bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Flow Behaviour of Concentrated Clay Suspensions Under High Pressures
Authors: Briscoe Brian J. , Luckham Paul F. , Ren Shao Ran 
Published: March 2011

AbstractThis paper describes part of recent studies (Briscoe, et al., Proc. 11th Inter. Congs. on Rheology, 588–590, Aug. 1992, Brussels; Briscoe, et al., The properties of drilling fluids at high pressures and high temperatures', submitted to Proc. Roy. Soc.,1992) of the rheology of concentrated clay dispersions (weight fraction from 7%–12%) under the conditions which commonly occur during oil-well drilling operations. The experimental data, which are reported in terms of the Bingham yield stress and the plastic viscosity, show that the application of high pressures modifies the Bingham characteristic parameters in a way which is both temperature and gelation-time (or shear history) dependent. The extent of this shearhistory effect may be described in terms of a “time-dependent gel strength”. The experimental results obtained with controlled shear-history measurements, using a high pressure and high temperature rolling-ball rheometer, support an extended induced volume change model, which presumes an equilibrium state for the system. The data also indicate that long time constants are associated with the gelation process at ambient temperatures of ca 20 °C. The time constants for the gelation process decrease as the temperature is increased indicating that the gelation is a thermally activated process.
NMR Studies of Solvent Dynamics in High Solids Alumina Slurries
Authors: Parker Anthony A. , Wilhelmy Deborah M. , Daunch William 
Published: March 2011

AbstractSolid state 13C NMR techniques have been used to study the mobility of both toluene and ethanol in slurries containing 70% alumina by weight. A comparison of relative signal intensities from cross polarization experiments, and from single excitation experiments under static conditions (no sample spinning) shows that a portion of the solvent molecules are immobilized with “solid” characteristics, while a majority of the molecules exist in mobile or “liquid” like environments. The immobilized solvent is rigid enough to cross polarize with protons, and hence it is characterized by long correlation times, and by a high viscosity. The remainder of the solvent is too mobile to cross polarize, and hence it is characterized by a lower viscosity. The results suggest that solvent is partitioned with the most viscous components being bound near the particle surfaces. These experiments and calculations will be discussed along with the implied effects of solvent partitioning on bulk rheological behavior.
Coarsening of a Quiescent Electrorheological Fluid I: Experiment
Authors: Martin James E. , Odinek Judy , Halsey Thomas C. 
Published: March 2011

AbstractWe report a real-time, two-dimensional light scattering study of the evolution of structure in a concentrated electrorheological fluid during the ‘liquid-solid’ phase transition. We find that after particle chaining along the electric field lines, strong light scattering lobes appear at a finite scattering wavevector q orthogonal to the field lines, and then brighten as they move to q=0. This indicates the existence of an unstable concentration fluctuation that signifies the segregation of chains into columns. In fact, the observed growth kinetics of the characteristic length, as well as the form of the structure factor, are qualitatively similar to two-dimensional spinodal decomposition in a system with a conserved order parameter.
Shear-Induced Structural Changes Observed in Concentrated Suspensions of Binary Blends of Fluorescent Particles of Differing Size and Color
Authors: Jansma J. B. , Qutubuddin S. 
Published: March 2011

AbstractShear-induced structural changes were observed in suspensions of binary blends of fluorescent particles of differing size and color. Median particle size ranged from 8.3 to 13.7 microns for the nearly spherical fluorescent particles. Concentrated aqueous suspensions were studied under shear flow in a Couette fixture modified to accommodate a fused silica cup. The color of the fluorescent particle blends was observed through the cup wall using photometric methods. Suspension color near the cup wall depended upon shear rate. A color shift occurred near the shear thinning to shear thickening transition. With increasing shear rate, the color contribution from the larger particles increased as the thickening transition occurred. Draining films of these suspensions on a flat fused silica plate were also studied using photometric readings from both the free surface and through the silica plate. Color measurements indicated highly non-uniform particle size distributions within the draining films, which varied with drain time.
Shear Thinning Properties of Dense Suspensions: Rheology and Flow Dichroism
Authors: Bender Jonathan W. , Wagner Norman J. 
Published: March 2011

