Research Facilities

NIST Center for Neutron Research

Materials Science Synchrotron X-Ray Beamlines

Magnetic Engineering Research Facility

Combinatorial Methods

Center for Theoretical and Computational Materials Science

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Research Facilities

NIST Center for Neutron Research

The NCNR operates as a national facility open to all qualified researchers. Under the general user program, the available time is allocated by a program advisory committee on the basis of scientific merit of written proposals. Participating research teams—which constitute another mode of utilization—are responsible for design, construction, and maintenance of the facilities in return for collaborative access to a fraction of the available time. Annually more than 1,700 researchers from government organizations, U.S. industrial and university laboratories, and foreign laboratories participated in research at the facilities, either collaboratively with NIST staff or on a proprietary basis. For further information, visit www.ncnr.nist.gov.

Crystallography and Microstructure

• BT-1 high-resolution neutron powder diffractometer. This instrument is used to obtain neutron powder diffraction data for crystallographic analysis by the Rietveld method or for other characterization purposes. It is a 32-detector instrument that can be used with three different monochromators and two different incident Soller collimators to tailor the instrument response to the needs of the experiment. Diffraction peak widths are as low as 10 minutes Δ d/d = 8 × 10^-4) with ideal Gaussian line shapes. The instrument can be used with furnaces, refrigerators, and cryostats so that data may be collected at temperatures from 0.3 K to 1200 K, and magnetic fields to 12 T. For room-temperature data collection, a six-position sample changer is available.
  
  
• BT-5 Perfect Crystal Diffractometer for Ultra-High Resolution Neutron Scattering (USANS). The newest instrument for small-angle scattering at the NCNR is a Bonse-Hart type, perfect crystal diffractometer. This instrument extends the measurement range of the pinhole collimation SANS instruments (at NG-1, NG-3, and NG-7) to larger sizes by over an order of magnitude, i.e., to over 5000 nm. The instrument utilizes two large triple-bounce channel-cut Si (220) perfect crystals to achieve angular resolution of a fraction of an arcsec. This instrument is used to characterize micrometer-scale (100 nm to > 5000 nm) structure in, for example, gels, composites, engineering alloys, structural ceramics and porous media. This instrument is part of the NSF/NIST Center for High Resolution Scattering.

• BT-8 diffractometer. This is a state-of-the-art diffractometer for residual stress, texture, and single-crystal studies. A basic monochromator drum has been modified to safely allow take-off-angles up to 120 degrees for high-resolution diffraction measurement of residual stresses. Unique primary and secondary beam-aperture systems, which allow a choice of potential sampling volumes from 5 × 5 × 5 mm³ down to 1 × 1 × 1 mm³, are incorporated. Each system translates toward or away from the sample to facilitate the study of large material structures or components without requiring realignment of apertures or repositioning of samples. The sample table has 170-millimeter translational motion in the x, y, and z directions and can accommodate samples up to 100 kg. Among the other features are a new 1-millimeter resolution position-sensitive detector system and a three-crystal monochromator system with remote selectability. One of the three is a double-focusing Si monochromator, with variable horizontal curvature.
  
  
• NG-3 30-meter small angle neutron scattering instrument. Sponsored by the National Science Foundation as part of the Center for High Resolution Neutron Scattering, this instrument is installed on a dedicated neutron guide, NG-3. Designed to cover a wide Q-range, from 0.015 nm^-1 to nearly 6 nm-¹, it is suitable for examining structural features in materials ranging from roughly 1 nm to 500 nm.
  
  
• NG-7 30-meter small-angle neutron scattering instrument. The 30-meter small-angle neutron scattering (SANS) instrument on neutron guide NG-7 is virtually identical to the NG-3 SANS. It is sponsored by NIST, the ExxonMobil Research and Engineering Co., the University of Minnesota, and the NSF-funded consortium Cold Neutrons for Biology and Technology comprised of researchers from the University of California at Irvine, the University of Pennsylvania, Rice University, Duke University, and Carnegie-Mellon University.

