Abstract--Raman and Fourier-transformed infrared spectra of natural trioctahedral chlorites of polytype IIb were obtained for a series of samples characterized by distinct Fe/(Fe + Mg) and Si/Al ratios ranging, respectively, from 0.04 to 0.94 and from 5.18 to 1.86. All samples were characterized by X-ray powder diffraction, and quantitative electron microprobe analysis. In the 3683-3610-cm -~ spectral range, the wave number of the OH-stretching band from the 2: l layer (band I) decreased with an increase of iron content at constant Al(IV) content. The more intense bands II and III at about 3600 cm l and 3500 cm -1, were assigned to hydroxyl groups involved in hydrogen bonds: (SiSi)O... HO, with the hydrogen bonds being roughly perpendicular to the basal plane, and (SiA1)O... HO, respectively. At higher tetrahedral A1 and octahedral Fe contents, spectra exhibited OH-bands II and III, respectively, at a lower frequency. Band III intensity increased and band II was enlarged for chlorites displaying higher AI(IV) contents.In the 1300-1350-cm l spectral range, most infrared spectra displayed intense bands at 1090, 1050, 990, and 960 cm ~, which were assigned to T-O stretching of symmetry species A1 and El. The second type of bands observed both in Raman and infrared spectra were at about 650-800 cm ~; they were assigned to OH vibrations and were strongly dependent on the composition of the interlayer octahedral sheet, especially on the Fe content.
The quantitative determination of crystallinities of polyethylene samples from the analysis of vibrational bands due to 6(CH,) twisting and v(CC) stretching in the Raman spectra between 950 and 1500 cm-' was assessed. Several methods based on manual resolution of band envelopes and on computer-derived information using Gaussian and Lorentzian profiles were compared. The major source of error was found to be the estimation of the amorphous and crystalline interphase content, ab . A new method for the determination of sample crystallinity is proposed based on the time-dependent Fourier transform deconvolution of the spectral region between 950 and ls00 cm-', which takes into account the baseline corrections and the influence of vibrational band shoulders in this region to obtain consistent values of a,, ab and a,.
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