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Plasma chemical reaction in plasma cleaning machine

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Published on:

06 Nov,2020

Plasma chemical reaction in plasma cleaning machine:

 

The chemical reaction initiated by plasma of plasma cleaning machine can be described as the following three stages. Plasma production stage, in which a large number of electrons and ions with higher energy are produced; At the activation stage of reactive molecules, high-energy electrons in the plasma collide with reactive molecules, thus causing changes in the internal energy of reactive molecules and causing excitation, dissociation and ionization of reactive molecules. The stage of product formation, in which the reactive species produced by excitation, dissociation, and ionization of reactive molecules are unstable and various chemical reactions take place between them to produce reaction products. Chemical reactions in plasma can be divided into homogeneous reaction, polyphase reaction and photochemical reaction. For convenience, let's use A and B for atoms; M is for molecule; The superscript * is the exciter group; Superscript + means positive ion; Superscript - negative ion; ∙ Denotes free radicals.

 

Plasma induced homogeneous reaction:

Plasma-induced homogeneous reactions occur between species in the gas phase, including inelastic collisions between electrons and heavy particles and inelastic collisions between heavy particles.

Collision reaction between electrons and heavy particles:

Inelastic collision is the main way for high-energy electrons to transfer energy to heavy particles in plasma of plasma cleaning machine. Inelastic collision leads to a variety of reactions, such as excitation, dissociation attachment, dissociation, dissociation ionization and recombination. The reaction can be described by the following equation:

Excitation (including rotation, vibration and electron excitation) : e+A2→A*2+e

Dissociation attachment: e+A2→A- +A+ +e

Disintegrate: e+A2→2A+e

Dissociation ionization: e+A2→A+ +A+2e

Compound: e+A+ →A +hv

 

Inelastic collision reaction between heavy particles:

Inelastic collisions between heavy particles occur between molecules, atoms, active groups and ions, and the reactions between heavy particles can be divided into ion-molecular reactions and active group-molecular reactions. It mainly includes penning dissociation, penning ionization, charge transfer, electron-ion recombination, ion-ion recombination, atomic recombination and atomic addition, etc. The reaction can be described by the following equation:

Penning dissociation: M*+A2→2A+M

Penning ionization: M* +A2→A+2+M+e

Charge transfer: M++A2→A+2+M    
                 M-+A2→A-2+M

Collision elimination: M+A-2→M+A2+e  

Binding attachment: A-+A→A2+e

Ion - ion recombination: M-+A-2→A2+M
                         M-+A+2→2A+M

Electron-ion recombination: e+A+2→2A
                         e+A+2+M→A2+M

Atomic recombination: 2A+M→A2+M

Atomic recombination: A+BC→AB+C

Atomic addition: A+BC+M→ABC+M

 

Polyphase reaction initiated by plasma:

In gas-solid plasma, the polyphase reactions occur between the gas-solid phase and the gas-solid phase. In gas-liquid plasma, the polyphase reactions occur between the gas-liquid phase and the liquid phase, and may also occur between the gas-liquid-solid three phases. The polyphase reactions induced by plasma, such as atom recombination, metastable deexcitation, atom deprivation and sputtering, are illustrated by the examples of gas phase and solid phase (S). The reaction can be described by the following equation:

Atomic composition: S-A+A→S+A2

Metastable state de-excitation: S+M* →S+M

Atomic deprivation:S-B+A→S+AB

Sputtering: S-B+M+→S+ +B+M

 

Plasma initiates photochemical reactions:

There are radiation lines from infrared to ultraviolet in the plasma of plasma cleaning machine, and the radiation lines in ultraviolet region will cause a variety of photochemical reactions. The ultraviolet ray in the plasma, whose radiation energy is 3 ~ 12eV, can break the chemical bond as follows, thus causing a series of photochemical reactions. R stands for alkyl:

RH +hv—>R·+H·

RF+hv—>R·+F·

Plasma chemical reaction in plasma cleaning machine

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