'Trophy molecule' breakthrough

Jun 29, 2012

Experts at The University of Nottingham are the first to create a stable version of a ‘trophy molecule’ that has eluded scientists for decades.

In research published in journal Science, the team of chemists at Nottingham has shown that they can prepare a terminal uranium nitride compound which is stable at room temperature and can be stored in jars in crystallized or powder form.

Previous attempts to prepare uranium-nitrogen triple bonds have required temperatures as low as 5 Kelvin (-268 °C) — roughly the equivalent temperature of interstellar space — and have therefore been difficult to work with and manipulate, requiring specialist equipment and techniques.

The breakthrough could have future implications for the nuclear energy industry — uranium nitride materials may potentially offer a viable alternative to the current mixed oxide nuclear fuels used in reactors since nitrides exhibit superior high densities, melting points, and thermal conductivities and the process the scientists used to make the compound could offer a cleaner, low temperature route than methods currently used.

The research has been led by Dr Stephen Liddle in the School of Chemistry and much of the practical work was completed by PhD student David King. The work was also supported by colleagues at the University of Manchester.

Uranium nitrides are usually prepared by mixing dinitrogen or ammonia with uranium under high temperatures and pressures. Unfortunately, however, the harsh reaction conditions used in the preparation introduces impurities which are difficult to remove. In recent years scientists have therefore focussed their attention on using low temperature, molecular methods but all previous attempts resulted in bridging, rather than the target terminal, nitrides.

The Nottingham team’s method involved using a very ‘bulky’ nitrogen ligand (an organic molecule bonded to a metal) to wrap around the uranium centre and to create a protective pocket in which the nitride nitrogen can sit. The nitride was stabilised during the synthesis by the presence of a weakly bound sodium cation (positively charged ion) which blocked the nitride from reacting with any other elements. In the final stage, the sodium was gently teased away, removing it from the structure and leaving the final, stable uranium nitride triple bond.

Dr Liddle said: “The beauty of this work is its simplicity — by encapsulating the uranium nitride with a very bulky supporting ligand, stabilising the nitride during synthesis with sodium, and then sequestering the sodium under mild conditions we were able to at long last isolate the terminal uranium nitride linkage.”

He added: “A major motivation for doing this work was to help us to understand the nature and extent of the covalency in the chemical bonding of uranium. This is fundamentally interesting and important because it could help in work to extract and separate the 2 to 3 per cent of the highly radioactive material in nuclear waste.”

The research was supported by the UK National Electron Paramagnetic Resonance (EPR) Facility, funded by the Engineering and Physical Sciences Research Council and based in the Photon Science Institute at The University of Manchester. The uranium-nitride contains an unpaired electron and by using EPR spectroscopy it was found that it behaves differently from similar compounds prepared at Nottingham.

Professor Eric McInnes, from The University of Manchester said: “EPR spectroscopy can give detailed information about the local environment of unpaired electrons, and this can be used to understand the electronic structure of the uranium ion in this new nitride. It turns out that the new nitride behaves differently from some otherwise analogous materials, and this might have important implications in actinide chemistry which is of vital technological and environmental importance in the nuclear fuel cycle.”

Explore further: Proteins: New class of materials discovered

Related Stories

How seawater could corrode nuclear fuel

Jan 26, 2012

Japan used seawater to cool nuclear fuel at the stricken Fukushima-Daiichi nuclear plant after the tsunami in March 2011 -- and that was probably the best action to take at the time, says Professor Alexandra ...

A safer route to a nuclear future?

Jun 13, 2012

By using thorium instead of uranium as fuel, nuclear power could be safer and more sustainable, according to new research.

Scientists find safer ways to detect uranium minerals

Nov 21, 2006

The threat of "dirty" bombs and plans to use nuclear power as an energy source have driven Queensland University of Technology scientists to discover a new, safer way of detecting radioative contamination in the ground. Professor ...

Recommended for you

Proteins: New class of materials discovered

4 hours ago

Scientists at the Helmholtz Center Berlin along with researchers at China's Fudan University have characterized a new class of materials called protein crystalline frameworks.

The fluorescent fingerprint of plastics

Aug 21, 2014

LMU researchers have developed a new process which will greatly simplify the process of sorting plastics in recycling plants. The method enables automated identification of polymers, facilitating rapid separation ...

Water and sunlight the formula for sustainable fuel

Aug 21, 2014

An Australian National University (ANU) team has successfully replicated one of the crucial steps in photosynthesis, opening the way for biological systems powered by sunlight which could manufacture hydrogen ...

Researchers create engineered energy absorbing material

Aug 21, 2014

(Phys.org) —Materials like solid gels and porous foams are used for padding and cushioning, but each has its own advantages and limitations. Gels are effective as padding but are relatively heavy; gel performance ...

User comments : 2

Adjust slider to filter visible comments by rank

Display comments: newest first

350
2 / 5 (4) Jun 29, 2012
This statement made me lol:

Dr Liddle said: The beauty of this work is its simplicity by encapsulating the uranium nitride with a very bulky supporting ligand, stabilising the nitride during synthesis with sodium, and then sequestering the sodium under mild conditions we were able to at long last isolate the terminal uranium nitride linkage.

Yes simplicity at it's finest.
ormondotvos
not rated yet Jun 29, 2012
Obviously not a chemist...