Category Archives: Material science

Ultra-complex Structure of Carbon Disulfide Proved under High Pressure (Material Science)

Non-molecular carbon disulfide (CS2) is widely viewed as a Bridgman’s polymer, [-(C=S)-S-]n, which found by Bridgman in 194 with high pressure techniques. In Bridgman’s polymer, there are only carbon-sulfur bonds without bonds about carbon atoms, and all carbon atoms are 3 fold coordinated, which is a little different from the carbon in carbon dioxide (CO2).

Recently, a research team from the Hefei Institutes of Physical Science (HFIPS) of the Chinese Academy of Sciences (CAS) has studied the structural evolution of disordered polymeric carbon disulfide upon compression and decompression, and found non-molecular carbon disulfide was a mixture containing 3 and 4 fold coordinated carbon atoms in different polymers, rather a pure Bridgman’s polymer. The results were recently published in J. Phys. Chem. Lett.

In this research, the team combined the spectroscopies, ab intio molecular dynamic (MD) simulation to search the structures and bonding behaviors of non-molecular carbon disulfide.

“Now we know more about the bonding behaviors of the class of group IV and VI, AB2 compounds,” said YAN Jinwei, a member of the team, “pressure increases the coordination of cation.” For example, the coordination goes from 4 to 6 in SiO2, GeO2, SiS2, but it goes from 2 to a mixture of 3/4 and then only have 4 at higher pressures, which is more likely to carbon disulfide.

The results showed that amorphous CS2 was a mixture compounds having 3 and 4 coordinated carbon atoms. This investigation promoted the understanding of the bonding behaviors of the class of group IV and VI AB2 compounds.

This work was supported by the National Natural Science Foundation of China, the Youth Innovation Promotion Association of CAS, the Innovation Grant of CAS, and the Science Challenge Project, ect.

Featured image: The fraction of C atoms with different coordination, as function of pressure from ab intio MD. (Image by YAN Jinwei) 

Provided by Chinese Academy of Sciences

If The Vibrations Increase on Cooling: Anti-freezing Observed (Material Science)

An international team has observed an astonishing effect in a nickel-oxide material when it cools: Instead of freezing, certain fluctuations even increase with falling temperature. Nickel oxide is a model system that is structurally similar to high-temperature superconductors. The experiment shows once again that the behavior of this class of material always has surprises in store.

In practically all matter, lower temperatures mean less movement of its microscopic components. The less heat is available as energy, the less often atoms change their location or magnetic moments change direction: They freeze. An international team led by scientists from HZB and DESY has now for the first time observed the opposite behavior in a nickel-oxide material that is closely related to high-temperature superconductors. Fluctuations in this nickelate do not freeze when it cools, but become faster.

We used the innovative technique of X-ray correlation spectroscopy for their observation: We were able to follow the order of elementary magnetic moments (spins) in space and time by means of coherent soft X-rays. As it cools down, the spins are arranged in a striped pattern. This order is not perfect at higher temperatures, but consists of a random arrangement of small, locally ordered areas. We found that this arrangement is not static but fluctuates on time scales of a few minutes. As the cooling continues, these fluctuations initially become slower and the individual structured areas grow. To this extent, this behavior corresponds to what a large number of materials show: the less thermal energy is available, the more fluctuations freeze and order increases.

However, it was completely unusual and never before observed that, with further cooling, the fluctuations became faster again, while the ordered areas shrank. The stripe order decays at low temperatures both spatially and through ever faster fluctuations and thus shows a kind of anti-freezing.

This observation may help to better understand the high temperature superconductivity in copper oxides (cuprates). In cuprates it is assumed that a stripe order similar to that in nickelates competes with superconductivity. There, too, the stripe order disintegrates at low temperatures, which was previously explained by the fact that the superconductivity that forms replaces the stripe order. Since there is no superconductivity in nickelates, but the stripe order still disintegrates at low temperatures, an important aspect seems to be missing from the previous description of cuprate superconductivity. It is possible that the stripe order in cuprates is not simply displaced, but also disintegrates for intrinsic reasons, thus clearing the field for the development of superconductivity.

The study shows the potential that coherent soft X-rays have for studying materials that are spatially inconsistent, especially those materials where this spatial inconsistency gives rise to new functionality. Correlation spectroscopy with lasers has been used for many decades, for example to study the movement of colloids in solutions. Transferred to soft X-rays, the technology can be used to track fluctuations in magnetic and, for example, electronic and chemical disorder in space and time.

The experiments described here were performed at the Advanced Light Source ALS, California.

