Shrikant Tiwari

Preparation of Perovskite‐Type Oxides of Cobalt by the Malic Acid Aided Process and Their Electrocatalytic Surface Properties in Relation to Oxygen Evolution

The electrocatalytic properties of perovskite-type cobalt oxides (La[sub 1[minus]x]Sr[sub x]CoO[sub 3], where x = 0, 0.2, 0.4), in the form of thin films on conductive supports, were studied by cyclic voltammetry and Tafel polarization techniques. The films had conductive and satisfactory adherent properties. The oxides were synthesized by a low temperature malic acid aided method. The cyclic voltammetry showed a pair of redox peaks prior to the onset of oxygen evolution on the oxide film with nickel support, while similar peaks were absent in the same oxide film on Pt and Ti. The anodic polarization studies indicated two Tafel slopes: 57 to 64 mV/decade at low and 100 to 130 mV/decade at high overpotentials, and first-order kinetics with respect to OH[sup [minus]] concentration. The electrocatalytic activity of La[sub 0.8]Sr[sub 0.2]CoO[sub 3] film on Ni was the highest among all the electrodes prepared. The Sr substitution enhanced the electrochemically active area greatly. Results of the present investigation have been compared to those reported for similar oxides obtained by other methods.

Preparation of thin Co3O4 films on Ni and their electrocatalytic surface properties towards oxygen evolution

Abstract Thin films of Co3O4 of varying thicknesses have been prepared on an Ni substrate by spray pyrolysis and sequential solution coatings and investigated for their physicochemical and electrochemical properties towards O2 evolution. The study indicated that the oxide roughness factor tended to level off with increasing thickness. Further, with an increase in oxide loading, the apparent electrochemical activity enhanced considerably at low range of loadings and then became relatively constant over a range of loadings. The higher loadings were found to be harmful. The layered oxide films (2.4–4.2 mg cm−2) prepared in sequential solution coatings exhibited greatest electrocatalytic activity in 1M KOH. However, the oxide electrode (loading: 3–5.7 mg cm−2) prepared by rotating spray pyrolysis produced the lowest oxygen overpotential—360 ± 3 mV against a current density of 1 A cm−2 in 30 w/o KOH at 70 °C. The oxygen evolution reaction at these film electrodes exhibited two Tafel slopes: 51–68 mV decade−1 at low overpotentials and 120–140 mV decade−1 at high overpotentials. The reaction orders with respect to OH− concentration were found to be ~ 1 for the layered and ~ 2 for the sprayed films. Based on the results, a suitable mechanism is also suggested for oxygen evolution.

Effects of Ni, Fe, Cu, and Cr Substitutions for Co in La0.8Sr0.2CoO3 on Electrocatalytic Properties for Oxygen Evolution

The influence of some transition metal ion substitutions in the active 0.2 mole strontium-doped lanthanum cobaltate (La{sub 0.8}Sr{sub 0.2}Co{sub 1-y}B{sub y}O{sub 3} with B = Ni, Fe, Cu, and Cr; 0.1 {<=} y {<=} 0.4) lattice was studied on the electrocatalytic properties of the oxide by cyclic voltammetry and Tafel polarization techniques. The cyclic voltammetry showed a pair of redox peaks prior to the onset of oxygen evolution, regardless of the nature of the substitution. The presence of Fe or Ni, in small quantities enhanced the electrochemically active area. The anodic polarization studies indicated two Tafel slopes: {approximately}2.3 RT/F at low and {approximately}2(2.3 RT/F) at high overpotentials. The oxygen evolution reaction on each B-site substituted perovskite followed first-order kinetics with respect to OH{sup {minus}} ion concentration. The La{sub 0.8}Sr{sub 0.2}Co{sub 0.9}Fe{sub 0.1}O{sub 3} and La{sub 0.8}Sr{sub 0.2}Co{sub 0.9}Ni{sub 0.1}O{sub 3} electrodes showed the highest electrocatalytic activity based on geometrical surface area. Copper and chromium substitutions had detrimental effects on the electrocatalytic activity.

Electrocatalytic properties of spinel-type MnxFe3 –x O4synthesized below 100 °C for oxygen evolution in KOH solutions

Some spinel ferrites (MnxFe3 –xO4; x= 0, 0.5, 1.0, 1.5) have been synthesized at 70 °C by the method of precipitation, for electrochemical characterization as oxygen anodes. The electrodes were prepared as films on a nickel substrate by painting with an oxide-slurry, followed by sintering at 400 °C. The electrocatalytic activity for O2 evolution was found to be a maximum with the MnFe2O4 electrode. Based on the observed current density at 0.625 V, the activity of MnFe2O4 was 20 times higher than that of Fe3O4. The reaction followed approximately second-order kinetics in [OH–] at the pure and manganese-substituted ferrite film electrodes. The Tafel slope values were ca. RT/F on Fe3O4 and Mn0.5Fe2.5O4 and ca. 2RT/3F on MnFe2O4 and Mn1.5Fe1.5O4. Based on the electrode kinetic results, a reaction mechanism for oxygen evolution is suggested.

