bluuebunny/crossref_metadata_2025 huggingface dataset:
The Role of Hydrogen In The Structure of γ-Alumina
Authors: Sohlberg Karl , Pennycook Stephen J. , Pantelides Sokrates T.
Published: April 2011

The structure of a-alumina (α-A12O3) is well known to be hexagonal close packed. In contrast, the structures of the so-called transition aluminas (-γ-alumina, η-alumina,…) are the subject of controversy. We report theoretical calculations which show that -γ-alumina is actually a sequence of compounds with the general formula H3mAl2−mO3. (0 ≤ m ≤ ⅓). m = ⅛ is a unique form, HAl5O8, with a perfect spinel structure. For m > 8, there are interstitial H atoms whereas for m < ⅛. there are vacancies. This picture is supported m > ⅛ by calculations of material density and proton vibrational frequencies. The results are in excellent agreement with measured values. The present new systematic approach accounts for a wide range of seemingly contradictory data and leads to the conclusion that γ-alumina behaves as a “reactive sponge” by storing and releasing water in a novel reactive way.
Three Dimensional Ultra-Small Pt Clusters on Carbon As Studied by A Novel Stem Technique
Authors: Yang J. C. , Bradley S. , Gibson J. M.
Published: April 2011

Very high angle (∼ 100mrad) annular dark-field (HAADF) images in a dedicated scanning transmission electron microscope (STEM) can be used to quantitatively measure the number of atoms in a cluster on a support material. We have developed a computer program which will automatically find the location of the particles and then integrate the intensity to find the number of atoms per cluster. We have examined ultra-small Pt clusters on a C substrate by this novel mass-spectroscopic technique. We discovered that the Pt clusters maintain their three-dimensional shape, and are probably spherical in shape.
Surface Mediation of NOxReduction/Oxidation in A Plasma
Authors: Balmer M.L. , Tonkyn R.G. , Yoon I. , Kolwaite A. , Barlow S.E. , Orlando T.M. , Hoard J.
Published: April 2011

NOxreduction efficiency under simulated lean burn conditions is examined for a nonthermal plasma in combination with borosilicate glass, alumina, Cu-ZSM-5 and Na-ZSM-5. The non-thermal plasma alone or with a packed bed of borosilicate glass beads converts NO to NO2and partially oxidizes hydrocarbons. Alumina and Na-ZSM-5 reduce a maximum of 40% and 50% of NOxrespectively; however, the energy cost is high for Na-ZSM-5. Cu-ZSM-5 converts less than 20% with a very high energy consumption.
Catalytic Activity of Ni/(P)Ti-HMS Catalysts with Varying Phosphorous Concentration in The reaction Of dehydrogenation of Cyclohexane
Authors: Halachev T. , Viveros T. , Perez G. , Dimitrov L.
Published: April 2011

Ni/(P)Ti-HMS catalysts were prepared and characterized by several physicochernical techniques. The addition of phosphorous to the original mesoporous materials modified the acid-base surface properties. The activity in cyclohexane dehydrogenation is higher than on conventional catalysts.
Microporous Silicon Nitride-Based Solid Bases
Authors: Bradley J. S. , Vollmer O. , Rovai R. , Lefebvre F.
Published: April 2011

High surface area, microporous, amorphous silicon imidonitride, characterized by infrared spectroscopy, MAS29Si NMR and surface area and porosity measurements has been prepared by the treatment of co-oligomers of methylsilazane and dimethyl silazanes with gaseous ammonia at temperatures up to 700°C. The material has a narrow pore-size distribution showing a maximum in the range associated with wide- pore zeolites (ca.0.72 nm mean). Variation of the organic content of the silazane is a means of controlling the surface area of the resulting solid. The Knoevenagel condensation reaction of benzaldehyde with a series of active methylene compounds has been used to probe the basicity and size-selectivity of these microporous solid base catalysts.
A Novel Versatile Process for the Production of Polymer Foams
Authors: Shastri V.P. , Martin I. , Langer R.
Published: April 2011

Porous polymeric media are used in several applications such as solid supports for separations and catalysis, as well as biomedical applications such as vascular grafts and wound dressings. We have developed a novel versatile process to produce polymeric cellular solids. This process which is based on a phase extraction-co-polymer precipitation is applicable to a wide range of polymer systems including water soluble polymers. It is capable of yielding polymer foams of high porosity (> 90%) and excellent mechanical characteristics in a very short time (less than 2 hours) without limitations in foam thickness. Polymer foam with such characteristics have great utility in tissue engineering applications. We have successfully explored polymer foams of biocompatible polymers produced by the presented approach for bone and cartilage engineering using bone marrow stromal cells.
Non-Destructive Evaluation of Synthetic Tissue Scaffolds With NMR
Authors: Garrido L.
Published: April 2011

Proton magnetic resonance imaging (MRI) is applied to determine non–destructively the open porosity of biodegradable scaffolds of poly(3–hydroxybutyrate-–3–hydroxyvalerate) in vitro and tissue infiltration in vivo. Porous matrices with copolymers having 12% and 24% 3–hydroxyvalerate (HV) are prepared using a solvent casting technique. The results of open porosity P(%) measured by MRI (PMRI) show good agreement with those obtained by gravimetry analysis (PGA). Thus, for scaffolds with 12% HV, PMRI = 91.0 ±1.0 (mean ± s.d.) and PGA = 88.0 ± 0.75; and for those with 24% HV, PMRI = 89.4 ±1.3 and PGA = 88.8 ± 1.0. Also, the extent of tissue infiltration in these scaffolds determined by MRI in vivo was similar to that observed by histology. These results illustrate the potential of MRI methods for investigating the behavior of biodegradable scaffolds non-invasively in applications for tissue engineering.
Bioresorbable Microspheres as Injectable Cell Carrier: FRom Preparation to in Vitro Evaluation
Authors: Senuma Y. , Franceschin S. , Hilborn J. G. , Tissiéres P. , Frey P.
Published: April 2011

