Preparation and Magnetic Properties of Monodisperse Nanocomposite Hollow Spheres

2007 ◽  
Vol 998 ◽  
Author(s):  
Chun-Rong Lin ◽  
Cheng-Chien Wang ◽  
I-Han Chen
Keyword(s):  
Particle Size ◽  
Electron Microscope ◽  
Saturation Magnetization ◽  
Magnetic Measurements ◽  
Spinel Ferrite ◽  
Sol Gel ◽  
Hollow Spheres ◽  
Core Shell ◽  
Ferromagnetic Behavior ◽  
Mixed Gas

ABSTRACTWe present a simple process to prepare the hollow ceramic (CoFe2O4/SiO2) composite nanospheres and hollow alloy (Co33Fe67/SiO2) composite nanospheres. The hollow CoFe2O4/SiO2 composite nanospheres were prepared by calcining polymer/CoFe2O4/SiO2 core/shell composite spheres which were synthesized by the sol-gel method following the chemical co-precipitation. In a typical process, the monodisperse polymer poly(MMA-co-MAA) latex (450 nm) was used as a core template. To create hollow CoFe2O4/SiO2 spherical structures with various sizes of CoFe2O4 nanoparticles, the hybrid PMMA/CoFe2O4/SiO2 core-shell spheres were subsequently calcined in the temperature range from 450 to 900°C for 4h. On the other hand, the hollow Co33Fe67/SiO2 composite nanospheres were formed by reduction of hollow CoFe2O4/SiO2 nanospheres in a stream of H2/Ar mixed gas at 900°C for 8 hrs. X-ray diffraction pattern shows that the coated phase of the hollow CoFe2O4/SiO2 composite nanospheres has a cubic spinel ferrite structure. Based on the thermogravimetric analysis (TGA), we found that the content of CoFe2O4 is 73 wt% in the hollow CoFe2O4/SiO2 composite shell. The scanning electron microscope and transmission electron microscope photographs show that the hollow spheres are uniform. According to the line scanning EDX analysis of the cross section of hollow spheres, the SiO2 is not only coated on the surface of sphere but also distributed over the shell of hollow sphere. The thickness of shell of hollow spheres is about 40 nm. Magnetic measurements show that the saturation magnetization is clearly decreases as the magnetic particle size decreased. This phenomenon can be interpreted as the effect of surface spin canting when the particle size is reduced. As for the hollow alloy (Co33Fe67/SiO2) composite nanospheres, the magnetic phase has a body-centered cubic structure and an average crystallite size of 28.7 nm. This alloy nanospheres exhibit a ferromagnetic behavior with saturation magnetization of 170 emu/g, coercivity of 250 Oe, and Curie temperature of 968 °C. Due to metallic and ferromagnetic behavior of Co33Fe67 nanoparticles, these hollow spheres can be used as a lightweight electromagnetic wave absorber.

Studies on structural and magnetic properties of Ni-Mg-Co spinel ferrite nanoparticles sintered at different temperatures

2020 ◽  
Vol 34 (03) ◽  
pp. 2050041
Author(s):  
Xiqian Zhao ◽  
Aimin Sun ◽  
Wei Zhang ◽  
Lichao Yu ◽  
Zhuo Zuo ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Saturation Magnetization ◽  
Spinel Structure ◽  
Cobalt Ferrite ◽  
Sintering Temperature ◽  
Spinel Ferrite ◽  
Sol Gel ◽  
Peak Height ◽  
Magnetic Stability

