Abstract
The role of trap characteristics in modulating charge transport properties is attracting much attentions in electrical and electronic engineering, which has an important effect on the electrical properties of dielectrics. This paper focuses on the electrical properties of Low-density Polyethylene (LDPE)/graphene nanocomposites (NCs), as well as the corresponding trap level characteristics. The dc conductivity, breakdown strength and space charge behaviors of NCs with the filler content of 0 wt%, 0.005 wt%, 0.01 wt%, 0.1 wt% and 0.5 wt% are studied, and their trap level distributions are characterized by isothermal discharge current (IDC) tests. The experimental results show that the 0.005 wt% LDPE/graphene NCs have a lower dc conductivity, a higher breakdown strength and a much smaller amount of space charge accumulation than the neat LDPE. It is indicated that the graphene addition with a filler content of 0.005 wt% introduces large quantities of deep carrier traps that reduce charge carrier mobility and result in the homocharge accumulation near the electrodes. The deep trap modulated charge carrier transport attributes to reduce the dc conductivity, suppress the injection of space charges into polymer bulks and enhance the breakdown strength, which is of great significance in improving electrical properties of polymer dielectrics.
Highlights
IntroductionVarious nanofillers, including oxides (e.g. aluminium oxide, silicon oxide, titanium oxide, magnesium oxide and zinc oxide), nitrides (e.g. aluminium nitride and boron nitride), montmorillonite (MMT) clay and so on, were doped into polymers to prepare NCs15–19
In previous investigations, various nanofillers, including oxides, nitrides, montmorillonite (MMT) clay and so on, were doped into polymers to prepare NCs15–19
It can be summarized that the composites with a filler content of 0.005 wt% have a lower dc conductivity, a higher breakdown strength and a much smaller amount of space charge accumulation than the neat Low-density Polyethylene (LDPE), which presents that the transport of charge carriers is suppressed by the well-distributed graphene
Summary
Various nanofillers, including oxides (e.g. aluminium oxide, silicon oxide, titanium oxide, magnesium oxide and zinc oxide), nitrides (e.g. aluminium nitride and boron nitride), montmorillonite (MMT) clay and so on, were doped into polymers to prepare NCs15–19. With the development of organic chemistry synthesis, the surface modification of nanofillers, such as surface grafting, were employed to achieve a better dispersion in polymer matrix, enhancing the effect of polymer-filler interaction zones[20, 21]. It is difficult for the common nanofillers mentioned above to achieve a specific surface area of 1000 m2/g in theory[22, 23]. The electrical properties of NCs, including the dc conductivity, breakdown strength and space charge behaviors, are measured Their trap level distributions are characterized by isothermal discharge current (IDC) tests. A schematic model is proposed for illustrating the trap modulated charge carrier transport in LDPE/graphene NCs, thereby further revealing the relationship between the trap level distributions and the electrical properties
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