bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Thermal Expansion Mismatch on Fiber Pull-out in Glass Matrix Composites
Authors: Deshmukh U. V. , Kanei A. , Freiman S. W. , Cranmer D. C.
Published: March 2011

Single fiber pull-out tests can be used to directly measure the fiber-matrix interfacial shear stress in glass matrix composites. The system under investigation consisted of a soda-lime-silica glass matrix containing SiC monofilaments with a carbon-rich surface. The presence of the carbon-rich layer on the surface of these fibers makes them non-wetting to most glasses; hence the fibers are held in the matrix only by frictional forces acting at the interface. The mechanical gripping responsible for this force can be changed by manipulating the glass matrix/fiber thermal expansion coefficient mismatch. Frictional stresses (τ) and friction coefficients (μ) obtained for SiC monofilaments in a soda-lime-silica glass matrix were compared with previously obtained data on a borosilicate glass matrix (τ = 2–3 MPa, μ = 0.72 ± 0.36). For the soda-lime-silica system, τ's of 4–20 MPa and μ of 0.10 ± 0.03 were obtained. τ in the soda-lime-silica system is higher due to the larger difference in thermal expansion mismatch between the fiber and matrix. The differences in μ may be due to lubrication effects caused by water at the fiber-matrix interface.
Electrochemical Synthesis of Zirconia
Authors: Switzer Jay A. , Phillips Richard J.
Published: March 2011

Zirconia powder was produced in aqueous solution from zirconyl nitrate using electrogenerated base. Both divided and undivided electrochemical cells were used. In the divided cell, hydroxide ion was discharged in the cathode compartment, and hydrated zirconia was produced. The as-produced material was weakly agglomerated, amorphous, and had a surface area of up to 316 m2/g. The surface area of the powder did not vary systematically with the electrosynthesis current density, but did depend on subsequent processing. Crystalline zirconia was produced by calcining in air at temperatures above 400°C. Tetragonal zirconia was the only phase observed until about 800°C. After calcining at 800°C the crystallite size increased to about 20nm and about 34% monoclinic zirconia was produced. When an undivided cell was used, the pH remained constant (1–1.5) throughout the electrosynthesis, and amorphous zirconia deposited on the cathode.
A Study of Solvent Effects on the Synthesis of Pure Component and Composite Ceramic Powders by Metal Alkoxide Hydrolysis
Authors: Harris Michael T. , Byers Charles H. , Brunson Ronald R.
Published: March 2011

The production of ceramics having high density, low porosity, and fine grains requires the use of high-purity metal oxide powders that consist of particles of uniform shape, size, and composition. Metal alkoxide hydrolysis is an attractive method for the synthesis of high-purity metal oxide particles. The nature of the precipitate formed is affected by the solvent.

This present study investigates the growth kinetics and characteristics of metal oxide particles (i.e., ZrO2 and TiO2) that are produced in various alcohol solvents (ethanol, 1-butanol, 2-butanol, and tert-butyl alcohol). Results are also presented for the synthesis of uniform homogeneous composite metal oxide particles (i.e., Y2O3-ZrO2 and ZrO2-TiO2) by low temperature metal alkoxide hydrolysis.
Structural Investigation of the Hydrolysis-Condensation Process of a Modified Titanium Alkoxide.
Authors: Babonneau Florence , Leaustic Anne , Livage Jacques
Published: March 2011

Titanium isopropoxide was modified with acetylacetone in order to get stable photosensitive colloids via an hydrolysis-condensation process. The various steps of this process were followed by infrared, 1H and 13C NMR and X-Ray absorption (XANES and EXAFS). The latter techniques provided some interesting structural data (coordination of titanium, Ti-O and Ti-Ti distances) on the various species, from the precursor to the colloids. A structural model is proposed for each one, with a scheme of the different reactions occuring during the process.
The Optical Behavior of Organic and Organometallic Molecules in Sol-Gel Matrices
Authors: Dunn B. , Knobbe E. , McKiernan J. M. , Pouxviel J. C. , Zink J. I.
Published: March 2011

The low temperatures involved in sol-gel processing have enabled organic and organometallic molecules to be incorporated in gel matrices. These molecules serve as optical probes to characterize gel chemistry and structure. The present paper describes the use of luminescence spectroscopy to detail matrix rigidity effects and protonation/deprotonation reactions during the sol-gel transition and subsequent aging processes. In separate experiments, the addition of a laser dye, rhodamine 6G, has enabled us to demonstrate lasing and optical gain in a silica gel.
Chemical Control of Stress in Sol-Gel Derived Titania Films and Their Pressure Dependent Optical Properties
Authors: Frydrych Wendy S. , Exarhos Gregory J. , Ferris Kim F. , Hess Nancy J.
Published: March 2011

