Abstract
Pure metallic Co, Ni, and their bimetallic compositions of Co3Ni, CoNi, and CoNi3 nanomaterials were prepared by solution combustion synthesis. Microstructure, phase composition, and crystalline structure of these nanoparticles (NPs) were characterized along with studies of their corrosion and dissolution properties in synthetic freshwater with and without natural organic matter (NOM). The nanomaterials consisted of aggregates of fine NPs (3–30 nm) of almost pure metallic and bimetallic crystal phases with a thin surface oxide covered by a thin carbon shell. The nanomaterials were characterized by BET surface areas ranging from ~ 1 to 8 m2/g for the Ni and Co NPs, to 22.93 m2/g, 14.86 m2/g, and 10.53 m2/g for the Co3Ni, CoNi, CoNi3 NPs, respectively. More Co and Ni were released from the bimetallic NPs compared with the pure metals although their corrosion current densities were lower. In contrast to findings for the pure metal NPs, the presence of NOM increased the release of Co and Ni from the bimetallic NPs in freshwater compared to freshwater only even though its presence reduced the corrosion rate (current density). It was shown that the properties of the bimetallic nanomaterials were influenced by multiple factors such as their composition, including carbon shell, type of surface oxides, and the entropy of mixing.
Highlights
Nanotechnology is a high-tech multi-billion industry that during the latest decades has penetrated numerous aspects of modern society
The images show the solution combustion synthesis (SCS) nanopowders to consist of both small flakes, which are not aggregated in large grains (Co, Fig. 2a), and non-uniform aggregates with an inhomogeneously distributed porosity ( Co3Ni (Fig. 2b), CoNi (Fig. 2c), CoNi3 (Fig. 2d) and Ni (Fig. 2e), respectively)
Engineered nanomaterials (NMs) obtained by the solution combustion synthesis (SCS) method are complex structures consisting of NPs with metallic cores with oxidized surfaces, and outer carbon shells
Summary
Nanotechnology is a high-tech multi-billion industry that during the latest decades has penetrated numerous aspects of modern society. One of the main factors for such great interest is their sometimes superior and unique functional properties in comparison with their bulk a nalogs[2] This has stimulated the development of new types of NMs of improved characteristics. Solid phase products form during exothermic redox reactions between components of a precursor, metal nitrates (oxidizer), and an organic fuel (reductant) which are mixed at a molecular level in a solution. Due to this feature, combustion of SCS precursors occurs even in inert atmospheres and in vacuum and result in high-quality NMs with homogeneous crystal phases. The φ value was for all NMs equal to 1.75, a value shown to be within an optimal range for SCS of pure metals like Co and Ni33,35
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