Microspheres of technogenic origin: the way to new technological solutions

The paper presents data on the ash microspheres compositions of domestic thermal power enterprises. The research results on the structural and phase features of the Kryvorizka TPP ash microspheres according to X­ray diffraction and electron microscopy data are provided. The physic­mechanical, thermophysical, and electrophysical properties of ash microspheres were determined. It is shown that zolospheres with a high iron oxide content (24—27 wt. %) are almost X­ray amorphous technogenic formations, but their heat treatment at temperature 850 °С allows to change of the phase composition in a directed manner. It was established that, as a result of such heat treatment, magimite, hematite, hercynite, as well as mullite and a small amount of magnesium spinel and quartz are formed in the zolospheres shells. The directed formation of various compounds in the phase composition of zolospheres allows to influence of such properties as thermal conductivity and TCLR, hardness, dielectric and magnetic characteristics, which determine the appropriate direction of their use. The work also highlights our own positive experience of ash spheres used to obtain composite materials for various functional purposes. It is shown that the ash spheres of most domestic TPPs have a similar chemical composition, contain small closed pores inside the shells, and are characterized by low thermal conductivity and СTE. Therefore, it is better to use them as a filler for composite insulation, including heat­insulating paints for building structures and communications. Zolospheres that acquire a crystalline structure through heat treatment increase their abrasiveness due to the formation of phases with high hardness (hercynite, magnesium spinel). It is expedient to use such ash spheres as a secondary filler of diamond­abrasive composites for instrumental purposes. During grinding, they form additional cutting surfaces, which helps to increase the processing productivity of highly plastic alloys by 1.7—1.8 times while ensuring the necessary quality of diamond processing (Ra = 0.20—0.25 μm.) and reducing its cost by 1.5 times. On the other hand, ash spheres, in the shells of which ferromagnetic compounds (maghemite, hematite) are formed during heat treatment, have prospects for use as a filler for radio­absorbing composite materials and coatings.