bluuebunny/crossref_metadata_2025 huggingface dataset:
Spa-Leed Measurements on Etched and Polished Silicon (111) Surfaces
Authors: Hahn Peter O.
Published: March 2011

The atomic structure of etched and polished Si (111) surfaces has been determined quantitatively on an atomic scale by SPA-LEED (spot profile analysis of low energy electron diffraction) in an ultrahigh vacuum. The energy dependant broadening of the diffracted electron beam yields the average size of step free terraces and the distribution of the atomic steps.

Whereas acid etched Si (111) wafers exhibit surfaces with very high step atom densities, alkaline etched Si (111) wafers show atomically very flat surfaces besides macroscopic steps. In chemo-mechanical polishing of these silicon wafers bright LEED patterns exhibiting the atomic structure at the actual surface were obtained. No damage or defects could be observed with LEED during this process. This indicates that the removal of Si is mainly controlled by chemical reaction. In an intermediate step the wafers exhibit a slight surface roughness (“haze”) observable by optical Nomarski contrast microscopy or by light scattering. This is correlated qualitatively to a broadening of LEED spots for a phase relation, indicating that the atomic steps are distributed over many atomic layers creating a superimposed long range roughness. After polishing this long range roughness (haze) disappears and atomically smooth surfaces were obtained. Haze free polished Si (111) wafers exhibit on average less than one atomic step for a row of 30 atoms which represents the instrumental resolution. Definitely misoriented wafers show regular terraces. The regularity is increasing with proceeding polishing. The number of atoms per terrace is correlated to the angle of misorientation, demonstrating the high quality of the polished wafer surface.
Growth of Large Crystalline Grain Al Thin Films on Amorphous Substrates
Authors: Sberveglieri G. , Canevari V. , Romeo N. , Spaggiari C.
Published: March 2011

(111) uniquely oriented large crystalline grain Al thin films have been grown on amorphous substrates such as glass or fused quartz. Al has been evaporated by means of an electron beam in a vacuum of 10-7 mbar which was obtained by a conventional oil diffusion pump in conjunction with a titanium sublimation pump and a series of shields cooled at the liquid nitrogen temperature. By studying the variation of the grain size as a function of the growth temperature, a large increase in the grain size has been found at a substrate temperature 100°C below the Al melting point. This has been interpreted as due to the beginning of the metal surface melting and, as a consequence, to the quasi rheotaxial growth of the metal on itself. When the growth has been carried out at a substrate temperature close to the Al melting point (625°C), the grain size has been found out to increase exponentially as a function of the film thickness with a slope which slows down at a thickness of about 1 pm. (111) oriented columnar grains with a size of 50 – 100 pm, hitherto unreported, have been obtained on glass substrates kept at a maximum temperature of 655 °C. The surface morphology of the Al films has been studied by SEM microscopy while the film structural properties have been studied by an X-ray powder-diffracto-meter and by computer - controlled pole figure goniometer.
High Resolution Auger Depth Profiles Using a Dual Ion Gun System
Authors: Ingrey S. , Cook J.P.D.
Published: March 2011

A dual ion gun system has been proposed (D.E. Sykes et al, Appl. Surf. Sci. 5(1980)103) to reduce texturing and improve depth resolution during Auger sputter depth profiling. We have evaluated this ion gun configuration by profiling a variety of multilayer structures. With careful alignment of the guns, we have obtained a dramatic decrease in ion-induced texturing often seen when a single ion gun is used. This effect was particularly pronounced for polycrystalline Al films on Si where an order of magnitude improvement in depth resolution was achieved. Further refinements of the technique include the use of low energy (IkeV) grazing incidence xenon ions and a small electron beam probe area. Depth profiles obtained from Ni/Cr, W/Si, and GaAs/GaAlAs multilayer structures will also be discussed.
Interconnects and Contacts for VLSI Applications
Authors: Sinha A. K.
Published: March 2011

The power of VLSI circuits is, to a large measure, derived through an extensive network of fine-line metalization interconnects used to wire up various components on the chip. For example, the 1Mb DRAM utilizes three levels of conductors to interconnect over one million each of transistors and capacitors on a chip. The combination of larger chip dimensions and finer scaling generates several technology concerns that must be addressed by a variety of measures, including an optimum choice of metalization processes. These concerns are related to parasitics, defect density and generic reliability.

This talk will review trends in materials/processes to control RC time constants, series resistances, fine-line metal defects during pattern transfer, control of topography-related defects and generic reliability related issues such as contact electromigration and ∝-particle sensitivities.
High Dose Implantation of Nickel into Silicon
Authors: Campisi G. J. , DIETRICH H. B. , Delfino M. , Sadana D. K.
Published: March 2011

Several silicon wafers were implanted with 58Ni+ at an energy of 170 keV and a current density of 12 μA cm-2 to doses between 5 × 1015 and 1.8 × 1018 ions cm-2. The substrates were phosphorus doped n-type <100> Czochralski grown silicon wafers. The wafers were water cooled during implantation and the surface temperatures was monitored with an infrared pyrometer and controlled to < 70°C. Samples were subsequently furnace annealed at 900°C for 30 min in nitrogen. The as-implanted and annealed samples were analyzed using cross-sectional transmission electron microscopy (XTEM), Rutherford backscattering (RBS) spectroscopy, spreading resistance depth profiling (SRP), and scanning electron microscopy (SEM). Micro-crystallites of NiSi2 (2–5nm) buried within an amorphous matrix formed during the 1.5 × 1017 ions cm-2 dose implantation. For higher doses above 3 × 1017 Ni+ cm-2, ion beam sputtering occurred. After annealing, rapid diffusion of nickel and solid-phase recrystallization of the amorphous regions occurred.
An Experimental Technique to Obtain the Specific Contact Resistance of Multi-Layer Interconnections
Authors: Harrison H. B. , Reeves G. K. , Walton A. J.
Published: March 2011

