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Materials science and engineering

Description: During FY-96, work within the Materials Science and Engineering Thrust Area was focused on material modeling. Our motivation for this work is to develop the capability to study the structural response of materials as well as material processing. These capabilities have been applied to a broad range of problems, in support of many programs at Lawrence Livermore National Laboratory. These studies are described in (1) Strength and Fracture Toughness of Material Interfaces; (2) Damage Evolution in Fiber Composite Materials; (3) Flashlamp Envelope Optical Properties and Failure Analysis; (4) Synthesis and Processing of Nanocrystalline Hydroxyapatite; and (5) Room Temperature Creep Compliance of Bulk Kel-E.
Date: February 1, 1997
Creator: Lesuer, D.R.
Partner: UNT Libraries Government Documents Department

Gender Equity in Materials Science and Engineering

Description: At the request of the University Materials Council, a national workshop was convened to examine 'Gender Equity Issues in Materials Science and Engineering.' The workshop considered causes of the historic underrepresentation of women in materials science and engineering (MSE), with a goal of developing strategies to increase the gender diversity of the discipline in universities and national laboratories. Specific workshop objectives were to examine efforts to level the playing field, understand implicit biases, develop methods to minimize bias in all aspects of training and employment, and create the means to implement a broadly inclusive, family-friendly work environment in MSE departments. Held May 18-20, 2008, at the Conference Center at the University of Maryland, the workshop included heads and chairs of university MSE departments and representatives of the National Science Foundation (NSF), the Office of Basic Energy Sciences of the Department of Energy (DOE-BES), and the national laboratories. The following recommendations are made based on the outcomes of the discussions at the workshop. Many or all of these apply equally well to universities and national laboratories and should be considered in context of industrial environments as well. First, there should be a follow-up process by which the University Materials Council (UMC) reviews the status of women in the field of MSE on a periodic basis and determines what additional changes should be made to accelerate progress in gender equity. Second, all departments should strengthen documentation and enforcement of departmental procedures such that hiring, promotion, compensation, and tenure decisions are more transparent, that the reasons why a candidate was not selected or promoted are clear, and that faculty are less able to apply their biases to personnel decisions. Third, all departments should strengthen mentoring of junior faculty. Fourth, all departments must raise awareness of gender biases and work to eliminate hostile attitudes ...
Date: December 1, 2008
Creator: Rockett, Angus
Partner: UNT Libraries Government Documents Department

Surface species formed by the adsorption and dissociation of water molecules on Ru(0001) surface containing a small coverage of carbon atoms studied by scanning tunneling microscopy

Description: The adsorption and dissociation of water on a Ru(0001) surface containing a small amount ({le} 3 %) of carbon impurities was studied by scanning tunneling microscopy (STM). Various surface species are formed depending on the temperature. These include molecular H{sub 2}O, H{sub 2}O-C complexes, H, O, OH and CH. Clusters of either pure H{sub 2}O or mixed H{sub 2}O-OH species are also formed. Each of these species produces a characteristic contrast in the STM images and can be identified by experiment and by ab initio total energy calculations coupled with STM image simulations. Manipulation of individual species via excitation of vibrational modes with the tunneling electrons has been used as supporting evidence.
Date: April 26, 2008
Creator: UCB, Dept of Materials Science and Engineering; Dept of Applied Science and Technology, UCB; Institut de Ciencia de Materials de Barcelona, Barcelona, Spain; Instituto de Ciencia de Materiales de Madrid, Madrid, Spain; Department of Mechanical Engineering, Yale University; Salmeron, Miquel et al.
Partner: UNT Libraries Government Documents Department

Numerical tools for atomistic simulations.