A new approach to the vesico-ureteral reflux could be a local regeneration of the defective vesicoureteral junction by transplanting living cells to the target site. The aim of this work is to provide a long-term effective treatment by producing bioresorbable microspheres which can act as support matrix for those cells, with the goal of an in vivo transfer of the in vitro cultured cells with a minimal surgical procedure. After microsphere degradation, the cells should be integrated into the muscular structure of the junction. Most innovative is that these are cultured muscle and urothelial cells from the bladder of the same patient.
Self-Reinforced Bioactive Glass-Bioabsorbable Polymer Composites
Authors: Niiranen Henna , Törmälä Pertti
Published: April 2011

Non-reinforced and self-reinforced bioactive-bioabsorbable composite rods were produced by extrusion and solid state die-drawing using P(L/DL)LA matrix and spherical glass particles. The structure and mechanical properties of composites were measured before and after die-drawing. The structure examination of composites by SEM showed the formation of fibrous reinforced structure of the polymer with spindle-shaped pores around the glass spheres during and oriented in the direction of die-drawing. Incorporation of glass into the polymer matrix turns the composite more brittle compared to neat polymer. By die-drawing the brittleness of the composite can be eliminated.

Not only the bioactivity and controlled degradation rate of composite but also structure and mechanical properties achieved during die-drawing make the self-reinforced bioactive glass- bioabsorbable polymer composites a novel implant material for temporary support of healing tissues.
Microstructural Investigation of the Oxide Scale on Zr-2.5NB and its Interface with the Alloy Substrate
Authors: Benezra V. , Mangin S. , Treska M. , Spector M. , Hunter G. , Hobbs L.W.
Published: April 2011

Oxidized Zr-2.5Nb is being developed as an articular bearing surface for the femoral component in total joint arthroplasty. It has so far demonstrated superior wear performance against ultrahigh molecular weight polyethylene (UHMWPE) with respect to traditional articulating materials such as Co-Cr-Mo alloys. In this investigation, we used thermogravimetric analysis, transmission electron microscopy, and in situ x-ray diffraction techniques to study the microstructure and stress state of the oxide scale grown on Zr-2.5Nb.

The oxidation temperature not only determines the kinetics of oxidation but the morphology of the various oxidation products. We have identified the oxidation products of both phases of the two phase alloy and correlated them with the original alloy microstructure. These include not only monoclinic zirconia but also small amounts of tetragonal zirconia and a mixed oxide phase combining both zirconium and niobium. The alloy microstructure both influences the final oxidation products and is reflected in the microstructure of the oxide. The oxide scale itself has a predominantly columnar microstructure which extends from the oxide/metal interface to the outer surface of the oxide. In situ x-ray diffraction measurements revealed that the oxide scale is stressed in compression following cooling and exhibits strong crystallographic texture. The oxide/metal interface is continuous, without pores or voids which might be detrimental to oxide adhesion. In addition, we have identified a phase which develops at the interface between the beta-zirconium grains and the oxide. We have also identified amorphous regions within the oxide scale which serve as sinks for silicon and other impurity elements found in the alloy.
Rapid Depth-Resolved Analysis of Nitride Layers (>50 Micrometers) on Prosthetic Devices by Radio Frequency Glow Discharge Atomic Emission Spectroscopy
Authors: Kenneth R. , Hartenstein Matthew L. , Compton Richard , Shetty Ravi
Published: April 2011

The ability to provide depth-resolved chemical information is an important attribute for analytical methods employed in the biomaterials laboratory, both research and production. Radio frequency glow discharge atomic emission spectroscopy (rf-GD-AES) is shown to provide profiles of nitrogen content in prosthetic alloys to depths of greater than 50 micrometers, with analysis times of less than 30 minutes.
Synthesis and Characterization of Calcium Phosphate Coatings by Metalorganic Chemical Vapor Deposition
Authors: Gao Y.
Published: April 2011

Thin coatings of various calcium phosphates including tricalcium phosphate (TCP), calcium pyrophosphate, and hydroxyapatite were synthesized by plasma-enhanced metalorganic chemical vapor deposition (MOCVD). Structure, composition, and surface morphology of the coatings were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. All coatings were very dense and free of cracks. X- ray diffraction showed that the as-grown coatings with the Ca/P ratio of 1.5±0.5 and 1.0±0.5 were crystalline μ- TCP and pyrophosphate, respectively. However, hydroxyapatite coatings with the Ca/P ratio of ∼1.67 were amorphous. The crystalline μ-TCP and pyrophosphate coatings exhibited strong growth texture. The textured orientations varied with different growth temperatures. In addition, the microstructure of the μ-TCP coatings strongly depended on the growth temperatures.
Optimising of the Physico-Chemical Properties of a Novel Barium Sulphate Preparation for the X-Ray Examination of the Intestine
Authors: Laermann Barbara , O'Brien Paul , Bartrama Clive
Published: April 2011

