Asit Baran Panda

Low temperature preparation of nanocrystalline solid solution of strontium barium niobate by chemical process

Abstract Nanocrystalline powders of strontium–barium–niobate (SBN) with the composition Sr x Ba 1− x Nb 2 O 6 (with x =0.4, 0.5 and 0.6) have been prepared using a single step chemical synthesis process starting from a precursor solution constituting of triethanolamine (TEA), niobium–tartarate and EDTA complexes of strontium and barium ions. The complete dehydration of the TEA-soluble metal ion complex precursor solution through heating yield in a fluffy, carbonaceous precursor material, which on heat-treatment at 750 °C/2 h resulted in the single phase SBN powders. The precursor and heat-treated powders have been characterized by thermal analysis and X-ray diffraction (XRD) studies. The crystallite size and average particle size as measured from X-ray broadening and transmission electron microscope were found to be 15 and 20 nm, respectively.

Chemical synthesis of nanocrystals of tantalum ion-doped tetragonal zirconia

Abstract A polymer matrix-based precursor solution method is explored for the preparation of tantalum ion-doped tetragonal (t) zirconia polycrystals. The matrix is composed of sucrose and polyvinyl alcohol (PVA), which are the dispersing agents for the metal cations and finally act as a template for the nanoparticle through the formation of a mesoporous structure. The t-phase is formed in powders of zirconia with 5, 10, 15 and 20 at.% tantalum ion, and the phase is stable up to the calcining temperature of 1100 °C. The particle size distribution is narrow with the size range 20–40 nm for the sample containing 5 at.% tantalum ions calcined at 700 °C. The stabilization of the metastable tetragonal form is probably due to the strong TaO bonds, which hinder the reorientation of atoms during phase transformation.

Preparation of Nanocrystalline Calcium Aluminate Powders

Nanocrystalline calcium aluminate (CaAl2O4and Ca3Al2O6) powders have been prepared by pyrolysis of complex compound of aluminium and calcium with triethanolamine (TEA). The soluble metal ion-TEA complex forms the precursor material on complete dehydration of the mixtures of the complex of calcium-TEA and aluminium-TEA. The single-phase CaAl2O4and Ca3Al2O6powders have resulted after heat treatment at 800° and 1000°C, respectively. The precursors and the heat-treated final powders have been characterized by X-ray diffractometry (XRD), differential thermal and thermogravimetric analysis TG/DTA, and transmission electron microscopy (TEM). The average particle sizes as measured by transmission electron microscopy studies are around 30–40 nm and 25–30 nm for CaAl2O4and Ca3Al2O6powders, respectively. These nano-sized powders are very suitable for making various nano-composites with polymers and inorganic compounds.

Preparation of nanocrystalline SrBi2Ta2O9 powders using sucrose-PVA as the polymeric matrix

Nanocrystalline powders of SrBi2Ta2O9 (Strontium Bismuth Tantalate) have been prepared through evaporation of a polymer-based aqueous precursor solution. The precursor solution was obtained by homogeneous dispersion of the water-soluble metal salts (i.e., strontium nitrate, bismuth nitrate and tartarate complex of tantalum) in a polymeric matrix created by an aqueous solution mixture of sucrose and polyvinyl alcohol. Complete evaporation of the precursor solution (at ∼200°C) resulted in a fluffy, porous, carbonaceous mass, which on calcination at 750°C/2 h yield the single-phase SrBi2Ta2O9 powders with average particle size ∼35 nm. The compacted powders, after sintering at 1000°C/4 h, show density of 96.8% of its theoretical value and dielectric constant value of 862 with Curie temperature (Tc) at 287°C, when measured at 100 KHz.

A novel solution-based method for the preparation of nanocrystalline single-phase 0.9Pb(Mg1/3Nb2/3)O3–0.1PbTiO3 powders

Abstract Nanocrystalline powders of solid solution of lead magnesium niobate–lead titanate with the ratio 9:1{0.9Pb(Mg 1/3 Nb 2/3 )O 3 –0.1PbTiO 3 }, have been prepared using a single-step chemical synthetic process starting from a precursor solution containing niobium/titanium tartarate and lead/magnesium triethanolamine (TEA) complexes. The soluble metal complex solution on complete dehydration followed by decomposition forms a black fluffy carbonaceous precursor material, which on calcination at 750 °C (2 h) results in single-phase pyrochlore-free pure 0.9Pb(Mg 1/3 Nb 2/3 )O 3 –0.1PbTiO 3 (0.9PMN–0.1PT) powders. The precursors and heat-treated powders have been characterized by infrared (ir) spectroscopy, thermal analysis, X-ray diffraction studies (XRD) and transmission electron micrograph (TEM). The crystallite size and average particle size as measured from XRD line broadening and TEM has been found to be 38 and 40 nm, respectively.

Nanofiller as Crosslinker for Halogen-Containing Elastomers

A Zn ion-coated nanosilica filler has been developed and tested, in chlorosulfonated polyethylene (CSPE) and polychloroprene (CR), as a vulcanizing activator, cum was reinforcing filler. In this study, ZnO was replaced by the Zn ion-coated nanosilica filler with an aim of studying the dual role of this nanofiller in CSPE and CR. In the case of CSPE vulcanizates, the presence of MgO deteriorated the state and rate of cure when the Zn ion-coated nanosilica filler was used, but in the case of CR it improved the state of cure and enhanced the modulus and tensile strength. The Zn ion-coated filler proved to be a better reinforcing-cum-curing agent than was externally added ZnO and NA-22 also proved to be a better curative in the presence of the Zn ion-coated nanosilica filler for both CSPE and CR.