Preparation and Characterization of Sodium Sulfate/Silicon Dioxide Composite As a Shape-Stabilized Solid–Liquid Phase Change Material

The composite of sodium sulfate (Na₂SO₄)/silicon dioxide (SiO₂) as a shape-stabilized solid–liquid phase change material (PCM) was prepared by sol-gel procedure using rice husk ash as silicon source. Inside the composite, the in-situ generated Na₂SO₄ acts as the solid-liquid phase change latent heat storage substance. As the supporting material, SiO₂ provides structural strength and prevents the leakage of the melted Na₂SO₄. The structure and composition of the prepared composite PCM were characterized using a scanning electronic microscope (SEM), Fourier transformation infrared spectroscope (FTIR) and x-ray diffraction (XRD). The results showed that the prepared Na₂SO₄/SiO₂ PCM was the hybrid of Na₂SO₄ and SiO₂, in which no new substance was produced during the phase change of Na₂SO₄. The in-situ generated Na₂SO₄ was fixed in the network of porous SiO₂. Shown by differential scanning calorimeter (DSC) analysis, the prepared Na₂SO₄/SiO₂ shape-stabilized PCM has a phase change enthalpy of 75-85 J/g with phase change temperature between 878-883^oC. The Na₂SO₄/SiO₂ composite was thermal stable and shape-stabilized during the melting-condensing cycles.