Fall 2019 Issue
Material World
When new materials are discovered and developed they can dramatically alter scientific fields and industries. That used to be a rare occurrence. Now greater computing power, innovative tools, and a deeper understanding of processing are giving scientists the opportunity to design or cultivate new materials more frequently than ever before.
At UTSA, Kimberly Andrews Espy, provost and vice president for academic affairs, and Bernard Arulanandam, interim vice president for research, have identified materials science as one of the university’s research specialties and noted its value to fundamental futures. Sombrilla Magazine has identified four fascinating materials research projects at UTSA that are either addressing critical issues facing society or potentially shifting the long-term outlook of certain industries.
Safer Nuclear Future
More than eight years have passed since the nuclear disaster at Fukushima, Japan, but thousands who evacuated the area have yet to return to their homes. While the world watched the most devastating nuclear incident since Chernobyl in 1986, world leaders acted quickly to ensure something similar wouldn’t happen in their countries. That’s why the U.S. Department of Energy made a concerted effort to accelerate fuel cycle research and the development of new, accident-tolerant nuclear fuels that could help sustain catastrophic accidents like the one that occurred at Fukushima.
UTSA materials physics professor Elizabeth Sooby Wood [pictured above] runs a lab studying accident-tolerant nuclear fuels, and in addition to backing by the DOE, the venture is supported by nearly $450,000 in grants from the Westinghouse Electric Co. “Very few university labs can work with uranium, so we’re combining a really diverse campus with a really rare skillset,” Wood says. “UTSA having that kind of training ground in a diverse area is something that’s very attractive to companies like Westinghouse, the Department of Energy, and the Nuclear Regulatory Commission.”
Wood notes that the Fukushima disaster was different than previous infamous meltdowns because it was caused by a loss of coolant. At the center of a nuclear plant’s reactor is the core, which contains uranium dioxide fuel stored in energy-rich pellets stacked inside metal rods. At Fukushima, a tsunami flood created power outages to several reactors, but the uranium dioxide fuel continued to generate heat. The overheated water became steam, which chemically reacted with the fuel rods’ zirconium cladding and subsequently caused radioactive material to leak.
While other labs are looking into a safer replacement for zirconium cladding, Wood’s lab is studying fuels that would handle the intense conditions brought about by a loss of coolant better than uranium dioxide, which has been the commercial standard for more than a half-century. Uranium silicide, in particular, has shown the potential to offer improved safety and fuel economy. Her team studies very small amounts of uranium silicide under extreme conditions, whether it’s 100% steam or a temperature of 2,200 degrees Fahrenheit. They then employ X-ray diffraction to see what chemical phases formed and scanning electromicroscopy to see what the bulk material looks like. “Is it cracked? Is it falling apart? Does it look like nothing happened? Those are the questions we try to answer, and then we iterate on that,” Wood says.
Because uranium silicide has more metallic and ductile properties than uranium, it can also better accommodate alloying additives like niobium and chromium that could further delay disastrous reactions during a loss of coolant accident in a commercial reactor. Westinghouse is highly interested in the performance of these additives and the tests have been promising so far. Wood says her goal is to produce something so robust that it’s ready for a formal radiation study.
Catalysts and Conversion
Gary Jacobs is a chemical engineering professor whose research specializes in heterogeneous catalysis and a process known as Fischer-Tropsch synthesis. As you can imagine, he has a difficult time describing his job at social functions or even to his family. Jacobs jokes that “Have you got two hours?” is his typical response as he clicks through slides breaking down FTS. The science may be complicated, but the research being carried out by Jacobs and his heterogeneous catalysis group—comprised mostly of graduate students from mechanical engineering and undergraduate students from chemical engineering—is highly valuable for both the petrochemical and renewable fuels industries.
Texas is currently the nation’s leading producer of natural gas and oil, as well as a major player in coal. “This is a good location for thinking about alternative energy pathways and Fischer-Tropsch synthesis,” says Jacobs, who came to UTSA from the University of Kentucky in 2017. FTS is essentially a series of chemical reactions used to convert synthetic gas derived from natural gas, biomass, or coal into liquid hydrocarbons. While high-temperature FTS produces gasoline-range hydrocarbons, Jacobs and his team focus on low-temperature FTS, a more environmentally friendly production process for hydrocarbons used in sulfur-free jet fuels and diesels, premium waxes, lubricants, alcohols, and other helpful products.
Specifically, his group produces and tests catalysts to improve this process. Catalysts are substances that increase the rate of chemical reactions, and they’re usually based on active metals like cobalt or iron. “We are trying to speed up reactions that we want, and inhibit reactions that we don’t want,” Jacobs says.
