Jetzt träumt der Wissenschaftler der Goethe-Uni vom Nobelpreis
Vergrößern
In diesem High-Tech-Labor am Riedberg macht Dr.
Lkhamsuren Bayarjargal Diamanten aus Kalkspat: Wegen der starken
Laserstrahlung forscht er mit Schutzbrille
Foto: Helmut Moeller
Von KITTI POHL
Frankfurt – Von so einem Mann träumt jede Frau: Dr. Lkhamsuren Bayarjargal (38) macht Diamanten aus Kalkspat. Dieses weiße Zeugs, das sich im Wasserkocher absetzt. Dafür bekam er jetzt den renommierten Max-von-Laue-Preis.
Diamanten,
das teuerste und härteste Mineral der Welt, können seit 60 Jahren
künstlich hergestellt werden, aus Graphit. Bis Bayarjargal am Campus Riedberg
die Kalkspat-Umwandlung gelang, hat er jahrelang geforscht: „Auf den
Kanaren und in Usbekistan sind Diamanten in Kalkspat-Lagerstätten
gefunden worden. Wir wollten herausfinden, ob die Diamanten dort
entstehen können, oder hereintransportiert wurden.“
Filmreifer Diamanten-Raub auf dem Gelände des
Brüsseler Flughafens: Die Beute: Edelsteine im Wert von 37 Millionen
Euro!
mehr...
Im Laserlabor am Riedberg erzeugte der mongolische
Wissenschaftler enormen Druck und Temperatur wie im Erdinnern. „Wenn Sie
den Eiffelturm umdrehen, mit der Spitze nach unten drücken, ist die
Druckstärke in etwa mit der in unserer Diamant-Stempelzelle
vergleichbar. Und der Laser ist so stark, der würde Ihnen sofort ein
Loch in den Bauch brennen! Bei 3000 Grad entstanden die Diamanten.“
Leider
keine, die funkeln und glitzern. Bayarjargals Diamanten sind so winzig,
dass man sie nur unterm Mikroskop sehen kann. Tausende hat der Mann
hergestellt, und alle zusammen wären kaum ein Fliegenschiss. Nix für uns Mädels. Aber für die Wissenschaft sind die Frankfurter Diamanten ein Schatz.
Bayarjargal will weiter forschen, 10 000 Grad erzeugen. Sein Traum? „Der Nobelpreis wäre nicht schlecht.“ Liebe
Leser, bevor Sie nun am Wassertopf kratzen, um aus Kalkspat Diamanten
zu machen: Sie brauchen eine halbe Mio Euro, super Kenntnisse in
Laser-Technologie und ungeheures experimentelles Talent ...
Vergrößern
In der Diamantstempelzelle wird enormer Druck erzeugt, ähnlich wie im Erdinnern
Foto: Helmut Moeller
Mehr aktuelle News aus Frankfurt und Umgebung lesen Sie hier auf frankfurt.bild.de.
Some current challenges in aerospace
engineering and fission/fusion applications require materials that are
mechanically and chemically stable at extreme conditions. One such class
of materials is ultrahigh-temperature ceramics, which are often binary
transition-metal carbides, borides, or nitrides. It is therefore of
great interest to understand how to synthesize new compounds of this
type. A research team from Germany, the United Kingdom, and Berkeley Lab
working at ALS Beamlines 12.2.2 and 12.3.2 has now synthesized and characterized two novel bulk rhenium nitrides, Re2N and Re3N. Both phases are extremely incompressible, and Re3N
is also better placed for potential technological applications than are
other incompressible transition-metal carbides and nitrides of the
period-six elements because it can be formed at relatively moderate
pressures and temperatures.
Seeking the Ultrahard and Incompressible
Materials that combine mechanical properties (ultrahardness,
ultra-incompressibility), thermal properties (ultrahigh melting point),
and chemical resistance are useful for numerous industrial applications,
such as cutting and grinding tools, abrasives, components of gas
turbines, coatings for high-speed drill bits, and electronic and
semiconductor components.
The hardest and most well-known such material is diamond. Because it
occurs naturally, it has become widely used, but even diamond has
limitations. For example, it is not effective for cutting material made
of iron. Though much effort has been exerted to find affordable
synthesis routes for diamond, it generally requires high pressure and
temperature, as do most materials of this kind, making it expensive. So,
the search for new ultrahard materials that combine these useful
mechanical, thermal, and chemical properties has intensified.
Future research will endeavor to further characterize the properties
of these new materials for industrial applications, and to synthesize
them in larger quantities and at lower cost.
The incorporation of nitrogen (black balls) into the
rhenium (light grey) hcp lattice (AB stacking sequence of rhenium atoms)
at increasing pressure and temperature conditions leads to the
formation of Re3N (ABB stacking) and Re2N (AABB sequence). Nitrogen atoms occupy interstitial sites between AA or BB layers only.
The introduction of smaller atoms such as boron, nitrogen, or carbon
into interstitial sites in close-packed transition-metal lattices leads
to dramatic changes in the physical properties of the compound with
respect to that of the metal. For example, the incorporation of carbon
into group IV or V transition metals leads to an increase in melting
temperature by 1000–1500 K, yielding binary transition-metal carbides
with extremely high melting points. This characteristic, in addition to
high hardness and incompressibility, is required for materials used in
abrasive or coating applications.
