bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies of Flow Fields in Low-Pressure Spraying Plasmas Using Laser Diagnostics
Authors: Hidaka R. , Ohki T. , Takeda J. , Kondo K. , Kanda H. , Muraoka K. , Akazaki M. , Maeda M. , Teshima K. 
Published: March 2011

AbstractIn order to make desirable surface layers by low pressure plasma spraying (LPPS), optimum operating conditions and plasma torch gun designs must be decided upon for understanding LPPS plasma and powder behavior. As the first step of this approach, LPPS plasmas without powders were measured by the Thomson scattering, the Michelson interferometry and a Pitot tube. These diagnostics revealed that LPPS plasma jets may be treated as supersonic neutral gas flows as the first approximation. In addition, the neutral particle temperature Tn and ion temperature Ti were found to be the same as the electron temperature Te, which is 1 eV at an oblique shock wave heating point and 0.2 eV at the sugsequent cooling point. LPPS plasmas and flows were modeled by a computer Simulation of a supersonic nozzle flow, 2nd yielded reasonable understanding of the thermodynamic and fluid-mechanical conditions.
Cars Diagnostics for Combustion and Plasma Processes
Authors: Eckbreth Alan C. , Stufflebeam John H. 
Published: March 2011

AbstractCoherent anti-Stokes Raman spectroscopy (CARS) is a powerful analysis approach for nonintrusive temperature and species measurements in hostile environments. Widely utilized in combustion, it may be able to significantly impact materials processing research. CARS is described and its applications to combustion and plasma process environments are reviewed and contrasted.
High-Speed Photography of Energetic Materials and Components with a Copper Vapor Laser
Authors: Dosser Larry R. , Reed John W. , Stark Margaret A. 
Published: March 2011

AbstractThe evaluation of the properties of energetic materials, such as burn rate and ignition energy, is of primary importance in understanding their reactions and the functioning of devices containing them. One method for recording such information is high-speed photography at rates of up to 20,000 images per second. When a copper vapor laser is synchronized with the camera, laser-illuminated images can be recorded that detail the performance of a material and/or component in a manner never before possible. The laser can also be used for ignition of the energetic material, thus eliminating the need for bridgewires or electric squibs that can interfere with photography. Details of such ignitions are readily observable, and the burn rate of a material can be determined directly from the film. There are indications that information useful for the modeling of pyrotechnic reactions will become available as well. Recent results from high-speed photography of several pyrotechnic materials and devices will be presented.
Development of Laser Diagnostics for Studies of High Temperature Plasmas and Plasma-Surface Interactions
Authors: Muraoka K. , Uchino K. , Kajiwara T. , Matsuo K. , Matsuda Y. , Kim H. , Maeda M. , Okada T. , Honda C. , Akazaki M. 
Published: March 2011

AbstractThe developments of the laser diagnostics at Kyushu University for studies of high temperature plasmas and plasma-surface interactions are reviewed, followed by the recent results and future plans.
Ion Current, Energy Distribution, and Radical Species Detection in RF Plasmas by Cylindrical Mirror Analyzer Quadrupole Mass Spectroscopy
Authors: Greene Wayne M. , Hartney Mark A. , Hess Dennis W. , Oldham William G. 
Published: March 2011

AbstractMass spectroscopy has been used to diagnose plasma processing atmospheres by detailing the flux of neutral and ion species and the energy distribution of ions impinging upon a substrate immersed in a glow discharge. The institution of a diagnostic tool to investigate the chemical (reactive neutral) and physical (ion) aspects involved in plasma processing is necessary to improve control and reliability in thin film materials processing. Research has focussed on ion-enhanced etching of tungsten thin films in NF3/O2 and the deposition of tungsten by the reaction of WF6 and H2 in rf glow discharge reactions.
Diagnostic Techniques for PACVD Systems for Depositing Protective Coatings
Authors: Roman Ward C. , Stufflebeam John H. , Eckbreth Alan C. 
Published: March 2011

