bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Tool Oscillation and Hole Roundness Error in a Quasi-Static Model of Reaming
Authors: Bayly Philip V. , Young Keith A. , Calvert Sean G. , Halley Jeremiah E.
Published: July 2002

A quasi-static model of reaming is developed to explain oscillation of the tool during cutting and the resulting roundness errors in reamed holes. A tool with N evenly-spaced teeth often produces holes with N+1 or N−1 “lobes.” These profiles correspond, respectively, to forward or backward whirl of the tool at N cycles/rev. Other whirl harmonics (2N cycles/rev, e.g.) are occasionally seen as well. The quasi-static model is motivated by the observations that relatively large oscillations occur at frequencies well below the natural frequency of the tool, and that in this regime the wavelength of the hole profile is largely independent of both cutting speed and tool natural frequency. In the quasi-static approach, inertial and viscous damping forces are neglected, but the system remains dynamic because regenerative (time-delayed) cutting and rubbing forces are included. The model leads to an eigenvalue problem with forward and backward whirl solutions that closely resemble the tool behavior seen in practice.
Comparative Measurements of Different Solar Flux Gauge Types
Authors: Kaluza and Jens , Neumann Andreas
Published: July 2002

At the DLR Solar Furnace, calorimeters or circular foil radiometers are used for calibrating video camera based flux mapping systems. For many years, we have been investigating the accuracy of these devices and have undertaken several efforts to check their performance. Furthermore, we developed new instruments and compared these devices to the existent ones. The most recent measurements were collected within the frame of an international campaign, called Intercomp 2000, located at the DLR Solar Furnace in Cologne. This was the opportunity to test our own flux gauges, the 10000 suns Kendall radiometer, the 5000 suns SunCatch calorimeter, 2 HyCal circular foil radiometers for 3000 suns and 2 more HyCal radiometers for 11000 suns. About 100 measurements were taken in the range from 0,5 MW/m2 up to 5 MW/m2. The Kendall radiometer and the SunCatch calorimeter agreed well within the 2% margin. The circular foil HyCal radiometers showed significantly larger deviations. This leads to the conclusion that we have to change the manufacturer-given calibration constants of the HyCal radiometers by using the data collected with either the SunCatch or the Kendall flux gauge.
Modeling Vibratory Drilling Dynamics
Authors: Batzer Stephen A. , Gouskov Alexander M. , Voronov Sergey A.
Published: July 2002

The dynamic behavior of deep-hole vibratory drilling is analyzed. The mathematical model presented allows the determination of axial tool and workpiece displacements and cutting forces for significant dynamic system behavior such as the engagement and disengagement of the cutting tool into the workpiece material and tool breakthrough. Model parameters include the actual rigidity of the tool and workpiece holders, time-varying chip thickness, time lag for chip formation due to tool rotation and possible disengagement of drill cutting edges from the workpiece due to tool and/or workpiece axial vibrations. The main features of this model are its nonlinearity and inclusion of time lag differential equations, which require numeric solutions. The specific cutting conditions (feed, tool rotational velocity, amplitude and frequency of forced vibrations) necessary to obtain discontinuous chips and reliable removal are determined. Calculated bifurcation diagrams make it possible to derive the relevant domain of user-specified system parameters along with the determination of optimal cutting conditions.
Contact Vibration of Micro-Textured Sliders
Authors: Xu Junguo , Tokisue Hiromitsu , Tanaka Hideaki , Matsumoto Masaaki
Published: July 2002

We have formed a micro-texture on a pico-slider’s air-bearing surface to reduce the vibration when the slider comes into contact with the disk. The contact between slider and disk was controlled by adjusting the ‘interference height.’ Our measurements show that, at a giving interference height there is a significant less vibration in the textured slider. This lower amplitude of vibration is attributed to the lower friction force, which is in turn due to the smaller area of contact. We have also introduced the concept of interference area and found that it provides a good explanation of measured vibration.
Improved Algorithm for Tolerance-Based Stiffness Optimization of Machining Fixtures
Authors: Hurtado Jose´ F. , Melkote Shreyes N.
Published: July 2002

Current fixture design methods rely extensively on heuristics and lack a formal engineering approach to determine the necessary stiffness, dimensions, etc. This paper presents a model for stiffness optimization of machining fixtures based on the tolerance limit specified for the machined part surface. Specifically, the model allows systematic determination of the optimum fixture stiffness needed to keep the contribution of fixture deflection to the machined feature tolerance within a designer-specified level. Based on the stiffness optimization model presented here, the optimum dimensions of the fixture elements can also be determined. The model development relies on rigid body analysis methods, contact mechanics principles, and consideration of bulk elasticity of the fixture. The model is generic enough to be used for the design of dedicated or flexible fixtures consisting of mechanical elements. Two examples, one involving a pin-array type flexible fixture and another involving a dedicated fixture, are presented to illustrate the applicability of the model.
Laminar Heat Transfer in the Entrance Region of Internally Finned Square Ducts
Authors: Sakalis V. D. , Hatzikonstantinou P. M.
Published: July 2002

