19 36 45 P. 13 JULY/AUGUST 2023 | VOL 181 | NO 5 Recycling Electric Vehicle Batteries ASM Materials Education Foundation Annual Report iTSSe Newsletter Included in This Issue SUSTAINABLE TONEWOODS FOR ACOUSTIC GUITARS GREEN MATERIALS ENGINEERING
19 36 45 P. 13 JULY/AUGUST 2023 | VOL 181 | NO 5 Recycling Electric Vehicle Batteries ASM Materials Education Foundation Annual Report iTSSe Newsletter Included in This Issue SUSTAINABLE TONEWOODS FOR ACOUSTIC GUITARS GREEN MATERIALS ENGINEERING
2023 INTERNATIONAL MATERIALS, APPLICATIONS & TECHNOLOGIES OCTOBER 16–19, 2023 | HUNTINGTON PLACE | DETROIT, MICHIGAN ADVANCED MATERIALS AND MANUFACTURING TECHNOLOGIES Featuring the Thermal Spray and Surface Engineering Forum Here’s what you can expect: • 5000 attendees • Over 450 technical presentations, keynotes, and panel discussions • More than 400 exhibitors • 2.5 days of exposition • Education courses and workshops • Networking events • Programming and activities for emerging professionals REGISTRATION OPEN ORGANIZED BY: PARTNERED WITH: CO-LOCATED WITH: Visit imatevent.org to learn more. IMAT 2023, co-located with Heat Treat and Motion + Power Technology Expo, unites different market segments that span the entire materials community and connects industry, academia, and government to solve global materials challenges. Core programming from all six of ASM International’s affiliate societies will serve as the backbone of IMAT’s technical sessions. IMAT will bring together all the global expertise you need to tackle modern materials challenges, address environmental issues, and incorporate the latest digital technologies.
2022 ANNUAL REPORT PUTTING MATERIALS SCIENCE ON THE MAP 36 2022 ASM FOUNDATION ANNUAL REPORT ASM’s Materials Education Foundation aims to inspire young people to pursue careers in materials, science, and engineering. IDENTIFICATION OF SUSTAINABLE TONEWOODS FOR ACOUSTIC GUITARS USING MATERIALS SELECTION SOFTWARE James D. Cotton and John D. Wolodko A search for alternative, sustainable tonewood species with sufficient acoustic performance is aided by the ANSYS Granta Selector. 13 ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 2 Close-up of wood grains on a Spanish guitar. Courtesy of Dancinghorseprojects/Dreamstime. On the Cover: 59 ASM NEWS The latest news about ASM members, chapters, events, awards, conferences, affiliates, and other Society activities. 31 TECHNICAL SPOTLIGHT KEEPING EV LITHIUM-ION BATTERIES ‘GREEN’ WITH CT-SCAN DATA ANALYSIS Fire risk in electric vehicle batteries can be reduced by detecting flaws through nondestructive visualization.
4 Editorial 5 Research Tracks 10 Machine Learning 6 Metals/Polymers/Ceramics 8 Testing/Characterization 11 Process Technology 12 Nanotechnology 71 Editorial Preview 71 Special Advertising Section 71 Advertisers Index 72 3D PrintShop TRENDS INDUSTRY NEWS DEPARTMENTS Check out the Digital Edition online at asminternational.org/news/magazines/am-p ASM International serves materials professionals, nontechnical personnel, and managers wordwide by providing high-quality materials information, education and training, networking opportunities, and professional development resources in cost-effective and user-friendly formats. ASM is where materials users, producers, and manufacturers converge to do business. Advanced Materials & Processes (ISSN 0882-7958, USPS 762080) publishes eight issues per year: January/February, March, April, May/June, July/August, September, October, and November/December, by ASM International, 9639 Kinsman Road, Materials Park, OH 44073-0002; tel: 440.338.5151; fax: 440.338.4634. Periodicals postage paid at Novelty, Ohio, and additional mailing offices. Vol. 181, No. 5, JULY/AUGUST 2023. Copyright © 2023 by ASM International®. All rights reserved. Distributed at no charge to ASM members in the United States, Canada, and Mexico. International members can pay a $30 per year surcharge to receive printed issues. Subscriptions: $499. Single copies: $54. POSTMASTER: Send 3579 forms to ASM International, Materials Park, OH 44073-0002. Change of address: Request for change should include old address of the subscriber. Missing numbers due to “change of address” cannot be replaced. Claims for nondelivery must be made within 60 days of issue. Canada Post Publications Mail Agreement No. 40732105. Return undeliverable Canadian addresses to: 700 Dowd Ave., Elizabeth, NJ 07201. Printed by LSC Communications, Lebanon Junction, Ky. 19 RECYCLING ELECTRIC VEHICLE BATTERIES: OPPORTUNITIES AND CHALLENGES Jaclyn Coyle, Kae Fink, Andrew Colclasure, and Matthew Keyser A surge in electric vehicle production is ushering in a new era of research on the best methods to recycle used lithium-ion batteries. 24 CONCRETE SUSTAINABILITY: A FUTURE PERSPECTIVE Christian Paglia As a material widely used around the world, the reuse, recycling, and environmental implications of concrete are important to consider. 28 CASE STUDY: MOLECULAR RECYCLING FOR A CIRCULAR ECONOMY One company is moving the needle in the plastic waste crisis using a depolymerization process called methanolysis to create new high-performance materials. 34 IMAT 2023 PROGRAM HIGHLIGHTS FEATURES JULY/AUGUST 2023 | VOL 181 | NO 5 ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 3 19 28 45 24 45 iTSSe The official newsletter of the ASM Thermal Spray Society (TSS). This timely supplement focuses on thermal spray and related surface engineering technologies along with TSS news and initiatives, and a preview of TS4E 2023.
