bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fly Ash As A Binder in Aggregate Base Courses
Authors: Zenieris Petros , Laguros Joakim G. 
Published: March 2011

ABSTRACTThe benefit of adding up to 35 wt% Class C high calcium fly ash to various types of fine and coarse aggregate pavement mixes is described and quantified. The mixes, which were compacted to maximum dry density at optimum moisture content, had variable compressive strengths during the first 28 days of curing; after that they assumed a relatively uniform pattern of strength gain reaching values as high as 11 MPa (1600 psi). Mixes containing 15% fly ash gave unacceptably low strengths. XRD measurements indicated massive formation of ettringite, transforming to monosulfoaluminate and the poorly crystallized hydrated phases of C-A-H, C-A-S-H and C-S-H. This transformation helps explain the gain in strength of the mixes with extended curing. SEM observations depicted progressive packing and densification of the skeletal matrix as the hexagonal phases and C-S-H gained higher crystallinity and formed aggregated masses. Furthermore, these observations suggest that fly ash acts predominantly as a chemical binder and partly as a filler in the aggregate mixes tested.
The Effect of Fly Ash on the Hydration of Cements At Low Temperature Mixed and Cured in Sea-Water
Authors: Jensen H.-U. , Pratt P. L. 
Published: March 2011

ABSTRACTThe use of fly ash as a partial replacement in cements is widespread because of reduced costs and the reported improvement in performance. Fly ash/cement blends have been used offshore for underbase grouting of gravity platforms, although the cold marine exposure may slow the pozzolanic reaction which is very sensitive to temperature. Sea-water could be used as mixing water under these conditions. This paper looks at how curing at 8°C, the use of sea-water as mixing water, and direct exposure to sea-water, influence the hydration, strength and microstructural development of an OPC and an SRPC with 30% fly ash replacement. The early heat evolution was measured with a conduction calorimeter, while the presence and development of hydration products were identified by DTA, TG and x-ray analysis. Scanning electron microscopy was used in two modes; secondary electron images of fracture surfaces were examined, and a quantitative description of microstructure was made possible by analysis of backscattered electron images of polished sections. The morphology and distribution of hydration products in the wet state was studied using an environmental cell in a high voltage electron microscope.
Evaluation of Leachate Generation at the Montour, Pennsylvania, Fly Ash Test Cell
Authors: Villaume J. F. , Bell J. W. , Labuz L. L. 
Published: March 2011

ABSTRACTThe Pennsylvania Power & Light Company, in cooperation with the Electric Power Research Institute, is studying leachate generation at a large outdoor test cell of compacted coal combustion fly ash constructed at the Montour Steam Electric Station in north-central Pennsylvania. The test cell design is identical to that of the plant's active dry fly ash disposal facility. Leachate initially generated at the test cell contained concentrations of chromium and selenium approximately ten times above EPA's assigned Maximum Contaminant Levels (MCL's) for drinking water. Concentrations of these two parameters have since decreased approximately five-fold. Similar reductions have occurred in the concentrations of several of the other trace metals measured in the leachate. The dominant reaction mechanisms controlling leachate composition were examined in an attempt to explain these and other observations. Deterministic chemical modeling was performed to aid in the interpretation of the data. The dynamics of leachate generation were also examined through an evaluation of the infiltration and redistribution of moisture.
X-Ray Powder Diffraction For Studying the Mineralogy of fly ash
Authors: McCarthy Gregory I. 
Published: March 2011

ABSTRACTA brief summary of the use of x-ray powder diffraction for studying the mineralogy of fly ash is presented. Mineralogies of low-, intermediate- and high-calcium fly ashes are discussed and illustrated by results from XRD characterization of U.S. National Bureau of Standards fly ash Standard Reference Materials.
Single Crystal Silicon Membranes
Authors: Fernandez Andres , Hren P. , Lee K. C. , Silcox J. 
Published: March 2011

ABSTRACTSelf-supporting, thin single crystal membranes can be fabricated from silicon wafers using ion implantation, anodic etching and subsequent annealing. Typically, membranes approximately 1200Å thick and about 250μm in diameter are formed in wafers 4 mil thick. Discs surrounding the membranes can be cut out to provide suitable TEM samples. In this paper, the steps for preparing such samples are presented with as much attention paid to experimental details as possible.
The Preparation of Mechanically Alloyed Powders for TEM Examination
Authors: Kamenetzky E. A. , Wall M. , Castro R , Tanner L. E. 
Published: March 2011

