Untitled

Jin

et al. 2013

SiC fiber-reinforced metal matrix composite is an interesting material for aerospace industry because of its excellent properties. However, these properties are greatly influenced by fiber microstructure and thermal residual stresses introduced by the preparation of the composites. Due to complicated preparation technology, microstructure and thermal stress along SiC fiber radius varies, which makes characterization difficult. Raman spectroscopy is a non-destructive technique which provides information, at micrometer scale, on the phase composition and the crystalline state (structure and texture) of materials. Line scanning was used to assess microstructure along SiC fiber radius embedded in Ti64. The SiC coating is subdivided into three concentric parts across the fiber diameter, according to the differences in intensity and width of SiC transverse optical phonon (TO) band. Part 2 is considered to be a buffer zone connecting Part 1 and Part 3 with different deposition conditions, respectively. Amorphous Si is detected throughout fiber radius, while crystalline Si is only detected in the outer part. Thermal residual stress along fiber radius in the composite was calculated by using SiC TO band shifts with a bare fiber as reference. A cylindrical model was also used to compare with the stress data obtained from Raman shift.

Section: Raman Mappingmentioning

confidence: 80%

Microstructure and thermal residual stress analysis of SiC fiber through Raman spectroscopy

Jin

et al. 2013

“…[1,5,12] Furthermore, polytypes of SiC possibly exists as well. [18] These reasons explain deviation between experimental and calculated spectrum in Fig. 4.…”

Section: Resultsmentioning

confidence: 97%

“…[17,18] In nano or defective materials, defects, amorphous phase, or grain boundary-related new vibration modes cannot be predicted through RWL model. Therefore, additional peaks (humps) should be added as assistance to fit experimental spectrum.…”

Section: Resultsmentioning

confidence: 99%

“…These new Raman features are clearly attributed to SiC microstructure. [1,18,19] In this paper, we discuss the relationship between Raman features and microstructure of CVD SiC fiber with the help of modified RWL model. Effect of geometries of weighting functions and preferred orientations in this model on the Raman lineshape is investigated.…”

Section: Introductionmentioning

confidence: 99%

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Raman investigation of defective SiC nanocrystals

Ouyang

et al. 2015

Phonon confinement effect and surface optical mode in SiC nanocrystal have been investigated through Raman spectroscopy. Considering high density of stacking faults in SiC grains, the correlation length of RWL (proposed by Richter, Wang, Li to explain phonon confinement in nano silicon) model is determined as a distance between nearby stacking faults. Thus, homogeneous region becomes thin slices in cylindrical SiC grains, which redefines weighting function. Effect of anisotropy of phonon dispersion curve is also analyzed during calculation. The additional 875-cm À1 band is attributed to defects and amorphous SiC, which is confirmed by transmission electron microscopy. SiC grains are approximated as column array with grain boundary substances regarded as surrounding medium, which explains surface optical phonon mode at 915 cm À1 .

“…Meanwhile SiC acoustic branch in the range of 100-600 cm À1 may also contribute to the intense signal. [20] Continuous peak shifts always reflect changes of Fig. 2) between SiC fiber and Ti 5 Si 3 (C x ) layer.…”

Section: Chemical Reaction In Interfacementioning

confidence: 90%

Raman investigation of chemical reaction product in thermal‐treated SiC_f/C/Mo/Ti6Al4V composite

Kou

et al. 2014

SiC fiber‐reinforced titanium matrix composite (TMC) is an interesting material for aerospace industry because of its excellent properties. Characterization of their interfacial reaction product is principal to further optimization of the TMCs. Here we report application of Raman spectroscopy to identify reaction products and their microstructural details in thermal‐treated SiCf/C/Mo/Ti6Al4V composite. Meanwhile TEM is performed to help explain phenomena in Raman result. Raman line scanning along interface indicates thickness of two sublayers (Ti5Si3(Cx) layer next to SiC fiber and TiCx layer next to matrix). The main Raman result of phase distribution is confirmed by TEM. While a 300‐nm Ti3SiC2 layer whose Raman features are similar with nearby Ti5Si3(Cx) layer is also detected. Raman peakshift in Ti5Si3(Cx) layer possibly results from residual stress or/and microstructural evolution caused by carbon solution. No evidence indicates Mo participation of interfacial reactions. However, Mo diffusion changes phase distribution of matrix alloy and affects interfacial reaction indirectly. Meanwhile, TEM and Raman results indicate that particles are TiCx and defective Ti3AlC2. Raman features of Ti3AlC2 particles differ from that of bulk material, which is attributed to defects. Although Ti3AlC2 formation mechanism is ambiguous, it possibly relates to TiCx formation nearby. Copyright © 2014 John Wiley & Sons, Ltd.