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Materials in a New Era: Proceedings of the 1999 Solid State Sciences Committee Forum III. Materials Education and Infrastructure Materials Education for the 21st Century Robert P.H. Chang Northwestern University The current state of affairs in U.S. education, although not altogether negative, should certainly give us pause. Over 90 percent of students now graduate from high school; 67 percent of them enroll in college. Approximately 14 million students were enrolled in colleges and universities in 1996. The number of students who enter college is not, however, commensurate with the number of degreed graduates. Indeed, the graduation rate of students attending NCAA Division I institutions in 1996 was a mere 56 percent. At the cost of approximately $10,000 per student per year in a public university, the college dropout rate means that taxpayers are suffering significant losses in both human and financial resources. Particularly in the areas of science and mathematics, students in the United States are lagging behind their international counterparts. The reasons for poor performance in mathematics and science include a dearth of teachers trained in the subject that they teach (only an estimated 30 percent of science and mathematics teachers actually majored in the subject that they are certified to teach) and students' failure to see the connections between scientific and mathematical principles and the world around them. Given students ' lagging interest in science and the fact that there are states, Illinois, for instance, that require high school students to take no more than 2 years of science, it is hardly surprising that science and engineering programs are now facing declining enrollments. In assessing the current state of education, we should also consider the changing population in the United States. Within the next 50 years, groups that are currently in the minority will become the majority. If members of minority groups are not able to receive a top-quality education, then our entire economy will suffer. As we enter the next century, we find ourselves faced with the challenge of improving our educational system overall. Those of us invested in materials education also face some formidable obstacles. Most importantly, the general public is not aware of the existence of materials science and engineering (MSE). This lack of awareness may be largely attributed to the almost total absence of MSE at the precollege level. Even at the college level, MSE programs number only slightly more than 100, out of the 4,000 colleges and universities in the United States. Only 45—fewer than one-half—of those 100 programs have materials science and engineering departments. Despite its low profile, materials science and engineering is an extremely important field for at least two reasons. First, MSE involves interdisciplinary teaching, drawing on concepts from engineering, biology, chemistry, physics, and mathematics. Second, these basic disciplines, through materials science and engineering, have countless industrial applications that benefit society. From seat belts and computers to items as basic and mundane as coffee filters, materials science and engineering contributes to the creation of products that allow us to perform daily tasks more safely and efficiently. Its connection to real-world applications makes MSE a desirable field for many students, who realize that a degree in MSE can secure them a good job. In fact, about 90 percent of students in MSE programs will ultimately work in industry. Only about 10 percent of graduate students in MSE, on the other hand, will pursue careers as serious researchers. Within the past several years, more and more students have been transferring from science departments into MSE or have been doing materials-related research. The graduate curriculum in MSE has also changed with the times. Specifically, the focus of study has shifted from areas like metallurgy to the study of electronic, polymeric, and biomolecular materials. Given these trends, the hiring of new faculty has been geared toward the recruitment of those with expertise in the study of new materials and in the study of materials at the atomic/molecular level, rather than at the macroscopic level. One of the most significant sources of support for materials science and engineering is the National Science Foundation (NSF). The NSF funds 28 Materials Research Science and Engineering Centers, all of which promote MSE's multidisciplinary approach to research NOTE: This article was prepared from written material provided to the Solid State Sciences Committee by the speaker.
