bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the Fracture Toughness Parameters for an MDF Cement Composite
Authors: Arzamendi M. , Sierakowski R. L. , Wolfe W. E. 
Published: March 2011

ABSTRACTThe experimental results of fracture toughness testing of a Macro Defect (MDF) Free cement are presented. The material, a hydraulic cement with hydrolyzed polyvinyl polymers, behaves much like a hardened ceramic with measured maximum compressive and tensile strengths of 380 MN/m2 and 69 MN/m2 respectively. Fracture toughness tests were performed on compact tension (CT) and single edge notched beam (SENB) specimens cut from test panels which were supplied in 3mm, 5mm and 10mm thicknesses. The results were evaluated with respect to the fracture toughness parameter Kic using a modification of standard test methods as determined by observed natural behavior. The MDF material exhibited an essentially linear elastic behavior with a fracture toughness slightly higher than typical values recorded for hardened cement paste.
Production and Characterization of Fly Ash from New South Wales Coals
Authors: Roper Harold , Baweja Daksh , Kirkby Graham A. 
Published: March 2011

ABSTRACTFactors affecting fly ash characteristics are examined by consideration of the various processes and constituents involved in its production. Coal conversion, boiler-furnace operations and collection procedures are discussed. Current classification schemes applied to fly ash, in particular to those for use as a pozzolanic mineral admixture in concrete are reviewed. The variability of the material is highlighted using physical and chemical data. Shape and size characteristics of selected fly ashes from sources within New South Wales, Australia are illustrated by electron micrographs. The influence of these properties on resultant concrete properties are briefly considered. The formation of nodules of fly ash material on the surface of fabric filters is chosen to illustrate the importance of physical and chemical conditions in the collection chamber, whereas pH changes with time of the water phase in contact with selected fly ashes demonstrate the importance of chemical characteristics of the collected materials. Such chemical characteristics may influence the path of pozzolanic reactions significantly.
Iowa Affiliate Research: Rapid Diagnostic Tests for Evaluating the Air Void System of Fly Ash Concrete
Authors: Zimmerman L. , Demirel T. , Bergeson K. , Schlorholtz S. 
Published: March 2011

ABSTRACTAn on-going fly ash research program, funded by six Iowa power companies and their marketing representative has been established at Iowa State University. The broad objective of the affiliate program is to conduct basic research on Iowa fly ashes that can be directly applied to increasing their utilization in the construction industry. The first year goal is to evaluate the influence of various Iowa fly ashes on the air void system of concrete. Previous research at Iowa State University had indicated that fly ash may be influencing air void distribution in fly ash concrete, and hence durability. A variety of combinations of aggregates, fly ashes, cements and admixtures are being evaluated for compatibility in concrete. Rapid diagnostic tests are being developed, including (1) a modified Hallimond tube flotation test to evaluate physico-chemical compatibility of combinations, and (2) LeMont image analysis techniques to analyze the air void system. Procedures and preliminary results are presented and discussed.
Chemical Changes Occurring During the Early Hydration of PFA-OPC Mixtures
Authors: Luke K. , Glasser F. P. 
Published: March 2011

ABSTRACTThe course of the initial set reactions of Portland cement-PFA blends is markedly influenced by the presence of fly ash. Data are presented on the effect of two Class F PFA materials blended with cement in 30:70 ratio. Selected analyses of the aqueous phase compositions at lh to 336h are presented. During the first 6h a nearly steady state aqueous phase composition is achieved with respect to Na, K and Ca concentrations. Following a renewed burst of hydration activity, Ca decreases rapidly in the interval 6–24 h while Na and K contents rise more gradually.
Analysis of the Cementitious and Pozzolanic Properties of a Silico-Aluminous (Class F) Fly Ash
Authors: Carles-Gibergues Andre , Aitcin Pierre-Claude 
Published: March 2011

