Office of Scientific and Technical Information
SciTec Connect (Office of Scientific and Technical Information - OSTI, U.S. Department of Energy)Not a member yet
500 research outputs found
Sort by
Radiation Chemistry of Simulated (99)Mo Product
No full textPharrnaceuticaI houses that produce {sup 99}Tc/{sup 99}Tc generators have on occasion received {sup 99}Mo that contained a black precipitate. Addition of sodium hypochlorite to product bottles prior to shipment prevents precipitate formation, indicating the precipitate is a reduced form of Mo. The radiation effects of the dose from {sup 99}Mo on the product and product bottle have been determined by irradiating simulated {sup 99}Mo product solutions with the {sup 60}Co source at Sandia National Laboratories' Gamma Irradiation Facility (GE). The GIF experiment successfully generated a black precipitate in amounts sufficient for isolation and analysis by infrared and Rrunan spectroscopy. Changes in the pH of the basic {sup 99}Mo product solution during irradiation were monitored by titration. ResuIts of these analyses and the nature of the process that generates the precipitate, a mixture of molybdenum oxides that forms in plastic bottles, but not in glass containers, are discussed
Foam Micromechanics
No full textFoam evokes many different images: waves breaking at the seashore, the head on a pint of Guinness, an elegant dessert, shaving, the comfortable cushion on which you may be seated... From the mundane to the high tech, foams, emulsions, and cellular solids encompass a broad range of materials and applications. Soap suds, mayonnaise, and foamed polymers provide practical motivation and only hint at the variety of materials at issue. Typical of mukiphase materiaIs, the rheoIogy or mechanical behavior of foams is more complicated than that of the constituent phases alone, which may be gas, liquid, or solid. For example, a soap froth exhibits a static shear modulus-a hallmark of an elastic solid-even though it is composed primarily of two Newtonian fluids (water and air), which have no shear modulus. This apparent paradox is easily resolved. Soap froth contains a small amount of surfactant that stabilizes the delicate network of thin liq- uid films against rupture. The soap-film network deforms in response to a macroscopic strain; this increases interracial area and the corresponding sur- face energy, and provides the strain energy of classical elasticity theory [1]. This physical mechanism is easily imagined but very challenging to quantify for a realistic three-dimensional soap froth in view of its complex geome- try. Foam micromechanics addresses the connection between constituent properties, cell-level structure, and macroscopic mechanical behavior. This article is a survey of micromechanics applied to gas-liquid foams, liquid-liquid emulsions, and cellular solids. We will focus on static response where the foam deformation is very slow and rate-dependent phenomena such as viscous flow can be neglected. This includes nonlinear elasticity when deformations are large but reversible. We will also discuss elastic- plastic behavior, which involves yield phenomena. Foam structures based on polyhedra packed to fill space provide a unify- ing geometrical theme. Because a two-dimensional situation is always easier to visualize and usually easier to analyze, the roots of foam micromechanics lie in the plane packed with polygons. There are striking similarities as well as obvious differences between 2D and 3D
Multi-Level Micromachined Systems-on-a-Chip: Technology and Applications
No full textResearchers at Sandia have recently designed and built several research prototypes, which demonstrate that truly complex mechanical systems can now be realized in a surface micromachined technology. These MicroElectro- Mechanical Systems (MEMS) include advanced actuators, torque multiplying gear tmins, rack and pinion assemblies, positionable mirrors, and mechanical discriminators. All of tile mechanical components are batch fabricated on a single chip of silicon using the infrastructure origimdly developed to support today's highly reliabk; and robust microelectronics industry. Sand ia is also developing the technology 10 integrate microelectronic circuits onto the s,ime piece of silicon that is used to fabricate the MEMS devices. This significantly increases sensitivity and reliability, while fhrther reducing package size and fabrication costs. A review of the MEMS technology and capabilities available at Sandia National Laboratories is presented
The Effect of Peel Stress on the Strength of Adhesively Bonded Joints
No full textComposite wind turbine blades are often attached to a metallic structure with an adhesive bond. The objective of this investigation is to determine which parameters affect the durability of these adhesively bonded joints. The composite-to-steel joint considered in this study typically fails when the adhesive debonds from the steel adherend. Previously, this joint was monotonically loaded in either compression or tension. Compressive and tensile axial loads of the same magnitude produce adhesive stresses with very similar magnitudes but opposite signs. (For the joint considered, tensile loads produce compressive peeh stresses in the adhesive at the location where debonding initiates.) The tensile specimens failed at much higher loads, establishing that the sign of the adhesive peel stresses strongly influences the single-cycle strength of these joints. Building on this earlier work, this study demonstrates that the adhesive peel stresses are also critical for fatigue loading. The results of low-cycle (axial) and high- cycle (bending) fatigue tests are presented. To complement the test results, finite element analyses demonstrate the localized nature of the peel stresses that develop in the adhesive. In addition, these analyses are used to investigate some of the causes of these peel stresses
