Materials science and engineering

Materials science and engineering

Date: February 1, 1997
Creator: Lesuer, D.R.
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.
Contributing Partner: UNT Libraries Government Documents Department
Gender Equity in Materials Science and Engineering

Gender Equity in Materials Science and Engineering

Date: December 1, 2008
Creator: Rockett, Angus
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) ...
Contributing Partner: UNT Libraries Government Documents Department
Living in a Materials World: Materials Science Engineering Professional Development for K-12 Educators

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

Date: June 1, 2011
Creator: Seifert, Anne & Nadelson, Louis
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 ...
Contributing Partner: UNT Libraries Government Documents Department
Reciprocal-Space Analysis of Compositional Modulation in Short-Period Superlattices Using Position-Sensitive X-Ray Detection

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

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.
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 ...
Contributing 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

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

Date: January 1, 1994
Creator: Todt, V.R.; Sengupta, S.; Chen, Y.L.; Shi, Donglu; Poeppel, R.; McGinn, P.J. et al.
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.
Contributing Partner: UNT Libraries Government Documents Department
Charge state defect engineering of silicon during ion implantation

Charge state defect engineering of silicon during ion implantation

Date: January 1997
Creator: Brown, R. A.; Ravi, J.; Erokhin, Y.; Rozgonyi, G. A. & White, C. W.
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.
Contributing Partner: UNT Libraries Government Documents Department
Tensile behavior of nanocrystalline copper

Tensile behavior of nanocrystalline copper

Date: November 1995
Creator: Sanders, P. G.; Weertman, J. R. & Eastman, J. A.
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.
Contributing Partner: UNT Libraries Government Documents Department
Exploring nanoscale magnetism in advanced materials with polarized X-rays

Exploring nanoscale magnetism in advanced materials with polarized X-rays

Date: May 1, 2011
Creator: Fischer, Peter
Description: No abstract prepared.
Contributing Partner: UNT Libraries Government Documents Department
Process Hood Stand Support Steel

Process Hood Stand Support Steel

Date: October 2, 2000
Creator: SINGH, G.
Description: No abstract prepared.
Contributing Partner: UNT Libraries Government Documents Department
Mechanical properties of nanophase metals

Mechanical properties of nanophase metals

Date: November 1994
Creator: Siegel, R. W. & Fougere, G. E.
Description: Nanophase metals have grain-size dependent mechanical properties that are significantly different than those of their coarse-grained counterparts. Pure metals are much stronger and apparently less ductile than conventional ones; intermetallics are also strengthened, but they tend toward increased ductility at the smallest grain sizes. These property changes are primarily related to grain size limitations, but they are also affected by the large percentage of atoms in grain boundaries and other microstructural features. Strengthening appears to result from a limitation of dislocation activity, while increased ductility probably relates to grain boundary sliding. A brief overview of our present understanding of the mechanical properties of nanophase metals is presented.
Contributing Partner: UNT Libraries Government Documents Department
FIRST PREV 1 2 3 4 5 NEXT LAST