Materials Connect

The real cost of our batteries

Nowadays, it is difficult to imagine daily life without using mobile devices, such as cell phones, tablets, or laptops. While our phones are lightweight and capable of lasting throughout the day, this wasn't always the case. These advances are, to a large extent, due to the development of new battery technologies over the years.

The lithium-ion batteries and their widespread use

In mobile applications, lithium-ion batteries (LIBs) prevail due to their high energy density, high output voltage (~3.6 V), and low self-discharge rate (less than 3% per month) [1]. Thanks to these characteristics, most electric vehicles (EVs) use this type of battery. LIBs are also commonly used to support the application of renewable energies by auxiliary energy storage systems [2,3]. Thus, the role of LIBs in reducing greenhouse gas emissions cannot be denied.

The dominant battery chemistry uses lithium cobalt oxide (LCO) as cathode and graphite as anode, but it is not the only one. There are batteries on the market that also use manganese, nickel, and phosphorus, among others.

But what about their ethical implications? pollution, water crisis, and violence

However, the great success and widespread use of this technology are causing several problems around the world, both social and environmental, which represent an even greater challenge. One of them, of course, is to obtain the raw materials necessary for its manufacture, mainly lithium and cobalt, which are obtained, to a greater extent, through mining. These materials, of course, are not renewable.

Obtaining lithium can pose significant problems. For example, in Bolivia, Argentina, and Chile is located the so-called "Lithium Triangle", which contains more than 75% of the supply of this metal worldwide. For extracting lithium from its salt flats, it is necessary to drill into the ground and pump water in order to obtain a brine rich in minerals. Subsequently, this brine is left to dry in the sun; during this process, some substances are added, such as hydrochloric acid, then it is evaporated for up to 18 months to obtain lithium carbonate. This activity consumes enormous amounts of water in a region that is extremely arid on its own, exacerbating the water scarcity that the inhabitants of the area already have to face. On the other hand, leaks can happen in evaporation pools, which causes contamination of the water supply with toxic chemicals [4].

Salar de Uyuni. Image from Alexander Schimmeck, via Unsplash

In other places such as Sichuan province, China, where lithium extraction is done by mining (which is more energy inefficient), this activity has contaminated water bodies, causing the death of cattle and thousands of fish [4].

Cobalt extraction also implies ethical problems; about 60% of the world's cobalt production comes from the Democratic Republic of the Congo. The abundance of a coveted material that is quite scarce in the rest of the world leads, among other things, to a poorly regulated industry, few security measures, high rates of child labor, and an increase in violence [5].

And still, the demand grows

Despite the conflicts that can be generated by the use of these materials, it is expected that by 2050 the demand for lithium and cobalt will increase by 488% and 460% respectively, compared to 2018 [5]. This is due to the goal of decarbonization (using electrifying transportation and creating battery banks for electrical networks), among other factors.

Taking into account that the battery of a compact electric car (for example, the Tesla Model S) uses around 12 kilograms of lithium, it is easy to imagine the problem that we will face in the coming years to meet the demand for lithium and cobalt.

Present and future challenges

With this, another exceedingly important challenge becomes present: the disposal of batteries that have finished their life cycle. Lithium-ion batteries (even small ones, such as cell phone batteries) must be disposed of carefully and correctly, as when they are dumped or illegally disposed of, they can cause landfill fires that are particularly difficult to control, in addition to releasing toxic gases. Also, if a lithium-ion battery leaks, it can release heavy metals and substances such as hydrofluoric acid, which can seep into the subsoil and contaminate water bodies.

On the other hand, this disposition of the batteries does not allow us to recover their components to reuse them. That is why recycling is so important. However, current recycling methods are energy inefficient and use significant amounts of water, and also require storage, which greatly increases the risk of fire in warehouses.

Besides, these processes are economically inefficient, so there is not enough incentive for the industry to invest in infrastructure and make an effort to increase the number of recycled batteries. Currently, only 12% of LIBs in the European Union (one of the best-regulated markets) are recycled, due, among other things, the export of batteries towards Asia. Again, this problem looks set to increase in the coming years, as the first LIBs used in electric vehicles will soon reach the end of their life cycle, leaving behind a need for recycling capacity like never before [3].

What can we do?

Thus, the importance of lithium-ion batteries in our daily lives and the benefits they bring us is clear. However, we cannot ignore that its widespread use implies huge challenges that we must solve. As materials scientists, we can contribute to this by creating cathodic and anodic materials that use less polluting or problematic materials. We can also look for better ways to reuse and recycle them, as well as promote a circular economy that allows us to reduce these intense mineral demands. One exciting initiative is the US Department of Energy's ReCell Center, where academia, industry, and national laboratories collaborate to improve recycling technologies. It is desirable that similar efforts be made around the world, and that all sectors of society give this issue the importance it deserves.