ABSTRACTTEM specimens of mechanically alloyed elemental Ni and Nb powders are prepared by a new procedure. The alloyed powders are mixed with smaller Al powders and fill an aluminum ring (3mm outer diameter). This composite is cold pressed together with the Al powders taking most of the deformation. The compacted specimen can be mechanically thinned. Electropolishing and ion milling can then proceed by standard methods with special precautions to minimize differential polishing or milling rates.The microstructural aspects of the formation of an amorphous phase by high-energy ball milling these powders have been studied. After 6 h each particle transforms to a heterogeneous layered composite of particles of one element in the matrix of the other. Particle size ranges from 15 nm to 90 nm. Mechanical alloying for 36 h results in the formation of an apparently uniform phase interspersed with a few small (4 nm to 30 nm) elemental crystalline particles. The uniformity of composition and the presence of C, O, and Fe were studied by EDX and EELS.
Tem Specimen Preparation by Mechanical Microthinning
Authors: Plummer H. K. , Shinozaki S. 
Published: March 2011

ABSTRACTMechanical abrasion has been used by the authors to prepare a variety of materials, mainly ceramics, which have been thinned to electron transparency. The basic premise of this technique is the rotation of a spherically shaped wood tool at right angles to a rotating 3mm specimen disk (∼100 μm thick). A slurry of 1/2 μm diamond powder in a glycerin vehicle thins the specimen and carries away the abraded matter. In addition to the wood tool other materials such as brass, teflon and polyethylene have been tried without success. Abrasion “marks” left on the thin specimen surface can be ignored in some situations or removed by a touch up ion milling at 3 keV for ∼1/2 hr. Recently, attempts to thin N+ implanted Al from the un-implanted side using a wood tool were found to be extremely time consuming, i.e. 60 hr or more. It was found that a spherical stainless steel tool produced a suitably thin transmission electron microscopy (TEM) specimen using glycerin as the vehicle and no diamond powder. Depending upon the pressure applied to the tool these specimens could be thinned in as little as 3 hr. The turning marks left by the lathe tool proved to be sufficient to thin the soft aluminum. From this result It appears that soft tools will thin hard materials and hard tools can be used to thin soft materials efficiently. A number of other specimens recently prepared using mechanical microthinning will also be presented.
Preparation of Electropolished Transverse Sections of Thin Aluminum Sheet for Transmission Electron Microscopy
Authors: Smith Steve 
Published: March 2011

ABSTRACTThe preparation of transverse section TEM foils from thin (0.2 mm to 1.5 mm) aluminum sheet would usually be accomplished by a combination of dimpling and ion milling. Both of these techniques are time consuming. A technique has been developed which allows these transverse section foils to be prepared by electropolishing, which greatly reduces the time required for specimen preparation. This technique also produces far more thin area for examination than a comparable foil which has been dimpled and ion milled, and eliminates artifacts produced by ion milling.
Simple Plan View Specimen Preparation Technique For Tem Investigation Of Semiconductors and Metals
Authors: Veirman A. De , Eysermans J. , Bender H. , Vanhellemont J. , Landuyt J. Van 
Published: March 2011

ABSTRACTThis paper discusses a rapid and simple specimen preparation technique which was originally developed for plan view TEM investigation of processed silicon, but which afterwards was modified for the study of GaAs, Al/Al2O3 and Silicon-On-Insulator (SOI) structures. The major advantage of this poor man's method is that no specialised nor expensive equipment is needed.A second technique is also described which is used in the case of unseeded SOI structures where the analysis of the top silicon layer is important.
A Controlled Method Of Preparing Plan-View Silicon Samples For Transmission Electron Microscopy Studies
Authors: Ellington Myrtle B. 
Published: March 2011

ABSTRACTTransmission electron microscopy (TEM) is an important technique for studies of extended defects and other microstructural features in semiconductor materials. An efficient, plan-view thinning technique is always desirable for these TEM studies. The problems associated with wet chemical thinning of silicon are often surface residues, pitting and rapid breakthrough. A controlled method for obtaining thin, plan-view TEM silicon samples by chemical thinning was developed and the method is described in this paper. Results indicate that the method minimizes the above cited problems and has several other advantages over previously reported thinning methods.
Techniques of Insulator/Semiconductor Heterostructure Specimen Preparation
Authors: Bahnck D. , Batstone J. L. , Phillips Julia M. 
Published: March 2011

