No abstract

Pre-ceramic organoelementoxanealumoxane oligomers whose pyrolysis results in oxide ceramics of multicomponent composition: aluminum yttrium (xY2O3·yAl2O3), yttrium aluminum silicate (xY2O3·yAl2O3·zSiO2), yttrium aluminum magnesium (xY2O3·yAl2O3·zMgO) ones, are modifiers of silicon carbide based composite materials that increase their resistance to high temperature oxidation.

Submicron powder Y3Al5O12 (YAG) aluminium yttrium garnet was synthesized from an Al-Y-ceramic-forming precursor, according to the method developed in the State Research Institute for Chemistry and Technology of Organoelement Compounds (SRICTO). The advantage of the method is the possibility of obtaining close to the stoichiometric phase and obtaining high purity nanopowder. In this work, we studied the effect of the pyrolysis temperature of the polymer (700°, 800° and 900°C) and grinding time on the rheological properties of the powder. It was shown that after pyrolysis at 700° and 800°C, the powder has an amorphous structure, the ultimate strain, in this case, being 6.1 and 8.1% of the initial size. The compressibility modulus decreases with increasing temperature from 34.5 to 19.4 MPa. Due to the formation of YAG crystals after pyrolysis at 900°C, the compressibility of the powder increases and the compacts become denser.

In this study, a detailed study of ceramic spinel powder obtained by the new method was carried out. Namely, the study of the influence of the pyrolysis temperature of the oligomer and grinding time on the microstructure, phase composition and rheological properties of spinel during pressing. Graphs of the dependences “stress-strain” and “stress – relative density” were obtained, which characterize the rheological properties of aluminium-magnesium spinel obtained in a new way. Analyzing the obtained dependences, we can conclude that with an increase in the pyrolysis temperature, spinel is more natural to deform, which is associated with a change in structure. According to the data obtained, a dependence on the growth of the elastic modulus after grinding is also observed.