Effect of composition and coating on the interparticle interactions and magnetic hardness of MFe2O4 (M = Fe, Co, Zn) nanoparticles

2017 ◽  
Vol 19 (12) ◽  
pp. 8363-8372 ◽  
Author(s):  
M. Virumbrales-del Olmo ◽  
A. Delgado-Cabello ◽  
A. Andrada-Chacón ◽  
J. Sánchez-Benítez ◽  
E. Urones-Garrote ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Magnetic Measurements ◽  
Interparticle Interactions ◽  
Mean Size ◽  
Magnetic Hardness ◽  
Zn Nanoparticles

Magnetic measurements and Raman spectroscopy of CoFe2O4 particles of 4.4 nm mean size are shown as an illustration.

scholarly journals From Disposal to Reuse: Production of Sustainable Fatty Acid Alkyl Esters Derived from Residual Oil Using a Biphasic Magnetic Catalyst

2020 ◽  
Vol 12 (23) ◽  
pp. 10159
Author(s):  
Adriano Lima da Silva ◽  
Carlos Bruno Barreto Luna ◽  
Ana Flávia Félix de Farias ◽  
Suelen Alves Silva Lucena de Medeiros ◽  
Simoni Margareti Plentz Meneghetti ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Fatty Acid ◽  
Magnetic Measurements ◽  
Magnetic Behavior ◽  
Biodiesel Production ◽  
Residual Oil ◽  
Sem Images ◽  
Production Chain ◽  
Magnetic Catalyst ◽  
Acidic Sites

The development of technologies to promote residual oil reuse has been encouraged, aiming to reduce the environmental impact and promote sustainability. In this study, a biphasic magnetic catalyst with composition equal to ZnO-Ni0.5Zn0.5Fe2O4 was synthesized and applied to the fatty acid alkyl ester (FAAE) production from residual oil. The ZnO-Ni0.5Zn0.5Fe2O4 catalyst was synthesized by combustion reaction and characterized by X-ray diffraction (XRD), textural analysis, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetry, particle size distribution, scanning electron microscopy, magnetic measurements, quantification of acidic sites by TPD-NH3, and catalytic tests. The efficiency of catalyst synthesis was evaluated by XRD, FTIR, and Raman spectroscopy experiments. Granulometric analysis and SEM images confirmed the presence of the agglomerates and particles with a wide size range. The catalyst presented soft magnetic behavior, with high saturation magnetization. Additionally, the catalytic activity of the ZnO-Ni0.5Zn0.5Fe2O4 system showed an average conversion of 73% for the methyl route. The results indicate that the reuse of residual oil is feasible for FAAE production, contributing to sustainable fuel development. Moreover, it allows the reintroduction of waste oil into the biodiesel production chain, reducing cost after process optimization.

Ferromagnetism, Raman Spectra and Photoluminescence of Sn0.91Co0.05Ce0.04O2 and Sn0.91Fe0.05Ce0.04O2 Nanorods

2012 ◽  
Vol 488-489 ◽  
pp. 226-229
Author(s):  
Jasneet Kaur ◽  
R.K. Kotnala ◽  
Vinay Gupta ◽  
Kuldeep Chand Verma
Keyword(s):  
Raman Spectroscopy ◽  
Magnetic Measurements ◽  
Room Temperature Ferromagnetism ◽  
Sol Gel ◽  
Stoichiometric Ratio ◽  
Chemical Route ◽  
Structural Modifications ◽  
Co Doping ◽  
Transmission Electron ◽  
20 Nm

In the present work, we have fabricated Sn0.91Co0.05Ce0.04O2 (SCC54) and Sn0.91Fe0.05Ce0.04O2 (SFC54) nanorods by a chemical route similar to sol-gel method. X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, photoluminescence (PL) and magnetic measurements are used to characterize these nanorods. XRD pattern shows the polycrystalline nature of rods and TEM confirms that the diameter of rods lie in the range of 15-20 nm and length 100-200 nm. It is observed that on Ce3+ co-doping, nanoparticles assembled themselves into rod like structures. The SCC54 and SFC54 specimens exhibit room temperature ferromagnetism. Their saturated magnetic moment and phase transition temperature is sensitive to their size and stoichiometric ratio. Raman spectroscopy shows an intensity loss of classical cassiterite SnO2 vibration lines, which is indication of significant structural modifications like crystallinity and nano metric size effects on the vibrational properties. From PL spectra, an intense blue luminescence centred at a wavelength of 532 nm is observed in the prepared SnO2 nanostructures, attributed to oxygen-related defects, introduced during the growth process.

