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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

Materials Science and Engineering

Description: Five papers are included: processing/characterization of laminated metal composites, casting process modeling, characterizing the failure of composite materials, fiber-optic Raman spectroscopy for cure monitoring of advanced polymer composites, and modeling superplastic materials. The papers are processed separately for the data base.
Date: March 1993
Creator: Lesuer, Donald 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

Inelastic neutron scattering for materials science and engineering

Description: The neutron is the ideal probe for studying the positions and motions of atoms in condensed matter. The main advantage of the neutron in inelastic scattering results from its heavy mass when compared to other particles which are used to probe materials such as the photon (light, x-rays, or {gamma}-rays) or the electron. The author discusses the application of neutron scattering to study a number of different materials related problems, including, hard magnets, shape memory effects, and hydrogen distribution in metals.
Date: December 31, 1995
Creator: Shapiro, S. M.
Partner: UNT Libraries Government Documents Department

Advanced soluble hydroliquefaction and hydrotreating catalysts

Description: The purpose of the present program is to develop soluble analogs of surface confined catalysts that can be impregnated directly into the coal structure at low temperatures. This approach should avoid problems related to surface area dependence, a two phase (surface- liquid) reaction system and, mass transport limitations.
Date: January 31, 1992
Creator: Laine, R.M. (Michigan Univ., Ann Arbor, MI (United States). Dept. of Materials Science and Engineering) & Stoebe, T. (Washington Univ., Seattle, WA (United States). Dept. of Materials Science and Engineering)
Partner: UNT Libraries Government Documents Department

Advanced, soluble hydroliquefaction and hydrotreating catalysts

Description: The purpose of the present program is to develop soluble analogs of surface confined catalysts that can be impregnated directly into the coal structure at low temperatures. This approach should avoid problems related to surface area dependence, a two phase (surface-liquid) reaction system and, mass transport limitations. Heteropolyanions (HPAs) offer the opportunity to develop soluble forms of surface confined catalysts. HPAs are multi-functional catalysts that could be used to promote both hydroliquefaction and hydrotreating. In theory, these functions could be employed sequentially or simultaneously and could permit exceptional control of liquefaction reactions and reaction conditions. Thus, the current research program involves efforts to evaluate HPAs as soluble liquefaction nd hydrotreating catalysts, with the goal of developing soluble analogs of surface confined catalysts.
Date: September 9, 1991
Creator: Laine, R.M (Michigan Univ., Ann Arbor, MI (United States). Dept. of Materials Science and Engineering) & Stoebe, T. (Washington Univ., Seattle, WA (United States). Dept. of Materials Science and Engineering)
Partner: UNT Libraries Government Documents Department

Advanced soluble hydroliquefaction and hydrotreating catalysts

Description: The purpose of the present program is to develop soluble analogs of surface confined catalysts that can be impregnated directly into the coal structure at low temperatures. This approach should avoid problems related to surface area dependence, a two phase (surface-liquid) reaction system and, mass transport limitations.
Date: November 22, 1991
Creator: Laine, R.M. (Michigan Univ., Ann Arbor, MI (United States). Dept. of Materials Science and Engineering) & Stoebe, T. (Washington Univ., Seattle, WA (United States). Dept. of Materials Science and Engineering)
Partner: UNT Libraries Government Documents Department

Advanced, soluble hydroliquefaction and hydrotreating catalysts

Description: Present hydroliquefaction of coal suffers from required high temperatures and high hydrogen pressures. Surface confined, organometallic catalysists are effective for hydrogenation and HDN of coal model compounds such as quinoline, but not of coal itself. Purpose of this program is to develop soluble analogs of surface confined catalysts that can be impregnated directly into the coal structure at low temperatures. The program consists of 3 major tasks: preparation of candidate HPA (heteropolyanion) precatalysts, HDN and HDO modeling studies, and direct liquefaction studies. During this period, preparation of [PRuMo[sub 11]O[sub 39]][sup 4[minus]] cluster gave essentially the same size particles and activities as for the mixed metal system. The RuMo bimetallic catalyst was made to work as a HDN catalyst for tetrahydroquinoline.
Date: September 8, 1992
Creator: Laine, R.M. (Michigan Univ., Ann Arbor, MI (United States). Dept. of Materials Science and Engineering) & Stoebe, T. (Washington Univ., Seattle, WA (United States). Dept. of Materials Science and Engineering)
Partner: UNT Libraries Government Documents Department