With future X-ray sources such as BESSY III, which will generate coherent X-rays that are many orders of magnitude more intense than today’s sources, it will be possible to extend this technology to faster fluctuations and shorter length scales and thus to observe effects that have not previously been achievable.

Featured image: The development of this pattern of spots over time shows microscopic fluctuations in the sample. © 10.1103 / PhysRevLett.127.057001

Reference: Alessandro Ricci, Nicola Poccia, Gaetano Campi, Shrawan Mishra, Leonard Müller, Boby Joseph, Bo Shi, Alexey Zozulya, Marcel Buchholz, Christoph Trabant, James CT Lee, Jens Viefhaus, Jeroen B. Goedkoop, Agustinus Agung Nugroho, Markus Braden, Sujoy Roy, Michael Sprung, and Christian Schüßler-Langeheine, “Measurement of Spin Dynamics in a Layered Nickelate Using X-Ray Photon Correlation Spectroscopy: Evidence for Intrinsic Destabilization of Incommensurate Stripes at Low Temperatures”, Phys. Rev. Lett. (2021): DOI: 10.1103 / PhysRevLett.127.057001

Provided by Helmholtz Association of German Research Centres

The Waste Product Which Could Help Mitigate Climate Change (Material Science)

Biochar can boost crop yields in poor soils and help stop the effects of climate change, study finds. So why aren’t we using it more?

A product made from urban, agriculture and forestry waste has the added benefit of reducing the carbon footprint of modern farming, an international review involving UNSW has found.

Visiting Professor in the School of Materials Science and Engineering at UNSW Science, Stephen Joseph, says the study published in GCB Bioenergy provides strong evidence that biochar can contribute to climate change mitigation.

“Biochar can draw down carbon from the atmosphere into the soil and store it for hundreds to thousands of years,” the lead author says.

“This study also found that biochar helps build organic carbon in soil by up to 20 per cent (average 3.8 per cent) and can reduce nitrous oxide emissions from soil by 12 to 50 per cent, which increases the climate change mitigation benefits of biochar.”

The findings are supported by the Intergovernmental Panel on Climate Change’s recent Special Report on Climate Change and Land, which estimated there was important climate change mitigation potential available through biochar.

“The intergovernmental panel found that globally, biochar could mitigate between 300 million to 660 million tonnes of carbon dioxide per year by 2050,” Prof. Joseph says.

“Compare that to Australia’s emissions last year – an estimated 499 million tonnes of carbon dioxide – and you can see that biochar can absorb a lot of emissions. We just need a will to develop and use it.”

Stable charcoal

Biochar is the product of heating biomass residues such as wood chips, animal manures, sludges, compost and green waste, in an oxygen-starved environment – a process called pyrolysis.

The result is stable charcoal which can cut greenhouse emissions, while boosting soil fertility.

The GCB Bioenergy study reviewed approximately 300 papers including 33 meta-analyses that examined many of the 14,000 biochar studies that have been published over the last 20 years.  

“It found average crop yields increased from 10 to 42 per cent, concentrations of heavy metals in plant tissue were reduced by 17 to 39 per cent and phosphorous availability to plants increased too,” Prof. Joseph says.

“Biochar helps plants resist environmental stresses, such as diseases, and helps plants tolerate toxic metals, water stress and organic compounds such as the herbicide atrazine.”

Benefits for plants

The study details for the first time how biochar improves the root zone of a plant.

In the first three weeks, as biochar reacts with the soil it can stimulate seed germination and seedling growth.

During the next six months, reactive surfaces are created on biochar particles, improving nutrient supply to plants.

After three to six months, biochar starts to ‘age’ in the soil and forms microaggregates that protect organic matter from decomposition.

Prof. Joseph says the study found the greatest responses to biochar were in acidic and sandy soils where biochar had been applied together with fertiliser.

“We found the positive effects of biochar were dose dependent and also dependent on matching the properties of the biochar to soil constraints and plant nutrient requirements,” Prof. Joseph says.

“Plants, particularly in low-nutrient, acidic soils common in the tropics and humid subtropics, such as the north coast of NSW and Queensland, could significantly benefit from biochar.

“Sandy soils in Western Australia, Victoria and South Australia, particularly in dryland regions increasingly affected by drought under climate change, would also greatly benefit.”

Stephen Joseph
Professor Stephen Joseph. © Photo: UNSW/Supplied

Prof. Joseph AM is an  expert in producing engineered stable biochar from agriculture, urban and forestry residues.

He has been researching the benefits of biochar in promoting healthy soils and addressing climate change since he was introduced to it by Indigenous Australians in the seventies.

