Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Carbon nanotubes grow in combustion flames

02.04.2014

A Japanese, American & Chinese team have revealed similarities between the molecular mechanism of carbon nanotube (CNT) growth and hydrocarbon combustion. The study published on Jan 24 in the journal Carbon, will identify new ways to control the growth of CNTs and increase the understanding of fuel combustion processes.

Professor Stephan Irle of the Institute of Transformative Bio-Molecules (WPI-ITbM) at Nagoya University and co-workers at Kyoto University, Oak Ridge National Lab (ORNL), and Chinese research institutions have revealed through theoretical simulations that the molecular mechanism of carbon nanotube (CNT) growth and hydrocarbon combustion actually share many similarities.


Copyright : ITbM, Nagoya University

In studies using acetylene molecules (ethyne; C2H2, a molecule containing a triple bond between two carbon atoms) as feedstock, the ethynyl radical (C2H), a highly reactive molecular intermediate was found to play an important role in both processes forming CNTs and soot, which are two distinctively different structures.

The study published online on January 24, 2014 in Carbon, is expected to lead to identification of new ways to control the growth of CNTs and to increase the understanding of fuel combustion processes.

CNTs are molecules with a cylindrical nanostructure (nano = 10E-9 m or 1 / 1,000,000,000 m). Arising from their unique physical and chemical properties, CNTs have found technological applications in the fields of electronics, optics and materials science.

CNTs can be synthesized by a method called chemical vapor deposition, where hydrocarbon vapor molecules are deposited on transition metal catalysts under a flow of non-reactive gas at high temperatures.

Current issues with this method are that the CNTs are usually produced as mixtures of nanotubes with various diameters and different sidewall structures. Theoretical simulations coordinated by Professor Irle have looked into the molecular mechanisms of CNT growth using acetylene molecules as feedstock (Figure 1). The outcome of their research provides insight into identifying new parameters that can be varied to improve the control over product distributions in the synthesis of CNTs.

High level theoretical calculations using quantum chemical molecular dynamics were performed to study the early stages of CNT growth from acetylene molecules on small iron (Fe38) clusters. Previous mechanistic studies have postulated complete breakdown of hydrocarbon source gases to atomic carbon before CNT growth.

“Our simulations have shown that acetylene oligomerization and cross-linking reactions between hydrocarbon chains occur as major reaction pathways in CNT growth, along with decomposition to atomic carbon” says Professor Stephan Irle, who led the research, “this follows hydrogen-abstraction acetylene addition (HACA)-like mechanisms that are commonly observed in combustion processes” he continues.

Combustion processes are known to proceed by the hydrogen-abstraction acetylene addition (HACA)-like mechanism. Initiation of the mechanism begins with hydrogen atom abstraction from a precursor molecule followed by acetylene addition, and the repetitive cycle leads to formation of ring-structured polycylic aromatic carbons (PAHs).

In this process, the highly reactive ethynyl radical (C2H) is continually being regenerated, extending the rings of PAHs and eventually forming soot. The same key reactive intermediate is observed in CNT growth and acts as an organocatalyst (a catalyst based on an organic molecule) facilitating hydrogen transfer reactions across growing hydrocarbon clusters. The simulations identify an intriguing bifurcation process by which hydrogen-rich hydrocarbon species enrich hydrogen content creating non-CNT byproducts, and hydrogen-deficient hydrocarbon species enrich carbon content leading to CNT growth (Figure 2).

“We started this type of research from 2000, and long simulation time has been a great challenge to conduct full simulations across all participating molecules, due to the relatively high strength of the carbon-hydrogen bond. By establishing and using a fast method of calculation, we were able to successfully incorporate hydrogen in our calculations for the first time, which led to this new understanding revealing the similarity between CNT growth and hydrocarbon combustion processes. This finding is very intriguing in the sense that these processes were long considered to proceed by completely different mechanisms” elaborates Professor Irle.

Results of these simulations illustrate the importance in the role of carbon chemical bonding and molecular transformations in CNT growth. Professor Irle explains, “Our simulations suggest new parameters, such as tuning hydrogen content to improve the control of CNT growth and soot formation. We wish to develop new methods to speed up techniques that will convince experimentalists and establish further tools to explore new possibilities that will contribute to the understanding of these important processes.”

