bluuebunny/crossref_metadata_2025_split huggingface dataset:
Observation of Large-Scale Structures in Unsaturated Materials
Authors: Maneval J. E. , Mccarthy M.J. , Whitaker S. 
Published: March 2011

ABSTRACTWe report here the use of nuclear magnetic resonance imaging in the observation of liquid-phase fraction distributions in a partially-wetted sample of glass beads. By combiningboth large- and small-scale imaging techniques, we can study the transition from local-averaged saturations to large-scale averaged saturations. The image data allows us to assess the utility of the large-scale measurements We comment on the reliability and generality of the measurements for our specific system.
The Granular Nature of High Rank Coals
Authors: Cody George D. , Larsen John W. , Siskin Michael , Cody George D. 
Published: March 2011

ABSTRACTWe present optical evidence in the visible and mid-infrared for the coal to graphite transformation proceeding via a nucleation mechanism. In the visible region, we show that changes in reflectivity that occur with increasing coal rank can be understood by an increase in the volume fraction of sub-microscopic “graphite-like” nuclei and a subsequent increase of the complex part of the dielectric constant with increasing coal rank. Optical phenomena associated with the granular nature of coal is also observed in the mid-infrared; specifically, measurements of absorption across the mid-infrared show a significant increase of absorption with increasing coal rank. This increase can be ascribed to absorption arising from a plasma resonance “graphite-like” material of the granular composite. A broad range of the optical repsroopnearntciees foofr hitghhe rank coals in the visible and mid-infrared can thus be readily understood and quantitatively modeled in terms of a granular medium consisting of nuclei of “graphite-like” material imbedded in an insulating organic matrix. If validated by further experimentation, this model should greatly expand current capabilities in the opticalcharacterization of high rank carbonaceous materials.
Melting Behavior in Granular Metal Thin Films
Authors: Unruh Karl M. , Patterson B.M. , Shah S.I. 
Published: March 2011

ABSTRACTGranular metal films consisting of small Sn, Bi, and Pb particles, typically from less than 100 Å to several 1000 Å in size and embedded in a SiO2 matrix, have been fabricated over a range of metal compositions by RF sputter deposition. Two different film geometries have been prepared, homogeneous films and multilayer films consisting of alternating layers of granular metal and SiO2. These films have been characterized by x-ray diffraction and transmission electron microscopy and their melting behavior studied by differential scanning calorimetry. As the concentration of the metal component is decreased, the average particle size decreases and the particle size distribution becomes more narrow. When the solid-liquid transition is studied, the melting temperature has been found to be increasingly depressed as the particle size is reduced. In the smallest particles the relative reduction in the melting temperature is greater than 10 percent. No strong evidence for melting point enhancements, due to pressureeffects arising from the different thermal expansions of the metal particles and the SiO2 matrix, has been observed in either the homogeneous or multilayer films.
Particle Shape Effects on Optical Absorption in Semiconductor Colloids
Authors: Persans P. D. , Lu E. , Haus J. , Wagoner G. , Ruppert A. F. 
Published: March 2011

ABSTRACTThe absorption spectrum of small MoS2 particles in colloidal dispersions differs significantly from that of bulk material. In particular the amplitude and position of exciton absorption peaks shifts when small particles are suspended in a dielectric fluid. Our results are compared with predictions of a Maxwell-Garnett effective medium theory for ellipsoidal particles. We find that particle aspect ratio is an important parameter for interpreting these changes.
Pt-SiO2 Granular Metals for Cryogenic Thermometry in High Magnetic Fields
Authors: Obaldia Elida De , Moustakas T.D. , Hettengier Jeff , Brooks J.S. 
Published: March 2011

ABSTRACTPt-SiO2 granular metal films were produced by RF diode sputtering and characterized as thermistors for cryogenic temperature measurements at high magnetic fields. The devices were found to have high sensitivity and small magnetoresistance. This, together with ease of fabrication and stability, makes such thermistor useful candidates for cryogenic thermometry.
Influence of the Morphology on the Optical Properties of Nanocermet Films: A Renormalization Approach
Authors: Berthier S. , Driss-Khodja K. 
Published: March 2011

