Raman spectra of a graphite–nontronite association in marbles from Oltrek Island (Lake Baikal, Russia)

Abstract

The graphite in marbles from Oltrek, an uninhabited island on Lake Baikal, has been investigated by micro‐Raman spectroscopy using visible and near‐ultraviolet wavelength excitation. All graphite samples exhibit a sharp first‐order Raman band at about 1,580 cm−1 with a width from 10 to 19 cm−1, and sometimes a D1 band with very low intensity, which is occasionally absent. Using Raman spectra data it was estimated that the temperature of graphite formation in the Oltrek marbles is about 530–650°C and possibly even higher. This evaluation is in good agreement with the temperatures (about 700°C) determined by a graphite isotope geothermometer of the graphite–calcite pair. Scanning electron microscopy images have recorded a сonical graphite morphology on the surface of plate crystals of graphite. Raman spectra of samples with cones about 200–400 nm sizes showed that the graphite was associated with nontronite in the specimens studied. Natural nontronite, a clay mineral of the smectite group, has not been well characterized using Raman spectroscopy. Here, the Raman spectra of the Oltrek nontronite were compared with the spectrum of nontronite from the weathered crust of the Salair Ridge, Russia. The formation of hexagonal–pyramidal structures on the surface of graphite with the participation of clay and bio‐organic matter in marble is discussed.

The use of Raman and infrared spectroscopy in determining the space symmetry group among the groups with the same rules of systematic absence in the diffraction patterns: Some basic principles and applications

“…gr C2/ m (C 2h ), the Raman and IR bands do coincide (Tables 1 and S2). Such coincidences have not been observed for the known vibrational spectra of nontronites, [39,[42][43][44] and this fact must then favor the C2/m symmetry (Figure 1). A detailed assignment of most of the observed vibrational modes in the IR and Raman spectra of kladnoite C 6 H 4 (CO) 2 NH (a natural phthalimide), obtained from the coal deposits where they were formed as a result of coal bed fires or burning of coal waste heaps, has been performed.…”

“…gr C 2/ m (C 2h 3 ) has vibrational bands that do not coincide in the IR and Raman spectra, but for the rest, that is, cases (C 2 3 , C s 3 , and C 1 1 ), the Raman and IR bands do coincide (Tables 1 and S2). Such coincidences have not been observed for the known vibrational spectra of nontronites, [ 39,42–44 ] and this fact must then favor the C 2/ m symmetry (Figure 1).…”

Integration of porous graphitic carbon and carbon fiber framework for ultrahigh sulfur-loading lithium–sulfur battery

“…There are two extra peaks at 2680 cm −1 and 3240 cm −1 in the Raman spectra for the GC and PGC samples, which are assigned to 2D 1 and 2D 2 modes, respectively. These are characteristic of GC, 57,58 illustrating the successful conversion from AC to GC. The characteristic graphitic structure guarantees a high conductivity of PGC.…”

A machine learning approach for the automated classification of bulk sp2 and sp3 carbon materials

“…The testing dataset for HOPG, 30–51 GC, 30,44,52–74 and DLC 15,30–32,75–91 were obtained from the literature. A web tool (WebPlotDigitizer) was used to extract the data points from the Raman spectra in the interval between 1050 and 1800 cm −1 from the literature data 92…”