4

Materials Science Challenges

The five technical areas for detailed studies are: structural and multifunctional materials; energy and power materials; electronic and photonic materials; functional organic and hybrid materials; and bio-derived and bio-inspired materials. The organization of the panels by function will encourage technical experts to participate, which will be crucial to their success. Members must also include systems thinkers and manufacturing experts. Each panel will attempt to quantify the impact of new materials and prosses and identify technical road blocks to their development. To facilitate management of the technical panels, a member of the study committee will chair each panel; in some cases they will also serve as co-chair or members of the panel (see Appendix C ).

Recommendation. Five technical panels should be established to address advances and challenges in materials science to meet twenty-first-century defense needs. The five technical panels should focus on the following areas: (1) structural and multifunctional materials; (2) energy and power materials; (3) electronic and photonic materials; (4) functional organic and hybrid materials; and (5) bio-derived and bio-inspired materials.

Recommendation. Over the next 12 months, each panel should meet about four times to assess research priorities in its respective area. The panels should coordinate their work to ensure that all important research areas are covered.

Recommendation. Based on the results of the panels’ assessments, the committee should integrate and prioritize the recommended research opportunities and recommend means of integrating materials and processing advances into new system designs.



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4 Materials Science Challenges The five technical areas for detailed studies are: structural and multifunctional materials; energy and power materials; electronic and photonic materials; functional organic and hybrid materials; and bio-derived and bio-inspired materials. The organization of the panels by function will encourage technical experts to participate, which will be crucial to their success. Members must also include systems thinkers and manufacturing experts. Each panel will attempt to quantify the impact of new materials and prosses and identify technical road blocks to their development. To facilitate management of the technical panels, a member of the study committee will chair each panel; in some cases they will also serve as co-chair or members of the panel (see Appendix C ). Recommendation. Five technical panels should be established to address advances and challenges in materials science to meet twenty-first-century defense needs. The five technical panels should focus on the following areas: (1) structural and multifunctional materials; (2) energy and power materials; (3) electronic and photonic materials; (4) functional organic and hybrid materials; and (5) bio-derived and bio-inspired materials. Recommendation. Over the next 12 months, each panel should meet about four times to assess research priorities in its respective area. The panels should coordinate their work to ensure that all important research areas are covered. Recommendation. Based on the results of the panels’ assessments, the committee should integrate and prioritize the recommended research opportunities and recommend means of integrating materials and processing advances into new system designs.

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STRUCTURAL AND MULTIFUNCTIONAL MATERIALS Scope This panel will focus on structural and mesoscopic and macroscopic multifunctional materials. The panel will begin by focusing on emerging materials and processes for fabricating structural (load-bearing) materials. The panel will then consider other functions that might be “built into” the structure, such as health monitoring, thermal-load dissipation, and electromagnetic radiation management. The panel’s investigation of multifunctionality will be limited to mesoscopic and macroscopic scales, such as thin laminates, mesoscopic trusses, “active” fibers (piezoelectrics, optics, etc.), and coatings. Multifunctionality introduced by atomic or molecular design will be addressed by the panel on functional organic and hybrid materials. The panel will not address research focused on incremental improvements of already commercialized materials, unless these changes are expected to lead to breakthroughs. The panel will identify research that could lead to the development of lighter, stiffer, or stronger materials. The impact of nanoscopic features of structural materials will be assessed, as well as nanoscale composites, including laminates and carbon nanotubes. Structurally efficient foams and engineered microtrusses will be discussed as a means of achieving lightweight structures with functionality, such as thermal-load dissipation. DOD has a special interest in harder, stronger materials for shock-absorbing structures for defeating projectiles. The panel will assess new computational tools for clarifying the response of materials and structures to projectile impact with the intent of combining these tools into an integrated approach to structural materials and structures that would be both lightweight and effective as armor. New tools for computational materials design will also be investigated, as well as the thermodynamic and kinetic databases necessary for their application. Another area of the panel’s investigation will be new materials (coatings, composites, etc.) for gun tubes. High-temperature materials are necessary for propulsion systems, high-velocity airframes, reentry vehicles, and other DOD special interests. Therefore, the panel will investigate new approaches to using/protecting carbon-carbon composites and ceramic-matrix composites, as well as low-cost processing of structural ceramics and ceramic composites. Other topics of interest to the panel will be concepts for refractory metal superalloys, novel metal-nonmetal composites, and amorphous/nanocrystalline Si-based materials (e.g., Si-B-C-N materials). High-performance, structural polymers are emerging, particularly high-temperature polymers and nanoscale polymer-inorganic composites as potential

