Landscapes give latitude to 2-D material designers

Rice, Oak Ridge scientists show growing atom-thin sheets on cones allows control of defects

Hands of Henry” (Nitant Gupta, c. 2017; WS2 on conical canvas)

Rice University researchers have learned to manipulate two-dimensional materials to design in defects that enhance the materials’ properties.

The Rice lab of theoretical physicist Boris Yakobson and colleagues at Oak Ridge National Laboratory are combining theory and experimentation to prove it’s possible to give 2-D materials specific defects, especially atomic-scale seams called grain boundaries. These boundaries may be used to enhance the materials’ electronic, magnetic, mechanical, catalytic and optical properties.

The key is introducing curvature to the landscape that constrains the way defects propagate. The researchers call this “tilt grain boundary topology,” and they achieve it by growing their materials onto a topographically curved substrate — in this case, a cone. The angle of the cone dictates if, what kind and where the boundaries appear.

The research is the subject of a paper in the American Chemical Society journal ACS Nano.

– See more at Rice News

Bubbles help new catalysts self-optimize

Rice, Lawrence Livermore scientists replace expensive platinum for efficient hydrogen production

Scientists at Rice University and the Lawrence Livermore National Laboratory have predicted and created new two-dimensional electrocatalysts to extract hydrogen from water with high performance and low cost.

In the process, they also created a simple model to screen materials for catalytic activity.

Several catalysts were modeled by Rice theoretical physicist Boris Yakobson and lead author Yuanyue Liu, a former graduate student in his lab, and made and tested by Rice materials scientists led by Pulickel Ajayan and Jun Lou. They found the new dichalcogenide catalysts matched the efficiency of platinum — the most common hydrogen evolution reaction (HER) catalyst in water-splitting cells — and can be made at a fraction of the cost.

The study appears in Nature Energy.

– See more at Rice News

Nothing Boring about the Thinnest Boron Ever

Department of Energy’s Office of Science (BES) highlights our work on 2D boron

… Can boron, which is adjacent to carbon on the Periodic Table, also form a 2-D material and, if so, what are its properties? Researchers at Rice University used theory and simulation techniques to identify possible 2-D boron structures. Their findings showed that, based upon the metal substrate used during the fabrication process, the structure of monolayer boron changed drastically. Using this information, researchers from Argonne National Laboratory, Northwestern University, and their collaborators from other institutions utilized the Department of Energy’s Center for Nanoscale Material, a user facility, to attempt the synthesis of borophene on a silver substrate.

– See more at science.energy.gov

Boron atoms stretch out, gain new powers

Rice simulations demonstrate 1-D material’s stiffness, electrical versatility

Hold on, there, graphene. You might think you’re the most interesting new nanomaterial of the century, but boron might already have you beat, according to scientists at Rice University.

A Rice team that simulated one-dimensional forms of boron — both two-atom-wide ribbons and single-atom chains — found they possess unique properties. The new findings appear this week in the Journal of the American Chemical Society.

For example, if metallic ribbons of boron are stretched, they morph into antiferromagnetic semiconducting chains, and when released they fold back into ribbons.

In The News

Nano-chimneys can cool circuits

chim_v2Rice scientists calculate tweaks to graphene would form phonon-friendly cones

A few nanoscale adjustments may be all that is required to make graphene-nanotube junctions excel at transferring heat, according to Rice University scientists.

The Rice lab of theoretical physicist Boris Yakobson found that putting a cone-like “chimney” between the graphene and nanotube all but eliminates a barrier that blocks heat from escaping.

The research appears in the American Chemical Society’s Journal of Physical Chemistry C.

Heat is transferred through phonons, quasiparticle waves that also transmit sound. The Rice theory offers a strategy to channel damaging heat away from next-generation nano-electronics.

– See more at Rice News

 

The “D-loops” are on Advanced Materials cover

adv_mater_coverThe December 14 issue of Advanced Materials features our work on carbon fibers on its back cover.