AbstractAn expression relating dichroism to the non-equilibrium structure was derived through Rayleigh-Gans light scattering theory. Comparison of this expression to a micromechanical expression for the thermodynamic contribution to the total stress demonstrates a stress-optical relationship. Optical dichroism and viscosity measurements on monodisperse, near hard-sphere suspensions as a function of shear rate, volume fraction, and particle size demonstrated the relationship experimentally. This work provides a rheo-optical method for determining the various contributions of the colloidal forces to the overall stress.
Nuclear Magnetiic Resonance Imaging (NMRI) of Flow-Induced Microstructure of Concentratied Suspensions
Authors: Chow A. W. , Sinton S. W. , Iwamiya J. H. 
Published: March 2011

AbstractThe application of nuclear magnetic resonance flow imaging (NMRI) to the study of Couette and falling-ball viscometry of solid/liquid suspensions is described. The suspension consisted of non-Brownian, monodisperse, neutrally-buoyant spheres of 50 vol%. NMRI data demonstrated flow-induced changes in the particle distribution in the suspension that strongly influence the accuracy in viscosity measurements using these flow geometries. In Couette flow, direct correlation between stress measurements and particle concentrations at various locations in the flow cell as a function of shear strain can be made. Our data directly confitrm the shearinduced particle migration theory proposed by Leighton and Acrivos.[1] In the falling-ball experiments, increased particle concentration at the leading edge and decreased concentration at the trailing edge of the ball was observed when the falling ball is big compared to the cylinder containing the suspension. This change in particle distribution can be directly related to the changes in fall velocity of the ball as a function of position in the cylinder.
Laser Fabrication of Micron-Size Structures on CdS
Authors: Daneu V. , Peers J. , Sanchez A. 
Published: March 2011

ABSTRACTWet and dry laser-etching experiments have been performed on polished CdS crystals, using a CW Ar laser, with the goal of writing patterns with μm linewidth. A nitric acid solution was found to exhibit no appreciable dark etching and high photoetching rate; surface roughening due to scattered light was its limitation. A dry, low-temperature (< 200°C) laser-etching process was also studied, and used to produce satisfactory line patterns with 1- to 5-μm linewidths and a 3:1 depth ratio.
Photoenhancement of Gas-Solid Reactions by Surface Excitation
Authors: Ashby Carol I. H. 
Published: March 2011

ABSTRACTUltraviolet irradiation of the surface of graphite leads to the enhancement of the reaction of graphite with hydrogen to form methane under conditions where photo-induced thermal effects are negligible. Wavelength dependence of the photoenhancement correlates with excitation of the π-valence to π-conduction transition of graphite centered at 260 nm. Subsequent formation of some reactive excited state species leads to enhanced reaction rates. Likely candidates for such reactive species have been identified by comparative kinetic studies of the thermal and the photoenhanced reactions. For example, at low temperatures (< 500 K), the rate-limiting step of the thermal reaction is addition of H to surface CH3 groups, and the observed photoenhancement can be explained by activation of these CH3 groups.
Local Crystal Orientation in Laser Annealed Silicon Using a Raman Microprobe
Authors: Farrow L. A. , Hopkins J.B. , Fisanick G J 
Published: March 2011

ABSTRACTIn this paper, we discuss the application of polarization selective Raman microprobe spectroscopy to the detailed, non-destructive analysis of the local crystal orientation of a polysilicon sample grown over SiO 2 pads and laser annealed. Intensity measurements taken as a function of input polarization angle are fit to an expression derived from the Raman scattering selection rules to calculate the angles by which the crystal structure is twisted within the original substrate plane, as well as the degree of tipping of the crystal plane away from the plane of the Si substrate. The results give some indication as to the direction of seeding during recrystallization.
Gas Phase Spectroscopy of a Ge Film LCVD Reactor
Authors: Osmundsen J. F. , Abele C. C. , Eden J. G. 
Published: March 2011

ABSTRACTThe gas phase photochemistry of an LCVD reactor used to grow polycrystalline Ge films was studied by absorption and emission spectroscopy. Upon photodissociating GeH4 (5% in an Ar or He carrier) at 248 nm (KrF laser), excited states of Ge and GeH are produced. Spatially, spectrally and temporally resolved atomic and molecular emissions are monitored as a function of gas pressure and laser intensity. These data lead to the conclusion that GeH2 is predominantly produced directly from GeH4 by The simultaneous absorption of two 5 eV (λ = 248 nm) photons.
Laser-Induced Fluorescence Detection of Diatomic Products of Reactive Ion Etching: SiN, SiO, and SiF
Authors: Walkup R. , Avouris Ph. , Dreyfus R.W. , Jasinski J.M. , Selwyn G.S. 
Published: March 2011