In order to study the effect of sintering temperature on the structure and magnetic properties of nickel-magnesium-cobalt ferrite, [Formula: see text] spinel ferrite with different sintering temperatures (500[Formula: see text]C, 600[Formula: see text]C, 700[Formula: see text]C, 800[Formula: see text]C, 900[Formula: see text]C and 1000[Formula: see text]C) was prepared by sol–gel method. The magnetic properties of the prepared samples were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Vibrating sample magnetometer (VSM). The results show that the sintering temperature has a significant effect on the structure and magnetic properties of nickel-magnesium-cobalt ferrite. Analysis of the XRD pattern confirmed that all samples showed a single-phase cubic spinel structure. The particle size of the prepared sample determined by the Scherrer equation was 51 nm to 135 nm. As the sintering temperature increases from 500[Formula: see text]C to 1000[Formula: see text]C, the intensity of all peaks gradually increases, the crystallinity and particle size of the sample increase significantly, but the coercive force decreases, the saturation magnetization, the residual magnetization and the squareness [Formula: see text] increase first and then decrease. Compared with other samples, the 800[Formula: see text]C sintered samples had the highest saturation magnetization (59.03 emu/g), remanent magnetization (30.65 emu/g) and squareness (0.519). The increasing peak height of [Formula: see text] at [Formula: see text] indicates that the cubic spinel structure samples have good crystallinity and magnetic stability.

Synthesis of Nickel-Based Ferrite Nanofibers and their Static Magnetic and Microwave Absorption Properties

2013 ◽  
Vol 631-632 ◽  
pp. 429-433 ◽  
Author(s):  
Yan Qiu Chu ◽  
Bin Zhang ◽  
Jun Xiang
Keyword(s):  
Microwave Absorption ◽  
Magnetic Measurements ◽  
Spinel Ferrite ◽  
Sol Gel ◽  
Absorption Properties ◽  
Microwave Absorption Properties ◽  
Practical Applications ◽  
Structure Morphology ◽  
Electrospinning Method ◽  
Absorption Performance

Ni0.5Zn0.5Fe2O4, Ni0.3Cu0.2Zn0.5Fe2O4 and Ni0.4Co0.2Zn0.4Fe2O4 spinel ferrite nanofibers with 60–100 nm in diameter were fabricated through the sol-gel assisted electrospinning method, followed by calcination at 600°C for 2h in air. The phase structure morphology and element composition of these nanofibers were determined by XRD, FE-SEM and EDS. Magnetic measurements were used to justify the ferromagnetic properties of these nanofibers. Microwave absorption, which was in the range of 2-18 GHz, was studied by a vector network analyzer. The adoption of Cu2+ and Co2+ substitution was found to improve the microwave absorption in relation to non-substituted NiZn ferrite nanofibers. Reflection loss exceeding –5 dB is obtained between 11 and 18 GHz for silicon rubber composites containing 15 vol% nickel-based ferrite nanofibers with coating thicknesses of 3 mm. The results indicate that the prepared nickel-based ferrite nanofibers possess good electromagnetic wave absorption performance in the Ku band and have great potential as microwave absorber for practical applications.

scholarly journals Size Effects on Magnetic Properties ofNi0.5Zn0.5Fe2O4Prepared by Sol-Gel Method

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Min Zhang ◽  
Zhenfa Zi ◽  
Qiangchun Liu ◽  
Peng Zhang ◽  
Xianwu Tang ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetic Measurements ◽  
Sol Gel ◽  
Domain Wall Motion ◽  
Blocking Temperature ◽  
Particle Sizes ◽  
X Ray Diffraction ◽  
Gel Method ◽  
Sol Gel Method ◽  
Cation Redistribution

Ni0.5Zn0.5Fe2O4particles with different particle sizes have been synthesized by sol-gel method. X-ray diffraction results show that all the samples are pure cubic spinel structure with their sizes ranging from 9 to 96 nm. The lattice constant significantly decreases with further increasing annealing temperature. The magnetic measurements show superparamagnetic nature below the particle size of 30 nm, while others show ferrimagnetic nature above the corresponding blocking temperature. The blocking temperature increases with the increase in particle size, which can be explained by Stoner-Wohlfarth theory. The saturation magnetization increases as the particle size increases, which can be explained by the cation redistribution on tetrahedral A and octahedral B sites and the domain wall motion. The variation of coercivity as a function of particle size is based on the domain structure.

