ABSTRACT
Bitumen (BIT) is an oil sub-product with many applications. A variety of literature reports the analysis of its optical properties, as the fluorescence and the Fourier transform infrared (FT-IR) optical transmittance (OT). We have performed photoluminescence (PL) on the visible region of the spectrum and OT on the visible-NIR in solutions of BIT in toluene at different concentrations. The results revealed a nonlinear, concentration-dependent effect attributed to intermolecular solvent-solute interactions. PL analysis of pure BIT as a function of the temperature and the laser pumping power pointed to the existence of nanosized crystalline inclusions on the amorphous BIT matrix with noticeable optical properties. The inference was confronted with the results of X-ray diffraction studies and literature reports. The possibility of the occurrence of a quantum size effect governing the luminescence is considered.
ABSTRACT
The present work describes the preparation and the investigation of the room temperature electrical and optical properties of a series of liquid nanocomposites (lnC) prepared with different concentrations of multiwalled carbon nanotubes (MWCNT) in a variety of liquid matrices: glycerin, Vaseline, glucose, propylene glycol and silicone oil (SIO). Special attention is deserved to the SIO matrix, owing to its convenient electrical properties for our purposes. We verified that a small percent fraction of MWCNT dispersed along the SIO matrix is capable of improving the electrical conductivity of the matrix by orders of magnitude, indicating that the MWCNT strongly participates in the electrical conduction mechanism. Also, the application of an external electric field to this lnC resulted in large changes in the optical transmittance, that were interpreted as a consequence of the fieldinduced MWCNT alignment into the liquid matrix. The characteristics of such a new category of nanocomposite in the liquid state suggest further studies.
ABSTRACT
The present work reports the results of structural and optical investigations in samples of natural dolomite, subjected to thermal treatment at different temperatures (500 â to 700 â) and times (one up to three hours). The motivation is the evaluation of the changes that may occur in carbonaceous asteroids and meteorites, respectively, subjected to the action of the solar radiation and heated during the fall in the atmosphere. We carried out scanning electron microscopy, electron dispersive spectroscopy, X-ray diffraction, optical reflectance and photoluminescence measurements.
ABSTRACT
The class of carbonaceous chondrite meteorites has carbon in their structures, similarly to the terrestrial calcite and dolomite rocks, and contains the group =CO3 linked to Ca and/or Mg, which may be, in principle, more susceptible to the action of the spatial gamma radiation (γ-R) due to the presence of these light-atom elements. On the present work, we used a variety of optical techniques to investigate the possible effects of γ-R produced by an artificial 192Ir source in terrestrial calcite and dolomite, which may allow to understand the effect of the spatial radiation in that celestial bodies of the solar system. As a result, we verified that the γ-R irradiation caused the effect of untrapping of electrons from deep color centers, that spatially migrate to other color centers on the samples, resulting on the change of the electron energetic configuration.
