31 Aug

Scientists Create First NonCarbon Material with NearDiamond Hardness

first_imgResearch scientists have created the first non-carbon-based material with a hardness approaching that of diamond. Their work could have a significant impact on technologies and industries that rely on diamond as a cutting and drilling tool and abrasive. Extremely hard yet metallically conductive: Researchers develop novel material with high-tech prospects Explore further Citation: Scientists Create First Non-Carbon Material with Near-Diamond Hardness (2007, March 28) retrieved 18 August 2019 from https://phys.org/news/2007-03-scientists-non-carbon-material-near-diamond-hardness.htmlcenter_img This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. The material is a boron nitride “nanocomposite.” This means that, rather than consisting of one large continuous crystal, it is made of crystalline boron-nitride grains that are each a few to several nanometers in size. Although research groups have previously reported boron carbonitride materials, claimed to be the second and third hardest materials after diamond, the particular versions, or “phases,” of those materials were unstable at high temperatures. In industry, this is a major drawback.“The real breakthrough would be a bulk material that is hard, tough, and thermally stable, and thus ideal for cutting and drilling. We are the first to synthesize a bulk noncarbon material that fits this description,” said Natalia Dubrovinskaia, a researcher with the University of Heidelberg and the University of Bayreuth, both in Germany, to PhysOrg.com. Dubrovinskaia is the lead author of the paper describing the new material, which appears in the March 8 edition of Applied Physics Letters.For many materials composed of crystalline grains, also referred to as polycrystalline materials, there is a grain size for which the material’s hardness is optimized. This size is often in the nanometer range.Along this line of thought, Dubrovinskaia and her colleagues synthesized and conducted several experiments on a series of polycrystalline and nanocrystalline phases of boron nitride. This characterization included measuring the samples’ “Vickers hardness,” a test that assigns a hardness value to a material based on how readily it is indented by diamond. That value can be expressed in terms of the pressure applied by the diamond – using the pressure unit “pascal” – before it makes an indentation. For very hard materials that usually means billions of pascals (gigapascals, GPa). Single-crystal diamond, the hardest type, has a hardness of about 100 GPa.The boron nitride nanocomposite synthesized by Dubrovinskaia and her group displayed a maximum hardness of 85 GPa at a grain size of about 14 nanometers, and is thermally stable up to 1600 degrees Kelvin (about 2400 degrees Fahrenheit). The material’s hardness arises from two factors: the nanoscale-grain-size effect and each grain’s two-phase composition. That is, each grain has a nanoscale crystalline structure and a sub-nanoscale structure. This complex composition significantly increases the bulk material’s mechanical strength.Prior to this research, the next hardest known material after single-crystal diamond was cubic boron nitride, a single-crystal phase of the material, which has a Vickers hardness of 50 GPa. That leaves a rather large 50 GPa gap.“This gap can be filled by boron nitride nanocomposites, particularly by tuning their grain size and the compositional structure of the grains,” says Dubrovinskaia. “These materials may come to play an important role in industry.”Citation: Natalia Dubrovinskaia, Vladimir L. Solozhenko, Nobuyoshi Miyajima, Vladimir Dmitriev, Oleksandr O. Kurakevych, and Leonid Dubrovinsky, “Superhard nanocomposite of dense polymorphs of boron nitride: Noncarbon material has reach diamond hardness.” Appl. Phys. Lett. 90, 101912 (2007)Copyright 2007 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.last_img read more

31 Aug

Qubits and Branes Share Surprising Features

first_img Citation: Qubits and Branes Share Surprising Features (2008, July 3) retrieved 18 August 2019 from https://phys.org/news/2008-07-qubits-branes-features.html Most recently, Duff and colleagues from Imperial College London and the Institute for Research in Fundamental Sciences in Tehran, Iran, have discovered another correlation. They’ve shown that the “branes” in string theory mathematically correlate to the qubits in quantum information theory. Their study, titled “Wrapped Branes as Qubits,” is published in a recent issue of Physical Review Letters.“These relations between black holes and qubits are still mysterious,” Duff told PhysOrg.com. “The significance of this recent paper is that, by invoking branes wrapping around the extra dimensions, it resolved the puzzle of why black holes should display any kind of two-valuedness: ‘To wrap or not to wrap; that is the qubit.’”In string theory, which requires extra dimensions, branes are theoretical objects that can be used to describe parts of the universe on a quantum scale. For instance, black holes can be described by four D3-branes intersecting at an angle, which can be useful for understanding the microscopic origins of black hole entropy.In the current study, the researchers have shown that four D3-branes can also be wrapped around the six extra dimensions of space (that exist in 10-dimensional string theory) in a way that closely resembles an entangled three-qubit state. As the physicists explained, the way that each D3-brane can wrap one way or the other around dimensions resembles the two states that a qubit can have. The researchers showed that a similar correlation exists between M2-branes, which can wrap in one of three ways around dimensions, and qutrits, which have three possible states.To mathematically demonstrate this connection, the physicists used a well-known fact from quantum information theory: a three-qubit state can be described by five parameters (four real numbers and an angle). They showed how these five parameters correspond to the four D3 branes and the branes’ angle of intersection. The work adds to a growing body of papers published in the past year on correlations between entanglement and black holes (or quantum gravity). As the physicists described, these papers are building a kind of dictionary of translations between phenomena in one language to the phenomena in the other. “When two very different areas of physics share the same mathematics, one can learn new things about each field by borrowing techniques from the other,” Duff said. “This has been a two-way pay-off and we are certain that yet more correlations will be discovered.” However, no one yet knows whether there are any physical reasons underlying these mathematical coincidences. As Duff said, “an underlying physical basis, if it exists, would be an extra bonus.”Still, understanding the mathematical correlations could be enough to lead to some interesting applications in quantum information theory.“The weird kind of numbers known as octonions have fascinated both mathematicians and physicists for decades,” Duff said. “But in their recent books, both Roger Penrose and Ray Streater have written them off as ‘lost causes in physics’ because they have so far failed to find any application. However, we believe that the tripartite entanglement of seven qubits (inspired by stringy black holes) provides a way of testing octonions in the laboratory, and this might find applications in QI, for example, in cryptography.”More information: Borsten, L.; Dahanayake, D.; Duff, M. J.; Ebrahim, H.; and Rubens, W. “Wrapped Branes as Qubits.” Physical Review Letters 100, 251602 (2008).Copyright 2008 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. What do black holes and entangled particles have in common? Until about a year ago, physicists thought that the two entities existed in completely separate worlds. Then, in 2007, physicist Michael Duff from Imperial College London demonstrated a correlation between the entanglement of three qubits and the entropy of a black hole. In the past year, several studies have demonstrated even more connections. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. (Left) A simulated view of a black hole, and (right) a qubit representation. Credit for black hole: Ute Kraus, physics education group, Theoretische Astrophysik Tübingen, Space Time Travel (http://www.spacetimetravel.org/).last_img read more