THE STUDY OF COPPER POWDERS OF VARIOUS MORPHOLOGICAL FORMS IN TEMPERATURE FIELDS

It is known that the catalytic activity of the same substance can vary significantly depending on the structure of its surface. It should be noted that many catalytic reactions occur at elevated temperatures. Therefore, the catalysts having “soft” metals (Cu, Zn, Au, Ag, Mg, etc.) as their active components with the specific internal structure and surface morphology have strong temperature limitation for use. The copper-based catalysts are widely used in the synthesis of various chemicals, in particular in the synthesis of aniline. In this paper, the authors give the comparative analysis of the temperature fields impact on the copper powders with the particles of roughly the same sizes, but with different internal structure and surface morphology. The electrolytic copper powders of four types were compared. The first type was represented by the crystals with the FCC-lattice; the particles of second and third types had the form of icosahedra (but of different surface morphology), six symmetry axes of the fifth order and were faceted by the crystal planes of {111} type. The fourth powder was represented by the large formations consisting of copper crystals of spherical shape. It is shown that particles with different initial internal structure and surface morphology suffer similar changes in the process of annealing in the air: agglomerating, whiskers growth in the oxidation process, the formation of cavities inside and the pores on the surface. However, for the icosahedral copper particles, the increased discharge of stored energy is observed when heated in the differential scanning calorimeter (DSC), which activates and accelerates the course of structural-phase transformations within the particles.