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Materials in a New Era: Proceedings of the 1999 Solid State Sciences Committee Forum and education. In addition, 4 of the 24 Science and Technology Centers that are sponsored by the NSF are administered through the Division of Materials Research. Finally, a number of NSF-sponsored Engineering Research Centers also do materials-related research. It is clear, when one looks at the state of education generally, as well as materials education specifically, from the earliest grades up through college and graduate school, that the precollege level requires the most attention. Elementary, middle, and high schools constitute the foundation of our educational system. Statistics show that as students progress through these grades, their proficiency scores on science tests drop dramatically. Fourth graders in the United States, for instance, scored an average of 565 out of 600 points on a science proficiency test, whereas 12th graders earned only 461 points. Additionally, U.S. students perform less competitively as they progress in school. Although the 4th graders placed second only to Japanese 4th graders, the 12th graders trailed students from all other countries in the study. In light of such findings, we can see that high school in particular is a crucial time for science education. Many high school students lose interest and then find themselves ill-prepared to face the rigors of college-level science courses. Why does this happen? Is there a big difference in the approaches to education, and in particular science education, between high school and college? Can we hold students ' insufficient preparation in high school responsible for the high dropout rate among college students? Most importantly, how can materials science education help to bridge this gap between high school and college, particularly in science and engineering? All materials education initiatives must undertake to: Foster greater awareness of the importance of MSE in society and among the general public; Introduce materials science and technology at the precollege level to enhance mathematics and science education; and Get teachers involved in materials science education and research. Many universities and centers have embarked on worthy initiatives to reach these goals. Northwestern University has programs for precollege materials science and technology education, for undergraduates (especially minority students) who are interested in materials science and engineering, and for professional development/teacher training. The desire to provide teachers with the tools to spark their students ' interest in science, mathematics, and technology, along with the wish to link university research to precollege education, led to the creation of the Materials World Modules (MWM). Developed with the support of a grant from the National Science Foundation, the Materials World Modules are handson, inquiry-based modules that focus on various topics in materials science. The modules have been designed to supplement middle and high school science, mathematics, and technology courses. Each module begins with a teacher demonstration that piques the students' interest. Next, students complete a series of inquiry-based activities, simulating the work that scientists do. Finally, each module culminates in two design challenges, where students simulate the work of engineers. Materials World Modules is a total materials educational program that also offers services such as workshops for teachers, an interactive CD-ROM, and a Web site where teachers can access help and resources on line. To date, MWM has been introduced in 450 schools nationwide and used by approximately 9,000 students and 450 teachers. At 16 hub sites in 14 states, teachers have been trained in MWM workshops. The next step for the Materials World Modules program will be MWM-2002, a delivery system via the Internet that will enable teachers to order and purchase customized modules on line and to receive teaching development and support services via an interactive Web site. In addition to the Materials World Modules program, Northwestern University has recently embarked on a collaborative effort with the Intel corporation to promote student participation in science fairs at seven sites in six states. This “Winning with Inquiry” initiative will involve the use of Materials World Modules, introducing students to materials science and technology. At the college level, Northwestern offers the Research Experience for Undergraduates and Minority Students Programs. Begun in 1986, these programs provide the opportunity for undergraduates from schools across the country to participate in research at Northwestern. These programs encourage promising undergraduates to pursue graduate studies in MSE by enabling them to experience interdisciplinary materials research under the direction of faculty advisors. Northwestern's Research Experience for Science Teachers allows high school teachers, and some college professors as well, to work with university professors during the summer on research projects related
