Influence of SiO2 pore structure on phase change enthalpy of shape-stabilized polyethylene glycol/silica composites

Polyethylene glycol (PEG2000)/silica (SiO2) composites with various weight percentages of PEG were prepared as solid–liquid shape-stabilized phase change materials using sol–gel method. In the composite, PEG and SiO2 were chosen as the phase change substance and the supporting material, respectively. The composites were characterized by differential scanning calorimetry and scanning electron microscope. The pore structure of the SiO2 matrix with removal of PEG was studied using N2 adsorption analysis. The phase change enthalpy of PEG in the composite was determined. It was lower than the theoretical value, and decreased with the increase of PEG content. PEG in the composite was strongly confined during the phase transition, and the confinement effect was related with the pore structure of the silica matrix. By correlating the phase change enthalpy with the average pore diameter of the SiO2 matrix by employing a confined phase change model with a constraint layer, the effect of the pore structure on phase transition of PEG was quantitatively evaluated. The phase change enthalpy of PEG in the composite depended on the average pore diameter of the SiO2 matrix, the pore geometrical shape, and the thickness of the PEG constraint layer.

[1]  R. Pellenq,et al.  Simple Phenomenological Models for Phase Transitions in a Confined Geometry. 1: Melting and Solidification in a Cylindrical Pore , 2002 .

[2]  T. Blach,et al.  Monitoring phase behavior of sub- and supercritical CO2 confined in porous fractal silica with 85% porosity. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[3]  A. Sari,et al.  Polyethylene glycol (PEG)/diatomite composite as a novel form-stable phase change material for thermal energy storage , 2011 .

[4]  L. Firlej,et al.  Adsorption and phase transitions in adsorbed systems: structural properties of CCl4 layers adsorbed on a graphite surface , 2007, Journal of molecular modeling.

[5]  Xingxiang Zhang,et al.  Polyurethane foam containing microencapsulated phase-change materials with styrene–divinybenzene co-polymer shells , 2009 .

[6]  Dong Zhang,et al.  Experimental study on the phase change behavior of phase change material confined in pores , 2007 .

[7]  Xingguo Li,et al.  Confinement effect of SiO2 framework on phase change of PEG in shape-stabilized PEG/SiO2 composites , 2012 .

[8]  V. V. Tyagi,et al.  PCM thermal storage in buildings: A state of art , 2007 .

[9]  Theo G. M. van de Ven,et al.  Association-induced polymer bridging by poly(ethylene oxide)-cofactor flocculation systems. , 2005 .

[10]  Khamid Mahkamov,et al.  Solar energy storage using phase change materials , 2007 .

[11]  P. Espeau,et al.  The phase transitions of n-alkanes in mesoscopic pores of graphite , 2005 .

[12]  N. Takagi,et al.  Electronic structure and femtosecond electron transfer dynamics at noble metal/tris - (8 -hydroxyquinoline) aluminum interfaces , 2005 .

[13]  K. Gubbins,et al.  Effects of confinement on freezing and melting , 2006, Journal of physics. Condensed matter : an Institute of Physics journal.

[14]  Peter T. Cummings,et al.  Phase Transitions of Water in Graphite and Mica Pores , 2011 .

[15]  A. Sharma,et al.  Review on thermal energy storage with phase change materials and applications , 2009 .

[16]  Xiaoxi Yang,et al.  Preparation and performance of form-stable polyethylene glycol/silicon dioxide composites as solid-liquid phase change materials , 2009 .

[17]  Wei Li,et al.  Preparation and characterization of polyethylene glycol/active carbon composites as shape-stabilized phase change materials , 2011 .

[18]  Luisa F. Cabeza,et al.  Review on thermal energy storage with phase change: materials, heat transfer analysis and applications , 2003 .

[19]  Gustavo Cáceres,et al.  Confined melting in deformable porous media: A first attempt to explain the graphite/salt composites behaviour , 2010 .

[20]  Yi Wang,et al.  Stearic acid/silica fume composite as form-stable phase change material for thermal energy storage , 2011 .

[21]  T. Akiyama,et al.  Impregnation of porous material with phase change material for thermal energy storage , 2009 .

[22]  Yining Huang,et al.  Phase Transitions of Naphthalene and Its Derivatives Confined in Mesoporous Silicas , 2011 .

[23]  Donghong Yu,et al.  Confined Crystallization Behavior of PEO in Silica Networks , 2000 .

[24]  G. Fang,et al.  Synthesis of shape-stabilized paraffin/silicon dioxide composites as phase change material for thermal energy storage , 2010 .