Novel barium sulphate preparations for X-ray contrasting with defined rheological properties have been developed which provide both low viscosity and high density. The relationship between volume fraction and both high-shear and low-shear viscosity was investigated to obtain the relative viscosity [η] and the limiting packing fraction Φm. The particles in a good preparation have a hydrophilic surface which allows the particles to penetrate through the mucus layer of the gastro-intestinal tract. Adsorption isotherms for chondroitin sulphate on barium sulphate from aqueous solution have been determined by spectrophotometry. FTIR spectroscopy and SEM has been used to analyse adsorption behaviour at a molecular level. Coating studies on mouse intestinal mucosa were carried out. A model for testing the coating thickness and particle packing of proprietary and test suspensions was developed. Surface and cross-sections characterisation of a novel test preparation on the intestinal model were determined using cryo scanning electron microscopy. In order to test the resolution obtained with novel material a phantom has been developed.
Mechanical Properties of Zr-Al-Cu-Ni Alloy Glass at Different Quenching Condition
Authors: Yabe H. , Toyoshima R. , Hiraiwa Y. , Oguri K. , Miyazawa Y. , Nishi Y.
Published: April 2011

The samples of Zr56Al9Cu5Ni30 alloy were prepared by liquid-quenching. The mechanical properties depend on the cooling condition. The Hv value (25g load) is 580 for slow cooled rate sample, whereas the Hv value is over 800 for fast cooled sample. Since the fast cooling enhances the sample hardness, these samples become brittle. The brittleness is evaluated by the critical deformation energy (Ec) of collapse.
The Shear Modulus of Glassy and Supercooled Liquid Pd40Ni40P20
Authors: Bains A. S. , Gordon C. A. , Granato A. V. , Schwarz R. B.
Published: April 2011

We have measured the shear modulus and its temperature dependence of Pd40Ni40P20 using an EMAT technique. The room temperature value of 3.92(1011) d/cm2 is in fair agreement with that of 3.66(1011) d/cm2 given earlier by He and Schwarz, using a resonant ultrasound spectroscopy technique. The relative change with temperature coefficient for T << Tg is 3.4(10−4) K−1. For the heating rate of ∼1 K/min used here, Tg = 565 K compared with a value of 575 K reported earlier. The shear modulus is continuous at Tg , but its temperature coefficient is larger by a factor of 6.5 for T >> Tg. During temperature cycling near but below Tg , irreversible aging effects are found showing that the amorphous state is not an equilibrium state. Near but above Tg, the cycling effects are reversible for time scales of the order of hours but not for time scales of the order of days, showing that metastable equilibrium states have not yet been fully attained. The results are in overall agreement with the predictions of the Interstitialcy Theory.
Significant Undercooled Liquid Region of Over 200K in Rare Earth Based Metallic Glasses
Authors: Lu Z. P. , Li Y. , Ng S. C. , Feng Y. P.
Published: April 2011

Using a newly developed temperature modulated differential scanning calorimetry (TMDSC), glass transition has been detected in several RE-Fe-Al (RE = ND, Pr, Sm and Y) metallic glasses, which can not be observed by a conventional DSC. Our results show that the glass transition occurred together with a small fraction crystallization in the as-spun samples, the final main crystallization transition occurred at higher temperature (over 720K) in these rare-earth based alloys. Large undercooled liquid regions up to 200K at a underlying heating rate of 5K/min have been observed in these glasses.
Viscosity, Relaxation and Crystallization Kinetics In Zr-Ti-Cu-Ni-Be Strong Bulk Metallic Glass Forming Liquids
Authors: Busch Ralf , Masuhr Andreas , Bakke Eric , Waniuk T. Andy , Johnson William L.
Published: April 2011

The high thermal stability of bulk metallic glass (BMG) forming liquids in the undercooled state allows for measurements of thermophysical properties in a large time and temperature window. In this contribution, results on viscous flow, relaxation and crystallization of Zr-Ti-Cu- Ni-Be BMG forming alloys are presented. The data are compared with the kinetics of other metallic and non-metallic liquids. BMG formers are relatively strong liquids with melt viscosities that are about three orders of magnitude larger than in pure metals and other alloys. The strong liquid behavior of these alloys is also reflected by a small entropy of fusion and a weak temperature dependence of the thermodynamic functions upon undercooling. The high viscosity and small driving force for crystallization are major contributing factors to the high glass forming ability and low critical cooling rate. The upper portions of experimental timetemperature- transformation diagrams down to the crystallization nose can be described well using the kinetics deduced from the viscosity data. For lower temperature the viscosity can not describe the crystallization kinetics. The time scale for structural relaxation becomes larger than for diffusive hopping processes. Diffusion stays relatively fast, whereas viscosity and structural relaxation time upon undercooling follow a Vogel-Fulcher-Tammann relation.
Crystallization of Supercooled Zr41Ti14Cu12Ni10B23 Melts During Continuous Heating and Cooling
Authors: Schroers Jan , Masuhr Andreas , Busch Ralf , Johnson William L.
Published: April 2011

The crystallization behavior of the bulk glass forming Zr41Ti14Cu12Ni10Be23 liquid was studied under different heating and cooling rates. Investigations were performed in high purity graphite crucibles since heterogeneous surface nucleation at the container walls does not effect the crystallization of the bulk sample. A rate of about 1 K/s is sufficient to circumvent crystallization of the melt while cooling from the equilibrium melt. In contrast, upon heating a rate of more than 150 K/s is necessary to avoid crystallization of Zr41Ti14Cu12Ni10Be23 samples. The difference between the critical heating and cooling rate is discussed within classical nucleation theory and diffusion limited crystal growth. The calculated difference of the critical heating and cooling rate can be explained by the fact that nuclei formed during cooling and heating are expose to different growth rates.
Atomic Diffusion in Bulk Metallic Glasses
Authors: Geyer Ulrich , Rehmet Achim , Schneider Susanne
Published: April 2011

