OUTGASSING OF METALS STIMULATED BY FRICTION

In addition to spontaneous outgassing of materials and desorption stim ulated by particle or photon bombardment, a gas release from mechanica lly affected materials was recently discovered as another source of ga ses in vacuum systems. Particularly outgassing due to operation of man ipulators and transmissions becomes limitation on attaining low pressu res in industrial uhv plants. An experimental device was built to stud y the gas release during friction in vacuum. Changes in the total and partial pressures were measured when a metal sample was rubbed by a to ol in a uhv chamber and influence of mutual movement speed, friction f orce, metal species, gas pressure, and temperature was studied. Result s of the extended series of experiments lead to the conclusion that ga ses dissolved in metals were the main source of the released gases. Ad sorbed gases were released by rubbing, too, but in an amount that was usually too small to be registered on the background of the gases rele ased from the bulk. Tribochemical reactions among gases dissolved in m etal, residual gases present in the uhv chamber, and material of the s ample were responsible for the release of gases that were neither diss olved in the bulk nor adsorbed on the surface, as methane and carbon o xides. (C) 1997 Elsevier Science Ltd. All rights reserved.