Tag Archives: niobium

Cannibalisitic nanostructures

I think this form of ‘cannibalism’ could also be described as a form of ‘self-assembly’. That said, here is an August 31, 2018 news item on ScienceDaily announcing ‘cannibalistic’ materials,

Scientists at the [US] Department of Energy’s [DOE] Oak Ridge National Laboratory [ORNL] induced a two-dimensional material to cannibalize itself for atomic “building blocks” from which stable structures formed.

The findings, reported in Nature Communications, provide insights that may improve design of 2D materials for fast-charging energy-storage and electronic devices.

An August 31, 2018 DOE/Oak Ridge National Laboratory news release (also on EurekAlert), which originated the news item, provides more detail (Note: Links have been removed),

“Under our experimental conditions, titanium and carbon atoms can spontaneously form an atomically thin layer of 2D transition-metal carbide, which was never observed before,” said Xiahan Sang of ORNL.

He and ORNL’s Raymond Unocic led a team that performed in situ experiments using state-of-the-art scanning transmission electron microscopy (STEM), combined with theory-based simulations, to reveal the mechanism’s atomistic details.

“This study is about determining the atomic-level mechanisms and kinetics that are responsible for forming new structures of a 2D transition-metal carbide such that new synthesis methods can be realized for this class of materials,” Unocic added.

The starting material was a 2D ceramic called a MXene (pronounced “max een”). Unlike most ceramics, MXenes are good electrical conductors because they are made from alternating atomic layers of carbon or nitrogen sandwiched within transition metals like titanium.

The research was a project of the Fluid Interface Reactions, Structures and Transport (FIRST) Center, a DOE Energy Frontier Research Center that explores fluid–solid interface reactions that have consequences for energy transport in everyday applications. Scientists conducted experiments to synthesize and characterize advanced materials and performed theory and simulation work to explain observed structural and functional properties of the materials. New knowledge from FIRST projects provides guideposts for future studies.

The high-quality material used in these experiments was synthesized by Drexel University scientists, in the form of five-ply single-crystal monolayer flakes of MXene. The flakes were taken from a parent crystal called “MAX,” which contains a transition metal denoted by “M”; an element such as aluminum or silicon, denoted by “A”; and either a carbon or nitrogen atom, denoted by “X.” The researchers used an acidic solution to etch out the monoatomic aluminum layers, exfoliate the material and delaminate it into individual monolayers of a titanium carbide MXene (Ti3C2).

The ORNL scientists suspended a large MXene flake on a heating chip with holes drilled in it so no support material, or substrate, interfered with the flake. Under vacuum, the suspended flake was exposed to heat and irradiated with an electron beam to clean the MXene surface and fully expose the layer of titanium atoms.

MXenes are typically inert because their surfaces are covered with protective functional groups—oxygen, hydrogen and fluorine atoms that remain after acid exfoliation. After protective groups are removed, the remaining material activates. Atomic-scale defects—“vacancies” created when titanium atoms are removed during etching—are exposed on the outer ply of the monolayer. “These atomic vacancies are good initiation sites,” Sang said. “It’s favorable for titanium and carbon atoms to move from defective sites to the surface.” In an area with a defect, a pore may form when atoms migrate.

“Once those functional groups are gone, now you’re left with a bare titanium layer (and underneath, alternating carbon, titanium, carbon, titanium) that’s free to reconstruct and form new structures on top of existing structures,” Sang said.

High-resolution STEM imaging proved that atoms moved from one part of the material to another to build structures. Because the material feeds on itself, the growth mechanism is cannibalistic.

“The growth mechanism is completely supported by density functional theory and reactive molecular dynamics simulations, thus opening up future possibilities to use these theory tools to determine the experimental parameters required for synthesizing specific defect structures,” said Adri van Duin of Penn State [Pennsylvania State University].

Most of the time, only one additional layer [of carbon and titanium] grew on a surface. The material changed as atoms built new layers. Ti3C2 turned into Ti4C3, for example.

“These materials are efficient at ionic transport, which lends itself well to battery and supercapacitor applications,” Unocic said. “How does ionic transport change when we add more layers to nanometer-thin MXene sheets?” This question may spur future studies.

“Because MXenes containing molybdenum, niobium, vanadium, tantalum, hafnium, chromium and other metals are available, there are opportunities to make a variety of new structures containing more than three or four metal atoms in cross-section (the current limit for MXenes produced from MAX phases),” Yury Gogotsi of Drexel University added. “Those materials may show different useful properties and create an array of 2D building blocks for advancing technology.”