  Together, the 30-meter SANS instruments combine long flight paths and variable collimation to provide flexibility, angular resolution, and beam intensities that compare favorably with any SANS instruments in the world. Large-area position-sensitive detectors provide exceptional sensitivity to materials structures ranging from roughly 1 nm to 500 nm. Computer automated equipment is available for maintaining samples at temperatures from 4 K to 700 K and in magnetic fields up to 2 T (20 kG). To extract structural information from the data, the researchers analyze SANS patterns with an interactive color graphics system and related programs. Polarized neutron capabilities are available on the NG-3 30-meter instrument.

• NG-1 8-meter small-angle neutron scattering instrument. The 8-meter SANS instrument is located at the end of neutron guide NG-1 where the guide cross section is 50 mm × 50 mm. This is a moderate resolution instrument suitable for examining structural features in materials from roughly 1 nm to 100 nm. This SANS instrument is used primarily for the study of polymers.
  
  
• NG-7 NIST/IBM/University of Minnesota neutron reflectometer. Neutron reflectometry probes the neutron scattering density at depths up to several thousand angstroms, with an effective depth resolution of a few angstroms. What is measured is the profile of reflectivity as a function of angle beyond the critical angle for total external reflection for samples that present a smooth, flat surface, preferably several square centimeters in area. The method is extensively used for studies of polymer and biological surfaces, Langmuir-Blodgett films, and thin films and multilayers of metals and semiconductors, both magnetic and non-magnetic. This cold neutron reflectometer permits routine measurement of reflectivities as low as 10^-7 in typical run times of a few hours. Independent movement of both sample and detector allows measurement of off-specular scattering. A position-sensitive detector permits simultaneous measurement of specular and off-specular scattering.
  
  
• NG-1 cold neutron reflectometer with polarized beam option. This reflectometer is used in investigations of magnetic multilayers, artificial biological membranes, semiconductor surfaces, and other materials and phenomena in surface and interfacial science. In contrast to the reflectometer on guide NG-7, the sample surface geometry is vertical rather than horizontal. Reflectivities below 10^-8 can be measured. It has full polarized beam capability, provided by transmission supermirror polarizers. The incident beam can be polarized, and polarization analysis of the reflected beam can be performed in a routine fashion. Polarization efficiencies as high as 98 percent are possible.

Materials Dynamics—Medium Resolution, Incident Neutrons: E>5 meV

• BT-2 triple-axis/polarized-beam spectrometer. This instrument is used extensively for magnetic scattering studies. It can be operated either as a standard triple-axis spectrometer or as a polarized-beam spectrometer, depending on the monochromator crystal choice, and has an incident neutron energy range from 5 meV to 54 meV. The monochromator can be selected to be a pyrolytic graphite (002) crystal for standard 3-axis operation or a ferromagnetic Heusler alloy crystal for polarized beam experiments. Remotely positionable filters, either 15.2 cm (6 inches) of cooled (77 K) polycrystalline Be, or 5.1 cm (2 inches) of pyrolytic graphite, may be inserted in the beam before the monochromator. The collimator housings before and after the sample position have been designed to provide guide fields for polarized beam operation, and the Soller collimators and blades are made from non-magnetic materials for the same reason. Spin-rotator devices can be mounted before and after the sample position to flip the neutron spins. There is also a guide field that can be selected by computer control to be either vertical to the scattering plane or in it. An extensive variety of ancillary equipment to control the sample environment is available.
  
  
• BT-4 triple-axis/filter-analyzer spectrometer (FANS). This inelastic scattering instrument offers choices for analyzer and monochromator that make it the most versatile of the thermal-neutron scattering instruments at NIST. One may use either the standard triple-axis analyzer or a cooled (77 K) filter analyzer, which covers a solid angle of about 4 percent of 4 pi steradians. The filter analyzer option employs a combination of polycrystalline Be, followed by a block of polycrystalline graphite. The latter determines the effective analyzer energy resolution, which in this case is 1.1 meV. The monochromator choices are Cu (220) for higher resolution studies or for measurements with higher incident neutron energies, and pyrolytic graphite (002) for lower incident energies, with moderate resolution and higher beam intensities. The incident neutron energy range is from 3.5 meV to 250 meV. Monochromator changes can be made within a few minutes from the instrument console. Both monochromators are vertically focusing with a radius of curvature, which changes to optimize intensity during the course of data acquisition.The instrument is particularly well-suited to measurements of the vibrational spectra of materials.
  
