Carbon nanotube nanoreactors to stabilize metastable structures

April 27, 2019

Various metastable structures are usually found in the phase diagram of most materials. Some structures can only exist under high temperature or high pressure conditions, while others have not yet been predicted to be in the established phase diagrams. The experimental detection of these structures is a big challenge. The inner cavities of carbon nanotubes have been adopted by the research group led by Prof. Jinying Zhang from Xi'an Jiaotong University to produce and stabilize the metastable structures from high pressure or high temperature to ambient conditions. The carbon nanotubes serve as reaction vessels and growth templates to produce metastable structures due to the size effects and special physical and chemical environments of carbon nanotubes. The special nano-space of the carbon nanotube provides high-pressure conditions for material reactions. The pressure is related to the carbon nanotube inner diameters and the matching of the nanotube walls with the encapsulated materials. The carbon nanotube walls simultaneously isolate the as-produced structures from the surrounding environments. The pressure and size effects of the carbon nanotubes stabilize the as-produced metastable structures to ambient conditions. The pressure produced by the carbon nanotubes to the encapsulated materials can reach as high as 60 GPa, resulting in the synthesis of metastable structures from the high pressure areas of phase diagram and new structures out of the phase diagram.

The β and γ phases are usually observed by silver iodides at ambient conditions. The phase structures will transform into α phase with increasing temperature. The tetragonal, rock-salt, and potassium hydroxide-like phases are detected subsequently with increasing pressures. The silver iodides have been encapsulated into two different types of carbon nanotubes. One is multi-walled carbon nanotubes (MWCNTs) with inner diameters of 4 to 8 nm and the other is single-walled carbon nanotubes (SWCNTs) with inner diameters of about 1.4 nm. Two different metastable silver iodide structures, including rock-salt and helix structures, have been produced and stabilized into ambient conditions by using the special nano-cavities of carbon nanotubes. The rock-salt phase is usually observed at pressure between 400 MPa and 11.3 GPa in the phase diagram, while the helix structure has not yet predicted in the phase diagram of silver iodides. The successful synthesis and stabilization of rock-salt and helix structures to ambient conditions by using carbon nanotube nanoreactors provide a new path to the synthesis and application of metastable structures from extreme conditions.
This research received funding from the National Natural Science Foundation of China (21771143). J. Zhang is supported by the Cyrus Tang Foundation through Tang Scholar Program.

See the article:

Hongyang Huang, Jinying Zhang, Yifan Zhang, Chengcheng Fu, Jialiang Huang, Yonghong Cheng, Chunming Niu, Xinluo Zhao and Hisanori Shinohara

Rock-salt and helix structures of silver iodides under ambient conditions

Natl Sci Rev (April 2019) doi: 10.1093/nsr/nwz041

The National Science Review is the first comprehensive scholarly journal released in English in China that is aimed at linking the country's rapidly advancing community of scientists with the global frontiers of science and technology. The journal also aims to shine a worldwide spotlight on scientific research advances across China.

Science China Press

Related Carbon Nanotubes Articles from Brightsurf:

How plantains and carbon nanotubes can improve cars
Researchers from the University of Johannesburg have shown that plantain, a starchy type of banana, is a promising renewable source for an emerging type of lighter, rust-free composite materials for the automotive industry.

New production method for carbon nanotubes gets green light
A new method of producing carbon nanotubes -- tiny molecules with incredible physical properties used in touchscreen displays, 5G networks and flexible electronics -- has been given the green light by researchers, meaning work in this crucial field can continue.

Growing carbon nanotubes with the right twist
Researchers synthetize nanotubes with a specific structure expanding previous theories on carbon nanotube growth.

Research shows old newspapers can be used to grow carbon nanotubes
New research has found that old newspaper provide a cheap and green solution for the bulk production of single walled carbon nanotubes.

Clean carbon nanotubes with superb properties
Scientists at Aalto University, Finland, and Nagoya University, Japan, have found a new way to make ultra-clean carbon nanotube transistors with superior semiconducting properties.

Dietary fiber effectively purifies carbon nanotubes
A dietary fiber can help separate out semiconducting carbon nanotubes used for making transistors for flexible electronics.

Why modified carbon nanotubes can help the reproducibility problem
Scientists at Tokyo Institute of Technology (Tokyo Tech) conducted an in-depth study on how carbon nanotubes with oxygen-containing groups can be used to greatly enhance the performance of perovskite solar cells.

Tensile strength of carbon nanotubes depends on their chiral structures
Single-walled carbon nanotubes should theoretically be extremely strong, but it remains unclear why their experimental tensile strengths are lower and vary among nanotubes.

New study reveals carbon nanotubes measurement possible for the first time
Swansea University scientists report an entirely new approach to manipulation of carbon nanotubes that allows physical measurements to be made on carbon nanotubes that have previously only been possible by theoretical computation.

Neural networks will help manufacture carbon nanotubes
A team of scientists from Skoltech's Laboratory of Nanomaterials proposed a neural-network-based method for monitoring the growth of carbon nanotubes, preparing the ground for a new generation of sophisticated electronic devices.

Read More: Carbon Nanotubes News and Carbon Nanotubes Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to