Yoshio Higashiyama

Decomposition of Dye in Water Solution by Pulsed Power Discharge in a Water Droplet Spray

A method for decomposing dye by spraying water solution of dye into nonequilibrium plasma in gas phase was investigated using a pulsed-corona discharge reactor. The corona reactor consists of a discharge wire and a cylindrical electrode. The water solution of indigo carmine with a concentration of 20 mg/L was sprayed into the reactor from a showerhead. The sprayed water solution was circulated into the reactor. The dependence of the discharging power injected into the reactor on the decomposition rates of chromogenic and unsaturated bonds in indigo carmine was investigated. Indigo blue was decolored by 1-min circulation with the discharging power of 8.6 W. The nuclear magnetic resonance spectrometry showed that indigo carmine was decomposed completely by 60-min treatment. The chromogenic and unsaturated bonds were almost decomposed at 9 and 360 J/mg, respectively. As the discharging power increased, the decomposition rates of both bonds in indigo carmine increased. The decomposition rates of the chromogenic bond showed equal values in equal discharging power regardless of the difference of discharge repetition rate and charging voltage of the capacitor. In contrast, the higher repetitive pulses were more effective for the decomposition of the unsaturated bond rather than the magnitude of charging voltage in equal discharging power.

Triboelectrification of plastic particles on a vibrating feeder laminated with a plastic film

Abstract The charging characteristics of polymer particles were investigated in order to develop an electrostatic separator for plastic-plastic mixtures which are to be recycled. The charging section of the proposed separator utilizes a vibrating feeder equipped with a charging plate. Plastic particles are charged by triboelectric charging while moving on the plastic plate. In order to increase the amount of a charge acquired by the plastic particles as well as to avoid an accumulation of a charge at the surface of the plastic plate, a plastic layer with a number of holes was formed by melting fine plastic powder over an aluminum plate. The charging characteristics of several kinds of plastic particles were investigated and the results show that the plastic-laminated vibrating plate is effective in charging plastic particles.

The electrorheological property of a polyaniline-coated copolystyrene particle suspension

Polyaniline-coated copoly (styrene styrenesulphonate) (PSS) particles were prepared by oxidative polymerization of aniline hydrochloride using ammonium persulphate in the presence of anionic PSS particles. Polyanilinecoated PSS particles were found to be higher dispersibility than polyaniline itself in an organic solvent. A suspension of polyanilinecoated PSS particle in silicone oil was found to exhibit high performance at higher temperature without the necessity for water.

Electrorheological property of a polyaniline-coated silica suspension

Abstract Silica particles, whose surfaces were completely covered with polyaniline, were prepared by oxidative polymerization of aniline with ammonium persulphate in the presence of silica particles. The electrorheological property of a suspension of polyaniline-coated silica particles dispersed in silicone oil was found to exhibit a high performance even at high temperatures.

Negative corona discharge at a tip of water cone deformed under dc field

Abstract The negative corona discharge phenomena occurring at a tip of water cone have been investigated focusing on the motion and the shape of the water surface using a high-speed video camera. The water cone is periodically formed from a water droplet located on a grounded electrode under dc field due to the electro-hydrodynamic instability. Negative corona discharge with trains of Trichel-like pulses occurred just after the formation of a cone jet. The magnitude and the pulse interval of the Trichel-like pulses gradually increase during the period that the conical surface returns to the initial ellipsoidal shape. The characteristics of the Trichel pulse occurring from the metal electrode simulating the shape of the water surface were also investigated. It is found that the increase in the magnitude and the interval of the trains of Trichel-like pulses with time at the tip of water drop are caused by the corona discharge from the tip of the water surface that deforms from a conical to an ellipsoidal shape.

DC corona discharge from water droplets on a hydrophobic surface

Corona discharge occurring in water droplets placed on the surface of a hydrophobic polymer sheet under DC field was investigated experimentally along with the behavior of droplets. Two kinds of hydrophobic insulating materials, PTFE and silicone rubber, were used. Two water droplets were placed at the border of the foil electrodes and the insulating sheet. The two droplets elongated in different ways and a water filament extended along the surface by the electrostatic force. Corona discharge occurred at the tip of water droplets before the filament formed. The discharge aspect and the behavior of water droplets strongly depends on the polarity of the applied voltage. This would affect the surface flashover voltage via water droplets.

