bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Application of the Neutron Probe to the Nondestructive Examination of Architectural and Archaeological Materials
Authors: Livingston Richard A. , Chang L. , Evans L.S. , Trombka J.I. 
Published: March 2011

AbstractThe neutron probe is a non-destructive technique for examining materials that is based on prompt neutron/gamma spectroscopy. It can be used either at a nuclear reactor or, with portable neutron sources, in the field or even underwater. Since it is sensitive to a wide range of elements, it can be applied to many problems in materials analysis and conservation. A description of the major features of the neutron probe's operation is presented, along with a case study of chloride deterioration of an historic brick structure at Colonial Williamsburg.
Prediction of Glass Durability as a Function of Environmental Conditions
Authors: Jantzen C. M. 
Published: March 2011

ABSTRACTA thermodynamic model of glass durability has been applied to natural, ancient, and nuclear waste glasses. The durabilities of over 150 different natural and man-made glasses, including actual ancient Roman and Islamic glasses (Jalame ca. 350 A. D., Nishapur 10-11th century A. D., and Gorgon 9-11th century A.D.), have been compared. Glass durability has been shown to be a function of the thermodynamic hydration free energy, δGhvd, which can be calculated from glass composition and solution pH. Using this approach the durability of the most durable nuclear waste glasses examined was ˜106 years by comparison with the durability of the natural basalts of ˜106 years. The least durable waste glass formulations were comparable in durability to the most durable simulated medieval window glasses of ˜103 years. In this manner, the durability of nuclear waste glasses has been interpolated to be ˜106 years and no less than 103 years.Hydration thermodynamics have been shown to be applicable to the dissolution of glass in various natural environments. Groundwater-glass interactions relative to geologic disposal of nuclear waste, hydration rind dating of obsidians, and/or other archeological studies can be modeled, e.g. the relative durabilities of six simulated medieval window glasses have been correctly predicted for both laboratory (one month) and burial (5 year) experiments.The effects of solution pH on glass dissolution has been determined experimentally for the 150 different glasses and can be predicted theoretically by hydration thermodynamics. The effects of solution redox (oxidation potential expressed as Eh) on dissolution of glass matrix elements such as Si and B have been shown to be minimal. The combined effects of solution pH and Eh have been described and unified by construction of thermodynamically calculated Pourbaix (pH-Eh) diagrams for glass dissolution. The Pourbaix diagrams have been quantified to describe glass dissolution as a function of environmental conditions by use of the data derived from hydration thermodynamics.
Progress in Halide Glass Fibers
Authors: Aggarwal Ishwar. D. 
Published: March 2011

ABSTRACTFluoride glasses are being considered for use in long distance, mid-infrared transmitting optical fibers. The multi-phonon edge of these fibers is shifted to longer wavelengths compared to silica fibers. The intrinsic loss is therefore lower (< 0.01 dB/km) and occurs at about 2.5 microns. Applications for these fibers include ultra-low loss communication links, radiation resistant links, remoting of IR focal plane arrays and IR power delivery. In addition, this ultra low loss optical fiber may be used for fiber guided missiles with capability for distances longer than 500 km. Most of the interest however, has been focused on development of ultra long (thousands of kilometers), repeaterless communication links. Such repeaterless links may decrease system cost and cable weight, while increasing overall reliability and ease of repair compared to silicate optical fibers.
Configured Semiconductor/Insulator Coatings for Corrosion Prevention
Authors: Jain F. C. , Rosato J. J. , Kalonia K. S. , Agarwala V. S. 
Published: March 2011

ABSTRACTSemiconductor and insulator coatings, appropriately configured in Metal-Semiconductor (MS) and Metal-Insulator (≈20–100Å)-Semiconductor (MIS) structural formats, are shown to result in the formation of a built-in active electronic barrier on metal surfaces. This interfacial electronic barrier impedes the transfer of electrons from the metal to oxidizing species present at the metal surface, thereby providing protection against corrosion. The effectiveness of the electronic barrier concept has been confirmed using weight-loss, and cathodic and anodic polarization measurements on aluminum samples coated with indium tin oxide ITO (semiconductor) and SiO2 (thin oxide/insulator) films. In particular, Al-ITO, Al-ITO-Si3N4, Al-SiO2-ITO, and Al-SiO2-ITO-Si3N4 structures were fabricated and tested in a 1% NaCl, pH-2 solution. The films were grown using chemical vapor deposition (CVD) and spray techniques to ensure high quality and reproducibility. Aluminum samples tested included commercial purity, high purity (polycrystalline and single crystalline), and alloy (7075-T6). The MS and MIS configurations were found to provide superior corrosion protection as compared to conventional insulating films (e.g., Al-Si3N4). The active electronic barrier approach is a generic methodology to inhibit corrosion, and it can be realized using other semiconductor/insulator combinations including semiconducting polymer coatings.
Materials for Rocket Engine Applications
Authors: Schoenman Leonard 
Published: March 2011

