Nitrogen Doping of Pyrolytic Graphite

Abstract

The radioactivation analysis by proton bombardment has been examined on the nitrogen-doped pyrolytic graphites which were prepared through the pyrolysis of pyridine at 2000°C under the pressure of a few milimeter mercury. Long slab test pieces with the dimension of 22mm×12mm each were cut out and exposed to the proton irradiation of 25 MeV-5μA for ten minutes, which led to the nuclear reaction of 14N (pα) C11.
The excitation function was measured by the so-called stacked-foil method. It has been found that the presence of 1ppm nitrogen in graphite gives rise to the saturation activity (thick target) of 5.3×10³ dpm by 11C after the proton irradiation of 15MeV-5μA. The nitrogen concentration was observed to vary from a few ppm up to several hundreds ppm as a function of depsite and annealing temperatures. X-ray diffraction works examined at the same time verifies that the layer spacing is independent of the nitrogen contetent.