KRS-5 Infrared Window Coating Oxidation Resistance
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Solution Overview
Problem
KRS-5 infrared transmissive members used in Fourier transform infrared spectrometers are prone to oxidation, leading to reduced infrared light transmittance and potential failure in sample irradiation due to the formation of thallium oxide on their surface.
Innovation Solution
A substrate composed of KRS-5 is coated with an infrared transmissive coating, such as parylene, diamond-like carbon (DLC), or fluorine, to enhance oxidation resistance, with the coating thickness optimized for maintaining transparency and oxygen barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If KRS-5 is used as the infrared transmissive member material, then wide infrared ray transmission range and moisture resistance are achieved, but oxidation resistance deteriorates leading to thallium oxide formation on the surface
Solution Approach 1:
An aluminum oxide coating layer is applied on the surface of the KRS-5 substrate to act as an intermediary barrier between the thallium-containing substrate and the oxidizing environment. This coating prevents direct contact between oxygen and the thallium atoms, thereby suppressing thallium oxide formation while maintaining infrared transmission properties.
Solution Approach 2:
The invention creates a composite structure combining KRS-5 substrate with an aluminum oxide coating layer. This composite material leverages the excellent infrared transmission and moisture resistance of KRS-5 while adding the oxidation resistance properties of aluminum oxide, achieving comprehensive protection against environmental degradation.
2Adaptability or versatility
If the infrared transmissive member is exposed to oxidizing environments, then operational flexibility is maintained, but infrared light transmittance decreases due to surface oxidation
Solution Approach 1:
The aluminum oxide coating serves as a protective intermediary that allows the KRS-5 member to operate in various environmental conditions without suffering from oxidation-induced transmittance loss. The coating is transparent to infrared light, ensuring that light transmission is not compromised while providing environmental stability.
Solution Approach 2:
The aluminum oxide coating creates an inert protective environment on the surface of the KRS-5 substrate, effectively isolating the reactive thallium atoms from atmospheric oxygen. This allows the infrared transmissive member to maintain consistent performance in oxidizing environments without requiring external protective measures.
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 coating significantly improves the durability and long-term infrared transmittance of KRS-5 members by suppressing oxidation, ensuring consistent infrared light transmission even in environments where oxidation progresses.
Implementation Method 1
thallium which is a component of KRS-5 is very prone to oxidation and thallium oxide may be formed on a surface of KRS-5
Implementation Method 2
KRS-5 is characterized in that it allows passage therethrough of infrared rays over a wide range from near-infrared rays to far-infrared rays
Data Source
AI summary
An infrared window includes a substrate composed of “KRS-5” as a raw material which is mixed crystal of thallium iodide and thallium bromide and an infrared transmissive coating that covers a surface of the substrate. A raw material for the infrared transmissive coating is parylene. A thickness of the infrared transmissive coating is set to a value at which an infrared absorptance is lower than 3%. The thickness of the infrared transmissive coating is set to a value at which the infrared absorptance is lower than 3%. The thickness of the infrared transmissive coating is set to a value within a range not smaller than 20 nanometers and smaller than 50 nanometers.