bluuebunny/crossref_metadata_2025 huggingface dataset:
Migration of Radioactive 85Sr, 134Cs and 60Co Through a Loess Soil Layer
Authors: Li Zhentang , Wang Hui , Takebe Shinichi , Tanaka Tadao
Published: April 2011

Column experiments have been completed on the migration of 85Sr, 134Cs and 60Co through a loess layer in order to examine the migration behavior of radionuclides in an aerated soil layer. Radionuclide concentration distributions between the effluent and the soil layer were measured after the solution containing the radionuclides was introduced into the column from the top of the soil layer and Fifty liters of the underground water were introduced at a constant flow. Results indicate most of the 85Sr, 134Cs and 60Co remained attached to the soil layer, and only a small amount of radionuclide was released from the soil layer. Within the soil layer, the migration depths of three radionuclides are 85Sr > l34Cs = 60Co.
Alteration Minerals in Granitic Rock at Ashio as Radionuclide Adsorption Materials
Authors: Hamasaki S. , Tsukimura K. , Fujimoto K. , Omura K. , Ikeda R.
Published: April 2011

Alteration minerals from a drill-core (maximum depth 2002 m) in the granitic rock at Ashio, central Japan, were studied by optical microscopy, X-ray diffractometry and analytical scanning electron microscopy. In the host rock, biotite is altered to chlorite and plagioclase to illite. Calcite has precipitated in veinlets and grain boundaries. The host rock close to fractures is strongly altered, whereas the rocks distant from fractures are less altered. Quartz, illite, chlorite, laumontite and calcite have precipitated on fracture walls. The alteration minerals are estimated to have formed in the range 140–200°C, higher than the present temperature (13°96°C). The chemical composition of the ground water in the granitic rock at Ashio was estimated thermodynamically from the mineral assemblage. The alteration reaction of palgioclase and the precipitation of calcite may occur simultaneously. The alteration minerals formed in the host rock and in the fractures may adsorb radionuclides effectively, and thus may inhibit radionuclide transport to biosphere.
Use of Natural Analog and Modeling Studies to Constrain the Effects of Magmatic Activity on Long-Term Geologic Repositories
Authors: Valentine Greg A. , Rosenberg N. D. , Crowe B. M. , Perry F. V.
Published: April 2011

Examples of the application of natural-analog studies to the estimation of the consequences of a volcanic eruption penetrating a radioactive waste repository are given, including the criteria for analog selection and new data from ongoing studies. Examples of early modeling results focusing on the spatial and temporal scale of subsurface processes are also provided. All of these examples are taken from studies of the potential Yucca Mountain repository, Nevada, but similar approaches could be applied in other areas. In addition, studies of subsurface processes initiated by magmatic events serve as useful analogs for repository thermal loading studies.
Photochemical Valence Adjustment of Pu and Np in Nitric Acid Solution for Separation and Co-Extraction
Authors: Wada Y. , Morimoto K. , Goibuchi T. , Tomiyasu H.
Published: April 2011

Photochemical redox reaction tests were corried out where the experimental variables were irradiation rate using a Hg lamp light and molarity of nitric acid containing different reductant reagents such as hydroxylamine(HAN), hydrazine(HDZ) and urea. Based on these tests, we confirmed that the valences of Pu and Np were easily photochemically adjusted to two conditions of Pu(IV,VI)-Np(V) and Pu(IV,VI)-Np(VI), indicating that photochemical valence adjustment for the separation and co-extraction of Pu and Np has excellent potential as an advanced process technology.
The Swiss Strategy for HLW Siting; Parallel Investigation of two Alternative Host Rocks
Authors: McCombie C. , McKinley I.G. , Lambert A. , Thury M. , Birkhäuser P.
Published: April 2011

Regional characterisation studies of two potential host rocks for a HLW repository - the crystalline basement and the Opalinus clay of Northern Switzerland - have now been completed and documented. Application is now proceeding for the legally required federal, cantonal and communal drilling permits to initiate parallel local investigations in both these formations. The decision to continue with work in both formations is a departure from previously published plans which is intended to maximise the probability that the next major milestone in the HLW programme - demonstrating the feasibility of siting for a deep geological repository in Switzerland - can be reached by the year 2000. This paper reviews the current status of the Swiss HLW programme and outlines the planned “Phase II” site characterisation of the two chosen sites.
Geological Characteristics of “Mayak” Enterprise Area Regarding Underground Nuclear Waste Disposal and Rehabilitation of Territory (Southern Urals, Russia)
Authors: Velichkin V. I. , Tarasov N. N. , Poluektov V. V. , Asadulin A. A.
Published: April 2011

The geological investigations necessary for the HLW underground disposal site selection were udertaken on the contaminated territory mostly covered by vegetation and water-bodies. For lack of availiable outcrops, special attention was given to detailed petrological and geochemical studies for more reliable extrapolations. As a result, models of structure, geochemical background, and rock basement origin scenario provided general criteria for selection of geological blocks suitable for HLW deep burial.
Microbial Considerations and Studies in the Canadian Nuclear Fuel Waste Management Program
Authors: Stroes-Gascoyne S. , West J.M.
Published: April 2011

