What type of epoxy is used to seal Ferrite Cores in high power applications? Is there any epoxy available on Ali-express?
What is the purpose of using epoxy?
It is usually a two-part epoxy. Most commercial epoxys will do. Just make sure that the core halves are well clamped until the epoxy has cured long enough to achieve its tensile strength.
This may be anywhere from 2 to 24 hours at room temperature, and sometimes may be accelerated with higher temperature.
Read the epoxy's datasheet.
The purpose is twofold: to maintain the intended gap (or lack of), and to prevent magnetostriction generating audible noise.