At ORNL’s Center for Nanophase Materials Sciences (CNMS), Yu Xie, Weiwei Sun and Paul Kent performed first-principles theory calculations to explain why these materials grew layer by layer instead of forming alternate structures, such as squares. Xufan Li and Kai Xiao helped understand the growth mechanism, which minimizes surface energy to stabilize atomic configurations. Penn State scientists conducted large-scale dynamical reactive force field simulations showing how atoms rearranged on surfaces, confirming defect structures and their evolution as observed in experiments.

The researchers hope the new knowledge will help others grow advanced materials and generate useful nanoscale structures.

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

In situ atomistic insight into the growth mechanisms of single layer 2D transition metal carbides by Xiahan Sang, Yu Xie, Dundar E. Yilmaz, Roghayyeh Lotfi, Mohamed Alhabeb, Alireza Ostadhossein, Babak Anasori, Weiwei Sun, Xufan Li, Kai Xiao, Paul R. C. Kent, Adri C. T. van Duin, Yury Gogotsi, & Raymond R. Unocic. Nature Communicationsvolume 9, Article number: 2266 (2018) DOI: https://doi.org/10.1038/s41467-018-04610-0 Published 11 June 2018

This paper is open access.

Cornwall (UK) connects with University of Southern California for performance by a quantum computer (D-Wave) and mezzo soprano Juliette Pochin

The upcoming performance of a quantum computer built by D-Wave Systems (a Canadian company) and Welsh mezzo soprano Juliette Pochin is the première of “Superposition” by Alexis Kirke. A July 13, 2016 news item on phys.org provides more detail,

What happens when you combine the pure tones of an internationally renowned mezzo soprano and the complex technology of a $15million quantum supercomputer?

The answer will be exclusively revealed to audiences at the Port Eliot Festival [Cornwall, UK] when Superposition, created by Plymouth University composer Alexis Kirke, receives its world premiere later this summer.

A D-Wave 1000 Qubit Quantum Processor. Credit: D-Wave Systems Inc

A D-Wave 1000 Qubit Quantum Processor. Credit: D-Wave Systems Inc

A July 13, 2016 Plymouth University press release, which originated the news item, expands on the theme,

Combining the arts and sciences, as Dr Kirke has done with many of his previous works, the 15-minute piece will begin dark and mysterious with celebrated performer Juliette Pochin singing a low-pitched slow theme.

But gradually the quiet sounds of electronic ambience will emerge over or beneath her voice, as the sounds of her singing are picked up by a microphone and sent over the internet to the D-Wave quantum computer at the University of Southern California.

It then reacts with behaviours in the quantum realm that are turned into sounds back in the performance venue, the Round Room at Port Eliot, creating a unique and ground-breaking duet.

And when the singer ends, the quantum processes are left to slowly fade away naturally, making their final sounds as the lights go to black.

Dr Kirke, a member of the Interdisciplinary Centre for Computer Music Research at Plymouth University, said:

“There are only a handful of these computers accessible in the world, and this is the first time one has been used as part of a creative performance. So while it is a great privilege to be able to put this together, it is an incredibly complex area of computing and science and it has taken almost two years to get to this stage. For most people, this will be the first time they have seen a quantum computer in action and I hope it will give them a better understanding of how it works in a creative and innovative way.”

Plymouth University is the official Creative and Cultural Partner of the Port Eliot Festival, taking place in South East Cornwall from July 28 to 31, 2016 [emphasis mine].

And Superposition will be one of a number of showcases of University talent and expertise as part of the first Port Eliot Science Lab. Being staged in the Round Room at Port Eliot, it will give festival goers the chance to explore science, see performances and take part in a range of experiments.

The three-part performance will tell the story of Niobe, one of the more tragic figures in Greek mythology, but in this case a nod to the fact the heart of the quantum computer contains the metal named after her, niobium. It will also feature a monologue from Hamlet, interspersed with terms from quantum computing.

This is the latest of Dr Kirke’s pioneering performance works, with previous productions including an opera based on the financial crisis and a piece using a cutting edge wave-testing facility as an instrument of percussion.

