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Balamurugan S.,Advanced Nanomaterials Research Laboratory | Parthiban P.,Advanced Nanomaterials Research Laboratory
Journal of Nanotechnology | Year: 2014

In this work, nanocrystalline MgO particles were prepared through combustion method using magnesium nitrate as oxidizer and hexamine as a fuel. The materials obtained by combustion method were subsequently annealed at 800°C for 3 h to improve the crystallinity and phase purity. The obtained MgO nanomaterials were characterized by powder X-ray diffraction analysis (XRD), infrared (IR) spectroscopy, photoluminescence (PL), near-infrared (NIR) spectroscopy, and scanning electron microscopy (SEM). The cubic crystal structure with lattice parameter, a = 0.4210(4) nm with average crystalline size of 22 nm, is obtained for the nano-MgO particles. The PL emission spectrum of nanocrystalline MgO materials exhibits three emission peaks at 432, 465, and 495 nm which are due to various structural defects. The SEM results expose the fact that the MgO nanomaterials are seemingly porous and highly agglomerated with fine particles. Owing to the higher reflectance of prepared nanocrystalline MgO, it can be used as NIR reflective pigments. The present results prove that the combustion technique using hexamine can produce the materials with high crystallinity. To the best of our knowledge, this is the first report on the synthesis of nanocrystalline MgO materials by combustion method using hexamine as a fuel. © 2014 S. Balamurugan et al.


Balamurugan S.,Advanced Nanomaterials Research Laboratory | Raja T.S.G.,Advanced Nanomaterials Research Laboratory
Journal of Nanoscience and Nanotechnology | Year: 2016

In this interesting article, the synthesis of nanocrystalline Gd2Ti2O7 material by ball milling followed by annealing, characterization and its application are reported. The Rietveld structural refinement data confirm the cubic pyrochlore Gd2Ti2O7 phase with lattice parameter, a = 1.022(9) nm. The particle size observed by HRSEM image concurs with the average crystalline sizes of particles extracted from XRD data. The optical properties of pyrochlore nanocrystalline Gd2Ti2O7 material are explored from UV-visible, FT-IR, NIR, PL, and Raman spectroscopic measurements. From the present investigation, it is identified that the Gd2Ti2O7 nanopowder may be used as solar reflective as well as color pigment due to its high NIR reflectivity (85-95%) under the wavelength of 750-2500 nm. Copyright © 2016 American Scientific Publishers All rights reserved.


Balamurugan S.,Advanced Nanomaterials Research Laboratory
Journal of Nanoscience and Nanotechnology | Year: 2015

The Cu doped ZnO, (Zn1-xCuxO)O (x = 0.02, 0.04, 0.06, 0.08, and 0.1) nanomaterials were prepared by ball milling technique (BMT), citrate sol gel (CSG), and molten salt flux (MSF) methods. The various as-prepared (Zn1-xCux)O materials were analyzed by powder X-ray diffraction (pXRD), FTIR, and SEM-EDX measurements in order to check the phase formation, purity, surface morphology and elements present in the annealed materials. Due to the preparation methods as well as doping of 'x' slight variations in cell parameters are seen. The average crystalline size of CSG method shows smaller size (25∼35 nm) than BMT and MSF approaches. The materials obtained by MSF technique reveal the average crystalline size in the range of 32∼72 nm whereas the BMT materials exhibit 36∼50 nm for the composition, 0.02 ≤ x ≤ 0.1. The presence of functional groups and the chemical bonding in (Zn1-xCux)O system is confirmed through FT-IR measurements. It is evident from the FT-IR data that bands seen at 400∼500 cm-1 are characteristics of M-O (M = metal ion) bonding in the studied materials. The micro images observed by SEM exhibiting polycrystalline character as compared with the crystallite size obtained from XRD. Among the three approaches employed in the present investigations, in terms of average particle size the CSG method may be concluded as an efficient method for the preparation of Zn1-xCuxO nanomaterials. Copyright © 2015 American Scientific Publishers


Balamurugan S.,Advanced Nanomaterials Research Laboratory
Journal of Superconductivity and Novel Magnetism | Year: 2016

We report here a simple solution combustion synthesis of nickel oxide (NiO) nanoparticles by using urea as a fuel and nickel nitrate as an oxidizer. The structural, morphological, optical, and magnetic properties of NiO nanoparticles were investigated by X-ray diffraction (XRD); highresolution scanning electron microscopy (HRSEM); Fourier transform infrared (FT-IR), nearinfrared (NIR), and UV-vis spectroscopic techniques; and vibrating sample magnetometer. The combustion-synthesized NiO nanoparticles have a cubic structure with an average crystalline size of ∼8 nm without any impurity. The agglomeration of fine particles with particle sizes in the range of 19.5 ∼22.4 nm is seen by HRSEM images. The FT-IR spectrum of NiO nanoparticles reveals that an absorption band at ∼493 cm −1 is due to the bending vibration of NiO phase. The NIR spectrum exhibits poor NIR reflectivity of the combustion product, NiO. The as-prepared combustion product was black in color in contrast to the usual light green color. The room-temperature magnetization of the as-prepared NiO nanoparticles reveals an antiferromagnetic behavior. © 2016 Springer Science+Business Media New York


