Optical investigation of fast pulsed discharge on surface of ceramics for environmental applications
Pulsed surface discharge on the surface of ceramics was investigated experimentally. Photon counting method was applied to clarify preceding phase of the discharges. The results indicated the effect of charge injection from electrodes. Pulsed surface discharge reactor for decomposition of nitrogen oxides utilizing honeycomb ceramics was proposed. Framing and streak observation was carried out with image converter cameras. Emission spectra from the discharge were investigated with spectrometer. Uniform surface discharges on honeycomb ceramics were successfully obtained utilizing pulsed power generator with a SI-thyristor.
Basic Characteristics of Dielectric Barrier Discharge Reactor Using Anodic Porous Alumina for NOx Removal
Dielectric barrier discharge (DBD), properly combined with porous ceramics and/or catalysts, is a promising technology for diesel exhaust gas treatment. In this study, anodic porous alumina, which has numerous pores with nanometer-order diameter and a high aspect ratio, has been examined for use as a barrier in a DBD reactor. The anodic porous alumina greatly improves the DBD reactor. Nevertheless, few reports describe DBD using the anodic porous alumina barrier. As described herein, the DBD reactor’s basic characteristics and NOx removal in atmospheric pressure air were studied to support its future development. Results were compared with those of a typical DBD to clarify the influence of anodic porous alumina on those characteristics.The electropolished 99.99% pure Al substrate was anodized in 1.0 M sulfuric acid of 10°C for 5 h at dc 24 V. The Al substrate and anodic porous alumina respectively act as the electrode and dielectric barrier of the DBD. The dry gas mixture of NO (several hundred ppm) / O2 (20%) / N2 was supplied into the DBD reactor at 1.0 L/min. The resultant voltage and current waveforms resembled those of a typical DBD. Results revealed that NO was mostly oxidized to NO2 ; about 20 ppm N2O was detected. Different from a typical DBD the NO2 increased characteristically as a function of operation time.
Investigation of Charge Injection in Gas-Impregnated Polyethylene by Measurement of Electroluminescence under AC Voltage
Electroluminescence (EL) in polyethylene (PE) impregnated with N2, O2 or SF6 gas has been measured under ac voltages to investigate the effect of impregnation gas on charge injection. EL is strongly dependent on the processes of electron injection and transport in the surface region of PE. The results of our measurements of EL indicate that the process of electron injection is greatly affected by the type of impregnation gas in PE. In particular, O2 gas which is electronegative and chemically reactive markedly affects the charge injection process, causing a reduction in EL inception voltage and barrier height at the electrode-polymer interface. The surface states induced by the presence of O2 gas or by oxidation of PE enhance the electron injection. However, electrons injected into such surface states likely contribute little to EL. N2 gas also causes a reduction in the EL intensity but does not induce a change in the EL inception voltage and the barrier height in comparison with those in the degassed case. N2 gas probably affects an electron transport process such as intermolecular conduction in the surface region of PE rather than the electron injection process.