350 Matching Results

Search Results

Advanced search parameters have been applied.

Oblique ion texturing of yttria-stabilized zirconia: The {l_brace}211{r_brace}<111> structure

Description: Amorphous (Zr,Y)O{sub x} films were synthesized by reactive magnetron sputtering and subsequently crystallized by oblique ion bombardment. Crystalline texture nucleated by the ion beam was replicated by solid-phase epitaxial growth throughout the formerly amorphous yttria-stabilized zirconia (YSZ) film. The resulting YSZ films have (211) orientation normal to the substrate with in-plane directions (111), parallel, and (110), transverse, to the azimuth of the ion beam. We hypothesize that the texture mechanism involves ion-induced film compression and shear. The results, taken together with prior work, show that oblique ion texturing of amorphous films is a general phenomenon that can be used to fabricate substrates with more than one type of crystallographic orientation.
Date: July 1, 2002
Creator: Berdahl, Paul; Reade, Ronald P.; Liu, Jinping; Russo, Richard E.; Fritzemeier, Les; Buczek, David et al.
Partner: UNT Libraries Government Documents Department

Characterization of microstructure and crack propagation in alumina using orientation imaging microscopy (OIM). December 1996

Description: A more complete description requires the lattice orientations of a statistically significant number of grains, coupled with morphology such as grain size and shape; this can be obtained using orientation imaging microscopy (OIM), which uses crystallographic orientation data from Backscattered Electron Kikuchi patterns (BEKP) collected using a SEM. This report describes the OIM results for alumina; these include image quality maps, grain boundary maps, pole figures, and lattice misorientations depicted on MacKenzie plot and in Rodrigues space. High quality BEKP were obtained and the images and data readily reveal the grain morphology, texture, and grain boundary misorientations, including those for cracked boundaries. A larger number of grains should be measured to make statistical comparisons between materials with different processing histories.
Date: December 1, 1996
Creator: Glass, S.J.; Michael, J.R.; Readey, M.J.; Wright, S.I. & Field, D.P.
Partner: UNT Libraries Government Documents Department

Modeling of the recrystallization textures of Al-alloys after hot deformation

Description: The recrystallization textures of Al-alloys can be explained by a growth selection of grains with an approximate 40{degree}<111> orientation relationship out of a limited spectrum of preferentially formed nucleus orientations. Accordingly, recrystallization textures can be modeled by the multiplication of a function f(g){sup nucl} describing the probability of nucleation of the various orientations with a function f(g){sup grow} representing their growth probability. Whereas the growth probability can be accounted for by a 40{degree}<111> transformation of the rolling texture, the nucleation probability of the respective grains is given by the distribution of potential nucleus orientations, which is known from local texture analysis for the most important nucleation sites in rolled Al-alloys, cube-bands, grain boundaries and second-phase particles. The contribution of each of these nucleation sites are determined according to an approach to calculate the number of nuclei forming at each nucleation site, which is based on microstructural investigations on the evolution of the various nucleation sites during deformation. The paper describes the model for recrystallization texture simulation in Al-alloys and gives examples of recrystallization textures of AA3004 deformed in plane strain compression at a variety of different deformation temperatures and strain rates.
Date: December 1, 1998
Creator: Engler, O. & Vatne, H.E.
Partner: UNT Libraries Government Documents Department

Design of surface texture for improved control of friction and formability of aluminum sheet products for automotive applications. Final technical report for period September 15, 1996 - July 14, 2000

Description: The frictional properties of interfaces are of interest in a broad range of applications. We have formulated a new plasticity model for interface friction and applied it to represent the frictional characteristics of A16111-T4 sheet against D2 tool steel for sheet forming applications.
Date: September 12, 2001
Creator: Anand, L.
Partner: UNT Libraries Government Documents Department

Tests of quark mass textures

Description: The classic hints on the structure of the quark mass matrices are shortly reviewed and the possibility of obtaining further information through precise texture analysis is discussed with the aid of a specific example.
Date: December 21, 2000
Partner: UNT Libraries Government Documents Department

