Crystallinity of bamboo-based carbon filaments for incandescent lamps examined by Raman spectroscopy as a nondestructive means of analysis.

The crystallinities of bamboo-based carbon filaments have been examined by Raman spectroscopy as a nondestructive means of analysis of the historical lamp (ca. 1890s) manufactured by Ichisuke Fujioka of Japan, and the results have been compared with results from the study of Edison's lamp (ca. 1889) and replica lamps produced in 1979. The crystallinities for the three carbon filaments have been evaluated in terms of the intensity ratio ID/IG, where ID is the intensity at 1350 cm(-1) for the D band originating from the defect of graphite and IG is the intensity at 1585 cm(-1) for the G band due to the stretching vibration of graphite layers. The ratios obtained are 0.3-0.4, 0.28-0.3, and 0.25-0.28 for the Fujioka, Edison, and replica lamps, respectively. The Raman spectrum of the bamboo-based carbon filament produced by thermal pyrolysis at 1273 K in a nitrogen atmosphere is significantly different from those of filaments inside the incandescent lamps. The raw bamboo filament was analyzed by ultraviolet (UV) Raman spectroscopy using an excitation wavelength of 325 nm from a HeCd laser to avoid the strong interference due to photoluminescence. An intense peak at 1585 cm(-1) was recognized, which was ascribed to the C=C bond vibration for the lignin component in the bamboo. The upper shift of the D band for the carbon filament pyrolyzed at 1273 K was confirmed by varying the excitation wavelength at 514.5 nm to 325 nm, and this behavior was interpreted on the basis of the double resonance Raman scattering mechanism.