Fluorescence properties and energy transfer mechanism of Sm ion in lead telluroborate glasses

We report the fluorescence properties of Sm³⁺-doped lead telluroborate glasses of composition PbF₂.TeO₂.H₃BO₃.Sm₂O₃ as a function of Sm³⁺ concentration. A Judd-Ofelt scheme was used to determine the intensity parameters and radiative properties of Sm³⁺ ion. The emission and decay measurements were carried out at 402 nm excitation. Beyond 1.0 mol% Sm³⁺ concentration, the luminescence quenching is observed. The decay curves of ⁴G_5/2 level are well fitted to a single exponential function. The evaluated radiative properties suggest that the ⁴G_5/2 → ⁶H_7/2 transition is responsible for reddish-orange luminescence which might be used in the development of visible lasers.     

Ionic conduction in polyether-based lithium arylfluorosulfonimide ionic melt electrolytes

We report synthesis, characterization and ion transport in polyether-based ionic melt electrolytes consisting of Li salts of low-basicity anions covalently attached to polyether oligomers. Purity of the materials was investigated by HPLC analysis and electrospray ionization mass spectrometry. The highest ionic conductivity of 7.1 × 10⁻⁶ S/cm at 30 °C was obtained for the sample consisting of a lithium salt of an arylfluorosulfonimide anion attached to a polyether oligomer with an ethyleneoxide (EO) to lithium ratio of 12. The conductivity order of various ionic melts having different polyether chain lengths suggests that at higher EO:Li ratios the conductivity of the electrolytes at room temperature is determined in part by the amount of crystallization of the polyether portion of the ionic melt.     

Heat transfer in micropolar boundary layer flow near a stagnation point

Using the micropolar theory, a set of boundary layer equations are obtained for the two dimensional flow of an incompressible micropolar fluid near a stagnation point. The boundary conditions of isothermal and insulated wall are taken with VISCOUS DISSIPATION effects. Numerical results for the temperature distribution has been shown graphically for different values of the material parameters and Prandtl number.     

First report on observation of abnormal creep in a Zr–2.5wt.%Nb alloy at low stresses

Low-stress creep behaviour of a two-phase Zr–2.5%Nb alloy, differently heat treated, has been investigated using helical test specimens. The phase diagram of the α (hcp) + β (bcc) alloy is characterized by the monotectoid reaction at 893 ± 10 K: β ₁ → (α + β ₂) where β ₁ (Zr–20Nb) and β ₂ (Zr–80Nb) have widely differing compositions. At the creep testing temperature, 818 K, which is close to but below the monotectoid temperature, the creep rate for samples with the equilibrium α + β ₂ structure has been found to be considerably higher, over an order of magnitude, than that in samples with the metastable α + β ₁ structure. Microstructural changes accompanying the markedly enhanced creep rate for the α + β ₂ structure at stresses as low as 1–4 MPa have been explained in terms of the relative stability of the β ₁ and the β ₂ phases during the creep process. An attempt has been made to elicit the likely mechanism underlying the observed enhancement of creep rate and the changes in morphology, composition and volume fraction of the β phase.     

Fed batch enzymatic saccharification of newspaper cellulosics improves the sugar content in the hydrolysates and eventually the ethanol fermentation by Saccharomyces cerevisiae

The newspaper is comprised of (w w^?1) holocellulose (70.0%) with substantial amount of lignin (16.0%). Bioconversion of the carbohydrate component of newspaper to sugars by enzymatic saccharification, and its fermentation to ethanol was investigated. Of various enzymatic treatments using cellulase, xylanase and laccase, cellulase enzyme system was found to deink the newspaper most efficiently. The saccharification of deinked paper pulp using enzyme cocktail containing exoglucanase (20 U g^?1), β-glucosidase (60 U g^?1) and xylanase (80 U g^?1) resulted in 59.8% saccharification. Among additives, 1% (v v^?1) Tween 80 and 10 mol m^?3 CoCl₂ improved the enzymatic hydrolysis of newspaper maximally, releasing 14.64 g L^?1 sugars. The fed batch enzymatic saccharification of the newspaper increased the sugar concentration in hydrolysate from 14.64 g L^?1 to 38.21 g L^?1. Moreover, the batch and fed batch enzymatic hydrolysates when fermented with Saccharomyces cerevisiae produced 5.64 g L^?1 and 14.77 g L^?1 ethanol, respectively.     

Effect of alkali and alkaline earth oxides on crystallization of Li2O-Al2O3-SiO2 glasses

The effect of alkali and alkaline earth oxides on the crystallization of lithia-alumina-silica glasses has been studied. Crystallization behaviour of glasses has been investigated using DTA and XRD techniques. The principal crystallization phases are identified asβ-spodumene solid solution and lithium metasilicate. The crystallization temperature of glasses decreases with increase in the values of the ionic field strength of the alkali and alkaline earth cations. Addition of these oxides at lower concentrations has no significant effect on the crystalline phases.     

Parametric investigation on anhydrous sodium metaborate (NaBO2) synthesis from concentrated tincal

In this study, anhydrous sodium metaborate (NaBO₂), an industrial and technologically important boron compound, synthesis from concentrated tincal (CT) was carried out. Experiments with different temperature and time were performed in the parametric investigation to map out the reaction mechanism. Crystalline phase characterization of metaborates products indicates that anhydrous NaBO₂ synthesis from CT occurred at 400 °C with 5 h of reaction conditions. At the end of synthesis, the obtained anhydrous NaBO₂ product can be used in many fields without having the calcination step due to the advantages of this method.