Extreme heat strengthens pure metals

Rule-breaking discovery reveals a new way to strengthen metal in extreme conditions

Northwestern University

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

There’s a reason why blacksmiths fire metals before hammering them. Heat always softens metal, making it more malleable and easier to reshape.

Or does it?

In a surprising new study, Northwestern University engineers discovered that, in extreme conditions, heat doesn’t soften pure metals — it strengthens them. 

Not only does this new finding challenge long-held assumptions of how metals behave, it also could provide new insights for designing metals for futuristic applications in extreme conditions, such as hypersonic flight, extraterrestrial construction and advanced manufacturing.

The study will be published Tuesday (Feb. 17) in Physical Review Letters.

“One of the most basic tenets in metallurgy is that if you heat a metal, it becomes softer,” said Northwestern’s Chris Schuh, who led the study. “That is metallurgy 101. But we found that if you heat a pure metal and attempt to deform it at extremely high speeds, it flips. The opposite happens and the metal strengthens, resisting the deformation. It’s counterintuitive and makes us realize that, if we want to design materials for extreme conditions, we need to step away from conventional knowledge.”

Schuh is the dean of Northwestern’s McCormick School of Engineering, where he also serves as the John G. Searle Professor of Materials Science and Engineering. Ian Dowding, a Ph.D. graduate from Schuh’s group, is the paper’s first author.

Pummeling metals with tiny particles

At everyday speeds, metals deform — meaning they bend, stretch or dent — in ways that scientists understand well. Heat helps atoms move, making metals softer and easier to shape. But when deformation happens extremely fast — in millionths or billionths of a second — those same rules no longer apply.

Because conventional tests cannot reach these extreme conditions, Schuh and Dowding turned to an unconventional approach. The team used a specialized technique that blasts hard, microscopic particles at speeds up to hundreds of meters per second. At these speeds, the tiny particles ballistically impact the metal, stretching the metal to 100 million percent of its original length in one second.

“Within the few seconds that it takes for a car to crash, we could do almost a billion of these experiments,” Schuh said. “It’s faster than the blink of an eye by 1,000 times.” 

The team also performed the experiment with metal samples ranging from high purity to slightly alloyed versions of nickel, titanium, gold and copper and from temperatures ranging from room temperature up to 155 degrees Celsius.

Strengthening pure metals with heat

The results revealed a stark divide. As temperatures increased, pure metals became stronger and harder. Alloyed metals, however, behaved typically — becoming softer when heated.

This finding shocked the researchers. For decades, engineers have added impurities (or alloying elements) to metals to make them stronger. Pure iron, for example, is soft and bends easily. But adding carbon transforms iron into steel — a metal strong enough to support the world’s tallest skyscrapers and bridges that can hold millions of tons of weight across their lifetimes.

“It’s pretty rare that you would ever come in contact with high purity metals,” Schuh said. “Engineers don’t use them because they’re not very strong. Almost every metal around you is an alloy. So, when we design metals, we’re often talking about alloy chemistry. But, in this regime of extreme deformation, heat makes pure metals stronger.”

Schuh says that atomic vibrations are responsible for this counterintuitive behavior. If a particle slams into a pure metal at an extreme speed, it meets resistance from the metal’s vibrating atoms. At any given moment, some atoms are vibrating in a direction that opposes the deformation. As the temperature increases, those vibrations intensify, making it harder for the fast-moving particle to deform the metal’s surface. So, the metal becomes stronger.

“If we smack a pure metal really fast, we’re asking the atoms to move faster than they really want to,” Schuh said. “So, they resist and push back. That’s where their source of strength comes from.”

But in alloys, impurities act as roadblocks that also resist deformations. In that case, heating the metal gives defects the energy to overcome these obstacles, restoring the typical hotter-is-softer behavior. Adding just 0.3% alloying elements was enough to completely reverse the metal’s counterintuitive response.

Purity as a materials design parameter

These findings have implications for technologies that operate under intense heat and extreme strain rates. By heating a pure metal, it could become more resistant to sandblasting, ballistics and hypersonic speeds. Engineers also could tune a metal’s response to high temperatures by adjusting its purity.

“In space, micro-meteorites fly around and crash into things,” Schuh said. “If we want to keep them from destroying a satellite, for example, we might consider choosing a different purity metal than we would have otherwise. We could design reactive systems that sense when micro-meteorites are nearby and increase heat to make the satellite’s shell stronger. At these extreme conditions, purity could become a design parameter.”