1.     Wu, Y. Lithium-ion batteries : fundamentals and applications. (CRC Press, 2015).
2.     Raw materials for a truly green future. Nature Reviews Materials vol. 6 455 Preprint at https://doi.org/10.1038/s41578-021-00333-9 (2021).
3.     Mrozik, W., Rajaeifar, M. A., Heidrich, O. & Christensen, P. Environmental impacts, pollution sources and pathways of spent lithium-ion batteries. Energy and Environmental Science vol. 14 6099–6121 Preprint at https://doi.org/10.1039/d1ee00691f (2021).
4.     Katwala, A. The spiralling environmental cost of our lithium battery addiction. Wired (2018).
5.     Herrington, R. Mining our green future. Nature Reviews Materials vol. 6 456–458 Preprint at https://doi.org/10.1038/s41578-021-00325-9 (2021).

 

The Silent Revolution in Electric Vehicles: From Silicon to Silicon Carbide

By Cullen Walsh

A Tesla vehicle can now travel over 300 miles on a single charge, matching the range of many combustion engine vehicles. One of the contributing factors that has helped make this possible was a relatively quiet decision by Tesla back in 2017 to start replacing silicon with silicon carbide in many of its power electronics. How could this seemingly simple change facilitate such drastic improvements, and what else could this material achieve?

Silicon Carbide Integrated Circuit Chip Developed by NASA. Source: NASA.

What is Silicon Carbide?

Silicon carbide is a crystalline compound made of silicon and carbon. It has been known about for over a century, having applications in abrasives and heating elements. Its use in solid-state devices began back in 1907 when it became the first material to reportedly demonstrate emission via electrical pumping. As a result, many of the first LEDs were made using silicon carbide. However, in the late 20th century, III-V materials, such as gallium nitride, became the dominant materials in LEDs due to their improved luminescence. Silicon carbide is now seeing a resurgence via its use in power electronics (electronics that process high voltages and currents). This is a result of recent improvements in its fabrication and its ability to handle high voltages, such as those coming from car batteries.

The Benefits of Silicon Carbide

One reason silicon carbide is able to operate under such high voltages is its wide bandgap (around 3x that of pure silicon). This imbues it with many beneficial qualities, one of which is a high breakdown voltage. Breakdown voltage is an important attribute of diodes, such as Schottky-barrier diodes, and field-effect transistors. It determines the maximum voltage that can be applied before atoms at the interface start to ionize. Once this occurs, electrons from the ionized atoms accelerate across the interface, striking and ionizing other atoms and creating an avalanche-type effect. This leads to reverse current in the diode, preventing it from operating properly, and can even result in permanent damage to the device. As a result, the breakdown voltage contributes to the upper limit of how much AC voltage a device can handle.

Silicon Carbide vs Silicon

Typical silicon-based Schottky-barrier diodes possess low breakdown voltages, limiting their use in high power electronics. In order to raise their breakdown voltage, the n-doped region of the diode needs to be made larger. However, this leads to increased resistance, causing heat dissipation and lower efficiency. In comparison, silicon carbide-based Schottky-barrier diodes have a smaller n-doped region and therefore generate less resistance, improving their efficiency and making them more compact. The same concept applies to silicon carbide-based MOSFETs where the drift layer can be made thinner, resulting in a lower internal resistance. These advantages provide silicon carbide-based devices with breakdown voltages in the range of 600-1000 V, allowing them to interface with typical electric car batteries. It also makes them smaller and more compact as well as more efficient energy converters. 

Another benefit of silicon carbide is its ability to operate under high temperatures. This material is an excellent thermal conductor, allowing it to efficiently dissipate heat even at high powers and with closely packed circuits. Its wide bandgap also helps prevent leakage current, which is current that flows across a diode in its ‘off’ state (when under reverse voltage), allowing it to act as a switch even at elevated temperatures. 

What’s Next?

These properties have made silicon carbide the go-to material in high power electronics. Currently, most silicon carbide used in commercial electronics goes into electric vehicles. However, this material has the potential to impact numerous industries via applications in HVACs, solar energy converters, 5G telecoms, and more. It is also being explored by NASA for use in future space compatible electronics due to its ability to function at elevated temperatures, powers, and radiation levels.

