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3 Materials Research Opportunities
Pages 104-161

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From page 104...
... A classical approach to evaluating MR opportunities is organized along specific types or classes of materials, such as metallic alloys, semiconductors, super­ onductors, c and ceramics; such a discipline-specific research focus strongly leverages current state-of-the-art knowledge and has a proven track record of successful MR advances as documented in part in Chapter 2. Alternatively, use-inspired research applications such as energy or data science can motivate broad crosscutting materials research and development (R&D)
From page 105...
... 3.1.1 Fundamental Studies of Classical Metals and Alloys Fundamental studies of metals and alloys underpin basic MR by illuminating with unprecedented clarity and fidelity the atomic and mesoscale processes as sociated with phase transformations and the formation and evolution of defects and interfaces, which govern the synthesis and performance of not only metals and alloys but also materials in general. Studies of metals have provided the basis for understanding the structure-dependent properties and processing of not only metals but also ceramics, semiconductors, composites, and hybrid materials across ever-broadening length and time scales.1 Buoyed by robust thermodynamic and structural databases, foundational advances in computational materials science and engineering coupled with in situ, in operando, and post-mortem three-dimensional (3D)
From page 106...
... For example, when it comes to mechanical behavior, one might be able to overcome the strength-ductility trade-off that is a long-standing dilemma in structural materials. With proper scientific understanding, one could envision tailoring the stacking fault energies, twin energies, phase instabilities, and so on to trigger multiple transformation toughening mechanisms.
From page 107...
... 3.1.3 Nanostructured Metallic Alloys Transformational advances in nanoscale materials synthesis, characteriza tion, and modeling have spawned a plethora of nanoscience activities to exploit processing-structure-properties relations and create nanostructured materials that exhibit ultrahigh strength and other unusual properties.3 Nanoscale disturbance of dislocation-based plasticity underpins the improved strength, but may reduce overall ductility. The strength-ductility trade-off is evidenced by the fact that nanocrystalline metals typically have higher hardness and strength than con ventional microcrystalline counterparts but generally exhibit much lower tensile ductility.
From page 108...
... 3.2 CERAMICS, GLASSES, COMPOSITES, AND HYBRID MATERIALS This section begins with a discussion of ceramics and inorganic glasses, the ubiquitous defect structures that determine their properties, and processing op portunities for greater energy efficiency. Also introduced are composites and hy brid materials, including hybrid nanocomposites and soft machines, a rich area of opportunity for MR demanding expertise in diverse materials types, and the interactions that occur at the interfaces between them.
From page 109...
... A "Defect Genome" initiative,9 whereby defects in ceramics over multiple length scales are characterized and their response under thermal gradients, stress, and electric or magnetic fields are understood and defect-defect interactions are made computationally and experimentally tractable, will add a new dimension to materials design. Ultimately, precise defect placement, coupled to atomic placement, would be the target.
From page 110...
... By coupling the Materials Genome with the Defect Genome, a fundamental under standing of this class of oxides can be achieved along with pathways for the design of new perovskites. Glasses A paper from 2013 lays out several areas of glass research important to the glass industry, including, among others, structure-property relations, densification, 10 P.R.
From page 111...
... 3.2.2 Composites and Hybrid Materials Composites The introduction of advanced polymer resin matrix materials and high-perfor mance fiber reinforcements will naturally provide increased structural performance (stiffness, strength, toughness) , but future applications will require exploitation of improved tailorability of properties and multifunctional performance.
From page 112...
... The opportunity for computation as well as data analytics for this class of materials is great. Fundamental research in these complex engineered materials may provide foundations for other complex engineered materials such as metama terials and biomaterials, collectively driving the cross-discipline training necessary for successful development of engineered and composite/hybrid materials.
From page 113...
... Hybrid Materials and Nanocomposites In the past decade, single-junction solar cells made of organo-metal-trihalide perovskites18 have gone from 3.8 percent conversion efficiency in 2009 to a record 22 percent in 2016.19 The perovskites take the structure AMX3, where A is an or ganic cation, commonly methylammonium (MA) or formamidinium (FA)
From page 114...
