What stress components drive mechanochemistry? A study of ZDDP tribofilm formation

Abstract

Zinc diakyldithiophosphate (ZDDP), the most widely used antiwear additive in engine oils, has been extensively studied over the last few decades to help understand the origin of its effectiveness. Glassy...

Acceleration of Diels-Alder reactions by mechanical distortion

“…To apply this model, the mean p in the nanoreactor contacts was determined as a function of F by dividing by the feature area. Our use of mean pressure is consistent with current published work on probe-based mechanochemistry ( 32 , 49 , 50 ). There was a spatial distribution of that pressure, as seen in our finite element simulations (fig.…”

Effects of surface chemistry on the mechanochemical decomposition of tricresyl phosphate

“…Previous experiments have shown that tribofilm growth is primarily controlled by shear stress and not the normal stress. 9,10,91 Moreover, from Fig. 3c, it is clear that the higher shear stress in the 100% TCP system leads to larger k values than for the 50% TCP, 50% DIDA systems, even at identical normal stress (Fig.…”

“…This reduction in shear stress is expected to due the lubricating effect of the low-friction ester base oil. 90 From previous mechanochemistry experiments of ZDDP tribofilm growth, 9,10,91 it is anticipated that the lower shear stress will result in lower reactivity for the 50% TCP, 50% DIDA than the 100% TCP system. Fig.…”

Molecular Probing of the Stress Activation Volume in Vapor Phase Lubricated Friction

“…A recent study has demonstrated that the contact pressure can hinder tribo−chemical reactions. 46 Physically, the vapor phase lubricated friction likely involves the local mobility of groups of 2-propanol molecules. As the partial pressure of the vapor phase lubricant is increased, the "mobile" volume also increases, suggesting that larger clusters of 2-propanol become involved in the shear process, as illustrated in Figure 4D.…”

“…The energy required to activate the shear process, Q ′ , was found to be ∼1.0 × 10 –19 J or 0.6 eV for all lubrication conditions (Figure S4), a typical energy for bonding at the molecular scale. ,,, This energy contains the pressure-induced barrier, i.e., p Ω; this suggests that as pressure increases in the contact, the required energy for the shear event will become larger and, thus, hamper the sliding process. A recent study has demonstrated that the contact pressure can hinder tribo–chemical reactions . Physically, the vapor phase lubricated friction likely involves the local mobility of groups of 2-propanol molecules.…”