Structural characterisation and electrical conductivity studies of BaMoO4 nanorods prepared by modified acrylamide assisted sol–gel process

Abstract

Scheelite type BaMoO₄ nanorods have been synthesised by modified acrylamide assisted sol–gel process. The prepared samples were characterised by X-ray diffraction (XRD), Fourier transform infrared (FTIR), Fourier transform Raman (FT-Raman), scanning electron microscope–energy dispersive X-ray (SEM–EDX) and transmission electron microscope (TEM) techniques. The crystalline phase and structure of the prepared samples were confirmed from the analysis of the obtained results of XRD, FTIR and FT-Raman respectively. The average crystallite size calculated using Scheeer’s formula and XRD data is found to be 98 nm. SEM images showed the formation one dimensional nanorods of diameter <300 nm. EDX spectra showed the existence of Ba, Mo and O elements of the prepared samples. From the TEM images, diameter and length of the rod are found to be 80 and 2070 nm respectively. The ac conductivities by impedance spectroscopy of the prepared BaMoO₄ samples were evaluated as a function of temperature ranging from 500 to 800°C in the air. The newly prepared BaMoO₄ nanorods showed electrical conductivity of 3·14×10^?3 S cm^?1.     

Melt processed elemental sulfur reinforced polyethylene composites

Elemental sulfur represents a largely unutilized resource for high performance materials development. In this context, elemental sulfur was investigated as reinforcing agent for high density polyethylene (HDPE) composites via extrusion. We were able to produce homogenous composites with sulfur content up to 30 wt %. Compounding was done at 190°C well above the polymerization temperature of elemental sulfur. Infrared and Raman spectroscopy showed that sulfur did not undergo chemical reaction with HDPE. Additionally, Raman spectroscopy showed that sulfur exists in its most stable allotrope, cyclooctasulfur (S₈). Differential scanning calorimetry (DSC) showed that sulfur is present in non‐orthorhombic crystal and X‐ray diffraction confirms the same. Results suggest that sulfur is predominantly in its cyclooctasulfur allotrope and occupies the amorphous region of HDPE. According to TEM and SEM microscopy, the composites were of high quality, smooth and without distinguishable defects. Quality and smoothness of composites depend on the experimental parameters and sulfur loading. The addition of elemental sulfur significantly improved the elongation at break of the composites from 835 to 1202% (43% increases with 15 wt % sulfur) despite the obvious fact that HDPE possess an already impressive elongation at break quality. Such phenomena have not been reported in the literature. The improved composites would be suitable for a variety of engineering applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43060.     

Thermal Expansion and Phase Stability Investigations on Cs-Substituted Nanocrystalline Calcium Hydroxyapatites

The high-temperature phase stability of Ca_10−x Cs _x (PO₄)₆(OH)₂, (x = 0–3) compositions synthesized by various wet chemical methods was investigated. The thermal expansion property of Ca₁₀(PO₄)₆(OH)₂ (abbreviated as CaHAp) and Cs-substituted CaHAp was measured by high-temperature XRD and dilatometry. The average crystallite size of the powders synthesized by wet chemical methods was found to be 10–50 nm range as shown by XRD and TEM. Up to 30 mol% Cs loading was observed to show only the apatite phase by XRD when the apatite powder was nanocrystalline in nature. However, high-temperature stability of the Cs-substituted system is limited to ≤5 mol%. Cs₃(PO₄) is observed to be separated out on heating the material above 773 K for compositions substituted with more than 5 mol% of Cs in the Ca-sublattice. The coefficient of thermal expansion measured by HTXRD is α_a = 12.42 × 10⁻⁶ K⁻¹, α_c = 14.98 × 10⁻⁶ K⁻¹; and α_a = 12.62 × 10⁻⁶ K⁻¹, α_c = 12.57 × 10⁻⁶ K⁻¹ for CaHAp and Ca_9.78Cs_0.2(PO₄)₆(OH)_1.96, respectively, in the temperature range of 298-1083 K. Bulk thermal expansion measurements are seen to be in agreement with the lattice expansion results.     

