On 10 December 2018, Professor Liangbing Hu from the University of Maryland at College Park, Dr. Wei Luo from Tongji University, and co-workers developed a method for catalyst-free, in-situ synthesis of carbon nanotubes in confined space via high temperature thermal shock. The related results were published in Research entitled “Catalyst- Free In Situ Carbon Nanotube Growth in Confined Space via High Temperature Gradient" (Research 2018 Article ID: 1793784 DOI: 10.1155/2018/1793784) https://spj.sciencemag.org/research/2018/1793784/.
Carbon materials, such as graphite, carbon nanotubes (CNTs) and graphene, have been widely used in the fields of batteries, capacitors and composite materials, and their demand has been increasing in recent years. Studies on the conversion between different types of carbon, especially from the rich low-cost carbon to high-end carbon allotropes, have attracted widespread interest. Conventional methods for synthesizing high-end carbon allotropes including chemical deposition, laser heating, conventional high-temperature furnace catalytic growth, etc., generally require the addition of a catalyst, take a long time, and/or consume a large amount of energy, which are disadvantageous for low-cost, large-scale, and rapid preparation of high-end carbon allotropes.
Recently, Professor Liangbing Hu of the University of Maryland at College Park, Dr. Wei Luo, a researcher at Tongji University, and co-workers have developed a method for catalyst-free, in-situ synthesis of carbon nanotubes in confined space via high temperature thermal shock. In the absence of an external catalyst or an external carbon source, biomass-derived amorphous carbon and defective reduced graphene oxide (RGO) can be rapidly converted to carbon nanotubes in a highly confined space by high temperature Joule heating.
Figure 1 Morphology and microstructure of the carbonaceous composite of carbon nanotubes in-situ grown in carbonized wood.
Combined with experimental measurements and molecular dynamics simulations, we propose the growth mechanism of carbon nanotubes in confined space via Joule heating. Defective locations in amorphous carbon or RGO produce high local temperatures due to high local electrical resistance, resulting in a high local temperature gradient that drives the migration of carbon atoms and promotes the growth of carbon nanotubes.
Figure 2 MD simulations of the catalyst-free, in situ, and fast formation of CNTs within the confined carbon structure.
For the first time, we realized the conversion of inexpensive carbon materials to high-end carbon allotropes without external catalysts or external carbon sources, and revealed that Joule heating-assisted, defects induced local ultra-high temperature gradients driving carbon nanotube growth mechanisms. This mechanism is equally applicable to the growth of other high aspect ratio nanomaterials. At the same time, the carbonaceous composite in which one-dimensional carbon nanotubes are grown in situ in a two-dimensional or three-dimensional carbon matrix has potential application prospects in energy storage, electrocatalysis, water treatment and other energy environmental fields.
Tag: Emerging materials research