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Stronger materials can flourish with new images of plastic flow

−2, which are obtained by hydrodynamic modeling (see “Methods” section). b Spatial overlap of the pump-probe in terms of crystal lattice and comparison of diffraction patterns of the environment between simulations and experiments. A simulated diffraction pattern is used to identify the detected lattice planes. Credit: DOI: 10.1038 / s41467-022-28684-z “width =” 800 “height =” 530 “/>

Fig. 1: Configuration for experiments with a laser pump and an electronic probe and the diffraction pattern of Al single crystals under ambient (uncompressed) conditions. Experimental setup for UED in situ under dynamic compression. The 3.7 MeV electrons generated by the radio frequency (RF) gun are focused by two separate solenoids per sample; the spot size of the electron beam at the sample site is 18184 μm × 250 μm (x × y), the charge of the electron beam is 9090 fCl, and the pulse duration is 00.6 ps. The sample is rotated around the Y axis at a certain angle to examine the lattice planes with the desired orientation (see bottom panel). The sample is flown by counter-propagation laser pulses (800 nm, 20 ps at half height, ≤10 mJ) with a Gaussian intensity profile (~ 360 μm at half height). The angle of incidence of the laser is close to normal. The inset shows the time of peak particle velocity and peak pressure in Al with a thickness of 200 nm, irradiated with a laser fluence of 4.3 J.−2, which are obtained by the method of hydrodynamic modeling (see section “Methods”). b Spatial overlap of the pump-probe in terms of crystal lattice and comparison of diffraction patterns of the environment between simulations and experiments. A simulated diffraction pattern is used to identify the detected lattice planes. Credit: DOI: 10.1038 / s41467-022-28684-z

Imagine you are throwing a tennis ball on a sleeping mattress. The tennis ball will slightly bend the mattress, but not forever – lift the ball back and the mattress will return to its original position and strength. Scientists call this the elastic state.


On the other hand, when you drop something heavy – like a refrigerator – a force pushes the mattress into what scientists call a plastic state. The plastic state in this sense is not the same as the plastic jug for milk in your refrigerator, but rather the constant readjustment of the atomic structure of the material. If you remove the refrigerator, the mattress will be compressed and, well, uncomfortable, to put it mildly.

But the elastic-plastic displacement of the material concerns more than the comfort of the mattress. Understanding what happens to material at the atomic level as it transitions from elastic to plastic under high pressure may allow scientists to develop more durable materials for spacecraft and fusion experiments.

So far, scientists have struggled to get clear images of the material’s transformation into plasticity, leaving them in the dark about what tiny atoms do when they decide to leave their cozy elastic state and go to the plastic world.

Now, for the first time, scientists from the Department of Energy’s SLAC National Accelerator Laboratory have received high-resolution images of a tiny aluminum single-crystal specimen as it transitions from an elastic state to a plastic one. The images will allow scientists to predict how a material behaves when it undergoes plastic transformation within five trillionths of a second of the phenomena occurring. The team released its results today The nature of communication.

The last sigh of the crystal

To make the images of the aluminum crystal sample, the scientists had to apply force, and the refrigerator was obviously too big. So instead they used a high-energy laser that hit the crystal hard enough to transfer it from elastic to plastic.

Because the laser generated shock waves that compressed the crystal, the scientists sent a beam of high-energy electrons through it using a fast SLAC “electronic camera” or a Megaelectronvolt Ultrafast Electron Diffraction (MeV-UED) device. This electron beam scattered from aluminum nuclei and electrons in the crystal, allowing scientists to accurately measure its atomic structure. Scientists took several pictures of the sample while the laser continued to compress it, and this series of images eventually turned out to be like a video with a book cover – a fragmentary film about the dance of crystal in plastic.

More precisely, high-resolution images showed scientists when and how line defects appeared on the sample – the first sign that the material was hit with too much force to restore it.

The defects of the line are similar to torn strings on a tennis racket. For example, if you use your tennis racket to lightly hit a tennis ball, the strings of your racket will vibrate slightly but return to the starting position. However, if you hit the racket on the bowling ball, the strings will fall out of place and will not be able to bounce. Similarly as high energy laser struck a pattern of aluminum crystal, some rows of atoms in the crystal shifted. Tracking these shifts – line defects – using an electronic MeV-UED camera showed the crystal’s journey from elastic to plastic.

