bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular Sieve Coated Saw Device for the Detection of Carbon Dioxide in the Presence of Water
Authors: Sun James T. , Dartt Christopher B. , Davis Mark E.
Published: June 2019

158 MHz SAW oscillators coated with organic polymers and zeolites were tested as sensors for monitoring the level of humidity and carbon dioxide in a flowing stream of nitrogen. All coatings exhibited responses to water vapor on the order of kilohertz frequency shifts, while the responses to carbon dioxide were significantly (generally one order of magnitude) smaller. The presence of CO2 dramatically interfered with the detection of water with poly-(ethylenimine) (PEI) coatings. Poly-vinyl pyridine (PVP) coatings showed large responses to water without any interference from CO2; CO2 produced little response whether water was present or not. ZSM-5 coatings also showed no evidence of interference between water and CO2; a detectable response for CO2 is possible in humid nitrogen.
Stm Studies of GMR Spin Valves
Authors: Misra R. D. K. , Ha T. , Kadmon Y. , Powell C. J. , Stiles M. D. , McMichael R. D. , Egelhoff W. F.
Published: June 2019

We have investigated the surface roughness and the grain size in giant magnetoresistance (GMR) spin valve multilayers of the general type: FeMn/Ni80Fe20Co/Cu/Co/Ni80Fe20 on glass and aluminum oxide substrates by scanning tunneling microscopy (STM). The two substrates give very similar results. These polycrystalline GMR multilayers have a tendency to exhibit larger grain size and increased roughness with increasing thickness of the metal layers. Samples deposited at a low substrate temperature (150 K) exhibit smaller grains and less roughness. Valleys between the dome-shaped individual grainsare the dominant form of roughness. This roughness contributes to the ferromagnetic, magnetostatic coupling in these films, an effect termed “orange peel” coupling by Néel. We have calculated the strength of this coupling, based on our STM images, and obtain values generally within about 20% of the experimental values. It appears likely that the ferromagnetic coupling generally attributed to so-called “pinholes” in the Cu when the Cu film thickness is too small is actually “orange peel” coupling caused by these valleys.
Hard Quasiamorphous Carbon - A Prospective Construction Material for Micro-Electro-Mechanical Systems
Authors: Dorfman Benjamin F. , Asoka-Kumar P. , Pollak Fred H. , Wan J. Z. , Zhu Qing
Published: June 2019

A new form of sp3/sp2 carbon has been fabricated which exhibits a large number of valuable properties. This material combines low density (≤1.65 g/cm3), low stress (≤0,05 GPa), low thermal expansion (1.6×10−6 K−1) with high hardness (˜ 30 GPa), modulus (˜ 200 GPa), cracking threshold (≥ 3 N), fracture toughness (≥ 10 MPa-m1/2), long-term thermal stability (≥ 450°C in air and ≥ 600°C without oxygen), extremely high thermal shock resistance, excellent interface and adhesion to silicon, metals, and ceramics and an absolute resistance to the silicon etching acids. Most of its properties are actually constant up to 700K. The material combines a basically amorphous structure with one-axis anisotropy and a graphite-like layered arrangement with a length scale of the modulation about 14Å. We refer to this quasi-amorphous material as QUASAM. This paper describes QUASAM synthesis conditions, growth front planarity and material characterization with high-resolution x-ray diffraction, positron annihilation spectroscopy, atomic force microscopy and micro-Raman spectroscopy. In addition the mechanical and thermal examination of QUASAM and QUASAM/Si will be presnted in terms of micro-electro-mechanical systems (MEMS) and the technology prospective requirements of MEMS.
Structural Characterization of P++ Si:B Layers for Bulk Micromachining
Authors: Wu K. C. , Shay P. A. , Borenstein J. T. , Fitzgerald E. A.
Published: June 2019

A range of techniques were used to characterize p++ silicon layers created by boron diffusion into (001) silicon wafers. These films were characterized by TEM, EBIC/ SEM, triple-axis XRD, SIMS, and modified Schimmel etching. Boron profiles predicted by SUPREM-3 process simulation software were compared to SIMS data. The results revealed gradients in boron and lattice constant, as well as a graded three-dimensional dislocation array from lattice-mismatch stress. Boron precipitation, induced by lattice-mismatch stress and concentrations above the solubility limit, was found to occur preferentially on dislocations. Additionally, the presence of dislocations was shown to affect the boron diffusion profile as well as etch morphology.
Characterization of the Piezoelectric Response of Aluminum Nitride Grown by dc Magnetron Sputtering for Applications in Thin-Film Resonators
Authors: Naik Rajan S. , Lutsky Joseph J. , Reif Rafael , Sodini Charles G.
Published: June 2019