The laminar, incompressible, hydrodynamically fully developed and thermally developing flow is studied in straight ducts of square cross section, containing four equal, symmetrical, straight, thin and with 100 percent efficiency internal fins. Both the duct wall and the fins are subjected successively to constant temperature boundary condition. Numerical results are obtained using an iterative ADI scheme for the friction number, the temperature distribution and the Nusselt number for the thermally developing and developed regions as functions of axial distance and fin height. Results obtained are in good agreement with the corresponding literature values. In the thermally developing region a high heat transfer coefficient is obtained. Friction number and Nusselt number in the thermally developed limit increase as the fin height increases until they reach their critical values at fin heights near 0.85 and 0.73 respectively.
Reliability Analysis for Rotor Rubbing
Authors: Zhang Yimin , Wen Bangchun , Leung Andrew Y. T.
Published: July 2002

The dynamic equations of the Jeffcott rotor with imbalance are concerned. The reliability of rotor systems with rubbing is examined. A statistical fourth moment method is developed to determine the first four moments of the system response and the state function. The distribution function of the system state function is approximately determined by using the Edgeworth series technique. Its reliability is obtained. The effect on the reliability of the shaft stiffness, the external damping coefficient, the degree of imbalance and the stator stiffness is studied. Numerical results are also presented and discussed.
A New Wave Technique for Free Vibration of a String With Time-Varying Length
Authors: Lee S.-Y. , Lee M.
Published: July 2002

We introduce a new technique to analyze free vibration of a string with time-varying length by dealing with traveling waves. When the string length is varied, the natural frequencies and vibration energy are not constant. Thus, free response is not represented by discrete standing waves but by traveling waves, and a given phase of oscillation travels along the string. String tension and nonzero instantaneous transverse velocity at the moving boundary results in energy variation. When the string undergoes retraction, free vibration energy increases exponentially with time, causing dynamic instability. The new wave technique gives the time-varying natural frequency and the exact amount of energy transferred into the vibrating string at the moving boundary.
Residual Stress Measurement in a Ceramic-Metallic Graded Material
Authors: Hill Michael R. , Lin Wei-Yan
Published: July 2002

This paper presents experimental measurements of the through-thickness distribution of residual stress in a ceramic-metallic functionally graded material (FGM). It further presents an error analysis and optimization of the residual stress measurement technique. Measurements are made in a seven-layered plate with a base of commercially pure titanium and successive layers containing an increasing proportion of titanium-boride, reaching 85% titanium-boride in the final layer. The compliance method is employed to determine residual stress, where a slot is introduced using wire electric-discharge machining and strain release is measured as a function of increasing slot depth. Strain release measurements are used with a back-calculation scheme, based on finite element simulation, to provide residual stresses in the FGM. The analysis is complicated by the variation of material properties in the FGM, but tractable due to the flexibility of the finite element method. The Monte Carlo approach is used for error analysis and a method is described for optimization of the functional form assumed for the residual stresses. The magnitude and variation of the resulting residual stress distributions and several aspects of the error analyses are discussed.
Dynamic Response Predictions for a Mistuned Industrial Turbomachinery
Rotor Using Reduced-Order Modeling
Authors: Bladh R. , Pierre C. , Castanier M. P. , Kruse M. J.
Published: July 2002

This paper explores the effects of random blade mistuning on the dynamics of an advanced industrial compressor rotor, using a component-mode-based reduced-order model formulation for tuned and mistuned bladed disks. The technique uses modal data obtained from finite element models to create computationally inexpensive models of mistuned bladed disks in a systematic manner. Both free and forced responses of the rotor are considered, and the obtained results are compared with “benchmark” finite element solutions. A brief statistical study is presented, in which Weibull distributions are shown to yield reliable estimates of forced response statistics. Moreover, a simple method is presented for computing natural frequencies of noninteger harmonics, using conventional cyclic symmetry finite element analysis. This procedure enables quantification of frequency veering data relevant to the assessment of mistuning sensitivity (e.g., veering curvatures), and it may provide a tool for quantifying structural interblade coupling in finite element rotor models of arbitrary complexity and size. The mistuned forced response amplitudes and stresses are found to vary considerably with mistuning strength and the degree of structural coupling between the blades. In general, this work demonstrates how reduced order modeling and Weibull estimates of the forced response statistics combine to facilitate thorough investigations of the mistuning sensitivity of industrial turbomachinery rotors.
The Relationship Between Frictional Resistance and Roughness for Surfaces Smoothed by Sanding
Authors: Schultz Michael P.
Published: July 2002

An experimental investigation has been carried out to document and relate the frictional resistance and roughness texture of painted surfaces smoothed by sanding. Hydrodynamic tests were carried out in a towing tank using a flat plate test fixture towed at a Reynolds number ReL range of 2.8×106−5.5×106 based on the plate length and freestream velocity. Results indicate an increase in frictional resistance coefficient CF of up to 7.3% for an unsanded, as-sprayed paint surface compared to a sanded, polished surface. Significant increases in CF were also noted on surfaces sanded with sandpaper as fine as 600-grit as compared to the polished surface. The results show that, for the present surfaces, the centerline average height Ra is sufficient to explain a large majority of the variance in the roughness function ΔU+ in this Reynolds number range.
Low-Frequency Regenerative Vibration and the Formation of Lobed Holes in Drilling
Authors: Bayly Philip V. , Lamar Michael T. , Calvert Sean G.
Published: July 2002