Description: The final report for a Laboratory Directed Research and Development project entitled 'Parallel Atomistic Computing for Failure Analysis of Micromachines' is presented. In this project, atomistic algorithms for parallel computers were developed to assist in quantification of microstructure-property relations related to weapon micro-components. With these and other serial computing tools, we are performing atomistic simulations of various sizes, geometries, materials, and boundary conditions. These tools provide the capability to handle the different size-scale effects required to predict failure. Nonlocal continuum models have been proposed to address this problem; however, they are phenomenological in nature and are difficult to validate for micro-scale components. Our goal is to separately quantify damage nucleation, growth, and coalescence mechanisms to provide a basis for macro-scale continuum models that will be used for micromachine design. Because micro-component experiments are difficult, a systematic computational study that employs Monte Carlo methods, molecular statics, and molecular dynamics (EAM and MEAM) simulations to compute continuum quantities will provide mechanism-property relations associated with the following parameters: specimen size, number of grains, crystal orientation, strain rates, temperature, defect nearest neighbor distance, void/crack size, chemical state, and stress state. This study will quantify sizescale effects from nanometers to microns in terms of damage progression and thus potentially allow for optimized micro-machine designs that are more reliable and have higher fidelity in terms of strength. In order to accomplish this task, several atomistic methods needed to be developed and evaluated to cover the range of defects, strain rates, temperatures, and sizes that a material may see in micro-machines. Therefore we are providing a complete set of tools for large scale atomistic simulations that include pre-processing of realistic material configurations, processing under different environments, and post-processing with appropriate continuum quantities. By running simulations with these tools, we are able to determine size scale effects that ...
Date: January 1, 2004
Creator: Fang, H. (Mississippi State University); Gullett, Philip Michael; Slepoy, Alexander (Sandia National Laboratories, Albuquerque, NM); Horstemeyer, Mark F. (Mississippi State University); Baskes, Michael I. (Los Alamos National Laboratory, Los Alamos, NM); Wagner, Gregory John et al.
Partner: UNT Libraries Government Documents Department

Living in a Materials World: Materials Science Engineering Professional Development for K-12 Educators

Description: Advances in materials science are fundamental to technological developments and have broad societal impacs. For example, a cellular phone is composed of a polymer case, liquid crystal displays, LEDs, silicon chips, Ni-Cd batteries, resistors, capacitors, speakers, microphones all of which have required advances in materials science to be compacted into a phone which is typically smaller than a deck of cards. Like many technological developments, cellular phones have become a ubiquitous part of society, and yet most people know little about the materials science associated with their manufacture. The probable condition of constrained knowledge of materials science was the motivation for developing and offering a 20 hour fourday course called 'Living in a Materials World.' In addition, materials science provides a connection between our every day experiences and the work of scientists and engineers. The course was offered as part of a larger K-12 teacher professional development project and was a component of a week-long summer institute designed specifically for upper elementary and middle school teachers which included 20 hour content strands, and 12 hours of plenary sessions, planning, and collaborative sharing. The focus of the institute was on enhancing teacher content knowledge in STEM, their capacity for teaching using inquiry, their comfort and positive attitudes toward teaching STEM, their knowledge of how people learn, and strategies for integrating STEM throughout the curriculum. In addition to the summer institute the participating teachers were provided with a kit of about $300 worth of materials and equipment to use to implement the content they learned in their classrooms. As part of this professional development project the participants were required to design and implement 5 lesson plans with their students this fall and report on the results, as part of the continuing education course associated with the project. 'Living in a Materials World' ...
Date: June 1, 2011
Creator: Seifert, Anne & Nadelson, Louis
Partner: UNT Libraries Government Documents Department

Thermocouples For High Temperature In-Pile Testing

Description: Many advanced nuclear reactor designs require new fuel, cladding and structural materials. Data are needed to characeterize the performance of these new materials in high temperature, oxidizing and radiation conditions. To obtain this data, robust instrumentation is needed htat can survive proposed test conditions. Traditional methods for measuring temperature in-pile degrade at temperatures above 1080 degrees C. Hence, a project was intiated to develop specialized thermocouples for high temperature in-pile applications (see Rempe and Wilkins, 2005). This paper summarizes efforts to develop, fabricate and evaluate these specialized thermocouples.
Date: November 1, 2005
Creator: Rempe, J. L.
Partner: UNT Libraries Government Documents Department

NHI Component Technical Readiness Evaluation System

Description: A decision process for evaluating the technical readiness or maturity of components (i.e., heat exchangers, chemical reactors, valves, etc.) for use by the U.S. DOE Nuclear Hydrogen Initiative is described. This system is used by the DOE NHI to assess individual components in relation to their readiness for pilot-scale and larger-scale deployment and to drive the research and development work needed to attain technical maturity. A description of the evaluation system is provided, and examples are given to illustrate how it is used to assist in component R&D decisions.
Date: September 1, 2007
Creator: Sherman, Steven R.; Wilson, Dane F. & Pawel, Steven J.
Partner: UNT Libraries Government Documents Department