... to drive the systems into metastable states exhibiting favorable properties and long lives or to push them into equilibrium states that are far from quiescent using electric or magnetic fields. With respect to polymer-nanoparticle hybrid materials and nanocomposites, setting out the behaviors of the phases in carefully outlined superstructures, as well as assembling the nanoparticles, has seen much advancement.
From page 115...
... Another area that is receiving considerable attention is that of "soft robotics," where the goal is to replace hard and stiff linkages and pneumatic actuators with softer, more compliant and active materials. The materials paradigm is that hard materials offer great structural capacity but very small displacements, while soft materials provide a much greater range of displacement but very low load-carrying capacity.
From page 116...
... First, however, the energy efficiency of magnetic polarization switching must be made competitive with that of electronic switching. One exciting research frontier is the study and demonstration of mechanisms for voltage-controlled magnetism in ferromagnetic and antiferromagnetic materials.22 Neuromorphic Devices Artificial neural networks are being aggressively explored as energy-efficient architectures for execution of machine learning algorithms.
From page 117...
... They cannot, however, be used at elevated temperatures because silicon creeps at elevated temperatures and junction leakage occurs at temperatures as low as 120°C.23 Ceramics such as silicon dioxide, silicon nitride, silicon carbide, and silicon-carbo-nitride have been incorporated into MEMS devices that can operate at higher temperatures, but wide application of these materials has been limited by low tensile strengths, high residual stresses, and complex fabrication processes.
From page 118...
... Electronic materials such as wide-bandgap semiconductors GaN, AlN, Ga2O3, and diamond have a higher breakdown field that can enable higher power density and gain at significantly higher frequencies, leading to disruptive advances in mm-wave and THz frequency communication and radar technologies. Research toward realization of high breakdown strength and synthesis of low-defect density layers could also enable highly efficient solid-state power electronics at volt ages ranging from a few hundred volts to tens of kilovolts.
From page 119...
... 3.4 QUANTUM MATERIALS Quantum materials were previously defined as materials whose properties cannot be explained by simple Fermi liquid theory, or those with strong electronic correlations. In the past decade, this definition has been broadened to include 2D and topological materials -- materials whose electronic functionality reaches be yond simple 3D metals, semiconductors, and insulators.
From page 120...
... The move of high-Tc superconductivity from being a "phenomenon" to a useful physi cal effect in a variety of copper oxide materials in the late 1980s and early 1990s has been transformational in extending superconductivity from a low-temperature physics phenomenon to a potentially useful applied technology.25 Superconduc tors with sufficiently high transition temperatures and sufficiently large current carrying capacity are being used in the form of coated conductors in the electricity grid, for superconducting magnetic energy storage, as turbine/motor components for enhanced energy efficiency, as transformers with less than half the weight of traditional transformers,26 and as quantum sensors as well as spintronics device elements in a number of emerging technologies. Nevertheless, a predictive un derstanding of high-Tc superconductivity currently remains beyond our grasp as a scientific grand challenge, something that will put computational efforts to the forefront in order to solve.
From page 121...
... Quantum matter, especially as it relates to QIS more broadly, has the opportunity to be a key research area for the next decade, and the discovery and understanding of novel superconductivity has the possibility to continue to drive this field. 3.4.2 Magnetic Materials Classical studies of magnetism will always have a place in materials character ization.
From page 122...
... . Spin-Dynamic Effects The research emphasis on magnetism shifted some 20 years ago toward spin dynamic effects; the past decade focused on linear spin transport.
From page 123...
... While the field of spin dynamics is very much theory-driven, ultrafast optical probes of spin dynamics, alongside the spin-Hall and inverse spin-Hall effects, are new tools that will result in experimental progress in this field. Antisymmetric Exchange Interactions It is likely that the field of antisymmetric exchange interactions will expand beyond the concept of skyrmions.
From page 124...
