Tag Archives: Albert G. Nasibulin

Boost single-walled carbon nantube (SWCNT) production

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I’m fascinated by this image,

Caption: Skoltech researchers have investigated the procedure for catalyst delivery used in the most common method of carbon nanotube production, chemical vapor deposition (CVD), offering what they call a “simple and elegant” way to boost productivity and pave the way for cheaper and more accessible nanotube-based technology. Credit: Pavel Odinev/Skoltech

If I understand it correctly, getting the catalyst particles into a tighter, more uniform formation is what could lead to a boost in the production of single-walled carbon nanotubes (SWCNTs).

The work was announced in a Nov. 30, 2020 news item in Nanowerk,

Skoltech [Skolkovo Institute of Science and Technology; Russia] researchers have investigated the procedure for catalyst delivery used in the most common method of carbon nanotube production, chemical vapor deposition (CVD), offering what they call a “simple and elegant” way to boost productivity and pave the way for cheaper and more accessible nanotube-based technology.

A Nov. 30, 2020 Skolkovo Institute of Science and Technology (Skoltech) press release (also on EurekAlert but published on Dec. 1, 2020), which originated the news item, explains in detail,

Single-walled carbon nanotubes (SWCNT), tiny rolled sheets of graphene with a thickness of just one atom, hold huge promise when it comes to applications in materials science and electronics. That is the reason why so much effort is focused on perfecting the synthesis of SWCNTs; from physical methods, such as using laser beams to ablate a graphite target, all the way to the most common CVD approach, when metal catalyst particles are used to “strip” a carbon-containing gas of its carbon and grow the nanotubes on these particles.

“The road from raw materials to carbon nanotubes requires a fine balance between dozens of reactor parameters. The formation of carbon nanotubes is a tricky and complex process that has been studied for a long time, but still keeps many secrets,” explains Albert Nasibulin, a professor at Skoltech and an adjunct professor at the Department of Chemistry and Materials Science, Aalto University School of Chemical Engineering.

Various ways of enhancing catalyst activation, in order to produce more SWCNTs with the required properties, have already been suggested. Nasibulin and his colleagues focused on the injection procedure, namely on how to distribute ferrocene vapor (a commonly used catalyst precursor) within the reactor.

They grew their carbon nanotubes using the aerosol CVD approach, using carbon monoxide as a source of carbon, and monitored the synthesis productivity and SWCNT characteristics (such as their diameter) depending on the rate of catalyst injection and the concentration of CO2 (carbon dioxide; used as an agent for fine-tuning). Ultimately the researchers concluded that “injector flow rate adjustment could lead to a 9-fold increase in the synthesis productivity while preserving most of the SWCNT characteristics”, such as their diameter, the share of defective nanotubes, and film conductivity.

“Every technology is always about efficiency. When it comes to CVD production of nanotubes, the efficiency of the catalyst is usually out of sight. However, we see a great opportunity there and this work is only a first step towards an efficient technology,” Dmitry Krasnikov, senior research scientist at Skoltech and co-author of the paper, says.

Here’s a link to and a citation for the paper,

Activation of catalyst particles for single-walled carbon nanotube synthesis by Eldar M.Khabushev, Julia V. Kolodiazhnaia, Dmitry V. Krasnikov, Albert G. Nasibulin. Chemical Engineering Journal DOI: https://doi.org/10.1016/j.cej.2020.127475 Available online 24 October 2020, 127475

This paper is behind a paywall.

New capacitor for better wearable electronics?

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Supercapacitors are a predictable source of scientific interest and excitement. The latest entry in the ‘supercapacitor stakes’ is from a Russian/Finnish/US team according to a June 11, 2020 Skoltech (Skolkovo Institute of Science and Technology) press release (also on EurekAlert),

Researchers from Skoltech [Russia], Aalto University [Finland] and Massachusetts Institute of Technology [MIT; US] have designed a high-performance, low-cost, environmentally friendly, and stretchable supercapacitor that can potentially be used in wearable electronics. The paper was published in the Journal of Energy Storage.

Supercapacitors, with their high power density, fast charge-discharge rates, long cycle life, and cost-effectiveness, are a promising power source for everything from mobile and wearable electronics to electric vehicles. However, combining high energy density, safety, and eco-friendliness in one supercapacitor suitable for small devices has been rather challenging.

“Usually, organic solvents are used to increase the energy density. These are hazardous, not environmentally friendly, and they reduce the power density compared to aqueous electrolytes with higher conductivity,” says Professor Tanja Kallio from Aalto University, a co-author of the paper.

The researchers proposed a new design for a “green” and simple-to-fabricate supercapacitor. It consists of a solid-state material based on nitrogen-doped graphene flake electrodes distributed in the NaCl-containing hydrogel electrolyte. This structure is sandwiched between two single-walled carbon nanotube film current collectors, which provides stretchability. Hydrogel in the supercapacitor design enables compact packing and high energy density and allows them to use the environmentally friendly electrolyte.