The study, “At extreme rates, pure metals thermally harden while alloys thermally soften,” was supported by the U.S. Department of Energy (award number DE-SC0018091).

---

Journal

Physical Review Letters

DOI

10.1103/2mm1-rx7q 

Article Title

At extreme strain rates, pure metals thermally harden while alloys thermally soften

Article Publication Date

17-Feb-2026

 

Protecting turfgrass from fungal foes

University of Delaware researchers report new understandings in how microbes protect plants

University of Delaware

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Charanpreet Kaur, a research associate at the University of Delaware, is lead author of a new paper that found a UD-developed beneficial bacterium has intriguing implications for manufacturing of biological treatments for fungal disease known as dollar spot.

view more 

Credit: Evan Krape/ University of Delaware

As any plant lover knows, fungal infections can be a harbinger of doom for vegetation.

One day your cherry tomatoes are going gangbusters in the garden and, seemingly overnight, sunken brown spots appear on the plant’s leaves, withering the foliage and the fruit ripening on its vines. Thanks, tomato blight fungus.

In blade grasses, such as turfgrass found on golf courses, athletic fields and lawns, dollar spot disease presents a similar challenge. The fungal disease is characterized by the appearance of circular spots of dead turf about the size of a silver dollar, hence the name dollar spot. It is a costly problem that can run upwards of $35,000 per year to manage at an average U.S. golf course. Multiplied across an approximately $40 billion turfgrass industry, mitigation measures are much needed. Therapeutic treatments made from biological materials, such as bacteria or microbes, are a promising solution for such situations.

Take UD1022 — a unique, University of Delaware-developed beneficial bacterium proven to boost plant defenses. Discovered by UD plant biologist Harsh Bais and colleagues, this novel strain of Bacillus subtilis helps a variety of plants resist soil‑borne diseases, retain moisture and develop stronger root‑to‑shoot growth, among other benefits.

In previous work, Bais and colleagues showed in lab studies that UD1022 was effective in controlling the growth of dollar spot fungus, Clarireedia jacksonii, found on turfgrass. 

Now, further research reported in the journal Plant Stress on the effect of UD1022 on dollar spot suggests intriguing implications for manufacturing of biological treatments for the fungal disease. 

In the paper, the research team showed that when they tested whether soil treated with UD1022 would be enough to prime turfgrass plants’ innate defense response to resist dollar spot infection — the way a flu vaccine primes the body to resist the flu virus — it wasn’t. 

This was curious, as the Bais lab previously had shown UD1022 effective in priming other plants, such as tomato, Arabidopsis and rice, against various fungal and bacterial pathogens. 

“It turns out that UD1022 is good at biologically controlling the growth of dollar spot in turfgrass, but only when the bacteria (UD1022) and the fungus (dollar spot) are in front of each other,” Bais said. 

Indeed, when the research team applied UD1022 directly to leaves affected with dollar spot, the plant experienced a 43.6% reduction in disease severity. But when the researchers applied UD1022 in the soil at the root level and later introduced dollar spot fungus on the leaves, there wasn’t a huge decline in disease symptoms on the leaves. This confirmed that while applying UD1022 to the root does trigger an innate defense response in the plant, it’s just not enough to ward off infection in the leaves, far from the root system.

“It's like there's a break in the communication line, and the mechanism of how UD1022 acts against dollar spot is very different,” Bais said. “With dollar spot fungus, UD1022 has to be there directly to antagonize the fungus.”

This coincides with the research team’s findings that results waned over time, which would inform formulation and application approaches for treating the disease. And if UD1022 is present on the leaves, but not alive, no go — the dollar spot fungus grew — which showed the UD1022 must remain viable to continually antagonize the fungus.

Taken together, Bais said these findings are informing what is known about biological approaches for mitigating dollar spot disease in turfgrass. For example, while UD1022 cannot do the whole job of deterring dollar spot in turfgrass, it can offer a more sustainable disease management strategy when used as a complement to currently available approaches already in the market. In addition, it is known that UD1022 can also increase drought tolerance in turfgrass, so it is a microbe that has both positive and negative effects on living and environmental stressors a plant might encounter that would benefit from the continual presence of UD1022. 