Large-amplitude vibrations in drilling often occur at frequencies near multiples of the rotation frequency, even when these are much lower than the system’s first natural frequency. These vibrations are responsible for out-of-round, “lobed” holes. A simplified model of the mechanics of this phenomenon is presented in this paper. The model includes cutting and “rubbing” forces on the drill, but inertia and damping of the tool are neglected at low speeds. This quasi-static model remains dynamic because of the regenerative nature of cutting; the force on each cutting element depends on both the tool’s current position and its position at the time of the previous tooth passage. Characteristic solutions, including unstable retrograde “whirling” modes, are found in terms of eigenvalues and eigenvectors of a discrete state-transition matrix. These unstable modes correspond closely to behavior observed in drilling tests.
Mechanical Modeling and Characterization of the Curing Process of Underfill Materials
Authors: Ernst L. J. , van ’t Hof C. , Yang D. G. , Kiasat M. S. , Zhang G. Q. , Bressers H. J. L. , Caers J. F. J. , den Boer A. W. J. , Janssen J.
Published: July 2002

Thermo-setting polymers are widely used as underfill materials to improve the reliability of electronic packages. In the design phase, the influence of underfill applications on reliability is often judged through thermal and mechanical simulations, under assumed operating conditions. Because of lacking insight into the mechanical processes due to polymer curing, the impact of processing induced residual stress fields is often neglected. To investigate the evolution of stress and strain fields during the curing process it is important to assume a more appropriate starting point for subsequent process modeling. Furthermore, study of possible damage originating from the fabrication process then comes within reach. To facilitate future analysis of stress and strain fields during the curing process a cure dependent constitutive relation is assumed. An approximate investigation method for the process-dependent mechanical properties, based on Dynamic Mechanic Analysis (DMA), is developed. As an illustration the parameter identification is performed for a selected epoxy resin.
Analyzing the Relationship of Presence and Immersive Tendencies on the Conceptual Design Review Process
Authors: Banerjee Pat , Bochenek Grace M. , Ragusa James M.
Published: July 2002

The conceptual design review process is a critical cost determining step for complex products such as ground vehicles. The use of virtual environments (VEs) in this process has become increasingly popular with the advancement of 3D visualization technologies. Important to feelings experienced by participants in a VE are two parameters: presence and immersion. Presence is defined as the subjective experience of being in one place while physically being situated in another. Immersion is a state characterized by perceiving oneself to be enveloped by, included in, and interacting in an environment that provides a continuous stream of stimuli. While different virtual reality (VR) devices provide different degrees of presence and immersion, the amount of each is also dependent on the individual. In this paper, a relationship among presence, immersive tendencies of individuals, and design comprehension are explored. Further, a methodology to find the best design review process subject to certain criteria is presented. The results of two experiments involving the CAVE Automatic Virtual Environment CAVE™2 are discussed and evaluated. In one case, the U.S. Army investigates the use of the CAVE as a conceptual design review environment for advanced military vehicles in a comparison test with its present method of concept presentation and review. In a second experiment, CAVE users responded to a survey to determine the potential of VEs to improve design comprehension and immersive tendencies. In both cases, positive presence and immersion results support the idea that VEs offer advantages for conceptual design reviews over more traditional methods.
Stress and Displacement Fields for Propagating the Crack Along the Interface of Dissimilar Orthotropic Materials Under Dynamic Mode I and II Load
Authors: Lee K. H.
Published: July 2002

General stress and displacement fields are derived as a crack steadily propagates along the interface of dissimilar orthotropic materials under a dynamic mode I and II load. They are obtained from the complex function formulation of steady plane motion problems for an orthotropic material and the complex eigenexpansion function. After the relationship between stress intensity factors and stress components for a propagating crack is defined, the stress, displacement components, and energy release rate with stress intensity factors are derived. The results are useful for both dissimilar isotropic and orthotropic and isotropic-orthotropic bimaterials, and homogeneous isotropic and orthotropic materials under subsonic crack propagation velocity. [S0021-8936(00)00601-2]
Biaxial Mechanical Properties of the Natural and Glutaraldehyde Treated Aortic Valve Cusp—Part I: Experimental Results
Authors: Billiar K. L. , Sacks M. S.
Published: July 2002

To date, there are no constitutive models for either the natural or bioprosthetic aortic valve (AV), in part due to experimental complications related to the AV’s small size and heterogeneous fibrous structure. In this study, we developed specialized biaxial testing techniques for the AV cusp, including a method to determine the local structure–strain relationship to assess the effects of boundary tethering forces. Natural and glutaraldehyde (GL) treated cusps were subjected to an extensive biaxial testing protocol in which the ratios of the axial tensions were held at constant values. Results indicated that the local fiber architecture clearly dominated cuspal deformation, and that the tethering effects at the specimen boundaries were negligible. Due to unique aspects of cuspal fiber architecture, the most uniform region of deformation was found at the lower portion as opposed to the center of the cuspal specimen. In general, the circumferential strains were much smaller than the radial strains, indicating a profound degree of mechanical anisotropy, and that natural cusps were significantly more extensible than the GL treated cusps. Strong mechanical coupling between biaxial stretch axes produced negative circumferential strains under equibiaxial tension. Further, the large radial strains observed could not be explained by uncrimping of the collagen fibers, but may be due to large rotations of the highly aligned, circumferential-oriented collagen fibers in the fibrosa. In conclusion, this study provides new insights into the AV cusp’s structure–function relationship in addition to requisite data for constitutive modeling. [S0148-0731(00)00901-8]
Helical Flow Around Arterial Bends for Varying Body Mass
Authors: Zabielski L. , Mestel A. J.
Published: July 2002