AECL Research is developing a concept for the permanent disposal of nuclear fuel waste. A program to address the potential effects of microbial action on the integrity of the multiple barrier system, on which the disposal concept is based has been initiated. This microbial program focusses on answering specific questions in areas such as the survival and growth of microbes in compacted clay buffer materials and the potential consequences for container corrosion and microbial gas production; microbial effects on transport of radionuclides through the buffer into the geosphere; the presence and activity of microbes in deep granitic groundwaters; and the effects of biofilms on radionuclide migration in the geosphere.
Effect of Crystallochemistry of Starting Materials on the Rate of Smectite to Illite Reaction
Authors: Sato Tsutomu , Murakami Takashi , Isobe Hiroshi , Ohnuki Toshihiko
Published: April 2011

A series of hydrothermal experiments was performed to determine the effect of layer charge of starting materials on the smectite to illite reaction rate that might be applied to nuclear-waste repository design. The experiments were conducted on K-saturated <2μm fractions of Wyoming smectite (SWy-1) and Tsukinuno smectite (SKu-F, commercially, Kunipia-F) in a closed system at temperatures of 95, 150, 200, 250, 300°C for run durations of up to 477 days with a 1:20 mass ratio of solid to deionized water. The mean layer charge and tetrahedral charge of SKu-F are larger than those of SWy-1. The proportion of smectite layers in illite/smectite interstratified minerals rapidly decreases, and then slowly decreases with increase in reaction time; a plot of In (100/% smectite) vs. time produces two distinct straight lines in all experiments. These lines are suggestive of two first-order kinetic processes with different rates for this reaction; the first process has a greater rate than the second one. An Arrhenius plot of the reaction rates for each process produces a folding and straight lines for the first and second processes, respectively, suggesting that there are at least two parallel processes in the first process, and a dominant process is different between high- and low-temperature reactions. The activation energies of the first and second processes determined from the plots are the same for the two starting materials, meaning that the reaction mechanisms for the two starting materials are the same. However, the rate of the first process is different between the two starting materials, although that of the second process is similar. The difference in the rate of the first process results possibly from the difference in the amount of layer charge between the two starting smectites.
Method of Designing Bentonite/Sand Mixture to Achieve the Target Permeability
Authors: Nakashima Hitoshi , Ishii Takashi , Nagasawa Tatsuro , Ogata Nobuhide , Komine Hideo
Published: April 2011

Bentonite/sand mixture is expected to be an effective component of barriers for radioactive waste disposal facility. Impermeable mixture can be obtained through enrichment of the bentonite content,but it is difficult to estimate a permeability of bentonite/sand mixture before permeability test. At designing of bentonite/sand mixture, we have to decide which sand to be used, and what bentonite content is. But.this means that designing will be a time-consuming task.
In this report, we made many kinds of bentonite/sand mixtures using some kinds of sand with different bentonite content, and permeability tests were conducted for these mixtures. After examination of the permeability tests results, the effective void ratio of bentonite/sand mixture which was obtained by compaction test, is an efficient parameter for estimation of the permeability.
Last of all, we propose the method of designing bentonite/sand mixture using the effective void ratio.
Diffusion Behavior for Se and Zr in Sodium-Bentonite
Authors: Sato Haruo , Yui Mikazu , Yoshikawa Hideki
Published: April 2011

Apparent diffusion coefficients for Se and Zr in bentonite were measured by in-diffusion method at room temperature using water-saturated sodium-bentonite. KunigelVl® * containing 50wt% Na-smectite as a major mineral was used as the bentonite material. The experiments were carried out in the dry density range of 400–1800kg/m3. Bentonite samples were immersed with distilled water and saturated before the experiments. The experiments for Se were carried out under N2 atmospheric condition (O2: 2.5ppm). Those for Zr were carried out under aerobic condition. The apparent diffusion coefficients decrease with increasing density of the bentonite. Since dominant species of Se in the pore water is predicted SeO32-, Se may be retarded by anion-exclusion because of negative charge on the surface of the bentonite and little sorption. The dominant species of Zr in the porewater is predicted Zr(OH)5- or HZrO3-. Distribution coefficient measured for Zr on the bentonite was about 1.0m3/kg from batch experiment. Therefore, the retardation may be caused by combination of the sorption and the anion-exclusion. A modelling for the diffusion mechanisms in the bentonite were discussed based on an electric double layer theory. Comparison between the apparent diffusion coefficients predicted by the model and the measured ones shows a good agreement.
Thermodynamic Properties of Water in Compacted Bentonite Under External Pressure-free Conditions
Authors: Torikai Yuji , Sato Seichi , Ohashi Hiroshi
Published: April 2011

In an attempt to determine the thermodynamic properties of water in bentonite, the vapor pressure of water in compacted bentonite was measured as functions of water content and temperature, under external pressure-free conditions. The relative partial molar Gibbs free energy ΔGH2O, enthalpy ΔHH2Oand entropy ΔSH2O of tne waler in bentonite were determined at temperature of 298.15K. The interlayer distance of montmorillonite in bentonite was also measured by X-ray diffraction.