The specific contact resistance between any two interconnecting layers is of vital importance in determining the total interconnection resistance of these layers. We present here an experimental technique to obtain the specific contact resistance when both of the conducting layers have finite conductivities of similar magnitudes. This structure is then used to obtain practical information on the poly to single crystal interconnection system, details of which are present. Finally a modification to this system is proposed and its status reviewed.
Stability Of Thin Film Amorphous Metal Alloys
Authors: Saris F. W. , Hung L. S. , Nastasi M. , Mayer J. W.
Published: March 2011

Thermal stability of self supporting amorphous films is reviewed in terms of a simple kinetic model. A semi-empirical relationship between the crystallization temperature and the heat of hole formation is applicable only for systems with negative heat of mixing.

Interaction of amorphous diffusion barriers with Si substrates and Al overlayers is also reviewed for near noble-refractory alloys. If their crystallization temperature is higher than their reaction temperature, there is no correlation between the two parameters. The reaction takes place when the annealing temperature reaches a value at which compounds can be formed of both constituents of the alloy. Finally, comparison is made to reactions of crystalline alloys with Si.
Mechanical and Thermo-Mechanical Protection by Alumina Sol-Gel Coatings
Authors: Gruninger Mark F. , Wachtman John B. , Haber Richard A.
Published: March 2011

Alumina coatings made by the sol-gel process using aluminum sec butox-ide can be made with variable surface area and porosity by firing on dense alumina substrates in the firing range 700 to 1000 C. These coatings are found to have large (over 100 MPa) compressive stresses and to cause a small but significant strengthening of the substrates. Within this firing range the surface area decreases while both the internal stress and strengthening effect increase with increasing firing temperature. Wear rate values are high but decrease with increasing firing temperature.
Problems In Realistic Modelling Of Interfacial Reactions
Authors: Allen Charles W. , Sargent Gordon A
Published: March 2011

For modelling the reaction of chemically distinct materials in which intermediate alloy phases are formed a simple thermodynamic description is not adequate. Despite thermodynamic prediction of multiple product phases, a single phase generally forms first which is not necessarily that of greatest thermodynamic stability or of simplest structure. Such initial reaction processes may be modelled as metastable perltectoid (solid-solid) or perltectlc (solid-liquid) reactions, characterized by large thermodynamic driving forces with superimposed kinetic and morphological constraints. The interfacial reaction problem is reviewed in light of heterogeneous nucleation theory with emphasis on non-classical aspects.
Multi-Step Micro-Crystallization Studies on Amorphous Fe90-x Six B10 Alloys
Authors: Minor W. , Malmhall R. , Roig Anna , Inoue A. , Rao K. V.
Published: March 2011

In order to elucidate the sensitivity and information that can be obtained from Magneto-Thermo-Gravimetric, MTG, technique, we present a comparative study of our results on structure relaxation as well as crystallization sequences as a function of time and temperature of amorphous Fe90-xSixB10 alloys in the Fe-rich regime, with those obtained from synchrotron Energy-Dispersive- X-ray-Diffraction, EDXD, and Differential Scanning Calorimetry, DSC methods.
Analysis of Rapid Solidification Process in The Double-Roller Method
Authors: Kogiku F. , Yukumoto M. , Shibuya K. , Ozawa M. , Kan T.
Published: March 2011

High-silicon steel was rapidly solidified to thin strips by the double roller method. Two typical macrostructures were observed: one with an equiaxed zone and the other without. The formation of the equiaxed zone is caused by an excessive gap between the rollers. Heat transfer calculations and dendrite arm syacing measurements both suggested that the cooling rate is about 103 to 104 K/sec.
Study of The Origin of The Magnetic Anisotropy in RF Sequential Co-Sputitered Co100-XBX and Co74Fe6B20 Thin Films
Authors: Kim D. Y. , Walser R. M.
Published: March 2011

We prepared thin, amorphous, compositionally modulated films (CMF) by RF sequential co-sputtering with Co, B, and Fe targets. In principle this technique can produce controlled, small (<15 Å) scale modulations in composition. The in-plane anisotropies and coercivities of the CMF were more than one magnitude larger than those of typical thin, homogeneous, amorphous, alloy films (AF). The increase in anisotropy was growth induced and could be reduced by annealing to values comparable to those of amorphous AF. The coercivity, however, could not be significantly decreased by annealing, except in CMvF with the highest boron concentration. The stability of the coercivity might, therefore, be an observable consequence of the small scale composition heterogeneity.
An Analytical Electron Microscopy Characterization of Melt-Spun Iron/Rare-Earth/Boron Magnetic Materials
Authors: Dickenson R.C. , Lawless K.R. , Hadjiipanayis G.C.
Published: March 2011

