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

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/(m² 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

Heat Transport in Clathrate Hydrates Controlled by Guest Frequency and Host–Guest Interaction

The underlying mechanism of common limited lattice thermal conductivity (κ) in energy-related host–guest crystalline compounds has been an ongoing topic in recent decades. Here, the guest-triggered intrinsic ultralow κ of the representative xenon clathrate hydrate was investigated using the time domain thermoreflectance technique and theoretical calculations. The localized guest modes were observed to hybridize with acoustic branches and severely limit the acoustic κ contribution. Besides, the strong mode coupling enables the reshaping of the overall lattice dynamics, especially for optical branches. More importantly, we identified that guest fillers prompt great phonon scattering in wide frequencies, which originates from both the guest-frequency-controlled enhancement of phase space and the host–guest-interaction-governed lattice anharmonicity. The extremely low guest frequency and strong host–guest interaction and coupling were thereby underlined to play vital but distinct roles in κ minimization. Our results unveil the dominant factors of guest reduction effects and facilitate the design of efficient thermoelectric or other thermal-related materials