The three dimensionally curved aortic arch is modeled as a portion of a helical pipe. Pulsatile blood flow therein is calculated assuming helical symmetry and an experimentally measured pressure pulse. Appropriate values for the Womersley and Reynolds numbers are taken from allometric scaling relations for a variety of body masses. The flow structure is discussed with particular reference to the wall shear, which is believed to be important in the inhibition of atheroma. It is found that nonplanar curvature limits the severity of flow separation at the inner bend, and reduces spatial variation of wall shear. [S0148-0731(00)00402-7]
An Axisymmetric Boundary Integral Model for Incompressible Linear Viscoelasticity: Application to the Micropipette Aspiration Contact Problem
Authors: Haider Mansoor A. , Guilak Farshid
Published: July 2002

The micropipette aspiration test has been used extensively in recent years as a means of quantifying cellular mechanics and molecular interactions at the microscopic scale. However, previous studies have generally modeled the cell as an infinite half-space in order to develop an analytical solution for a viscoelastic solid cell. In this study, an axisymmetric boundary integral formulation of the governing equations of incompressible linear viscoelasticity is presented and used to simulate the micropipette aspiration contact problem. The cell is idealized as a homogenous and isotropic continuum with constitutive equation given by three-parameter E,τ1,τ2 standard linear viscoelasticity. The formulation is used to develop a computational model via a “correspondence principle” in which the solution is written as the sum of a homogeneous (elastic) part and a nonhomogeneous part, which depends only on past values of the solution. Via a time-marching scheme, the solution of the viscoelastic problem is obtained by employing an elastic boundary element method with modified boundary conditions. The accuracy and convergence of the time-marching scheme are verified using an analytical solution. An incremental reformulation of the scheme is presented to facilitate the simulation of micropipette aspiration, a nonlinear contact problem. In contrast to the halfspace model (Sato et al., 1990), this computational model accounts for nonlinearities in the cell response that result from a consideration of geometric factors including the finite cell dimension (radius R), curvature of the cell boundary, evolution of the cell–micropipette contact region, and curvature of the edges of the micropipette (inner radius a, edge curvature radius ε). Using 60 quadratic boundary elements, a micropipette aspiration creep test with ramp time t*=0.1 s and ramp pressure p*/E=0.8 is simulated for the cases a/R=0.3, 0.4, 0.5 using mean parameter values for primary chondrocytes. Comparisons to the half-space model indicate that the computational model predicts an aspiration length that is less stiff during the initial ramp response t=0-1 s but more stiff at equilibrium t=200 s. Overall, the ramp and equilibrium predictions of aspiration length by the computational model are fairly insensitive to aspect ratio a/R but can differ from the half-space model by up to 20 percent. This computational approach may be readily extended to account for more complex geometries or inhomogeneities in cellular properties. [S0148-0731(00)00503-3]
Tailoring the Microstructure of a Metal-Reinforced Ceramic Matrix Composite
Authors: Sbaizero O. , Pezzotti G.
Published: July 2002

Alumina matrix was prepared with varying amounts of metal molybdenum particles of two different grain sizes. R-curves were determined during stable crack propagation and a piezo-spectroscopic technique was used to assess the bridging stresses developed along the crack wake (at the metal/matrix interface) at the critical condition for crack propagation. In both kinds of composites, the toughness monotonically increases with the amount of molybdenum added. In addition, bridging stress and therefore toughness were higher when coarser particles were present. The theoretical R-curves calculated from the discrete (microscopic) bridging stress distribution obtained by in situ Raman spectroscopy were in good agreement with the experimental data. [S0094-4289(00)02003-X]
Sub-Scale Demonstration of the Active Feedback Control of Gas-Turbine Combustion Instabilities
Authors: Sattinger Stanley S. , Neumeier Yedidia , Nabi Aharon , Zinn Ben T. , Amos David J. , Darling Douglas D.
Published: July 2002

Described are sub-scale tests that successfully demonstrate active feedback control as a means of suppressing damaging combustion oscillations in natural-gas-fueled, lean-premix combustors. The control approach is to damp the oscillations by suitably modulating an auxiliary flow of fuel injected near the flame. The control system incorporates state observer software that can ascertain the frequency, amplitude, and phase of the dominant modes of combustion oscillation, and a sub-scale fuel flow modulator that responds to frequencies well above 1 kHz. The demonstration was conducted on a test combustor that could sustain acoustically coupled combustion instabilities at preheat and pressurization conditions approaching those of gas-turbine engine operation. With the control system inactive, two separate instabilities occurred with combined amplitudes of pressure oscillations exceeding 70 kPa (10 psi). The active control system produced four-fold overall reduction in these amplitudes. With the exception of an explainable control response limitation at one frequency, this reduction represented a major milestone in the implementation of active control. [S0742-4795(00)00702-X]
Performance of a Reduced NOx Diffusion Flame Combustor for the MS5002 Gas Turbine
Authors: Feitelberg Alan S. , Starkey Michael D. , Schiefer Richard B. , Pavri Roointon E. , Bender Matt , Booth John L. , Schmidt Gordon R.
Published: July 2002