Iron/rare-earth/boron permanent magnet materials have recently been delveloped to reduce the need for the strategic element cobalt, which was previously the primary canponent of high-energy magnets. These materials are generally produced by annealing rapidly solidified ribbons or by conventional powder metallurgy techniques. This paper will report results from an analytical electron microscopy characterization undertaken to establish the relationship between the magnetic properties and the microstructure of two iron/rare-earth/boron (Fe/RE/B) alloys. Ribbons of Fe75Pr15B10 and Fe77Tb15B8 were produced by melt-spinning. To obtain optimum magnetic properties, both alloys were then annealed at 700°C, the FePrB ribbons for 6 minutes and the FeTbB ribbons for 90 minutes. Foils for transmission electron microscopy were prepared by ion-milling the ribbons on a cold stage and examined using a Philips 400T TEM/STEM equipped with an energy dispersive x-ray unit.
New Microstructural Model for Sputtered Co-Cr Magnetic Thin Films
Authors: Niimura Yoshiro , Naoe Masahiko
Published: March 2011

Rapidly solidified Co-Cr thin films with a perpedicular magnetic anisotropy have been extensively investigated as one of the most promising media for perpendicular magnetic recording system. Most of these films used to be prepared by conventional RF diode sputtering and vacuum evaporation methods. We have developed the Facing Targets Sputtering apparatus which is able to deposite the magnetic thin films without the bombardment by high energy particles to the substrate along with the capabilities to deposit films under wide range of argon gas pressure at high deposition rate. It has been found that the texture and crystallographic structure of the sputtered films are primarily dependent on the argon gas pressure and the films prepared by the Facing Targets Sputtering exhibit quite different properties from the films prepared by conventional methods. The films deposited in the argon gas at the low pressure on the plasma-free substrate using the Facing Targets Sputtering are composed of the fine polyhedral grains packed densely from the initial growth layer to the surface layer of the film. They show exellent c-axis orientation of hcp crystallites, smoother surface textures and the superior perpendicular magnetic anisotropy as compared with the films composed of so-called columnar grains deposited in the argon gas at the higher pressures using the conventional RF diode sputtering. These results imply that the sputtering apparatus which is capable to deposit Co-Cr films in the argon gas at relatively low pressure is indispensable for the preparation of superior perpendicular magnetic recording media. Therefore, the Facing Targets Sputtering apparatus seems to be quite suitable for this purpose. Further, we have proposed a new micro structural model with fine polyhedral grains obtained by our sputtering method, because this model will have the ideal structural characteristics for ultra high density perpendicular magnetic recording.
Rapidly Solidified Metal Foils by Melt Overflow
Authors: Gaspar Thomas , Hackhan Lloyd E. , Sahai Yogeshwar , Clark W.A.T. , Wood John
Published: March 2011

A single roller technique called melt overflow for direct casting metallic sheet, strip or foil is described. A simiple heat transfer nodel is developed to predict foil thickness frorn process parameters. The model agrees with thickness of Ti-6Al-4V cast strip. Cooling rates as high as 105 K/s are estimated from measuremnents of secondary dendrite arm spacings in 7075 aluminum alloys. Applications include magnesium-graphite composites.
Formation of A Quasicrystalline Phase from The Glassy State in Pd-U-Si
Authors: Drehman A. J. , Poon S. J. , Lawless K. R.
Published: March 2011

Metallic glasses of composition Pd58.8U20.6Si20.6 can be transformed to a metastable single phase with quasicrystall ne order by thermal annealing. The icosahedral symmetry of this phase was verified by both electron and x-ray diffraction. Although the metallic glass can be formed over a broad compositional range the homogeneity range of this icosahedral phase is less than 1%. This indicates strong chemical ordering in the quasicrystalline state.
Metastable Extensions of Intermediate Phases in Some Aluminum - Rare-Earth Metal Systems
Authors: Quan M.X. , Haldar P. , Werth J. , Giessen B.C.
Published: March 2011

Using the arc-furnace hammer-and-anvil method, metastable alloys in the Al-rich portions of four Al-RE systems (10-30 at. pct. RE; Re = Gd, Ho, Er and Y) were prepared and examined by XRD. The principal results are: all equilibrium alloy phases [Al4RE (T phase), Al3RE (CN12 close-packed phases) and Al2RE (Laves phase)] have substantial metastable solid solubilities for excess Al; e.g., in the Al-Y system, L phase is extended from 66.7 up to 86 at. pct. Al, suppressing any formation of the Al3RE phase in that system.

For early RE elements up to and including Gd, T phase is favored; for alloy chemically intermediate RE elements such as Y, L phase is dominant and for late RE elements (after Ho), the CP phases are extended most. DSC work indicates the formation of additional metastable phases occurring during equilibration.
Properties of Aluminum Thin Films Prepared by Targets Facing Type of Sputtering System
Authors: Hirata T. , Kaku S. , Naoe M.
Published: March 2011

The Targets Facing Type of Sputtering (TFTS) system can deposit very dense films on substrates at a high rate without undesirable influences of the plasma. Using this system, Al films 0.7 ∿ 1.5 µm thick were deposited in an argon gas pressure PAr of 9.7 × 10−2 Pa.

The grains with irregular shape grew as PAr became high. However, the number of grains per unit area decreased and their size became small when the bias voltage to the substrate Vb was -40 V. Consequently, the film surfaces became smooth. The Al films became hardest at Vb of about -40 V and were twice as hard as ones prepared without the bias voltage.

