Rice University researchers see nanodiamonds created in coal fade away in seconds
Images taken by Rice University scientists show that some diamonds are not forever.
The Rice researchers behind a new study that explains the creation of nanodiamonds in treated coal also show that some microscopic diamonds only last seconds before fading back into less-structured forms of carbon under the impact of an electron beam. The research by Rice chemist Ed Billups and his colleagues appears in the American Chemical Society’s Journal of Physical Chemistry Letters.
Billups and Yanqiu Sun, a former postdoctoral researcher in his lab, witnessed the interesting effect while working on ways to chemically reduce carbon from anthracite coal and make it soluble. First they noticed nanodiamonds forming amid the amorphous, hydrogen-infused layers of graphite.
It happened, they discovered, when they took close-ups of the coal with an electron microscope, which fires an electron beam at the point of interest. Unexpectedly, the energy input congealed clusters of hydrogenated carbon atoms, some of which took on the lattice-like structure of nanodiamonds.
“The beam is very powerful,” Billups said. “To knock hydrogen atoms off of something takes a tremendous amount of energy.”
Even without the kind of pressure needed to make macroscale diamonds, the energy knocked loose hydrogen atoms to prompt a chain reaction between layers of graphite in the coal that resulted in diamonds between 2 and 10 nanometers wide.
But the most “nano” of the nanodiamonds were seen to fade away under the power of the electron beam in a succession of images taken over 30 seconds.
“The small diamonds are not stable and they revert to the starting material, the anthracite,” Billups said.
Billups turned to Rice theoretical physicist Boris Yakobson and his colleagues at the Technological Institute for Superhard and Novel Carbon Materials in Moscow to explain what the chemists saw. Yakobson, Pavel Sorokin and Alexander Kvashnin had already come up with a chart — called a phase diagram — that demonstrated how thin diamond films might be made without massive pressure.
They used similar calculations to show how nanodiamonds could form in treated anthracite and subbituminous coal. In this case, the electron microscope’s beam knocks hydrogen atoms loose from carbon layers. Then the dangling bonds compensate by connecting to an adjacent carbon layer, which is prompted to connect to the next layer. The reaction zips the atoms into a matrix characteristic of diamond until pressure forces the process to halt.
Natural, macroscale diamonds require extreme pressures and temperatures to form, but the phase diagram should be reconsidered for nanodiamonds, the researchers said.
“There is a window of stability for diamonds within the range of 19-52 angstroms (tenths of a nanometer), beyond which graphite is more stable,” Billups said. Stable nanodiamonds up to 20 nanometers in size can be formed in hydrogenated anthracite, they found, though the smallest nanodiamonds were unstable under continued electron-beam radiation.
Billups noted subsequent electron-beam experiments with pristine anthracite formed no diamonds, while tests with less-robust infusions of hydrogen led to regions with “onion-like fringes” of graphitic carbon, but no fully formed diamonds. Both experiments lent support to the need for sufficient hydrogen to form nanodiamonds.
Kvashnin is a former visiting student at Rice and a graduate student at the Moscow Institute of Physics and Technology (MIPT). Sorokin holds appointments at MIPT and the National University of Science and Technology, Moscow. Yakobson is Rice’s Karl F. Hasselmann Professor of Mechanical Engineering and Materials Science, a professor of chemistry and a member of the Richard E. Smalley Institute for Nanoscale Science and Technology. Billups is a professor of chemistry at Rice.
The Robert A. Welch Foundation, the Ministry of Education and Science of the Russian Federation and the Russian Foundation for Basic Research supported the research.
David Ruth | Eurek Alert!
A feel for flight: How bats are teaching scientists to build better aircraft
04.05.2015 | Columbia University Medical Center
ORNL researchers probe chemistry, topography and mechanics with one instrument
04.05.2015 | DOE/Oak Ridge National Laboratory
Scientists from Nepal, Switzerland and Germany was now able to show how erosion processes caused by the monsoon are mirrored in the sediment load of a river crossing the Himalaya.
In these days, it was again tragically demonstrated that the Himalayas are one of the most active geodynamic regions of the world. Landslides belong to the...
A world-class prime systems integrator and electronic systems provider known for its rapid, innovative, and agile technology solutions, Sierra Nevada Corporation (SNC) is currently developing a new space transportation system called the Dream Chaser.
The ultimate aim is to construct a multi-mission-capable space utility vehicle, while accelerating the overall development process for this critical capability...
Today, textiles are used for more than just clothes or bags – they are high tech materials for high-tech applications. High-tech textiles must fulfill a number of functions and meet many requirements. That is why the Fraunhofer Institute for Silicate Research ISC dedicated some major developing work to this most intriguing research area. The result can now be seen at Techtextil trade show in Frankfurt from 4 to 7 May. On display will be novel textile-integrated sensors, a unique multifunctional coating system for textiles and fibers, and textile processing of glass, carbon, and ceramics fibers to fiber preforms.
Thin materials and new kinds of sensors now make it possible to integrate silicone elastomer sensors in textiles. They are suitable for applications in medical...
KAIST researchers published an article on the development of a novel technique to precisely track the 3-D positions of optically-trapped particles having complicated geometry in high speed in the April 2015 issue of Optica.
Daejeon, Republic of Korea, April 23, 2015--Optical tweezers have been used as an invaluable tool for exerting micro-scale force on microscopic particles and...
A very small and rare species of shark is swimming its way through scientific literature. But don't worry, the chances of this inches-long vertebrate biting...
23.04.2015 | Event News
23.04.2015 | Event News
13.04.2015 | Event News
04.05.2015 | Health and Medicine
04.05.2015 | Life Sciences
04.05.2015 | Physics and Astronomy