Diffusion experiments in bulk metallic glasses are reviewed. Measurements carried out so far are focused on Zirconium based alloys and cover the amorphous and deeply undercooled liquid states as well as the equilibrium and slightly undercooled melts. Experimental findings are compared with theoretical predictions for atomic transport in glass forming systems.
Bulk Glass-Forming Metallic Alloys: Science and Technology [1998 Mrs Medal Award Lecture, Presented at Symposium Mm]
Authors: Johnson William L.
Published: April 2011

The paper begins with some brief remarks about the history and background of the field of bulk glass-forming metallic alloys. This is followed by a discussion of multicomponent glass-forming alloys and deep eutectics, the chemical constitution of these new alloys, and how they differ from metallic glasses of a decade ago or earlier. The development of bulk glass forming alloys has led to interesting studies of the deeply undercooled liquid alloys, which are made possible by the exceptional stability with respect to crystallization. Recent advances made in this area will be illustrated by several examples. The paper continues with a discussion of some of the physical properties of bulk metallic glasses. Mechanical properties are specifically discussed. Some interesting potential applications of bulk metallic glasses will be mentioned.
High Dynamic Mechanical Strength of Zirconium-Based Bulk Amorphous Alloys
Authors: Zhang Tao , Inoue Akihisa
Published: April 2011

A bulk amorphous Zr55Al10Ni5Cu30 alloy prepared by squeeze casting was found to exhibit high mechanical strength values, i.e., uniaxial tensile fracture strength (σt) of 1850 MPa, three-point bending strength (σb) of 3200 MPa, bending fatigue strength (σf) of 1100 MPa, Charpy impact fracture energy (Ef) of 135 kJ/m2 and fracture toughness of 68 MPa√m. The σb, σf and Ef are about two times higher than those for the corresponding bulk amorphous alloys prepared by unidirectional solidification and powder consolidation techniques, though the σt of the squeeze cast sample is higher by about 15 % than those for the other samples. The remarkable increases in the σb, σf and EF are presumably due to the introduction of high compressive residual stress of about 1240 MPa in the outer surface region only for the squeeze cast sample. The finding of the effectiveness of the compressive residual stress on the increase in the mechanical strength under the bending stress mode is important and expected to be widely used as a new strengthening mechanism for bulk amorphous alloys, as is the case for reinforced oxide glasses subjected to strengthening treatment.
Deformation Behavior in La55Al25Ni20 Metallic Glass
Authors: Kawamura Y. , Nakamura T. , Inoue A.
Published: April 2011

We investigated the deformation behavior of the supercooled liquid in a La55Al25Ni20 (at.%) metallic glass ribbon that has a wide supercooled liquid region of 65 K before crystallization. The deformation of the metallic glass was divided into three types, namely, homogeneous deformations with and without a stress overshoot and an inhomogeneous deformation. The supercooled liquid above the glass transition temperature (Tg) exhibited a Newtonian viscosity and superplastic-like behavior during isothermal tensile deformation. The metallic glass was elongated as much as 1000 % at high strain rates ranging from 10−2 s−1 to 10o s−1 without embrittlement. The maximum elongation to failure was in excess of 1800 % at a strain rate of 1.7×10−1 s−1 and at 503 K (Tg+20 K, 0.71Tm) under about 40 MPa.
Synthesis and Properties of Bulk Metallic Glass Matrix Composites
Authors: Choi-Yim Haein , Busch Ralf , Johnson William L.
Published: April 2011

Bulk metallic glass matrix composites are processed and investigated by X-ray diffraction, DSC, optical microscopy, SEM, microprobe, TEM, and mechanical testing. Ceramics such as SiC, WC, or TiC, and the metals W or Ta are introduced as reinforcements into the metallic melt. The metallic glass matrix remains amorphous after adding up to 30 vol% of particles. The thermal stability of the matrix does not deteriorate after adding the particles. ZrC layers form at the interfaces between the bulk metallic glasses and the WC or SiC particles. Si and W are released into the matrix in which Si enhanced the glass forming ability. The composites are tested in compression and tension experiments. Compressive strain to failure increases by over 300% compared to the unreinforced Zr57Nb5Al10Cu15.4Ni12.6 and the energy to break of the tensile samples increases by over 50% adding 15 vol. % W.
Calculation of Mechanical, Thermodynamic and Transport Properties of Metallic Glass Formers
Authors: Çağin Tahir , Kimura Yoshitaka , Qi Yue , Li Hao , Ikeda Hideyuki , Johnsonb William L. , Goddard William A.
Published: April 2011

Recently, we have parametrized Sutton-Chen type empirical many body force fields for FCC transition metals to study the thermodynamic, mechanical, transport and phase behavior of metals and their alloys. We have utilized these potentials in lattice dynamics calculations and molecular dynamics simulations to describe the structure, thermodynamic, mechanical and transport properties of pure metals and binary alloys in solid, liquid and glass phases. Here, we will describe these applications: mechanical properties of binary alloys (Pt - Rh) and viscosity of a binary alloy, (Au - Cu), as a function of composition, temperature, and shear rate, crystal-liquid, liquid-crystal phase transformation in (Ni - Cu), liquid to glass transformation in a model glass former, (Ag - Cu).
Tribological Characteristics of Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 Bulk Metallic Glass
Authors: Fu Xi-Yong , Rigney D. A.
Published: April 2011

