This work summarizes the recent progress on the thermal transport properties of 3D nanostructures, with an emphasis on experimental results. Depending on the applications, different 3D nanostructures can be prepared or designed to either achieve a low thermal conductivity for thermal insulation or thermoelectric devices or a high thermal conductivity for thermal interface materials used in the continuing miniaturization of electronics. A broad range of 3D nanostructures are discussed, ranging from colloidal crystals/assemblies, array structures, holey structures, hierarchical structures, to 3D nanostructured fillers for metal matrix composites and polymer composites. Different factors that impact the thermal conductivity of these 3D structures are compared and analyzed. This work provides an overall understanding of the thermal transport properties of various 3D nanostructures, which will shed light on the thermal management at nanoscale.
A Schottky UV photodetector based on graphene/ZnO:Al nanorod-array-film (AZNF) structure has been fabricated. Different from the previously reported graphene/ZnO photodetectors, this photodetector has a stable Schottky barrier which does not disappear under UV light. Thus, the UV photodetector can work as a high-performance self-powered device. The key to improve the stability of the Schottky barrier is a two-step surface treatment process. As a result, the self-powered photodetector exhibits a UV-to-visible rejection ratio of about 1 × 10, a responsivity of 0.039 A W, a short rise time of 37 μs, and a decay time of 330 μs. Furthermore, the photodetector is able to keep the responsivity under low light conditions. In comparison with the previously reported graphene/ZnO UV photodetectors, the photodetector exhibits a higher responsivity at zero bias and a faster response speed. This study provides a potential way to fabricate high-performance self-powered UV photodetectors.
The direct-current simulation burning method was used to investigate the burn-resistant behavior of Ti14 titanium alloy. The results show that Ti14 alloy exhibits a better burn resistance than TC4 alloy (Ti-6Al-4V). Cu is observed to preferentially migrate to the surface of Ti14 alloy during the burning reaction, and the burned product contains Cu, Cu 2 O, and TiO 2 . An oxide layer mainly comprising loose TiO 2 is observed beneath the burned product. Meanwhile, Ti 2 Cu precipitates at grain boundaries near the interface of the oxide layer, preventing the contact between O 2 and Ti and forming a rapid diffusion layer near the matrix interface. Consequently, a multiple-layer structure with a Cu-enriched layer (burned product)/Cu-lean layer (oxide layer)/Cu-enriched layer (rapid diffusion layer) configuration is formed in the burn heat-affected zone of Ti14 alloy; this multiple-layer structure is beneficial for preventing O 2 diffusion. Furthermore, although Al can migrate to form Al 2 O 3 on the surface of TC4 alloy, the burn-resistant ability of TC4 is unimproved because the Al 2 O 3 is discontinuous and not present in sufficient quantity.
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