Passive cooling techniques are widely sought-after solutions to thermal management issues in high power electronics due to increased energy dissipation in reduced areas. Phase change materials (PCMs) present a promising secondary passive thermal management opportunity by absorbing a large amount of energy as an isothermal process. This phenomenon can be utilized in various ways as a thermal management tool; including temperature spike alleviation, energy storage, and secondary passive cooling. Though PCMs have promising passive cooling ability, often it is difficult to select an appropriate or effective PCM for the specific application due to deficiencies in a particular material property. Previous studies have demonstrated the ability to alter PCM properties through the homogeneous inclusion of nanoparticles. Thermal conductivity is a particularly important metric for enhancement via nanoparticles due to the typically low conductivity of PCMs with high latent heats. Previous studies demonstrate the successful augmentation of this property. A large limiting factor to enhanced PCM passive cooling is related to the propagation of the melt front, representing the region of large energy absorption. In many cases, the melt front moves too slowly to effectively transfer energy away from the device. Slow material response time can also be problematic in the re-solidification process, limiting cyclability. Work has been conducted to monitor the melt front response to a thermal load. Early in the melting process, conduction dominates the heat transfer mechanism. This paper will examine the impact of nanoparticle inclusion as a means of controlling the melt front propagation. Using nanoparticles to control the composite thermal conductivity should lead to optimization ability of PCM melt characteristics to align with thermal management needs.

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Magnetic field sensors based on the Hall-effect have a variety of applications such as current sensing in power electronics and position and velocity sensing in vehicles. Additionally, they have benefits such as easy integration into circuits, low manufacturing cost, and linearity over a wide range of magnetic fields. However, in order to use these devices in an industrial or automotive setting, the effect of high temperatures on the reliability of the Hall-effect sensors needs to be evaluated. This study focuses on the effect of high temperature on the electrical and material properties of novel gallium nitride (GaN)-based Hall-effect sensors and the impacts on the reliability of these devices. Changes in device properties such as resistance and electrical response, as well as on the metallic contacts, are examined, using two sets of devices made with different substrates and contact metals. A probe station is used to characterize electrical responses, while an X-ray Photoelectron Spectrometer (XPS) and Electron-Diffuse X-ray (EDX) are used to characterize material interactions. The findings include saturation curves, the presence of gallium on the contacts of the octagonal device, and the activation energy of reaction responsible for resistance increase for the octagonal AlGaN/GaN devices. Additionally, the Greek cross AlGaN/GaN Hall sensors showed excellent thermal stability.

High power electronics are a key component in the electrification of aircraft. Large amounts of power need to be handled onboard to generate sufficient lift for flight. The transient nature of the aircraft's mission profile produces varied loading and environmental influences, making consistent cooling and device reliability difficult to maintain. Due to limitations in weight and performance metrics, the thermal management capability becomes a key inhibiting factor in preventing adoption of all electric aircraft. Many efforts are focused on the improvement of high-powered electronics such as the inverters, batteries, and motors, but there is a need for increased focus on the implications of each improved device on the total system with regards to thermal management. To address the many concerns for thermal management within aviation, this paper will review the prevalent factors of flight and couple them to their respective challenges to highlight the overarching effort needed to successfully integrate efficient electric propulsion devices with their protective thermal management systems. A review will be combined with a brief analytical study over inverter cooling to examine the effects of various transient parameters on the device temperature of an inverter in flight. The impact of failure in the cooling systems on the shutdown process will also be examined. Both studies are tied to the motivation for examining the impacts of new and transient challenges faced by electric power systems and help signify the importance of this focus as these systems become more present and capable within the aviation industry.