The study presents the “D-loops”, a new type of structural defect in carbon fibers, which may have highly detrimental effect on their mechanical properties and can define a new fundamental upper limit to their strength. These defects form exclusively during polyacrylonitrile (PAN) carbonization, act as stress concentrators in the graphitic basal plane, and cannot be removed by local annealing.

Related:

Luqing Wang wins 2016 Shell Graduate Fellowship

Luqing Wang, a 4th-year graduate student in Yakobson Group, has received the 2016 Shell Graduate Fellowship awarded by the Ken Kennedy Institute for Information Technology.k2i-shell

The Ken Kennedy Institute is dedicated to the advancement of research in the fields of computing, data science and information technology, and the award recipients were selected on the basis of their research proposals which contribute to computing and data issues the oil and gas industry currently faces.

While a majority of the program’s fellowship awards are funded by energy industry players, including BP, ExxonMobil, Schlumberger and Shell, support is also provided from the Ken Kennedy Cray Graduate Fellowship, the Andrew Ladd Memorial Excellence Fund in Computer Science Fellowship and funding from the annual Rice Oil and Gas High Performance Computing Conference (OG-HPC).

– See more at Rice News

Henry Yu wins 2nd place in the NSCI Science Image Contest

solenoid_smallHenry Yu, a 4th year graduate student in the Applied Physics/MSNE program, has won 2nd place in the 2016 NSCI Image Contest held by the Wiess School of Natural Sciences, Rice University. The image shows a graphite screw dislocation structure as a nano solenoid, which can hold magnetic field orders of magnitude greater than that of planet Earth. It was produced from an actual atomic geometry, using VMD, our own Edgecount tool, MeshLab, Python scripting, and the mighty Gimp.

To learn more about the science behind the image, see:
– Rice News: Graphene nano-coils are natural electromagnets
– F. Xu, H. Yu, A. Sadrzadeh, and B. I. Yakobson, “Riemann Surfaces of Carbon as Graphene Nanosolenoids“, Nano Lett. 16, 34–39 (2016)

Explaining the gap between strength of ideal graphene and practical carbon fibers

Rice researchers simulate defects in popular fiber, suggest ways to improve it 

d-loop

The D-shaped loop, due to the misfusion of PAN-based nanoribbons, seen as a puckered-rug illustration by graduate student Nitant Gupta.

Carbon fiber, a pillar of strength in materials manufacturing for decades, isn’t as good as it could be, but there are ways to improve it, according to Rice University scientists.

They found the polymer chains that make up a common carbon fiber are prone to misalign during manufacture, a defect the researchers compared with a faulty zipper that weakens the product.

The Rice lab of theoretical physicist Boris Yakobson set out to analyze these overlooked defects and suggest how they might be curtailed. The lab’s work appears this month in Advanced Materials.

– See more at Rice News

New Wave of 2D Boron

Rice University researchers say 2-D boron may be best for flexible electronics

2d-b-waveThough they’re touted as ideal for electronics, two-dimensional materials like graphene may be too flat and hard to stretch to serve in flexible, wearable devices. “Wavy” borophene might be better, according to Rice University scientists.

The Rice lab of theoretical physicist Boris Yakobson and experimental collaborators observed examples of naturally undulating, metallic borophene, an atom-thick layer of boron, and suggested that transferring it onto an elastic surface would preserve the material’s stretchability along with its useful electronic properties.

Highly conductive graphene has promise for flexible electronics, Yakobson said, but it is too stiff for devices that also need to stretch, compress or even twist. But borophene deposited on a silver substrate develops nanoscale corrugations. Weakly bound to the silver, it could be moved to a flexible surface for use.

The research appears this month in the American Chemical Society journal Nano Letters.

In The News

Ultra-flat circuits will have unique properties

Rice University lab studies 2-D hybrids to see how they differ from common electronics

The old rules don’t necessarily apply when building electronic components out of two-dimensional materials, according to scientists at Rice University.2d-junct

The Rice lab of theoretical physicist Boris Yakobson analyzed hybrids that put 2-D materials like graphene and boron nitride side by side to see what happens at the border. They found that the electronic characteristics of such “co-planar” hybrids differ from bulkier components.

