Captured CO2 and enlarged alloys triumph

Researchers at Sandia have secured two prestigious R&D 100 Awards for 2024, distinguishing themselves among competitors from 16 countries, including the U.S., China and others from Europe and Asia.

The awards recognize the 100 most outstanding advances in applied technologies. R&D World Magazine, which presents the annual awards, focuses on practical impact over pure research, evaluating entrants based on their products’ design, development, testing and production.

The awards highlight “demonstrable technological significance compared with competing products and technologies,” for example, smaller size, faster speed or greater efficiency or environmental impact. Once dubbed “the Oscars of invention,” the R&D 100 Awards continue to be a coveted recognition.

Since their inception in 1963, the R&D 100 Awards have recognized Sandia innovations 152 times, including this year’s honors. One of the winning projects, led by researcher Tuan Ho, aims to reduce the airborne carbon dioxide that is increasingly warming the atmosphere. The other project, led by researcher Sal Rodriguez, seeks to produce industrially useful sizes of extremely strong heat-resistant materials.

Machinable, larger-scale, self-healing RHEAs

Sal Rodriguez faced an unexpected challenge four years ago when he tried to enlarge samples of superalloys known as refractory high-entropy alloys: they broke.

“This is not supposed to happen,” Sal thought.

RHEAs were developed by aerospace engineers who needed high-temperature, high-strength materials for extreme environments. Despite their impressive melting temperatures — among the highest in the periodic table — and extraordinary strength, Sal’s team discovered that about 99% of RHEAs are brittle at room temperature, making them difficult to machine as they shatter like glass when drilled or cut.

“We were excited when we first manufactured our RHEAs,” Sal said. “What a disappointment to create alloys that can reach temperatures in excess of 2,000 Kelvin (about 3,140 degrees Fahrenheit) while retaining structural integrity, yet most were not machinable.”

Rather than abandon the project, Sal focused on the elusive 1% of RHEAs that exhibited ductility.

“The goal is to turn this technology into a multi-billion-dollar industry in critical areas such as energy, aerospace and electronics,” Sal said. “Because the field is so new, most research has focused on nano-, micro- and millimeter-scale RHEA samples, making it challenging to scale up for commercial applications. Just the same, we decided to see if we could find what we needed in the non-brittle 1%.”

Through years of testing, Sal’s team identified two key factors. On the downside, increasing the length revealed the impact of crystalline structures called material grains, which diminished material properties at larger scales. “Once we increased the manufacturing length to a few millimeters and centimeters, the RHEAs began breaking apart due to manufacturing stresses and impurities,” he said.

Conversely, in their heated, liquid state, the RHEAs exhibited potential for turbulence and swirl that enhanced the mixture of elements.

“After years of research and continuous improvement, we have demonstrated game-changing technology,” Sal said.

The team continuously redesigned, re-manufactured and re-tested RHEA samples. “As we observed what worked and what did not, we developed novel element combinations and advanced manufacturing parameters, extending the length scale, ductility, endurance under harsh environments, material quality and machinability of our RHEA components.”

Their efforts culminated in a homogeneous, micro-crack-free, highly machinable RHEA that set world records for both length and mass — 10.3 inches and 7.72 pounds — smashing previous records of 2 inches and about a quarter pound. Additionally, they demonstrated self-healing at the macroscale and corrosion resistance in nuclear molten salts at a world record temperature of 965 degrees Celsius (1,769 F).

“Our work has attracted the attention of several large companies,” Sal said, mentioning Northrop Grumman Corp. in San Diego, Dynetics Corp. in Huntsville, Alabama, and Albuquerque’s Westwind Computer Products Inc., which specializes in advanced alloy manufacturing.

The project received support from the DOE Technical Commercialization Office. Other Sandia researchers instrumental in the project were Rob Sharpe, Moises Beato, Mark Rodriguez and the Molten Salts team. Other collaborators included California Nanotechnologies, DRS Research, Plasma Technology Inc., Applied Surface Engineering and the University of New Mexico.

Low-cost direct air capture of CO2 with clay nano-interlayers

Tuan Ho and his team have developed a remarkably simple and potentially inexpensive method that relies on basic materials properties and a little chemistry to capture atmospheric carbon dioxide, thought to be a key contributor to climate change.

“Stabilizing CO2 emission levels while supporting economic development is essential for a sustainable future,” Tuan said.

While capturing CO2 from point sources like coal-fired power plants is an obvious strategy, current carbon-capture technologies often require extensive energy infrastructure, such as pipelines for CO2 transport. In contrast, direct air capture technology is more portable and easily distributed, making it suitable for a variety of locations.

However, existing methods typically rely on strong chemical bonding, requiring energy intensive, high-temperature treatment of around 900 degrees Celsius (1,652 F) for CO2 release and material regeneration.

The Sandia technology, however, is based on weak chemical interactions of CO2 with an aqueous solution confined in nanoscale interlayers of expansive clay. The approach relies on three key components: manipulable clay nanoscale interlayers, the enhanced solubility of nanoconfined CO2 compared to bulk water and rapid nanofluidic flow within the interlayers.

Instead of temperature swings, this technology uses humidity changes to capture and regenerate materials, making the process less costly and energy intensive.

First, air or flue gas is introduced into a clay column at high relative humidity, causing the clay to expand and open nanoscale interlayers for CO2 uptake. The measured CO2 uptake in clay interlayers can be 55 times higher than in bulk water. Regeneration occurs by flowing dry CO2 through the material, reducing relative humidity and collapsing the clay so it releases both water vapor and dissolved CO2. The clay is then ready for the next cycle.

Tuan’s Sandia research team included Yifeng Wang, Susan Rempe, Guangping Xu, Timothy Zwier, Melissa Mills, Eric Coker, Carlos Jove-Colon and Nabankur Dasgupta, in collaboration with Professor Cliff Johnston at Purdue University.

The idea stemmed from the team’s expertise in such fundamental science areas as nanoconfinement, clay minerals and CO2 capture and in computational and experimental methods.

“We intend to continue exploring the fundamental scientific questions that have emerged during this project, advancing the field of CO2 capture and contributing to sustainable solutions for climate change,” Tuan said.

The research was funded by Sandia’s Earth Science Laboratory Directed Research and Development investment area.