Polymeric electrolytes for ambient temperature lithium batteries

Description: A new type of highly conductive Li{sup +} polymer electrolyte, referred to as the Innovision polymer electrolyte, is completely amorphous at room temperature and has an ionic conductivity in the range of 10{sup {minus}3} S/cm. This report discusses the electrochemical characteristics (lithium oxidation and reduction), conductivity, and physical properties of Innovision electrolytes containing various dissolved salts. These electrolytes are particularly interesting since they appear to have some of the highest room-temperature lithium ion conductivities yet observed among polymer electrolytes. 13 refs. 11 figs., 2 tabs.
Date: July 1, 1991
Creator: Farrington, G.C. (Pennsylvania Univ., Philadelphia, PA (United States). Dept. of Materials Science and Engineering)
Partner: UNT Libraries Government Documents Department

Wetting and dispersion in ceramic/polymer melt injection molding systems

Description: This program had two major areas of emphasis: (1) factors influencing state of particulate dispersion and rheological properties of ceramic powder/polymer melt mixtures, and (2) effect of interfacial bonding strength on mechanical and rheological properties of ceramic particle/polymer composites. Alumina and silica in various polyethylenes were used.
Date: January 1, 1993
Creator: Sacks, M.D. (Florida Univ., Gainesville, FL (United States). Dept. of Materials Science and Engineering) & Williams, J.W. (Florida Univ., Gainesville, FL (United States). Dept. of Materials Science and Engineering 3M Co., St. Paul, MN (United States))
Partner: UNT Libraries Government Documents Department

Multidisciplinary study of phase separation in a supersaturated Ni-Si alloy

Description: The subject of {gamma}{prime} precipitation in a Ni-12.5 at. % Si alloy has been studied by modern diffraction and scattering techniques in the small-angle and large angle regimes, and by transmission electron microscopy. Special attention is placed upon the mechanism and kinetic evolution of {gamma}{prime} precipitates as a function of ageing conditions. Methods are shown for the determination of interdiffusion coefficient, the interfacial energy and the coherent solubility. The strain effect, due to lattice mismatch, on the spatial correlation and preferred alignment of precipitates is addressed. Scaling law for the particle growth has been tested against the current theories. Results obtained from the three mutually beneficial techniques are shown to be consistent, thereby allowing an integral view of the phase separation process in this system. 29 refs., 19 figs., 3 tabs.
Date: July 1, 1990
Creator: Chen, Haydn (Illinois Univ., Urbana, IL (USA). Dept. of Materials Science and Engineering) & Epperson, J.E. (Argonne National Lab., IL (USA))
Partner: UNT Libraries Government Documents Department

Simultaneous chromizing-aluminizing coating of low alloy steels by a halide-activated pack cementation process

Description: The simultaneous chromizing-aluminizing of low-alloy steels has achieved Kanthal-like surface compositions of 16--2lCr and 5--8 wt%Al by the use of cementation packs with a Cr-Al masteralloy and an NH[sub 4]Cl activator salt. An initial preferential deposition of Al into the alloy induces the phase transformation from austenite to ferrite at the 1150[degrees]C process temperature. The low solubility of carbon in ferrite results in the rejection of solute C into the core of the austenitic substrate, thereby preventing the formation of an external Cr-carbide layer, which would otherwise block aluminizing and chromizing. The deposition and rapid diffusion of Cr and Al into the external bcc ferrite layer follows. Parabolic cyclic oxidation kinetics for alumina growth in air were observed over a wide range of relatively low temperatures (637--923[degrees]C).
Date: November 1, 1992
Creator: Geib, F.D. & Rapp, R.A. (Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering)
Partner: UNT Libraries Government Documents Department

