3,539 Matching Results

Search Results

Advanced search parameters have been applied.

in subjects: "Crystal Structure"

open access

Performance aspects of de Laval spray-forming nozzles

Spray forming is a multiphase fabrication technology in which a spray of finely atomized liquid droplets is directed onto a suitably shaped substrate or pattern to produce a coherent, near-net-shape deposit The technology can simplify materials processing where simultaneously improving product quality. Researchers at the Idaho National Engineering Laboratory (INEL) are developing spray-forming technology for producing near-net-shape solids and coatings of a variety of metals, polymers, and comp… more

Date: January 1, 1993

Creator: McHugh, K.M. & Key, J.F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Solidification behavior and microstructural analysis of austenitic stainless steel laser welds

Solidification behavior of austenitic stainless steel laser welds has been investigated with a high-power laser system. The welds were made at speeds ranging from 13 to 60 mm/s. The welds sowed a wide variety of microstructural features. The ferrite content in the 13-mm/s weld varied from less than 1% at the root of the weld to about 10% at the crown. The duplex structure at the crown of the weld was much finer than the one observed in conventional weld metal. However, the welds made at 25 and … more

Date: January 1, 1981

Creator: David, S.A. & Vitek, J.M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Multilayer relaxation in metallic surfaces as demonstrated by LEED analysis

Theoretical motivations are reviewed for investigation of multilayer relaxation in relatively simple metallic surfaces. Results from LEED analyses are presented which serve to demonstrate that multilayer relaxation measurably exists in Cu(100) and Cu(110) surfaces. The results from two independent LEED analyses for Cu(110) are shown to be in much better agreement with each other than the LEED results are with multilayer relaxation results obtained by high energy ion scattering. Multilayer relax… more

Date: July 1, 1982

Creator: Davis, H. L. & Noonan, J. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Atomic bonding at ceramic interfaces using scanning tunnelling microscopy

Progress made during Space charge calculations are given for pure SrTiO3. The first two years of the above listed grant can be considered in terms of three approaches which converge in the third year. Specifically, results in STM analyses of oxide grain boundaries, in design and construction of a new microscope, and in theoretical calculations of space charge are summarized here. For clarity, calculation methodology is detailed in Appendix I. Publications, presentations, supported students are … more

Date: February 1, 1992

Creator: Bonnell, D. A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Effects of temperature and impurities on the atomic displacement energy during electron irradiation

The threshold energy for Frenkel pair production (E/sub d/) is a parameter of importance when theoretical calculations of displacement damage rates are needed to predict long term radiation effects in materials. Hence it is desirable to understand how the threshold energy may be affected by important environmental factors such as temperature and impurities. Copper and Cu--Al alloys were studied as model pure metal and metal-impurity systems. Irradiations were performed in a high voltage electro… more

Date: June 1, 1977

Creator: Drosd, R. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Constant stress of XD trademark TiAl containing nitrogen

Ti-47at%Al+7vol%(TiN+TiB{sub 2}) alloys, produced by the Martin Marietta XD{trademark} process, were subjected to tensile constant stress creep deformation in the range 760--850{degree}C temperature and 138--276 MPa (20--40 ksi) stress. These alloys have a matrix of TiAl and Ti{sub 3}Al initially containing 1 to 10 {mu}m diameter equiaxed particles of TiB{sub 2} and Ti{sub 2}AlN. Microstructures were examined using optical, SEM and TEM methods in an attempt to correlate the substructures with t… more

Date: January 1, 1990

Creator: Robertson, E. & Martin, P. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Modeling shockwave deformation via molecular dynamics

Molecular dynamics (MD), where the equations of motion of up to thousands of interacting atoms are solved on the computer, has proven to be a powerful tool for investigating a wide variety of nonequilibrium processes from the atomistic viewpoint. Simulations of shock waves in three-dimensional (3D) solids and fluids have shown conclusively that shear-stress relaxation is achieved through atomic rearrangement. In the case of fluids, the transverse motion is viscous, and the constitutive model of… more

Date: January 1, 1987

Creator: Holian, B. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Preliminary report: examination of H8 and B8 leadscrews from Three Mile Island Unit 2 (TMI-2)

One of the TMI-2 core examination tasks is the analysis of the control rod drive leadscrews, which were removed from the reactor head as part of the July 1982 closed-circuit television inspection of the damaged core. One leadscrew was removed from each of three different core positions: H8, from the center of the core; E9, from approximately midradius; and B8, from near the outer edge. This report presents and discusses the following: leadscrew acquisition, sample types, and analytical techniqu… more

Date: April 1, 1985

Creator: Vinjamuri, K.; Akers, D. W. & Hobbins, R. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Magnetism of thin film multilayers: An analogue of interacting platelets

