Sepiolite Nanocarriers as a Matrix for Controlled Thermal Energy Storage

Applying the eutectic hydrated salt (EHS) mixture of Na₂HPO₄·12H₂O and Na₂SO₄·10H₂O in a 1:1 weight ratio as a phase-change material and natural sepiolite nanocarriers as a matrix, the form-stable phase-change composite EHS@sepiolite was fabricated by vacuum impregnation. Due to the high porosity of sepiolite and its nanofibrous structure with internal channels, the effective loading of the phase-change material reached as high as 88 wt %. The melting temperature of the composite was 38.1 °C and its melting enthalpy was 185 J g^-1. The crystallinity of the hydrated salt mixture was retained after loading into the sepiolite matrix. The composite demonstrated high stability over 50 heat uptake/release cycles maintaining its melting temperature and melting enthalpy the same. The combination of natural sepiolite nanocarriers and crystallohydrates is a cheap and efficient nanoscale energy storage system with high potential for practical applications and upscaling because of their natural abundance.