Highly Stable and Conductive Microcapsules for Enhancement of Joule Heating Performance

Abstract

Nanocarbons show great promise for establishing the next generation of Joule heating systems, but suffer from the limited maximum temperature due to precociously convective heat dissipation from electrothermal system to surrounding environment. Here we introduce a strategy to eliminate such convective heat transfer by inserting highly stable and conductive microcapsules into the electrothermal structures. The microcapsule is composed of encapsulated long-chain alkanes and graphene oxide/carbon nanotube hybrids as core and shell material, respectively. Multiform carbon nanotubes in the microspheres stabilize the capsule shell to resist volume-change-induced rupture during repeated heating/cooling process, and meanwhile enhance the thermal conductance of encapsulated alkanes which facilitates an expeditious heat exchange. The resulting microcapsules can be homogeneously incorporated in the nanocarbon-based electrothermal structures. At a dopant of 5%, the working temperature can be enhanced by 30% even at a low voltage and moderate temperature, which indicates a great value in daily household applications. Therefore, the stable and conductive microcapsule may serve as a versatile and valuable dopant for varieties of heat generation systems.

Thermal and Electrical Properties of Nanocomposites Based on Self‐Assembled Pristine Graphene

“…In addition, our composite demonstrates Joule heating, a process of directly heating a conductive material, such as a percolated network of nanocarbons within a matrix, by the flow of current. This type of heating has been previously studied using carbon nanotubes, rGO, pure graphite, and chemical vapor deposition (CVD) grown graphene, with proposed applications such as defoggers, composite manufacturing and repair, the detection of internal and surface damage in situ using thermographic imaging, and as an external stimulus for stimuli responsive materials in shape memory or recovery …”

The micro‐/nano‐PCMs for thermal energy storage systems: A state of art review

“…The conductive EPCMs convert the electrical energy into heat on applying the small input voltage and store that heat in form of latent heat while melting of the PCMs within the microcapsule and nanocapsule. Zheng et al presented a joule heating system to reduce the convective heat transfer from electrothermal system to the surrounding by inserting the highly conductive and stable microcapsules of docosane and GO‐CNT as core and shell material, respectively. The results shown in Figure A‐E illustrate that with loading of 5 % of micro‐PCMs, the working temperature can be improved by 30 % even at lower voltage and ambient temperature, which ensures a potential usage in daily household heat storage applications.…”

“…A, Illustration of convective heat dissipation in a Joule heating structure composed of nanocarbons, B, illustration of prevented heat dissipation in a PCM capsule incorporated system, C, temperature evaluation curves of an electrothermal structure containing 25 vol.% micro‐PCM capsules, D, as a function of voltage, the balanced surface temperatures obtained at 20min heating are demonstrated, and E, a collection of temperature evolution curves of an electro‐thermal structure containing 25 vol.% micro‐PCM and a neat electro‐thermal heater under 6 V repeated for 100 cycles . Reproduced with the permission of the American Chemical Society [Colour figure can be viewed at wileyonlinelibrary.com]…”

Metal–Organic Framework Based Microcapsules

“…[1,2] As aresult, microcapsules have played vital roles in various applications,s uch as adsorption and separation, [3,4] drug delivery, [5] encapsulation, [6] and so on. [7,8] Up to now,t he shells of most microcapsules are made of polymers owing to their mechanical flexibility.H owever,t he low thermal stability and chemical incompatibility with inorganic materials naturally limit their use.T oo ur knowledge,n early all microcapsules have enclosed structures with one exposed surface.The enclosed structures and intact shells will cause alow mass transfer rate for substances. [9] Designing and constructing microcapsules with open-mouthed structures (such as bowl-like,J anus structures) has been regarded as as trategy to increase mass transfer rates.…”