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Communication
Journal of
Nanoscience and Nanotechnology
Vol. 14, 2679–2682, 2014
www.aspbs.com/jnn
Thermogravimetric Analysis of Atomized Ferromagnetic
Composites with Multiwalled Carbon Nanotubes:
An Unusual Behavior of Nickel in Nanospace
Xu Chen
1
, S. Gupta
1
, and K. S. V. Santhanam
1 2 ∗
1
Center for Materials Science and Engineering, Rochester Institute of Technology, Rochester 14623, NY, USA
2
School of Chemistry and Materials Science, Rochester Institute of Technology, Rochester 14623, NY, USA
A spin polarization of atomized ferromagnetic atoms like cobalt or nickel in nano space results in
the modification of the electron configuration in the ferromagnetic atom that changes its oxidative
property. We have prepared cobalt and nickel composites with multiwalled carbon nanotubes using
atomized cobalt and nickel particles, for investigating their thermal oxidative behavior by thermo
gravimetric analysis (TGA). The composites showed the absence of a thermal oxidation in the
temperature range of ambient to the break down temperature of multiwalled carbon nanotubes at
800
C. At this temperature while Co composite forms cobalt oxide, the Ni composite becomes
volatile that results in the divergent behavior of the two ferromagnetic compounds with a weight
gain observed in TGA for Co and a loss for Ni. The mechanisms operating in the two cases are
discussed in this work.
Keywords: Cobalt, Nickel, Carbon Nanotubes, Thermogravimetry, Carbonyls.
We wish to report thermal oxidation of atomized cobalt
and nickel in nanospace that is amenable for examination
by thermogravimetric analysis.
1–6
The oxidation results in
the gain of the material due to the addition of oxygen to
the metal by the reaction
Ms + O
2
g → MOs (1)
where M is a atomized Co or Ni. This conversion is
an activation process requiring a threshold temperature
for the reaction to proceed at a measureable rate. This
threshold temperature is defined as the characteristic tem-
perature for that atom that can be determined by the
weight gain/loss analysis in the TGA experiment. The
TGA characterization of Co and Ni salts have been ana-
lyzed extensively in the literature.
7–26
The formation of
oxides at the characteristic temperature has been earlier
discerned by Fourier Transform Infrared Spectroscopy.
6
When the ferromagnetic atom is in the environment of
multiwalled carbon nanotubes, the above oxidation is
inhibited due to the spin polarization effect described
by Mott and Fagan.
2
The density functional calculations
∗
Author to whom correspondence should be addressed.
predicted spin poarization as shown below. The initial
electronic configuration of Co and Ni are respectively
Co:1s
2
2s
2
2p
6
3s
2
3p
6
3d
7
4s
2
and Ni:1s
2
2s
2
2p
6
3s
2
3p
6
3d
8
4s
2
.
The composite of Co or Ni is expected to have spin
polarization that will result in the electronic configuration,
Co:MWCNT:1s
2
2s
2
2p
6
3s
2
3p
6
3d
9
4s
0
and Ni:MWCNT:1s
2
2s
2
2p
6
3s
2
3p
6
3d
10
4s
0
. At a temperature where MWCNT
breaks down in the oxygen atmosphere, it results in the
oxidation of carbon nanotubes that results in the weight
loss
6
in TGA. This weight loss occurs as a consequence
of the formation of the gaseous species that escapes into
the atmosphere. Consequently, at this temperature, one
would expect to observe the weight due to the metal
residue. However, in the several experiments carried out,
we observed deviations contrasting the behavior of Co and
Ni composites. With Ni-MWCNT composite, there is loss
of Ni atoms that is not observed with the Co composite.
This paper discusses the possible reasons for the divergent
behavior of the two composites.
Chemicals
Atomized Cobalt (Atlantic Equipment Engrs, NJ, Lot
610514, CAS-74440-48-4) and atomized Nickel (Atlantic
Equipment Engrs, NJ, lot # 609527-2, CAS-74440-02-0)
J. Nanosci. Nanotechnol. 2014, Vol. 14, No. 3 1533-4880/2014/14/2679/004 doi:10.1166/jnn.2014.8509 2679