He says biochar has been used for production of crops and for maintaining healthy soils by Indigenous peoples in Australia, Latin America (especially in the Amazon basin) and Africa for many hundreds of years.

Biochar has also been recorded in the 17th Century as a feed supplement for animals.

But while Australian researchers have studied biochar since 2005, it has been relatively slow to take off as a commercial product, with Australia producing around 5000 tonnes a year.

“This is in part due to the small number of large-scale demonstration programs that have been funded, as well as farmers’ and government advisors’ lack of knowledge about biochar, regulatory hurdles, and lack of venture capital and young entrepreneurs to fund and build biochar businesses,” Prof. Joseph says.

In comparison, the US is producing about 50,000 tonnes a year, while China is producing more than 500,000 tonnes a year.

Needs to be economically viable

Prof. Joseph, who has received an Order of Australia for his work in renewable energy and biochar, says to enable widespread adoption of biochar, it needs to be readily integrated with farming operations and be demonstrated to be economically viable.

“We’ve done the science, what we don’t have is enough resources to educate and train people, to establish demonstrations so farmers can see the benefits of using biochar, to develop this new industry,” he says.

However this is slowly changing as large corporations are purchasing carbon dioxide reduction certificates (CORC’s) to offset their emissions, which is boosting the profile of biochar in Australia.

Biochar has potential in a range of applications.

Prof. Joseph co-authored a recent study in International Materials Reviews which detailed the less well-known uses of biochar, such as a construction material, to reduce toxins in soil, grow microorganisms, in animal feed and soil remediation.

UNSW has a collaborative grant with a company and a university in Norway to develop a biochar based anti-microbial coating to kill pathogens in water and find use in air filtration systems, he says.

Read the GCB Bioenergy study.

Featured image: An international review study details for the first time how biochar improves the root zone of a plant. Photo: Shutterstock.

Provided by UNSW

Using Graphene Foam To Filter Toxins From Drinking Water (Material Science)

MIT-led research team fashions graphene foam into device that can extract uranium and other heavy metals from tap water.

Some kinds of water pollution, such as algal blooms and plastics that foul rivers, lakes, and marine environments, lie in plain sight. But other contaminants are not so readily apparent, which makes their impact potentially more dangerous. Among these invisible substances is uranium. Leaching into water resources from mining operations, nuclear waste sites, or from natural subterranean deposits, the element can now be found flowing out of taps worldwide.

In the United States alone, “many areas are affected by uranium contamination, including the High Plains and Central Valley aquifers, which supply drinking water to 6 million people,” says Ahmed Sami Helal, a postdoc in the Department of Nuclear Science and Engineering. This contamination poses a near and present danger. “Even small concentrations are bad for human health,” says Ju Li, the Battelle Energy Alliance Professor of Nuclear Science and Engineering and professor of materials science and engineering.

Now, a team led by Li has devised a highly efficient method for removing uranium from drinking water. Applying an electric charge to graphene oxide foam, the researchers can capture uranium in solution, which precipitates out as a condensed solid crystal. The foam may be reused up to seven times without losing its electrochemical properties. “Within hours, our process can purify a large quantity of drinking water below the EPA limit for uranium,” says Li.

paper describing this work was published in this week Advanced Materials. The two first co-authors are Helal and Chao Wang, a postdoc at MIT during the study, who is now with the School of Materials Science and Engineering at Tongji University, Shanghai. Researchers from Argonne National Laboratory, Taiwan’s National Chiao Tung University, and the University of Tokyo also participated in the research. The Defense Threat Reduction Agency (U.S. Department of Defense) funded later stages of this work.

Targeting the contaminant

The project, launched three years ago, began as an effort to find better approaches to environmental cleanup of heavy metals from mining sites. To date, remediation methods for such metals as chromium, cadmium, arsenic, lead, mercury, radium, and uranium have proven limited and expensive. “These techniques are highly sensitive to organics in water, and are poor at separating out the heavy metal contaminants,” explains Helal. “So they involve long operation times, high capital costs, and at the end of extraction, generate more toxic sludge.”

To the team, uranium seemed a particularly attractive target. Field testing from the U.S. Geological Service and the Environmental Protection Agency (EPA) has revealed unhealthy levels of uranium moving into reservoirs and aquifers from natural rock sources in the northeastern United States, from ponds and pits storing old nuclear weapons and fuel in places like Hanford, Washington, and from mining activities located in many western states. This kind of contamination is prevalent in many other nations as well. An alarming number of these sites show uranium concentrations close to or above the EPA’s recommended ceiling of 30 parts per billion (ppb) — a level linked to kidney damage, cancer risk, and neurobehavioral changes in humans.

