News & Media
Oxide interfaces in disarray
Exploration of disorder at material interfaces could lead to better device performance
The structure of an interface at which two materials meet helps determine the performance of the computers and other devices we use every day. However, understanding and controlling interface disorder at the atomic level is a difficult materials science challenge.
A research team at PNNL and Texas A&M University combined cutting edge imaging and numerical simulations to examine disordering processes in widely used oxide materials. They found that certain oxide interface configurations remain stable in extreme environments, suggesting ways to build better performing, more reliable devices for fuel cells, space-based electronics, and nuclear energy.
Visualizing the disordering process
As reported in Advanced Materials Interfaces (“Asymmetric Lattice Disorder Induced at Oxide Interfaces,” DOI: 10.1002/admi.201901944) the team set out to examine interfaces between pyrochlore-like and perovskite oxides, two common classes of functional materials used in energy and computing technologies. While most past work has focused on individual bulk materials, less attention has been paid to interfaces connecting them, as would be the case in a device. In particular, it is not clear how interface features, such as composition, bonding, and possible defects, govern disordering processes.
Funded by PNNL’s Nuclear Process Science Initiative (NPSI), the team employed experimental and theoretical methods to study the interface at different stages of disorder introduced through ion irradiation. They imaged the local structure of the material using high-resolution scanning transmission electron microscopy and convergent beam electron diffraction, which showed that the bulk of the two materials disordered (amorphized) before the interface. After further irradiating the material, they found that a band region near the interface had remained crystalline, while the rest of the structure had become amorphous.
To understand this behavior, the team turned to a technique called electron energy loss spectroscopy, which allowed them to examine the atomic-scale chemistry and defects formed at the interface. Their measurements revealed the presence of substantial amounts of defects called oxygen vacancies, which can greatly affect properties such as magnetism and conductivity. Based on these observations, the team constructed a theoretical model of the interface and explored the effect of different interface configurations on the tendency to form vacancies.
“In our model we are able to systematically vary interface features, such as crystal structure, intermixing, and strain, to see their effect on defect formation. We found that the structure of the materials on both sides of the interface can influence where defects are likely to form first,” explained Steven R. Spurgeon, a PNNL materials scientist. “Our model suggests that by selecting appropriate crystal structures and controlling how they connect, it may be possible to dictate the sequence of defect formation, which would allow us to enhance the properties of these materials.”
The team is exploring other interface structures and chemistries, with an eye toward improving the performance of oxides used in extreme environments.
The study was conducted as part of the NPSI project, “Damage Mechanisms and Defect Formation in Irradiated Model Systems,” led by Spurgeon.
Solving an ergonomic problem to enable safeguards research
PNNL-WSU collaboration develops the future workforce
Performing nuclear safeguards work safely and developing the next generation workforce are complementary goals of a longstanding program sponsored by the National Nuclear Security Administration’s Office of International Nuclear Safeguards. This program pairs PNNL research staff with Washington State University engineering students to provide solutions to enable nuclear safeguards research at PNNL.
In December, a team of WSU students delivered their solution to some ergonomic issues faced by PNNL physicist Mike Cantaloub and his team in a laboratory containing sensitive high-purity germanium detectors. These detectors are arranged in a tall fixture containing lead shielding to reduce the effects of naturally occurring atmospheric radiation and enable the accurate identification of radioactive isotopes in samples. Staff members using this instrument have to remove a 25-lb. plug detector, reach down to place samples, and then replace the plug detector. These activities have the potential for ergonomic injury to staff members and damage to the detectors.
WSU students Darin Malihi, Jared Oshiro, Martin Gastelum, Jacob Lazaro, Nicholas Takehara, and Saul Ramos designed and fabricated equipment that works similar to the weight training machines found in a gym—a lifting arm with a counter weight. The team also developed a solution to place the sample, a holder that is affixed to the bottom of the plug detector. Their solutions allow researchers to remove the detector quickly and efficiently and avoid reaching down to place the sample for detection.
“The solution devised by the team makes day-to-day operations in this laboratory safer and more efficient for the nuclear safeguards research team," said PNNL mechanical engineer and advisor to the WSU team, Patrick Valdez.
Improving nuclear waste storage models by studying the chemistry of material interactions
WastePD EFRC research on the glass-steel interface was published in Nature Materials
PNNL Launches Marine Renewable Energy Database
Tethys Engineering addresses industry’s technical and engineering challenges
Marine renewable energy (MRE) has the potential to provide 90 gigawatts of power in the United States through waves and tidal and ocean currents.
To harness the ocean’s energy, the MRE industry needs to understand how to address technical and engineering challenges such as efficient power takeoff, device survivability, and grid integration.
PNNL developed Tethys Engineering in September 2019 to allow sharing resources around the deployment of devices in corrosive, high-energy marine environments. The recently launched Tethys Engineering online database includes collected and curated documents surrounding the technical and engineering development of MRE devices. Users can search and filter results to intuitively identify information relevant to developers, researchers, and regulators.
Tethys Engineering includes more than 3,000 journal articles, conference papers, reports, and presentations related to wave, current, salinity gradient, and ocean thermal energy conversion technologies. The database contains information from around the world.
The Tethys Engineering database was created as a companion to the already established Tethys website, which focuses on the environmental effects of the MRE industry.
Data Assimilation Impact of In Situ and Remote Sensing Meteorological Observations on Wind Power Forecasts during the First Wind Forecast Improvement Project (WFIP)
During the first Wind Forecast Improvement Project (WFIP) new meteorological observations were collected from a large suite of instruments, including wind velocities measured on networks of tall towers provided by wind industry partners, wind speeds measured by cup anemometers mounted on the nacelles of wind turbines, and by networks of Doppler sodars and radar wind profilers. Previous data denial studies found a significant improvement of up to 6% RMSE reduction for short-term wind power forecasts due to the assimilation of all of these observations into the NOAA Rapid Refresh (RAP) forecast model using a 3dvar GSI data assimilation scheme. As a follow-on study, we now investigate the impacts of assimilating into the RAP model either the additional remote sensing observations (sodars and wind profiling radars) alone, or assimilating the industry provided in situ observations (tall towers and nacelle anemometers) alone, in addition to the standard meteorological data sets that are routinely available. The more numerous tall tower/nacelle observations provide a relatively large improvement through the first 3-4 hours of the forecasts, which however decays to a negligible impact by forecast hour 6. In comparison the less numerous vertical profiling sodars/radars provide an initially smaller impact that decays at a much slower rate, with a positive impact present through the first 12 hours of the forecast. Large positive assimilation impacts for both sets of instruments are found during daytime hours, while small or even negative impacts are found during nighttime hours.
Wilczak J.M., J. Olson, I. Djalaova, L. Bianco, L.K. Berg, W.J. Shaw, and R.L. Coulter, et al. 2019. "Data Assimilation Impact of In Situ and Remote Sensing Meteorological Observations on Wind Power Forecasts during the First Wind Forecast Improvement Project (WFIP)." Wind Energy 22, no. 7:932-944. PNNL-SA-132499. doi:10.1002/we.2332