The Particles of Contact Activation

Particles formed by arcing on relay contacts both in various activating (organically contaminated) atmospheres and in central office atmospheres have been examined and analyzed by various techniques including Auger, thermal, and scanning electron microscopy analyses. Carbonaceous particles were obtained on Au, Pd, Ag, Pd-Ag, Pd-S, Pd-Pb, Cu, Ni, AI, and C electrodes. In addition to these carbonaceous particles, metallic particles were also observed. Scanning electron micro- scopy revealed that small (< 450Å diameter) carbonaceous particles cluster to form larger (~0.1 µm diameter) particles. No distinction could be made between the laboratory and field produced particles. Contact activation or the enhancement of arc durations was observed to be possible for all electrodes examined using the nominally resistive break arcs in all the heavily organically contaminated atmospheres used (benzene, toluene, naphthalene and diethylphthalate at partial pressures of 100 torr, 30 torr, 0.09 torr and 3.8 X 10-3 torr, respec- tively).