A poor understanding of interfacial phenomena is a critical issue that hinders the development of high-performance nanocarbons/Al composites. In this study, the interfacial strength between a single carbon nanotube (CNT) and the Al matrix was quantitatively evaluated as 24.8 MPa using an in-situ pullout system inside an SEM chamber, indicating an approximately 60% load transfer efficiency at the nanocarbon-Al interface. This result confirms that insufficient interfacial strength is the primary reason for the lower composite strength compared to theoretical estimations. To further enhance interfacial load transfer, a combination of CNT surface modification and interfacial reaction control was proposed. Mild acid treatment not only mitigated CNT aggregation in the metal matrix but also effectively controlled the formation of nanodefects on the CNT surface. Moreover, precise heat treatments were employed to facilitate interfacial reactions between CNTs and the Al matrix. The effects of heat treatment conditions on the morphology and size of the Al₄C₃ phase, as well as its formation mechanism, were clarified based on microstructure observations. Furthermore, the influence of interfacial reactions on the mechanical performance and thermal expansion behaviors of nanocarbon/Al composites was analyzed in detail, demonstrating that the formation of appropriate carbides significantly could improve the interfacial bonding. The findings of this study provide guidelines for designing high-quality nanocarbon-metal interfaces and offer new insights into the functionalization of composite materials.

Thermoelectric conversion is expected to be useful for improving energy efficiency. Developments of high-performance thermoelectric materials, however, are challenging because of the trade-off between electrical and thermal properties. Here, we show our studies of enhancing thermoelectric power factor by using the interaction of carriers and magnetism. The first example is the antiferromagnetic semiconductor CuFeS₂. A high power-factor of 1 mW/K²m is achieved for the CuFeS₂-based alloys, where the antiferromagnetic ordering of Fe magnetic moment is coupled with the carrier electrons, leading to large Seebeck coefficients. This finding motivated us to the second example, dilute magnetic semiconductors CuGa_1-xMn_xTe₂. Enhanced power factor and ZT are obtained for slight Mn-doping with x = 0.01 to 0.03. Strong coupling of carriers and magnetic moments was clarified by the magnetic and transport measurements. Finally, the case of itinerant-electron ferromagnet is described. Magnetization studies demonstrate that the Heusler alloys Fe₂V_1-xM_xAl_1-ySi_y (M = Cr, Fe) are classified as itinerant-electron weak ferromagnetic metals. Distinct increase in the Seebeck coefficient around the Curie temperature is observed, indicating the contribution of spin fluctuation. Increase in thermopower due to magnetic interaction occurs in a wide temperature range, thereby is helpful for the application of thermoelectric devices near room temperature.