Materials Science Forum Vols. 830-831

Abstract: In recent years phase change materials have emerged to be ideal energy storage materials for their higher energy density over sensible heat storing materials. Use of phase change materials (PCM) have been successfully implemented at lower temperature applications with various organic compounds. On the other hand, high temperature applications have been solely dominated by various salts, their eutectics and mixtures as phase change materials. This work discusses the suitability of metals and alloys for thermal energy storage applications as the phase change material. Metals offer superior thermal conductivities with considerable energy density compared to salts. Here, two alloys namely, Sn-0.3Ag-0.7Cu (SAC) solidifying over 212-224°C and ZA8 (Zn-8%Al) solidifying over 378-405°C have been studied. Thermal analysis of PCMs using Computer Aided Cooling Curve Analysis (CA-CCA) and DSC technique were performed to predict the solidification path. In addition to this, Newtonian technique was employed to estimate the latent heat of fusion for these phase change materials. Cooling rate curves and Fraction Solid curves offered a better insight into their ability to receive and discharge heat over the concerned temperature range.

Abstract: The structural and superconducting properties of iron sheathed mono-filamentary superconducting wires of MgB₂ with and without Fe addition processed at a relatively low temperature of 600 °C were investigated. The transport critical current density (J_C) of the superconducting composite wires is found to increase steadily with an increase in Fe content to an optimum of 10 wt.% is reached. The magnetic J_C and flux pinning analysis of the samples carried out up to a field of 9 T also show significant enhancements throughout the entire field of study. Another observation is that the T_C of the composites doesn’t vary much, indicating that the added Fe has not gone in to the MgB₂ lattice.

Abstract: In this work we demonstrate that La₂NiMnO₆ exhibits a colossal magneto-dielectric (MD) effect (5%-55%) over a broad range of temperatures (100–270 K), when compared to other Rare Earth (RE = Pr, Sm, and Tb) containing Ni-Mn double perovskites. The noticeable magneto-dielectric effect in RE₂NiMnO₆ signals the influence of spin orientations in the two magnetic sublattices on the spin-lattice coupling. Finally with the help of Raman spectroscopy we clarify that the presence of spin-phonon coupling alone is not the cause for the observed colossal MD effect in RE₂NiMnO₆.

Abstract: The aim of the present investigation is to enhance in-vitro bioactivity and protein adsorption of porous titanium with 3D interconnected pores by various chemical treatments (alkali, dual acid, citric acid and fluoride treatments). The untreated and treated samples were characterized using X-ray powder diffraction (XRD), optical microscopy and scanning electron microscopy (SEM). The protein adsorption study was carried out with Bradford’s reagent using Bovine Serum Albumin (BSA). The optical microscopy reveals that untreated Ti sample exhibited 41.36% surface porosity. The in-vitro bioactivity of the treated and untreated Ti sample was evaluated by immersing them in simulated body fluid (SBF) for different time intervals. The immersed samples were characterized using XRD and SEM to confirm the growth and morphology of apatite. It was observed that apatite deposition of fluoride treated sample was denser than other treated samples for the same period immersed in SBF. All the surface treated samples showed good protein adsorption. The alkali treated sample showed maximum protein adsorption amongst other chemically treated samples which may be due to enhanced micro-roughness and strong electrostatic affinity between the protein and the surface. The enhanced in vitro bioactivity in the surface treated porous titanium indicates that the healing time of the bone and implant in patients can be reduced with good osseointegration.

Abstract: Herein, we report a simple method towards achieving graphene oxide-silicon nanoparticle (GO-Si NP) composite in aqueous solution. The preparation method is environmental friendly and the product formed was characterized using various techniques such as SEM, EDAX, XRD etc. The results confirm the formation of the nanocomposite and the composites with various percentage of Si NP was prepared and is expected to improve the cycling stability of Si NP as an anode material in lithium battery.

Abstract: A novel process for the preparation of a nickel foam from nickel oxide has been studied. The solid organic foam prepared by the thermo-foaming of a nickel oxide powder dispersion in molten sucrose is heat treated at the 1000 °C in an inert atmosphere to produce the nickel foam. The nickel foam produced has interconnected cellular structure with porosity ~ 94%.

Abstract: Shape memory polymer composites (SMPC) are a new kind of smart materials where many researches have been carried out. In SMPC, shape memory polymers serves as a matrix material and particles or fibers act as reinforcements. As structural applications demand structures to withstand load and stiffness, particles reinforced SMPC does not serve for it. Therefore fiber/fabric reinforced SMPC used widely for such applications. SMPC’S changes its shape during a typical thermo-mechanical cycle and retracts to its original shape upon external stimulus (temperature). Molecular mechanism is the driving force of these SMP’s. SMP consists of 1.molecular switches and 2. netpoints. This project deals with Epoxy shape memory resin (Matrix material) and fabrics such as Glass, Kevlar and Carbon (Reinforcements).A Comparative analysis was carried out to find which combination gives the best results by bend test. Different orientations were tried for bidirectional fabrics such as (0/90)_3, (0/45)₃, ((0/90)/(±45)/(0/90)) specimens. Finally it was concluded that Carbon fabric which has the orientation of (0/90/±45/0/90) gives better shape memory performance.

Abstract: ZnO nanoparticles (NPs) with different morphologies were synthesized via green route using Kalonji seed extract (KSE) as fuel. The formation of ZnO nanostructures (NSs) were characterized by XRD, SEM, UV-vis. The influence of KSE concentration on the morphology, UV visible absorption, and photocatalytic activity of ZnO NPs were investigated. The various morphologies of ZnO NPs probed for the photocatalytic degradation of Methylene blue (MB). The enhanced photocatalytic activities of ZnO nanoflower was attributed to small crystallite size, more surface defects, wide band gap and capability for reducing the electron-hole pair recombination. In addition, ZnO NPs showed significant antibacterial activity against Gram –ve bacterial strain Klebsiella aerogenes when compared to Gram +ve bacterial strain Staphylococcus aureus.

Abstract: Silicone rubber composites filled with fused silica were prepared through sigma mixing followed by hot pressing. Filling fraction of fused silica in the silicone rubber matrix was varied from 0-0.51 volume fraction (V_f) and its effects on dielectric properties at different frequencies, thermal properties and moisture absorption were investigated. The results indicate that with the increase of filler volume fraction the relative permittivity increases and dielectric loss decreases. The coefficient of thermal expansion decreased and the moisture absorption increased marginallyas the filler loading increased.

Abstract: We report the synthesis of Y₂O₃:Mg²⁺ (0.5-9mol %) nanoparticles (NPs) with different morphologies via ecofriendly, inexpensive and simple low temperature solution combustion method using Aloe Vera gel as fuel. The formation of different morphologies was characterized by PXRD, SEM, UV-Visible, PL techniques etc. The PXRD data confirms the formation of single phase Y₂O₃ with cubic crystal structure. The influence of Mg ions concentration on the morphology, UV absorption and PL emission were investigated in detail. NPs exhibit white light emission with CIE chromaticity coordinates (0.317, 0.32 and 0.308, 0.359) and correlated color temperature values 6298 and 6674 respectively. These findings show a great promise of Y₂O₃: Mg²⁺ NPs as a phosphor in warm white LEDs.