  
• BT-9 triple-axis spectrometer. This instrument is a conventional triple-axis spectrometer, usually employing a vertically focusing pyrolytic graphite monochromator. A new monochromator assembly is in construction, which will permit remote selection of a focusing Cu (220) monochromator, Ge (311) or PG (002), providing an incident energy range from 10 meV to 100 meV.
  
  
• BT-7 thermal triple-axis spectrometer. This instrument currently employs a double monochromator system of pyrolytic graphite to produce a fixed incident energy of 13.5 meV. However, a new state-of-the-art thermal triple axis instrument is under construction and will be installed in 2003. This new instrument takes full advantage of the large diameter beam tubes at the NCNR and will employ horizontal focusing for both monochromator and analyzer systems. Combined, these improvements will boost the observed signal by two orders of magnitude for problems where the relaxed Q resolution can be employed. Full polarized beam capability also is under development and will be implemented as soon as available.

Materials Dynamics—High Resolution, Incident Neutrons E=1-15 meV

• Spin-polarized triple-axis spectrometer (SPINS). This instrument is part of the Center for High Resolution Neutron Scattering supported by the National Science Foundation. Two-thirds of its beam time is reserved for guest researcher experiments through the NCNR proposal system. Located on guide NG-5, it is currently operated in four different modes: a conventional triple-axis mode, a horizontally focusing analyzer mode, a flat-analyzer mode employing a position-sensitive detector, and a polarized beam mode. A vertically focusing pyrolytic graphite (PG) monochromator produces a high intensity beam with a wavelength from 2.2 Å to 6.1 Å (17 meV down to 2 meV). Energy resolution is in the range of 30 meV to 1 meV, depending on incident wavelength and collimation. In the horizontally focusing analyzer mode, a multicrystal analyzer with 11 independently rotating 2 cm × 15 cm (width × height) PG blades can be used to focus scattered neutrons of a particular energy onto a single detector (diameter of 2.54 cm and length of 15 cm) and yield a signal increase of a factor of approximately four by relaxing the Q (wave vector) resolution. Alternatively, the analyzer can be used in flat mode with a position-sensitive detector to simultaneously collect data over a region of wave vector and energy. In the polarized beam mode of operation, supermirror transmission polarizers, consisting of a stack of single-crystal Si plates with Fe/Si supermirror coatings, are inserted in the incident and scattered beams.
  
  
• NG-6 Fermi-chopper time-of-flight spectrometer. This spectrometer directs a monochromatic pulse of neutrons at a sample and measures the energies of scattered neutrons by using the time a neutron takes to travel from the sample to the detectors. The pulsed monoenergetic neutron beam is produced by a combination of monochromator crystals and a Fermi chopper. The double monochromator consists of two PG crystals, one of which can be curved vertically to focus neutrons onto the sample position. The curvature can be varied automatically to adjust for changes in monochomator-sample distances as the incident energy is varied. Two Fermi choppers with different blade curvatures are available. An oscillating radial collimator between the sample and detectors eliminates scattering from cryostat and furnace shields around the sample position. The range of incident energies available on this instrument, the first of two time-of-flight spectrometers operating in the NCNR, is from 2.2 meV to 15 meV. With the energy resolution ranging from 60 µeV to 1000 µeV, the spectrometer allows a broad range of quasielastic scattering experiments on diffusive motions in solids and liquids, and inelastic scattering experiments on magnetic and vibrational excitations.
  
  
• Disk chopper time-of-flight spectrometer (DCS). The DCS measures the energies of scattered neutrons using the time a neutron takes to travel from the sample to the detectors. The pulsed monoenergetic neutron beam is produced by a set of disk choppers which rotate at speeds up to 20,000 rpm. There are three slots in the disks. By appropriately phasing these disks, the resolution of the instrument can be changed without having to change the incident wavelength or the speed of the choppers. Noteworthy features include a large range of incident neutron energies (0.5 meV to 20 meV) and 913 detectors which continuously cover 5 percent of 4 pi steradians. This extremely flexible spectrometer can be used for a broad range of quasielastic scattering experiments on diffusive motions in solids and liquids, the dynamics of biomolecules, and inelastic scattering experiments on magnetic and vibrational excitations. This instrument is part of the NSF/NIST Center for High Resolution Scattering (CHRNS).
  
