bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrical Conductivity in (Gdl-xCax)2Sn2O7±δPyrochlore System
Authors: Yu Tae-Hwan , Tuller Harry L. 
Published: April 2011

AbstractElectrical conductivity measurements were performed on Gd2Sn207as a function of temperature, P02and Ca doping concentration. An effective frenkel constant and oxygen vacancy mobility were derived. The high level of intrinsic anion disorder found in this study is consistent with expectations based on the cation radius ratio (rA/rB) which was earlier found to be important in determining anion disorder in A2B207pyrochlore compounds [1]. The magnitude of the ionic conductivity in Gd2Sn2O7was found to be depressed relative to Gd2(Til-xZrx)207based systems due to a high oxygen vacancy migration energy.
Oxygen Permeability of Strontium-Doped LaCoO3-δPerovskites
Authors: Van Doorn RenÉ H. E. , Kruidhof H. , Bouwmeester H.J.M. , Burggraaf A.J. 
Published: April 2011

AbstractOxygen permeation rates are reported for 2 mm thick La1-xSrxCoO3-δ(0 ≤x≤0.8) in the temperature range 700 ≤T1100 °C and oxygen partial pressure range 7.0 x 103- 1.0 x 105Pa. With the exception ofx= 0.6 permeation rates increase with an increase in Sr doping level. The oxygen permeation can be described by Wagner theory. An anomaly is observed in the oxygen permeation between 750 - 775 °C, which is attributed to an order-disorder transition. It is further shown that the partial pressure at the low partial pressure side of the membrane has an important influence on the permeation rate. The (calculated) ionic conductivities and oxygen vacancy diffusion coefficients are among the highest reported in literature.
Microstructure-Conductivity Relationships in Solid Anisotropic Ionically Conducting Materials
Authors: Butchereit E. , Schoonman J. , Zandbergen H. W. , Lutz-Elsner C. , Schreiber M. , Wang P. 
Published: April 2011

AbstractIn a randomly oriented polycrystalline ionically conducting material the total conductivity is reduced by the lengthening of the effective conduction pathway which is determined by the microstructure. It is, therefore, desirable to develop a better understanding of the relationship between the conductivity and the microstructure of the ceramic material.This work focused on the quantification of the various contributions to the overall conductivity. Na-β” alumina ceramics with different microstructures but the same chemical composition were used as samples. Conductivity data were obtained by impedance spectroscopy measurements (IS) carried out in a temperature range from 350 to -30 °C at frequencies from 1 Hz to 500 KHz. An attempt has been made to calculate distinct geometric factors for the specific values of the grain and grain boundary contribution. These were inferred from the sample geometry, Laser Scanning Microscope (LSM) pictures, microstructural observations by image analysis, Transmission Electron Microscope (TEM) pictures, and considerations of the current pathways in the anisotropically conducting ceramic.
Electrical Conductivity and Raman Studies of B2O3-Na2O-NaI Glass Systems
Authors: Choi Byoung-Koo , Shin Kyoung-Hee , Lee Hyo-Kyoung 
Published: April 2011

AbstractGlasses of B2O3-Na2O-Na2I2 have been prepared over a wide range of compositions on the basis of a fixed O/B ratio and a fixed Na/B ratio, respectively. Raman spectra and the ionic conductivity have been measured to elucidate the role of the iodide. In the fixed O/B ratio, a drastic increase of the conductivity with the addition of iodide is observed. The conductivity results are found to be consistent with the Raman results. In the fixed Na/B ratio, the substitution of iodide does not influence significantly the glass structure as well as the ionic conductivity.
Effect of the Crystallinity of V6O13 Films on the Electrochemical Behavior of Lithium Microbatteries
Authors: Gorenstein A. , Khelfa A. , Guesdon J.P. , Julien C. 
Published: April 2011

