scholarly journals Magnetic Study of CuFe2O4-SiO2 Aerogel and Xerogel Nanocomposites

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2680
Author(s):  
Alizé V. Gaumet ◽  
Francesco Caddeo ◽  
Danilo Loche ◽  
Anna Corrias ◽  
Maria F. Casula ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Sol Gel ◽  
Porous Silica ◽  
Chemical Properties ◽  
Silica Matrix ◽  
Superparamagnetic Nanoparticles ◽  
Blocking Temperature ◽  
Copper Ferrite ◽  
Transmission Electron ◽  
Magnetic Features

CuFe2O4 is an example of ferrites whose physico-chemical properties can vary greatly at the nanoscale. Here, sol-gel techniques are used to produce CuFe2O4-SiO2 nanocomposites where copper ferrite nanocrystals are grown within a porous dielectric silica matrix. Nanocomposites in the form of both xerogels and aerogels with variable loadings of copper ferrite (5 wt%, 10 wt% and 15 wt%) were synthesized. Transmission electron microscopy and X-ray diffraction investigations showed the occurrence of CuFe2O4 nanoparticles with average crystal size ranging from a few nanometers up to around 9 nm, homogeneously distributed within the porous silica matrix, after thermal treatment of the samples at 900 °C. Evidence of some impurities of CuO and -Fe2O3 was found in the aerogel samples with 10 wt% and 15 wt% loading. DC magnetometry was used to investigate the magnetic properties of these nanocomposites, as a function of the loading of copper ferrite and of the porosity characteristics. All the nanocomposites show a blocking temperature lower than RT and soft magnetic features at low temperature. The observed magnetic parameters are interpreted taking into account the occurrence of size and interaction effects in an ensemble of superparamagnetic nanoparticles distributed in a matrix. These results highlight how aerogel and xerogel matrices give rise to nanocomposites with different magnetic features and how the spatial distribution of the nanophase in the matrices modifies the final magnetic properties with respect to the case of conventional unsupported nanoparticles.

scholarly journals Preparation and Magnetic Properties of ZnFe2O4Nanotubes

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Yan Xu ◽  
Yantian Liang ◽  
Lijuan Jiang ◽  
Huarui Wu ◽  
Hongzhi Zhao ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Room Temperature ◽  
Sol Gel ◽  
Anodic Aluminum Oxide Template ◽  
Blocking Temperature ◽  
Outer Diameter ◽  
X Ray Diffraction ◽  
X Ray ◽  
Anodic Aluminum ◽  
Transmission Electron

Ordered ZnFe2O4nanotube arrays with the average outer diameter of 100 nm were prepared in porous anodic aluminum oxide template using an improved sol-gel approach. The morphology was studied by transmission electron and field emission scanning electron microscope. X-ray diffraction result shows that the nanotubes were polycrystalline in structure. The magnetic properties of the prepared ZnFe2O4nanotubes were also studied. The results show that the sample shows typical superparamagnetism at room temperature and obvious ferromagnetism below blocking temperature.

Structure and Magnetism of Nanocrystalline KδMnO2

1999 ◽  
Vol 602 ◽  
Author(s):  
R.M. Stroud ◽  
E. Carpenter ◽  
V.M. Browning ◽  
J.W. Long ◽  
K.E. Swider ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Sol Gel ◽  
Blocking Temperature ◽  
X Ray Diffraction ◽  
Surface Layers ◽  
Mixed Valency ◽  
Transmission Electron ◽  
Typical Particle ◽  
20 Nm

AbstractThe structure and magnetic properties of sol-gel-synthesized, nanocrystalline KσMnO2 were investigated. The nanoparticles were determined by x-ray diffraction and high-resolution transmission electron microscopy to be single-crystal rods of the cryptomelane phase of MnO2, with a typical particle size of 6 nm × 20 nm. The field and temperature dependence of the magnetization indicates superparamagnetic behavior, with a blocking temperature of 15K. The dependence of the magnetic properties on particle size, surface layers and mixed valency is discussed.

scholarly journals The Influence Of NO/O2 On The NOx Storage Properties Over A Pt-Ba-Ce/γ-Al2O3 Catalyst

2019 ◽  
Vol 17 (1) ◽  
pp. 1459-1465
Author(s):  
Xuedong Feng ◽  
Jing Yi ◽  
Peng Luo
Keyword(s):  
Sol Gel ◽  
Chemical Properties ◽  
No Oxidation ◽  
Test Results ◽  
X Ray Diffraction ◽  
Storage Performance ◽  
Transmission Electron ◽  
Temperature Programmed ◽  
Physical And Chemical ◽  
Al2o3 Catalyst

