Browsing by Author "Dhanasekhar, C."

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    Magnetic behavior of polymorph composite nickel titanate nanofibers
    (Royal Society of Chemistry, 2021) Kumar, B.; Dhanasekhar, C.; Anandhan, S.; Kalpathy, S.K.
    Polymorph (spinel/ilmenite) composite nanofibers of nickel titanate (NTO) were prepared by a sol-gel assisted electrospinning process followed by pyrolysis using the styrene-acrylonitrile copolymer as a precursor at three different pyrolysis soaking temperatures (i.e. T= 773, 973, and 1173 K). The magnetic behavior of these composite NTO nanofibers was studied under isothermal and non-isothermal conditions in the temperature range of 20-300 K. The magnetic parameters such as coercivity (Hc), remanence (Mr), and saturation magnetisation (Ms) were found to be strongly dependent onT. The highestHcandMrwere observed for NTO nanofibers developed at 973 K, which have a mosaic structured morphology with spinel and ilmenite NTO crystallite sizes of ~39 nm and ~24 nm, respectively. On the other hand, the highestMsand switching field distribution were observed for mosaic structured NTO nanofibers having smaller crystallites (~13 nm and 24 nm for spinel and ilmenite NTO, respectively, with high inter-particle distance and high porosity) developed at 773 K, which are also rich in spinel NTO content. The correlation between the variation in magnetic behavior and structural/morphological features of NTO nanofibers is useful for NTO-based soft magnetic and multiferroic applications. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2021.
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    Pyrolysis-controlled synthesis and magnetic properties of sol gel electrospun nickel cobaltite nanostructures
    (2018) Kumar, B.S.; Dhanasekhar, C.; Venimadhav, A.; Kalpathy, S.K.; Anandhan, S.
    Nickel cobaltite (NCO) is a binary transition-metal oxide, which is extensively used as an electrocatalyst and magnetic material. NCO nanofibers and NCO/graphene composite exhibit high electrochemical reactivity due to the directional bridging of NCO particles. This makes NCO a promising candidate electrode material for use in supercapacitors and batteries. Besides, NCO is also a promising magnetic material due to its unique structural composition, where the cations are seated in octahedral sites surrounded by oxygen vacancies. In the present work, a simple and reliable method was discovered for tuning the morphological and structural changes of nickel cobaltite (NCO) nanoparticles, which were reshaped along the NCO nanofibers, by controlling the pyrolysis soaking time. As the pyrolysis soaking time increases, NCO transforms from inverse spinel to normal spinel; and the morphology of NCO nanoparticles changes from spherical to rod-like. These changes were validated by the hypsochromic peak shifts in Raman, and FTIR spectroscopies. The magnetic measurements reveal changes in the shape of the hysteresis loop, which are explained on the basis of structural and morphological changes in the nanostructure. The net magnetisation increases and coercivity decreases, with an increase in pyrolysis soaking time. These changes in magnetic parameters are attributed to structural changes caused by the formation of oxygen vacancies, and surface effects due to switching in morphology of the NCO nanoparticle. [Figure not available: see fulltext.]. 2018, Springer Science+Business Media, LLC, part of Springer Nature.
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    Pyrolysis-controlled synthesis and magnetic properties of sol–gel electrospun nickel cobaltite nanostructures
    (Springer New York LLC barbara.b.bertram@gsk.com, 2018) Kumar, B.S.; Dhanasekhar, C.; Adyam, A.; Kalpathy, S.K.; Anandhan, S.
    Nickel cobaltite (NCO) is a binary transition-metal oxide, which is extensively used as an electrocatalyst and magnetic material. NCO nanofibers and NCO/graphene composite exhibit high electrochemical reactivity due to the directional bridging of NCO particles. This makes NCO a promising candidate electrode material for use in supercapacitors and batteries. Besides, NCO is also a promising magnetic material due to its unique structural composition, where the cations are seated in octahedral sites surrounded by oxygen vacancies. In the present work, a simple and reliable method was discovered for tuning the morphological and structural changes of nickel cobaltite (NCO) nanoparticles, which were reshaped along the NCO nanofibers, by controlling the pyrolysis soaking time. As the pyrolysis soaking time increases, NCO transforms from inverse spinel to normal spinel; and the morphology of NCO nanoparticles changes from spherical to rod-like. These changes were validated by the hypsochromic peak shifts in Raman, and FTIR spectroscopies. The magnetic measurements reveal changes in the shape of the hysteresis loop, which are explained on the basis of structural and morphological changes in the nanostructure. The net magnetisation increases and coercivity decreases, with an increase in pyrolysis soaking time. These changes in magnetic parameters are attributed to structural changes caused by the formation of oxygen vacancies, and surface effects due to switching in morphology of the NCO nanoparticle. [Figure not available: see fulltext.]. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.