Effect of Surrounding Gas Pressure on Triboemission of Charged Particles and Photons from Wearing Ceramic Surfaces

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Abstract
Triboemission of charged particles and photons during scratching of Al2O3 surfaces with a diamond stylus was investigated under various pressures of Ar, He and O2 gases. The results showed that the emission intensity of negatively and positively charged particles and photons peaked, dependent on the gas pressure at a pressure inherent to gas, while the friction coefficient was shown to be independent of gas type and gas pressure. The ratio of the charge intensity of the negative to positive particles was unaffected by gas pressure and the values were identical to those of the mobility ratios of the negative to positive, ions under any gas pressure. The three kinds of emission peaks for positive and negative particles and photons appeared at the same pressure inherent to gas. The peak values in charged particles decreased in the order O2 > Ar > He, while those of photon emission decreased in the inverse order of the charge intensity, i.e., He > Ar > O2. The gas pressure at which the emission curve peaked increased in the order O2 < Ar < He. All of this triboemission behavior could be explained by the ionization characteristics of the surrounding gas discharge model at the wearing contacts.