17 25 35 P. 12 SEPTEMBER 2023 | VOL 181 | NO 6 Additive Manufacturing of Electric Motors Advances in Laser Processing HTPro Newsletter Included in This Issue MATERIALS FOR FUSION POWER ADVANCED MANUFACTURING
17 25 35 P. 12 SEPTEMBER 2023 | VOL 181 | NO 6 Additive Manufacturing of Electric Motors Advances in Laser Processing HTPro Newsletter Included in This Issue MATERIALS FOR FUSION POWER ADVANCED MANUFACTURING
DECEMBER 5–7, 2023 | NAPLES, FL REGISTRATION NOW OPEN Recharge in the company of visionaries, connect with other materials executives who share your fire about the future of the materials world, and unlock new thinking to spark innovation. This year’s summit will convene a powerful collection of groundbreaking innovators and top subject-matter experts, focused on the following domains: • Materials 4.0 — Materials Genome Deployment • Nexus of Data Science and Materials Science • Industry 4.0 — The New Manufacturing Landscape • Materials Sustainability in the 21st Century Plan today to join other materials executives and ASM leaders during this exclusive two-day summit, featuring keynotes, expert panel sessions, and numerous networking opportunities. Be sure to arrive early to relax and connect with your peers during an informal golf outing! REGISTER TODAY! asmsummitevent.org
53 ASM NEWS The latest news about ASM members, chapters, events, awards, conferences, affiliates, and other Society activities. THE ‘SOFTER’ SIDE OF FUSION MATERIALS DEVELOPMENT Brenda L. Garcia-Diaz, Dale Hitchcock, George Larsen, Tyler Guin, Bob Sindelar, Rebecca J. Dylla-Spears, G. Jackson Williams, Xiaoxing Xia, and G. Elijah Kemp The development of polymers, traditionally neglected in fusion materials research, is crucial to the success of commercial fusion energy. 12 ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 2 The National Ignition Facility’s preamplifier module at the Lawrence Livermore National Laboratory. Courtesy of Lawrence Livermore National Laboratory. On the Cover: 64 3D PRINTSHOP Researchers look at methods to combine two kinds of materials using additive manufacturing. 25 TECHNICAL SPOTLIGHT ADVANCES IN LASER PROCESSING This guide outlines recent advances in the various methods of laser technology and appropriate manufacturing applications.
4 Editorial 5 Feedback 5 Research Tracks 10 Machine Learning 6 Metals/Polymers/Ceramics 8 Testing/Characterization 11 Emerging Technology 63 Editorial Preview 63 Special Advertising Section 63 Advertisers Index 64 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-e ective 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. 6, SEPTEMBER 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. 17 ADDITIVE MANUFACTURING OF ELECTRIC MOTORS Tuomas Riipinen, Jenni Pippuri-Mäkeläinen, and Aino Manninen The manufacture of electric motors using additive methods offers potential advantages of increased efficiency, weight reduction, and customizability over traditional processes. 20 TECHNICAL SPOTLIGHT: ADVANCEMENT IN ENGINEERED INTEGRAL PATHWAYS FOR MANUFACTURED STRUCTURES A new friction stir processing method creates subsurface integral pathways in components that can be used for wiring, gases, fluids, powders, or as a lightweighting technique. 29 IMAT 2023 SHOW PREVIEW IMAT—the International Materials, Applications & Technologies Conference and Exhibition—and ASM’s annual meeting will be held in Detroit, October 16-19. FEATURES SEPTEMBER 2023 | VOL 181 | NO 6 ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 3 17 2023 INTERNATIONAL MATERIALS, APPLICATIONS & TECHNOLOGIES OCTOBER 16–19, 2023 | HUNTINGTON PLACE | DETROIT, MICHIGAN SHOW PREVIEW ASM International invites you to participate in its largest fall event, IMAT 2023—the International Materials, Applications & Technologies Conference and Exhibition. Join us in the Motor City, Detroit, from October 16–19 for a comprehensive lineup of technical sessions, high level keynotes, networking events, and an exhibit floor. With a focus on Advanced Materials and Manufacturing Technology, the conference combines with a two-anda-half day exposition to bring together major OEMs, materials partners, and suppliers to highlight advanced materials, processes, and applications throughout the materials community. No other conference integrates applied materials technologies and applications with economics, environmental issues, and enabling digital technologies. With its broad reach, ASM unites different market segments that cross the entire materials world and connects industry, academia, and government to solve global materials challenges. The result is a program rich with top-notch experts brought to you by ASM, the Heat Treating Society, and our organizing partner, the Association for Materials Protection and Performance. The event is also colocated with Motion + Power Technology Expo, which brings an additional 200 exhibits. Join us for this exciting one-of-a-kind materials event! TECHNICAL PROGRAM IMAT features robust programming with over 350 technical presentations in 17 topic areas and a groundbreaking Materials Innovation Session. For details on session topics and schedule, visit imatevent.org. The IMAT event is proud to be co-located this year with Heat Treat 2023. For details on heat treat programming, see page 50 in this issue. SPONSORS: CORPORATE SUPPORTERS: Subject to change. Sponsors current as of August 22, 2023. PARTNERED WITH: CO-LOCATED WITH: ORGANIZED BY: CORPORATE SPONSOR: 29 35 20 35 HTPro The official newsletter of the ASM Heat Treating Society. This supplement focuses on heat treating technology, processes, materials, and equipment, and features a preview of Heat Treat 2023, to be held in Detroit from October 17-19.