4 ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 ASM International 9639 Kinsman Road, Materials Park, OH 44073 Tel: 440.338.5151 • Fax: 440.338.4634 Joanne Miller, Editor joanne.miller@asminternational.org Victoria Burt, Managing Editor vicki.burt@asminternational.org Frances Richards and Corinne Richards Contributing Editors Anne Vidmar, Layout and Design Allison Freeman, Production Manager allie.freeman@asminternational.org Press Release Editor magazines@asminternational.org EDITORIAL COMMITTEE Adam Farrow, Chair, Los Alamos National Lab John Shingledecker, Vice Chair, EPRI Somuri Prasad, Past Chair, Sandia National Lab Beth Armstrong, Oak Ridge National Lab Margaret Flury, Medtronic Surojit Gupta, University of North Dakota Nia Harrison, Ford Motor Company Michael Hoerner, KnightHawk Engineering Hideyuki Kanematsu, Suzuka National College of Technology Ibrahim Karaman, Texas A&M University Ricardo Komai, Tesla Bhargavi Mummareddy, Dimensional Energy Scott Olig, U.S. Naval Research Lab Christian Paglia, SUPSI Institute of Materials and Construction Amit Pandey, Lockheed Martin Space Satyam Sahay, John Deere Technology Center India Kumar Sridharan, University of Wisconsin Jean-Paul Vega, Siemens Energy Vasisht Venkatesh, Pratt & Whitney ASM BOARD OF TRUSTEES David B. Williams, President and Chair Pradeep Goyal, Senior Vice President Navin Manjooran, Vice President Judith A. Todd, Immediate Past President John C. Kuli, Treasurer Burak Akyuz Amber Black Ann Bolcavage Pierpaolo Carlone Elizabeth Ho man Toni Marechaux André McDonald U. Kamachi Mudali James E. Saal Sandra W. Robert, Executive Director STUDENT BOARD MEMBERS Jaime Berez, Ashlie Hamilton, Nicole Hudak Individual readers of Advanced Materials & Processes may, without charge, make single copies of pages therefrom for personal or archival use, or may freely make such copies in such numbers as are deemed useful for educational or research purposes and are not for sale or resale. Permission is granted to cite or quote from articles herein, provided customary acknowledgment of the authors and source is made. The acceptance and publication of manuscripts in Advanced Materials & Processes does not imply that the reviewers, editors, or publisher accept, approve, or endorse the data, opinions, and conclusions of the authors. SUSTAINABILITY SUPERHEROES One of ASM’s superpowers is that we have members working with all types of materials in nearly every conceivable application around the globe. This Green Materials Engineering issue of AM&P showcases just a few of those unique materials and applications that reflect the breadth of our reach. One well-known ASM member, Jim Cotton, FASM, is passionate about materials, guitars, and sustainability. He found a unique way to bring that trio of interests together for our lead article. According to Jim, many tree species that historically were used in guitar production are now rare, protected, or extinct. So, he set out to discover comparable species of tonewoods that could be crafted into high-quality instruments. Using materials selection software, he plugged in his criteria and let the tool filter down the choices. The resulting “green grains” produced more than just the published article. Pictured here is Jim with a guitar he commissioned based on his research findings. It’s made solely of tonewoods near his home in the Pacific Northwest: The top is western red cedar, the body is Douglas fir, and the fretboards are from claro walnut. Growing up, I took classical guitar lessons on a Yamaha and then later added an Alvarez Yairi acoustic guitar to expand my repertoire. Although diligent about keeping the instruments polished, I never gave much thought to the origin or species of the wood. Thanks to Jim, I’ll look at my guitars’ grains with new appreciation. From the idyllic tonewoods of the U.S., we now move to the high stakes realm of concrete particles in Switzerland. In his article, Christian Paglia offers insight into the challenging but important endeavors of reuse and recycling of concrete aggregates used in the construction sector. My own research found that the World Business Council for Sustainable Development, headquartered in Switzerland, has been working for the past decade on getting 24 cement producers from more than 100 countries to work together toward more sustainable production practices. With assistance from Battelle Memorial Institute in Columbus, Ohio, they have sustainability goals outlined for the industry for the next 20 years. Lastly, we turn to batteries. We present two articles that address the rising issues around the power source in electric vehicles. One discusses the vital importance of lithium-ion battery testing, and the other examines best practices for reclaiming and recycling graphite, lithium, nickel, cobalt, and manganese from the electrodes of spent batteries. These articles are evidence that ASM’s scope, and the vast work of our members, goes well beyond primary metals. ASM is indeed “everything material.” Jim Cotton, one of our sustainability superheroes, is in tune with that. joanne.miller@asminternational.org Jim Cotton’s commissioned guitar.
ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 5 A $162 million investment from the U.S. National Science Foundation (NSF) will support development of advanced materials at nine Materials Research Science and Engineering Centers (MRSECs), with each to receive $18 million over six years. In total, NSF now supports 20 such centers. The nine just announced will pursue a broad range of projects involving semiconductors, artificial intelligence, biotechnology, sustainable energy sources and storage, advanced manufacturing, quantum computing and sensing, and other areas of critical materials research: Illinois Materials Research Science and Engineering Center: Located at the University of Illinois Urbana-Champaign, the center will investigate: how strain in materials can be used to control the motion of electrons and can enable novel information storage and processing models in quantum materials as well as for energy production and storage; and how materials with light-controlled conduction of ions will benefit applications in new electrochemical manufacturing, energy, and information technologies. Center for Dynamics and Control of Materials: Located at The University of Texas at Austin, the center will design: new soft biomaterials whose structure and function can be actively controlled and used for applications such as synthetic cells and adaptive thermal coatings; and atomically thin materials with novel structures that can be useful for microelectronics, quantum information processing, and other applications. University of Washington Molecular Engineering Materials Center: This center will develop materials in which light can tune the magnetic properties of individual electrons for applications RESEARCH TRACKS A researcher working at the MRSEC at the University of California, San Diego. Courtesy of Erik Jepsen/UCSD. in quantum information processing and sensing, as well as “elastic quantum matter” materials in which strain forces produce and influence quantum-scale effects. Northwestern University Materials Research Science and Engineering Center: This center aims to create bio- inspired materials that can be programmed to perform self- directed functions such as self-healing and shape-morphing, which could be used in food storage or wound care, as well as materials that conduct both electrons and ions, similar to how brain neurons work. Laboratory for Research on the Structure of Matter: Located at the University of Pennsylvania, the center will develop: new materials that can adapt to their surroundings, with applications ranging from flexible materials that can deflect the energy of a hammer blow to soft robots that can perform complex tasks; and tissue-like synthetic biomaterials made from cellular building blocks capable of controlled release of key molecules inside cells. Materials Research Laboratory at UCSB: Located at the University of California, Santa Barbara, the center will focus on developing: new chemistries and processing methods to enable solvent-free manufacturing of sustainable polymers with improved recyclability; and adaptive biomaterials that mimic living systems with applications in soft implants and haptics. Wisconsin Materials Research Science and Engineering Center: Located at the University of Wisconsin- Madison, the center will develop: new types of glassy materials, such as flexible metallic and thin organic semiconducting glasses with applications from electronic displays to new formulations of drug molecules into pill form; and thin, crystalline-based membrane materials that feature ultrafast magnetic switching properties that can advance information processing, data storage, and quantum computing. Center for Advanced Materials & Manufacturing: Located at the University of Tennessee, Knoxville, the center is dedicated to: accelerating the design of quantum materials and systems through artificial intelligence, with potential advances in materials for energy harvesting, quantum computing and novel sensing applications; and developing materials that can withstand the extreme temperatures and pressures needed for nuclear fusion and hypersonic defense systems. Center for Materials Innovations at Michigan: Located at the University of Michigan-Ann Arbor, the center will focus on developing: new layered materials with tailored nanoscale structures to enable elusive quantum states for quantum information processing; and new recyclable polymeric materials capable of self- healing with potential applications in additive manufacturing. For more information, visit nsf.gov. MATERIALS RESEARCH CENTERS GET $162 MILLION BOOST FROM NATIONAL SCIENCE FOUNDATION
ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 6 METALS | POLYMERS | CERAMICS Fort Wayne Metals, Ind., a manufacturer of precision wire-based materials, acquired specialized wiredrawing equipment from Plansee SE, Austria, to facilitate tantalum production. Tantalum processing will begin by the end of the year. fwmetals.com. MAGNESIUM ALLOY BONDING Due to their low density and excellent strength-to-weight ratio, magnesium alloys are considered the next-generation base metal for multi-material design and have been touted as a possible replacement for conventional steels when appropriate. However, due to the immiscible nature of magnesium and iron, it’s been a challenge for scientists to develop bonding technology that successfully combines the alloys with structural steels. Now, a research team from Tohoku University, Japan, has succeeded in establishing a dealloying bonding technology that obtains a strong mechanical bond between iron and magnesium. “Our dealloying reaction derives from the miscibility and immiscibility of the constituent elements in the bond, and also helped create a 3D, interlocked microstructure at the interface of the two materials,” explains researcher Kota Kurabayashi. He also points out BENEFICIAL BAND FORMATION Researchers at the University of Wisconsin–Madison recently found that under the right conditions, shear bands can improve the ductility, or the plasticity, of a material. Using a combination of experimental characterization and simulations, the team identified potential strategies for encouraging shear bands. The work could lead to new ways of increasing toughness in a wide array of materials. After finding plasticity-promoting shear bands in a brittle intermetallic material called samarium cobalt, the team hypothesized that these types of beneficial bands could form in materials that easily transition between crystalline and amorphous phases. To test this, they looked at aluminum samarium, a glassy material studied extensively by lead researcher Izabela Szlufarska and colleagues in the NSF-supported Materials Research Science and Education Center at UW–Madison. Using atomic-level simulations, Szlufarska’s group predicted that the crystalline form of this material should also form shear bands under stress. They not only confirmed the finding in the lab, but also varied the atomic composition of the aluminum samarium, making versions where shear bands led either to fracture or to plasticity. This new understanding led the team to propose criteria for screening new materials that might exhibit similar properties and for identifying when shear bands are beneficial. They hope the new parameters will make it possible to search databases for materials that could benefit from doping or engineering to promote shear band formation. Next, the team intends to test traditional structural materials like oxides, carbides, and borides to determine how they can be optimized. wisc.edu. From le : Professor Izabela Szlufarska along with graduate students Xuanxin Hu and Nuohao Liu have developed new criteria for determining whether shear bands are beneficial or harmful to certain crystalline materials. Courtesy of University of Wisconsin–Madison. Polymer Resources Ltd., Farmington, Conn., upgraded and expanded its compounding facility in Rochester, N.Y., to support a 40% increase in overall compounding capacity. The updated plant also features increased grinding and shredding capacity for recycling plastic. prlresins.com. BRIEFS Researchers successfully established a strong mechanical bond of immiscible iron and magnesium.
ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 7 that the new approach provides an ideal mechanical bonding method to create a strong anchoring effect between materials that cannot form strong bonds. www.tohoku.ac.jp/en. COPPER GEOCHEMISTRY REVEALS HISTORY The distribution of metal goods, specifically early copper artifacts, is considered to have a high cultural and historical significance in European prehistory. However, limited information exists about how copper was used and dispersed in Neolithic Europe. To gain a better understanding, a research team from Kiel University, Germany, studied the geochemistry of early copper artifacts, revealing changes in distribution networks across prehistoric Europe. The researchers analyzed 45 copper objects, including axes, chisels, and other items, from various sites dating to the 4th and 3rd millennia B.C. of Northern Central Europe and Southern Scandinavia. The team examined the lead isotopic signature of the copper objects to link them to previously sampled sources of ore around the European continent. Their data indicate that artifacts from before 3500 B.C. derived exclusively from mines in southeast Europe, especially Serbian mining areas, while later artifacts include ores from the eastern Alps and Slovak Mountains and, much later, potentially the British Isles. Their results also indicate fluctuations in metallurgic activity over time, including a decrease in the prevalence of copper artifacts around 3000 B.C. These changes in the origins and availability of copper likely reflect differences in distribution networks through time, probably influenced by changing economies, social structures, communication networks, and technologies across prehistoric Europe. Further study of the sources and uses of copper artifacts will enhance our understanding of how metal goods were produced and distributed around the continent in the past. www.uni-kiel.de/en, plos.org. Copper axe from Frömkenberg, Germany, in an SEM. The origin of the axe’s copper was identified as the Belovode region of Serbia. Courtesy of Christin Szillus/Kiel University. THE ASM INTERNATIONAL 2023 CATALOG IS NOW AVAILABLE! Visit asminternational.org/store to view the catalog and shop ASM’s o erings today! www.masterbond.com Hackensack NJ, 07601 USA ∙ +1.201.343.8983 ∙ main masterbond.com Protection from many aggressive chemicals Acids, bases and many solvents Good flow properties Mixed viscosity, 75°F 15,000-25,000 cps Service temperature range -60°F to +450°F [-51°C to +232°C] Two Part Epoxy Supreme 62-1 SUPER TOUGHENED EPOXY RESISTS High Temperatures & Chemicals
8 ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 A critical step of the analysis was simulating the magnetic fields within the iron arsenide sample, for which the team wrote new software called Magnstem. The program allowed the scientists to add magnetic effects specific to their material and study its impact on electron beam patterns. By combining 4D-STEM with Magnstem simulations, researchers resolved magnetic order down to 6 angstroms. illinois.edu. TWEAKING THERMAL CONDUCTIVITY IN REAL TIME Researchers led by two teams at the University of Minnesota Twin Cities (U of M) discovered a new method to tune the thermal conductivity of materials to control heat flow in real time. They report their tuning range is the highest ever recorded among one-step processes in the field, and could enable development of more energy-efficient electronic devices. Typically, the thermal conductivity of a material is a constant value. Yet the U of M scientists discovered a simple process to tune this value in lanthanum strontium cobaltite, a material often used in fuel cells. Just as a switch controls electricity flow to a light bulb, the new method provides a way to turn heat flow on and off in devices. The materials synthesis team fabricated the lanthanum strontium cobaltite devices using electrolyte gating, in which ions are driven to the material’s surface. This allowed TESTING | CHARACTERIZATION IMAGING MAGNETISM IN ANGSTROMS Researchers at the University of Illinois Urbana-Champaign developed a new electron microscopy technique that can resolve magnetic behavior on the scale of angstroms. They then used this method to fully resolve the antiferromagnetic order in iron arsenide for the first time. “The best techniques before now have achieved resolutions of a few nanometers. We have vastly exceeded that record,” says Professor Pinshane Huang. To achieve the higher resolution, the team used 4D scanning transmission electron microscopy (STEM). While standard STEM techniques record drops in the electron beam’s intensity as it interacts with the material, 4D-STEM captures full 2D scattering patterns as the beam scans along the two directions of the material’s surface. These data allowed the scientists to search the full beam patterns for the more intricate signals of atomic antiferromagnetism. Triangular holes make this material more likely to crack from left to right. Courtesy of N.R. Brodnik et al./Phys. Rev. Lett. Researchers at The University of Tokyo studied the flow of thermal energy in purified graphite ribbons and showed that heat can move more like a liquid under certain conditions, rather than diffusing randomly. The discovery could lead to more efficient heat removal from electronic devices. tinyurl.com/bddmtdtm. D-STEM performed on a sample of iron arsenide. Courtesy of Grainger College of Engineering at the University of Illinois Urbana-Champaign. A research team led by scientists from Ohio University, Athens, and Argonne National Laboratory, Lemont, Ill., report taking the world’s first x-ray signature of just one atom. This pioneering achievement, funded by the DOE, could revolutionize the way scientists detect materials. tinyurl.com/3wn4x83e. BRIEFS
ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 9 University of Minnesota Twin Cities mechanical engineering Ph.D. students Yingying Zhang and Chi Zhang conduct measurements using a home-built system involving ultrafast laser pulses. Courtesy of Dingbin Huang/U of M. the mechanical engineering team to manipulate the material by applying a low voltage to it. “Our results establish low-power, continuously tunable thermal conductivity over an impressive range, opening up some pretty exciting potential device applications,” explains researcher Chris Leighton. umn.edu. HARNESSING X-RAYS FOR HYDROGEN RESEARCH A research team led by the DOE’s Argonne National Laboratory (ANL) used powerful x-ray beams to develop a new understanding of materials critical to the efficient production and use of hydrogen. As part of their study, the scientists report progress in developing a tool that enables them to characterize the materials with a new level of detail. Working at the Advanced Photon Source (APS) at Argonne, researchers aimed an intense x-ray beam onto a single grain of platinum. Diffraction patterns from that grain were then collected on an x-ray detector and the patterns were converted into images of the sample using customized computer algorithms. A nanodroplet chemical cell was used to control the chemical reaction happening on the platinum grain to produce hydrogen in an electrolyzer, which makes hydrogen fuel from water using electricity; in a reverse operation, the device becomes a fuel cell and converts hydrogen fuel back to electricity. The team’s prototype enabled the investigation of a single nanograin and will allow scanning of all grains in a realistic electrolyzer or fuel cell when the APS upgrade is complete next year. When the revamped APS goes live in 2024, its x-ray beams will be up to 500 times brighter than they are today. anl.gov. An intense x-ray beam (in pink) is focused into a small spot on a single nanoscale grain of a platinum electrode (highlighted within the droplet), then di raction interference patterns of the grain are collected on an x-ray detector (the black screen). Courtesy of Dina Sheyfer/ANL. The Thermal Spray Society (TSS) is dedicated to the expansion of knowledge, technical information, safety guidelines, and best processes and procedures in this unique and valuable surface application. With an unparalleled international community and network, TSS members have access to a global marketplace that continues to grow. Visit asminternational.org for more information. UPCOMING SHOWS Thermal Spray of Suspensions & Solutions Symposium + EBCS (TS4E) SEPTEMBER 12–13, 2023 | UNIVERSITY WEST, SWEDEN International Materials, Applications & Technologies (IMAT) Advanced Materials and Manufacturing Technologies OCTOBER 16–19, 2023 | DETROIT, MICHIGAN International Thermal Spray Conference and Exposition Advancing Thermal Spray Technology: Innovations, Applications and Sustainability APRIL 29–MAY 1, 2024 | MILAN, ITALY ASM Global Materials Summit An Exclusive Event for Materials Industry Executives DECEMBER 5–7, 2023 | NAPLES, FLORIDA International Thermal Spray Conference and Exposition MAY 5–8, 2025 | VANCOUVER, CANADA North American Cold Spray Conference SEPTEMBER 10–11, 2024 | NATIONAL RESEARCH COUNCIL OF CANADA, BOUCHERVILLE
ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 10 MACHINE LEARNING | AI A new report titled “AI for Science, Energy, and Security” presents a comprehensive vision for the Department of Energy to expand its work in the scientific use of artificial intelligence (AI). The study describes scientific grand challenges where AI plays a major role, such as transportation, national security, and development of next-generation materials. tinyurl.com/5n6rsnc4. BRIEF MACHINE LEARNING SUPPORTS SOLID-STATE BATTERIES Researchers at Duke University, Durham, N.C., and their colleagues discovered the atomic mechanisms that make compounds known as argyrodites promising candidates for both solid-state battery electrolytes and thermoelectric energy converters. Their results, and the machine learning approach used to achieve them, could lead to new energy storage applications for electric vehicles and other applications. “Every electric vehicle manufacturer is trying to move to new solid- state battery designs, but none of them are disclosing which compositions they’re betting on,” says associate professor Olivier Delaire. He and his colleagues looked at one promising candidate made of silver, tin, and selenium (Ag8SnSe6). Using a combination of neutrons and x-rays, the team bounced these fast-moving particles off atoms within samples of Ag8SnSe6 to reveal its molecular behavior in real time. Researcher Mayanak Gupta then developed a machine learning approach to make sense of the data and created a computational model to match the observations using quantum mechanical simulations. The results show that while the tin and selenium atoms create a relatively stable scaffolding, it is far from static. The crystalline structure constantly flexes to create windows and channels for the charged silver ions to move freely through the material: The tin and selenium lattices remain solid while the silver is in a nearly liquid-like state, according to Delaire. These results along with the approach of combining advanced experimental spectroscopy with machine learning could help researchers make faster progress toward replacing lithium-ion batteries in crucial applications. duke.edu. SOFTWARE SPEEDS POLYMER DISCOVERY A software program called PySoftK that aims to advance the discovery of new polymers has been developed by a team of interdisciplinary researchers at King’s College London. PySoftK uses artificial intelligence (AI) to identify new polymer materials, which could be used across a wide range of applications in energy storage, medical technology, and more. The software facilitates the use of computer simulations at a complex molecular scale to design new polymer materials. The program could change the way scientists investigate the relationship between the chemical structure and function of new polymeric materials, by providing a robust dataset for researchers to train AI to identify desirable polymer properties. Over the past few decades, molecular scale simulations have improved scientific understanding of the relationship between chemical structure and function in increasingly complex polymers. However, more recent advances in computing power and computational algorithms have Illustration of hybrid crystalline-liquid atomic structure in superionic phase of Ag8SnSe6. Tube-like filaments show the liquid-like distribution of silver ions flowing through the crystalline scaffold of tin and selenium atoms. PySoftK uses AI to identify new polymer materials for use in applications from energy storage to medical technology. enabled scientists to investigate more complex systems and provide more accurate predictions using molecular- scale simulations at speed. This can lead to faster and more cost-effective materials design. “By offering a set of tools and programming modules to automate the process of curating, modeling, and creating libraries of polymers, PySoftK facilitates the generation of large databases on which to train future machine learning and deep learning models. This allows researchers to move their focus away from exhaustive library maintenance and onto discovering new materials,” says Professor Chris Lorenz. www.kcl.ac.uk.
ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 1 1 PROCESS TECHNOLOGY MAKING ATOMICALLY PRECISE METAL OXIDES A breakthrough method developed by University of Minnesota-Twin Cities, Minneapolis, researchers is making it easier to create high-quality metal oxide thin films out of stubborn metals that have historically been difficult to synthesize in an atomically precise manner. The research paves the way for scientists to develop better materials for various next-generation applications including quantum computing, microelectronics, sensors, and energy catalysis. So-called stubborn metal oxides— such as those based on ruthenium or iridium—play a crucial role in numerous strength is recovered through the growth and connection of matter from opposite fracture surfaces.” The researchers developed a model to gauge the efficacy of their repairs in restoring mechanical strength based on the geometry of the fracture, the original strength of the overall structure, the strength of the nickel coating, and other process parameters. They applied their model to three different alloys, including two aluminum alloys commonly used in aircraft wings and fuselages, considered previously to be unweldable. The team plans to expand upon their work with the 3D-printed structure by designing and fabricating components that factor repairs needed beforehand to ensure effective recovery of strength is more easily facilitated. upenn.edu. applications in quantum information sciences and electronics. However, converting them into thin films has been a challenge for researchers due to the inherent difficulties in oxidizing metals using high-vacuum processes. While some researchers have successfully achieved oxidation, the methods used thus far have been costly, unsafe, or have resulted in poor material quality. Now, the University of Minnesota researchers found that incorporating epitaxial strain—effectively stretching the metals at the atomic level— significantly simplifies the oxidation process of these stubborn metals. With this groundbreaking discovery, the researchers aim to empower scientists worldwide to synthesize these novel materials. twin-cities.umn.edu. REPAIRING FRACTURED METALS A team of researchers at the University of Pennsylvania, Philadelphia, discovered a new technique to restore metals’ strength and toughness. The researchers used their novel electrochemical healing method to repair fractured metals in various metallic materials, including steel, aluminum alloys, and complex 3D-printed structures under room-temperature conditions. “We call our method electrochemical healing because it more closely resembles how our bodies repair a bone fracture,” says lead researcher Zakaria H’sain. “The healing matter is transported to the fracture site and GE Renewable Energy and Keystone Tower Systems, with help from the DOE, began operating the first wind turbine whose tower was built using spiral welding, which takes flat-rolled steel and curls it into a cylinder. The process makes it possible to build wind turbine towers onsite with just one machine. ge.com. Novelis Inc., Atlanta, announced the debut of its new roll forming development line in Novi, Mich. The experimental line will enable year-round, in-house R&D on roll forming, with the goal of creating a robust process that can produce large volumes of highstrength aluminum auto parts. novelis.com. BRIEFS University of Minnesota researchers developed a breakthrough method for creating high-quality metal oxide films for quantum computing and microelectronics applications. Courtesy of Olivia Hultgren/University of Minnesota. In this 3D graphic of an octet-truss lattice structure, the insets show how nickel ions can easily access the fractured internal strut, where they are reduced to nickel metal during electrochemical healing. Courtesy of Zakaria H’sain.
ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 12 NANOTECHNOLOGY SELF-ASSEMBLING CRYSTAL STRUCTURES Scientists at Cornell University, Ithaca, N.Y., used a targeted computational approach to find more than 20 new self-assembled crystal structures. The team conducted a targeted search for previously unknown low-coordinated assemblies within a vast parameter space spanned by particles interacting via isotropic pair potentials. Low particle coordination is a structural characteristic key to the functional properties of many technologically important materials, including metal-organic frameworks, clathrates, and zeolites, as well as photonic crystals such as diamond. The researchers developed a new functional form for particle interactions in which all features can be tuned independently. By systematically changing pairs of parameters in simulation, the researchers were able to control various features of the particles’ interaction landscape. A wealth of complexity and symmetry is apparent within these crystal structures. The work demonstrates that complicated structures can develop from simple interactions and adds new theoretical structures for others working in the field. The team’s flexible and intuitive interaction potential design serves as an important step toward determining the characteristics of particle interactions that lead to certain structural properties, useful for establishing synthetic rules to make target structures. The findings suggest that there are potentially limitless new and exotic material configurations possible through controlled selfassembly. “This is the first time that we’re quantifying the relationship of this isotropic pair potential with the crystal structures that result,” says lead researcher Julia Dshemuchadse. “These new crystal structures can now serve as design targets for researchers who actually make nanoparticles and colloids.” cornell.edu. TRANSFORMABLE NANOSCALE DEVICES A finding by University of California, Irvine, physicists revealed the potential for nanoscale devices to transform into many different shapes and sizes while Conceptual image showcasing several interaction potential shapes, represented by stems, that lead to the self-assembly of new low-coordinated crystal structures, represented by flowers. existing in solid states. The discovery of this new property could fundamentally change the nature of electronic devices as well as the way scientists research atomic-scale quantum materials. Researchers found that for a particular set of materials, they could make modifiable nanoscale electronic devices that aren’t stuck together. The physicists explain that the modular parts allow for modification of size and shape after a device has been made. Until now, this was considered by scientists to be impossible. What they saw specifically was that tiny nanoscale gold wires could slide with very low friction on top of van der Waals materials. Taking advantage of these slippery interfaces, they made electronic devices comprised of single-atom thick sheets of graphene attached to gold wires that can be transformed into a variety of different configurations. The team expects their work could usher in a new era of quantum science research. uci.edu. Triangular holes make this material more likely to crack from le to right. Courtesy of N.R. Brodnik et al./Phys. Rev. Lett. Using a new microscopy technique that employs blue light to measure electrons in semiconductors and other nanoscale materials, a research team at Brown University, Providence, R.I., is at the forefront of developing new ways to study these components. The findings are a first in nanoscale imaging and offer a solution to a persistent problem that has limited the study of key phenomena in a variety of materials that could lead to more energyefficient electronics. brown.edu. BRIEF The golden parts of the device depicted in this graphic are transformable. Courtesy of Yuhui Yang/UC.
