Method for producing carbon- or graphite-foam parts
A method for producing carbon or graphite foam parts with high purity level for high-temperature insulation under vacuum or protective gas, as insulating material or as filter material, includes the following steps: introducing dry, foamable starch ( 1 ) into an open-top container ( 2 ) having a round or angular cross section, until the base ( 3 ) of the container ( 2 ) is covered amply and uniformly with starch ( 1 ); introducing the container ( 2 ) partly filled with starch ( 1 ) into an oven ( 4 ), and heating the container ( 2 ) to a foaming temperature of >180° C. over a prolonged period of several hours to foam the starch ( 1 ), until the container ( 2 ) has filled completely with carbon foam ( 6 ); withdrawing the container ( 2 ) from the oven ( 4 ) and extracting the carbon foam ( 6 ) after sufficient cooling, and optionally portioning the carbon foam ( 6 ) into carbon foam parts ( 6.1 ).
1. A method for producing carbon or graphite foam parts, comprising:
introducing dry, foamable starch ( 1 ) into an open-top container ( 2 ) having a base ( 3 ) with a round or angular cross section, until the base ( 3 ) of the container ( 2 ) is covered uniformly and the container is filled with starch ( 1 ) for more than 10% and no more than 30%;
introducing the container ( 2 ) partly filled with starch ( 1 ) into an oven ( 4 );
heating the container ( 2 ) to a foaming temperature of >180° C. to foam the starch ( 1 ) until the container ( 2 ) has filled completely with carbon foam ( 6 );
withdrawing the container ( 2 ) from the oven ( 4 );
extracting the carbon foam ( 6 ) after cooling, and
portioning the carbon foam ( 6 ) into carbon foam parts ( 6 . 1 ).
2. The method as claimed in claim 1 ,
wherein the starch ( 1 ) is corn starch, tapioca starch, wheat starch, rice starch or potato starch.
3. The method as claimed in claim 1 , further comprising:
supplying steam to the starch ( 1 ) in the oven ( 4 ) during foaming operation.
4. The method as claimed in claim 1 ,
wherein the starch ( 1 ) is foamed over a period of more than 8 hours.
5. The method as claimed in claim 1 ,
wherein the foaming temperature for the starch ( 1 ) is 200° C. or more.
6. The method as claimed in claim 1 ,
wherein the foaming is carried out at
a temperature between 165° C. and 175° C. for a more than 2 and less than 12 hours, followed by
a temperature between 175° C. and 185° C. for a more than 2 and less than 12 hours, followed by
a temperature between 185° C. and 195° C. for a more than 2 and less than 12 hours, followed by
a temperature between 195° C. and 205° C. for a more than 2 and less than 12 hours.
7. The method as claimed in claim 1 , further comprising:
lining the carbon foam parts ( 6 . 1 ) with one of aluminum foil, paper, baking paper, and cloth.
8. The method as claimed in claim 1 , further comprising:
impregnating the carbon foam parts ( 6 . 1 ) with a PVA adhesive.
9. A method for producing carbon or graphite foam parts, comprising:
introducing dry, foamable starch ( 1 ) into an open-top container ( 2 ) having a base ( 3 ) with a round or angular cross section, until the base ( 3 ) of the container ( 2 ) is covered uniformly and the container is filled with starch ( 1 ) for more than 10%;
introducing the container ( 2 ) partly filled with starch ( 1 ) into an oven ( 4 );
heating the container ( 2 ) to a foaming temperature of >180° C. to foam the starch ( 1 ) until the container ( 2 ) has filled completely with carbon foam ( 6 );
withdrawing the container ( 2 ) from the oven ( 4 );
extracting the carbon foam ( 6 ) after cooling,
portioning the carbon foam ( 6 ) into carbon foam parts ( 6 . 1 ); and
carbonizing the carbon foam parts ( 6 . 1 ) at a temperature above 1000° C. under vacuum.
10. A method for producing carbon or graphite foam parts, comprising:
introducing dry, foamable starch ( 1 ) into an open-top container ( 2 ) having a base ( 3 ) with a round or angular cross section, until the base ( 3 ) of the container ( 2 ) is covered uniformly and the container is filled with starch ( 1 ) for more than 10%;
introducing the container ( 2 ) partly filled with starch ( 1 ) into an oven ( 4 );
heating the container ( 2 ) to a foaming temperature of >180° C. to foam the starch ( 1 ) until the container ( 2 ) has filled completely with carbon foam ( 6 );
withdrawing the container ( 2 ) from the oven ( 4 );
extracting the carbon foam ( 6 ) after cooling,
portioning the carbon foam ( 6 ) into carbon foam parts ( 6 . 1 ); and
graphitizing the carbon foam parts ( 6 . 1 ) at a temperature above 1700° C.
11. The method as claimed in claim 10 , wherein the thermal treatment of the carbon foam parts ( 6 . 1 ) for graphitizing takes place under a pressure of >500 mbar.
12. The method as claimed in claim 11 , further comprising:
preheating the carbon foam parts ( 6 . 1 ) with a flat heating ramp in a vacuum oven to no more than 500° C. to volatilize volatile constituents ahead of the thermal treatment.
13. The method as claimed in claim 10 , further comprising:
converting the graphitized carbon foam parts ( 6 . 1 ) into SiC in an oven ( 4 ) at a conversion temperature of >1200° ° C. with supply of SiO with argon as carrier gas under a pressure between 30 mbar and 950 mbar.
14. The method as claimed in claim 13 ,
wherein the conversion temperature is no more than 1600° C.