4 ADVANCED MATERIALS & PROCESSES | SEPTEMBER 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 Kingsley Amatanweze, Karthikeyan Hariharan, Denise Torres 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. ENERGY GAINS In a recent survey, manufacturing executives were asked about the energy-related challenges they face. The results, compiled by ABI Research, showed that energy costs (42%) and interaction with utilities (41%) were the two biggest pain points for today’s manufacturers. We offer some relief and hope to those executives. First, the U.S. Department of Energy (DOE) recently announced the selection of its new director for the Advanced Materials and Manufacturing Technologies Office. Christopher Saldaña, who comes from Georgia Tech and Penn State, takes the post and is charged with driving innovation to transform materials and manufacturing related to America’s energy future. Pursuing sustainable supply chains and net-zero emissions are on his docket. Second, in this issue of AM&P, we provide glimpses into a bright future through articles on advanced manufacturing techniques as well as groundbreaking developments in a promising, sustainable energy source—fusion power. Our lead article focuses on what the DOE calls “a major scientific breakthrough decades in the making that will pave the way for advancements in national defense and the future of clean power.” Last December and again this past July, Lawrence Livermore National Laboratory’s (LLNL) National Ignition Facility (NIF) successfully achieved fusion ignition—with a net energy gain—thus giving hope for a viable, carbon-free power source to come. We are honored to have the participation of LLNL staff in this issue through their contributions to the lead article including the compelling image on this issue’s cover. As the article developed, I witnessed an amazing collaboration between Savannah River National Laboratory (SRNL) and LLNL. Many brilliant minds contributed individual particles. Brenda Garcia-Diaz, the lead author from SRNL, found a way to fuse all those elements from both teams and—just like her subject matter—what the group released is more powerful and more significant because of the collaboration. A similar type of fusion will take place this October in Detroit. Attendees will come together to participate in two co-located conferences IMAT and Heat Treat— in addition to the Motion + Power Technology Expo. The synergy that comes from the attendees co-mingling will undoubtedly generate enormous amounts of creative energy when these participants unite under one convention roof. At IMAT, you can continue learning more about energy advances including and beyond nuclear, by attending Dr. Evelyn Wang’s keynote talk on Monday, October 16. Wang, as the director of Advanced Research Projects Agency-Energy, will likely have to field funding requests for many clean energy proposals in the coming years, as both government and private enterprise are inspired and encouraged by LLNL’s successful shots. It’s anyone’s guess if we’ll achieve commercialized fusion power in 10 years, or 20, or 30. But with laser focus, talented engineers and physicists will continue to work toward that goal. In the meantime, Lawrence Livermore has given us a monumental burst of energy. joanne.miller@asminternational.org NIF laser beams illuminate a target as illustrated by Jake Long/LLNL.
ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 5 DOE FUNDS COMPUTATIONAL MATERIALS The Department of Energy renewed funding for the Midwest Integrated Center for Computational Materials (MICCoM), headquartered at the DOE’s Argonne National Laboratory in Lemont, Illinois. The grant supports another three years at $3 million per year. Partnering universities include The University of Chicago, University of Notre Dame, and the University of California, Davis. MICCoM’s mission is to apply theoretical methods and software to the understanding, simulation, and prediction of materials properties at the atomic and molecular scale. To achieve this, MICCoM develops and disseminates a suite of interoperable computer tools. It also establishes the validity of theoretical models and codes for determining the characteristics and behavior of materials. Another part of its mission is to provide searchable materials data that are reproducible with small margins of error, an urgent need in light of artificial intelligence and machine learning. Over the next three years, MICCoM will also emphasize energy saving by designing materials for low-power microelectronics. anl.gov. CASE PROJECT SUPPORTS CLEAN STEELMAKING Chemical engineer Rohan Akolkar of Case Western Reserve University, Cleveland, is leading a research team working to develop a zero-carbon, electrochemical process to produce iron metal from ore. Research partners include Lawrence Livermore National Laboratory (LLNL), The University of Arizona, and Cleveland-Cliffs Inc., the largest flat-rolled steel company in North America and a key supplier of automotive-grade steel. Akolkar’s team recently received $1 million from FEEDBACK / RESEARCH TRACKS the DOE’s Industrial Efficiency and Decarbonization Office. If it works, the project could be a first step toward eliminating greenhouse gas emissions by eventually replacing blast-furnace ironmaking with a new