Discharge frequency

Lydic, R., McCarley, R. W. Hobson, J. A. (1987). Serotonin neurons and sleep. I. Long term recordings of dorsal raphe discharge frequency and PGO waves. Arch. Ital. Biol. 125, 317-43. 

Effect of Discharge Frequency on the Plasma Polymerization of Ethane... 

Most of plasma polymerizations have been carried out in the frequency range from 50 Hz to 13.56 MHz with using the capacitively coupled discharge system (.4,16). For the inductively coupled discharge system, a frequency of 13.56 MHz was mostly used as a discharge frequency (17,18). In this paper, the discussion will be concentrated on the discharge in the capacitively coupled discharge system. 

In this study, the plasma polymerization and the discharge phenomena were studied as a function of the discharge frequency. In order to support the speculation of the polymerization mechanism, infrared spectra and the dielectric properties were also measured for the samples formed in the same discharge frequency range. 

Figure 1. Diagram of apparatus (M) monomer reservoir (F) flow meter (VG) vacuum gage (mercury manometer) (E) electrode (T) liquid nitrogen trap (P) mechanical pump (V,) needle valve (Vt) stop valve (Vs) pressure control valve (OSC) discharge frequency oscillator (AMP) amplifier (1MC) impedance matching circuit...

The PPE films for the infrared spectra measurement were formed on NaCl or KC1 crystals at three different discharge frequencies. For the discharge frequencies of 1 KHz and 100 KHz, the two films were polymerized at 0.5 torr, 20 cm3STP/min and 10 watts. Another one was prepared at 13.56 MHz, 2.0 torr, 20 cm3STP/min and 50 watts. Infrared spectra were recorded with a Perkin-Elmer Model 137 Spectrometer. 

The effects of discharge frequency on the polymer growth rate were studied at a pressure of 0.5 torr, a flow rate of 20 cm3STP/min and a power level of 10 watts. All other parameters remained constant. The growth rates were plotted in the frequency range from 50 Hz to 13.56 MHz as shown in Fig. 3(a). The frequency dependence on growth rate may be divided into three regions of dis-... 

Figure 3. Effect of discharge frequency on the growth rate of plasma-polymerized ethane and the discharge voltage and current of ethane at 0.5 torr, 20 cm STP/min, and 10 W at room temperature (a) growth rate (b) discharge voltage...

Figure 5. IR absorption at photon of 10.6 ym vs. the discharge frequency used for film formation ( ) polymerized at 0.5 torr, 20 cm3STP/min, and 10 W (A) polymerized at 2.0 torr, 20 cm3STP/min, and 10 W...

Therefore, it must be supposed that the continuous electron emission from the surface of insulating film on the cathode will be existed by the ion bombardment. The work function for the electron emission from the surface of insulating film may be larger than that from the metal surface. Thus the cathode fall in front of the insulating film must be larger than that of metal surface. At a high discharge frequency where the inertia of an... 

In region I, polymerization may be initiated by ion bombardment and the deposition rate may be propotional to the number of ions (27). In this study, the discharge current was almost constant in the discharge frequency region from 50 Hz to 200 KHz. If the effective discharge current is I and the shape of discharge current wave is sinusoidal, the mean current which will flow to either electrode may be calculated by the following equation ... 

Nc is a function of reverse of frequency. In the low frequency region, most ions will arrive to the cathode in a half cycle of the discharge frequency. The low frequency was defined as follows,... 

From the above calculations, the discharge frequency effect on the growth rate of the film can be explained qualitatively. 

Polymerization Mechanism in Region III. In region III, all the electrons cannot be transported to the anode in a half cycle of the discharge frequency. A possible charge transportation mechanism is an ambipolar diffusion of ion and electron pairs which will cause polymerization. The diffusion of free radicals may also contribute to the polymerization. In our experiment, the contribution of these two mechanisms cannot be distinguished because the ion and electron pairs behave as neutral gases. 

These absorptions may reflect the degree of crosslinking and/or the degree of degradation which is proportional to the amount of residual free radicals. The relative absorptions per thickness at 10.6 pm are plotted against the discharge frequency as shown in Fig. 5. The absorptions near 10 pm of the film formed in region HL... 

Figure 8. Activation energy plot for plasma-polymerized ethane formed at discharge frequencies of 5KHz (X) and 13.56 MHz ( )...

The discharge frequency for these varies from plant to plant. Some or all of the various types of wastewater streams occur at almost all of the plant sites in the industry. However, most plants do not have distinct and separate discharge points for each source of wastewater rather, they combine certain streams prior to final discharge. 

The role of gas phase initiation processes was further explored by Tibbitt et al. . These authors proposed that the polymerization of unsaturated hydrocarbons in a 13.56 MHz plasma is initiated by free radicals formed in the gas by electron-monomer collisions, the initiation reactions listed in Table 6. Moreover, it was assumed that the formation of free radicals on the polymer surface due to the impact of charged particles could be neglected. This assumption is supported by the fact that at 13.56 MHz and pressures near one torr the discharge frequency is significantly greater than either f, or f and that as a result the fluxes of charged particles to the electrode surfaces are quite small. 

Effect of discharge frequency on the rate of ethane plasma polymerization [after Morita... 

Surface free radicals are assumed to be produced by the dissociation of bonds at the polymer surface as well as by the adsorption of radicals from the gas phase. New polymer is formed by the recombination of surface and gas phase free radicals. Within the context of this model, the rate of polymerization should depend upon the rates at which surface and gas phase free radicals are produced. The influence of the discharge frequency on the rates of these processes can now be examined. 

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