This paper describes a reduced NOx diffusion flame combustor that has been developed for the MS5002 gas turbine. Laboratory tests have shown that when firing with natural gas, without water or steam injection, NOx emissions from the new combustor are about 40 percent lower than NOx emissions from the standard MS5002 combustor. CO emissions are virtually unchanged at base load, but increase at part load conditions. The laboratory results were confirmed in 1997 by a commercial demonstration test at a British Petroleum site in Prudhoe Bay, Alaska. The standard MS5002 gas turbine is equipped with a conventional, swirl stabilized diffusion flame combustion system. The twelve standard combustors in an MS5002 turbine are cylindrical cans, approximately 27 cm (10.5 in.) in diameter and 112 cm (44 in.) long. A small, annular, vortex generator surrounds the single fuel nozzle that is centered at the inlet to each can. The walls of the cans are louvered for cooling, and contain an array of mixing and dilution holes that provide the air needed to complete combustion and dilute the burned gas to the desired turbine inlet temperature. The new, reduced NOx emissions combustor (referred to as a “lean head end,” or LHE, combustor) retains all of the key features of the conventional combustor; the only significant difference is the arrangement of the mixing and dilution holes in the cylindrical combustor can. By optimizing the number, diameter, and location of these holes, NOx emissions were substantially reduced. The materials of construction, fuel nozzle, and total combustor air flow were unchanged. The differences in NOx emissions between the standard and LHE combustors, as well as the variations in NOx emissions with firing temperature, were well correlated using turbulent flame length arguments. Details of this correlation are also presented. [S0742-4795(00)01602-1]
The Change in Overstrain Level Resulting From Machining of an Autofrettaged Thick-Walled Cylinder
Authors: Perl M.
Published: July 2002

An analytical model for predicting the level of autofrettage following either inner, outer, or combined machining of a gun barrel is developed based on Hill’s (Hill, R., 1950, The Mathematical Theory of Plasticity, Clarendon Press, Oxford, U.K.) solution for the autofrettage residual stress field. The analysis results in very simple algebraic expressions for the post-machining level of autofrettage in terms of the original level induced in the blank tube. In parallel, a finite element analysis of the machining process is performed in which the residual stress field is simulated by an equivalent thermal load. The numerical results are found to be in excellent agreement with the analytical ones. Thus, as an equivalent thermal load can always be determined, either analytically or numerically, for any other approximations to the residual stress field due to autofrettage (Perl, M., 1988, ASME J. Pressure Vessel Technol., 110, pp. 100–102), the foregoing methodology can be readily applied, enabling the determination of post-machining autofrettage level in these cases. [S0094-9930(00)00501-1]
SrSO4 by XPS
Authors: Vasquez Richard P.
Published: July 2002

X-ray photoelectron spectroscopy measurements of the principal core levels for high purity strontium sulfate are presented.
SrF2 by XPS
Authors: Vasquez Richard P.
Published: July 2002

X-ray photoemission measurements for high purity, ultradry SrF2 which has not been exposed to the atmosphere are presented. The data include the valence band region and energy losses from the principal core levels. Comparison of energy losses from the Sr 3d and Sr 4p peaks shows that a reported Sr 4s satellite peak is actually an energy loss peak associated with the Sr 4d.
Characterization of Polystyrenes (1 kDa) Functionalized With and Without a Perfluorinated Endgroup by TOF-SIMS: Observation of Intact Oligomers and Endgroup Effects
Authors: Belu A. M. , Hunt M. O. , DeSimone J. M. , Linton R. W.
Published: July 2002

TOF-SIMS measurements of 1 kDa polystyrene functionalized with a perfluoroalkyl endgroup are presented. Intact oligomer signals in the high mass range and fragment signals in the low mass range are observed (monolayer sample preparation on a silver substrate). The successful functionalization of the polystyrene with the perfluoroalkyl endgroup can be confirmed by the masses at which the intact oligomer signals arise. The high mass region of the spectrum is compared to TOF-SIMS measurements of polystyrene with a proton endgroup. The signal for a polystyrene oligomer with a proton endgroup with a specific degree of polymerization (n) arises at a lower mass because of the absence of the perfluoroalkyl endgroup. The effect of endgroup on the ion transformation probability of intact oligomers is demonstrated in a TOF-SIMS spectrum of a physical mixture (1:1 mole ratio) of polystyrene with a proton endgroup and polystyrene with a perfluoroalkyl endgroup.
Hydroxyapatite Characterized by XPS
Authors: Raikar Ganesh N. , Ong Joo L. , Lucas Linda C.
Published: July 2002

