bluuebunny/crossref_metadata_2025_split huggingface dataset:
Laser Diagnostics for Investigation of Particle Formation Processes
Authors: Semerjian H. G. , Zachariah M. R. , Presser C. 
Published: March 2011

AbstractFormation, growth and deposition of particles represent a critical part of several important industrial processes, such as production of carbon black, optical fibers, micro-electronic components, and metal and ceramic powders. Laser diagnostic techniques are utilized to develop a fundamental understanding of these processes.Formation of carbonaceous soot particles has been studied in laminar, coannular, hydrocarbon diffusion flames. Laser extinction/scattering, laser scattering dissymmetry, and velocimetry measurements have been used to determine particle volume fraction, size, number density and velocity. From this set of data, particle formation and growth rates have been determined for different fuels and at different temperatures. Similar techniques have been used to study silica particle formation in an opposed jet diffusion flame, where silicon is introduced in the form of silane (SiH4) into the fuel stream (H2/Ar); the oxidant is an O2/Ar mixture. The advantage of this geometry is that, along the stagnation point streamline, the flow may be considered one-dimensional. This should allow the extension of the results of this study to practical CVD or MCVD processes for optical fibers. Laser diagnostic techniques are also being used to investigate metal powder atomization processes, and the effect of operating conditions on particle size distribution.
Optical Measurements of Soot Particles in Flames
Authors: Santoro Robert J. 
Published: March 2011

AbstractThe formation and growth of soot particles in combustion systems represents an area of significant research interest. Critical to progress in this area has been the development of suitable optical diagnostic techniques. Principal among these has been the utilization of laser light scattering techniques to obtain particle size and concentration information. When combined with measurements of other quantities such as the velocity, the resulting spatially and temporally resolved measurements can be used to examine particle processes such as coagulation and surface growth. In the present work, the results from studies conducted in laminar diffusion flames involving laser based measurements of the soot particle and velocity fields are reviewed. As an example of the utility of such an approach, these results are used to examine the evolution of the particle surface area for a series of simple hydrocarbon fuels. The results indicate that the available surface area varies strongly with the fuel molecular structure. However, the specific surface growth rate is observed to be similar for all the fuels studied.
High Sensitivity Measurement of Flame Radicals by Frequency Modulation Spectroscopy
Authors: Woody Bernard A. 
Published: March 2011

AbstractFrequency modulation spectroscopy (FMS) is a new combination of optical absorption spectroscopy and radio technology which increases absorption sensitivity by orders of magnitude. Extremely weak atomic and molecular lines and stronger absorbers at low number densities, previously accessible only to fluorescence techniques, are readily detected.Information obtainable through FMS include species number density, lineshape and temperature. Data interpretation is straightforward without regard to such problems as quenching, alternate excited state reaction channel loss and source/absorber solid angle and spectral response calibration, since the technique probes the lower state population via line of sight, volume integration. Application of the technique to the study of radical species such as CH, CN, and NO2 produced in flames and low pressure reactor vessels has made absorption studies of these systems feasible for the first time. The technique has also been used to study such diverse problems as the effect of fuel additives on the production of soot, and the concentration and distribution of the chemical intermediates, BH, BO, and BO2, in microwave driven reactive flows. Feasibility studies to determine if FMS can assist in the diagnostic and control problems of chemical vapor deposition in the semiconductor industry have recently been initiated.
Laser-Induced Fluorescence Measurement of Free Radical Intermediates
Authors: Crosley David R. 
Published: March 2011

AbstractLaser-induced fluorescence (LIF) provides a means for sensitive, selective and nonintrusive measurements of reactive intermediates, often free radicals, which control the chemistry of combustion. The same approach can be used to detect in the gas phase, atoms, radicals and ions which are reactive intermediates in materials processing. This article briefly examines the use of LIF in combustion. It includes a description of the LIF spectroscopic method as employed for quantitative measurements, and the use of LIF in a semiquantitative manner with extension to the simultaneous detection of more than one species.
Optical Methods for Plasma Edge Diagnostics in Magnetic Confinement Experiments
Authors: Hintz E. , Bogen P. 
Published: March 2011