AbstractPACVD techniques for depositing protective coatings are an emerging field in plasma processing technology. Technology transfer is limited by a lack of understanding of the basic mechanisms involved in the gas phase plasma chemistry. The aspects of plasma species concentration and distribution and plasma gas temperature are fragmentary and unclear. Laser diagnostic techniques represent a critical starting point for providing some of this needed information. The techniques are in-situ, nonintrusive, and give excellent spatial and temporal resolution. Numerous diagnostic techniques for detailed coating characterization are available, but a correlation of the PACVD parameters with some of the key coating properties is required. Thus, a predictive capability that is lacking in the present science base can be established together with important phenomenological aspects needed for efficient deposition of high quality protective coatings. As the mechanisms become better understood, use of remote sensors and A.I may then be introduced. This paper will review selected diagnostic techniques available for characterizing these nonequilibrium reactive plasmas and the coatings.
Thin Film Adhesion to Ion Bombarded Surfaces
Authors: Ingemarsson P. Anders , Tombrello T. A. 
Published: March 2011

AbstractWe report on the use of 20 MeV C14+ ion beams for pre-irradiation of Si, SiO2 and Al2O3 surfaces with resulting alterations in the adhesion of subsequently deposited Au and Ag thin films. The effect does not follow the same pattern for Au and Ag films, nor is there a simple correlation to the previously observed adhesion effect induced by ion irradiation after film deposition. Possible mechanisms, both for pre-irradiation and post-irradiation effects, are discussed, as is the importance of chemical structures with respect to interfacial bond strength.
Photo-Chemical Changes of Aluminium Films on Silicon
Authors: Kellock A. J. , Williams J. S. , Nyberg G. L. , Liesegang J. 
Published: March 2011

AbstractX-ray Photoelectron Spectroscopy and Rutherford Backscattering Spectroscopy with channeling are employed to study surface and interface changes resulting from irradiation of thin Al films on Si-SiO2 substrates using < 6eV visible photons. Results indicati that surface oxidation and bonding rearrangements at the Al-SiO2-Si interface can take place at room temperature under photon bombardment. These changes are correlated with enhanced adhesion and modification of film etch properties which are also a result of photon irradiation.
Gallium Arsenide and Silicon Optical Assemblies: An Advanced Glass-Polymer-Semiconductor Adhesion Process
Authors: Vendura George J. 
Published: March 2011

AbstractA simple adhesion process has been developed for applying glass lenses to the active surfaces of Si and GaAs optical devices such as detectors and solar cells [1]. The method, which uses a film of fluorinated ethylene propylene (FEP) offers reliability, cost and throughput advantages over the conventional dimethyl silicone adhesive. Critical to the process is the ion bombardment of individual surfaces before assembly. The resulting enhanced adhesion suggests some modification of surface properties. Four possible mechanisms are briefly discussed. The technique is believed to have broad applicability to amorphous and crystalline semiconductor systems and devices other than those under test.
The Influence of Alloy Chemistry on Controlling Fiber Volume Fraction in Ni-Base Mc Aligned Eutectics
Authors: Jackson M. R. , Walter J. L. 
Published: March 2011

ABSTRACTFor the Ni-base TaC eutectics, it has been shown previously that carbide volume fraction is a strong function of Ta/C ratio. Now in a number of Ni,Cr-TaC and Ni,Cr,Al-TaC alloys, Cr has been observed to have only a small influence on volume fraction of carbide, while Al has a major influence acting to decrease the volume fraction. The Al present in the matrix causes the phase equilibrium to approach that of a much greater Ta/C ratio. This analysis has been extended to more complex NiTaC alloys as well. For the simple Ni-Cr-Ta-C alloys, creep behavior has been studied as a function of volume fraction of carbide.Other carbide systems have been evaluated as well, including TiC and NbC. A general understanding of volume fraction differences between these systems and TaC can be reached by consideration of ideal solution behavior and the appropriate phase diagrams.
Feasibility Of Directional Solidification Of Lanthanum Hexaboride In a Boron Matrix
Authors: Logan Kathryn V. 
Published: March 2011