Their results appear this month in the American Chemical Society journal Nano Letters.

Shrinking electronics means shrinking their components. Academic labs and industries are studying how materials like graphene may enable the ultimate in thin devices by building all the necessary circuits into an atom-thick layer.

– See more at Rice News

Luqing Wang wins Franz and Frances Brotzen Fellowship Award

Luqing Wang, a third-year graduate student in Yakobson’s Group, has received the 2016 Franz and Frances Brotzen Fellowship Award from the MSNELuqing Department. To honor Franz R. Brotzen, the Stanley C. Moore Professor Emeritus of Materials Science and a former dean of engineering, this fellowship was established by David Lee Davidson and his wife, Patricia, and to support an endowed fellowship for graduate students researching in the area of materials science.

Luqing’s research focuses on predicting novel properties and understanding the cutting-edge mechanism of new two-dimensional materials based on  first-principles calculations. She explores many-body and spin-orbit effects on the electronic structure of strained monolayer transition metal dichalcogenides, and the enhanced electro-mechanical anisotropy of phosphorene caused by the effects of uniaxial stress along an arbitrary direction. She also works on morphologies and phase transitions in tin sulfides, as well as routes for their controlled synthesis.

Yakobson Group at the Spring ’16 Faculty Data Science Meetup

Check out our posters at the Spring ’16 Faculty Data Science Meetup hosted by the poster_tinyKen Kennedy Institute for Information Technology (April 13, 2016, 3-5pm, BioScience Research Collaborative Building (BRC) Event/Exhibit Hall):

Digging into Big Data of 2D nanomaterials… for fun and profit

Steady progress in computing power has motivated computational materials scientists to try new approaches to modeling materials. Here we explore data-driven and data-centric approaches to explain the properties and behavior of real advanced materials or accelerate the discovery of new ones. Often, this necessitates the sampling of enormous configurational spaces due to chemical and/or structural variety and processing the associated `big-data’ computational output. Selected examples are presented illustrating a state-of-the-art approach that allows for an elegant use of statistical mechanics methods (“cluster expansion”) in combination with first-principles density-functional theory (DFT) calculations, leading to a thorough exploration of the configurational space.

Materials systems include the alloys of two-dimensional transition-metal dichalcogenides M1-xM’xX2yX’2(1-y), the 2D materials family within the B-N-C phase diagram, the peculiar, no longer hypothetical,  2D polymorphs of elemental boron, as well the end-caps of single walled carbon nanotubes.

Can Two-Dimensional Boron Superconduct?

Rice University scientists predict 2-D material – no longer theoretical – has unique propertiesimg4news_small

Rice University scientists have determined that two-dimensional boron is a natural low-temperature superconductor. In fact, it may be the only 2-D material with such potential.

Rice theoretical physicist Boris Yakobson and his co-workers published their calculations that show atomically flat boron is metallic and will transmit electrons with no resistance. The work appears this month in the American Chemical Society journal Nano Letters.

The hitch, as with most superconducting materials, is that it loses its resistivity only when very cold, in this case between 10 and 20 kelvins (roughly, minus-430 degrees Fahrenheit). But for making very small superconducting circuits, it might be the only game in town.

– See more at Rice News

The Carbon NanoSolenoid on the Cover of Nano Letters

Nano Letters features our work on the Cover of its January 2016 issue

nalefd_v016i001.inddGraphene forms helicoids, akin to the mathematical Riemann surface for log(z), naturally occurring as screw dislocations in graphite or anthracite. In the Nano Letters paper, we demonstrate that the miniscule pitch of such winding carbon ribbons endows them with largest magnetic inductance per volume, which surpasses any current technologies. If voltage is applied, electrical current must flow helically, producing near the center strong magnetic field orders of magnitude greater than that of planet Earth.

The image was produced from the actual atomic geometry, using VMD, our own Edgecount tool, MeshLab, Python scripting, and the mighty Gimp.