ABSTRACTIn order to take into account the actual morphology of the inhomogeneous media, we have developed, effective medium models based on a 2D and 3D position space renormalization /1,2/. These models predict the dipolar resonance and the percolation transition with critical exponents in good agreement with theoretical values and fairly reproduce most of the experimental results, whatever the concentration is. Further more, this allows a valuable comparison of the predictions of our models when applied on different lattices like real digitized TEM of cermet films or randomly occupied lattices.
Simulation of Composite Optical Properties Close to Percolation Threshold
Authors: Brouers F. , Clerc J.P. , Giraud G. 
Published: March 2011

ABSTRACTWe analyze the optical properties of a metal-insulator composite thin film close to the percolation transition pc. Using a mean field approximation, it is possible to predict the existence of an optical threshold at a concentration p* slightly larger than pc. At that concentration defined by the vanishing of the real part of the dielectric constant and which depends of the relaxation time and therefore of the microgeometry, the composite optical absorption is frequency independent up to the near infrared frequencies. This property has been observed in a number of granular and cermet films.We show that this property is quite general and can be obtained by generalizing the percolation scaling laws to a mixture of resistors, inductors and capacitors. The quality factor is shown to be a relevant physical quantity.We report and discuss the results of simulations on real analogic LCR circuits and on computer which confirm and explicit these conclusions.
Classical and Nonclassical Optical Diffusion
Authors: Drake J. M. , Genack A. Z. 
Published: March 2011

ABSTRACTWe present a brief summary of our recent work on classical and nonclassical optical diffusion in disorder metal oxides. Results on the optical transmission through a slab of titania spheres is presented and discussed in some detail illustrating the experimental method for obtaining the optical diffusion coefficient and photon absorption time from the transmission data. We conclude that the optical field-field correlation function with frequency is the Fourier transform of the time of flight distribution.
Phonon Dispersion in Suspensions of Hard Sphere Colloids*
Authors: Weitz D.A. , Liu J. , Ye L. , Sheng Ping 
Published: March 2011

ABSTRACTWe use Brillouin scattering to measure the dispersion of the propagating acoustic modes in a suspension of hard sphere colloids. We find two distinct longitudinal modes when the sound wavelength becomes comparable to the sphere diameter. The higher frequency mode has a velocity intermediate between those of the pure solid and the pure liquid phases, and its velocity increases with increasing volume fraction, ø. The lower frequency mode has a velocity less than the velocities in either the pure fluid or pure solid phases, and its velocity decreases with increasing ø. We interpret the higher frequency mode as a compressional wave which propagates through both the solid and the fluid, as expected for a composite medium. The lower frequency mode has not been observed before, and is interpreted as a surface acoustic mode, which propagates between adjacent spheres through a decaying portion of the excitation in the fluid.
An Investigation of Diffusion Bonding for Ti–6AI–4V Titanium Alloys
Authors: Huang Wei-Dong , Zhang Zong-Yuan , Lin Zhao-Rong 
Published: March 2011

Based on current theories of diffusion and creep cavity growth (or closure) at high temperatures, a physical analysis of diffusion bonding for the Ti–6Al–4V titanium alloy is given. The diffusion bonding is mainly pictured as a two—stage process:1. The shrinkage process of cavities with shape change from elliptical to cylindrical;2. In the second stage, the radii of the cylindrical cavities arc reduced and eliminated.In addition, according to experimental work and previous theoretical models of diffusion bonding, a new model has been established in this paper, which can be used to predict the effect of process variables, such as temperature, pressure, surface roughness and bonding time on the bonding degree for Ti–6Al–4V by using mechanisms of creep and diffusion.
Superplasticity in Ll2 Intermetallic Alloys
Authors: Nieh T. G. 
Published: March 2011