It is unusual for a material to go from the lab bench to industry and displace silicon. However, as we start to reach the limit of how small silicon transistors can become and how many we can fit on a chip, the desire to look beyond silicon is only increasing. Silicon carbide may just be the tip of the iceberg, kicking off a new era where new materials outcompete silicon in novel applications.

Combating CO2 Emissions: Iron and Steel Industry Going Green

Iron and steel have always been at the center of world technological advancement. The products of iron and steel are interwoven into human history and lifestyles. The production processes of these materials are usually massive, ubiquitous, and operate around the clock. The products of iron and steel range from the cutlery on our dining tables to knives in our kitchens, to some bed frames in the bedrooms, lamp-holders all around the house, door hinges, railings, and even our vehicles. This unending list extends to innumerable pieces of machinery and equipment in different industries around the globe. The iron and steel-making industry, as one of the top contributors to global greenhouse gas (GHG), emits about 8% of global CO₂ (carbon dioxide)⁽¹⁾.

 

Photo by Markus Distelrath on Pexels (For illustration purposes only)

CO₂ is mainly produced as a by-product when carbon is used to extract metallic iron from its ores. Iron ores usually exist as oxides. Since carbon is easily accessible and readily reacts with oxygen, it is used as a reducing agent to separate (metallic) iron from its oxides. Not only that, a network of CO₂-emitting facilities is used at the mining field down to the factory. Considering the quantity of greenhouse gas that may be emitted during the mining operations⁽²⁾ and production stages, the iron and steel industry could be one of the key players in combatting global warming. 

In order to tackle these huge challenges of CO₂ emissions, the iron and steel industry is setting up various regulatory procedures and supports for helpful research. Avenues employed to combat CO₂ emissions involve reducing the quantity of carbon used during production, capturing the CO₂ emitted during production, substituting carbon with more environmentally friendly chemicals, or completely avoiding carbon use during most of the production processes. 

In the decarbonization of production processes, the most common strategy is the adoption of low-emission programs. The low-emission programs encourage the use of low-emission equipment. An example is the industrial shift from blast furnaces to electric furnaces. The traditional blast furnace is coal-fired, with high CO₂ emission. It is encouraging to know that giants in steel production, such as ArcelorMittal and Baowu Steel Group top the Green Steel Tracker⁽¹⁾ program list - declaring their commitments to the global net-zero goals⁽³⁾⁽⁴⁾.

Carbon capture, utilization, and storage (CCUS)⁽⁵⁾ is another program for decarbonizing production processes. This program basically targets the recovery of CO₂ from gaseous waste. Hence, it is also called the carbon-negative initiative. It extends to the direct/indirect use (or storage) of generated CO₂. Various strategies are employed to convert CO₂ to valuable materials⁽⁶⁾ like polymers, fertilizers, proteins, and foams. CO₂ can be stored safely underground⁽⁷⁾ for many years – in rock reservoirs under the sea, empty oil fields, or empty gas fields. In fact, researchers claim that stored CO₂ can transform into solid minerals (carbonates) if it comes in contact with certain rocks rich in very reactive metallic elements such as calcium, iron, and magnesium.

Interestingly, one cutting-edge method of combatting CO₂ emission in iron and steel production is Molten Oxide Electrolysis, a net-zero steel production technique. It is a result of research works⁽⁸⁾ that began in the early 1980s by Professors Donald Sadoway and Antoine Allanore at the Massachusetts Institute of Technology (MIT)⁽⁸⁾. This concept prevents the production of CO₂. It involves the utilization of electrolysis in the iron and steel-making process with O₂ as the by-product. This technique is being championed by a company called Boston Metal⁽⁹⁾, situated in Massachusetts, USA. Already there is news about BMW and  BHP Ventures partnering with Boston Metal.

Through multiple avenues of combatting CO₂ such as decarbonization of production processes, carbon capture, utilization, and storage, the iron and steel industry is working determinedly, championing the global net-zero emission plans. Many are joining this drive daily; if we keep it going, we will be a few years less in actualizing the net-zero goals. Then, our beautiful Earth would have less CO₂ to struggle with!

On the hunt for a catalyst capable of efficient hydrogen production

It’s generally agreed that changes to our energy mix can help tackle climate change. While nuclear power is considered to be a low CO₂ emission technology for generating electricity, one suggestion is to use hydrogen to fuel our cars and heat our homes. Hydrogen can be generated from fossil fuels or by splitting water. While this latter method can be done using electrolysis, it is energy intensive. An alternative is to use ionising radiation.

