3 research outputs found

    Tuning the Interfacial Thermal Conductance between Polystyrene and Sapphire by Controlling the Interfacial Adhesion

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    In polymer-based electric microdevices, thermal transport across polymer/ceramic interface is essential for heat dissipation, which limits the improvement of the device performance and lifetime. In this work, four sets of polystyrene (PS) thin films/sapphire samples were prepared with different interface adhesion values, which was achieved by changing the rotation speeds in the spin-coating process. The interfacial thermal conductance (ITC) between the PS films and the sapphire were measured by time domain thermoreflectance method, and the interfacial adhesion between the PS films and the sapphire, as measured by a scratch tester, was found to increase with the rotation speed from 2000 to 8000 rpm. The ITC shows a similar dependence on the rotation speed, increasing up to a 3-fold from 7.0 ± 1.4 to 21.0 ± 4.2 MW/(m<sup>2</sup> K). This study demonstrates the role of spin-coating rotation speed in thermal transport across the polymer/ceramic interfaces, evoking a much simpler mechanical method for tuning this type of ITC. The findings of enhancement of the ITC of polymer/ceramic interface can shed some light on the thermal management and reliability of macro- and microelectronics, where polymeric and hybrid organic–inorganic nano films are employed

    Role of Hydrogen Bonds in Thermal Transport across Hard/Soft Material Interfaces

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    The nature of the bond is a dominant factor in determining the thermal transport across interfaces. In this paper, we study the role of the hydrogen bond in thermal transport across interfaces between hard and soft materials with different surface functionalizations around room temperature using molecular dynamics simulations. Gold (Au) is studied as the hard material, and four different types of organic liquids with different polarizations, including hexane (C<sub>5</sub>H<sub>11</sub>CH<sub>3</sub>), hexanamine (C<sub>6</sub>H<sub>13</sub>NH<sub>2</sub>), hexanol (C<sub>6</sub>H<sub>13</sub>OH), and hexanoic acid (C<sub>5</sub>H<sub>11</sub>COOH), are used to represent the soft materials. To study the hydrogen bonds at the Au/organic liquid interface, three types of thiol-terminated self-assembled monolayer (SAM) molecules, including 1-hexanethiol [HS­(CH<sub>2</sub>)<sub>5</sub>CH<sub>3</sub>], 6-mercapto-1-hexanol [HS­(CH<sub>2</sub>)<sub>6</sub>OH], and 6-mercaptohexanoic acid [HS­(CH<sub>2</sub>)<sub>5</sub>COOH], are used to functionalize the Au surface. These SAM molecules form hydrogen bonds with the studied organic liquids with varying strengths, which are found to significantly improve efficient interfacial thermal transport. Detailed analyses on the molecular-level details reveal that such efficient thermal transport originates from the collaborative effects of the electrostatic and van der Waals portions in the hydrogen bonds. It is found that stronger hydrogen bonds will pull the organic molecules closer to the interface. This shorter intermolecular distance leads to increased interatomic forces across the interfaces, which result in larger interfacial heat flux and thus higher thermal conductance. These results can provide important insight into the design of hard/soft materials or structures for a wide range of applications
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