Attempts were made to directionally solidify lanthanum hexaboride as uniformly spaced rods, less than one micron in diameter, in a boron matrix. Lanthanum hexaboride and boron powders were combined in a near eutectic mixture, formed into right circular cylinders and melted by RF induction heating in a pure hydrogen atmosphere using a modified internal zone melting technique.Ball milling, uniaxial cold pressing, isostatic pressing and hot pressing were investigated as possible means of increasing the sample density before melting in the RF induction furnace. RF coupling was achieved directly in the hot pressed pellet, and indirectly through the use of a molybdenum preheater in the uniaxially cold pressed pellets. Internal zone melting and conventional crucible melting in various materials were tried.Directional growth was observed in the pellets that were uniaxially cold pressed and preheated with a molybdenum tube sleeve. Lanthanum hexaboride fibers with an ℓ/d ratio of about ten to one and other forms of aligned microstructures were observed in selected areas of the pellet.
The Long Term Structural Stability of the Eutectic Composites Cd-Zn and Pb-Cd
Authors: Delamore G.D. , Van De Merwe R.W. , Dunne D.P. , Smith R.W. 
Published: March 2011

ABSTRACTIt is shown that marked microstructural coarsening can occur when eutectic composites are exposed for relatively short periods to temperatures approaching 0.9 TM (where TM is the eutectic melting temperature in °K). Less well known and, perhaps, of more practical importance, are the microstructural changes and consequent changes in properties which result from prolonged exposure at 'safe' operating temperatures, e.g. 0.5 Tm.Cd-Zn and Pb-Cd eutectic specimens of various thermal histories were examined immediately on preparation and subsequently re-examined after storage at ambient laboratory temperatures for up to 1000 days. In general, microstructural changes from the as-grown and heat-treated conditions were observed. In some cases for the Pb-Cd alloy this consisted of only slight thickening of the already coarse larnellae terminations. However, in the more rapidly frozen, and therefore microstructurally finer, specimens marked discontinuous coarsening was observed, but confined to eutectic-cell-wall regions. There the coarse precipitates grew at many angles, including being perpendicular to the eutectic habit plane but were not separated by any well-defined large angle grain boundaries.It was concluded that high temperature degradation occurs mainly by continuous coarsening, whereas at lowtemperatures, microstructural changes are effected mainly by discontinuous coarsening.
Off-Axis Tensile Properties of γ/γ'-αMo Ds Eutectic
Authors: Hu Z. Q. , Zhang J. H. , Xu Y. B. , Zhang Z. Y. , Zhang Y. S. , Tang Y. J. 
Published: March 2011

ABSTRACTThis paper reports a study of off-axis tensile properties of γ/γ'-αMo Ds eutectic and the dynamic fracture process directly observed with a scanning electron microscope. If the loading direction deviates from the Mo fiber growth direction, the tensile strength and ductility decrease gradually. During the loading process, two types of cracking are observed: one is cracking of the fiber, and the other is delamination along the fiber-matrix interface. In plastic deformation, slip can pass through both the matrix and the fiber. As a rule, the thicker fibers are cracked earlier than the thinner ones, because they have less defects and better ductility. Delamination is the main source of final fracture.
The low Cycle Fatigue Behavior of Three advanced
Nickel-Base Eutectic Composites
Authors: Ishii T. , Duquette D. J. , Stoloff N. S. 
Published: March 2011

AbstractThe low cycle fatigue behavior at 25°C and 825°C of three advanced nickel-base eutectics is described. Fatigue lives are shown to obey a linear relation with plastic strain range (Coffin-Manson relation) but lives are much lower than are observed for conventional metals and alloys. Cyclic hardening and softening were observed in each alloy at 25 °C; however, this behavior differs from the classical saturation behavior observed with isotropic materials.
Internal Friction of Cast Graphite-Magnesium Composites
Authors: Armstrong J. H. , Rawal S. P. , Misra M. S. 
Published: March 2011

AbstractInternal friction behavior in cast 8-ply [0°1 P55Gr/Mg-0.6%Zr alloy and P55Gr/Mg-1%Mn composites as a function of vibratory strain amplitude was measured at 80 kHz using a Marxtype piezoelectric composite oscillator. Both the matrix and composite exhibited strain amplitude independent internal friction below ε ≈ 10−6, while significant strain amplitude dependence was noted at higher strain levels. A maxima in damping was observed for most of the specimens tested. Heat treatment to enlarge grain size was found to increase both the strain amplitude independent and dependent internal friction of the composite. Strain amplitude dependence of the internal friction, including the existence of the maxima, was explained by the Granato-Lucke (G-L) dislocation internal friction model. Dislocation densities obtained from various TEM images from the fiber-matrix interface were compared to values predicted by G-L theory.
High-Energy High-Rate Processing of High-Temperature Metal-Matrix Composites
Authors: Persad C. , Raghunathan S. , Lee B.-H. , Bourell D. L. , Eliezer Z. , Marcus H. L. 
Published: March 2011