Spatial Variation of Soil Type and Soil Moisture in the Regional Atmospheric Modeling System

Description: Soil characteristics (texture and moisture) are typically assumed to be initially constant when performing simulations with the Regional Atmospheric Modeling System (RAMS). Soil texture is spatially homogeneous and time-independent, while soil moisture is often spatially homogeneous initially, but time-dependent. This report discusses the conversion of a global data set of Food and Agriculture Organization (FAO) soil types to RAMS soil texture and the subsequent modifications required in RAMS to ingest this information. Spatial variations in initial soil moisture obtained from the National Center for Environmental Predictions (NCEP) large-scale models are also introduced. Comparisons involving simulations over the southeastern United States for two different time periods, one during warmer, more humid summer conditions, and one during cooler, dryer winter conditions, reveals differences in surface conditions related to increases or decreases in near-surface atmospheric moisture con tent as a result of different soil properties. Three separate simulation types were considered. The base case assumed spatially homogeneous soil texture and initial soil moisture. The second case assumed variable soil texture and constant initial soil moisture, while the third case allowed for both variable soil texture and initial soil moisture. The simulation domain was further divided into four geographically distinct regions. It is concluded there is a more dramatic impact on thermodynamic variables (surface temperature and dewpoint) than on surface winds, and a more pronounced variability in results during the summer period. While no obvious trends in surface winds or dewpoint temperature were found relative to observations covering all regions and times, improvement in surface temperatures in most regions and time periods was generally seen with the incorporation of variable soil texture and initial soil moisture.
Date: June 27, 2001
Creator: Buckley, R.
Partner: UNT Libraries Government Documents Department

Surface Textures of Unglazed Pottery

Description: This study, "Surface Textures of Unglazed Pottery," will record and evaluate a series of experiments performed that can be achieved on unglazed ceramic ware....The problem will be limited to experiments using a red clay from Horatio, Arkansas, a buff clay from Trenton, New Jersey, and a tan clay from Athens, Texas. The specimens will be fired at the temperature of 1643 degrees Fahrenheit...Experiments performed with the three clays will fall into three categories: (1) textures resulting from introduction of foreign matter into the clay (2) textures resulting from surface treatments of green ware and (3) textures resulting from surface treatments of bisque-fired ware. The experiments will be described and the fired clay specimens -- tiles 2"x2"x1/4" will be evaluated according to esthetic and practical standards.
Date: August 1957
Creator: Poole, Jerry Dwayne
Partner: UNT Libraries

Bioremediation of Petroleum Hydrocarbons in Heterogeneous Soils

Description: Western Research Institute (WRI) in conjunction with the University of Wyoming, Department of Renewable Resources and the U.S. Department of Energy, under Task 35, conducted a laboratory-scale study of hydrocarbon biodegradation rates versus a variety of physical and chemical parameters to develop a base model. By using this model, biodegradation of Petroleum hydrocarbons in heterogeneous soils can be predicted. The base model, as developed in this study, have been tested by both field and laboratory data. Temperature, pH, and nutrients appear to be the key parameters that can be incorporate into the model to predict biodegradation rates. Results to date show the effect of soil texture and source on the role of each parameter in the rates of hydrocarbon biodegradation. Derived from the existing study, an alternative approach of using CO{sub 2} accumulation data has been attempted by our collaborators at the University of Wyoming. The model has been modified and fine tuned by incorporating these data to provide more information on biodegradation.
Date: March 2, 2006
Creator: Jin, Song; Fallgren, Paul & Brown, Terry
Partner: UNT Libraries Government Documents Department

Development of texture during deformation of hexagonal close packed metals.