The critical challenge lay in finding a practical remediation process exclusively sensitive to uranium, capable of extracting it from solution without producing toxic residues. And while earlier research showed that electrically charged carbon fiber could filter uranium from water, the results were partial and imprecise.

Wang managed to crack these problems — based on her investigation of the behavior of graphene foam used for lithium-sulfur batteries. “The physical performance of this foam was unique because of its ability to attract certain chemical species to its surface,” she says. “I thought the ligands in graphene foam would work well with uranium.”

Simple, efficient, and clean

The team set to work transforming graphene foam into the equivalent of a uranium magnet. They learned that by sending an electric charge through the foam, splitting water and releasing hydrogen, they could increase the local pH and induce a chemical change that pulled uranium ions out of solution. The researchers found that the uranium would graft itself onto the foam’s surface, where it formed a never-before-seen crystalline uranium hydroxide. On reversal of the electric charge, the mineral, which resembles fish scales, slipped easily off the foam.

It took hundreds of tries to get the chemical composition and electrolysis just right. “We kept changing the functional chemical groups to get them to work correctly,” says Helal. “And the foam was initially quite fragile, tending to break into pieces, so we needed to make it stronger and more durable,” says Wang.

This uranium filtration process is simple, efficient, and clean, according to Li: “Each time it’s used, our foam can capture four times its own weight of uranium, and we can achieve an extraction capacity of 4,000 mg per gram, which is a major improvement over other methods,” he says. “We’ve also made a major breakthrough in reusability, because the foam can go through seven cycles without losing its extraction efficiency.” The graphene foam functions as well in seawater, where it reduces uranium concentrations from 3 parts per million to 19.9 ppb, showing that other ions in the brine do not interfere with filtration.

The team believes its low-cost, effective device could become a new kind of home water filter, fitting on faucets like those of commercial brands. “Some of these filters already have activated carbon, so maybe we could modify these, add low-voltage electricity to filter uranium,” says Li.

“The uranium extraction this device achieves is very impressive when compared to existing methods,” says Ho Jin Ryu, associate professor of nuclear and quantum engineering at the Korea Advanced Institute of Science and Technology. Ryu, who was not involved in the research, believes that the demonstration of graphene foam reusability is a “significant advance,” and that “the technology of local pH control to enhance uranium deposition will be impactful because the scientific principle can be applied more generally to heavy metal extraction from polluted water.”

The researchers have already begun investigating broader applications of their method. “There is a science to this, so we can modify our filters to be selective for other heavy metals such as lead, mercury, and cadmium,” says Li. He notes that radium is another significant danger for locales in the United States and elsewhere that lack resources for reliable drinking water infrastructure.

“In the future, instead of a passive water filter, we could be using a smart filter powered by clean electricity that turns on electrolytic action, which could extract multiple toxic metals, tell you when to regenerate the filter, and give you quality assurance about the water you’re drinking.”

Featured image: A reusable 3D functionalized reduced graphene oxide foam (3D‐FrGOF) is used as an in situ electrolytic deposition electrode to extract uranium from contaminated water. Credit: MIT

Reference: Wang, C., Helal, A. S., Wang, Z., Zhou, J., Yao, X., Shi, Z., Ren, Y., Lee, J., Chang, J.-K., Fugetsu, B., Li, J., Uranium In Situ Electrolytic Deposition with a Reusable Functional Graphene-Foam Electrode. Adv. Mater. 2021, 2102633.

Provided by MIT

A New, Faster Way To Process Diblock Polymer Materials (Material Science)

Chemical engineering researchers developed a new way to process diblock polymer materials that significantly reduces production time.

Chemical Engineering researchers recently discovered a better way to make a new class of soft materials—reducing a process that used to take five months down to three minutes. 

Connor Valentine, a chemical engineeringOpens in new window Ph.D. student, and Lynn Walker, professor of chemical engineering, work with diblock polymers. Diblock polymers are chain-like molecules where one end of the chain is hydrophobic, and the other is hydrophilic. Molecules like this are used in soap because the hydrophobic side grabs onto dirt and oil, but the hydrophilic side keeps the molecules dissolved into the water.

When these molecules are placed in water at high enough concentrations, they begin to form clusters: the hydrophilic parts clump together in the center of the ball in order to avoid water. The hydrophobic sides arrange into a brush-like layer on the outside of the ball, protecting the hydrophobic center.

As you add more polymers into the water, however, they begin to run out of room and stack themselves intelligently and spontaneously. It would be as if you were trying to fit the maximum number of tennis balls in a box—you would carefully stack each layer.

