(83e) Energy Storage Materials with Nano-Encapsulated Inclusions of an Easy to Melt Metal

Metal based energy storage materials have advantages of high thermal conductivity and potentially high strength [1].  The main issue limiting their development is that the metal that melts upon heating (and thus serves as an energy storage medium) needs to be contained.  Containment of liquid metals is difficult; often bulk containers are used [2].  Bulk containers limit significantly the types of structures that can be manufactured using the metal-based energy storage materials.  In this study, a preparation a composite energy storage material will be introduced and material properties will be characterized.  The material consists of a metal or metal/ceramic matrix with nanosized inclusions of an easy to melt metal encapsulated in protective ceramic shells.  In this study, bismuth is selected as an easy to melt metal; bismuth inclusions are encapsulated in alumina shells within an aluminum or aluminum/alumina matrix.  Similarly, Sn, In, or other low melting point metals can be used. The composite material prepared as a powder is readily consolidated.  Both, thermal and mechanical stability will be presented and discussed.  The composite material is compared to a reference composite with the same bulk composition but without encapsulation for Bi inclusions.  It is observed that without encapsulation, Bi is redistributed within the material upon heating and melting, with a tendency to accumulate at its surface.  Encapsulated Bi remains inside the composite matrix even after the Bi melting point is substantially exceeded.  Materials with and without nano-encapsulated Bi behave qualitatively different upon mechanical loading at different temperatures.  The material with encapsulated inclusions is much stronger than its counterpart, with nominally the same bulk composition.

References

[1] H. Ge, H. Li, S. Mei, J. Liu, Low melting point liquid metal as a new class of phase change material: An emerging frontier in energy area, Renewable Sustainable Energy Rev., 21 (2013) 331-346.

[2] A.J. Spero, F.S. Wyle, Design of high energy density thermal storage device, in:  US20110308762A1, Thermal Storage Systems, USA . 2011, pp. 12 pp.