Nav: Home

Stressing and straining: Geochemists answer fundamental question of mineral reactions

March 07, 2019

For geoscientists, looking at how minerals react in different conditions can provide a great deal of information about the characteristics of the materials that make up our world. In some cases, merely exposing minerals to water-based environments can yield interesting properties and results.

In a new study from the U.S. Department of Energy's (DOE) Argonne National Laboratory, scientists placed small iron oxide particles in an acidic solution, causing the oxidation of iron atoms on the surface of the particles. As the reaction progressed, the researchers observed strain that built up and penetrated inside the mineral particle.

"What's really novel about this work is that we're doing it with geological minerals that can have irregular morphologies, as opposed to idealized particles with well-defined shapes. It's a new application of these tools to understand how [oxidation] happens in nano-sized minerals." -- Paul Fenter, Argonne physicist

The shape of the particles controlled the degree and type of strain, said Argonne physicist Paul Fenter. "When we look at how things react, we are not typically worrying so much about the shape or morphology of the material. In this case, we have a result in which the spatial distribution of reactivity within the particle is not uniform, which we think is ultimately controlled by its size and shape," he said.

In looking at the iron oxide particles, also known as magnetite, Fenter and his colleagues observed the formation of hematite, a reaction that begins at the particle surface. "Essentially, what's happening is that we're changing from one kind of rust into a different kind of rust," said postdoctoral researcher Ke Yuan, the first author of the study.

When the researchers observed the changes in the particle caused by the oxidation, they observed strain that penetrated inside the material, as well as the appearance of isolated defects. "We're moving away from an understanding of these reactions as happening uniformly in one big clump of material toward a more sophisticated understanding of how the particle shape and morphology can alter and influence how a reaction proceeds," Fenter said.

"Even though these particles are all magnetite, they all react in somewhat different ways, and so this is a challenge for understanding how reactions proceed in systems where you have different micro- and nanostructures of the particles," Yuan added.

To identify the strain distributions in the material, the researchers used a technique called coherent diffraction imaging (CDI), which allowed them to peer into the atomic lattice of the material. Using CDI at Argonne's Advanced Photon Source (APS), a DOE Office of Science User Facility, the scientists were able to detect a small reduction in the lattice spacing -- less than one percent -- as a result of the oxidation of the iron. This small differentiation in the lattice spacing was spread unevenly throughout the iron oxide particles; the researchers believe it to be responsible for creating the defects that the scientists observed.

"The APS's ability to provide brilliant coherent X-rays makes it unique for this kind of experiment," said APS beamline scientist Wonsuk Cha. "By generating highly penetrating X-rays with substantial coherent flux, and then combining them with dedicated X-ray imaging instrumentation, we can map the internal structure and strain in materials in 3D with nanoscale spatial resolution and atomic sensitivity."

According to Fenter, applying CDI to real, geochemically relevant materials represents a leap forward for the technique. "What's really novel about this work is that we're doing it with geological minerals that can have irregular morphologies, as opposed to idealized particles with well-defined shapes," he said. "It's a new application of these tools to understand how this behavior happens in nano-sized minerals."

"It's a good model system for natural systems," Yuan added. "It gives us a good way to understand the reactivity of complex natural systems." 

Fenter explained that the findings could have relevance more broadly for the geoscience community. Future studies that look at how ions bind to a mineral's surface could be affected by strain, even when that strain originates from the inside of the material, he said.
-end-
An article based on the study, "Oxidation induced strain and defects in magnetite crystals," appeared in the February 11 issue of Nature Communications. Other Argonne authors include Sang Soo Lee and Andrew Ulvestad. Hyunjung Kim of Sogang University in South Korea and Bektur Abdilla and Neil Sturchio of the University of Delaware also contributed.

The work was funded by the DOE's Office of Science.

Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

The U.S. Department of Energy's Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, visit the Office of Science website.

DOE/Argonne National Laboratory

Related Iron Articles:

Tackling iron and zinc deficiencies with 'better' bread
The health effects of zinc and iron deficiencies can be devastating, particularly in developing countries.
Imprecise iron supplementation can spur increase in Salmonella
Individuals who do not produce enough iron are anemic, and often experience fatigue.
Treating nutritional iron-deficiency anemia in children
In a study published by JAMA, Jacquelyn M. Powers, M.D., M.S., of the Baylor College of Medicine, Houston, and colleagues compared two medications, ferrous sulfate and iron polysaccharide complex, for the treatment of nutritional iron-deficiency anemia in infants and children.
Cells pumping iron to prevent anemia
Researchers identify the gene Regnase-1 as a regulator for iron metabolism by degrading Transferrin Receptor 1 (TfR1) mRNA.
Helping plants pump iron
Salk researchers identify genetic variants that help plants grow in low-iron environments, which could improve crop yields.
Iron deficiency restrains marine microbes
Iron is a critical nutrient in the ocean. Its importance for algae and the nitrogen cycle has already been investigated in detail.
Compound corrects iron-delivery defects
Investigators from Brigham and Women's Hospital, in collaboration with colleagues at University of Illinois Champaign-Urbana, describe a compound known as Hinokitiol which can correct iron-delivery defects in preclinical models.
How photosynthetic cells deal with a lack of iron
University of Freiburg researchers discover a small RNA molecule in cyanobacteria that affects metabolic acclimation.
A novel form of iron for fortification of foods
Whey protein nanofibrils loaded with iron nanoparticles: ETH researchers are developing a new and highly effective way of fortifying iron into food and drinks.
Researchers 'iron out' graphene's wrinkles
Engineers at MIT have found a way to make graphene with fewer wrinkles, and to iron out the wrinkles that do appear.

Related Iron Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".