STUDY OF Y-Ba-Cu-O SUPERCONDUCTORS PREPARED WITH THE OXALATE PRECIPITATION/EVAPORATION METHOD

1990 ◽  
Vol 04 (19) ◽  
pp. 1237-1244 ◽  
Author(s):  
TH. LEVENTOURI ◽  
E. LIAROKAPIS ◽  
L. MARTINEZ ◽  
F.D. MEDINA ◽  
M. MORENO ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Raman Spectroscopy ◽  
Magnetic Measurements ◽  
Preparation Procedure ◽  
X Rays ◽  
Evaporation Method ◽  
Preparation Conditions ◽  
Oxalate Precipitation ◽  
Scanning Electron

A study is presented on a series of Y-Ba-Cu-O superconductors prepared with the Oxalate Precipitation/Evaporation method. The effect of the preparation conditions on the properties of these superconductors has been studied with X-rays, scanning electron microscopy, Raman spectroscopy, and magnetic measurements. The experiments show that good quality superconductors can be fabricated with this preparation procedure and also indicate that the properties of these materials are very sensitive to the preparation conditions.

Cr-Doping-Induced Ferromagnetism in CeO2-δ Nanopowders

2014 ◽  
Vol 975 ◽  
pp. 42-49
Author(s):  
Nilson S. Ferreira ◽  
Marcelo Andrade Macedo
Keyword(s):  
Raman Spectroscopy ◽  
Saturation Magnetization ◽  
Calcination Temperature ◽  
Room Temperature ◽  
Magnetic Measurements ◽  
Room Temperature Ferromagnetism ◽  
Sol Gel ◽  
Fluorite Structure ◽  
Sol Gel Process ◽  
Cr Doping

The room-temperature ferromagnetism of Cr-doped cerium oxide (Ce0.96Cr0.04O2δ) nanopowders synthesized using a sol-gel process is reported in this paper. XRD and Raman spectroscopy confirm that the Cr atoms successfully displaced some of the Ce atoms in the CeO2lattice without forming any impure phases. The results also confirmed that all calcined samples exhibited a single-phase fluorite structure. The crystallite size (as confirmed by XRD) and the particle size (as confirmed by Raman spectroscopy) increased as the calcination temperature increased. Magnetic measurements indicated that the room-temperature ferromagnetism of the sample was sensitive to the calcination temperature. When the calcination temperature increased, the saturation magnetization decreased while the coercivity increased, which corresponds to less dense and larger particles. The calcined sample at 400°C exhibited superior magnetic properties with the highest saturation magnetization (Ms) of 2.5 × 10-2emu/g (Hc~ 1.27 kOe). The results of the Raman and X-ray photoelectron spectroscopies suggest that the nature of the observed room temperature ferromagnetism in the samples are likely a result of the oxygen vacancies induced by Cr-doping in CeO2.

scholarly journals Degradation of magnetic nanoparticles mimicking lysosomal conditions followed by AC susceptibility

2015 ◽  
Vol 60 (5) ◽  
Author(s):  
Lucía Gutiérrez ◽  
Sonia Romero ◽  
Gustavo B. da Silva ◽  
Rocío Costo ◽  
Maria D. Vargas ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Nanoparticles ◽  
Magnetic Measurements ◽  
Degradation Products ◽  
Ac Susceptibility ◽  
Degradation Process ◽  
Interparticle Interactions ◽  
Biological Media ◽  
Transmission Electron

