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In this paper, we report a new modified solution combustion synthesis technique for one-step production of metallic Co nanoparticles. The main unique feature of our approach is the use of microwave-assisted foam preparation. Also, the effect of different types of fuels (urea, citric acid, glycine, and hexamethylenetetramine) on the combustion process and characteristics of resultant solid products were investigated. It was shown that the combination of microwave-assisted foam and hexamethylenetetramine as a fuel allows us to produce metallic Co nanoparticles with the broad size distribution (∼5-40 nm), high coercivity (370 Oe), and high value of saturation magnetization (137 emu/g) by the one-step solution combustion synthesis under normal air atmosphere without any post reduction.

Graphene (G) and metal-decorated G nanocomposites are among the most promising materials for a wide variety of practical applications, and, therefore, the development of fast and reliable methods for nanocomposite synthesis is an important task. Herein we report the new fast approach for solution combustion synthesis (SCS) of large-area G−metallic nanocomposites in an air atmosphere. The G-based nanocomposites were obtained by a SCS using copper and nickel nitrates, as well as their stoichiometric mixture as the metal source and citric acid as a fuel and carbon source. The G structures started on the catalytic surface of freshly synthesized metallic nanograins during the combustion process and formed large-area freestanding films due to the high-energy and fast synthesis process. We proposed a mechanism of formation of the G-based nanocomposites. The phase compositions, structural features, and magnetization behavior of G@Cu, G@Ni, and G@CuNi nanocomposites are carefully studied and described. G@metal nanocomposites were studied as a material for the creation of a highly effective sensing element of semiconductor gas sensors.

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