AbstractWith the purpose of studying the influence of NO/O2 on the NOx storage activity, a Pt-Ba-Ce/γ-Al2O3 catalyst was synthesized by an acid-aided sol-gel method. The physical and chemical properties of the catalyst were characterized by X-ray diffraction (XRD) and Transmission Electron Microscope (TEM) methods. The results showed that the composition of the catalyst was well-crystallized and the crystalline size of CeO2 (111) was about 5.7 nm. The mechanism of NO and NO2 storage and NOx temperature programmed desorption (NO-TPD) experiments were investigated to evaluate the NOx storage capacity of the catalyst. Pt-Ba-Ce/γ-Al2O3 catalyst presented the supreme NOx storage performance at 350℃, and the maximum value reached to 668.8 μmol / gcat. Compared with O2-free condition, NO oxidation to NO2 by O2 had a beneficial effect on the storage performance of NOx. NO-TPD test results showed that the NOx species stored on the catalyst surface still kept relatively stable even below 350℃.

Bioencapsulation in Sol-Gel Glasses

1998 ◽  
Vol 519 ◽  
Author(s):  
L. Bergogne ◽  
S. Fennouh ◽  
J. Livage ◽  
C. Roux
Keyword(s):  
Sol Gel ◽  
Porous Silica ◽  
Silica Matrix ◽  
Whole Cells ◽  
The Past ◽  
Wide Range ◽  
Activity Of Enzymes ◽  
Gel Glasses ◽  
Micro Organisms

AbstractBioencapsulation in sol-gel materials has been widely studied during the past decade. Trapped species appear to retain their bioactivity in the porous silica matrix. Small analytes can diffuse through the pores allowing bioreactions to be performed in-situ, inside the sol-gel glass. A wide range of biomolecules and micro-organisms have been encapsulated. The catalytic activity of enzymes is used for the realization of biosensors or bioreactors. Antibody-antigen recognition has been shown to be feasible within sol-gel matrices. Trapped antibodies bind specifically the corresponding haptens and can be used for the detection of traces of chemicals. Even whole cells are now encapsulated without any alteration of their cellular organization. They can be used for the production of chemicals or as antigens for immunoassays.

Rapid Synthesis and Characterization of Maghemite Nanoparticles

2008 ◽  
Vol 8 (2) ◽  
pp. 861-866 ◽  
Author(s):  
Bilsen Tural ◽  
Macit Özenbaş ◽  
Selçuk Atalay ◽  
Mürvet Volkan
Keyword(s):  
Particle Size ◽  
Elevated Temperatures ◽  
Sol Gel ◽  
Volume Ratio ◽  
Silica Matrix ◽  
Superparamagnetic Nanoparticles ◽  
Maghemite Nanoparticles ◽  
Gelation Temperature ◽  
Iron Oxide Particles ◽  
Evaporation Surface

Fe2O3–SiO2 nanocomposites were prepared by a sol–gel method using various evaporation surface to volume (S/V) ratios ranging from 0.03 to 0.2. The Fe2O3–SiO2 sols were gelated at various temperatures ranging from 50 °C to 70 °C, and subsequently they were calcined in air at 400 °C for 4 hours. The structure and the magnetic properties of the prepared Fe2O3–SiO2 nanocomposites were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), differential thermal analysis (DTA), and vibrating sample magnetometer (VSM) measurements. The gelation temperature of the Fe2O3–SiO2 sols influenced strongly the particle size and crystallinity of the maghemite nanoparticles. It was observed that the particle size of maghemite nanoparticles increased with the increasing of the gelation temperature of the sols, which may be due to the agglomeration of the maghemite particles at elevated temperatures inside the microporosity of the silica matrix during the gelation process, and the subsequent calcination of these gels at 400 °C resulted in the formation of large size iron oxide particles. Magnetization studies at temperatures of 10, 195, and 300 K showed superparamagnetic behavior for all the nanocomposites prepared using the evaporation surface to volume ratio (S/V) of 0.1, 0.2, 0.09, and 0.08. The saturation magnetization, Ms, values measured at 10K were 5.5, 8.5, and 9.5 emu/g, for the samples gelated at 50, 60, and 70 °C, respectively. At the gelation temperature of 70 °C, γ-Fe2O3 crystalline superparamagnetic nanoparticles with the particle size of 9±2 nm were formed in 12 hours for the samples prepared at the S/V ratio of 0.2.