The sliding characteristics of Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 bulk metallic glass have been examined in vacuum and in air using a pin/disk geometry without lubrication. The counterface material was either the same metallic glass (self-mated) or 52100 steel. Normal load was 0.1–1 kgf. The test system was equipped for continuous measurement of friction force. In addition, a Kelvin probe allowed continuous monitoring of changes in the structure and chemistry of the disk surface. Post-test characterization included optical and electron microscopy, X-ray diffraction and EDS of worn surfaces and debris. Friction coefficients in both vacuum and air were typical of those expected for ductile materials, with values ranging from 0.4 to 0.9 (higher values with lower load). Wear rates and average debris size increased with load. Wear rates were larger in air than in vacuum. Wear surface appearance and chemical composition were influenced by plastic deformation, material transfer and environmental interactions. After tests in air, the wear tracks and debris had a granular appearance and oxygen concentrations were high. Changes in the Kelvin probe signal correlated well with visual observations and with concentrations of oxygen detected by EDS.
Free Volume Changes in Bulk Amorphous Alloys During Structural Relaxation and in the Supercooled Liquid State
Authors: Nagel C. , Rätzke K. , Schmidtke E. , Faupel F.
Published: April 2011

Volume changes in Zr46.7Ti8.3Cu7.5Ni10Be27.5 and Zr 65Al7.5Ni10Cu17.5 bulk metallic glasses have been observed by positron annihilation and density measurements. At low cooling rates excess volume of the order of 0.1 % is quenched in both glasses. Isothermal relaxation kinetics below the glass transition temperature obey a Kohlrausch law with exponents of β≈(0.3 ± 0.1). Structural relaxation is not accompanied by embrittlement, as indicated by simple mechanical tests. The outer surface plays a crucial role in annealing of excess volume, which can be restored by annealing above Tg. The observed free volume changes are at variance with the behavior of a perfectly strong glass. The temperature dependence of the positron lifetime is discussed in terms of thermal detrapping from shallow traps.
High-Temperature Stability of Amorphous Al2O3 Deposited on Si and CeO2-stabilized ZrO2 by Metalorganic Chemical Vapor deposition
Authors: Meyer J. D. , Lee W. Y.
Published: April 2011

Aluminum acetylacetonate and water vapor were used to deposit an amorphous A1203 seal coating on Si and CeO2-stabilized ZrO2 (CSZ) produced by air plasma spray. The A1203 coating prepared at ∼500°C was ∼2.5μm thick, uniform, and non-porous. The crystallization and adhesion characteristics of the A1203 coating were examined by thermally annealing the A12 03- coated Si and CSZ substrates in air. The amorphous coating crystallized to metastable A1203 phases within 20 hours at temperatures as low as 700°C. The coating on Si spalled upon annealing whereas the coating on CSZ did not spall, but microcracked extensively due to the significant volume shrinkage associated with crystallization.
SiO2 Film Coatings with VUV Excimer Lamp CVD
Authors: Kurosawa K. , Takezoe N. , Yanagida H. , Nomura R. , Yokotani A.
Published: April 2011

Silica film coatings were demonstrated using photo-chemical vapor deposition with a 172-nm Xe excimer lamp. Tetraethoxyorthosilicate (TEOS) molecules were successfully dissociated into SiO2+2C2H5-OH+;(residual C and H) with the 7.2-eV photons. The films were deposited onto a quartz or Al203 single crystal substrate with the deposition rate of 1 nm/min. The films were uniform and smooth enough for optical applications.
Metal / Silicon Multilayers Produced by Low-Temperature MOCVD
Authors: Hamelmann F. , Haindl G. , Klipp A. , Majkova E. , Kleineberg U. , Jutzi P. , Heinzmann U.
Published: April 2011

W/Si and Mo/Si multilayers with 20 periods (doublelayer spacing d = 24nm) were deposited on silicon substrates using (remote-) plasma-enhanced MOCVD. The substrate temperature was below 200°C, which is necessary to avoid interdiffusion of the layers. The layer thickness and growth was controlled by an in situ soft x-ray reflectivity measurement. The characterisation of the multilayers showed an excellent growth of the silicon layers, while the metal layers are rough with embedded crystallites.
A new low Temperature Chemical Vapor Deposition Technique for Growing Thin Films of Ti, TiN on Copper and TiO2, TixSiyon Silicon
Authors: Hendricks J. H. , Aquino M. I. , Zachariah M. R.
Published: April 2011

In this paper, we present a process which has the benefits of operating at lower temperatures than conventional CVD, that uses low cost precursors, and produces only environmentally benign byproducts. This new method for depositing Ti, TiN, TiO2, and Ti.Siy thin films has been demonstrated using a coflow diffusion reactor to react Na metal vapor with TiCl4as described by the following equation: 4Na(g) + TiCl4(g)---Ar---> Ti(s) + 4NaCl(g). In this reaction, sodium strips chlorine from titanium tetrachloride freeing titanium metal to grow into a thin film on a substrate placed in the reaction zone. TiN and TiO2films were produced by the introduction of N2gas or O2gas into the reactor, respectively. Using this reaction chemistry, we have produced Ti and TiN thin films on Cu substrates at 610 °C (considerably lower than the 900 °C to 1200 °C required for conventional thermal CVD of titanium) and TiO2and titanium silicides (TixSiy) films on silicon substrates. Thermodynamics calculations indicated that this class of chemistry is generic and that a wide range of metals and ceramics could be grown; and preliminary experiments do suggest that TiC and SiC thin films can be grown using this process. The thin films were primarily analyzed by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), and Raman pectroscopy.
Polymer Multi-Layer Processing of Thin Film Materials
Authors: Miller T. A. , Mikhael M. G. , Ellwanger R. , Boufelfel A. , Booth D. , Yializis A.
Published: April 2011

