bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sodium Sulfur Battery Accomplishments and Remaining Problems
Authors: Fischer Wilfried 
Published: March 2011

AbstractNaS batteries are at a state of development at which the principal problems are resolved and prototype batteries have been tested for major applications such as electric vehicle propulsion and off-peak electric energy storage in electric networks. An overview will be presented on the state of development and on application tests performed so far.Nevertheless, cell and battery ccmponents need to be further optimized. Major areas for potential improvements are the beta alumina solid electrolyte with regard to conductivity, mechanical strength and life, the metal ceramic joint, the cell casing with regard to corrosion resistance, and the vacuum thermal enclosure with regard to a lower thermal conductivity. Possible solutions will be discussed.
A Gamma-Ray Spectrometer For Measurement Of The Water Diffusivity Of Cementitious Materials
Authors: Quenard D. , Sallee H. 
Published: March 2011

AbstractA gamma ray spectrometer using an Americium source has been built. The source and the detector are mounted on two separate towers and can move vertically. The studied sample is mounted on a platform that can move horizontally. The movements of the towers and the platform are controlled and synchronized by a computer which is also used to define the parameters of each test, to run the test, and to collect the data. This equipment has been used to analyze the capillary moisture transfer through two cement pastes.
Relationships Between Permeability, Porosity, Diffusion And Microstructure Of Cement Pastes, Mortar, And Concrete At Different Temperatures
Authors: Roy Della M. 
Published: March 2011

AbstractPermeabilities to water and diffusion of ionic species in cementitious grouts, pastes and mortars are important keys to concrete durability. Investigations have been made of numerous materials containing portland and blended cements, and those with fine-grained filler, at room temperature and after prolonged curing at several elevated temperatures up to 90°C. These constitute part of studies of fundamental material relationships performed in order to address the question of long-term durability. In general, the permeabilities of the materials have been found to be low [many <10−8 Darcy (10−13 m·s−1)] after curing for 28 days or longer at temperatures up to 60°C. The results obtained at 90°C are somewhat more complex. In some sets of studies of blended cement pastes with w/c varying from 0.30 to 0.60 and cured at temperatures up to 90°C the more open-pore structure (at the elevated temperature and higher w/c) as evident from SEM microstructural studies as well as mercury porosimetry are generally correlated also with a higher permeability to liquid. The degree of bonding and permeability evident in paste or mortar/rock interfacial studies present somewhat more conflicting results. The bond strength (tensile mode) has been shown to be improved in some materials with increased temperature. The results of permeability studies of paste/rock couples show examples with similar low permeabilities, and some with increased permeability with temperature.Ionic diffusion studies also bring important bearing to understanding the effect of pore structure. The best interrelationships between chloride diffusion and pore structure appear to relate diffusion rate to median pore size. Similar results were found with “chloride permeability” test.
The Divided Flow Permeameter
Authors: Jefferis Stephan A. , Mangabhai Raman J. 
Published: March 2011

AbstractIn permeameters for rigid materials such as concrete, cement paste, or rock the sample is generally sealed into the test cell with a resin or with a pressurised membrane and the permeability is calculated from the total flow through the apparatus. Clearly any leakage around the edge of the sample or other inhomogeneity in the peripheral region will lead to inaccuracy in the measured permeability. This problem is particularly severe with low permeability materials such as concrete and is further exacerbated by the fact that the true permeability of concrete can vary by many orders of magnitude and there may be little information with which to assess whether particular test results are reasonable.The divided flow permeameter offers a technique by which edge leakage and other edge effects can be assessed and several permeability results obtained from different areas of a single sample. The basic principle of this permeameter is that either the inflow or the outflow surface, or both, of the sample are divided into separate flow regions. Provided that there is no difference in pressure between the regions there should be no tendency for flow between them and the flow through each should be proportional to its area.As the technique gives several permeability results for a single sample information about permeability variation within the sample can be obtained; for example data on microcracking, moisture distribution etc. The technique can be used with gas or liquid permeants. The divided flow permeameter system developed at King's College is inexpensive and with a simple system of ‘0’ rings a flow division head can be fitted to many conventional permeameters.
Numerical Modeling Of The Freezing Process In A Cementitious Matrix
Authors: El-Korchi Tahar , Alexandrou Andreas N. , Sullivan John M. 
Published: March 2011