Optical properties and durability of thin films are influenced by strain which can be evaluated from frequency shifts of the lattice phonon lines in measured Raman spectra. The response of titania samples to applied pressure is reported in this work. Anatase and rutile samples of thin films (sol-gel and sputter deposited) and bulk materials have been subjected to hydrostatic pressures approaching 100 kbar in a diamond anvil cell. Results indicate that the rutile samples exhibit similar responses to applied pressure. Anatase sol-gel films exhibit a pressure-dependent response that suggests that the sol-gel film is more compressible than the bulk material, and a pressure-induced phase transformation observed for the bulk material is inhibited in the anatase sol-gel film. The anomalous pressure response of the anatase sol-gel film may result from the film microstructure which has been shown by transmission electron microscopy to consist of spheres of crystalline TiO2 surrounded by microscopic voids.
An Electron Microscopy Study of the Alkaline Hydrolysis Products of Tetraethoxysilane
Authors: Adams Jeffrey , Baird Thomas , Braterman Paul S. , Cairns James A. , Segal David L.
Published: March 2011

The hydrolysis of tetraethoxysilane was studied in an ethanol-water system with ammonium hydroxide catalyst. Reactions were carried out with water concentrations of 5M and 10M and ammonia concentrations up to 1.7M, and the products examined by electron optical methods. Variation of reagent concentrations lead to changes in the product morphology from small irregular particles, through roughly spherical and spherical particles to large fused particles. Within the range of particulate material the variations in size can be related to the effect of reagent concentrations by consideration of the reactions occurring. The effect on morphology of replacing ammonia with ethylamine was investigated and resembles that of the use of much higher ammonia concentrations.
Comparison of Several CU(I) and CU(II) Precursors for the Sol-Gel Preparation of HighTCSuperconducting Metal Oxides
Authors: Accibal Mariquita A. , Draxton Jonathan W. , Gabor Allen H. , Gladfelter Wayne L. , Hassler Beth Anne , Mecartney Martha L.
Published: March 2011

A comparison of the use of three different coordination compounds of copper as precursors for the sol-gel synthesis of YBa2Cu3O7-δ has been made. For yttrium, the tris(isopropoxide) was used exclusively, while the use of both Ba(O-i-Pr)2and Ba(OCH2CH2OEt)2(preparedin situfrom Ba metal) as sources for Ba were studied. After dissolving Y(O-i-pr)3, a Ba source, and the copper(I) alkoxide, [Cu(O-i-Bu)]4, hydrolysis led immediately to an orange gelatinous solid which yielded YBa2Cu3O7-δ upon firing in oxygen. Copper(II) acetate was found to give heterogeneous mixtures under our conditions and was not further studied. Copper(II) acac (acac = acetylacetonate) yielded the best results. Partially hydrolyzed solutions of Cu(acac)2, Ba(OCH2CH2OEt)2, and Y(O-i-pr)3were spin coated on SrTi03 (100) and fired under oxygen to give oriented (baxis normal to the surface) thin films of YBa2Cu3O7-δ. The onset of superconductivity for the films was 92 K, but they did not reach zero resistance until much lower temperatures.
Branching Theory in Sol-Gel Processing
Authors: Peppas Nikolaos A. , Scranton Alec B. , Tsou Andy H. , Edwards Dawn E.
Published: March 2011

The complex sequence of the hydrolysis/polymerization reaction of certain types of alkoxysilanes is modelled using a novel approach based on the branching theory. Network formation is described, resulting from the reaction of multifunctional oligomers. Expressions are derived for the critical silane conversion at the gel point, the molecular weight, and changes in the sol and gel fractions as a function of time.
NMR Characterization of Precursors to Chemically Derived Ceramics
Authors: Basil John D. , Lin Chia-Cheng
Published: March 2011

