The discovery of an extremely inexpensive material that is lightweight enough to protect satellites from debris in outer space, strong enough to support the walls of pressurized vessels under average conditions on Earth, and heat-resistant at 1,500 degrees Celsius (or 2,732 degrees Fahrenheit) to protect instruments from flying debris raises the question: What single material could do all of this? Sandia National Laboratories found the sweetest answer.
It is, in fact sugar. It is made up of very thin layers from confectioners’ sugar, purchased from grocers and then burned to carbon black. This is followed by slightly thicker layers that are made of silica which is the most widely used material on Earth. The end result is a fine layer cake or, more precisely, the organic layering of seashells, with each layer helping to contain and mitigate shock.
Guangping Xu from Sandia, who led the development of this new coating, said that it can withstand a variety of insults, including shock and Xray. “This material has not been easily available. Our layered nanocomposite is a replica of a seashell structure.
Xu stated, “The self-assembled covering is not only lightweight, mechanically strong, and thermally stable enough that it can protect instruments in experimental fusion devices against their own created debris at temperatures up to 1,500 C.”
“And that might be only the beginning,” said Rick Spielman (consultant and senior scientist at University of Rochester’s Laboratory for Laser Energetics). He was credited with the initial design of Sandia’s Z machine, one of many destinations for which the new material is designed. “There are probably a hundred applications we haven’t thought of.” He sees potential electrode applications delaying rather than blocking surface electron emissions. Supporting nuclear survival
The coating can be layered on many substrates without environmental problems. This was the subject of a Sandia Patent Application in June 2021, a talk at a pulsed energy conference in December 2021, and again in a technical article in MRS AdvancesXu is the lead author of this book.
This work was done to prepare for the increased shielding required to protect diagnostics, test objects, and drivers in the future’s more powerful pulsed power machines. The pulsed-power Z machine by Sandia, currently the most powerful X-ray producer on Earth, and its successors will require even greater debris protection to prevent forces comparable to many sticks of dynamite exploding close at range. Chad McCoy loads sample coatings to Sandia’s Z-machine
Chad McCoy, a physicist at Sandia National Laboratories’ Z Machine loads samples of coatings into holders. Researchers will be able to see how certain coatings protect objects stacked behind Z. (Photo by Bret. Click the thumbnail to view a high-resolution version.
“The new shielding should positively impact our nuclear survival mission,” stated Chad McCoy, paper author and Sandia scientist. “Z is the best Xray source in the universe, but only a few percent of the energy is released. The rest are shock and debris. We want to find out if any debris has damaged our samples or altered its microstructure when we study how matter, such as metals, interacts with Xrays. We are currently at the limit of protecting sample materials from unwelcome insults. However, more powerful testing machines will require greater shielding. This new technology may be able to provide appropriate protection.
Other, less-specialized uses are also possible.
Because the shield is lightweight and environmentally friendly, it can be carried into space to serve as a protective layer for satellites. It is also lighter than heavier shielding that is less effective in protecting against space junk collisions. McCoy stated that satellites in space are constantly being hit by debris moving at the same speed as Z. “With this coating we can make debris shield thinner and decrease weight.”
When added ounces are not an issue, thicker shield coatings can be used to reinforce the walls of pressurized vessels. Expect dramatic cost savings
Guangping claims that the material cost to make a 2-inch-diameter coating of the new protective material is only 25 cents. A beryllium wafer, which is the closest match to the new coating’s thermal and mechanical properties and is used at Sandia’s Z machine and other locations as protective shields, costs $700 at current market prices for a 1-inch square, 23 micron-thick wafer. This wafer is 3,800 times more costly than the new film.
Both coatings can withstand temperatures up to 1,000 C. However, the new coating is also environmentally friendly. To aid the coating process, only ethanol is used. Toxic conditions are created by beryllium. It must be removed from the environment. How testing was done
Sandia coating strength is dependent on the principle of alternating organic layers with inorganic layers. This is a key factor in seashell longevity. Hongyou Fan, Sandia manager, and paper author, said that the organic sugar layers which have been reduced to carbon black act as a sealant. They prevent cracks from spreading through inorganic silica structures and provide layers of cushioning that increase the structure’s mechanical strength. This was also reported in a Sandia earlier attempt to imitate the seashell mode 20 years ago.
Greg Frye Mason, Sandia campaign manager for Assured Survival and Agility With Pulsed Power or ASAP, Laboratory Directed Research and Development campaign campaign funding the research initially had doubts about carbon insertion.
He stated, “I thought that organic layers would limit applicability because most degrade by 400-500 C.”
However, the carbon-black idea proved to be robust to well above 1,000 C, which was the greatest risk Frye Mason saw as a possible for the project.
Initial testing at Sandia revealed that the thickness of seashell-like coatings varied from a few layers to 13 layers. After being heated in pairs, the alternating materials were pressed against one another to crosslink their surfaces. These interwoven nanocomposite layers made of silica and burnt sugar were tested and found to be 80% stronger than silica and thermally stable at 1,650 C. Later sintering efforts revealed that the layers could be self-assembled using a spin-coating process and that their individual surfaces could still be crosslinked satisfactorily. This eliminates the need to bake each layer individually. The more efficient process produced almost the same mechanical strength.
ASAP funded research into the coating to develop methods to protect diagnostics, test samples, and next-generation pulsed power machine (NGPM) from flying debris.
Frye-Mason stated, “This coating qualifies.”