Washington, Dec 11 (PTI) Scientists have for the firsttime turned diamond into graphite using ultra-short flashesof an X-ray laser.
It is a decisive step forward in understanding thefundamental behaviour of solids when they absorb energeticradiation, researchers said.
For the first time, the researchers including FranzTavella from SLAC National Accelerator Laboratory in the US,were able to follow the graphitisation in a time-resolvedmanner.
"In addition to these fundamental aspects, understandingthe graphitisation process is important for diamond-basedtechnologies, since diamond is increasingly used forpractical applications," said Tavella, first author of thestudy published in the journal High Energy Density Physics.
Diamond and graphite are different forms of carbon thatdiffer in their inner crystal structure. Diamond is thehigh-pressure phase that forms deep in the earth.
Under normal conditions, diamond is metastable, meaningthat it converts back to graphite when the process isinitiated with sufficient energy.
There are different ways to trigger the conversion ofdiamond to graphite, for instance by simply heating thediamond under exclusion of oxygen or even with an aimedmechanical stroke, researchers said.
With heat and high pressure, graphite can be convertedinto synthetic diamonds that already have quite a marketworldwide, they said.
The team used the Italian soft X-ray free-electron-laserFERMI to shoot ultra-short flashes at tiny diamond sliceswith a thickness of just 0.3 millimetres.
"Usually, if you shoot such intense laser pulses at solidmatter, it becomes unordered, or amorphous. Diamond is adifferent example," researchers said.
It can switch its internal structure to a differentorder, thereby turning into graphite.
"In principle, it was known that if you send enoughenergy into diamond, it should graphitise. But it was notknown exactly how this happens," said Sven Toleikis fromGerman national research centre DESY.
There are two possible paths: the common so-calledthermal transition during which the absorbed energy istransferred to the internal crystal lattice of the diamonduntil it re-organises itself into the graphite structure.
Another is a non-thermal mode, where the energy absorbedby just a small fraction of the electrons in the diamondchanges the internal potential energy surface, triggering are-arrangement of the crystal lattice, researchers said.
"Non-thermal transition is much faster than thermal, thelatter occurring on picosecond timescales," said Beata Ziajafrom DESY. A picosecond is a trillionth of a second. PTI SARSAR.
This is unedited, unformatted feed from the Press Trust of India wire.