Aluminum nitride is a promising material for use in thin-film bulk acoustic wave resonators for applications in RF bandpass filters. This paper discusses the requirements needed for a dc magnetron sputtering system to grow piezoelectrically active films with x-ray diffraction rocking curves of 3.3° on silicon substrates, 5° on aluminum substrates and oxygen concentrations of l at.%. For applications in integrated resonators, a materials characterization is insufficient in predicting the subsequent device performance. A simple acoustic device structure which allows a quick measurement of the device performance is used to extract maximum effective coupling coefficients keff2 of 0.009% at 3.4GHz and 0.002% at 2.4GHz for two different films with rocking curves of 5.7° and 9.0° respectively. This parameter extraction technique may be used to make relative comparisons between films grown under different deposition conditions.
The Effect of Inorganic Thin Film Material Processing and Properties on Stress in Silicon Piezoresistive Pressure Sensors
Authors: Bitko G. , McNeil A. C. , Monk D. J.
Published: June 2019

Silicon bulk micromachined piezoresistive pressure sensors are sensitive to stresses caused by the application of inorganic thin films typically used for passivation purposes, and the change in stress that is caused by temperature changes in the operating environment of the sensor. Stress behavior over temperature is characterized for both thermal oxides grown on silicon at thicknesses from 0.18 μm to 0.36 μm, and PECVD silicon nitride films at thicknesses from 0.40 μm to 0.80 μn. Electrical parametric behavior is characterized for typical piezoresistive pressure sensors with these thin films deposited and patterned in several proposed passivation schemes. A finite element analysis is performed to predict how device parameters vary as a function of thin film patterning and properties. Correlations are drawn between model predictions, independent thin film behavior, and device performance.
Polymers for Optical-Communications Device Fabrication-Optical Adhesives and Polyimide Waveguides-
Authors: Maruno T.
Published: June 2019

Two types of novel organic materials have been specifically developed for the fabrication of optical-communications systems devices. One is a UV-curable durable epoxy adhesive featuring refractive index controllability, low shrinkage during curing, and a low heat-expansion coefficient. These optically transparent adhesives are refractive index controllable between 1.45 and 1.59, and have been successfully applied to many optical devices that require return losses of more than 40 dB. The precision adhesives show an extremely low volume shrinkage of less than 2% during curing. The submicron positioning accuracy of these adhesives allows the fabrication of highperformance laser-diode modules and optical modulators. The other type of material is a fluorinated polyimide (F-PI) for optical waveguides; it features high optical transparency from visible to near-infrared and good heat resistance. Buried optical waveguides fabricated from F-PI operate in a single mode. They also exhibit a low loss of less than 0.3 dB/cm at the wavelength of 1.3 μm, and are heat and moisture resistant: the increase in optical loss is less than 5% after heating at 300°C for lh or after exposure to 85% relative humidity at 85°C for 24h.
Technology for Microassembling
Authors: Johansson S.
Published: June 2019

The various problem areas regarding assembling of microelements into complex microsystems are reviewed and the joining techniques are emphasised in particular. The dis,-ussion is focused on the fabrication of microrobotic systems and the various joining techniques are compared with respect to the potential of fulfilling the demands for such a process. Factor.; such as processing conditions, precision, stability, materials limitations, bond and device strength are included in the comparison. Different methods for handling and manipulating microelements are discussed and the experimental equipment used in our own investigations is presented.
Xrd and Xtem Investigation of Polycrystalline Silicon Carbide on Polycrystalline Silicon
Authors: Roy S. , Zorman C. A. , Wu C. H. , Fleischman A. J. , Mehregany M.
Published: June 2019

