Long-term thermal behaviour of silver and graphene nanoparticle-enhanced phase change materials under accelerated thermal stress

Long-term performance of a nano enhanced phase change material (NePCM) plays a crucial role in its application for thermal-related application. PCMs often encounter challenges related to their stability and reliability in maintaining effective thermal regulation. Over time, they tend to degrade and lose their storage capability due to prolonged exposure to the ambient environment and repeated melting/freezing cycles. Therefore, it is essential to assess the cycle test stability of PCMs to ensure their long-term durability before integrating them into thermal systems. However, relevant long-term stability assessment of the NePCMs has been rarely reported. This study, therefore, investigate the stability and durability of the RT50 (a commercial PCM) based NePCM, with silver (Ag) and graphene (Gr) NPs as nano-additives. Accelerated thermal cycling method with up to 3000 cycles was adopted to evaluate the durability PCM (RT50) and its NePCM (0.8%Ag/RT50 & 0.6%Gr/RT50). Moreover, their key properties including the microstructure, chemical stability, optical absorbance, thermal reliability and energy storage ability are examined at regular interval. The results show that NePCMs possess excellent thermal chemical stability even after 3000 thermal cycles, and latent heat (slight reduction approximately 10 %). It is worth noting that owing to the stronger intermolecular force between RT50 and Gr, the energy storage capacity of Gr/RT50 NePCM is observed to display an increasing trend with thermal cycling. Overall, the prepared NePCM has validated the long-term reliability, and pave ways for its thermal regulation application.