The origin of the unusual properties is the complex bonding found in
these compounds, where there are metal–metal, metal–nonmetal, and
nonmetal–nonmetal contacts. Combining metals with high densities of
valence electrons (such as rhenium, osmium, and iridium) with light
elements is especially promising; however, extreme pressure and
temperature conditions are required to induce reactions.
In order to synthesize rhenium nitrides, rhenium foil was pressurized
in the range from 10–27 GPa together with nitrogen within a
diamond-anvil pressure cell and then heated by two laser beams, one from
each side, up to 2800 K. Re3N can be synthesized between 10.5–16 GPa and 1700–2250(150) K, and Re2N
was obtained at 20(2) GPa and ~2000 K. Reaction products were analyzed
by powder x-ray diffraction, in combination with density functional
theory calculations. Structural models were proposed and further
confirmed by x-ray Laue microdiffraction, allowing for detailed analysis
of phase distribution and grain sizes within the samples.
Typical results from white-beam x-ray microdiffraction. Left: An image indexed with the unit cell of Re3N.
The indices of a few reflections are shown as examples. The red dotted
curves indicate extensions of the indexed Laue zones. Middle and right: A
map of the phase distribution (Re3N and Re in black and blue areas, respectively) and the distribution of the Re3N grains and their sizes (~3–8 µm) derived from the c-axis orientation of Re3N.
By combining a heavy transition metal with a light,
covalent-bond-forming element and adding pressure and temperature,
researchers synthesized two novel materials with both high
incompressibility and proposed high hardness. An incompressible material
is difficult to compress elastically. It is resistant to volume and/or
linear compression. A hard material resists plastic (as opposed to
elastic) deformation, which involves irreversible motion of the atoms
with respect to each other.
Interesting results were obtained on the crystal chemistry of
period-six transition-metal nitrides and carbides. Researchers found
that nitrogen dissociates during Re3N and Re2N synthesis, similar to the phase formation of TiN, TaN, and Ta2N3
from the elements. This is in contrast to other known transition-metal
nitrides of period-six elements with higher atomic numbers, i.e., OsN2, IrN2, and PtN2. Close structural relationships are observed with rhenium carbide, Re2C, which was also synthesized at high pressures and temperatures.
Re3N and Re2N were characterized to be
ultra-incompressible, with bulk moduli of >400 GPa, similar to the
most incompressible binary transition-metal carbides and nitrides found
to date and significantly less compressible than pure rhenium. The
rhenium nitrides synthesized here are potential candidates as ultrahard
materials and may find some special applications in electron
conductivity at extremely high temperatures and pressures.
Bottom row: Wolfgang Morgenroth, Björn Winkler,
Alexandra Friedrich, and Florian Schröder. Top row: Lkhamsuren
Bayarjargal, Jasmin Biehler, Nadine Rademacher, and Erick A.
Juarez-Arellano.
Research conducted by A. Friedrich, B.
Winkler, L. Bayarjargal, and W. Morgenroth (Geowissenschaften,
Goethe-Universitat, Germany), E.A. Juarez-Arellano (Universidad del
Papaloapan, Mexico), V. Milman (Accelrys, UK), K. Refson
(Rutherford-Appleton Laboratory, UK), and M. Kunz and K. Chen (ALS).
Research funding: The German Research
Foundation and the Federal Ministry of Education and Research (Germany).
Operation of the ALS is supported by the U.S. Department of Energy,
Office of Basic Energy Sciences.
Publication about this research: A.
Friedrich, B. Winkler, L. Bayarjargal, W. Morgenroth, E.A.
Juarez-Arellano, V. Milman, K. Refson, M. Kunz, and K. Chen, "Novel
rhenium nitrides," Phys. Rev. Lett.105, 085504 (2010).
Эрдэм
шинжилгээний түвшинд алмазыг хиймэл аргаар буюу шохойн чулуунаас гарган
авч болохыг тэрээр баталсан байна. Энэ нь тун энгийн арга бөгөөд үүгээр
хүссэн хэмжээнийхээ алмазыг гарган авч болох юм.
Энэ
нээлтийг хийсний дараагаар бүх л эмэгтэйчүүд Л.Баяржаргал шиг залууг
мөрөөдөж байна гэсэн хөгжөөнт яриа хүртэл Германд гарчээ. Германыг
бүхэлд нь шуугиулж тун удахгүй дэлхий нийтийг байлдан дагуулах энэ
нээлтийг хийсэн 38 настай залуу монгол эрдэмтэн олон жилийн турш хийсэн
судалгаа шинжилгээнийхээ ажлыг амжилттай дуусгасандаа ихэд сэтгэл
хангалуун байгаа гэнэ. Гэсэн ч шинжлэх ухааны оргил гэж байдаггүй
болохоор Л.Баяржаргал улам ч гайхалтай нээлтүүдийг цаашид хийсээр байх
болно хэмээн найдаж байна. Хүн төрөлхтний олон зуун жилийн хүсэл
мөрөөдөл болох хамгийн үнэтэй энэ чулууг хиймэл аргаар тэр тусмаа
шохойн чулуунаас гаргаж авах арга замыг тэр нээж чадлаа.
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