13 ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 IDENTIFICATION OF SUSTAINABLE TONEWOODS FOR ACOUSTIC GUITARS USING MATERIALS SELECTION SOFTWARE James D. Cotton, FASM,* Issaquah, Washington John D. Wolodko, FASM,* University of Alberta, Edmonton, Canada A search for alternative, sustainable tonewood species with su cient acoustic performance is aided by the ANSYS Granta Selector. *Member of ASM International Image courtesy of Irvin Guitars, Bremerton, Washington. SUSTAINABLE TONEWOODS
14 ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 Over a century ago, the Martin Guitar Company (Nazareth, Pa.) established four benchmark species as key ingredients of a high-quality instrument: old growth Adirondack Spruce (Picea rubens), Brazilian Rosewood (Dalbergia nigra), Honduran Mahogany (Swietenia macrophylla), and African Ebony (Diospyros crassiflora)[1-3]. Though derived from Old World luthier principles, they came to represent the ideal combination of raw materials that allowed a balanced tone to project from an attractive, portable, and playable instrument. It was so good in fact, that this quadrumvirate became the benchmark of what a great acoustic guitar should be. Other manufacturers, like Gibson, Fender, Yamaha, and Washburn also adopted this combination and the resulting scooped midrange frequency curve became the sound that allowed human voices to soar above hundreds of projected harmonics, yet at a volume that could compete with the popular mandolins and banjos of the day. The Martin D-28 exemplified this design and became the standard following its introduction in 1931[4] (Fig. 1). At present, nearly 2,000,000 acoustic guitars are sold annually in the U.S., a mere quarter of global sales[5]. However, this growth has constraints. Old growth spruce forests, the main source of coveted straight-grained soundboards, are being increasingly protected for their ecological, bio- diversity, and carbon sequestration benefits[6,7]. And other tonewoods have greater sourcing challenges. Brazilian Rosewood and Honduran Mahogany are currently listed as endangered by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)[8]. In 2017, all rosewood species were likewise protected and the only instrument-grade ebony available is from Cameroon. Though these species continue to be offered in new instruments, unreliable availability has led to an ongoing search for substitutes[2,9-13]. Substitutes are often sought by trial-and-error among similar species in an effort to replicate the performance of the benchmarks. However, similar market forces can create similar problems, e.g., a Rosewood substitute species, Sapele (Entandrophragma cylindricum), has reportedly suffered from overharvesting[8]. This article describes an effort to identify tonewood substitutes using the ANSYS Granta Selector[14] based on derived performance objectives for physical and mechanical properties. These objectives are then combined with those for species morphology, producibility, and sustainability to arrive at sustainable and viable tonewood substitution options that meet manufacturer and customer expectations. Because of required larger starting stock dimensions, only the acoustic guitar top (soundboard) and body (sides and back) are discussed here. METHOD AND RESULTS The principles of multiple objective materials selection are well established and described elsewhere[15,16]. Prior work[2,17-20] has described formulae correlating with acoustic performance, typically incorporating density, modulus, and damping coefficient as key properties, but generally did not include process metrics such as ease of cutting, formability, bondability and finishability, mature tree form and size, and environmental sustainability. These factors are experientially considered by instrument manufacturers and there have been dozens of alternative tonewood species explored, many commercialized, based on similarity to benchmarks[2,13]. For example, Godin Guitars (Canada) transitioned from neotropical mahogany to local Black Cherry (Prunus serotina) in 2008 for the body of a classical model[21], and Breedlove Guitars builds with local Oregon Myrtlewood (Umbellularia californica) collected from downed trees[22]. Taylor Guitars cleverly upcycles local end-of-life trees removed from urban landscapes, such as Shamel Ash (Fraxinus uhdei) and Red Ironbark (Eucalyptus sideroxylon)[23]. Such efforts to source locally have had success and are consistent with sustainable practices. Fig. 1 — Traditional Martin D-28 acoustic guitar with benchmark tonewoods indicated. Fig. 2 — Flow diagram for tonewood selection.