Catalysts are also very important to the water-gas shift reaction being implemented in the production and purification of hydrogen for fuel cell vehicles. “This is very futuristic,” Jacobs says. “They have developed fuel cell vehicles and portable power devices, but in order to get them into the hands of the public, they need to get the costs down—not only for the vehicle itself but also for the fuel cell and the fuel processor.”
In fuel cell vehicles, compressed hydrogen is used to generate electricity to power the motor, but hydrogen production simultaneously produces carbon monoxide that poisons catalysts on the fuel cell. The low-temperature water-gas shift reaction converts that carbon monoxide and generates more hydrogen gas. However, doing that in a portable power device presents thermodynamic and kinetic challenges for the catalysts currently used in the industry. “You’ll be starting up and shutting down very rapidly, so you need a catalyst that can do that. You want a catalyst that is going to pack a punch with a small weight and a small volume at low temperature,” Jacobs explains. “That’s what we’re trying to accomplish.”
Jacobs has extensively worked with Honda Research in this field. His team is also collaborating with Brazil’s National Institute of Technology on the conversion of bioethanol into hydrogen.
Dissipating Devastation
Two earthquakes over the Fourth of July holiday this year accounted for the biggest tremors that Southern California had experienced in 20 years. According to the U.S. Geological Survey, the pair of earthquakes also accounted for approximately $1 billion in economic losses. While many Californians are still picking up the pieces, mechanical engineering professor David Restrepo is honing materials that could make those expensive post-earthquake reconstruction efforts a thing of the past.
Restrepo’s lab recently won funding to test architectural materials that can help reduce the disruptive movements that occur during seismic events. Architects currently rely on thick, elastic dampers to mitigate a building’s movement during tremors, but these damping devices can permanently deform upon impact and melt during fires. Restrepo’s goal is to develop building materials that can both bear the weight of a structure while expending the energy of an earthquake.
“We’re working on getting new architectural materials with the right shape that can deform upon an earthquake, trap the energy, dissipate it, and then return to its undeformed state without the need of extra processing or repairs,” Restrepo says.
A building’s walls can shear and separate during an earthquake, so Restrepo aims to place repeating structures known as periodic cellular materials within the walls to avoid this deformation. In addition to absorbing high levels of energy this solution would reduce structural steel and construction costs as well as the weight of materials. Restrepo and his team are assessing flexible architectural materials and working on mathematical formulas to calculate the strength required for an optimal product.
Restrepo hopes to incorporate this science not only in buildings but in cars and other structures that could potentially sustain high impacts. “This is not just about buildings,” he says. “It’s also about saving lives.” He is currently collaborating on the research with civil engineers at Colombia’s Universidad EAFIT, and they’re hoping to have results by the end of this year.
A Landslide Solution
“In China they really suffer from landslides,” says Jie Huang, an associate professor of geotechnical engineering at UTSA. He’s not sugar-coating it. Although 25 to 50 people in the U.S. die each year in landslides, more Chinese people often perish in a single event. In 2017 a single landslide buried more than 140 people in the Sichuan province of southwestern China. Nine years earlier the Wenchuan earthquake set off a large series of landslides that accounted for 20,000 deaths in the province. Events like these also cost billions annually in property damage and pour millions of tons of soil into China’s rivers.
Landslides often occur when heavy rainfall hits sloping areas with weak, loose soil. The problem with planning against one is that the loose layer of soil is often too far underground to be detected with the naked eye. “Predicting is the hard part,” Huang says. The U.S. Army Corps of Engineers now uses drones to capture daily images of areas that could be a potential landslide hazard, but that scope is extremely limited, and it doesn’t help large, mountainous, developing countries where landslides continue to be the most devastating.
To make soil stronger along those steep and rocky slopes, Huang came up with a practical solution: a solution. He came up with a mixture of soil, fertilizer, soil conditioner, fiber, cement, and a water retention agent that improves the growth of vegetation in landslide-prone areas. Plants absorb water and reduce the kind of water infiltration that weakens soil and causes landslides. If someone wanted to grow landslide-halting plants, they would usually achieve this through hydroseeding, which uses a pump to blast seeds over a surface. However, hydroseeding is often ineffective in dense, rocky areas because the seeds don’t stick when they’re spread.
