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

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 is a cover story in the September issue of Nature Energy.

– See more at Rice News

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

The 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:

• Rice News: Study explains strength gap between graphene, carbon fiber
• Futurity.org: Bad ‘zipper’ explains trouble with carbon fibers
•  E. S. Penev, V. I. Artyukhov, B. I. Yakobson, “Basic structural units in carbon fibers: Atomistic models and tensile behavior”, Carbon 85, 72–78 (2015)

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.

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, 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)

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

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

Luqing Wang, a third-year graduate student in Yakobson’s Group, has received the 2016 Franz and Frances Brotzen Fellowship Award from the MSNE 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.

Check out our posters at the Spring ’16 Faculty Data Science Meetup hosted by the Ken 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 M_1-xM’_xX_2yX’_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.

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

Graphene 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.