Interpretation of (Pu,U) matrix effect on atomization of analytes during GF-AAS analysis

Atomization of Al, Cr, Cu, Cs, Mn, Ni and Sr in (Pu,U) matrix was studied and the effect of Pu/(Pu + U) composition of the matrix on analyte absorbance was investigated. The changes observed in the absorbance signals for the analytes with change in composition of (Pu,U) matrix were correlated with relative oxygen partial pressures of the analyte oxides, UO₂, PuO₂ and the purge gas. The studies were utilised for the direct determination of trace levels of these analytes in (Pu,U) matrix containing 25 at.% Pu by graphite furnace atomic absorption spectrometry (GF-AAS) with a relative precision of approximately ±10%.     

Structural and Chemical Evolution of Highly Fluorinated Li-Rich Disordered Rocksalt Oxyfluorides as a Function of Temperature

Li-rich disordered rocksalt (DRS) oxyfluorides have emerged as promising high-energy cathode materials for lithium-ion batteries. While a high level of fluorination in DRS materials offers performance advantages, it can only be achieved via mechanochemical synthesis, which poses challenges of reproducibility and scalability. The definition of relationships between fluorination and structural stability is required to devise alternative methods that overcome these challenges. In this study, the thermal evolution of three highly fluorinated phases, Li₂TMO₂F (TM = Mn, Co, and Ni), is investigated in an inert atmosphere. Diffraction and spectroscopic techniques are utilized to examine their electronic and chemical states up until conditions of decomposition. The analysis reveals that the materials phase-separate above 400 °C, at most. It is also observed that heat-treated DRS materials exhibit intricate changes in the local coordination of the metals, including their spin, and ordering compared to the pristine states. The changes upon annealing are accompanied by a modulation of the voltage profile, including reduced hysteresis, when used as electrodes. These results provide an in-depth understanding of the fundamental crystal chemistry of DRS oxyfluorides in view of their promising role as the next generation of Li-ion cathodes.     

Tailoring the Structural and Optical Parameters of Eu3+:CeO2-SiO2 Nanopowder Via Thermal Treatment

Silicon - Nanocrystalline Eu3+:CeO2-SiO2 powder samples were prepared by sol-gel technique. This technique is suitable for large-scale production and it is also a cost effective process. The...     

Tuning of structural,optical, and magnetic properties of ultrathin and thin ZnO nanowire arrays for nano device applications

One-dimensional (1-D) ultrathin (15 nm) and thin (100 nm) aligned 1-D (0001) and (0001¯) oriented zinc oxide (ZnO) nanowire (NW) arrays were fabricated on copper substrates by one-step electrochemical deposition inside the pores of polycarbonate membranes. The aspect ratio dependence of the compressive stress because of the lattice mismatch between NW array/substrate interface and crystallite size variations is investigated. X-ray diffraction results show that the polycrystalline ZnO NWs have a wurtzite structure with a = 3.24 Å, c = 5.20 Å, and [002] elongation. HRTEM and SAED pattern confirmed the polycrystalline nature of ultrathin ZnO NWs and lattice spacing of 0.58 nm. The crystallite size and compressive stress in as-grown 15- and 100-nm wires are 12.8 nm and 0.2248 GPa and 22.8 nm and 0.1359 GPa, which changed to 16.1 nm and 1.0307 GPa and 47.5 nm and 1.1677 GPa after annealing at 873 K in ultrahigh vacuum (UHV), respectively. Micro-Raman spectroscopy showed that the increase in E₂ (high) phonon frequency corresponds to much higher compressive stresses in ultrathin NW arrays. The minimum-maximum magnetization magnitude for the as-grown ultrathin and thin NW arrays are approximately 8.45 × 10⁻³ to 8.10 × 10⁻³ emu/g and approximately 2.22 × 10⁻⁷ to 2.190 × 10⁻⁷ emu/g, respectively. The magnetization in 15-nm NW arrays is about 4 orders of magnitude higher than that in the 100 nm arrays but can be reduced greatly by the UHV annealing. The origin of ultrathin and thin NW array ferromagnetism may be the exchange interactions between localized electron spin moments resulting from oxygen vacancies at the surfaces of ZnO NWs. The n-type conductivity of 15-nm NW array is higher by about a factor of 2 compared to that of the 100-nm ZnO NWs, and both can be greatly enhanced by UHV annealing. The ability to tune the stresses and the structural and relative occupancies of ZnO NWs in a wide range by annealing has important implications for the design of advanced photonic, electronic, and magneto-optic nano devices.     

