Non-Thermal Atmospheric Pressure Discharges

The polarity of an electrode where the high electric field is located distinguishes between negative corona (around the cathode) and positive corona (around the anode). Ignition of the negative corona is based on secondary emission from the cathode similarly to the Townsend breakdown (see Section 4.1.1)  

Taking into account that ln(l/y) 6-8, ignition of the positive corona requires slightly higher electric fields (Lowke D Alessandro, 2003). The igniting electric field for the coaxial electrodes in air can be calculated using the empirical Peek formula  

The current-voltage characteristic /(E) of a corona around a thin wire with radius r, length L, and characteristic size R can be expressed as (Fridman Kennedy, 2004 A. Fridman et al., 2005) 

For example, a relevant expression for corona generated in atmospheric air between a sharp-point cathode with radius r = 3-50 pm and a perpendicular flat anode on the distance 

The corona ignition voltage in this case, F =2.3 ky does not depend on d (Goldman Goldman, 1978). Based on the current-voltage characteristic (4-112), power released in the corona discharge is 

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The reverse process is obvionsly exothermic. Dilnted ozone mixtures are relatively stable at low temperatures. However, even a relatively small heating leads to ozone decomposition, which can be explosive if the O3 concentration is sufficiently high. Thus, effective O3 synthesis should be performed at low temperatures, typically at room temperature. Carrying out the highly endothermic process (6-63) at room temperatnre requires the application of strongly non-equilibrium methods of chemical synthesis. Non-eqnilibrinm plasma of a dielectric barrier, pulsed corona, and other non-thermal atmospheric-pressure discharges are some of the most efficient methods for practical ozone production. 

Contribution of Reactive Neutral Species to Sterilization Effect of Non-Thermal Plasma. Compare contribution to sterilization of OH-radicals generated in plasma and then transported to the surface of biomaterials (see section 12.5) with that of OH-radicals produced inside of the biomaterials from plasma-generated charged particles (see section 12.1.4). Analyze rates of OH-production by surface bombardment with electrons and with positive and negative ions. What is the effect of electric field in the non-thermal atmospheric-pressure air discharges on the balance between the channels of OH production ... 

Atmospheric chemical plasma treatment systems are typically non-thermal, atmospheric-pressure, glow-discharge plasma systems that generate uniform and homogenous treatments. The level of surface tension and iongevity of treatment are both typically higher than air plasma treatment effects, and similar in treatment effect to flame plasmas. 

Contribution of the Electron Flux from Non-Thermal Plasma into Deactivation of Bioiogicai Micro-Organisms. Based on the equation (12-1) describing contribution of the non-thermal plasma electrons into sterilization, derive corresponding formula for the survival curve. Compare the curve related to contribution of plasma electrons with experimental survival curves for atmospheric-pressure discharges presented in Section 12.2. 

Khacef, A., Cormier, J.M. and Pouvesle, J.M. (2002) NOx remediation in oxygen-rich exhaust gas using atmospheric pressure non-thermal plasma generated by a pulsed nanosecond dielectric barrier discharge, J. Phys. D Appl. Phys. 35, 1491-8. 

A non-thermal corona discharge occurs at high pressures (including atmospheric pressure) oifly in regions of sharply non-uniform electric Adds. The fleld near one or both... 

Atmospheric-pressure non-thermal discharges in air are probably the most important systems, where the three-body attachment plays a key role in the balance of charged particles ... 

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