The step coverage of these Al films was very satisfactory to the wiring of the integrated circuit (IC) by adjusting Vb and PAr at the proper values.
Rapidly Solidified Titanium
Authors: Froes F. H. , Rowe R. G.
Published: March 2011

The attributes and requirements for rapid solidification (RS) are discussed and related to the characteristics of the titanium system. The extreme reactivity of liquid titanium requires the development of RS production methods tailored to this system. Compaction and processing techniques are presented followed by a discussion of the various alloy classes which have been produced by the RS approach: conventional alloys such as Ti-6Al-4V, rare earths, metalloids, eutectoid formers, beta alloys, amorphous materials, high aluminum alloys, aluminides, and other minor classes. Finally some thoughts on the future of this technology are presented.
Formation of Metastable Phases in Rapidly Quenched Binary Ti Alloys
Authors: Whang S.H. , Chi C.S.
Published: March 2011

Rapid quenching of binary Ti alloys from the melt results in various metastable phases. A systematic study has been conducted in order to elucidate principles associated with the formation of metastable phases in binary Ti alloys resulting from rapid quenching. These metastable phases that include α’, α” phases, metastable β phase, and w phase are discussed with regard to their occurrence and the extension of a phase as a function of cooling rate. Effect of cooling rate and mechanical stress applied during cooling on metastable phase formation was investigated.
Rare Earth Oxide Dispersoid Stability and Microstructural Effects in Rapidly Solidified Ti3Al and Ti3A1-Nb
Authors: Sutliff J. A. , Rowe R. G.
Published: March 2011

The microstructures of titanium aluminide alloys containing a rare earth oxide dispersion have been characterized using analytical electron microscopy. The alloys, based on Ti3A1 (alpha-2), contained 0 to 10.7 atom% Nb and 0.5 atom% Er. Alloys were rapidly solidified by melt spinning and were subsequently consolidated by HIP and extrusion. The microstructure of each alloy was examined in the as-cast, as-HIP'ed, and as-extruded conditions. A fine dispersoid spaced less than 100 nm apart was observed in ribbon aged at 750°C. The effects of processing conditions on the dispersoid distribution as a function of matrix chemistry were studied. Hot deformation was also examined to investigate the nature of the interaction between the dispersoids and the matrix during deformation.
Mechanical Properties of Rapidly Solidified Nickel-Base Superalloys and Intermetallics
Authors: Taub A. I. , Jackson M. R.
Published: March 2011

The improvements in the mechanical properties of nickel-base alloys that have been made possible by rapid solidification processing are reviewed. The results of processing by powder metallurgy, laser melting, low pressure plasma deposition and spray forming are examined. In general, the increased homogeneity obtained by rapid solidification allows for increased alloying and improved hot workability. The refined grain size improves the low and intermediate temperature strength, but leads to lower strengths at high temperature. For the high temperature applications, post solidification grain growth is required, as for example the directional recrystallization of powder metallurgy preforms. The development of a novel means of producing a fine dispersion from amorphous alloy precursors and the recent work attempting to improve the ductility of the intermetallic phases NiAl and Ni3A1 are also described.
The Strengthening Mechanism in Consolidated Rapidly Solidified Alloys
Authors: Otooni Monde A.
Published: March 2011

Attempts have been made to study mechanisms of strengthening in the Ni68W22C8B2 and the Ni45CO20 Cr10MO4Fe5B16 alloy systems during their amorphous crysialline transitions. In the Ni68W22C8B2 system where amorphous particulates of varying sizes have been cons Ti a ed at high pressure and low temperature (3.6 MPa, and 673°K respectively), the initial stage of crystallization is marked by transformation of the localized regions of the specimen. These crystallized regions contain microcracks and voids. Microhardness measurements from the consolidated specimens indicate an increasing trend in the microhardness with decreasing particulate sizes. Premature failures of the consolidated specimen during tensile stress measurements have been attributed to the presence of microcracks and voids in these specimens. In the Ni45Co20Crl0Mo4Fe5B16 alloy system isothermal annealing of an initially amorphous alloy has been allowed to produce grains of varying sizes. The tensile stress measurements from these thermally annealed ribbons indicate two distinctly different functional relationships between the strength, σ, and the grain size parameter, λ. In the early stage of transformation where grain reach a maximum growth of up to 400 Å, the functional form of the strength, σ, with the grain parameter, λ, is σ = σ + K Log λ, where σO and K are constants. During latter stages of transformation, where grains larger than 400 Å have been formed, the strength, σ, varies with the inverse square root of the grain sizes. This latter relationship is analogous with the well known Hall-Petch relationships, which describes the strength, σ, as a function of the grain sizes in conventionally processed alloys.
Microstructural Characterization of Rapidly Solidified Type 304 Stainless Steel
Authors: Wright R. N. , Flinn J. E. , Korth G. E.
Published: March 2011