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structurally efficient materials. The panel will include fabrication and scale-up of these exotic new materials. In a related area, resistance to fire damage, with an emphasis on the maintenance of structural integrity, will also be investigated. The space environment places special requirements on materials in terms of weight, stiffness, and deployability. Large-area, polymer-film structures and dimensionally stable mirrors will require new approaches, particularly in light of reliability requirements. Revolutionary processing approaches leading to low cost and high performance will be investigated. Free-form processing, rapid prototyping, and liquid/vapor sources, as in spray forming, laser sintering, and so forth will be reviewed. Multifunctionality in terms of sensing/activating, energy absorption, tailorable thermal expansion, and conductivity will be another focus area, as will highly unitized structures with localized placement of material to achieve a function. The panel will investigate the use of deterministic damage models with real-time sensor input of environmental parameters as a means of incorporating path dependence into lifetime predictions of structures. Dynamic stealth materials that allow the operator/system to change the signature characteristics at will to meet real-time threats will be investigated in terms of structural materials with built-in or overlaid stealth capabilities. Finally, ideas for improving reliability, dependability, and affordability will be pursued with regard to currently deployed materials and structures and new materials that are emerging for deployment after 2020. New techniques for nondestructive investigation/nondestructive evaluation would reveal smaller flaws earlier in component life, sense internal flaws under coatings and in rivet holes, and scan and assess aircraft condition without human attendants. The ultimate goal is to understand failure initiation sufficiently well to place embedded sensors in critical areas to provide for continuous health monitoring. Changing over to computer-assisted component design will require the development of property databases and improved design education, both aimed at improving component reliability and affordability. New coatings schemes that incorporate erosion/corrosion protection and low observability will be included in the panel’s study. Operational support materials (lubricants, coolants, sealants, hydraulic fluids) will be investigated in terms of potential breakthroughs for the 2020 time frame. A preliminary outline of the report is provided in Appendix D . Methodology This panel will meet four times. At the first meeting the subject matter will be organized by aligning topics with panel members’ expertise. Preliminary writing/outlining assignments will be made. At least three speakers representing

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broad subareas of the topic will be invited (e.g., structurally efficient materials, deterministic models of damage, high-performance structural polymers and nanocomposites). The panel will make a preliminary outline focusing on subsequent meetings and speaker selection. At the second meeting, the panel will invite a few generalists to fill gaps identified at the end of the first meeting. Specialists will be invited to complete this one-day workshop. One day will be spent reviewing progress in writing assignments and on realigning assignments, as necessary. A list of speakers will be completed to address the remaining topics included in the report. A one-day workshop with specialized speakers will lead off the third meeting. The panel will then meet for a day to discuss preliminary conclusions and recommendations and to incorporate crosscutting issues into the panel report. Before the fourth meeting, members will distribute their writing assignments to all panel members. The panel chairman will assemble the report, including a preliminary draft of conclusions and recommendations. Obvious gaps in the report will be highlighted for discussion. At this meeting, the final report will be assembled and gaps filled (see Appendix C for a proposed schedule). Required Expertise Panel members will have to be experts in many areas, including manufacturing (e.g., joining, secondary fabrication); structural design; metallurgy; ceramics; polymers and polymer composites; computational materials science; aerospace/space applications for materials; land and sea applications for materials. Materials Advances to Meet Long-Term Needs Smart Materials There are many applications for structural materials that contain sensors and simple logic circuits that enable a structure to react to the signal from the sensor. A simple example would be a structure that sustains battle damage resulting in reduced stiffness or strength, which can be sensed ultrasonically; the structure could then react by reconfiguring to reduce the load on the damaged components. Ultimately, a material might be self-healing by an in situ repair.

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Computationally Driven Materials Development and Modeling Complex problems in materials design can be solved with modern computational capabilities. DOD’s needs include first-principles calculations at the atomic and small-molecule levels and large-scale modeling of complex electronic and photonic devices. In the structural materials arena, thermodynamic and kinetic modeling of complex alloys might someday be carried out and verified by experiments. Deterministic models of material damage would be useful for lifetime predictions. Nanotechnology With advances in the design and assembly of materials at the nanoscopic level, new materials will be lighter, stiffer, and stronger. The intercalation of polymers into layered materials has been shown to result in much stiffer polymer nanocomposites than one would predict from the rule of mixtures. Nanocrystalline or amorphous silicon-based ceramics fabricated from polymer precursors could lead to ultrahigh strength and thermal stability at temperatures approaching 1,500°C. High-Temperature Materials In addition to the examples cited above, DOD needs monolithic refractory superalloys that can increase the turbine inlet temperature of gas turbine engines by 300°F (from 2,800°F to 3,100°F) by 2020. This will require that ceramic-matrix composites advance from the research stage to the engineering-application stage in the range of 1,500°C and beyond for heat engines, reentry vehicles, and hypersonic airframes and engines. Space Structures Large-area, thin-film polymer and composite structures must be developed for mirrors and antennas. Deployability and dimensional stability are required features for space structural materials. Ultralight weight, stiffness, and strength are also required.

