Search

As electronic devices continue to shrink in size while increasing in power, the generation of significant waste heat has become a major obstacle to further progress. Effective thermal management is crucial for the ongoing development of electronic devices. One promising approach to tackle this challenge is by manipulating the orientation of materials to enhance their anisotropic thermal conductivity, thereby enabling efficient heat dissipation in electronic devices. This paper aims to provide a comprehensive review of various strategies used to prepare oriented materials and their applications in the field of electronic device thermal management. Additionally, the challenges associated with these processes are summarized, offering insights into the current limitations and potential areas for improvement. [ABSTRACT FROM AUTHOR]

Thermal management of electronic devices under extreme temperature conditions is very important. Carbon-based materials with low thermal resistance are beneficial for cooling electronic devices, while aerogels with high thermal resistance play a role in thermal insulation. However, achieving both thermal conduction and thermal insulation using the same material is a significant challenge. Herein, a graphene aerogel was synthesized by a solvothermal method, and the thermal resistance of the graphene aerogel was decreased by high-temperature annealing. The elastic graphene aerogel with tunable thermal resistance makes it possible to have dual functions of thermal insulation and thermal conduction. The thermal resistance of the graphene aerogel with 80% compressive strain is 3.3 times lower than that of the original state. During the process of thermal management for lithium-ion batteries (LIBs), the original graphene aerogel acts like a thermal insulator, preventing heat loss from LIBs when the ambient temperature is low (−20 °C), resulting in a temperature improvement of 9 °C and enhancing the discharge capacity of LIBs by 26%. In contrast, when the operating temperature is high (40 °C), the compressed graphene aerogel with low thermal resistance acts as a thermal interface material, dissipating the excessive heat from LIBs and preventing overheating. [ABSTRACT FROM AUTHOR]

WTe2, a low-symmetry transition metal dichalcogenide, has broad prospects in functional device applications due to its excellent physical properties. When WTe2 flake is integrated into practical device structures, its anisotropic thermal transport could be affected greatly by the substrate, which matters a lot to the energy efficiency and functional performance of the device. To investigate the effect of SiO2/Si substrate, we carried out a comparative Raman thermometry study on a 50 nm-thick supported WTe2 flake (with κzigzag = 62.17 W·m−1·K−1 and κarmchair = 32.93 W·m−1·K−1), and a suspended WTe2 flake of similar thickness (with κzigzag = 4.45 W·m−1·K−1, κarmchair = 4.10 W·m−1·K−1). The results show that the thermal anisotropy ratio of supported WTe2 flake (κzigzag/κarmchair ≈ 1.89) is about 1.7 times that of suspended WTe2 flake (κzigzag/κarmchair ≈ 1.09). Based on the low symmetry nature of the WTe2 structure, it is speculated that the factors contributing to thermal conductivity (mechanical properties and anisotropic low-frequency phonons) may have affected the thermal conductivity of WTe2 flake in an uneven manner when supported on a substrate. Our findings could contribute to the 2D anisotropy physics and thermal transport study of functional devices based on WTe2 and other low-symmetry materials, which helps solve the heat dissipation problem and optimize thermal/thermoelectric performance for practical electronic devices. [ABSTRACT FROM AUTHOR]

Steadily, continuously, and precisely adjusting infrared emissivity of materials is of great importance for various applications, such as thermal camouflage. Herein, a method is proposed to fine-tune the emissivity of multilayer graphene (MLG) by ion intercalation with assistance of pulse voltage. The dynamic ion intercalation process in MLG-based emissivity modulators is investigated by a home-made electrical-optical synchronizing test system, which consists of a potentiostat and a thermal camera. It is observed that the apparent temperature of MLG is closely correlated with pulse duration and residual charges. Based on a second-order RC model, the ion transportation and charge transfer in the modulator are likely affected by three factors (i.e., internal resistance, electric field, and concentration gradient), which changes the doping level of MLG. Hence, the emissivity of MLG can be finely adjusted by regulating the duration of the voltage pulse. This also leads to a wavelength dependence of emissivity modulation, which is confirmed by Fourier transform infrared spectroscopy. The observations offer a promising venue for precise and continuous adjustment of MLG's emissivity, which is of great significance for many practical applications, such as simulating complex and subtle thermal images. [ABSTRACT FROM AUTHOR]

Actively controlling the infrared emissivity of materials is critical for many applications, such as radiative cooling and thermal camouflage. Multilayer graphene (MLG) has shown great potential as a functional material with a tunable infrared emissivity. However, the spatial homogeneity in adjusting MLG's emissivity through ion intercalation is rather poor, which limits its practical applications. Here, we study how mixing various molecular components (e.g., ethanol) with ionic liquids affects the performance of MLG-based infrared emissivity modulators. The results indicate that introducing a moderate concentration of molecular components not only significantly improves spatial homogeneity in tuning emissivity but also enhances modulation depth, dynamic response, and the stability of the modulators. This is likely due to the increasing conductivity of the mixture and the improved wetting properties between the mixture and the separator, which leads to more effective charge transfer from ions in ionic liquids to carbons in graphene. The microscopic structure of MLG, revealed by Raman spectroscopy, confirms that the improvement in modulator performance is mostly due to homogeneous transportation of ions in the modulators. This not only sheds light on the underlying physics of the modulator but also greatly expands the options when selecting ionic liquids, thereby opening a new route for the modulator design. [ABSTRACT FROM AUTHOR]