Effect of load-induced oxygen absorption in YBa$_{2}$Cu$_{3}$O$_{6+x}$ on mechanical properties of the "Polyimide–YBa$_{2}$Cu$_{3}$O$_{6+x}$" system

We have studied the effect of oxygen absorption by disperse powder fillers made of high-temperature superconductor YBa$_{2}$Cu$_{3}$O$_{6+x}$ (YBCO) with concentrations of 0.05, 0.1, and 0.5 mass % on mechanical properties of polyimide composite materials (PCMs) in the form of films. It has been established that an adsorption boundary layer consisting of an aggregate of several transition layers with a varying structure is formed between filler particles and the matrix. A sharp increase in relative elongation (strain) $\Delta\varepsilon_c$ , which is observed for a PCM with YBCO fillers in the form of a jump in the region of loads of 40–47 MPa, is due to the fact that the bonds between the matrix macromolecules and the molecules in the vicinity of the upper boundary layer are ruptured, leading to a strain jump. An increase in the filler concentration increases the rigidity of the bonds between macromolecules in the boundary layers, leads to a shift of $\Delta\varepsilon_ c$ to the region of low stresses, and reduces its value.