Producing a survey for the next decade of a field as immense and significant as materials science—and a report that contributes to advancing the field—is a complex and engaging responsibility. As in most areas of science, the pace of change in materials research (MR) is accelerating owing to new tools and insights. By studying earlier decades and reading the reports that were produced, researchers know to expect the unexpected, which is precisely the allure of science.
There have been surprises, to be sure, in the past decade. It is useful to examine a few examples of important developments that were not foreseen. For example, although graphene was first reported in 2004, it was given scant mention in the previous decadal survey in 2010. Since then, graphene has spawned an exciting field of other two-dimensional (2D) materials, and perhaps more importantly, it has instigated work on new physical phenomena, with potential utility in many electronics applications such as solar cells, transistors, camera sensors, digital screens, and semiconductors. Soon after the discovery of graphene, theorists predicted what are now called topological insulators, materials that are insulators in the interior, owing to a Fermi level that falls within the bulk bandgap, but whose surface contains conducting states. As a result, electrons move along only the surface of such materials. (See Figure 1.1.)
Moreover, the electrons flowing over the surface of a topological insulator are all aligned in a specific way: their spins are locked at right angles to their direction of motion. The original theoretical proposal pointed to graphene as an example, but the spin-orbit interaction in graphene is too weak for practical realizations. In 2008, materials exhibiting the predicted properties were synthesized with crystalline
structures based on bismuth antimonide and related materials. Symmetry-protected topological order has now been shown to occur in three-dimensional (3D) materials as well. These recent discoveries contributed to recognition in the 2016 Nobel Prize in physics of earlier work by Thouless, Kosterlitz, and Haldane on phase transitions and transport, where topology plays a crucial role. This was a gratifying capstone to a body of work in the past decade that was not anticipated 10 years ago. Subsequent chapters of this report discuss these discoveries and the opportunities based on them in more detail.
Another surprise of the past decade has been the evolution of additive manufacturing (AM), which has existed for decades and was initially known as stereo-lithography or rapid prototyping. Within the past decade, AM has emerged as an important process, which can be used not only for mass production but also for one-off fabrication on demand.1 This general methodology was not mentioned in the last decadal report, perhaps for understandable reasons. Early AM was really
2D printing, over and over again, albeit interfaced with computer-aided design (CAD), which was very useful for producing realistic prototype models of objects ranging from medical devices to parts of complex shape.
Early AM was almost exclusively with polymeric materials. The 2010s were the decade in which parts made of metals like aluminum and titanium were first produced. They are now significant in many industries—aerospace in particular. (See Figure 1.2 and Case 2 in Section 5.3.) With the application of light and other fields to change the material during the process, AM is no longer actually printing in 3D at all but instead is using spatially controlled polymerization (polymers) or fusion (metals and ceramics). With the advantages of CAD for AM, it is clear that much more is coming, as discussed in subsequent sections.
While some developments in the past decade were near-total surprises, others were the product of diligent work directed at a previously unrealized but desired scientific or technological objective. Self-healing polymers fall into this latter category, as they have been a recurring scientific goal for many years. Soft organic materials often have mechanical properties roughly similar to human tissue, so it is natural to explore self-healing in that domain of soft, noncovalently bonded materials produced, for example, by hierarchical self-assembly. Such materials have various uses, but they are not usually physically robust. Welding of polymers by diffusive interpenetration, induced by heating or solvents, is possible but of limited
use. Other major materials advances from the past decade include light-emitting diode (LED) lighting, flat panel displays, and improved batteries. In this survey, there is room to mention only a few examples, but all of them do have an effect on society.
Self-healing of polymers realized a new paradigm with the development of polymers with dynamically reconfigurable covalent bonds. One example, a remarkable new class of plastics now known as vitrimers (a term for glass-like polymers), was unanticipated 10 years ago. Vitrimers exhibit properties similar to silica glasses but in which the covalent bond network topology can be rearranged by exchange reactions without depolymerization. They remain insoluble and yet processable as bulk materials. The development of vitrimers, and other polymers with dynamic covalent bonds, has spawned new synthesis and processing research, discussed in Chapter 2.