AbstractAdvances in kinetic energy storage devices have opened up a new approach to powder processing of High Temperature Composites. The processing consists of internal heating of a customized powder blend by a fast electrical discharge of a homopolar generator. The high-energy high-rate “lMJ in 1s” pulse permits rapid heating of a conducting powder in a cold wall die. This short time at temperature approach offers the opportunity to control phase transformations and the degree of microstructural coarsening not readily possible using standard powder processing approaches. This paper will describe the consolidation results of two high temperature composite materials, (W-Ni-Fe)/B4C and (Ti3Al+Nb)/SiC. The focus of this study was the identification of the reaction products formed at the matrix/reinforcement interface as a function of input energy and applied stress. Input energies beyond a threshold value for each system were required to produce detectable reaction products. In the (W-Ni-Fe)/B4C system, the reaction products formed at 4000 kJ/kg input energy under 420 MPa applied stress were a series of complex carbides and borides including W2C, FeWB, Fe3C, Fe6W6C and Ni4B3. The intermetallic Fe7W6was also observed. In the (Ti3Al+Nb)/SiC system, the reaction products observed at 3400 kJ/kg and 210 MPa were TiC and TiSi2.
Role of Fiber-Matrix Interfacial Shear Stress on the Toughness of Reinforced Oxide Matrix Composites
Authors: Singh Raj N. 
Published: March 2011

AbstractMullite and zircon ceramic matrix composites uniaxially reinforced with as-supplied and BN-coated silicon carbide filaments were fabricated. The filament-matrix interfacial shear stresses were measured by a modified indentation technique and mechanical properties were determined in flexure mode. Significant improvements in strength and toughness were observed for the composites in comparison to monolithic mullite and zircon ceramics. Lower filament-matrix interfacial shear stresses were measured in composites with BN-coated filaments than in composites containing as-supplied filaments. The influence of filament-matrix interfacial shear stress on the critical stress for first matrix cracking, maximum composite strength, and toughness of the composites were studied.
New Pathways to Processing Composites
Authors: Mehrabian Robert 
Published: March 2011

AbstractCompositing routes are reviewed for the fabricaiton of metal and metalceramic matrices combined with ceramic reinforcements and/or ductilizing phases. The important role of micromechanics in elucidating microstructural design principles to guide the processing “pathways” is emphasized. Specific processing techniques are described including incorporation of particles and fibers into melts, melt infiltration into preforms, powder metallurgy and melt oxidation.
Phase Stability and Interface Reactions in the Al-SiC System
Authors: Lee Doh-Jae , Vaudin Mark D. , Handwerker Carol A. , Kattner Ursula R. 
Published: March 2011

AbstractThe Al-SiC system has been used as a model system in an examination of phase stability in the presence of a liquid phase and microstructure development in metal-matrix composites. The Al-Si-C phase diagram has been calculated for temperatures between 500°C and 1500°C. The phases formed between Al(liquid) and SiC at 920°C have been determined experimentally, using analytical electron microscopy, in both fiber and particulate composites and compared with what is predicted from the equilibrium phase diagram. The morphologies and the spatial distributions of phases have also been examined in addition to the phase analysis. The only phases found were Al, Al4C3, SiC, and Si. Although Al4SiC4 is calculated to be stable at 920°C, it was not found. The SiC grain structure was found to influence strongly the morphology of the Al4C3-SiC and Al-SiC interfaces.
Elevated Temperature Slow Plastic Deformation of NiAl/TiB2 Particulate Composites
Authors: Viswanadham R. K. , Whittenberger J. Daniel , Mannan S. K. , Sprissler B. 
Published: March 2011