You would think that the best way to generate hydrogen from water using radiation would be to simply irradiate as much of it as possible but some studies show that spreading an incredibly thin layer over a surface can actually generate more hydrogen than simply irradiating a large volume of it.

Bulk water radiolysis

When water is irradiated it can split apart into different combinations of electrons, hydroxide, peroxide and proton (e^-, OH^-, H₂O₂ and H⁺ respectively). These different species undergo a series of ultra-fast reactions that depend on the ability of these chemical fragments to diffuse through the water. When an individual gamma ray passes through bulk water it creates a track of ionised water molecules that spread out as they begin to react. Gamma rays travel very far in water which leads to a lot of water being ionised.

Some of the reactions in water radiolysis. Primary yields are commonly quoted and refers to the initial interaction of ionising radiation with matter; the period where a track, and spurs from the track, are produced.  Primary yields from the radiolysis of pure water are found by including a scavenger, a chemical that will quickly react with a targeted water fragment before it diffuses into bulk solution, effectively preventing it from reacting with the species of interest. The primary yield of H₂ can be found by including KBr; the bromide ions prevent the reaction of hydroxyl radical with molecular hydrogen. Credit: L Leay, adapted from various sources.

 

Alpha particles can also lead to the splitting of water. The alpha particles don’t travel as far as gamma rays. They still create tracks the way that gamma rays do and the ionised water molecules will still diffuse and react with other water molecules that weren’t hit by the alpha particle. Since the track is shorter, the energy is deposited into a much smaller volume of water, and so many more water fragments are created in a smaller space. A higher density of water fragments can lead to more chemical reactions and so the amount of hydrogen produced can increase. The key to generating hydrogen from water radiolysis lies in generating many fragments in a small volume and so increasing the chances that they can react in the right way. 

Now, take that water and spread it over a surface and you’ll see something quite different. 

Catalysis on a surface

Spreading water over a surface means that the water fragments don’t have as much space to diffuse; some of the reactions that may happen in the glass of water don’t happen as often. There are dozens of reactions happening between the water fragments; some lead to the generation of molecular hydrogen and some prevent it. Some of those reactions can stop hydrogen gas from forming.

The chemical make-up of the material that you use to make your surface is also important. Some materials such as tenorite (CuO) tend to generate less hydrogen gas than the glass of water does while zirconia generates more hydrogen. Some materials like silica don’t change the amount of hydrogen produced. No one knows for sure why this is but it could have something to do with the material also absorbing some of the radiation then transferring it to the water.

The nanostructure of the material is important too and studies from related fields can inform the search for a catalyst. For example, calcium-silicate-hydrates in cement pastes, which are usually studied to understand how nuclear waste might evolve over the associated long timescales, lead to nm thick layers of water sandwiched between sheets of calcium and silicate. In this material the calcium ions can trap electrons and these ions just so happen to sit in regions rich in structural water and OH groups. Since much of the hydrogen gas is formed by reactions that involve solvated electrons, it seems that this could be an excellent way of producing hydrogen.

Outlook

So what might the future technology to drive the hydrogen economy look like? Given that many nations already use nuclear power to generate electricity, it could be that this by-product is simply captured from the reactor core. This might give rise to questions about another Fukushima-like incident but it’s important to remember that the explosion at Fukushima-Daichi was caused by an unexpectedly severe event and, as its sister plant, Fukushima-Daini showed, was preventable. The nuclear industry, even with a safety record that surpasses many other industries, has learned a lot from that event.

It might also be possible to build some sort of water processing plant that spreads water over a surface and passes it through a radiation field. The radiation could be delivered by radioactive material, a particle accelerator or an x-ray generator.  This sort of conveyor-belt for water radiolysis may seem a bit far-fetched, but if climate change is to be halted, it would seem that future technologies may have to get radical (radiation chemistry pun intended).

 

 

For more information on water radiolysis see S. Le Caer’s 2011 article in Water.

For a detailed analysis of radiolytic hydrogen production from cement pastes, see S. Le Caer et al, 2017 in Cement and Concrete Research.

COVID-19 impact in education and R&D in Chile

Between the Andes to the east and the Pacific Ocean to the west is one of the longest and narrowest countries of the world - the Republic of Chile. Chile is most known for its Nobel laureates in literature, its world-class wines, its copper resources, and its educational system. Chile’s literacy rate is 96%, the highest in Latin America. According to the recently released Global Innovation Index 2020, Chile is the top innovative country from Latin America and the Caribbean, scoring 33.86/100 (for comparison, the USA scored 60.56/100). The index notes that Chile’s strengths lie in its institutions, educational level, competition factors, market scale, market capitalization, the applied tariff rate, and business sophistication. Chile’s research and development (R&D) budget (0.35% GDP) fluctuated substantially in recent years, and it is the lowest since 2011, with a stagnated 493 researchers in R&D per million people (for comparison: the USA has 4,412 researchers per million people). Such numbers continue declining, given the economic and social crisis from last year that culminated in the 2019-2020 Chilean protests and intensified with the COVID-19 global pandemic.