When they form these stacks, they are called crystals, because the organizational patterns will repeat over and over in every direction. Crystalline structures like this are found throughout nature, including in gemstones, metals, and polymeric materials. People have taken advantage of the repeating and consistent spacing to create polymeric membranes for filtering water and gases. There are also exciting potential uses in new soft materials, with applications that include medical implants, adhesives, sustainable food packaging, liquid beauty products, and even condiments.

Diblock polymers in crystal format
The polymer aggregates form spheres, which pack tightly into layers at high concentrations. Around 40% by weight of this sample is water. © Source: Connor Valentine

However, the problem comes in when researchers are trying to make specific crystalline structures. Engineers need to be able to consistently produce crystals with specific arrangements and sizes so that they can achieve the desired material performance at market scale. However, processing issues can arise when they don’t fully understand the forces driving crystal formation. The wrong temperature change, mixing speed, or formulation can cause crystals to suddenly form, degrade, or transition to another crystalline organization. The accompanying change in material properties can jam mixers, ruin equipment, and result in a worthless final product.

In the case of this work, the desired crystalline state can take months to form at room temperature. This can cause huge issues, with companies discovering they have a product with completely different properties after three months—maybe it’s chunky, or it’s become stiff—or perhaps the company just has to wait three months to sell their product because it takes that long to get the gel consistency they desire.

Two different crystal formations
Two crystalline phases found in the diblock polymer materials used in this work. With the proper thermal and shear processing, these “unit cells” can repeat hundreds of thousands of times in every direction in perfect symmetry. © Source: Connor Valentine

“It’s important for people to understand how these polymer molecules will turn into crystals,” says Valentine. “And that’s not just if they turn into the crystal they want, it’s the rate of it, the speed. Also, are there going to be other crystal phases present? Is every piece of that crystalline material going to be oriented consistently?”

Valentine and Walker worked with collaborators from the University of Minnesota, who discovered that the rate of heating and cooling can produce intermediate crystal structures that last for several months. Valentine’s team built on the work of their collaborators and investigated the impact of shear processing on these crystal structures. Shear processing is a broad term that includes steps like mixing, painting, coating, and shaking—the material is moving. The speed, duration, and direction of shear can really matter for materials like those used in this work.

“Ketchup is a great example about why shear processing affects soft materials because ketchup has a yield stress and thins when you mix or process it,” explains Valentine. “If you’re trying to get ketchup out of a glass bottle and it is gel or solid-like, it will not flow. But small taps (on the correct part of the bottle) will get the ketchup to flow very nicely. The shear is changing the microstructure of the ketchup, which then changes the flow properties. It’s important we understand how shear impacts any material we work with in the same way.”

Changing crystal formations over time
Collaborators from the University of Minnesota showed in a previous paper that this crystal structure transition can take up to five months after heating and cooling.Source: Connor Valentine
Changing crystal formations over time when shear processing is added
Valentine and his team were able to show that shear processing can be used to control the rate of this same transition, accelerating it to occur in as little as three minutes.Source: Connor Valentine

In this work, the authors used an oscillatory shear flow, which involves placing the gel or soft material between two parallel plates—where the top plate can rotate back and forth. Researchers can control the speed and length of the top plate. When Valentine and his team put the diblock polymer crystals into this shear cell, they were able to cause the crystalline phase to change into the equilibrium structure within three minutes. The Minnesota team had previously found this same structural change to take almost five months sitting at room temperature without shear.

“Shear processing can help with the dynamics, the speed, and the rates of structural change, not just the final result, which is something people don’t really think about,” says Valentine. “They often think when you shear these materials, it’s going to change the structure into something different, but that’s not necessarily true.”You might also like…

The team was able to measure these results by visiting the Advanced Photon Source Synchrotron accelerator at Argonne National Laboratory, which is essentially a mile-wide particle accelerator. Electrons are accelerated around the circle of the facility at almost the speed of light, and every time they turn, an x-ray beam leaves the circle. They used these high-intensity x-ray beams to measure the crystal structure in real-time.

Their findings, published in ACS Macro Lettersnot only showed that the speed increase occurs, but also detailed how to tune the shear parameters to achieve the desired rate of crystal formation. They even found that you can prevent the change from happening entirely if the shear is at very low frequencies with very long cycles of oscillation.

“We were able to show that this shear processing step is just a very controllable way to get the structure you want and how fast you want it,” says Valentine.

The research was done in collaboration with Ashish Jayaraman and Mahesh K. Mahanthappa, both of the University of Minnesota.

Photo at top by Argonne National Laboratory shows Advanced Photon Source Synchrotron accelerator, a mile-wide particle accelerator.