ABSTRACTA silico-aluminous (Class F) French fly ash has been studied during the last ten years. While over this period the fly ash was produced from different bituminous coals, it has demonstrated high constancy in terms of its chemical and physical composition as well as cementitious properties. The first part of this paper gives a complete physico-chemical characterization of this fly ash, including chemical composition, mineralogical composition of its crystallized fraction, chemical composition of its glass, grain-size distribution, specific surface area, and bulk density. The second part deals with physico-chemical experiments performed to determine the cementitious components of this fly ash through its dissolution in pure water and in lime water. The lime water experiment was also carried out on a washed sample containing few residual sulfates. This series of experiments demonstrates the importance of sulfates in this particular fly ash, especially during the early stages of hydration. Their action results in the formation of ettringite. The cementitious role of these sulfates has been confirmed by comparing the compressive strength of mortar cubes containing washed and nonwashed fly ash. After 7 days, mortar cubes made with this fly ash showed a slight compressive strength increase when compared to a reference mix containing the same amount of quartz. This compressive strength increase can be related to the formation of C-S-H due to the pozzolanic reaction. After 8 months, the pozzolanic reaction had consumed most of the lime generated by the hydration of C2S and C3S, so that practically no portlandite remained in the mortar.
Evaluation of Fly Ash on the Basis of Mass Equivalent, Maturity Equivalent and Permeance
Authors: Mills R. H. 
Published: March 2011

ABSTRACTCombinations of two types of commercially available Fly Ash (FA) and Portland cement (PC) were tested for compressive strength and permeance to gas flow. The cementitious components were combined in the concrete mixture in proportions PC/FA = 100/0, 75/25, 60/40 and 45/55 for a range of water/cement ratio, and equal workability. Strength and maturity efficiency factors were satisfactory for 75/25 and 60/40 blends. Gas tightness was improved at all levels of Fly Ash substitution.
Engineering and Microstructural Studies of Western-Canadian Fly Ash Bricks
Authors: Day Robert L. , Joshi Ramesh C. , Slota Rudolf J. , Langan Brian W. 
Published: March 2011

ABSTRACTAn experimental programme was undertaken to determine whether Canadian fly ash, and in particular Western-Canadian fly ash, can be used to replace clay as the main ingredient in brick-masonry units.These preliminary examinations show that Western-Canadian fly ash as the solid material, combined with an adequate binder, can be used to produce a superior ceramic material. Strengths are very much higher than that revuired for load-bearing masonry elements, densities are approximately 800 kg/m3 less than a normal clay brick and the material is durable to freezing and thawing. X-ray analysis and scanning electron microscopy clearly show chemical and physical changes which occur to the material due to firing. These chemical changes appear to be closely related to the subsequent strength which is developed.Bricks manufactured from Alberta fly ash appear to be a viable alternative to standard clay brick. A substantially stronger and more economical brick may be possible; fly-ash bricks can be manufactured with lower firing temperatures of shorter duration. This, in itself, could lead to the realization of significant energy savings. Also, if large quantities of fly ash can be used in the brick industry, then significant gains will be made toward the elimination of this waste product from the environment and conservation of natural resources.
Mineralogy of Fixed-Bed Gasification Ash Derived from North Dakota Lignite
Authors: Stevenson Robert J. , McCarthy Gregory J. 
Published: March 2011

ABSTRACTThe mineralogy of nine ash samples derived from North Dakota lignite and gasified in three different fixed-bed producers was determined by x-ray diffraction (XRD) and scanning electron microscopy (SEM). The gasifiers had maximum temperatures in the 1100–1250°C range, but included several differences in ash residence time, oxidizing gas and pressure, and ash handling conditions. The lignite gasified came from the same geologic formation, but the mines were separated by 20 km. Despite these differences, all of the ash specimens had the same basic mineralogy: glass at the 15–30 wt.% level; a crystalline phase assemblage of ortho- and pyro-silicates (merwinite, dicalcium silicate (C2S), C2S-like phases, and melilite), network aluminosilicates (nepheline, carnegieite, and a sodalite-structure phase), oxides (ferrite spinel, hematite, and periclase), and calcite along with residual lignite minerals (quartz and felspar). SEM morphologies and XRD comparisons of the amounts of crystalline phases in size fractions both indicated that some of the phases (particularly merwinite and carnegieite) crystallized during cooling of portions of the ash that had melted during gasification.
Speciation in Size and Density Fractionated Fly Ash
Authors: Hemmings Raymond T. , Berry Edwin E. 
Published: March 2011

