A. Balakrishnan

Electrospun α-Fe2O3 nanostructures for supercapacitor applications

Herein, we report the facile synthesis of two α-Fe2O3 nanostructures with different morphologies via an electrospinning technique using ferric acetyl acetonate as a precursor and polyvinyl acetate and polyvinyl pyrrolidone as the respective polymers. The as-electrospun metal oxide–polymer composite fibers were sintered at 500 °C to obtain two distinct nanostructures, denoted as nanograins and porous fibers throughout this manuscript. These crystalline nanostructures were characterized using powder X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX) and transmission electron microscopy (TEM). The characterization results elucidated the predominance of hematite (α-Fe2O3) with particle sizes of 21 and 53 nm, for the respective nanostructures. Electrophoretic deposition was carried out in order to fabricate thin film electrodes, which were then subjected to electrochemical analysis. Electrochemical characterization revealed that both of the fabricated electrodes exhibited excellent performance in 1 M LiOH electrolyte with specific capacitance values of 256 and 102 F g−1 for the porous fiber and nanograin structures, respectively, at a scan rate of 1 mV s−1 and excellent capacitance retention, even after 3000 cycles, thus making them promising electrode materials for energy storage devices.

In vitro biocompatibility of equal channel angular processed (ECAP) titanium

This work attempts to understand the in vitro biocompatibility of ultrafine grained titanium prepared by the ECAP route. The results obtained from the mouse fibroblast cell line 3T3 showed a better cell adherence and cell proliferation on ECAP titanium specimen compared to the coarse grain Grade-2 Ti and Ti6Al4V alloy. This could be attributed to the increased surface energy and grain boundary energy and possibly the presence of a large number of nano-size conical groove-like structures (at triple point junctions of grain boundaries on the surface) in the ECAP Ti specimen compared to the coarse grain Grade-2 Ti and Ti6Al4V alloy.

An effective route to produce few-layer graphene using combinatorial ball milling and strong aqueous exfoliants

In this paper, a simple, cost effective, and scalable process for production of few-layer graphene is reported by combining ball milling with exfoliants. The graphene was derived from low-cost graphite, which was subjected to high-energy ball milling in an aqueous medium containing a strong exfoliant (1-pyrenecarboxylic acid) and a common solvent methanol. Such a combinatorial approach has not been used before. At a fixed concentration of 1-pyrenecarboxylic acid, the extent of exfoliation was found to be strongly dependent upon the energy input from the ball milling process (expressed as number of hours of milling) and the solvent used. The graphene produced had the distinctive Raman signature, x-ray diffraction crystallinity, scanning electron microscopic image features, transmission electron microscopic images, and high conductivity values (6.7 × 103 S m−1) in 4-probe electrical measurements all of which compared reasonably with typical values achieved for few-layer graphene. Application of the few-laye...

Synthesis and pressureless sintering of Ti3SiC2 powder

Ti 3 SiC 2 powder of about 96 wt% purity was produced using TiC x and Si powders. The synthesis process was characterized by an exothermic reaction at ∼985 °C and low activation energy (∼27 kJ/mol) of conversion. Almost complete conversion to Ti 3 SiC 2 phase was observed during sintering. The onset temperature of sintering was found to be at about 1060 °C using dilatometer. The density of nearly 99% (theoretical) was achieved through the pressureless sintering of Ti 3 SiC 2 powder by 1 and 2 wt% Si powder additions. The sample (without sintering aid) sintered at 1500 °C for 4 h showed uniformly distributed angular grains, whereas the bimodal nature of the microstructure was observed when Si was added as a sintering aid.

Surface Strengthening of Zirconia Toughened Alumina (ZTA) Using Glass Infiltration Technique

Molten Soda lime glass (SLG) was penetrated into the surface of ZTA at 1500°C for the holding time of 1 to 10 h. The depth of the glass penetration increased with increasing holding time. The thermal expansion mismatch and elastic property mismatch between the penetrated glass and ZTA produced residual compression in the surface region during cooling. This residual compression enhanced the flexural strength and fracture toughness remarkably.

Synthesis and Characterization of Electrophoretically Deposited Nanostructured LiCoPO4 for Rechargeable Lithium Ion Batteries

Nanosized LiCoPO4 (LCP) was prepared using a simple sol-gel method. For the first time, electrophoretic deposition process was employed to fabricate a LiCoPO4 cathode material in order to improve the electrochemical performance. The prepared powder was deposited on titanium plate by electrophoretic deposition and their electrochemical properties were studied. The electrochemical properties were analyzed by using cyclic voltagramm studies, impedance studies, and charge/discharge tests. The thickness of the prepared cathode material was found to be 11-12 µm by using scanning electron microscope. The initial specific capacity and the charge transfer resistance (Rct) of the prepared cathode was 103 mAh/g and 851 Ω, respectively. The charge/discharge profiles showed moderate columbic efficiency of 70%.

Electrochemical behavior of Calcium Titanate Coated Ti-6Al-4V Substrate in Artificial Saliva

In this study, calcium titanate (CaTiO ) gel was prepared by mixing calcium nitrate and titanium isopropoxide in 2-methoxy-ethanol. CaTiO gel was single-layer coated on Ti-6Al-4V using a sol-gel dip-coating technique. The coating was calcined at 750 C in air by utilizing a very slow heating rate of 2 C/min. The crystalline phases of the coating were characterized by x-ray diffraction using a slow scan rate of 1 /min. The morphology of the coating was analyzed by scanning electron microscopy. The corrosion behavior of Ti-6Al-4V samples coated with CaTiO films were tested in an artificial saliva solution by potentiodynamic polarization and were quantified by the Tafel extrapolation method. The electrochemical parameters showed a considerable increase in the corrosion resistance for the CaTiO -coated Ti-6Al-4V samples compared to bare substrates.

Strength and Reliability Performance of Hydroxyapatite Coatings on Titania Treated Ti6Al4V Alloy Using Sol-Gel Precursor

In this study hydroxyapatite (HA) was coated by sol-gel method on Ti6Al4V alloy substrates: on micropolished surface and after titania (titanium oxide) treatment. Former shows the cracks and poor bonding of HA whereas latter shows coating without cracks and higher bonding strength. The higher bonding strength of HA coating in titania treated sample could be attributed to the increased roughness by titanium oxide layer.

Crack behavior of Surface Strengthened Zirconia-Alumina Composite During Indentation

ZTA tubes were prepared by centrifugal casting and sintered at for 2 hrs. The ZTA tubes were machined into specimens of mm. Molten Soda lime glass (SLG) was penetrated into the surface of ZTA at an optimized condition of for the holding time of 5 h and furnace cooled. The extra glass on the surface was removed using a resin bonded diamond wheel. The glass penetrated samples were tested for their flexural strength using four point bend test. Vickers Indentation cracks were made on the glass penetrated surface at different loads of 9.8 N, 49 N, 98 N and 196 N. The residual compression on the surface enhanced the flexural strength and crack arrest behaviour remarkably. This was attributed to the thermoelastic mismatch between the glass and ZTA matrix during cooling.