Chandran Sudakar

Bio: Chandran Sudakar is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Magnetization & Thin film. The author has an hindex of 32, co-authored 140 publications receiving 3204 citations. Previous affiliations of Chandran Sudakar include Wayne State University & Indian Institute of Science.

Influence of chemical solution growth and vacuum annealing on the properties of (100) pseudocubic oriented BiFeO3 thin films

Abstract: BiFeO3 (BFO), a Pb-free perovskite oxide, is being explored for its potential use in a multitude of applications. We report on the oriented growth of BFO thin films using a facile metal-organic chemical solution deposition. Unlike the growth characteristics observed in Si/SiO2 and glass/FTO substrates, the solution growth process on sapphire (0001) is found to yield highly oriented thin films along (100)pc planes. Furthermore, annealing in air (BFO-A) and high-vacuum (BFO-V) ambients are done to explore the tunable limits of its physical properties. Temperature-dependent Raman studies highlight the high quality of thin films with sharp changes in Raman modes around transition temperatures. In addition, the films exhibit a hitherto unreported anomalous shift in A1(TO) and E(TO) modes around 450 K. The bandgap of BFO-V (Eg = 2 eV) is lower than that of BFO-A (Eg = 2.12 eV) and exhibits an increased defect photoluminescence emission. The magnetization (M) is twofold higher for BFO-V [M ≈ 42 (67) emu/cm3 at 300 K (5 K)]. In-plane and out-of-plane M vs H plots show larger anisotropy and hard hysteresis for BFO-A compared to BFO-V. Piezoelectric switching with d33 values of 5–10 pm/V is the characteristic of BFO ferroelectric materials. Photoconductivity measurements show a one order increase due to vacuum annealing. Carrier generation and recombination lifetimes are twofold faster in BFO-V as compared to BFO-A thin films. The controllable physical properties of oriented BiFeO3 thin films will be useful in magnetoelectrics and photoferroelectrics applications.

Quantifying magnetic nanoparticles in non-steady flow by MRI.

Abstract: This work compares the measured $${{R}_{2}^*}$$ of magnetic nanoparticles to their corresponding theoretical values in both gel phantoms and dynamic water flows on the basis of the static dephasing theory. The magnetic moment of a nanoparticle solution was measured by a magnetometer. The $${{R}_{2}^*}$$ of the nanoparticle solution doped in a gel phantom was measured at both 1.5 and 4.7 T. A total of 12 non-steady state flow experiments with different nanoparticle concentrations were conducted. The $${{R}_{2}^*}$$ at each time point was measured. The theoretical $${{R}_{2}^*}$$ on the basis of the magnetization of nanoparticles measured by the magnetometer agree within 11% of MRI measurements in the gel phantom study, a significant improvement from previous work. In dynamic flow experiments, the total $${{R}_{2}^*}$$ calculated from each experiment agrees within 15% of the theoretical $${{R}_{2}^*}$$ for 10 of the 12 cases. The MRI phase values are also reasonably predicted by the theory. The diffusion effect does not seem to contribute significantly. Under certain situations with known $${{R}_{2}^*}$$ , the static dephasing theory can be used to quantify the susceptibility or concentration of nanoparticles in either a static or dynamic flow environment at a given time point. This approach may be applied to in vivo studies.

Enabling high-rate capability by combining sol-gel synthesis and solid-state reaction with PTFE of 4.2 V cathode material LiVPO4F/C

Abstract: LiVPO4F (LVPF) is a promising high voltage (4.2 V vs. Li/Li+) and high energy density (655 Wh kg−1) cathode material for lithium ion batteries. The challenge is to prepare phase pure and conducting material suitable for battery application. In this work carbon coated LiVPO4F (LVPF/C) is synthesized by sol-gel method, and the effect of carbon coating and control on F content on the structure, morphology, electrochemical properties of LVPF/C are studied comprehensively. Li3V2(PO4)3 and Li9V3(P2O7)3(PO4)2 form as minor secondary phases when LVPF is prepared without carbon source. In contrast Li3V2(PO4)3 and V2O3 are found when lauric acid is used as carbon source. Using optimal concentration of polytetrafluoroethylene (35 wt. % PTFE) and lauric acid (27 wt. % LA) in the synthesis yields carbon coated LVPF (LVPF/C-35) with best electrochemical performance. Lattice parameters of LiVPO4F are consistent with the reported values. Electrochemical properties of the LVPF/C-X cathodes (X = 25, 35 and 45 wt. % PTFE) show the discharge capacities of ∼ 85.4 (∼ 7), ∼ 114.7 (∼ 84.1), ∼ 102.7 (∼ 14.2) mA h g−1 at 0.1C (10C) rates, when scanned in the voltage range of 3.0–4.5 V vs. Li/Li+. A flat potential profile at ∼ 4.2 V vs. Li/Li+ is seen during charging-discharging profiles of the LVPF/C-X samples. From CV studies, the diffusion coefficient is found to be of the order of 10−16 cm2s−1 during oxidation and reduction. BET surface area is more (∼ 75.95 m2 g−1) for LVPF/C-35 compared to other two samples. From Electrochemical impedance spectroscopy, the influence of charge-transfer resistance resulting from the cathode electrolyte interface layer on electrochemical properties is studied.