Raja T.S.G.,Advanced Nanomaterials Research Laboratory | Sreenija S.V.,Advanced Nanomaterials Research Laboratory | Balamurugan S.,Advanced Nanomaterials Research Laboratory
AIP Conference Proceedings | Year: 2015

In this brief article, the synthesis of nanocrystalline CoFe2O4 material by molten salt flux (NaCl:KCl) method and their characterization by XRD, FTIR, and HRSEM-EDX are reported. The molten salt flux synthesized material reveals single cubic CoFe2O4 phase with lattice parameter, a = 0.8384(6) nm and average crystalline size, D of 44.66 nm. The fine particles with the size of 147 ∼ 386 nm is seen through HRSEM images on the surface of nanocrystalline CoFe2O4 materials. © 2015 AIP Publishing LLC.


Balamurugan S.,Advanced Nanomaterials Research Laboratory
International Journal of Modern Physics B | Year: 2012

The magnetic and transport properties of lightly Ce doped, Y 1-xCe xSr 2Ru 0.9Cu 2.1 O 7.9 (x = 0.05 and 0.1) samples have been studied and their results are compared with the pristine rutheno-cuprate, YSr 2Ru 0.9Cu 2.1O 7.9. The electron doping due to Ce 4+ for Y 3+ ion impacts on the physical properties of the present system. The tetragonal stabilized samples exhibit magneto superconducting properties under zero field cooled condition (H = 10 Oe) and the diamagnetic onset transition, T d shift slightly towards higher temperature with the increase of "x". Weak antiferromagnetic like hysteresis curves are seen for these samples at 2 K in the magnetic field strength up to ±10 kOe and the magnetization moment, M (μ B/Ru) decreases with increase of "x". While the magnetic property of the present system is due to canted Ru moments, the superconducting signal originates from CuO 2 plane. Through electrical resistivity measurements we observe that none of the samples exhibit bulk superconductivity down to 2 K. However the x = 0.05 sample reveals lowest resistivity in the entire temperature range than x = 0 and 0.1 samples. The isothermal magnetoresistance, MR(H) measured at different temperatures vary with tuning of "x". While x = 0.1 doped sample shows lower -MR (∼ 8%), the pristine sample exhibits maximum -MR (45%) at 2 K under ±90 kOe field condition. © 2012 World Scientific Publishing Company.


Balamurugan S.,Advanced Nanomaterials Research Laboratory
Journal of Superconductivity and Novel Magnetism | Year: 2014

The physical properties of high-pressure synthesized polycrystalline Cu(Re0.69-x Mo x Ca0.31)Sr2O 6 samples are reported in this article to attract the scientific community. The present system undergoes a structural phase transition from cubic symmetry (for x=0, 0.1) to tetragonal for 0.2≤x≤0.4 and again cubic perovskite structure for x=0.5 and 0.6. The pristine compound (x=0) undergoes a ferromagnetic (ferrimagnetic) transition with high T c∼460 K. Neither the Curie temperature nor the effective magnetic moment is enhanced upon Mo substitution. The mechanism of the suppression of ferromagnetism in the present system is discussed assuming a localized electron system which is reminiscent of W substitution (Balamurugan et al. in J. Appl. Phys. 101:09N501, 2007). The temperature dependence of electrical resistivity, ρ decreases with x=0-0.4 and then increases for x=0.5 and 0.6. Though the suppression of ferromagnetism in the present system is similar to W-substitution, interestingly the former one (Mo) shows different results on structural and transport electrical properties which urge for further studies. The interesting aspect of the present work is for x=0.6, the specific heat data shows significant electronic contribution, whereas the resistivity measurement reveals insulating behavior. © 2013 Springer Science+Business Media New York.


Brightlin B.C.,Advanced Nanomaterials Research Laboratory | Balamurugan S.,Advanced Nanomaterials Research Laboratory
Journal of Superconductivity and Novel Magnetism | Year: 2016

