Preparation of NaF Microcapsules for High-Temperature Thermal Storage.

Area of Science:

• Materials Science
• Nanotechnology
• Chemical Engineering

Background:

• Phase change materials (PCMs) are crucial for thermal energy storage.
• Sodium fluoride (NaF) possesses a high melting point and latent heat, making it a promising PCM.
• Encapsulation is necessary to improve the stability and handling of NaF for practical applications.

Purpose of the Study:

• To develop a novel carbon-shelled NaF phase change microcapsule (NaF@C).
• To investigate the morphology, composition, and thermal properties of the NaF@C microcapsules.
• To evaluate the thermal stability and potential applications of the NaF@C microcapsules in extreme high-temperature environments.

Main Methods:

• Preparation of NaF@C microcapsules via phase separation and carbonization of phenolic resin.
• Characterization using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS).
• Thermal property analysis using differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA).

Main Results:

• Successfully synthesized NaF@C microcapsules with a core-shell structure, sized 3-5 μm.
• Determined a melting point of 988 °C and an enthalpy of 192 J/g for the NaF@C microcapsules.
• Demonstrated excellent thermal stability, retaining powder morphology and showing no NaF leakage after 30 heat treatment cycles at 1100 °C.

Conclusions:

• The developed NaF@C microcapsules offer a stable and effective solution for thermal energy storage at ultra-high temperatures.
• The carbon shell effectively prevents NaF leakage and maintains structural integrity.
• These microcapsules show significant potential for thermal protection and management in demanding applications like aerospace and solar energy.