The microstructures of rapidly solidified Type 304 stainless steel powders produced by vacuum gas (VGA) and centrifugal atomization (CA) have been examined. The solidification morphology and phase distribution have been characterized using optical and scanning electron microscopy, and the relative amounts of ferrite and austenite have been quantified using x-ray diffraction. Most CA powder particles contain both fcc and bcc phases, with the bcc phase predominating at small particle sizes and the fcc phase at large particle sizes. The VGA powder generally contains less ferrite, with very little dependence on the particle size. The ferrite was metastable and transforms to austenite on annealing at 900°C.
Rapid Solidification of An Al2O3-25WT.PCT.ZrO2 Oxide Alloy
Authors: Ando Teiichi , Shiohara Yuh , Flemings M.C.
Published: March 2011

TEM observation of the morphology of alumina dendrites in a rapidly solidified Al203-25w/oZrO22 oxide alloy revealed three distinct dendrite morphologies corresponding to α-, γ- and δ- aluminas. STEM analysis showed the center of the α and γ dendrites to be solute poor, but the δ dendrite center to be solute rich, indicating possible solute trapping. Theoretical calculations show interface growth velocities in excess of 3m/sec.
Thermal Stability of Rapidly Quenched TI-NI-AL Amorphous Alloys
Authors: Aoki K. , Hiraga K. , Masumoto T.
Published: March 2011

Ti-Ni-Al alloys were rapidly quenched from a molten state by the melt spinning method. Three kinds of metastable phases, namely, amorphous,nonequilibrium and quasicrystalline phases are formed in these alloys. The amorphous phase is formed in the range of 35 to 70 at% Ti and 0 to 25 at% Al. The nonequilibrium phases are formed in the composition range of 25 to 33 at% Ti. On the other hand, fine quasicrystalline phases are distributed in the amorphous matrix of the Ti-rich alloys. Crystallization temperatures and the hardness of the amorphous alloys were also examined.
Thermodynamics and Kinetics of Crystal-Amorphous Transformation in A1–x Bx Alloys During Reaction with Hydrogen
Authors: Yeh X. L. , Johnson W. L. , Tang J. Y. , Shi C. R. , Keck W. M.
Published: March 2011

The kinetics of amorphous phase formation in polycrystalline A1–xBx (A=Zr, Hf, B=Pd, Rh,.15<x<.25) alloys during reaction with hydrogen has been studied by x-ray diffraction, +19F nuclear reaction depth profiling, TEM and electron diffraction. The formation of the amorphous hydride phase is observed by TEM to begin at grain bounderies of the polycrystalline Zr1–xRhx much in the same manner that “melting” nucleates at grain boundaries. TEM micrographs further show that the phase boundary between the crystalline and amorphous phases remains sharp during the growth of the amorphous phase. Both x-ray diffraction and nuclear depth profiling studies suggest that the overall rate of transformation to the amorphous hydride phase is limited by the rate of hydrogen permeation through the sample surface.

Based on the present experiments and an analysis of the relevant free energy curves, we discuss the thermodynamic and kinetic aspects of this effect to explain why an amorphous phase is formed.
Thermal Stability and Phase Transformation in Hfl-xCux Metallic Glasses
Authors: Schulz R. , Leem N. L. , Clemens B. M.
Published: March 2011

In this paper we report the difference in the structures, physical properties and thermal behaviors of two compositions of amorphous Hf-Cu. One (Hf50CU50) is near the eutectic composition and the other (Hf67Cu33) corresponds to an intermetallic compound. Transmission and scanning electron microscopy (TEM, SEM), differential scanning calorimetry (DSC), electrical resistivity and high-angle X-ray diffraction have been used to study these glasses in detail. Amorphous Hf67 Cu33 is structurally stable up to the crystallization temperature, while Hf50 Cu50 undergoes a ductile to brittle transition associated with a chemicai phase segregation at temperatures far below the glass transition. An anomalous behavior in the resistivity is associated with this phase transformation.
The Leaching Behaviour of the Swedish KBS-Glasses ABS 39 and ABS 41
Authors: Hermansson Hans-Peter , Christensen Hilbert , Werme Lars , Ollila Kaija , Lundqwist Rune
Published: March 2011

The planned Swedish KBS glass corrosion investigation program comprises experiments with inactive glasses containing simulated waste, prolonged in-situ tests, the characterization of corrosion products, immiscibility studies, and corrosion experiments with “hot” glass.

This presentation gives a short description of the entire program. It focuses thereafter on some recent leaching results with the inactive KBS glass qualities ABS 39 and ABS 41, which were leached in a manner similar to the PNL MCC–1 test procedure.
A Methodology for Characterizing Brittle Fracture of Solid Waste Forms in Accidental Impacts
Authors: Mecham William J. , Jardine Leslie J. , Steindler Martin J.
Published: March 2011

A general method for characterizing the major practical effects of accidental impacts on waste packages and for evaluation of scale-model tests has been partially developed. Impact fracture of brittle waste forms has been shown elsewhere to produce particulates whose size distributions are described by the lognormal probability distribution. The model proposed for fragment generation involves the transformation of impact (kinetic) energy into elastic strain energy which is followed by fracture and energy dissipation into heat by the fracture particulates. The peak stresses developing during compressions are approximated as a function of time using elastic theory for a wide range of practical impact conditions for typical (glass) waste forms. The proposed methodology requires experimental validation in terms of correlation of stress and energy parameters with particulate parameters describing the results of fracture. Two kinds of preliminary correlations are presented: (1) calculations of stress parameters for a range of impact conditions; and (2) averages of particulate parameters obtained in standard impact tests.
Processing Effects on the Behavior of Titanate Waste Forms in Aqueous Solutions
Authors: Dosch R. G.
Published: March 2011