Synthesis and properties of TiO2, NiO and ZnO nanoparticles and their possible biomedical application

2019 ◽  
Vol 2 (98) ◽  
pp. 81-84
Author(s):  
K. Szmajnta ◽  
M. Szindler
Keyword(s):  
Particle Size ◽  
Electron Microscope ◽  
Chemical Composition ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Biomedical Application ◽  
Sol Gel ◽  
Scattering Method ◽  
Gel Method ◽  
Sol Gel Method

Purpose: The main purpose of this publication is to bring closer method of synthesis and examining basic properties of TiO2, ZnO and NiO nanoparticles (NPs), and investigate their possible biomedical application. Design/methodology/approach: Nanopowders were made with sol-gel method. Surface morphology studies of the obtained materials were made using Zeiss's Supra 35 scanning electron microscope and the structure using S/TEM TITAN 80-300 transmission electron microscope. In order to confirm the chemical composition of observed nanopowders, qualitative tests were performed by means of spectroscopy of scattered X -ray energy using the Energy Dispersive Spectrometer (EDS). The DLS (Dynamic Light Scattering) method was used to analyse the particle size distribution using the AntonPaar Litesizer 500 nanoparticle size analyser. Changes in particle size distribution at elevated temperatures were also observed. The TiO2, ZnO and NiO NPs with spherical shape were successfully produced by sol-gel method. Findings: The diameter of the as prepared nanoparticles does not exceed 25 nm which is confirmed by the TEM analysis. The highest proportion among the agglomerates of the nanoparticles has been shown to show those with a diameter of 80 to 125 nm. The qualitative analysis of EDS confirmed the chemical composition of the material. Practical implications: Nanoparticles (NPs) has been receiving an incrementally increasing interest within biomedical fields researchers. Nanoparticles properties (physical, chemical, mechanical, optical, electrical, magnetic, etc.) are different from the properties of their counterparts with a larger particle size. Originality/value: The nanoparticles were prepared using sol-gel method which allows the particle size to be controlled in a simple way.

Preparation, Characterization and Visible-Light Catalytic Activity of Core-Shell Structure NiFe2O4@TiO2 Ferrite Nanoparticles

2016 ◽  
Vol 680 ◽  
pp. 272-277
Author(s):  
Zhou Li Lu ◽  
Peng Zhao Gao ◽  
Rui Xue Ma ◽  
Yu Kun Sun ◽  
Dong Yun Li
Keyword(s):  
Catalytic Activity ◽  
Visible Light ◽  
Shell Structure ◽  
Shell Thickness ◽  
Spinel Ferrite ◽  
Sol Gel ◽  
Magnetic Core ◽  
Core Shell ◽  
Calcination Temperatures ◽  
Core Shell Structure

The core-shell structure NiFe2O4@TiO2 nanoparticles was successfully prepared using a sol-gel method, the influence of shell thickness and calcination temperatures on the composition, microstructure, magnetic properties and visible-light catalytic activity of the nanoparticles was studied by XRD, TEM, Uv–vis, vibrating sample magnetometer, etc. Results showed the main composition of core in NiFe2O4@TiO2 was spinel ferrite, and the shell was anatase TiO2, and theshell thickness increased significantly with the increase of TiO2 content, ranging from 10nm to 50nm. The Ms and Mr of nanoparticles decreased with the increase of TiO2 content, and no obvious reaction between the magnetic core and shell occurred; visible-light degradation percent of NiFe2O4@TiO2 nanoparticles increased along with the increase of TiO2 content, whereas the recovery rate of it decreased. Degradation percent and the recovery percent of NiFe2O4@TiO2-50 still reached 93.7% and 90.5%, even after 10 cycle times, respectively, possessing the excellent long-term stability.