Progress is being made toward manufacturing materials with magnetic properties tailored to the desired application. This result is reached in several steps, which are monitored with different optical techniques such as polarized neutron reflectometry. First, ferromagnetic, metallic films (of Fe, Co, Ni, Gd), a few nanometers thick, are prepared by vapor deposition. Their magnetization can be tuned by changing the chemistry of thickness of the films, and can be biased by embedding the films into… more

Date: November 1, 1991

Creator: Felcher, G. P. & Huang, Y. Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Equivalent beam averaging (EBA) of I-V spectra for LEED analysis

An equivalent beam averaging (EBA) procedure is described which has proved to be very useful to enhance I-V profile data collected for LEED analyses. Specific analyses are documented where application of EBA has led to improved agreement between calculated and experimental I-V profiles. The procedure also has been substantiated by examination of representative I-V profiles which were calculated to correspond to the incident beam slightly misaligned from, and exactly aligned with, the surface no… more

Date: August 1, 1982

Creator: Davis, H. L. & Noonan, J. R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Leed investigation of (111) oriented Si, Ge and GaAs surfaces following pulsed laser irradiation

The low energy electron diffraction (LEED) patterns obtained from clean (111) oriented Si, Ge, and GaAs single crystals subsequent to their irradiation with the output of a pulsed ruby laser in an ultra-high vacuum (UHV) environment suggest that metastable (1 x 1) surface structures are produced in the regrowth process. Conventional LEED analyses of the Si and Ge surfaces suggest that they terminate in registry with the bulk but that the two outermost interlayer spacings differ from those of th… more

Date: November 1, 1980

Creator: Zehner, D. M.; Noonan, J. R.; Davis, H. L.; White, C. W. & Ownby, G. W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Ternary superconductors

Ternary superconductors constitute a class of superconducting compounds with exceptional properties such as high transition temperatures (approx. =15.2 K), extremely high critical fields (H/sub c2/ > 60 Tesla), and the coexistence of superconductivity and long-range magnetic order. This has generated great interest in the scientific community and resulted in a large number of experimental and theoretical investigations in which many new ternary compounds have been discovered. A review of some o… more

Date: January 1, 1986

Creator: Giorgi, A. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

In-situ study of cascade defects in silver by simultaneous transmission electron microscopy and electrical resistivity measurements at low temperatures

A helium-cooled double-tilt specimen stage for transmission electron microscopy (TEM) with the capability of simultaneous electrical resistivity measurements was constructed and used to study defect-production, migration, clustering and recovery processes in ion-irradiated silver. Vacuum-evaporated thin film specimens were irradiated with 1 MeV Kr -ions up to a dose of 4.0 x 10 ions/cmS, at T = 10K in the microscope, using the HVEM-tandem accelerator ion beam interface system in the Argonne Nat… more

Date: December 1, 1985

Creator: Haga, K.; King, Wayne E.; Merkle, K. L. & Meshii, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Laser-Zone Growth in a Ribbon-to-Ribbon (Rtr) Process. Silicon Sheet Growth Development for the Large Area Silicon Sheet Task of the Low-Cost Silicon Solar Array Project. Technical Quarterly Report No. 7, January 1--March 31, 1978. Motorola Report No. 2256/9

Substantial progress has been made both in crystal growth and in processing. A growth rate of 12.5 cm/min with 2 cm wide ribbon was achieved. This high growth-rate ribbon has a dendritic structure. The maximum non-dentritic growth rate was increased to 8 to 9 cm/min by using active cooling (inert gas jets) to steepen the postheater temperature gradient. Also, RTR ribbon was grown from 2.5 cm wide CVD polycrystalline feedstock. Doped CVD feedstock can now be grown in widths from 1 in. to 3 in., … more

Date: January 1, 1978

Creator: Gurtler, R. W.; Baghdadi, A.; Legge, R.; Sopori, B. & Ellis, R. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The Oxidation Behavior of Tungsten and Germanium Alloyed Molybdenum Disilicide Coatings

A two-step coating process was used to produce a (Mo,W)(Si,Ge){sub 2} coating on niobium. After exposure to high temperatures, a lower silicide layer forms underneath and is effective in arresting cracks. The oxidation weight-gain kinetics are parabolic following an initial transient period. Test coupons coated with (Mo,W)(Si,Ge){sub 2} passed 200 one-hour cycles at 1370{degree}C and 60 one-hour cycles at 1540{degree}C. These results, along with evidence of a thick protective glass layer, sugge… more

Date: November 1, 1991

Creator: Mueller, A.; Wang, Ge; Rapp, R. A.; Courtright, E. L. & Kircher, T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Study of solid metal/ceramic reactions. Progress report, March 17, 1980-January 15, 1981

This study is concerned with the solid state reactions between silicon-based structural ceramics and a simple model superalloy. During this past year, considerable effort was devoted to phase identification using microprobe, x-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM) analyis techniques. The relatively simple Si-C-Ni-Cr-Al system was found to be even more complex than anticipated, with at least 14 individual phases identi… more