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Materials in a New Era: Proceedings of the 1999 Solid State Sciences Committee Forum to their subject area. At the college and graduate level, we must expand materials programs to more colleges and universities, involve college and university professors in materials-related research and teaching, and work toward the collective development of materials courses among science and engineering departments. Industry should also have a significant input in course design for MSE. Finally, at the college and graduate level, we can aim to set up interactive video linkage to other universities —especially minority institutions—whose students can then take advantage of existing courses, seminars, and research collaborations from MSE programs. Northwestern, for instance, is currently in the process of developing interactive video linkage to minority institutions. Northwestern is also piloting a master's degree in Materials Technology and Education. This degree prepares students to teach technicians in community colleges. The requirements include at least three courses in the School of Education, as well as real classroom and research experience. At the global level, the United States has the opportunity to set itself up as a role model for other countries wishing to improve and expand materials education at all levels of education and among the general public. International collaboration will also help to ensure greater success for all countries striving to attain these goals. To foster greater collaboration and communication, a series of workshops has been held and will continue to be held in preparation for building a Materials World Network for Education, Research, and Technology. Four NSF-sponsored workshops have already taken place, and a fifth is planned in Africa for the year 2000. Meeting the Challenge in Neutron Science Thom Mason Scientific Director, Spallation Neutron Source Oak Ridge National Laboratory Thom Mason discussed the development of neutron-scattering research and the opportunities for new science presented by the Spallation Neutron Source (SNS). The development of neutron scattering has always depended on the availability of new, more powerful sources and techniques. Although the neutron was discovered in 1932, it was not until the late 1940s—after the first reactors were constructed—that sufficient neutron fluxes were available for diffraction experiments. These first experiments, performed by Ernest Wollan and Clifford Shull at the Oak Ridge Graphite Reactor, demonstrated the importance of neutron scattering for determining the atomic-scale structure and magnetic behavior of materials. In 1957, the National Research Universal reactor became operational in Canada. This reactor design was specifically optimized for neutron production. The increased flux and lower background enabled the development of neutron spectroscopy—the use of inelastic neutron scattering to determine the dynamical properties of atoms in materials. Bertram Brockhouse led the development of neutron spectroscopy and, together with Shull, shared the 1994 Nobel Prize in Physics for the development of neutron-scattering techniques for studies of condensed matter. The development of cold neutron sources and neutron guides in the 1970s stimulated applications of neutron scattering to studies of large-scale structures including polymers, macromolecular systems, and biological structures. Cold sources shift the spectrum of reactor neutrons from a peak temperature of approximately 300 K (corresponding to a wavelength of 1.7 Å) to 25 K or lower. This greatly increases the numbers of longer wavelength neutrons in the range from 2 to 20 Å, corresponding to important length scales in polymer chains, large molecules, and membranes. Neutron guides efficiently transport neutrons away from the reactor to experimental halls where background levels are greatly reduced. These developments, implemented first on a large scale at the Institut Laue Langevin in France, opened new areas of science and sensitivity to neutron scattering. Today, we sit at another threshold in the development of neutron scattering. Pulsed spallation neutron sources, based on neutrons produced by bombarding heavy metal atoms with high-energy protons, are demonstrating exceptional promise in neutron scattering from studies of superconductivity to nondestructive measurements of internal stresses in turbine engines. These neutron sources produce intense pulses of neutrons at repetition rates of 10 to 60 pulses per second. The neutrons are moderated and transmitted through beam guides to experiments surrounded by hundreds of detectors. The pulsed time structure and large num-
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Materials in a New Era: Proceedings of the 1999 Solid State Sciences Committee Forum ber of detectors result in enormous data rates for many important scattering experiments, resulting in increased sensitivity and sample throughput. The neutron is a weakly interacting, nonperturbing probe of matter with simple, well-understood coupling to atoms and spins. The high penetrating power of neutrons means that extreme sample environments can be easily accommodated by passing the neutron beam through the walls of cryostats, furnaces, or pressure vessels. It also means that the interior of bulk samples and manufactured components can easily be probed with neutrons. Unlike x-rays, neutron-scattering cross sections are similar across the periodic table, making light and heavy elements equally visible. In addition, neutron-scattering cross sections are isotope specific, making it possible to distinguish hydrogen from deuterium, for example, in specially prepared samples. This sensitivity to light elements and isotopes makes neutrons particularly useful in determining the location and behavior of hydrogen and other low-Z elements in materials. The energies and wavelengths of neutrons are well matched to atomic and molecular length scales and excitation energies in materials, making the neutron an outstanding probe of structure and dynamics in superconductivity, magnetism, phase transitions, electronic properties, nonequilibrium phenomena, and macromolecular systems. The Spallation Neutron Source, presently under development at Oak Ridge National Laboratory, will be the world's most