Indira Gandhi Center for Atomic Research
Mamallapuram, India
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Das S.,Indira Gandhi Center for Atomic Research | Jayaraman V.,Indira Gandhi Center for Atomic Research
Progress in Materials Science | Year: 2014

Metal oxides possess exceptional potential as base materials in emerging technologies. In recent times, significant amount of research works is carried out on these materials to assess new areas of applications, including optical, electronic, optoelectronic and biological domains. In such applications, the response and performance of the devices depend crucially, among other factors, on the size, shape and surface of the active oxide materials. For instance, the electronic and optical properties of oxides depend strongly on the spatial dimensions and composition [1]. The large number of atoms on the surface, and the effective van der Waals, Coulombic and interatomic coupling significantly modify the physical and chemical properties of the low dimensional oxide materials vis-á-vis its bulk counterparts. As a result, low dimensional oxide materials, such as nanoparticles, nanospheres, nanorods, nanowires, nanoribbon/nanobelts, nanotubes, nanodisks, nanosheets evoke vast and diverse interests. Thermal and physical deposition, hydro/solvothermal process, spray-pyrolysis, assisted self-assembly, oil-in-water microemulsion and template-assisted synthesis are regularly employed to synthesis one-, two- and three-dimensional nanostructures, which have become the focus of intensive research in mesoscopic physics and nanoscale devices. It not only provides good scopes to study the optical, electrical and thermal properties in quantum-confinement, but also offers important insights for understanding the functional units in fabricating electronic, optoelectronic, and magnetic devices of nanoscale dimension. Tin oxide (SnO2) is one such very important n-type oxide and wide band gap (3.6 eV) semiconductor. Its good quality electrical, optical, and electrochemical properties are exploited in solar cells, as catalytic support materials, as solid-state chemical sensors and as high-capacity lithium-storage. Previously, Chopra et al. [2] reviewed different aspects of transparent conducting SnO2 thin films. Wang et al. [3] discussed device applications of nanowires and nanobelts of semiconductor oxides, including SnO2. Batzill et al. [4] discussed about the surface of single crystalline bulk SnO2. However, it is understood that neither there is any comprehensive review on various crystallographic phases, polymorphs, bulk modulus, lattice parameters and electronic states of SnO2, nor there is any updated compilation on the recent progress and scope on SnO2 nanostructures. Therefore, the proposed review covers the past and recent progress on the said topics and is summarized in the following manner. The available theoretical and experimental works on crystal structures, bulk modulus, lattice parameters are reviewed in details. The electronic states and the band structures of these phases are discussed next. Active crystal surfaces of SnO2 play vital roles in its many interesting properties, including sensing and catalytic applications. So, a short review is written on its different surfaces, its electronic structures and density of states. The discussion on the importance of morphological variations on the properties of SnO2 is followed by a review on different methods for obtaining such structures. A detail survey on the existing literature on techniques and mechanisms for the growth of nanostructures are included. SnO2 is efficiently employed in gas sensing applications. A review on such applications is compiled based on the role of morphology and performance. The future course of SnO2 as an important material in the contemporary research is also discussed. © 2014 Elsevier Inc. All rights reserved.

Shima P.D.,Indira Gandhi Center for Atomic Research | Philip J.,Indira Gandhi Center for Atomic Research
Journal of Physical Chemistry C | Year: 2011

We discuss a new methodology to tune the thermal properties of magnetic nanofluids from low to very high values by varying the magnetic field strength and its orientation. This is achieved by varying the mode of conduction of heat, through nanoparticles and base fluid, from a series to parallel mode. Because the parallel mode has a geometric configuration that allows the most efficient means of heat propagation through nanoparticle paths, very large thermal conductivity enhancement is achieved with parallel fields. With the increase in nanoparticle size, the field-induced k enhancement also increases because of enhanced dipole-dipole interactions. Furthermore, we also demonstrate that the thermal and rheological properties of such response stimuli fluids are reversibly switchable and may find applications in miniature devices such as micro- and nano-electromechanical systems. © 2011 American Chemical Society.