Smartphone touch screen technology, which made its appearance at the beginning of the past decade, created entirely new roles for glass. This glass serves three functions: it enables user input, protects the display beneath it, and transmits the information on the display to the user even after years of use, in addition to resisting breakage owing to accidental drops. The material has to be mechanically durable, scratch resistant, thin, stiff, dimensionally stable, flat, smooth, impermeable to water, and transparent to both visible light and radio waves. Corning was able to surmount all of these challenges in a very short time through application of deep understanding of glass composition and manufacturing technology. The short time scale dictated older, familiar glass technology and existing manufacturing facilities as the starting point. Successive matters of processing conditions, bubble formation, and color formation were solved to yield Gorilla Glass,2 which was not mentioned in the last decadal survey but is now nearly a $400 million annual market for Corning.
This set of prefatory examples has been selected to make several points. The first has already been expressed—namely, that none of these interesting developments was foreseen clearly as recently as 10 years ago—and so the committee introduces this decadal survey with humility. On the other hand, there were previous accomplishments on which these particularly striking advances in the past decade were built. Graphene set the stage for topological insulators. Repetitive 2D printing of polymers gave rise to a much broader field of AM. A search for robustly self-healing materials led to the unique chemistry and properties of vitrimers and other
2 See M.S. Pambiachi, M. Dejneka, T. Gross, A. Ellison, S. Gomez, J. Price, Y. Fang, P. Tandon, D. Bookbinder, and M.-J. Li, 2016, “Corning Incorporated: Designing a New Future with Glass and Optics,” pp. 1-38, in Materials Research for Manufacturing: An Industrial Perspective of Turning Materials into New Products (L.D. Madsen and E.B. Svedberg, eds.), Springer.
polymers with dynamically reconfigurable covalent bonds. Motivation supplied by emerging smartphone technology spurred the development of Gorilla Glass.
A second point is that some important developments were the product of pure discovery-driven science (topological insulators), while others were concerted technological efforts (Gorilla Glass), and still others some combination of the two (AM and vitrimers). This is a strong argument for supporting MR across a span of technology readiness levels, and for creating environments in which basic and applied research, as well as academic and industrial research, interact intimately.
A third point from these examples is that two are from industry and two are from academic institutions (one U.S., one international), providing evidence of the broad range of institutions generating modern, advanced materials science.
The current decadal survey paid particular attention to understanding the industrial point of view, as the translation from basic research in universities and national laboratories into industry is the most effective path for deriving societal benefit in the form of useful products from basic MR. To assess how industries viewed the impact of materials science and materials engineering as enabling technologies, a selection of companies from different sectors were asked to provide their input by responding to four requests and questions:
- Identify scientific achievements in MR, including materials synthesis and processing, made in the past decade that have enabled your industry to make major breakthroughs in product development.
- Identify scientific materials roadblocks or new materials that must be addressed for your industry to make the next major advance in technology or product development.
- Are there enabling technologies and tools (e.g., advanced characterization, computation, synthesis and processing) needed to make these advances happen?
- In terms of materials research and development within your organization, is it conducted in-house in the United States or globally, with U.S. universities or with universities outside the United States? If you work internationally, why?
Sixteen companies, spanning a range of sizes and technology sectors, responded to these four requests. The high-level challenges and opportunities common across the different industry sectors are summarized below. The committee believes that this input from industry is important to assess the overall societal benefit of MR.
The combined responses to the first inquiry highlighted the importance of advances in properties of materials, development of new materials and coatings,
increased durability of materials, and weight reduction. Advances in materials synthesis and processing, deposition processing methods, robotics, and high-throughput discovery, in addition to the growth in AM for low-volume components, were seen as enabling technology developments. Sustained by efforts such as Integrated Computational Materials Engineering (ICME)3 and the Materials Genome Initiative (MGI), computational approaches, statistical analysis, and data analytics have been used to reduce the cost of developing a new material for a specific application. Incorporation of these approaches were seen as impacting not only how materials were developed but also the in silico testing of components to determine their functionality and durability.
