Magnetic Field-Induced Orientation of Modified Boron Nitride Nanosheets in Epoxy Resin with Improved Flame and Wear Resistance

In this work, self-lubricating boron nitride nanosheets (BNNs) were decorated with flame-retardant zinc ferrite (ZnFe2O4), followed by stearic acid modification to obtain magnetic and hydrophobic properties. Under the external magnetic field, the obtained ZnFe2O4–BNNs can be well ordered into one-dimensional orientation in the epoxy resin (EP) matrix—enabling improved flame retardant properties. Compared to a randomly oriented ZnFe2O4–BNN equivalent, the well-orientated ZnFe2O4–BNNs (at 10% mass fraction) reduce the peak heat release rate and CO production by 47 and 51%, respectively. Furthermore, the ZnFe2O4–BNN/EP composite monoliths demonstrate excellent durability, displaying continued superhydrophobicity under Taber abrasion, high external pressure, knife scratch, long-term exposure to acids/bases, and harsh UV irradiation. In addition, the result shows that the well-oriented ZnFe2O4–BNN/EP composite demonstrates better tribological performance and the friction coefficient is reduced by 76.9%.