Structure and properties of a series of modified polydimethylsiloxane (PDMS) elastomers reinforced by {ital in situ} generated silic particles were investigated. The PDMS elastomer was modified by systematically varying the molecular weight between reactive groups incorporated into the backbone. Tetraethoxysilane (TEOS) and partial hydrolyzate of TEOS were used to generate silic particles. Chemistry and phase structure of the materials were investigated by {sup 29}Si magic angle spinning nuclear magnetic resonance spectroscopy and swelling experiments.
Conventional III-V metallizations chemes such as Au/Ge/Ni, Ti/Pt/Au, and Au/Be were found to display poor thermal stability on both GaN and InGaN, with extensive reaction and contact degradation at {le}500 C. By contrast, W was found to produce low contact resistance ({rho}{sub c}{similar_to}8x10{sup -5}{Omega}cm{sup 2}) to n-GaN. Ga outdiffusion to the surface of thin (500 A) W films was found after annealing at 1,100 C, but not at 1000 C. Interfacial abruptness increased by 300A after 1,100 C annealing. In the case of WSi{sub X} (X=0.45), Ga outdiffusion was absent even at 1,100 C, but again there was interfacial broadening and some phase changes in the WSi{sub X}. On In{sub 0.5}Ga{sub 0.5}N, a minimum specific contact resistivity of 1.5 x10{sup -5}{Omega}cm{sup 2} was obtained for WSi{sub X} annealed at 700 C. These contacts retained a smooth morphology and abrupt interfaces to 800 C. Graded In{sub X}Ga{sub 1-X}N layers have been employed on GaAs/AlGaAs HBTs (heterojunction bipolar transistors), replacing conventional In{sub X}Ga{sub 1-X}As layers. R{sub C} values of 5x10{sup -7}{Omega}cm{sup 2} were obtained for nonalloyed Ti/Pt/Au on the InGaN, and the morphologies were superior to those of InGaAs contact layers. This proves to have significant advantages for fabrication of sub-micron HBTs. Devices with emitter dimensions of 2x5{mu}m{sup 2} displayed gains of 35 for a base doping level of 7x10{sup 19}cm{sup -3} and stable long-term behavior.
Microtags are microscopic computer-generated holograms with 130-nm features and are mass-producible with EUVL. This fabrication method renders microtags difficult to counterfeit. Applications includ tagging and tracking of microprocessors, memory chips, currencey, and credit cards.
In the present study we are developing an experimental fracture material property test method specific to dynamic fragmentation. Spherical test samples of the metals of interest are subjected to controlled impulsive stress loads by acceleration to high velocities with a light-gas launcher facility and subsequent normal impact on thin plates. Motion, deformation and fragmentation of the test samples are diagnosed with multiple flash radiography methods. The impact plate materials are selected to be transparent to the x-ray method so that only test metal material is imaged. Through a systematic series of such tests, both strain-to-failure and fragmentation resistance properties are determined through this experimental method. Fragmentation property data for several steels, copper, aluminum, tantalum and titanium have been obtained to date. Aspects of the dynamic data have been analyzed with computational methods to achieve a better understanding of the processes leading to failure and fragmentation, and to test an existing computational fragmentation model.
Neutron powder diffraction at pressures to 6 kbar in gaseous Ne has been used to study the pressure-induced phase transition and compressibilities of Na{sub 2}CsC{sub 60}. The pressure-induced phase can be achieved by compression to about 5 kbar at room temperature. If cooled, this phase can be retained below 200 K upon release of the pressure. The structure is orthorhombic as previously reported (but may differ in its detailed crystal structure) with lattice constants near 80 K and ambient pressure of a=9.385 A, b=10.06 A, and c=14.36 A. Corresponding linear compressibilities are 0.0004, 0014, and 0.0017 kbar{sup -1}, respectively. Identical pressure temperature cycling results in a superconductor with an unexpectedly low pressure dependence for {Tc} while in this phase. Models for the superconducting behavior of this compound are discussed.