powerful pulsed neutron source. The SNS is being constructed by a collaboration of Argonne, Brookhaven, Lawrence Berkeley, Los Alamos, and Oak Ridge national laboratories. Scheduled for completion at the end of 2005, the SNS will provide the nation with unprecedented capabilities in neutron scattering, satisfying a long-recognized scientific need. The SNS will be a 1 MW source, easily upgraded to 4 MW, supporting over 40 instruments. An initial complement of 10 instruments surrounding a target station operating at 60 pulses per second is currently being developed, and a second target station and additional instruments are in the planning stage. More than 2,000 scientists from universities, industry, and government laboratories are expected to perform neutron-scattering research at the SNS each year. The SNS will enable new science in engineering materials, surfaces and interfaces, magnetic and superconducting systems, macromolecular science and biological structures, real space imaging of living systems, and many other areas of condensed-matter science where increased peak fluxes, signal-to-noise ratios, and data rates contribute to improved sensitivity. In studies of engineering materials, the SNS will provide submillimeter resolution for nondestructive measurements of strain, composition, texture, and plastic deformation history inside bulk materials and components. Neutron reflectrometry will provide monolayer sensitivity for investigations of thin magnetic films and molecular transport studies across biological membranes. Complex, interacting systems such as low-dimensional magnets and charge and spin ordering in superconductors will become increasingly accessible to fundamental study at the SNS. In biological systems, the SNS will help establish the link between structure and function by enabling studies in solution, by locating functional subunits within larger assemblies, and by exploiting hydrogen-deuterium contrast to locate hydrogen in biological molecules. New developments in imaging science are expected based on using the tunability of neutron energies to enhance sensitivity for selected nuclei in living systems. With these and other unique capabilities, the SNS represents the future of neutron scattering—a field that is providing much of our current understanding of condensed matter including magnetism, superconductivity, complex fluids and polymers, and the structure and dynamics of materials. Toward a Fourth-Generation Light Source David E. Moncton Associate Laboratory Director, Advanced Photon Source Argonne National Laboratory Historically, x-ray research has been propelled by the existence of urgent and compelling scientific questions and by the push of powerful and exquisite source technology. These two factors have gone hand-in-hand since Roentgen discovered x-rays. Here we review the progress being made with existing third-generation synchrotron-radiation light sources and the prospects for a fourth-generation light source with dramatically improved laser-like beam characteristics. The central technology for high-brilliance x-ray NOTE: This article was prepared from written material provided to the Solid State Sciences Committee by the speaker.
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Materials in a New Era: Proceedings of the 1999 Solid State Sciences Committee Forum beams is the x-ray undulator, a series of alternating-pole magnets situated above and below the particle beam. When the particle beam is oscillated by the alternating magnetic fields, a set of interacting and interfering wave fronts is produced, which leads to an x-ray beam with extraordinary properties. Third-generation sources of light in the hard x-ray range have been constructed at three principal facilities: the European Synchrotron Radiation Facility (ESRF) in France; the Super Photon Ring 8-GeV (or Spring-8) in Japan; and the Advanced Photon Source (APS) in the United States. Undulator technology is also used on a number of low-energy machines for radiation in the ultraviolet and soft x-ray regimes. At the APS, these devices exceed our original expectations for beam brilliance, tunability, spectral range, and operational flexibility. Figure 1 presents the tuning curves of the first few harmonics, showing x-ray production from a few kiloelectronvolts to better than 40 keV. High-brilliance radiation extends to over 100 keV. Figure 1. Tuning curves for the on-axis brilliance, first three odd harmonics of APS undulators. The new science coming from the APS depends on its unique beam characteristics. A very high degree of collimation makes it possible to monochromate 20 keV x-ray beams to ~1 meV. These beams can be used for triple-axis inelastic scattering studies of lattice dynamics that had previously been the sole province of neutron scattering. But the most important aspect of x-ray inelastic scattering will be in charge excitations rather than in lattice dynamical excitations. Beautiful work in that respect is ongoing at the ESRF and beginning at the APS. Although the x-ray beams from undulators are not substantially coherent, their extreme brilliance allows one to extract a small coherent fraction, which contains a significant number of photons. Recently, x-ray photon correlation spectroscopy methods have been developed to exploit this coherence for measuring the dynamics of fluid systems. The unique characteristics of undulator radiation have recently been applied to macromolecular crystallography. The results have been spectacular. It is now possible, with a good crystal, to get a data set for a structure determination in well under 1 hour. In some cases, 15 or 20 minutes are adequate to collect all of the data necessary for structure determination. The