... Intrinsic properties such as lack of a bandgap and poor out-of-plane thermal conductivity limit some applications. In 2011, a high-performance single-layer MoS2 transistor created excitement over the use of transition metal dichalcogenides in beyond complementary metal oxide semiconductor devices, as graphene had lacked a natural bandgap.
From page 125...
... Energy Storage, Electrical Interconnects, and Mechanical Devices Devices such as super capacitors, fuel cells, and rechargeable batteries are see ing an increased usage of 2D materials and should witness significant growth in the next decade. R&D to lower the manufacturing cost and time would accelerate their implementation.
From page 126...
... Further devices, such as ultrafast inductors and fault-tolerant quantum computing elements, become possible when the topological materials are coupled to systems such as ferromagnets or superconductors. It should be noted that topological effects typically occur without requiring extreme conditions such as low temperatures or high magnetic fields.
From page 127...
... These materials play a significant role in meeting the grand challenges facing global society. Polymer science and engineering research and the plastics industry are inti mately connected.
From page 128...
... polymers for the energy-water nexus, such as membranes and antibi ofouling materials; (4) smart construction materials that improve energy efficiency and transport clean water; and (5)
From page 129...
... development of polymer-based tissue engineering to minimize the use of animal models in drug and materials testing. An August 2016 NSF workshop, "Frontiers in Polymer Science and Engineer ing" (co-sponsored by the Air Force Research Laboratory/Air Force Office of Sci entific Research, Army Research Office, DOE/Basic Energy Sciences (BES)
From page 130...
... Polymer materials synthesis includes higher-order structure formation and su pramolecular assembly for in situ access to complex nano-objects and ­ olymerize p preorganized monomers to create programmed architectures. Noncovalent bonding, including mechanical interlocking via catenanes and rotaxanes, is as yet under­ exploited in creating higher-order structures.
From page 131...
... 3.5.2 Biomaterials and Bio-Inspired Materials Future directions for the broader objective of deepening our mastery of bio molecular materials science will require integration of advanced synthesis, novel characterization tools, and computation. Advances in polymer science will be criti cal in developing this frontier given the essential role of covalent macromolecules in cell components as well as plant and animal extracellular matrices.
From page 132...
... -led Tis sue Chip Initiative35 is developing human tissue chips that accurately model the structure and function of human organs for improved drug screening, pushing the frontier between semiconductor technology and soft matter. One important opportunity in inorganic biomaterials is further work on metal lic materials composed of biometals that could not only resorb after implantation but also deliver metal ions for a bioactive function.
From page 133...
... Furthermore, they can be designed through self-assembly strate gies with the biomolecular structures present in cell components and their extra cellular matrices. Soft biomaterials have traditionally been composed of polymers, and opportunities in this area will continue to develop with advances in polymer science that are described elsewhere in this report.
From page 134...
... In this regard, it will be important to learn more about the energy landscapes of assemblies used to create soft biomaterials in order to select the right pathways for their synthesis. Possibly the most important opportunities lie in structural control in supramolecular assemblies on scales that are much smaller 36 R
From page 135...
... An important opportunity from polymer science in this context will be to establish whether meaningful functions can arise from the long-sought objective of achieving molecular precision in synthetic polymers. The combination of structural control and dynamic behavior in soft bioma terials is important not only in the use of biomaterials for regeneration and drug delivery that dominated the past decade but also to take advantage of new mate rials in important applications such as development of organoids for biological research, gene editing, microbiome control, modification of decellularized organs for transplantation, and development of organs on a chip to understand disease and create new therapies, among others.
From page 136...
... For example, surfactant-coated nanoparticles segregate on the sur face of chiral, cholesteric liquid crystals vesicles and can form patterns following 37 J.W.Rocks, N Pashine, I
From page 137...
... Soft matter experiments now collect staggering amounts of data -- for example, from high-speed videos. Identifying physically relevant features in even one of these videos presents a daunting challenge.
From page 138...