ABSTRACTAdvanced rocket engine combustion devices operate in a highly dynamic thermochemical environment that challenges the material research community to provide solutions to heretofore unsolved technical problems. The paper outlines a range of needs and corresponding operating environments that typically exceed the melting temperature of most materials, imposes heating and cooling rates measured in thousands of degrees per second, provides cyclic, highly oxidizing, and reducing combustion environments often found side-by-side, including nonequilibrium gas compositions not readily producible in the laboratory.The stringent design requirements for minimum weight, impeccable quality control, and high reliability most often make the material cost contribution a secondary factor in relation to the total end-item cost. This provides new opportunities for the use of ultra high-tech material/material processing that would ordinarily be rejected for economic reasons.
Modification of Optical Properties in Transition Metal Ion Implanted Silica
Authors: Whichard G. , Mogul H. C. , Weeks R. A. , Stark J. D. , Zuhr R. 
Published: March 2011

ABSTRACTEllipsometric and ion backscattering techniques were used to investigate the changes in refractive index and thicknest of a surface layer of high purity silica modified by transition metal ion implantation. Samples were implanted with Cr+, Mn+, and Fe+ ions to doses ranging from 0.5 × 1016 to 6.0 × 1016 ions/cm2. The refractive index of the ion implanted region increased with increasing implantation dose. A single layer model for the implanted region was determined to be consistent with the ion backscattering profiles and ellipsometric data.
Monolithic GaAs/Si Integration
Authors: Turner George W. , Choi H. K. , Mattia J. P. , Chen C. L. , Eglash S. J. , Tsaur B-Y. 
Published: March 2011

ABSTRACTThe recent demonstrations of room-temperature cw operation of diode lasers fabricated in GaAs/AlGaAs layers grown on Si wafers have encouraged efforts to develop monolithic GaAs/Si integration technology for applications such as optical interconnects between VLSI subsystems. This paper summarizes our current work in this area, which is focused on the development of a highspeed, MSI-scale monolithic GaAs/Si test chip that integrates Si MOSFET circuits with diode lasers, LEDs, photoconductive detectors, and MESFET logic circuits fabricated in GaAs/AlGaAs layers grown by molecular beam epitaxy. Growth issues and processing considerations that affect device and circuit performance are addressed, and the characteristics of LEDs monolithically integrated with Si driver circuits and of GaAs microwave MESFETs fabricated on high-resistivity Si substrates are reported.
In Situ Control of Energy Bandgap by Laser Enhanced Metalorganic Chemical Vapor Deposition
Authors: Epler J. E. , Chung H. F. , Treat D. W. , Paoli T. L. 
Published: March 2011

ABSTRACTLaser-assisted crystal growth experiments have been performed in an upflow vertical metalorganic chemical vapor deposition reactor. An Ar+ laser (514.5 nm) is used to locally heat and photo-excite the surface adlayer during growth. The laser irradiation is observed to enhance the growth rate and Al composition of AlGaAs if the substrate temperature is ˜580 °C. The laser-grown AlGaAs epitaxy is single crystal with good surface morphology and is used to fabricate multiple wavelength light emitting diodes.
Optical Properties of Se+- and Zn+-Implanted GaAs: Photoluninescence Behavior at the Band-Edge
Authors: Makita Yunosuke , Mori Masahiko , Lee Hae-Chol , Kanayama Toshihiko , Ohnishi Nobukazu , Tanaka Hideki , Phelan Paul , Matsumori Tokue 
Published: March 2011

