Atmospheric effects of friction,friction noise and wear with silicon and diamond. Part III. SEM tribometry of polycrystalline diamond in vacuum and hydrogen |
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Authors: | Gardos Michael N Gabelich Stephen A |
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Affiliation: | (1) Sensors & Electronic Systems, aytheon Systems Company, El Segundo, CA 90245, USA |
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Abstract: | In this part III of a multi-part paper series, the results of additional SEM tribometric experiments are described, performed
with polished, mostly C(100)-oriented polycrystalline CVD diamond film PCDC(100) vs. PCDC(100)] counterfaces sliding in
Torr and in 0.1–0.3 Torr partial pressures of pure hydrogen gas. These tests were completed under a 28 g (0.27 N) normal
load, under standard and slow thermal ramping conditions at temperatures ranging from room temperature to 1000°C. The friction data were examined per the computer logging and analysis techniques described in part I. The treatment of
the data is similar to that of Si in part II: the maximum and the average coefficients of friction (MAX.COF and COF) and their
ratios (the friction noise FN) are employed to measure possible lubricative interaction of the diamond surfaces with rarefied
hydrogen. The results indicate that excited species of molecular hydrogen enter into tribothermally catalyzed reactions not
only with Si but with PCDC(100) surfaces as well. Similar to the behavior of Si, the most beneficial friction-reducing regime occurs in a temperature range
just before the thermal desorption of adsorbates. The general magnitudes of MAX.COF, COF and the FN are significantly lower
than those of the Si crystallinities, in both vacuum and
. The wear rate of the PCDC(100) film characteristic of the standard thermal ramping test procedure performed mostly in
is around
, in good agreement with the wear rate previously measured in vacuum for unpolished, fine-cauliflowered diamond films. The
data indicate that smooth polycrystalline diamond is a significantly better bearing material for miniaturized moving mechanical
assembly applications than Si.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | polycrystalline diamond (100)-texture polishing tribometry vacuum hydrogen high temperatures friction friction noise noise reduction wear dangling bonds adsorbates desorption chemisorption re(de)construction tribocatalysis |
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