Relation of Certain Quantum Chemical Parameters to Lubrication Behavior of Solid Oxides

Abstract

Abstract:It is well-documented that certain oxides (such as Re 2 O 7 , B 2 O 3, MoO 3 , V 2 O 5 , etc.) can provide friction coefficients of 0.1-0.3 to sliding surfaces at elevated temperatures and thus they are often referred to as lubricious oxides in the tribology literature. In a recently proposed crystal chemical model, Erdemir was able to establish a close correlation between the reported friction coefficients of such oxides and their ionic potentials [1]. In the present paper, we expand on this original concept and explore the relevance of two other quantum chemical parameters, electronegativity and chemical hardness, to the lubricity of solid oxides. These parameters have already been used by scientists to explain the nature of tribochemical interactions between various oil additives and sliding surfaces. It is conceivable that electronegativity and chemical hardness may also be strongly related to the extent of adhesive interactions and shear rheology of solid oxides and hence to their lubricity. The new results have confirmed that electronegativity, like ionic potential, is indeed a valid quantum chemistry parameter that can be used in predicting the lubrication behavior of solid oxides. Generally, the higher the electronegativity of the solid oxides is, the lower the friction coefficients will be. However, chemical hardness did not yield a similar trend. In light of these new findings, we propose some guidelines for the formulation of novel oxide or alloy systems that can lead to the formation of lubricious oxides at elevated temperatures. The findings of this study may pave the way for designer-based tribosystems in general and smart tribochemical systems in particular in future tribological applications such as dry machining.

Atmospheric aging and surface degradation in As2S3 fibers in relation with suspended-core profile

“…Thus, a question arises about the limits in depth reached by the hydrolysis process, as well as the resulting changes in glass composition. The resulting local drift of the glass composition will induce a local shift of the glass nano-mechanical properties, especially the friction properties [32]. Thus, at the boundary between contaminated and uncontaminated zones, the friction properties change and become inhomogeneous over these two zones.…”

Effect of Cu Content on the Structure, and Performance of Substoichiometric Cr–N Coatings

“…These values are related to coefficient of friction values of 0.40 and 0.18-0.22, respectively. Also, it is important to consider that according to the crystal chemistry approach, proposed by Erdemir et al [40], these differences could be partly due to the different coordination chemistry of Cr 2 O 3 (6) and CuO (4) phases. The different coordination numbers in the two cases as indicated by numbers in parentheses imply different response to adhesive interactions.…”

Superior MgH2 Kinetics with MgO Addition: A Tribological Effect

“…At such high temperatures, oxides such as TiO 2 and MgO are known to be effective lubricants providing low frictions coefficients to sliding tribological interfaces [47]. In a recently proposed model, Erdemir reported a correlation between friction coefficients and electronegativity [48]. The higher the electronegativity of a solid oxide is, the lower the friction coefficient would be.…”