The second inquiry was designed to identify the improvement on material properties or performance of new models or computational methods, or of experimental tools, needed to address the specific roadblocks preventing the next major technology advance within their own spheres. Industries identified several areas in which advances would have impact. Accelerated discovery of new materials or the optimum structure and composition of a material and moving beyond the advances enabled by the ICME approach to “materials by design” was seen as enabling breakthroughs in the future.
For example, the need for new materials to go “beyond silicon” for increased power, frequency, or improved energy efficiency in information technologies; to extend performance of materials through novel coatings or clean energy-storage technologies; and to create materials in which the sensors are an embedded and integrated component of the material were all seen as areas of opportunities that would be accelerated by utilizing an integrated computational materials science and engineering approach.4 Others saw the potential impact on their industry of adopting an integrated computational science and engineering methodology, as this approach had yet to be implemented within their sector. Enhancements in synthesis and processing, deposition techniques, and joining technologies, especially between dissimilar materials, were identified as areas in which advances were needed to enable use of new materials and to improve product design. It also was noted that there was a need to be able to scale the synthesis and processing methods used for small batches in university research laboratories to industrial-scale manufacturability. Scalability science was seen as an area of opportunity to realize significant gains when producing new materials at larger volumes. For the potential of AM to be realized, it was pointed out that there was a pressing need to understand the process itself, to control the process at all length scales to optimize
3 National Research Council, 2008, Integrated Computational Materials Engineering: A Transformational Discipline for Improved Competitiveness and National Security, The National Academies Press, Washington, D.C., p. 132.
4 Defined as ICME.
the functionality and properties, to determine the properties of materials produced by AM, and to accelerate component certification. Last, it was recognized that there was a pressing need for a shift in the education of students to create a workforce skilled in the use of data analytics, materials informatics, and computational methods to increase the rate of innovation in MR.
For the third inquiry, several technologies were identified that would enable the breakthroughs discussed in response to item 2. In the area of theory, modeling, and simulation, advances were identified that included computer modeling and simulation of processes that occur during synthesis and processing—particularly in the area of AM. There is an ongoing need to advance the realization of the vision of accelerated materials discovery and development enabled by computer simulations and to actually produce new materials faster. New computational chemistry tools are needed to improve the predictions around chemical reactions and their resulting products. Advances are required for predictive models that describe the evolution of material properties for materials exposed to harsh environments, where the environment is defined by the material and application. The models and simulations must predict the long-term properties of materials in specific environments as new materials are being deployed in applications with a design life of 50 years and beyond. Last, there is a need to develop tools to enable the rapid exploration of materials and processing space to discover new materials and compositions and to optimize the synthesis and processing routes to make them with the desired properties.
With advances in synthesis and processing methods, there is a need for new in situ diagnostic capabilities to understand the physical and chemical reactions. To have meaningful impact, these diagnostic tools need to be coupled with computational tools to analyze and interrogate the data and to make decisions. It was noted that the introduction of machine learning algorithms and data analytics had the potential to accelerate insight and advances in this area. Coupled with the use of theory, modeling, and simulations to identify potential new properties, structures, and compositions of materials was the need for the development of high-throughput screening and testing methods.
