• N C Sarmah

      Articles written in Bulletin of Materials Science

    • Fourier–transform infrared spectroscopic characterization of naturally occurring glassy fulgurites

      B J Saikia G Parthasarathy N C Sarmah G D Baruah

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      We report here for the first time the spectroscopic characterization of natural fulgurites of Garuamukh. On April 22, 2005 at 04 : 00 local time, large amounts of black-brown colour of colloidal solution came out from below the earth’s surface at Garuamukh near Nagaon town (latitude 26°20′39″N, longitude 92°41′39″E, Assam, India) with fire and smoke. This colloidal solution got transformed into fulgurites, glassy material, within a few hours. We present here the characterization of the fulgurites by Fourier transform infrared (FTIR) absorption, X-ray diffraction and X-ray fluorescence methods. The amorphous nature of the substance has been confirmed by Fourier transform infrared spectra of the fulgurites, which exhibit prominent absorption band in the region 400–1200 cm-1, the basic component of amorphous silica. The present study might have significant implications in understanding the thermodynamic properties of naturally occurring glasses, which are formed by shock metamorphism.

    • Fourier transform infrared spectroscopic estimation of crystallinity in SiO2 based rocks

      Bhaskar J Saikia G Parthasarathy N C Sarmah

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      We present here optical properties and crystallinity index of quartz (SiO2) in natural rocks samples from the Mikir and Khasi hills, Assam, India. Infrared spectroscopy has been used to study the structure of quartz in rock samples and estimate the mining quality of quartz mineral, which is substantiated by calculating the crystallinity index. Systematic investigations of structure have been carried out in between 10 𝜇m (1000 cm–1) and 20 𝜇m (500 cm–1) bands of silicates. Investigation is based on the assignment of infrared bands to certain structural groups of SiO4 tetrahedra. The crystallinity of samples has been ascertained by comparing the ratio of intensity of the characteristic peak at 778 and 695 cm–1 with the corresponding ratio for a standard sample. The crystallinity parameter is calculated by using a standard procedure which can be used to estimate the distribution of quartz in various rocks for mining purpose. The infrared spectroscopic investigation is found to be an ideal tool for structure elucidation and for estimating quartz crystallinity of the natural samples.

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