Discussion on Non-Linear Conductivity Characteristics With Space Charge Behavior of Modified Epoxy for Spacecraft

Abstract

High-energy electrons in space can penetrate into dielectric materials on spacecraft and cause deep dielectric charging which is often harmful. The level of charging is determined not only by the incoming flux but also by the rates of electron accumulation and electron leaking. It is desirable to enable faster leaking of the accumulated charge. This paper discusses the nonlinear conductivities with space charge behavior of two samples of modified epoxy. They were obtained respectively by adding zinc oxide (ZnO) particles of two different sizes ( $2~\mu \text {m}$ , $10~\mu \text {m}$ ) to pure epoxy (EP). We studied the conductivities of the samples and the space charge effects in strong electrical fields. Our results showed that the nonlinear conductivity threshold of $2~\mu \text {m}$ modified EP (ME2) was $1.7\times 10^{7}$ V/m whereas that of $10~\mu \text {m}$ modified EP (ME10) was $1.4\times 10^{7}\text {V}$ /m. These values are 50% and 40% higher than that of EP respectively. These results suggest that the modified epoxy materials (ME2 and ME10), if used on spacecraft, are better than pure EP for leaking away the accumulated charge, thus reducing the dielectric charging level. Meanwhile, space charge distribution tests indicated that $10~\mu \text {m}$ modified EP (ME10) had a nice charge dissipation performance, while $2~\mu \text {m}$ modified EP (ME2) did not have space charge accumulation. Finally we make the conclusion that nonlinear conductivity performance can affect space charge distribution for dielectric to a certain degree.