In order to support advanced manufacturing, Sandia has acquired the capability to produce plastic prototypes using stereolithography. Currently, these prototypes are used mainly to verify part geometry and ``fit and form`` checks. This project investigates methods for rapidly testing these plastic prototypes, and inferring from prototype test data actual metal part performance and behavior. Performances examined include static load/stress response, and structural dynamic (modal) and vibration behavior. The integration of advanced non-contacting measurement techniques including scanning laser velocimetry, laser holography, and thermoelasticity into testing of these prototypes is described. Photoelastic properties of the epoxy prototypes to reveal full field stress/strain fields are also explored.
W, WSi{sub 0.44} and Ti/Al contacts were examined on n{sup +} In{sub 0.65}Ga{sub 0.35}N, InN and In{sub 0.75}Al{sub 0.25}N. W was found to produce low specific contact resistance ({rho}{sub c} {approximately} 10{sup {minus}7} {Omega} {center_dot}cm{sup 2}) ohmic contacts to InGaN, with significant reaction between metal and semiconductor at 900 {degrees}C mainly due to out diffusion of In and N. WSi{sub x} showed an as-deposited {rho}{sub c} of 4{times}10{sup {minus}7} {Omega} {center_dot}cm{sup 2} but this degraded significantly with subsequent annealing. Ti/Al contacts were stable to {approximately} 600 {degrees}C ({rho}{sub c} {approximately} 4{times}10{sup {minus}7} {Omega} {center_dot}cm{sup 2} at {le}600 {degrees}C). The surfaces of these contacts remain smooth to 800 {degrees}C for W and WSi{sub x} and 650 {degrees}C for Ti/Al. InN contacted with W and Ti/Al produced ohmic contacts with {rho}{sub c} {approximately} 10{sup {minus}7} {Omega} {center_dot}cm{sup 2} and for WSi{sub x} {rho}{sub c} {approximately} 10{sup {minus}6} {Omega} {center_dot}cm{sup 2}. All remained smooth to {approximately} 600 {degrees}C, but exhibited significant interdiffusion of In, N, W and Ti respectively at higher temperatures. The contact resistances for all three metalization schemes were {ge} 10{sup {minus}4} {Omega} {center_dot}cm{sup 2} on InAlN, and degrades with subsequent annealing. The Ti/Al was found to react with the InAlN above 400 {degrees}C, causing the contact resistance to increase rapidly. W and WSi{sub x} proved to be more stable with {rho}{sub c} {approximately} 10{sup {minus}2} and 10{sup {minus}3} {Omega} {center_dot}cm{sup 2} up to 650 {degrees}C and 700 {degrees}C respectively.
As photovoltaic (PV) electrical power systems gain increasing acceptance for both off-grid and utility-interactive applications, the safety, durability, and performance of these systems gains in importance. Local and state jurisdictions in many areas of the country require that all electrical power systems be installed in compliance with the requirements of the National Electrical Code{reg_sign} (NEC{reg_sign}). Utilities and governmental agencies are now requiring that PV installations and components also meet a number of Institute of Electrical and Electronic Engineers (IEEE) standards. PV installers are working more closely with licensed electricians and electrical contractors who are familiar with existing local codes and installation practices. PV manufacturers, utilities, balance of systems manufacturers, and standards representatives have come together to address safety and code related issues for future PV installations. This paper addresses why compliance with the accepted codes and standards is needed and how it is being achieved.
Phase II work for this Laboratory Directed Research and Development project is presented. Historically, high velocity, solid, electrically conducting armatures or projectiles have been utilized to generate or magnify existing electric fields in magnetohydrodynamic (MHD) devices. Useful power can be extracted from high velocity ionized, electrically conductive plasma jets. The MHD device current output can be switched to power other devices. The purpose of this project is to investigate the use of an Explosively-Driven Ionized Plasma Jet Generator (EDMG) to more efficiently obtain velocities much higher than can be achieved with solid armatures or projectiles. The armature velocity is one of the more important parameters in the electric field magnification process. The ionized plasma jet is generated by explosively collapsing a gas (neon, argon, xenon, hydrogen) filled cavity and directing the jet through a shocktube or core of an MHD device. Data are presented for two different size and configuration explosive drivers, one explosive (COMP-C4), one gas (argon), different driver pressures (90-200 psia), different shocktube or test section pressures (0.01-11.7 psia), and for two different shocktube inside dimensions. Measured time-of-arrival, current, voltage, resistance, power and energy data are presented for tests conducted. Measured time-of-arrival and plasma flow velocity data are compared to the predicted CTH hydrocode data. CTH code calculations are also presented to compare EDMG performance of various test gases and various explosive liner materials.