Hydrothermal Synthesis of CoFe2O4 Nanoparticles and their Magnetic Properties

2013 ◽  
Vol 821-822 ◽  
pp. 1358-1361 ◽  
Author(s):  
Fan Zhang ◽  
Rui Liang Su ◽  
Li Zhi Shi ◽  
Yang Liu ◽  
Yan Na Chen ◽  
...  
Keyword(s):  
Particle Size ◽  
Magnetic Properties ◽  
Room Temperature ◽  
Magnetic Measurements ◽  
Spinel Ferrite ◽  
Synthesis Method ◽  
Ferrite Nanoparticles ◽  
Particle Sizes ◽  
Naoh Solution ◽  
20 Nm

CoFe2O4 (CFO) nanoparticles was synthesized by a simple hydrothermal method using NaOH solution as a mineralizer at 200 °C for 4 h. It was found that CFO particle sizes decreased firstly and then increased with the increasing of NaOH concentration, and had a minumum value about 10-20 nm when selected 4 mol/L NaOH solution, indicating the NaOH concentration played an important role in controlling the particle size of CFO powders. The room temperature magnetic measurements showed that the saturation magnetization value was 48 emu/g, which is less than the bulk value. The synthesis method is possible to be a general approach for the preparation of other spinel ferrite nanoparticles.

scholarly journals Structure and Magnetic Properties ofY3−xErxFe5O12(x=0.2,1.0, and 2.0) Thin Films Prepared by Sol-Gel Method

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Ramadan Shaiboub ◽  
Noor Baa'yah Ibrahim ◽  
Mustaffa Abdullah ◽  
Ftema Abdulhade
Keyword(s):  
Thin Films ◽  
Saturation Magnetization ◽  
Single Phase ◽  
Annealing Temperature ◽  
Magnetic Measurements ◽  
Sol Gel ◽  
Spin Effect ◽  
Gel Method ◽  
Sol Gel Method ◽  
Surface Spin

NanoparticlesY3−xErxFe5O12(x=0.2, 1.0, and 2.0) thin films were prepared by sol-gel method and treated at 800, 900, and 1000∘C, respectively, for 2 h. The films have single phase garnet structure and the sizes of particles are in the range of 44 to 83 nm. The magnetic measurements show that the saturation magnetization decreased with increasing of Er concentration for all samples treated at different annealing temperatures. The saturation magnetization increased with the particle size due to the enhancement of the surface spin effect. The coercivity initially decreased forx=1.0and then increased forx=2.0with increasing annealing temperature.

Pre-lithiated Li(NixMnyCoz)O2 nanoparticles with a double-layer lithium structure

2020 ◽  
Vol 13 (04) ◽  
pp. 2050020
Author(s):  
Suihan Cui ◽  
Qingdong Ruan ◽  
Cuiqing Jiang ◽  
Tijun Li ◽  
Zheng Jin ◽  
...  
Keyword(s):  
Particle Size ◽  
Electron Microscope ◽  
Double Layer ◽  
Transmission Electron Microscope ◽  
Sol Gel ◽  
Particle Diameter ◽  
Reversible Capacity ◽  
Transmission Electron ◽  
Capacity Improvement ◽  
Li Ion

Li(NixMnyCoz)O2 cathode materials (NMC) have advantages such as the good Li ion diffusivity, stable reversible capacity, and environmental compatibility in spite of a low actual capacity. Although a double-layer lithium structure can be generated by pre-lithiation, the thickness is very small and the capacity improvement is limited. In this work, a series of Li([Formula: see text][Formula: see text][Formula: see text])O2 nanoparticles are prepared by the sol–gel method and centrifugation and the pre-lithiation process are monitored by transmission electron microscope (TEM). A double lithium structure of about 10 nanometers thick is produced on the NMC materials with different sizes. With decreasing NMC particle size, the proportion of the double-layer lithium structure increases and reaches 48% for a particle diameter of 100[Formula: see text]nm. The results reveal a viable means to improve the capacity of NMC materials in charging and discharging.

