ИСТИНА

Unique conductive, structural, optical and chemical properties of carbon nanotubes (CNTs) open the way for their applications in many fields of science and chemical technology as catalytic supports, electrode materials, adsorbents, additives, electronics etc. However, low bulk density and the powdery nature of CNTs hamper their utilization in many areas, which makes their compaction important for practical use. Spark plasma sintering (SPS) is a promising and widely used tecqnique for the production of CNT contained materials. At the same time, CNTs are usually used as an additive to metals or ceramics and only few papers are dedicated to the sintering of materials contained CNTs as a base component. This work is devoted to the synthesis of a new type of 3D-material, in which carbon encapsulated cobalt nanoparticles are embedded into the dence framework of CNTs (Fig.1a,b). For this purpose, oxidized CNTs decorated by 4–6 nm Co oxide nanoparticles were sintered by SPS at different temperature (Ts) and cobalt content at 30 MPa. Obtained composites were carefully charactrized by electron microscopy, XPS, XRD, Raman spectroscopy and vibrational magnetometry. We found that the Co particle size, electrical conductivity and ferromagnetic properties of composites can be tuned in a wide range by varying Ts. Under SPS the defects in CNTs are transformed into graphitic shells that stabilize cobalt metal crystallites, which enhances the conductivity of composite (up to 12500 Sm/m). Catalytic properties of the sintered samples contained 10 wt.% of Co were studied in CO hydrogenation. It was found that cobalt nanopparticles covered with carbon shell are active in this process without pre-activation and that hydrocarbons up to C12 can be synthesized at 20–50% CO conversion. Promising properties of produced materials for the magnetic separation were also demonstrated.