High Temperature Materials Laboratory Research Articles

Herman Postma

Herman Postma, longtime director of Oak Ridge National Laboratory (ORNL), died of a cerebral hemorrhage on 6 November 2004 while on vacation in Hawaii.Postma was born in New Hanover County in North Carolina on 29 March 1933. His parents had emigrated from the Netherlands, and were still struggling financially, but Postma proved to be an outstanding student and won a full scholarship to Duke University. In 1955, he graduated at the top of his class with a BS in physics. He entered graduate school at Harvard University under adviser Richard Wilson, who recalled, “Herman was one of the few of my students who did not have to have everything explained three times before it was understood. He was very self-directed.” Postma’s dissertation was entitled “The Elastic Scattering of 146 MeV Polarized Protons by Deuterons.” During graduate school, Postma spent summers at ORNL to work on research projects in nuclear physics. During those summers he met his future wife, Pat, who was a mathematician at the laboratory. After graduation in 1959, he joined the laboratory’s thermonuclear division to work on controlled fusion. In those early days of fusion research, optimism was rampant. A commonly heard prognosis was that fusion would be a useful source of energy in 10 years. (Now, some 50 years later, a commercial fusion device is projected to appear in 25 years.) ORNL scientists worked on a succession of mirror machines, designated as DCX-1, DCX-2, and so forth, with molecular-ion injection into a plasma contained in magnetic mirrors. Postma was a pioneer in the investigation of the properties of energetic particles in such containments. Using masterful and ingenious experimental techniques, he developed new diagnostics for measuring plasma characteristics and found plasma densities to be 107 particles/cm3, some seven orders of magnitude too low for a thermonuclear reactor. By then, Postma, who had become director of ORNL’s thermonuclear division in 1967, abandoned the mirror technology and decided to build a tokamak, dubbed the ORMAK. ORNL has pursued the tokamak technology ever since.At age 39, Postma was appointed director of ORNL, a post he held until his retirement in 1988. During his tenure, the laboratory was buffeted by radical changes in Washington, DC. The Atomic Energy Commission was replaced by the Energy Research and Development Administration, and later absorbed by the Department of Energy. Through those turbulent years when it seemed that the emphasis on science was replaced by one on compliance, Postma steered the laboratory with skill and intelligence. ORNL ceased to be primarily a reactor laboratory and became a truly multidisciplinary research institution. The research program was broadened to include all forms of energy, as well as the environmental consequences of energy production and use. Under his leadership, ORNL became particularly eminent in energy conservation, a still-undervalued option nationally.In the sciences, there was growth in nuclear physics with a new accelerator and in materials science with a new state-of-the-art high-temperature materials laboratory, and a reinvigorated neutron-scattering program on ORNL’s High Flux Isotope Reactor. Under Postma’s direction, ORNL’s computing capabilities were revived with a new emphasis on parallel computing. His management style contributed to such technical advances. His office was always open, he managed the laboratory in collegial fashion with subordinate managers, and he insisted on fiscal discipline. Postma was scrupulously fair, but tough-minded. He insisted on peer review to establish the value and relevance of research, and he worked hard to master ORNL’s multifaceted programs.Postma developed a strong relationship between ORNL and the neighboring University of Tennessee. During his tenure, joint professorships and distinguished scientist positions were created. Even joint buildings were erected.As his job demanded, Postma served on many committees and panels. He was most proud of his election to the Duke University Board of Trustees (1987–99) and his appointment by the governor of Tennessee to the state’s Higher Education Commission (1984–92). He gave generously of his time to civic affairs; the business community held him in high regard.After his retirement from ORNL, Postma spent three years as senior vice president of Martin Marietta Energy Systems before taking a full retirement.Postma will be remembered for his incisive leadership of ORNL, his ability to understand issues quickly, and his knack for making informed, fair, and mostly successful decisions. That ORNL continues to flourish is in great measure due to his stewardship.All of us who know the laboratory and value its many contributions to the nation recognize the debt we owe to Herman Postma. Herman Postma PPT|High resolution© 2005 American Institute of Physics.