Optimization of Coal Particle Flow Patterns in Low N0x Burners
No full textThe proposed research is directed at evaluating the effect of flame aerodynamics on NOX emissions tlom coal fired burners in a systematic manner. This fimdamental research includes both experimental and modeling efforts being petiormed at the University of Arizona in collaboration with Purdue University. The objective of this effort is to develop rational design tools for optimizing low NOX burners to the kinetic emissions limit (below 0.2 lb./MMBTU). Experimental studies include both cold and hot flow evaluations of the following parameters: flame holder geometry, secondary air swirl, primary and secondary inlet air velocity, coal concentration in the primary air and coal particle size distribution. Hot flow experiments will also evaluate the effect of wall temperature on burner performance. Cold flow studies will be conducted with surrogate particles as well as pulverized coal. The cold flow furnace will be similar in size and geometry to the hot-flow furnace but will be designed to use a laser Doppler velocimeter/phase Doppler particle size analyzer. The results of these studies will be used to predict particle trajectories in the hot-flow fhrnace as well as to estimate the effect of flame holder geometry on furnace flow field. The hot-flow experiments will be conducted in a novel near-flame down-flow pulverized coal furnace. The fhrnace will be equipped with externally heated walls. Both reactors will be sized to minimize wall effects on particle flow fields. The cold-flow results will be compared with Fluent computation fluid dynamics model predictions and correlated with the hot-flow results with the overall goal of providing insight for novel low NOX burner geometry's
Task 6.7.3 - Interfacial Mass Transport Effects in Composite Materials
No full textAdvanced metal-matrix composites (MMCS) consisting of titanium-based alloys possess some unique mechanical, physical, and chemical characteristics that make them highly desirable for aircraft and gas turbine engines. Tailoring MMC properties is essential for advanced product design in materials processing. The main factors that affect materials processing and, further, the nature of a metal-ceramic interface, its structure, and morphological stability is liquid surface mass transport related to adhesional wetting physical effect) and reactive wetting (chemical effect). Surfaces and interfaces dominate many of the technologically important processes in composite materials such as liquid-solid sintering and joining. The objective of this work is threefold: 1) to get insight into the role of the nonstoichiometry of chemical composition in ceramic materials used as reinforcement components in MMC processing, 2) to extend previous energetic analysis of mass transport phenomena to wetting behavior between liquid metal and the quasi-solid like skin resulting from the presolidification of liquid on nonstoichiometric solids on a scale of interatomic distance, and 3) to provide experimental verification of our concept
Real Time Air Monitoring Using Open-Path FTIR
No full textOver the last several years there has been renewed interest in the use of open-path Fourier Transform Infrared (FTIR) spectroscopy for a variety of air monitoring applications. The intersect has been motivated by the need for new technology to address the regulator requirements of the Clean Air Act Amendment of 1990. Interest has been expressed in exploring the applications of this technology to locate fugitive-source emissions and measuring total emissions from industrial facilities
Connecting Remote Clusters with ATM
No full textSandia's entry into utilizing clusters of networked workstations is called Computational Plant or CPlant for short. The design of CPlant uses Ethernet to boot the individual nodes, Myrinet to communicate within a node cluster, and ATM to connect between remote clusters. This SAND document covers the work done to enable the use of ATM on the CPlant nodes in the Fall of 1997
Electrochemical cell for in-situ x-ray characterization
No full textAn electrochemical cell suitable for in-situ XRD analysis is presented. Qualitative information such as phase formation and phase stability can be easily monitored using the in-situ cell design. Quantitative information such as lattice parameters and kinetic behavior is also straightforward. Analysis of the LiMn&sub2;O&sub4; spinel using this cell design shows that the lattice undergoes two major structural shrinkages at approx. 4.0 V and approx. 4.07 V during charging. These shrinkages correlate well with the two electrochemical waves observed and indicate the likelihood of two separate redox processes which charging and discharging