Materials Science and Engineering

This book deals mainly with following areas XRD line profile analysis: In chapter II methods of precise and accurate estimation of crystallographic parameters using statistical techniques such as maximum likelihood method, & min-max method, have been developed and applied to extract different crystallographic parameters. In chapter III methods were developed to ascertain which analytical function can describe an experimentally observed XRD peak best. In chapter IV short comings of Voigt & pseudo-Voigt functions when subjected to Warren-Averbach and variance method of size-strain analysis, were discussed.In chapter V, a new method of structure refinement- an alternative to Rietveld method was proposed and applied to powder data of tungsten oxide.This method requires no apriori assumption regarding the functional nature of observed peaks.

In 1981 Solomon proposed a method of estimating aromatic carbon content of bituminous coals from their FTIR data and showed its correlation with the experimentally observed fixed carbon (FC). Present work aims to study the applicability of Solomon's method to five Indian lignites, viz. one Neyveli lignite and four Barmer (area Mahabarshivkur, Barmer, Rajasthan) lignite samples collected from four different locations. It is revealed that Solomon's method of ascertaining aromatic carbon content is also applicable to lignites with slight modification. Excellent correlation has been observed between aromatic carbon content Car and fixed carbon FC. Moreover, distribution of hydrogen in Indian lignites are studied and their gasification ability are predicted using Pradier's method in terms of the ratio of integral intensity of streching modes of (CH2/CH2 + CH3) in the region of 2800-3000 cm-1. Observed bands are assigned according to Painter et al. Peculiarly enough, no band at or around 3030 cm-1 assigned to aromatic C-H streching was observed in case of Neyveli and Barmer lignite B.

The interlayer spacing of hydrogenated amorphous carbon obtained through the pyrolysis of benzene, was found to change considerably on sonication (0.166 to 4.5 h) as observed from electron diffraction studies. The broadening of diffraction rings was found to change with sonication time, suggesting a contineous change in the degree of crystallinity. The electron micrographs also change from jumbled globular threads (on 0.166 h sonication) to discrete beady chains (on 4.5 h sonication). FTIR studies show that the sp3CH2(sym) stretching mode at around 2850 cm-1 and the sp3CH2(asym) stretching mode at around 2920 cm-1 are particularly sensitive to sonication. Upto 2 h sonication the concentration of sp3CH2(sym) steadily rises and on further sonicationits concentration gradually drops to an almost constant value. Plot of optical density (O.D.) at 2850 cm-1 as a function of sonication time shows a gaussian distribution. This property may be utilised to sense the ultrasonic waves end ascertain its dose.
Revue / Journal Title
Journal of the Indian Chemical Society    ISSN  0019-4522  CODEN JICSAH
Source / Source
2007, vol. 84, no4, pp. 370-372 [3 page(s) (article)]
Langue / Language
Anglais
Editeur / Publisher
Indian Chemical Society, Calcutta, INDE  (1928) (Revue)
Mots-clés d'auteur / Author Keywords
Sonication
;
pyrolytic carbon
;
electron diffraction
;
Localisation / Location
INIST-CNRS, Cote INIST : 556, 35400015990527.0130

Nº notice refdoc (ud4) : 18741194

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Structurally distinguishable phases of the substances present in four hydraulic (Portland) cement samples and in one white cement sample manufactured in India, were identified from their respective XRD diagrams and subsequently quantitatively analyzed using quantitative phase analysis program based on Rietveld refine ment (Bish and Howard, 1988). Phases present in all the hydraulic cement samples are tricalcium silicate (Alite and Haturite, C3S), dicalcium silicate (Larnite, C2S), brownmillerite, both orthorhombic and monoclinic phases (tetracalcium aluminoferrate, C4AF) and tricalcium aluminate (C3A). A small amount of gypsum, periclase, bassenite and other minerals were also found to be present in four Portland clinkers, while a sizeable chunk of calcium silicate hydrate gel (CAHG) was found to be present in three samples. In the white cement, as expected, neither form of brownmillerites were detected. Credibility, merits and demerits of the method used were discussed.

In 1981 Solomon proposed a method of estimating aromatic carbon content of bituminous coals from their FTIR data and showed its correlation with the experimentally observed fixed carbon (FC).Present work aims to study the applicability of Solomon's method to five Indian ...