The fourth and final inquiry was designed to assess how and where U.S. industries conduct research and how they interact specifically with U.S. universities. The responses varied depending on the nature of the industry, with some conducting all of their research in-house because of the proprietary nature of their products, the need to protect prior intellectual property (IP), and the complexity often associated with negotiating IP agreements with U.S. universities. Other companies conduct research in their facilities but have collaborations with other industries and universities globally. The reason for conducting the research with entities across the world varied and included access to a diverse talent pool, geolocation in relation to their global business, specific research expertise that might not be available
in the United States, and gaining access to unique facilities and capabilities. This latter interaction was especially significant in cases of specialized experimental tools or tools that were too expensive for a single company to own and operate. Here, the major scientific facilities operated by the Department of Energy and the National Science Foundation (NSF) are noteworthy. It was noted that in some areas, the United States had ceded leadership in MR in a specific area, requiring that companies must conduct research outside the United States. The responses from industry raised some concerns about the state of industrially relevant or industrially sponsored research being conducted at U.S. universities. Some responses implied that industrial research being conducted at universities outside the United States is increasing, owing to difficulties in reaching IP agreements and the cost of conducting research at U.S. universities.
This entrée into the current decadal survey concludes with some observations concerning defense and national security. Materials research plays an important role in U.S. national defense. It is easy to see how new materials with improved properties can produce, for example, better armor that also weighs less, systems that can deliver more power to the warfighter in the field, and materials that can withstand extreme conditions for more efficient aerospace components, allowing for faster flight while using less fuel. Not only are new materials for new systems important for U.S. national defense, but also today there are many legacy systems where spare parts are increasingly harder to get. There are also many situations where materials used in the past are no longer desired. One such recent example is in corrosion-protective hexavalent chromium coatings that are effective but toxic. It is clear that advanced materials are key to many of the Department of Defense funding and operational initiatives. The major mission agencies, including the Air Force, Navy, and Army, gave presentations to the committee during the November 2017 committee meeting. One of the key aspects discussed was the importance of better understanding how and why materials fail when used under extreme conditions, and by extension how to avoid such failures. MR issues focusing on failures will always benefit from more data, and thus better characterization techniques would be beneficial, especially in situ methods that would work at extreme conditions; today, many failure processes are often not fully understood, thus preventing the design of mathematical models for use in predicting the material behavior. Clearly, there are opportunities for MR to make inroads not only in modeling at multiple length scales, but also for in situ characterization. Although motivated by differing objectives, there is strong convergence in the priorities of both the commercial and the defense sectors on the need for strong emphasis on advancing computational and data science, and for investment in increasingly powerful characterization
tools, including those that can work under challenging conditions such as extreme pressure and under real-time process conditions.
National security considerations also play a significant role in developing best steps forward in the area of international collaboration. Sections in this report that discuss collaborations at facilities such as the International Space Station, European Organization for Nuclear Research, Synchrotron-Light for Experimental Science and Applications in the Middle East, and Laser Interferometer Gravitational-Wave Observatory, and also Section 5.4, emphasize the value of engaging on the international level, but impediments are appearing and increasing. Although the concerns leading to these impediments are serious and must be respected, U.S. MR will be held back if sensible ways to collaborate and to exchange personnel and basic science information are not only allowed but are also encouraged. Cooperation, even in the face of competition and political conflicts, is a long-standing U.S. tradition dating back to the Cold War and before.
Three prominent conclusions can be derived from the information presented in this chapter. The first is that surprises occur because of both fundamental exploratory research and persistent pursuit of challenging goals with no precise roadmap for their attainment. The second is that the investigation of industry perspectives revealed many pieces of useful information, but none more prominent than the increasingly essential role of integrated computational materials science, data science, and machine learning. This is reinforced in subsequent chapters based on capabilities in universities, industry, and national laboratories. The third conclusion is that industrial-university research relationships should be further optimized to make them more fruitful and rewarding to all participants.
