Characterization of the anisotropy of pyrolytic carbon by Raman spectroscopy

Evaluation of thermal conductivity of the constituent layers in TRISO particles using Raman spectroscopy

“…For the buffer layer, the IPyC layer and the OPyC layer, the polarization ratio (RT) was 1.16, 1.09 and 1.21 respectively. In the previous study, the polarization ratio (RT) higher than 1.05 suggested that the PyC layer had low texture [24]. Therefore, all the PyC layers in this study have low texture, which also agrees with the OAF data listed in Table 1.…”

“…the intensity ratio of I(x, x)/I(y, y)) could provided the best correlation with the texture of the PyC layers, which has been previously confirmed by texture measured using the orientation angles from transmission electron microscope [24]. The polarization ratios (RT) can be calculated by dividing the integrated intensity of the first order peaks between 900 cm -1 and 1850 cm …”

“…Figure 5 shows the polarized Raman spectra of the buffer layer, the IPyC layer, and the OPyC layer, measured using two polarization configurations of {z (x, x) -z} and {z (y, y) -z}. As the scattering efficiency depends on the relationship between the polarization of the incident and scattered light, and the direction of the crystal planes [24], the intensity ratios at different polarization configurations can be related to the grain orientation. Besides, the polarization ratios (RT) (i.e.…”

Thermal conductivity mapping of pyrolytic carbon and silicon carbide coatings on simulated fuel particles by time-domain thermoreflectance

“…The main concern on this method is that the coatings on a rod or disk shape substrate have different microstructure from those on spherical substrates [13,14]. Not until recently when Rochais et al [6] characterized TRISO particles by photoreflectance microscopy has the thermal conductivity value for each layer been measured more accurately.…”

Numerical modeling of carbon/carbon composites with nanotextured matrix and 3D pores of irregular shapes

“…When the material is produced by CVI, the manufacturing parameters include temperature, pressure, residence time and the choice of precursor gas. It has been shown that variations in these parameters may result in isotropic, low-, medium-or high-textured PyC (Reznik and Hüttinger, 2002;López-Honorato et al, 2010). The level of texture can also change with the distance from the substrate Piat et al, 2008).…”