  
• High-flux backscattering spectrometer (HFBS). The HFBS provides an energy resolution of less than 1 µeV enabling scientists to perform ultrahigh-energy resolution studies of the low-frequency dynamics in materials. This high resolution limits the intensity of neutrons. Thus the HFBS employs state-of-the-art neutron optics to maximize the count rate. These devices include a 4-meter-long converging guide, a large spherically focusing monochromator, a 12-square-meter spherically focusing analyzer that covers about 20 percent of 4 pi steradians, and a novel device known as a phase-space transform chopper. The monochromator and analyzer are Si (111) crystals, which in backscattering provided a neutron energy of 2.08 meV. The energy of neutrons incident of the sample can be varied over a range of up to -50 µeV to +50 µeV by Doppler motion of the monochromator. Applications of backscattering spectroscopy include rotational tunneling, molecular reorientation, diffusive motions in solids and liquids, the dynamics of glass transitions, and critical scattering near phase transitions. This instrument is part of the NSF/NIST Center for High Resolution Neutron Scattering (CHRNS).
  
  
• Neutron spin echo spectrometer (NSE). The NSE spectrometer is the highest resolution neutron spectrometer in North America, bridging the gap between conventional inelastic neutron scattering and dynamic light scattering. The instrument consists of a variety of devices for manipulating the neutron spin including two large solenoids and a variety of polarizers and spin flippers. A polarized netutron beam is directed down one of the solenoids causing the spin of neutron to precess approximately 100,000 times. The neutron then scatters from the sample and enters the second solenoid, which again causes the spind to precess. The polarization of the neutrons which emerge from the second solenoid is measured yielding information on the difference in the neutron energy in the two arms of the instrument. This unusual approach allows the NSE technique, unlike other neutron spectroscopic methods, to provide dynamic information directly in the time, rather than energy, domain. The instrument allows scientists to collect data for Fourier times ranging from less than 0.01 nsec to other 100 nsec over a Q range 0.01-1 inverse Angstroms. The NSE is optimized for measurements of soft condensed matter systems such as polymers and biological dynamics and for the dynamics associated with glass transitions and phase transitions. This instrument is part of the NSF/NIST Center for High Resolution Scattering (CHRNS).

Chemical Analysis

• Elemental analysis. Neutron activation analysis is performed utilizing clean facilities for sample preparation, sample irradiation facilities with neutron fluence rate from 3 x 10¹¹ to 1 x 10¹⁴ /cm²s, semi-hot and warm radiochemistry laboratories, and both high-rate and low-background radiation counting. Development of methodology has aimed at accuracy and sensitivity over concentrations ranging from pg/g to 100 percent. Radiochemical separations for specific elements and multielement analysis at the ultratrace level are available. A thermal neutron-capture prompt-gamma activation analysis facility is operational, with a neutron fluence rate of 3 x 10⁸ /cm²s in a 2-centimeter-diameter sapphire-filtered beam.
  
  
• Cold neutron depth profiling. With a measured chemical sensitivity 20 times that of the previous NIST thermal-beam instrument, this station at NG-0 features automated sample handling, near real-time spectral processing, goniometer positioning of sample and detectors, and sample temperature control. NDP is used to measure the concentration and distribution of certain light elements such as boron, lithium, and nitrogen on solid matrices. Typical limit of detection for boron in silicon is in the parts per billion range. Profiling of these elements in thin films is obtained over the depth of about 1 µm, with a resolution varying from a few nm to a few hundred nm, depending on the element and the matrix.
  
  
• Cold neutron prompt-gamma-ray activation analysis. Sensitivity is the highest in the world, with a thermal equivalent neutron fluence rate of 9 x 108 /cm2s. The high quality of the neutron beam and the low background at NG-7 allow close sample-detector spacing, resulting in high counting efficiency, especially in the energy region below 1 MeV. This instrument provides non-destructive quantitative analysis of chemical elements, such as hydrogen (detection limit <2 µg), which are difficult to detect by other means.