Featured image: The blue end of each chain is soluble in water, while the yellow end is not. The yellow ends aggregate together in an effort to separate from the water. These ball-shaped clusters are called micelles. Source: Connor Valentine

Reference: Connor S. Valentine et al, Shear-Modulated Rates of Phase Transitions in Sphere-Forming Diblock Oligomer Lyotropic Liquid Crystals, ACS Macro Letters (2021). DOI: 10.1021/acsmacrolett.1c00154

Provided by Carnegie Mellon University, Department of Chemical Engineering

CO2 As A Raw Material For Plastics And Other Products (Material Science)

Carbon dioxide is one of the main drivers of climate change – which means that we need to reduce CO2 emissions in the future. Fraunhofer researchers are highlighting a possible way to lower these emissions: They use the greenhouse gas as a raw material, for instance to produce plastics. To do this, they first produce methanol and formic acid from CO2, which they convert via microorganisms into building blocks for polymers and the like.

Separation smear for isolation of single colonies of M. extorquens AM1 on a methanol-containing minimal medium agar plate.
Setup of a bioreactor for growing large amounts of biomass of M. extorquens AM1.
Above: Separation smear for isolation of single colonies of M. extorquens AM1 on a methanol-containing minimal medium agar plate. © Fraunhofer IGB Below: Setup of a bioreactor for growing large amounts of biomass of M. extorquens AM1. © Fraunhofer IGB

As fossil-based raw materials are burned, CO2 is released into the air. So far, the CO2 concentration in the earth’s atmosphere has already risen to around 400 parts per million (ppm) equivalent to 0.04 percent. In comparison: Until the middle of the 19th century, this value was still in the range of 280 ppm. The increased level of carbon dioxide has a significant impact on the climate. Since January 1, 2021, CO2 emissions from the combustion of fossil fuels have thus been subject to carbon pricing – meaning that manufacturing companies have to pay for their CO2 emissions. As a result, a large number of companies are looking for new solutions. How can the costs associated with CO2 emission pricing be reduced? How can CO2 emissions be reduced through biointelligent processes?

Catalytic chemistry and biotechnology – a winning combination

Researchers are currently developing approaches to this in the EVOBIO and ShaPID projects at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB. They are working on both projects in collaboration with several Fraunhofer Institutes. “We use the CO2 as a raw material,” says Dr. Jonathan Fabarius, Senior Scientist Biocatalysts at Fraunhofer IGB. “We’re pursuing two approaches: First, heterogeneous chemical catalysis, by which we convert the CO2 with a catalyst to methanol. Second, electrochemistry, by which we produce formic acid from CO2.” However the unique feature lies not in this CO2-based methanol and formic acid production alone, but in its combination with biotechnology, more specifically with fermentations by microorganisms. To put it more simply: The researchers first take the waste product CO2, which is harmful to the climate, to produce methanol and formic acid. In turn, they use these compounds to “feed” microorganisms that produce further products from them. One example of this kind of product is organic acids, which are used as building blocks for polymers – a way to produce CO2-based plastics. This method can also be used to produce amino acids, for example as food supplements or animal feed.

The novel approach offers a host of advantages. “We can create entirely new products, and also improve the CO2 footprint of traditional products,” Fabarius specifies. While conventional chemical processes require a lot of energy and sometimes toxic solvents, products can be produced with microorganisms under milder and more energy-efficient conditions – after all, the microbes grow in more environmentally friendly aqueous solutions.

Metabolic engineering makes it possible

The research team uses both native methylotrophic bacteria, i.e. those that naturally metabolize methanol, and yeasts that cannot actually metabolize methanol. The researchers also keep a constant eye on whether new interesting organisms are discovered and check them for their suitability as “cell factories.” But how do these microorganisms actually make the products? And how can we influence what they produce? “In principle, we use the microorganism’s metabolism to control product manufacture,” explains Fabarius. “To do so, we introduce genes into the microbes that provide the blueprint for certain enzymes. This is also known as metabolic engineering.” The enzymes that are subsequently produced in the microorganism catalyze the production of a specific product in turn. In contrast, the researchers specifically switch off genes that could negatively influence this production. “By varying the genes that are introduced, we can produce a wide range of products,” Fabarius enthuses.

