In this study, FeB sub(x)Fe sub(2-x)O sub(4) nanoparticles (NPs) were synthesized by the polyol method. The M-H hysteresis curves exhibit superparamagnetic characteristics that are both coercivity ...and remanent magnetization values are negligible. The particle size dependent Langevin function was applied to calculate the magnetic particle dimensions around 9 nm. The measured magnetic moments of NPs are in range of (1.52-2.2) mu sub(B) and almost half or less with respect to 4 mu sub(B) of bulk Fe ferrite. Magnetic anisotropy was specified as uniaxial and calculated effective anisotropy constants (K sub(eff )) are between 43.3 10 super(4) and 19.4 10 super(4) emu/g. The UV-Vis diffuse reflectance spectroscopy and Kubelka-Munk theory were used to determine the optical properties. The estimated optical band gap values (2.15-2.48 eV) of FeB sub(x)Fe sub(2-x)O sub(4) NPs are bigger with respect to reported values (1.88-2.12 eV) for Fe sub(3)O sub(4) NPs in the literature. The bigger E sub(g )values are mainly attributed to B concentration and partly to quantum confinement effect.
Abstract In this study, a facile method is described for the Cu deposited Piperidine-4-carboxylic acid (Hpipe-4) coated magnetite (Fe sub(3)O sub(4)) nanoparticles. For which, Fe sub(3)O sub(4) was ...used as magnetic core, Hpipe-4 as linker and active copper nanoparticles as the catalyst. For the reduction of Cu super(2+) to Cu super(0) was accomplished by NaBH sub(4). The phase and morphology of the as-prepared product is characterized by means of X-ray powder diffractometry, energy dispersive spectrometry, Scanning electron microscopy. Magnetic and catalytic properties of the product were followed by vibrating sample magnetometer and UV-Vis spectrophometer respectively. Experiments showed that the as-prepared Fe sub(3)O sub(4) Hpipe-4 Cu nanocatalyst owned strong catalytic activity for the reduction of some aromatic nitro-compounds and organic azo dyes and also emphasizes the effect of copper nanoparticles on the degradation of rate of hazardous compounds by NaBH sub(4). Fe sub(3)O sub(4) Hpipe-4 Cu nanocatalyst show great promise for the treatment of industrial dye pollutants hence environmental protection. Graphical Abstract
Polyaniline (PANI)aMnFe2O4 nanocomposite was successfully synthesized by using 1-butyl-3-methyl-imidazolium bromide as ionic liquid and cetyl trimethylammonium bromide as surfactant via in situ ...polymerization. Structural, morphological, spectral and magnetic investigation of the product were done by X-ray powder diffractometry, fourier transform infrared spectroscopy, thermal gravimetric analyzer, transmission electron microscopy, vibrating sample magnetometry respectively. Electrical properties of PANIaMnFe2O4aCTAB nanocomposite was characterized with a measurement of an impedance spectroscopy, which was evaluated at frequency range varying from 1 Hz to 3 MHz for temperature range of 20a120 degree C. In general ac conductivity remained almost unchanged until it reaches up to 160 kHz, and then reduced slightly almost for all temperatures except for some slight fluctuation somehow.
For the synthesis of Fe
3
O
4
@Tween20 nanocomposite, two surfactants (Tween20 and oleic acid) were used to overcome the aggregation. The nanoparticles were used to prepare a water-based Fe
3
O
4
...@Tween20 nanocomposite using oleic acid and Tween20 as surfactants ( Fe
3
O
4
colloidal superparticles were developed by introducing Tween20 as a surface modification agent to maintain the colloidal stability of the
F
e
3
O
4
superparamagnetic nanoparticles (SPION)). Vaseline and the synthesized iron oleate were used for the polyol synthesis of Fe
3
O
4
@Tween20 nanocomposite. The product has superparamagnetic property. Fourier transform infrared spectroscopy (FT-IR) and thermal gravimetric analysis (TGA) proved the presence of both surfactants on the surface of the Fe
3
O
4
nanoparticles. The product may have potential use in magnetic resonance imaging and hyperthermia.
Display omitted
► Superparamagnetic-like behavior of TREG-Mn0.2Co0.8Fe2O4 nanocomposite was observed. ► Due to its small size and superparamagnetism, it is looked for biomedical application. ► The ac ...conductivity showed an indication of ionic conductivity. ► dc conductivity of the nanocomposite is found to obey the Arrhenius plot.
Triethylene glycol (TREG) stabilized Mn0.2Co0.8Fe2O4 NPs was synthesized by a glycothermal reaction. XRD analysis identified the product as Mn0.2Co0.8Fe2O4 with a high phase purity. Nano-sized particles with an average size of about 6–8nm were obtained with nearly single crystalline nature with TEM analysis. Superparamagnetic-like behavior of TREG stabilized Mn0.2Co0.8Fe2O4 NPs was observed by VSM. The binding between TREG and Mn0.2Co0.8Fe2O4 NPs was investigated with FT-IR and found to be via O on the TREG and NP surface. TG analysis indicated that the Mn0.2Co0.8Fe2O4 NP content was about 40%, with a TREG-shell content to be around 60%. Overall conductivity of the nanocomposite is in the range of 10−10 to 10−7Scm−1 with a strong dependence on temperature and frequency, indicating ionic conductivity. The nanocomposite exhibited lower ɛ’ and ɛ″ compared to TREG stabilized Mn0.2Co0.8Fe2O4 NPs due to the doping of co-doping of manganese and cobalt.
We have investigated the stability of the pulse frequency second derivatives (ν) of PSR 0823+26, 1706-16, 1749-28 and 2021+51 that show significant quadratic trends in their pulse-frequency histories ...in order to determine whether the observed second derivatives are secular or if they arise as part of noise processes. We have used time-of-arrival (TOA) data extending to more than three decades, which are the longest time-spans ever taken into account in pulse-timing analyses. We investigated the stability of the pulse-frequency second derivative in the framework of low-resolution noise power spectra estimated from the residuals of pulse frequency and TOA data. We have found that the ν terms of these sources arise from the red torque noise in the fluctuations of pulse-frequency derivatives, which may originate from the external torques from the magnetosphere of the pulsar.
PDF
