Influence of treated nano-alumina and gas-phase fluorination on the dielectric properties of epoxy resin/alumina nanocomposites

In this study, epoxy resins incorporated with nano-alumina (nano-Al
₂
O
₃
) are prepared with different concentrations of 0, 1, 3 and 5 wt%. The obtained epoxy resin/Al
₂
O
₃
nanocomposites are subsequently fluorinated using F
₂
/N
₂
mixture (F
₂
/N
₂
20% v/v) at 0.05 MPa and 40°C. The nano-Al
₂
O
₃
is treated with silane coupling agent γ-aminopropyltriethoxysilane (KH550) to restrict aggregation. The chemical bonding is examined by Fourier-transform infrared spectroscopy. The cross-section and surface morphological analyses are performed using scanning electron microscopy. In addition, the DC surface resistivity is measured using a resistivity test fixture. The variations in electrical properties induced by fluorination are characterized based on dielectric measurements. The experimental results show that chemical bonds are formed between nano-Al
₂
O
₃
and the coupling agent (KH550). Moreover, the results confirm that fluorination significantly alters the morphology and chemical structure of the sample surface. Gas-phase fluorination produces shallow traps, which consequently reduce the surface resistivity. The treatment of nano-Al
₂
O
₃
increases the trap energy level to yield higher surface resistivity. Furthermore, the treated Al
₂
O
₃
nanoparticles show improved distribution and dispersion in epoxy resin, exhibiting good dielectric performance of the nanocomposite.