It is probable that one fourth of the total water included in the bentonite at water content of 20.3wt% and dry density of 1.76 × 103kg/m3 is nearly free water; the water is not regarded as dilute electrolytic solution but the solution with higher ionic strength. Another one fourth of the water in the bentonite at the water content is bound water; the partial molar entropy of the bound water referred to pure water is from a half to whole of solidification entropy of pure water. The remainder is regarded as intermediately bound water.
Corrosion of Iron and Migration of Corrosion Products in Compacted Bentonite
Authors: Kozaki T. , Imamura Y. , Takada J. , Sato S. , Ohashi H.
Published: April 2011

For safety assessment of the geological disposal of the high level radioactive waste, it is necessary to study corrosion of the overpack materials and migration of the corrosion products in the compacted bentonite. In the present study, average corrosion rates of iron foil and apparent diffusion coefficients of the corrosion products were determined using a neutron- activated iron foil. The average corrosion rates were on the order of 10-6m/y, while apparent diffusion coefficients were in the range from 10-12 to 10-14m2/s. No tendency to decrease in the corrosion rates with increasing corrosion time was observed. This suggests that the iron foil corrodes under reducing condition. Asymmetric concentration profiles of iron corrosion products were obtained in some experiments. It can be considered that either cathodic or anodic reaction would dominantly occur on one side of the iron foil surfaces and that each reaction would change the pH in pore water of bentonite specimens adjacent to the iron foil surfaces.
Formation and Durability of Hydrated Layers for Several Oxide Glasses
Authors: Nishii Junji , Akai Tomoko , Yamashita Masaru , Yamanaka Hiroshi , Wakabayashi Hajimu
Published: April 2011

Formations and durabilities of hydrated layers were compared between a soda-aluminosilicate (NAS), a soda-lime-aluminosilicate(NCAS) and a soda-lime-alumino-borosilicate(NCABS) glasses. The first step of our study was to prepare the optically transparent hydrated layers on the surface of specimens by an autoclave(400 °C, 20 kgf/cm2) treatment. Distributions of OH groups in hydrated layers were analyzed by an etch sectioning and FTIR measurement. The rates of hydration of the glasses were in the order NAS»NCAS>NCABS. The hydration of the NCABS glass, which is a modified nuclear waste glass, required the treatment longer than those of the NAS and NCAS glasses. In the second step, we investigated the durabilities of hydrated layers by immersing the specimens into a distilled water at 100 °C. The dissolutions of hydrated layers were confirmed for each glass. The dissolution rates of hydrated layers were in the order NCAS>NCABS»NAS. It has become apparent by an XPS analysis that the highest durability of the hydrated NAS glass was due to the formation of a sodium free Al2O3-SiO2 layer on the surface. The hydrated layer of the NCAS glass, while the sodium ions were almost leached out during immersion, dissolved to water most quickly than those of other glasses. In the hydrated layer of the NCABS glass, a half amount of sodium and boron ions remained and inhibited the dissolution of hydrated layer.
Flow-Diversion Barriers for HLW and LLW Disposal Under Partially Saturated Conditions
Authors: Apted M. J. , Salter P. F. , Conca J. L.
Published: April 2011

An innovative EBS design of sand-gravel layers for waste disposal under partially saturated conditions is described. Advantages of this EBS are 1) as a hydraulic barrier to advective inflow from the surrounding rock, and 2) as a diffusion barrier to the transport of dissolved or colloidal radionuclides. This sand-gravel barrier design for unsaturated sites is analogous to EBS designs using compacted bentonite backfills/buffers in saturated repository sites. Percolation box experiments, field tests, and natural analogues supporting the advantageous performance of this flow-diversion design are described and estimates for source-term release are calculated.
Study of the Leaching Behaviour of Sintered UO2 in Groundwater Using Nuclear Microprobe Techniques
Authors: Trocellier Patrick , Gallien Jean Paul , Cachoir Christelle , Toulhoat Pierre
Published: April 2011

The leaching behaviour of sintered UO2 pellets has been studied in synthetic groundwater at 96 °C under strictly controlled conditions (CO2 partial pressure, O2 partial pressure, pH and redox potential). Results obtained in oxidizing conditions (O2 content varying from 5 to 25 ppm) show a strong initial uranium release in solution during the first five days and a solubility control essentially driven by the growth of U(VI) species such as oxides, hydrates and carbonates. Results obtained in reducing conditions (use of a mineralogical buffer of Ni(0)/Ni(ll) with E0 = -0.257 Volts) show a very weak uranium release in solution close to 10-11 mole/l and a solubility control essentially driven by the formation of U(IV) compounds such as coffinite or uraninite.
Prediction of the Oxidative Dissolution Rates of Used Nuclear Fuel in a Geological Disposal Vault Due to the Alpha Radiolysis of Water
Authors: Sunder S. , Shoesmith D.W. , Miller N.H.
Published: April 2011

Effects of alpha radiolysis of water on the corrosion of nuclear fuel (UO2) have been investigated in solutions at pH = 9.5, i.e., a value close to that expected in groundwaters at the depth of the disposal vault proposed in the Canadian nuclear fuel waste management program, CNFWMP. The corrosion potentials of UO2 electrodes exposed to the products of alpha radiolysis of water were monitored as a function of alpha flux and exposure time in a specially designed thin-layer cell. The oxidative dissolution rates of UO2 are calculated from the steady-state values of the corrosion potential using an electrochemical model. A procedure to predict the dissolution rate of used nuclear fuel in groundwater as a function of fuel cooling time is described, and illustrated by calculating the dissolution rates for the reference used fuel in the CNFWMP (Bruce CANDU reactor fuel, burnup 685 GJ/kg U). It is shown that the oxidative dissolution of used fuel in the CNFWMP will be important only for time periods ≤ 600 a at this burnup and assuming no decrease in pH.
Crevice Corrosion - NaCl Concentration Map for Alloy 625 at Elevated Temperature
Authors: Amano Toshiaki , Kojima Yoichi , Tsujikawa Shigeo
Published: April 2011