The ORNL Aberration-Corrected STEM/TEM Project

Field emission electron microscopes operating at 200kV or 300kV and incorporating aberration correctors for either the incident electron probe or for the primary aberrations of the objective lens (OL) are currently under development for several laboratories in the world. OL-corrected instruments require monochromators for the electron beam, built into the electron gun prior to the accelerating stages, in order to optimize the contrast transfer characteristics of the objective lens to push the instrumental resolution limit to well beyond 0.1nm. This will allow the point resolution limit as controlled by the correction of spherical aberration Cs to potentially extend to the instrumental limit of better than 0.1nm. Figure 1 shows the contrast transfer characteristics of a Cs-corrected 200kV TEM, both without and with a beam monochromator.Dedicated STEM instruments such as the 300kV VG-603 and lOOkV VG-501 at Oak Ridge National Laboratory, and other VG instruments at Cornell University and IBM Co. are also being adapted (by Nion Co., Kirkland, WA) to incorporate aberration correctors for the incident probe. The aim is to improve the resolution of the VG-603 instrument in dark-field imaging mode, for example, from 0.13nm to 0.05nm. in another ORNL project, the High Temperature Materials Laboratory has contracted JEOL Ltd. to construct a STEM-TEM instrument with a probe corrector designed and built by CEOS GmbH (Heidelberg, Germany).

Teaching Microscopy and Microscope Theory Based on Remote Instrument Access and Instrument Automation

Abstract The intense use of computers to operate electron microscopes as well as the ability to control microscopes remotely over the Internet, is increasingly changing the way electron microscopes are being used and how microscopy is being taught. Practically all of the top-of-the-line electron microscopes offered by the microscope vendors today are fully computer controllable, and provide for digital imaging. The combination of both features with the ever increasing speed of computers has created a situation that has and will continue to change the way electron microscopists work. Lehigh University together with Oak Ridge National Laboratory have collaborated since 1996 to make the instrumentation in the High Temperature Materials Laboratory at ORNL available for teaching purposes. The primary instrument being used is the Hitachi HF-2000 field emission TEM, which is controlled by Gatan's DigitalMicrograph™ (DM) software and uses a Ik by Ik CCD camera for digital imaging.

The High Temperature Material Laboratory: A National User Facility For Advanced Materials Characterization

Abstract The High Temperature Materials Laboratory (HTML, Fig. 1) is a national resource for materials characterization sponsored by the Department of Energy’s Office of Transportation Technology, Assistant Secretary for Energy Efficiency and Renewable Energy. The HTML comprises six principal user centers: Materials Analysis, Thermophysical Properties, X-ray and Neutron Diffraction, Mechanical Characterization and Analysis, Residual Stress, and Machining and Inspection Research. Instruments available at the user centers have extensive capabilities for characterizing the microstructure, microchemistry, and physical and mechanical properties of materials over a wide range of temperatures. Details of all the capabilities of the various user centers are available on the World Wide Web at http://www.ms.ornl.gov/htmlhome/default.htm.http://www.nice.org.uk/page.aspx?o=43210 To date, more than 300 different institutions, evenly divided between university and industry, have formal research agreements with the HTML. Three separate programs are available to meet the needs of these users as well as those from federal agencies wishing to gain access to the HTML.