Dr. Ing. Alberto Monsalve González, a professor from the Metallurgical Engineering Department of the Universidad de Santiago de Chile, explains how the pandemic affected his work, Chilean education, and R&D. While his research projects on nanocomposites and metal alloys are mostly frozen, he focuses on writing articles and planning future work. Prof. Monsalve González commented that, with limited resources available, their government did some cuts in grants for post-graduate students, named ‘Becas Chile’. As future budget cuts were already announced, he is worried about the future of R&D. “Unfortunately, this will negatively impact the R&D in our country for the next [several] years,” he says. Prof. Monsalve González points out that materials science researchers could help prevent and minimize the effect of future pandemics. “There are not enough studies on antibacterial and antivirus effect of copper and its alloys. Another opportunity is the use of carbon compounds for effective filters for mechanical respirators and air-conditioning equipment,” he says.

Prof. Monsalve González is worried about the students. He mentioned that since research laboratories at Universidad de Santiago de Chile are closed, students working on their theses will not finish on time. “This is a huge problem for our students because the actual crisis has delayed one year of many students' graduation,” he says. While other countries adopted a hybrid system of education, Chile preferred to keep it virtual mode only. Prof. Monsalve González worries about the quality of education through this modality. “Some universities have made a heroic effort to give teachers and students connectivity facilities to carry out online courses. The success of this kind of classes must be evaluated in the future,” he says. Prof. Monsalve González points out the constant evaluation of their educational system by adding: “Finally, it should be noted that the quality of university education in Chile [has been] under permanent review and study before this health crisis.”

When asked about his experiences with the new modalities of conferences, he confessed missing the one-to-one contact through in-person conferences and he has coped through the new modality. “Without a doubt, this aspect of our work has completely disappeared. Still, the online conferences, webinars, the free access to some publications, and the virtual contact by networks have helped to mitigate the lack of in-person contact with other researchers [around] the world,” he says.

-Mônica Jung de Andrade

COVID-19 impact in education and R&D in Argentina – presidential views

In the Pampas grass of the Americas, bordering five of the South American countries, is the Argentine Republic. While Argentina has three Nobel Prizes in the sciences and a successful nuclear program, its research and development (R&D) expenditure has been in decline for the last four years. As in most countries, the COVID-19 global pandemic reinforced these budget cuts and the R&D budget (0.54% GDP) is the lowest from the last 10 years.

Raúl Bolmaro and Orlando Auciello, both Argentinian citizens, working in R&D as full professors, and highly active in their professional associations in Argentina and the USA, respectively, explain further how the pandemic affected their work, and affected Argentinian R&D and its collaborations.

Prof. Raúl Bolmaro (Universidad Nacional de Rosario) and president of the Argentinian MRS (Asociación Argentina de Materiales).                                               Prof. Orlando Auciello (University of Texas at Dallas) and past president of the Materials Research Society (2013).

Prof. Bolmaro at the Universidad Nacional de Rosario, who is also the director of a research institute and president of the Asociación Argentina de Materiales (Argentinian MRS), has switched his activities strictly to a “home office” to draft scientific papers using past experimental results and ideas. He says that the accumulated knowledge on smart materials and characterization techniques have re-oriented his research group’s activities in support of bio-chemical and bio-technological developments, pursuing either detection, treatment, or relief techniques. Nevertheless, his activities also involve keeping the infrastructure of the institute ready for all areas. “Further continuing our regular research topics may seem somehow a waste of time; however, life must continue, considering that COVID-19 might be around for such a long time,” he says.

On the other hand, Prof. Auciello—who also holds a US citizenship and is on the faculty at the University of Texas-Dallas (UTDallas)—has been able to continue research on campus since January because his group is working on his patented technology of antiviral ultrananocrystalline diamond (UNCD) coating with pores ≤10 nm for application on protective masks to stop the transmission of the COVID-19 virus. “The COVID-19 virus, which has diameters in the range 60-140 nm, is not stopped efficiently by current masks with pores of 10-30 microns,” he says. His research group has continued its collaboration with colleagues in México, Argentina, Panama, and Brazil. Prof. Auciello says that the international collaborations facilitated the advancement of his research. “We have been doing clinical trials on UNCD-coated dental implants, in México, since 2018. The USA-México collaboration is enabling the introduction of the revolutionary UNCD-coated dental implants in México by 2021-2022. So, collaboration with scientists from Latin America has been and will continue to be extremely productive to insert new medical devices in the market,” he says.