The microindentation behavior of several mollusk shells

Description: An investigation of the relationship between structure and mechanical behavior is reported for mollusk shells employing foliated, nacreous, and crossed-lamellar structures by microindentation in the Knoop and Vickers geometries. Indentation damage zones develop crack systems that reflect the micro-architecture. For the crosed-lamellar structure, the system of cracks about the indentation normally developed in a brittle material is suppressed. Previous reports that shells are harder than the corresponding minerals, calcite and aragonite, are confirmed, but it is found that this effect can be strongly dependent on orientation. This anomalous hardness is not an artifact of the indentation test technique, since scratch tests confirm the relative hardness of shell over the mineral. It is suggested that microstructural organization is of central importance in producing this hardness, as opposed to intrinsic properties of the mineral or matrix phases. 17 refs., 6 figs., 1 tab.
Date: January 1, 1990
Creator: Laraia, V.J. & Heuer, A.H. (Case Western Reserve Univ., Cleveland, OH (USA). Dept. of Materials Science and Engineering)
Partner: UNT Libraries Government Documents Department

Microstructural influence on the work hardening of aluminum-lithium alloy 2090 at cryogenic temperatures

Description: Previous studies indicate that the work hardening characteristics of a Vintage III 2090-T81 12.7-mm (0.5-in.) plate is highly dependent on the through-thickness position. This dependency has been linked to two distinctly different microstructures existing as laminates within the plate. An investigation of the two microstructures by both optical and transmission electron microscopy reveal a difference in the distribution of grains and subgrains. It is believed that these factors affect the work hardening characteristics by governing the manner in which slip is transmitted from grain to grain. The findings are positive as they suggest a practical means by which improvements in work hardening can be obtained through modifications of the microstructure at the polygranular level. 24 refs., 7 figs.
Date: June 1, 1991
Creator: Chu, D.; Tseng, C.T. & Morris, J.W. Jr. (Lawrence Berkeley Lab., CA (United States) California Univ., Berkeley, CA (United States). Dept. of Materials Science and Engineering)
Partner: UNT Libraries Government Documents Department

Atomic structures and compositions of internal interfaces

Description: This research program addresses fundamental questions concerning the relationships between atomic structures and chemical compositions of metal/ceramic heterophase interfaces. The chemical composition profile across a Cu/MgO {l brace}111{r brace}-type heterophase interface, produced by the internal oxidation of a Cu(Mg) single phase alloy, is measured via atom-probe field-ion microscopy with a spatial resolution of 0.121 nm; this resolution is equal to the interplanar space of the {l brace}222{r brace} MgO planes. In particular, we demonstrate for the first time that the bonding across a Cu/MgO {l brace}111{r brace}-type heterophase interface, along a <111> direction common to both the Cu matrix and an MgO precipitate, has the sequence Cu{vert bar}O{vert bar}Mg{hor ellipsis} and not Cu{vert bar}Mg{vert bar}O{hor ellipsis}; this result is achieved without any deconvolution of the experimental data. Before determining this chemical sequence it was established, via high resolution electron microscopy, that the morphology of an MgO precipitate in a Cu matrix is an octahedron faceted on {l brace}111{r brace} planes with a cube-on-cube relationship between a precipitate and the matrix. First results are also presented for the Ni/Cr{sub 2}O{sub 4} interface; for this system selected area atom probe microscopy was used to analyze this interface; Cr{sub 2}O{sub 4} precipitates are located in a field-ion microscope tip and a precipitate is brought into the tip region via a highly controlled electropolishing technique.
Date: March 1, 1992
Creator: Seidman, D.N. (Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering) & Merkle, K.L. (Argonne National Lab., IL (United States))
Partner: UNT Libraries Government Documents Department

