Advanced Three-Dimensional Structural Carbon Nanomaterials

[摘要] Carbon nanomaterials, such as carbon nanotubes (CNTs) and graphene, aremost intensively investigated carbon allotropes because of their outstandingphysical and chemical properties. Recently, it has been realized that threedimensional(3D) carbon-based structures with nanoscale interconnection providethe remarkably improved properties required for critically needed applications. Theproperties of 3D-CNTs and graphene architectures can be tweaked for variousapplications. Therefore, 3D carbon-based solids with nanoscale intermolecularjunctions present an exciting research area and provide opportunities forfabrication of various 3D-macroscopic architectures with unexpected properties.The creation of nanoengineered 3D-macroscopic structures in a scalable syntheticprocess still remains a challenge. The fundamental problem is the difficulty inintroducing atomic-scale junctions between individual nanoscale structures so thatthey can be organized as covalently interconnected nanostructured networks withcontrollable physical characteristics, such as density and porosity. Here, 3Dstructures have been created using chemical vapor deposition method, solutionbasedchemistry technique and welding method via hypervelocity impact method togenerate atomic-scale junction between carbon nanostructures.The scalable fabrication of 3D macroscopic scaffolds with differenthierarchical interconnected structures and soldering-like junctions between CNTsusing chemical vapor deposition (CVD) technique is reported. These intermolecularjunctions of CNTs result in a high thermal stability, high electrical conductivity,excellent mechanical properties, as well as excellent structural stability in aconcentrated acid, base, and organic solvents. The CNT solids with such tremendousproperties represent the next generation of carbon-based materials with a broadrange of potential applications; we demonstrate here a couple such utility impactdamping, removal oil from contaminated water and as a marker for the oil industry.Additionally, in situ nano-indentation inside a scanning electron microscopy (SEM)were used to determine the mechanical response of individual covalent junction,formed in different configurations such as ;;X”, ;;Y” and ;;” shapes betweenindividual CNTs. Fully atomistic reactive molecular dynamics simulations are usedto support the experimental results as well as to study the deformation behavior ofjunctions.Vertically aligned multiwall carbon nanotube forests (NTF) synthesized bywater assisted CVD method and both sides functionalized with differentfunctionalities as hydrophobic and hydrophilic. The produced hygroscopic nanotubeforest demonstrate for water harvesting from air.The second approach has been used in this work is solution chemistry to generatecrosslinking nanotube structures. The scalable synthesis of 3D macroscopic solids madeof covalently connected nanotubes via Suzuki cross-coupling reaction, a well-knowncarbon-carbon covalent bond forming reaction in organic chemistry. The resulting CNTssolids are made of highly porous, interconnected structures made of chemically crosslinkedcarbon nanotubes after freeze-drying process. CNTs solids demonstrated one suchutility in the removal of oil from contaminated water.In another approach hypervelocity impact method was used to investigatemechanical behavior of CNTs. The hypervelocity impact of CNT bundles againstmetallic targets resulted their unzipping along the tube axis, which leads to the formationof graphene nanoribbons, nanodiamonds and covalently interconnected carbonnanostructures depending on the velocity and impact geometry. This new process canproduce chemical-free, high-quality graphene nanoribbons. The experimental resultssupported by fully atomistic reactive molecular dynamics simulations were used to gainfurther insights of the pathways and deformation and fracture mechanisms

[发布机构] Rice University

[效力级别] Carbon