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Reliability, Dependability, Survivability, and Affordability The cost of maintaining current DOD assets now surpasses expenditures for new materiel. Methods of ensuring the reliability of structural materials must be developed so that lifetimes can be predicted. New manufacturing and fabrication processes must be developed to produce affordable structures. Processing and Fabrication New methods of processing currently specified materials must be found to make them more affordable. Processing of new materials, such as composites, new polymers, nanostructured metals, and ceramics, must be scaled up and automated. Rapid prototyping must be a priority to accelerate assessments of new materials in component form. Composite Technology The only realistic scheme for achieving some performance goals with regard to density, stiffness, strength, and multifunctionality is to design composite structures. New light-metal matrix composites, high-performance polymer-matrix composites, intermetallic-matrix composites, and ceramic-matrix composites all appear attractive in terms of performance. Research on automated manufacturing and highly tailored architecture will be necessary to qualify these materials for Defense After Next. Multifunctional Materials The types of functionality that might be built into structures include stealth, health monitoring, energy absorption, tailorable thermal properties, and self-healing.

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ENERGY AND POWER MATERIALS Scope The panel on energy and power materials will focus on emerging materials and processes to meet DOD needs in the 2020 time frame for components capable of generating, converting, and storing energy and power. In addition, materials and processes required for sensing and for controlled dissipation of energy will be addressed for DOD needs not covered by other panels. The panel will identify improvements to experimental and computational methods to accelerate the development of new materials and processes to support DOD energy and power needs. The panel will also examine research directions for power and energy-related technologies that could have a significant impact on reliability, supportability, and life-cycle costs. A summary of areas specifically included and excluded from the panel’s study is provided in the next few paragraphs. Emerging materials and processes for energy storage (e.g., electrical, electrochemical, mechanical, and magnetic) will be a major area of focus. This area includes challenges to the development of improved batteries (primary, secondary, and reserve batteries based on various principles) for a broad range of DOD applications. It also includes novel approaches to capacitors for storing electrical energy. This category also encompasses fuels and propellants that could provide a significant advantage to the military in the 2020 time frame but that are either not used currently or are only beginning to be seriously considered. The panel will identify these fuels and propellants and seek to identify materials challenges to their development. The panel will also consider novel explosive materials in its study. The panel will not address materials that rely on structural integrity for mechanical energy storage (e.g., flywheels), which will be covered by the structural and multifunctional materials panel. The energy and power materials panel will attempt to identify challenges to efficient energy conversion. One important component of this category includes fuel cells for both small- scale and large-scale energy conversion systems. Structural materials for converting chemical energy into thrust, such as those used in turbine/turboshaft engines and other propulsion systems, will be excluded from this panel’s study, as will structural materials for hypersonic and rocket propulsion. These structural materials will be addressed by the structural and multifunctional materials panel. The impact of structural materials for use in very small-scale applications, such as materials and processes for microturbines useful in supporting systems, such as individual soldiers or mini/microuninhabited air vechicles, will be included.