electrolytic-iron production process. Akolkar says his team has developed a novel electrolysis method: Using molten salts, electrochemistry can be performed at moderately high temperatures, which allows electrolytic metal production to be accomplished cost-effectively and at industrial scale. The DOE announced the Case award as part of a $135 million initiative involving 40 projects at universities, national laboratories, and companies in 21 states. The goal is to reduce industrial carbon pollution and move the U.S. toward a net-zero emissions economy by 2050. The Case project is among 10 focused on decarbonizing iron and steel. The DOE also funded projects for decarbonizing chemicals, cement and concrete, food and beverage products, paper and forest products, and other end products across a wide range of industries. case.edu. Akolkar leads Case’s clean steelmaking research team. AM&P WINS EDITORIAL AWARD Advanced Materials & Processes (AM&P) received some exciting feedback from the organizers of the prestigious 2023 Tabbie Awards conducted by Trade Association Business Publications International (TABPI). AM&P won the Silver Award for Editor’s Column! The winning column, “Preserving Culture,” appeared in AM&P April 2022. Revisit it here: https://static. asminternational.org/amp/202204/8/. AM&P also won Tabbies in the Technical Article category in 2021 for “Historic Monel—Part II” and in 2019 for an article in the Automotive Aluminum series. FEEDBACK We welcome all comments and suggestions. Send letters to joanne.miller@asminternational.org. 2023
ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 6 METALS | POLYMERS | CERAMICS A new Rare-Earth Metals Market report projects 12.33% global growth from 2021-2026, from $5.3 billion to $9.6 billion. Permanent magnets are the largest user of rare earth elements, with two main applications including hybrid car engines and wind turbines. Asia Pacific is the fastestgrowing market for rare earth metals due to the increase in production and consumption of rare earth metals in China. marketsandmarkets.com. as a collaboration between the Georgia Tech team and Novelis, a leading manufacturer of aluminum and the world’s largest aluminum recycler, based in Warren, Ohio. The team knew that aluminum would have energy, cost, and manufacturing benefits when used as a material in the battery’s anode, but pure aluminum foils were failing rapidly when tested in batteries. Instead of using pure aluminum in the foils, the researchers added small amounts of other materials to the aluminum to create foils with varied microstructures. They tested over 100 different materials to understand how they would behave in batteries. The team observed that the augmented aluminum anode could store more lithium than conventional anode materials, and therefore more energy. In the end, they created high energy density batteries that could potentially outperform lithium-ion batteries. Now, they’re currently working to scale up the size of the batteries SELF-HEALING METALS Researchers from the DOE’s Sandia National Laboratories and Texas A&M University report pieces of metal cracking and then fusing back together without any human intervention. “What we have confirmed is that metals have their own intrinsic, natural ability to heal themselves, at least in the case of fatigue damage at the nanoscale,” says Sandia’s Brad Boyce. The fissure that disappeared was a nanoscale yet consequential fracture. In 2013, Michael Demkowicz, then at MIT and now at Texas A&M, began challenging conventional materials theory. He published a new theory based on computer simulations that showed under certain conditions, metal should be able to weld shut cracks formed by wear and tear. The discovery that his theory was true came inadvertently at the Center for Integrated Nanotechnologies. When the discovery was made, scientists were evaluating how cracks formed and spread through a nanoscale piece of platinum using an electron microscope technique. About 40 minutes into the experiment, the damage reversed course. One end of the crack fused back together, leaving no sign of the former injury. Boyce shared his findings with Demkowicz, who then recreated the experiment on a computer model, substantiating that the phenomenon witnessed at Sandia was the same one he had theorized years earlier. “The extent to which these findings are generalizable will likely become a subject of extensive research,” says Boyce. sandia.gov. ALUMINUM ANODES FOR BETTER BATTERIES Using aluminum foil, a research team from the Georgia Institute of Technology, Atlanta, is creating batteries with higher energy density and greater stability. The project began Sandia researcher Ryan Schoell studies fatigue cracks at the nanoscale using a specialized transmission microscope technique. Courtesy of Craig Fritz. Reflex Advanced Materials Corp., Vancouver, Canada, received approval in August for exploration drilling at its Ruby Graphite project in Montana, with permits from the Bureau of Land Management and the Montana Department of Environmental Quality. The drill program aims to define potential graphitic mineralization and determine the site’s geological characteristics. reflexmaterials.com. BRIEFS Graduate student researcher Yuhgene Liu holds an aluminum material used in solidstate batteries.
ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 7 to understand how size influences the aluminum’s behavior. The group is also actively exploring other materials and microstructures with the goal of creating cost-effective foils for battery systems. gatech.edu. THE TRUE SHAPE OF LITHIUM Researchers at the University of California, Los Angeles (UCLA) achieved a fundamental discovery that could lead to safer lithium-metal batteries with the ability to outperform today’s lithium-ion batteries. Metallic lithium reacts so easily with chemicals that, under normal conditions, corrosion forms almost immediately while the metal is being laid down on a surface such as an electrode. But the UCLA investigators developed a technique that prevents that corrosion and showed that, in its absence, lithium atoms assemble into a surprising shape—the rhombic dodecahedron, a 12-sided figure similar to dice used in common role-playing games like Dungeons and Dragons. At tiny scales, a lithiumion battery stores positively charged lithium atoms in a cage-like structure of carbon that coats an electrode. By contrast, a lithium-metal battery coats the electrode with metallic lithium. The coating packs 10 times more lithium into the same space compared to lithium-ion batteries, which accounts for the increase in both performance and danger. The process for laying down the lithium coating is based on a 200-plusyear-old technique that employs electricity and electrolyte solutions. Often, the lithium forms microscopic branching filaments with protruding spikes. In a battery, if two of those spikes crisscross, it can cause a short circuit that could lead to an explosion. The revelation of the true shape of lithium—that is, in the absence of corrosion—suggests that the explosion risk for lithium-metal batteries can be abated, because the atoms accumulate in an orderly form instead of one that can crisscross. The discovery could also have substantial implications for high-performance energy technology. ucla.edu. Researchers developed a way to deposit lithium metal onto a surface while avoiding a layer of corrosion that usually forms. Courtesy of Li Lab/UCLA. Harnessing the power of ASM’s webinar platform, QuesTek will host a 7-part, 30-minute webinar series. Join to discover the possibilities of engineering materials for the future, Integrated Computational Materials Engineering (ICME) Advantage, and digital transformation. Upcoming webinars include: • August 31: Utilizing ICME to overcome materials challenges and accelerate alloy development • September 13: Alloy composition and processing optimization with ICME • September 28: Accelerated qualification and certification of materials with ICMD® design software • October 5: ICME applications for AM: Rapid additive manufacturing parameter set development • November 9: Using ICME to predict advanced materials properties: high and low cycle fatigue • November 16: Physics-based modeling & machine learning to solve materials challenges • December 5: Designing materials using ICMD® Scan QR code to register today! Webinars
8 ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 USING X-RAY SCATTERING TO MEASURE NANOCOMPOSITES Researchers at the University of Montpellier, France, are using small- angle x-ray and neutron scattering to measure nanocomposite structures. However, experiments thus far have revealed a surprising lack of nano- particle structure in certain nanocomposite materials whose molecular skeletons are reinforced with nanoparticles previously treated with polymer adsorption. In a new approach, the research team shows that these patterns can only be produced through attractive interactions between nanoparticles with a diverse array of shapes and sizes. The team’s results highlight the rapidly improving capabilities of small-angle scattering instruments and could also help researchers to advance their techniques for studying nanocomposites— with applications in areas including small electronics, biological tissue engineering, and strong, lightweight TESTING | CHARACTERIZATION CUTTING INTO MATERIAL BEHAVIOR To better understand the behavior of metals under extreme conditions, researchers at Texas A&M University, College Station, are utilizing a traditional manufacturing tool—metal cutting. Because the cutting process involves locally shearing or deforming the metal to extreme levels under high rates, the A&M team hypothesized that it could provide fundamental information on the material’s strength, resistance to plastic deformation, or irreversible shape change. According to assistant lead researcher Dinakar Sagapuram, “The research opens a new and interesting application for metal cutting as a property test that material scientists and physicists can use to test their theories. The number of mathematical theories of metal plasticity under high strain rates far outstrips the experimental data. So, the property information obtained using metal cutting can test which theories are valid and which are not.” The team used a high-speed camera to observe how metals deform and shear when they encounter a sharp cutting tool and then use this information to deduce their basic property information. Some advantages of using metal cutting over current testing methods include its simplicity and its ability to produce a range of conditions. These states can be difficult to achieve using conventional tests but are important from the standpoint of various engineering applications. tamu.edu. Triangular holes make this material more likely to crack from left to right. Courtesy of N.R. Brodnik et al./Phys. Rev. Lett. ASTM International recently published ASTM G224, Standard Practice for Operating UVC Lamp Apparatus for Exposure of Materials, outlining basic principles for operating test instruments to evaluate the durability of materials exposed to UVC light. Q-Lab Corp., Westlake, Ohio, led the development of this standard, which provides information on apparatus, specimens, and exposure conditions. astm.org. This side-by-side photo shows how researchers can see different behaviors of metal when it is cut. The gray knife is visible on the right of both photos. Courtesy of Dr. Dinakar Sagapuram. These images reflect the simulation of diversity in nanoparticle sizes: (a) hard spheres; (b) before annealing; and (c) after annealing. (a) (b) (c) BRIEF
ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 9 materials for aircraft. This discovery offers important insights into the molecular properties of nanocomposites and how they could be engineered to optimize their unique properties. www.umontpellier.fr/en/. A LOOK AT HOW BENJAMIN FRANKLIN MADE BANKNOTES For the past seven years, a team of researchers at the University of Notre Dame, Indiana, has been studying the printing process used by Benjamin Franklin to print money notes for the American Colonies. During his career, Franklin printed nearly 2,500,000 banknotes using what the researchers have identified as highly original techniques. Led by Khachatur Manukyan, the research team used cutting-edge spectroscopic and imaging instruments. The tools enabled them to get a closer look than ever before at the inks, paper, and fibers that made Franklin’s bills distinctive and hard to replicate. Manukyan and his team determined the chemical elements used for each item in Notre Dame’s collection of Colonial notes. The counterfeits, they found, have distinctively high quantities of calcium and phosphorus, but these elements are found only in traces in the genuine bills. Another of Franklin’s innovations was in the paper itself—Franklin included tiny fibers in the form of colored silks in the paper pulp, visible as pigmented squiggles within the banknotes. The team also discovered that notes printed by Franklin’s network have a unique look due to the addition of a translucent material they identified as muscovite. The team speculates that Franklin initially began adding muscovite to make the printed notes more durable but continued to add it when it proved to be a helpful deterrent to counterfeiters. Manukyan said that it is unusual for a physics lab to work with rare and archival materials, and that it poses special challenges. “Few scientists are interested in working with materials like these. In some cases, these bills are one-of-a-kind. They must be handled with extreme care, and they cannot be damaged,” he says. For him, the project is a testament to the value of interdisciplinary work. nd.edu. Khachatur Manukyan and his team use cutting-edge spectroscopic and imaging instruments to conduct an in-depth study of the materials that made the Benjamin Franklin bills so unique. Courtesy of Barbara Johnston/University of Notre Dame. LE-237i-3 2023.ps T:\MISC\ADS\LE-237\LE-237i-3 2023.cdr Thursday, August 10, 2023 3:36:47 PM Color profile: Disabled
ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 10 MACHINE LEARNING | AI SUPER SPEEDY POLYMER DISCOVERY Researchers at the University of Wisconsin-Madison are combining machine learning predictions with molecular dynamics simulations to dramatically speed discovery of new polyimides with excellent mechanical and thermal properties. In their study, the engineers first collected opensource data of the chemical structures of all the existing dianhydride and diamine/diisocyanate molecules, then took that data and built a library of eight million hypothetical polyimides. The team used a computer to combine these building blocks together, which allowed them to organize all possible combinations into a huge database. They then created multiple machine learning models for the thermal and mechanical properties of polyimides based on experimentally reported values. Using a variety of machine learning techniques, the researchers identified the chemical substructures that are most important for determining individual properties. Applying their machine learning models, the team obtained predictions for the properties of all eight million hypothetical polyimides. Then they screened the entire dataset and identified the three best hypothetical polyimides with combined properties superior to those of existing polyimides. They checked their work by building all-atom models for their top three candidates and conducted molecular dynamics simulations to calculate a key thermal property. “The molecular dy- namics simulations were in good agreement with the predictions from the machine learning models, so that gives us confidence that our predictions are quite reliable,” says lead researcher Ying Li. “In addition, the simulations showed that these new polyimides would be easy to synthesize.” wisc.edu. MACHINE LEARNING FOR MATERIAL MODELING Scientists from the Center for Advanced Systems Understanding (CASUS) at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Germany, and Sandia National Laboratories, Albuquerque, N.M., developed a machine learning-based simulation method that surpasses traditional electronic structure simulation techniques. Their Materials Learning Algorithms (MALA) software stack reportedly enables access to previously unattainable length scales. Lenz Fiedler, MALA’s key developer, explains, “MALA integrates machine learning with physics-based approaches to predict the electronic structure of materials. It employs a hybrid approach, utilizing an established machine learning method called deep learning to accurately predict local quantities, complemented by physics algorithms for computing global quantities of interest.” Machine learning is being used to discover and design new polymers. Courtesy of Xin Zou/UW-Madison. The MALA software stack takes the arrangement of atoms in space as input and generates fingerprints known as bispectrum components, which encode the spatial arrangement of atoms around a Cartesian grid point. The machine learning model in MALA is trained to predict the electronic structure based on this atomic neighborhood. A significant advantage of MALA is its machine learning model’s ability to be independent of the system size, allowing it to be trained on data from small systems and deployed at any scale. The team achieved a speedup of more than 1000 times for smaller system sizes, consisting of up to a few thousand atoms, compared to conventional algorithms. Further, the team demonstrated MALA’s capability to accurately perform electronic structure calculations at a large scale, involving more than 100,000 atoms. “The key breakthrough of MALA lies in its capability to operate on local atomic environments, enabling accurate numerical predictions that are minimally affected by system size. This groundbreaking achievement opens up computational possibilities that were once considered unattainable,” says Attila Cangi of CASUS. www.helmholtz.de/en. Deep learning simulation of more than 10,000 beryllium atoms. Courtesy of HZDR/CASUS.
ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 1 1 MATERIAL MOVES MATTER In Japan, a group of researchers from the RIKEN Center for Emergent Matter Science developed a unique composite material that acts in a non- reciprocal way. Based on nanofillers embedded in a hydrogel, the material can channel mechanical energy in one direction but not the other. The team was able to use vibrational up-anddown movements with their composite material to make liquid droplets rise within a material against gravity. Using this material could thus make it possible to make use of random vibrations and move matter in a preferred direction. To create this uniform and scalable material, scientists took a hydrogel and embedded graphene oxide nanofillers into it at a tilted angle. The hydrogel was fixed to the floor, so that the top part could move when subjected to a shear force, but not the bottom. When shear force is applied from right to left into the leaning nanofillers, they tend to buckle and hence lose their resistance. But if the force comes from the other direction, and the nanofillers are facing away from it, the applied shear merely makes them stretch even longer and they’re able to maintain their strength. This allows the sheet to deform in one direction but not the other. The group measured this difference, finding that the material was approximately 60 times as resistant in one direction than the other. According to the researchers, their next goal is to find applications for the material and use it to make effective use of vibrational energy, which up until now has been seen as waste. www.riken.jp/en. LENS MATERIAL FOR SELF-DRIVING CARS Researchers at the Korea Research Institute of Chemical Technology (KRICT) and Kyungpook National University, both in South Korea, developed a material that can heal scratches on the sensor of an autonomous vehicle within 60 seconds. According to the team, they were able to activate the self-healing properties by using a simple tool—such as a magnifying glass—to irradiate focused sunlight. EMERGING TECHNOLOGY Scientists at the DOE’s Oak Ridge National Laboratory, Tenn., invented a coating made of carbon nanotubes that could dramatically reduce friction in load-bearing systems with moving parts, from vehicle drivetrains to wind turbines. The researchers say it reduces the friction of steel on steel by at least a factor of 100. ornl.gov. BRIEF Self-healing mechanism of lens material for self-driving cars utilizing sunlight, a dynamic polymer network, and photothermal dye. Courtesy of KRICT. Schematic depicting the preparation of a composite hydrogel with unidirectionally aligned graphene oxide nanosheets. Courtesy of Science (2023), DOI: 10.1126/ science.adf1206. Because self-healing is favorable when molecular movement within the polymer is free, flexible materials are generally used by scientists to ensure high performance. However, lenses and protective coating materials are made of hard materials, and thus challenging to activate the self-healing function. To solve this problem, the researchers combined a thiourethane structure and a transparent photothermal dye to design a dynamic chemical bond in which the polymers repeat both disassembly and recombination under irradiation of sunlight. The team’s material shows optimized self-healing performance, even when scratches cross each other, and maintains 100% of the self- healing efficiency even if the process of scratching and healing at the same location is repeated more than five times. www.krict.re.kr/eng/, en.knu.ac.kr/ main/main.htm.
12 ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 THE ‘SOFTER’ SIDE OF FUSION MATERIALS DEVELOPMENT Brenda L. Garcia-Diaz,* Dale Hitchcock,* George Larsen, Tyler Guin, and Bob Sindelar Savannah River National Laboratory, Aiken, South Carolina Rebecca J. Dylla-Spears, G. Jackson Williams, Xiaoxing Xia, and G. Elijah Kemp Lawrence Livermore National Laboratory, Livermore, California The development of polymers, traditionally neglected in fusion materials research, is crucial to the success of commercial fusion energy. *Member of ASM International FUSION MATERIALS
13 ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 The U.S. target for energy transition to non-carbon emitting power sources by 2050 has sparked the formation of commercial ventures to develop fusion energy as a potential source of baseload power. Utility executives working with the National Academies of Science, Engineering, and Mathematics (NASEM) committee wrote a report entitled “Bringing Fusion to the U.S. Grid,” and indicated that there is a window for fusion energy to help with plant replacements in the 2050 timeframe[1]. At the same time, researchers have recently demonstrated significant improvements in key technologies for fusion such as high temperature superconducting (HTS) magnets. Improvements in the magnets have been projected to allow a 50× reduction in the volume of a fusion reactor. This would make fusion vessels more compact than the ITER project, an international collaboration to demonstrate key magnetic confinement fusion energy (MFE) technologies[2,3]. In addition, inertial confinement fusion energy (IFE) has become more pro- mising due to recent experiments at the National Ignition Facility (NIF) that achieved a target gain (fusion out / laser in) greater than 1[4]. OPPORTUNITIES AND CHALLENGES The commercial opportunity for fusion in the 2050s as well as the advances in fusion technologies have generated significant interest from private investors. Private investment in the fusion industry is now over $6 billion and companies are already starting to build pre-pilot plant testing facilities to demonstrate different aspects of their fusion technologies[4]. Private investors are taking a portfolio approach to fusion investments and are funding a variety of different fusion energy technologies including multiple MFE concepts (tokamaks, stellarators, axis-symmetric mirrors, Z-pinches), multiple IFE concepts in terms of driver and target types (laser indirect drive, laser direct drive, laser fast ignition, pulsed power, shock-driven), as well as hybrid concepts between MFE and IFE such as MagLIF. Most of the companies have aggressive timelines to get to a fusion pilot plant (FPP) by the mid 2030s[4]. The U.S. Department of Energy (DOE) has recently announced a fixedprice milestone payment program based on the NASA Commercial Orbital Transportation Services (COTS) program to help encourage commercial space flight, which included companies such as SpaceX. The goal of the DOE Milestone-Based Fusion Development Program is to create public-private partnerships to support fusion energy commercialization[5]. The Milestone Program will support companies as they solve the technical challenges on the way to commercializing fusion and will support collaborations with universities and national labs. Technology