Regularities of formation of structure and properties of porous composites based on basalt fiber in the process of thermocycling

The results of studying the structure and properties of two compositions of porous composite materials of the CaO–MgO–FeO(Fe2O3)–Al2O3–SiO2 system based on basalt fiber formed during thermal cycling are presented. The samples made from the mixture of composition I had the following structure: basalt fiber (37 wt.%) + mullite-silica fiber (19 wt.%) + modifier Al 2(SO4)3 as a binder (11 wt.%) + blowing agent (19 wt.%) + porcelain as a hardener (4 wt.%) + plasticizer (11 wt.%); II composition: basalt fiber (52 wt.%) + SiO2 (15 wt.%) + blowing agent (1 wt.%) + porcelain (aluminosilicate) as hardener (6.5 wt.%) + plasticizer (CMC, 6.5 wt.%) + limestone flour (calcium carbonate, CaCO3, 19 wt.%). Thermal cycling was carried out in three temperature ranges of 750–770 °C, 1025–1075 °C, 1070–1090 °C in order to obtain certain structure and properties of composites pressed under pressure of 20, 40 and 60 MPa. To control surface morphology, changes in phase composition, amorphousness and fine structure parameters, porosity, permeability and strength properties, samples were evaluated at each process cycle. On the basis of established patterns of structure formation, modes of formation of pore space are proposed with preservation of porosity not lower than 45 %, strength 5–25 MPa, shrinkage in the process of sintering – not more than 20 %. The studied composite materials can be used to create filter elements of systems for separating, cleaning, converting liquid and gaseous media.