HIGH TEMPERATURE NANOMANUFACTURING FOR EMERGING TECHNOLOGIES
MetadataShow full item record
High temperature processing can provide sufficient activation energy for materials’ compositional, structural, and morphological evolutions, and is essential for various kinds of reactions, synthesis, and post-treatment. However, the current high temperature heating sources, mostly furnaces, are far from satisfying for nanomaterials processing owing to their bulky size and limited temperature and ramp range (~1300 K, ~10 K/min). In this thesis, we have focused on the study of electrical triggered Joule heating as a new route for high temperature engineering of nanomaterials toward nanomanufacturing. We developed facile, highly stable and controllable heating strategies for micro/nanoscale high temperature engineering. Ultrahigh temperature annealing (>2500 K) is applied to carbon nanomaterials to address the defects and poor interfacial problems. In the carbon nanofibers (CNFs), the high temperature graphitizes the carbon nanomaterials with significantly improved crystallinity and less defects. Importantly, the rapid heating (~100 K/min) leads to junction welding at fiber intersections. Similarly in carbon nanotubes (CNTs), welded CNTs is achieved by incorporating a thin polymer coating, followed by high temperature annealing to form 3D interconnected structures, defined as an “epitaxial welding” process. Ultrafast thermal shock (~2000 K in 55 ms) is applied to metal salt loaded carbon substrates for in-situ synthesis of ultrasmall, well-dispersed nanoparticles. Metal salts decompose rapidly at high temperatures and nucleate into well-dispersed nanoparticles during the rapid cooling (rate of ~10E5 K/s). By varying the composition in salt mixtures, we synthesized bimetallic, multimetallic and high entropy alloy nanoparticles (HEA-NPs) containing up to 8 different and immiscible elements. The high temperature leads to atomic mixing in the liquid alloy state, while rapid quenching freezes the completely mixed state to form solid solution nanoparticles with a narrow size distribution. This is for the first time HEA-NPs were synthesized, enabled by the unique thermal shock method. We also developed scalable approaches such as employing non-contact radiative heating for large scale substrates (either conductive or non-conductive) and continuous roll-to-roll production. The high temperature engineering on nanomaterials are highly facile, energy-efficient, and reliable toward scalable nanomanufacturing. More exciting results and products are expected for various nanomaterials during/after the unique high temperature engineering.