AbstractA numerical model has been developed that predicts the freezing process in a cementitious matrix. Freezing point depression due to pore size characteristics is incorporated into the numerical model. An idealized pore size distribution based on a mature paste with a water-cement ratio of 0.6 was adopted. The pore size range was randomly distributed over the test domain. Results are shown for the advancement of the freezing fronts and the progression of the isotherms.
Chlorides In Concrete
Authors: Hansson Carolyn M. , Berke Neal S. 
Published: March 2011

AbstractChlorides are currently the main culprit in the deterioration of concrete structures in most parts of North America and Europe. During the last few years the authors have investigated the following properties: (i) the steady state diffusion of chlorides through cement pastes; (ii) penetration of chlorides into mortar and concrete; (iii) the binding of chlorides in the paste phase; (iv) the threshold value of chlorides below which corrosion of reinforcement is unlikely to occur; and (v)the relationship between the electrical resistivity and diffusivity of paste, mortar, and concrete. The variables investigated include water/cement ratio, cement type, curing conditions, effects of admixtures, and pozzolanic additions and the cover depth.
Microstructures Of Modified Hardened Cement Pastes
Authors: Kurdowski W. , Petri M. , Trybalska B. 
Published: March 2011

AbstractThe influence of different admixtures: gypsum, tartaric acid, silica fume and C4A3S upon the HCP developing microstructures has been studied. Investigations of flexural strength, E-modulus, porosity, DT-analysis, X-ray analysis and SEM observations were carried out. The obtained results showed that these samples differ in microstructure and porosity.
Effect of Curing on Some Pore Structure-Dependent Properties of Concrete
Authors: Gebauer J. , Torrent R. J. 
Published: March 2011

AbstractThe effect of the curing conditions on two properties of concrete, strongly dependent upon the pore structure, namely the strength development and the carbonation rate, was studied in the laboratory. The influence of the cement type, mix proportions and specimen size on the measured properties is also discussed. The importance of the quality of the “covercrete” for good durability is emphasized.
Dielectric Response Of Polymer-Modified Cements With Controlled Porosity.
Authors: Polo G. Vazquez , Martina E. , Castaño V. M. 
Published: March 2011

AbstractPolymer-modified cements were prepared macro-defect free by adding poly(vinyl acetate) to the normal water/cement mixture. The resulting samples, that corresponded to different volume porosity, were subjected to capacitance measurements in the range 5 Hz to 13 Mhz.
The Effect Of W/C Ratio And Cement Type On The Longevity Of Grouts For Use In A Nuclear Fuel Waste Disposal Vault
Authors: Onofrei Maria , Gray Malcolm 
Published: March 2011

AbstractCement-based grouts are being considered for use as sealing materials in the Canadian concept for nuclear fuel waste disposal. This paper describes laboratory studies of the longevity of these materials, with special emphasis on the effect of hardened grout porosity and cement type. The longevity properties determined for reference grout (90% Type 50 cement, 10% silica fume and superplasticizer) are compared with those of a slag cement grout.The fractional factorial statistical method of Box-Behnken was used to design a series of leach tests, which covered a wide range of conditions that could occur in a nuclear waste disposal vault. The leach tests have been carried out to determine the effect of temperature, ionic strength of groundwater, and cation exchange capacity (CEC) of clay (which may be in contact with the grout) on the leach resistance of the cement. The temperature ranged from 25 to 150°C and the ionic strength of the groundwaters from 0.0015 to 1.37 mol. Leach rates of Ca and Si were taken as the major indicators of the long-term chemical stability of the grouts.Preliminary analysis suggests that the reference grout would be more stable than slag cement in the high-temperature environment of a nuclear fuel waste disposal vault. Within the ranges investigated, decreasing the porosity appears not to significantly decrease leach rates.
Factors Affecting The Ability Of A Fly Ash To Contribute To The Sulfate Resistance Of Fly Ash Concrete
Authors: Mccarthy G. J. , Tikalsky P. J. , Carrasquillo R. L. , Manz O. E. , Thedchanamoorthy A. 
Published: March 2011