As a past president of the Materials Research Society (MRS), Prof. Auciello, who has been a strong advocate for substantial changes in terms of diversity within MRS awards and is part of the diversity committee at UTDallas, says, “[Professional scientific] societies should have more minorities, from within and outside the USA, involved in committees and [positions that influence] Society direction.”

When asked about the impact of the pandemic on the educational system in Argentina, Prof. Bolmaro pours his frustration about the 200 days of frozen activities followed by classes on virtual mode and its difficulty to deliver experimental courses that shape many of the skills needed for technical knowledge. “The complete learning-teaching interaction has been damaged profoundly, despite the efforts made by professors and students to imagine new ways for transferring back and forth information and knowledge,” he says. Like its neighboring countries, undergraduate education at all Argentinian public universities is tuition-free. However, Prof. Bolmaro worries about the students from less economically favored families during this pandemic.

“The economic burden of getting your own electronic devices falls on your own shoulders, already weakened by successive social and economic crises,” he says. With sadness, he adds, “What has been for many years a motive for pride (tuition-free education) has become the main source for despair among the students who cannot sometimes even go back to their home cities or countries.”

He is very concerned about the declining situation of R&D in Argentina as well. “We must take in account that Argentina has been economically declining for the last 30 years and with a stagnated per capita national income for more than a decade,” he says. Prof. Bolmaro goes further explaining the decline of both infrastructure and salaries in the Argentinian R&D. R&D recovery in a post-pandemic situation is alarming, as he points out. “The main problem will come from the needs of renovation and spare parts for fixing an already aging large science equipment and facilities. Salaries have been cut to a third in terms of dollars in the last year, which makes the research activity less attractive to new generations,” he says.

When asked about how they have been coping with the exchange of knowledge through virtual conferences versus in-person conferences, Prof. Bolmaro and Prof. Auciello both agreed that the only drawback is not being able to interact personally with more scientists, but they both have observed the several advantages of the virtual conferences, such as the more efficient use of time and resources. Prof. Auciello has been able to deliver talks to Dubai, Europe, and Asia, by either sending the talk in a video format and being present to answer questions, or presenting it live. He seems satisfied with his virtual experiences: “Given my age, I need to apply the science-based knowledge and look for keeping my health,” he says.

Prof. Bolmaro, who has also been able to deliver talks and online classes to various countries, adds: “Because of being somehow in the end of the world, as sometimes the south cone and Patagonia are called, our journeys to attend conferences and workshops are reduced to no more than one every year in average, if we are talking about northern hemisphere events.” He believes the post-pandemic situation will have its own challenges for organizing international conferences: “We hope for having better funding when the activities reopen, but we keep thinking about the long journeys that we will have to endure and survive in the expected interregnum of better COVID safety in the north and poor coverage in the south. Organizing international conferences will become such a challenge, with a transition perhaps dominated by hybrid-conducted ones.”

-Mônica Jung de Andrade

COVID-19 R&D Impact in Uruguay

In South America, Uruguay is showing an inverse trend seen in its neighboring countries. Whilst only 0.48% of GDP is invested in R&D, scientists are being the protagonists in this. Uruguay is dealing well with the pandemic, and their coronavirus cases are far fewer than its neighbors, thus the only Latin American country in the EU’s Covid-19 “safe list.” Ivana Aguiar and María Eugenia Pérez, who are professors at Universidad de la República and deeply engaged volunteers within the Materials Research Society (MRS) since 2011, explain how the COVID-19 pandemic has further impacted education and R&D in Uruguay.

Unlike most of the countries during this pandemic and the big economy deficit of Uruguay, most of the budget dedicated to research is not under the budget cut policies—at least for this year. The government reflected on the scientists’ role to contain the pandemic situation and the research community has been key to developing tests for the pandemic.

Prof. Aguiar and Prof. Pérez work with semiconductor nanomaterials for radiation detection, photocatalysis for water remediation, and medical applications. When asked how the COVID-19 pandemic affected their lab activities, they were unanimous that even though they are now slowly going back to normal, some of their planned lab activities had been postponed. Both are taking advantage of many virtual conferences to share their research, and they were pleased to see an increasing offer of webinars from MRS. Prof. Aguiar, who has organized the MRS virtual event “Sustainability in my Community” during the 2016 MRS Spring Meeting, was happy to learn about the latest news of a virtual mode for the next MRS meeting.

