黑料福利网

Waxes are widely known as the material candles or polishes are made of. At room temperature, they are malleable solids, and upon heating they become liquid. Waxes have a high specific heat capacity and can store and release a significant amount of thermal energy during melting, making them interesting candidates for energy storage purposes.

From clean oil-based material to waste
鈥楿nfortunately, their thermal conductivity is very poor, making it hard for the material to take up or release the heat,鈥� explains project leader Alexey Lyulin. 鈥業n a previous project, called Wax+, we have demonstrated that by adding graphene layers to paraffin, we can significantly improve its thermal conductivity. However, in that research we used clean, monodispersed, oil-based waxes. Now, we want to take the next step and move toward waxes that are extracted from plastic waste streams.鈥�

Together with his 黑料福利网 colleagues , Henk Huinink and Heiner Friedrich, Lyulin is collaborating with the universities of Antwerp, Ghent and Twente to tackle the challenges that come with this ambition. 鈥極ur Belgian colleagues have developed a method to extract low-molecular-mass paraffin waxes from plastic waste streams through chemical pyrolysis 鈥� heating waste in absence of oxygen. The resulting stream of paraffine will be composed of a variety of polymers with different lengths and masses. How can we make such materials stable, and for example prevent these waxes from leaking through the graphene shells we add to them?鈥�

Simulations and experiments
In the new project, two PhD researchers will be working on different aspects of the task at hand. The first researcher is a joint PhD between 黑料福利网 and University of Twente, who will be simulating the interface between the wax and the graphene in order to predict how the thermal conductivity of the combined system is influenced by for example the morphology and composition of the wax. The second PhD student will be shared between two experimental groups of 黑料福利网, and will be more focused on the chemical synthesis and characterization of the wax/graphene combination.

According to literature, the thermal conductivity of the combination will not be that much higher than that from the wax alone. 鈥楤ut we want to go orders of magnitude higher. To that end, we will explore exotic morphologies. One of our current ideas is to grow 鈥渉airs鈥� of wax to improve the interface between the wax and the graphene. It would be great if we could achieve good conductivity, and also explain why we were successful by providing insights in mechanisms of thermal losses and gains.鈥�

Together with Bernard Geurts in Twente, Lyulin himself will be focusing on the simulation part. Heiner Friedrich from the Department of Chemical Engineering and Chemistry will synthesize and characterize the wax/graphene droplets. And finally, Henk Huinink from Lyulin鈥檚 own department will measure the resulting thermal conductivity.

Wax filled walls
The resulting wax is envisioned to be used for short term heat storage, Lyulin explains. 鈥榃e are for example considering applications in the built environment, where we insert the wax into the walls. During the day, the wax takes up the heat from the sun and melts, thus cooling the house. During the night, the wax crystallizes into a solid, releasing the heat again, preventing the house from  cooling down.鈥