High Temperature Thermocouples For In-pile Applications

Description: Traditional methods for measuring temperature in-pile degrade at temperatures above 1080 degrees C. Hence, a project has been initiated to explore the use of specialized thermocouples that are composed of materials that are able to withstand higher temperature, in-pile test conditions. Results from efforts to develop, fabricate and evaluate the performance of these specialized thermocouples are reported in this paper. Candidate materials were evaluated for their ability to withstand irradiation, to resit material interactions and to remain ductile at high temperatures. In addition, candidate thermocouples were evaluated based on their resolution over the temperature ranges of interest. Results from these evaluations are reported, and additional on-going development activities are summarized.
Date: October 1, 2005
Creator: Rempe, J. L. & Wilkins, S. C.
Partner: UNT Libraries Government Documents Department

Underground Corrosion After 32 Years: A Study of Fate and Transport - Annual Report, June 2004

Description: In 1970, the National Bureau of Standards (NBS), now call National Institute of Standards and Technology (NIST), implemented the most ambitious and comprehensive long-term corrosion behavior test to date for stainless steels in soil environments. Over 32 years have passed since scientists buried 6,324 specimens from stainless steel types, specialty alloys, composite configurations, and multiple material forms and treatment conditions at six distinctive soil-type sites throughout the country. At the start of this research project, more than 190 specimens per site, exceeding a total of 1000 specimens, remained undisturbed, a buried treasure of subsurface scientific data. This research project advocates the completion of the NIST corrosion study along with a thorough examination of the soil and environment surrounding the specimens. The project takes an interdisciplinary research approach that will correlate the complicated interrelationships among metal integrity, corrosion rates, corrosion mechanisms, soil properties, soil microbiology, plant and animal interaction with corrosion products, and fate and transport of metallic ions. The results will provide much-needed data on corrosion rates, underground material degradation, and the behavior of corrosion products in the near-field vadose zone. The data will improve the ability to predict the fate and transport of chemical and radiological contaminants at sites throughout the DOE complex. The research scope is focused on one of the six available sites, Site D, near Wildwood, NJ.
Date: June 1, 2004
Creator: Flitton, Kay Adler
Partner: UNT Libraries Government Documents Department

Atmospheric Pressure Plasma Process And Applications

Description: This paper provides a general discussion of atmospheric-pressure plasma generation, processes, and applications. There are two distinct categories of atmospheric-pressure plasmas: thermal and nonthermal. Thermal atmospheric-pressure plasmas include those produced in high intensity arcs, plasma torches, or in high intensity, high frequency discharges. Although nonthermal plasmas are at room temperatures, they are extremely effective in producing activated species, e.g., free radicals and excited state atoms. Thus, both thermal and nonthermal atmosphericpressure plasmas are finding applications in a wide variety of industrial processes, e.g. waste destruction, material recovery, extractive metallurgy, powder synthesis, and energy conversion. A brief discussion of recent plasma technology research and development activities at the Idaho National Laboratory is included.
Date: September 1, 2006
Creator: Kong, Peter C. & Myrtle
Partner: UNT Libraries Government Documents Department

Critical Heat Flux In Inclined Rectangular Narrow Long Channel

Description: In the TMI-2 accident, the lower part of the reactor pressure vessel had been overheated and then rather rapidly cooled down, as was later identified in a vessel investigation project. This accounted for the possibility of gap cooling feasibility. For this reason, several investigations were performed to determine the critical heat flux (CHF) from the standpoint of invessel retention. The experiments are conducted to investigate the general boiling phenomena, and the triggering mechanism for the CHF in a narrow gap using a 5 x 105 mm2 crevice type heater assembly and de-mineralized water. The test parameters include the gap size of 5 mm, and the surface orientation angles from the downward facing position (180o) to the vertical position (90o). The orientation angle affects the bubble layer and escape from the narrow gap. The CHF is less than that in a shorter channel, compared with the previous experiments having a heated length of 35 mmin the copper test section.
Date: May 1, 2005
Creator: Rempe, J. L.; Noh, S. W.; Kim, Y. H.; Suh, K. Y.; F.B.Cheung & Kim, S. B.
Partner: UNT Libraries Government Documents Department

Engineering Analysis of Intermediate Loop and Process Heat Exchanger Requirements to Include Configuration Analysis and Materials Needs

