Fabrication and Properties of Carbon-Encapsulated Cobalt Nanoparticles over NaCl by CVD.

Haipeng Li,Hongshui Wang,Baoe Li,Zhumabay Bakenov,Yongguang Zhang,Desmond Adair,Chunyong Liang,Yue Li

doi:10.1186/s11671-016-1645-9

Haipeng Li, Hongshui Wang + Show 6 more

Open Access

https://doi.org/10.1186/s11671-016-1645-9

Copy DOI

Abstract

Carbon-encapsulated cobalt (Co@C) nanoparticles, with a tunable structure, were synthesized by chemical vapor deposition using Co nanoparticles as the catalyst and supported on a water-soluble substrate (sodium chloride), which was easily removed by washing and centrifugation. The influences of growth temperature and time on the structure and magnetic properties of the Co@C nanoparticles were systematically investigated. For different growth temperatures, the magnetic Co nanoparticles were encapsulated by different types of carbon layers, including amorphous carbon layers, graphitic layers, and carbon nanofibers. This inferred a close relationship between the structure of the carbon-encapsulated metal nanoparticles and the growth temperature. At a fixed growth temperature of 400 °C, prolonged growth time caused an increase in thickness of the carbon layers. The magnetic characterization indicated that the magnetic properties of the obtained Co@C nanoparticles depend not only on the graphitization but also on the thickness of the encapsulated carbon layer, which were easily controlled by the growth temperatures and times. Optimization of the synthesis process allowed achieving relatively high coercivity of the synthesized Co@C nanoparticles and enhancement of its ferromagnetic properties, which make this system promising as a magnetic material, particularly for high-density magnetic recording applications.

Highlights

Magnetic metal nanoparticles have attracted significant attention due to their enhanced electronic and magnetic properties
We proposed a simple and economic approach to synthesize high-purity carbon-encapsulated cobalt (Co@C) nanoparticles using the chemical vapor deposition (CVD) method with a water-soluble material as a catalytic support
A high coercivity of the material enables its withstanding a larger degree of demagnetization, which is very useful in fabrication and application of Carbon-encapsulated cobalt (Co@C) nanocomposite in the area of high-density magnetic recording materials

Summary

Background

Magnetic metal nanoparticles (such as Co, Ni, and Fe) have attracted significant attention due to their enhanced electronic and magnetic properties. We proposed a simple and economic approach to synthesize high-purity carbon-encapsulated cobalt (Co@C) nanoparticles using the CVD method with a water-soluble material as a catalytic support. Sodium chloride (NaCl) is used as a catalytic support, while cobalt and acetylene are employed as a graphitization catalyst and carbon precursor, respectively Using this water-soluble material as a catalytic support instead of ceramic materials means that the catalytic support is removed by simple washing with water and centrifugation, which simplifies obtaining high-purity CEMNPs. the effect of synthesis temperature and time on the structure and magnetic properties of Co@C composites are discussed. A high coercivity of the material enables its withstanding a larger degree of demagnetization, which is very useful in fabrication and application of Co@C nanocomposite in the area of high-density magnetic recording materials

Methods

Results and Discussion

Conclusions