The International Security Program Initiative at Sandia National Laboratories (SNL) is dedicated to achieving a global nuclear security structure that reduces the danger of nuclear and other weapons of mass destruction. SNL is the principle Department of Energy (DOE) laboratory, jointly funded by the DOE and the Department of Defense (DoD), and is responsible for developing technology, concepts, and hardware to protect nuclear weapons and materials at facilities, and during transportation. SNL is working cooperatively with scientists and engineers in various institutes, laboratories, and other organizations within the countries of the Former Soviet Union (FSU) to reduce the risk of nuclear weapons proliferation. One major step toward achieving worldwide protection and control of nuclear materials and weapons proliferation is being accomplished by the DOE National Laboratories on work with the FSU in the area of Material Protection, Control, and Accountability (MPC&A). This report focuses on the accomplishments and status of work under the MPC&A program at Sandia. In addition, brief summaries of other areas of FSU cooperation are included such as Industrial Partnering Program (IPP); Lab-to-Lab; Safe and Secure Dismantlement (SSD); Safety and Security Technology; and Energy and Environment.
This report discusses a novel fabrication process to produce nearly perfect optics. The process utilizes vacuum deposition techniques to optimally modify polished optical substrate surfaces. The surface figure, i.e. contour of a polished optical element, is improved by differentially filling in the low spots on the surface using flux from a physical vapor deposition source through an appropriate mask. The process is expected to enable the manufacture of diffraction-limited optical systems for the UV, extreme UV, and soft X-ray spectral regions, which would have great impact on photolithography and astronomy. This same technique may also reduce the fabrication cost of visible region optics with aspheric surfaces.
Hydrous Metal Oxides (HMOs) are chemically synthesized materials which contain a homogeneous distribution of ion exchangeable alkali cations that provide charge compensation to the metal-oxygen framework. In terms of the major types of inorganic ion exchangers defined by Clearfield, these amorphous HMO materials are similar to both hydrous oxides and layered oxide ion exchangers (e.g., alkali metal titanates). For catalyst applications, the HMO material serves as an ion exchangeable support which facilitates the uniform incorporation of catalyst precursor species. Following catalyst precursor incorporation, an activation step is required to convert the catalyst precursor to the desired active phase. Considerable process development activities at Sandia National Laboratories related to HMO materials have resulted in bulk hydrous titanium oxide (HTO)- and silica-doped hydrous titanium oxide (HTO:Si)-supported NiMo catalysts that are more active in model reactions which simulate direct coal liquefaction (e.g., pyrene hydrogenation) than commercial {gamma}-Al{sub 2}O{sub 3}-supported NiMo catalysts. However, a fundamental explanation does not exist for the enhanced activity of these novel catalyst materials; possible reasons include fundamental differences in support chemistry relative to commercial oxides, high surface area, or catalyst preparation effects (ion exchange vs. incipient wetness impregnation techniques). The goals of this paper are to identify the key factors which control sulfided NiMo catalyst activity, including those characteristics of HTO- and HTO:Si-supported NiMo catalysts which uniquely set them apart from conventional oxide supports.
During April-May, 1995, Sandia National Laboratories, in cooperation with Trans-Pacific Geothermal Corporation, drilled a 5825{prime} exploratory slimhole (3.85 in. diameter) in the Vale Known Geothermal Resource Area (KGRA) near Vale, Oregon. This well was part of Sandia`s program to evaluate slimholes as a geothermal exploration tool. During drilling we performed several temperature logs, and after drilling was complete we performed injection tests, bailing from a zone isolated by a packer, and repeated temperature logs. In addition to these measurements, the well`s data set includes: 2714{prime} of continuous core (with detailed log); daily drilling reports from Sandia and from drilling contractor personnel; daily drilling fluid records; numerous temperature logs; pressure shut-in data from injection tests; and comparative data from other wells drilled in the Vale KGRA. This report contains: (1) a narrative account of the drilling and testing, (2) a description of equipment used, (3) a brief geologic description of the formation drilled, (4) a summary and preliminary interpretation of the data, and (5) recommendations for future work.
