The influence of silica matrix on the crystal structure and high frequency performance of cobalt nanoparticles

• Published in: Journal of solid state chemistry 2010-07, Vol.183 (7), p.1555-1560
• Main Authors: Lu, Xuegang, Liang, Gongying, Sun, Qianjin, Yang, Caihua
• Format: Article
• Language: English
• Subjects: CHALCOGENIDES; CHEMICAL REACTIONS; COBALT; COERCIVE FORCE; COMPOSITE MATERIALS; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; CRYSTAL LATTICES; CRYSTAL STRUCTURE; CUBIC LATTICES; ELEMENTS; Exact sciences and technology; FCC LATTICES; High frequencies; HYDROGEN; MAGNETIC MATERIALS; Magnetic permeability; MAGNETIC PROPERTIES; MAGNETIZATION; MATERIALS; Materials science; METALS; Methods of nanofabrication; Nanocomposite; Nanocomposites; Nanoparticles; Nanoscale materials and structures: fabrication and characterization; NANOSCIENCE AND NANOTECHNOLOGY; NANOSTRUCTURES; NONMETALS; Other topics in nanoscale materials and structures; OXIDES; OXYGEN COMPOUNDS; PERMEABILITY; Permeability spectra; PHYSICAL PROPERTIES; Physics; PRECIPITATION; REDUCTION; SEPARATION PROCESSES; SILICON COMPOUNDS; Silicon dioxide; SILICON OXIDES; Spectra; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; TRANSITION ELEMENTS
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2010.04.031

Cobalt–SiO 2 nanocomposites were successfully synthesized by chemical precipitation combined H 2 reduction method. The influence of SiO 2 matrix on the crystal structure and high frequency magnetic properties of cobalt nanoparticles was investigated. Amorphous SiO 2 layer, which is adhered to Co particle surface through Si–O–Co bonds, inhibits the growth of the nanoparticles and stabilizes the face-centered-cubic (FCC) structured Co. The FCC-cobalt/SiO 2 nanocomposites exhibit soft magnetic behavior with saturation magnetization ( M s ) about 125 emu/g and coercivity ( H c ) smaller than 100 Oe. The permeability spectra of Co/SiO 2 nanocomposites depend on the SiO 2 contents. When the SiO 2 content is greater than 8 wt%, the permeability spectra demonstrate notable high frequency characteristic, in which the real part μ′ of the permeability is almost independent of frequency and the imaginary part μ″ remains extremely low in high frequency range. Co NPs are encapsulated by SiO 2 mediated by Si–O–Co bonds. This SiO 2 matrix stabilizes FCC-Co and improves the high-frequency performance of Co NPs.