Hydroxyapatite [Ca10(PO4)6(OH)2] is commonly used as a coating material on orthopedic and dental implants. Hydroxyapatite is the major inorganic component of bone and is biocompatible with tissues when used on implants. Quality control tests are critical for the proper calcium to phosphorous ratio and also for checking for the presence of impurities. Being an important surface analytical tool used in the field of biomaterials, x-ray photoelectron spectroscopy was used to examine as-received hydroxyapatite pressed powders.
Epitaxial growth and physical properties of Permalloy film deposited on MgO(001) by biased dc plasma sputtering
Authors: Ishino Masaki , Yang Jiping , Makihara Kenji , Shi Ji , Hashimoto Mituru
Published: July 2002

Permalloy films 5 to about 40 nm thick were deposited on MgO(001) substrates at 230 °C by biased dc plasma sputtering at 2.7 kV in pure Ar gas using a Ni0.77Fe0.23 target. A bias voltage Vs between 0 and −150 V was applied to the substrate during deposition. The initial growth structure and physical properties of epitaxial films were investigated by x-ray photoelectron spectroscopy, reflection high energy electron diffraction, transmission electron microscopy, and by measuring electrical and magnetic properties. Epitaxial FCC–Ni1−xFex (Permalloy) films, where x is scattered between 0.36 and 0.32, could be prepared with NiFe(001)[010]∥MgO(001)[010] in full thickness independently of Vs. However, films with lower electrical resistivity and with higher saturation magnetization having an atomically smooth surface could be prepared at Vs=−90 V. The film was composed of discrete islands of at least 5 nm thickness at an initial growth stage. Misfit dislocations were already formed even in isolated islands along the MgO 100 direction with lattice expansion along the same direction. The practical lattice misfit f computed from transmission electron diffraction patterns gradually increased reaching the theoretical value with an increase in thickness up to 17 nm. Such an f dependence on thickness could be reasonably simulated on the basis of van der Merwe’s model. Thus the epitaxial Permalloy film grows forming misfit dislocations as well as expanding the lattice at the MgO interface to keep a balance between the energies of strain and dislocation. Under the application of Vs, the initial discrete island structure on the MgO substrate might be modified not only by accelerated incoming ions but also by charged ions on the insulating substrate.
Atomic force microscopy investigation of nanometer-scale modifications of polymer morphology caused by ultraviolet irradiation
Authors: Nowicki M. , Kaczmarek H. , Czajka R. , Susła B.
Published: July 2002

The surface morphology of polystyrene (PS), poly(ethylene oxide) (PEO), (PS) and polystyrene/poly(methyl methacrylate) blend (PS/PMMA) before and after ultraviolet (UV) irradiation was studied by means of atomic force microscopy. It was shown that the UV-induced changes were more noticeable on PS and PS/PMMA blend than on PEO samples. Moreover, the UV irradiation of PS sample doped with poly(methyl methacrylate) caused distinct changes in surface morphology. The nanometer-scale structures of the rod-like shape bumps of diameter of 300 nm and the height of 75 nm were created. We also showed that the very small forces of 0.2 nN are high enough to modify the surface of PS sample.
Mass spectrometry study during the vapor deposition of poly-para-xylylene thin films
Authors: Fortin J. B. , Lu T.-M.
Published: July 2002

A differentially pumped quadrupole mass spectrometer was used to analyze the vapor species present in the deposition chamber during the vapor deposition of poly-para-xylylene (parylene) thin films. The partial pressure in the deposition chamber of volatile contamination originating in the dimer source, di-para-xylylene, was determined. The solvents xylene and acetone, as well as water, were determined to be the main contaminants. Fragmentation patterns of the monomer and dimer were gathered and the composition of the main peaks in each pattern was determined. The largest peak was 104 atomic units (amu) in the monomer pattern and 103 amu in the dimer pattern. The quantitative conversion of dimer to monomer was studied as a function of the pyrolysis furnace temperature from 345 to 665 °C for pyrolysis tube liners of quartz, copper, and nickel. It was found that conversion begins at around 385 °C, and by 565 °C 100% of the dimer flowing through the pyrolysis zone is converted (or cracked) into the monomer.
Molecular approach toward information storage based on the redox properties of porphyrins in self-assembled monolayers
Authors: Roth Kristian M. , Dontha Narasaiah , Dabke Rajeev B. , Gryko Daniel T. , Clausen Christian , Lindsey Jonathan S. , Bocian David F. , Kuhr Werner G.
Published: July 2002

A molecular approach to information storage is described that uses porphyrins attached to a Au microelectrode as the memory storage element. A set of four zinc porphyrins has been examined, with each porphyrin bearing three mesityl groups and one S-acetylthio-derivatized linker of structure 1-[AcS-(CH2)n]-4-phenylene (n=0, 1, 2, or 3). Each porphyrin forms a self-assembled monolayer (SAM) on the Au microelectrode. Information is stored in the multiple oxidation states (neutral, monocation, dication) of the porphyrin. The charge retention time for each of the porphyrin monocations is in the regime of hundreds of seconds and varies with molecular structure (t1/2=116, 167, 656, and 885 s for n=0–3, respectively). The redox process in the SAM can be cycled thousands of times under ambient conditions without loss of signal, thus the loss in charge does not stem from decomposition. The fact that the system (1) is fabricated by self-assembly, (2) is addressed electrically, (3) operates under ambient conditions, (4) can be cycled multiple times, (5) requires no moving parts for reading and writing, and (6) is scalable to small dimensions make this approach attractive for molecular-based information storage.
Calixarene G-line double resist process with 15 nm resolution and large area exposure capability
Authors: Kedzierski Jakub , Anderson Erik , Bokor Jeffrey
Published: July 2002