The repassivation potentials, Er.crev’s, for metal/metal-crevice of Alloy 625 were determined in 0.3–10% NaCl solutions for temperatures up to 250 C. The Er.crev’s were found to be the least noble at temperatures around 100 and 125 C. The Er.crev became more noble as temperature increased; this tendency was particularly strong in diluted solutions. Based on the experimental data, a crevice corrosion map showing the critical condition in terms of temperature and NaCl concentration was presented. As for the map, a wide repassivation region was found in elevated temperatures, similar to that of commercially pure titanium, C.P.Ti.
Development of Secondary Phases on Synroc Leached at 150˚C
Authors: Lumpkin Gregory R. , Smith Katherine L. , Blackford Mark G.
Published: April 2011

Electron microscopy techniques were used to identify secondary phases on the surface of Synroc after exposure to doubly deionized water (DDW) at 150 ˚C for time periods up to 532 days. After one day, Ti02 develops on perovskite in the form of polycrystalline crusts of anatase or epitaxial crystals of brookite (± anatase), and as scattered single crystals on hollandite and rutile-Magnéli phases. With increasing exposure time the anatase crusts exhibit slow grain growth and development of preferred orientation; whereas, the epitaxial brookite crystals appear to grow more rapidly. Dissolution of perovskite and P-bearing intermetallic particles results indirectly in the precipitation of monazite after 84 days. Additional alteration products observed over a range of time include crystalline Al-O-H phases and amorphous to poorly crystalline Fe-O-H phases which form as a result of the dissolution of Al-rich oxides and Fe-bearing intermetallic grains, respectively. A poorly crystalline Ru-O-H phase was found as an alteration product of Ru-bearing intermetallic particles after exposure to DDW for 336 days.
Characterization of Highly Waste Loaded Glass for HLW
Authors: Kawamura Kazuhiro , Ohuchi Jin
Published: April 2011

Possibility of highly waste loaded borosilicate glasses up to 65wt% were investigated for HLW. In the case the waste was loaded at a content higher than 45wt%, apatite crystal was identified in the glasses. Adding above 2.5wt% of M0O3, yellow phase was observed in the 45wt% waste glass. In the case the composition of actual waste was simulated, waste(25–45wt%) glasses were characterized. Chemical durability of 45wt% waste glass was equivalent to that of 25wt% waste glass under the condition of Na20 content lower than 12wt%. Rheological behavior of 45wt% waste glass was equivalent to that of 25wt% waste glass in the range of melting temperature. Electrical resistivity of 45wt% waste glass were a little lower than that of 25wt% waste glass and it depended on the noble metal content. The Time-Temperature-Transformation (T-T-T) diagram and the leach rate of heat treated glass indicated a good thermal stability of highly waste loaded glass below the glass transition temperature. Possibility of high waste loading up to 45wt% was elucidated.
Generation Mechanism of Hydrogen Gas from Hardened Cement Paste by γ-Irradiation
Authors: Noshita K. , Nishi T. , Matsuda M.
Published: April 2011

Hydrogen gas is generated from cementitious waste forms by radiolysis of water. In the case of low level radioactive waste, gas yields have been confirmed to be sufficiently low by irradiation experiments. However, studies have suggested that the hydrogen generation rate in cementitious waste forms is larger than the rate calculated from the g-value (H2 yields for 100eV absorbed). In this paper, the factors that increase the gas generation were investigated quantitatively. Two factors were identified, the effect of an organic diethylene glycol which reacts with hydrogen radicals to produce hydrogen, and the effect of electrons generated in the cementitious matrix which decompose water to hydrogen. The hydrogen generation rate was confirmed to drop less than the rate calculated from the g-value when these factors were eliminated.
Ion Mixing of Pulsed Laser Deposited Hydroxylapatite (HA)
Authors: Alford T.L. , Russell S.W. , Pizzicont V.B. , Mayer J.W. , Levine T.E. , Nastasi M. , Cotell C.M. , Auyeung R.C.Y.
Published: April 2011

The use of ion-beam techniques to enhance selected properties of bioactive materials, such as the adhesion of hydroxylapatite (HA) coatings on titanium-based substrates has been investigated. In this study, very thin HA films on titanium substrates were created by pulsed laser deposition techniques. Ion irradiations were carried out using 260-keV argon ions, with fluences of 0.25-50×1015ions/cm2, and at room temperature. Rutherford backscattering spectrometry was used to evaluate sample composition before and after irradiation. The amount of mixing was quantified by the mixing rate (the amount of atomic displacement due to an irradiation fiuence). This pilot data indicates that mixing was evident after sufficient ion irradiation. The ramification of this preliminary study has provided a quantitative measure of ion mixing as a potential prosthetic biomaterial surface modification technique.
Anomalous Diffusion of Implanted Chlorine in Silicon
Authors: Datar Sameer A. , Gove H. E. , Teng R. , Lavine J. P.
Published: April 2011

