Highly Transparent Phase Change Smart Windows Enabled by Refractive-Index-Matched n-Octadecane@SiO₂ Microcapsule...

Area of Science:

• Materials Science
• Energy Science
• Optics

Background:

• Phase change materials (PCMs) are vital for passive energy saving in buildings, particularly for window applications requiring both thermal regulation and optical transparency.
• Challenges with traditional PCMs include liquid leakage during phase transition and light scattering, which degrade optical properties and image clarity.
• Developing PCMs that maintain high transparency and prevent leakage is crucial for advanced smart window technologies.

Purpose of the Study:

• To create a highly transparent phase change composite for window applications.
• To overcome the limitations of liquid leakage and light scattering in PCMs.
• To achieve effective temperature regulation without compromising optical performance.

Main Methods:

• Fabrication of submicron core-shell microcapsules using n-octadecane (core) and silica (shell) via a microencapsulation strategy.
• Dispersion of microcapsules within a refractive-index-matched polymer matrix to minimize interfacial light scattering.
• Evaluation of thermal properties (melting enthalpy) and optical performance (transmittance, fluctuation, cycling stability).

Main Results:

• The microencapsulated PCM exhibited a high melting enthalpy of 155.3 J g^-1.
• The composite achieved a visible light transmittance of 83.75% with minimal transmittance fluctuation (~5%) during phase transition.
• Excellent cycling stability was demonstrated, with only 0.35% optical attenuation after 100 thermal cycles.

Conclusions:

• A novel microencapsulation strategy successfully created a transparent phase change composite for smart windows.
• The composite effectively balances thermal energy storage with high optical transparency and stability.
• This approach offers a promising solution for energy-efficient smart windows and flexible electronic applications.