ABSTRACTMorphological, chemical and mineralogical speciation of fly ash from a power plant burning sub-bituminous coal has been investigated by examination of size and density fractions. It was found that whereas, fractionation by size revealed little information as to speciation among particle types, separation of the ash into six density fractions showed major differences in properties associated with true particle density. In particular it was found that at least two types of glass co-exist in the ash: “Glass I” – a predominantly silico-aluminous glass associated with particles of low density (cenospheres); “Glass II” – a calcium alumino-silicate glass associated with high-density particles. These glasses were found to differ greatly in composition and to be characterized by shifts in the position of the 2-theta of the XRD-halo. In addition, it was shown that cryptocrystalline mullite is associated only with the low-density particles. It is proposed that particles comprising low-density fractions can be considered as glassceramics with low degrees of crystallization. Particles of high-density are better described as the products of internal lime-sinter reactions.
GaAs MESFET's on Silicon Substrates for Digital IC Applications
Authors: Shichijo Hisashi , Lee Jhang Woo 
Published: March 2011

ABSTRACTThe characteristics of GaAs MESFETs in GaAs-on-Si have been studied in detail for digital IC applications. The device structure utilizes GaAs and AlGaAs undoped buffer layers grown on a 3 degrees off (100) silicon substrate by MBE. The threshold voltage of the MESFET is adjusted by recessing the gate.The maximum observed transconductance of 135 mS/mm is comparable to what is expected from the bulk GaAs device with the same parameters. The device also shows good pinch-off characteristics. Both enhancement and depletion mode MESFETs have been fabricated.
Tunneling Spectroscopy of Single-Crystal CoSi2 and NiSi2 Epilayers on n-type Si
Authors: Hauenstein R. J. , Schowalter L. J. , Hunt B. D. , Marsh O. J. , McGill T. C. 
Published: March 2011

ABSTRACTElectron tunneling spectroscopy experiments have been performed on single-crystal epitaxial silicide films grown on (111)-oriented (off 4 °) Si:As. 250 Å-thick films of CoSi2, and type-A and -B NiSi2 on degenerate substrates (Nd = 2 × 1019 cm−3) have been studied. All spectra show forward bias peaks at energies corresponding to k-conserving bulk Si phonons while in reverse bias only the Si TA phonon is observed for NiSi2 /Si structures. Plots of dV/dI vs. V for CoSi2 /Si structures yield maxima at a forward bias of 39meV, indicating an enhancement in n-type dopant concentration within ˜ 100 Å or more of the silicide-silicon interface.
Properties and Applications of Molecular Beam Epitaxial Silicides
Authors: Wang K. L. , Kao Y. C. 
Published: March 2011

ABSTRACTTransition metal silicides are now being used as essential and integral elements of microelectronics technology. Epitaxial growth and deposition provide additional flexibility for many device and circuit applications.In this paper, various epitaxial growth techniques, namely solid phase epitaxy and molecular beam epitaxy are reviewed. The resulting morphology, crystallinity, and Schottky barrier heights as well as deep-level defects are contrasted. The parallel and perpendicular strains as a function of film thickness is reported.Application of the epitaxial silicide in improving conventional integrated circuits as well as in fabricating new devices are discussed.
Growth of Group IV-IV Heterostructures: Initial Stages of Interface Formation
Authors: Gossmann H.-J. , Feldman L. C. 
Published: March 2011

ABSTRACTThe two major issues in the growth of a heterostructure are (1) the degree of perfection of the overlayer and (2) the sharpness of the interface. The initial stages of interface formation play a crucial role in this respect. Relevant questions are addressed under atomically clean conditions in the Si/Ge Si/Si and Ge/Sn systems, using ion scattering surface analysis, low energy electron diffraction and Auger electron spectroscopy. Of particular interest with respect to (1) is the general role of reconstruction in epitaxial growth: A necessary condition for perfect growth is the reordering of the substrate surface reconstruction. We show that the deposition temperature necessary to achieve this reordering depends strongly on the topography of the substrate reconstruction. For example, Ge deposition at room-temperature reorders the Si(100)2×1 reconstruction but not the Si(111)7×7, implying different epitaxial temperatures for these two substrates. To illustrate (2) we discuss the complex growth and anomalous diffusion found in the Ge/Sn system. Below a certain critical coverage Θc (1.15·1015 cm−2) no indiffusion of the Sn overlayer takes place, even at 700 K, although above Θc severe indiffusion does occur at this temperature. This result is discussed in terms of theories of surface segregation.
GaAs/Ge Crystal Growth on Si and SiO2/Si Substrates
Authors: Ohmachi Yoshiro , Shinoda Yukinobu , Oku Satoshi 
Published: March 2011

ABSTRACTAn approach to the composite layer growth of GaAs/Ge on Si(100) and insulator–coated Si(100) has been investigated. To overcome a problem of antiphase disorder of GaAs occurring along with epitaxial growth on Ge, thermal etching on Ge surfaces in hydrogen was introduced just prior to the growth. Antiphase–domain–free GaAs grown on a Ge(100) wafer exhibited mirror surfaces, photoluminescence characteristics comparable to those of homoepitaxial layers, and low etch–pit densities. The autodoping of Ge into GaAs induced a highly doped interfacial layer several thousand angstroms thick. The present study also involves heteroepitaxial growth of Ge on Si by vacuum deposition and Ge crystal growth on insulating layers over Si by LESS method.
Material Characterization of Epitaxial GaAs and Ge Films on (100) Si Substrates
Authors: Awal M. Abdul , Lee El Hang , Koos G. L. , Chan E. Y. , Celler G. K. , Sheng T. T. 
Published: March 2011

ABSTRACTWe report some results on the chemical, structural and electrical characterization of Ge and GaAs films, grown on Si (100) substrates by electron-beam evaporation and MOCVD, respectively. Good quality Ge films have been obtained at 700°C substrate temperature at a growth rate of 5 nm/sec in 5 × 10−7 torr. Similarly, good GaAs films were obtained at 650°C and at 0.3 nm/sec. RBS data for GaAs films (1.1 μm) show Xmin approaching 3.5%, and Ge films (1.5 μm) around 3.6%. Photoluminescence of the same films show peaks around 852 nm with FWHM of 14 meV. Cross-sectional TEM and etching show a near-exponential decrease in defect density away from the Ge/Si interface. Detailed characterization results of the S-R, I-V, C-V, and X-ray studies are also described.
Kinetics of Rapid Thermal Oxidation of Silicon
Authors: Lassig Stephan E. , Debolske Thomas J. , Crowley John L. 
Published: March 2011

ABSTRACTThis paper presents kinetic data for the rapid thermal oxidation (RTO) of <100 silicon using a wall stabilized low pressure arc lamp as the heating source. The data shows a single activation energy of 1.31 eV over the temperature range of 900°C to 1200°C and times of 60 seconds to 240 seconds. Comparisons are made with published kinetic data of RTO using tungsten-halogen lamp source [1] and with furnace oxidation kinetics for short times (<240 sec.) [2]. “Wet” oxidation results using O2:H2 as the oxidizing ambient reveal a lower activation energy and preexponential coefficient than the dry oxidation. Also presented are results using an experimental set-up which exhibits ultraviolet enhanced oxidation.
Rapid Thermal Processing of Gate Dielectric Films and their Characterization
Authors: Flowers D. L. , Nulman J. , Krusius J. P. 
Published: March 2011

ABSTRACTRapid thermal processing has been used to grow high quality, low defect density, low mobile charge, dielectric films of oxide and nitrided oxide. Suitable annealing can lower the fixed charge and interfacial trap density present in these filmsto acceptably low levels. Both RTA and RTN were shown to improve the dielectric properties of the grown oxides. These filmsshould be strong candidates for use in high density, shallow junction, integrated circuits where a minimal time/temperature constraint is imposed on further processing after diffusion.
Oxidation of Silicon and Nitridaticn of SiO2 by Rapid Thermal Processes
Authors: Chan Tung N. , Caratini Y. , Buevoz J.L. 
Published: March 2011

ABSTRACTThin gate oxides of 30 to 150 Å have been grown in a rapid thermal annealing machine. Experiments were performed in the temperature range of 1000 to 1250°C for an oxidation time of 5 to 60 s. The fairly extensive kinetics data show that linear growth occurs with an activation energy Ea of 1.4 eV for the 5-60 s period. The oxide homogeneity was evaluated and gave a value of 1.9 A for a mean oxide thickness of 102 A. The electrical characteristics of Al-gate capacitors were assessed by C-V and I-V measurements. Rapid thermal nitridation of a 96 A SiO2 has been performed at a temperature of 1150°C for a nitridaticn time up to 150 s. An average breakdown field of 14.6 MV/cm has been obtained for MIS capacitors. High resolution TEM show a good interface SioXNY-Si.
Rapid Thermal Processing for Self-Aligned Silicide Technology
Authors: Ku Y. H. , Lee S. K. , Louis E. , Shih D. K. , Kwong D. L. 
Published: March 2011

ABSTRACTA self-aligned titanium silicide process which combines the use of ion-beam mixing and rapid thermal processing (RTP) has been developed for CMOS VLSI applications. Shallow silicided junctions are formed by implanting dopants into silicide layers previously formed by ion-beam mixing with Si ions and low temperature annealing, and the subsequent drive-in of the implanted ions into the Si substrate during high temperature RTP. In addition, the formation of TiN on TiSi2 is achieved simultaneously during this process as a diffusion barrier for Al metallization. Short-channel MOS transistors with SALICIDE structure have been successfully fabricated and tested. Results of the impurity diffusion in silicide layer, the impurity segregation at both silicide/Si and oxide/silicide interfaces, contact stabilit of Al/TiN/TiSi2 structure, and device characteristics will be reported. Issues related to this process and its application to submicron device fabrication are discussed and foreseeable problem areas identified.
Low Temperature Rapid Thermal Formation of Tin Barrier Layers
Authors: Barney Cohen Barney Cohen , Jaim Nulman Jaim Nulman 
Published: March 2011

ABSTRACTTiN and TiN/TiSi2 films, formed by reacting titanium sputtered onto source-drain and field areas, may be used as local interconnects, low resistance plated junctions, and diffusion barriers. This paper discusses the application of RTP to the low temperature reaction of titanium on silicon and oxide substrates. By adjusting temperature and ambient the nitridation and silicidation reactions may be controlled to provide the desired TiN-TiSix thickness ratio. The advantages of ammonia ambient are discussed.
Characterization of Process Uniformity and Control of Titanium Silicide Formed by Rapid Thermal Processing (RTP)
Authors: David Hodul David Hodul , Sandeep Mehta Sandeep Mehta 
Published: March 2011

ABSTRACTSputtered titanium films with thicknesses in the range of 300 to 1200Å were processed in a commercial rapid annealing system to form TiSi2 films. The films were first reacted at low temperatures (500-700°C), etched in ammonia/peroxide solution, and then reacted at 850-900°C to simulate a typical self-alignedsilicide (salicide) process. A method to correctfor dynamic temperature nonuniformities and the resulting etch nonuniformities will be discussed. Sheet resistance maps of the resulting films will be presented. In addition, film properties were measured as a function of annealing ambient in particular, the effects of oxygen contamination were studied.
Properties Of High Dose Low Temperature Rapid Thermally Annealed Gallium Implanted Silicon
Authors: Lee Y.H. , Harrison H.B. , Pogany A.P. , Olson G.L. 
Published: March 2011

ABSTRACTHigh doses: 1, 3 and 6×1015/cm2 of Ga71+ ions were implanted into <100> silicon at 100keV and annealed in the temperature regime of 550-675° C for seconds to tens of seconds. Two different annealing rigs were used; however the physical and electrical results obtained from each provided remarkably similar results.We have observed a regrowth rate/dose dependency through both our physical and electrical measurements that provide surprisingly good correlation. We also note that for the highest dose complete solid phase epitaxial regrowth is inhibited, and for temperatures as low as 640°C and times as short as 9sec. onset of movement of the gallium toward the surface is observed. We also show that extremely high free carrier concentrations of gallium can be obtained under the correct anneal conditions.
Raman Scattering from Rapid Thermally Annealed Tungsten Silicide
Authors: Samhita Dasgupta Samhita Dasgupta , Kumar Sandeep , Jackson Howard E. , Boyd Joseph T. 
Published: March 2011

ABSTRACTRaman Scattering as a technique for studying the formation of tungsten silicide is presented. The tungsten silicide films were formed by rapid thermally annealing tungsten films that were sputter deposited on silicon substrates. The Raman scattering data is correlated with data from resistivity measurements, Auger and Rutherford Backscattering measurements, and scanning electron microscopy.
Slip Free Rapid Thermal Processing
Authors: Blake Julian , Gelpey Jeffrey C. , Moquin John F. , Schlueter James , Capodilupo Ron 
Published: March 2011

ABSTRACTSlip is a primary concern in Rapid Thermal Processing (RTP). Diagnostics for slip are compared, including: visual inspection, differential interference contrast microscopy (Nomarski), X-ray topography, decorative etching and optical surface scanning. Data from each technique are presented. RTP control parameters (temperature uniformity, heat up and cool down rates, edge cooling) and substrate parameters (wafer size, oxygen content, edge damage) which may have an effect on slip are discussed. Typical results for implant annealing sequences on a water-wall DC arc lamp RTP system are presented and used to suggest techniques for process optimization.