Scientists now have high-resolution images of these defects in the line, showing how quickly the defects grow and how they move when they appear, said SLAC scientist Menzhen Mo.

“Understanding the dynamics plastic deformation will allow scientists to add artificial defects to the lattice structure, “Moe said.” These artificial defects can provide a protective barrier that prevents deformation of materials under high pressure in extreme conditions. “

Moment UED to shine

The key to the experimenters ’fast and clear images were the high-energy MeV-UED electrons, which allowed the team to sample the images every half second.

“Most people use relatively little electron energy in experiments with UEDs, but we use 100 times more energetic electrons in our experiment,” said Xie Wang, a scientist with SLAC. “At high energy you get more particles in a shorter pulse, which provides 3D images of excellent quality and a more complete picture of the process.”

Researchers hope to apply their new understanding of plasticity to a variety of scientific applications, such as strengthening materials used in high temperatures. nuclear fusion experiments. Siegfried Glenzer, director of the science of high energy density, said that to predict their performance in a future fusion reactor is urgently needed to better understand the reaction of materials in extreme conditions.

“Hopefully, the success of this study will motivate the introduction of higher laser power to test a greater variety of important materials,” Glenzer said.

The team is interested in testing materials for experiments to be conducted at ITER Tokamak, a facility that hopes to become the first to produce sustainable fusion energy.


Atomic gold melting film can help develop materials for future fusion reactors


Additional information:
Menzhen Mo et al., Ultrafast visualization of initial plasticity in dynamically compressed matter, The nature of communication (2022). DOI: 10.1038 / s41467-022-28684-z

Citation: New images of plastic flow (2022, February 25), obtained on February 25, 2022 from https://phys.org/news/2022-02-stronger-materials-bloom-images-plastic.html, can flourish more strong materials

This document is subject to copyright. Except for any honest transaction for the purpose of private study or research, no part may be reproduced without written permission. The content is provided for informational purposes only.



Reported by Source link

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Stronger materials can flourish with new images of plastic flow

−2, which are obtained by hydrodynamic modeling (see “Methods” section). b Spatial overlap of the pump-probe in terms of crystal lattice and comparison of diffraction patterns of the environment between simulations and experiments. A simulated diffraction pattern is used to identify the detected lattice planes. Credit: DOI: 10.1038 / s41467-022-28684-z “width =” 800 “height =” 530 “/>

Fig. 1: Configuration for experiments with a laser pump and an electronic probe and the diffraction pattern of Al single crystals under ambient (uncompressed) conditions. Experimental setup for UED in situ under dynamic compression. The 3.7 MeV electrons generated by the radio frequency (RF) gun are focused by two separate solenoids per sample; the spot size of the electron beam at the sample site is 18184 μm × 250 μm (x × y), the charge of the electron beam is 9090 fCl, and the pulse duration is 00.6 ps. The sample is rotated around the Y axis at a certain angle to examine the lattice planes with the desired orientation (see bottom panel). The sample is flown by counter-propagation laser pulses (800 nm, 20 ps at half height, ≤10 mJ) with a Gaussian intensity profile (~ 360 μm at half height). The angle of incidence of the laser is close to normal. The inset shows the time of peak particle velocity and peak pressure in Al with a thickness of 200 nm, irradiated with a laser fluence of 4.3 J.−2, which are obtained by the method of hydrodynamic modeling (see section “Methods”). b Spatial overlap of the pump-probe in terms of crystal lattice and comparison of diffraction patterns of the environment between simulations and experiments. A simulated diffraction pattern is used to identify the detected lattice planes. Credit: DOI: 10.1038 / s41467-022-28684-z

Imagine you are throwing a tennis ball on a sleeping mattress. The tennis ball will slightly bend the mattress, but not forever – lift the ball back and the mattress will return to its original position and strength. Scientists call this the elastic state.


On the other hand, when you drop something heavy – like a refrigerator – a force pushes the mattress into what scientists call a plastic state. The plastic state in this sense is not the same as the plastic jug for milk in your refrigerator, but rather the constant readjustment of the atomic structure of the material. If you remove the refrigerator, the mattress will be compressed and, well, uncomfortable, to put it mildly.