ABSTRACTLaser-induced fluorescence is used to detect a variety of silicon-containing diatomic radicals produced by the reactive ion etching and glow discharge sputtering of silicon and its oxide and nitride. The products include SiN, SiO, and SiF. Examination of the concentration of these molecules as a function of plasma conditions provides information about their production mechanisms.
Study of Photo-Induced Thin Film Growth on Cds Substrates.*
Authors: Arnone C. , Call' C. , Riva-Sanseverino S. 
Published: March 2011

ABSTRACTPhoto-induced growth of ZnS on CdS has been studied using amorphous (thin film) and single-crystal substrates. The effect has been found to occur for light of wavelength shorter than the CdS absorption edge; a maximum light-induced thickness enhancement of 700 Å has been obtained for the ZnS film, with a growth rate of 2000 Å/min. The lightinduced growth, with its observed “memory” of several minutes is consistent with photo-desorption of an adlayer.
Electromagnetically-Induced Surface Microstructures and Enhanced Field Effects in Laser Processing
Authors: Brueck S. R. J. , Ehrlich D. J. , Murphy D. V. , Tsao J. Y. 
Published: March 2011

ABSTRACTThe presence of microstructures on surfaces undergoing laser processing modifies the electromagnetic boundary conditions and can lead to dramatic changes in the intensity of the local electromagnetic fields and hence in the reaction rates and final morphologies resulting from the laser reaction. Examples are presented for periodic structures on planar surfaces — the rippling of Ag surfaces during laser oxidation; and for isolated dielectric structures — enhanced scattering (∼ 100x) due to dipolar resonances in Si particles.
Complete Fabrication of Bipolar Devices in Silicon
Authors: Lloyd M. L. , Ibbs K. G. 
Published: March 2011

ABSTRACTUV laser photochemical doping offers the possibility of direct fabrication of semiconductor devices by high-intensity photolithographic projection. We have recently demonstrated control of parameters such as dopant concentration and junction depth to the extent that npn structures can be readily produced.Recent work also indicates that contact resistance can be dramatically reduced from the levels found using simple probes, by the low-temperature laser deposition of metals, and that this technique also can be used to connect elements in a circuit.In this paper the progress made towards the fabrication of complete planar devices is described and the I-V characteristics of some simple diodes are shown.
Resonance Fluorescence and Photon Trapping of Two Atoms on a Metallic Surface
Authors: Huang Xi-Yi , Liu K. C. , George Thomas F. 
Published: March 2011

ABSTRACTSurface-dressed optical Bloch equations are derived for the purpose of evaluating the resonance fluorescence spectrum of two interacting identical atoms near or adsorbed on a metal surface. The derivation takes into account the influence of reflected photons, dephasing due to atomic collisions, the linewidth of the driving laser field and the resonance excitation of surface plasmons. A unique behavior of the surfacemodified fluorescence, not seen in analogous gas cell experiments, is predicted. Under the appropriate circumstance, a photon emitted from one of the two atoms can be trapped by the two-adatom-surface system, and this is studied by means of a theory which treats the atoms and their surface images on the same footing.
Theoretical Aspects of Laser-Induced Periodic Surface Structure Formation
Authors: Hutchinson Michael , Lee Ki-Tung , Murphy William C. , Beri A. C. , George Thomas F. 
Published: March 2011

ABSTRACTLaser-induced periodic pattern formation has been observed on a variety of substances. In particular, low-power lasers have been used to deposit a pattern on a metal surface. For a relatively smooth surface grating, this pattern can be explained in terms of a perturbative solution of Maxwell's equations. However, as the surface grating is enhanced by this initial deposition, the perturbative solution breaks down. An alternate non-perturbative solution of Maxwell's equations for such rough surfaces is considered here.
The Influence of Laser Radiation on an Absorbing Aerosol
Authors: Morse T.F. , DiGiovanni D. , Cipolla J.W. 
Published: March 2011

