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Photocatalysis as an advanced reduction process (ARP): the reduction of 4-nitrophenol using titania nanotubes-ferrite nanocomposites
摘要： TiO2 photocatalysis is an advanced process, employed worldwide for the oxidation of organic compounds, that leads to significant technological applications in the fields of health and environment. The use of the photocatalytic approach in reduction reactions seems very promising and can open new horizons for green chemistry synthesis. For this purpose, titanium dioxide nanotubes (TNTs) were developed in autoclave conditions using TiO2 P25 as a precursor material. Based on these nanotubular substrates, TiO2/CoFe2O4 (TCF) nanocomposites were further obtained by wet impregnation method. The materials were thoroughly characterized and their structural, textural, vibrational, optoelectronic and magnetic properties were determined. The composite materials combine absorbance in the visible optical range and high BET surface area values (~100 m2/g), showing extremely high yield in the photocatalytic reduction of 4-nitrophenol (4-NP), exceeding 94% within short illumination time (only 35 min). The developed nanocomposites were successfully reused in consecutive photocatalytic experiments and were easily removed from the reaction medium using magnets. Both remarkable recycling ability and high-performance stability in the photocatalytic reduction of nitrophenol were observed, thus justifying the significant economic potential and industrial perspectives for this advanced reduction process.
关键词： Cobalt ferrite,4-nitrophenol reduction.,Nanocomposite photocatalyst,TiO2 nanotubes
更新于2025-09-23 15:23:52
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Composite BNT-BT0.08/CoFe2O4 with core-shell nanostructure for piezoelectric and ferromagnetic applications
摘要： In this work, we report on the synthesis and characterization of BNT-BT0.08/CoFe2O4 biphasic composite with core-shell structure. This artificial core (BNT-BT0.08)/shell (CoFe2O4) heterostructure was prepared by sol-gel method and the resulting composite was characterized in term of microstructure, dielectric, piezoelectric and magnetic properties. BNT-BT0.08/CoFe2O4 sintered ceramic shows high permittivity (ε′ ≥ 30) and high dielectric losses (tan δ ≥ 10) in the low frequency range (ν ≤ 104 Hz), remnant polarization (Pr) of ～7.7 μC/cm2 and, remanent magnetization (Mr) of 24 emu/g at 5 K and of 14 emu/g, at room temperature. The present study reveals that the ferroelectric, piezoelectric and magnetic properties of this new architectured composite depend on the amount of each component and, can be tailored by adjusting their synthesis conditions. BNT-BT0.08/CoFe2O4 core-shell material investigated in this work provides a novel way to exploit new applications for the multifunctional composite, such as piezoelectric sensor, magnetoelectronic sensors and data storage devices.
关键词： Sol-gel processes,Composite core-shell,((Bi0.5Na0.5)0.92Ba0.08TiO3),Cobalt ferrite (CoFe2O4),Lead-free piezoelectric
更新于2025-09-23 15:23:52
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Blocking and remanence properties of weakly and highly interactive cobalt ferrite based nanoparticles
摘要： We compare both magnetic blocking properties and remanence curves for dilute ferrofluid and powder samples of ferrite magnetic nanoparticles. Low field DC magnetization, AC susceptibility, isothermal remanent magnetization and DC demagnetization techniques are employed to investigate the role of interparticle magnetic interactions on the superparamagnetic relaxation, the magnetic anisotropy and on the super-spin-glass state in closely packed particles. The samples used herein are 3 nm sized spinel-type nanocrystals made of a cobalt ferrite core covered by a layer of maghemite on its outermost surface and can be obtained as aqueous colloidal dispersions thanks to this core-shell strategy. They show large anisotropy attributed to an enhanced surface contribution and the blocking temperature is shifted towards higher values as interparticle distance decreases. For all investigated diluted liquids and powder samples the frequency dependency of the peak temperature is well accounted by a Vogel-Fulcher law, with the insertion of a phenomenological temperature associated to the magnitude of interparticle dipolar interactions. The fractional change of the peak temperature per decade of frequency enlights the presence of interactions between particles in dilute liquids and of a spin-glass-like state in powder samples. The remanence curves always show global demagnetizing behavior, attributed to the combination of both spin surface disorder and interparticle dipolar interactions, the former being predominant in isolated nanoparticles and the latter in powder samples. However, in the most compacted powder, exchange interaction between surface ions of different particles becomes more pronounced and promotes an additive magnetizing effect.
