Materials Connect

Measuring atoms by combining advanced science with everyday items

One of the things that fascinates me about materials science is that we often end up focusing on the small scale so that we can understand how the material in our hands behaves. In order to do this, we often combine creativity with well understood scientific concepts to come up with a novel approach to our experiments.

Let’s start with simply explaining the scientific concepts. Atoms like to have a bit of space around them, and they also like to sit with their friends. They form bonds in very particular ways and this makes them quite predictable which means it’s easy to measure the arrangement of atoms in a material. We can do this using x-ray diffraction which creates a pattern that is unique to that material. To get really detailed information on the atomic arrangement, we need the sort of x-ray intensity that a synchrotron can provide.

Earlier this year, my research group had the opportunity to use the UK’s national synchrotron, Diamond Light Source, to make some measurements of glass. The glass we’re interested in is a borosilicate and also contains sodium and lithium. Some of our samples also had calcium and zinc added to them. These glasses are used to immobilize nuclear waste and we want to understand their bond structure so that we can generate some accurate molecular models to predict how they will interact with the waste, and with the ionizing radiation emitted by the waste.

The set up that we used on the beamline at the synchrotron has a rack that can accommodate multiple samples that had been powdered. Remote control from a computer means we can move individual samples into the beam of x-rays. The samples need to rotate so the best thing to use to hold each sample is a drill bit. Since the sample tubes are so slim it turns out that a dental drill is actually the best thing for the job.

Normally a sample for xPDF analysis would be powdered and ‘scooped’ in to a glass capillary tube. Since we’re analyzing glass, we fix a Kapton tube (the orange cylinder) onto the end of the glass capillary and put our sample in there. The ends are sealed with superglue.

The x-rays travels along a pipe, passing through our samples to reach the other side. Only some of the beam is spread out by the atoms in our sample and hits the detector, a giant black screen that absorbs the light and converts it in to an electric current which we can measure. The pattern on the detector can tell us a lot about the arrangement of atoms in our glass, we just need to interpret it.

Samples are loaded onto a rack of dental drills. The rack can be moved around by remote control and the drills spin when data are being collected. The large black panel in the top right of the photo is the detector that we used.

The fuzzy rings in the pattern are caused by x-rays that have been scattered by disordered atoms – they do not sit in neat little rows but instead have plonked themselves in random locations. This is quite typical of glass; it’s a disorganized mess. Since glass doesn’t have any long range order, determining the arrangement of the atoms can be quite challenging. This is exactly why we’re using a synchrotron to get detailed information which we can then process further.

In some of our samples, we can see some more defined rings. These might indicate that the sample contains some degree of crystallinity. These possibly slightly crystalline samples have all been treated with high intensity gamma rays at The University of Manchester's Dalton Cumbrian Facility in the UK. It’s unlikely that gamma irradiation would lead to the formation of crystalline regions but it’s intriguing. Since radiation usually makes crystalline material amorphous, glass is considered to be very radiation tolerant: it’s already amorphous. Ionizing radiation can cause some changes in the glass though, usually by producing free radicals and color centers. Oxygen bonds can also be broken which may lead to the formation of molecular oxygen and bubbles.

A representation of the image collected when diffracted x-rays arrive at the detector. The fuzzy rings indicate that the samples is amorphous while the more defined ring hints that there may be more order to some part of the sample.

The fuzzy rings on the detector can be converted into a graph and the data can be further manipulated to provide pair distribution functions (PDF). A good overview of the steps involved is given in a review article (Royal Society Publishing). Our glass contains boron which is unusual in that it can exist in two coordination states with the ratio of states determined by the glass composition and thermal history. We use NMR to find the population of 3 and 4 coordinated boron and this information assists with our PDF analysis.

After refining our data, we will obtain the average distance between different pairs of atoms in our glass. This sort of detailed information can be helpful in identifying the presence of nanoparticles, for finding defects in a lattice or in our case, to determine whether there has been any change in the structure as a result of irradiation. The data analysis can take months to complete and is a first step in building our models of the chaotic glass structure. By doing so, we’ll get a very good picture of what the atoms in our glass are doing now, which will help predict how large glass blocks will immobilize nuclear waste over thousands of years and withstand the radiation being emitted by the waste.

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