Mn0.2Co0.8Fe2O4 and encapsulated Mn0.2Co0.8Fe2O4/SiO2 magnetic nanoparticles for efficient Pb2+ removal from aqueous solution

2019 ◽  
Vol 80 (2) ◽  
pp. 377-386
Author(s):  
Kamal R. Awad ◽  
M. M. S. Wahsh ◽  
Shaimaa T. El-Wakeel ◽  
Kingsley I. Ochiabuto ◽  
A. G. M. Othman ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Particle Size ◽  
Magnetic Nanoparticles ◽  
Spinel Ferrite ◽  
Sol Gel ◽  
Solution Ph ◽  
Transition Electron Microscopy ◽  
Auto Combustion ◽  
Langmuir Isotherm Model ◽  
Modified Stöber Method

Abstract Sol-gel auto-combustion technique was used to synthesize spinel ferrite nanoparticles of Mn0.2Co0.8Fe2O4 (MCF). Using the modified Stöber method, these magnetic nanoparticles were encapsulated with silica to form the core/shell Mn0.2Co0.8Fe2O4/SiO2 (MCFS). The phase composition, morphology, particle size, and saturation magnetization of the encapsulated nanoparticles were studied using X-ray diffraction (XRD), high resolution-transition electron microscopy (HR-TEM), and vibrating sample magnetometer (VSM). HR-TEM images indicated that particle size of the nanoparticles ranged from 15 to 40 nm, and VSM measurements showed that Ms of uncoated and coated samples were 65.668 emu/g and 61.950 emu/g and the Hc values were 2,151.9 Oe and 2,422.0 Oe, respectively. The effects of metal concentration, solution pH, contact time, and adsorbent dose of the synthesized nanoparticles on lead (Pb2+) ions removal from an aqueous solution were investigated. Based on Langmuir isotherm model, the results for peak adsorption capacity of the adsorbent under optimal conditions was 250.5 mg/g and 247 mg/g for MCF and MCFS, respectively. We concluded that Pb2+ adsorption occurred via a chemisorption mechanism based on the analysis of adsorption kinetics. The adsorbents displayed consistent adsorption efficiencies following three cycles of regeneration, indicating that these magnetic nanoparticles are promising candidates for wastewater purification.

scholarly journals Green Synthesis of Co-Zn Spinel Ferrite Nanoparticles: Magnetic and Intrinsic Antimicrobial Properties

Materials ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5014
Author(s):  
Alexander Omelyanchik ◽  
Kateryna Levada ◽  
Stanislav Pshenichnikov ◽  
Maryam Abdolrahim ◽  
Miran Baricic ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Magnetic Nanoparticles ◽  
Chemical Composition ◽  
Saturation Magnetization ◽  
Cobalt Ferrite ◽  
Spinel Ferrite ◽  
Ferrite Nanoparticles ◽  
Ferromagnetic Behavior ◽  
Wide Range ◽  
Auto Combustion

Spinel ferrite magnetic nanoparticles have attracted considerable attention because of their high and flexible magnetic properties and biocompatibility. In this work, a set of magnetic nanoparticles of cobalt ferrite doped with zinc was synthesized via the eco-friendly sol-gel auto-combustion method. Obtained particles displayed a room-temperature ferromagnetic behavior with tuned by chemical composition values of saturation magnetization and coercivity. The maximal values of saturation magnetization ~74 Am2/kg were found in cobalt ferrite nanoparticles with a 15–35% molar fraction of cobalt replaced by zinc ions. At the same time, the coercivity exhibited a gradually diminishing trend from ~140 to ~5 mT whereas the concentration of zinc was increased from 0 to 100%. Consequently, nanoparticles produced by the proposed method possess highly adjustable magnetic properties to satisfy the requirement of a wide range of possible applications. Further prepared nanoparticles were tested with bacterial culture to display the influence of chemical composition and magnetic structure on nanoparticles-bacterial cell interaction.

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