Structural,Thermal and Luminescence Study of Ceria Nanocrystals Dispersed in Silica Matrix

Silicon - Ceria (CeO2) nanocrystals dispersed in silica were prepared by sol-gel, a very suitable method for large-scale production. The formation of cubic fluorite structure of CeO2 nanocrystals...     

Assessment of proteolysis in ultra‐high temperature milk using attenuated total reflectance–Fourier transform infrared spectroscopy

This study investigated the suitability of attenuated total reflectance–Fourier transform infrared spectroscopy (ATR‐FTIR) as an alternative technique to assess proteolysis in ultra‐high temperature (UHT) milk. Commercial UHT milk samples were stored (5 and 30 °C) and analysed for four months. Milk samples were treated with acetic acid and trichloroacetic acid to obtain milk extracts containing peptides. The concentrated extracts were subjected to ATR‐FTIR, and the spectrum was obtained. Results were compared with techniques like high‐performance liquid chromatography, fluorescamine and 2,4,6‐trinitrobenzenesulphonic acid. The present study indicated that ATR‐FTIR‐based method can be used as an alternative method for assessing proteolysis in UHT milk.     

Embedded macroporous elastomers by hydrostatic fracturing for flexible strain‐sensor applications

A method is proposed for fabricating flexible materials embedded with macroporous regions by inducing fractures under point loading. Possible use of these structures in strain sensing is demonstrated. Injecting air at high pressure through a needle‐tip generates 3‐dimensional fractures in homogeneously crosslinked polydimethylsiloxane (PDMS) media, whereas a 2‐dimensional planar fracture is generated in a sandwich‐like structure wherein a softer layer is bounded by two stiffer layers. Size‐dependence of 3‐dimensional fractures on stiffness of the media which is controlled by the crosslinker concentration shows a maximum, suggesting an optimal stiffness for generating largest fracture. The size of the 2‐dimensional fractures (～5 cm) generated inside the sandwiched layer is huge as compared to the 3‐dimensional fractures (～1 mm) under the similar conditions. Two dimensional fractured surfaces show ridges with feature length monotonically becoming smaller with stiffness. Embedded rough planar domains are created by introducing 2‐dimensional fractures at distances close enough to overlap. Using this method an embedded 2‐dimensional porous domain of polyaniline nanostructures is realized in flexible PDMS matrix. An Ohmic nature of these embedded polyaniline domains with an ability to change resistance under compression establishes their suitability for developing inexpensive and flexible strain sensors. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43681.     

Quality evaluation of black CTC teas based upon seasonal variations

Effects of seasonal variations on the colour and chemical constituents of Indian black tea were investigated. The experimentation involved collection of different black tea samples that were cultivated at the same tea garden but harvested in three different seasons. Measurement of moisture content was done along with theaflavins (TFs), thearubigins (TRs) and colour (CIE La*b* values) of the brewed tea liquor using spectrophotometric approach. The correlation analysis between chemical constituents, that is, TFs and TRs, moisture content, colour and quality grading was done by using principal component analysis (PCA). The results suggest that quality of tea is dependent upon seasonal variations in terms of chemical changes such as TFs, TRs and moisture content, which also correlate well with colour. The efficacy of the colour of brewed tea liquor in explaining the changes in tea quality due to seasonal variations can be beneficial for scientific fixation of prices at tea auction centres.     

Economic Analysis of Recreation Access at a Lake Facing Water Crisis due to Municipal Water Demand

Water Resources Management - Droughts and water demand for competing uses such as municipal supply, nature-based recreation, and fisheries have added challenges in lake management. Sustaining the...