Huang’s engineered mixture includes added soil and adhesive that allows the seeds to grow in unusual places, while the water retention agent removes the need for plant maintenance. “This way, they’ll grow through cracks in the rock and even off a slope,” he says. Huang’s article about the mixture and its experimental study was published in the scientific journal Landslides, and the solution itself has performed quite well in pilot tests in western China.
Borophene Revolution
Physics professor Arturo Ponce-Pedraza recalls the moments in which he, Ph.D. student Diego Alducin, and former physics department chair Miguel Yacaman identified and captured images of a two-dimensional layer of boron atoms in 2015. Borophene, as it’s now commonly called, had been synthesized by a team at Northwestern University that sent the sample to UTSA for analysis. “When we imaged the borophene using the annular bright field method, we got very excited,” Ponce-Pedraza says with a grin. “We sent the image back right away—the same day after the microscopy session—and they got very excited.”
That collective excitement was more than justified. The existence of borophene had been theorized since the 1990s, but this identification sent ripples through the scientific world. For years chemists, physicists, and engineers had been imagining a new industrial revolution built around graphene (a two-dimensional layer of carbon atoms) because of its phenomenal ability to conduct electricity at room temperature. Since that 2015 discovery by Northwestern and UTSA, however, researchers have found that borophene is stronger and more flexible than graphene.
The potential applications of borophene are, frankly, mind-blowing. Scientists predict that it will be key to improved hydrogen storage and more powerful lithium-ion batteries, which is fantastic news for the growing electric car industry. Because it’s more flexible than graphene, borophene also has holds plenty of promise for the future of foldable electronics. Researchers have even speculated that borophene could spark the next generation of wearable technology, quantum computers, and biomolecule sensors due to its capacity as a superconductor.
Don’t run off to add the Apple Boro-Phone Plus to your wish list just yet, though. It will likely take at least another decade before borophene is widely integrated in any kind of electronics. Large quantities of borophene have yet to be produced and the 2D material has only been stable under certain isolated conditions. In our environment, Ponce-Pedraza says, it currently oxidizes and degrades. “Producing it on a large scale will be challenging. It’s very sensitive, especially because it’s one single layer of atoms that interacts with nitrogen and oxygen.” Ponce-Pedraza used aberration-corrected electron microscopy to identify borophene and he continues to study the electric and environmental responses of the 2D layer. Such research of borophene’s properties are crucial to an industry that aims to produce it in bulk in the 2030s.
Saving Energy, Earning Acclaim
Banglin Chen has been nothing short of prolific since the time he arrived at UTSA. As the Dean’s Distinguished Chair Professor of Chemistry and Microsoft’s Endowed Professor, Chen’s work on gas storage, gas separation, photonics, sensing, and heterogeneous catalysis has been published more than 40,000 times in the nearly 300 peer-reviewed articles and books with citations. His findings have been published in Science, Nature Materials, Nature Energy, Advanced Materials, Energy, Journal of the American Chemical Society, and Environmental Science.
Chen added two more accolades to his résumé this year. In March he received the distinguished Humboldt Research Award, which is given to researchers whose fundamental discoveries, new theories, and insights have made a significant impact on their disciplines. In July Chen was elected to become a Foreign Fellow of the European Academy of Sciences in recognition of his vast contributions to science and technology research. Chen, a chemist who specializes in nanoporous materials, says the two distinctions go hand in hand. “I was quite excited,” he says of winning the Humboldt award. “Such an honor motivated me to achieve more not only on the science itself but also on the science and technology bridge between Europe and the United States.”
Chen’s research interest is the use of metal-organic frameworks as materials for gas storage and gas separation to lower energy and economic costs. He is currently developing membranes to commercialize materials for large-scale gas separations. This kind of innovation is incredibly valuable to the petroleum industry because it would allow manufacturers to perform the separations for far less money than standard oil-refinement techniques require.
Chen, along with postdoctoral students Libo Li and Ruibiao Lin, also solved a major obstacle in the plastics field. The industry has long struggled to extract ethylene—the molecule used to create polyethylene, the plastic used to make shopping bags and other everyday containers. Chen and his team showed that a modification to a well-studied metal organic framework enabled it to separate purified ethylene out of a mixture with ethane. “Ethylene/ethane separation is one of the most important industrial separations because of the very importance of ethylene, which costs a lot of energy to make,” he explains.
When making polyethylene, the ethylene must be highly purified for the manufacturing process to work, but the current industrial technology for separating ethylene from all the other hydrocarbons is a high-energy process that cools down the crude to more than 100 degrees below zero Celsius. This proposed alternative method of separation would drastically reduce the energy needed to make the 170 million tons of ethylene manufactured each year throughout the world.
