Flat Metal Particle Composition for Heat Ray Shielding
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Solution Overview
Problem
Current reflective materials using silver nanoparticles face issues with light resistance due to instability and sulfurization/oxidization, leading to reduced plasmon reflection and transmittance, and existing solutions do not effectively address these problems.
Innovation Solution
Incorporating a metal nobler than silver, such as gold or palladium, in an amount of 10^-3 to 5 atomic% near the surfaces of silver nanoparticles to enhance stability and prevent plasmon reflection degradation, while maintaining high transmittance and selectivity for reflection wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silver nanoparticles are used for reflective materials, then high reflectivity and transmittance are achieved, but light resistance deteriorates due to sulfurization and oxidization
Solution Approach 1:
The patent creates a composite nanoparticle structure where a core silver nanoparticle is coated with a shell of noble metal (gold, palladium, or platinum). This composite structure combines the high reflectivity and transmittance properties of silver with the superior oxidation and sulfurization resistance of the outer noble metal shell, thereby resolving the contradiction between achieving high optical performance and maintaining light resistance.
Solution Approach 2:
The invention applies the noble metal coating specifically at the surface and outer shell region of the silver nanoparticle, rather than throughout the entire particle. This local application of the noble metal provides protection against sulfurization and oxidization at the critical surface interfaces while preserving the bulk silver nanoparticle's optical properties for high reflectivity and transmittance.
2Stability of the object's composition
If other metals are added to silver nanoparticles, then thermal stability is improved, but plasmon wavelength changes and light resistance deteriorates
Solution Approach 1:
The noble metal is positioned exclusively at the outer shell and surface regions of the silver nanoparticle, providing thermal stability through the stable crystal structure of the noble metal while maintaining the plasmon resonance properties of the silver core. This localized arrangement prevents the noble metal from altering the plasmon wavelength.
Solution Approach 2:
The core-shell composite structure allows the silver core to maintain its plasmon resonance characteristics for optimal optical performance while the outer noble metal shell provides thermal stability and protection against environmental degradation, achieving both thermal stability and light resistance simultaneously.
3Reliability
If a large amount of resin is added to protect noble metal particles, then light resistance is improved, but the composition becomes unstable and plasmon reflection is reduced
Solution Approach 1:
Instead of using large amounts of resin to protect the noble metal particles, the invention creates a direct composite material where the noble metal forms a coherent shell around the silver nanoparticle core. This intrinsic composite structure provides protection against sulfurization and oxidization without requiring excessive resin, thereby maintaining composition stability and preserving plasmon reflection properties.
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 approach results in a stable flat metal particle composition with improved light resistance and selective reflection properties, suitable for heat ray and infrared ray films, offering high transmittance and radio wave transparency.
Implementation Method 1
nanoparticles have a size smaller than wavelengths of light and thus attract attention as a material with low light scattering. Among others, research has been made on metal nanoparticles in various fields, since they have electrical conductivity, thermal conductivity, favorable refractive index, catalytic activity, and other features.
Implementation Method 2
the transparent conductive materials disclosed in the above prior art documents utilize conductivity of silver and thus possess problematic sulfurization and oxidization. Meanwhile, in reflective materials utilizing plasmon, a small degree of oxidization or sulfurization on contact points or surfaces does not problematic.
Data Source
Figure 1A~2A
Figure 2B~2C
AI summary
A flat metal particle-containing composition including flat metal particles containing silver and a metal nobler than the silver, wherein the metal nobler than the silver is located near surfaces of the flat metal particles and wherein an amount of the metal nobler than the silver is 10-3 atomic% to 5 atomic% relative to the silver contained in the flat metal particles.