The diffusion of implanted chlorine in silicon wafers is studied with neutron activation/accelerator mass spectroscopy (NA/AMS). Depth profiles are obtained from as-implanted and annealed samples. While there is a marked difference between the annealed and as-implanted profiles for the lowest implant dose studied, 1013/cm2, the chlorine from the higher dose implants is virtually immobile. The diffusion of implanted chlorine in silicon is characterized by the apparent absence of indiffusion for the experimental conditions studied. However, outdiffusion is rapid at low concentrations for anneal temperatures of 1100°C and above. This behavior is qualitatively similar to that reported for fluorine in silicon at lower temperatures.
A Study of Loop Evolution During Inert Ambient Annealing and Reaction Between Point Defects and Dislocation Loops During Oxidation of Silicon
Authors: Liu J. , Jones K. S.
Published: April 2011

In the first part of this work, a plan-view TEM study has been made of the time-dependent annealing behavior of end of range (type II) dislocation loops introduced by lxl015/cm2 50KeV Si+ implantation into silicon. The activation energy for loop growth was determined to be 1.0±0.2eV from the Arrhenius plot of loop growth rate versus the reciprocal of annealing temperature. In the second part of this study, a thin boron layer was used as a diffusion monitor. The number of injected interstitials as a result of oxidation was measured by TEM. The diffusivity of boron with and without the presence of loops was studied by fitting experimental SIMS profiles with FLOOPS simulations. The interaction between loops and interstitials was determined to be diffusion limited.
A New Approach To Microporous Materials — Application Of Ion Beam Technology To Polyimides Membrane
Authors: Xu X.L. , Dolveck J.Y. , Boiteux G. , Escoubes M. , Monchanin M. , Dupin J.P. , Davenas J.
Published: April 2011

Recently engineered porous materials have been attracted more attentions because of their potential applications in several industrial sectors, such as high efficiency gas separation membrane, catalytic membranes for chemical processing and so on. In spite of their desirable applications, these porous materials have not been realized due to several technical barriers, for example, lack of pore size control. There is a general viewpoint that for conventional gas separation membranes one cannot increase both permeability and permselectivity of the product gas simultaneously. This general viewpoint implies that the conventional methods of gas separation membrane fabrication cannot precisely control the pore size. In this work iodine diffusion property and gas permeation properties of ion beam irradiated polyimides films have been investigated. Small fluence irradiation can raise significantly the iodine penetration in the energy deposition range and permeabilities of the films both for H2 and CH4. After higher fluence irradiation, the implanted layers become stopping layers blocking iodine diffusion into the film and both the permeability for H2 and permselectivity for (H2/CH4) of the film increase hugely. We related the small fluence effects to defects created by irradiation and higher dose effects to the new materials formation of which the pore size is well defined. From these results we can perhaps have a peep at a new way to microporous materials.
Contamination Monitoring Using Surface Photovoltage and Application to Process Line Control
Authors: Jastrzebski Lubek , Lagowski Jacek , Henley Worth , Edelman Piotr
Published: April 2011

Surface photovoltage (SPV) measurements of lifetime and charge are used by the silicon industry for real-time, non-contact monitoring of alkalide and heavy metal contamination during IC processing. Information about contamination present at the surface or in the bulk of a silicon wafer is derived from their effects on measured electronic characterization. Identification and detection, with a sensitivity of ppq (107 cm'3), of Fe and Cr in the bulk of p-type silicon is possible via monitoring of their decomposition/pairing kinetics with boron. We will show the most important examples of the application of SPV to monitor critical IC processing steps. The allowable contamination thresholds in IC processing lines are a very strong function of technology and are different for various metals.
Monitoring of the Early Stages of Thin Film Growth by the Generation From Second Harmonic Radiation of Supported Metal Particles
Authors: Götz T. , Hoheisel W. , Buck M. , Dressier C. , Eisert F. , Träger F.
Published: April 2011

Optical second harmonic generation (SHG) of metal clusters supported on a dielectric substrate has been investigated. The SHG intensity was detected in situ as a function of cluster size during the nucleation of the particles at constant number density. SH radiation is detectable for particles as small as approximately 1 nm. In further experiments the chemisorption of oxygen on the surface of the metal particles was studied. The SHG signal strongly decreases as a function of oxygen coverage and disappears almost completely upon chemisorption of only one monolayer.
Correlation of Roughness, Impurity, Infra-Red Emissivity and Sputter Conditions for Aluminium Films
Authors: Wang C.H. , Shih W.C. , Somekh R.E. , Evetts J.E. , Jackson D.
Published: April 2011

We report the results of a study of IR emissivity of aluminium films as a function of impurity level, film thickness and sputtering conditions. Preliminary work suggests that for a given level of film impurities and deposition conditions, the JJR emissivity can be minimized with a certain film thickness. The influence of impurity level, film thickness, and sputter pressure on IR emissivity has been correlated with the resistivity and the surface roughness (measured by atomic force microscopy). The results are discussed in the general context of the Drude theory with allowances for the observed roughness.
Ion-Assisted Pulsed Laser Deposition of Amorphous Tetrahedral-Coordinated Carbon Films
Authors: Friedmann T.A. , Tallant D.R. , Sullivan J.P. , Siegal M.P. , Simpson R.L.
Published: April 2011

