Preparation and properties of hydroxyapatite aerogel composite phase change materials

To address energy shortage and environmental pollution, scientists are working to develop methods for the production, conversion, and storage of new energy sources. The development of thermal energy storage (TES) is considered to be one of the most effective energy conservation and environmental protection strategies for utilizing various renewable energy sources. Energy storage technology can solve the contradiction between energy supply and demand in time and space and also improve energy efficiency. Currently, TES includes mainly sensible heat storage, latent heat storage, and thermochemical energy storage. The latent heat TES based on phase change materials (PCMs) is an efficient technology that is being actively pursued owing to high storage density in a small temperature region, which is essential for accelerating new energy development and improving energy efficiency. In this paper, hydroxyapatite aerogels with self-supporting network structure were prepared via a hydrothermal method using calcium oleate as a precursor. Self-supporting hydroxyapatite-based composite phase change materials were synthesized using the impregnation method. The morphology and thermal properties of the prepared composite phase change materials were characterized and tested by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetry, and differential scanning calorimetry. The experimental results show that the composite phase change materials of hydroxyapatite aerogels loaded with octadecanol or paraffin have good thermal properties. The measured values of melting enthalpy and solidified enthalpy of the 60% paraffin@HAP composite phase change materials are 85.10 and 85.30 J·g⁻¹, respectively, and its crystallinity is 81.50%. The measured values of melting enthalpy and solidified enthalpy of the 60% octadecanol@HAP composite phase change material are 113.78 and 112.25 J·g⁻¹, respectively, and its crystallinity is 86.20%. In addition, the composite has good thermal and chemical stability. Furthermore, the hydroxyapatite substrate has the advantages of good flame retardancy, corrosion-free characteristics, safety, and environmental protection, which effectively expands the practical application of phase change materials in the field of intelligent thermal insulation textiles and building materials.