Ion mixing of semiconductor layered-structures

Description: This research is a collaborative program between the University of California at San Diego and Cornell University to investigate the phenomenon of ion mixing in semiconductor layered structures. The research effort also involves interactions with Oak Ridge National Laboratory under the Surface Modification and Characterization Collaborative Research Center Program. During the current period of investigation, we investigated parameters that could affect ion-mixing rates in semiconductors. We found that the use of shallow dopants as the mixing ion did not increase the mixing rate, thus indicating that electrically active ions (or the Fermi level) do not play a significant role in ion-mixing. On the other hand, the presence of mismatch strain in Ge/Si layered structures can affect the mixing rate, especially in the temperature independent regime. Mismatch strain can also affect the solid-phase regrowth kinetics of amorphous layers of Ge-Si alloys. In summary, we found that ion mixing kinetics depend primarily on the ion and the target mass and the target temperature. Mixing rates can also be affected, to a certain extent, by thermodynamic driving forces (such as the cohesive energy and the stored strain energy of the system). Impurities do no play a significant role in mixing kinetics. 1 fig., 1 tab.
Date: January 1, 1991
Creator: Lau, S.S. (California Univ., San Diego, La Jolla, CA (United States)) & Mayer, J.W. (Cornell Univ., Ithaca, NY (United States). Dept. of Materials Science and Engineering)
Partner: UNT Libraries Government Documents Department

Atomic structures and compositions of interfaces

Description: This research program focuses on an experimental study of the structure and chemistry of metal/metal oxide internal interfaces; the latter are mainly created, although not exclusively, by internal oxidation of binary or ternary metal alloys that are solid-solution phases prior to the internal oxidation treatment. The principal research tools are transmission electron microscopy (TEM), high resolution microscopy (HREM), analytical electron microscopy (AEM) and atom-probe field-ion microscopy (APFIM). The APFIM technique is used to determine the chemical composition of the interfacial region on an atomic scale. Initial studies are foucused on Pd/NiO, Cu/MgO, Cu/Al{sub 2}O{sub 3}, Cu/SiO{sub 2} interfaces, as well as metal oxides in Pt-based alloys. Topics of importance include coherency effects, misfit dislocations, structure of the terminating layer between the metal and the metal oxide, microstoichiometry, dipole space charge effects, and distributions of impurities and point defects at the interfacial region.
Date: September 1, 1990
Creator: Seidman, D.N. (Northwestern Univ., Evanston, IL (United States). Dept. of Materials Science and Engineering) & Merkle, K.L. (Argonne National Lab., IL (United States))
Partner: UNT Libraries Government Documents Department

Is K[sub 3]C[sub 60] a line phase

Description: We present x-ray diffraction evidence that K[sub I]C[sub 60] with x as low as 1.6 exhibits phase-pure fcc structures over some temperature range. These results have implications for the equilibrium binary phase diagram, and for the possibility of testing the hypothesis that fullerene superconductors are doped Mott-Hubbard insulators.
Date: January 1, 1993
Creator: Zhu, Q.; Fischer, J.E. (Pennsylvania Univ., Philadelphia, PA (United States). Dept. of Materials Science and Engineering) & Cox, D.E. (Brookhaven National Lab., Upton, NY (United States))
Partner: UNT Libraries Government Documents Department

Free energy simulation of grain boundary segregation and thermodynamics in Ni sub 3-x Al sub 1+x

Description: The free energy simulation method is employed to study segregation to {Sigma}5 and {Sigma}13 (001) twist grain boundaries and their free energies in ordered Ni{sub 3-x}Al{sub 1+x}. In the temperature range studied (300--900K), it is shown that there is almost no segregation, strong Al segregation, and weak Ni segregation to the grain boundary for the stoichiometric, Al-rich, and Ni-rich bulk compositions respectively. It is also shown that the segregation is limited to a few (002) planes around the grain boundary and its magnitude decreases with increasing temperature. For Al-rich bulk composition, it is demonstrated that segregation at low temperature substantially lowers the grain boundary free energy. 8 refs., 7 figs.
Date: January 1, 1990
Creator: Najafabadi, R.; Wang, H.Y.; Srolovitz, D.J. (Michigan Univ., Ann Arbor, MI (USA). Dept. of Materials Science and Engineering) & LeSar, R. (Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