Besides reading and writing articles, for them it has been a period focused on teaching in a completely virtual-mode classroom, which demanded a lot of time to adapt for both students and educators. Even though COVID-19 cases in Uruguay are low, Universidad de la República plans to continue virtual-mode classes for the next semester as well. Commenting further about the positive impact of virtual modality, which was already a trend, Prof. Pérez says, “It actually helped to connect more often with people I would not be in contact with so often, and I believe that commerce, meetings, etc. will be kept virtual to a high degree [in the post-pandemic situation].” With her little daughter at home while she works, it has been more challenging for Prof. Aguiar, “It is difficult to concentrate in long-time activities while working from home.”

When asked about what they expect the post-pandemic R&D situation in Uruguay will look like, they both said that science visibility during this pandemic will positively impact R&D budget prospects. Prof. Pérez says, “In terms of science policy, we showed that science is a critical aspect of a country’s development. This was the case for Uruguay, in which very little of the GDP was destined to research. Scientists should make themselves heard about the importance of scientific research and promoting science careers in the country.”

- Monica Jung de Andrade

COVID-19 R&D Impact in Brazil

In a country where 1.26% of GDP is invested in R&D (47% of it is from the private sector), Brazilians have been with a shortage on research funding for a while, preventing its further growth. Since the recession in the economy in 2015-2016, Brazilian researchers have been struggling to obtain funds for their research. Osvaldo N. Oliveira Jr., who is a professor at the University of São Paulo and past president of the Brazilian MRS (Sociedade Brasileira de Pesquisa em Materiais, SBPMat), explains how the COVID-19 pandemic has further impacted research in Brazil.

Whilst as a supervisor and group leader, Prof. Oliveira Jr. works from home through virtual meetings with his students and collaborators, as well as taking part in webinars (either attending in the audience or delivering lectures). “These activities do not replace attending conferences in person, but they minimize the possible isolation one may feel,” he says. However, at his laboratory, he says that only a few students are working now, and a number of experiments had to be postponed. Prof. Oliveira Jr., who is a world-renowned expert in ultrathin film sensors, adds, “In the other area I have been working on, related to artificial intelligence, research has been continued and even strengthened.”

He believes the following three major topics/areas will see further investments in R&D with the COVID-19 pandemic:

• new fast, accurate and low-cost diagnostic methodologies based on immunosensors and genosensors for infection outbreaks;
• new materials with antimicrobial properties for prevention and novel therapeutic strategies;
• integration of machine learning and other artificial intelligence methods into materials applications, such as data analysis for diagnosis and to search for new molecules and materials for therapy.

Together with collaborators from different fields, Prof. Oliveira Jr.’s research group is working on topics from items 1) and 2) above. Prof. Oliveira Jr. says, “We are investing heavily on new strategies for data analysis, with the hope of integrating data from text, clinical exams, and images into a single system for diagnosis.”

When asked about the funding impact on R&D in Brazil with the COVID-19 pandemic, Prof. Oliveira Jr. feels disheartened. He mentioned that the extra funds to address the pandemic is insufficient to compensate the other cuts that caused a shortage of scholarships for graduate students and post-docs.

He says, “Today, many scientists with PhDs have to live with savings they may have made or with help from their families. With all the visibility that science has had in the media, I am hopeful that the government agencies and companies will realize that investing in research is the only way forward for the security of the country.”

- Monica Jung de Andrade

Gold extends the exfoliation of 2D materials to a large range of compounds

A two-dimensional (2D) material such as graphene is highly versatile. It can be wrapped up into zero-dimensional fullerenes, one-dimensional nanotubes, or stacked into three-dimensional graphite. Such 2D materials emerge as the building blocks for all other applications and now researchers are on a quest to diversify the family of the ultrathin 2D materials.    

This quest to diversify the materials options is demanding. The success requires an industrial-scale method that produces high-quality 2D crystals. Many approaches have been developed but most of them are limited in yield, lateral size and contamination. At present, the preparation of 2D crystals can be categorized into two methods, bottom-up and top-down approach, depending on the direction in the production.

Category I – Synthesis from bottom to up

Epitaxial growth and chemical vapor deposition (CVD) can produce thickness-controllable 2D graphene crystals with a desirable, large single crystal (millimeter scale). However, the quality suffers from scalable growth for many other materials using the synthesis methods, particularly for heterostructured materials. 

