bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Prediction of Turbomachinery Flows Using Near-Wall Reynolds-Stress Model
Authors: Gerolymos G. A. , Neubauer J. , Sharma V. C. , Vallet I.
Published: July 2002

In this paper an assessment of the improvement in the prediction of complex turbomachinery flows using a new near-wall Reynolds-stress model is attempted. The turbulence closure used is a near-wall low-turbulence-Reynolds-number Reynolds-stress model, that is independent of the distance-from-the-wall and of the normal-to-the-wall direction. The model takes into account the Coriolis redistribution effect on the Reynolds-stresses. The five mean flow equations and the seven turbulence model equations are solved using an implicit coupled OΔx3 upwind-biased solver. Results are compared with experimental data for three turbomachinery configurations: the NTUA high subsonic annular cascade, the NASA_37 rotor, and the RWTH 1 1/2 stage turbine. A detailed analysis of the flowfield is given. It is seen that the new model that takes into account the Reynolds-stress anisotropy substantially improves the agreement with experimental data, particularily for flows with large separation, while being only 30 percent more expensive than the k−ε model (thanks to an efficient implicit implementation). It is believed that further work on advanced turbulence models will substantially enhance the predictive capability of complex turbulent flows in turbomachinery.
Thermoelasticity Solutions for Straight Beams
Authors: Copper C. D. , Pilkey W. D.
Published: July 2002

This paper presents a thermoelastic solution technique for beams with arbitrary quasi-static temperature distributions that create large transverse normal and shear stresses. This technique calculates the stress resultants and centroid displacements along a beam. Then, the stress resultants and temperature distribution are used to calculate the stress distributions on a cross section of the beam. Simple examples demonstrate the numerical efficiency of the proposed technique and the inadequacy of the strength of materials theory to solve these types of problems.
The Effect of Finite Amplitude Disturbance Magnitude on Departures From Laminar Conditions in Impulsively Started and Steady Pipe Entrance Flows
Authors: Moss E. A. , Abbot A. H.
Published: July 2002

The aim of this study was to investigate first departures from laminar conditions in both impulsively started and steady pipe entrance flows. Wall shear stress measurements were conducted of transition in impulsively started pipe flows with large disturbances. These results were reconciled in a framework of displacement thickness Reynolds number and a velocity profile shape parameter, with existing measurements of pipe entrance flow instability, pipe-Poiseuille and boundary layer flow responses to large disturbances, and linear stability predictions. Limiting critical Reynolds number variations for each type of flow were thus inferred, corresponding to the small and gross disturbance limits respectively. Consequently, insights have been provided regarding the effect of disturbance levels on the stability of both steady and unsteady pipe flows.
Nanostructure, Effective Properties, and Deformation Pattern of the Cochlear Outer Hair Cell Cytoskeleton
Authors: Spector Alexander A. , Ameen Mohammed , Charalambides Panos G. , Popel Aleksander S.
Published: July 2002

We consider the mechanical properties of the outer hair cell cytoskeleton. The cytoskeleton is represented as a set of microdomains of different sizes and orientations composed of actin filaments and spectrin crosslinks. An intermediate material between domains is also introduced. The domain characteristics are randomly generated and the histograms of the cytoskeleton stiffness moduli are obtained. We solve an inverse problem and estimate the stiffness of the crosslink and connective molecule in the intermediate material. We discovered a pattern of highly inhomogeneous deformation of the cytoskeleton where the circumferential strain is primarily determined by the deformation of the intermediate material.
Delay-independent Stability of Uncertain Control Systems
Authors: Tuzcu Ilhan , Ahmadian Mehdi
Published: July 2002

This paper will provide a study of the delay-independent stability of uncertain control systems, represented by a family of quasipolynomials with single time-delays. The uncertain systems that are considered here are delay differential systems whose parameters are known only by their lower and upper bounds. The results are given in the form of necessary and sufficient conditions along with the assumptions for the quasipolynomial families considered. The conditions are transformed into convenient forms, which provide analytical expressions that can be easily checked by commercially available computing tools. For uncertain systems represented by families of quasipolynomials, it is shown that the delay independent stability for the extreme values of parameters is not sufficient for the delay independent stability of the entire family. In addition, the family must satisfy some conditions for the interior values of each parameter within specially constructed frequency ranges. The implementation of the theorem that is suggested is demonstrated on an example system that includes a single degree of freedom system with an active vibration absorber, namely the Delayed Resonator.
On the Constitutive Relation for the Reynolds Stresses and the Prandtl-Kolmogorov Hypothesis of Effective Viscosity in Axisymmetric Strained Turbulence
Authors: Jovanovic´ J. , Otic´ I.
Published: July 2002

The constitutive relation for the Reynolds stress tensor is considered for turbulence developing in axisymmetric strain fields. It is confirmed that the Reynolds stress tensor is aligned linearly with the mean strain rate. In contrast to the Prandtl-Kolmogorov, hypothesis, the effective viscosity is found to grow in proportion to the anisotropy of turbulence and the length scale based on the magnitude of the mean strain rate. Using invariant theory the effective viscosity is determined for the limiting states of turbulence. Additional analysis of the constitutive relations is supplemented for the dissipation and pressure-strain correlations. It is shown that analytical derivations are in excellent agreement with the data obtained from direct numerical simulations. [S0098-2202(00)02801-7]
Validation of Hyperbolic Model for Water-Hammer in Deformable Pipes
Authors: Hadj-Taı¨eb E. , Lili T.
Published: July 2002

