The metal vapor synthesis technique was employed to prepare Co nanoparticles. The characteristics and properties of the particles were studied by transmission electron microscopy, X-ray diffraction, temperature-progra...The metal vapor synthesis technique was employed to prepare Co nanoparticles. The characteristics and properties of the particles were studied by transmission electron microscopy, X-ray diffraction, temperature-programmed desorption, chemisorption and magnetic measurements. The experimental results showed that the particle size of Co powders depended on the initial Co concentration in the toluene matrix, reaching average crystallite diameter of 1.5 nm for the highest concentration (6.4 at. pct) investigated. The particles with size of 10 nm exist, due to the agglomerates of microcrystallites. The Co particles were surrounded by a thin carbonaceous layer formed due to toluene decomposition on cocondate melt-down and subsequent warming to room temperature. The carbonaceous layer was composed primarily of C1 fragments. The Co powders demonstrated ferromagnetic behavior.展开更多
Monodisperse Fe-based and Co-based nanopar-ticles exhibit unique magnetic properties. They play important roles in magnetic storage and biomedical application. Their chemical synthesis and performance enhancement draw...Monodisperse Fe-based and Co-based nanopar-ticles exhibit unique magnetic properties. They play important roles in magnetic storage and biomedical application. Their chemical synthesis and performance enhancement draw a lot of study interest. Investigations of magnetic metallic nano-particles are very active in many scientific fields. This paper reviews the present advances in chemical synthesis, perfor-mance enhancement, and potential applications of monodis-perse Fe-based and Co-based nanoparticles.展开更多
In this contribution, a comparative study of metallic cobalt micro and nanoparticles obtained in solution by four different chemical routes is reported. Classic routes such as borohydride reduction in aqueous media an...In this contribution, a comparative study of metallic cobalt micro and nanoparticles obtained in solution by four different chemical routes is reported. Classic routes such as borohydride reduction in aqueous media and the so-called polyol methodology were used to obtain the cobalt nanostructures to be studied. Using CTAB as surfactant, cobalt hollow nanostructures were obtained. The use of strong reducing agents, like sodium borohydride, favors the formation of quasi-monodispersed nanoparticles of about 2 nm size but accompanied with impurities; for hydrazine(a mild reducer), nanoparticles of larger size are obtained which organize in spherical microagglomerates. Valuable information on the particles thermal stability and on nature of the species anchored at their surface was obtained from thermogravimetric curves. The samples to be studied were characterized from UV-vis, IR, X-ray diffraction, and electron microscopy images(scanning and transmission).展开更多
文摘The metal vapor synthesis technique was employed to prepare Co nanoparticles. The characteristics and properties of the particles were studied by transmission electron microscopy, X-ray diffraction, temperature-programmed desorption, chemisorption and magnetic measurements. The experimental results showed that the particle size of Co powders depended on the initial Co concentration in the toluene matrix, reaching average crystallite diameter of 1.5 nm for the highest concentration (6.4 at. pct) investigated. The particles with size of 10 nm exist, due to the agglomerates of microcrystallites. The Co particles were surrounded by a thin carbonaceous layer formed due to toluene decomposition on cocondate melt-down and subsequent warming to room temperature. The carbonaceous layer was composed primarily of C1 fragments. The Co powders demonstrated ferromagnetic behavior.
基金partially supported by the National Basic Research Program of China(No.2012CB932702)the National Natural Science Foundation of China(Nos.51071022,51271020,and 11174031)+3 种基金the Program for Changjiang Scholars and Innovative Research Teams in University(PCSIRT)Beijing Nova Program(No.2011031)the Fundamental Research Funds for the Central Universitiesthe State Key Laboratory of Advanced Metals and Materials(No.2011-Z03)
文摘Monodisperse Fe-based and Co-based nanopar-ticles exhibit unique magnetic properties. They play important roles in magnetic storage and biomedical application. Their chemical synthesis and performance enhancement draw a lot of study interest. Investigations of magnetic metallic nano-particles are very active in many scientific fields. This paper reviews the present advances in chemical synthesis, perfor-mance enhancement, and potential applications of monodis-perse Fe-based and Co-based nanoparticles.
基金partially supported by the Consejo Nacional de Ciencia y Tecnología(CONACYTMéxico)under Grant SEP-CONACyT 2009No.129048
文摘In this contribution, a comparative study of metallic cobalt micro and nanoparticles obtained in solution by four different chemical routes is reported. Classic routes such as borohydride reduction in aqueous media and the so-called polyol methodology were used to obtain the cobalt nanostructures to be studied. Using CTAB as surfactant, cobalt hollow nanostructures were obtained. The use of strong reducing agents, like sodium borohydride, favors the formation of quasi-monodispersed nanoparticles of about 2 nm size but accompanied with impurities; for hydrazine(a mild reducer), nanoparticles of larger size are obtained which organize in spherical microagglomerates. Valuable information on the particles thermal stability and on nature of the species anchored at their surface was obtained from thermogravimetric curves. The samples to be studied were characterized from UV-vis, IR, X-ray diffraction, and electron microscopy images(scanning and transmission).
