Heat treat configuration for porous carbon-carbon composites
View Patent ↗A method of heat treating a substrate for a fuel cell includes stacking substrates to form a group. A dimension is determined for a plate corresponding to a resulting mass that is less than a predetermined mass. The plate is arranged above the group to apply a weight of the plate to the group. The resulting masses for spacer plates and intermediate lifting plates, for example, are minimized to reduce the pressure differential between the bottom and top substrates in the heat treat assembly. In another disclosed method, a dimension for a plate, such as a top plate, is determined that corresponds to a resulting mass that is greater than a predetermined mass. The plate is arranged above the group to apply a weight of the plate to the group. The top plate resulting mass is selected to minimize a variation in the average pressure of the substrates throughout the heat treat assembly.
1. A method of heat treating a stack of porous carbon-carbon composites comprising the following steps in order:
determining a thickness and planform of a plate;
determining the number of porous carbon-carbon composites per plate;
stacking the determined number of porous carbon-carbon composites to form a group between plates;
determining the number of groups per stack;
selecting the size and number of any intermediate lifting plates;
arranging each component within the stack such that the pressure differential between the top-most composite and bottom most composite in the stack is within +/−30%; and
heating the porous carbon-carbon composites.
2. The method according to claim 1 , wherein the stacking step includes arranging the porous carbon-carbon composites in groups of between approximately 50 and 200 porous carbon-carbon composites.
3. The method according to claim 1 , wherein the plate is a spacer plate, and the arranging step is arranging the spacer plate between groups of porous carbon-carbon composites.
4. The method according to claim 3 , wherein the determining step includes determining a weight of the spacer plate.
5. The method according to claim 3 , wherein the determining step includes determining a planform of the spacer plate, the planform being approximately equal to the planform of the porous carbon-carbon composite.
6. The method according to claim 5 , wherein the planform of the spacer plate is less than approximately two inches greater than the planform of the porous carbon-carbon composites.
7. The method according to claim 3 , wherein the determining step includes determining a thickness of the spacer plate, the thickness is less than approximately one half inch.
8. The method according to claim 7 , wherein the thickness is between one eighth to three eighths of an inch.
9. The method according to claim 1 , comprising multiple spacer plates and groups arranged in alternating relationship to provide multiple porous carbon-carbon composite assemblies, a first porous carbon-carbon composite assembly arranged on a first lifting plate, a second lifting plate arranged on the first porous carbon-carbon composite assembly and a second porous carbon-carbon composite assembly arranged on the second lifting plate, wherein the determining step includes determining the presence and size for the second lifting plate.
10. The method according to claim 1 , wherein the pressure differential is less than approximately +/−25%.
11. The method according to claim 1 , wherein the pressure differential is less than approximately +/−15%.
12. The method according to claim 1 , wherein the heated porous carbon-carbon composites have a density in the range of 0.51-0.55 g/mL.