High resolution 29Si NMR spectroscopy has been used to study the hydrolysis and condensation reactions of TEOS and related silicon alkoxides under a range of conditions selected to model initial steps in the formation of ceramic precursors. Kinetic results have led to a detailed description of the role of various reaction parameters and to differences in reactivity of various polyethoxysiloxanes. Reactivity studies have provided insight into the processes that form multicomponent alkoxide/oxide materials. Titanium alkoxides in particular can act as catalysts for silanol condensation in addition to forming Si-O-Ti linkages, and the former role may predominate in certain systems.
Chemical Precursors to Zinc Sulfide: ZnS Whisker Synthesis
Authors: Guiton Theresa A. , Czekaj Corinna L. , Rau Melinda S. , Geoffroy Gregory L. , Pantano Carlo G.
Published: March 2011

A variety of reactions employing organometallic precursors have been explored for the synthesis of ZnS. One of the most successful routes involves the reaction of [EtZn(SButS)]5 with H2S at ambient or sub-ambient temperature to yield a precipitate which is subsequently heated under flowing H2S at 500°C to yield a mixture of sub-micron particles and single-crystal ZnS whiskers. Transmission electron micrographs of the [EtZn(SBut)]5 products indicate that the ZnS morphology is critically dependent upon the rate of H2S reaction. Corresponding x-ray/ electron diffraction, electron microscopy, elemental analysis, NMR and infrared spectroscopies have been conducted. A summary of the chemical methods, product characterization results, and proposed synthesis mechanisms will be presented.

The authors gratefully acknowledge the Office of Naval Research for the support of this research under Contract N0014–86-K-0191.
The Effect of Trioxane in HF-Catalyzed Sol-Gel Reactions of Tetraethoxysilane
Authors: Dorain Paul B. , Rafalko Joseph J. , Feeney James E. , Forbes Charles E. , Carney Raymond V. , Che Tessie M.
Published: March 2011

Porous silica glasses have been prepared using an HF-catalyzed tetraethoxysilane(TEOS)-ethanol-water formulation. The optical and physical properties of these glasses, which find use as host matrices for optical organic dyes, can be further improved with the addition of 1,3,5-trioxane to the sol-gel chemical system. In order to understand the effect of trioxane, the time-dependent concentrations of the species involved in TEOS hydrolysis and condensation have been followed by Raman, FT-IR, and NMR spectroscopie methods in both HF-catalyzed TEOS-ethanol-water systems with and without trioxane.
Silicon-29 Nuclear Magnetic Resonance Spectroscopy of Silicon Ethoxide and Titanium Ethoxide Sols: Resonance Assignments and Solution Stability
Authors: Boulos E. N. , Carduner K. R. , Carter R. O. , Best M. F.
Published: March 2011

Silicon-29 NMR spectroscopy has been widely applied to characterize the development of molecular complexity of silicon alkoxide sols. In the present study, the progression of molecular complexity of partially hydro-lyzed/condensed tetraethoxysilane (TEOS) sols with increasing H2O/TEOS ratio is demonstrated by the study of a carefully prepared set of solutions. Intriguing trends in the 29si NMR spectra of increasingly hydro-lyzed sols are discussed. In an set of samples, TEOS is replaced in part by tetraethoxytitane, Ti(OEt)4 (TEOT). The effects on the 29Si NMR spectrum due to the presence of TEOT are presented and interpreted in terms of changes in the distribution of siloxane monomers and oligomers in solution. Preliminary data on the stability of these solutions with time are reported.
An Analytical and Experimental Study of Plasma Spraying of Alumina
Authors: Varacalle D. J.
Published: March 2011

As part of an investigation of the dynamics that occur in the plume of a typical thermal spray torch, an analytical and experimental study of the plasma spraying of alumina is being performed; preliminary results are reported here. Numerical models of the physical processes in the torch column and plume were used to determine the temperature and flow fields. Computer simulations of particle injection (15, 34, and 53 μm alumina particles) are also presented. The alumina experiments were conducted at a 35 kW power level using a 100 scfh argon and 15 scfh hydrogen gas mixture for two alumina powders. The quality of the coatings is discussed with respect to porosity, sample metallography, and microhardness.
Oxide-Diamond Composite Coating Via Sol-Gel Method
Authors: Nazeri-Eshghi Azar , Mackenzie J. D. , Yang J.-M.
Published: March 2011

Use of micron-size particles of synthetic diamond in oxide matrices prepared by sol-gel processing is explored. Alumina and borosilicate-diamond composite coatings are deposited on soda-lime microscope glass and fused silica substrates using dipping technique and thermophoresis. By varying the thermal gradient between the substrate and the solution, the quality of the films and the concentration of the particles can be controlled.
Experiences with Sol-Gel Bonded High Porosity Alumina Fiber Materials for Filter Applications
Authors: Handrick Karin E. , Mohlratzer August , Ostertag Rolf , Sporn Dieter , Schmidt Helmut
Published: March 2011

High porous alumina fiber structures appear promising for hot gas filtration in particular for diesel particulate traps. For this purpose, however, a method is required for manufacturing of stable shapes resistant to the blow-out by the gas flow. The sol-gel-process was expected to be the best suited method for fiber bonding to provide the required stability.