New pour-in-place, low density, rigid polyurethane foam kits have been developed to mechanically stabilize damaged explosive ordnance. Although earlier foam systems used chlorofluorocarbons as blowing agents, the current versions rely on carbon dioxide generated by the reaction of isocynates with water. In addition, these kits were developed to manually generate small quantifies of rigid foam in the field with minimal or no protective equipment. The purpose of this study was to evaluate and summarize available hazard information for the components of these rigid foam kits and to provide recommendations for personal protective equipment to be used while performing the manual combination of the components. As with most rigid foam systems, these kits consist of two parts, one a mixture of isocyanates; the other, a combination of polyols, surfactants, and amine catalysts. Once completely deployed, the rigid foam is non-toxic. The components, however, have some important health effects which must be considered when establishing handling procedures.
In this continued study, the microstructural evolution and peel strength as a function of thermal aging were evaluated for four Sn-Ag solders deposited on double layered Ag-Pt metallization. Additionally, activation energies for intermetallic growth over the temperature range of 134 to 190{degrees}C were obtained through thickness measurements of the Ag-Sn intermetallic that formed at the solder-metallization interface. It was found that Bi-containing solders yielded higher activation energies for the intermetallic growth, leading to thicker intermetallic layers at 175 and 190{degrees}C for times of 542 and 20.5 hrs, respectively, than the solders free of Bi. Complete reaction of the solder with the metallization occurred and lower peel strengths were measured on the Bi-containing solders. In all solder systems, a Ag-Sn intermetallic thickness of greater than {approximately}7 {mu}m contributed to lower peel strength values. The Ag-Sn binary eutectic composition and the Ag-Sn-Cu ternary eutectic composition solders yielded lower activation energies for intermetallic formation, less microstructural change with time, and higher peel strengths; these solder systems were resilient to the effects of temperatures up to 175{degrees}C. Accelerated isothermal aging studies provide useful criteria for recommendation of materials systems. The Sn-Ag and Sn-Ag-Cu eutectic compositions should be considered for future service life and reliability studies based upon their performance in this study.
Experimental results and a mathematical model are presented to describe differential evaporation rates in electron beam melting of titanium alloys containing aluminum and vanadium. Experiments characterized the evaporation rate of commercially pure titanium, and vapor composition over titanium with up to 6% Al and 4.5% V content as a function of beam power, scan frequency and background pressure. The model is made up of a steady-state heat and mass transport model of a melting hearth and a model of transient thermal and flow behavior near the surface. Activity coefficients for aluminum and vanadium in titanium are roughly estimated by fitting model parameters to experimental results. Based on the ability to vary evaporation rate by 10-15% using scan frequency alone, we discuss the possibility of on-line composition control by means of intelligent manipulation of the electron beam.
Thermal, electrochemical and transition metal mediated reactions of phosphaacetylene monomers were conducted in attempts to form novel polyphosphaacetylenes as a new class of potentially electrically conducting polymers. Molecular modeling was used to simulate the molecular conformations of optimized, isolated oligomers to identify the proper monomeric repeat units for highly conjugated molecules. Electrodeposition of suitable monomers led to low molecular weight oligomers. Thermal polymerization of phosphaacetylene monomers bearing aromatic substituents ed to the formation of polyhedral cage oligomers. Under metathesis polymerization conditions the phosphaacetylene monomers form unique complexes via an unprecedented sequence of intermediates which suggest that metathesis to linear oligomers is achievable. Conductivity measurements on electrodeposited oligomers indicate modest electrical conductivity.
