bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric Relaxation in Small Confining Geometries
Authors: Arndt M. , Kremer F.
Published: April 2011

Broadband dielectric spectroscopy (10−2 Hz – 109 Hz) is employed to study the molecular dynamics of the glassforming liquid salol (phenyl salicylate) being contained in (dielectric inactive) porous glasses with pore sizes of about 2.5 nm, 5.0 nm and 7.5 nm. Besides the bulk relaxation (I) of salol, two further dielectric loss processes are observed due to the geometrical constraint of the inner surfaces of the pores: the “interfacial relaxation” (II) and a Maxwell-Wagner polarization (III). The “interfacial relaxation” is assigned to the restricted dynamics of the molecules close to the inner surface of the pores. It shows a strong pore-size dependence for pores < 5 nm both in relaxation rate and dielectric strength.
Vesicles and Passages Between Lamellas inLαMembrane Phases
Authors: Golubović Leonardo
Published: April 2011

We consider entropic effects of vesicles and passages confined between lamellas in fluid membrane lamellar (Lα) phases. We show that their presence induces attractive interactions between lamellas which strongly compete with steric repulsion in the vicinity of phase transitions from the lamellar to isotropic membrane phases. An interplay between steric repulsion and entropic interactions mediated by passages and vesicles determines the inter-lamellar distance reached at these transitions. This distance crucially depends on the membrane Gaussian bending rigidity constant.
Surfactant Self-Assemblies Near Contact Lines and their Effect on Wetting by Surfactant Solutions
Authors: Frank B. , Garoff S.
Published: April 2011

Surfactant self-assembly at the liquid-vapor, solid-liquid, and solid-vapor interfaces controls the wetting behavior of advancing surfactant solutions. While different surfactants exhibit different static and dynamic wetting properties, we show that these behaviors can be understood through an examination of microscopic structures driven by surfactant-surface interactions. We examine surfactant solutions exhibiting complete and partial static wetting as well as spreading by dendritic pattern formation and unsteady, stick-jump behavior. In each case, the observed behavior is related to the structure of the surfactant assemblies in the vicinity of the contact line.
Static and Dynamic Perturbations of Droplet Microemulsion by Confinement and Adsorption of Polymer
Authors: Lal Jyotsana , Farago Bela , Auvray Loic
Published: April 2011

The effects induced on the structure and dynamics of dilute microemulsion droplets by the confinement of polymer chains inside the droplets and by the adsorption of polymer on the surfactant shells from the outer continous phase were studied. The local structure changes were observed by small angle neutron scattering (SANS). The curvature fluctuations and the size distribution of the droplets increase for both chains inside and outside by different possible mechanisms, an induced size polydispersity minimizing osmotic stresses in the first case, a lowering of the film rigidity in the second one. Neutron spin echo techniques (NSE) were also used to probe the shape fluctuations of the same droplets with and without polymer. A sharp characteristic peak due to the contribution of the 1=2 mode is exhibited by the spectrum of relaxation times as a function of wavevector q. The height of this peak is decreased with the addition of polymer. i.e. the fluctuation of the 1=2 modes are dampened with the addition of polymer. The effect on the elastic coefficient K of the surfactant layer will be discussed below.
Relative Activity and Selectivity of Nanoscale Mo2N, Mo2C and MoS2 Catalysts Synthesized by Laser Pyrolysis
Authors: Ochoa R. , Hager G. T. , Lee W. T. , Bandow S. , Givens E. , Eklund P. C.
Published: April 2011

Nanoscale and well dispersed catalyst particles offer a large number of advantages: no diffusion resistance, easy accessibility to reactants, and a large number of active sites. In coal liquefaction, highly dispersed catalysts are especially needed because the catalyst particles are only able to influence reactions within their immediate vicinity.
Structural Characterization of Nanocrystalline Mo and W Carbide and Nitride Catalysts Produced by Co2 Laser Pyrolysis
Authors: Bi Xiang-Xin , Chowdhury K. Das , Ochoa R. , Lee W. T. , Bandow S. , Dresselhaus M. S. , Eklund P. C.
Published: April 2011