A mathematical formulation is presented to describe the transient flow of homogeneous gas–liquid mixtures in deformable pipes. The mixture density is defined by an expression averaging the two-component densities where isothermal evolution of the gaseous phase is admitted. Instead of the void fraction, which varies with pressure, the gas–fluid mass ratio (or the quality), assumed to be constant, is used. By application of the conservation of mass and momentum laws, a nonlinear hyperbolic system of two differential equations is obtained for the two principal dependent variables, which are the fluid pressure and velocity. Consideration is given in this paper to the numerical solution of these equations by the method of characteristics and the finite difference conservative scheme. The finite difference scheme computes the pressure by using a Newton–Raphson iterative formula, where the pressure wave speed takes place explicitly. To verify the validity of the computed results, comparison has been made with those of the numeric-experimental example of Chaudry et al. “Analysis of Transient in Bubbly Homogeneous Gas–Liquid Mixtures,” 1990. ASME J. Fluids Eng., 112, pp. 225–231. [S0098-2202(00)00301-1]
Experimental Analysis of Thermal Instability in Natural Convection
Between Horizontal Parallel Plates Uniformly Heated
Authors: Manca O. , Morrone B. , Nardini S.
Published: July 2002

An experimental investigation of natural convection between horizontal, heated, parallel plates in air was carried out by visualizing the flow and measuring the air temperature. Grashof numbers, based on the plate spacing, varied in the 1.22×105-1.06×106 range. Flow patterns and probable onset of secondary motions were observed for three heating modes: (1) both plates heated, (2) upper plate heated and lower one unheated, and (3) upper plate unheated and lower one heated. The main flow pattern resembled a C shape (C loop) for all modes. In fact, the flow penetrated inside the cavity close to the leading edge of the lower plate and exited from the upper part, by reversing its motion between the plates. When the lower plate was heated, flow visualization showed that secondary flows were added to the C loop main flow. Such secondary structures arose as thermals, then changed into longitudinal vortices and, in the upper region of the open-ended cavity, a chaotic motion was detected. The existence of these structures was confirmed by measurements of instantaneous temperature values. They showed that the greater the Grashof number the more chaotic the flow in the outflow branch of the C loop when the lower plate was heated and the upper one was unheated. [S0022-1481(00)01801-6]
Buoyancy-Driven Flow Reversal Phenomena in Radially Rotating
Serpentine Ducts
Authors: Hwang J. J. , Wang W.-J. , Chen Cha'o Kuang
Published: July 2002

Convective characteristics are analyzed numerically in a rotating multipass square duct connecting with 180-deg sharp returns. Isoflux is applied to each duct wall and periodic conditions are used between the entrance and exit of a typical two-pass module. Emphasis is placed on the phenomenon of buoyancy-driven reversed flow in the serpentine duct. Predictions reveal that the radial distance from the rotational axis to the location of flow separation in the radial-outward duct decreases with increasing the Richardson number. In addition, the local buoyancy that is required to yield the radial flow reversal increases with increasing the rotation number. This buoyancy-driven reversed flow in the radial-outward duct always results in local hot spots in the cooling channels. The critical buoyancy for the initiation of flow reversal is therefore concluded for the design purpose. [S0022-1481(00)01101-4]
Plastic Collapse of Stainless Steel Optical Tubes Used in Steel Armored Cables
Authors: Slotboom Oscar F. “Erik”
Published: July 2002

Thick-walled stainless steel optical tubes used in steel armored cables sustain severe forces arising from the axial strain of the bulk cable, core pressure caused by the squeezing effect of the helically wrapped armor wires, and external forces on the cable. The conditions which result in collapse of the optical tube are investigated by applying established plasticity theory and then extending this theory to develop new equations for the case of a work-hardening material. The theoretical criteria for the onset of tube collapse are identified. Theoretical, experimental, and field results are then combined to identify conditions which increase the risk of tube collapse. It is concluded that tube collapse will not occur in properly manufactured cables unless one or more of four special conditions exist. These conditions are unusually large external pressure on the tube caused by more than two layers of steel armor, non-hydrostatic radially-dominated external pressure on helical tubes, severe external forces on the cable, and amplification of core pressure on the optical tube resulting from the cable geometric design. [S1050-0472(00)01202-2]
The Design, Generation, and Simulation of Meshing of Worm-Gear Drive With Longitudinally Localized Contacts
Authors: Seol I. H.
Published: July 2002

The design and simulation of meshing of a single enveloping worm-gear drive with a localized bearing contact is considered. The bearing contact has a longitudinal direction and two branches of contact path. The purpose of localization is to reduce the sensitivity of the worm-gear drive to misalignment. The author’s approach for localization of bearing contact is based on the proper mismatch of the surfaces of the hob and drive worm. The developed computer program allows the investigation of the influence of misalignment on the shift of the bearing contact and the determination of the transmission errors and the contact ratio. The developed approach has been applied for K type of single-enveloping worm-gear drives and the developed theory is illustrated with a numerical example. [S1050-0472(00)00502-X]
Sensor Optimization for Fault Diagnosis in Multi-Fixture Assembly Systems With Distributed Sensing
Authors: Khan A. , Ceglarek D.
Published: July 2002