This study examines, from a systems engineering design perspective, the potential of kinetic energy weapons being used in the role of a conventional strategic weapon. Within the Department of Energy (DOE) complex, strategic weapon experience falls predominantly in the nuclear weapons arena. The techniques developed over the years may not be the most suitable methodologies for use in a new design/development arena. For this reason a more fundamental approach was pursued with the objective of developing an information base from which design decisions might be made concerning the conventional strategic weapon system concepts. The study examined (1) a number of generic missions, (2) the effects of a number of damage mechanisms from a physics perspective, (3) measures of effectiveness (MOE`s), and (4) a design envelope for kinetic energy weapon concepts. With the base of information a cut at developing a set of high-level system requirements was made, and a number of concepts were assessed against these requirements.
We describe measurements, modeling, and mitigation experiments on the effects of anode and cathode plasmas in applied-B ion diodes. We have performed experiments with electrode conditioning and cleaning techniques including RF discharges, anode heating, cryogenic cathode cooling and anode surface coatings that have been successful in mitigating some of the effects of electrode contamination on ion diode performance on both the SABRE and PBFA accelerators. We are developing sophisticated spectroscopic diagnostic techniques that allow us to measure the electric and magnetic fields in the A-K gap, we compare these measured fields with those predicted by our 3-D particle-in-cell (PIC) simulations of ion diodes, and we measure anode and cathode plasma densities and expansion velocities. We are continuing to develop E-M simulation codes with fluid-PIC hybrid models for dense plasmas, in order to understand the role of electrode plasmas in ion diode performance. Our strategy for improving high power ion diode performance is to employ and expand our capabilities in measuring and modeling A-K gap plasmas and leverage our increased knowledge into an increase in total ion beam brightness to High Yield Facility (HYF) levels.
The high peak power, single-pulse technology developed for government programs during the mid-60`s through the mid-80`s is being adapted for use in continuously operating, high average power commercial materials processing applications. A new thermal surface treatment technology, called ion beam surface treatment (BEST), uses repetitive high energy (kJ`s per pulse), pulsed ({le}500 ns) ion beams to directly deposit energy in the top 1-20 micrometers of the surface of any material. A high average power IBEST processing system is made up of a magnetic pulse compressor (MPC) a magnetically confined anode plasma (MAP) ion beam source, an ion beam transport system, a materials handling system and various cooling and reset systems. System issues such as cost, reliability, size, maintainability, and design-for-manufacturability that were of secondary importance behind specific performance requirements for the earlier government applications are now the primary issues in proposed industrial systems. Research systems are now obtaining lifetime, reliability, and design-rules information for high average power short-pulse components. Beam sources are being developed that are suitable for industrial systems operating at 5-100 kW, 0.1-2.0 MeV, and {le}500 ns pulse widths. Capitol equipment costs, operating and financing costs, and sizing issues are being weighed against specific economic benefits obtained in short-pulse ion beam treatment of selected products. Dependable equipment designers and suppliers, facility integrator, and servicing organizations are being combined with development teams from end-user companies for final technology integration into major manufacturing facilities. An BEST prototype commercial system is being designed and fabricated by QM Technologies for initial operation in mid-1997.
The Molina Member of the Wasatch Formation has been cored in order to assess the presence/absence and character of microbial communities in the deep subsurface. Geological study of the Molina Member was undertaken in support of the microbiological tasks of this project, for the purposes of characterizing the host strata and of assessing the potential for post-depositional introduction of microbes into the strata. The Molina Member comprises a sandy fluvial unit within a formation dominated by mudstones. Sandy to conglomeratic deposits of braided and meandering fluvial systems are present on the western and eastern margins of the basin respectively, although the physical and temporal equivalence of these systems cannot be proven. Distal braided facies of planar-horizontal bedded sandstones are recognized on the western margin of the basin. Natural fractures are present in all Molina sandstones, commonly as apparent shear pairs. Core from the 1-M-18 well contains natural fractures similar to those found in outcrops, and has sedimentological affinities to the meandering systems of the eastern margin of the basin. The hydrologic framework of the Molina, and thus any potential post-depositional introduction of microbes into the formation, should have been controlled by approximately east-west flow through the natural fracture system, the geometries and extent of the sandstones in which the fractures occur, and hydraulic gradient. Migration to the well site, from outcropping recharge areas at the edge of the basin, could have started as early as 40 million years ago if the cored strata are connected to the eastern sedimentary system.