Description: The need to locate advanced hydrogen production facilities a finite distance away from a nuclear power source necessitates the need for an intermediate heat transport loop (IHTL). This IHTL must not only efficiently transport energy over distances up to 500 meters but must also be capable of operating at high temperatures (>850oC) for many years. High temperature, long term operation raises concerns of material strength, creep resistance and general material stability (corrosion resistance). IHTL design is currently in the initial stages. Many questions remain to be answered before intelligent design can begin. The report begins to look at some of the issues surrounding the main components of an IHTL. Specifically, a stress analysis of a compact heat exchanger design under expected operating conditions is reported. Also the results of a thermal analysis performed on two ITHL pipe configurations for different heat transport fluids are presented. The configurations consist of separate hot supply and cold return legs as well as annular design in which the hot fluid is carried in an inner pipe and the cold return fluids travels in the opposite direction in the annular space around the hot pipe. The effects of insulation configurations on pipe configuration performance are also reported. Finally, a simple analysis of two different process heat exchanger designs, one a tube in shell type and the other a compact or microchannel reactor are evaluated in light of catalyst requirements. Important insights into the critical areas of research and development are gained from these analyses, guiding the direction of future areas of research.
Date: September 1, 2005
Creator: Lillo, T.M.; Williamson, R.L.; Reed, T.R.; Davis, C.B. & Ginosar, D.M.
Partner: UNT Libraries Government Documents Department

Natural Convection Heat Transfer Experiment in a Hemispherical Pool

Description: Natural convection plays an important role in determining the thermal load from molten core accumulated in the reactor vessel lower head during a severe accident. Several numerical and experimental programs were conducted to study the heat transfer in the molten pool. Previous investigations were mostly related to the rectangular and semicircular pools. Except for COPO, UCLA, ACOPO, and BALI, previous investigations suffer from inadequate representation of high modified Rayleigh number (Ra') in the hemispherical pool that may be formed in the reactor core and lower plenum. Thus, experimental work is conducted utilizing SIGMA SP (Simulant Internal Gravitated Material Apparatus Spherical Pool) producing high Ra' turbulent natural convection in a hemispherical pool up to 5.3 x ~1011. The heating method has already been tested in SIGMA CP (Circular Pool). Six thin cable-type heaters, each with a diameter of 6 mm, are employed to simulate internal heating in the pool. They are uniformly distributed in the hemispherical pool to supply a maximum of 7.8 kW power to the pool. SIGMA SP has the inner and outer diameters of 500 mm and 520 mm, respectively. The upper flat plate and the curved wall of pool, with a 10 mm thick stainless steel plate, are cooled by a regulated water loop. A water-cooling system is used to maintain the temperature of water surrounding the test section nearly constant with time. This study focuses on quantifying the directional heat losses, angular heat flux distribution, and temperature distribution inside the molten pool.
Date: May 19, 2005
Creator: Rempe, J. L.; Lee, S. D.; Son, H. M.; Suh, K. Y.; F.B.Cheung & Kim, S. B.
Partner: UNT Libraries Government Documents Department

Reciprocal-Space Analysis of Compositional Modulation in Short-Period Superlattices Using Position-Sensitive X-Ray Detection

Description: Epitaxial growth of AlAs-InAs short-period superlattices on (001) InP can lead to heterostructures exhibiting strong, quasi-periodic, lateral modulation of the alloy composition; transverse satellites arise in reciprocal space as a signature of the compositional modulation. Using an x-ray diffractometer equipped with a position-sensitive x-ray detector, we demonstrate reciprocal-space mapping of these satellites as an efficient, nondestructive means for detecting and characterizing the occurrence of compositional modulation. Systematic variations in the compositional modulation due to the structural design and the growth conditions of the short-period superlattice are characterized by routine mapping of the lateral satellites. Spontaneous compositional modulation occurs along the growth front during molecular-beam epitaxy of (AlAs) (InAs)n short-period superlattices. The modulation is quasi-periodic and forms a lateral superlattice superimposed on the intended SPS structure. Corresponding transverse satellites arise about each reciprocal lattice point, and x-ray diffraction can be routinely used to map their local reciprocal-space structure. The integrated intensity, spacing, orientation, and shape of these satellites provide a reliable means for nondestructively detecting and characterizing the compositional modulation in short-period superlattices. The analytical efficiency afforded by the use of a PSD has enabled detailed study of systematic vacations in compositional modulation as a function of the average composition, the period, and the growth rate of the short- period superlattice
Date: November 10, 1998
Creator: Ahrenkiel, S.P.; Follstaedt, D.M.; Lee, S.R.; Millunchick, J.M.; Norman, A.G.; Reno, J.L. et al.
Partner: UNT Libraries Government Documents Department