Sensing for the system-wide diagnosis of dimensional faults in multi-fixture sheet metal assembly presents significant issues of complexity due to the number of levels of assembly and the number of possible faults at each level. The traditional allocation of sensing at a single measurement station is no longer sufficient to guarantee adequate fault diagnostic information for the increased parts and levels of a complex assembly system architecture. This creates a need for an efficient distribution of limited sensing resources to multiple measurement locations in assembly. The proposed methodology achieves adequate diagnostic performance by configuring sensing to provide an optimally distinctive signature for each fault in assembly. A multi-level, two-step, hierarchical optimization procedure using problem decomposition, based on assembly structure data derived directly from CAD files, is used to obtain such a novel, distributed sensor configuration. Diagnosability performance is quantified in the form of a defined index, which serves the dual purpose of guiding the optimization and establishing the diagnostic worth of any candidate sensor distribution. Examples, using a multi-fixture layout, are presented to illustrate the methodology. [S1087-1357(00)70801-X]
Effect of Pad/Caliper Stiffness, Pad Thickness, and Pad Length on Thermoelastic Instability in Disk Brakes
Authors: Hartsock Dale L. , Fash James W.
Published: July 2002

Thermoelastic instability (TEI) results in uneven heating of the rotor and the development of hot spots in automotive disk brake systems. The hot spots cause rotor distortion and thickness variation which can cause torque variation resulting in brake roughness or low frequency noise. Lee and Barber (1993, ASME J. Tribol., 115, pp. 607–614) developed an analytical model to predict the critical speed above which TEI would occur. This paper describes enhancements to the model to include the effects of caliper/pad stiffness, the pad friction material thickness, and the pad length. The effects of these changes on the predicted speed are calculated and compared to the original model. [S0742-4787(00)01402-8]
Aerothermal Investigations of Mixing Flow Phenomena in Case of Radially Inclined Ejection Holes at the Leading Edge
Authors: Bohn Dieter E. , Kusterer Karsten A.
Published: July 2002

A leading edge cooling configuration is investigated numerically by application of a three-dimensional conjugate fluid flow and heat transfer solver, CHT-flow. The code has been developed at the Institute of Steam and Gas Turbines, Aachen University of Technology. It works on the basis of an implicit finite volume method combined with a multiblock technique. The cooling configuration is an axial turbine blade cascade with leading edge ejection through two rows of cooling holes. The rows are located in the vicinity of the stagnation line, one row on the suction side, the other row is on the pressure side. The cooling holes have a radial ejection angle of 45 deg. This configuration has been investigated experimentally by other authors and the results have been documented as a test case for numerical calculations of ejection flow phenomena. The numerical investigations focus on the aerothermal mixing process in the cooling jets and the impact on the temperature distribution on the blade surface. The radial ejection angles lead to a fully three-dimensional and asymmetric jet flow field. Within a secondary flow analysis, the cooling fluid jets are investigated in detail. The secondary flow fields include asymmetric kidney vortex systems with one dominating vortex on the back side of the jets. The numerical and experimental data show a respectable agreement concerning the vortex development. [S0889-504X(00)00102-1]
Bayerite (β-Al(OH)3) by XPS
Authors: Rotole John A. , Sherwood Peter M. A.
Published: July 2002

The XPS spectra of Bayerite were collected with a VSW HA150 using monochromatic Al Kα x-radiation. Monochromatic radiation provides a distinct clarity to the peak structure in the valence band of Bayerite due to the absence of interfering x-ray satellites from the intense O 2s region. Variations in the intensities and peak separation of the two-peak structure in the valence bands of the oxides, hydroxides, and oxyhydroxides of aluminum allow one to distinguish between these compounds. The valence band, survey, and the Al 2s, Al 2p, O 1s, and C 1s core levels are reported.
Fluorocarbon polymer deposition kinetics in a low-pressure, high-density, inductively coupled plasma reactor
Authors: Sowa M. J. , Littau M. E. , Pohray V. , Cecchi J. L.
Published: July 2002

Maintaining dimensional control and adequate throughput during the etching of submicron features requires plasma etch tools that operate at low pressures and high densities, such as inductively coupled plasmas (ICPs). Unfortunately, in this regime, it has proven difficult to achieve a stable, reproducible chemistry for selective oxide etching of contacts and vias. In particular, it is difficult to control the passivating polymer film which provides etching selectivity to silicon, nitride, and photoresist. As a first step toward sorting out the complicated oxide etching chemistry, we have measured and modeled the kinetics of the polymer film deposition in an ICP reactor for C2F6/H2 and CHF3 chemistries. Using a unique application of statistical design of experiments, we have explored the pressure range of 3–15 mTorr, power range of 300–2000 W, residence times from 0.5 to 1.0 s, and magnetic field from 0 to 24 G. Polymer deposition rates on a bare Si wafer are measured using a laser interferometer. The concentration of fluorocarbon radicals, CF, CF2, and CF3, are measured in the plasma using wavelength modulated infrared diode laser absorption spectroscopy. Additional measurements include actinometric F atom density and ion saturation current. These measurements are analyzed in terms of a polymer deposition model and the important physical phenomena are inferred. Significantly, we find a unique polymer deposition mechanism over the entire range of tool parameters including direct deposition of CF and ion-assisted deposition of CF2.
Chemical vapor deposition of Ru thin films by direct liquid injection of Ru(OD)3 (OD=octanedionate)
Authors: Lee Jung-Hyun , Kim Joo-Young , Rhee Shi-Woo , Yang DooYoung , Kim Dong-Hyun , Yang Cheol-Hoon , Han Young-Ki , Hwang Chul-Ju
Published: July 2002