Iron and Iron-oxide on Silica Nanocomposites Prepared by the Sol-gel Method

2002 ◽  
Vol 17 (3) ◽  
pp. 590-596 ◽  
Author(s):  
G. Ennas ◽  
M. F. Casula ◽  
G. Piccaluga ◽  
S. Solinas ◽  
M. P. Morales ◽  
...  
Keyword(s):  
Sol Gel ◽  
Silica Matrix ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Gel Method ◽  
Sol Gel Method ◽  
Silica Nanocomposites ◽  
Transmission Electron ◽  
Nanometric Particles

γ–Fe2O3/SiO2 and Fe/SiO2 nanocomposites, with a Fe/Si molar ratio of 0.25, were prepared by the sol-gel method starting from ethanolic solutions of tetraethoxysilane and iron (III) nitrate. After gelation the xerogels were oxidated or reduced. Samples were investigated by transmission electron microscopy, x-ray diffraction, differential scanning calorimetry, and thermogravimetry. Magnetic properties of the samples were investigated at room temperature (RT) and at 77 K. Nanometric particles supported in the silica matrix were obtained in all cases. Bigger particles (10 nm) were obtained in the case of Fe/SiO2 nanocomposites with respect to the γ–Fe2O3/SiO2 samples (5–8 nm). A slight effect of sol dilution on particle size was observed only in the case of γ–Fe2O3/SiO2 nanocomposites. A superparamagnetic behavior was shown at RT only by γ–Fe2O3/SiO2 nanocomposites. Iron-based composites exhibited coercivity values higher than 700 Oe at RT.

scholarly journals Influence of preparation method on structural, optical and magnetic properties of nickel ferrite nanoparticles

2017 ◽  
Vol 35 (1) ◽  
pp. 58-65 ◽  
Author(s):  
Ayaz Arif Khan ◽  
M. Javed ◽  
A. Rauf Khan ◽  
Yousaf Iqbal ◽  
Asif Majeed ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Nickel Ferrite ◽  
Sol Gel ◽  
Chemical Properties ◽  
Magnetic Behavior ◽  
Sem Images ◽  
Vis Spectroscopy ◽  
Nickel Ferrite Nanoparticles ◽  
Optical And Magnetic Properties ◽  
Co Precipitation

AbstractNanocrystalline NiFe2O4 particles were prepared by conventional sol-gel, citrate-nitrate sol-gel combustion and co-precipitation methods. The synthesized samples were annealed at 1000 °C for two hours and structural, chemical, morphological, optical and magnetic properties of nickel ferrite were investigated. The structural properties were investigated by X-ray diffraction (XRD) technique which confirmed the formation of single phase NiFe2O4 particles derived by the three methods. The chemical properties were analyzed by Fourier transform infrared (FT-IR) spectroscopy which confirmed the corresponding vibration modes in the samples. The optical properties were studied by UV-Vis spectroscopy. The morphological study of the as-synthesized samples was carried out by scanning electron microscopy (SEM). SEM images showed the agglomerated nanoparticles of NiFe2O4. The magnetic properties were investigated by vibrating sample magnetometer (VSM), which showed that the calcined samples exhibited typical magnetic behavior.

scholarly journals Магнитные свойства двухфазных магнитных боросиликатных стекол, содержащих наночастицы beta-Fe-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- и Fe-=SUB=-3-=/SUB=-O-=SUB=-4-=/SUB=-

2020 ◽  
Vol 46 (16) ◽  
pp. 28
Author(s):  
С.А. Борисов ◽  
А.А. Набережнов ◽  
B. Nacke ◽  
A. Nikanorov
Keyword(s):  
Magnetic Properties ◽  
Magnetic Fields ◽  
Fe3o4 Nanoparticles ◽  
Superparamagnetic Nanoparticles ◽  
Blocking Temperature ◽  
Neel Temperature ◽  
Specific Magnetization ◽  
Borosilicate Glasses ◽  
Néel Temperature ◽  
Two Phase

The magnetic properties of two-phase borosilicate glasses containing in the skeleton a mixture of β-Fe2O3 and Fe3O4 nanoparticles have been studied. The sizes of nanoparticles have been determined, the value of blocking temperature (TB ~ 330 K) for ensemble of superparamagnetic nanoparticles is obtained. It is shown that in the high applied magnetic fields the specific magnetization of these glasses increases sharply at approaching and below Neel temperature for the bulk β-Fe2O3.

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