... Lightweighting with architected materials -- that is, materials having a designed topological distribu tion of composite cells -- offers increased energy efficiency, payload capability, and life cycle performance as well as increased quality of life via less invasive implants, high-performance prosthetics, and functional exoskeletons. Lightweighting through the design and manufacturing of architected structural materials thus holds great promise for numerous technologies including aerospace, transportation, energy generation, and industries that employ large rotating components.
From page 139...
... There are also opportunities in designing metamaterials having multifunctional properties -- for example, thermal and electrical conductivity for energy efficiency. 3.7 MATERIALS FOR ENERGY, CATALYSIS, AND EXTREME ENVIRONMENTS 3.7.1 Materials for Energy Energy expenditures correspond to approximately 10 percent of the world's economic output; annual energy expenditures in the United States have routinely
From page 140...
... Materials discovery and exploitation will continue to be a central element of any effective energy strategy. Opportunities for significant advances in research on materials for energy fall into several large categories, including energy conversion, energy storage, energy efficiency, materials for energy, and resource sustainability.
From page 141...
... Energy efficiency in transportation may be enabled by appropriately architected metamaterials leading to lighter weight while retaining high strength. The inter-relationships between energy and water have recently been recognized by NSF, DOE, and other agencies.
From page 142...
... Defects, dopants, hybrid formations, and layered heterostructures are thus among the strategies being pursued to produce not only 2D molybdenum disul fide, but also other 2D transition metal dichalcogenides, such as graphitic carbon nitride, hexagonal boron nitride, as well as graphene. They offer the potential for catalyzing important reactions, such as higher alcohol formation from synthetic gas (formed by a combination of carbon monoxide and hydrogen)
From page 143...
... Le, et al., 2016, Heterogeneous metal-free hydrogenation over defect-laden hexagonal boron nitride, ACS Omega 1:1343, © 2016 American Chemical Society. 3.7.3 Materials for Extreme Environments There is growing demand for high-performance materials capable of satis factory operation under a variety of extreme operating environments.44 These demanding applications include, for example, lightweight, high-strength, and high-toughness materials.
From page 144...
... processes in irradiated materials offers realistic optimism that materials resistant to radiation-induced property degradation at energy-relevant elevated temperatures up to displacement damage levels more than twice the current best-performing structural materials (i.e., >500 displacements per atom) are conceivable to be successfully developed during the coming decade.
From page 145...
... Collec tively, the emergence of these new advanced tools offers significant opportunities to dramatically improve understanding of performance limits and fundamental degradation mechanisms in materials under extreme operating conditions. Extreme operating conditions represent a crosscutting materials opportunity both in terms of R&D to develop new materials capable of satisfactory performance under extreme conditions and harnessing extreme or nonequilibrium test condi tions to obtain new insight on material properties and degradation mechanisms (e.g., phase stability of materials under extreme pressures)
From page 146...
... The scientific issues differ between large-scale purification, which might include desalination or waste water reclamation, and remediation, which might include cleaning up contaminated groundwater or oil spills. Box 3.1 describes one such effort, the development of the Oleo Sponge by scientists at DOE's Argonne National Laboratory.
From page 147...
... SOURCE: Excerpt from L Lerner, 2017, "Argonne Invents Reusable Sponge That Soaks Up Oil, Could Revolutionize Oil Spill and Diesel Cleanup," March 6, https://www.anl.gov/articles/ argonne-invents-reusable-sponge-soaks-oil-could-revolutionize-oil-spill-and-diesel-cleanup.
From page 148...
... The conversion of water to H2 and O2 is one of the most practical carbon-neutral schemes to store solar energy on a global scale,49 requiring new, efficient catalytic materials. The solar energy stored by water splitting may be released in the useful form of electricity by a fuel cell.
From page 149...
... Further materials discoveries in advanced catalysts and separation science enhance the efficient use of energy and clean water, thereby advancing energy and water sustainability. The emergence of sustainability as a key theme in MR has both necessitated a broader focus on integrated materials solutions and enhanced the utility of these advances.