Using both XRD and HRTEM lattice imaging, we have shown that CO2 laser pyrolysis (LP) produces nanoscale transition metal carbide and nitride catalysts, including cubic Mo2C, Mo2N, and W2N, which possess highly crystalline structures in their as-synthesized form In contrast, LP-produced W2C in its hexagonal phase is disordered. Clear lattice expansion, induced by the small crystallite size of the nanoparticles has been observed for LP-produced Mo2C particles, which have a typical crystallite size of 2 nm. No carbon coating was observed in HRTEM for LP-produced Mo2C particles. Furthermore, Mo=N and Mo=C bonding in Mo2N and Mo2C, respectively, were identified by an XPS measurement, which also reveals the presence of a thin oxide layer formed on the particle surface during the passivation process. Finally, the average crystallite sizes determined from HRTEM and XRD are in good agreement, indicating that the line broadening observed in XRD is due to the small crystallite size of the nanoparticles.
Effect of the Heat Treatment on the Lithium Insertion Process in MoO3
Authors: Yebka B. , Julien C.
Published: April 2011

We have studied the electrochemical characteristics of Li/MoO3-based batteries in relation with the morphology of the cathode-active material. The oxides and oxide-hydrates of molybdenum have been prepared with various degrees of heat treatement. The samples were characterized by X-ray diffraction, Raman spectroscopy, and conductivity measurements. The effect of the heat treatment on structural, optical and electrochemical properties are presented in this work. Thermodynamics and kinetics of lithium insertion were studied in MoO3 cathodes. Diffusion coefficients and enhancement factors were calculated as functions of the degree of lithium intercalation in the domain of the galvanic cell reversibility.
Complete Conductivity Spectra of Crystalline and Glassy Fast Ion Conductors Up to Far Infrared Frequencies
Authors: Cramer C. , Graeber R. , Ingram M.D. , Saatkamp T. , Wilmer D. , Funke K.
Published: April 2011

Complete conductivity spectra have been taken of a lithium ion conducting glass of composition B2O3 · 0.56Li2O · 0.45LiBr and of lithium stabilized Na-β″-alumina, at various temperatures. — In the glass, it has forthe first time been possible to separate the hopping and vibrational contributions to theconductivity. The resulting hopping conductivity spectra display high-frequency plateaux similar to those known to exist in crystalline solid electrolytes like RbAg415 and Na-β-alumina. In the dispersive regime, the spectra are characterized bytwo different power-law exponents, p = 0.6 and q = 1.3. The data are evaluated by combined application of the jump relaxation model and the dynamic structure model. — Na-β″-alumina has pronounced high-frequency plateaux between about 200 GHz and 400 GHz. The hopping observed in the spectra can be decomposed into hops that are a priori unsuccessful and others that can be treated in terms of the jump relaxation model. The latter fraction is found to increase with increasing temperature.
A Comparative Study of LiMn204 From Various Sources
Authors: Oyang B. , Greenbaum S. G. , Boer M.den , Massucco A. , McLin M. , Shi J. , Fauteux D.
Published: April 2011

A process recently developed at Arthur D. Little, Inc. has enabled the direct and rapid production of LiMOx intercalation cathode materials having specific and controlled geometric and topographic attributes. Results of a comparative study of the electrochemical and spectroscopic characteristics of LiMn204 from several commercial sources and LiMn204 prepared using our process are reported. Improved electrochemical performance observed for the LiMn204 cathode material produced using ADL's process are tentatively related to the small and uniform grain size and to the possible additional influence of electronic defects associated with surface states.
Electrochemical Studies of Perovskite Mixed Conductors
Authors: Brosha Eric L. , Chung Brandon W. , Garzon Fernando H.
Published: April 2011

Research into the growth of high-quality single crystal thin films of high transition temperature (Tc) superconductors have stimulated interest in other perovskite metal oxides with a variety of physical properties.1 Thin films of perovskite materials are among the major focal research areas for optical, sensor, electronic, and superconducting applications.1 Two lanthanumbased oxygen/electronic conducting perovskite oxides of particular interest for high temperature fuel cell electrodes and interconnects and for other electrochemical applications such as oxygen separation devices are Lal-xSrxMnO3-y and Lal-xSrxCoO3-y. The La-based perovskites are valuable for these technologies because they reduce interfacial resistances by eliminating the need for a three phase contact area (gas, metal electrode, electrolyte).2 In addition, these oxides may also serve a valuable role as novel catalysts or catalytic supports; however, little is known about what catalytic properties they may possess.
Electrical Conductivity in (Gdl-xCax)2Sn2O7±δPyrochlore System
Authors: Yu Tae-Hwan , Tuller Harry L.
Published: April 2011

Electrical 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

Oxygen 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

In 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

Glasses 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

Electrochemical 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

The 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

By-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

A 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

The 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

Computer 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

This 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

Modern 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

A 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

This 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

Using 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

The 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

In 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

Microstructural 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

A 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

Vanadium 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

In 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

The 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

Medium 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.
Light Scattering Study of the Evolution of the Surface Morphology During Growth of Ingaas on GaAs
Authors: Lavoie C. , Haveman B. , Nodwell E. , Pinnington T. , Tiedje T. , Goldman R. S. , Kavanagh K. L. , Hutter J. L. , Bechhoefer J.
Published: April 2011

