The fabrication and insulation performance of TiO2 coating with reticulated porous structure for HTS magnet coils

Titanium dioxide (TiO 2 ) ceramic coating, characterized by high thermal conductivity and remarkable chemical stability, leading to extensive application in providing electrical insulation within superconducting coils. However, the development of such ceramic insulation coatings to facilitate the preparation of high-performance superconducting magnets is extremely challenging, due to the complex heat treatment process of bismuth system high temperature superconductivity (HTS) wires. A novel strategy for fabricating a porous TiO 2 insulation layer with a three-dimensional (3D) reticular architecture based on highly dispersed ceramic slurry has been reported herein. To enhance the structural strength and oxygen permeability of the coating, polyethylene glycol and oligomeric ethyl silicate were introduced as modifiers to construct a grid-like porous framework. The as-prepared insulation coating possesses micron-sized pore and crack structures. The high-temperature stability of the insulation layer and its compatibility with the heat treatment of Ag-sheathed Bi-2223 wire was verified by measuring the effect of coating on the critical current. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDS) show that this insulation coating with a thickness of approximately 25 μm can significantly inhibit the diffusion of metal sheath components and Bi. In addition, the TiO 2 insulation coating has also been successfully prepared on Bi-2223 tape by a reel-to-reel coating system. The results indicates that the TiO 2 insulation coating has great application potential as an insulation material for HTS magnets and provides new insights for the development of effective insulation material for Bi-2212 wires.