Dosimetry and Fundamental Neutron Physics

• Neutron standards and dosimetry. A number of neutron fields for standards and dosimetry are available. These include Cf fission sources, a D₂O-moderated Cf source, a ²³⁵U cavity fission source, two thermal column beams, and an intermediate-energy standard neutron field.
  
  
• Fundamental physics station. Occupying an end guide position in the guide hall, the physics station now provides three independently operable beams: NG-6, the polychromatic (white) neutron beam; NG-6M, a monochromatic neutron beam with a wavelength of about 5 angstroms; and NG-6U, a monochromatic beam with a wave length of about 9 angstroms. The NG-6U beam is operated in collaboration with a team from Harvard University to make ultracold neutrons by inelastic scattering in superfluid ⁴He.
  
  
• Neutron Interferometry and Optics Facility. This facility, located in the guide hall of the NCNR, is the world's premier user facility for neutron interferometry and related neutron optical measurements. A neutron interferometer (NI) splits, then recombines, neutron waves. This gives the NI its unique ability to experimentally access the phase of neutron waves. Phase measurements are used to study the magnetic, nuclear, and structural properties of materials, as well as fundamental questions in quantum physics. Related, innovative neutron optical techniques for use in condensed matter and materials science research are being developed.
  
  
• Neutron Radiography and Tomography. The BT-6 beam in the confinement building has been reconfigured as a dedicated neutron radiography/tomography facility for investigations of hydrogen fuel cell performance and other imaging applications where neutrons are much more sensitive than X-rays.

Other Capabilities

• Instrument development station. A cold neutron beam position deliberately has been left uninstrumented, except for the provision of an optical bench and positioning devices, in order to allow for development of new neutron beam methods and devices, especially in the areas of neutron optics and neutron-based chemical analysis methods. A particularly interesting and successful project that has been carried out at this station in recent years has to do with neutron focusing using capillary optics to produce a neutron lens.
  
  
• Irradiation facilities. Four pneumatic tubes with fluence ranges of 3 × 10¹¹ n/cm²/s to 2 × 10¹⁴ n/cm²/s for irradiations of seconds up to hours are available. These use polyethylene irradiation containers with volumes up to 40 mL. The cadmium ratio range for these facilities is 4 to 3000 (Au). For long irradiations, 6-centimeter- and 9-centimeter-diameter in-core thimbles are used. These are D₂0 filled with fluences of 2-4 × 10¹⁴ n/cm²/s.
  
  
• Neutron radiography. Radiography facilities are available at a highly thermalized beam of the thermal column. Fluences range from 10⁵ n/cm²/s to 10⁷ n/cm²/s, depending on resolution, with a Cd ratio of 500:1 and an L/D ratio adjustable from 20:1 to 500:1. Facilities for autoradiography of paintings, including labs and a darkroom, are available. This facility currently is being modified to allow new studies using tomographic methods.

Applications: The unusual sensitivity and range of measurements possible at the NCNR provide applications in materials structures, materials dynamics, chemical analysis, and neutron physics. Currently operational instruments are used to study crystal structures, microstructures, and molecular dynamics in the bulk and surfaces of metals, ceramics, polymers, composites, and biological materials. Systems under study include colloidal mixtures, catalysts, thin films, layered structures, and interfaces; magnetic systems including amorphous magnets and spin glasses, superconductors, and magnetic multilayers; hydrogen in metals; shear-induced phenomena; molecular geometry of polymer and biological macromolecules; chemical composition of semiconductors; and other advanced materials. Other major programs include studies in environmental chemistry, nutrition, biomedicine, energy, and electronic devices, with emphasis on Standard Reference Materials for these applications, ultralight mass assay for commercial track recorder detectors, absolute fission-rate measurements, and development of thermal neutron beam monitors.