AbstractThe radial extension of the plasma edge being determined by the ionisation length of the atomic hydrogen, the rtanges of the main plasma parameters to be covered are: 1010 cm-3 < ne <. 1013cm-3 5 eV < Te- < 100 eV, density of neutral particles below 1010 cm-3. Physical quantities to be measured are the electron density ne and temperature Te, the density and temperature (velocity distribution) of hydrogen and of the main impurities (oxygen, carbon, metals). Relying mainly on emission spectroscopy, laser induced fluorescence and atomic beam methods, most of these quantities can be determined with the desired space and time resolution. Experimental arrangements will be described and typical results will be presented.
Self Bias of an R.F. Driven Probe in an R.F. Plasma
Authors: Benjamin N M P , Braithwaite N St J , Allen J E 
Published: March 2011

AbstractAn effect of sinusoidal r.f. voltages between a plasma and a floating Langmuir probe (or other electrode) is to produce a d.c. self bias voltage. This effect has previously been studied with r.f. applied to probes in d.c. plasmas, and the results have often been referred to in connection with d.c. probes in r.f. plasmas, although the situation is slightly different. In the current work a ‘d.c.’ probe in an r.f. plasma is examined. However, the r.f. potential difference between probe and plasma is first compensated for by superimposing a synchronous signal of appropriate amplitude and phase on to the d.c. circuit. Thus the probe can perform essentially d.c. type measurements on the r.f. plasma. The deliberate reintroduction of a measure of r.f. between probe and plasma is accomplished by overdriving the compensation signal thereby generating a controlled amount of self bias.The observed variation of probe bias with r.f. overdrive is in good agreement with analytic theory based upon modified Bessel functions as used for d.c. generated plasmas. This work is of general interest in probe diagnostics of r.f. generated plasmas, and understanding the self bias of isolated electrodes.
Optical Imaging Diagnostics for Fusion Plasmas
Authors: Allen S. L. 
Published: March 2011

AbstractImaging diagnostics are used for spatially-and temporally-resolved quantitative measurements of plasma properties such as the ionization particle source, particle and energy loss, and impurity radiation in magnetically confined fusion plasmas. Diagnostics equipped with multi-element solid-state detectors (often with image intensifiers) are well suited to the environment of large fusion machines with high magnetic fields and x-ray and neutron fluxes. We have used both conventional (16 ms/frame) and highspeed video cameras to measure neutral deuterium Hα, (6563 Å) emissions from fusion plasmas. Continuous high-speed measurements are made with video cameras operating at 0.1–0.5 ms/frame; gated cameras provide snapshots of 10–100 μs during each 16-ms video frame. Digital data acquisition and absolute intensity calibrations of the cameras enable detailed quantitative source measurements; these are extremely important in determining the particle balance of the plasma. In a linear confinement device, radial transport can be determined from the total particle balance. In a toroidal confinement device, the details of particle recycling can be determined. Optical imaging in other regions of the spectrum are also important, particularly for the divertor region of large tokamaks. Absolutely calibrated infrared cameras have been used to image the temperature changes in the walls and thereby determine the heat flux. Absolutely calibrated imaging ultraviolet spectrometers measure impurity concentrations; both spatial and spectral imaging instruments are employed. Representative data from each of these diagnostic systems will be presented.
Spectroscopic Study and Amorphous Film Deposition in RF and Pulsed Plasma Processings
Authors: Ebihara Kenji , Kanazawa Seiji , Maeda Sadao 
Published: March 2011

AbstractProcessing plasmas generated by three types of discharges are diagnosed spectroscopically in order to estimate the quantitative relationship between plasma parameters and electrical and optical properties of deposited materials. An rf discharge is capacitively produced by a 13.56 MHz rf oscillator. A microwave generator operating at 2.45 GHz is used to supply power to a discharge cavity. Further a pulsed plasma which is inductively generated by pulsed current ( 70 kA peak ) is applied to study dissociation process in the transient plasma and possibility of a novel processing system. The gases used are methane for amorphous carbon formation and silane for amorphous silicon deposition. Measurements of optical emission spectrum are performed to estimate the processing plasma state by the relative spectral intensity method and the Doppler-broadening method.
The Effect of Ar+ Ion Implantation on the Impact-Abrasive Wear Property of Cu-Polyimide System
Authors: Koh S. K. , Pae K. D. 
Published: March 2011