15 ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 The next stage selected for species with a mature tree form amenable to economical extraction of quartersawn panels for modern soundboard production, typically, 21.6 x 53.3 cm, with long dimension parallel to the grain. This is supported by a straight growth habit and minimum mature bole diaThe present exercise identifies potential tonewood substitutes among the 214 tree species contained in the ANSYS Granta Selector database by characterizing acoustic performance of benchmark species commonly used in acoustic guitar soundboard and body components. Though a small fraction of over 73,000 estimated tree species[24], it is about one seventh of the 1575 commercially significant timber species[25]. After identifying species with similar acoustic performance to benchmark species, both soundboard and body subsets were filtered separately through three additional stages, tree form, sustainability, and producibility, using commercial spreadsheet functions. Tree form selected only for species with a mature size and form amenable to economical acoustic guitar manufacture. Sustainability was treated by eliminating any species with a documented extinction risk in the CITES Checklist[8] or the International Union for Conservation of Nature and Natural Resources (IUCN) Red List[26]. Finally, the remaining species were scored for producibility via two metrics, workability (ease of cutting) and finishability (ease of bonding, staining, etc.), converted to “good, average, or poor” ratings based on data from The Wood Database[27]. Species with a poor rating for either resulted in rejection. The spreadsheet output provided separate lists of down-selection tonewood species for both soundboard and body applications. A flow diagram for the selection process is shown in Fig. 2. Soundboard (top). In the case of soundboards, Bremáud[28]—based on the work of Barlow[17]—proposed a metric termed the Acoustic Conversion Efficiency (ACE), defined as: where E is Young’s Modulus, ρ is density, and tan δ is the damping coefficient (all properties were assessed as averages in the longitudinal tree growth direction). Figure 3 plots ACE ranges calculated for all 214 species, ordered from high to low, with higher values deemed to be better. The box selects the range bounding Sitka Spruce (Picea sitchensis), a benchmark acoustic soundboard tonewood, and contains 47 species. A second sub-selection (not shown) from this subset confirmed the compressive strength of all 47 would meet or exceed that of Sitka Spruce and thereby support full string tension. TABLE 1 — DOWNSELECTED SOUNDBOARD AND BODY TONEWOOD TREE SPECIES Soundboard (top) species Body (back & sides) species Noble Fir (Abies procera) Alaskan Yellow Cedar (Chamaecyparis nootkatensis) European Spruce (Picea abies) Douglas Fir (Pseudotsuga menziesii) White Spruce (Picea glauca) Black Cherry (Prunus serotina) Red Fir (Abies magnifica) Western Hemlock (Tsuga heterophylla) Silver Fir (Abies alba) Ekop (Didelotia brevipaniculata) Western White Pine (Pinus monticola) Pilon (Hyeronima alchorneoides) Sitka Spruce (Picea sitchensis) Bigleaf Maple (Acer macrophyllum) Western Red Cedar (Thuja plicata) Determa (Sextonia rubra; Ocotea rubra) White Fir (Abies concolor) Slash Pine (Pinus elloittii) Eastern White Pine (Pinus strobus) Radiata Pine (Pinus radiata) Douglas Fir (Pseudotsuga menziesii) Norway Pine (Pinus resinosa) Yellow Poplar (Liriodendron tulipifera) Scotch Pine (Pinus sylvestris) Sugar Pine (Pinus lambertiana) Swamp Tupelo (Nyssa aquatica) Norway Pine (Pinus resinosa) Angelique (Dicorynia guianensis) Ponderosa Pine (Pinus ponderosa) Fig. 3 — Acoustic conversion e iciency (ACE) box selection plot for soundboards. The box represents the selection of 47 species close to the benchmark species, Sitka Spruce.
16 ADVANCED MATERIALS & PROCESSES | JULY/AUGUST 2023 meter and length of 61 cm and 3 m[3], respectively. This eliminated another 18 species, leaving 29. Six more species were eliminated for sustainability and another eight for producibility, as described above, resulting in the final list of 15 potential soundboard species shown in Table 1. Body (back and sides). The degree to which body woods contribute to the tone profile of acoustic guitars depends on many factors[29]. Therefore, again, we merely endeavored to match key properties of benchmark body tonewoods while supporting producibility and sustainability goals. Analysis was carried out similar to the soundboards, utilizing selection metric values spanning those for Brazilian Rosewood to Honduran Mahogany, since the latter species is also a well-established body tonewood. The ACE value range for the benchmark body tonewoods is shown in Fig. 4 containing 196 species. A second metric was then applied using a standard solution (a pressure sensor) within the Selector[14] to select for species supporting fundamental resonance modes[30] similar to the benchmarks. This metric is termed the Sensitivity to Pressure Difference (SPD) and defined as where σ is the yield strength and E is the Young’s Modulus. The body wood subset was reduced from 196 to 186 after box selection for SPD, per Fig. 5. Further down-selection for acoustic impedance, compressive strength, and volumetric drying shrinkage was carried out sequentially, resulting in 123, 113, and 72 species passing, respectively (figures not shown). These stages were added for the body woods in particular to account for transfer of acoustic energy within the body cavity, and the fabricability demanded by complex forming operations, e.g., during steam-forming the side wall radii. Further down-selection for sustainability and producibility, as described above, resulted in a final list of 14 potential body tonewood species, per Table 1. DISCUSSION The results in Table 1 identify tree species that could serve as soundboards and bodies for acoustic guitars and also meet key producibility and sustainability requirements. In the case of the 15 soundboard species, all are coniferous boreal forest softwoods with the exception of Yellow Poplar. The coniferous species consists of three spruce, four fir, five pine, plus Western Red Cedar (not a true cedar), and Douglas Fir (not a true fir). Various cedar species, including Western Red Cedar, are established soundboard materials Fig. 4 — Acoustic conversion energy box selection for body tonewoods. Fig.5 — Sensitivity to pressure di erence (SPD) box selection for body tonewoods. for classical guitars. Yellow Poplar is utilized for some solid body guitars and organ soundboards, and also as the inexpensive inner layer of some laminated wood panels. The other species are not known to be used commercially for musical instruments. The 14 down selected body species in Table 1 are roughly split between softwoods and hardwoods, which is an interesting result given that production body tonewoods are by and large fabricated from tropical hardwoods. Of the hardwood species shown, four—Ekop, Pilon, Determa, and Angelique—do originate in tropical
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