Modeling of transformation toughening in brittle materials

Description: Results from modeling of transformation toughening in brittle materials using a discrete micromechanical model are presented. The material is represented as a two-dimensional triangular array of nodes connected by elastic springs. Microstructural effects are included by varying the spring parameters for the bulk, grain boundaries, and transforming particles. Using the width of the damage zone and the effective compliance (after the initial creation of the damage zone) as measures of fracture toughness, we find that there is a strong dependence of toughness on the amount, size, and shape of the transforming particles, with the maximum toughness achieved with the higher amounts of the larger particles.
Date: January 24, 1992
Creator: LeSar, R.; Rollett, A.D. (Los Alamos National Lab., NM (United States)) & Srolovitz, D.J. (Michigan Univ., Ann Arbor, MI (United States). Dept. of Materials Science and Engineering)
Partner: UNT Libraries Government Documents Department

In-situ observations of high temperature surface processes on. alpha. -alumina bulk crystals

Description: Reflection electron microscopy (REM) was applied to image in-situ the dynamic changes of atomic-height steps on the surfaces of {alpha}-alumina bulk crystals heated to high temperatures. Atomic diffusion, desorption and adsorption processes on cleaved {alpha}-alumina (012) surfaces were directly observed at temperatures of 1470 to 1670 K. The surface started to show visible structural changes at 1470--1520 K. The main surface process appears to be atomic desorption, which creates large, flat vacancy-type terraces on the surface. 7 refs., 6 figs.
Date: January 1, 1990
Creator: Wang, Z.L. (Oak Ridge National Lab., TN (USA) Tennessee Univ., Knoxville, TN (USA). Dept. of Materials Science and Engineering) & Bentley, J. (Oak Ridge National Lab., TN (USA))
Partner: UNT Libraries Government Documents Department

Dynamical simulation of dislocation microstructure

Description: We report the development of a computer simulation technique to model the motion of a large number of mutually interacting dislocations under the influence of an applied stress. The dislocation motion is simulated using a method akin to molecular dynamics except that dislocation coordinates are employed instead of atomic coordinates. The formation of dislocation substructure is studied as a function of applied stress and density and the resulting spatial distribution of dislocations is analyzed. 5 refs., 3 figs.
Date: January 1, 1989
Creator: Gulluglo, A.; Srolovitz, D.J.; LeSar, R.; Lomdahl, P.S. (Michigan Univ., Ann Arbor, MI (USA). Dept. of Materials Science and Engineering & Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department

Mechanisms for cleavage and intergranular embrittlement in Fe

Description: The mechanism of cleavage in bcc Fe has been investigated with electronic structure calculations and compared to similar calculations modeling cleavage in other bcc materials (Li, Nb, Mo). It has been found in the BCC materials we have studied that those known to undergo (100) cleavage show enhancement of the density of states (DOS) on the virtual surface layer as the material is strained to failure. Using total energy calculations it is shown that there is a point of inflection (corresponding to the point of maximum force versus displacement) in the total energy at nearly the same point as the maximum enhancement in the DOS. We conjecture that this point represents the transition state for the fracture process. Extending these ideas, the electronic structure near a Fe(111) grain boundary has been calculated both with and without segregated P. We find clear evidence for the formation of a P band of states, suggesting the existence of P-P interactions within the segregated layer. A chemical model of strain-induced bond failure is suggested in which bonds parallel to the fracture surface compete with the cohesive Fe-Fe bonds normal to the surface. 7 refs., 5 figs.
Date: January 1, 1987
Creator: Eberhart, M.E.; MacLaren, J.M. (Massachusetts Inst. of Tech., Cambridge, MA (USA). Dept. of Materials Science and Engineering & Los Alamos National Lab., NM (USA))
Partner: UNT Libraries Government Documents Department