Pure Ru thin films were deposited on Si substrate using Ru (OD)3 (OD = octanedionate) as a new liquid precursor with a newly designed warm wall reactor by metalorganic chemical vapor deposition (MOCVD). Resistivity and film structure were largely dependent on MOCVD process parameters such as deposition temperature, O2/(O2+Ar) ratio, and reactor pressure. With the increase of O2/(O2+Ar) ratio, minimum resistivity (20 μΩ cm) was obtained and then the resistivity was increased due to the abnormal increase of surface roughness. By modifying the position of a single quartz injector, uniform deposition of Ru thin films on an 8 in. Si wafer could be obtained.
Passivation of the Ge/InP(110) interface by As interlayers: Interface reactions and band offsets
Authors: Preobrajenski A. B. , Schömann S. , Gebhardt R. K. , Chassé T.
Published: July 2002

The formation of the Ge/InP(110) interface at room temperature and the influence of an additional arsenic interlayer on the interface chemistry, the film growth, and the electronic properties of this heterostructure have been investigated using core and valence level photoemission and low-energy electron diffraction. We have shown that an As interlayer at the Ge/InP(110) interface can completely suppress the interface reaction of the Ge with the substrate at room temperature, including partial In–Ge exchange and In segregation. The electronic situation at the interface is characterized by an anomalous evolution of the surface Fermi level with Ge coverage on InP(110) and a high valence band offset of ΔEv=1.01±0.07 eV, which is reduced to ΔEv=0.78±0.07 eV for Ge/As/InP(110). We may attribute the differences of the measured valence band offsets to a reaction-induced interface doping of the InP at the real Ge/InP(110) interface, which introduces an interface dipole layer. A calculation of this interface dipole contribution (0.38 eV) using the model of interface induced gap states gives a fair estimate for the experimentally observed difference of the valence band offsets.
Investigation of hollow cathode effects on the structure of bulk films
Authors: Stowell W. R. , Chambers D.
Published: July 2002

In a hollow cathode discharge, there is a higher degree of ionization than in the abnormal glow discharge which is characteristic of sputtering and ion plating. A hollow cathode discharge was formed between parallel plates. Metal was evaporated from a source below the hollow cathode and was deposited onto the cathode plates. The pressure–voltage-plate spacing relationship between the cathode plates was related to the deposition efficiency. The grain structure of the deposited metal is reported upon. The evaporation source was a boat-type evaporator. The source metals were copper and silver.
Composition, mechanical properties, and structure of electrodeposited cobalt–iron alloys
Authors: Sadak J. C. , Sautter F. K.
Published: July 2002

Electrodeposited films of cobalt–iron traditionally have been thought of in terms of their magnetic properties. The current investigation, however, has demonstrated that the mechanical properties of bulk coatings of cobalt–iron alloys can be equally attractive. Bulk coating (> 100 μ) of cobalt–iron have been electrodeposited in the concentration range of 1%–12.6% Fe as a function of cathodic current density (1–10 A/dm2), electrolyte temperature (60–90 °C) and ferrous concentration in the electrolyte (0.5–5.0 g/liter Fe++). Microstructure–mechanical property relationships, including yield strengths, ultimate tensile strengths and microhardnesses, have been determined for these materials after a 15 min, 482 °C (900 °F) stress relief anneal. Room temperature yield strengths as high as 102 kg/mm2 (145 000 psi) and ultimate tensile strengths of up to 135 kg/mm2 (192 000 psi) have been obtained. The general trends indicate that lower electrolyte temperatures, and higher iron contents yield coatings with greater strength.
Proximity effect correction using pattern shape modification and area density map
Authors: Takahashi Kimitoshi , Osawa Morimi , Sato Masami , Arimoto Hiroshi , Ogino Kozo , Hoshino Hiromi , Machida Yasuhide
Published: July 2002

A proximity effect correction program in which forward scattering is corrected by shape modification and backscattering is corrected by dose modulation is developed. The amount of the shape modification is determined in such a manner that the full width at half maximum of the forward scattering profile is equal to the designed size. The half maximum of the forward scattering profile is equalized by the dose modulation after the amount of the backscattering is evaluated by the area density map method. This algorithm automates pattern biasing to improve the resolution and assures the resulting pattern size is as designed. The following features are included to improve the conventional methods: The area density map is smoothed iteratively to include higher order effect. Smaller meshes are used for better discretization accuracy. Auxiliary shots are generated to refine correction units where the spatial profile of the deposited energy is steep. The corrected results of 60 nm lines are also presented.
A Model for Molecular Flow of Reactive Species through Cylindrical Reactors
Authors: Baker Bill R. , Wood Bernard J.
Published: July 2002