The main tasks of the development-work were a uniform isotropie fiber-distribution, the adaptation of the sol-gel-process to the application, and the deliberate synthesis of the gel-derived alumina bonding phase.

The appropriate fibrous structure was obtained by a repeated filtration of sol/fiber suspensions. The properties of the ceramic binder were adapted by concentrating the sol and/or adding aluminas or aluminium hydroxides.

Testing of prototypes with optimized structures has shown, however, that the stability of the structure decreased after thermal load. The thermal fatigue of x-A12O3 is assumed to be responsible for this failure.
The Influence of Alkali Metal Hydroxides on Silica Condensation Rates: The Role of Ion Pairing
Authors: McCormick A. V. , Bell A. T. , Radke C. J.
Published: March 2011

The condensation kinetics and the role of Ion pairing are investigated for silicate anions in alkaline solutions. Selective, and non-selective inversion recovery experiments are performed using the Si NMR spectrum of alkali metal silicate solutions. In this way the rates of condensation of silicate monomers is studied as a function of the nature of the base. These rates exhibit maxima with increasing cation size. The maxima are interpreted in terms of the concentration and activity of ion pair intermediates of the Si exchange reaction.

Interactions between alkali metal cations and larger silicate anions in silicate solutions are investigated using NMR spectroscopy of the cations. The chemical shift and the resonance llnewidths are used to estimate the concentration of cation-silicate ion pairs. The concentration of pairs involving large anions increases with increasing cation size. Thus it is expected that condensation kinetics are influenced by the size of the silicate fragment.
Optical Characterization of Silica Aerogel
Authors: Hrubesh Lawrence W. , Alviso Cynthia T.
Published: March 2011

Two optical methods are described for mapping the local variations of refractive index within monoliths of porous silica aerogel. One is an interferometrie measurement that produces “iso-index” fringes in a two dimensional image; an orthogonal view gives the third dimension information. The other method uses the deflection of a He-Ne laser beam to map the gradient index within a sample. The quantification of the measurements is described and the accuracy of the results is discussed.
Rheological Monitoring of Gelation Kinetics of Siuca Sols
Authors: Khan S. A. , Rabinovich E. M. , Prud'homme R. K. , Sammon M. J. , Kopylov N. J.
Published: March 2011

Dynamic oscillatory measurements at low strains are used to monitor the gelation kinetics of particulate aqueous sols composed of alkoxide-derived silica powders. The dynamic storage modulus is sensitive to the sizes of the growing clusters below the gel point. A transition in the modulus is observed and large normal forces are measured at the gel point. These tests do not disrupt gel structure (in contrast to shear viscosity measurements) and therefore the measurement process does not alter the gelation kinetics. To facilitate gelation of sols composed of low-surface area silica particulates, silica powders doped with F ions were added to the undoped powder in various concentrations (10, 15 and 20 wt.%). These additions allowed a change in gelation time from 80 min. (for 10% of the F containing powder) to 17 min. (for 20%).
Polymetallic Alkoxides - Precursors for Ceramics
Authors: Mehrotra Ram C.
Published: March 2011

Beginning with the work of Dislich, metal alkoxides have been increasingly used for the preparation of oxide-ceramics by the ‘sol-gel’ process. In spite of higher initial cost of alkoxides, their main advantages are (i)homoge-neous mixing at molecular level in the initial solution; (ii)ease of hydrolysis; and (iii) lower sintering temperatures.

Although the formation of new chemical bonds between different alkoxides employed in the starting mixed solution has been envisaged, the actual isolation of a large variety of polymetallic alkoxides in our laboratories has given an entirely new turn to the expectations (e.g., preparation of spinel from magnesium bis-tetraalkoxyaluminates) from this process. Some such possibilities are being presented for synthesis of novel ceramic materials.