Date: January 26, 1981

Creator: Mehan, R. L. & Jackson, M. R.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

High Temperature Properties and Processes in Ceramics: Thermomigration. Annual Report, April 1, 1976--December 31, 1976. [Summary of Research Activities at MIT]

A summary is given of research progress in the following areas: thermal gradients and defects in FeO, thermomigration in Fe--Al spinels, application of an ion microprobe to analysis of concentration gradients in ceramics, and anion self-diffusion in aluminium oxide. (SDF)

Date: January 1, 1976

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Research on Mechanisms of Stress Corrosion Cracking in Zircaloy

The results of internal gas pressurization tests, primarily at 320/sup 0/C, on cladding tubes from two suppliers, Supplier A and Supplier B, are presented. The two lots show a substantial difference in iodine SCC susceptibility so a test matrix is used to resolve the relative contributions of surface condition, residual stress, and texture. Additional tests with constant deflection split-ring specimens and with unstressed cladding segments are used to understand crack initiation and the early c… more

Date: June 1, 1981

Creator: Knorr, D. B. & Pelloux, R. M.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Grain Boundaries in Complex Oxides

A quantitative comparison was achieved between space charge theory and segregation at grain boundaries in the model system TiO[sub 2]. The ionic space charge can be titrated from negative to positive potential. A space charge model was developed that includes the lattice defect chemistry. Defect formation energies in the Frenkel pair for TiO[sub 2] were studied. Grain boundary enthalpy was measured during coarsening. It was shown that it is the barium vacancy that forms near surfaces in donor-d… more

Date: May 1, 1993

Creator: Chiang, Yet-Ming.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Ground Boundaries

The present document is a progress report describing the work accomplished on the study of grain boundaries in Ag, Au, Ni, Si, and Ge. Research was focused on the following four major efforts: study of the atomic structure of grain boundaries by means of x-ray diffraction, transmission electron microscopy and computer modeling; grain boundary migration; short-circuit diffusion along grain boundaries; and development of Thin-Film Deposition/Bonding Apparatus for the manufacture of high purity bi… more

Date: January 1, 1990

Creator: Balluffi, R.W. & Bristowe, P.D.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

The role of <100> edge dislocations in nucleating radiation-induced colloid particles in sodium chloride

A theoretical program to investigate the role of dislocations in the nucleation of sodium colloids in irradiated rock salt has been outlined. As the first study in the investigation the interaction of radiation-produced defects with the <001> edge dislocation in rock salt, i.e., the edge dislocation in the principal slip system of NaCl, has been considered. The interaction potential between a symmetric defect and the <001> edge dislocation has been determined on the basis of anisotropic elastic… more

Date: September 1, 1982

Creator: Teutonico, L. J.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Electronic structure studies of high-T/sub c/ perovskites and related materials

We have performed 2D-ACPAR measurements on La/sub 2/CuO/sub 4/ and NiO. The ACPAR distributions were very isotropic, with small anisotropic deviations on the order of 10% of the total counts. It was not possible to clearly discern a Fermi surface in either set of data, nor was it possible to identify any features with the symmetry and periodicity of the crystalline reciprocal lattices. Attempts to model both systems by starting with a localized ionic picture and allowing covalency overlap to ta… more

Date: October 1, 1988

Creator: Wachs, A. L.; Turchi, P. E. A.; Kaiser, J. H.; West, R. N.; Howell, R. H.; Jean, Y. C. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Materials Dependence of Deformation Texture Development in Various Deformation Modes

Attempts to understand the development of deformation textures have long been hampered by the following dichotomy: in theory, one expects orientation changes to be governed entirely by the geometry of deformation and thus to be the same for all materials of the same lattice structure and the same deformation modes; yet in experiments, one observes differences between different materials of the same lattice structure. The current work represents an effort to address this problem anew. Four fcc s… more

Date: January 1, 1987

Creator: Stout, M.G.; Kallend, J.S.; Kocks, U.F.; Przystupa, M.A. & Rollett, A.D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Irradiation-induced segregation in Ni--Si alloys. [525/sup 0/C with 3 MeV /sup 58/Ni/sup +/ ions]

Radiation-induced segregation was studied in an Ni-1 at. % Si alloy after irradiation at a temperature of approximately 525/sup 0/C with 3-MeV /sup 58/Ni/sup +/ ions. Profiles of alloy composition as a function of depth from the irradiated surface were obtained by standard Auger techniques and ion-sputtering at room temperature. Rapid segregation of Si toward the irradiated surface was observed. The solubility limit of Si in Ni was reached at the surface after a dose of only 0.05 dpa. Segregati… more

Date: January 1, 1978

Creator: Rehn, L. E.; Okamoto, P. R.; Potter, D. I. & Wiedersich, H.

Item Type: Article

Partner: UNT Libraries Government Documents Department