Materials Science Forum Vols. 830-831

Abstract: Carbon based adsorbent materials are prepared from sucrose using copper as hard pore template. The adsorbent materials were obtained by heating mixtures of sucrose and copper sulphate at temperatures in the range of 200 to 1000 °C for polymerization and carbonization followed by removal of copper template by leaching with dilute nitric acid. The copper templates were produced by the carbothermal reduction of copper oxide obtained by the decomposition of copper sulphate. The surface area and porosity measurements showed the presence of micropores in the carbon samples. The micropores are generated both by an in situ activation and carbothermal reduction of the copper oxide. The microporous carbon showed good CO₂ adsorption characteristics.

Abstract: In the present study we prepared NiFe₂O₄, Ni_0.95Cu_0.05Fe₂O₄ and Ni_0.94Cu_0.05Co_0.01 Fe₂O₄ thin films by metallo-organic decomposition method (MOD) using spin coating technique. The samples were characterized by XRD. XRD patterns of thin films confirmed the formation of cubic spinel structure without any secondary phase. For microstructural analysis we characterized samples by Scanning Probe Microscope (SPM). From Atomic force microscopy (AFM), we analyzed surface morphology, calculated grain size, roughness and porosity. It has been found that grain size and roughness affected by Cu, Co substitution. After this we carried out magnetic force microscopy (MFM) on the samples. Effect of substitution on magnetic grains was observed from MFM.

Abstract: Co_0.6Zn_0.4Fe₂O₄ (CZFO), Pb_0.76Ca_0.24TiO₃ (PCT) thin films and Co_0.6Zn_0.4Fe₂O₄ – Pb_0.76Ca_0.24TiO₃(CZFO/PCT) composite thin film were prepared by chemical solution method using metello – organic precursor. Structural and microstructural properties were studied by using XRD and Atomic force microscopy (AFM) respectively. XRD patterns confirme cubic spinel structure for CZFO ferrite and perovskite structure for PCT ferroelectric phase without any impurity phase formation. Grain size and roughness were calculated from AFM images. Grain size and roughness of composite thin film are decreased in comparison to individual phases (CZFO,PCT). Magnetic properties were studied using VSM.

Abstract: We have studied the impact of simultaneous Ba²⁺ doping at Sm³⁺ site (hole doping) and F^- doping at O^2- site (electron doping) on the structural and superconducting properties of Sm1111 system using a single source, BaF₂. With BaF₂ doping the extent of layering of the grains and the grain size have been improved considerably. High transport current of 875 A/cm² at 12 K has been achieved for the doped sample. The binary doped sample shows higher T_C of 51 K than the corresponding F-alone doped sample. In addition, substantially high values of H_C2 and better J_C-H behavior are observed for the BaF₂ doped samples. These results strongly indicate the scope for SmFeAsO based conductors with higher current carrying capacity.

Abstract: Polymer based insulating dielectric materials have been replaced ceramic dielectric materials in the recent past due to their better electric, thermal and mechanical properties. They are user friendly and can be poured into any shape and size. In this work, room temperature vulcanized silicone rubber (RTVSR) is used as the base insulating material on account of its hydrophobicity and consequent low leakage losses. Further, addition of nanosized fillers into bulk polymers has often been seen to improve their electrical and non-electrical properties. Here, nanosized alumina fillers have been used in the RTVSR matrix. A concentration level of 3% by weight of nanoAlumina (Al₂O₃) is used. Mechanical mixing and ultrasonic mixing are used for reducing the agglomeration of nanofillers. In this work, we study the effect of incorporation of nanofillers into RTVSR on its propensity to tracking and associated degradation. Inclined plane test for erosion (IPT) as per the IEC60587 is performed. To estimate the extent of erosion, SEM and weight loss analysis are also done. Silicone rubber filled with nanosized alumina is seen to have a greater resistance to erosion in comparison to pure silicone rubber.