AbstractA thin Cu film(400 Å) was deposited on a smooth polyimide(PI) substrate. Ar+ ion implantation onto the Cu/PI film has been shown to mix Cu and PI and to modify the impact-abrasive wear property. Ar+ ions with energies of 200 keV, and dosage between 1015 to 4×1016 ions/cm2 were used. The surface analyses were carried out with RBS, X-ray and Optical Microscope. The wear properties of the Cu-PI system were determined by a newly constructed Impact-Abrasive Wear Tester. An X-ray diffraction study shows an increase in Cu( 111 )peak with Ar+ ion dosage. The wear property was found to be a function of ion energy, ion dosage, crystallinity of Cu, the amount of mixing of Cu and PI, and the damage of PI substrate due to ion implantation.
On the Adhesion of LPCVD WSi2 to Doped and Undoped Polysilicon
Authors: Shenai K. , Piacente P. A. , Lewis N. , McConnell M. D. , Smith G. A. , Baliga B. J. 
Published: March 2011

AbstractWe report on the adhesion characteristics of Low Pressure Chemical Vapor Deposited (LPCVD) WSi2 to doped and undoped polysilicon when used for fabricating silicon discreie and integrated devices. About 3000Å of silicon rich (Si:W atomic ratio of 2.6) LPCVD WSi2 was deposited on 6 kÅ of polysilicon and annealed in nitriding and oxidizing ambients at various temperatures from 1000°C to 1100°C to lower the sheet resistance. Detailed material analyses of as-deposited and annealed polycides were performed using Auger, SIMS, RBS, TEM, and SEM and electrical conductivities of the films were measured using the four point probe. In some samples, the oxide grown on the silicide film was wet etched prior to implanting and diffusing As corresponding to the source/drain diffusions in power FET's. It was observed that polysilicon doping, WSi2 deposition and annealing, oxide or nitride etching, implantation and diffusion of As - all had significant impact on the grain structures of silicide and polysilicon, adhesion of the silicide film to polysilicon, and the electrical conductivity of the silicide. In samples where the oxide grown on the silicide was wet etched, enhanced grain boundary related oxidation of the silicide and polysilicon and seepage of the wet etchant through sequential etching of grain boundary oxide resulted in poor adhesion of WSi2 grains to polysilicon and eventual silicide peeloff. This problem was severe in samples which were not implanted with As but subjected to 900°C, 60 min. source drive.
Computer Simulation of Elastic Properties of Grain Boundary Materials
Authors: Wolf D. , Lutsko J. F. 
Published: March 2011

AbstractLattice statics and lattice dyanamics computer simulation methods are applied to investigate the elastic properties of grain boundaries in fcc metals. The elastic constants in the GB reigon are found to differ significantly from their bulk ideal-crystal values. Due to the broken symmetry in the GB region a pronounced anisotropy of the elastic properties is observed. Whereas Young's moduli are found to increase in the GB region, the shear moduli and Poisson's ratios generally decrease. The magnitude of these effects is shown to depend sensitively on the GB structure.
Auger Analysis of a Fiber/Matrix Interface in a Ceramic Matrix Composite
Authors: Honecyt Frank S. , Pepper Stephen V. 
Published: March 2011

AbstractAuger electron spectroscopy (AES) with depth profiling was used to characterize the fiber/matrix interface of SIC fiber, reaction bonded Si3N4 matrix composite. Depth profiles of the “as received” double coated fiber revealed concentration oscillations which disappeared after annealing the fiber in the environment used to fabricate the composite. After the composite was fractured, the Auger depth profiles indicated that failure occurred in neither the ß-SiC fiber body nor in the Si3N4 matrix but in the fiber coating itself.
Fracture Mechanics of Low Molecular Weight Polymers
Authors: Mikos Antonios G. , Peppas Nikolaos A. 
Published: March 2011

AbstractA novel analysis is presented to explain mechanistic aspects of the fracture of low molecular weight polymers. The fracture energy is calculated as a function of the mean interpenetration distance of a polymer chain which has been derived from the solution of the Fokker-Planck equation. Experimental results with monodisperse polystyrene have been used to validate the theory.
Monocarbide Characterization In Nickel-Base Mc Aligned Eutectics
Authors: Jackson M.R. , Gigliotti M.F.X. , Yang S.W. , Walter J.L. 
Published: March 2011