This study analyzes findings from a national survey of 2,490 randomly selected members of the US public conducted between September 30 and November 14, 1995. It provides an over time comparison of public perceptions about nuclear weapons risks and benefits and key nuclear policy issues between 1993 and 1995. Other areas of investigation include policy preferences regarding nuclear proliferation, terrorism, US/Russian nuclear cooperation, and personal security. Public perceptions of post-cold war security were found to be evolving in unexpected ways. The perceived threat of nuclear conflict involving the US had not declined, and the threat of nuclear conflict between other countries and fears of nuclear proliferation and terrorism had increased. Perceived risks associated with managing the US nuclear arsenal were also higher. Perceptions of external and domestic benefits from US nuclear weapons were not declining. Support was found for increasing funding for nuclear weapons safety, training, and maintenance, but most respondents favored decreasing funding for developing and testing new nuclear weapons. Strong support was evident for programs and funding to prevent nuclear proliferation and terrorism. Though skeptical that nuclear weapons can be eliminated, most respondents supported reducing the US nuclear arsenal, banning nuclear test explosions, and ending production of fissile materials to make nuclear weapons. Statistically significant relationships were found between perceptions of nuclear weapons risks and benefits and policy and spending preferences. Demographic variables and basic social and political beliefs were systematically related both to risk and benefit perceptions and policy and spending options.
This document provides an overview of the processes used to access the performance of the Waste Isolation Pilot Plant (WIPP). The quantitative metrics used in the performance-assessment (PA) process are those put forward in the Environmental Protection Agency`s Environmental Standards for the Management and Disposal of Spent Nuclear Fuel, HIgh-LEvel and transuranic radioactive Wastes (40 CFR 191).
A bench-scale experiment was designed and constructed to determine the effective thermal diffusivity of crushed tuff. Crushed tuff particles ranging from 12.5 mm to 37.5 mm (0.5 in. to 1.5 in.) were used to fill a cylindrical volume of 1.58 m{sup 3} at an effective porosity of 0.48. Two iterations of the experiment were completed; the first spanning approximately 502 hours and the second 237 hours. Temperatures near the axial heater reached 700 degrees C, with a significant volume of the test bed exceeding 100 degrees C. Three post-test analysis techniques were used to estimate the thermal diffusivity of the crushed tuff. The first approach used nonlinear parameter estimation linked to a one dimensional radial conduction model to estimate thermal diffusivity from the first 6 hours of test data. The second method used the multiphase TOUGH2 code in conjunction with the first 20 hours of test data not only to estimate the crushed tuffs thermal diffusivity, but also to explore convective behavior within the test bed. Finally, the nonlinear conduction code COYOTE-II was used to determine thermal properties based on 111 hours of cool-down data. The post-test thermal diffusivity estimates of 5.0 x 10-7 m{sup 2}/s to 6.6 x 10-7 m{sup 2}/s were converted to effective thermal conductivities and compared to estimates obtained from published porosity-based relationships. No obvious match between the experimental data and published relationships was found to exist; however, additional data for other particle sizes and porosities are needed.
The `Red Forest` radioactive waste burials created during emergency clean-up activities at Chernobyl Nuclear Power Plant represent a serious source of radioactive contamination of the local ground water system with 9OSr concentration in ground water exceeding the drinking water standard by 3-4 orders of magnitude. In this paper we present results of our hydrogeological and radiological `Red Forest` site characterization studies, which allow us to estimate 9OSr subsurface migration parameters. We use then these parameters to assess long terrain radionuclide transport to groundwater and surface water, and to analyze associated health risks. Our analyses indicate that 9OSr transport via ground water pathway from `Red Forest` burials to the adjacent Pripyat River is relatively insignificant due to slow release of 9OSr from the waste burials (less than 1% of inventory per year) and due to long enough ground water residence time in the subsurface, which allows substantial decay of the radioactive contaminant. Tins result and our previous analyses indicate, that though conditions of radioactive waste storage in burials do not satisfy Ukrainian regulation on radiation protection, health risks caused by radionuclide migration to ground water from `Red Forest` burials do not justify application of expensive countermeasures.