Contact: J. Michael Rowe

Materials Science Synchrotron X-Ray Beamlines

Synchrotron radiation sources provide intense beams of X-rays for leading-edge research in a broad range of scientific disciplines. The Synchrotron Beam Line Operation and Development project in MSEL's Ceramics Division includes the operation of experimental stations at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory, and at the Advanced Photon Source (APS) at Argonne National Laboratory. The Advanced Photon Source is one of three hard X-ray third-generation synchrotron radiation light sources in the world—the brightest sources of X-ray beams available. NIST is a partner at the APS with University of Illinois at Urbana/Champaign, Oak Ridge National Lab, and UOP, in a collaboration called UNICAT. At the UNICAT facility, scientists can examine the microstructure of metals, ceramics, polymers and biomaterials, in detail not possible before. The emphasis at both facilities is on microstructure characterization. Scientists from NIST, industry, universities, and other government laboratories, come to the UNICAT beam lines at the APS and the NIST advanced materials characterization beam lines at the NSLS to perform state-of-the-art measurements. Use of the NIST facilities at the APS and the NSLS are open to all qualified researchers in the scientific community.

The experiments available at the APS include high-resolution X-ray diffraction, ultra-small-angle X-ray scattering (USAXS), surface and interface scattering, X-ray diffraction imaging, X-ray absorption fine structure (XAFS) spectroscopy, diffuse scattering, X-ray microbeam diffraction and fluorescence, and coherent X-ray scattering. Experimental techniques available at the NSLS include XAFS, standing wave X-ray measurements, and ultra-soft-X-ray absorption measurements.

The USAXS instrument offers continuously tunable optics for anomalous USAXS, 1,000 times the intensity of earlier USAXS instruments, high sensitivity and high resolution at low scattering vector, and a scattering vector range from below 0.00012 Å-1 to above 0.5 Å-1. As one of the few small-angle X-ray scattering instruments in the world for which a primary absolute calibration is available, the data from the NIST instrument serves an important role in setting scattering standards. In an optional configuration of this instrument, side-reflection optics enables USAXS measurements of anisotropic as well as isotropic materials.

The high-resolution, monochromatic X-ray diffraction imaging camera at the APS is the only dedicated monochromatic facility of its type in this country, and is the only instrument able to support experiments at the highest resolution. It supports a range of imaging studies such as imaging of semiconductor crystals, photonic materials, and biological crystals.

At the U7A beam line at the NSLS, the NIST/Dow Materials Science end station receives photons in the soft-X-ray energy range from ~ 150 eV to 1000 eV, covering the K-edges of boron, carbon, nitrogen, oxygen and fluorine. It uses a unique focusing multiplayer mirror system for soft X-ray absorption spectroscopy and a new non-destructive photon-in photon-out detector system, which allows the in-situ observation of the chemical species under real reaction conditions. The end station can make direct comparisons between the surface and bulk of a sample by measuring simultaneous electron yield (5 nm depth sensitivity) and fluorescence yield (200 nm) spectra.

Availability: Beam time is available to qualified scientists provided safety requirements are met and scheduling arrangements can be made. Proposals for collaborative use of the facility are reviewed at NIST; proposals for independent use of the NIST facilities should be submitted to directly to the Independent Investigator Program at the APS or the General User Program at the NSLS.

Contact: Gabrielle G. Long

Magnetic Engineering Research Facility

Capabilities: This facility is specifically designed for advancing key enabling technologies in the field of ultrahigh-density data storage. Films can be deposited both by the methods preferred in basic research (molecular beam epitaxy) and by the methods of industrial manufacturing (magnetron sputtering). Numerous in-situ structural characterization techniques are available, including scanning tunneling microscopy, X-ray photoelectron spectroscopy, Auger electron spectroscopy, ion scattering spectroscopy, low-energy electron diffraction, reflection high-energy electron diffraction, and mass spectrometry. For in-situ magnetic measurements, both a superconducting magnet and an electromagnet are built into the instrumentation and are equipped for magnetoresistance and magneto-optical Kerr effect measurements.

This array of in-situ instrumentation allows measurements to be made on samples at every step of fabrication with the most modern surface, interface, and magnetic diagnostics. Properties that can be investigated include elemental composition, thickness, atomic structure, roughness, and magnetic and magnetoresistive properties. These measurements allow researchers to establish the correlations between the film structure and properties and to use the resulting insights to help industry establish a scientific basis for their manufacturing processes.