ABSTRACTRecent advances in superplasticity of L12 intermetallic alloys are reviewed. Results show that superplastic elongations of over 500% can be obtained in this group of materials. These intermetallic alloys include nickel silicide, Ni3 Si, and nickel aluminide, Ni3Al. In this review, the superplastic properties of these alloys are presented. The microstructural characteristics, e.g., grain size, phases, and texture, are described and correlated to the superplastic properties. The effects of alloying additions, temperature, and strain rate on the superplastic properties of these materials are discussed. In addition, the superplastic deformation mechanisms are proposed. Comparison of the superplastic characteristics of the intermetallic alloys are made with metal alloys and ceramic materials.
Superplasticity of Ultra-High Carbon Steels Containing 3-5%Aluminum
Authors: Kum Dong-Wha , Kang Hyung , Kim Tong-Hoon 
Published: March 2011

ABSTRACTTo study the effect of Al on superplasticity of ultra-high carbon steel (UHCS), 3–5%Al was added to the UHCS, and superplastic behavior was measured at 700–800°C. To produce the fine and superplastic microstructure, an isothermal rolling at 700°C was used, and the grain size of ferrite was less than about 2μm in diameter after the process.Significant improvement in superplasticity was observed; the strain-rate sensitivity was high upto a strain-rate of 10−2 s−1, and 402% elongation was measured at 750°C and at an engineering strain-rate of 5000%/min(i.e., 8.3×10−2s−1). It has been determined that the Al-addition leads to a finer grain size, which, in turn, improved the superplastic properties of the ultra-high carbon steels.
Significance of High Rate Superplasticity in Metallic Materials
Authors: Furushiro Norio , Hori Shigenori 
Published: March 2011

ABSTRACTIt has been expected that “High rate superplastic materials” will be developed for industrial applications. The Dorntype equation for high temperature deformation suggests that strain rate can be increased if the grain size is decreased. This means that grain refinement can effectively establish high strain rate superplastic materials.It is well known that a high degree of grain size refinement will result from the addition of zirconium to Al-base alloys. Powder-metallurgical processing with rapidly solidified powders is also available for the improvement of superplasticity by both the refinement of the solidified structure and the maintenance of the stable fine structure of a 7475 Al alloy during recrystallization and deformation. Therefore. P/M 7475 Al alloys containing Zr up to 0.9 wt% were selected as candidate specimens. The objective of the present paper includes the clarification of the role and the effective amount of Zr to obtain high strain rate superplastic materials. As a result, the addition of 0.3%Zr or more is effective in grain refinement of the P/M 7475 Al alloy. However, alloys containing 0.7 and 0.9 wt%Zr only show superplasticity at 793K. The optimum strain rate is shifted to a higher range with increasing Zr. The alloy of 7475 Al-0.9%Zr shows the maximum elongation of 900% at the remarkably high strain rate of 3.3×10−1 s−1.The deformation mechanism of such high stain rate superplasticity will be discussed briefly, by considering the effect of the fine particles of Zr on superplastic behavior.
A Mechanism of Superplastic Deformation and Deformation Induced Grain Growth Based on Grain Switching
Authors: Sato Eiichi , Kuribayashi Kazuhiko , Horiuchi Ryo 
Published: March 2011

ABSTRACTGrain growth depending on strain is generally observed during structural superplasticity. A new deformation model is proposed in order to explain this grain growth.This model is based on grain switching by Ashby and Verrall. The modification is to introduce grain size irregularity. The grain structure with minimum irregularity consists of one 5–7 pair in hexagonal array, which corresponds to edge dislocation. While the tensile stress oblique to the pair results the grain switching described by dislocation glide, the stress parallel to it results the grain switching which transforms the pentagon into the quadrilateral and then removes it. The latter can be described by dislocation climb and results the enhancement of grain growth. The expansion into three dimensions is discussed.
Superplasticity in Geological Materials
Authors: Paterson M. S. 
Published: March 2011

ABSTRACTThe term “superplasticity” is taken as meaning high-strain-rate-sensitivity flow when it is used in geological contexts involving predominantly compressive stress states. Such flow has been observed in calcite and olivine polycrystalline aggregates in laboratory tests and the mechanism deduced to be diffusion-controlled granular flow. From microstructural observations, similar deformation processes are inferred to have occurred in a number of geological situations. On the basis of extrapolation from experiment to geology, superplastic flow might be expected under some geological conditions in calcite and olivine rocks at grain sizes approaching the order of one millimetre, while there are indications that the grain size limit for quartzites may be rather smaller. However, the knowledge of superplasticity in most rocks is still very fragmentary, especially in regard to mechanisms where a fluid phase may be involved, as in porous rocks.
Low Temperature Sintering and Deformation of Nanocrystalline TiO2
Authors: Hahn H. , Logas J. , Höfler H. J. , Kurath P. , Averback R. S. 
Published: March 2011