Abstract: The lithium-sulphur (Li-S) system is one of the most promising candidates for high energy density applications. Sulphur has several drawbacks such as poor conductivity, large volumetric expansion upon lithiation, dissolution of the intermediate polysulfides during charge-discharge processes. The objective of the present work is to prepare a ternary composite of MWCNT/S/conducting polymer system with unique characteristics to be used as a cathode material for lithium sulphur batteries. The synthesis has been carried out in two steps. Sulphur is introduced onto the surface of MWCNT by the chemical reaction between sodium thiosulphate and hydrochloric acid. In the second step, polyindole is produced by insitu reaction from indole monomer by using FeCl₃ as oxidising agent. The MWCNT and conducting polymer help to improve the conductivity of sulphur. The composite material is characterised by TGA, FTIR, SEM-EDS and XRD analysis. The polyindole formation is confirmed by using FTIR and SEM-EDS. Electrochemical studies have been performed to demonstrate MWCNT/sulphur/polymer composites as a cathode material for rechargeable lithium –sulphur batteries.

Abstract: Nanocrystalline Mn_xCe_1-xO₂ (0 ≤ x ≤ 0.5) powders have been synthesized by microwave refluxing method. XRD, Raman spectroscopy and TEM analysis confirm the substitution of Mn in cerium oxide to a large extent. With increased Mn content, the crystallite size and lattice parameter found to be decreased. In addition, shifting of Raman main band towards lower frequency side was also observed with increased Mn. This could be attributed to the distortion of lattice of CeO₂ due to the lattice strain induced by substitution of Mn.

Abstract: CdSiO₃: Ce³⁺ (1-11mol %) nanophosphors were prepared by low temperature solution combustion method using Oxalyl di-hydrazine (ODH) as fuel. The final products were well characterized by PXRD and SEM. The optical properties of the nanophosphors were investigated by Photoluminescence studies. PXRD results evident that CdSiO₃ phosphor shows pure single monoclinic structure. The average crystallite size was calculated using Debye – Scherer’s formula and was found to be in the range of 30-40 nm. The SEM micrographs show phosphors with high porosity and irregular shaped particles. Photoluminescence peaks observed at 454, 563 and 679 nm under 397 nm excitation was due to transition from 5d state to the ²F_5/2 and ²F_7/2 components of the ground state of Ce³⁺ in CdSiO₃ host material. CdSiO₃:Ce³⁺ nanophosphors show an intense yellow emission with CIE coordinates (0.47, 0.50) with average correlated color temperature value 3284 was within the range of vertical day light. The present study successfully demonstrates solution combustion synthesis of nanophosphors for display applications.

Abstract: This paper presents the development of silver nanoparticles entrapped starch-polyacrylic acid hydrogel by a one step facile strategy. Formation of silver nanoparticles was confirmed by TEM and SPRE. Hydrogen bond interaction present in the hydrogel network was manifested from the FTIR spectroscopy. Silver nanoparticles in the face centred cubic lattice were confirmed by XRD. Visco-elastic properties studied by rheological analysis showed storage modulus of ~1500 Pa and exhibited a high storage modulus than loss modulus revealing the formation of strong gels. Phase transition temperature was confirmed by DSC. Antimicrobial screening studies of these hybrid gel exhibited antimicrobial activity to E.coli and S.aureus suggesting its applications for gram + ve and gram - ve bacteria.

Abstract: Lead Free Ferroelectric Na_0.5Bi_0.5TiO₃ (NBT) Ceramic has been synthesized using sol gel method. The prepared NBT samples have been sintered at different temperatures 850°C, 950°C, 1050°C and 1150°C to achieve best sintering temperature. Structural analyses have been carried out using XRD and FTIR measurements. XRD patterns confirm perovskite structure having rhombohedral symmetry for all samples which is also supported by characteristic absorption band at ~627cm^-1 in FTIR spectra. Dielectric properties of NBT samples with frequency and temperature have been studied. NBT sample sintered at 1050°C exhibit comparatively high value of dielectric constant (ε’) and phase transition temperature (T_m). Ferroelectric properties of NBT samples have been studied at room temperature. Comparatively, better ferroelectric properties are observed for NBT sample having remnant polarization (P_r)~ 14.7 μC/cm²and coercive field (E_c)~ 26.8 kV/cm sintered at 1050°C.