VO2 Nanoparticle Media with Refractive Index Matching for Transparency
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Solution Overview
Problem
Existing thermochromic materials like VO2 face a trade-off between visible light transmittance (VLT) and solar modulation (ΔTsol) due to their high refractive index (RI), leading to reduced optical transparency and practical applications in smart fenestrations.
Innovation Solution
Nanoparticles with a thermochromic core and a low refractive index shell, such as a gradient copolymer, are used to match the refractive index of the surrounding medium, enhancing transparency and thermochromic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick VO2 coating is used to achieve high solar modulation, then solar modulation performance is improved, but visible light transmittance deteriorates due to increased light scattering and opaqueness
Solution Approach 1:
The patent segments the VO2 coating into discrete nanoparticles dispersed within a matrix material, replacing the conventional thick continuous coating. This segmentation allows the system to achieve solar modulation through nanoparticle phase transitions while maintaining visible light transmittance by avoiding the light scattering issues associated with thick continuous coatings.
Solution Approach 2:
The patent changes the physical state and optical properties of the VO2 material by controlling nanoparticle size, shape, and dispersion characteristics. By adjusting these parameters, the system achieves high solar modulation at specific wavelengths while maintaining transparency in the visible range, resolving the trade-off between modulation performance and visible light transmittance.
2Reliability
If VO2 material is used to achieve thermochromic solar radiation blocking, then solar modulation capability is improved, but optical transparency deteriorates due to high refractive index mismatch
Solution Approach 1:
The patent applies local quality by designing nanoparticles with specific size ranges (5-500 nm) and controlling their spatial distribution within the matrix. This localized approach ensures that the high refractive index VO2 material provides solar modulation only at specific locations and wavelengths, while the overall composite maintains optical transparency through the matrix material and controlled nanoparticle dispersion.
Solution Approach 2:
The patent creates a composite material system combining VO2 nanoparticles with a transparent matrix material. This composite structure allows the VO2 nanoparticles to provide thermochromic solar modulation functionality while the matrix material maintains optical transparency, effectively resolving the refractive index mismatch problem that plagues pure VO2 coatings.
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 nanoparticle-containing medium achieves improved optical transparency by reducing light scattering at the core-shell interface, allowing at least 50% transmission of visible electromagnetic radiation while maintaining thermochromic properties.
Implementation Method 1
VO2 can transit between the monoclinic (M) semiconducting phase to the rutile (R) metallic phase. Such reversible temperature-induced phase transitions of VO2 result in a VO2-based coating capable of modulating the solar radiation in the NIR regime
Implementation Method 2
the refractive index (RI) of a nanoparticle comprising thermochromic material (such as VO2) can be made closer to the refractive index of a surrounding medium by tethering a material (such as a gradient copolymer) to the core region of the nanoparticle to modify the refractive index of the nanoparticle
Data Source
AI summary
The present disclosure is generally directed to nanoparticle-containing media exhibiting enhanced optical transparency, related nanoparticles, and associated systems and methods. In certain embodiments, the refractive index (RI) of a nanoparticle comprising thermochromic material (such as VO2) can be made closer to the refractive index of a surrounding medium by tethering a material (such as a gradient copolymer) to the core region of the nanoparticle to modify the refractive index of the nanoparticle. Modifying the refractive index of the nanoparticle to be closer to the refractive index of the medium that contains the nanoparticle can render the nanoparticle-containing medium (also referred, to herein as a composite) more transparent to various wavelengths of electromagnetic radiation while imparting thermochromic properties to the nanoparticle-containing medium.