| Foam |
Density Range |
Cell Size |
Dopants |
Chemical Composition |
Production Issues |
| Resorcinol-Formaldehyde Aerogel (RF) |
20-850 mg/cm3 |
nm |
Chemical modification Physical dispersions |
62 wt% C, 38 wt% O & H
Carbonized 93 wt% C |
Molded to shape
Supercritical drying
Carbonized is machined |
Research into RF foam continues today. The foam is produced by reacting resorcinol and formaldehyde. It is an aerogel that has nanometer scale cell size. It can be molded to shape and used as RF, or it can be heated to 1000º C in an inert atmosphere where it becomes an almost pure carbon aerogel. Carbonized RF (CRF) can be machined to shape. Schafer was also part of the LLNL research team that first created microencapsulated RF shells.
 
Examples of RF and CRF foam. The foam on the left is an RF foam in which 70 micron diameter polystyrene beads have been distributed throughout. The foam on the right is a machined CRF disk. Note the chip in the bottom right hand corner. This foam is very brittle. |
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The advantages of RF are its very small cell size and its well understood gelling mechanism (this allows RF to be microencapsulated and particles can be suspended in it). The limitations are that the density cannot be less than 20 mg/cc, that it does contain oxygen, and that it requires super critical drying (an expensive and time consuming step). The advantages of CRF are its very small cell size; its limitations are that it cannot be less dense than 20 mg/cc and it requires extensive processing – the super critical drying of RF plus the carbonization step. |
Resorcinol-Formaldehyde Aerogel (RF)