Electrical and magnetoresistance properties of composites consisting of iron nanoparticles within the hexaferrites

Abstract: Nanocomposites containing Fe or FeCo (Fe-rich) dispersed in hexaferrites (M, W, or Y phase) are realized by the heterogeneous solid-gas reduction under H2 + N2. Transmission electron microscopy (TEM) studies show that metal nanoparticles precipitate coherently as thin flakes along the a-b planes of the hexaferrite lattice above the characteristic reduction temperature, TR >375°C. The electrical resistivity measurements reveal that the charge transport mechanism in the composites is by tunneling, whereas samples having higher fractions of the alloy particles show metallic behavior. Controlled reduction at TR leads to apparent insulator-metal changeover in the ρ versus T plot. This changeover persists even in the presence of a high magnetic field (7 T) and is ascribed to the percolation of metal particles caused by the difference in the coefficient of thermal expansion between the constituents. In the insulator regime, negative magnetoresistance (MR) of ∼5–9% is observed at 25°C. Further, ρ-T curves by the two-probe method exhibit hysteretic behavior caused by large inhomogeneity in the distribution of metal content and the time-dependent charge accumulation (Coulomb blockade) at the metal granules for these composites. They also exhibit nonlinearity in the current-voltage (I-V) characteristics with the nonlinearity coefficient ranging from 1.2 to 1.4 at different temperatures.

Semiconductor-based Photocatalytic Hydrogen Generation

Abstract: 2.3. Evaluation of Photocatalytic Water Splitting 6507 2.3.1. Photocatalytic Activity 6507 2.3.2. Photocatalytic Stability 6507 3. UV-Active Photocatalysts for Water Splitting 6507 3.1. d0 Metal Oxide Photocatalyts 6507 3.1.1. Ti-, Zr-Based Oxides 6507 3.1.2. Nb-, Ta-Based Oxides 6514 3.1.3. W-, Mo-Based Oxides 6517 3.1.4. Other d0 Metal Oxides 6518 3.2. d10 Metal Oxide Photocatalyts 6518 3.3. f0 Metal Oxide Photocatalysts 6518 3.4. Nonoxide Photocatalysts 6518 4. Approaches to Modifying the Electronic Band Structure for Visible-Light Harvesting 6519

Understanding TiO2 photocatalysis: mechanisms and materials.

Abstract: Jenny Schneider,*,† Masaya Matsuoka,‡ Masato Takeuchi,‡ Jinlong Zhang, Yu Horiuchi,‡ Masakazu Anpo,‡ and Detlef W. Bahnemann*,† †Institut fur Technische Chemie, Leibniz Universitaẗ Hannover, Callinstrasse 3, D-30167 Hannover, Germany ‡Faculty of Engineering, Osaka Prefecture University, 1 Gakuen-cho, Sakai Osaka 599-8531, Japan Key Lab for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China

Ferromagnetic materials

Abstract: In this chapter, we will restrict our attention to the ferrites and a few other closely related materials. The great interest in ferrites stems from their unique combination of a spontaneous magnetization and a high electrical resistivity. The observed magnetization results from the difference in the magnetizations of two non-equivalent sub-lattices of the magnetic ions in the crystal structure. Materials of this type should strictly be designated as “ferrimagnetic” and in some respects are more closely related to anti-ferromagnetic substances than they are to ferromagnetics in which the magnetization results from the parallel alignment of all the magnetic moments present. We shall not adhere to this special nomenclature except to emphasize effects, which are due to the existence of the sub-lattices.

Advanced Nanoarchitectures for Solar Photocatalytic Applications

Abstract: UV-Visible ار راد ن .د TiO2 ( تیفرظ راون مان هب نورتکلا یاراد یژرنا زارت لماش VB و ) رگید زارت ی یژرنا اب ( ییاناسر راون مان هب نورتکلا زا یلاخ و رتلااب VB یم ) .دشاب ت ود نیا نیب یژرنا توافت یژرنا فاکش زار ، پگ دناب هدیمان یم .دوش هک ینامز زا نورتکلا لاقتنا VB هب VB یم ماجنا دریگ ، TiO2 اب ودح یژرنا بذج د ev 2 / 3 ، نورتکلا تفج کی دیلوت یم هرفح .دیامن و نورتکلا هرفح ی نا اب هدش دیلوت یم کرتشم حطس هب لاقت ثعاب دناوت شنکاو ماجنا اه یی ددرگ . TiO2 دربراک ،دراد یدایز یاه هلمج زا یم ناوت اوه یگدولآ هیفصت یارب (CO2) و بآ و ... نآ زا هدافتسا درک .

Titanium dioxide-based nanomaterials for photocatalytic fuel generations.

Abstract: Generations Yi Ma,† Xiuli Wang,† Yushuai Jia,† Xiaobo Chen,‡ Hongxian Han,*,† and Can Li*,† †State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences and Dalian National Laboratory for Clean Energy, 457 Zhongshan Road, Dalian 116023, China ‡Department of Chemistry, College of Arts and Sciences, University of Missouri-Kansas City, 5100 Rockhill Road, Kansas City, Missouri 64110, United States