Some other aspects of this survey of MR that have been less prominent in previous reports are more extensive and penetrating insights into the role of MR in international economic competitiveness and of national security. Chapter 5 develops the case, based in part on the 2016 book Advanced Materials Innovation, Managing Global Technology in the 21st Century,5 that over three-quarters of all economic growth in coming decades will be attributable to the development and application of advanced materials, and that investments in MR are tied directly to national competitiveness and economic prosperity. This is an important new lens through which researchers must evaluate the importance of MR. MR exerts its influence demonstrably in many sectors of the economy, including computer and information technology, energy, biotechnology and healthcare, transportation,
5 S.L. Moskowitz, 2016, Advanced Materials Innovation: Managing Global Technology in the 21st Century, Wiley, Hoboken, N.J.
construction, and manufacturing. One way to look at where MR can have an important societal impact in the coming decade is to consider what MR can do in advancing the 14 Engineering Grand Challenges set up by the National Academy of Engineering6—these span the gamut from improving health to preventing climate change. The committee encourages the reader of this survey to consider the many opportunities available in providing access to clean water, improving the urban infrastructure, engineering better medicines, reverse-engineering the brain, and making solar energy economical, to mention just a few of many more challenges. On the international front, the committee is cognizant of the fact that several economies—China’s in particular—have significantly increased research and development spending. In 2010, China, with the second largest science base in the world, spent about $212 billion gross (government and industry) on R&D, less than the United States ($408 billion). By 2015, China’s expenditures had nearly doubled, to $409 billion, while those of the United States increased to only $496.6 billion.7 Viewed in light of the influence of MR on the economy, this is a significant fact.
Key Finding: Advanced materials are increasingly central to everyday life and well-being. New developments are products of the broad and interdisciplinary field of materials science, drawing on all the traditional fields of science, engineering, and more recently, computer and data science (algorithms, big data, artificial intelligence, machine learning), with the special perspective that comes from a focus on materials. The health and future growth of materials research, and its capability to serve society, depend critically on the flow of information among its stakeholders, from university researchers to industrial engineers to government labs.
Key Recommendation: Government agencies, led by the Office of Science and Technology Policy, should work with high priority to foster communication among materials research stakeholders through the support of interdisciplinary research and the development of modalities for freer flowing interactions among universities, private enterprise (including startup ventures), and national laboratories.
7 National Science Foundation, 2018, Science and Engineering Indicators 2018, NSB-2018-1, Digest NSB-2018-2, National Science Board, National Center for Science and Engineering Statistics, Alexandria, Va., January.
Key Finding: Many of the real-world challenges and opportunities in materials research occur at the intersections among traditional disciplines, and at the interfaces between fundamental and applied research. Pure science is stimulated by proximity to applied research. Collaboration and information transfer among different disciplines and among academia, industry, and government laboratories greatly increases the likelihood of successfully meeting these challenges and capitalizing on these opportunities.
Key Recommendation: The White House Office of Science and Technology Policy should provide leadership in the development of awards that enable diverse funding agencies to work together when needed to facilitate collaboration among university and industry researchers.
Key Recommendation: The National Science Foundation (NSF) should develop a new type of center that will enable, and indeed stimulate, students, faculty, and industrial scientists and engineers to work side by side. Such a Discovery to Translation Materials Research Center would create a unique learning and research environment. The effort should be supported by several NSF directorates and should continue for a minimum of a decade.
Key Finding: The integrated computational materials science and materials engineering methodology has had a significant impact on product development in specific industries, as the committee has learned through industrial input. There is potential for further impact through the inclusion of integrated data sciences into the materials research for all length scales and material types.
Key Recommendation: All government agencies funding materials research should encourage the use, when appropriate, of computational methods, data analytics, machine learning, and deep learning in the research they fund. They should also encourage universities to provide students of science and engineering exposure to these new methods by 2022.
Key Finding: Basic research in fundamental science directions, meaning work that neither anticipates nor seeks a specific outcome, is the deep well that both satisfies our need to understand our universe and feeds the technological advances that drive the modern world. It lays the groundwork for future advances in materials science as in other fields of science and technology. Discoveries without immediate obvious application often represent great technical challenges for further development (e.g., high-Tc superconductivity, carbon nanotubes) but can also lead to very important advances, often years in the future.
Key Recommendation: It is critically important that fundamental research remains a central component of the funding portfolio of government agencies that support materials research. Paradigmchanging advances often come from unexpected lines of work.