x-ray step in a structure determination is no longer the rate-limiting step. The current ability to do structures at synchrotron x-ray sources would seem to be an ideal solution to determining the better than 100,000 structures whose codes are contained in the human genome. Such a “structural genomics” enterprise has generated considerable excitement. But structural biologists will be able to go beyond static structures. X-ray beams from the APS undulators are so intense, one can acquire a high-quality diffraction pattern in a single pulse. These pulses are on the order of 100 ps long, and each of them contains enough photons to get a reasonable diffraction pattern from a good biological crystal. That capability opens the possibility of studying the time evolution of a molecular structure, for example, by using a laser to initiate a chemical reaction. Very simple developments in instrumentation can have a profound scientific impact. Because the beam from APS undulators exhibits a high degree of brilliance and collimation, Fresnel zone plate lenses work extremely well to provide very-high-quality focal characteristics. With our most successful Fresnel lenses, we are able to achieve focal spots down to 100 nm and to preserve very high optical efficiency (in the 10 percent to 30 percent range). That small focal spot can be used for studying how the properties of materials vary on the submicrometer length scale. In another application, we propose to mount a number of Fresnel lenses on a chip. We would use these lenses
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Materials in a New Era: Proceedings of the 1999 Solid State Sciences Committee Forum to simultaneously probe a number of microsamples deposited on a second chip that have gradients in their chemical composition or in their preparation parameters and thus obtain data in a highly parallel fashion. The sample chips could be used for x-ray diffraction experiments or x-ray microscopy experiments. Those same samples could be put into other instruments that would measure their physical properties, such as specific heat or conductivity. Thus, one can develop methodologies for accumulating very large databases, which will be very useful for studying complex materials problems, such as high-critical-temperature superconductors. Concurrent with developing new applications for third-generation light sources, the community is thinking about the fourth generation of light sources (Figure 2) based on x-ray free-electron lasers (FELs). The most compelling parameter associated with this technology will be peak brilliance. It now appears possible to obtain a beam with peak brilliance 10 orders of magnitude higher than we have in APS today. That beam will also have a time-average brilliance higher by six orders of magnitude and a time-average flux higher by two orders of magnitude. Any new facility must serve a broad clientele, so R&D is under way to develop superconducting linacs, which should be capable of serving multiple (~100) beamlines simultaneously. It also appears possible to design a source that could serve the entire spectral range, from the infrared to the hard x-ray regime, in order to eliminate the need for different energy machines for different regions of the electromagnetic spectrum. Figure 2. Comparison of technical parameters for third- and fourth-generation x-ray sources. The technology for this next-generation light source is based on undulators just like those at the APS, but with significant interaction between the high-density particle beam generated in the linac and the electromagnetic field it generates. It is this interaction that produces the lasing action. There are different ways to achieve that lasing action in an FEL; but in the x-ray range, we will rely on self-amplified spontaneous emission. If the electron density is high enough, then the field that it produces causes an interaction that creates a lasing action. The undulator has to be long in order for that interaction to build up. At the APS, our undulators are typically a few meters long and produce beams which, 20 m away from the source, are on the order of ~1 mm in size. The new facility will have undulators that are ~100 m long and its beam will be on the order of 1/10 mm in size at 100 m. Of the many scientific opportunities associated with this new facility, a few are extremely compelling. One is the large quantitative improvement in coherence. We expect significant advances in imaging structures using x-ray holographic methods, which could revolutionize structural chemistry and biology. And since this fully coherent beam will be only 100 fs long rather than the 100 ps at the APS, there will be opportunity for significant improvement in time-resolved measurements in what is clearly a very important time regime. But the advance that can potentially change the paradigm for x-ray research in the next century will be a 1010 to 1012 increase in photon degeneracy. It will enable the multiphoton methods that are not possible with third-generation sources, permit the study of x-ray nonlinear processes in matter, and perhaps open some new regimes of fundamental high-field physics, a very recent idea. To have this major fourth-generation user facility ready by the year 2010, an aggressive R&D program must begin now. Fourth-generation lightsource technology development represents a bigger step than did third-generation light-source technology. But existing linear accelerators, including those at Argonne National Laboratory, Brookhaven National Laboratory, and the Stanford Synchrotron Radiation Laboratory, offer a cost-effective way to reduce technical risk and begin to explore the extraordinary scientific possibilities that lie ahead.
