Chemical Characterisation of Bulk and Melt-spun Ribbons of NiMnIn alloy using Inductively Coupled Plasma Optical Emission Spectrometry

Method development for the analysis of NiMnIn, a new magnetocaloric effect (MCE) material using inductively coupled plasma optical emission spectrometry (ICPOES) is discussed. Spectral interference of Ni and Mn on the analysis of In were studied. The process of method validation was carried out using various analytical techniques like conventional wet chemical techniques and instrumental techniques such as atomic absorption spectrometry. All the techniques show a close agreement in values, thus this method could be applied for regular analysis of NiMnIn alloys. A comparative chemical analysis of bulk and melt-spun ribbons of this alloy is also discussed.Defence Science Journal, 2011, 61(3), pp.270-274, DOI:http://dx.doi.org/10.14429/dsj.61.39

Effect of Ag+ ion Concentration on the Reaction Kinetics and Shape of Nanoparticles Synthesised by Green Chemical Approach

The effect of varying Ag+ ion concentration on the green chemical reaction with a fixed tea aliquot concentration has been studied in detail with the help of UV-visible absorption spectra. With increase in the concentration of Ag+ solution the position of surface plasmon band systematically increased from 435 nm – 450 nm. The reaction followed first order kinetics and the rate of reaction increased in a linear fashion with k = 3.54 x 10-4 min-1 for 0.5 mL to k = 1.86 x 10-3 min-1 for 3.0 mL Ag+ solution. X-ray diffraction patterns showed an enhanced (200) reflection for 3.0 mL Ag sample. The shape of Ag nanoparticles could be effectively tuned from spherical to cuboid with increase in silver content as evidenced from scanning electron and transmission electron micrographs. The average particle size of Ag NPs increased from 25 nm to 55 nm with increase in the Ag+ content of the reaction

Microstructure and Mechanical Properties of Tungsten Heavy Alloy Prepared Using Tungsten Metal Powder Produced from Heavy Alloy Scrap

Tungsten metal powder, using a hydrometallurgical route, was extracted from tungsten heavy alloy scrap that was generated during machining of penetrator cores for the manufacture of Fin Stabilised Armour Piercing Discarding Sabot (FSAPDS). The powder was subjected to extensive characterisation that included physical property evaluation and analysis of the alloy chemistry in order to assess its suitability for the preparation of tungsten heavy alloys with enhanced mechanical properties. Subsequently, a tungsten heavy alloy based on W-Ni-Co was consolidated using this powder through liquid phase sintering followed by heat treatment and swaging operations to realize long rods (~500 mm). This was followed by a detailed characterisation that included microstructure and mechanical property. The mechanical properties of these rods are promising, exhibiting a good balance of tensile and impact properties, which in turn underscores the potential of these recycled powders in the production of premium quality heavy alloy long rods for stringent applications such as kinetic energy penetrators. &nbsp

REE geochemistry of seawater from Afanasy-Nikitin Seamount in North Central Indian Ocean by high resolution inductively coupled plasma mass spectrometry

339-347<span style="font-size:9.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="" lang="EN-US">REE (Rare Earth Elements)  and yttrium in sea water samples, from the Afanasy-Nikitin Seamount (ANS) located around 3o South latitude and 83o East longitude in the north central Indian Ocean were precisely determined by high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) method. A modified procedure has been designed for determination of REE and yttrium wherein the water samples were subjected to a pre-concentration step using bis-2-ethylhexyl phosphoric acid (HDEHP) complexing agent. Sea water reference materials such as NASS-5 and SLEW-3 were used for calibration as well as to check the accuracy of the procedure adopted.  Samples were analyzed for REE and yttrium by HR-ICP-MS. Precisions achieved for various rare earths and yttrium is better than 8% RSD with comparable accuracies. Limit of detection (3σ) were generally in the range of 0.02-1.2 pg/ml range for all these elements. This method facilitates rapid and interference-free determination of REE and yttrium from relatively small volume of sea water (10 ml).  Recoveries for different REE and Y were better than 5%, and accuracy and precision of the determinations are within 8% RSD. The Ce-negative anomalies with smooth normalized-REE patterns obtained for both certified reference materials and samples further substantiate that the procedure adopted and the data generated are extremely accurate. A slight enrichment of heavy REE were observed in the central Indian Ocean waters which might be attributed to the river flows containing more dissolved trace elements including REE. A sharp negative Ce-anomaly in the normalized REE distribution patterns indicates that the source of REE in particular Ce in marine sediments is seawater. Results of the variation in REE concentrations with depth indicated that the physico-chemical conditions of bottom ocean water follow a very complex mechanism.</span