Abstract:There are significant differences in the field dependence of conductivity in low-density polyethylene as reported by various investigators. These differences are attributable partly to the presence of different kinds of impurities in variable concentrations in polyethylene samples of various origin, but are mainly due to the different measurement procedures adopted. The significance of the time which elapses after the application of voltage to the electrodes, as well as the effect of conditioning, e.g. thermal… Show more
“…With the lapse of polarization time, the polarization comes into stable state gradually and the conduction current becomes dominant 34 . However, for the 0.5 wt% LDPE/graphene composites, the charging current decays slowly during the measuring time and still does not reach a steady state up to 2000 s, which is ascribed to the injection and accumulation of space charge in the bulk rather to a slow polarization process 35 .Figure 2( a ) DC conductivity of LDPE/graphene NCs as a function of polarization time under 10 kV/mm. ( b ) Weibull distribution of dc breakdown strength of LDPE/graphene NCs.
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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.
“…With the lapse of polarization time, the polarization comes into stable state gradually and the conduction current becomes dominant 34 . However, for the 0.5 wt% LDPE/graphene composites, the charging current decays slowly during the measuring time and still does not reach a steady state up to 2000 s, which is ascribed to the injection and accumulation of space charge in the bulk rather to a slow polarization process 35 .Figure 2( a ) DC conductivity of LDPE/graphene NCs as a function of polarization time under 10 kV/mm. ( b ) Weibull distribution of dc breakdown strength of LDPE/graphene NCs.
…”
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.
“…We noticed that the measured values of the current were identical for each period, even for the longest times, and that they were reproducible whatever the value of the half-period in the explored range of 1 s to 100 s. Thus, in these measurements, the conditioning action of usual dc voltage measurements is avoided. This effect had already been observed at higher electric field for periods of 1 000 s [8]. Measurements made using the IRLAB apparatus gave, as expected, the same values of G as in Figure 2 for t = 0.7 s. …”
Section: Experimental Results and Commentssupporting
The question of the relevance of the methods presently used to characterize the resistivity of insulating solids is discussed from a critical examination of the standards. A brief review of the involved phenomena is given, which, if necessary, emphasizes the complexity of the subject. The interest of a method of characterization derived from the alternate square wave method, perfectly suited to liquids, is pointed out. Results of measurements on polymers are presented and discussed.
“…Equation The full curve superimposed over the circles represents the best fitting line to (1) and the best fitting parameters are presented in the inset. The values are in agreement with those reported in the literature for similar isochronal measurements [13]. The three contributions to the measured current, namely Ohmic, space charge limited current (SCLC) and power law term in the right-hand side of (1) are represented in Figure 1 by dotted, dashdotted and dash-dash-doted lines, respectively.…”
The electrical conduction of LDPE was investigated. Results were obtained using isothermal charging and discharging currents, thermally stimulated charging and discharging current measurements. The conduction process is strongly influenced by the charge stored in the sample. The apparent activation energy W is about 0.70 eV. It changes with the isochronal measuring time and at low fields with temperature. As the applied field or charging time increase the space charge stored in the sample increases and implicitly W decreases. The results for long times (days) attest a new conduction mechanism: the space-charge-controlled conductivity.
11" International Symposium on Electrets, 2002 0-7803-7560-2/02/$17.00 0 2002 IEEE
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