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Materials in a New Era: Proceedings of the 1999 Solid State Sciences Committee Forum Smaller Facilities—Opportunities and Needs J. Murray Gibson University of Illinois at Urbana-Champaign and Argonne National Laboratory Smaller-scale facilities often fall through the large crack that lies between the laboratory of an individual principal investigator and the large-scale facilities such as synchrotrons or neutron sources. Although the capital equipment investment in an individual researcher 's laboratory is typically less than $100,000, the equipment in a smaller facility is typically worth between $100,000 and $10 million. A large facility costs more than $100 million. Such facilities provide capabilities that are far beyond what is available in the laboratory of an individual researcher. Activities usually involve visualization, atomic manipulation, materials synthesis and processing, and/or materials testing. Smaller facilities are found at 4 Department of Energy (DOE) national centers, 26 National Science Foundation (NSF) Materials Research Science and Engineering Centers (MRSECs), and about 100 smaller centers throughout the United States. An example of a smaller facility is the DOE-supported Materials Research Laboratory at the University of Illinois, Urbana-Champaign. Characterization capabilities include Auger electron spectroscopy, Rutherford backscattering, x-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy, atomic force microscopy, secondary ion mass spectrometry, and x-ray diffraction. The capital equipment in the center is worth about $50 million. Operating costs are approximately $1.5 million per year. Replacement costs for the capital equipment average about $2.5 million per year. Many of the techniques found in smaller-scale facilities have improved dramatically over the last decade. As an example, the resolution of scanning electron microscopy has improved at the rate paralleling Moore's law. New characterization techniques have steadily entered the materials analysis arsenal, resulting from fundamental advances made in a variety of fields. The accomplishments of characterization techniques found in smaller facilities have been very impressive in the 1990s. For example, scanning probe microscopies have developed and proliferated. These techniques are widely used in furthering understanding of thin film growth. It is now possible to watch atoms migrate across surfaces and to image electronic states from dopants and imperfections in semiconductors. Surface atoms can now be manipulated, one atom at a time, to make quantum corrals or whimsical atomicsize figures. New magnetic probes have emerged, including magnetic force microscopy and scanning electron microscopy with polarization analysis. Transmission electron microscopy holography has been used to image vortices in superconductors. Low-energy electron microscopy was invented decades ago, but recent improvements have made it considerably more usable and more widely available. Transmission electron microscopy was used to discover carbon nanotubes and probe the physical and electronic structure of interfaces. Interface and surface science studies have elucidated the Si surface structure at the Si/SiO2 interface, they have provided fundamental information on bonding and adhesion, and they have given insight into catalysis via particle characterization and activity and zeolite structure determinations. Various techniques have probed the relationship between defects and critical currents in high-temperature superconductivity. Looking to the future, it seems clear that the techniques resident in smaller-scale facilities will continue to improve as we seek an ever more detailed view of the atomic-scale world. Some of the directions that appear particularly promising include “smart” tips on scanning probe microscopes that will have the ability to recognize and locate specific molecular species. The semiconductor industry will demand increasingly higher sensitivity analysis, particularly of surfaces, as design rules continue to shrink. Recent developments in microelectromechanical devices and systems raise the possibility of designing and performing portable microexperiments on very small samples, areas, or volumes. Increases in computational power and the advent of the Internet offer opportunities for remote control of apparatus and automated data analysis. Thirty years of work on electron optics has paid off with the development of aberration corrections that promise to have tremendous impact on the resolution obtainable in various electron microscopies, especially on the scanning electron microscopy of large samples (e.g., semiconductor wafers). Work on this problem required decades of patient investment in research—investment that was not made in the United States but instead occurred in Europe, particularly in Germany,
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Materials in a New Era: Proceedings of the 1999 Solid State Sciences Committee Forum and in Asia. A direct ramification of this is that the United States is now behind the rest of the world in being able to access newly available technology. Smaller-scale facilities lack the visibility of large-scale facilities or the broad recognition of importance that principal investigator research enjoys. This leads to concerns that such facilities will increasingly be caught in a budget squeeze between the two ends of the funding spectrum. It is critical to realize the important role that smaller-scale facilities play—reports of microcharacterization appear in 30 percent of recently published materials physics articles and in 45 percent of materials chemistry articles. Facilities offer the ability to maintain and operate such capabilities efficiently. They also offer access to expert advice on the techniques, educational opportunities, and centers for technique development. The face of materials research would be unimaginably different without adequately supported facilities of this kind.
Representative terms from entire chapter: