bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass Transfer from Penetrations in Waste Containers
Authors: Pescatore C. , Sastre C. 
Published: March 2011

AbstractRecent studies have indicated that localized corrosion of a relatively small area of a waste container may impair the containment function to such an extent that larger releases may be possible than from the bare waste form. This would take place when a large number of holes coexist on the container while their concentration fields do not interact significantly with each other. After performing a steady state analysis of the release from a hole, it is shown that much fewer independent holes can coexist on a container surface than previously estimated. The calculated radionuclide release from multiple independent holes must be changed accordingly. Previous analyses did not proceed to a correct application of the linear superposition principle. This resulted in unacceptable physical conclusions and undue strain on the performance assessment necessary for a container licensing procedure. The paper also analyzes the steady state release from penetrations of finite length and whose concentration fields interact with one another. The predicted release from these penetrations is lower than the previously calculated release from holes of zero thickness. It is concluded here that the steady-state release from multiple holes on a waste container can not exceed the release from the bare waste form and that multiple perforations need not be a serious liability to container performance.
Predicting the Long Term Corrosion of Metal Containers for Nuclear Waste Disposal
Authors: Marsh G. P. 
Published: March 2011

AbstractThe prediction of the long term corrosion of metal containers for nuclear waste under geological disposal conditions requires the extrapolation of corrosion data over several hundred years. There is a general trend to use either simulation or ‘worst case’ experiments as a means of materials selection, but neither really addresses the problem of long term extrapolation. It is proposed that such an extrapolation can only be done convincingly if it is based on a sound and generally accepted mechanistic understanding of the processes involved. If such knowledge does not exist the first step must be to acquire it through experimental mechanistic studies. Subsequently such knowledge should be formulated into mathematical models, which can be used to make long term predictions, and which can be validated by comparison with short term experimental results. The application of this combined mathematical modelling/experimental approach is illustrated for three corrosion processes which may affect carbon steel containers, namely general corrosion, localised attack and stress corrosion cracking.
Spent Fuel: Characterization Studies and Dissolution Behaviourunder Disposal Conditions
Authors: Johnson L. H. , Shoesmith D. W. , Stroes-Gascoyne S. 
Published: March 2011

AbstractThe concept of disposal of unreprocessed spent fuel has now been under study internationally for over ten years. Considerable progress has been made in understanding the factors that will control radionuclide release from spent fuel in an underground disposal vault. This progress is reviewed and the research areas of significance in providing further data for source term models are discussed. Key areas for future research are identified; these include improved characterization of spent fuel to determine the inventories of fission products at grain boundaries, together with their release kinetics; and a better understanding of the effects of solution chemistry on spent fuel dissolution, in particular the effects of salinity, redox chemistry, and radiolysis of groundwater. Approaches to modelling the dissolution of spent fuel are discussed, and a possible approach for developing an oxidative dissolution model is outlined.
Electron Microscopical Studies of Tricalcium Silicate - Fly Ash Blended Pastes
Authors: Rodger S. A. , Groves G. W. 
Published: March 2011

SUMMARYFly ash (FA) is becoming a common addition to ordinary portland cement (OPC) both in Europe and in the USA. Although a great deal of work has been carried out to characterize fly ashes from different sources, less work has been reported in the literature as to the exact nature of the reaction products when fly ash blends are hydrated. Microstructural studies carried out using scanning electron microscopy (SEM) of fracture surfaces have been summarized by Diamond [1]. The results often show a shell of reaction product around the fly ash residues. Some authors have postulated the formation of a duplex film of calcium hydroxide (CH) and calcium silicate hydrate (C-S-H) around the particles. However SEM alone cannot reveal the composition of features in the microstructure and interpretation on the basis of the morphology of the features may be misleading. Some analytical electron microscopy has been carried out using crushed particles of blended pastes [2] but this technique results in a loss of information about the location of analyzed areas.
Sulfate-Resistant Portland Cement from Lime-Soda Sinter Process Residue
Authors: Chesley J. A. , Burnet G. 
Published: March 2011

ABSTRACTA by-product (residue) from the Ames Lime-Soda Sinter Process for recovering alumina from power plant fly ash consists largely of dicalcium silicate and can be used as a raw material for the manufacture of sulfate-resistant (Type V) portland cement. Utilization of the residue will eliminate the need for its disposal and will improve the economic feasibility of the lime-soda sinter process. Laboratory burnability tests were used to identify optimum cement mixes and burning temperatures from both clinker quality and economic perspectives. At a typical kiln temperature of 1450°C, cements that formed concrete that exceeded ASTM specifications for strength were obtained for a limited range of lime-saturation factors and silica ratios. A highly conservative cost estimate for a combined alumina recovery and cement manufacturing facility for a 1000 MWe coal-fired power station gave a 4.7% internal rate of return.
The Long Term Effect on Cement Mortar by Admixture of Spray Drying Absorption Products
Authors: Jeppesen K. G. 
Published: March 2011

ABSTRACTPreliminary investigations have shown that the substitutions of up to 10% fly ash (FA), with spray drying absorption products (SDA), in cement mortars (cement: 80% rapid portland cement (RPC), 10–20% FA, 0–10% SDA) results in low early strength of the same magnitude as in mortar with 80% RPC + 20% FA. After storing for 3 months under wet or moist conditions the strengths of some of the SDA-containing mortars had surpassed the strength of the (80% RPC + 20% FA) mortar. Dry stored SDA-containing mortars showed a higher tendency to desiccate. Determination of SO32− showed quick oxidation to SO42− and XRD revealed the formation of ettringite. After a year the strengths of mortars made of 100% RPC, (80% RPC + 20% FA) and (80% RPC + 10% FA + 10% SDA) stored wet or moist were equal. Attempts to use synthetic CaSO3 · ½H2O (CS·½H) as a retarding agent for cement hydration failed, but conductivity measurements of tricalcium aluminate (C3 A)-CS · ½H mixes showed reaction. SEM and XRD investigations identified calcium aluminate sulphite hydrate (C4ASH8). DTA–DTG examinations of synthetic C4ASH8 showed the formula to be C4ASH11. A modification of the instructions for preparation of mortar prisms resulted in the desired retarding reaction between the C3A from portland cement (PC)-clinker and synthetic CS · ½H and SDA-products as well. The resulting C4ASH11 proved to be very unstable and changed to ettringite within a very short time. Use of the modified instructions for preparation of mortar prisms containing SDA resulted in satisfactory early strengths. A series of mortar prisms with increasing content of SDA (x% RPC, (100-x)% SDA in cements; 0<x<80) were prepared and stored under wet, moist and dry conditions. These mortars, now one year old, show a gradual development of properties. Mortars with a SDA content in cement >80% cannot be stored wet. The effects on mortars of the individual constituents of the SDA-products are studied by XRD, development in strength and density. Fragments of 2 year old SDA containing cement mortars and SDA containing concrete from a parking place have been studied.
Characterization of North American Lignite Fly Ashes II. XRD Mineralogy
Authors: McCarthy G. J. , Johansen D. M. , Thedchanamoorthy A. , Steinwand S. J. , Swanson K. D. 
Published: March 2011

ABSTRACTX-ray powder diffraction has been used to determine the crystalline phase mineralogy in samples of fly ash from each of the lignite mining areas of North America. The characteristic phases of North Dakota lignite fly ashes were periclase, lime, merwinite and the sulfate phases anhydrite, thenardite and a sodalite-structure phase. Mullite was absent in these low-Al2O3 ashes. Montana lignite ash mineralogy had characteristics of ND lignite and MT subbituminous coal fly ashes; mullite and C3A were present and the alkali sulfates were absent. Texas and Louisiana lignite fly ashes had the characteristic mineralogy of bituminous coal fly ash: quartz, mullite, ferrite-spinel (magnetite) and minor hematite. Even though their analytical CaO contents were 7–14%, all but one lacked crystalline CaO-containing phases. Lignite fly ashes from Saskatchewan were generally the least crystalline of those studied and had a mineralogy consisting of quartz, mullite, ferrite spinel and periclase. Quantitative XRD data were obtained. The position of the diffuse scattering maximum in the x-ray diffractograms was indicative of the glass composition of the lignite fly ash.
The Use of Glass Slides for Preparing Cross-Section TEM Samples of Discrete Transistors
Authors: Cowden William G. , Datye Abhaya K. 
Published: March 2011

ABSTRACTA procedure for preparing cross-section samples of specific regions on an integrated circuit die is outlined. The procedure involves the use of glass slabs to prepare the sample stack used for cross-sectioning. The transparent glass slabs on the top surface of the die enable monitoring of the region of interest during the thinning process. This ensures that the region of interest will be located in the electron-transparent section used for TEM imaging. Samples prepared using this technique are sturdy enough to survive successive thinning and observation in a TEM. The glass slides do not give any charging problems and generally thin much slower than the silicon so as to provide added stability to the sample. An additional advantage is that the sample thickness can be accurately measured using the vernier attachment on an optical microscope during the sample thinning process. The imaging of specific NMOS transistors fabricated on buried oxide layers is illustrated.
Equipment for Preparing Electropolished TEM Specimens at Controlled and Low Temperatures
Authors: Franetovic Vjekoslav 
Published: March 2011

ABSTRACTA cooling device for use with the Fishione twin-jet electropolisher Model 110 has been developed for electropolishing TEM specimens at controlled and low temperatures necessary for some materials. This consists of an explosion-proof pump circulating methanol through a specially designed stainless steel bath, and a copper coil immersed in a mixture of methanol and dry ice in a dewar. A thermocouple with a temperature control unit provides precise temperature control.With this device, electropolishing can be conducted at temperatures as low as −55°C. This allows electropolishing of certain materials which cannot be polished with conventional equipment. The precisely controlled temperature also improves the performance of the electropolishing equipment at all temperatures because the success of electropolishing depends on maintaining constant conditions during the process. The unit further allows the use of aggressive electrolytes and preparation of solutions which could otherwise become hazardous due to heat buildup during electropolishing or preparation.
A New Method of Preparing Tilt Boundaries for High Resolution Electron Microscopy
Authors: Krakow William , Castańo Victor 
Published: March 2011

ABSTRACTA new method of preparing bicrystal substrates of NaCl with a common tilt zone axis has been developed. Upon a lateral overgrowth of NaCl, bridging the two mechanically polished and oriented crystals, very thin films can then be vapor deposited. Au bicrystals of ∼ 75Å thickness and b.c.c. Cr films of similar thickness with grain boundaries have been fabricated.
A Polishless Method For Preparation Of Cross-Sectional Tem Samples
Authors: Wetzel J. T. , Danner D. A. 
Published: March 2011

ABSTRACTCross-sectional samples for Transmission Electron Microscopy (TEM) have been made without the use of mechanical polishing and ion beam milling. Instead of traditional methods, we have used a combination of electron beam (e-beam) lithography for metal lift-off and reactive ion etching (RIE) to produce TEM samples of selected areas. The sample integrity for handling, dropping and ease of use is excellent, and the large amount of transparent area available for study is nearly 2 orders of magnitude larger than that given by traditional methods. The thickness of the samples is somewhat extreme, on the order of 0.50–1.0μm, but efforts are being made to reduce this dimension in order to make the method applicable to the whole range of materials used in silicon technology.
Cross-Sectioning Specific Devices and Regions in I.C. Wafers
Authors: Brown J. N. , Sheng T. T. 
Published: March 2011

ABSTRACTLine widths of less than a micron and junction depths within devices of the order of a thousand angstroms are common practice In today's electronic components. Transmission electron microscopy (TEM) is fast becoming a very valuable and often essential tool in many areas of semiconductor manufacture. The characterization of a given device structure is often required to fully understand its electrical behavior. This paper will review the methods that can be used to prepare cross-sectional samples from specific regions within an integrated circuit device for examination in the TEM.
Ion Milling of Compound Semiconductors for Transmission Electron Microscopy
Authors: Cullis A G , Chew N G 
Published: March 2011

ABSTRACTSerious artefactual structures can be introduced into transmission electron microscope specimens of compound semiconductors when the latter are prepared by ion milling under non-optimum conditions. In the present investigations, the nature of these artefacts is characterised and results obtained using conventional argon ion milling are compared with those obtained using alternative ion species, including iodine ions. This work demonstrates the large improvement in specimen structural quality which can be achieved by combining a logical selection of ion species with a careful choice of milling conditions.
Six-Inch Diameter GaAs on Si Wafers
Authors: Salerno Jack P. , Hill D. S. , Lee J. W. , McCullough R. E. , Fan John C. C. 
Published: March 2011

AbstractThe growth of high-quality single crystal GaAs on Si wafers up to six inches in diameter by organometallic chemical vapor deposition (OMCVD) is reported. These wafers have specular surfaces, excellent thickness uniformity, and are shown to have properties comparable to those of smaller diameter GaAs on Si wafers. The mechanical and electrical properties of the six inch GaAs on Si wafers are shown to be suitable for GaAs device fabrication.
Omvpe Growth and Characterization of GaAs on Si for Device Applications
Authors: Shastry S. K. , Zemon S. , Armiento C. , Stern M. B. , Levinson M. , Lehman L. , Rothman M. , Dugger D. , Hefter J. 
Published: March 2011

AbstractSignificant progress has been made in the OMVPE growth of GaAs directly on Si by the previously reported low-temperature growth technique. These films have been characterized by low-temperature PL, SIMS, TEM, and DLTS. The epitaxial layers, whose quality has been determined by PL measurements (4.2 K PL spectral width of heavy-hole exciton ≈ 3 meV), were implanted with 29Si+ for fabrication of MESFET channels. Background concentrations of ≈ 1014 cm−3 have been achieved for the first time after rapid thermal annealing without the need to use oxygen implantation or vanadium doping. SIMS measurements do not show Si pileup on the surface or much Si diffusion at the GaAs-Si interface, a significant improvement over earlier results. DLTS measurements and electrical characterization of the GaAs-Si heterojunction diode indicate the presence of only two trap levels (< 1014 cm−3 in concentration) in the GaAs ≥ 2.5 μm away from the interface.
Principles and Applications of Metalorganic Chemical Vapor Deposition for the Growth of ih-V Compounds on Si Substrates
Authors: Dupuis Russell D. 
Published: March 2011

AbstractThe use of the metalorganic chemical vapor deposition thin film materials technology in the heteroepitaxial growth of GaAs on Si substrates is of increasing interest for a wide variety of applications. This paper will describe the principles and applications of this materials technology and discuss possible future approaches to the growth of high-quality HI-V heteroepitaxial layers on Si substrates.
Growth and Characterization of Lpe GaAs on GaAs-Coated Si Prepared By Mbe
Authors: Sakai Shiro , Chang S.S. , Matyi R.J. , Shichijo H. 
Published: March 2011

AbstractGaAs has been successfully grown by LPE on partly covered (windowed) GaAs-on-Si substrates prepared by MBE. Almost dislocation-free layers were obtained in narrow stripe windows. The grown layers were characterized by photoluminescence and Hall effect measurement. The photoluminescence polarization indicated that a uniaxial tensile stress along the stripe direction is applied in the mesa stripe LPE layer while it is biaxial in the wide GaAs layer on Si. The stress relaxation in the direction perpendicular to the stripe is discussed.
Capacitance Transient Analysis of Mbe Grown Gaas on Silicon Substrates
Authors: Burns G. F. , Chong T. C. , Fonstad C. G. 
Published: March 2011

AbstractCapacitance transient spectroscopy has been applied to identify deep levels associated with heteroepitaxial GaAs grown on silicon. Results from p+n diode test structures reveal creation of the electron trap EL2 and a high density of hole states in the bandgap. This is the first reported observation of hole traps in MBE GaAs on Si. The activation behavior of the electron and hole signal peaks fits the signature of two different charge states associated with EL2, a native point defect complex seen in MOCVD, VPE, and bulk-grown GaAs, but not usually observed in MBE grown GaAs. Interstingly, the spectra seen show many similarities with earlier deep level transient spectroscopy (DLTS) observations on plastically deformed GaAs.
Resonant Photoluminescence Excitation in GaAs Grown Directly on Si
Authors: Zemon S. , Jagannath C. , Shastry S. K. , Miniscalco W. J. , Lambert G. 
Published: March 2011