“Biologicals like UD1022 cannot solve everything — it’s not a silver bullet. You need to keep evolving your approach,” Bais said.

Bais hopes to develop a new pipeline for biologicals like UD1022, with the potential to make greater headway against plant pathogens. Along those lines, he plans to explore the compatibility of a synthetic microbial community composed of 10-15 beneficial microbes that his laboratory has isolated over the last 21 years for use in multiple systems, during sabbatical work at Pacific Northwest National Laboratory (PNNL) in 2027. 

According to Bais, the biggest challenge in using a microbial consortium is evaluating the level of persistence of these microbes on the root surface. Bais said this is because root colonization by benign microbes is the most important factor in triggering plant health benefits against living and environmental stressors.

“Using a champion root colonizer like UD1022 in consortium with other beneficial microbes, it will be interesting to evaluate the community for root colonization and its subsequent implications on plant and soil health,” he said. 

The future work will involve using this synthetic microbial consortium in a turfgrass system or other staple monocots (single-bladed plants) like sorghum and corn, to test UD1022’s effect and plant response under realistic environmental scenarios, such as drought and dollar spot together.

“Plants go through multiple stress at a time, they don’t grow in isolation, and the compatibility of microbes in a community is very important,” said Bais. “For example, usually when plants go through a physical stress such as drought, they're more prone to fungal infection. It’s something we’re interested in at this point in time, and this paper provides a segue to our next work.”

Co-authors on the paper include Bais, Charanpreet Kaur, the paper’s lead author and a research associate in the Bais lab, and Erik Ervin, professor of turfgrass and horticultural systems and associate dean in UD’s College of Agriculture and Natural Resources.

---

Journal

Plant Stress

DOI

10.1016/j.stress.2025.101158 

 

Research advances in porous materials, as highlighted in the 2025 Nobel Prize in Chemistry

Study involving researchers from a FAPESP-supported center presents a new molecular architecture based on zirconium metal-organic frameworks (MOFs) designed for efficiently degrading emerging water contaminants

Fundação de Amparo à Pesquisa do Estado de São Paulo

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

 

image: 

Results show removal efficiencies greater than 95% for different contaminants

view more 

Credit: CDMF

Brazilian scientists have made advances in an area recognized by the 2025 Nobel Prize in Chemistry: the development and application of metal-organic frameworks (MOFs). These are porous crystalline materials that have the potential to revolutionize environmental and energy technologies.

The study involved researchers affiliated with the Center for Development of Functional Materials (CDMF), a FAPESP Research, Innovation, and Dissemination Center (RIDC) based at the Federal University of São Carlos (UFSCar).

The study introduces a novel molecular architecture based on zirconium MOFs that is designed to efficiently degrade emerging water contaminants, including industrial dyes and antibiotics. This research builds upon the scientific advances that led to last year’s Nobel Prize in Chemistry being awarded to Susumu Kitagawa, Richard Robson, and Omar Yaghi for creating a new form of molecular architecture. The laureates were responsible for establishing the fundamentals of MOFs, which are materials formed by the combination of metal ions and organic ligands that organize themselves into highly porous crystalline networks.

The researchers’ work was published in Advanced Sustainable Systems. In the article, they describe developing an innovative heterostructure that integrates a zirconium MOF (Zr-MOF), which is known for its high chemical stability, with the semiconductor silver pyrophosphate. This combination creates a material that can efficiently absorb sunlight, promote the separation of electrical charges, and generate reactive species that degrade persistent pollutants in aqueous media.

The results demonstrate removal efficiencies greater than 95% for different contaminants, as well as the transformation of these substances into significantly less toxic intermediates. This was confirmed through advanced liquid chromatography coupled with mass spectrometry analyses and phytotoxicity tests. One unique aspect of the study is its use of optical modeling based on the Six-Flux model. This model revealed that the material absorbs nearly seven times more photons in the visible spectrum than in the ultraviolet range. This finding reinforces the potential of the material for sustainable, solar-powered applications.

About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.

