Design of synthesis route for inorganic shape-stabilized phase change materials. Direct sol–gel process versus vacuum impregnation method

  • Yanio E. Milian
  • Svetlana UshakEmail author
Original Paper: Sol–gel and hybrid materials for energy, environment, and building applications


Recently, sol–gel techniques for synthesize inorganic shape-stabilized phase change materials (SS-PCMs) were proposed to successfully improve thermal properties and to accomplish real applications for latent thermal energy storage (TES). In this work, the use of sol–gel process was deeply investigated to develop inorganic SS-PCM, using tetraethyl orthosilicate (TEOS) as monomer and Na2SO4.10H2O as phase change material (PCM). In addition, the influence of pH (acid and basic hydrolysis) and PCM content in the physic and thermal properties of achieved materials were analyzed. Stabilized materials were characterized by infrared spectroscopy, X-ray diffraction, scanning electronic microscopy, scanning differential calorimetry, and thermogravimetry. The characterization results established that direct sol–gel method via acid hydrolysis showed potential to develop inorganic SS-PCMs. However, results indicate that the Na2SO4.10H2O loses water molecules during synthesis, resulting in the anhydrous compound Na2SO4-SiO2; therefore, materials were proposed for high temperature TES applications. Melting point of 880–886 °C and enthalpy of fusion of 23–100 kJ kg−1 were obtained for materials with 20–60 wt.% of PCM content. The new obtained SS-PCMs have enhanced thermal properties, compared with anhydrous Na2SO4: latent storage range RL among 0.1–3.0 °C and thermal cycle stability, for high TES. In addition, direct sol–gel technique was compared with vacuum impregnation method, employing SiO2 as support material. Impregnation procedures were not successfully achieved in this work to stabilize the PCM, which prove the superior significance of direct sol–gel method.


  • New inorganic SS-PCM based on Na2SO4 and SiO2 with sol–gel method.

  • Influence of pH and amount of PCM for direct sol–gel synthesis.

  • Direct sol gel method was compared with vacuum impregnation.

  • SiO2 materials (–SiOH and –SiOR) as support materials for vacuum impregnation.

  • Direct sol gel method, via acid hydrolysis show best results.


Sol–gel methods Vacuum impregnation Inorganic shape-stabilized phase change materials SiO2 tetraethyl orthosilicate 



Thermal energy storage


Tetraethyl orthosilicate


Phase change material


Shape-stabilized phase change materials


Core-shell encapsulation


Scanning electron microscopy


Energy dispersion spectroscopy


X-Ray diffraction


Fourier transform infrared spectroscopy


Differential scanning calorimetry




Sol–gel method


Latent storage range

T(onset, melting)

Onset melting temperature

T(endset, solidification)

Endset solidification temperature


Calculated PCM content (wt.%)


Experimental PCM content (wt.%)


Melting point (°C)


Solidification point (°C)


Enthalpy of fusion (kJ kg−1)


Enthalpy of solidification (kJ kg−1)

% ΔH

Reduction of the enthalpy of fusion in the SS-PCMs


Enthalpy of fusion of the PCM


Enthalpy of fusion of the SS-PCM


Atomic number

Normal/Atomic C.

Normal/atomic concentration (wt./at.%)



The work is partially funded by the Chilean government CONICYT/FONDAP No 15110019, CONICYT/FONDECYT REGULAR N°1170675, and CONICYT/PCI/REDES N°170131. YM would like to thanks CONICYT/BECA DE DOCTORADO NACIONAL 2015 N°21150240 for his doctorate scholarship, CORFO 16ENI2-71940 INGENIERIA2030 projects.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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© Springer Science+Business Media, LLC, part of Springer Nature 2019

Authors and Affiliations

  1. 1.Department of Chemical Engineering and Mineral Processing and Center for Advanced Study of Lithium and Industrial Minerals (CELiMIN)Universidad de AntofagastaAntofagastaChile

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