ALD Coated O-ring for Cryogenic Vacuum Sealing
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Solution Overview
Problem
Existing coated O-rings, such as fluoroelastomer O-rings, fail to reduce gas and water diffusion effectively at vacuum pressures below 10−5 mbar, especially when exposed to cryogenic temperatures, where water freezing can further exacerbate permeation issues.
Innovation Solution
A thin inorganic coating with a thickness between 10 nm and 1 μm, specifically between 20 nm and 50 nm, is applied using Atomic Layer Deposition (ALD) to the O-ring, comprising metal oxides like SiO2, Al2O3, and TiO, which adheres well to the elastomer and reduces water vapor diffusion while maintaining elasticity, and optionally covered with a protective polymer film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a coating is applied to the O-ring to reduce gas and water diffusion, then permeation resistance is improved, but the coating may crack when the O-ring deforms
Solution Approach 1:
The patent applies a thin inorganic coating layer (10 nm to 1 μm) on the O-ring surface that maintains flexibility and adheres to the elastomer substrate during deformation. The thin film structure allows the coating to bend and deform with the O-ring without cracking, while still providing effective barrier properties against gas and water permeation.
Solution Approach 2:
The patent creates a composite structure by combining the elastomer O-ring substrate with an inorganic coating layer. This composite material approach allows the organic elastomer to provide elasticity and deformation capability while the inorganic coating provides permeation resistance, with the two materials working together to resolve the contradiction between flexibility and barrier performance.
2Reliability
If a thick coating is applied to reduce permeation, then diffusion resistance is improved, but the O-ring loses elasticity and mechanical flexibility
Solution Approach 1:
The patent utilizes a thin film coating approach where the inorganic layer thickness is carefully controlled (10 nm to 1 μm) to provide sufficient diffusion resistance while remaining thin enough to allow the underlying elastomer to maintain its elasticity and mechanical flexibility. The thin film does not significantly constrain the deformation capability of the O-ring.
Solution Approach 2:
The patent optimizes the thickness parameter of the coating layer to achieve the desired balance between diffusion resistance and elasticity. By controlling the thickness within a specific range (10 nm to 1 μm), the coating provides adequate barrier properties without compromising the mechanical properties of the O-ring.
3Reliability
If a coating is applied to enhance chemical resistance, then chemical stability is improved, but the manufacturing complexity increases
Solution Approach 1:
The patent replaces traditional mechanical or chemical coating methods with Atomic Layer Deposition (ALD), a vapor-phase deposition technique. This substitution allows for precise control of coating thickness at the nanometer scale, uniform coverage, and excellent adhesion to the elastomer substrate, while enabling automated manufacturing processes.
Solution Approach 2:
The patent utilizes ALD process parameters (temperature, precursor flow, deposition time) to precisely control the coating thickness and properties. By optimizing these parameters, the manufacturing process achieves high-quality coatings with consistent performance while maintaining manufacturing efficiency and reducing complexity through process integration.
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 coated O-ring exhibits significantly reduced water vapor diffusion, maintaining mechanical properties and adhering to deformations, making it suitable for dynamic applications without compromising elasticity or increasing material costs.
Implementation Method 1
the coating is a thin inorganic coating with a thickness between 10 nm and 1 μm, more specifically between 20 nm and 100 nm, most specifically between 20 nm and 50 nm, resulting in an O-ring that shows a lower permeation than an uncoated O-ring
Implementation Method 2
Inventors found that applying the layer with, for example, Atomic Layer Deposition (ALD) resulted in a coating that shows good adherence to the elastomer
Data Source
AI summary
The invention relates to a coated O-ring for forming a seal, in which the core of the O-ring comprises a polymer and/or synthetic rubber, and the coating comprises an inorganic coating with a thickness between 10 nm and 1 μm, resulting in an O-ring that shows a lower permeation than an uncoated O-ring and where the coating shows little or no cracking when the local curvature of the O-ring in any direction is changed by 20%.The coating is preferably applied by Atomic Layer Deposition, but also other deposition techniques such as (PE)CVD, E-beam evaporation, and reactive evaporation may be used.A further elastomer layer may cover the one or more coating layers for further mechanical and/or chemical protection.