Table of Contents

Abstract: It is well-documented that certain oxides (such as Re₂O₇, B₂O₃, MoO₃, V₂O₅, 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.

Abstract: 3-Alkyl(aryl)-4-amino-4,5-dihydro-1H-1,2,4-triazol-5-ones (1) reacted with 5-methylfuran-2-carboxyaldehyde to afford the corresponding 3-alkyl(aryl)-4-(5-methyl-2-furylmethylenamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones (2). Four newly synthesized compounds have been characterized by elemental analyses, IR, ¹H-NMR, ¹³C-NMR and UV spectral data. In addition, isotropic ¹H- and ¹³C-nuclear magnetic shielding constants of compounds 3 were calculated by employing the direct implementation of the gaugeincluding-atomic-orbital (GIAO) method at the B3LYP density functional and HF levels of the theory. The geometry of each compound has been optimized using a 6-311G basis set. Nuclear shielding constants were also calculated by using 6-311G basis set. Theoretical values are compared to the experimental data.