But the elastic-plastic displacement of the material concerns more than the comfort of the mattress. Understanding what happens to material at the atomic level as it transitions from elastic to plastic under high pressure may allow scientists to develop more durable materials for spacecraft and fusion experiments.

So far, scientists have struggled to get clear images of the material’s transformation into plasticity, leaving them in the dark about what tiny atoms do when they decide to leave their cozy elastic state and go to the plastic world.

Now, for the first time, scientists from the Department of Energy’s SLAC National Accelerator Laboratory have received high-resolution images of a tiny aluminum single-crystal specimen as it transitions from an elastic state to a plastic one. The images will allow scientists to predict how a material behaves when it undergoes plastic transformation within five trillionths of a second of the phenomena occurring. The team released its results today The nature of communication.

The last sigh of the crystal

To make the images of the aluminum crystal sample, the scientists had to apply force, and the refrigerator was obviously too big. So instead they used a high-energy laser that hit the crystal hard enough to transfer it from elastic to plastic.

Because the laser generated shock waves that compressed the crystal, the scientists sent a beam of high-energy electrons through it using a fast SLAC “electronic camera” or a Megaelectronvolt Ultrafast Electron Diffraction (MeV-UED) device. This electron beam scattered from aluminum nuclei and electrons in the crystal, allowing scientists to accurately measure its atomic structure. Scientists took several pictures of the sample while the laser continued to compress it, and this series of images eventually turned out to be like a video with a book cover – a fragmentary film about the dance of crystal in plastic.

More precisely, high-resolution images showed scientists when and how line defects appeared on the sample – the first sign that the material was hit with too much force to restore it.

The defects of the line are similar to torn strings on a tennis racket. For example, if you use your tennis racket to lightly hit a tennis ball, the strings of your racket will vibrate slightly but return to the starting position. However, if you hit the racket on the bowling ball, the strings will fall out of place and will not be able to bounce. Similarly as high energy laser struck a pattern of aluminum crystal, some rows of atoms in the crystal shifted. Tracking these shifts – line defects – using an electronic MeV-UED camera showed the crystal’s journey from elastic to plastic.

Scientists now have high-resolution images of these defects in the line, showing how quickly the defects grow and how they move when they appear, said SLAC scientist Menzhen Mo.

“Understanding the dynamics plastic deformation will allow scientists to add artificial defects to the lattice structure, “Moe said.” These artificial defects can provide a protective barrier that prevents deformation of materials under high pressure in extreme conditions. “

Moment UED to shine

The key to the experimenters ’fast and clear images were the high-energy MeV-UED electrons, which allowed the team to sample the images every half second.

“Most people use relatively little electron energy in experiments with UEDs, but we use 100 times more energetic electrons in our experiment,” said Xie Wang, a scientist with SLAC. “At high energy you get more particles in a shorter pulse, which provides 3D images of excellent quality and a more complete picture of the process.”

Researchers hope to apply their new understanding of plasticity to a variety of scientific applications, such as strengthening materials used in high temperatures. nuclear fusion experiments. Siegfried Glenzer, director of the science of high energy density, said that to predict their performance in a future fusion reactor is urgently needed to better understand the reaction of materials in extreme conditions.

“Hopefully, the success of this study will motivate the introduction of higher laser power to test a greater variety of important materials,” Glenzer said.

The team is interested in testing materials for experiments to be conducted at ITER Tokamak, a facility that hopes to become the first to produce sustainable fusion energy.


Atomic gold melting film can help develop materials for future fusion reactors


Additional information:
Menzhen Mo et al., Ultrafast visualization of initial plasticity in dynamically compressed matter, The nature of communication (2022). DOI: 10.1038 / s41467-022-28684-z

Citation: New images of plastic flow (2022, February 25), obtained on February 25, 2022 from https://phys.org/news/2022-02-stronger-materials-bloom-images-plastic.html, can flourish more strong materials

This document is subject to copyright. Except for any honest transaction for the purpose of private study or research, no part may be reproduced without written permission. The content is provided for informational purposes only.



Reported by Source link

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