Titanate processing parameters including temperature, waste loading, redox conditions, and additives used to promote specific phases were evaluated with respect to their effect on leaching of Cs, Mo, Ca, Sr, Ba, U, Gd, and Ti in the range of 22°-150°C in leachates which included deionized water, acidic (pH 2), and basic (pH 12) solutions. Surface analyses and microstructural characterization were used to relate observed leaching behavior to processing parameters. Redox conditions were found to be very important with respect to Cs (and Mo) retention. Two Cs-bearing phases were found in titanate prepared under oxidizing conditions. One had a hollandite structure and the other contained Cs, Mo, Ca, and Fe as major constituents. The latter phase, which was more susceptible to leaching, was not observed in titanates prepared using adequate reducing conditions. Where applicable, a reference glass (PNL 76–68) was included in the leaching tests. Comparative leach rates for elements common to both waste forms were generally one to four orders of magnitude lower for the titanates within the range of conditions used.
The Use Of 222Rn as a Flow Path Monitor for Studies of Radionuclide Transport in Fissures
Authors: Hines J. , Cohen D. , Fried S. , Friedman A. M.
Published: March 2011

A technique has been developed using 222Rn as a flow path monitor. Its principle advantage over other radiotracers or dyes is that while the Kd of Rn gas in water solution is zero and hence follows the water path, its 210Pb daughter is retained strongly by rock. The immobilized 210Pb is not subject to diffusion, an important consideration in the proposed Nevada Field Test. To evaluate the technique, a series of laboratory scale experiments have been performed. Artificial fissures consisting of glass plates and prepared flat surfaces were coupled to insure well characterized fissures. Water solutions of radiotracer were metered through these fissures and the discharge monitored to produce breakthrough curves as a function of flow rate. The rock surfaces were analysed for radionuclide concentration and the rock sectioned for diffusion profile into the rock.
Formation and Properties of Americium Colloids in Aqueous Systems
Authors: Olofsson U. , Allard B. , Andersson K. , Torstenfelt B.
Published: March 2011

The formation and sorption properties of colloidal americium in aqueous solutions have been studied with variations of pH (2–12), ionic strength (0.01–1.0 M NaClO4), americium concentration (10−7 −10−11 M) and storage time (6 h–6 months). A large fraction of the americium is sorbed on the container walls or on Al2O3 in the pH-range 7–11. Around pH 5–8 and at pH above 12 centrifugable fractions (particle sizes greater than 100 nm) are obtained. The fraction formed at pH above 12, which seems to be a true hydroxide colloid, migrates through an A12O3-filled column with very little retention. The average charge of americium species in solution changes from positive values at pH below 7–8 to negative values at pH above 10–11, as indicated from electromigration studies.
Iron-Enriched Basalt for Containment of Nuclear Wastes
Authors: Welch J M. , Schuman R. P. , Sill C. W. , Kelsey P. V. , Henslee S. P. , Tallman R. L. , Horton R. M. , Owen D. E. , Flinn J. E. , Idaho Eg&g
Published: March 2011

Iron-enriched basalt (IEB) has been investigated as a containment medium for defense transuranic (TRU) and defense high-level wastes (HLW). IEB samples have been fabricated incorporating simulated and actual defense TRU wastes generated at the Rocky Flats Plant (RFP), and simulated defense high-level wastes. These samples were tested for leaching resistance and fracture toughness. Cesium and strontium volatility from an IEB melt was also assessed, using radioactively spiked samples.
Radionuclide Migration: Laboratory Experiments with Isolated Fractures
Authors: Rundberg R. S. , Thompson J. L. , Maestas S.
Published: March 2011

Laboratory experiments examining flow and element migration in rocks containing isolated fractures have been initiated at the Los Alamos National Laboratory. Techniques are being developed to establish simple fracture flow systems which are appropriate to models using analytical solutions to the matrix diffusion - flow equations, such as those of I. Neretnieks [1]. These experiments are intended to be intermediate steps toward larger scale field experiments where it may become more difficult to establish and control the parameters important to nuclide migration in fractured media.

Laboratory experiments have been run on fractures ranging in size from 1 to 20 cm in length. The hydraulic flow in these fractures was studied to provide the effective apertures. The flows established in these fracture systems are similar to those in the granite fracture flow experiments of Witherspoon et al. [2]. Traced solutions containing 85Sr and 137Cs were flowed through fractures in Climax Stock granite and welded tuff (Bullfrog and Tram members, Yucca Mountain, Nevada Test Site). The results of the elutions through granite agree with the matrix diffusion calculations based on independent measurements of Kd. The results of the elutions through tuff, however, agree only if the Kd values used in the calculations are lower than the Kd values measured using a batch technique. This trend has been previously observed in chromatographic column experiments with tuff.
Zirconolites from Sri Lanka, South Africa and Brazil
Authors: Ewing Rodney C. , Haaker Richard F. , Headley Thomas J. , Hlava Paul F.
Published: March 2011