Geordie Rose, CTO and Founder, D-Wave Systems, said:

“D-Wave’s quantum computing technology has been investigated in many areas such as image recognition, machine learning and finance. We are excited to see Dr Kirke, a pioneer in the field of quantum physics and the arts, utilising a D-Wave 2X in his next performance. Quantum computing is positioned to have a tremendous social impact, and Dr Kirke’s work serves not only as a piece of innovative computer arts research, but also as a way of educating the public about these new types of exotic computing machines.”

Professor Daniel Lidar, Director of the USC Center for Quantum Information Science and Technology, said:

“This is an exciting time to be in the field of quantum computing. This is a field that was purely theoretical until the 1990s and now is making huge leaps forward every year. We have been researching the D-Wave machines for four years now, and have recently upgraded to the D-Wave 2X – the world’s most advanced commercially available quantum optimisation processor. We were very happy to welcome Dr Kirke on a short training residence here at the University of Southern California recently; and are excited to be collaborating with him on this performance, which we see as a great opportunity for education and public awareness.”

Since I can’t be there, I’m hoping they will be able to successfully livestream the performance. According to Kirke who very kindly responded to my query, the festival’s remote location can make livecasting a challenge. He did note that a post-performance documentary is planned and there will be footage from the performance.

He has also provided more information about the singer and the technical/computer aspects of the performance (from a July 18, 2016 email),

Juliette Pochin: I’ve worked with her before a couple of years ago. She has an amazing voice and style, is musically adventurousness (she is a music producer herself), and brings great grace and charisma to a performance. She can be heard in the Harry Potter and Lord of the Rings soundtracks and has performed at venues such as the Royal Albert Hall, Proms in the Park, and Meatloaf!

Score: The score is in 3 parts of about 5 minutes each. There is a traditional score for parts 1 and 3 that Juliette will sing from. I wrote these manually in traditional music notation. However she can sing in free time and wait for the computer to respond. It is a very dramatic score, almost operatic. The computer’s responses are based on two algorithms: a superposition chord system, and a pitch-loudness entanglement system. The superposition chord system sends a harmony problem to the D-Wave in response to Juliette’s approximate pitch amongst other elements. The D-Wave uses an 8-qubit optimizer to return potential chords. Each potential chord has an energy associated with it. In theory the lowest energy chord is that preferred by the algorithm. However in the performance I will combine the chord solutions to create superposition chords. These are chords which represent, in a very loose way, the superposed solutions which existed in the D-Wave before collapse of the qubits. Technically they are the results of multiple collapses, but metaphorically I can’t think of a more beautiful representation of superposition: chords. These will accompany Juliette, sometimes clashing with her. Sometimes giving way to her.

The second subsystem generates non-pitched noises of different lengths, roughnesses and loudness. These are responses to Juliette, but also a result of a simple D-Wave entanglement. We know the D-Wave can entangle in 8-qubit groups. I send a binary representation of the Juliette’s loudness to 4 qubits and one of approximate pitch to another 4, then entangle the two. The chosen entanglement weights are selected for their variety of solutions amongst the qubits, rather than by a particular musical logic. So the non-pitched subsystem is more of a sonification of entanglement than a musical algorithm.

Thank you Dr. Kirke for a fascinating technical description and for a description of Juliette Pochin that makes one long to hear her in performance.

For anyone who’s thinking of attending the performance or curious, you can find out more about the Port Eliot festival here, Juliette Pochin here, and Alexis Kirke here.

For anyone wondering about data sonficiatiion, I also have a Feb. 7, 2014 post featuring a data sonification project by Dr. Domenico Vicinanza which includes a sound clip of his Voyager 1 & 2 spacecraft duet.

Yarns of niobium nanowire for small electronic device boost at the University of British Columbia (Canada) and Massachusetts Institute of Technology (US)

It turns out that this research concerning supercapacitors is a collaboration between the University of British Columbia (Canada) and the Massachusetts Institute of Technology (MIT). From a July 7, 2015 news item by Stuart Milne for Azonano,

A team of researchers from MIT and University of British Columbia has discovered an innovative method to deliver short bursts of high power required by wearable electronic devices.

Such devices are used for monitoring health and fitness and as such are rapidly growing in the consumer electronics industry. However, a major drawback of these devices is that they are integrated with small batteries, which fail to deliver sufficient amount of power required for data transmission.

According to the research team, one way to resolve this issue is to develop supercapacitors, which are capable of storing and releasing short bursts of electrical power required to transmit data from smartphones, computers, heart-rate monitors, and other wearable devices. supercapacitors can also prove useful for other applications where short bursts of high power is required, for instance autonomous microrobots.