ABSTRACTTechniques for the preparation of specimens for Transmission Electron Microscopy analysis are described. Cross-sectional specimens of insulator/semiconductor heterostructures have been successfully prepared. The problem of differential thinning rates and interface amorphization during argon ion-milling have been overcome using low argon ion accelerating voltages and shallow angles of incidence. Techniques for preparation of plan view specimens include the preparation of silicon substrates for in-situ crystal growth in an ultrahigh vacuum Transmission Electron Microscope.
Preparation of Vitrified TEM Samples for the Direct Observation of Sol and Gel Structures
Authors: Bailey Joseph K. , Bellare Jayesh R. , Mecartney Martha L. 
Published: March 2011

ABSTRACTDirect observation of structure in liquid phase materials is made possible by a cryo-vitrification technique in which a thin liquid sample is frozen at a high cooling rate to prevent crystallization. We have applied this technique to observe the evolution of structure in ceramic sols and gels using TEM. The sample preparation technique is described in detail and results obtained from colloidal and polymeric sols and gels are presented to show the usefulness of the technique. Artifacts arising from radiation damage and beam heating are also discussed.
GaAs/Si Nucleation and Buffer Layer Growth
Authors: Koch Stephanie M. , Hull Robert , Rosner S. Jeffrey , Harris James S. 
Published: March 2011

AbstractWe investigate two aspects of the initial stages of GaAs/Si growth: the effects of Si misorientation on GaAs island nucleation, and the structural changes occurring upon heating the buffer layer to the final deposition temperature. We observe that the GaAs islands tend to nucleate at Si surface steps and grow along them. The shape of the islands depends on the degree and direction of the Si misorientation from (100). Island coalescence occurs as the film grows, such that a 500Å film is almost completely continuous. In situ heating of a 30A film to 5750C for 15 minutes causes the islands to agglomerate, while similar treatment of the 500A film does not appear to expose more of the underlying substrate and in fact improves the film crystallinity.
The Role of thin Low Temperature Deposited GaAs Films on the two Step Growth of GaAs on Si By Mocvd
Authors: Inuzuka Hajine , Suzuki Yasutoshi , Awano Naomi , Hara Kunihiko 
Published: March 2011

AbstractThe structural change of the thin low temperature (~450°C) deposited GaAs films and the role for conventional temperature growth were studied by RHEED and cross-sectional TEN observation. The formation of the threedimensional high quality single crystalline islands from continuous twin GaAs layer deposited at low temperature (~450°C) was clarified. These three-dimensional islands act as the seeds for conventional temperature growth.
Photoluminescence Studies of Annealed GaAs Films Grown on Si Substrates
Authors: Bugajski M. , Nauka K. , Rosner S.J. , Mars D. 
Published: March 2011

AbstractLow temperature (T - 5K) photoluminescence (PL) has been measured on a variety of as-grown and annealed GaAs films grown on Si substrates by the MBE technique. The PL spectra of the annealed GaAs layers showed an apparent difference between the nomigally undoped samples with free carrier concentrations below 1015 cm−3 and the layers with dopant concentrations exceeding 1017 atoms cm−3 . The annealing caused an increase of both excitonic and defect related PL intensities in low doped samples. In heavily doped layers the annealing suppressed excitonic emission and strongly enhanced defect related luminescence bands. Observed post annealed infrared shifts of the PL peaks in the excitonic region are explained assuming a tetragonally distorted GaAs lattice under tensile stress, and an increase in stress after high temperature annealing.
Heterostructures of GaAs and AlAs on Silicon: X-Ray Analysis and Excimer Laser Annealing
Authors: Georgakilas A. , Fatemi M. , Fotiadis L. , Christou A. 
Published: March 2011

AbstractOne micron thick AlAs/GaAs structures have been deposited by molecular beam epitaxy onto high resistivity silicon substrates. Subsequent to deposition, it is shown that Excimer laser annealing up to 120mJ/cm2 at 248nm improves the GaAs mobility to approximately 2000cm2 /v-s. Dislocation density, however, did not decrease up to 180mJ/cm2 showing that improvement in transport properties may not be accompanied by an associated decrease in dislocation density at the GaAs/Si interface.
High Quality GaP Growth on Si Substrates By Mocvd
Authors: Uchida K. , Kohama Y. , Tajima M. , Soga T. , Jimbo T. , Umeno M. 
Published: March 2011

