Characterization of materials by micro-Raman spectroscopy

Huong, Pham V.; Verma, A. L.; Chaminade, Jean‐Pierre; Nganga, L.; Frison, Julien

doi:10.1016/0921-5107(90)90064-i

Cited by 42 publications

(6 citation statements)

References 9 publications

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“…However, non-stoichiometric TiC 1−x has been reported to be Raman-active, probably due to the presence of carbon vacancies, deformation defects and lattice imperfections contained in the off-stoichiometric TiC 1−x structure. A Raman spectroscopic signal for off-stoichiometric TiC 1−x has been reported by Lohse et al [25], Klein et al [36], Amer et al [37], Huong et al [39], Oláh et al [40] and Pellegrino et al [41]. Essentially, Klein et al reported normal vibrations of off-stoichiometric TiC 1−x bonds that corresponds to total vibrational Γ = A 1g + E g + T 2g of Raman-active modes [36].…”

Section: Raman Spectroscopy Analysismentioning

confidence: 78%

Study of reaction sequences during MSR synthesis of TiC by controlled ball milling of titanium and graphite

Oghenevweta

Wexler

Całka

2018

Materials Characterization

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During reactive ball milling of Ti and C, mechanically induced self-propagating reaction (MSR) synthesis of TiC is reported to occur via a process including initial formation of small amounts of TiC prior to exothermic ignition, followed by MSR and the formation of stiochiometric TiC (Dorofeev et al., 2011; Oghenevweta et al., 2016 [1, 2]). However, both the chemical evolution and mechanisms of reaction and growth of TiC both prior to, during and after ignition are not fully understood. This research focuses on fundamental understanding of the reaction sequences during MSR synthesis of TiC from elemental Ti and C (graphite). Magnetically controlled ball milling of stoichiometric (1:1) powder mixtures of titanium (Ti) and graphite (C) was performed under He gas with the exothermic ignition point by determined via in-situ temperature measurement. X-ray diffraction, Scanning Transmission Electron Microscopy (STEM) with electron energy loss spectroscopy (EELS), Raman Spectroscopy and X-ray Photoelectron Spectroscopy (XPS) were employed to interpret the reaction sequences. The reaction sequence involved the following: During milling prior to ignition, severely deformed Ti, spheriodised graphite and amorphous carbon forms, and minor amounts of off-stiochiometric nano-TiC 1−x crystals. In addition to the formation of TiC 1−x , XPS revealed the formation of oxide skins coating the surface regions of the milled powders. There is also an evolution towards stiochiometric TiC with increasing milling time. Immediately after ignition, a reacted product comprising a mixture of multi-layer stacks of thin TiC plates form, in addition to a matrix comprising large TiC particles which have been liquid phase sintered under the high local heat of reaction by thin layers of unreacted Ti. MSR occurs via a dual mechanism involving rapid growth of existing TiC, plus nucleation and growth of new TiC. High spatially resolved EELS combined with STEM revealed additional information about the inhomogeneous chemical environment of the milled powders.

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Section: Raman Spectroscopy Analysismentioning

confidence: 78%

Study of reaction sequences during MSR synthesis of TiC by controlled ball milling of titanium and graphite

Oghenevweta

Wexler

Całka

2018

Materials Characterization

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“…3(a)) over the range of 100 and 2000 cm −1 revealed five characteristic bond vibrations, located at 262, 424 and 612, 1334 and 1585 cm − 1 . The first three peaks (262, 424 and 612 cm − 1 ) are due to chemical bond vibrations consistent with non-stoichiometric TiC phase while the last two are associated with the A 1g and E 2g C\ \C bond vibrations of graphite particles [11][12][13][14]. A Raman signal associated with non-stoichiometric TiC reportedly occurs due to carbon deficiency and defect accumulation in the TiC during its formation [11][12][13][14][15][16].…”

Section: Resultsmentioning

confidence: 93%

Early stages of phase formation before the ignition peak during mechanically induced self-propagating reactions (MSRs) of titanium and graphite

2016

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“…Many experimental methods have been used to evaluate the oxygen content in the high-T c superconductors samples:, iodometric titration [16][17][18][19], coulometric titration [17,20], thermogravimetric analysis [16,18,21], micro-Raman spectroscopy [22], spectrophotometric method [23][24][25], volumetric method [26] but all these measurements are destructive, so one knows the characteristics of the sample when it is no more useful. From these considerations the importance of a non-destructive method for the oxygen evaluation in high-T c superconductors become obvious.…”

Section: Introductionmentioning

confidence: 99%