AbstractThe objective of this summary is to report on work in progress that is examining parameters, measurable through chemical and XRD analyses, that could indicate whether a fly ash will enhance, degrade or have no effect on the sulfate resistance of fly ash concrete.
The Influence of Pore Structure on the Properties of Cement Paste: Initial Observations about Research-in-progress
Authors: Lange D. A. , Jennings H. M. , Shah S. P. 
Published: March 2011

AbstractInitial observations of the influence of pore structure on material properties of cement paste are described. The total porosity is held constant and pore structure is altered by use of a superplasticizer. Corresponding changes in strength and fracture energy are observed. Changes in the cement paste pore structure are evaluated by analysis of images obtained by optical microscopy. The technique is a direct method of measurement that avoids assumptions about pore geometry.
Microdefects and Impurities in Dislocation-Free Silicon Crystals
Authors: Abe Takao , Harada Hirofumi , Chikawa Jun-Ichi 
Published: March 2011

ABSTRACTMicrodefects in striated (swirl defects) and nonstriated distribution (D-defects) have been observed in float-zoned crystals doped with various impurities by x-ray topography following copper decoration. A new type of defects were found to be present in swirl-free and D-defect-free regions and to become invisible by doping gallium. This gallium effect led to the conclusion that they are microprecipitates produced from residual oxygen impurity in FZ crystals. Effects of various impurities on defect formation indicate that D-defects are of vacancy agglomerates. It was observed that swirl defects are formed when the temperature gradient near the interface is high, and that their formation is suppressed by doping nitrogen. Formation processes of microprecipitates, swirls, and D-defects are discussed on the basis of observation of their mutual interaction and the impurity effects.
Thermal Donor Formation by the Agglomeration of Oxygen in Silicon
Authors: GÖsele U. , Tan T. Y. 
Published: March 2011

ABSTRACTWe suggest that thermal donor formation in silicon involves fast-diffusing, gas-like molecular oxygen in dynamical equilibrium with atomic oxygen in interstitial position. We will discuss still remaining difficulties in understanding thermal donor formation in the light of recent experimental observations by Stavola, Patel, Kimerling and Treeland, indicating that the diffusivity of interstitial oxygen apparently depends on the thermal history of the silicon sample.
Complex Defects in GaAs and GaP
Authors: Lin-Chung P. J. 
Published: March 2011

ABSTRACTA study of the electronic states associated with divacancy defects and with the defect complexes involving an anion antisite with a group IV atom (Ac-IV) in GaAs and GaP is reported. The local densities of states have been determined using the large cluster recursion approach. The properties as well as the position of the gap states of the divacancy defect in GaAs are found to be consistent with the experimental results for the EL2 level. The change of the position of the defect levels of (Ac-IV) as a result of the change of bonding is analyzed. The effect of GaAs-A&As interface on the (Ac-IV) defect level is also examined.
Enhanced Inp Substrate Protection for Lpe Growth of Ingaasp DH Lasers
Authors: Besomi P. , Wilson R. B. , Wagner W. R. , Nelson R. J. 
Published: March 2011

ABSTRACTThermal degradation of InP single crystal substrates prior to LPE growth has been virtually eliminated by using an improved protection technique. The phosphorus partial pressure provided by a Sn-In-P solution localized inside an external chamber surrounding the InP substrate prior to growth prevents thermal damage to the surface. Nomarski contrast photomicrographs,photoluminescence and X-ray diffractometric measurements indicate that InP substrates protected by this method suffer negligible deterioration, in contrast to the results of the more commonly used cover wafer method.
The Electrical Behavior of Grain Boundaries in Silicon
Authors: Seager C. H. 
Published: March 2011