Applications: This facility is used to prepare magnetic spin valves possessing giant magnetoresistance (GMR) effects and to study the science underlying their fabrication. These devices, which are partially comprised of 1- to 2-nanometer-thick alternating layers of Co and Cu, are being used in all current computer hard disk read-heads and may form the basis for a new generation of non-volatile memory chips to compete with dynamic random access memory. For the past three years in this highly competitive area, Magnetic Engineering Research Facility (MERF) activities have led the world in devices possessing the largest GMR values with the switching fields small enough for devices. Through close association with the National Storage Industry Consortium, which comprises the leading magnetic recording companies, NIST has provided the MERF results to the recording industry on a continuous basis. Fierce competition is under way to dominate this key technology of the information storage industry. The introduction of GMR heads means that only eight years elapsed between the discovery of the GMR effect and its introduction into commercial products. The MERF facility is used to support U.S. industry in the competition by making measurements that industry is not equipped to make. This approach is leading to the development of improved GMR read-heads to help keep U.S. industry competitive in world markets.

Availability: The MERF is open to all qualified U.S. researchers who are interested in collaborative research. Scientists from industry particularly are encouraged to take advantage of the opportunities for collaborative research of interest to their companies. Several such collaborations presently are under way. However, facility time can be made available for new collaborations if the proposed research is designed to promote the agenda of our customers.

Contacts: William F. Egelhoff, Jr. and Robert D. Shull

Combinatorial Methods

New, more complex materials are increasingly in demand for applications in areas such as biotechnology, microelectronics and nanotechnology. The use of combinatorial methods—which comprise a special set of tools and techniques—enables scientists to rapidly explore a wide range of material characteristics in parallel and on a miniaturized scale. The Combinatorial Methods Program at NIST (see www.nist.gov/combi) was initiated to develop this methodology to learn more about materials and their structure, properties, and processing, data that can help manufacturers accelerate the development of new materials.

The program has demonstrated the ability to successfully develop novel combinatorial methods for polymer "library" preparation and characterization, and validation of combinatorial measurements through well-defined problems in polymer materials science such as mapping phase boundary, stability and wettability of thin films, co-polymer morphology, crystallization, and demonstrated new knowledge discovery in the process. State-of-the-art on-line data analysis tools, process control methodology, and data archival methods are being developed. The program works closely to address issues of the multiphase materials, electronic materials, and biomaterials for their structure and properties characterization. A multitier consortium directly serves the needs of industrial customers.

Researchers in the Polymers Division have developed novel combinatorial methods for polymer "library" design and characterization. These include gradient flow coating with elevated temperature control, automated interferometric mapping of film thickness and refractive index, composition gradient library preparation, UV and wet etch for gradient surface hydrophobicity modification of inorganic and polymer surfaces, infrared spectroscopic composition mapping, temperature gradient processing stage, automated optical reflection and transmission microscopy with polarization and process control programming, automated multi-solvent contact angle instrument, high throughput opto-adhesion methodology, and state of the art on-line data analysis tools for image and pattern processing.

Combinatorial and high-throughput measurement techniques available in the facility include:

• gradient flow coating method
• multilens JKR (Johnson-Kendall-Roberts) for quantitative adhesion measurements
• mechanical properties—copper-grid multiple crazing and film fracture technique, and modulus of gradient polymer coatings
• UV methods for surface energy gradients, gradient cross-linking and curing, chemical and topographically multiply patterned substrates
• IR imaging for automated chemical mapping of coatings
• automated optical microscopy with gradient hot stage for in-situ crystallization, curing, phase separation, film drying, film wettability
• confocal microscopy for florescence studies of gradient samples (e.g., polymer curing on gradient temperature stage)
• molecular probes and optical detection for high-throughput transport studies in polymeric membranes (with NIST Boulder)
• gradient composition extrusion of nanocomposites (for flammability studies with NIST fire researchers) and micro hot-plates for calorimetry
• gradient composition polymer films from heated polymer solution

Contact: Alamgir Karim

Center for Theoretical and Computational Materials Science

The NIST Center for Theoretical and Computational Materials Science (CTCMS) is a research program addressing industry's needs for theory and modeling tools for materials design and processing. Founded in 1995, the CTCMS is a center of expertise in computational materials research that develops tools and techniques and fosters collaborations. CTCMS goals are to investigate important industrial problems in materials theory and modeling with novel computational approaches, create innovative and productive opportunities for collaboration in materials theory and modeling, develop powerful new tools for materials theory and modeling, and accelerate their integration into industrial research.