AbstractElectrochemical characteristics of Li/V6O13 microbatteries are evaluated in relation with the crystallinity and morphology of thin-film cathodes. Thin films of V6O13 were prepared using the flash evaporation technique. Amorphous and polycrystalline samples were characterized by X-Ray diffraction, Raman spectroscopy and conductivity measurements. The effect of either deposition parameters or post-deposition treatment are presented in this work. Thermodynamics and kinetics of lithium insertion were studied in V6O13 thin films obtained with various growth conditions. Discharge curves present different types of behavior depending on the cathode morphology. Diffusion coefficients and enhancement factors were calculated as a function of the degree of lithium intercalation.
The Evolution of Cementitious Materials Through History
Authors: Bonen David , Tasdemir Mehmet A. , Sarkar Shondeepl. 
Published: April 2011

AbstractThe use of cementitious materials dates back to the beginning of the Epipaleolithic period. Examples for ancient cementitious materials from Israel, Egypt, Turkey, and Italy are numerous.Prior to Aspdin's patent of portland cement at the first half of the 19th century, cementitious materials were composed of earth, mixture of earth and limestone, calcium sulfates, and slaked lime with and without pozzolans. The latter comprises pozzolanic materials from volcanic and sedimentary origin, crushed burnt clay brick, and dust brick. Frequently, organic fibers were incorporated for reinforcement. This paper describes the evolution of the cementitious materials through time and highlights the durability of ancient cementitious materials as compares to that of portland cement concrete.Although modem concrete is characterized by its high strength and low permeability, it often faces durability problems. In turn, ancient concretes examined exhibit low strength but have proved to be durable materials. Microstructural examination reveals that the groundmass of the latter has been carbonated and is highly porous. Nevertheless, no specific cracking pattern could be observed. The outstanding performance of ancient concrete structures implies that thermodynamic stability rather that mechanical strength is a key point for a long-term durability.
Mineralogical Transformations and Microstructure After Disposal of Cementitious Advanced Coaltechnologyby-Product
Authors: McCarthy G.J. , Butler R.D. , Brekke D.W. , Adamek S.D. , Parks J.A. , Foster H.J. , Solc J. 
Published: April 2011

AbstractBy-products from two advanced coal technologies, Fluidized Bed Combustion (FBC) and Limestone Injection Multistage Burner (LIMB), were found to be cementitious when mixed with water and compacted. However, exposure to natural conditions in test cells resulted in losses of strength and increases in permeability over a period of years. Changes in mineralogy and microstructure with time in recovered core samples have been characterized by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). Up to 80 wt% of the core materials had converted to crystalline hydrate phases by the end of two years. Ettringite, gypsum and portlandite were the initial hydration products. In the LIMB materials, formation of thaumasite in microfractures, channels and voids was detected after one year, and in the FBC material after two years. Thaumasite formation was accompanied by reductions in gypsum and portlandite; it did not appear to be forming at the expense of ettringite. EDS examination of many ettringite and thaumasite crystals showed that the former always contained some Si and the latter some Al, which is evidence for ettringite-thaumasite solid solution. Thaumasite formation accompanied marked losses in strength and increases in permeability.
Performance of Cement-Basedseal Systemcomponents Inawaste Disposal Environment
Authors: Malone Philip G. , Wakeley Lillian D. , Burkes J.Pete , Mcdaniel Andearl W. 
Published: April 2011

AbstractA grout based on portland cement, Class F fly ash, and bentonite clay was developed as part of the closure system of shallow subsurface structures for disposal of low-activity radioactive wastes. Heat output, volume change, and compressive strength of the sealing grout were monitored with time, at elevated temperature, and in physical models, to determine if this closure grout could maintain adequate volume stability and other required physical properties in the internal environment of the disposal structure.To determine if contact with an alkaline liquid waste would cause chemical deterioration of the sealing grout, cured specimens were immersed in a liquid waste simulant containing high concentrations of sodium and aluminum salts. Over a period of 21 days at 60 °C, specimens increased in mass without significant changes in volume. X-ray diffraction of reacted specimens revealed crystallization of sodium aluminum silicate hydrate.The new phase has an X-ray diffraction pattern similar to that of the commercial syntheticzeolite, Losod. Scanning electron microscopy used with X-ray fluorescence showed that clusters of this phase had formed in grout pores, to increase grout density and decrease its effective porosity. The testing was repeated at 100 °C for 5 days using a simulant containing sodium hydroxide and aluminum nitrate and the results were similar. Physical and chemical tests collectively indicate acceptable performance of this grout as a seal-system component.
Reversible and Irreversible Electrically-Induced Shape Changes in Cement-Basedmaterials
Authors: Li Jhe-Fang , Yuan Li-Jian , Viehland Dwight 
Published: April 2011