Zirconolites, CaZrTi2O7, from Sri Lanka and Pala Bora, South Africa, and a calzirtite, CaZr3 TiO9, from Jacupiranga, Brazil, were examined using the electron microprobe, x-ray diffraction (annealing study), transmission electron microscopy, scanning electron microscopy and optical microscopy. The x-ray data indicate that all three zirconolites are metamict. Both Sri Lanka zirconolites are amorphous to the limits of resolution of the electron microscope (֮10 A). The Pala Bora zirconolite is largely amorphous but contains isolated domains (50–200 A) of crystalline material which may be the result of post—metamict recrystallization and alteration. The only other significant evidence for chemical alteration was the lower Th concentration (1–2 weight percent) and slightly lower analytic totals for the rims of the Sri Lanka zirconolites. Upon annealing at 1130°C for 5 hours, all three zirconolites recrystallized as microcrystalline aggregates. Refined unit cell parameters and volumes are consistent with published data for synthetic zirconolites. Both Sri Lanka zirconolites contain microvoids, spherical in shape, and 200 Angstroms to 2 microns in size. This porosity may be the result of helium accumulation arising from the decay of U and Th. The calzirtite was highly crystalline, exhibited no porosity, and was unchanged by the annealing treatment.
Migration Rates of Brine Inclusions in Single Crystals of Nacl
Authors: Chou I-Ming
Published: March 2011

Rock-salt deposits have been considered as a possible medium for the permanent storage of high-level radioactive wastes and spent fuel. Brine inclusions present in natural salt can migrate toward the waste if the temperature and the temperature gradients in the vicinity of the radioactive waste are large enough. This migration is due to the dissolution of salt at the hot side of the salt-brine interface, ion diffusion through the brine droplet, and the precipitation of salt at the cold side of the salt brine interface.
Permeability, Swelling and Radionuclide Retardation Properties of Candidate Backfill Materials
Authors: Westsik J. H. , Bray L. A. , Hodges F. N. , Wheelwright E. J.
Published: March 2011

A backfill placed between a nuclear waste canister and the host geology of a nuclear waste repository can impede the migration of water through the waste package and retard the movement of radionuclides into the geologic formation. Hydraulic conductivities and swelling pressures are being determined as functions of the density of the compacted backfill, temperature, radiation dose, hydraulic head and the chemical composition of the permeating fluid. Bentonite clays and bentonite/sand mixtures have received initial emphasis. Sodium bentonite and calcium bentonite samples compacted to a dry density of 2.1 g/cm3 had hydraulic conductivities in the range of 10−12 to 10−13 cm/s. In addition, batch distribution ratios (Rd) for Sr, Cs, Am, Np, I, U and Tc have been measured for a number of candidatebackfill materials. Both initial permeability and sorption studies have used a synthetic basaltic ground water.
PNL-Sandia HLW Package Interactions Test: Phase One
Authors: Molecke Martin A. , Bradley Donald J. , Shade John W.
Published: March 2011

The first phase of a complex high-level waste (HLW) package interactions test in a salt environment has been completed. The test system consisted of PNL 76–68 HLW glass (loaded with inactive fission products and 238U) surrounded by a stainless steel waste canister, a TiCode- 12 overpack, a bentonite/sand backfill, excess brine leachant, and a bedded rock salt container, all heldwithin a 19-liter autoclave. All components were physically compromised in order to force wasteform-barrier-salt interactions to occur during this 95-day, 250°C overtest. Analyses of leachant, wasteform, and all barrier surfaces were performed. Test data included the synergistic effects between barriers and confirmed previous analyses of simpler systems. The glass wasteform exhibited some surface alteration but was not dissolved to any significant degree. The TiCode-12 overpack showed minimal uniform corrosion and no localized attack. Observed mineralogical alteration of the backfill was minimal.
Implantation and Industrial Metal Processing
Authors: Fromson Robert E. , Kossowsky Ram
Published: March 2011

The potential for reducing indirect manufacturing costs and the challenge to improve component performance justify active consideration of ion implantation in industrial metal processing. The need for interaction between the scientific community and the industrial community is shown with specific examples of methods employed by Westinghouse for accelerating this interaction.

A review of implantation activities at Westinghouse include basic technology studies, equipment considerations, material evaluation capabilities, factory trial results, and some of the planned areas of future interest. The preferred characteristics of targets of opportunity are identified and needed advances in technology and equipment are discussed.
Experimental and Theoretical Analyses of Small-Scale Radionuclide Migration Field Experiments
Authors: Erickson K. L. , Fortney D. R.
Published: March 2011

Analyses have been completed which provide guidance for conducting radionuclide migration field experiments. Characterization of nonwelded tuffs and laboratory experiments defining dominant chemical phenomena were used to develop a model for describing migration in fractured porous rock. Criteria for obtaining optimum experimental conditions were developed in terms of the key variables dominating migration in a given rock type, namely the fracture aperture, distribution coefficient, and average fluid velocity. For simple dissolved species, which are reversibly sorbed, variations in fracture aperture and fluid velocity affect experiment results much more than variations in distribution coefficient. Therefore, the experiment should be designed to optimize hydrogeologic conditions rather than sorption properties.
Radiation Induced Sodium Metal Colloid Formation in Natural Rock Salt From Different Geological Localities
Authors: Loman J. M. , Levy P. W. , Swylertt K. J.
Published: March 2011

