Five NaNO3/diatomite composite phase change materials (CPCM) for thermal energy storage with different mass content of diatomite were prepared using the mixing and sintering method. Diatomite and NaNO3 were employed as carrier material and phase change material respectively. The compressive strength

thermal properties

microscopic morphology

photoelectron spectroscopy and thermal analysis were carried out. The compressive strength of the CPCM was enhanced with the mass fraction of diatomite increasing from 30% to 35% and 40% and showed brittle characteristic. When the mass fraction of diatomite reached 45% and 50%

the NaNO3/diatomite CPCM performed the paddy behavior. The DSC characterization results revealed that diatomite had little effect on the latent heat and phase-change temperature of NaNO3. The obtained results of LFA tests showed that the thermal conductivity of the CPCM decreased with the increase of the temperature. At the given temperature

the thermal conductivity of the NaNO3/diatomite CPCM showed upward trend with the mass fraction of diatomite increases. It was also observed that the enhancing rate of the thermal conductivity was eight times larger when increasing the mass fraction of diatomite increased from 30% to 35% compared with the mass fraction increasing from 35% to 50%. Compared with pure NaNO3

with the diatomite mass fraction increasing from 30% to 50%

the average specific heat capacity of the NaNO3/diatomite CPCM performed the upward and downward trend within the room temperature-phase transition and the end of the phase transition-the highest temperature range. The SEM and EDS results showed that the NaNO3/diatomite CPCM have dense structure with NaNO3 adsorbed uniformly inside the diatomite. The desirable compressive strength and thermal properties of the NaNO3/diatomite CPCM can be achieved by optimizing the mass ratio of diatomite. The NaNO3/diatomite CPCM with 35% (mass) diatomite behaved superior overall performance according to the work in this paper.