AbstractThe electromechanical behavior of hardened portland cement paste has been investigated as a function of measurement frequency and DC electrical bias using an inductance technique. Large field-induced shape changes on the order of 104 Å have been found in millimeter thick specimens exposed to moisture. Both reversible and irreversible contributions to the total electrically-induced strain were observed. In addition, strong hysteresis effects were found on cycling a large AC field. Dry samples were found to exhibit no field-induced deformations. The mechanism underlying this anomalous behavior is believed to be an electro-osmotically induced swelling of the gel-pore structures.
Multi-Scale Digital-Image-Based Modelling of Cement-Based Materials
Authors: Bentz D.P. , Garboczi E.J. , Jennings H.M. , Quenard D.A. 
Published: April 2011

AbstractComputer modelling of the properties and performance of cement-based materials is complicated by the large range of relevant size scales. Processes occurring in the nanometersized pores ultimately affect the performance of these materials at the structural level of meters and larger. One approach to alleviating this complication is the development of a suite of models, consisting of individual digital-image-based structural models for the calcium silicate hydrate gel at the nanometer level, the hydrated cement paste at the micrometer level, and a mortar or concrete at the millimeter level. Computations performed at one level provide input properties to be used in simulations of performance at the next higher level. This methodology is demonstrated for the property of ionic diffusivity in saturated concrete. The more complicated problem of drying shrinkage is also addressed.
Fracture Mechanical Properties of Rocks and Mortar/Rock Interfaces
Authors: Hassanzadeh Manouchehr 
Published: April 2011

AbstractThis study has determined the fracture mechanical properties of 9 types of rock, namely fine-, medium- and coarse-grained granites, gneiss, quartzite, diabase, gabbro, and fine- and coarse-grained limestones. Test results show among other things that quartzite has the highest compressive strength and fracture energy, while diabase has the highest splitting tensile strength and modulus of elasticity. Furthermore, the strength and fracture energy of the interfacial zone between the rocks and 6 different mortars have been determined. The results showed that, in this investigation, the mortar/rock interfaces are in most cases weaker than both mortars and rocks.
Monitoring of Concrete Quality in High Performance Civil Engineering Constructions
Authors: Henrichsen Anders , Laugesen Peter 
Published: April 2011

AbstractModern high performance concretes (HPCs) are well characterized by their materials, compositions, and other characteristics, and usually documented by ‘test samples’ from laboratory specimens and trial castings. The characteristics are applied for construction design and estimations of service life time. However, in these young constructions, the internal structure of the HPC often reveals serious differences from that of the ‘test sample concrete’. Accordingly, the characteristics of the constructional concrete may be dramatically different from the expectations, often leading to increased rate of deterioration. A series of examples of such failures in the internal structures from major European HPC civil engineering constructions are presented. A test method is presented for the evaluation of the internal structure of the concrete as it exists in the actual structure. This test method is based on reground vacuum impregnated full sections of concrete core samples, cored from the construction at the moment of stripping the form work. Thus it is made possible to assess the structure during production. The cost of applying the test method approximates 0.1 % of the concrete value.
Interfacial Debonding and Sliding in Brittle Cementmatrix Composites from Steel Fiber Pullout Tests
Authors: Shannag M. Jamal , Hansen Will , Brincker Rune 
Published: April 2011

AbstractA specially designed single fiber pullout apparatus was used to provide simultaneous results on total fiber displacement versus load in addition to monitoring the fiber displacement at the free end. In this apparatus the fiber was going through the entire specimen, which made it possible to determine the point of complete debonding. To control the embedment length a plastic tube was inserted around the fiber. The described fiber pullout test method coupled with an appropriate analysis provides a quantitative determination of interfacial properties which are relevant to toughening of brittle materials through fiber-reinforcement. The technique was used on a high strength cement-based matrix called the Densified Small Particle system (DSP), and on an ordinary strength matrix. Other parameters investigated included fiber embedment length and fiber volume fraction in the cement matrix. The results indicate that: (1) the dense DSP matrix has significantly improved interfacial properties as compared to the ordinary strength matrix; (2) the major energy of pullout in both systems is due to sliding; and (3) both the debonding energy and sliding energy increase with fiber embedment length. These results are important in the understanding of the role of steel fibers in improving the tensile properties of high performance fiber reinforced composites.
Damage Evolution of Fiber/Mortar Interface During Fiber Pullout
Authors: Geng Yiping , Leung Christopher K.Y. 
Published: April 2011