###

This article “Quantum chemical simulations reveal acetylene-based growth mechanisms in the chemical vapor deposition synthesis of carbon nanotubes” by Ying Wang, Xingfa Gao, Hu-Jun Qian, Yasuhito Ohta, Xiaona Wu, Gyula Eres, Keiji Morokuma, Stephan Irle is published online on January 24, 2014 in Carbon.
DOI: 10.1016/j.carbon.2014.01.020 Carbon 2014, 72, 22-37

This work was conducted with Professor Ying Wang of Nagoya University and the Chinese Academy of Sciences, Professor Xingfa Gao of the Chinese Academy of Sciences, Professor Hu-Jun Qian of Jilin University, Professor Yasuhito Ohta of Kyoto University, Xiaona Wu of Nagoya University, Professor Gyula Eres of Oak Ridge National Laboratory and Professor Keiji Morokuma of Kyoto University and Emory University.

###

About WPI-ITbM (http://www.itbm.nagoya-u.ac.jp/)

The World Premier International Research Center Initiative (WPI) for the Institute of Transformative Bio-Molecules (ITbM) at Nagoya University in Japan is committed to advance the integration of synthetic chemistry, plant/animal biology and theoretical science, all of which are traditionally strong fields in the university. As part of the Japanese science ministry’s MEXT program, the ITbM aims to develop transformative bio-molecules, innovative functional molecules capable of bringing about fundamental change to biological science and technology. Research at the ITbM is carried out in a “Mix-Lab” style, where international young researchers from multidisciplinary fields work together side-by-side in the same lab. Through these endeavors, the ITbM will create “transformative bio-molecules” that will dramatically change the way of research in chemistry, biology and other related fields to solve urgent problems, such as environmental issues, food production and medical technology that have a significant impact on the society.


Author Contact
Professor Stephan Irle
Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University
Furo-Cho, Chikusa-ku, Nagoya 464-8601, Japan
TEL: +81-52-747-6397 FAX: +81-52-788-6151
E-mail: sirle@chem.nagoya-u.ac.jp

Public Relations Contact
Dr. Ayako Miyazaki
Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University
Furo-Cho, Chikusa-ku, Nagoya 464-8601, Japan
TEL: +81-52-789-4999 FAX: +81-52-789-3240
E-mail: ayako.miyazaki@itbm.nagoya-u.ac.jp

ITbM Press Office
press@itbm.nagoya-u.ac.jp

Nagoya University Public Relations Office
TEL: +81-52-789-2016 FAX: +81-52-788-6272
E-mail: kouho@post.jimu.nagoya-u.ac.jp

Associated links

Journal information

Carbon 2014, 72, 22-37

Ayako Miyazaki | ResearchSEA News
Further information:
http://www.researchsea.com

Further reports about: CNTs Carbon Chinese Kyoto Nagoya acetylene combustion hydrocarbon mechanism mechanisms processes soot

More articles from Physics and Astronomy:

nachricht Taking a spin on plasma space tornadoes with NASA observations
20.11.2017 | NASA/Goddard Space Flight Center

nachricht NASA detects solar flare pulses at Sun and Earth
17.11.2017 | NASA/Goddard Space Flight Center

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A “cosmic snake” reveals the structure of remote galaxies

The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.

Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...

Im Focus: Visual intelligence is not the same as IQ

Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.

That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...

Im Focus: Novel Nano-CT device creates high-resolution 3D-X-rays of tiny velvet worm legs

Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.

During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....

Im Focus: Researchers Develop Data Bus for Quantum Computer

The quantum world is fragile; error correction codes are needed to protect the information stored in a quantum object from the deteriorating effects of noise. Quantum physicists in Innsbruck have developed a protocol to pass quantum information between differently encoded building blocks of a future quantum computer, such as processors and memories. Scientists may use this protocol in the future to build a data bus for quantum computers. The researchers have published their work in the journal Nature Communications.

Future quantum computers will be able to solve problems where conventional computers fail today. We are still far away from any large-scale implementation,...

Im Focus: Wrinkles give heat a jolt in pillared graphene

Rice University researchers test 3-D carbon nanostructures' thermal transport abilities

Pillared graphene would transfer heat better if the theoretical material had a few asymmetric junctions that caused wrinkles, according to Rice University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Ecology Across Borders: International conference brings together 1,500 ecologists

15.11.2017 | Event News

Road into laboratory: Users discuss biaxial fatigue-testing for car and truck wheel

15.11.2017 | Event News

#Berlin5GWeek: The right network for Industry 4.0

30.10.2017 | Event News

 
Latest News

Antarctic landscape insights keep ice loss forecasts on the radar

20.11.2017 | Earth Sciences

Filling the gap: High-latitude volcanic eruptions also have global impact

20.11.2017 | Earth Sciences

Water world

20.11.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>