Recovery of High Purity Y2O3 by Solvent Extraction Route Using Organo-Phosphorus Extractants

A rare earth concentrate assaying about 60% Y₂O₃, is generally obtained directly from Y rich minerals like xenotime or from monazite after preliminary fractionation of rare earths chloride as is practised currently at Indian Rare Earths Ltd.. Alwaye. Using this intermediate concentrate. SX process has been developed in our laboratory to purify Y (>99.9%) in presence of NH₄SCN. The process parameters for DEHPA and PC 88A systems have been optimised using a computer program in BASIC. The DEHPA flowsheet has been tested at bench-scale to produce several kilograms of 93% Y₂O₃. During these trials certain problems were faced due to high acidities. With PC 88A there were no problems and the flowsheet based on the solvent was confirmed at pilot-plant level. The solution containing 93% pure Y₂O₃, is purified further by another cycle of SX with 50% TBP in kerosene in presence of 1.0 M NH₄ SCN. The impurities are extracted leaving >99.9% pure Y₂O₃ in the aqueous phase. The process parameters optimised for obtaining >90% recovery of Y₂O₃ are described.     

Design of microstrip hyperbolic line to match a complex impedance to a standard coaxial transmission line

Based on the solution of the Riccati equation, a hyperbolically tapered microstrip transmission line for matching a complex load to a standard coaxial cable is designed. An iterative procedure is used to yield the phase constant leading to an accurate design. A numerical example is considered. The result shows that a tremendous reduction in the size of matching components can be achieved if hyperbolic instead of uniform transmission lines are used. This is highly advantageous in the miniaturization of solid state circuits.     

Modelling of acidification kinetics and textural properties in dahi (Indian yogurt) made from buffalo milk using response surface methodology

The simultaneous effects of fermentation temperature (20.8–29.2C), total solids (TS) level (13–16% w/v) and total inoculum level (1–4% v/v) on the acidification process in buffalo milk fermented with dahi culture were explored by means of response surface methodology. The changes in lactose content and lactic acid in buffalo milk (14.5% TS) inoculated with 2.5% culture were investigated during fermentation at 27.5C. The utilization of lactose followed first order kinetics during dahi fermentation. The syneresis increased with increase in fermentation temperatures. A firmer gel was achieved with a medium acidification rate in the range of fermentation temperatures from 27C to 29.2C, medium TS of 14.5–15%, and at a total inoculum level of 2.5%.     

Self-propagating high temperature synthesis (SHS) of titanium carbide

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Pd grating obtained by direct micromolding for use in high resolution optical diffraction based sensing

Pd grating patterns have been fabricated using the process of micromolding in capillary employing a Pd alkanethiolate precursor, which could be converted to metal in situ by thermolysis. Thus generated Pd grating were uniform in width (~950?nm) and spacing (~450?nm) over millimeter square areas on glass substrates. Importantly, the pattern when used as an optical grating produced a diffraction pattern with a high resolution (>2000); the intensities of widely separated (diffraction angle, ~26·8°) diffracted spots could be measured using a simple photodiode. By varying the concentration of Pd precursor (2?mM to 25?mM), thickness of the resulting gratings could be adjusted in the range of ~15?C115?nm. By adjusting the grating parameters optimally, a maximum diffraction efficiency of 36% has been achieved. Thus fabricated Pd grating was used as seed catalyst to deposit Cu by electroless plating. The Cu deposition process has also been monitored by employing AFM, SEM and EDS analysis. The diffraction efficiency values corroborate well with the changes in the grating thickness due to Cu deposition. The grating structures presented can be reproducibly fabricated for rapidly emerging optical diffraction based sensing applications. This has been demonstrated in the case of aqueous Cu^2?+? by depositing the latter electrolessly on Pd.     

Microwave assisted synthesis of poly(2-hydroxyethylmethacrylate) grafted agar (Ag-g-P(HEMA)) and its application as a flocculant for wastewater treatment

Poly(2-hydroxyethylmethacrylate) chains were grafted onto the backbone of agar using a microwave assisted method involving a combination of microwave irradiation and ceric ammonium nitrate to initiate the grafting reaction. The synthesized graft copolymers were characterized by intrinsic viscosity measurements, Fourier transform infrared spectroscopy, elemental analysis (C, H, N, O and S) and scanning electron microscopy. Ag-g-P(HEMA)-2 showed a much higher flocculation efficacy than agar. The optimized dosage of flocculation for Ag-g-P(HEMA)-2 in the wastewater was found to be 0.75 ppm. Compared to agar, Ag-g-P(HEMA)-2 was found to considerably reduce the pollutant load in the wastewater.     

Swift heavy ion irradiation induced modification of structure and surface morphology of BiFeO3 thin film

BiFeO₃ (BFO) thin films of thickness about 800 nm deposited on Si (100) substrates by sol–gel spin coating method were irradiated by 200 MeV Ag ions. Modification of structure and surface morphology of the films under irradiation was studied using glancing incidence X-ray diffraction (GIXRD) and atomic force microscope (AFM). Fluence dependence of GIXRD peak intensity indicated formation of 10 nm diameter cylindrical amorphous columns in crystalline BFO due to 200 MeV Ag ion irradiation. AFM analysis indicated that the pristine film consists of agglomerated grains with diffuse grain boundary. Irradiation led to reduced agglomeration of the grains with the formation of sharper grain boundaries. The rms roughness (σ _rms) estimated from AFM analysis increased from 6·2 in pristine film to 12·7 nm when the film irradiated at a fluence of 1 × 10¹¹ ions cm ^???2 . Further irradiation led to decrease of σ _rms which finally saturated at a value of 7–8 nm at high ion fluences. The power spectral density analysis indicated that the evolution of surface morphology of the pristine film is governed by the combined effect of evaporation condensation and volume diffusion processes. Swift heavy ion irradiation seems to increase the dominance of volume diffusion in controlling surface morphology of the film at high ion fluences.