Resonance phenomena of a single water droplet located on a hydrophobic sheet under AC electric field

Resonance vibration of a water droplet located on the surface of a hydrophobic sheet under an AC electric field was investigated experimentally. In order to confirm the effect of the surface property of hydrophobic material on the resonance phenomena of a water droplet, three kinds of hydrophobic materials-silicone rubber (SR), polytetrafluoroethylene (PTFE) and polydimethylsiloxane-grafted fluoropolymer (PGF) sheet-were used. A single water droplet with a volume from 3 to 30 /spl mu/l was placed between parallel electrodes which formed a uniform electric field in the tangential direction along the surface of the hydrophobic sheet. A water droplet under an AC field vibrates strongly only at a particular frequency range. The resonance frequency where the water droplet vibrates strongly decreases with increasing the volume of the water droplet. The resonance frequency on the SR sheet is lower than that on the PTFE and the PGF sheet. The resonance frequency and the magnitude of the deformation of the water droplet depend on the surface properties of the hydrophobic material.

The behavior of charged conducting particles in electric fields

The presence of metal particles within gas insulated switchgear (GIS) might initiate a sparkover and lead to fatal failure of electric power transmission system. In order to investigate the behavior of a particle in GIS, model electrodes and a measuring system were constructed. The motion of a particle was investigated by using a CCD camera and a high-speed video camera. Different shapes of elongated particles were made from 0.1 mm and 0.25 mm diameter wires. The measured values of lift-off field strength of a particle lying on the electrode agreed quite well with the theoretical prediction. The initial raising up of particle usually started at the sharper edge as expected. There were two types of different mode of particle motions; one is bouncing motion between two electrodes or one electrode and the other the standing motion on the electrode. Interesting thing is that the standing motion on the upper electrode when a negative voltage is applied to the upper electrode. This phenomenon could be explained from the difference of positive and negative corona currents starting from both edges of a standing particle.<<ETX>>

Electrification of polymer surface caused by sliding ultrapure water

It has been thought that the conductivity of pure water is high enough to neglect the streaming electrification. However, with the advancement of semiconductor industries, even ultrapure water appeared to cause electrification problems at the washing and the rinsing processes of semiconductor wafers. The investigation on the electrification phenomenon of polymer (PTFE) surface with ultrapure water is described in this article. Water droplets are always charged positively after sliding on the PTFE surface, and the surface potential on PTFE is almost negative and varied along the path of droplets becoming positive downstream. As the conductivity of water becomes closer to that of ideal water, the amount of droplet charge increases drastically. This electrification phenomenon is also enhanced by decreasing the thickness of the PTFE plate. It suggests that the Coulomb force between the charge on the PTFE surface and the minor image charge is an important factor. The authors have proposed a model which is based on the electric double layer similar to conventional streaming electrification for insulating liquid, assuming that the charged droplet leaves the excess positive charge on the polymer surface.<<ETX>>

Behavior of water droplets located on a hydrophobic insulating plate under DC field

The behavior of water droplets placed on the surface of a hydrophobic polymer plate under a DC field was investigated experimentally. In order to confirm the effect of hydrophobicity on the movement of the water droplet, three kinds of hydrophobic insulating materials-PTFE, silicone rubber (SR) and ethylene propylene rubber (EPDM)-were used. Water droplets were placed on the insulating plate in contact with the aluminum foil electrode or placed between the thin foil electrodes. A single droplet placed in contact with the electrode on the SR or EPDM plate was elongated and a water filament extended along the surface by the electrostatic force, while that on the PTFE plate left the electrode. The water droplet placed on the border of electrode at the PTFE plate was deformed and formed a semi-cone at a triple junction. The apparent contact angle varied with time for a constant applied voltage and some amounts of charge were emitted by micro discharge or by ejection of small droplets. The behavior of the droplets under DC field strongly depends on not only the hydrophobicity but also the surface property of an insulating plate.