Description: Goals of this work: 1. Gain understanding of microscopic deformation mechanisms in anisotropic materials. 2. Create model which may be used as a resource for Finite Element Codes.
Date: January 1, 2002
Creator: Brown, D. W. (Donald W.); Agnew, S. R. (Sean R.); Blumenthal, W. R. (William R.); Holden, T. M. (Thomas M.); Tomé, C. N. (Carlos Norberto), & Bourke, M. A. (Mark A.)
Partner: UNT Libraries Government Documents Department

Multi-Grained Level of Detail for Rendering Complex Meshes Using a Hierarchical Seamless Texture Atlas

Description: Previous algorithms for view-dependent level of detail provide local mesh refinements either at the finest granularity or at a fixed, coarse granularity. The former provides triangle-level adaptation, often at the expense of heavy CPU usage and low triangle rendering throughput; the latter improves CPU usage and rendering throughput by operating on groups of triangles. We present a new multiresolution hierarchy and associated algorithms that provide adaptive granularity. This multi-grained hierarchy allows independent control of the number of hierarchy nodes processed on the CPU and the number of triangles to be rendered on the GPU. We employ a seamless texture atlas style of geometry image as a GPU-friendly data organization, enabling efficient rendering and GPU-based stitching of patch borders. We demonstrate our approach on both large triangle meshes and terrains with up to billions of vertices.
Date: November 6, 2006
Creator: Niski, K; Purnomo, B & Cohen, J
Partner: UNT Libraries Government Documents Department

Crystallographic texture effects on mixed-mode strain localization for lower-symmetry metals

Description: A bifurcation analysis is used to understand the damage realized in flatplate gas-gun specimens that were machined from a highly-textured plate stock of Zr. These low-symmetry material specimens were tested to insipient failure and subsequently soft-recovered. Post-mortem data sets consisting of EBSD imaging of metallographic samples cut from the recovered targets show very different texture-dependent damage morphologies depending on the initial texturekarget orientation at impact.
Date: January 1, 2003
Creator: Maudlin, P. J. (Paul J.); Mason, T. A. (Thomas A.); Gray, G. T. (George T.), III; Bourne, N. K. & Bingert, J. F. (John F.)
Partner: UNT Libraries Government Documents Department

Sensitivity of Simulated Anisotropy to Initial Texture Definitions

Description: Free compression tests were performed on 0.040 inch thick 5754 aluminum sheet stock producing a slight in-plane anisotropy. A visco-plastic self-consistent (VPSC) deformation modeling code was used to model the mechanical properties and resultant deformation textures. Calculations using a discretized description of the initial texture simulated the deformation texture very closely. Simulation of the mechanical properties were also captured nicely with one exception. The direction of simulated in-plane anisotropy was reversed from the experimental results. Simulation of the impact of various texture components on the anisotropy indicted that the shift of texture toward stronger brass, {l_brace}110{r_brace}&lt;112&gt;, and Goss, {l_brace}110{r_brace}&lt;001&gt;, components led to the reversal of anisotropy. The simulated deformation texture was more intense than the experimental texture in the brass and Goss positions. This result suggests that the more intense simulated texture components may be responsible for the reversal of an isotropy.
Date: August 1, 1999
Creator: Necker, C.T.; Tome, C.N.; Jean-Prost, F. & Korzekwa, D.A.
Partner: UNT Libraries Government Documents Department

In-situ Phase Transformation and Deformation of Iron at High Pressure andTemperature

Description: With a membrane based mechanism to allow for pressure change of a sample in aradial diffraction diamond anvil cell (rDAC) and simultaneous infra-red laser heating, itis now possible to investigate texture changes during deformation and phasetransformations over a wide range of temperature-pressure conditions. The device isused to study bcc (alpha), fcc (gamma) and hcp (epislon) iron. In bcc iron, room temperature compression generates a texture characterized by (100) and (111) poles parallel to the compression direction. During the deformation induced phase transformation to hcp iron, a subset of orientations are favored to transform to the hcp structure first and generate a texture of (01-10) at high angles to the compression direction. Upon further deformation, the remaining grains transform, resulting in a texture that obeys the Burgers relationship of (110)bcc // (0001)hcp. This is in contrast to high temperature results that indicate that texture is developed through dominant pyramidal&lt;a+c&gt; {2-1-12}&lt;2-1-13&gt; and basal (0001)-{2-1-10} slip based on polycrystal plasticity modeling. We also observe that the high temperature fcc phase develops a 110 texture typical for fcc metals deformed in compression.
Date: July 1, 2008
Creator: Miyagi, Lowell; Kunz, Martin; Knight, Jason; Nasiatka, James; Voltolini, Marco & Wenk, Hans-Rudolf
Partner: UNT Libraries Government Documents Department