From page 150...
... 150 F r o n t i e r s o f M at e r i a l s R e s e a r c h BOX 3.2 Aluminum-Cerium Alloys The Critical Materials Institute, which is part of the Ames Laboratory, conceived Al-Ce alloys (see Figure 3.2.1) as a means of using excess cerium produced by rare-earth mines, to improve the economics of extracting critical elements such as neodymium and dysprosium.
From page 151...
... First-order phase transitions and their accompanying enthalpy changes likely are the most widely used form of heat storage and conversion, the most ubiquitous example being the three-centuries-old and still widely used steam power systems that enabled the Industrial Revolution. 3.9.1 Thermal Energy Storage Solar-thermal electricity generation presently is in large-scale use.53 The tech nology today is more costly than photovoltaic electricity without storage, but it has one major advantage in that the heat from the sun can be stored during daytime hours, then used during high-electric-demand evening hours.
From page 152...
... . It is unlikely that further reducing the lattice thermal conductivity, the main contribution to the doubling of ZT achieved in the past 20 years,55 will result in significant future progress because the lattice thermal conductivity of modern thermoelectric materials is close to the amorphous limit.
From page 153...
... The most intriguing possible application for active thermal circuits would be in increasing the thermodynamic efficiency of heat engines operating under time-dependent loads. Indeed, by combining a pair of heat switches with a pair of heat reservoirs (thermal energy storage devices)
From page 154...
... , heat engines are more efficient when they operate over larger temperature differences. At left is a conventional thermodynamic cycle that generates work W from such cyclical heat: the heat engine operates over an average temperature difference ΔTavg.
From page 155...
... should maintain ro­ bust programs to support, and in some cases expand, fundamental research in long-established areas such as metals, alloys, and ceramics. Key Finding: Quantum materials science and engineering, which can in clude superconductors, semiconductors, magnets, and two-dimensional and topological materials, represents a vibrant area of fundamental research.
From page 156...
... Creative approaches for funding materials research toward sustainability goals should be devel­ oped by the National Science Foundation, the Department of Energy, and other agencies. Finding: Sustainability and environmental impact have special import in the domain of polymer materials research owing to the dual factors of the massive accumulation of discarded polymeric materials in the environment and the unique challenges to polymer recyclability.
From page 157...
... Finding: The real and potential importance of composite and hybrid ­materials is enormous, encompassing a diversity spanning organo-metal hydride perovskites for photovoltaics, to polymers reinforced with micro- or nanoscale inorganic particles to yield unique properties, to natural biohybrid ­ aterials with steep m spatial gradients in their properties. The important zone in composite or hybrid materials is very frequently at the interfaces between materials types.
From page 158...
... Finding: Advances in polymer science across the board, from polymer phys ics to new, applied, functional, organic materials, are often driven by powerful polymer synthesis capabilities. Recommendation: Examples of directions in polymer materials synthesis that should be pursued vigorously by the community include precision synthesis (synthetic methods aimed at biological levels of control of mac­ romolecular structure)
From page 159...
... Finding: Heat management is an integral part of the design of many systems and for batteries, electronic circuits, engines, turbine blades, and materials for extreme environments. Heat management, storage, conversion to electricity, and active control of heat flow promise improvements in energy efficiency and size and cost reductions in a wide variety of technologies.
From page 160...
... Steps should be taken by the National Science Foundation and Department of Energy, possibly in cooperation with other government agencies such as the National Institute of Standards and Technology and the Department of Defense, to encourage research proposals related to solid state devices for thermal energy conversion, rectification, and switching. Finding: Metals and semiconductors have long been among the most impor tant of drivers of the U.S.
From page 161...
... Recommendation: All agencies, particularly the National Institutes of Health, which has a very specific interest in biomaterials, should participate in supporting fundamental science of these materials at a level relevant for their mission during the next decade. The Department of Defense should expand its research funding in this area as part of its interest in human machine interaction and warfighter performance augmentation.


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