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Advanced materials and processes for power generation components for 2020 systems will be examined. Important applications will include advanced motors and generators; electric propulsion for ships and ground vehicles; power generation components (e.g., high-power, solid-state switches, electric drives) for land and amphibious vehicles; and power conditioning and transmission equipment. Potential materials for these applications include high-temperature, low-loss, soft magnetic materials and advanced superconductors (for high-efficiency shipboard motors). The panel will also look into materials challenges to be met in fielding advanced weapons, that is, placing energy on target. Energy-on-target includes materials for some of the most advanced weapons systems concepts under consideration, including particle beams, advanced high-energy lasers, acoustic and high-power microwave weapons, and electromagnetic guns, in addition to conventional warheads (e.g., kinetic-energy penetrators). This area will be coordinated with the electronic and photonic materials panel to identify common materials themes and challenges. For example, advanced laser materials may be applicable in different forms to both high-speed data communications and low-energy laser weapons. In this area, the panel will work closely with the structural and multifunctional materials panel; areas such as gun-tube materials will be excluded because they will be considered by the structural and multifunctional materials panel. Materials problems specifically related to electromagnetic launchers (e.g., rail erosion in plasma railguns) are significant and have been examined for several decades. It is unclear whether these problems can be overcome to the point that practical, weight-efficient, electromagnetic weapons systems could be fielded by 2020. The panel will, therefore attempt to articulate the remaining challenges but will not delve into this area; as noted above, the panel will consider the development of materials for high-energy-density storage that could accelerate these materials into applications. The need to dissipate or control the effects of energy in its various forms is ubiquitous, and aspects of this overall need will be addressed by several panels. Materials challenges for effective kinetic-energy dissipation (e.g., novel armor) will be addressed in close coordination with the structural and multifunctional materials panel, with the latter addressing integrated structural armor and this panel addressing both transparent armor and body armor. The panel will also address materials challenges for hardening against high-energy and low-energy lasers. Dissipation of other forms of energy (acoustic, thermal, electromagnetic) will be coordinated on a case-by-case basis with other panels, as appropriate. Like challenges in energy dissipation, challenges in sensing energy or power will also be divided among various panels. Sensors will be exceedingly important to DOD capabilities in terms of understanding and reacting to the battlefield environment. Sensors are often electronic/photonic; they can be based on bio-

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derived or bio-inspired materials and often involve functional organic and hybrid materials. The panel on energy and power materials will examine only materials challenges for novel sensors for energy (e.g., optical, thermal, mechanical) required by DOD that are not being covered by other panels. Natural energy sources (water, wind, biomass, etc.) and potential shifts in the reliance of DOD on these sources will not be addressed by this panel. The need for changing U.S. reliance on energy sources, particularly from fossil fuels to renewable resources, has been well documented. Morever, if the rate of change in petroleum-based fuel prices begins to accelerate dramatically, a substantial U.S. initiative to develop and apply alternative energy sources will probably follow, with DOD being a major beneficiary. However, materials and process challenges that could significantly improve DOD’s ability to harvest energy from various sources, thereby improving field power-generating capability and decreasing the logistics burden involved in supporting expeditionary forces, will be explored. In addition, the panel will consider other potentially unique DOD power/energy requirements that would not otherwise be met. Figure 4-1 shows the areas included and excluded by the energy and power materials panel. A preliminary outline of the panel report is provided in Appendix D . Methodology The energy and power materials panel study will be quite broad in terms of scope, range of applications and systems, and materials and process challenges. Several areas of overlap with other panels have already been identified and assigned to other panels. Undoubtedly, there will be more. Work by this panel will, therefore, be closely coordinated with the work of other panels. In addition, joint panel sessions will be held, to review proceedings of other panels and minimize overlap (some overlap is desirable to ensure that nothing is missed). Members of this panel will meet four times (schedule shown in Appendix C ), with each meeting lasting two or three days. The first meeting will be primarily focused on organization, familiarizing panel members with study objectives, and assigning tasks. Topic responsibilities will be assigned in keeping with the expertise of panel members. At this meeting, approximately three speakers with broad knowledge in at least one major category will be invited to present overviews to provide a context for the panel’s activities. A preliminary report outline will then be prepared, and the potential contents of each subsection (and issues that may be unique to those sections) will be discussed. At the conclusion of the first meeting, preliminary information-gathering and writing assignments will be made, gaps in coverage will be identified, and potential speakers for the next meeting will be identified.

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FIGURE 4-1 Areas included in and excluded from the energy and power materials panel.