Polymer Multi-Layer (PML) processing is a high speed industrial scale process for depositing thin polymer films. Moving substrates of arbitrary width can have one micron (typ.) polymer films deposited at speeds measured in hundreds of meters per minute. A wide variety of chemical functionality available in the precursor materials allows a variety of chemical, electrical, and optical applications. The polymer characteristics can be further augmented by subsequent deposition of inorganic materials. Recent advances with dielectric, electrolytic, photonic, barrier, chemical affinity, energetic, and piezoelectric thin film polymer materials are discussed.
Structure and Strength of Rapidly Quenched Cu-Al2O3 Composites
Authors: Il'Insky A. I. , Terletsky A. S. , Zozulya E. W.
Published: April 2011

Microstructure of dispersion hardened composites (DC) Cu-Al2O3 prepared by simultaneous vacuum vapor condensation of Cu and A12O3 was studied by X-ray diffractometry and transmission electron microscopy methods. After high temperature annealing at 900°C for 2 hours the composites retain the submicrocrystalline structure and high level of strength -0.9 GPa. It has been found that strain hardening of vacuum deposited Cu-A12O3 composites takes place in three stages that is not typical for well-known composites of metallurgical origin.
Carbon-Nitride, Diamond-Like-Carbon and Silicon-Based Films Synthesized by Electron Cyclotron Resonance Chemical Vapor Deposition
Authors: Moran M. B. , Johnson L. F.
Published: April 2011

Carbon-nitride and diamond-like-carbon films were deposited by electron cyclotron resonance chemical vapor deposition (ECR-CVD) using carbon precursors in either a nitrogenor an argon-high-density plasma. The carbon precursors were tetrachloroethylene (C 2C14), ethylene (C2H4) and neopentane (C5H12). Electron spectroscopy for chemical analysis (ESCA) and Fourier transform infrared (FTIR) spectroscopy showed three distinct chemical compositions: chlorine-doped carbon nitride (CNx:Cl), hydrogenated carbon nitride (CNx:H) and hydrogenated amorphous carbon (a-C:H). FTIR spectroscopy revealed a fourth composition: chlorine-doped amorphous carbon (a-C:Cl). ESCA analysis of the a-C:Cl film was not performed. Microstructures ranging from amorphous to microcrystalline were observed using differential interference contrast (DIC) optical microscopy and atomic force microscopy (AFM). Plasma etching of the substrate prior to film growth and biasing of the stage during film growth strongly influence the resulting microstructure. 100-μm-size, stacked, pyramidal CNx:Cl crystallites were deposited onto a glass microscope slide through a combination of substrate preetching and rf-biasing of the stage during film growth. In later experiments, pulsed-dc-highvoltage biasing of the stage during the growth process resulted in the deposition of 1-jim-size, rectangular- and triangular-shaped CNx:Cl crystallites onto fused silica.

Chlorinated instead of hydrogenated precursors were used to eliminate hydrogen incorporation during the growth of the ECR-CVD carbon nitride films. Chlorinated hydrocarbon precursors like trichloroethylene (C2HC13) and C2C14 reduce the amount of hydrogen in the plasma and make the formation of CN bonds more favorable. The results also show that doublebonded CC precursors are needed for N2 to react with carbon. However, when a hydrogenated precursor like C2H4 is used with a N2 plasma, hydrogen reacts with the CC double bond to form CH and NH bonds faster than N2 can react to form double- and single-bonded CN. The disadvantages of using chlorinated-carbon precursors are that the resulting CNx:Cl films contain a small amount of chlorine (Cl), are porous and are unstable with respect to moisture incorporation.

It is much easier to obtain stable, dense films using chlorinated precursors if more conventional materials are deposited. Silicon dioxide (SiO2) and silicon nitride (Si3N4) films were deposited by ECR-CVD using trichlorosilane (SiHC13). The films showed no degradation or moisture incorporation after several months.
Low Temperature Synthesis of Si-C-N and C-N Films by IR-laser Assisted ECR-PECVD
Authors: Zhu Shen , White H. W.
Published: April 2011

A new synthesizing method, IR-laser-assisted electron-cyclotron-resonance plasma-enhanced chemical vapor deposition (LA-ECR-PECVD), has been used to fabricate Si-C-N and C-N films on steel substrates at low temperatures (< 650 °C). Methane/nitrogen or carbon dioxide/nitrogen gases are dissociated to methane radicals and nitrogen plasma by the IR-laser and ECR to enhance the species' energy. An IR-laser beam (pulsed Nd:YAG laser, 1064 nm) was introduced into the growth chamber for two purposes: (1) to add Si atoms by ablating a Si target, and (2) to enhance the plasma concentration in the gas phase. An infrared vibration mode located at 1256 cm-l wavenumber was observed in Si-C-N and C-N films, although these films have an amorphous phase. The C-N film also has a Raman shift at 1276 cm-l. The AFM images reveal many islands with a size ranging from 50 nm – 150 nm in films.
Growth of Diamond on Sapphire by Pulsed Laser Ablation under Oxygen Atmosphere
Authors: Yoshimoto M. , Hishitani Y. , Maruta H. , Koinuma H. , Tachibana T. , Nishio S. , Kakihana M.
Published: April 2011

We examined the possibility of nucleation and growth of diamond via a hydrogen-free vapor phase route of pulsed laser ablation of a graphite target in a low-pressure pure oxygen atmosphere. The present evidences from microscopic, diffraction and spectroscopic techniques indicate that high-quality (111)-oriented diamond crystals could be nucleated and grown on ultra smooth sapphire (single-crystal α - A12O3)substrates at the temperatures lower than 600°C under the optimized growth conditions of oxygen pressure (around 0.15 Torn) and laser ablation (pulsed laser fluence of 3 x 108W/cm2at 5Hz).
Functionally gradient PECVD Ti(C,N) coatings
Authors: Shieh J. , Wang H. L. , Tsai M. S. , Hon M. H.
Published: April 2011