ABSTRACTDespite the fact that lattice imaging studies have shown that grain boundaries in group IV semiconductors often have structures which are complicated and inhomogeneous on the scale of tens-tohundreds of angstroms, simple theories assuming uniform double depletion layers have recently been shown to successfully predict many of the majority carrier transport properties of these defects. On the other hand our knowledge of the interaction of grain boundaries with minority carriers is in a considerably more primitive state. I will describe recent attempts to understand the effects of illumination on grain boundary potential barrier heights and the influence of these defects on the optically generated minority carrier population. Quantifying this latter interaction is particularly important in estimating the performance of polycrystalline solar cells. Simple but elegant scanned excitation measurements for measuring s, the minority carrier recombination velocity at grain boundaries, will be reviewed. I will discuss recent measurements of s as a function of temperature and illumination intensity and show how these data can be correlated with zero-bias impedance measurements.
The Interface Structure of Grain Boundaries in Polysilicont
Authors: Johnson S. M. , Yoo K. C. , Rosemeier R.G. , Soltani P. , Lin H. C. 
Published: March 2011

ABSTRACTNormal grain growth in polysilicon material proceeds by a twinning mechanism such that the individual grain orientations are related by single or multiple twinning steps. The twinning relationship between adjacent grains can result in the alignment of their boundary interfaces along certain planar segments which have a very low electrical activity. The varying degree of electrical activity of these boundaries, and boundary positions, is attributed to the smaller dislocation portion of the larger change in orientation across the grains.
Enhanced Diffusion of Phosphorus at Grain Boundaries in Silicon
Authors: Cheng L.J. , Shyu C.M. , Stika K.M. 
Published: March 2011

ABSTRACTIt is found that the grain boundaries in cast polycrystalline silicon material capable of enhancing diffusion always have strong recombination activities. Both phenomena could be related to the existence of dangling bonds at boundaries. Because the enhanced diffusion is an atomic transport phenomenon and the recombination is an electronic process, the relationship between the two phenomena is still not clear at this moment. The present study gives the first evidence that incoherent second order twins of {111/115} type are phosphorus diffusion-active.
Degradation Behavior of Optoelectronic Devices
Authors: Matsui Junji 
Published: March 2011

ABSTRACTVarious degradation modes and features of crystalline defects associated with the degradation observed both in GaA1As/GaAs and InGaAsP/InP double heterostructure light emitting sources (LED's and Lasers) are reviewed, noticing similarities and differencies between those two material systems. Non-existence of rapid degradation in the quaternary caused by DLD formation (dislocation motion) will be discussed in terms of atomic rearrangements arouna the dislocation core.
Measurements of Ion-Implantation Damage in GaP
Authors: Myers D. R. , Peercy P. S. , Gourley P. L. 
Published: March 2011

ABSTRACTWe have applied stress measurements using the cantilever beam technique and Raman spectroscopy to characterize the dose dependence of damage production for He+, C+, or Ar+ implants into GaP. Stress increases monotonically with dose until a speciesdependent critical dose is reached. Above that dose, the material yields at an integrated lateral stress of ∼2×105 dynes/cm2 corresponding to an expansion of ∼1% in the implanted volume. The dose dependence of stress scales well with the volume density of ion energy deposited into atomic collisions. Raman measurements indicate that the material is still crystalline when the yield stress is reached.
Non Destructive Optical Analysis of Implanted Layers in GaAs by Raman Scattering and Spectroscopic Ellipsometry
Authors: Biellmann Joseph , Prevot Bernard , Schwab Claude , Theeten Jean-Bernard , Erman Marko 
Published: March 2011

ABSTRACTNon destructive analysis by Raman Scattering (RS) and Spectroscopic Ellipsometry (SE) is demonstrated on B+- and Se+ shallow implanted GaAs. Qualitative informations are obtained from 1st and 2nd order RS spectra. The former are analysed using the intensity ratio of the T0 and L0 modes, which defines a lattice potential perfection scale. The SE analysis of the E1, E1 +Δ1 structure in the imaginary part of the dielectric function confirms the RS results and its multilayer analysis yields the depth profile of the implanted ions.
Direct Evidence of Diffusion of Self-Interstitials in Silicon
Authors: Das Gobinda 
Published: March 2011