Reactions of polymetallic alkoxides with water, alcohols andβ-diketones would be discussed to throw light on their hydrolysis process in the presence of other alcohols and chelating ligands.
Techniques for Archaeothermometry
Authors: Palmiter Terese V. , Johnson Paul F.
Published: March 2011

This paper describes methods which have been used for the retrospective estimation of the firing temperatures of ancient ceramics, ranked by the reviewers in order of applicability from those considered least effective to the most successful. The techniques discussed include those that correlate color, physical, elastic and electronic properties, thermoluminescence sensitivity, morphology, mineralogy, and thermal behavior with temperature.
Glass Hydration Mechanisms with Application to Obsidian Hydration Dating
Authors: White William B.
Published: March 2011

Chemical analysis of typical obsidians place them with a group of silica- and alumina-rich glasses constructed of a three dimensional framework of silica and alumina tetrahedra with nearly all tetrahedra sharing corners. Raman and infrared spectra of unweathered obsidians confirm the high degree of polymerization as well as some additional structural disorder. Analysis of dissolution rates of various glasses shows obsidian to be among the most stable, comparable to the most durable synthetic glasses. Surface layers on glasses can be chemically characterized by depth-profiling techniques such as SIMS and SIPS that give depth-concentration profiles for individual elements. Hydration rinds on glasses can be structurally characterized by infrared spectroscopy which shows both hydration and re-polymerization as the rinds age. Because obsidians are already completely polymerized glasses, their hydration rinds are mainly a result of hydrolysis and alkali exchange.
Radiographic Imaging Technologies for Archaeological Ceramics
Authors: Ellingson William A. , Vandiver Pamela B. , Robinson Thomas K. , Lobick John J.
Published: March 2011

In archaeological studies of ceramic materials, nondestructive evaluation (NDE) methods are needed to better understand the nature and evolution of ceramic fabrication techniques [1] and even to authenticate ancient ceramics [2]. The desired data are similar to those sought in modern fine ceramics, especially advanced structural ceramics [3]. X-ray imaging technologies, developed to characterize structural ceramics, were applied to three samples, a modern and two archaeological ceramics, in order to obtain fabrication information. They were imaged using various X-ray image receivers: electrostatic receivers (Xeroradiography Xerox 125 and 175, Xerox Medical Systems, Pasadena CA), photostimulable phosphors (Fuji Photo Film Co., Japan, 1985 Prototype System FCR-101), and high-resolution industrial X-ray film (Kodak, Rochester, N.Y.). Ultrasound and dye penetrants had failed to reveal methods of manufacture in the ancient ceramics because of their highly porous fabric (1).
Protective Coatings for Stained Glass
Authors: Colby Mary W. , Yuen Ting J. , Mackenzie J. D.
Published: March 2011

The protection of glass against water-initiated chemical corrosion is a significant problem. Presently, organic polymers and inorganically modified polymers are being used to protect art glass. However, the service life and durability of these coatings are not entirely satisfactory. Oxide coatings would offer much greater resistance to water penetration. Water permeability through a polymer coating is some ten orders of magnitude larger than that through an oxide coating. This, coupled with a higher scratch resistance, makes oxide coatings promising candidates for the protection of stained glass. Methods to deposit an oxide on glass at relatively low temperatures include sol-gel processing and vapor deposition. This paper compares the performance of different oxide and non-oxide coatings and presents methods for the deposition of oxide coatings at low temperatures.
The Structure of Works of Art and Historic Artifacts
Authors: Meyers By Pieter
Published: March 2011

Past civilizations almost always have left us with some of their products. These remains may include the remnants of entire cities with palaces, temples, houses, cemeteries, including written records of the activities of their people as well as artifacts produced and used by these people. Such artifacts are most useful if they are found in the context of their previous use. Unfortunately, that is often not the case. Many archaeological objects appear on the art market or exist in museums or private collections without a reliable provenance.
Ancient Marble Sculpture: Geochemical Characterization of Surficial Weathering Products
Authors: Margolis Stanley V. , Preusser Frank , Showers W.J.
Published: March 2011

Quantitative scientific determination of the authenticity and age of marble sculpture is an important goal of geo-archaeologists and conservation scientists. Geochemical and petrographic techniques are used here to investigate rock weathering and mineral alterations responsible for the “patina” and alteration layers on marble sculpture. We present oxygen and carbon isotopic, scanning electron microscopic and electron microprobe analyses of both fresh marble and weathering crusts materials from cores taken from Cycladic and Archaic Greek sculptures and from ancient quarries, to evaluate these techniques as indicators of antiquity.

