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In the Raman analysis of tribofilms produced from organic precursors, the D- and G-band features are often observed, which resemble the characteristic bands of diamond-like carbon (DLC), amorphous carbon (a-C), or graphitic materials. This study reports experimental evidence that the D- and G-bands features in the Raman spectra of tribofilms could be generated by photochemical degradation of triboproducts due to the focused irradiation of laser beam during the Raman analysis, indicating that they are not unique to the genuine structure of the tribofilm produced via friction. This finding suggests that other complementary and non-destructive characterization is required to determine whether DLC, a-C, or graphitic species are produced tribochemically by frictional shear. 

Abstract Vibrational spectroscopy has been widely used to investigate various structural aspects of the glass network, and there are a plethora of papers reporting subtle but consistent changes in infrared and Raman spectral features of glass upon alterations of glass compositions, thermal histories, mechanical stresses, or surface treatments. However, interpretations of such spectral features are still obscured due to the lack of well‐established physical principles accurately describing vibrational modes of the non‐crystalline glass network. Due to the non‐equilibrium nature of the glass network, three‐dimensionally connected without any long‐range orders, vibrational spectral features of glass cannot be interpreted using the analogy with those of isolated molecular moieties or crystalline counterparts. This feature article explains why such comparisons are outdated and describes the recent advances made from theoretical calculations of vibrational spectral features of amorphous networks or comparisons of computational results with experimental data. For the interpretation of vibrational spectral features of silica and silicate glasses, the following empirical relationships are suggested: (i) the intensity‐weighted peak position of the Si‐O‐Si stretch mode negatively correlates with the weighted average of the Si‐O bond length distribution, and (ii) the broad band of the Si‐O‐Si bending mode negatively correlates with the Si‐O‐Si bond angle distribution. Selected examples of vibrational spectroscopic imaging of surface defects are discussed to deliberate the implication of these findings in the structure‐property relationship of silica and silicate glass materials. Unanswered questions and continuing research challenges are identified.