Detailed view of a bioreactor for growing large amounts of biomass of M. extorquens AM1.
Isolated dye from bioreactor cultivations of M.  extorquens AM1 on methanol as a substrate or on formic acid (formate) as a substrate.
Above: Detailed view of a bioreactor for growing large amounts of biomass of M. extorquens AM1. © Fraunhofer IGB. Below: Isolated dye from bioreactor cultivations of M. extorquens AM1 on methanol as a substrate or on formic acid (formate) as a substrate. © Fraunhofer IGB

The research team is working on the entire production chain: starting with the microorganisms, followed by the gene modifications and the upscaling of production. While some manufacturing processes are still at the laboratory stage, other products are already being produced in bioreactors with a capacity of ten liters. As for the industrial application of such processes, Fabarius envisages their implementation in the medium to long term. Ten years is a realistic time horizon, he says. However, pressure on industry to establish new processes is increasing.

Featured image: Light micrograph of cells of the gram-negative bacte-rium Methylorubrum extor-quens AM1. © Fraunhofer

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Provided by Fraunhofer

Scientists Synthesize a Material Which Can Completely Replace Natural Gypsum in the Construction Industry (Material Science)

An international team of scientists has proposed a method of production of high-quality gypsum binders based on synthetic calcium sulfate dihydrate produced from industrial waste. Tests of the obtained material have shown that it not only meets all the requirements for materials of this class, but also surpasses binders based on natural gypsum in several parameters. The work has been published in the Journal of Industrial and Engineering Chemistry.

Gypsum binders are widely used in construction. They have valuable properties such as low weight, low heat and sound conductivity, fire resistance, and they are easy to shape. In addition, gypsum-based binders are hypoallergenic and do not cause silicosis, an occupational disease for builders and repairmen caused by inhalation of dust containing free silicon dioxide. At the same time, the cost of gypsum materials is low, as are the costs of heat energy for their production.

A group of scientists from NUST MISIS, Belarusian State Technological University, University of Limerick and the Institute of General and Inorganic Chemistry of the National Academy of Sciences of Belarus has proposed an innovative method of producing high-strength binders based on synthetic gypsum obtained from industrial waste by neutralizing spent sulfuric acid and carbonate components. Researchers mixed sulfuric acid from waste heat-resistant fibers with water and limestone. The content of calcium sulfate dihydrate in the obtained synthetic gypsum was at least 95% of the mass of the final product.

In the course of the study, scientists obtained three types of synthetic gypsum samples: building gypsum, high-strength gypsum and anhydrite. The building gypsum was made using traditional technology in a gypsum boiler. Anhydrite was also produced according to the traditional technology for this type of gypsum material by firing followed by cooling. An autoclave was used to synthesize high-strength gypsum.

The researchers point out that one of the advantages of producing building gypsum materials from synthetic calcium sulfate dihydrate is that the synthetic gypsum is obtained immediately in the form of a powder product. In the traditional production of gypsum powder, gypsum has to be crushed to the desired state, which requires a significant amount of electricity. Thus, the method proposed by scientists for the production of binders based on synthetic gypsum will significantly reduce production costs by simplifying the production technology. At the same time, the building gypsum obtained in the course of the study fully meets the requirements for gypsum binders of the G5 — G7 grades, for high-strength gypsum — the requirements for gypsum grades G10 — G22.

Synthetic gypsum, obtained from waste sulfuric acid and limestone waste, can completely replace natural gypsum for the production of gypsum binders in countries that do not have gypsum stone deposits.

Featured image: Natural gypsum stone. Credit: Maksim Safaniuk

Reference: Maksim Kamarou et al, High-quality gypsum binders based on synthetic calcium sulfate dihydrate produced from industrial waste, Journal of Industrial and Engineering Chemistry (2021). DOI: 10.1016/j.jiec.2021.05.006

Provided by MISIS

Twist Brings New Possibilities For Ultra-thin 2D Materials (Material Science)

A new study from The Australian National University (ANU) shows how the ability of 2D materials to convert sunlight into electricity can be controlled by simply “twisting” the angle between two ultra-thin layers correctly.

The new class of materials (2D) are 100,000 times thinner than a single sheet of paper and could be used in a huge range of technology, including solar cells, LED lights and sensing devices.

However, one material alone has limited applications, so they often come in a pair. Two different 2D materials are stacked together to move positive and negative charges in opposite directions, generating electricity.

Lead author of the report Mr Mike Tebyetekerwa says it opens up exciting opportunities.

“This study essentially provides a bit of a how-to guide for engineers,” Mr Tebyetekerwa said.

“We’re looking at 2D materials that have just two atom-thin layers stacked together.

“This unique structure and large surface area make them efficient at transferring and converting energy.”

In 2019 Mr Tebyetekerwa and co-author Dr Hieu Nguyen demonstrated the maximum potential of 2D materials to generate electricity using sunlight.

“It’s an exciting new field. Simply twisting the two ultrathin layers can dramatically change the way they work,” Dr Nguyen said.