ABSTRACTThe sintering and deformation kinetics of nanocrystalline (n-) TiO2 were studied. It was found that pressureless sintering yields densities above 95 % with modest increase in grain size whereas pressure assisted sintering (1GPa) results in high density samples without grain growth. In addition compression tests were performed. Large true strains up to 0.6 and strain rates as high as 8 × 10−5 s−1 were observed at 810 °C without fracturing. The sintering and creep results are discussed in terms of the microstructure and diffusion coefficients in n-TiO2.
Effects of Azidosilane Treatments of Wood and Cellulose Fiber Surfaces on Adhesion to Polypropylene
Authors: Kolosick Paul C. , Scott C.T. , Koutsky J.A. , Myers G.E. 
Published: March 2011

ABSTRACTWood strip surfaces (Aspen and Birch) and cellulose fibers (Birch, pulped paper fibers) were treated with azidosilane coupling agent, via immersion in methylene chloride and methanol solutions respectively, and then subsequently dried. Polypropylene films were compression molded to the wood surfaces and peel forces were measured. The treated cellulose fibers were suspended and mixed with polypropylene fibers in water, formed into thin sheets by wet forming, dried, and compression molded to melt the polypropylene.Treated wood surfaces gave two to six times the dry peel force versus untreated wood surfaces. However, the wet peel force of treated wood degraded to that of untreated wood. The elongation, fail stress, and tensile energy absorption of treated molded sheets were all increased over the untreated fibers for both dry and wet testing; the wet-tested properties were especially enhanced by the silane treatment.
Tensile Creep of Paperboard—Effect of Humidity Change Rates
Authors: Gunderson Dennis E. , Tobey Wayland E. 
Published: March 2011

ABSTRACTExperimental results now available are not adequate to define the mechanism of cyclic creep response of paperboard or to test plausible hypotheses. The present study examines the effect of rate-of-change of humidity on tensile creep response while monitoring the quantities of water adsorbed and desorbed by the specimen. Relative humidity is cycled between 30 and 90 percent relative humidity. Rate of humidity change in each cycle is held constant at values from 0.01 to 6 percent relative humidity per minute. Moisture sorbed by the web in each cycle is resolved to an accuracy better than ±0.05 percent moisture content. Results suggest that cyclic creep response is independent of the rate at which humidity changes. The results appear to reject the hypothesis that cyclic creep behavior is the result of a progressive increase in equilibrium moisture content.
Paper Coatings: High Performance Composites?
Authors: Lepoutre Pierre 
Published: March 2011

ABSTRACTA pigmented paper coating is a composite material made of pigment, polymeric binder and microvoids. Its structure is designed to meet a difficult balance of optical, mechanical and fluid transport properties. The coating must be opaque and bright. It should withstand in-plane and out-of-plane stresses during calendering, printing, and converting operations. It should allow controlled movement of liquids and fluids during high speed printing and glueing.The structure of paper coatings is examined and relationships between surface and bulk structural parameters and end-use properties are discussed. Namely, it is shown how pigment size and size distribution, its shape and orientation, the colloidal interactions between pigment and binder in the suspension all affect the final structure and properties. Finally, the profound influence of the porous network on the optical, mechanical and printing properties is emphasized.
The Performance of Precipitated Calcium Carbonate Fillers in Fine Quality Printing and Writing Papers
Authors: Gill Robert A. 
Published: March 2011