In-situ elastic light scattering is used to measure the evolution of the surface morphology of InxGa1−xAs films during molecular beam epitaxy growth on GaAs substrates. The in-situ measurements are compared with ex-situ measurements of the surface morphology on quenched films by optical scatterometry and atomic force microscopy (AFM). The AFM results are in good agreement with the rms roughness obtained from light scattering and both techniques detect the onset of misfit dislocation formation in this system.
Investigation of Local Structures Around Mn Atoms in In1-xMnxAs Diluted Magnetic Semiconductors Using Exafs
Authors: Soo Y. L. , Huang S. W. , Ming Z. H. , Kao Y. H. , Munekata H. , Chang L. L
Published: April 2011

Extended x-ray absorption fine structure (EXAFS) techniques have been used to investigate the local structures in Inl-xMnxAs films grown by molecular beam epitaxy (MBE) under different processing conditions. For samples grown at low substrate temperatures (near 200°C) or with a low Mn concentration (about 1 atomic%), the Mn atoms can substitute for In in the InAs host, thus indicating that III-V diluted magnetic semiconductors (DMS) can indeed be prepared by substitutional doping of magnetic impurities. On the other hand, substitution dose not take place in high Mn concentration (above 10%) samples grown at high substrate temperatures (around 300°C); these samples contain a large amount of MnAs clusters and become ferromagnetic
A Real-time X-ray Scattering Study of Sputtering Growth of TiN Films
Authors: Jel J. H. , Noh D. Y. , Kim H. K. , Liang K. S.
Published: April 2011

We report the results of a real-time synchrotron x-ray scattering study of the growth of TiN thin films on Si(001) substrates by RF sputtering. Our experiemnts show that the morphology of the TiN films strongly depends on growth conditions. After the nucleation and growth takes place with random crystallographic orientation at the very early stage, the films grow with a preferred orientation. Such preferred orientation was found to depend on both the sputtering power and the carrier gases used in the sputtering. Generally, the final morphology assumes either (111) or (002) crystallographic orientation. Using Ar sputtering, a cross-over effect from (002) to (111) was observed at intermediate time. The nature of the observed morphological changes is discussed.
In-Situ Observation of Chemical Vapor Deposition of Thin Sige Films by Optical Reflection Interferometry
Authors: Ritter G. , Tillack B. , Weidner M. , Böbel F. G. , Hertel B.
Published: April 2011

Chemical Vapor Deposition of Si1-x Gex – films on Si (100) and of polycrystalline Si1-x Gex, layers on SiO2 – coated substrates have been performed at a pressure of 200 Pa in the temperature range of 500°C – 800°C, correspondingly. To observe the growth process and to characterize the growing thin films at deposition conditions an optical reflection interferometer (PYRITIERS) has been used. Comparing the data obtained at growth temperature with ex- situ measurements by spectroscopic ellipsometry the temperature dependence of optical constants of SiGe films have been evaluated. The reflectivity measurements during the deposition process allow to study the quality of the heteroepitaxial film, even in the initial stage of epitaxial growth.
Neutron Reflection Studies of Swelling of Chemically End-Grafted Polymer Chains
Authors: Karim Alamgir , Satija S.K. , Gallagher P. , Douglas J.F. , Fetters L.J.
Published: April 2011

Neutron reflection is used to compare the swelling of two chemically end-grafted polystyrene brushes having different grafting densities exposed to a theta solvent cyclohexane and to a good solvent toluene. The relative swelling of tie brushes with a variation of solvent quality becomes smaller and the temperature dependence becomes weaker with an increase of grafting density. This type of swelling is very similar to polymer networks where an increase of cross-linking density leads to a decreased range of swelling and diminished dependence of the swelling. Our model density profile fits to the body of both brushes is parabolic in a good solvent so that some fluctuation effects, as found generally in lower density brushes, are obtained as the brush expands.
Neutron and Gamma-Ray Scattering at the University of Missouri Research Reactor Center
Authors: Rhyne James J.
Published: April 2011

The neutron and gamma-ray scattering facilities at the University of Missouri Research Reactor Center include six elastic and inelastic neutron scattering instruments currently in operation and three additional ones under construction. A gamma-ray diffraction and quasi-elastic spectrometer are also available. The Center has no formal user program, but encourages external collaborative work particularly that involves graduate student thesis research.
Phonon Characteristics of High Tc Superconductors from Neutron Doppler Broadening Measurements
Authors: J Trela Walter , Eric lynn J , H Kwei George , Meggers Kay
Published: April 2011

