A facile and novel approach to magnetic Fe@SiO₂and FeSi₂@SiO₂nanoparticles

Abstract

Fe@SiO 2 and FeSi 2 @SiO 2 nanoparticles with core@shell structure have successfully been synthesized by direct silane silicification of Fe 2 O 3 nanoparticles. The as-prepared samples were characterized by N 2 physisorption, X-ray diffraction, transmission electron microscopy, temperature programmed reduction of H 2 , X-ray photoelectron spectroscopy, M€ ossbauer spectroscopy, and superconducting quantum interference magnetometry. It was found that the amorphous SiO 2 shell was formed to protect the core against oxidation when the reduced Fe 2 O 3 nanoparticles were silicified by silane. When the reduced Fe 2 O 3 nanoparticles were exposed to air, a Fe 2 O 3 layer was formed. The structure of the core changed from cubic Fe to orthorhombic FeSi 2 with increasing silicification temperatures from 350 to 550 C, due to the dissolution of Si atoms into the iron lattice. The magnetic characterization showed that all samples have ferromagnetic nature and the saturation magnetization values drastically decreased with increasing silicification temperature. This novel methodology can be applied to synthesis of Co@SiO 2 and Ni@SiO 2 with core@shell structure. The as-prepared Fe@SiO 2 and FeSi 2 @SiO 2 nanoparticles with core@shell structure can find applications in magnetically separable catalysts, biomedicines, and magnetically recording materials.

Effects of temperature and surface orientation on migration behaviours of helium atoms near tungsten surfaces

“…There have been a number of MD simulations that deal with the interaction of helium atoms with tungsten [7][8][9][10][11][12][13][14][15][16][17][18]. The He atoms, starting from their incidence on a surface, are generally considered to experience two major phases.…”

Carbonylative Suzuki–Miyaura cross-coupling by immobilized Ni@Pd NPs supported on carbon nanotubes

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Ni@Pd nanoparticles supported on ionic liquid‐functionalized KCC‐1 as robust and recyclable nanocatalysts for cycloaddition of propargylic amines and CO2

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