Analysis and design of Tree Based Interleaver for multiuser receivers in IDMA scheme

Here, we propose a novel tree based interleaver (TBI) for generating user specific chip-level interleaving sequences for various users in an IDMA system, which reduces computational complexity drastically. This interleaver also solves the memory cost problem and reduces the amount of information exchange between mobile stations and base stations required to specify the interleaver. Simulation results are presented to show that the proposed TBI perform well as compared to master random and random interleavers in an IDMA scheme.

Electrocatalytic activity of high specific surface area Perovskite-type LaNiO3 via sol-gel route for electrolytic oxygen evolution in alkaline solution

Abstract Lanthanum nickelate was synthesized by a sol-gel method at low temperature (500 °C) and its interfacial electrochemical and electrocatalytic properties in 1 M KOH were investigated in film form on Ni. The oxide film was obtained by painting a slurry of oxide powder and Triton X-100 and subsequent sintering at 400 °C. The cyclic voltammetry of the oxide electrode in 1 M KOH indicated the formation of the diffusion-controlled quasi-reversible Ni(II)-Ni(III) redox couple, prior to the onset of O 2 evolution. The oxygen evolution reaction followed approximately first order kinetics in OH − concentration. The Tafel slope was 65 mV decade −1 . The electrocatalytic activities of LaNiO 3 prepared by different methods have been compared.

Physicochemical and electrocatalytic properties of LaNiO3 prepared by a low-temperature route for anode application in alkaline water electrolysis

LaNi1−xFexO3 (x = 0, 0.25, 0.5) has been synthesized by the hydroxide solid solution precursor method for electrochemical characterization as oxygen anode in strongly alkaline medium. Studies were made at the oxide film, which was obtained by the oxide-slurry painting technique. The cyclic voltammetric study showed the formation of a diffusion-controlled quasireversible redox couple, Ni(ii)/Ni(iii), (E0 ∼- 430 ± 10 mV) at the oxide surface in 1 m KOH. The reaction was observed to follow approximately first-order kinetics in OH− concentration. Values of the Tafel slope ranged between 59 and 86 mV decade−1 with all the oxide film electrodes. The electrocatalytic activity was found to be greatest with the Ni/LaNi0.75Fe0.25O3 electrode. A comparison was made between the electrocatalytic activities of LaNiO3 prepared by the hydroxide solid solution precursor and by the hydroxide coprecipitation technique.

Newborn's ear recognition: Can it be done?

Abduction, swapping and mix ups are the unfortunate events that could happen to infants while in hospital premises and medical personnel are finding it difficult to curb this unfortunate incidents. Existing biometric and non biometric methods fail to provide enough level of security and research done to solve this problem is minimal. This paper introduces the concept of using ear recognition for identification of newborn and presents automatic ear recognition algorithm. The main contribution of this research is (i) preparation of a new born ear database of 210 individuals with slight variations in illumination and pose (ii) testing of different ear matching algorithms. On an ear biometric database of 210 infants it is concluded that ear can be used as biometric feature to identify the newborn.

Intelligent Method for Face Recognition of Infant

Mixing, abduction and illegal adoption of infant is a global challenge and the research done to solve this problem is minimal. Traditional methods of biometric and non biometric techniques have their own limitations and fail to provide required level of security. The task of face recognition has been actively researched in recent year and automatic face recognition of infant is not reported in the literature. The contributions of this research are: (i) Design and implementation of intelligent face recognition technique to recognize infant. (ii) Preparing an infant face database of 150 individuals with slight variations in pose, illumination; expression and quality. The results on the infant database are very encouraging.

Can face and soft-biometric traits assist in recognition of newborn?

Most of the biometric research being done is for adults and the identification accuracy of newborn are least reported in the literatures. In this paper we propose a novel biometric identification method for newborn babies using their face and soft biometrics. Accurate patient identification (ID) is essential for patient safety, especially with our smallest and most vulnerable pediatric patients. The main contribution of the research are (a) the preparation of face and soft biometric database of newborn. (b) Testing the algorithm for identification of 210 newborn. The combined use of all the four soft biometric traits results in an improvement of approximately 6% over the primary biometric system.