Category II – Thin it down production

Liquid-based ion-intercalation and liquid exfoliation are used as one of the top-down methods. By immersing bulk crystals in the liquid, the strength that holds the adjacent layers together in the crystals decreases. With forces applied to the layers, either by sonication or rapid mix, the additional shear force would push the layers apart. Yet, as chemical methods, the solvents often contaminate the 2D products.  

Mechanical exfoliation has been a unique top-down production method of emergent 2D materials. As the origin of the successful 2D graphene, mechanical exfoliation, also known as the scotch-tape method, produces the most high-quality thin layer with few defects due to the absence of chemical processing. While mechanical exfoliation often suffers smaller sizes (from a few microns up to 100 microns) of 2D crystals, a group of researchers believes that they can improve the method by identifying suitable substrates that firmly adhere to 2D flakes without losing the structures and properties.  

 

Au assisted mechanical exfoliation for 2D materials

A new study, published in Nature Communication in May 2020, demonstrated a gold (Au)-involved mechanical exfoliation that successfully isolated 40 different 2D materials as single crystals, including transition-metal-dichalcogenides, metal trichlorides, black phosphorus and magnetic compounds. 

Au is known to have a strong affinity for chalcogens, especially to sulfur atoms that lead to the self-assembled monolayer. In exfoliating 2D crystals, Au serves as a substrate to hold and adhere to the topmost layer of a bulk crystal. The group VIA chalcogens (S, Se, Te) and VIIA halogens (Cl, Br, I) at the terminated surface in most 2D materials interact strongly with Au, thus enabling the adhesion between Au and the crystals. 

The authors used the scotch-tape method in making the 2D material. Once the bulk crystal is brought in contact with the Au deposited substrate, gentle pressure is applied on the tape to establish a crystal/Au contact. Peeling off the tape removes the majority of the crystal, leaving one or a few large-area monolayer flakes on the Au surface. 

The thickness of Au requires only a few nanometers. This thin layer of Au can be applied on a variety of substrates such as silicon wafer, transparent quartz sapphire, and flexible plastic films, demonstrating the versatile applications.

 

(a): The Au-involved mechanical exfoliation process. A thin layer of Au is deposited onto a substrate covered with a thin Titanium (Ti) layer (magenta) that facilitates the adhesion. Then, a cleaved bulk crystal on tape is brought in touch with the Au layer. Peeling off the tape will result in the 2D flakes on the Au surface. (b)-(d): Limited only by the size of bulk crystals, the 2D flakes are at millimeters size. The exfoliated 2D materials can sit on (b) substrates of SiO₂/Si wafer, (c) transparent sapphire and (d) flexible plastic substrate, demonstrating the versatility of applications. (e): This Au-involved substrate method is compatible with CVD-grown 2D materials, such as MoS₂.

 

(f) to (g): Optical images of the resulting large exfoliated 2D crystals. The highlighted red box is hardly accessible using other mechanical exfoliation methods at the present technique. (bottom): heterostructured MoS₂/WSe₂ with Raman spectroscopy characterization.

 

The systematic studies on the efficient exfoliation assisted by an Au adhesion layer to a layered crystal provide access to a broad spectrum of millimeter-sized monolayer materials. The high quality of the exfoliated monolayers, one benefit of the mechanical approach, along with the large-area 2D flakes can support the exploration of the ultrathin 2D materials. 

With the improved reliability to extract atomically thin crystals, the size of the resulting 2D layers would depend on the quality of bulk crystals. As in the successful silicon technology, the extraction of wafers from large, high-quality single silicon crystals has been key. For industrial applications of 2D materials, the focus of materials research may shift toward yielding high-quality layered crystals.

 

Chiung-Wei Huang acknowledges Tianyu Liu, Laura Leayn and Hortense Le Ferrand for the thoughtful suggestions.

COVID-19: From my home office to yours – we’re in it together!

Like many folks around the world, MRS staff - since March 16^th - has been working from home in order to stem the spread of the 2019 novel coronavirus.

From our home offices, we’ve been covering materials-related COVID-19 news such as a podcast episode on the development of a microneedle array that is key to a skin patch that delivers a vaccine, and a webinar on how materials research can counter the pandemic.

Researchers on COVID-19 are working at breakneck speed that it’s actually difficult to keep up with all the news! We’ve captured some of the more relevant news articles and linked these on the MRS COVID-19 Information and Resources page. This is where we also keep updates regarding the MRS Meetings for 2020.

Stay safe! Stay well!

-Judy Meiksin