Methods for combining fast optical lithography and slower high-resolution calixarene electron-beam lithography are presented. These methods rely on dividing the pattern into low-resolution and high-resolution components and exposing each with optical and electron-beam lithography steps, respectively. Patterns produced in this way have a minimum linewidth of 15 nm, and arbitrarily large low-resolution features. Although the procedures take two steps, for many patterns the total exposure time is significantly lower then it would be with a single step calixarene-only process. The optical and electron-beam exposures were aligned using SiGe zero-level alignment marks. A 5 nm misalignment between subsequent electron beam exposures is demonstrated.
High Vacuum Gas Friction Manometer
Authors: Fremerey J. K.
Published: July 2002

A new version of the well-known “spinning rotor pressure gauge,” which was described in 1962 by Beams and co-workers, is presented. The magnetic suspension is now achieved under a permanent magnet by means of a servo current which is applied to the rf sensing coil. The system involves negligible power dissipation. Instead of optical devices inductive pickup coils are used in the horizontal damping system as well as for the determination of the rotor frequency. The whole system thus avoids undesired heat and radiation transfer to the rotor and vacuum chamber. The gas pressure sensitivity is of the order 10−9 Torr.
The Separation Efficiency of the Molecular Distillation
Authors: Maa Jer Ru , Tsay Sun Yuan
Published: July 2002

Under idealized conditions, the relative volatility of the molecular distillation of a binary mixture is higher than that of equilibrium distillation by a factor of (M2/M1)1/2, where M2 and M1 are the molecular weights of the less and more volatile components, respectively. But in practice, this advantage of molecular distillation is usually not observed experimentally. This deficiency of separation efficiency of molecular distillation is now explained by computing the effects of surface cooling, surface depletion of the more volatile component, and the nonideality of the liquid mixtures. It is noted that shorter exposure time of the liquid surface is desirable for the design of an efficient molecular still. For the estimation of the separation efficiency of molecular stills whose exposure time of the liquid surface is not controlled mechanically, the surface renewal model is considered to be more realistic.
Cr–Cu and Cr–Cu–Cr Thin Film Metallization
Authors: O'Neill J. J. , Vossen J. L.
Published: July 2002

Thin film sandwiches of Cr–Cu and Cr–Cu–Cr are widely used for a number of electronic applications, but there has been no report of any systematic investigation of interactions or stability in these films. We have studied diffusion, oxidation, and stability in these films using resistometric techniques and electron diffraction and have found that these systems are useful only at low temperature (< 175°C) in oxidizing environments. At high temperatures in any environment, oxidation and diffusion result in many problems: resistivity instabilities, oxidation, hardening (bonding problems), variable solderability, and extreme difficulty in dielectric overcoating. Techniques are discussed to circumvent some of these problems.
The Design of Double Focusing Wien Filters
Authors: Collins R. E.
Published: July 2002

Conditions for stigmatic focusing in the Wien filter velocity selector are described. Two analyzers, designed according to these principles, have been built; preliminary results are presented. The application of this type of device as an electron spin rotator is discussed.
Optical Waveguides Fabricated by Ion Implantation
Authors: Namba S. , Aritome H. , Nishimura T. , Masuda K. , Toyoda K.
Published: July 2002

Optical waveguides are formed by implantation of various ions (H+, H2+, He+, Li+, and B+) in fused quartz and the properties of mode propagation are investigated at 6328 Å. The origin of the refractive index change is discussed from the ESR measurement. The depth distribution of defects is measured by ESR measurements and the effective thickness of the high-refractive index region is estimated from the measured depth distribution of defects. In as-implanted samples, the propagation loss decreases with decreasing fluence, but a minimum fluence is required for a given implantation energy for the lowest mode to be propagated. The propagation loss is explained to be internal absorption due to color centers introduced by ion implantation. It is shown that the propagation losses are different for various implanted ions. Annealing behavior of the propagation loss and the refractive index change is also presented.
Intensity singularities in the soft x-ray appearance potential spectra of the samarium N5 and M5 levels
Authors: Chamberlain M. B. , Baun W. L.
Published: July 2002

We have obtained soft x-ray appearance potential spectra of the N and M levels of samarium metal by scanning the electron excitation energy from 50 through 1560 eV. Newly observed line-like x-ray emission singularities are identified for excitation energies near the ionization potentials of the N5 and M5 levels. The excitation of the singularities depends upon both the energy of the incident electron and the angular momentum of the core state vacancy. The singularities are attributed to final state interactions between the inner vacancy and a two-electron bound state at the site of the core vacancy.
Focused electron beam induced deposition of gold
Authors: Utke I. , Hoffmann P. , Dwir B. , Leifer K. , Kapon E. , Doppelt P.
Published: July 2002