Calcitic marbles exhibit an altered weathering crust of variable thickness, where calcite has been recrystallized and interpenetrated with inclusions of iron oxide, clay minerals, gypsum and other authigenic minerals. The thickness and composition of these crusts varies with soil and water chemistry as well as marble density, texture and age.

Microprobe analyses indicate trace element gradients from fresh to weathered calcite. Carbon and oxygen isotopes can differentiate between insitu alteration and precipitated carbonate. Dolomitic marbles can exhibit calcitic surficial layers formed by dedolomitization, which can be confirmed by isotopic and microprobe analyses.

Analyses of known forgeries, ancient quarry samples and artificially weathered marbles have further documented our criteria and show that the majority of diagnostic geochemical and mineralogical features seen on ancient Greek sculptures cannot be accurately duplicated by artificial means.
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

The 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.
Pixe Spectrometry as an Aid to Reconstruction of Ancient Processes of Bronze Production
Authors: Swann C.P. , Fleming S.J.
Published: March 2011

The process of translating copper ore into a finished bronze involved a series of discrete steps (Fig. 1), the products and by-products of which comprise a diversity of materials. The full characterization of these materials, and thereby the reconstruction of how the metalworking artisans of a particular culture went about their craft, requires a variety of analytical tools, each applied with specific interpretive goals in mind. For example, the use of high power optical microscopy (with magnifications ranging 10x to 400x) allows a qualitative description of ore and slag petrography [1], and the definition of individual phases in metal microstructure (see, for example, refs. [2,3]); the use of high temperature cell (HTC) microscopy, offers a novel means of studying a slag's thermodynamic properties [4]; and so on.
Prediction of Glass Durability as a Function of Environmental Conditions
Authors: Jantzen C. M.
Published: March 2011

A 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

Fluoride 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

Semiconductor 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.
Degradation of Non-Oxide Reinforcement and Oxide Matrix Composites
Authors: Hermes E. E. , Kerans R. J.
Published: March 2011

The objective of this work was to determine the mechanisms of oxidative degradation of two non-oxide reinforced oxide composites. The composite systems studied were: (1) SiC whiskers in MgAl2O4 spinel and (2) SiC whiskers in 3Al2O3–2SiO2 (mullite). The components of the composites were chosen for their stability, purity, thermochemical compatibility, and oxidation resistance.
Materials for Rocket Engine Applications
Authors: Schoenman Leonard
Published: March 2011

Advanced 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

Ellipsometric 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

The 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

Laser-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

Ion 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

Using 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.
The Optical Properties of Nitrogen Implanied Allminum Nitride Films
Authors: Fujihana Takanobu , Kobayashi Kenzo , Namba Susumu , Dai Yisheng , Iwaki Masaya
Published: March 2011

Effects of N-implantation on the composition depth profile, the chemical bonds and the optical transmittance of AlNx films have been investigated by means of Auger Electron Spectroscopy (AES), Fourier Transform Infrared (FT-IR) spectroscopy and visible transmission spectroscopy. AINx films were deposited on silicon (111) and commercial glass by an Activated Reactive Eyaporation (ARE) technique near room temperature. The 40 and 80 keV N+ -implantations were carried out at room temperature with doses ranging from 5×1016 to 5×1017 ions/cm2. The result of AES measurements revealed that the as-deposited AlNx film on Si consists of the AIN layer near the topsurface and the Al-rich layer near the interface. The concentration of nitrogen in the films increases as the N-dose increases up to 1×1017 ions/cm2. The N-implantation at a dose of 5×1017 ion/cm2 causes the interface between the film and the Si substrate to mix rather than increase the nitrogen concentration in the film. This higher dose implantation makes the FT-IR absorption peak corresponding to Al-N bonding become clear, and it makes the optical transmittance at a wavelength of 4400 Å go from 7% for as-deposited AINx film up to 70–90%. It is concluded that N-implantation into AlNx films causes the formation of AIN with a stoichiometric ratio to improve optical properties of the film.
Laser-Assisted Etching of Lithium Niobate
Authors: Orloff Glennis J. , Bernasek Steven L. , Wolk Gary L. , Coyle R. J.
Published: March 2011

Laser-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

The 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

R7T7 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

Using 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

The 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

Surface 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

Copper 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

Previous 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.