A parametric study has been performed of amorphous tetrahedral carbon (a-tC) films produced by ion- assisted pulsed laser deposition (IAPLD). The ion voltage, current density, and feed gas composition (nitrogen in argon) have been varied. The resultant films were characterized by thickness, residual stress, Raman spectroscopy, and electrical resistivity. The Raman spectra have been fit to two gaussian peaks, the so called graphitic (“G”) peak and the disorder (“D”) peak. It has been found that the magnitude of the D peak and the residual compressive stress are inversely correlated. At low beam voltages and currents, the magnitude of the D peak is low, increasing as the ion beam voltage and current are raised. The ion beam voltage has the most dramatic effect on the magnitude of the D peak. At low voltages (200–500 V) the magnitude of the D peak is greater for ion beams with high percentages of nitrogen possibly indicative of C-N bonding in the films. At higher voltages (500 - 1500V) the D peak intensity is less sensitive to the nitrogen content of the beam.
A Numerical Simulation of Pulsed Laser Deposition
Authors: Laughlin William T. , Lo Edmond Y.
Published: April 2011

A numerical simulation of the pulsed laser deposition process has been developed. This model is applied to pulsed laser deposition of carbon, a solid lubricant material. At laser fluences above the ablation threshold, the vapor density and temperature at the substrate are sufficiently high that a continuum flow exists. For typical pulsed laser deposition parameters, plume vapor temperatures and densities are insufficient for significant ionization. However, plume absorption does take place and is regulated by wavelength dependent absorption cross sections of the molecular species. Vapor expansion velocities depend on the absorption of laser radiation and thus the laser wavelength. A simple kinetic theory of deposition predicts the film deposition rate and film thickness profile.
Composition and Phase Control for Molybdenum Nitride thin Films
Authors: Mudholkar Mandar S. , Thompson Levi T.
Published: April 2011

Molybdenum nitrides are active and selective hydrodenitrogenation (HDN) catalysts. The catalytic properties of molybdenum nitrides were found to be dependent on the structural properties. The purpose of research described in this paper was to synthesize molybdenum nitride thin films with well defined structures and stoichiometries using ion beam assisted deposition. The films were deposited by evaporating Mo metal, and simultaneously bombarding the growing film with low energy nitrogen ions. The phase constituents of the films were determined using x-ray diffraction and the film composition was obtained by Rutherford backscattering spectrometry.

The film composition and phase constituents were strong functions of the ion-to-atom arrival rate ratio, ion energy and ion angle of incidence. Differences in the film composition for different arrival rate ratios and ion angles of incidence were interpreted based on reflection and sputtering effects. Our results suggest that phase formation was governed by the effective energy density per deposited atom. Evaluation of the effective energy density per deposited atom and its physical significance in ion beam assisted deposition is discussed.
EPR Studies of E-Beam and Gamma Irradiated ZnGeP2: A Nonlinear Optical Material for the Infrared
Authors: Rakowsky M.H. , Lauderdale W.J. , Mantz R. A. , Pandey R. , Drevinsky P.J.
Published: April 2011

Zinc germanium phosphide is a nonlinear optical material for efficient frequency conversion in the mid-IR spectral region. One challenge in the development of ZnGeP2 is to reduce the near band edge absorption in the 0.7 to 2.5 micron region. Several methods have been used to ascertain the origin of this absorbance. One method, electron paramagnetic resonance (EPR), has been used to characterize the paramagnetic native acceptor in ZnGeP2 by studying as-grown, thermally annealed, electron-beam irradiated, and gamma irradiated single crystals. Each of the these processing routines improves the optical transparency with a concurrent decrease in the concentration of paramagnetic centers and defect site symmetry as seen in the EPR spectra. High energy e-beam and gamma irradiation may cause compensation, movement, or creation of new defects. In addition, nuclear magnetic resonance (NMR) has been used to further characterize several samples of as-grown, annealed and polycrystalline ZnGeP2. Preliminary calculations of the defect energetics have been conducted using atomistic simulation techniques employing the shell model to describe the lattice. Interionic potentials between the constituent ions were obtained by performing quantum cluster calculations on ZnGeP2.
Characterization and Performance of Carbon Films Deposited by Plasma and Ion Beam Based Techniques
Authors: Walter K.C. , Kung H. , Levine T. , Tesmer J.T. , Kodali P. , Wood B.P. , Rej D.J. , Nastasi M. , Koskinen J. , Hirvonen J-P.
Published: April 2011

Plasma and ion beam based techniques have been used to deposit carbon-based films. The ion beam based method, a cathodic arc process, used a magnetically mass analyzed beam and is inherently a line-of-sight process. Two hydrocarbon plasma-based, non-line-of-sight techniques were also used and have the advantage of being capable of coating complicated geometries. The self-bias technique can produce hard carbon films, but is dependent on rf power and the surface area of the target. The pulsed-bias technique can also produce hard carbon films but has the additional advantage of being independent of rf power and target surface area. Tribological results indicated the coefficient of friction is nearly the same for carbon films from each deposition process, but the wear rate of the cathodic arc film was five times less than for the self-bias or pulsed-bias films. Although the cathodic arc film was the hardest, contained the highest fraction of sp3 bonds and exhibited the lowest wear rate, the cathodic arc film also produced the highest wear on the 440C stainless steel counterface during tribological testing. Thus, for tribological applications requiring low wear rates for both counterfaces, coating one surface with a very hard, wear resistant film may detrimentally affect the tribological behavior of the counterface.
Negative-Ion Implantation
Authors: Ishikawa Junzo
Published: April 2011

