We report the effect of compositional variation (Si/Al ratios of infinity, 11, 5, 3, 2, 1.4, and 1) on the vibrational properties of sodalite (framework code SOD), one of the simplest zeolite frameworks, through density functional theory (DFT) calculations. Additionally, we report the results of testing our DFT calculations on experimentally obtained infrared spectra of sodalites using different synthesis conditions to obtain spectra for sodalites with Si/Al = 1 and Si/Al → ∞ (siliceous sodalite). The experimental spectra are in good agreement with our DFT calculations in terms of predicting the characteristic vibrational modes of sodalites. However, we observe substantial peak broadening in the asymmetric stretching region and additional peaks in the experimental spectra that are not present in the calculated spectra. The second part of the study tests whether these additional peaks could arise from the existence of defects (i.e., hydroxyl groups and/or adsorbed water) in synthetic sodalite powders. The vibrational spectra in the high-frequency OH stretching region from DFT calculations are also compared to the experimental spectra. With the help of DFT calculations and prior studies, we conclude that the defects in siliceous sodalites are likely to be silanol (SiOH) groups. Although hydroxyl groups and adsorbed water are not the only defects that can occur in zeolitic materials, our DFT calculations suggest that their inclusion is able to account for many of the discrepancies between the experimental and simulated spectra.

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The solar energy is one of the most promising energy sources today. In this context, the goal of this work is to produce selective surfaces for receiver tubes of parabolic trough collectors (PTCs). Ideally, solar collectors should have an absorbing surface that has high absorptance for radiation in the solar energy spectrum and, at the same time, low emittance. Therefore, Ni/NiO selective surfaces were produced with Ni in the first film and NiO in the second film. The method used was by electrolytic deposition of nickel on stainless steel AISI 304, followed by oxidation in a muffle furnace. The thicknesses of the coatings were measured with the photometer Digimess, making it possible to verify their variations and the surface irregularities typical of the electrodeposition procedure. The NiO film was observed in scanning electron microscope (SEM). The film hardness was evaluated by the pencil hardness test and the adhesion by the tape test.