AbstractA deeper knowledge on the effects of the degradation of magnetic nanoparticles on their magnetic properties is required to develop tools for the identification and quantification of magnetic nanoparticles in biological media by magnetic means.Citric acid and phosphonoacetic acid-coated magnetic nanoparticles have been degraded in a medium that mimics lysosomal conditions. Magnetic measurements and transmission electron microscopy have been used to follow up the degradation process.Particle size is reduced significantly in 24 h at pH 4.5 and body temperature. These transformations affect the magnetic properties of the compounds. A reduction of the interparticle interactions is observed just 4 h after the beginning of the degradation process. A strong paramagnetic contribution coming from the degradation products appears with time.A model for the

Structural characterization of TiO2 nanopowders by Raman spectroscopy

2015 ◽  
Vol 1806 ◽  
pp. 1-6
Author(s):  
Sergey Mamedov
Keyword(s):  
Raman Spectroscopy ◽  
Raman Spectra ◽  
Structural Characteristics ◽  
Structural Features ◽  
Preparation Methods ◽  
Mean Size ◽  
Tio2 Nanopowders ◽  
The Mean ◽  
Nano Size

ABSTRACTTiO2 nanopowders obtained using different methods with the mean size of 5, 15, and 30 nm have been investigated by Raman spectroscopy in wide spectral range. Nano-size of TiO2 crystals lead to a shift and broadening of the first-order Raman lines through a relaxation of the q = 0 selection rule and effects on to the position, width and asymmetry of a Raman bands. The details of the evolution of the 142.9 cm-1 Raman line shape on the size and distributions of the nanopowders are presented and discussed in frame of confined phonons model. Analysis of Raman spectra shows that structural characteristics of nanopowders may be different even size of the nanopowders is the same. Structural features of the material depend on preparation methods/conditions and can be extracted from Raman spectra of the material.

Comparative Analysis of γ-Fe2O3 Nanoparticles Magnetic Interactions in Different Polymeric Nanocomposites

2009 ◽  
Vol 152-153 ◽  
pp. 269-272 ◽  
Author(s):  
Tatiana S. Gendler ◽  
Alla A. Novakova ◽  
V.N. Prudnikov ◽  
G.P. Aleksandrova ◽  
L.A. Grishchenko
Keyword(s):  
Electron Microscopy ◽  
Magnetic Measurements ◽  
Magnetic Behavior ◽  
Superparamagnetic Nanoparticles ◽  
Magnetic Interactions ◽  
Self Organization ◽  
Polymeric Nanocomposites ◽  
Interparticle Interactions ◽  
Transmission Electron ◽  
The Comparative Study

The comparative study of Fe2O3 4-10nm nanoparticles incorporated in arabinogalactan and polyvinyl alcohol matrixes was performed by means of magnetic measurements in wide 5-900K temperature range, Mossbauer spectroscopy and transmission electron microscopy. The processes of nanoparticles different self-organization inside various polymer matrixes were revealed. These processes lead to unusual magnetic behavior of initially superparamagnetic nanoparticles owing to interparticle interactions.

CHARACTERIZATION OF ta-C AND GRANULAR Co-C FILMS PREPARED BY PULSED FILTERED VACUUM ARC DEPOSITION

2000 ◽  
Vol 14 (02n03) ◽  
pp. 321-332 ◽  
Author(s):  
S. P. WONG ◽  
H. WANG ◽  
N. KE ◽  
W. Y. CHEUNG ◽  
M. F. CHIAH ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Electrical Transport ◽  
Annealing Temperature ◽  
Rutherford Backscattering Spectrometry ◽  
Magnetic Measurements ◽  
Perpendicular Magnetic Anisotropy ◽  
Vacuum Arc ◽  
Electrical Measurements ◽  
Force Microscopy ◽  
Domain Structures