AbstractTo enhance the high temperature strength of aluminides, NiAl–iB2 composites with particulate contents up to 30 vol. pct. were made by XDTM synthesis and hot pressed to full density. Microstructures of these composites were characterized by optical, scanning and transmission electron microscopy (TEM). The average size of the TiB2 particles was about 1 μm, and the average grain size of the NiAl matrix was on the order of 10 μm. Elevated temperature compression testing was conducted on these composites in air at 1200 and 1300 K with strain rates varying from −10−4 to −10−7 s−1. Flow strengths were found to increase with increasing TiB2 content; for example, the 20 vol. pct. TiB2 composite was three times stronger than unreinforced NiAl. Post test TEM analysis showed that the primary feature of the dislocation substructure of deformed NiAl was well defined subgrain boundaries, whereas the structure of the higher volume fraction composites consisted of a very high density of tangled dislocations, loops and subgrain boundaries connecting particles. These observations suggest that TiB2 particles can stabilize a completely different dislocation structure than that normally found in NiAl.
The Gel Route to Yttrium Oxide
Authors: Ribot F. , Sanchez C. , Livage J. 
Published: March 2011

ABSTRACTSynthesis of pure Y2O3 Powders have been performed through the sol-gel process. Stable colloids in the range of 500 Å to 2000 Å have been obtained by hydroxylation of yttrium-aquo ions performed through an anion exchange resin.The chemical nature of these sols and gels investigated by GTA, DTA and EXAFS is in close agreement with Y(OH)3nH2O. Scattering experiments (S.A.N.S, S.A.X.S, light scattering) show that these colloids are made of anisotropie particles, that can be described as platelets 30 Å thick, 500 Å large and a few thousand Angstroms long.This synthesis can be extended to other rare earth colloids.
Structural Characterization of Polysilicate Intermediates Formed During Sol-Gel Polymerization
Authors: Klemperer W. G. , Mainz V. V. , Ramamurthi S. D. , Rosenberg F. S. 
Published: March 2011

ABSTRACTIdentification of polysilicate intermediates formed during sol-gel processing of silica gels and glasses is an important step toward understanding the nature of this process on a molecular level. Although capillary gas chromatography using mass spectrometric detection gives the molecular formulas for low molecular weight intermediates [1], this approach is only semi-quantitative and provides no structural information. An improved protocol has been developed that allows structural assignment and quantitative determination of the principal mono- through hexasilicate structural isamers formed by hydrolysis of methanolic tetramethylorthosilicate in the presence of HC1. This protocol combines quenching by diazomethane, fractionation using spinning band column distillation, identification by capillary gas chromatography, and structural characterization using 29Si{1H} NMR techniques (l-pulse, ID-INADEQUATE, and 2D-INADEQUATE) to provide structural assignments and response factors for the components separated by gas chromatography.
Structural Organization of Early Gels and Precipitates of Chemically Bonded Ceramics
Authors: White William B. , Vesper Dorothy J. , Kraus Julia 
Published: March 2011

ABSTRACTCeramic precursor materials in the silica-alumina-phosphous pentoxide system can be retained as solutions under suitably high or low pH conditions. Molecular species in these solutions have been characterized by their sharp, well-defined Raman spectra. Changes in pH or reduced water activity by addition of miscible organic solvents takes the system across sharp precipitation boundaries. Precipitates can take the form of colloidal gels, polymerized gels, or crystallites depending on chemical composition and rate of precipitation. Raman spectra of precipitates immersed in their parent solutions have much less structure and broader bands. Information of the structural characteristics of the precipitates are deduced from band widths and the amount of fine structures related to the coherence length for Raman scattering. Phosphate-rich compositions tend to be more highly ordered with more detailed spectra than the silicate rich compositions.
Multi-Phasic Nanocomposite Sol-Gel Processing of Cordierite
Authors: Kazakos-Kijowski Ann , Komarneni Sridhar , Roy Rustum 
Published: March 2011

ABSTRACTCordierite (Mg2Al4Si5O18) powders prepared from compositionally triphasic nanocomposite gels led to enhanced densification when compared to powders made by the conventional SSG route. The densification of the sintered cordierite pellets was determined by utilizing the Archimedes method and the microstructure of the pellets was examined with a scanning electron microscope (SEM). Bulk densities of monophasic, triphasic nanocomposite (two sols and one solution) and truly triphasic nanocomposite (three sols) pellets sintered at 1300°C for 2 hours were 2.01 g/cm3 (80% relative density), 2.42 g/cm3 (96% relative density) and 2.51 g/cm3 (100% relative density) respectively. The enhanced densification of α-cordierite utilizing triphasic nanocomposite sol-gel processing is, at least in part, due to the contribution of the heat of reaction from the three components.