Ti(C,N) hard coating is well known as a suitable material for protecting substrate, and functionally gradient design is a method to improve the performance of it. In this study, functionally gradient Ti(C,N) coatings were performed by the technique of capacitive RF PECVD based on the investigation of Ti(C,N) monolayers with different C and N ratios. The results show that the composition and growth rate of Ti(C,N) monolayers are influenced by the nitrogen/methane ratio as other deposition parameters are fixed. A model is also proposed from the results obtained and is employed to calculate the reaction gas ratio and duration time needed for deposition in the gradient coating. The elements of Ti and N in the gradient coatings were analyzed by Auger electron spectroscopy (AES) and revealed that the composition changed linearly as designed. The residual stress of the gradient coatings was also measured to show that the gradient design provides the possibility for adjusting the stress distribution of PECVD hard coatings.
Oxidation of PECVD SiC Deposited from Trimethylsilane
Authors: DiFonzo Peter A. , Massuda Mona , Kelliher James T.
Published: April 2011

The stoichiometric composition and oxidation rates ( wet or dry ) of plasma enhanced chemical vapor deposited (PECVD) silicon carbide (SiC) films are effected by the deposition conditions of trimethylsilane (3MS) and carrier gas. We report the oxidation kinetics of SiC thin films deposited in a modified commercial PECVD reactor. A standard horizontal atmospheric furnace in the temperature range of 925–1100°C was used in the oxidation. Oxidized films were measured optically by commercially available interferometer and ellipsometer tools in addition to mechanically using a commercially available profilometer. Activation energies of the parabolic rates were in the range of 20.93 to 335.26 kJ/mol.
Improved Microstructures for Thermal Barrier Coatings Produced by Glancing Angle Deposition
Authors: Harris K. D. , Vick D. , Brett M. J. , Robbie K.
Published: April 2011

A new approach to deposition of thin films for thermal barrier applications is described. During electron beam evaporation, the extreme shadowing effect that is present at highly oblique incidence is employed to introduce porosity into thin films of zirconia. Using controlled substrate motion a solid capping layer may be applied to these porous films. By depositing layers of porous material and capping in an alternating fashion a new structure is produced which warrants evaluation as an improved thermal barrier coating.
Sensitivity Analysis of Uranium Solubility Under Strongly Oxidizing Conditions
Authors: Liu L. , Neretnieks I.
Published: April 2011

To evaluate the effect of geochemical conditions in the repository on the solubility of uranium under strongly oxidizing conditions, a mathematical model has been developed to determine the solubility, by utilizing a set of non linear algebraic equations to describe the chemical equilibria in the groundwater environment. The model takes into account the predominant precipitation-dissolution reactions, hydrolysis reactions and complexation reactions that may occur under strongly oxidizing conditions. The model also includes the solubilitylimiting solids induced by the presence of carbonate, phosphate, silicate, calcium, and sodium in the groundwater. The thermodynamic equilibrium constants used in the solubility calculations are essentially taken from the NEA Thermochemical Data Base of Uranium, with some modification and some uranium minerals added, such as soddyite, rutherfordite, uranophane, uranyl orthophosphate, and becquerelite. By applying this model, the sensitivities of uranium solubility to variations in the concentrations of various groundwater component species are systematically investigated. The results show that the total analytical concentrations of carbonate, phosphate, silicate, and calcium in deep groundwater play the most important role in determining the solubility of uranium under strongly oxidizing conditions.
Effective Reactive Surface Area: an Anisotropic Property of Physically and Chemically Heterogeneous Porous Media
Authors: Smith Robert W. , Schafer Annette L.
Published: April 2011

Although transport calculations are often formulated in terms of mass-based isotropic distribution coefficients, it is the abundance of reactive surface areas of subsurface materials that controls contaminant adsorption. In water-saturated homogeneous systems devoid of advective fluxes (e.g., batch experiments), the available reactive surface area is similar to the total surface area (as measured by conventional methods such as BET gas adsorption). However, in physically and chemically heterogeneous systems with advective fluxes, the effective reactive surface area (i.e., the surface area that a packet of advecting water interacts with) is smaller than the laboratory measured surface area and is a complex function of advective velocity and the correlation structures of the physical and chemical heterogeneities. Theoretical derivations for an important but simple type of heterogeneity (fine-scale horizontal layering) suggest that the effective reactive surface area is an anisotropic property of the medium and is inversely correlated with the anisotropy in hydraulic conductivity. The implications of reactive transport anisotropy include the concept that the retardation factor should be treated as a directional property rather than being treated as a constant. Furthermore, because of the inverse relationship between effective reactive surface area and hydraulic conductivity, batch adsorption experiments tend to overestimate the retention of contaminants relative to intact natural materials.
Radioiodide Sorption to Sediment Minerals
Authors: Kaplan D. I. , Serne R. J. , Parker K. E. , Kutnyakov I. V.
Published: April 2011