ABSTRACTHigh temperature (1200°C) HCI oxidation treatment has been employed to float-zone (FZ) silicon wafers (625μm thick) containing swirl defects in order to study their diffusion characteristics. In treated wafers, swirl defects can be eliminated from both surfaces up to a depth of ∼30μm. In the bulk of the wafers, however, large swirl defects (A-swirls) rearrange themselves into many small defects. The untreated portions of wafers contain large swirl defects (A-swirls) that extend up to both surfaces. Since swirl defects are primarily clusters of silicon self-interstitials, their rearrangement in the bulk and elimination from the surfaces demonstrate that migration of interstitials takes place on a large scale and is not confined to SiO2/ silicon interface only. The above observations appear to provide direct evidence for the dominant role of self interstitials for diffusion mechanism in silicon at high temperature and can be rationalized in terms of an interstitialcy mechanism. Alternatively, however, dominance of interstitials can be related to a higher migration energy of vacancies proposed in a model where both species coexist at high temperature. The preference of one model over another must await theoretical calculations of diffusion energetics derived from both models.
Enhanced Wear Resistance by Compressive Strengthening a Novel Combination of Laser and Ion Implantation Technology
Authors: Beurs H. De , Hosson J. Th. M. De 
Published: March 2011

AbstractDespite the advantages of laser processing for the production of wear resistant materials, laser surface melting results in tensile stresses because the melted layer shrinks during resolidification. These tensile stresses may lead to severe cracking of the material and to deleterious effects on the wear behaviour. Our basic idea presented in this paper is to convert the high tensile stresses in the laser melted surface into a compressive state after implantation. In general, neon implantation is not very effective in the reduction of wear rates. However, neon implantation into laser melted steel turns out to reduce the wear rate substantially.
The Causes of Property Variations of Ibad-Titanium Nitride
Authors: Kant R. A. , Dillich S. A. , Sartwell B. D. , Sprague J. A. 
Published: March 2011

AbstractThe influence of the growth conditions on the composition, microstructure, and mechanical properties of TiN formed with low energy Ar+ ion bombardment during reactive physical vapor deposition was studied. The ratios of the incident ion and atom fluxes at the growth surface were varied systematically and were found to have a strong influence on both the composition and the microstructure of the films. These changes correlated well with measured changes in mechanical and optical properties. The films were examined using Auger electron spectroscopy, transmission electron microscopy, and their mechanical properties were studied using hardness, friction, and wear testing.
Microstructural Studies of IAD and PVD Cr Coatings by Cross Section Transmission Electron Microscopy
Authors: Cheng C. C. , Erck R. A. , Fenske G. R. 
Published: March 2011

AbstractCross section transmission electron microscopy was used to study the microstructure and interface structure of Cr films deposited by ion-assisted deposition as a function of the incident ion energy. High-energy ion bombardment (1 keV) was found to enhance the adhesion of the deposited film owing to the formation of an intermixed layer, whereas deposition with lowenergy ions (100 eV) was found to reduce or eliminate grain boundary porosity. A tailored Cr film with excellent adhesion and no grain boundary porosity was deposited by combining highand low-energy ion bombardment.
In-Vacuo, Tribological Properties of “High-Rate” Sputtered MoS2 Applied to Metal and Ceramic Substrates.
Authors: Roberts E W , Price W B 
Published: March 2011

AbstractStudies of the tribological properties of molybdenum disulphide deposited at the high rates afforded by magnetron sputtering have shown such films to exhibit low friction and high endurance under vacuum. However such studies have mostly been confined to bearing steels. This paper reports on the extension of such studies by presenting measurements of friction coefficient and endurance obtained for thin films of “high-rate” molybdenum disulphide applied to substrates of 440C steel, 52100 steel, titanium alloy 318 andsilicon nitride. The results are interpreted in terms of substrate-related parameters such as film adhesion and elastic modulus of substrate materials. Preliminary evidence relating the degree of film adhesion to the existence of interfacial chemical compounds, identified using surface analytical techniques (XPS, SIMS), is presented.