Surface-mediated Al particles are synthesized by incorporating the stable fluoride reaction of Al-F on a pure Al surface in place of natural oxides. Al particles with fluoro-polymer directly adsorbed on the surface show a considerable capability to overcome limitations caused by the surface oxide. Here, we report that Al fluoride when spontaneously formed at the poly(vinylidene fluoride)/Al interface serves as an oxidation-protecting layer while also providing an efficient combustion path along which the internal Al rapidly reacts with external oxygen atoms. Both thermal oxidation and explosion tests of the poly(vinylidene fluoride)/Al particles show superior exothermic enthalpy energy and simultaneously rapid oxidation reactivity compared to those of Al₂O₃ passivated Al particles. It is clearly elucidated that the enhanced energetic properties of Al particles mediated by poly(vinylidene fluoride) originate from the extraordinary pyrolytic process of Al fluoride occurring at a low temperature compared to Al₂O₃ passivated Al. Hence, these results clarify that the surface mediation of Al particles can be significantly considered as advanced technology for many energetic applications.

Aluminum powders are known to provide outstanding volumetric exothermic enthalpy energy during thermal oxidation. However, the amount of energy released tends to be limited by the dense surface oxide (Al₂O₃) layer of the powder. Hence, a prerequisite for improving the reactivity of passivated Al particles is to remove the Al₂O₃ film from the surface. Considering that the self-propagating high-temperature synthesis (SHS) reaction of Ni and Al can generate additional exothermic heat in Al powder, Ni can be considered as a promising alternative to the surface oxide layer. Here, we report oxide-layer-free fine Al particles with a characteristic Ni/Al interface, where a Ni layer replaces the Al₂O₃ film. The microstructure of the synthesized powder consists of a 200-nm-thick Ni layer homogeneously coated on the Al surface, which has nanosized craters caused by the geometrical removal of Al₂O₃. Thermal analysis and in-situ heating transmission electron microscopy (TEM) results clearly show that active interdiffusion of atoms through the Ni/Al interface results in the formation of intermetallic compounds to provide additional exothermic energy, compared to the result for simply mixing Ni and Al powders. Hence, these findings provide new routes for the design and application of reactive metallic particles using the SHS reaction.

Alumina nanoparticle‐dispersed bismuth‐antimony‐tellurium matrix (Al₂O₃/BST) composite powders were fabricated by using ball milling process of alumina nanoparticle about 10 nm and p‐type bismuth telluride nanopowders prepared from the mechanochemical process (MCP). The fabricated Al₂O₃/BST composite powders were a few hundreds of nanometer in size, with a clear Bi_0.5Sb_1.5Te₃ phase. The composite powders were consolidated into p‐type bulk composite by spark plasma sintering process. High‐resolution TEM images reveal that alumina nanoparticles were dispersed among the grain boundary or in the matrix grain. The sintered 0.3 vol.% Al₂O₃/BST composite exhibited significantly improved power factor and reduced thermal conductivity in the temperature ranging from 293 to 473 K compared to those of pure BST. From these results, the highly increased ZT value of 1.5 was obtained from 0.3 vol.% Al₂O₃/BST composite at 323 K.

Carbon nanotube/bismuth‐selenium‐tellurium composites were fabricated by consolidating CNT/Bi₂(Se,Te)₃ composite powders prepared from a polyol‐reduction process. The synthesized composite powders exhibit CNTs homogeneously dispersed among Bi₂(Se,Te)₃ matrix nanopowders of 300 nm in size. The powders were densified into a CNT/Bi₂(Se,Te)₃ composite in which CNTs were randomly dispersed in the matrix through spark plasma sintering process. The effect of an addition of Se on the dimensionless figure‐of‐merit (ZT) of the composite was clearly shown in 3 vol.% CNT/Bi₂(Se,Te)₃ composite as compared to CNT/Bi₂Te₃ composite throughout the temperature range of 298 to 473 K. These results imply that matrix modifications such as an addition of Se as well as the incorporation of CNTs into bismuth telluride thermoelectric materials is a promising means of achieving synergistic enhancement of the thermoelectric performance levels of these materials.