Statistical information on the phonon frequency spectrum of materials can be obtained by neutron transmission techniques if they contain nuclei with low energy resonances, narrow enough to be Doppler-broadened. We have carried out measurements using this technique for the doped 2-1-4 system, La2.xBaxCuO4. Two samples with slightly different concentrations of barium, one superconducting, the other not, were examined. Pure Lanthanum Cuprate was also studied. Neutron cross section measurements have been made with high energy resolution and statistical precision on the 60m flight path of LANSCE, the pulsed spallation neutron source at Los Alamos National Laboratory. Measurements on all three materials were made over a range of temperatures from 15K to 300K, with small steps through the critical temperature region near 27K. No significant changes in the mean phonon energy of the lanthanum atoms were observed near the critical temperature of the super-conducting material. It appears however that the mean phonon energy of lanthanum in the superconductor is considerably higher than that in the non-superconductors.
Local Atomic Structure of Plzt Determined by Real-Space Refinement of Neutron-Powder-Diffraction Data
Authors: Teslic S. , Egami T.
Published: April 2011

The local atomic structure of (Pb1-x Lax)( Zry Ti1.y)1.x/4O3 (PLZT) has been examined by means of pair-distribution function (PDF) analysis derived from neutron powder diffraction. We find that atoms are displaced from the atomic sites in the average periodic structure by a significant amount. The directions and magnitudes of the atomic displacements in PLZT are very similar to those found in Pb(Mg1/3Nb2/3)O3 (PMN). The short- and intermediate-range structural changes between ferroelectric, relaxor and antiferroelectric PLZT phases were compared.
Polarized Neutron Scattering Study Of Early Stage Phase Separation in a NI-13AT%AL Alloy
Authors: Staron P. , Kampmann R. , Wagner R.
Published: April 2011

The nucleation stages of the decomposition reaction in a 58Ni-13at%Al alloy at T=450° C have been investigated by means of small- and wide-angle polarized neutron scattering. The use of the 58Ni isotope for the sample preparation tremendously reduced the incoherent scattering of the matrix. This, together with the application of polarized neutrons for experiments at T = 12 K, made the detection of extremely small Ni3Al clusters, not accessible to other microanalytical tools, with diameters D < 1 nm feasible.
Slowing Down of Molecular Reorientations in [Ni(NH3)6](N03)2
Authors: Janik Jerzy A. , Mayer Jacek , Krawczyk Jan , Riste Tormod , Otnes Kaare , Janik Janina M. , Stanek Teresa
Published: April 2011

Quasielastic neutron scattering measurements of [Ni(NH3)6](N03)2 were made with two different resolutions of ca. 140 and 30 μeV. The following suggestions are analyzed:

1. The NH3 rotational diffusion model is more adequate than NH3 120° jump model.

2. Some NH3 groups slow down whereas some rotate rapidly.

3. There exists an additional QNS component close to the phase II/phase III transition.
Optical Transitions in Strained Si1−yCy and Si1−x−yGexCy Layers on Si(001)
Authors: Ostena H.J. , Kissinger W. , Weidner M. , Eichler M.
Published: April 2011

The addition of carbon atoms into Si or SiGe layers on Si opens the possibility for strain and bandstructure engineering. In this paper we will investigate the influence of carbon on the optical transitions of Si1−yCy and Si1−x−yGexCy layers grown pseudomorphically on Si(0O1) substrate using solid source MBE incluing also full strain-compensation. The layers were investigated by spectroscopic ellipsometry and electroreflectance spectroscopy for y ≤ 1.2 %. From the numerical derivatives of the measured dielectric constants, we determined the critical points energies E01, E1 and E2 as a function of the carbon content y. This shift was analyzed by measuring and fitting electroreflectance spectra at 80K and ellipsometry data at room temperature, resulting in a weak and nearly linear dependence on the carbon content at all transitions. These dependencies indicate that the interpretation of optical spectra of C-containing alloys can not be performed straightforward by simple interpolating between the appropriate band structures of silicon, germamum and carbon. An analysis based on only strain-induced contributions also does not describe the experimental results correctly. For a description of the observed energy shifts for pseudomorphic Si1−X−yGexCy we have to consider at least strain-induced effects and effects due to alloying.
Strain-Compensation in InAsP/GaInP Multiple Quantum Wells for 1.3 μm Wavelength
Authors: Mei X. B. , Tu C.W.
Published: April 2011