A Telepresence Microscopy Research Session In The DOE2000 Materials Microcharacterization Collaboratory

Abstract One of the primary research components of the DOE2000 Materials Microcharacterization Collaboratory involves studies of catalyst materials for reduction of NOx emissions from diesel engine exhausts. A series of experimental catalysts is currently under investigation with colleagues from Ford Research Laboratory. The major thrust of this research is the study of catalyst reactions to determine the progressive changes in the structure and morphology of the catalytic materials with temperature and time under conditions simulating diesel exhaust exposures. Because the High Temperature Materials Laboratory (HTML) provides an ex-situ reactor system that permits TEM samples to be examined after sequential reactions without intermediate atmospheric exposures, the research was undertaken on a collaboratory basis, with microscopy sessions conducted remotely via telepresence. This permits Ford scientists to interact with HTML (and/or other collaboratory) scientists during the TEM sessions, but does not require their time and involvement during the actual reactor runs. The first of these telepresence sessions was held recently, as described below.

Computer Control of Transmission Electron Microscopes: Possibilities, Concepts and Present Limitations

Abstract The electron microscope laboratory at the High Temperature Materials Laboratory in Oak Ridge National Laboratory runs essentially film free. This is possible due to the use of TV-rate and slow-scan CCD cameras together with fast desktop computers connected through Ethernet to network servers for image storage; and a variety of hard copy output devices. In our experience, the functionality of a film-free laboratory goes beyond the simple replacement of film material with some other storage media. For example, the time and effort to produce a final hardcopy image has been reduced effectively from several hours to several minutes. At the same time, data accuracy has increased due to the high linearity of the CCD cameras and data safety is improved due to automated nightly backups.

Building Data Storage Systems And Data Networks To Support Digital Microscopy

Abstract As laboratories like the Materials Analysis User Center (MAUC) in the High Temperature Materials Laboratory, at Oak Ridge National Laboratory move from analog to digital imaging systems, the process for acquiring, processing, analyzing, and publishing research results is changing. In this case since original scientific data exist only in digital form, analog systems for gathering, staring, and transmitting data are being set aside in favor of digital systems. In order to adequately protect original scientific data and to ensure that digital laboratories have the same (or greater) functionality as analog laboratories, scientists must focus on building information systems that make data highly available, highly reliable, and quickly accessible. Meeting these three objectives imposes special requirements for both data storage systems and data networks.

Computer control of Transmission Electron Microscopes possibilities, concepts and present limitations

The electron microscope laboratory at the High Temperature Materials Laboratory in Oak Ridge National Laboratory runs essentially film free. This is possible due to the use of TV-rate and slow-scan CCD cameras together with fast desktop computers connected through Ethernet to network servers for image storage and a variety of hard copy output devices. In our experience, the functionality of a film-free laboratory goes beyond the simple replacement of film material with some other storage media. For example, the tim and effort to produce a final hardcopy image has been reduced effectively from several hours to several minutes. At the same time, data accuracy has increased due to the high linearity of the CCD cameras and data safety is improved due to automated nightly backups.The present all-digital setup of our TEMs has already changed the routines on how an TEM is run. Two si uations occur regularly: 1) one microscopist moves back and forth between the TEM and the computer and 2) two microscopists run the computer and/or TEM as a team. Unfortunately, the tasks of recording an image and running the microscope are still very much separated.

Carbon-based materials thermal development testing and selection process for first wall and divertor applications

Carbon-based materials are being investigated for use as plasma facing surfaces in the burning plasma experiment (BPX) fusion device. Specifically, carbon-carbon (C-C) composites have been proposed in designs for both inboard limiter and divertor surfaces. This paper describes a development program to test and evaluate candidate composites and to select the composite type most suitable for the BPX requirements. Tests were formulated to examine the effects of composite architectures (fiber type, fiber placement and volume fraction, and matrix fraction) and composite processing on composite conductivity. Specimens of 1D, 2D, and 3D C-C composite architectures were tested in the High Temperature Materials Laboratory at Oak Ridge National Laboratory using an automated laser flash system to determine the thermal diffusivity of these candidate materials. Costs were considered as part of the selection process. Results indicate that a relatively inexpensive, low conductivity, multidimensional fiber composite will meet design requirements for the inboard limiter design. The high heat flux in the divertor region necessitates further material development to achieve a material that will meet this region's performance requirements.