The Fourier transform infrared (FTIR) spectral analysis has been carried out for sediments of Vellar river, Tamilnadu collected at various depths from twenty seven different locations. The minerals such as quartz, feldspar (microcline and orthoclase), kaolinite, palygorskite, calcite, aragonite, montmorillonite, cerussite, hematite, sepiolite, magnesium oxalate and organic carbon are identified. Among these, quartz, feldspar and kaolinite are the major minerals and palygorskite, calcite, aragonite, montmorillonite, cerussite, hematite, sepiolite, magnesium oxalate and organic carbon are minor and traces. The relative distribution of these three major minerals was determined by computing the extinction co-efficient. The crystalline nature of quartz is judged by calculating crystallinity index which shows that the crystalline nature decreases with increase of depth. The observation made through relative distribution, shows that the amount of quartz and feldspar are relatively reduced and that of kaolinite is increased from upper to inner depth. As the depth increases the bands of kaolinite progressively broaden and shift to higher wave number side which suggests that the content of kaolinite increases with disorderedness. From XRD analysis, the minerals such as monazite, zircon and kyanite are additionally identified. The crystalline nature of quartz is also confirmed.
In the recently developed high-sensitive CaSO4 : Dy
phosphor, sieving before the high-temperature sintering treatment has successfully
eliminated particle agglomeration during subsequent sintering, and has
further enhanced its thermostimulated luminescence (TSL) sensitivity to
γ-rays. The reduction in TSL sensitivity of higher sized grains
observed earlier following the procedure of sieving after sintering has also more
or less vanished. Maximum TSL sensitivity is seen after sintering around
700°C, whereas maximum photoluminescent (PL) sensitivity is seen after
sintering around 325°C. While the observed increase in TSL sensitivity
(by 30%) with increasing sintering temperature in the range 325-700°C
is explained on the basis of diffusion of Dy3+ ions from
the surface to the whole volume of the grains (0-75 µm), the drastic
decrease (by a factor of 3) in PL sensitivity with increasing sintering
temperature is explained on the basis of change in the Dy3+
environment on the grain surface perhaps due to oxygen incorporation.
Washing with water and acetone, which affect mainly the surface traps,
enhances the PL sensitivity of CaSO4 : Dy slightly; however, it does not
influence TSL sensitivity very significantly. Grinding reduces PL in
general, but no such trend was noticed in TSL which supports the conclusion
that PL originates mainly from surface traps since grinding affects mainly
the grain surface. However, the sharp reduction in TSL and PL
sensitivities observed at 400°C indicates that an unusual process
takes place near that sintering temperature.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.