关键词： cobalt ferrite nanoparticles,superparamagnetism,magnetic interactions,blocking temperature,spin-glass state,remanence curves
更新于2025-09-19 17:15:36
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Cobalt ferrite decorated multiwalled carbon nanotubes as the electrode for efficient field electron emission
摘要： In the present study, Cobalt Ferrite (CF) nanoparticles with different weight concentrations were successfully decorated on Multi-Walled Carbon nanotubes (MWCNT) using a simple glycol assisted chemical route. The physicochemical and electronic properties of CF decorated MWCNTs (MWCNT-CF) were accomplished with the help of different techniques such as X-ray Diffraction (XRD), Raman Spectroscopy, Transmission Electron Microscopy (TEM), X-ray Photo-electron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR). Further, the effect of CF concentration on Field Emission (FE) characteristics of MWCNT-CF is investigated. The FE studies revealed that, CF decorated MWCNT emitter (MWCNT-CF; 1:1) exhibits lower turn on (0.52 V/μm, at 10 μA/cm2) and threshold fields (0.62 V/μm, at 100 μA/cm2) in contrast to pristine CF, MWCNT, and MWCNT-CF (1:0.5 and 1:2). Interestingly, from the MWCNT-CF (1:1) emitter, very high emission current density ~ 10408 μA/cm2 has been extracted at a relatively lower applied field of 1.18 V/μm. The enhancement in FE characteristics of MWCNT-CF emitters is attributed to lowering of work function measured from the UPS analysis and increased number of emitting sites. The results imply that very high current density field emitters can be fabricated using a simple strategy based on the decoration of MWCNT’s with CF nanoparticles.
关键词： Reflux,Cobalt Ferrite,Multiwalled Carbon Nanotubes,Field Emission,Nanoparticles
更新于2025-09-19 17:13:59
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Bulk and surface characterisation of micrometer-thick cobalt ferrite films grown by IR PLD
摘要： We have studied micrometer-thick cobalt ferrite films deposited on Si (100) single crystal substrates by nanosecond pulsed laser deposition at 1064 nm.The thickness of the deposited films (1.3 μm) was monitored by AFM. The chemical and structural characterisation of the films was carried out by Raman spectroscopy and transmission M?ssbauer spectroscopy at 300 and 26 K. For comparison purposes, transmission M?ssbauer data at these two temperatures were also recorded from a commercial cobalt ferrite powder and the home-made target used to grow the films. The surface characterisation was performed by X-Ray Photoelectron Spectroscopy (XPS) and Integral Low Energy Electron Spectroscopy (ILEEMS). XPS showed Co and Fe to be present as Co2+ and Fe3+, as expected for cobalt ferrite. The Raman spectra showed the lines characteristic of cobalt ferrite. The M?ssbauer spectra, both in the transmission and backscattering modes, were fitted to two sextets whose hyperfine parameters are in good agreement with those expected from Fe3+ cations occupying the tetrahedral and octahedral sites in the spinel-related structure. No significant differences were observed in the relative areas of the two sextets in the transmission and ILEEMS spectra, suggesting that the cation distribution at the surface and the bulk are not too different. However, the relative areas of the two components changed drastically with temperature both in the spectra of the films as in those recorded from the cobalt ferrite standards. We discuss the possible origin of the evolution with temperature of those relative areas.
关键词： X-ray photoelectron spectroscopy,Raman spectroscopy,Cobalt ferrite,M?ssbauer spectroscopy,Pulsed laser deposition
更新于2025-09-10 09:29:36