AbstractGaP crystals are grown on Si substrates by MOCVD. Double crystal X-ray diffraction indicates that the crystal quality of GaP layers greatly improves when AsH3 is supplied before growth. The FWHM of (400) diffraction peak of the GaP layer decreases as the thickness increases and the best FWHM of 112.5 arcs is obtained at a thickness of 5 μm. The GaP/Si interface is characterized using secondary ion mass spectroscopy (SIMS) to demonstrate the effect of AsH3.
Oriented Growth of SrTiO3 Films on Si(100) Substrates Using In—situ Cleaning By Excited Hydrogen
Authors: Ishiwara Hiroshi , Azuma Kazumutsu 
Published: March 2011

AbstractIn—situ cleaning of Si surfaces in vacuum was successfully performed using excited hydrogen and it was applied to epitaxial growth of SrTiO3 films on Si(100) substrates. Epitaxial growth of SrTiO3 films was observed under optimum cleaning conditions, however, the epitaxial nature was found to be destroyed for films thicker than 50 nm, which is probably due to the non—stoichiometry of the films. The electrical properties of the initially epitaxial SrTiO3 films grown on the cleaned Si substrates were better than those of polycrystalline ones.
Heteroepitaxial Growth of A1203 Thin Films on Si By Lpcvd
Authors: Ishida M. , Katakabe I. , Ohtake N. , Nakamura T. 
Published: March 2011

AbstractHeteroepitaxial A1203 thin films were grown successfully on Si(lO0) substrates by low—pressure chemical vapor deposition (LP—CVD). The growth was performed at a pressure of 30 Torr by pyrolysis of N2 bubbled AI(CH3)3 and N20 at substrate temperatures above 1000ºC.RHEED patterns indicated that the grown films were ɤ—Al203 single crystals with an orientation relationship of ɤ—Al203(l00)//Si(l00). The ɤ—A1203 films were stable and did not show phase transition after a 1140ºC heat—treatment for 2hr. MOS capacitors with 500—Å—thick A1203 films as a gate insulator showed highfrequency capacitance—voltage (C—V) curves without hysteresis. The A1203 interface state density determined from quasi—static C—V measurements was 1.7 X 1011cm-2eV-1. It can be seen that ɤ—Al203 film is a promising new insulator for Si on Insulator (SOI) structures.
New Directions in the Growth of Epitaxial Insulators and Metals on Silicon
Authors: Phillips Julia M. , Batstone J. L. , Hensel J. C. 
Published: March 2011

AbstractBy nature of their high degree of crystalline perfection, epitaxial insulators and metals on semiconductors are structurally characterizable to a considerably greater extent than are polycrystalline or amorphous materials. This offers the possibility of correlating the detailed structure of these thin epitaxial films and their interfaces with their electrical properties. We have recently found evidence for the influence of the atomic structure of the CaF2/Si(ll1) interface on its electrical properties. Wehave also studied the structural and electrical properties of ultrathin epitaxial cobaltsilicide layers on Si(111).
Growth of Thin Epitaxial CoSi2 Layers on Si(100)
Authors: Yalisove S. M. , Tung R. T. , Batstone J. L. 
Published: March 2011

AbstractThe growth of high quality, thin (14-70 Å) epitaxial CoSi2 layers on Si(100) substrates have been observed. Three types of films have been grown on the Si(100) substrate; pure CoSi2(100), pure CoSi2(110), and mixed CoSi2(100)+CoSi2(110). The CoSi2(110) can exist in two 90º rotated variants on the Si(100) surface and these are observed. Methods to isolate the epitaxial orientations are described. Results from in-situ LEED and AES as well as ex-situ RBS and plan view TEM are presented.
Electrical & Structural Properties of TiSi2 Films
Authors: Ravindra N.M. , Fink T. , Moerkirk R.P. , Fathy D. 
Published: March 2011

AbstractStudies of the electrical and structural properties of TiSi2 films formed during the fabrication of shallow junctions by ion implanting As+ into p–Si through Ti films are reported here. Electrical measurements of the temperature dependent specific contact resistance and structural measurements such as transmission electron microscopy have been performed on these device structures. The specific contact resistance is seen to decrease with increasing measurement temperature. These studies have been carried out on furnace and rapid thermally annealed films.
Propagation of Dislocations Through GeSi/Si Strained Layers and Superlattices
Authors: Hull R. , Bean J.C. , Leibenguth R.E. 
Published: March 2011