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The second meeting will be heavily oriented toward fact finding and filling in the knowledge base. Speakers will address broad gaps identified during the first meeting. Specialists will then present a focused views of the current status and prospects in specific areas to be investigated by the energy and power panel. Progress on the preliminary writing assignments made at the prior meeting will be discussed, and the outline will be refined and adjusted. During the second meeting, the level of detail of the panel report will be specified. Writing assignments will then be modified based on the revised (and more detailed) report outline. The third meeting will involve some outside speakers but will focus mainly on the writing assignments. A major objective of this meeting will be to complete a rough draft of the panel report. Given the broad scope of the power and energy panel, information on possibilities and materials challenges in certain areas may require some additional fact finding. However, panel members will focus on the specific content of their sections. Approximately 50 percent of the meeting will be devoted to identifying and discussing conclusions of the study; discussing the status of writing assignments; identifying issues that have arisen during writing; discussing balance among subsections in terms of level of detail and overall perspective; and generating content for subsections. A rough draft of all panel report sections will be assembled and provided to panel members. The fourth meeting will focus on finalizing the draft report. Between the third and the fourth meetings, revised drafts of report subsections will be obtained from each member, assembled into a single document, and combined with tentative panel conclusions and recommendations. The assembled draft will be provided to each member prior to the meeting for review and modification. At the meeting, omissions, segues, and other gaps in the report will be identified and supplied. The entire content of the draft report will be assembled, reviewed by the panel, and finalized. Required Expertise The power and energy materials panel will involve approximately six individuals with expertise in the research and development of materials and processes for applications and components covered by the panel. One potential mix of areas of expertise, based on academic training, would include the following topics: chemistry/electrochemistry, polymer science, ceramics, chemical engineering, mechanical engineering/thermal processes, aerospace engineering, metallurgy, and condensed matter physics. A mix of expertise, based on work experience, would include: energy storage and conversion (batteries, fuel cells, etc.); electromagnetic materials (guns, motors, etc.); manufacturing; armor materials; small power generation (microturbines, pulse detonation engines, etc.);

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Materials and Processing for Microelectromechanical Systems-Based, Mobile Power Components Recent developments have shown the feasibility of producing microturbines in silicon capable of high power-to-weight ratios. Efforts are now under way to translate these advances into materials more characteristic of turbine engines (e.g., silicon carbide). Further advances in the processing of traditional structural materials at the microscale might lead to high-efficiency, lightweight power modules for mini and micro-uninhabited air vehicles and other DOD systems with low power requirements. Materials Development for Mobility and Supportability The availability of lighter weight, higher energy-density materials should extend mission duration while reducing the logistics tail required to support them. The availability of lighter, higher energy-density energy sources should also have positive impacts on system maintainability. The panel will examine the effects of materials improvements on various crosscutting issues. ELECTRONIC AND PHOTONIC MATERIALS Scope The panel on electronic and photonic materials will cover materials research needs for the Defense After Next in four areas: (1) electronics; (2) optoelectronics and photonics; (3) sensors; and (4) microsystems. Packaging issues will also be considered, as necessary. The need for research on organic materials that perform these functions (e.g., organic electronic or optical materials) will be covered by the functional organic and hybrid materials panel. Progress in electronic and photonic materials and their derivatives, such as sensors and microsystems, is occurring at an extremely rapid rate, fueled by tremendous investments by the private sector. As a result, this panel will carefully consider which future defense needs can be met by monitoring developments in industry and which needs are specific to DOD and, therefore, in need of DOD investment. Each section of the panel report, therefore, will discuss (1) future defense needs; (2) commercial and other drivers for the technologies needed by DOD; and (3) an assessment, based on these two factors, of the need for DOD investment in a particular technical area. A preliminary outline of the panel report is included in Appendix D .

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Panel Composition The panel will be cochaired by two members of the Committee on Materials Research for Defense After Next. Approximately four other panel members will be named, one representing each of the four general areas outlined above. Ideally, panel members will be generally knowledgable about at least one of the four major areas covered by the panel. Other desired expertise includes (1) general knowledge of DOD vision and system needs; (2) general knowledge of the areas of emphasis and scope of corporate, university, and government laboratory research; (3) knowledge of current commercial drivers for technologies of potential interest to DOD; and (4) knowledge of specialists to invite to address the panel. Methodology The panel will perform its work over the course of approximately one year (see schedule in Appendix C ). Prior to the first meeting, information on DOD system needs (including this interim report) will be provided to the panel members. At the first meeting, the panel will be briefed on long-term DOD directions and system needs, either by an expert or the panel cochairs. This will be followed by a discussion of potential significant advances in electronic and photonic materials led by individual panel members and, perhaps, selected invitees. The briefings and discussion will provide a background for selection of focus areas in which DOD could invest most profitably. These selections will facilitate the development of a draft outline for the panel report and the selection of speakers for the next one or two meetings. The second meeting will feature speakers who will address the technical areas of emphasis identified at the first meeting. Panel members will report on background information they have gathered on the section(s) for which they are responsible, either through individual discussions or searches of the literature. Each of the four sections of the report will be covered by at least one speaker. A combination of general speakers and specialists working in the areas of most interest will be included. Based on these talks, the panel will refine the outline and discuss preliminary observations and possible conclusions. The third meeting will feature additional speakers addressing important issues that have not yet been covered adequately. Panel members will present refined outlines of the section(s) for which they are responsible. System and crosscutting issues that underlie materials or technology choices will be discussed. Preliminary conclusions and recommendations will be outlined.