The scientists managed to improve the volumetric capacitive performance, high energy density and power density for the prototype over analogous supercapacitors described in previous research. “We fabricated a prototype with unchanged performance under the 50% strain after a thousand stretching cycles. To ensure lower cost and better environmental performance, we used a NaCl-based electrolyte. Still the fabrication cost can be lowered down by implementation of 3D printing or other advanced fabrication techniques,” concluded Skoltech professor Albert Nasibulin.

Here’s a link to and a citation for the paper,

Superior environmentally friendly stretchable supercapacitor based on nitrogen-doped graphene/hydrogel and single-walled carbon nanotubes by Evgeniia Gilshtein, Cristina Flox, Farhan S.M. Ali, Bahareh Mehrabimatin, Fedor S.Fedorov, Shaoting Lin, Xuanhe Zhao, Albert G. Nasibulin, Tanja Kallio. Journal of Energy Storage Volume 30, August 2020, 101505 DOI: https://doi.org/10.1016/j.est.2020.101505

This paper is behind a paywall.

I’m trying to remember if I’ve ever before seen a material that combines graphene and single-walled carbon nanotubes (SWCNTs). Anyway, here’s an image the researchers are using illustrate their work,

Caption: This is an outline of the new supercapacitor. Credit: Pavel Odinev / Skoltech

“Control my chirality, please,” said the carbon nanotube to the researchers

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A combined Finnish, Russian, and Danish team have found a way to control the chirality of single-walled carbon nanotubes according to an Apr. 30, 2013 news item on Azonano,

An ultimate goal in the field of carbon nanotube research is to synthesise single-walled carbon nanotubes (SWNTs) with controlled chiralities. Twenty years after the discovery of SWNTs, scientists from Aalto University in Finland, A.M. Prokhorov General Physics Institute RAS in Russia and the Center for Electron Nanoscopy of Technical University of Denmark (DTU) have managed to control chirality in carbon nanotubes during their chemical vapor deposition synthesis.

The Aalto University Apr. 29, 2013 news release, which originated the news item, goes on to explain,

 Over the years, substantial progress has been made to develop various structure-controlled synthesis methods. However, precise control over the chiral structure of SWNTs has been largely hindered by a lack of practical means to direct the formation of the metal nanoparticle catalysts and their catalytic dynamics during tube growth.

– We achieved an epitaxial formation of Co nanoparticles by reducing a well-developed solid solution in CO, reveals Maoshuai He, a postdoctoral researcher at Aalto University School of Chemical Technology.

– For the first time, the new catalyst was employed for selective growth of SWNTs, adds senior staff scientist Hua Jiang from Aalto University School of Science.

By introducing the new catalysts into a conventional CVD reactor, the research team demonstrated preferential growth of semiconducting SWNTs (～90%) with an exceptionally high population of (6,5) tubes (53%) at 500 °C. Furthermore, they also showed a shift of the chiral preference from (6,5) tubes at 500 °C  to (7, 6) and (9, 4) nanotubes at 400 °C.

– These findings open new perspectives both for structural control of SWNTs and for elucidating their growth mechanisms, thus are important for the fundamental understanding of science behind nanotube growth, comments Professor Juha Lehtonen from Aalto University.

For anyone like me who needs a description of chirality, there’s this from Wikipedia,

Chirality (pron.: /kaɪˈrælɪtiː/) is a property of asymmetry important in several branches of science. The word chirality is derived from the Greek, χειρ (kheir), “hand”, a familiar chiral object.

An object or a system is chiral if it is not identical to its mirror image, that is, it cannot be superposed onto it. A chiral object and its mirror image are called enantiomorphs (Greek opposite forms) or, when referring to molecules, enantiomers. A non-chiral object is called achiral (sometimes also amphichiral) and can be superposed on its mirror image.

…

Human hands are perhaps the most universally recognized example of chirality: The left hand is a non-superimposable mirror image of the right hand; no matter how the two hands are oriented, it is impossible for all the major features of both hands to coincide.[2] This difference in symmetry becomes obvious if someone attempts to shake the right hand of a person using his left hand, or if a left-handed glove is placed on a right hand. In mathematics chirality is the property of a figure that is not identical to its mirror image.

One of the researchers notes why they, or anyone else, would want to control the chirality of carbon nanotubes, from the news release,

– Chirality defines the optical and electronic properties of carbon nanotubes, so controlling it is a key to exploiting their practical applications, says Professor Esko I. Kauppinen, the leader of the Nanomaterials Group in Aalto University School of Science.

ETA Apr. 30, 2013 at 4:20 pm PDT: Here’s a link to and a citation for the team’s published paper,

Chiral-Selective Growth of Single-Walled Carbon Nanotubes on Lattice-Mismatched Epitaxial Cobalt Nanoparticles by Maoshuai He, Hua Jiang, Bilu Liu, Pavel V. Fedotov, Alexander I. Chernov, Elena D. Obraztsova, Filippo Cavalca, Jakob B. Wagner, Thomas W. Hansen, Ilya V. Anoshkin, Ekaterina A. Obraztsova, Alexey V. Belkin, Emma Sairanen, Albert G. Nasibulin,  Juha Lehtonen, & Esko I. Kauppinen. Scientific Reports 3, Article number 1460  doi:10.1038/srep01460 Published15 March 2013

This article is open access.