ABSTRACTWhen aerosol particles are immersed in a gas in which a temperature gradient is present, a force proportional to this gradient moves these particles toward the lower temperature. This is the thermophoretic force.It is responsible for the deposition of aerosol particles in processes employed in the manufacture of gradient index silicon dioxide, germanium dioxide optical fiber preforms.The deposition efficiency is approximately 50%, and in order to increase this efficiency, we have examined the interaction of an absorbing silicon dioxide aerosol with carbon dioxide laser radiation.The resulting temperature profile mirrors the intensity distribution, since the aerosol temperature is proportional to the local laser intensity.The absorbed radiation thus creates a temperature gradient that results in additional thermophoretic and convective motion. A simple model of laser-induced buoyant convection and thermophoresis is presented, and it is shown how deposition efficiency can be increased with laser radiation.Theoretical and preliminary experimental results are discussed.
Chemical Vapor Deposition of Silicon Films by Pulsed CO2 Laser Irradiaton of Silane
Authors: Pauleau Y. , Stawski R. , Lami Ph. , Auvert G. 
Published: March 2011

ABSTRACTSilane molecules have been irradiated by a pulsed CO2 laser operating at 10.59 μm. The threshold of silicon formation by homogeneous dissociation of silane has been investigated as a function of laser fluence (0.1–3.5 J/cm2) and silane pressure (1–100 Torr). Silicon films have been deposited on quartz substrates using the laser beam either perpendicular or parallel to the substrate surface. The crystallographic structure and deposition rate of these silicon films are found to be dependent on the incident angle of the laser beam, silane pressure, substrate temperature and laser fluence. The growth mechanism of these films is discussed.
Temperature Distributions in CW Laser Induced Pyrolytic Deposition
Authors: Piglmayer Klaus , Doppelbauer Josef , BÄuerle Dieter 
Published: March 2011

ABSTRACTTemperature distributions induced by cw laser radiation absorbed on the surface of combined structures, consisting of discs or of stripes on semi - infinite plane substrates, are calculated for different material parameters and different geometries. The relevance of the numerical results is demonstrated by comparison with earlier experimental data obtained in pyrolytic laser-induced chemical vapor deposition.
Laser-Induced Chemical Vapor Deposition of Silicon Nitride Films
Authors: West Gary A. , Gupta Arunava 
Published: March 2011

ABSTRACTFilms of silicon nitride have been deposited using a continuous wave CO2 laser to excite gaseous mixtures of silane and ammonia. A typical deposition rate is 150Å/min. The hydrogen film content and its dependence on the substrate deposition temperature are similar to that observed for plasma CVD silicon nitride. The CO2 laser CVD films are silicon rich with a Si/N ratio = 1.2 at a NH3/SiH4 gas flow ratio of 1000. Conformal step coverage is observed on patterned silicon oxide features.
Beam-Assisted CVD of Microelectronic Films
Authors: Emery K. A. , Thompson L. R. , Bishop D. , Zarnani H. , Boyer P. K. , Moore C. A. , Rocca J. J. , Collins G. J. 
Published: March 2011

ABSTRACTThe properties of SiO2 and Si3 N4 films deposited by an ArF excimer laser, glow discharge electron beam and conventional plasma-enhanced CVD are compared. The deposition apparatus, technique, and conditions in addition to the physical, chemical and electrical properties of the films are discussed.
Silicon CVD by Twin-Beam Processing
Authors: David Binnie T. , Colles M. J. , Wilson J. I. B. , West J. 
Published: March 2011

ABSTRACTThe technique of simultaneous twin-beam processing has been investigated and used to deposit thin films of silicon on a silicon substrate.An argon ion laser was used to create a large concentration of free carriers in the Si conduction band. These carriers were spatially localized in the beam spot on the surface of the substrate. The effective absorption coefficient of 10.6 radiation (carbon dioxide laser) can thus be increased to greater than 104 cm−1 . Experimental evidence illustrates that this efficient coupling of the high-power CO2 radiation (10–30 W) to the otherwise non-absorbing silicon can be totally controlled by the low-power (1–4 W) argon ion incident beam. The difference between absorption increase due to optically created carriers and thermally created carriers is clearly illustrated.This synergistic effect has been used to induce pyrolytic deposition of Si from SiH4 non-flowing gas onto a Si substrate. Lines and spots of various widths and thicknesses have been grown by the controlling low-power argon ion beam spot.Preliminary investigations on the quality of the deposits using i.r. spectroscopy ellipsometry, SEM and Auger analysis have been carried out.
Molecular Simulation of Adsorption of Simple Gases in Aluminophosphates and Pillared Clays
Authors: Cracknell Roger , Koh Carolyn A , Thompson Stephen M , Gubbins Keith E 
Published: March 2011