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The fourth and final meeting will focus on a discussion of the sections of the report, which have been previously submitted. The conclusions will be finalized and a draft report assembled. Materials Advances to Meet Long-Term Needs At the December 1999 Defense Science and Technology Reliance Subarea for Materials and Processes Meeting, the DOD panel on materials for electronic and sensor systems outlined the general areas in which materials advances would be necessary to meet DOD needs in the 2020 time frame. The following system needs were identified: information gathering, which would be accomplished by appropriate sensors information processing, which would require new approaches to signal processing, memory, and computation transmission of information, which, above all, would require extremely high bandwidth protection of information, which would involve both hardware and software approaches to nonvolatile information storage and encryption The range of the electromagnetic spectrum that has been identified as being of particular interest for sensors is very large, from 0.3 to 100 m. High-power, compact, tunable lasers in this range could be used for active imaging and targeting, as well as remote detection of chemical and/or biological agents. Similarly, heterodyne receivers based on narrow line-width lasers in this range could serve as low-noise detectors. Finally, electromagnetic windows in the same range that are resistant to high temperatures and shock could protect the vulnerable parts of the sensor. The fabrication of any elements that operate over such a large wavelength region, or even a sizable portion of it, is likely to require very complex and precisely controlled combinations of materials graded on the scale of the wavelengths involved. Such needs may well be unique to DOD and could require significant DOD investment. An analysis of DOD materials and process needs for communications, computation, and signal processing indicates that communications and processing will be done optically at very high bandwidth (> 10 GB/sec), perhaps with free space communications or third- (3G) or fourth-generation (4G) wireless communications at megabyte rates. High-power (both peak and average) semiconductor lasers, fiber lasers, and materials and devices for ultrafast switching of signals will all be needed. New components (e.g., thin-film resonators) and “systems on a chip” will be needed for 3G/4G wireless

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communicators. Research in this area is already a major topic of interest at government research laboratories. DOD investment will also be necessary to keep abreast of recent industrial developments and to tailor recent advances to meet unique defense needs. Other DOD needs include high-power, high-frequency, and high-temperature electronics, terahertz electronics, nonvolatile, very high-density, radiation-hard memories, and systems on a chip or integrated microsystems. There are likely to be commercial drivers for some of the foundational technologies, such as microsystems, but other needs on this list may be DOD specific. Future materials systems with specific functionalities addressing particular system needs are: molecular systems, including carbon-based nanostructures quantum semiconductor nanostructures, such as superlattices, quantum wires, and quantum dots photonic bandgap materials magnetic thin films for spintronics ferroelectrics and low k dielectric materials for memories new piezoelectric, ferroelectric, and thermoelectric materials FUNCTIONAL ORGANIC AND HYBRID MATERIALS Scope This panel will consider potential research opportunities in the area of organic and organic/inorganic hybrid materials, in which physical phenomena are present primarily as a result of molecular design and/or architectural textures with supramolecular, microscopic, or nanoscopic length scales. The materials will include both low and high molar-mass organic molecules with one, two, or three dimensionality, as well as integration of these with ceramic and metallic components. Systems that are functional in a macroscopic (e.g., load-bearing) sense will not be included (see structural and multifunctional materials panel); neither will inorganic semiconducting assemblies (see electronic and photonic materials panel). However, materials that combine active organic moieties with inorganic semiconductors will be addressed, as will novel carbon structures (fullerene and related structures) that have functionalities relevant to this panel. Some overlaps will be inevitable, particularly when mechanical properties are involved. The panel will be guided by the overall objective of considering systems that have a high probability of defense applications in a 20-year time frame. Therefore,