ABSTRACTIn the aligned Ni-MC eutectic alloys being developed for jet engine blade applications, the fibers are considered to be Tac, Tic, etc. In fact, these fibers will contain Cr, Mo, W and possibly other elements as substitutions for the “M” constituent, and often will not be stoichiometric. Quantitative chemical analysis of fibers is difficult because of their size. However, lattice parameter measurements can be used to learn much a out the carbide chemistry and stoichiometry. Results will be described in detail for fibers extracted from simple Ni-TaC, Ni,Cr-TaC and Ni,Cr,AI-Tac systems. In addition, experiments on mixed (Ta,V)C and (Ta,Ti)C carbides will be discussed. Carbide lattice parameters can be understood in terms of the free energies of formation of the various carbides.
Selective Etching and Laser Melting Studies of Monotectic Composite Structures
Authors: Angers L. M. , Grugel R. N. , Hellawell A. , Draper C. W. 
Published: March 2011

Thin slices of directionally solidified, fibrous composite, monotectic alloy samples have been selectively etched to remove the fibrous phase, so to produce fine sieves of filters having pore diameters ≲10μm. Alloys in systems Al-In, Al-Bi and CuAl-Pb have been examined using as etchants aqueous nitric acid (Al-In, Al-Bi) and aqueous citric acid (CuAl-Pb) without applied anode voltages. These alloys and etchants illustrate examples in which fiber and matrix are attacked to different extents (Al-In), the phase interface is selectively attacked (Al-Bi) or only the fibers are attacked (CuAl-Pb). Hole sizes and perfection are compared for etching times, concentrations and anode voltage.Laser melting of the surface of CuAl-Pb samples has been used to screen or frame areas of the composite microstructure and also shows how local melting of the fibrous Pb phase can be used to assess the heat affected zone.
Microstructural Perturbations in Directionally Solidified Al-In, Al-Bi and Zn-Bi Monotectic Alloys
Authors: Toloui B. , Macleod A. J. , Double D. D. 
Published: March 2011

ABSTRACTStudies have been made of the microstructures developed in directionally solidified monotectic Al-In, Al-Bi and Zn-Bi alloys, as a function of growth velocity and temperature gradient. With increasing growth velocity and decreasing gradient the microstructures show transitions from regular rod-like arrangements of the lower melting point phase, through arrays of aligned droplets to coarse irregular droplet dispersions. Intermediate stages show rods with longitudinal shape perturbations of a classic Rayleigh-type instability. The changes are discussed in terms of oscillatory instabilities at the solid-liquid interface (enhanced by increasing growth velocity and decreasing temperature gradient) coupled with ripening effects in the solid + liquid region behind the interface.
Quantitative Evaluation of the Interfacial Free Energies at A Solid-Liquid Lamellar Eutectic Interface
Authors: Kaukler W. F. , Rutter J. W. 
Published: March 2011

The solid-liquid interfacial free energies of each of the individual phases comprising the eutectic system, Carbon Tetrabromide-Hexachloroethane, were measured as a function of composition using a “grain boundary groove” technique. Thermodynamic data were combined with groove shape measurements made from high resolution optical photomicrographs of the solid-liquid interfaces to give the interfacial free energy data. An interfacial free energy balance at the eutectic trijunction was performed to obtain all the forces acting on that point. The three interphase interfacial free energies at the eutectic trijunctions as well as a solid-solid phase boundary torque were evaluated.It was found that the solid-liquid interfacial free energies of the two phases of the eutectic could be evaluated from photomicrographs of growing or stationary eutectic interfaces. In addition, it was found that for a substantial range of freezing conditions the eutectic interface shape can be predicted from a knowledge of the interfacial free energies alone.
The Quaternary System Fe-Cr-Mn-C and Aligned Ferrous Superalloys
Authors: Lemkey F. D. , Thompson E. R. , Schuster J. C. , Nowotny H. 
Published: March 2011

