Editorial Feature

Understanding Materials with Radiation

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Radiation is commonly understood but its effects are not, and scientists have been working for years to gain an understanding. They have utilized many methods to do so, including testing radiation effects on materials to better understand their properties and uses. The typical radiation applied is ionizing: electromagnetic energy that knocks electrons out of atoms to produce ions, as opposed to the non-ionizing form that is found in magnetic resonance imaging (MRI) or microwaves.

Novel Uses of Radiation on Material

Crystal Dislocations

The winner of the 2016 Del Favero Doctoral Thesis Prize Lecture at the Massachusetts Institute of Technology’s Department of Nuclear Science and Engineering, Mingda Li PhD has investigated how crystal dislocations (a byproduct of radiation) can be made in lattice structures. He primarily used microscopy and spectroscopy for these investigations.

A defect in a precise location in a lattice structure can alter the material’s electronic properties. Overall, radiation energy can create defects more homogeneously and with a higher density than mechanical or chemical methods, a feature that could be particularly useful in applications such as thermoelectrics.

Monolayers

Researchers at Department of Energy’s SLAC National Accelerator Laboratory placed monolayer samples of molybdenum disulfide (that have a wrinkled surface) into a beam of very energetic electrons using a technique known as ultrafast electron diffraction (UED). Electrons in ultrashort pulses scattered off the sample’s atoms to produce a signal on a detector so that scientists knew where the atoms were located. The team then used ultrashort laser pulses to excite motions in the material, causing the scattering pattern to change over time.

The technique enabled the observation of the motions of electrons and atomic nuclei within molecules in less than a tenth of a trillionth of a second, and showed, for the first time, how the substance’s surface ripples form and evolve in response to laser light.

Data showed that the light pulses generated wrinkles with more than 15% of the layer’s thickness in about a trillionth of a second. These results indicated that the monolayers of different materials could be put together to engineer mixed materials with new optical, mechanical, electronic and chemical properties.

GdSi

Researchers at U.S. Department of Energy's (DOE's) Advanced Photon Source (APS) and Argonne National Laboratory applied a 4-ID-D x-ray beamline at GdSi, a compound of gadolinium (Gd) and silicon (Si). X-rays penetrated the crystalline fleck, providing information about the locations and states of its atoms and electrons.

Despite shrinking to one-seventh of its original volume, the team discovered that GdSi’s magnetism remained strong, which was not expected. By forming a resilient superstructure, following the electrons’ response to the harsh conditions, researchers believe that the material might be useful for digital memory as it needs to stand up to extreme exposures.

Asphaltene

Private energy technology company PetroBeam uses high-energy electrons to cause hydrocarbon cracking reactions. A proprietary process cracks asphaltenes, or what the company’s calls the most difficult component of crude oil, so that the molecular weight of the feedstock shifts for overall density and viscosity reduction.

Laboratory scale tests showed that the e-beam processing disrupts and partially decomposes heavy components, such as asphaltenes, in crude oil and bitumen. Commercialization of the technique is occurring with investments from Ion Beam Applications S.A., a global leader in electron beam accelerators, that is considered to have approximately 80% of the installed power worldwide.

PetroBeam states that it can significantly reduce the capital intensity of refining heavy oil. By using its process to treat the feedstock leaving primary distillation, a refinery could expand its coking capacity by approximately 30% at a capital cost of $3,000 per bbl/d, which the company estimates could be recovered within 12–18 months of process initiation.

References and Further Reading

Radiation Physics Today for Materials Science

Seeing Magnetic Excitations With X-Rays

Earth-Crushing Pressure? This Electron Spin Doesn't Care

Petrobeam

Ultrafast 'Electron Camera' Visualizes Ripples in 2-D Material

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