An analytical model, describing the flux of reactive-gaseous species surviving transit through a cylindrical reactor with apertures at either end, is developed. The magnitude of the surviving flux is evaluated as a function of the reaction probability of the wall, which may be discontinuous from point-to-point within the reactor, and of the relative dimensions of the vessel. Numerical solutions were obtained for vessels with values of the ratio length–radius in the range 2–6. The model is compared with a simplified approximation that is particularly applicable for reactor geometries with small values of length–radius.
The Behavior of Ions in a BAG Structure
Authors: Comsa George
Published: July 2002

Collector and grid end-cap currents were measured as a function of pressure, electron current, grid, and end-cap potentials in a Bayard–Alpert gauge-like geometry. After an analysis of the electrical fields produced in the grid volume by electrode potentials and electron and ion space charges, the main experimental results are discussed. An explanation is proposed for the discrepancy between the experimental and theoretical values of the collection factor, for the mechanism leading to an increased collection when positive grid end-caps are used, and for other experimental results. The information obtained is useful for a better understanding of the processes taking place in Bayard–Alpert gauges; some light is thrown upon the difficulties which might occur when using the Bayard–Alpert geometry as a spectrometer for subthermal velocities.
Mass Spectrometric Studies on the Limitations of Oil Diffusion Pumped Coaters
Authors: Huber W. K. , Rettinghaus G.
Published: July 2002

The residual gas conditions in numerous commercial oil diffusion pumped coaters have been examined by mass spectroscopy during an extensive program. Particular regard is devoted to organic contamination. The main topics covered are: hydrocarbon partial pressures and their determining parameters in systems equipped with water-cooled and deep-cooled baffles; the influence of oil backstreaming; suitable measures to reduce contamination; a discussion of various contamination sources, for example, the foreline system. The pump fluid was found not to be the most important contaminant in many cases, particularly in coaters working under normal production instead of laboratory conditions. Whereas a slight contamination by pump fluid vapor cannot be avoided completely unless by deep-cooled baffles, all other contaminations are avoidable in principle without such devices. Some operational suggestions are given.
Two-Layer Approach in Making Insulating Films Less Than 100 Å Thick
Authors: Hsieh E. J.
Published: July 2002

The merit of making very thin insulating layers less than 100 Å thick, by successively forming two layers of different dielectric films, was evaluated. The basic test structure was a capacitor with its insulating layer made up of different thickness combinations of thermally grown Al2O3 and vacuum-evaporated SiO. The two-layer dielectric films always give superior yields. In general, the result seems to indicate that a thinner insulating layer can be made from two layers of different dielectric films than from a single layer of either material.
Scrap Recovery and Casting with a Nonconsumable Electrode
Authors: Vaia Albert R. , Akers Ronald R. , Damon Sam
Published: July 2002

This report discusses results from melting with water-cooled nonconsumable electrodes since their introduction to the industry at the 1969 Vacuum Metallurgy Conference in Pittsburgh. In production these electrodes have proven to be attractive for the first melting of titanium sponge and scrap directly into remelt electrodes thereby avoiding the electrode fabrication step previously required. They have also been applied to reclamation of small superalloy scrap directly into forgeable ingot avoiding the two-step practices of air induction melting followed by consumable melting and are currently being used to replace the graphite electrode melting and casting of uranium carbide fuel rods. Experiments reported in this paper were conducted to determine the application of the nonconsumable melting technique to some of the many problems in scrap recovery and the casting industry. For example, we have investigated isolation of high density inclusions from titanium scrap, elimination of low density inclusions, effect of superheating on metal fluidity in casting, and the operation of nonconsumable electrodes at low pressure.
Selected Properties of Beryllium-Base Alloys Consolidated by Vacuum-Arc Melting
Authors: Armantrout C. E. , Sims C. O.
Published: July 2002

A preliminary survey of beryllium-base alloys was conducted by melting and testing small button-shaped ingots. Hardness and impact resistance were compared with those of pure beryllium. Structures were examined by microprobe analysis and conventional metallographic techniques. Larger homogeneous ingots of alloys showing promise were then consolidated by consumable electrode arc melting of pressed electrodes of beryllium and the intermetallic compound NiAl. The ingots were formed into rods of 1.7-cm (58-in.) diameter at reductions of 9-1 by impact extrusion. Evaluation of the rods was by tensile tests, hardness measurements, and microprobe analysis. Tensile properties at room temperature ranged from about 51 000 to 55 000 psi; tensile modulus was 30−50 × 106 psi; elongation was about 1% at room temperature and 2–9% at 600 °C.
Hollow-Cathode Discharge Melting of Ti–6Al–4V and Nb–56Ti–3.3Zr Alloys
Authors: Takei Hiromichi , Ishigami Yuji
Published: July 2002