Negative-ion implantation is a promising technique for forthcoming ULSI (more than 256 M bits) fabrication and TFT (for color LCD) fabrication, since the surface charging voltage of insulated electrodes or insulators implanted by negative ions is found to saturate within so few as several volts, no breakdown of insulators would be expected without a charge neutralizer in these fabrication processes. Scatter-less negative-ion implantation into powders is also possible. For this purpose an rf-plasma-sputter type heavy negative-ion source was developed, which can deliver several milliamperes of various kinds of negative ion currents such as boron, phosphor, silicon, carbon, copper, oxygen, etc. A medium current negative-ion implanter with a small version of this type of ion source has been developed.
Structures of Bonding Interface by Forming Hydrogen Bridges
Authors: Nagakubo M. , Suzuki H. , Idogaki T. , Hattori T.
Published: April 2011

Direct bonding by forming interface hydrogen bridges has been investigated for both combinations of AI.Si and Al.PZT{Pb(Zr,Ti)03). Hydrogen bridges are formed between OH-groups and oxygen atoms on each bonding surface. Therefore, the surface adsorbing of OH-groups (hydrophilic treatment) is required to the pre-treatment of bonding surface. In this study, two ways of conventional hydrophilic treatment by wet-process and novel treatment by the surface bombardment of hydro-ions(H2O+, OH+, O+, and others) in vacuum (dry-process) have been examined.

Each bonding surface is contacted in the air after the hydrophilic treatment. In the case of hydrophilic treatment by wet-process, the bonding strength of Al-Si shows about 20 MPa after the heat treatment of above 350°C. As for the dry-process, both combinations of At.Si and AI.PZT are bondable, and their strength shows the similar tendency as wet-process with the time and the temperature of heat treatment. However, the bonding area increases more quickly than the ones of wet process. From the results of SIMS and cross-sectional TEM observation of AlSi bonding interface, it is suggested that these bonding are caused by the hydrogen bond formation without interfacial water molecules.
High Resolution Electron Microscopy and Computer Simulation Studies of the Atomic Structure of Tilt Boundaries in TiO2
Authors: Liu Yaping , Majid Imtiaz , Vander Sande John B.
Published: April 2011

The atomic structure of [001] tilt grain boundaries of Σ25 (210), Σ5 (310), Σ213 (320) and Σ217 (410) in TiO2 (rutile) were studied using high resolution electron microscopy and computer simulation. Regularly separated small steps (1/2 [120] high) and big steps (3/2 [120] high) which contain secondary dislocations were found in the (210) boundary as a result of deviation from the exact Σ5 misorientation and (210) symmetric plane. Similar steps were also found in (310) and (320) boundaries. Flat segments between the steps were found to have very accurate misorientation of their, Σ's and a nearly symmetric boundary plane. Their rigid body translation, volume expansion and relaxed structures were determined by comparing HRTEM images with computer calculated structures and simulated images. An irregular core structure was found in the (410) boundary when its misorientation deviated 2° from the exact Σ17 misorientation.
The Interaction of Twin Boundaries with Grain Boundaries in YBa2Cu3O7-δ
Authors: Wang Jenn-Yue , King Alexander H.
Published: April 2011

Twins in YBa2Cu3O7-δ may be “correlated” at [001] tilt grain boundaries (i.e. twin boundaries from one grain may meet twin boundaries from the other grain in quadruple junctions) and the twins may also be narrowed or “constricted” at the boundary. These effects are more pronounced in the regime of small angle grain boundaries. Based on TEM observations, a tentative threshold misorientation angle of approximately 15° is identified, below which there is a significant driving force reducing the system energy by correlation. The energies of various grain boundary domain structures associated with the twins were estimated on the basis of the dislocations they contain. Success has been obtained in explaining twin correlation in symmetrical tilt boundaries.
Orientation Relationships and Interfaces Between Low Symmetry Phases in The Yttria-Alumina System
Authors: Hay R. S.
Published: April 2011

Interphase boundaries and orientation relationships for yttria - yttrium-aluminum monoclinic and yttrium-aluminum monoclinic - yttrium-aluminum perovskite eutectics were observed by standard and high resolution TEM techniques. Three and five orientation relationships were found for each system, respectively. These eutectics all had a monoclinic phase and therefore had little potential for high symmetry overlap. In many cases low index planes with similer spacings or spacing multiples were parallel. However, presence of a monoclinic phase made definition of a three-dimensional low index near-CSL very difficult, so a combination of planes corresponding to reciprocal-space directions and zones corresponding to real-space directions were often needed for a geometric description of the orientation relationship. In general, two planes and the real-space direction corresponding to the zone for these planes described the orientation relationships. The disregistry between reciprocal-space coincidence sites was not localized by dislocations large enough to be visible.
Effects of Annealing on The Structure of Ta2N Thin Films Deposited on Al2O3
Authors: Angelo James E. , Moody N.R. , Venkataraman S.K. , Gerberich W.W.
Published: April 2011

The microstructure of Ta2N thin films deposited by d.c. magnetron sputtering on (1120) surface of Al2O3 is investigated using transmission electron microscopy. The effects of exposing the thin film structure to a 600°C air environment are also explored. It will be shown that under the standard deposition conditions, stresses exist in the thin film structure which leads to the formation of a textured structure in the as-deposited Ta2N. Exposure of the thin film structure to an air environment transforms the Ta2N to Ta2O5 in the orthorhombic structure. In addition, evidence for a epitaxial relationship between the Ta2O5 and Al2O3 will be presented.
The Stability of MoSi2 Films in Vacuum and Oxidizing Atmospheres
Authors: Kolaya L.E. , Duquette D.J. , Hudson J.B.
Published: April 2011