Mahendran V.,Indira Gandhi Center for Atomic Research | Philip J.,Indira Gandhi Center for Atomic Research
Applied Physics Letters | Year: 2012

We have developed a simple sensor for imaging internal defects in materials using a magnetically polarizable nanoemulsion. The gradient in the magnetic flux lines around the defective region leads to the formation of one-dimensional nanodroplet arrays along the field direction, which incredibly diffract the incident white light to produce bright colors. As the diffracted wavelength has a direct correlation with the defect features, this approach enable visual inspection of ferromagnetic components and has several advantages over existing flux leakage sensors in terms of cost, re-usability and complexity. © 2012 American Institute of Physics.

Felicia L.J.,Indira Gandhi Center for Atomic Research | Philip J.,Indira Gandhi Center for Atomic Research
Langmuir | Year: 2013

Oil-based nanofluid containing surfactant-capped magnetite nanoparticles are synthesized by a simple coprecipitation approach, and their magnetorheological properties are studied for different magnetic field strengths and volume fractions. We observe a distinct "plateau-like region" in the shear thinning viscosity curve, under an external magnetic field, possibly due to a peculiar alignment of the chains with respect to the field direction where the structure is stable against fragmentation. The observed plateau regime is reminiscent to that of kinetically arrested gel networks. Interestingly, such a plateau regime has been observed only above certain critical magnetic field when the dipolar interaction strength is much greater than the thermal energy where the aggregation becomes a nonequilibrium transport-limited process. The good collapse of specific viscosity data against Mason number for different magnetic field strengths onto a single curve suggests the dominance of hydrodynamic and magnetic forces on thermal force above a certain magnetic field strength. The observed increase in both static and dynamic yield stresses under the magnetic field confirms the formation of columnar structures that hinder the flow behavior. The hysteresis observed in the magnetic sweep experiments shows the inability of the chains to relax within the measurement time. The dynamic measurements confirm that the field-induced structures impart elastic behavior to the dispersion, which is found to increase with magnetic field and saturates at higher field strengths. © 2012 American Chemical Society.

Raj A.S.,Indira Gandhi Center for Atomic Research | Murali N.,Indira Gandhi Center for Atomic Research
IEEE Transactions on Industrial Electronics | Year: 2013

Bearing faults of rotating machinery are observed as impulses in the vibration signal, but it is mostly immersed in noise. In order to effectively remove this noise and detect the impulses, a novel technique with morphological operators and fuzzy inference is proposed in this paper. The effectiveness of the morphological operators lies with the correct selection of structuring elements (SEs). This paper also proposes a new algorithm for this SE selection based on kurtosis, thereby making the analysis free of empirical methods. When analyzed with three different sets of faults, the results show that this method is effective and robust in bringing out the impulses. With fuzzy inference being coupled to this new technique, it makes the algorithm to be able to detect early faults also. © 2012 IEEE.

Choudhary B.K.,Indira Gandhi Center for Atomic Research
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science | Year: 2014

Tensile tests were performed at strain rates ranging from 3.16 × 10-5 to 3.16 × 10-3 s-1 over the temperatures ranging from 300 K to 1123 K (27 C to 850 C) to examine the effects of temperature and strain rate on tensile deformation and fracture behavior of nitrogen-alloyed low carbon grade type 316L(N) austenitic stainless steel. The variations of flow stress/strength values, work hardening rate, and tensile ductility with respect to temperature exhibited distinct three temperature regimes. The steel exhibited distinct low- and high-temperature serrated flow regimes and anomalous variations in terms of plateaus/peaks in flow stress/strength values and work hardening rate, negative strain rate sensitivity, and ductility minima at intermediate temperatures. The fracture mode remained transgranular. At high temperatures, the dominance of dynamic recovery is reflected in the rapid decrease in flow stress/strength values, work hardening rate, and increase in ductility with the increasing temperature and the decreasing strain rate. © 2013 The Minerals, Metals & Materials Society and ASM International.

