Journal of Sol-Gel Science and Technology (2018) 86:664–674
ORIGINAL PAPER: NANO-STRUCTURED MATERIALS (PARTICLES, FIBRES,
COLLOIDS, COMPOSITES, ETC.)
Pyrolysis-controlled synthesis and magnetic properties of sol–gel
electrospun nickel cobaltite nanostructures
B. Sachin Kumar
Sreeram K. Kalpathy
Received: 18 December 2017 / Accepted: 24 April 2018 / Published online: 11 May 2018
© Springer Science+Business Media, LLC, part of Springer Nature 2018
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.
Nickel cobaltite (NCO) nanoﬁbers with in situ formed graphene-like structure.
Evidence of inverse to normal spinel transformation in NCO crystal structure.
Change in coercivity of NCO nanoﬁbers as a function of NCO nanoparticle shape.
Synergism of NCO nanoparticle and graphene-like structure on electrical resistivity.
* S. Anandhan
Department of Metallurgical and Materials Engineering, National
Institute of Technology Karnataka, Mangalore 575025, India
Cryogenic Engineering Center, Indian Institute of Technology,
Kharagpur 721302, India
Department of Metallurgical and Materials Engineering, Indian
Institute of Technology Madras, Chennai 600036, India