A pulsed filtered vacuum are deposition system was used to prepare ta-C thin films and granular Co-C films. The ta-C films prepared at various substrate bias voltages were characterized using Raman spectroscopy and spectroscopic ellipsometry of which the results confirmed that these ta-C films exhibit high sp 3 fraction of over 80%. The composition of the granular Co-C films prepared by the same system was determined by non-Rutherford backscattering spectrometry. The properties of these Co-C Films, as deposited and after vacuum annealing at various temperatures, were studied using Raman spectroscopy, electrical measurements, magnetic measurements by a SQUID magnetometer, atomic force microscopy and magnetic force microscopy. It was found that the dependence of the Raman spectra of these films on annealing temperature was associated with the formation and dissociation of a cobalt carbide phase and the graphitization of amorphous carbon. The magnetic properties showed complicated composition and annealing temperature dependence. The optimum annealing temperature for the maximum coercivity was found to depend on the composition of the film. For a film of Co 65 C 35 after annealing at 623K in vacuum for one hour, the coercivity was measured to be 460 Oe at 300K and 1380 Oe at 3K. Clear MFM images of the domain structures were observed for films after annealing at sufficiently high temperature, showing that there was perpendicular magnetic anisotropy in these films. A nearly-temperature-independent electrical resistance in the range from 20K to 300K was also observed. A more detailed analysis indicated that the low temperature electrical transport is consistent with a theory for granular metal films.

scholarly journals Nanocrystalline/Nanosized Fe3O4 Powder Obtained by Mechanosynthesis

2015 ◽  
Vol 13 ◽  
pp. 9-14
Author(s):  
Traian Florin Marinca ◽  
Bogdan Viorel Neamţu ◽  
Ionel Chicinaş ◽  
Olivier Isnard
Keyword(s):  
Milling Time ◽  
Magnetic Measurements ◽  
Early Stage ◽  
Particle Size Analysis ◽  
Size Analysis ◽  
X Ray Diffraction ◽  
Ceramic Method ◽  
Median Diameter ◽  
Mean Size ◽  
Nanometric Particles

Nanocrystalline/nanosized magnetite - Fe3O4powder was obtained by mechanical milling of well crystallized magnetite obtained by ceramic method starting from stoichiometric mixture of commercial hematite - Fe2O3and iron - Fe powders. The mean crystallites size of the magnetite is decreasing upon increasing the milling time down to 6 nm after 240 minutes of milling. After 30 minutes of milling an undesired hematite phase is formed in the material. The amount of this phase increases upon increasing the milling time. In the early stage of milling (up to 30 minutes) the existence of nanometric particles (mean size below 100 nm) is noticed. The d50median diameter decreases first (up to 5 minutes of milling) and after that, an increase follows for milling times up to 120 minutes. Saturation magnetization decreases upon increasing the milling time and is more difficult to saturate. X-ray diffraction, laser particle size analysis and magnetic measurements have been used for powder characterization.

Synthesis of magnetic spinel ferrite CoFe2O4 nanoparticles from ferric salt and characterization of the size-dependent superparamagnetic properties

2000 ◽  
Vol 72 (1-2) ◽  
pp. 37-45 ◽  
Author(s):  
Chao Liu ◽  
Adam J. Rondinone ◽  
Z. John Zhang
Keyword(s):  
Neutron Diffraction ◽  
Magnetic Measurements ◽  
Spinel Ferrite ◽  
Sodium Dodecyl ◽  
Blocking Temperature ◽  
Size Dependent ◽  
Ferric Salt ◽  
Mean Size ◽  
High Degree ◽  
Superparamagnetic Properties

The CoFe2O4 nanoparticles have been synthesized by using a stable ferric salt of FeCl3 with a micellar microemulsion method. The normal micelles are formed by sodium dodecyl sulfate (NaDS) in aqueous solutions. The mean size of the nanoparticles can be controlled from less than 4 nm to about 10 nm through controlling the concentrations of the reagents. The neutron diffraction in combination with the Rietveld refinement shows that these CoFe2O4 nanoparticles have a high degree of inversion with 66% of the tetrahedral sublattice occupied by Fe3+. Magnetic measurements and neutron diffraction studies demonstrate the superparamagnetic nature of these CoFe2O4 nanoparticles. The size-dependent superparamagnetic properties of CoFe2O4 nanoparticles have also been systematically studied. The blocking temperature and coercive field of the nanoparticles increase with increasing size of the nanoparticles. The superparamagnetic behaviors of CoFe2O4 nanoparticles are consistent with the Stoner-Wohlfarth theory of single domain particles.

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