We show that high-quality strain-compensated InAsxP1−x/GayIn1−yP multiple quantum wells (MQWs) can be grown by gas-source molecular beam epitaxy on InP substrates even though the InAsxP1−x quantum wells have a large lattice mismatch (∼ 1.3%) with respect to InP. Very sharp satellite peaks in double-crystal X-ray diffraction and narrow line width in low-temperature photoluminescence (FWHM of 4 meV at 9 K) are obtained from MQWs of up to 50 periods. Strain compensation allows a wide range of the net strain around the ideally compensated point, where the net strain equals zero, without degrading crystalline quality.
Triangular Step Instability and 2D/3D Transition During the Growth of Strained Ge Films on Si(100)
Authors: Chen K. M. , Jesson D. E. , Pennycook S. J. , Mostoller M. , Kaplan T. , Thundat T. , Warmack R. J.
Published: April 2011

We show that an activation energy barrier exists to the formation of wavy step edges due to stress-driven 2D instability. The barrier height and the barrier width depend sensitively on the surface stress anisotropy and step free energy. The large misfit strain of Ge films significantly reduces the barrier by lowering the SB step energy, inducing SA steps to undergo a triangular instability even during low temperature growth of Ge on Si(100). The step instability results in a novel arrangement of stress domains, and the interaction between the domains causes a spatial variation of surface strain with a surprisingly large influence on the energy barrier for island nucleation. Calculations indicate a dramatic enhancement in the nucleation of 3D islands at the apex regions of triangular steps, in good agreement with our experimental measurements.
Hall Mobility in Strained SiGe p-Mosfets
Authors: Garchery L. , Sagnes I. , Campidelli Y. , Berenguer M. , Badoz P.A. , Guldner Y. , Zanier S.
Published: April 2011

One of the limiting factors in the performance of future CMOS integrated circuits is the low hole mobility which causes the transconductance of p-channel transistors to be inferior to those of n-channel devices. One promising way of enhancing hole mobility is to introduce a buried SiGe layer under the gate of p-MOS transistors. The mobility improvement thus results from, i) reduction in surface scattering (by moving carriers away from scattering sites at the Si/SiO2 interface), and ii) higher in-plane hole mobility in biaxally strained SiGe layers.
GexSi1−x Heterojunction Internal Photoemission Structures by Ultra High Vacuum Chemical Vapor Deposition
Authors: Strong R. , Greve D.W. , Schlesinger T.E. , Weeks M.M. , Pellegrini P.W.
Published: April 2011

GexSi1−x, heterojunction internal photoemission devices for detection of infrared radiation have been fabricated from films grown by ultra high vacuum chemical vapor deposition (UHV/CVD). Films and devices were characterized by Fourier transform infrared spectroscopy (FTIR), photoresponse, and electrical measurements. Detector efficiencies were found to increase substantially (from ∼ 1.5 to ∼ 20% per eV) as the boron concentration in the absorbing layer was increased from 1×1020 to 2.5×1020 cm−3. Increases in boron concentration beyond 2.5×1020 cm−3 did not significantly improve device performance. This result is attributed to incomplete dopant activation at higher boron concentrations.
Structural and Optical Properties of Sigec Alloys and Multi-Quantum Wells Grown by Rapid Thermal Chemical Vapor Deposition
Authors: Boucaud P. , Guedj C. , Julien F. H. , Bouchier D. , Boulmer J. , Lourtioz J.-M. , Bodnar S. , Regolini J. L. , Finkman E.
Published: April 2011

We have investigated structural and optical properties of SiGeC layers. Bulk and multiquantum wells heterostructures were grown by rapid thermal chemical vapor deposition. The photoluminescence of these structures exhibits two distinct features : deep level photoluminescence associated with localized states and bandedge photoluminescence which gives an indication of the band gap variation due to carbon incorporation in substitutional sites. In the case of multiquantum wells heterostructures, a strong segregation is reported as the growth temperature is decreased. An alternate technique to incorporate carbon in SiGe layers, the pulsed laser induced epitaxy with an excimer laser, is presented. The incorporation of carbon in substitutional sites is evidenced by Raman spectroscopy. As the laser flux is increased, new Raman lines associated to carbon-induced disorder are observed in the spectra.
A Dodson-Tsao Relaxation Approach to The Crystallographic Tilting In (100) Heteroepitaxial Systems
Authors: Riesz Ferenc
Published: April 2011

The tilt of epilayer lattice planes in (100) zinc blende lattice-mismatched heterostructures is calculated numerically using the Dodson-Tsao plastic relaxation model. Tilt is calculated as a function of growth temperature, initial defect density and substrate miscut angle. The results are explained by looking at the time evolution of the excess stresses of the opposing slip systems during strain relaxation.