The stability of MoSi2, films with respect to mass loss at high temperature has been investigated in vacuum and dry air environments at temperatures up to 1300° C. Samples were sputter deposited films of approximate composition MoSi3, on sapphire substrates. Post heat treatment analysis by X-ray diffraction, scanning electron microscopy, and electron microprobe analysis indicated that the films recrystallized, and that phase separation of the excess silicon from the MoSi2, occurred early in the heating process. With continued heating, silicon was lost from the films by evaporation, leading to the conversion of the films to Mo5Si3. The rate of mass loss was much less in the air environment due to the formation of a SiO2, layer which served as a diffusion barrier to silicon. Evidence of a reaction along the MoSi2,/A12O3 interface was observed visually, but could not be detected chemically.
Low Temperature - High Pressure Oxidation of 3C-SiC
Authors: Caragianis-Broadbridge Christine , Walden Barbara L. , Blaser Juliana , Yang Cleva Ow , Paine David C.
Published: April 2011

Single crystal films of n-type 3C-SiC were hydrothermally processed at pressures ranging from 10 to 70 MPa at 550°C. To study the effects of initial thin film microstructure on hydrothermal processing, two different samples of CVD-grown SiC were studied: one, 200 nm thick, contained low angle boundaries and a high density of planar defects; the other, 3500 nm thick, was planar and contained relatively few defects. Raman Spectroscopy, X-Ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to study the chemistry and microstructure of the SiC material both before and after hydrothermal treatment. This study reveals that low temperature (T=550°C) oxidation of single crystal epitaxial SiC is possible but that the resulting oxide film microstructure is strongly dependent on the initial film microstructure and oxidation is greatly enhanced along low angle grain boundaries and on planar defects.
Thermodynamic Stability of Binary Oxides in Contact with Silicon
Authors: Hubbard K. J. , Schlom D. G.
Published: April 2011

Using tabulated thermodynamic data, a comprehensive investigation of the thermodynamic stability of binary oxides in contact with silicon at 1000 K was conducted. Reactions between silicon and each binary oxide at 1000 K, including those involving ternary phases, were considered. Sufficient thermodynamic data exists to conclude that all binary oxides except the following are unstable in contact with silicon at 1000 K: LiO2, the alkaline earth oxides (BeO, MgO, CaO, SrO, and BaO), the column IIIB oxides (Sc2O3, Y2O3, and Re2O3 where Re is a rare earth), ThO2, ZrO2, HfO2, and Al2O3. Of these remaining oxides, sufficient thermodynamic data exists to conclude that MgO, CaO, and ZrO2 are thermodynamically stable in contact with silicon at 1000 K.
Interfaces of Ionically Conducting Materials: Electrochemical Properties
Authors: Maier Joachim
Published: April 2011

This contribution summarizes former results and presents recent findings concerning interfacial properties in solid state ionics but also stresses the model role of ionic conductors for typical ceramic problems. Moreover, recently developed and improved electrochemical techniques allowing spatial resolution are discussed, viz. a two-dimensional impedance spectroscopy as well as a combination of microelectrochemistry and atomic force microscopy.
Growth and Structure of Al/MgO Interfaces
Authors: Wagner T. , Ruhle M.
Published: April 2011

The A1/MgO system has been used as a model system to study growth processes and structure at metal/ceramic interfaces. Aluminum films were grown on air-cleaved MgO (100) substrates in ultra high vacuum (UHV) by molecular beam epitaxy (MBE). The substrates and films were characterized by reflection high energy electron diffraction (RHEED), x-ray diffraction (XRD), conventional transmission electron microscopy (CTEM), and high resolution transmission electron microscopy (HREM). XRD measurements exhibited a pronounced {100} texture. Employing electron diffraction in the TEM on cross sectional samples, we observed the following orientation relationship between Al and MgO: (100)A1 II (100)MgO; [010]A1 II [010]MgO. The atomistic structure of the interface was investigated by HREM. Regions of structural defects can be identified clearly at the interface.
Atomistic Study of Energy and Structure of Surfaces in NiO
Authors: Yan M. , Chen S. P. , Voter A. F. , Mitchell T. E.
Published: April 2011

The structure and energy of surfaces in NiO have been studied by atomistic calculations employing short range Buckingham potentials fitted to properties of NiO. The polarizability of lattice anions is included by using the shell model. The results show that the surface energy depends strongly on surface orientation, and the {100} surface has the lowest energy. Surfaces with higher energy prefer to reconstruct into {100} facets to lower their energy and to stabilize their structure.
Theory on the Structure of Twin Boundaries in La2−x,BaxCuO4
Authors: Cai Zhi-Xiong , Welch David O.
Published: April 2011

The structure of the twin boundary in the low-temperature-orthorhombic phase of La2−xBaxCuO4 is studied using a Landau-type free energy model which reproduces the x − T phase diagram. The La2−xBaxCuO4 compound has a body-centered tetragonal (HTT) structure at high temperatures. Upon cooling it undergoes a structural phase transition to a low-temperature orthorhombic structure (LTO structure) which is caused by the tilting of the CuO6 octahedra about the (110) and (110) directions. Depending on the doping level x, the LTO structure may go through another phase transition at an even lower temperature to a low-temperature tetragonal phase (LTT phase). We find that the existence of LTT phase greatly changes the characteristics of the twin boundary in the LTO phase. LTT phase exists at twin boundaries of the LTO phase at temperatures well above the LTT to LTO transition temperature.