ABSTRACTA challenge exists for wider application of low cost iron-base alloys in the extreme conditions of high temperature, hot corrosion, and high stress experienced in gas turbine engines. In response to this challenge the constitution of the quaternary, Fe-Cr-Mn-C, and to a lesser extent the quinary, Fe-Cr-Mn-Al-C, systems were examined for in situ composite alloy candidates. Multivariant eutectic compositions, determined from phase equilibria, were directionally solidified to produce aligned composites consisting of M7C3carbides within a gamma iron matrix. The composition and lattice parameters of the carbide and matrix phases were determined to establish their respective stabilities. Stress rupture tests in the direction of phase alignment for certain compositions (e.g., Fe-20 wt% Cr-lO wt% Mn-3.2 wt% C) indicated strength values comparable to cast nickel-base superalloys and exceeded those of the strongest iron-nickel superalloys developed for automotive turbines. Results of cyclic sulfidation testing at 9000 indicated a balance of Cr and Al content to be important to the achievement of outstanding surface stability.
Off-Axis Mechanical Properties of A Cellular Al-Al 3Ni Directionally Solidified Eutectic
Authors: Hetzner Dennis W. , Oliver Ben F. , Becker William T. 
Published: March 2011

ABSTRACTIngots having a cross-sectional area of 1.27 cm × 10.8 cm were directionally solidified for testing off-axis tensile properties. To avoid macroscopic banding due to inductive melting and thermal convection, growth rates of 2.2 cm/min were required. The resulting solidification structures were cellular.The macroscopic tensile behavior of the eutectic alloy was similar to that observed for mechanically formed fiberreinforced composite materials; in particular, three distinct modes of fracture occurred. In Region I, where the angle(ϕ) between the growth direction and the tensile axis was small, the tensile strength of the composite was inversely proportional to cos2 ϕ. In Region II (20° ≤ ϕ ≤ 55°) and Region III (60° ≤ ϕ ≤ 90°), the tensile strength of the composite was inversely proportional to sin ϕ, cosϕ, and sin 2ϕ, respectively.For all regions, failure was initiated by the fracture of large Al3Ni intercellular blades. In Region I, fracture was by a combination of tensile overload on a plane perpendicular to the tensile axis or shear on a plane inclined to the tensile axis at approximately 45°. In Region II, failure was by shear in a plane containing the growth direction and in a direction parallel to the fibers. For Region III, failure was by plane strain constraint with shear perpendicular to the longitudinal axis of the fibers.The fracture of large intercellular Al3Ni blades can be explained by the variation of S13 about the tensile axis, and the corresponding intercellular tensile strains which result. In Region II, metallographic examination of tensile specimens shows a Poisson's ratio effect to be contributing to the strength of the composite; occasionally shear between adjacent cells is observed. By using the yield strengths of specimens having fibers oriented parallel to and perpendicular to the tensile axis, an approximate yield surface can be constructed. This yield surface accurately predicts the transition in failure mode from Region II to Region III.
Processing of Polymeric Precursor, Ceramic Matrix Composites
Authors: Diefendorf R. J. , Boisvert R. P. 
Published: March 2011

AbstractCeramic matrix composites have been produced by utilizing polymer pyrolysis as the processing technique. The precursor, polyvinylsilane, is a viscous, thermosetting polymer which yields a predominantly SiC ceramic material when pyrolyzed. This organometallic polymer in combination with SiC fibers and SiC whiskers was used to fabricate ceramic matrix composites. One of the major problems with a brittle/brittle composite system in which strong coupling exist between the fibers and matrix is the characteristic catastrophic failure that occurs once the strain to failure of one of the constituents is exceeded. This brittle behavior can be altered by the application of a suitable barrier layer between the fiber and matrix. Due to the success of a barrier layer between fiber and matrix in producing higher performance composites, multiple barrier layers were used to further improve the performance of the ceramic composite.
Theoretical Analysis of Chemical Vapor Infiltration in Ceramic/Ceramic Composites
Authors: Tai Nyan-Hwa , Chou Tsu-Wei 
Published: March 2011

AbstractA model for the deposition of alumina and titanium carbide within a ceramic fiber bundle from the chemical reactions has been examined in this paper. The model considers vapor diffusion, chemical reaction on the inner surface of the capillary, deposition film growth, porosity, and effects of reactants composition at various reactor temperature and pressure. Binary, multicomponent diffusion and Knudsen diffusion have been taken into account for the different stages of the CVI process. Furthermore, both diffusion controlled and reaction controlled processes have been examined in order to determine the dominating process in chemical vapor infiltration.