ABSTRACTIon implantation of Se+ and Zn+ ions into GaAs was carried out and characterization was performed by photoluminescence and Raman scattering at 2 K and room temperature, respectively. For comparison, implantation of Cd+ ions was also performed and further. a series of Si-doped GaAs samples were prepared by molecular beam epitaxy. In the Se+-implanted samples. with Se concentration between 1×1016 cm−3 and 5×1019 ca−3 the dominant radiative transition was the band-to-band emission, (B-B). No energy shift characteristic of (B-B) was observed but instead, the formation of a complex radiative center between donor impurities and implantation-induced damages, [D.LD] was revealed. This was in contrast to the Si-doped GaAs which displayed a pronounced energy shift of (B-B) towards higher energies with increasing Si concentration. The results suggest that (B-B) (reflecting the raising of the quasi Fermi-energy due to the increase of net free electron concentration) is significantly suppressed in the donor-ion implanted GaAs due to the presence of unremovable damages caused by implantation. In the Zn+ -implanted GaAs, the dominant emission was [g-g] which is formed just below the bound exciton emissions. The energy shift of [g-g] towards lower energies with increasing implanted Zn concentration was reproducibly observed. Thus clear differences in the PL spectra of donor- and acceptor-implanted samples were observed near the fundamental band edge. It was suggested that residual radiation damages suppress (B-B) but have little effect on acceptor-related emissions.
Variations of Electron Traps in MBE AlxGa1−xAs by Rapid Thermal Processing
Authors: Ueda H. , Kitagawa A. , Tokuda Y. , Usami A. , Wada T. , Kano H. 
Published: March 2011

ABSTRACTUsing deep level transient spectroscopy we have studied the variations of electron traps in molecular beam epitaxial (MBE) AlxGa1−xAs by rapid thermal processing (RTP) using halogen lamps. RTP was performed at 700, 800 and 900 °C for 6s under a SiO2 cap and a capless condition. It is found that during RTP the electron traps with the thermal activation energies of 0.89 and 0.99 eV are produced in Al0.lGa0.9As and Al0.3Ga0.7As, respectively. The thermal activation energies of these traps are close to the reported ones for the trap EL2 in AlxGaM1−xAs. Therefore, these traps are probably related to the trap EL2. In the RTP samples under a capless condition, the concentrations of the trap EL2 in AlxGa1−xAs (x=0.1, 0.3) decreases from the surface to the deeper position in MBE layers, while the depth profile of the trap EL2 in GaAs is flat. It is suggested that the origin of the trap EL2 formation in AlxGa1−xAs is different from one in GaAs.
Laser-Assisted Etching of Lithium Niobate
Authors: Orloff Glennis J. , Bernasek Steven L. , Wolk Gary L. , Coyle R. J. 
Published: March 2011

ABSTRACTLaser-assisted dry etching of lithium niobate, LiNbO3, as well as other electro-optic materials could be an industrially important process in the fabrication of optical waveguides. In this investigation, an excimer laser (ArF; 193nm) was used to conduct etching reactions using nitrogen trifluoride, NF3. Enhancement of etching was observed by comparing the etch rate for a gas assisted process with that of a purely photoablative process. Chemical analysis of the etched features via Auger electron spectroscopy and correlation of a simple rate equation with the experimental data revealed that lasersurface interactions are responsible for the laser-assisted etching process.
Passivation of GaAs Mesfet's with PECVD Silicon Nitride Films of Different Stress States
Authors: Chang Edward Y. , Cibuzar Gregory T. , Yard Thomas K. , Pande Krishna P. 
Published: March 2011

ABSTRACTThe passivation of GaAs MESFET's with PECVD silicon nitride films of both compressive and tensile stresses is reported. The shift of MESFET parameters due to passivation was found to be dependent upon gate orientation. For example, it is found that the shifts of threshold voltage are of opposite sign for MESFET's oriented along [011] and [011] directions. Our experiments show that nitride of tensile stress is preferable for MESFET's with [011] oriented gates. The shifts in VTH IDSS and GM of the devices before and after nitride passivation are lesd thaw s% if the nitride of appropriate stress states are used for passivation.Breakdown voltage of the MESFET's after nitride deposition was also studied. It is found that the process with higher hydrogen incorporation tends to reduce the surface oxide and increase the breakdown voltage after nitride deposition.
R7T7 Light Water Reference Glass Sensitivity to Variations in Chemical Composition and Operating Parameters
Authors: Pacaüd F. , Jacquet-Francillon N. , Terki A. , Fillet C. 
Published: March 2011