Sound ingots of titanium and Ti–6Al–4V alloy, 110-mm diam×400 mm long, were cast in a 60-kW HHCD furnace. Oxygen and hydrogen levels were reduced considerably. Triple melting and casting of Nb–56Ti–3.3Zr alloy in an 80-kW HHCD furnace produced a satisfactory superconducting material on which test data is reported. A description of the furnace and the operating procedure is outlined.
Vacuum Casting of Cored Nickel-Alloy Precision Castings
Authors: Quigg R. J.
Published: July 2002

Cast-in cooling passages are required to enable superalloy airfoils to stand up at the present day turbine inlet temperatures. These cooling passages are obtained by casting around ceramic cores. These cores engender problems in handling, core distortion, core removal, and wall thickness measurements. In this paper, each of these problems was discussed.
Environmental Aspects of Reactive Metal Production
Authors: Worcester S. A. , Aschoff W. A.
Published: July 2002

If vacuum metallurgy were the segment of the production of reactive metals with which one needed to be concerned, environmental aspects would be relatively simple to control. Air pollution could be handled by proper use of vapor and mist traps on mechanical pump exhausts and in the vicinity of oil reclaimers. Prevention of water pollution might prove to be more of a problem because of the difficulties in disposing of both mechanical pump and diffusion pump oils. An integrated plant for producing such a metal as zirconium uses relatively large quantities of chemicals which may be detrimental to the environment, if not carefully controlled. Chlorine, hydrochloric acid, nitric acid, sulfuric acid, hydrofluoric acid, ammonia, ammonium thiocyanate, and methyl isobutyl ketone are among those difficult to handle materials encountered in such an operation. Not only is disposal of waste products a potential evnironmental problem, containment of the reagents themselves present some unusual challenges. In many cases, a bootstrap approach is used wherein a reactive metal such as zirconium is found to possess the necessary corrosion resistant and noncontaminating properties highly desirable in equipment used for handling reagents or by-products encountered in its production.
Investigation of Factors Affecting the Composition of an Alloy Coating Deposited by Sputtering
Authors: Stowell W. R. , Chambers D. L. , Carmichael D. C.
Published: July 2002

Sputtering of relatively thick deposits of alloys for use as protective coatings has shown that the composition of the target is usually not exactly reproduced in the deposit. The elemental values of sputtering rates also do not apply directly to sputtering from alloys, although they are useful in examining the change in alloy composition of the deposit as compared to the original target. To investigate some of the basic relationships involved, a study is being conducted on the sputtering of the system copper–silver. This is a simple eutectic system and thermodynamic data are available. Results of experiments on sputtering of this alloy was presented and underlying relationships were discussed. Substrate biasing has been found to significantly affect the deposited composition of sputtered alloys. The effect of an increasing substrate bias on the composition of sputter-deposited copper–silver alloy was examined in this investigation and the result related to the basic alloy properties. The interaction of deposition variables such as sputtering rate and substrate temperature was also discussed. Copper off-sputters from a forming film more rapidly than does silver. This result is unexpected because the sputtering yield for silver is higher than for copper.
Electron-Induced Ion Desorption from the System Platinum/Hydrogen/Carbon Monoxide
Authors: Huber W. K. , Rettinghaus G.
Published: July 2002

Electron-induced ion desorption has been studied with the systems platinum–hydrogen and platinum–hydrogen–carbon monoxide. A number of competing phenomena have been separated by examining the influence of the main parameters involved such as electron energy, H2 and CO partial pressures, and thermal treatment. Particular attention was devoted to the influence of the electron current on the state of the systems. A preliminary interpretation of the observations is attempted by assuming different hydrogen adsorption states whose features are shifted as a result of electron bombardment and CO coadsorption.
Acoustoelectric Device Applications of Piezoelectric and Semiconducting Thin Films
Authors: Turner C. W.
Published: July 2002

Recent advances in microwave acoustics techniques have resulted in a growing demand for high-quality thin films for use in various acoustic devices. Oriented piezoelectric films were first used to increase the efficiency of transducers for bulk acoustic waves at frequencies above the limit of crystal plate resonators. Although extensive application of these transducers in both passive and active devices has become possible with the improvements in film quality, it now appears that surface elastic waves will afford the main vehicle for thin-film acoustic device applications. The properties of surface waves are discussed here and the principal devices currently under investigation are described. The detailed requirements of thin films suitable for surface wave devices are presented together with examples of the shortcomings of currently available films. Particular attention is focused on amplifying structures employing either large area oriented piezoelectric films or high-mobility single-crystal semiconductor films.
Applications of the Scanning Electron Probe Microanalyzer
Authors: Kyser David F.
Published: July 2002