Melt-processing high-T{sub c} superconductors under an elevated magnetic field [Final report no. 2]

Description: This report presents models for crystallographic texture development for high temperature superconducting oxides processed in the absence of a magnetic field and in the presence of a high magnetic field. The results of the models are confirmed through critical experiments. Processing thick films and tapes of high temperature superconducting oxides under a high magnetic field (5-10T) improves the critical current density exhibited.
Date: September 5, 2001
Creator: Sande, John B. Vander
Partner: UNT Libraries Government Documents Department

High Rate Laser Pitting Technique for Solar Cell Texturing

Description: High rate laser pitting technique for solar cell texturing Efficiency of crystalline silicon solar cells can be improved by creating a texture on the surface to increase optical absorption. Different techniques have been developed for texturing, with the current state-of-the-art (SOA) being wet chemical etching. The process has poor optical performance, produces surfaces that are difficult to passivate or contact and is relatively expensive due to the use of hazardous chemicals. This project shall develop an alternative process for texturing mc-Si using laser micromachining. It will have the following features compared to the current SOA texturing process: -Superior optical surfaces for reduced front-surface reflection and enhanced optical absorption in thin mc-Si substrates -Improved surface passivation -More easily integrated into advanced back-contact cell concepts -Reduced use of hazardous chemicals and waste treatment -Similar or lower cost The process is based on laser pitting. The objective is to develop and demonstrate a high rate laser pitting process which will exceed the rate of former laser texturing processes by a factor of ten. The laser and scanning technologies will be demonstrated on a laboratory scale, but will use inherently technologies that can easily be scaled to production rates. The drastic increase in process velocity is required for the process to be implemented as an in-line process in PV manufacturing. The project includes laser process development, development of advanced optical systems for beam manipulation and cell reflectivity and efficiency testing. An improvement of over 0.5% absolute in efficiency is anticipated after laser-based texturing. The surface textures will be characterized optically, and solar cells will be fabricated with the new laser texturing to ensure that the new process is compatible with high-efficiency cell processing. The result will be demonstration of a prototype process that is suitable for scale-up to a production tool and process. The ...
Date: January 10, 2013
Creator: Herfurth, Hans J. & Pantsar, Henrikki
Partner: UNT Libraries Government Documents Department

Influence of large-strain deformation on the microstructure, texture, and mechanical response of tantalum bar

Description: Numerous studies have established the influence of impurities, crystallographic texture, temperature, and strain rate separately or collectively on the constitutive response of annealed tantalum, in particular plate Ta-stock. However, fewer detailed studies have examined the evolution of crystallographic texture and the mechanical response of tantalum bar or rod material following prestraining to large strains {epsilon} > I. In this paper the influence of large plastic prestraining on the microstructure evolution, texture evolution, and mechanical response of high-purity tantalum bar material is presented. Tantalum cylinders annealed at 1200 {degrees}C were quasi-statically upset forged, with intermediate lubrication, to true strains of 0.4, 0.95, and 1.85. Microstructural and textural banding within the starting Ta-bar was characterized in detail. It was found that different oriented bands evolved differently during large-strain forging leading to significant scatter in the mechanical response. Aspects of defect storage, work-hardening response, and texture evolution in Ta-bar as a function of forging strain are discussed.
Date: March 1, 1996
Creator: Gray, G.T. III; Bingert, S.R.; Chen, S.R.; Bingert, J.F. & Wright, S.I.
Partner: UNT Libraries Government Documents Department