Codeposition of hydrocarbons is a severe problem during focused electron beam writing of pure metal nanostructures. When using organometallic precursors, a low metal content carbonaceous matrix embedding and separating numerous nanosized metal clusters is formed. In this work, we present a new and easy approach to obtain high purity gold lines: the use of inorganic PF3AuCl as a precursor. Electrical resistivities as low as 22 μΩ cm at 295 K (ten times the bulk Au value) were obtained. This is to our knowledge the best value for focused electron beam deposition obtained from the vapor phase so far. No special care was taken to prevent hydrocarbon contamination. The deposited nanostructure consists of gold grains varying in size and percolation with beam parameters.
Initial growth analysis of Si overlayers on cerium oxide layers
Authors: Kim Chong Geol
Published: July 2002

CeO(OH) 2 and Ce(OH)4 capped on cerium oxide were observed in x-ray photoemission spectroscopy. Since the cerium oxide surface is partially covered with hydroxide before Si deposition, the Si layer is expected to have a poor crystal quality at the initial Si growing stage. Cross-sectional transmission electron microscopy analysis verified that there was not SiO2, but amorphous Si and Ce2O3 between the Si overlayer and CeO2. The reason why SiO2 is not formed is explained. The transition of the growth mode for the Si overlayer was observed in atomic force microscopy images. It is confirmed that the growth mode of Si on CeO2/Si is step flow at the low deposition rate and island growth at the high deposition rate.
Modeling particle formation during low-pressure silane oxidation: Detailed chemical kinetics and aerosol dynamics
Authors: Suh S.-M. , Zachariah M. R. , Girshick S. L.
Published: July 2002

A detailed chemical kinetic model is presented for silicon oxide clustering that leads to particle nucleation during low-pressure silane oxidation. Quantum Rice–Ramsperger–Kassel theory was applied to an existing high-pressure silane oxidation mechanism to obtain estimates for the pressure dependence of rate parameters. Four classes of clustering pathways were considered based on current knowledge of reaction kinetics and cluster properties in the Si–H–O system. The species conservation equations and a moment-type aerosol dynamics model were formulated for a batch reactor undergoing homogeneous nucleation and particle growth by surface reactions and coagulation. The chemical kinetics model was coupled to the aerosol dynamics model, and time-dependent zero-dimensional simulations were conducted. The effects of pressure and temperature were examined, and the main contributing processes to particle formation and growth were assessed, for conditions around 0.8 Torr, 773 K, and an initial oxygen-to-silane ratio of 15.
Effects of oxygen flooding on crater bottom composition and roughness in ultrashallow secondary ion mass spectrometry depth profiling
Authors: Ng C. M. , Wee A. T. S. , Huan C. H. A. , See A.
Published: July 2002

The effect of oxygen flooding during ultrashallow depth profiling using secondary ion mass spectrometry (SIMS) was studied on a silicon sample implanted with 2 keV boron. SIMS depth profiles were obtained on a Cameca IMS6f using low energy (1 keV) O2+ primary beams at 56° incident angle. Different oxygen flooding conditions were used to investigate the dependence of crater bottom composition and roughening on oxygen partial pressure. The development of surface oxidation state and the thickness of the silicon oxide layer formed at the crater bottom during sputtering were determined using small area high resolution x-ray photoelectron spectroscopy. It is shown that the oxidation states during sputtering are dominated by Si0 (elemental Si) and Si4+(SiO2) with small contributions from other silicon suboxides, i.e., Si1+(Si2O), Si2+(SiO), and Si3+(Si2O3). The calculated equilibrium oxide thickness was found to increase with oxygen partial pressure. The sputtering induced surface roughening on the crater bottom was characterized using atomic force microscopy as a function of depth and oxygen partial pressure. Surface roughening appears to be suppressed under higher oxygen partial pressures, and is related to the nature of the oxide formed.
Characterization of atomic-layer-deposited silicon nitride/SiO2 stacked gate dielectrics for highly reliable p-metal-oxide-semiconductor field-effect transistors
Authors: Nakajima Anri , Yoshimoto Takashi , Kidera Toshirou , Obata Katsunori , Yokoyama Shin , Sunami Hideo , Hirose Masataka
Published: July 2002

An extremely thin (∼0.4 nm) silicon nitride layer has been deposited on thermally grown SiO2 by an atomic-layer-deposition (ALD) technique. The ALD silicon nitride is thermally stable as confirmed by x-ray photoelectron spectroscopy. The surface microroughness measured using atomic force microscopy is extremely small (average surface microroughness Ra of 0.031 nm) for the ALD silicon nitride on SiO2, especially in the thin thickness region (<0.5 nm). A smooth interface between the ALD silicon nitride and the poly-Si gate was also confirmed by transmission electron microscopy. The ALD technique allows us to fabricate an extremely thin, very uniform silicon nitride layer with atomic scale control. The boron penetration through the stacked gate dielectrics has dramatically been suppressed, and the reliability of the metal-oxide-semiconductor diodes with the stacked gate dielectrics has been significantly improved as confirmed by capacitance–voltage, gate current–gate voltage, and time-dependent dielectric-breakdown characteristics.