The electron probe micoranalyzer, which was initially introduced by Castaing, has proven to be a versatile and important instrument in the fields of ceramics, metallurgy, mineralogy, biology, and solid-state electronics. A review is presented, beginning with the various interaction effects which occur when 5–50 keV electrons impinge on solids. These effects include characteristic and continuum x-ray emission, primary and secondary backscattered electron emission, and production of excess electron-hole pair in semiconductors. The characteristic or line x-ray emission is produced by direct ionization of the target atoms with subsequent radiative decay, and is used for nondestructive qualitative and quantitative analysis with micron spatial resolution. For trace analysis, the limit of detectability is approximately 100 ppm at best. With a typical analysis volume of 1 μm3 and a mass density of 10 g/cm3, this corresponds to a weight sensitivity of approximately 10−15 g. Experimental results are given for the quantitative analysis of sputtered EuO films with thicknesses between 0.3 and 0.5 μm. Scanning electron microscopy can be performed with primary and secondary electrons, as well as x-ray emission. A 200 mesh Cu grid superimposed on a 1000 mesh Ag grid is used as a target to illustrate the use of secondary electron emission intensity for topology micrographs, primary backscattered electron intensity for mass-density micrographs, and characteristic x-ray intensity for elemental micrographs. In addition to composition, the electron probe can be used to determine the thickness of thin films. By increasing the accelerating voltage of the electron beam until penetration to the substrate is accomplished, the thickness of phospho-silicate glass films in the range 700–4000 Å can be determined with an accuracy of ±150 Å. The chemical valence state of atoms can be studied with the long wavelength x-ray spectra. For example, the wavelength position of the peak intensity from Si has been used to reveal the presence of both metallic Si and Si4+ in silicon oxide thin films. In addition, the intensity ratio of two different x-ray lines from the first transition series elements varies with chemical state. Particular attention is devoted to the use of cathodoluminescence for characterizing direct band-gap semiconductors such as GaAs. Band-edge luminescence can be used in a scanning electron microscope mode to display inhomogeneities such as edge dislocations and p-n junctions, as well as bulk dopant inhomogeneities. The voltage dependence of cathodoluminescence can be used to determine transport properties such as minority carrier diffusion length and surface recombination velocity. Transient cathodoluminescence can be used to determine minority carrier lifetime. The quantitative analysis of rare earth materials by cathodoluminescence has also been used to detect trace concentrations. These methods are applicable to epitaxial thin films in general, and to polycrystalline films in some particular cases.
Preparation and Superconducting Properties of Niobium–Zirconium Thin Films
Authors: Spitzer Hermann J.
Published: July 2002

Nb–Zr thin films (3000–4000 Å thick) have been prepared by dc sputtering at 350 °C and 630 °C. Measurements of the Jc–H characteristics in transverse fields of up to 85 kOe and of Tc’s were carried out as a function of composition. We also investigated the effects of different substrate materials and deposition rates on the superconducting properties of Nb-66 at.% Zr thin films deposited at 630 °C. The results show a distinct dependence of Jc–H data on the substrate temperature: Maximum critical fields of up to 60 kOe at 103 A/cm2 are observed for films deposited at 350 °C, whereas some films deposited at 630 °C are still superconducting at 85 kOe with current densities of 105 A/cm2. The Tc vs composition curve has a maximum at approximately 30 at.% and appears to be insensitive to deposition temperature at higher Zr concentrations. Additional annealing after deposition seems to increase Tc. The lower deposition rates yielded films with higher Tc’s and better Jc–H characteristics.
Theories and Models of the Amorphous State
Authors: Allgaier R. S.
Published: July 2002

This paper discusses some theories and models, mainly those developed for amorphous semiconductors by Mott, Cohen, and Böer. The relationships between the theoretical work and a number of structural, optical, and electrical characteristics of amorphous materials are considered. Particular attention is paid to the question of whether or not the traditional interpretations of experimental measurements and the conventional language in which they are described may be applied to amorphous materials.
Coadsorption of Hydrogen and Carbon Monoxide on (111) Platinum
Authors: Baldwin Vaniah H. , Hudson John B.
Published: July 2002

The coadsorption of hydrogen and carbon monoxide on the (111) face of a platinum single crystal has been studied by a combination of thermal flash desorption and electron impact desorption (EID) techniques in ultrahigh vacuum. Several compositions over the range from 0%–100% CO have been studied, over a total pressure range from 5×10−9 to 5×10−7 Torr. The observed adsorption behavior is complex, indicating multiple binding sites for both gases. In addition, the EID studies show the formation of a surface species containing both H and CO. This same species has also been observed when formaldehyde was adsorbed directly from the vapor.
Analysis of Solvent Redistribution during Vapor Deposition of Alloy Films from a Molten Source
Authors: McCloskey John C.
Published: July 2002

Composition variations occurring in vapor-deposited alloy films have been quantitatively evaluated by treating the vapor deposition process as a solidification process. A mathematical model appropriate for solute redistribution during the solidification of a binary alloy was used to explain and predict compositional variations in vapor-deposited Ni–Fe films. Predictions based on such a model agree with recent experimental measurements during the final 50% of film formation. In earlier stages of vapor deposition, predicted film composition exceeds measured composition by approximately 3%.
Diffusion in Thin Film Couples of Platinum–Gold
Authors: Nowak Welville B. , Dyer Richard N.
Published: July 2002

The interdiffusion of platinum and gold films, a couple utilized in beam-lead microcircuits, has been studied for temperatures up to 550 °C, Gold-on-platinum couples and separate platinum and gold films, 80–450 nm thick, were deposited by electron beam evaporation onto oxidized (111) silicon substrates. Diffusion was monitored by means of spectral reflectance versus wavelength in the band 500–1000 nm. The separate metal films showed good adhesion and stable reflectances (after an initial change) for at least 6 h at diffusion temperatures, in contrast to the couples. Analysis of platinum diffusion through the gold films yielded an activation energy about 38 kcal/g-atom and a pre-exponential factor of the order 10−3 cm2/sec, values close to those for volume diffusion. The pre-exponential factor especially is dependent upon film deposition conditions.
Effect of Surface Charge on the Superconducting Transition Temperature and Normal-State Conductivity of Disordered Metal Films
Authors: Felsch W. , Glover R. E.
Published: July 2002