Charge state defect engineering of silicon during ion implantation

Description: Effects of in situ interventions which alter defect interactions during implantation, and thereby affect the final damage state, have been investigated. Specifically, we examined effects of internal electric fields and charge carrier injection on damage accumulation in Si. First, we implanted H or He ions into diode structures which were either reverse or forward biased during implantation. Second, we implanted B or Si ions into plain Si wafers while illuminating them with UV light. In each case, the overall effect is one of damage reduction. Both the electric field and charge carrier injection effects may be understood as resulting from changes in defect interactions caused in part by changes to the charge state of defects formed during implantation.
Date: January 1997
Creator: Brown, R. A.; Ravi, J.; Erokhin, Y.; Rozgonyi, G. A. & White, C. W.
Partner: UNT Libraries Government Documents Department

Melt-texturing of carbon containing YBa{sub 2}Cu{sub 3}O{sub 7-x}: Influence of processing parameters on microstructure and flux-pinning behavior

Description: A detailed study of the flux-pinning behavior of sintered and melt-textured YBa{sub 2}Cu{sub 3}O{sub 7-x} has been carried out by means of microstructural investigations (optical microscopy, SEM, TEM, EDS, DTA, and XRD) and magnetization measurements. It was found that both microstructure and magnetization behavior strongly depend on the starting material, the production method, and the maximum processing temperature. In our experiments, the critical current density, J{sub c}, increased with increasing processing temperature between 920{degrees}C and 1050{degrees}C (25 - 130 emu/cm{sup 3}), but those samples processed at temperatures just above the peritectic transformation point (1020 OC and 1030 OC) exhibited a decreased J{sub c}. The carbon content of the starting powder and the powder`s melting behavior seem to play an important role in the development of microstructure and flux-pinning behavior during melt-texturing. A comparison of our data with previously published results shows that an optimized melt-texturing process can result in materials with critical current densities comparable to those of samples produced by Quench-Melt Growth.
Date: January 1, 1994
Creator: Todt, V.R.; Sengupta, S.; Chen, Y.L.; Shi, Donglu; Poeppel, R.; McGinn, P.J. et al.
Partner: UNT Libraries Government Documents Department

Tensile behavior of nanocrystalline copper

Description: High density nanocrystalline copper produced by inert gas condensation was tested in tension. Displacements were measured using foil strain gauges, which greatly improved the accuracy of the strain data. The Young`s modulus of nanocrystalline copper was found to be consistent with that of coarse-grained copper. Total elongations of {approx} 1% were observed in samples with grain sizes less than 50 nm, while a sample with a grain size of 110 nm exhibited more than 10% elongation, perhaps signifying a change to a dislocation-based deformation mechanism in the larger-grained material. In addition, tensile tests were performed as a function of strain rate, with a possible trend of decreased strength and increased elongation as the strain rate was decreased.
Date: November 1995
Creator: Sanders, P. G.; Weertman, J. R. & Eastman, J. A.
Partner: UNT Libraries Government Documents Department

Experiments showing dynamics of materials interfaces

Description: The discipline of materials science and engineering often involves understanding and controlling properties of interfaces. The authors address the challenge of educating students about properties of interfaces, particularly dynamic properties and effects of unstable interfaces. A series of simple, inexpensive, hands-on activities about fluid interfaces provides students with a testbed to develop intuition about interface dynamics. The experiments highlight the essential role of initial interfacial perturbations in determining the dynamic response of the interface. The experiments produce dramatic, unexpected effects when initial perturbations are controlled and inhibited. These activities help students to develop insight about unstable interfaces that can be applied to analogous problems in materials science and engineering. The lessons examine ``Rayleigh-Taylor instability,`` an interfacial instability that occurs when a higher-density fluid is above a lower-density fluid.
Date: February 1997
Creator: Benjamin, R. F.
Partner: UNT Libraries Government Documents Department