Atmospheric pressure chemical vapor deposition (APCVD) was used to grow silicon carbide (SiC) on as-deposited and annealed polycrystalline silicon (polysilicon) films which were deposited on oxidized Si wafers. X-ray diffraction (XRD) reveals that SiC films grown on asdeposited polysilicon have a (110) orientation. XRD performed on as-deposited polysilicon before and after SiC growth reveals that the orientation of polysilicon changes from (110) to a mixture of (110) and (11) during growth of 2 μm-thick SiC films. Cross-sectional transmission electron microscopy (XTEM) images of the SiC/polysilicon interface show that the SiC appears to be unaffected by the recrystallization of the underlying polysilicon during the SiC growth. XRD from samples of SiC grown on annealed polysilicon show that both films have (110) and (111) orientations. For SiC films grown on annealed polysilicon substrates, XTEM images show that the crystallinity of the annealed polysilicon substrate does not significantly change during SiC growth. Furthermore, an investigation of the SiC/annealed-polysilicon interface using selected area diffraction (SAD) shows that an epitaxial relationship exists between the polysilicon and SiC grains.
Improved Autoadhesion Measurement Method for Micromachined Polysilicon Beams
Authors: Boer Maarten P. de , Michalske Terry A.
Published: June 2019

We have measured autoadhesion (e.g. stiction) of individual polysilicon beams by interferometric optical microscopy. Untreated cantilever beams were dried from water in air, while treated beams were coated with a hydrophobic molecular coating of octadecyltrichlorosilane (ODTS). Adhesion values obtained for beams adhered to the substrate over a long length (large d) are independent of beam length with values of 16.7 and 4.4 mJ/m2 for untreated and treated samples respectively. These values can be understood in terms of differences in surface chemistry and polysilicon roughness. Using the shortest length beam which remains attached to the substrate, adhesion values were 280 and 16 mJ/m2 respectively. These higher values may be a result of capillarity effects. We recommend that measurements be made on beams in which d is large, in contrast to the current practice of noting the shortest beam adhered.
Optical Losses in Amorphous Silicon Solar Cells due to Back Reflectors
Authors: Sopori B. L. , Madjdpour J. , Von Roedern B. , Chen W. , Hegedus S. S.
Published: June 2019

We have used a new numerical model and here present initial results on how texturing and backreflectors affect the maximum achievable short-circuit current densities in amorphous silicon solar cells.
Dependence of Reliability of Ultrathin Mos Gate Oxides on the Fermi Level Positions at Gate and Substrate
Authors: Yang Tien-Chun , Bhat Navakanta , Saraswat Krishna C.
Published: June 2019

We demonstrate that the reliability of ultrathin (< 10 nm) gate oxide in MOS devices depends on the Fermi level position at the gate, and not on the position at the substrate for constant current gate injection (Vg-). The oxide breakdown strength (Qbd) is less for p+ poly-Si gate than for n+ poly-Si gate, but, it is independent of the substrate doping type. The degradation of oxides is closely related to the electric field across the gate oxide, which is influenced by the cathode Fermi level. P+ poly-Si gate has higher barrier height for tunneled electrons, therefore, the cathode electric field must be higher to give the same injection current density. A higher electric field gives more high energy electrons at the anode, and therefore the damage is more at the substrate interface. Different substrate types cause no effect on the oxide electric field, and as a result, they do not influence the degradation.
Effect of Cl in Gate Oxidation
Authors: Mertens P. W. , McGeary M. J. , Schaekers M. , Sprey H. , Vermeire B. , Depast M. , Meuris M. , Heyns M. M.
Published: June 2019

The present study reviews the use of Cl in gate oxidation furnaces for growth of high quality gate oxides with a thickness in the range of 2 to 15 nm. The following, commercially available, “state of the art” Cl-precursors have been tested: 1,1,1- trichloroethane (TCA), irons-1,2-dichloroethylene (DCE) and oxalyl chloride (OC). Different parameters were evaluated including: metal removal efficiency, poly-silicon haze, Fe bulk incorporation, carrier lifetime and Cl-incorporation in the oxide. Cl2was identified as the active component in Cl-oxidation. As a consequence, OC was identified as being the most efficient Cl-source. In particular, OC is the most suited Cl-source for applications requiring reduced oxygen concentration, such as the manufacturing of ultra thin gate oxides.
The Effect of Roughness Features on Mos Surface Electric Field and Fowler-Nordheim Tunneling Behavior
Authors: Lin Heng-Chih , Kan Edwin C. , Yamanaka Toshiaki , Fang Simon J. , Eason Kwame N. , Helms C. R.
Published: June 2019

