Synergistically Enhanced Thermal and Mechanical Properties of CNT-Modified Docosane@SiO₂ Nanocapsules for Advanced Thermal Energy Storage

This study presents a novel strategy for synthesizing carbon nanotube (CNT)-modified n-docosane@SiO₂ (C22@SiO₂) phase change nanocapsules with simultaneously enhanced latent heat, thermal conductivity, and mechanical strength. A critical pretreatment step involving the ultrasonic dispersion of CNTs in tetraethyl orthosilicate (TEOS) for ≥3 hours was critical, enabling effective adsorption of TEOS onto CNT surfaces and thereby facilitating their co-encapsulation with C22 within SiO₂ shells via interfacial polycondensation. Systematic optimization revealed that a 3-hour dispersion was essential for forming structurally intact capsules, achieving an encapsulation efficiency of 80.2% and a melting enthalpy (ΔH_m) of 188.5 J·g^-1. The optimal CNT loading of 0.05 g maximized core crystallinity (66.75%) and latent heat (ΔH_m: 188.5 J·g^-1 vs. 168.3 J·g^-1 for unmodified capsules), while reducing the melting point by 2.4 °C due to molecular interactions between CNTs and C22, as confirmed by solid-state ¹H NMR. The optimized capsules (denoted as P-CNT-0.05) exhibited a 36.8% higher thermal conductivity (0.52 W·m^-1·K^-1), a 338.9% increase in Young’s modulus (3964 MPa), near-zero leakage (0.88% mass loss after heating), and stable performance over 100 thermal cycles. This work provides a scalable route to multifunctional phase change nanocapsules with triply enhanced energy storage capacity, heat transfer efficiency, and mechanical durability, demonstrating great potential for advanced thermal management applications.