AbstractWe report Grand Canonical Monte Carlo (GCMC) simulation studies of the adsorption and heat of adsorption of simple inert gases in two model microporous materials: aluminophosphates (AℓPO4-5, AℓPO4-8 and VPI-5) and alumina-pillared clays. The intermolecular potentials are spherical Lennard-Jones for both the fluid-fluid and fluid-solid interactions; both structured and structureless walls are considered. For argon in VPI-5 and AℓPO4-5 we find qualitative agreement with experiment, but the predicted maximum adsorption is about 20% higher than that obtained experimentally; possible reasons for this discrepancy are discussed. For the pillared clays we find a first order phase transition below some critical pillar density. This finding seems to be in qualitative agreement with existing experimental data.
Confinement Between Rough Substrates: Fluctuation-Induced Forces, and Other Manifestations
Authors: Kardar Mehran , Li Hao 
Published: March 2011

AbstractMost surfaces are rough. In many cases the roughness is self-affine, with a width w that scales with the observation length L as w ∼ LC. We consider the medium confined between two such plates, and discuss how the dependence of various quantities on the separation of plates is modified by their roughness. Specific examples include fluctuation–induced forces, shifts in critical temperatures, and capacitance.
Dielectriic Dispersion Measurements of Salt-Water Saturated Porous Glass Compared with Local Porosity Theory.
Authors: Hansen B. D. , Haslund E. , Hilfer R. , NØst B. 
Published: March 2011

AbstractA recent study [1] of the dielectric frequency response of a two component composite performed on a single specimen shows that local porosity theory LPT [2] represents a substantial improvement compared with other theories predicting the complex dielectric dispersion [3,4,5]. The purpose of the present work is to extend this investigation to a systematic study on several specimens with different compositions.
Directed Polymers in Restricted Geometries
Authors: Zumofens G. , Klafter J. , Blumen A. 
Published: March 2011

AbstractWe study numerically directed polymers in random potential fields for one-dimensional and fractal substrates. For fractal substrates the time evolution of the mean transverse fluctuations depends besides on the randomness of the potential also on the fractal nature of the substrate. The two effects enter in a subordinated way, i.e. the corresponding characteristic exponents due to the potential and the substrate combine multiplicatively. For a one-dimensional substrate the propagator P(x, t), the probability distribution of the transverse displacement x(t), follows the scaling form P(x, t) ∼ 〈x2(t)〉-1/2f (ξ), where ξ is the scaling variable ξ = x/〈x2(t)〉1/2. The numerical results support the scaling function f (ξ) ∼ exp (-cξδ) with δ > 2 which indicates an “enhanced” Gaussian behavior. These results are compared with those of a related “toy model”.
Spatiially Resolved Spectra of Miicro-Crystals and Nano-Aggiregates in Doped Polymers
Authors: Birnbaum Duane , Kook Seong-Keun , Kopelman Raoul 
Published: March 2011

AbstractNear-field optics techniques make it possible to by-pass the optical diffraction limit (“uncertainty principle) and attain spatial resolution of λ/50 or better. We present near-field scanning optical spectroscopy (NSOS) data on α and ß mixed micro-crystals of perylene and on various aggregates of tetracene doped into PMMA. The spatial resolution is limited by the size of the scanning photon tip and its distance from the sample. We use nanofabricated optical fiber tips (aluminum coated) that are as small as 100 nm. These can be piezoelectrically scanned close to the sample. Fluorescence spectra easily differentiate between adjoining microcrystallites of α and β perylene, giving spectra identical with those of large (>1 cm) single crystals. The apparently homogeneous molecularly doped polymer samples of tetracene/PMMA have regions that fluoresce anywhere between green and red. Thus the spatially resolved spectra are much sharper and more detailed than the broad and featureless bulk spectra. The different emission spectra are attributed to different aggregates of the tetracene guest embedded in the PMMA host