“The key is to carefully select the matching pair and stack them in a particular way.”

The study has been published in Cell Reports Physical Science.

Featured image: Dr. Hieu Nguyen and Mike Tebyetekerwa © ANU

Provided by Australian National University

Pine Sap–based Plastic: A Potential Gamechanger For Future of Sustainable Materials (Material Science)

Over the past 100 years, plastics and polymers have changed the way the world operates, from airplanes and automobiles to computers and cell phones—nearly all of which are composed of fossil fuel-based compounds. A Florida State University research team’s discovery of a new plastic derived from pine sap has the potential to be a gamechanger for new sustainable materials.

Associate Professor of Chemistry and Biochemistry Justin Kennemur, the principal investigator on the study detailing the new discovery, said this was a significant step in the right direction for new plastics and is a gateway discovery that could lead to several new materials.

“What we know currently is this glassy, thermally stable plastic can be melted and shaped at a higher temperature and cools into a hard plastic at ambient temperatures,” Kennemur said. “One of the next goals is to learn some of the mechanical properties of these polymers. However, this material has many structural features that mirror the plastics we use every day, so there is promise for a multitude of applications.”

The team’s findings were published in the journal ACS Macro Letters.

“Ninety-nine percent of plastics today are produced from finite fossil fuels with increasing demand and limited geographic availability,” he said. “Producing materials from renewable resources, and particularly pine sap, which may be harvested without killing the tree, is a noteworthy effort.”

Alpha-pinene, the most abundant molecule produced from pine sap, is notoriously difficult to turn into plastics so it currently has limited uses. It’s primarily found in turpentine-based cleaners and solvents. Mark Yarolimek, an FSU doctoral student in polymer chemistry who led the study, first synthetically modified the alpha-pinene to make the compound known as delta-pinene.

“I put alpha-pinene through a series of chemical reactions, multiple purifications, and some trial and error, which eventually proved successful in converting it to delta-pinene,” he said. “Once we obtained purified liquid delta-pinene, I converted that into the resultant plastic, poly-delta-pinene, through one final chemical reaction.”

Yarolimek and Heather Bookbinder, who served as an undergraduate researcher on the project before graduating with a bachelor’s in exercise physiology in 2020, then performed a range of “polymerizations”—chemical reactions to transform small liquid molecules into solid macromolecules—to test how effective this molecule was at becoming a plastic.

Credit: Florida State University

These tests included measuring how much delta-pinene was converted to plastic in a single reaction, how well the researchers could control molecule growth, and how condition variability affected the materials. They also characterized the various material properties of the plastic, such as what temperature at which the polymer melts and how much heat it can withstand before it decomposes, as well as exploring the materials’ molecular structure.

Brianna Coia, a graduate researcher in the Kennemur Group, simultaneously analyzed the delta-pinene to understand if it possessed the proper thermodynamic properties to undergo polymerization. With resources from the FSU Research Computing Center, Coia performed density functional theory calculations, and her computational results paralleled well Yarolimek and Bookbinder’s experimental findings.

Yarolimek said converting such biomass molecules into new high-performance plastics, like this one, is essential to continuing our way of life. The team has already worked with the FSU Office of Commercialization to file a patent for the material they discovered.

“Instead of regressing to the 18th century when petroleum runs out, the switch to biobased plastics will allow us to push further forward into what comes next,” he said.

Making new biobased plastics is only half of the conversation—the other involves the ultimate fate of the plastic, Kennemur said. For this high-performance material, having a short shelf life from being biodegradable would be undesirable, but it still needs a way to be recycled. That may mean developing decomposition processes via a chemical stimulus.

“Our research is invested in both. We make new materials, but we are also investigating their chemical recyclability,” he said. “We made this new plastic, but this is just the beginning. We need to also learn how to unmake the plastic and we have plans to start investigating that.”

Kennemur said his student researchers largely deserve the credit for the discovery while his role was to guide their efforts.

“Being a part of this research team was probably one of the most educational and interesting experiences I had during my time at FSU,” Bookbinder said. “In my opinion, hands-on experience is the most engaging way to learn and has a long-lasting effect. I will talk about the research and my role in the experience for the rest of my life.”

Featured image: Graphical abstract. Credit: DOI: 10.1021/acsmacrolett.1c00284

Reference: Mark R. Yarolimek et al, Ring-Opening Metathesis Polymerization of δ-Pinene: Well-Defined Polyolefins from Pine Sap, ACS Macro Letters (2021). DOI: 10.1021/acsmacrolett.1c00284

Provided by Florida State University