ABSTRACTR7T7 glass samples were tested to determine their sensitivity to variations in the chemical composition and in industrial scale operating parameters. Variations investigated included the composition of the feed solution and the glass frit, the frit/glass ratio and the glass melting temperature. The iniportant properties of the resulting glasses were measured. Permissible variation ranges defined on the basis of the results obtained ensure that the glass properties remain acceptable compared with the reference glass.
Repository Source Term for Vitrified High Level Waste
Authors: Hough A , Marples JAC 
Published: March 2011

ABSTRACTUsing doped glasses, the concentrations in aqueous solutions of Tc, Np, Pu and Am have been measured, over periods of up to 12 months, in the presence of various possible components of a future repository for vitrified high-level waste. The experiments were carried out under the reducing conditions anticipated in a repository. One possible repository design would incorporate a 20cm thick iron ‘overpack’ round the glass cylinders and a backfill of Ordinary Portland Cement (OPC) and Pulverised Fuel Ash (PFA). With this combination, the concentrations of Tc, Np, Pu and Am in the ‘repository’, after an 0.45um filtration, were respectively 7×10−9M, 7×10−10M, 2×10−12M and 2×10−12M i.e 0.1, 4, 1 and 45 times the ‘Limiting Concentration’ which, if present in drinking water, would lead to an annual dose of lmSv to someone drinking 2 litres per day.
The Fracture and Aerosol Release of Impacted HLW Glasses and HLW Canisters
Authors: Scheibel Hans G. , Friehmelt V. , Froehlich H. 
Published: March 2011

ABSTRACTThe fracture and release mechanism of radioactive aerosols of HLW glass and HLW canisters are studied experimentally by laboratory scale and full scale drop tests. The experimental conditions model the conditions of accidental drops in a deep salt repository. The laboratory scale drop tests have a scaling factor of 1:10. Accelerated probes of simulated HLW glass impact on a ground plate and the size distributions of broken fines and released aerosols are measured by sieving and scanning electron microscopy (SEM) of aerosol samples.The impact velocity is determined as the dominating impact parameter. Further parameters tested, such as waste glass composition, cooling time (residual thermal stresses), probe temperature at impact, and ground characteristics, show no measurable influence. Source terms of released respirable aerosols are evaluated for two reference cases, borehole drop (impact velocity v = 80 m/s) and reloading hall drop (v = 14 m/s), the values being 0.1 % and to 2.10-4 % respectively of the glass probe mass. The full scale drop tests are performed with European Standard HLW canisters. The canisters keep their integrity in all tests up to drop heights of 14 m. On opening the canisters, the broken fines are analyzed by sieving. The results are in good agreement with the small scale tests and confirm their acceptability for use in a safety analysis.
UO2 Corrosion Study in Mineral Water: A Surface Analysis Approach
Authors: Franco P. , Trocellier P. , Menes F. 
Published: March 2011

ABSTRACTSurface examination of sintered UO2 pellets, leached in groundwater at 90°C, have been conducted and the main results are described. They show the presence of a hydrated layer in which the uranium content decreases with leaching time. The oxidation state of uranium seems to remain (IV). The major components of the layer are magnesium and silicon. The growth of the surface layer in mineral water involves a decrease of uranium release in opposition to its continuing increase i n deionized water.
The Corrosion of Copper in NaCl Solution and Under Simulated Disposal Conditions
Authors: King Fraser , Litre Cindy 
Published: March 2011

ABSTRACTCopper is being considered as a possible container material for the disposal of nuclear fuel waste in Canada. The mechanism of the uniform corrosion of copper is being investigated in aerated 1 mol·dm-3 NaCl and under simulated disposal conditions. In NaCl solution, the rate of corrosion of a copper rotating disc electrode (RDE) is controlled partly by the rate of transport of copper complex ions away from the electrode surface. Similarly, under simulated disposal conditions, the rate of corrosion may be controlled by the transport of copper through compacted buffer material. However, longer-term results are needed to prove this latter statement.
In-Situ Corrosion Studies on Cast Steel for a High-Level Waste Packaging in a Rock Salt Repository
Authors: Schwarzkopf W. , Smailos E. , Koster R. 
Published: March 2011

