The long-standing popularity of thermoelectric materials has contributed to the creation of various thermoelectric devices and stimulated the development of strategies to improve their thermoelectric performance. In this review, we aim to comprehensively summarize the state-of-the-art strategies for the realization of high-performance thermoelectric materials and devices by establishing the links between synthesis, structural characteristics, properties, underlying chemistry and physics, including structural design (point defects, dislocations, interfaces, inclusions, and pores), multidimensional design (quantum dots/wires, nanoparticles, nanowires, nano- or microbelts, few-layered nanosheets, nano- or microplates, thin films, single crystals, and polycrystalline bulks), and advanced device design (thermoelectric modules, miniature generators and coolers, and flexible thermoelectric generators). The outline of each strategy starts with a concise presentation of their fundamentals and carefully selected examples. In the end, we point out the controversies, challenges, and outlooks toward the future development of thermoelectric materials and devices. Overall, this review will serve to help materials scientists, chemists, and physicists, particularly students and young researchers, in selecting suitable strategies for the improvement of thermoelectrics and potentially other relevant energy conversion technologies.

Advanced Thermoelectric Design: From Materials and Structures to Devices

One-dimensional carbon nanotubes and two-dimensional graphene nanosheets with unique electrical, mechanical and thermal properties are attractive reinforcements for fabricating light weight, high strength and high performance metal-matrix composites. Rapid advances of nanotechnology in recent years enable the development of advanced metal matrix nanocomposites for structural engineering and functional device applications. This review focuses on the recent development in the synthesis, property characterization and application of aluminum, magnesium, and transition metal-based composites reinforced with carbon nanotubes and graphene nanosheets. These include processing strategies of carbonaceous nanomaterials and their composites, mechanical and tribological responses, corrosion, electrical and thermal properties as well as hydrogen storage and electrocatalytic behaviors. The effects of nanomaterial dispersion in the metal matrix and the formation of interfacial precipitates on these properties are also addressed. Particular attention is paid to the fundamentals and the structure–property relationships of such novel nanocomposites.

Recent progress in the development and properties of novel metal matrix nanocomposites reinforced with carbon nanotubes and graphene nanosheets

Functionally graded materials: A review of fabrication and properties

Based on the concept of band bending at metal/semiconductor interfaces as an energy filter for electrons, we present a theory for the enhancement of the thermoelectric properties of semiconductor materials with metallic nanoinclusions. We show that the Seebeck coefficient can be significantly increased due to a strongly energy-dependent electronic scattering time. By including phonon scattering, we find that the enhancement of $ZT$ due to electron scattering is important for high doping, while at low doping it is primarily due to a decrease in the phonon thermal conductivity.

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Theory of enhancement of thermoelectric properties of materials with nanoinclusions.

Progress in additive manufacturing on new materials: A review

Concept and P/M fabrication of functionally gradient materials

Interface and interfacial reactions in multi-walled carbon nanotube- reinforced aluminum matrix composites

On the role of amorphous intergranular and interfacial layers in the thermal conductivity of a multi-walled carbon nanotube-copper matrix composite

Fabricating high-strength Al matrix composites without sacrificing their electrical conductivity is a critical issue in the design of Al-based conductors. Here, we demonstrate for the first time, an example of improving the interfacial load transfer and strength of few-layer graphene (FLG)/Al composites by an appropriate interfacial reaction. Monocrystalline Al4C3 nanorods that tightly conjoined the FLG platelets with the Al matrix were produced by manipulating the sintering temperature. As revealed by transmission electron microscopy and by a shear lag model that provides a quantitative estimate of the strengthening, the Al4C3 nanorods ensured an efficient load transfer at the FLG-Al interface, thereby giving rise to a considerable enhancement of strength in the composite. Moreover, the electrical conductivity is almost as high as that of pure Al, which could be a significant step toward the preparation of high-performance Al-based conductors.

Akira Kawasaki

Papers

Concept and P/M fabrication of functionally gradient materials

Interface and interfacial reactions in multi-walled carbon nanotube- reinforced aluminum matrix composites

On the role of amorphous intergranular and interfacial layers in the thermal conductivity of a multi-walled carbon nanotube-copper matrix composite

Interfacial reaction induced efficient load transfer in few-layer graphene reinforced Al matrix composites for high-performance conductor

Worldwide trends in functional gradient materials research and development