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the focus is likely to be on materials that are presently either at an extremely early stage of development (e.g., ferromagnetic organic compounds) or are as yet unknown (e.g., superconducting macromolecules). Functionalities expected to be of prime interest include those associated with electronic, optical, magnetic, and thermal properties.The combination of two or more of these functionalities will be a core focus. A preliminary outline of the panel report is provided in Appendix D . Methodology The methodology adopted by the panel will generally follow procedures evolved in discussions with the overall study committee. Panel members will have broad expertise in the range of organic functional materials outlined above. The fields represented will thus include low molar-mass organic materials, macromolecular organic materials, polymer-ceramic hybrid materials, and metal-based functional materials that incorporate organic moieties. Panel members will be responsible for writing relevant sections of the final report. The panel chair will identify topics that appear to require additional or special attention and will contribute appropriate input in these areas. This panel will be relatively small, which will facilitate interactions between panel members between formal meetings. Information will be gathered by both formal briefings during the panel sessions and surveys of the literature, which will be a main responsibility of the panel chair and vice chair. Briefings will be conducted during four meetings by relevant experts identified by the panelists. Each panelist will also be given the opportunity at any early stage to present an overall review of his/her area of expertise. The panel will meet four times (see Appendix C ). The first meeting will be devoted to a general overview of the charge to the panel and a discussion of the relevance of the charge to DOD problems. The panelists will present briefings in their respective subareas; and speakers for subsequent meetings will be identified. The second meeting will include briefings by a limited number of speakers in the four major areas of investigation. Topic overlaps and coordination and/or liaison with other panels will be explored. Gaps in coverage will be identified and remedied. A plan for the panel report will be developed to ensure reasonable organizational uniformity. The third meeting will be devoted to a review of preliminary drafts of subarea reports and a limited number of briefings in specific areas. The fourth meeting will necessarily be devoted to a detailed review by the panelists of the subarea reports they had submitted to the chairman and members prior to the meeting.

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Materials Advances to Meet Long-Term Needs Efficient, Organic, Light-Emitting Diodes Versatile, conjugated macromolecules with good mechanical properties will have to be developed to provide efficient, low-pollution, low-voltage light sources for multiple applications in addressable displays and as large-area devices. Color changes by variation of electric field for use in camouflage and extension beyond the visible spectral range would be desirable adjunct properties. Efficiencies in the range of 100 lumens/watt (comparable to present-day fluorescent sources), will be necessary, a huge difference from the current 10 lumens/watt. Optically Transparent Ferromagnetic Materials These materials will have multiple applications, ranging from sensor devices to displays. The development of magnetic nonmetallics is also an obvious weight reduction strategy for all electromagnetic areas and, possibly, for magnetic thin films. Photorefractive Macromolecules These macromolecules will be necessary for optical data storage and other applications in photonic technology. Such materials combine photoconductivity with an electro-optical nonlinearity to modulate refractivity in a grating configuration. The optical energy of two incident beams can be exchanged asymmetrically, a property that has potential applications in information storage and holography. Multifunctional polymers or a combination of advanced materials with greatly enhanced photorefractive performance levels are long-term goals for DOD photonic applications. Optical Power Limiters Optical power limiters will be important for laser protection. Lightweight organic systems that are wavelength adaptable may eventually lead to the development of hybrid organic-ceramic materials. Nonlinear absorption, reverse saturatable absorption, and nonlinear refraction are all functions that would be useful in this application.

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Environmentally Stable, Highly Conducting Macromolecules Electrically conducting polymers that are stable and readily processible will be applicable in many DOD systems. These materials would be next-generation systems, follow-ons from the present limited-use polyacetylenes and similar macromolecules. New materials, for example, that combine a high third-order optical nonlinearity function with electrical conductivity and would have applicability in opto-electronic systems. Efficient, stable, conducting polymers also have obvious uses as charge carriers, in electrodes batteries and capacitors, and shielding. Transparency is important in coating applications. Photoconductive Photovoltaic Materials Materials that combine these traditional inorganic functions with light weight, versatility, and easy processibility are highly desirable for multiple DOD applications. Piezo-Sensitive Multifunctional Materials These materials will be necessary for sensor applications in a wide range of contexts. The basic requirements of light weight, processibility, and versatility will require that new classes of materials be developed. Additional Comments The common basis of materials advances sought by DOD are low cost, easy processibility, low maintenance, light weight, and efficiency. Multiple functionality is an attractive avenue of approach to meeting these fundamental requirements. Successful novel materials will be those that can advantageously replace existing materials by virtue of making improvements in one or more of the parameters listed above or, more rarely, by presenting an entirely new property set. Clearly, the latter category is highly serendipitous and seldom achieved. Nevertheless, in a 20-year time frame, a number of totally unforeseeable materials developments could very well take place. DOD should have an infrastructure in place to recognize and exploit these opportunities as part of the materials research strategy.

