Transmission electron microscopy (TEM), Mössbauer spectroscopy and magnetization measurements were used in the present study to investigate a non-aqueous ironnitride-based magnetic fluid (MF) sample containing about 2×10 16 particle/cm 3 . The TEM micrographs indicated spherical-shaped iron nitride nanoparticles with an average diameter of 12.3 nm and diameter dispersity of 0.14. The 77 K Mössbauer spectrum of the frozen MF sample indicated the presence of about 95% of the γ′-Fe 4 N phase, with a residual 5% of the ɛ-Fe 4 N phase. The temperature dependence of the magnetization was investigated under zero-field-cooled (ZFC) condition, in the temperature range of 4 to 165 K. The ZFCdata were curve-fitted using a new approach that takes into account the particle size distribution and the temperature dependence of the magnetocrystalline anisotropy, making the description of the experimental situation more realistic.
The process of reconstruction of pre-fabricated films comprising maghemite
nanoparticles deposited onto flat glass substrates triggered by immersion into
aqueous solutions of meso-2,3-dimercaptosuccinic acid (DMSA) at increasing
concentration (0.025, 0.050, and 0.100 mol/L) is herein reported. The
evolution of this process was assessed by measuring the time (t) dependence
of the particle analysis histogram width (W) extracted from atomic force
microscopy images. Furthermore, a physical picture to model the film reconstruction
which provides reconstruction time constants associated to single particles
(τ1) and small agglomerates
(τn), the key units associated to the
process, ranging from τ1 = 2.9
and
τn = 3.4 hour
(0.025 mol/L) to
τ1 = 5.1 and
τn = 4.6 hour
(0.100 mol/L) is proposed. The nanoparticle-based film reconstruction
triggered by an exogenous stimulus, the use of the W versus t data to
describe the process and the model picture accounting for the recorded data have not
been previously reported.
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