advancements in several materials science topics are needed in to achieve economic viability of fusion. Many of the reviews on materials science for fusion focus on plasma-facing materials and structural materials for a fusion device that can withstand the high temperatures and withstand high fluxes of displacive damage from 14 MeV neutrons in a D-T device[6-9]. This is still a very important area of research, but as the challenge for fusion has expanded to designing and constructing an entire FPP, the materials science challenges also increase in the areas needed to create an entire support system for the fusion device such as the breeding blanket, fuel cycle, target synthesis, power cycle, and remote maintenance. Each of these parts of an FPP will have unique challenges that will require novel solutions in reduced activation alloys, materials durability in molten metals or molten halides, low-defect and high throughput polymer target synthesis, tritium effects on materials, welding and joining, adsorbents, catalysis, and many other areas. This article provides an overview of the materials science and technology challenges that will need to be addressed in the process of getting to an FPP with a focus on the mechanically “soft” materials such as polymers that will serve functional needs in a fusion pilot plant. There are excellent recent high-level reviews on fusion materials research that are focused on first wall materials and structural materials that experience high temperatures and high amounts of radiation[10], but there are many polymeric materials that will be critical to enable fusion energy that Fig. 1 — Experimentally inferred Lawson parameters for fusion experiments. Reproduced from Ref. 15.
14 ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 of the foam micro- and macroscopic properties (e.g., density, compositional, or structural gradients). Some IFE companies are also investigating advanced high-gain IFE concepts such as “fast ignition” that use composite targets, which incorporate mid-tohigh-Z structures such as focusing cones imbedded in polymer shells. These advanced targets will also require high quality manufacturing to ensure consistent ignition in an IFE plant with high energy gain (Fig. 2)[19]. Deuterated polymer precursor manufacturing. Materials other than polymers have been proposed for use as encapsulants in IFE targets, each having their own advantages and dis- advantages[18]. However, polymer-based capsules offer a relatively high tech- nology readiness level (TRL), lower cost, and simpler fabrication. Thus, they remain the leading candidate for current and future IFE facilities, especially IFE power plants, where vast quantities of targets per day will be needed. Despite the high TRL for existing polymer capsules, the current target fabrication process cannot be scaled to meet the unprecedented fueling demands of an IFE power plant. Microfluidic-based fabrication and low-density polymer foams are representative of some concepts proposed in the literature to meet the scaling challenges[16,20]. One particular challenge that polymer targets present for the fusion fuel cycle is that the hydrogen atoms in targets synthesized from normal have received less attention and this article seeks to highlight some of those research areas. IFE FUSION MATERIALS RESEARCH Inertial-confinement fusion energy (IFE) has been an increasing part of the discussion around fusion commercialization after an experiment, or “shot” at the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory in California in December 2022 achieved ignition[4] and was recently repeated in July 2023 with greater yield. Both of these shots were preceded by another shot in August of 2021 that achieved near-unity gain and helped to guide experiments, with results published in peer-reviewed literature[11-13]. Ignition is a state when the energy produced by the fusion reaction exceeds the energy input into the reaction (Fig. 1)[15]. IFE was an area of research leading up to the early 2010s but efforts were reduced after NIF did not achieve ignition during the first few years of operation. Successful shots at NIF have reignited commercial interest in IFE and currently two of the eight companies within the FES Milestone Program are pursuing IFE concepts. The success in getting to ignition with IFE has created renewed interest in research topics that would enable IFE and that research includes many areas where advanced materials development and manufacturing are needed. Open questions exist about surrogacy of material lifetime studies as pulsed fusion schemes have unique temperature and incident particle or debris conditions for which the instantaneous damage rates can be up to six orders of magnitude higher than MFE reactors[14]. Meeting the strict tolerances and quantities for fusion targets remain a challenge where one design of IFE targets are polymer capsules having a diameter around 5 mm and which need sphericity > 99.9%[16]. Imperfections in targets are known to lead to asymmetries during implosions and other complications that can reduce energy gain during the fusion event. To operate an IFE plant, approximately 500,000 targets per day (assuming 6 Hz rate) could be needed[17]. Developing high throughput target manufacturing that can produce hundreds of millions of high-quality targets per year will be critical to the success of IFE. IFE target manufacturing. The target synthesis can be performed using multiple methods including multi- solvent synthesis and co-axial nozzle alignment with CO2 drying[18]. Incorporation of mid-to-high-Z material layers to improve direct laser coupling, mitigate beam imprint or x-ray/hot-electron preheat, or stabilize implosions can be performed by sputtering, doping, or other methods. Alternatively, next- generation target fabrication methods using microfluidics and/or additive manufacturing are also being actively explored. In particular, two-photon poly- merization (2PP)—a 3D printing method based on raster scanning a tightly focused femtosecond laser spot to polymerize complex parts with nanoscale resolution—is a promising approach to additively manufacture inertial confinement fusion (ICF) targets with high precision, superior reproducibility, and scalability than current fabrication techniques. Liquid deuterium- tritium (DT) wetted foam layer capsule designs are considered a critical aspect of most direct and indrect drive IFE concepts, but little is currently understood about the impact of the foam on the target performance; additive manufacturing uniquely offers the potential of unprecedented, architected control Fig. 2 — (a) Schematic of integrated cone-in-shell fast ignition target from initial experiments; and (b) photograph of gold re-entrant target from experiments on OMEGA at the University of Rochester Laboratory for Laser Energetics (LLE). Reproduced from Ref. 18.