---

Journal

Advanced Sustainable Systems

DOI

10.1002/adsu.202501297 

Article Title

Solar-Responsive Zr-MOF/Ag4P2O7 Heterostructures for Sustainable Photocatalytic Degradation of Emerging Water Contaminants

 

Sour grapes? Taste, experience of sour foods depends on individual consumer

Even the same concentration of sour organic acids — naturally occurring or artificially added sour sources in foods — result in different perception, liking and intake for people, researchers find

Penn State

FacebookXLinkedInWeChatBlueskyMessageWhatsAppEmail

UNIVERSITY PARK, Pa. — Biting into a tart green apple is a different taste and sensory experience than sucking juice from a lemon — and both significantly vary from accidentally consuming spoiled milk. Each of these foods contains a different organic acid that gives rise to the flavor commonly referred to as “sour,” even when the taste and related mouthfeel sensations such as puckering and drying vary drastically from food to food and person to person. Now, Penn State researchers have found that while some of that difference comes from individual perceptions, the acids themselves vary in sourness, even at the same concentrations.

The researchers, who recently published their findings online in advance of the March issue of Food Quality and Preference, explained the work builds on their 2024 study that revealed roughly one in eight adults like intensely sour sensations and exceptionally sour foods. This new study dives deeper into why different acids taste differently sour, why people disagree on how sour things taste, and why some people love sour foods while others really don’t.

“Beyond just being interesting, these findings might help guide the food industry in making formulations for sour foods because these different acids have subtle taste and mouthfeel nuances to them,” said study senior author Helene Hopfer, associate professor of food science in the College of Agricultural Sciences. “We found that sourness isn’t experienced as just taste — it's also puckering and it's also drying. Equal amounts of different acids do not create equal sourness or mouthfeel. People vary widely in both how much sourness they like and how strongly they perceive it.”

The researchers recruited 71 everyday consumers — not trained tasters — who eat or drink sour foods at least once a month. The participants tasted water solutions containing equal amounts of five acids: lactic — found in sauerkraut, pickles and milk; malic — found in Granny Smith apples, fumaric — found in papayas, pears and plums; tartaric — found abundantly in grapes; and citric — in citrus fruits and juice. Each acid was tested at four increasing concentrations. Participants rated sourness, puckering, drying and overall liking.

“Because all these different organic acids are widely used by the food industry, and they're food safe, there's a lot of conventional wisdom, ‘well, you use this one for this application or use that one for that application,’” said study coauthor John Hayes, professor of food science. “But we really wanted to unpack all of that and do a systematic apples-to-apples comparison.”

The results suggest that different acids do not taste equally sour, even at the same concentration. Overall, citric acid produced the strongest sourness and puckering overall. Lactic acid produced the least sourness and puckering. More specifically, the participants generally fell into one of three groups: those who more immediately disliked the taste as sourness increased; those who more gradually disliked the taste as sourness increased; and those who liked the food experience more as the sourness increased.

The groups didn’t just taste and like sourness differently — they experienced it differently, Hayes noted. The group that more sharply disliked the taste rated sourness, puckering and drying as more intense, especially at high concentrations. This effect was strongest for non-citric acids. The opposite group that liked the sourness reported consuming more citrus fruit juices and tart fruits.

“Equal amounts of different acids do not create equal sourness or mouthfeel,” Hayes said. “People vary widely in both how much sourness they like and how strongly they perceive it. These differences matter most for acids other than citric acid and could be important for food formulation, product optimization and tailoring sour foods to different consumer segments.”

Using validated surveys, Hayes and colleagues previously found that those who like spicy food tend to have specific personality characteristics, like being motivated by rewards and an inclination toward taking risks. They also previously found that those who like and seek out bitter tastes, like pale ales, are also more prone to taking risks. However, in this study, the participants who prefer sour taste did not demonstrate different personality traits from the other groups, so sour preference seems linked to dietary exposure, not personality, Hayes said.

“We looked at whether or not personality traits were related to strong liking of sour taste because we've done a lot of work showing that people who like the burning sensation from chili peppers are risk takers and adventure seekers,” he said. “We wondered whether people who were a little more sensation seeking or risk taking and adventurous might strongly like sour taste. We thought that might explain why those one in eight adults really likes intensely sour sensations. But that didn't work out— there was no relationship.”

Study first author Astrid D'Andrea recently earned her master’s degree in food science from Penn State.

The U.S. Department of Agriculture’s National Institute of Food and Agriculture funded this research.

---

Journal

Food Quality and Preference

DOI

10.1016/j.foodqual.2025.105811 

Method of Research

Experimental study

Subject of Research

People

Article Title

Consumer segmentation for sourness: exploring perception, liking, personality, and intake