Laboratory studies were conducted to quantify and understand the processes by which iodide (I−) sorbs to minerals found in subsurface arid sediments. Little or no I− sorbed to montmorillonite (Kd = −0.42 ± 0.08 mL/g), quartz (Kd = 0.04 ± 0.02 mL/g), vermiculite (Kd = 0.56 ± 0.21 mL/g), calcite (Kd = 0.04 ± 0.01 mL/g), goethite (Kd = 0.10 ± 0.03 mL/g), or chlorite (Kd = −0.22 ± 0.06 mL/g). A significant amount of I− sorbed to illite (Kd = 15.14 ± 2.84 mL/g).). Upon treating the iodide-laden illite with dissolved F−, Cl−, Br−, or 127I−, desorption (or isotopic exchange in the case of 127I) removed, respectively, 43 ± 3%, 45 ± 0%, 52 ± 3, and 83 ± 1 % of the I− originally adsorbed to the illite. The fact that such large amounts of I− could be desorbed suggests that the I− was weakly adsorbed, and not chemically bonded to a soft metal, such as mercury or silver, that may have existed in the illite structure as trace impurities. Finally, I− sorption to illite was strongly pH-dependent; the Kd values decreased from 46 to 22 mL/g as the pH values increased from 3.6 to 9.4. Importantly, I− sorbed to illite even under alkaline conditions. Together, these experiments suggest that illite removed I− from the aqueous phase predominantly by reversible physical adsorption to the pH-dependent edge sites. Illites may constitute a substantial proportion of the clay-size fraction of many arid sediments and therefore may play an important role in retarding I− movement in these sediments.
Development of a ceramic waste form for high-level waste disposal
Authors: Esh D. W. , Goff K. M. , Hirsche K. T. , Battisti T. J. , Simpson M. F. , Johnson S. G. , Bateman K. J.
Published: April 2011

A ceramic waste form is being developed by Argonne National Laboratory* (ANL) as part of the demonstration of the electrometallurgical treatment of spent nuclear fuel [1]. The halide, alkaline earth, alkali, transuranic, and rare earth fission products are stabilized in zeolite which is combined with glass and processed in a hot isostatic press (HIP) to form a ceramic composite. The mineral sodalite is formed in the HIP from the zeolite precursor. The process, from starting materials to final product, is relatively simple. An overview of the processing operations is given. The metrics that have been developed to measure the success or completion of processing operations are developed and discussed. The impact of variability in processing metrics on the durability of the final product is presented. The process is demonstrated to be robust for the type and range of operation metrics considered and the performance metric (PCT durability test) against which the operation metrics are evaluated.
Migration of Plutonium in a Simulated Engineered Barrier System Consisting of Waste Glass and Ompacted Bentonite
Authors: Inagaki Y. , Saito R. , Furuya H. , Idemitsu K. , Arima T. , Banba T. , Maeda T. , Matsumoto S. , Tamura Y. , Kikkawa S.
Published: April 2011

In a simulated engineered barrier system consisting of a simulated HLW glass doped with Pu, a compacted bentonite and water under reducing conditions, migration tests of Pu from the glass into the bentonite through water were performed. The following results were obtained: (1) The presence of bentonite enhances the glass dissolution while it has no remarkable influence on the concentration of Pu dissolved species in the solution. (2) Only a small part of the leached Pu, which may correspond to the dissolved species, can diffuse into the bentonite with the apparent diffusion coefficient of 3×10−14m2/s. (3) Interactions between the glass and the bentonite have no remarkable influence on the diffusion of Pu.
Production And Characterization Of A Plutonium-238 Loaded Ceramic Waste Form For The Study Of The Effects Of Alpha Decay Damage
Authors: Steven M. , Frank Steven M. , Esh David W. , Johnson Stephen G. , Noy Marianne , O'Holleran Thomas P.
Published: April 2011

Argonne National Laboratory has developed a glass-bonded sodalite ceramic waste form to immobilize fission products and plutonium that accumulate during the electrometallurgical conditioning of spent nuclear fuel. To investigate the effects of alpha decay damage on the structure and leaching characteristics of the ceramic material, 238Pu has been incorporated into the ceramic waste form. The 238pu,with its high specific activity, significantly increases the rate of alpha damage to the waste form. Long term studies have begun with periodic examination of the 238Pu loaded ceramic material. A number of characterization techniques are used to study the alpha decay damage on the structure of the waste form. In addition, PCT type leachate studies will be performed to determine the effect of alpha decay damage on the durability of the ceramic waste form. Preliminary results from this study are presented.
Radiolytic Gas Generation in Chemically-bonded Iron Phosphate Ceramic Forms used for Immobilization of Plutonium Ash Residues
Authors: Aloy Albert S. , Kolycheva T.I. , Knecht D. A. , Macheret Y.
Published: April 2011

Iron phosphate ceramic (IPC) samples were prepared with plutonium-238, and radiolytic gas generation was detennined for exposure times of up to 195 days. The specific activity of the synthesized IPC samples was 1.91 mCi/g. The composition of the generated gases was determined to contain mainly H, and lower amounts of O2, CO2 and CO. The molecular hydrogen G value (molecules of H2 per 100 eV absorbed dose) depended on the sample preparation methodology, ranging from 0.07 at 79 days for sample IPC-2 to 0.34 at 119 days for sample IPC-1. This difference could be due to different total amount (wt.%) of free water resulting in sample preparation. The leach rate data for radioactive and non-radioactive IPC samples obtained by the ANSI/ANS 16.1 procedure resulted in Leachability Indexes of 13.7 for Pu and 15.4 for Ce, above the NRC LLW acceptance minimum index of 6.
Radiological Properties of Heavy Liquid Metal Targets of Accelerator Driven Systems
Authors: Pankratov D. V. , Yefimov E. I. , Ignatiev S. V. , Levano V. I.
Published: April 2011

The long-lived radioactivity of lead-bismuth coolant (LBC) inside the targets of the accelerator driven systems (ADS) is estimated. It is determined by both spallation and fission products of lead and bismuth nuclides. Based on US safety standards the radiotoxicity of targets was calculated for different cooling down periods. In order to estimate the total radioactivity of 1-MW power target circuit (TC), which is developing now at IPPE, the contribution of its main components are preliminarily analyzed.