AbstractThis study aims at connecting the change in interfacial properties of FRC during fiber pullout to the microstructural features of the interface. The interfaces between steel, polypropylene and nylon fibers and mortar are investigated by SEM and EDXA at four stages during fiber pullout (a) before debonding; (b) right after debonding; (c) pullout 1 mm and (d) pullout 10 mm. Since fiber pullout is found to be sensitive to lateral compression, microscopic studies are carried out on fibers pulled out with and without lateral compression.For steel FRC, significant damage occurs at the interfacial transition zone (ITZ) of the mortar. Regardless of the presence or absence of lateral compression, it is found that the “abrasion and grinding effect” is the major mechanism leading to the rapid decline of the pullout force and interfacial friction. Based on SEM and EDXA results, an interfacial damage evolution process is proposed.For polymeric FRC's, the damage occurs mainly on the polypropylene and nylon fibers and the ITZ of the mortar experiences much less damage. The surface of the polypropylene fiber is shaved and abraded during the pullout process. The surface of the nylon fiber is peeled and shaved which contributes to the increase of the pullout force and interfacial friction.
Bond Properties of Micro-Fibers in Cementitious Matrix
Authors: Katz Amnon , Li Victor C. 
Published: April 2011

AbstractUsing a new technique for pullout test of microfibers, the interfacial bond properties of two carbon fibers having a diameter of 10 µm and 46 µm were tested and compared with those of high modulus polyethylene and steel fibers having a diameter of 42 µm and 18 µm, respectively. The fibers were embedded in cement matrices of different water to binder ratio and silica-fume content.By studying the complete pullout load-pullout displacement curve and by using Environmental Scanning Electron Microscope (ESEM), it was found that the bond mechanism is mainly of friction for the fine and smooth carbon and polyethylene fibers. For the large carbon fiber and steel fiber, mechanical anchorage is the main bond mechanism.
The Fiber-Matrix Interface in Fiber Reinforced Concrete Studied by Contact Electrical Resistivity Measurement
Authors: Fu Xuli , Chung D.D.L. 
Published: April 2011

AbstractThe contact electrical resistivity of the fiber-matrix interface was found to correlate strongly with the shear debonding strength. In the case of the interface between stainless steel fiber and cement paste, the contact resistivity increased linearly with increasing debonding strength and interfacial phase(s) of volume resistivity higher than that of cement paste enhanced the bonding.
Microstructure of Steam Cured Concretes Deteriorated by Alkali-Silica Reaction
Authors: Bournazel Jean Pierre , Moranville-Regourd Micheline 
Published: April 2011

AbstractIn order to know the main cause of the cracking of concrete ties we tried to reproduce the deterioration process in the laboratory, using the same thermal cycle and the same materials. Model concretes were first steam cured then examined for ASR using the CSA-A-23-2-14A accelerated test. Linear expansion of concrete prisms were measured and fracture surfaces of concrete after treatment were observed under scanning electron microscope. They showed ASR gels and secondary ettringite. A simultaneous thermal mechanical computation gave the global microcracking of concrete induced by steam curing. A second computation showed the accelerating role of temperature on the local development of ASR products.
Microstructural Features of Freeze-Thaw Deterioration of Concrete
Authors: Bakharev Tanya , Struble Leslie J. 
Published: April 2011

AbstractMicrostructural features associated with freeze - thaw deterioration have been studied using scanning electron microscopy and mathematical modelling. Concrete subjected to freeze—thaw cycles in the laboratory and concrete deteriorated in the field were examined in the SEM (BEI). The microcracks produced after a few freeze—thaw cycles are largely vertical and extend deep (several millimeters) into the specimen. With additional cycles horizontal cracks are produced, connecting the vertical cracks to produce spalling. This crack development probably results from localized expansive stresses produced by hydraulic pressure, as described by Powers, plus localized shear stresses produced by differential volume changes.
Pillaring of Layered Double Hydroxides Possessing Variable Layer Charge with Vanadium Polyoxoanions
Authors: Kooli F. , Rives V. , Ulibarri M.A. , Jones W. 
Published: April 2011

