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Int. J. Mol. Sci., Volume 6, Issue 6 (June-August 2005), Pages 203-229

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Research

Open AccessArticle Relation of Certain Quantum Chemical Parameters to Lubrication Behavior of Solid Oxides
Int. J. Mol. Sci. 2005, 6(6), 203-218; doi:10.3390/i6060203
Received: 1 April 2005 / Accepted: 18 May 2005 / Published: 24 August 2005
Cited by 26 | PDF Full-text (171 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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. Full article
Open AccessArticle Synthesis and GIAO NMR Calculations for Some Novel 4-Heteroarylidenamino-4,5-dihydro-1H-1,2,4-triazol-5-one Derivatives: Comparison of Theoretical and Experimental 1Hand 13C- Chemical Shifts
Int. J. Mol. Sci. 2005, 6(6), 219-229; doi:10.3390/i6060219
Received: 7 April 2005 / Accepted: 21 August 2005 / Published: 25 August 2005
Cited by 25 | PDF Full-text (109 KB) | HTML Full-text | XML Full-text
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 [...] Read more.
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. Full article

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