On the metastability of an Au-Sn phase prepared by splat cooling

The heat of formation of the metastable phase y(Au-Sn) with the D8_1-3 (γ-brass) structure containing 20.5 at. pct Sn was measured by tin solution calorimetry as △Hγ = —0.94 ±0.16 kcal/g-atom. Its free energy of formation was estimated and suggests that y at low temperatures comes close to being an equilibrium phase. The undercooling required for the formation of y was also estimated. This undercooling is prohibitively high (285 to 440 K) for an alloy containing 20.5 at. pct Sn, but is moderate (70 to 160 K) for an alloy containing 29.0 at. pct Sn. This difference explains why y forms only in splat-cooled melts with an excess of =>7.5 at. pct Sn above the composition of the γ phase.     

Safety evaluation of ambrette (<Emphasis Type="Italic">Abelmoschus moschatus</Emphasis> linn) seed oil

The seeds of ambrette (Abelmoschus moschatus Linn), after selective extraction of fragrance from the seed coat, are flaked and extracted with hexane to obtain a fatty oil. The FA composition and iodine value of the oil indicate it possesses saturated, monounsaturated, and polyunsaturated FA in ratios close to the recommendations of the United Nations World Health Organization; these characteristics make it suitable as an edible oil. Acute oral toxicity and safety evaluation in a 13-wk feeding trial on albino rats showed the oil is comparable to groundnut oil in all the parameters and is suitable for edible use.     

Safety of ciprofloxacin therapy in children: magnetic resonance images, body fluid levels of fluoride and linear growth

We evaluated the safety of ciprofloxacin administered in a dose of 15-25 mg/kg for 9-16 days, in a case series of 58 children who were between 8 months and 13 years of age. No arthropathy was observed during therapy and follow-up. Blinded evaluation of 22 pairs of nuclear magnetic resonance scans obtained before and between day 10 and 15 of therapy did not reveal any cartilage damage. After the first dose of ciprofloxacin (10 mg/kg), serum fluoride levels increased at 12 h in 15 of 19 (79%) patients; 24-h urinary fluoride excretion was higher on day 7 compared with basal values in 16 of 18 (88.9%) patients. Height z scores of 53 patients at a mean of 22.5 months of follow-up were not significantly different from basal scores (p = 0.12). In conclusion, ciprofloxacin may be recommended for use in children for short duration when effective alternative antibacterials are unavailable. However, there is a need for further studies to evaluate the tissue accumulation of fluoride and its potential to cause toxic effects.     

Effects of silicon addition on the first stage of

The influence of silicon on the precipitation kinetics of Al-Cu-Mg alloys is not yet understood, although its effect on the improvement of mechanical properties is well established. In this study, the kinetics of the first stage of precipitation in Al-1.52 pct Cu-0.75 pct Mg alloy con-taining 0.49, 0.76, and 1.03 pct Si were investigated by differential scanning calorimetry. From the calorimetric data, the extent of reactionY and the reaction rate(dY/dt) were evaluated as functions of the reaction temperature. The rates are expressible by the relation(dY/dt) = (1 —Y)k₀ exp(— Q*/RT), whereK ₀ is the frequency factor andQ* is the activation energy. For the alloys containing 0.49, 0.76, and 1.03 pct Si, the activation energies are 76.7, 70.1, and 64.6 kJ/mole, respectively, andk ₀ changes systematically with silicon content. Critical analysis of these results and those available in the literature on the silicon-free and 0.23 pct Si containing alloys shows that GP zones precipitate in the 0.49, 0.76, and 1.03 pct Si alloys, while only GPB zones precipitate in the silicon-free and 0.23 pct Si containing alloys. The sudden change in the precipitation behavior occurs due to the preferential removal of magnesium from the matrix by the insoluble particles which are present in 0.49, 0.76, and 1.03 pct Si alloys. The alteration of the matrix composition is also responsible for systematic decrease in the activation energy.