Polyfurfuryl Alcohol Resin Research Articles

Switching phenomena in glassy carbon

Reversible switching effect was studied in carbonized polyfurfuryl-alcohol resin. Switching appears after heattreatment at a temperature of 300°C. The maximum temperature range for both heattreatment and measurements at elevated temperature was limited by melting of aluminum electrodes (659·7°C). Measurements were performed up to the temperature of 600°C. First of all the memory of the low resistance state was studied as a function of heattreatment temperature. A correlation between the memory time of the sample and resistivity of the carbon used was established. No essential differences in switching effect were observed between evaporated carbon and glassy carbon. The results indicate that in the low resistance state carriers are concentrated on the conducting paths and remain there for days. The equilibrium in which the sample remains in the high resistance state is restored by diffusion of carriers away from the path. The unexpected result is that the switching effect is present even at temperature as high as 600°C (the sample was kept in high vacuum). Although the memory time is much shorter at elevated temperature, the sample can be switched to low and high resistance states.

Fabrication of low-density carbon honeycomb

Fabrication steps for preparing a low density (0.20 g/cc), high purity, carbon honeycomb having a dovetail-cell geometry are described. The method involves multiple polyfurfuryl alcohol resin impregnation treatments of an expanded cotton-linter honeycomb mounted on a framework of steel rods, followed by coking to carbon by heating to 1000°C in an inert gas atmosphere.