For identifying electron and hole traps in polymeric materials, we combine the isothermal relaxation current theory and surface potential decay together and present a model called isothermal surface potential decay (ISPD). A non-contact measurement setup is specially designed, which features that energy distribution of electron or hole-type traps can be discriminated with negative or positive corona charging, respectively. By measuring the ISPD characteristics of low-density polyethylene and polypropylene films, their trap distributions are obtained, revealing the different semi-crystalline morphology of these two materials. The results we obtained may imply the essentially distinct nature of electron/hole traps: inter-chain for electron-type traps and intra-chain for hole-type traps, which is in agreement with other researchers' molecular modeling results.

The performances of slug flow gas–liquid reactors are mostly determined by slug length, especially for the high gas–liquid flow rate ratio condition. This work is the first time to report the short bubble generated with high frequency in a capillary embedded step T‐junction microdevice. The aspect ratio of bubble could be around 0.5 with a frequency higher than 750 s−1 when the gas–liquid flow rate ratio is even higher than 5. The specific surface area of the generated gas–liquid microdispersion system is larger than 10,400 m2/m3. The short bubble formation process includes two periods, and its formation mechanism is mainly because of the relatively higher pressure drop in the step T‐junction, which provides a much higher breakup force for the squeezing flow. Finally, two models are developed to predict the bubble frequency and volume. This work provides a highly promising dispersion technology for the gas–liquid process intensification in microreactors.

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The accumulated charges on the insulator surface become a key factor to incur surface flashover. The charge accumulation process is closely related to the surface condition. This research investigates the effects of surface roughness on surface charge accumulation behavior and surface flashover performance of alumina-filled epoxy resin spacers in SF6/N2 mixtures under DC voltage. The insulator is prepared with only half surface subjected to rough treatment. The accumulated charges are distributed in two regions. Considerable homo-charges are located near the high voltage (HV) electrode and few hetero-charges are near the grounded (GND) electrode (region I). These charges are injected by electrodes. The bipolar charges between HV and GND electrodes (region II) originate from gas ionization. Surface rough treatment can suppress surface charge accumulation and improve surface insulation strength. When increasing surface roughness, surface charge declines first slowly (stage I) and then rapidly (stage II), which coincides with the two stages of surface flashover voltage increment. Surface charge declination at stage I is mainly due to the increase in surface conductivity, while at stage II, the introduced deep traps also play a role. Surface flashover voltage increment at stage I is mainly due to the extended creepage distance, while at stage II, the declination of surface charge also plays a role. Besides, the block of electron avalanche development by the roughed surface is also responsible for the increase in surface flashover voltage at these two stages.

The influence of residual charge on propagation of surface discharge is experimentally investigated using high-speed framing and streak cameras, and an electrostatic probe. When consecutive impulse voltages are applied 25 times with a change in polarity, the propagation length of the surface discharge increases gradually from 79 to 164 mm and hardly converges. Under such a condition, the potential gradient in the surface leader channel decreases with the consecutive number of impulses, while that in the surface streamer remains constant and the value is 0.5–0.6 kV mm−1. With the residual charge of a previous opposite polarity discharge on an insulator, the propagation velocity increases to three to eight times as large as that of the surface discharge on a clear insulator without any residual charge. The peak current of the surface discharge with a residual charge also becomes much higher than that without a residual charge.

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Generation of bubbles in a T-junction microdevice is vital to microfluidic applications for its advantages of easy fabrication and scaling-up, but the bubble generation in liquids with a higher viscosity in the T-junction is rarely reported for the unstable dispersion behavior under the constant flow rate-driven condition. Accordingly, this work investigates the bubble generation rules in liquids with a higher viscosity (45.6−240.5 mPa•s) under the constant-pressure method. It shows that the bubble formation process in higher viscous liquids contains three stages, expansion, shrinking, and necking, which are obviously different from the filling and squeezing stages in the lower viscous liquid. Importantly, the generation of satellite bubbles as a new bubble generation performance could be observed for the first time in the gas−liquid microdispersion process. The new dispersion mechanism and some novel phenomena are revealed by the interface evolution rules. Finally, a novel mathematical model is developed to predict the bubble length.