Measurements were made of the shifts with added electrostatic charge of the normal-state residual conductivity and superconducting transition temperature of films of amorphous Bi and Ga, metastable crystalline Ga, and disordered crystalline Pb. For the amorphous Bi samples adding electrons increased both the superconducting transition temperature Tc and the residual contivity σ0. For the other materials adding electrons lowered both Tc and σ0. In each case removing electrons produced a shift of equal magnitude but of opposite sign to that observed for negative charging. For a given applied charge the shifts in Tc and σ0 were proportional to the reciprocal of the film thickness within the accuracy of the measurements. Results were reproducible from sample to sample. The correlation between the signs of the shifts Tc and σ0 for the metals investigated was the reverse of that observed previously for Sn, In, and Tl. Measurements were also made of the effect of condensed oxygen on the superconducting transition temperature of the films. Physically adsorbed oxygen lowered Tc for all of the materials. Increasing the temperature to the point that a reaction between the metal and the condensed oxygen began produced a further reduction in Tc for Pb and metastable crystalline Ga.
Feasibility of Thin Film Thickness Monitoring by Holographic Interferometry
Authors: Balasubramanian N. , Anderson R. M. , Stevenson W. H.
Published: July 2002

This paper describes a potential technique for dynamically monitoring the thickness of a vacuum deposited thin film by holographic interferometry. This technique does not require the use of high quality optical components, the use of optical quality windows in the vacuum chamber wall, or the use of optically smooth film substrates. Experimental data are presented to substantiate the feasibility of the proposed technique. Several potential applications and the inherent advantages of this measurement method are discussed.
A Gas Analyzer for Trace Impurity Analysis
Authors: Elford M. T. , Milloy H. B.
Published: July 2002

A commercial residual gas analyzer has been modified by the addition of a directed gas jet to enable impurity concentrations to be measured in the low parts per million range. Particular attention has been paid to the abundance of N2 in Ne and Ar. The errors in the abundance measurements are estimated to be less than 0.2 ppm at 0.2 ppm of N2 in Ne and 0.6 ppm at 5 ppm of N2 in Ar. The choice of operating parameters, sources of error and advantages of this type of analyzer are discussed.
The Forgotten Sprengel–Babo Pump: A Continuously Recycling Positive-Displacement Mercury-Drop Gas Pump
Authors: Myer Jon H.
Published: July 2002

An outline of the history and evolution of the Sprengel-Babo pump is presented. A pump based on the original design was developed that can overcome large pressure differences and that is capable of evacuating containers to the vapor pressure of mercury. This apparatus substitutes for the positive-displacement Toepler pump usually employed in sealed circulating and metering vacuum systems and performs as an economical, low-capacity, high-vacuum pump.
The Physics of Some Superconducting Devices
Authors: Giaever Ivar
Published: July 2002

This is a brief review of some of the more common superconductive devices suitable for computer applications. None of the devices have emerged beyond the laboratory stage, mainly because of the low temperature requirements. Because of the increased sophistication in the integrated semi-conducting technology, it appears that superconducting devices can only succeed when their function is unique; for example, the ac Josephson effect is under serious consideration as a tool to determine the international voltage standard.
Kinetic Theory of a Modified Knudsen’s Absolute Manometer
Authors: Wu Yau , Dutt Birendra
Published: July 2002

The revised theory of thermal transpiration by Wu has been applied to the case of a modified Absolute Manometer for any temperature ratios and arbitrary accommodation coefficients on the boundaries of the three plates. According to the Lockenvitz’s approximate theory the pressure on the central vane is independent of its temperature. This paper explicitly shows that the pressure on the central vane is dependent on its temperature. A comparison of both theories has been discussed extensively for arbitrary temperature on the central plate.
Adsorbed CO2 Detection Using Attenuated Total Reflection
Authors: Novotny Donald B.
Published: July 2002

The use of the infrared attenuated total reflection technique (ATR) was explored as a sensitive procedure for the measurement of surface coverages of carbon dioxide films condensed on silicon. The technique of ATR appears to be feasible for the study of monolayer coverages. It was also demonstrated that the surface condensed CO2 molecule does not exhibit a rotation.
Elastic and Inelastic Low-Energy Electron Diffraction (LEED) from Solids
Authors: Laramore G. E.
Published: July 2002

A brief survey of some of the recent literature on elastic and inelastic low-energy electron diffraction (LEED) from solids is given, Our present knowledge of the electron-solid force law is discussed. The state of the art of theoretical model calculations of LEED intensity profiles is described and compared with the current status of experimental measurements. Prescriptions for obtaining surface crystallographic information directly from the experimental LEED profiles are described. The use of inelastic LEED as a spectroscopic probe of the electronic excitations of the surface region of solids is also mentioned.