AbstractWe describe new results observed during resonant excitation in the excitonic region of GaAs grown directly on Si by organometallic vapor phase epitaxy. Two resolved features were found in the light hole photoluminescence (PL) region, one identified with a free exciton process and the other with donor-related transitions. Features which track the laser excitation line were observed and identified with a process in which a donor is excited from the n=l ground state to an n=2 excited state. The PL excitation spectra associated with these features have spectral widths as narrow as 1.5 meV. PL spectral widths of ~3 meV have been attained for the heavy hole exciton band, representing the narrowest value obtained for OMVPE material and an improvement of about 30% over our best previous results.
The Stimulated Crystallization of Amorphous SiO2Films on Si Substrates Induced By Laser and Thermal Treatments
Authors: Edelman Felix 
Published: March 2011

AbstractThe transformation of amorphous to crystal (a-c) structure of Si02layers, thermally grown on both (100) and (111) Si substrates, was carried out by CO2laser, flash-lamp, and furnace heat: treatments. All the treatments resulted in S102crystallization according to two different mechanisms: normal and self-sustained growth processes. The kinetic characteristics of the S102crystallization process such as incubation time, rates of nucleation and growth, and the microstructure of the Si-Si02interface were investigated and are discussed from the point of view of growth theory. The a-c transformation in Si3N4and SixOyNzfilms on Si substrates is also discussed.
Nucleation and Growth of CrSi2 on Si(111)
Authors: Fathauer R.W. , Grunthaner P.J. , Lin T.L. , Chang K.T. , Mazur J.H. 
Published: March 2011

AbstractChromium disilicide layers have been grown on Si(111) in a commercial molecular beam epitaxy machine. Islands are found to nucleate with more than one epitaxial orientation, and three different orientations have been identified: CrSi2(0001)//Si(111) with CrSi2 [1010]//Si[110]. CrSi2(0001)//Si(111) with CrSi2[ll20]//Si[1l0], and CrSi2(1100)//Si(111) with CrSi2[000l]//Si[112]. Very thin (2 nm) layers have been studied under a variety of growth conditions to determine factors controlling the orientation of nuclei. The degree and direction of substrate misorientation, the growth technique, and the use of a CoSi2 buffer layer are all factors affecting the morphology of CrSi2 islands.
Epitaxial Gold in Au/Si Eutectic Reaction and Epitaxial Aluminum Spikes in Al-1%Si/Ti-W/Si System
Authors: Chang Peng-Heng 
Published: March 2011

AbstractEpitaxial regrowth of gold film on Si as a result of Au/Si eutectic reaction and epitaxial aluminum spikes forming at IC contacts during sintering have been investigated by transmission electron microscopy (TEM). For gold film on Si, three types of epitaxy were observed: (1) the crystal structures of the two lattices are exactly the same, (2) the two structures have the orientation relationship of Au(111)//Si(111) and Au[132]//Si[231] and (3) 20° misorientation from the relationship in (2). Two orientation relationships were observed in the case of Al spike in Si: (1) Al[011]//Si[123] and Al(200)//Si(11), (2) Al[001]//Si[112] and 2° misorientation between Al(200) and Si(111). Possible mechanisms are proposed to explained the observed epitaxial growth.
Model for Heteroepitaxy on Patterned Substrates
Authors: Kao Y. C. , Wang K. L. 
Published: March 2011

AbstractIn this work, a new model based on energy balance for heteroepitaxial growth on a patterned substrate and an additional thin buffer layer on top of it has been developed. The structure used in our model is assumed to be GeSi/buffer-Si/patterned-Si and comparisons are made with simple crystalline GeSi/Si. However, the model described here is quite general and can be adopted for any other material systems. Using this model, coupled with experimentally known material constants, the critical layer thickness (hc) of a lattice mismatched heterolayer can be determined for a patterned substrate, having a characteristic “seed pads” size (l), and a buffer layer thickness (hb). The dislocation-free condition under this case is also established.