This paper reports the eco-friendly synthesized BaFe12O19 phase materials by a molten salt flux approach and their experimental findings. The reaction mixture (BaCO3 and Fe2O3) annealed with the mixture of salt (NaCl:KCl) flux yielded good quality nanocrystalline hexagonal ferrite BaFe12O19 phase materials. The plate-like hexagonal-shaped BaFe12O19 phase morphology with random particle sizes of ∼370 to 940 nm is seen for the good quality flux-annealed sample. The room-temperature magnetic hysteresis loop of the BaFe12O19 sample exhibits hard ferromagnetic saturation magnetization (Ms) of 50.23 emu/g at 15 kOe, and coercive field (Hc) is 3500 Oe. The determined energy bandgap (Eg) is found to be 3.58 eV for the BaFe12O19 phase material. The Fourier transform infrared (FT-IR) spectral features confirm the presence of Fe–O and Ba–O bonds in the flux-synthesized BaFe12O19 materials. The photoluminescence (PL) emission peak (∼360 nm) intensity of BaFe12O19 materials varies regardless of annealing temperatures. The different salt flux-synthesized BaFe12O19 materials appear as brown- and dark gray-colored powders that can be applied as a ceramic color pigment due to its high NIR reflectivity. © 2016 Springer Science+Business Media New York


Balamurugan S.,Advanced Nanomaterials Research Laboratory
Journal of Superconductivity and Novel Magnetism | Year: 2012

In order to check the solubility of Zn in the (Sr 1-xZn x)CoO 3 perovskite structure and their research findings, several polycrystalline samples have been prepared under wide extreme synthesis conditions at 6 GPa/1300- 1650 °C. While 0.05 ≤ x ≤ 0.3 compositions revealed single phased cubic structure materials, x >0.3 showed multiphased materials for (Sr 1-xZn x)CoO 3 system. Like other substituted perovskite cobalt oxide systems (Ca, Y, Ho and Ce), the transport properties of the present materials show rather sizable changes with respect to 'x', although there are insignificant variations in lattice parameter and in Curie temperature, Tc. All the present samples show soft ferromagnetism with Tc in the range of 272-285 K for 0.05 ≤ x ≤ 0.3. The effective paramagnetic moment, Peff determined from the paramagnetic region decreases upon the substitution of Zn for Sr-site. These Peff (3.3-2.8 μB/Co) values for 0.05 ≤ x ≤ 0.3 compositions seem to suggest that the Co 4+ lie in intermediate spin (IS) state for the present (Sr 1-xZn x)CoO 3 series, although they are slightly smaller than those expected for IS-Co 4+; Peff = 3.87 μB/Co. The electrical resistivity is found to increase with increase of 'x' for the investigated samples. The temperature and field dependence of both positive and negative magnetoresistance (MR) are noted for the Zn substituted samples. About 5% of -MR is observed for x = 0.05 sample around the transition temperature (280 K) under the field strength difference, ΔH = 90 kOe. The present research findings are compared with our previous results on different perovskite cobalt oxides. ©Springer Science+Business Media, LLC 2012.


Balamurugan S.,Advanced Nanomaterials Research Laboratory
Journal of Superconductivity and Novel Magnetism | Year: 2012

In this present investigation, both YBa 2Ru 0.85 Cu 0.15O 6 and Sr 2Re 0.69Ca 0.31CuO 6 perovskite compounds were prepared through high pressure/high temperature (HPHT) synthetic route. The as-prepared samples were structurally characterized by powder X-ray diffraction technique and their magnetic properties were measured. Both compounds crystallized in cubic symmetry with a different space group. The refined lattice parameter for the YBa 2Ru 0.85Cu 0.15O 6 and Sr 2Re 0.69Ca 0.31CuO 6 compounds are found to be a = 8.332(2) Å with space group, Fm- 3m (225) and a = 7.967(4) Å space group Pm-3m (221), respectively. The cuprate ordered perovskite compound shows ferromagnetism with high Curie temperature, T c at ∼450 K whereas the YBa 2Ru 0.85Cu 0.15O 6 compound reveals mixed magnetic natures below ∼170 K which is complicated by the presence of magnetic order in the Ru and Cu sublattices. Below 170 K, the compound shows two antiferromagnetic-like transitions (in ZFC mode) at ∼135 K and ∼60 K. With a further decrease of temperature (below 60 K), the susceptibility crosses negative (diamagnetic) signal at ∼35 K and shows maximum negative susceptibility at ∼11 K. By decreasing the temperature below 11 K, the negative susceptibility decreases and shows positive magnetic susceptibility at 2 K. In the fc mode curve, the sample shows broad antiferromagnetic like transition at ∼55 K. At low temperature (below 30 K), an increase in susceptibility signal is seen in the fc magnetic susceptibility curve. The magnetic parameters, such as Weiss temperature, θ w and the effective paramagnetic moment, p eff ob- tained from the linear region of χ -1(T ) plots are found to be -307.25 K and 3.74 μ B/Ru, respectively, for the YBa 2Ru 0.85Cu 0.15O 6 compound. The negative sign of θ w reveals the antiferromagnetic correlations of the compound. While these studied compounds are already known to the literature, the synthesis method (HPHT) employed for the present YBa 2Ru 0.85Cu 0.15O 6 compound is a new approach and quite different from the routine conventional solid state synthesis approach. © Springer Science+Business Media, LLC 2011.

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