4. Conclusions
The gradient-distribution Al2O3/LDPE nanocomposites with multi-layered structure were prepared in this paper. Compared with the general mean-distribution structured monolayer composites, these composites with unique morphology have excellent electrical properties as follows. For the gradient-distribution structured LDPE nanocomposites, there was no clear interface between the adjacent layers, though they were prepared through two-time hot pressing progress. This continuous morphology can well avoid the air layer. Meanwhile, the polymer molecules in thermal motion during the hot pressing process, makes the whole molecule rearrangement. This rearrangement of molecule chains contributes to its forming stable conformation, which has the minimum molecular force. Space charge amount of the gradientdistribution structured LDPE nanocomposites is less than that of the mean-distribution structured ones as the trap near the composites surface can capture the injected charges. The captured charges can distort the electric field in the vicinity of the interface, which will decrease the charge injection. Thus, the space charges can be suppressed. Meanwhile, the nano-Al2O3 tends to distribute in the interface between the neighbouring layers. It suggests that the carriers prefer to conduct through this interaction zone, then causing the space charge suppression.
