid.  
     
     
         25 . The process of any one of claims  23  or  24  wherein the expanding is by microwave or RF heating.  
     
     
         26 . The composite material of  claim 1  wherein the expanded graphite is grafted with acrylamide.  
     
     
         27 . The method of  claim 12  wherein the expanded graphite is grafted with acrylamide.  
     
     
         28 . The method of  claim 23  wherein the expanded graphite is grafted with acrylamide.