15 ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2023 hydrocarbon precursors (C-H) are “protium” or 1H. Protium is an impurity in the fuel cycle (which uses deuterium and tritium) and needs to be removed. Using deuterated polymers (C-D) is a potential method to significantly reduce the protium impurities introduced to the fuel cycle. However, currently deuterated polymer precursors are only synthesized in small volumes because there is not significant demand. Research is ongoing into catalysts and methods that can be used to deuterate polymers to high percentages of deuterium via isotopic exchange or other methods (Fig. 3)[21]. Currently, research into polymer precursor deuteration has been able to achieve up to 99% conversion of polymers in batch synthesis over multiple days. Research is ongoing to see how polymer precursor deuteration can be made more effective through higher activity catalysis as well as utilizing continuous flow processing[22]. POLYMERS FOR JOINING AND SEALING Tritium-resistant polymers for fluid/gas seals. Tritium fuel cycles for defense applications have long avoided the use of polymeric materials because they are rapidly degraded by tritium. This has included the development of expensive all-metal vacuum pumps and seals. In a limited number of components such as valve seats where metal sealing options are not an option, ultra-high molecular weight polyethylene (UHMW) or Vespel have typically been used. However, the choice of these materials was done empirically with very little consideration of the effects that govern the material degradation mechanisms. Indeed, tritium exposures of polymers have yielded a catalog of materials performance. However, detailed studies on the degradation mechanisms are conspicuously absent. This is further complicated by the fact that some materials, specifically fluoropolymers, widely used for their chemical resistance, perform very poorly in a tritium envi- ronment. It is well known that fluoropolymers generally display poor stability in any radiation environment[23], however, in tritium service the problem is magnified due to the formation of tritiated hydrofluoric acid byproduct which is highly corrosive and toxic[24]. Figure 4 shows PTFE and Nafion fluoro- polymers that have been exposed to tritium during accelerated aging tests. Both polymers show significant signs of degradation due to the beta decay of tritium to Helium-3. With respect to fusion energy, there is a significant need for improved polymeric materials with higher resistance to tritium degradation due to the near continuous operation and economics of bringing power to the grid. Research groups are beginning to develop new polymers for fusion applications based on the needs in fusion energy systems. Initial efforts suggested that increasing the aromaticity of the carbon filler in commodity polymers can improve their resistance to degradation in a tritium environment. However, these materials are still not suitable for long-term service in a high concentration tritium environment. More recent work is focused on developing new polymer backbone formulations to further increase resistance to tritium degrad- ation. Figure 5 shows new polymer materials that exhibit improved resistance to tritium exposure. Further development of tritium-resistant polymers for fuel cycle applications is needed[25]. Other joining and sealing materials. A fully functional power plant would also involve use of a variety of soft materials such as potting materials, sealants, and adhesives within optical, diagnostic, mechanical, and electrical assemblies. These materials must be evaluated for functional survivability under the unique thermal and radiation environments to which they would be exposed based on their locations and shielding. Several studies have shown, for example, that commonly used polymers such as polydimethylsiloxanes, polyvinylformal, and polytetrafluoroethylene are susceptible to radiation-induced property changes such as reduced adhesion and failure loads as well as changes in modulus[26-30]. Understanding of the degradation conditions, as well as mechanisms involved, may en- able design and development of new damage-resistant soft materials that allow long-term performance under these extreme conditions. ~AM&P Note: For additional reading on high-Z layer beam mitigation, fast ignition, and 2PP ICF capsules, the LLNL staff recommends Ref. 31-36. Portions of this work were performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344 and partially funded by the LLNL IFE Institutional Initiative and the LLNL LDRD program under tracking code 23-FS-018 and 23-ERD-027. Fig. 3 — Hydrogen isotope exchange of polymer precursor molecules. Reproduced from Ref. 21. Fig. 4 — Effects of tritium exposure on polymer materials: (a) unexposed PTFE; (b) PTFE exposed to tritium; and (c) Nafion exposed to tritium. Fig. 5 — New polymeric materials in development that have shown improved irradiation resistance.
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