Preparation of Ni-Cu Catalyst for Carbon Nanofiber Production by the Mechanochemical Route

The development of effective catalytic systems for the synthesis of carbon nanomaterials by catalytic pyrolysis is a relevant direction for modern science. In this work, the peculiarities of the microdispersed alloy Ni0.89Cu0.11 synthesis by mechanochemical alloying of metal powders in a planetary mill were investigated. The evolution of morphology and phase composition of Ni-Cu composite depending on the diameter of the milling balls and the activation time was studied using X-ray diffraction and particle size analyses, and scanning electron microscopy. The conditions corresponding to the formation of a single-phase Ni-Cu solid solution were determined and a scheme for the appearance of microdispersed alloy particles during the activation process was proposed. The prepared samples of the Ni-Cu composite were tested as catalyst precursors in the ethylene decomposition at 550 degrees C accompanied with the formation of carbon filaments. An extreme character of the carbon yield dependence on the activation time was found. The maximum carbon yield of 68-78 g/g(cat) after 15 min of reaction was achieved on the sample activated for 5-7 min and possessing slab morphology. The complete disintegration of the microdispersed Ni-Cu alloy was observed after similar to 1 min of a contact with the reaction medium. The resulting active particles were shown to catalyze the growth of carbon filaments. According to EDX data, the average content of copper in the composition of the active particles was estimated to be equal to its initial concentration in the alloy (similar to 12 at.%).