Effect of hot isostatic pressing on nanopore in glass-like carbon prepared from phenol-formaldehyde resin

The effect of a hot isostatic pressing (HIP) treatment on glass-like carbon (GC) was investigated by a small-angle X-ray scattering (SAXS) method. The sample was prepared from phenol-formaldehyde resin at 1700 degreesC and then HIP-treated at 2500 degreesC at 200 MPa in inert gas atmosphere. The structure change in pores was expected, because the bulk density of the HIP-treated GC is higher than those of untreated GCs. In order to contrast the HIP-treatment effect, SAXS measurements on untreated GCs were also carried out. The scattering intensity from the HIP-treated GC was weaker than that from the GC which was heat-treated only at the same temperature 2500 degreesC. On the other hand, the distance distribution function (DDF) analysis showed that the sizes and shapes of nanopores for the both GCs are almost the same. It was proved that the HIP process contributes to not reducing the size but decreasing the number of nanopores in the GC. The facts suggest that the size of uncrushed nanopores will be the minimum one for each heat-treated GC. (C) 2001 Elsevier Science Ltd. All rights reserved.