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Core/shell structure containing Fe/SiO2 composite nano particles with high stability and method for making same

A technology with composite nanoparticles and high stability, which is applied in chemical instruments and methods, inorganic pigment treatment, fibrous fillers, etc. It can solve the problems of high equipment requirements, cumbersome preparation process, spontaneous combustion, etc., and achieve easy process control and high improvement. The effect of frequency characteristics and simple preparation process

Inactive Publication Date: 2005-03-16
NANJING UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, nano-sized transition metals are very easy to oxidize in air and even spontaneously ignite at room temperature, which seriously hinders the practical application of iron nanoparticles.
At present, iron nanoparticles are generally prepared in vacuum (less than 10 -6 Pa) or in inert gases such as argon and helium at low pressure, the preparation process is loaded down with trivial details, equipment requirements are high, and it is not suitable for large-scale production

Method used

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  • Core/shell structure containing Fe/SiO2 composite nano particles with high stability and method for making same
  • Core/shell structure containing Fe/SiO2 composite nano particles with high stability and method for making same
  • Core/shell structure containing Fe/SiO2 composite nano particles with high stability and method for making same

Examples

Experimental program
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Effect test

Embodiment 1

[0014] Example 1: under strong stirring, 0.01mol FeCl 2 4H 2 O and 0.015mol citric acid were dissolved in 100mL of absolute ethanol, and stirred continuously at 60°C for 6 hours to form a uniform transparent sol; add 0.083mL tetraethyl orthosilicate, evaporate and dehydrate at 80°C until a xerogel was formed; Pre-calcined at 450°C for 3 hours, and then reduced in a tube furnace at 800°C for 4 hours in a hydrogen atmosphere. The obtained product has an average particle size of about 5 nanometers and is amorphous SiO 2 The shell, the core is a composite nanoparticle of α-Fe in the cubic crystal phase, and the saturation magnetization is 197Am 2 / kg, coercivity 2.6kA / m. Magnetic spectrum measurements of the product show that at frequencies up to 10 8 Before Hz, μ’ is stable at 16, while μ” is very low. The magnetic spectrum measurement results are shown in figure 1 Curve a.

[0015] Similar results to the above were obtained using ferric chloride, ferric nitrate.

Embodiment 2

[0016] Example 2: under strong stirring, 0.01mol FeCl 2 4H 2 O and 0.015mol citric acid were dissolved in 100mL of absolute ethanol, and stirred continuously at 60°C for 6 hours to form a uniform transparent sol; add 0.34mL tetraethyl orthosilicate, and evaporate and dehydrate at 80°C until a xerogel was formed; Pre-calcined at 450°C for 3 hours, and then reduced in a tube furnace at 800°C for 4 hours in a hydrogen atmosphere. The obtained product has an average particle size of about 5 nanometers and is amorphous SiO 2 The shell, the core is a composite nanoparticle of α-Fe in the cubic crystal phase, and the saturation magnetization is 168Am 2 / kg, coercivity 3.8kA / m. The magnetic spectrum measurement results of the product show that μ’ is basically constant in the entire measurement frequency range, and the loss μ” is very low, almost approaching 0. The magnetic spectrum measurement results are shown in figure 1 Curve c.

Embodiment 3

[0017] Example 3: under strong stirring, 0.01mol FeCl 2 4H 2 O and 0.015mol citric acid were dissolved in 100mL of absolute ethanol, and stirred continuously at 60°C for 6 hours to form a uniform transparent sol; add 0.167mL tetraethyl orthosilicate, evaporate and dehydrate at 75-80°C until a xerogel is formed; xerogel Pre-calcined at 450°C in air for 3 hours, and then placed in a tube furnace in a hydrogen atmosphere for reduction at different temperatures (400-800°C) for 4 hours. When the reduction temperature is 400°C, the resulting product contains a large amount of unreduced Fe 3 o 4 ; The product obtained at a reduction temperature above 500°C has amorphous SiO 2 The shell, the core is a composite nanoparticle of α-Fe in the cubic crystal phase, and the XRD spectra of the samples obtained by different reduction temperatures are shown in figure 2 ; The reduction temperature has little effect on the particle size of the product, see the TEM photo image 3 ; The magne...

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Abstract

The invention discloses a core / shell-structure-containing Fe / SiO2 composite nano particles with high stability and its preparing process which comprises, using ferric salt as raw material, organic acid as complexing agent, absolute ethyl alcohol or isopropyl alcohol as dissolvent so as to form uniform non-aqueous gel, charging silicic acid ethyl acetate, evaporating and dehydrating to form gel, preparatory roasting in air to remove the organics, deacidizing at different temperature in H2 atmosphere.

Description

technical field [0001] The invention relates to a Fe / SiO with core / shell structure, high magnetization and high stability 2 Composite nanoparticles and methods for their preparation. Especially Fe / SiO with particle size less than 10nm 2 Composite nanoparticles and methods for their preparation. Background technique [0002] Iron metal has the largest magnetic moment among the magnetic transition elements. The iron nanoparticle made of iron metal has the characteristics of quantum size effect, small size effect, surface effect, etc., so it exhibits many unique properties, and has broad applications in catalysis, optoelectronics, medicine, magnetic media, high-performance magnetic liquid, etc. application prospects. The research on the preparation and properties of iron nanoparticles has aroused widespread interest. However, nano-sized transition metals are very easy to oxidize in air and even spontaneously ignite at room temperature, which ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C09C1/22C09C3/06
Inventor 钟伟汤怒江都有为
Owner NANJING UNIV
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