Triboplasma Generation and Triboluminescence in the Inside and the Front Outside of the Sliding Contact

Abstract

Previously, high-intensity triboplasma was discovered in the rear outside gap of the sliding contact by measuring the triboluminescence. However, we have almost no information on the triboplasma generation inside of the sliding contact. This is because the intensity of the photon emission from the inside of the sliding contact is too weak to be detected compared to that from the highintensity rear outside plasma. On the other hand, plasma generated at the front outside of the contact was also difficult to observe since the intensity was also so weak. In the present article, the author investigated the triboplasma generation at the inside, front outside and very vicinity of the sliding contact together with the rear outside of the sliding contact by measuring the two-dimensional images and intensities of the UV, visible and IR photons emitted from the sliding contact while sliding a diamond pin with a 4-mm tip radius on a sapphire disk in dry sliding in dry air under a normal force of 2 N and a sliding velocity of 34 cm/s. The results showed that extremely weak triboplasma is generated even in the small asperity gap of the sliding contact, that the sliding contact is surrounded by weak circular plasma and that weak plasma is generated further in the front of the sliding contact. Namely, four kinds of triboplasma were observed inside and outside of the sliding contact including the previously reported rear outside high-intensity plasma, (1) weak front outside plasma, (2) weaker circular outside plasma surrounding the contact, (3) weakest inside plasma and (4) high-intensity plasma, visible at the rear outside of the contact. Based on the experimental results, a new model of triboelectromagnetic phenomena has been proposed.

Triboelectric microplasma powered by mechanical stimuli

“…The solar-powered plasma needs a transformer and an energy storage device for dark environment 23 . Triboplasma, induced near contact point where the diamond slides on sapphire surface under pressure, is limited to in situ applications 29 – 31 . Therefore, the investigation on portable and self-powered plasma generation using ambient mechanical energies is impending and worthwhile, even though it is both scientifically and technically challenging.…”

Surface Chemistry Dependence of Mechanochemical Reaction of Adsorbed Molecules—An Experimental Study on Tribopolymerization of α-Pinene on Metal, Metal Oxide, and Carbon Surfaces

“…Mechanochemistry refers to reactions activated by mechanical forces. − Compared to conventional thermochemistry, electrochemistry, and photochemistry where reactions are induced by heat, potential bias, or light irradiation, the molecular mechanisms or key parameters governing yield or selectivity of mechanochemical reactions are much less studied and understood. When a substantial amount of frictional heat is generated at high sliding speeds and not dissipated fast enough through conduction to the solid substrate, the thermal activations of interfacial molecules can be considered to play important roles. , When severe wear of solid materials occurs at high applied loads or under poorly lubricated conditions, then reactive surface sites such as dangling bonds or emission of charged particles (electrons or ions) or photons could be involved in the initiation of chemical reactions of molecules present on the wearing surface. − At a relatively low load and/or under slow sliding speed conditions, frictional heating and triboemissions are insignificant, but mechanochemical reactions can still take place. − …”

Tribo-induced photoluminescent behavior of graphene and YSZ:Er/graphene composite films

“…1,2 However, attempts to observe and predict those changes at nanoscale or microscale levels proved to be especially difficult. 3,4 Therefore, a deeper understanding of the friction process is sought in order to develop an effective early warning system capable of monitoring and locating friction-induced failure in situ. In the past decade, several tribological mechanisms have been proposed to explain the friction processing of freshly worn surfaces along with the associated formation and transfer of debris.…”