ABSTRACTPrevious corrosion studies performed on a number of materials have shown that unalloyed steels are promising materials for long-term resistant packagings to be used in disposal of heat-generating wastes in rock salt formations. This is the reason why those steels are the subject of more detailed investigations. This paper reports an in-situ experiment conducted in the Asse salt mine in which the influence of selected characteristics (welding, shape) of containers on the corrosion behaviour of cast steel was studied. The material was tested in NaCl brine which might intrude into an HLW borehole in an accident scenario. For this, an electron beam welded cast-steel tube was stored for 18 months in a 2-m deep heated borehole and the annular gap between the tube and the borehole wall was filled with saturated NaCl brine. The vertical temperature profile in the borehole was in the range from 90°C to 200°C; the maximum temperature occurred in the center of the heated zone and the minimum temperature in the upper parts of tube.Under the testing conditions cast steel was subjected to general corrosion at a maximum corrosion rate of 120 μm/a. Considering this magnitude of the corrosion rates, the resulting corrosion allowances are technically acceptable for a packaging having long service-lives. Pitting and crevice corrosion as well as stress-corrosion cracking did not occur in cast steel, and electron beam welding did not exert a noticeable influence on cast-steel corrosion. With these results available, cast steel continues to be considered as a promising HLW packaging material.
Immobilization of Cs-137, Co-60, Mn-54 And Sr-85 in Cement-Waste Composition
Authors: Plećaš I. , Drljača J. , Perić A. , Kostadinović A. 
Published: March 2011

ABSTRACTTo assess the safety for disposal of radioactive waste cement composite, the leaching of Cs-137, Co-60, Mn-54 and Sr-85 from a waste composite into a surounding fluid has been studied [1, 2]. Leaching tests were carried out in accordance with a method recommended by IAEA |2, 3|. Determination of retardation factors, KF, and coefficients of distribution, kd, using a simplified mathematical model for analysing the migration of radionuclides, has been developed. |4, 7, 8|Results presented in this paper are examples of results obtained in a 10 year mortar and concrete testing project, which will influence the design of the engineered trenche system for future central Yugoslavian radioactive waste storage center. |7, 8|.
The Effects of Radiation on Intermediate Level Waste Forms
Authors: Wilding C. R. , Phillips D. C. , Lyon CE. 
Published: March 2011

ABSTRACTThe effects of accelerated gamma and alpha irradiation experiments on cement grouts alone and grouts containing simulated combustible plutonium contaminated material (PCM) at a number of dose rates and under various environmental and confinement conditions are considered. Cracking and spallation can occur over a wide range of water/cement ratios at a high dose rate of 2.8 Gys-1 for grouts based on blast furnace slag compositions. Grouts based on pulverised fuel ash do not show any signs of spallationand cracking. One possible reason for this is the accumulation of radiolytic gases to high pressures in pores in the cement. It has been demonstrated that under some circumstances, at the Laboratory scale, PCM waste form can swell sufficiently to rupture its container and may disintegrate.
Equilibrium Concept for the Assessment of the Actinide Release from Waste Forms into Salt Brines
Authors: Rudolph G. , Vejmelka P. , Köster R. 
Published: March 2011

ABSTRACTA novel approach for the assessment of the radionuclide release from a nuclear waste repository after an accidental water ingression is proposed: after a short time a stable final condition is assumed to be established in the near-field of the waste form in which each radionuclide is at equilibrium between the dissolved phase and the various solid phases. The total release may be assessed from the concentration in solution and the flow rate out of the near-field.An experimental program stimulated by this concept includes studies on the solubility of actinide compounds in salt brines in equilibrium with cement. In Q-brine (a salt brine rich in magnesium chloride, pH = 6.5) the concentrations of U, Np, Pu and Am in solution are determined by a sorption equilibrium, in sodium chloride brine (pH = 12–13) by the solubility of the respective hydroxide.
Effect of Humic Substances on Americium (III) Retention onto Silica
Authors: Moulin Valerie , Stammose Denise 
Published: March 2011

ABSTRACTThe migration/retention phenomena of radionuclides in geological systems are of great interest for the safety assessment of a nuclear disposal. Interactions at solid/liquid interfaces play a significant role in the speculation and transport of radionuclides in aquifer systems. Oxide surfaces and humic substances which occur in natural waters in large concentration ranges (from few mg/1 to several hundred mg/1) may have a major influence on radionuclides behaviour. For this purpose, studies have been carried out on a ternary system: oxide-humic substances-americium (III). The influence of pH, ionic strength and humic concentration on the adsorption of americium onto silica has been investigated. The ionic strength of the solution (0.1 and 0.01) has little effect on the americium adsorption. In the presence of humic materials, the fixation of americium is enhanced at low pH (pH<5) whereas, at higher pH (pH>5), the adsorption is lowered and dependent of humic concentration.