The vibrational modes of the β-Si3N4 Raman active bands appearing in the wave number region between 110 and 1100 cm−1 were determined by the polarization and the crystallographic orientation dependence of the Raman intensities of the bands using micro-Raman spectroscopy. The laser beam was focused onto a single grain with the shape of a regular hexagon or elongated hexagon on the sintered ceramic plate. The three intense bands appearing at about 185, 208, and 230 cm−1 were attributed to the vibrational modes of E2g, Ag, and E1g, respectively. The remaining peaks were also assigned to the irreducible representations.
The adsorption behaviors of cesium ion on silk fibroin (SF) fibers in aqueous solution were investigated for applications to purify the contaminated water by radioactive cesium ion. The ability of adsorption of cesium was smallest among the other metal ions compared. Tendency of such adsorption was explained in terms of the stability of the combination between the ions and the SF. The optimal condition for adsorption of cesium ion was searched. The thermodynamic adsorption behavior was discussed using the Langmuir and the Freundlich equilibrium adsorption models.
The stress dependence of the β-Si3N4 infrared-active band appearing at ∼1020 cm−1 was evaluated by using micro-FT-IR. A four-point-bending jig was built to apply stress to the sample. Two β-Si3N4 ceramics, prepared by pressureless sintering and hot-pressed sintering, were examined. The hot-pressed sample showed a linear relation to applied stress, whereas the pressureless sintered sample showed relatively scattered stress dependence due to the inferior signal-to-noise ratio of the spectra. The stress dependence parameter of the 1020 cm−1 band was evaluated as ∼2 cm−1/GPa.
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