ABSTRACTThe trend toward alkaline papermaking has accelerated over the past four years due to the availability of inexpensive, high quality precipitated calcium carbonate. This movement has been largely brought about through on-site production of precipitated calcium carbonate (PCC). Over ten facilities exist in North America providing the host mills with custom-made PCC products to provide specific properties for the paper grades being manufactured.Laboratory studies were recently conducted to investigate the performance of paper-grade PCC fillers in fine quality printing papers. This investigation focused on the effect of changes in PCC particle size, size distribution, surface area, and morphology on paper properties. The PCC fillers were also compared to other filler materials such as ground limestone and kaolin.In general, the results show that sheet properties are greatly influenced by the size and shape of the PCC product used. The data reveal strong correlations between average particle size and/or surface area, and sheet properties such as opacity, porosity, tensile strength, bulk, and sizing within certain filler morphologies.
UV-Visible Response of Kraft Lignin in Soft Wood Black Liquor
Authors: Dong Daojie , Fricke Arthur L. 
Published: March 2011

ABSTRACTUV-visible light absorption is an analytical method that is commonly used to determine the concentration of lignin in solution; however, there are uncertainties with this method, particularly for use in determining lignin concentration in black liquors. To try to resolve these uncertainties, a detailed study of UV-visible absorption by lignin in solution has been made.A dual beam UV-visible instrument capable of repetitive scan was used. The effects of lignin concentration, lignin molecular weight, molecular weight dispersion, and solvent were examined as well as the effect of the reference solvent. Measurements were made for lignin dissolved in dilute caustic, DMF, THF, and DMSO. Measurements for soft wood black liquors were also made. A refined method for determining lignin concentration in soft wood black liquors resulted that is now being used in our research to evaluate lignin concentration in soft wood black liquor.The results of the current work have led to improvements in this analytical method so that it appears to be less affected by lignin characteristics and by solution complexities.
Micromechanics Models for Predicting the Elastic and Strength Behavior of Paper Materials
Authors: Perkins Richard W. 
Published: March 2011

ABSTRACTThis paper presents a review of micromechanics models that have been used to predict the elastic and strength behavior of paper materials. The models discussed are based on a fiber network model that takes into account the properties of the fibers and the properties of the fiber-to-fiber bond.Elastic models are described for a range of paper density and basis weight ranging from tissue papers to paperboard materials. The effects of fiber curl for low density systems is discussed. Models for predicting both the initial modulus of the paper and the nonlinear elastic behavior for small finite strains is presented. Differences between tensile and compressive straining regimes are addressed.Limit load theory is discussed for predicting the strength of the network. Damage mechanics theory is employed to take into account hypothesized processes of fiber fracture and bond delaminations, and to relate the inelastic network micromechanics to the prediction of the strength of the material.
Improvement of Inp-GaAs-Si Quality by Thermal-Cycle Growth
Authors: Vernon S.M. , Keavney C.J. , Gagnon E.D. , Karam N.H. , Haegel N.M. , Mazzi V.P. 
Published: March 2011

ABSTRACTSingle-crystal films of InP have been deposited on GaAs, GaAs-coated Si, and InP substrates by metalorganic chemical vapor deposition (MOCVD). Defect-reduction schemes involving various thermal annealing recipes have been developed and characterized. Material quality has been assessed by a variety of methods including transmission electron microscopy, X-ray rocking curve analysis, low-temperature photoluminescence, lifetime measurements, Hall-effect measurements, electrochemical profiling, and Nomarski microscopy. The use of either a thermal-cycle-growth or a thermal-cycle-annealing process leads to heteroepitaxial InP film quality which is significantly improved over that of its as-grown state, with the thermal-cycle growth appearing to be the more effective technique.
Misfit Dislocations at Mismatched Epitactic Heterojunctions
Authors: Zhu Jane G. , Carter C. Barry , Palmstrom Chris J. 
Published: March 2011

ABSTRACTThe formation and structures of misfit dislocations are significant factors in understanding heteroepitaxy of lattice-mismatched materials. In this study, GaAs/Si, CoGa/GaAs and ErAs/GaAs heterojunctions in materials grown by molecular-beam epitaxy have been characterized using transmission electron microscopy. Different types of misfit dislocations have been generated at these interfaces. The different dislocation configurations are discussed, along with interactions between 60° and 90° dislocations in GaAs/Si heterojunctions; the 60° dislocations might be associated with surface steps or edges of islands. The growth of antiphase boundary structures in the CoGa and ErAs grown on GaAs are proposed.