Viswanathan R.,Indira Gandhi Center for Atomic Research
Journal of Nuclear Materials | Year: 2014

Clad corrosion being one of the factors limiting the life of a mixed-oxide fast reactor fuel element pin at high burn-up, some aspects known about the key elements (oxygen, cesium, tellurium, iodine) in the clad-attack are discussed and many Fuel-Clad-Chemical-Interaction (FCCI) models available in the literature are also discussed. Based on its relatively superior predictive ability, the HEDL (Hanford Engineering Development Laboratory) relation is recommended: d/μm = ({0.507 × [B/(at.% fission)] × (T/K-705) × [(O/M)i-1.935]} + 20.5) for (O/M)i ≤ 1.98. A new model is proposed for (O/M)i ≥ 1.98: d/μm = [B/(at.% fission)] × (T/K-800)0.5 × [(O/M)i-1.94] × [P/(W cm-1)]0.5. Here, d is the maximum depth of clad attack, B is the burn-up, T is the clad inner surface temperature, (O/M)i is the initial oxygen-to-(uranium + plutonium) ratio, and P is the linear power rating. For fuels with [n(Pu)/n(M = U + Pu)] > 0.25, multiplication factors f are recommended to consider the potential increase in the depth of clad-attack. © 2013 Elsevier B.V. All rights reserved.

Philip J.,Indira Gandhi Center for Atomic Research | Shima P.D.,Indira Gandhi Center for Atomic Research
Advances in Colloid and Interface Science | Year: 2012

Colloidal suspensions of fine nanomaterials in the size range of 1-100 nm in carrier fluids are known as nanofluids. For the last one decade, nanofluids have been a topic of intense research due to their enhanced thermal properties and possible heat transfer applications. Miniaturization and increased operating speeds of gadgets warranted the need for new and innovative cooling concepts for better performance. The low thermal conductivity of conventional heat transfer fluid has been a serious impediment for improving the performance and compactness of engineering equipments. Initial studies on thermal conductivity of suspensions with micrometer-sized particles encountered problems of rapid settling of particles, clogging of flow channels and increased pressure drop in the fluid. These problems are resolved by using dispersions of fine nanometer-sized particles. Despite numerous experimental and theoretical studies, it is still unclear whether the thermal conductivity enhancement in nanofluids is anomalous or within the predictions of effective medium theory. Further, many reports on thermal conductivity of nanofluids are conflicting due to the complex issues associated with the surface chemistry of nanofluids. This review provides an overview of recent advances in the field of nanofluids, especially the important material properties that affect the thermal properties of nanofluids and novel approaches to achieve extremely high thermal conductivities. The background information is also provided for beginners to better understand the subject. © 2012 Elsevier B.V.

Fast Breeder Reactors (FBRs) are emerging as vital source of power generation in India towards meeting energy security and sustainability for the growing economy of India. The success of FBR programme depends on continuous operation of reactor system and reprocessing and waste management facilities to ensure economy and also to achieve sustained fissile material production for several FBRs planned in future. Extensive research and development in domains of materials and manufacturing technologies are demanded towards development of FBRs and their associated fuel cycle technologies. This paper highlights the work and the approaches adopted at the Indira Gandhi Centre for Atomic Research, Kalpakkam for the successful development of materials, manufacturing and inspection technologies for both reactor and reprocessing facilities of the current and future Indian FBR programme. © 2011 Published by Elsevie Ltd.

Nandi P.K.,Indira Gandhi Center for Atomic Research
Journal of physics. Condensed matter : an Institute of Physics journal | Year: 2010

We calculate properties like equilibrium lattice parameter, bulk modulus and monovacancy formation energy for nickel (Ni), iron (Fe) and chromium (Cr) using Kohn-Sham density functional theory (DFT). We compare the relative performance of local density approximation (LDA) and generalized gradient approximation (GGA) for predicting such physical properties for these metals. We also make a relative study between two different flavors of GGA exchange correlation functional, namely PW91 and PBE. These calculations show that there is a discrepancy between DFT calculations and experimental data. In order to understand this discrepancy in the calculation of vacancy formation energy, we introduce a correction for the surface intrinsic error corresponding to an exchange correlation functional using the scheme implemented by Mattsson et al (2006 Phys. Rev. B 73 195123) and compare the effectiveness of the correction scheme for Al and the 3d transition metals.

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