Capabilities: To use the nation's resources more effectively, the CTCMS integrates ongoing research at various institutions by forming multidisciplinary and multi-institutional research teams as required to attack key materials issues. The CTCMS has three principal activities, all operating interactively: planning, research, and technology transfer. Workshops are held as the first step in defining technical research areas with significant technological impact, identifying team members, and building the infrastructure for collaborative research. The CTCMS provides an infrastructure and support for its members, including an interactive World Wide Web information server (www.ctcms.nist.gov) and modern computing and workshop facilities.

Applications: Current research areas include theory and simulation of phase transformation kinetics and morphology, micromagnetics, composite materials, foams, microstructure and dynamics of disordered and partially ordered materials, complex fluids, materials reliability, reactive wetting, pattern formation, crystal growth, sintering, and solidification. Simulation techniques include finite element, finite difference, Lattice Boltzmann, molecular dynamics, Monte Carlo, phase field and cellular automata methods. Current CTCMS working groups include:

• Phase field modeling tools: The phase field method has become one of the most flexible and powerful methods for predicting the evolution of materials microstructure. We are focusing on the development of both new applications for this method and tools enabling the solution of the complex equations which emerge from these models.
  
  
• Matinformatics: With the advent of combinatorial materials science, huge amounts of data are being generated, and this information needs to be both accessible and interpreted. This effort is bringing cutting-edge information technology together with experts in data-mining to develop the tools and techniques needed to manage the ever-increasing volume of materials information.
  
  
• WWW tools for scientific collaboration: We are working with information science specialists to develop Web-based tools for scientific collaboration.
  
  
• First principle methods in phase diagrams: Using a fundamental, quantum-mechanical, description to derive the properties of matter, is the ultimate goal of materials modeling. This effort uses electronic structure calculations to derive the phase stability of alloys, with particular focus on ferroelectrics.
  
  
• Object-oriented finite element modeling of composite materials. We are developing a set of object-oriented finite element modeling tools to improve the characterization and property prediction of composite materials. Public domain software tools are available at www.ctcms.nist.gov.
  
  
• Structure-property relations in polymer nanocomposites: This working group is exploiting molecular simulation methods to characterize structure in composite materials, and to relate structure to the ultimate material properties and functionality.
  
  
• Microstructure and dynamics of frustrated materials. This working group is applying new computational capabilities to characterize the relationship between microstructure and dynamics in glasses, plastics, and other amorphous materials and developing a new set of measurement standards.
  
  
• Tools for neutron scattering measurements. While neutron scattering has become a critical tool for the probing of matters properties, interpreting the results of the experiment present a host of challenges for the scientist. This effort is attempting to develop a better theoretical framework for the interpretation of such experiments, bringing together some of the Green's function library. This team of researchers is developing an interactive, electronic library tool of Green's function and boundary element solutions to reduce the time and cost of industrial component design.

The CTCMS also hosts Web pages with resources and tools in the following areas:

• Micromagnetic materials: This working group is addressing the need for accurate, standardized micromagnetics modeling tools. Software tools developed by the group and selected sample geometries may be found at www.ctcms.nist.gov.
  
  
• Solder interconnect design: The solder interconnect design team is developing public-domain software tools to improve electronic packaging processes. Tools developed by the solder group that model standard solder interconnect geometries are available at www.ctcms.nist.gov

Availability: The CTCMS facilitates numerous interactions between industry, academia, NIST, and other government and national labs to apply materials theory and modeling to solve U.S. industrial problems in materials design and processing. Researchers interested in joining existing efforts or starting new ones are encouraged to contact the CTCMS. The center welcomes proposals for focused workshops in materials theory and modeling at any time. Proposals will be funded on the basis of scientific merit and availability of funds. Computing and workshop facilities are available to U.S. industry, other government agencies, and academia for collaborative research projects. The CTCMS participates in the National Research Council postdoctoral fellowship program and hosts short-term and long-term visitors.

Contact: James Warren

Date created: Jan. 22, 2003
Last modified: Aug. 02, 2007
Contact: inquiries@nist.gov