AbstractA range of layered double hydroxides (LDHs) with Ni/Al and Mg/Al as the M(II)/M(III) cations and containing carbonate as the charge balancing anion have been synthesised. A variation in the M(II)/M(III) ratio between 2 and 6 has been attempted with the influence of the M(II)/M(III) ratio upon the subsequent exchange of carbonate by [V10O28]6- (at pH 4.5) examined. Complete exchange is obtained for all ratios, although the crystallinity of the products varies. For M(II)/M(III) ratios > 4, the product crystallinity is poor. In addition, a second phase is detected for all ratios. In the case of Ni/Al, the amount of vanadium incorporated is found to depend upon the Al content whereas for Mg/Al the amount incorporated is constant. Overall, the replacement of carbonate by decavanadate does not appear to have any significant effect on the textural characteristics (e.g. surface area or porosity) of the pillared products.
Vanadium Containing Large Pore Zeolites with ZSM-12 and SSZ-24 Structures
Authors: Sayari Abdelhamid 
Published: April 2011

AbstractVanadium containing large pore silica zeolites with ZSM-12 and SSZ-24 structures were synthesized and characterized. Incorporation of V in the zeolite framework was evidenced mainly by EPR and51V NMR techniques.
Use of the Multiple-Beam Interferometry in Measurement of Shells for Laser Fusion Targets
Authors: Veselov A. V. , Komleva G. V. , Mrachkovskij V. I. 
Published: April 2011

AbstractIn selection of shells for laser fusion targets, measurement of the wall nonuniformity with an accuracy better then 100 Å is needed. With this aim, the possibility of using multiplebeam interferometry for shell inspection has been investigated. Technical approaches have been found which have made possible the advantages of multiple-beam interferometry. For one of methods, bases on the multiple-beam interference used to process oscillograms, the sensitivity of 20 Å has been obtained in the wall nonuniformity measurements.
Microsphere Fabrication and Applications: an Overview
Authors: Wilcox David L. , Berg Morris 
Published: April 2011

AbstractThe diversity of applications for spherical materials, often referred to as hollow or solid microspheres, microballoons, shells and microcapsules, span a wide range of technologies and attracts the talents of individuals from a broad set of disciplines. Consequently, this knowledge and capability is widely dispersed. A prime objective of this symposium was to bring that diverse community together to share, for mutual benefit, that knowledge and capability. This article highlights some of these diverse technologies and applications and identifies some of the many important literature sources encountered.
Some Comments on the Production of Medium Sized Spherical Particles by Anion and Water Extraction Variant of Sol-Gel Process
Authors: Deptula A. , Łstoke;ada W. , Olczak T. , Chmielewski A. 
Published: April 2011

AbstractMedium sized spherical particles (with diameters below 100 μm) of ceramic materials (Al203 and Al203 +8%TiO2) were produced in the following steps: (1) preparation of concentrated hydroxide sols of cations by extraction of anions using Primene JMT, (2) formation of sol emulsion in 2-ethylhexanol-1 containing various amounts of surfactants (EH), (3) gelation of emulsion drops by extraction of water with partially dehydrated EH, (4) non-destructive thermal treatment. Principal properties of the sol depend on the temperature of the extraction process. For preparation of lowanionic sols a two step extraction process, separated by digestion of the aqueous phase at boiling point, was necessary. It was found that the parameters of emulsion formation as well as the properties of the sols significantly influence the particle size distribution. It was concluded that lowering of the sol- EH interracial tension by the surfactant does not influence the process. On the contrary the “anti-clustering” effect of surfactants is essential for preparation of perfect spherical powders. The thermal decomposition of gels to oxides is determinant for densities, specific surface area and carbon content. Medium sized spherical powders are free flowing. The compactibility and sinterability of those powders are poor. However drastic reduction of particle size by milling (connected with their transformation to irregular shape) significantly improves the sinterability.