AI Article Synopsis
- Appropriate microemulsion systems were used to produce hexagonal cobalt and cobalt-nickel alloy nanoparticles with cetyltrimethylammonium bromide as a surfactant at high temperatures, achieving stabilization of hexagonal cobalt at very small sizes.
- Annealing hcp cobalt nanoparticles in hydrogen at 700 degrees Celsius transformed them into fcc cobalt nanoparticles, with microscopy revealing spherical nanoparticles in different sizes and structures.
- Electrochemical tests indicated that cobalt nanoparticles outperform cobalt-nickel alloy nanoparticles at voltages below 0.65 V, whereas the alloy shows better efficiency at higher voltages, and all nanoparticles display ferromagnetism, though saturation magnetization is reduced due to potential surface oxidation.
Article Abstract
By choosing appropriate microemulsion systems, hexagonal cobalt (Co) and cobalt-nickel (1:1) alloy nanoparticles have been obtained with cetyltrimethylammonium bromide as a cationic surfactant at 500 degrees C. This method thus stabilizes the hcp cobalt even at sizes (<10 nm) at which normally fcc cobalt is predicted to be stable. On annealing the hcp cobalt nanoparticles in H(2) at 700 degrees C we could transform them to fcc cobalt nanoparticles. Microscopy studies show the formation of spherical nanoparticles of hexagonal and cubic forms of cobalt and Co-Ni (1:1) alloy nanoparticles with the average size of 4, 8 and 20 nm, respectively. Electrochemical studies show that the catalytic property towards oxygen evolution is dependent on the applied voltage. At low voltage (less than 0.65 V) the Co (hexagonal) nanoparticles are superior to the alloy (Co-Ni) nanoparticles while above this voltage the alloy nanoparticles are more efficient catalysts. The nanoparticles of cobalt (hcp and fcc) and alloy (Co-Ni) nanoparticles show ferromagnetism. The saturation magnetization of Co-Ni nanoparticles is reduced compared to the bulk possibly due to surface oxidation.
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| http://dx.doi.org/10.1016/j.jcis.2009.04.062 | DOI Listing |
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