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BIO-DERIVED AND BIO-INSPIRED MATERIALS Scope This panel will explore the potential impact of bio-inspired and bio-derived materials concepts on defined DOD needs in the 2020 time frame. Areas in which biological approaches suggest attractive solutions to meeting these needs will be identified and prioritized. Biology represents a successful strategy for the design of materials, the fabrication of parts and components, and the integration of parts into systems that can meet complex performance requirements in a variety of stringent environments. The possibility of incorporating the principles of biology into modern engineering and scientific practice is an emerging focus of applied materials science. Combinatorial synthesis has been defined as computer-enabled, real-time evolutionary engineering. The broad range of performance characteristics now possible in polyolefins with controlled-backbone architecture is analogous to the control of protein function through the control of primary structure. Modern biology and medicine are elucidating the mechanisms of cell differentiation, tissue growth, and pathogen attack through the identification of site-specific, receptor/binding site chemistry. Application of this information to the synthetic material/biological system interface is accelerating the design of materials that emulate functions of the extracellular matrix, leading to improved materials for tissue-engineering scaffolds, wound healing, and drug delivery. The potential impact of the integration of biology and materials science on the achievement of twenty-first-century DOD goals defines the scope of the bio-derived and bio-inspired materials panel (see Box 4-1 ). Specific areas to be examined by the panel will include: structural materials: weight reduction, ballistic protection, environmentally driven responsiveness, and self-healing functional materials: sensors, diagnostics, fast switching, molecular circuits, and high-density energy storage battlefield/civilian chemical and biological warfare identification, interdiction, and counteraction medical: battlefield wound identification and countermeasures A preliminary outline of the panel report is provided in Appendix D .

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BOX 4-1 Scope of the Bio-derived and Bio-inspired Materials Panel Biomaterials Application in vivo use protheses tissue engineering drug delivery Bio-inspired Materials improved performance combinatorial synthesis nanotechnology self-assembly Bio-derived Materials bio-enabled performance extremers genetic modification DNA memory devices Methodology The panel will meet four times, following the schedule shown in Appendix C . At the first meeting, the panel will be briefed on DOD needs, the overall objectives of the larger study, and the scope of the panel’s assignment. In this context, the panel will then define its priorities, members’ areas of responsibility, and areas requiring external expert-led discussions. Experts in key areas will be selected to address the panel at future meetings. The panel will review its membership with respect to appropriate breadth to complete the assignment as charged. Finally, the panel will prepare an initial outline of the report. The second meeting will focus on briefings by, and discussions with, experts chosen at the first panel meeting. The need for additional expert visitors will be discussed, and appropriate speakers for the third panel meeting will be identified, if necessary. The report outline will be critically reviewed and initial writing assignments defined. Discussions of report conclusions and recommendations will be initiated.

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The third meeting will commence with discussions with the remaining invited experts. The report outline and writing assignments will be finalized. Key issues to be emphasized in the report will be identified, and approaches for integrating the report into a cohesive document will be discussed. A lexicon of important terms will be prepared. Conclusions and recommendations will be further refined. A schedule for the completion of writing assignments will be adopted. The fourth meeting will be dedicated to completing the report and finalizing the conclusions and recommendations. If possible, this will be completed in one day; a second day will be scheduled as a contingency. Panel Composition The panel will be chaired by a member of the Committee on Materials Research for Defense After Next. Four panel members will be chosen to represent the broad interdisciplinary nature of the field and will have expertise in medicine, molecular biology, biochemistry, and biorelevant ceramics. Panelists will be chosen for a combination of their specific expertise and a general appreciation of the field. It is expected that one panel member will be a member of an NRC committee that conducted a study on the impact of biotechnologies on the future army. Advanced Biomaterials to Meet Long-Term Needs Silk-Mimetic, Tough, Ballistic Protection Fibers Spider silk, although lower in tensile modulus and strength than many synthetic high-performance fibers, exhibits much better toughness and compressive performance than these materials. These attributes, combined with the inherent comfort of silk, make it an attractive target for the next generation of military protective garments. Aptamer-Based Pathogen Receptors Aptamers are synthetically produced peptides that behave similarly to naturally occurring protein sequences in their ability to bind to pathogens and other biological entities. Produced combinatorially, aptamers offer an attractive route to broad-based protection strategies for biological warfare.

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Nacre-Inspired Hard Armor DOD has identified a need for lightweight, damage-resistant vehicles, lightweight tanks, improved airframes, and so forth. The shells of bivalves, made of protein calcium carbonate arranged in thin parallel plates, combine extreme toughness with longitudinal stiffness and damage tolerance. A tank armor material based on this concept has been produced and is currently being tested. DNA-Based Circuitry and Information Storage The controlled complexity that marks the primary structure and assembly behavior of DNA allows for high-density information storage in biology and has the potential to be the basis of very high-density information storage in nonbiological systems, either through the use of DNA or with DNA-mimetic molecules. DNA assembly can be the basis of molecular-scale circuitry. Given DOD’s needs for small, flexible computing and communications devices, this technology is very promising for future systems.