AbstractWe describe in-situ transmission electron microscope observations of the relaxation of strained layer GeSi/Si epitaxy. Dynamic observations of misfit dislocations in these structures reveal that dislocation nucleation and growth activation barriers, as well as interactions, limit the rate at which strain is relieved. The equivalence of threading and misfit dislocations in this system is demonstrated. Extension of the principles learnt from these single layer experiments to threading dislocation propagation through multilayer structures, enables us to understand the relative inefficiency of GeSi/Si strained layer superlattices in blocking threading dislocations.
The Influence of Substrate Surface Chemistry on GaAs - on - Si Growth
Authors: Bringans R. D. , Olmstead M. A. , Ponce F. A. , Biegelsen D. K. , Krusor B. S. , Yingling R. D. 
Published: March 2011

AbstractSeveral surface treatment techniques have been used to study the effect of the Si surface on subsequent GaAs-on-Si epitaxy. In particular, the effect on the degree of island formation is addressed. Experiments have been carried out with GaAs film thicknesses in the range from one monolayer to around 50nm. Core level spectroscopy results for the monolayer films give information about the bonding character at the interface and suggest methods of improving the degree of two-dimensional growth. A particular Ga-prelayer technique is examined with high resolution TEM and found to give significantly different results than the standard MBE growth technique.
Electronic Properties of Si - Ge Micro Nipi Structures
Authors: Yang L. H. , Fong C. Y. , Nelson J. S. 
Published: March 2011

AbstractElectronic properties of the n-doping--insulator--p-doping--insulator structures in ultra thin strained [001] Si - Ge superlattice have been studied theoretically. The Ge - layer is used as one of the insulating region. The Al and As atoms are treated as impurities. The superlattice ((Si)10 -(Ge)2) exhibits an indirect gap in reciprocal space and the staggered band alignment in real space. With doping, the samples show a direct band gap and staggered band alignment. The acceptor state is associated with the Al-Si bonding state, while the donor state is derived from the As s-like state. The separation of the charge carriers in the real space can be obtained.
New Approach to Growth of High-Quality GaAs Layers on Si Substrates
Authors: Varrio Jukka , Salokatve Arto , Asonen Harry , Hovinen Minna , Pessa Markus , Ishida Koichi , Kitajima Hiroshi 
Published: March 2011

AbstractGaAs layers were grown on Si (001) substrates by molecular beam epitaxy (MBE) and migration enhanced epitaxy (MEE). They were examined by transmission electron microscopy, doublecrystal X-ray diffraction and Rutherford backscattering/channeling technique. Initial layer growth in both MEE and MBE was governed by three-dimensional nucleation but a stronger tendency for GaAs islands to align along the surface steps of Si was observed in the case of MEE. There was no measurable tilt between the (001) planes of GaAs and Si if growth was initiated by MEE at low temperature, prior to further growth by MBE at higher temperatures. On the contrary, the tilt angle was 0.34• when the entire structure was prepared by conventional two-step MBE. Rutherford backscattering measurements indicated a significant reduction in the density of defects throughout MEE/MBE GaAs in comparison with MBE GaAs.
Advanced Sensing of Materials Processing
Authors: Wadley Haydn N. G. , Kahn Arnold H. , Johnson Ward 
Published: March 2011

AbstractTo implement new process control strategies including Intelligent Processing of Materials, advanced sensors are required to nonintrusively evaluate process and microstructure variables. Researchers increasingly are looking to innovative extensions of traditional nondestructive evaluation technologies, such as ultrasonics, acoustic emission, and eddy current methodologies for this. Here, the nature and characteristics of emerging sensors based upon these new measurement methods are described and examples of their application discussed.
Optical Diagnostics for a High.Power, RF-Inductively Coupled Plasma
Authors: Nogar N. S. , Keaton G. L. , Anderson J. E. , Trkula M. 
Published: March 2011

AbstractEmission spectroscopy and laser-induced fluorescence have been used to monitor the field and tail-flame regions of a Hull-design1inductively coupled plasma. This plasma is used for a variety of syntheses2,3including SiC, TiC, BN, AlN and diamond. Temporallyand spatially-resolved spectra of both pure Ar and Ar/gas mixtures have been studied as a function of RF power, pressure and flow rate. Preliminary data suggest that the system is far from local thermodynamic equilibrium.