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@SiO 2 (C22@SiO 2 ) 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 SiO 2 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 1 H 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. From a Facile Pre-dispersion to Triply-Enhanced Performance: Core-Encapsulation of CNTs Boosts Latent Heat, Thermal Conductivity, and Mechanical Strength of Phase-Change Nanocapsules. • A surfactant-free CNT pretreatment is developed for core-modification of phase-change nanocapsules. • Simultaneous enhancement in latent heat, thermal conductivity, and mechanical strength is achieved. • The optimal nanocapsules exhibit a high latent heat of 188.5 J/g and a 36.8% improved thermal conductivity. • Young's modulus is dramatically increased by 338.9% with a transition from plastic to elastic behavior. • Molecular interactions between CNTs and docosane boost crystallinity and depress the melting point.