A July 7, 2015 MIT news release provides more detail about the research,

The new approach uses yarns, made from nanowires of the element niobium, as the electrodes in tiny supercapacitors (which are essentially pairs of electrically conducting fibers with an insulator between). The concept is described in a paper in the journal ACS Applied Materials and Interfaces by MIT professor of mechanical engineering Ian W. Hunter, doctoral student Seyed M. Mirvakili, and three others at the University of British Columbia.

Nanotechnology researchers have been working to increase the performance of supercapacitors for the past decade. Among nanomaterials, carbon-based nanoparticles — such as carbon nanotubes and graphene — have shown promising results, but they suffer from relatively low electrical conductivity, Mirvakili says.

In this new work, he and his colleagues have shown that desirable characteristics for such devices, such as high power density, are not unique to carbon-based nanoparticles, and that niobium nanowire yarn is a promising an alternative.

“Imagine you’ve got some kind of wearable health-monitoring system,” Hunter says, “and it needs to broadcast data, for example using Wi-Fi, over a long distance.” At the moment, the coin-sized batteries used in many small electronic devices have very limited ability to deliver a lot of power at once, which is what such data transmissions need.

“Long-distance Wi-Fi requires a fair amount of power,” says Hunter, the George N. Hatsopoulos Professor in Thermodynamics in MIT’s Department of Mechanical Engineering, “but it may not be needed for very long.” Small batteries are generally poorly suited for such power needs, he adds.

“We know it’s a problem experienced by a number of companies in the health-monitoring or exercise-monitoring space. So an alternative is to go to a combination of a battery and a capacitor,” Hunter says: the battery for long-term, low-power functions, and the capacitor for short bursts of high power. Such a combination should be able to either increase the range of the device, or — perhaps more important in the marketplace — to significantly reduce size requirements.

The new nanowire-based supercapacitor exceeds the performance of existing batteries, while occupying a very small volume. “If you’ve got an Apple Watch and I shave 30 percent off the mass, you may not even notice,” Hunter says. “But if you reduce the volume by 30 percent, that would be a big deal,” he says: Consumers are very sensitive to the size of wearable devices.

The innovation is especially significant for small devices, Hunter says, because other energy-storage technologies — such as fuel cells, batteries, and flywheels — tend to be less efficient, or simply too complex to be practical when reduced to very small sizes. “We are in a sweet spot,” he says, with a technology that can deliver big bursts of power from a very small device.

Ideally, Hunter says, it would be desirable to have a high volumetric power density (the amount of power stored in a given volume) and high volumetric energy density (the amount of energy in a given volume). “Nobody’s figured out how to do that,” he says. However, with the new device, “We have fairly high volumetric power density, medium energy density, and a low cost,” a combination that could be well suited for many applications.

Niobium is a fairly abundant and widely used material, Mirvakili says, so the whole system should be inexpensive and easy to produce. “The fabrication cost is cheap,” he says. Other groups have made similar supercapacitors using carbon nanotubes or other materials, but the niobium yarns are stronger and 100 times more conductive. Overall, niobium-based supercapacitors can store up to five times as much power in a given volume as carbon nanotube versions.

Niobium also has a very high melting point — nearly 2,500 degrees Celsius — so devices made from these nanowires could potentially be suitable for use in high-temperature applications.

In addition, the material is highly flexible and could be woven into fabrics, enabling wearable forms; individual niobium nanowires are just 140 nanometers in diameter — 140 billionths of a meter across, or about one-thousandth the width of a human hair.

So far, the material has been produced only in lab-scale devices. The next step, already under way, is to figure out how to design a practical, easily manufactured version, the researchers say.

“The work is very significant in the development of smart fabrics and future wearable technologies,” says Geoff Spinks, a professor of engineering at the University of Wollongong, in Australia, who was not associated with this research. This paper, he adds, “convincingly demonstrates the impressive performance of niobium-based fiber supercapacitors.”

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

High-Performance Supercapacitors from Niobium Nanowire Yarns by Seyed M. Mirvakili, Mehr Negar Mirvakili, Peter Englezos, John D. W. Madden, and Ian W. Hunter. ACS Appl. Mater. Interfaces, 2015, 7 (25), pp 13882–13888 DOI: 10.1021/acsami.5b02327 Publication Date (Web): June 12, 2015

Copyright © 2015 American Chemical Society

This paper is behind a paywall.