Titanium-Coated Gas Chamber for Halocompound Plasma Abatement
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Solution Overview
Problem
Plasma abatement devices face efficiency reduction and corrosion issues when treating gas streams containing halocompounds like HBr, HCl, and Cl2, due to the stripping of passive surface oxide layers from stainless steel components, leading to degradation and interference with microwave operation.
Innovation Solution
The inner surfaces of the gas chamber and resonant cavity are formed or coated with titanium, a corrosion-resistant and diamagnetic material that maintains a protective oxide layer, reducing conductor losses and enhancing plasma quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If stainless steel is used for the inner surface of the gas chamber, then the device structure is simple and cost-effective, but the passive surface oxide layer is stripped by acidic gases leading to corrosion and efficiency reduction
Solution Approach 1:
The patent applies composite materials by coating the stainless steel inner surface with titanium, creating a dual-layer structure. The stainless steel provides structural strength and cost-effectiveness, while the titanium coating provides corrosion resistance against acidic gases like HF, HCl, and HBr. This composite approach resolves the contradiction by combining the advantages of both materials.
2Productivity
If stainless steel is used for the inner surface, then manufacturing is simple, but conductor losses increase and plasma quality degrades due to corrosion
Solution Approach 1:
The patent applies local quality by selectively coating only the inner surface of the gas chamber that contacts the plasma and acidic gases with titanium. This localized treatment protects the critical areas from corrosion and maintains plasma quality, while the rest of the stainless steel structure remains unchanged, preserving manufacturing simplicity.
3Duration of action of stationary object
If the passive oxide layer is present on stainless steel, then corrosion protection is provided initially, but the layer is stripped by halocompounds and water vapor leading to degradation
Solution Approach 1:
The patent applies preliminary action by pre-coating the stainless steel surface with titanium before the device operates. This titanium coating forms a stable oxide layer in advance that resists stripping by halocompounds and water vapor, preventing the corrosion that would otherwise occur during normal operation and extending the service life of the gas chamber.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The use of titanium surfaces improves the efficiency and durability of the plasma abatement device by preventing corrosion and maintaining high plasma quality, even in the presence of halocompounds and water vapor, thus enhancing the removal of hazardous species from the gas stream.
Implementation Method 1
a microwave plasma is initiated and sustained between the two electrodes from the gas flowing between the electrodes
Implementation Method 2
species within the gas stream are subjected to impact with energetic electrons causing dissociation into reactive species
Implementation Method 3
reaction of CF4 with water vapour will form CO2 and HF, and Cl2 can form HCl within the chamber
Implementation Method 4
In the presence of air, a passive surface oxide layer is formed, which protects the underlying stainless steel from corrosion
Implementation Method 5
an electrically conductive material that is resistant to corrosion during treatment of a gas containing a halocompound and water vapour
Data Source
AI summary
A plasma abatement device comprises a gas chamber having a gas inlet for receiving a gas to be treated by the device and a gas outlet, at least part of the inner surface of the gas chamber being formed from, or coated with, an electrically conductive material that is resistant to corrosion during treatment of a gas containing a halocompound and water vapor.