Radiation damage has been studied in natural rock salt from various localities, including potential repository sites. In the 100 to 300 C range the damage consists of point defects, primarily F-centers, and colloidal metal sodium particles. With increasing dose the F-centers grow to a saturation level, reached at 107 –108 rad, that decreases with increasing temperature to a negligible level at 300 C. Colloid concentration vs. irradiation-time curves follow nucleation and growth curves accurately described by C tn, or C(dose)n, relations at large irradiation times. For fourteen samples,n = 1.85± 0.18 but the values of C vary by a factor of more than 103. The constant C is related to the sample strain, the impurity and void content, dose rate, and possibly other factors. The currently available data indicate that rock salt adjacent to radioactive waste canisters, at a temperature of 150 C, will contain between 0.01 and 10 mole percent of sodium metal when the total dose reaches 1010 rad.
Novel Experiments for Understanding the Shallow Land Burial of Low-Level Radioactive Wastes
Authors: Depoorter G. L. , Hakonson T. E.
Published: March 2011

Data on the basic processes that occur in the shallow land burial of low-level radioactive wastes are needed to engineer facilities with guaranteed performance, to validate models for system predictions, and to provide input to models that consider contaminant pathways out of the facility. Two types of novel experiments that will provide experimental data on the basic processes in shallow land burial facilities are described in this paper. Generic experiments that give data on the movement of water and radionuclides and an experiment that is particularly important for semi-arid sites are described.
Nuclear Waste Disposal: The Interface Between Performance Assessment and Research
Authors: Lyon R.B.
Published: March 2011

The potential impact of the post-closure phase of a nuclear fuel waste disposal project is radiation dose to man. Radiation dose is estimated as the end product of a total systems analysis. Field and laboratory research must be assimilated in a form that can be accepted by the total systems analysis procedure. A central focus of this assimilation must be the consideration of uncertainties in the analysis and data used. Irreducible uncertainty arises because of the wide variability in natural systems and the unprecedented extrapolation into the distant future. The SYVAC computer program provides a framework for assimilation of the results of the field and laboratory research with a systematic treatment of uncertainty. A SYVAC assessment of the post-closure performance of a Canadian nuclear waste disposal facility is presented with particular illustrations of the interface between the assessment models and data and the field and laboratory research.
Radiation Effects in Nuclear Waste Glasses
Authors: Denatale J. F. , Mcelfresh D. K. , Howitt D. G.
Published: March 2011

The radiation damage of a nuclear waste glass is shown to be associated with enhanced phase decomposition, oxygen bubble formation, and, when the glass is exposed to air saturated water, enhanced leaching.
Photoinduced Paramagnetic Defects in Amorphous Silicon Dioxide
Authors: Stathis J. H. , Kastner M. A.
Published: March 2011

Several paramagnetic defects are created by exposure of amorphous SiO2 to sub-band-gap light. The spectra of the dominant centers can be isolated by using their annealing, microwave power, and excitation-photonenergy dependence. The results are discussed in terms of specific models for the intrinsic defects in a-SiO2.
Electron Paramagnetic Resonance and Optical Study of Radiation-Induced Defect Centers in Doped Silica Glasses
Authors: Schwartz Robert N. , Tangonan Gregory L. , Blair G. Richard , Chamulitrat Walee , Kevan Larry
Published: March 2011

Gamma- and UV-induced defect centers in germanium and fluorine doped silica have been studied by electron paramagnetic resonance (EPR) spectroscopy. The complex spectrum at g≃2 in γ-irradiated germanium doped glass corresponds to a superposition of resonances from several germanium E′-centers. In UV-irradiated samples, however, the EPR spectrum is dominated by only one type of germanium E′-centers. Significant spectral simplification of γ-irradiated germanium doped silica can be achieved by heating or broadband photoirradiation. Similar results are observed in multimode germanium doped core optical fibers. UV-induced optical loss spectra in the 0.5–1.5 μm wavelength range were also measured in these core fibers as well as the growth kinetics of the UL-induced absorption. Gamma-irradiation of fluorine doped silica generated two different types of silicon E′-centers, Ea1. At lower radiation dose one sees a mixture of Ea1 and Ea2, but at higher radiation dose Ea2 dominates. A spectrum dominated by the Ea2 variant is also observed in LW-irradiated samples and in photobleached low gamma dose samples.
Transition Metal Ion Species in Glass: A Comparison of Optical Absorption and Luminescence Evidence
Authors: White William B. , Knight Diane S.
Published: March 2011

Optical absorption spectra of d-d transitions can be interpreted through crystal field theory as evidence for at least four kinds of species: traditional network modifier ions (Mn2+, Fe2+, and Ni2+), octahedral complexes (Cr3+, Mn3+), tetrahedral complexes (Co2+, Fe3+), and network-forming ions (Ti4+, Fe3+). Absorption spectra measure only majority species since crystal field bands are broad and overlapping. Luminescence spectra reveal minority species if these species happen to be efficient emitters under laser excitation. Doublet-quartet emission bands (Cr3+) are independent of crystal field but allow the distinction between species because of small differences in bonding which shifts the Racah B parameter. Quartet-sextet emission (Mn2+, Fe3+) is strongly dependent on coordination number and bond lengths. Qualitative, but not quantitative, changes in speciation can be followed as glass composition is varied. Conceptually, the complexation of transition metal ions in insulator glasses results from a competition between the transition metal and the glass-forming framework for p-orbital electrons of non-bridging oxygens. Complexation is further enhanced in clustered glasses where the ions segregate into the more depolymerized units.