Giant inverse elastocaloric effect of n-alkanes imbedded in a carbon-frame for room temperature thermal management

Solid-state refrigeration technology, which utilizes phase transition materials responsive to an external field through which heat is exchanged with the environment, serves as a promising alternative to traditional vapor-compression refrigeration technologies. However, many existing solid-state refrigeration materials are limited by low latent heat, large external driving forces, high thermal hysteresis, or low thermal conductivity, limiting practical applications. In this work, through molecular dynamics simulations and thermodynamic analysis, we predict giant inverse elastocaloric effects in the composited alkane and carbon nanotube/graphene architectures. At near room temperature under a moderate compressive stress of ∼75 MPa, the estimated adiabatic temperature change (ΔT) and isothermal entropy change (ΔS) reach ∼23 K and 200 J kg^-1 K^-1, respectively, demonstrating an excellent elastocaloric performance and efficiency. The refrigeration efficiency (ΔT/Δσ) and thermal conductivity (κ) are significantly improved by one order of magnitude, reaching ∼500 K GPa^-1 and ∼12 W m^-1 K^-1, respectively. Moreover, the application of compressive strain is able to bear the giant reversible elastocaloric effect, achieving cooling and heating with minimal hysteresis effects and no mechanical fatigue. The present work provides atomic-scale insights and important guidance for the design of n-alkanes as the prototypical amorphous polymers with eCE for room temperature solid-state refrigeration.