Sequentially Activated Low-E Coating Silver Agglomeration
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Solution Overview
Problem
Conventional low-E coatings for window applications have suboptimal emissivity and trade-offs between thermal performance and visual properties, with existing activation methods like thermal tempering and flash lighting not achieving the lowest possible emissivity due to silver agglomeration and inefficient energy transfer.
Innovation Solution
A two-stage activation method involving non-equilibrium preconditioning with specific frequency photons followed by equilibrium thermal activation, which rearranges silver atoms to energetically favorable positions and aligns chemical potentials, reducing agglomeration and enhancing emissivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If thermal activation is applied to lower emissivity, then emissivity is reduced, but silver agglomeration occurs causing loss of film smoothness
Solution Approach 1:
The patent applies a preliminary flash light treatment before thermal activation to pre-arrange silver atoms in energetically favorable positions. This preliminary action reduces subsequent silver migration during thermal processing, allowing thermal activation to achieve lower emissivity without excessive agglomeration and loss of film smoothness.
Solution Approach 2:
The patent combines flash light treatment and thermal activation in a continuous two-stage process. The flash light preparation stage creates optimal atomic arrangements that continue to benefit during the subsequent thermal activation stage, maintaining both low emissivity and film smoothness through continuous useful action rather than separate independent treatments.
2Manufacturing precision
If conventional flash light activation is used, then emissivity is reduced, but energy transfer is inefficient due to reflection in the near-IR spectrum
Solution Approach 1:
The patent changes the wavelength parameter of the activation light from conventional near-IR (800-1200 nm) to visible spectrum wavelengths (400-700 nm). This parameter change avoids the plasma wavelength region where silver reflects near-IR light, enabling efficient energy absorption and transfer to the silver atoms for effective emissivity reduction.
Solution Approach 2:
The patent converts the harmful reflection effect in the near-IR spectrum into a benefit by selecting visible wavelengths. The same plasma oscillation that causes near-IR reflection is exploited to identify the optimal visible wavelength range for absorption, turning the reflection problem into a guide for selecting the correct activation wavelength.
3Stability of the object's composition
If room temperature deposition is used, then silver agglomeration is reduced, but emissivity performance is suboptimal
Solution Approach 1:
The patent applies preliminary flash light treatment to room temperature deposited silver layers to activate and rearrange the silver atoms without thermal processing. This preliminary activation achieves low emissivity while maintaining the uniformity benefits of room temperature deposition, as the flash light provides the necessary atomic rearrangement without the agglomeration caused by prolonged thermal exposure.
Solution Approach 2:
The patent replaces the conventional thermal mechanism (heat treatment) with a photonic mechanism (flash light treatment) for activating the silver layer. This substitution allows achieving the same atomic rearrangement and emissivity reduction without the harmful thermal effects, maintaining film uniformity while improving optical performance.
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
This approach achieves emissivity levels lower than conventional methods, with a 20% improvement in reducing emissivity while maintaining good visible transmission, and can further lower emissivity to 0.011 or less with optimal thermal treatment.
Implementation Method 1
activation via a non-equilibrium preconditioning activation that uses photons with specific frequencies / frequency ranges
Implementation Method 2
followed by a more equilibrium thermal activation
Data Source
Figure 1
Figure 2A~2C
Figure 3
AI summary
Certain example embodiments relate to coated articles with sequentially activated low-E coatings, and/or methods of making the same. In certain example embodiments, one or more infrared reflecting layers is/are activated via a non-equilibrium preconditioning activation that uses photons with specific frequencies/frequency ranges, followed by a more equilibrium thermal activation. The preconditioning activation aids in a rearranging the silver atoms to energetically favorable positions, while helping to avoid their unwanted agglomeration. The more equilibrium thermal stage of activation aids in aligning the chemical potentials of the layers of the stack and in further densification of the preconditioned silver layer. Doing so, in turn, helps to reduce the likelihood of stresses building-up in the coating, the formation of point and dimensional defects, other unwanted efficiency-reducing phenomena, and/or the like. Advantageously, emissivity can be lowered to a value lower than that achievable using conventional thermal, flash, and laser scanning, approaches alone.