Interfacial and thermophysical engineering for enhanced thermal performance of boron carbide-modified HITEC nanocomposites in high-temperature thermal energy storage applications

HITEC-type nitrate-nitrite molten salts are promising heat transfer fluid and thermal energy storage media for intermediate-temperature concentrated solar power (CSP), yet their deployment is constrained by moderate heat-transfer capability and limited high-temperature robustness. This study introduces B 4 C as a non-oxide ceramic nanoadditive and systematically evaluates its structure–property impact in HITEC. Pristine HITEC and B 4 C-modified compositions (0.5 – 2.0 wt.%) were synthesized using a unified protocol to enable direct comparison. Phase integrity and chemical framework preservation were examined by XRD and FT-IR, while morphology and additive distribution were assessed by FE-SEM/EDX. Thermophysical behavior was quantified by DSC for melting-solidification characteristics and temperature-dependent C p , high-temperature stability was evaluated by TGA, and thermal conductivity was measured using the transient plane source method. The results show that B 4 C incorporation preserves the characteristic HITEC phase constitution and nitrate-nitrite bonding features, indicating predominantly physical integration. Thermal conductivity increases monotonically with loading and reaches a maximum enhancement of 50.42% at 2.0 wt.% B 4 C. The liquid-phase C p exhibits an optimum response, achieving a maximum enhancement of 34.25% at 1.5 wt.% B 4 C. Phase-change energetics are strengthened, with the maximum melting enthalpy increase corresponding to 15.13% at 1.5 wt.% B 4 C. Thermal stability is improved, as the decomposition onset shifts from 612 °C for pristine HITEC to 661 °C at 2.0 wt.% B 4 C, corresponding to an 8.01% increase in upper operating temperature. Overall, these multi-parameter gains support HITEC-B 4 C nanocomposites as practical candidates for CSP-relevant operation requiring faster heat exchange, higher sensible storage density, and improved safety margins under cyclic service.