For future CMOS GSI technology, Si/SiO2 interface micro-roughness becomes a non-negligible problem. Interface roughness causes fluctuations of the surface normal electric field, which, in turn, change the gate oxide Fowler-Nordheim tunneling behavior. In this research, we used a simple two-spheres model and a three-dimensional Laplace solver to simulate the electric field and the tunneling current in the oxide region. Our results show that both quantities are strong functions of roughness spatial wavelength, associated amplitude, and oxide thickness. We found that RMS roughness itself cannot fully characterize surface roughness and that roughness has a larger effect for thicker oxide in terms of surface electric field and tunneling behavior.
Identification of the Microscopic Structure of New Hot Carrier Damage Centers in Short Channel Mosfets
Authors: Billman C. A. , Lenahan P. M. , Weber W.
Published: June 2019

We show, for the first time, that E'like centers can be generated in hot hole stressing of short channel metal oxide silicon field effect transistors (MOSFETs). Prior to this study only Pb centers had been directly linked to this stressing phenomenon.
Kinetics of Cu Segregation in Al-Cu(1at% Cu) Interconnects Studied by Resistance Measurements
Authors: Kalkman A. J. , Verbruggen A. H. , Janssen G. C. A. M. , Radelaar S.
Published: June 2019

The time-dependence of the growth of Al2Cu precipitates in Al-Cu(lat% Cu) thin films is studied by means of resistance measurements at different temperatures. The samples are annealed at 400°C for 1 hour, and then quickly cooled down to room temperature. Afterwards, the samples are heated within one minute to a measurement temperature between 140 °C and 240 °C. Growth of precipitates causes a well defined decrease in resistance. The observed resistance decrease does not follow an exponential decay. In the investigated temperature range the resistance decrease can be accurately modelled by (R(t)-R∞) = (Ro-R∞)exp(-(t /τ)n), with the time constant τ= τ0 exp(Ea / kT). Excellent fits were obtained resulting in n = 0.66±0.05, independent of temperature, and Ea= 0.81±0.03 eV. This value for the activation energy agrees very well with the activation energy that has been reported in literature for both electromigration failure in Al-Cu and grain-boundary diffusion of Cu in Al. The value we found for n is intriguingly close to 2/3 and deviates strongly from the values of n reported for bulk Al-Cu (n = 1.5–1.8) in the same temperature range.
Thermal Conductivity Measurements of Interlevel Dielectrics
Authors: Varner Elizabeth B. , Marieb Thomas , Mack Anne Sauter , Lee Jin , Meyer William K. , Goodson Kenneth E.
Published: June 2019

The thermal conductivity of interlevel dielectrics (ILD) in interconnect structures is an important parameter in determining the temperature rise in the interconnects during use. Numerous researchers have previously shown that the thermal conductivity of thin film dielectrics can be significantly lower than that of bulk materials. As new materials, such as low-dielectric constant materials, are considered for use as ILD's, methods are needed for measuring the thermal conductivity of the these materials to determine whether they can adequately conduct heat away from interconnect lines. Many methods reported in the literature use patterned metal lines atop the dielectric on a Si substrate as combination Joule heaters and temperature sensors, and extract the thermal conductivity from a model of heat conduction through the dielectric to the substrate. One drawback of these methods is the lack of agreement of the conductivity determined from the different techniques. For example, a thermal conductivity ranging from 0.6 to 1.4 W/m-K was calculated for a 1.25 μm thick PTEOS oxide using five different methods on the same test structure. In this paper we present a unique combination of test structures, experimental methods, and heat conduction models that highlight the limitations of some of the models and methods. We also show good agreement in the thermal conductivity determined from both an experimental method and a finite element model, and suggest that these two techniques yield an accurate measure of the thermal conductivity of thin film dielectrics.
Interconnect Limits on Gigascale Integration (GSI)
Authors: Davis J. A. , Meindl J. D.
Published: June 2019

Opportunities for Gigascale Integration (GSI) are governed by a hierarchy of physical limits. The levels of this hierarchy have been codified as: 1) fundamental, 2) material, 3) device, 4) circuit and 5) system. Many key limits at all levels of the hierarchy can be displayed in the power, P, versus delay, td, plane and the reciprocal length squared, L-2, versus response time, τ, plane. Power, P, is the average power transfer during a binary switching transition and delay, td, is the time required for the transition. Length, L, is the distance traversed by an interconnect that joins two nodes on a chip and response time, τ, characterizes the corresponding interconnect circuit. At the system level of the hierarchy, quantitative definition of both the P versus td and the L-2 versus τ displays requires an estimate of the complete stochastic wiring distribution of a chip.

Based on Rent's Rule, a well known empirical relationship between the number of signal input/output terminals on a block of logic and the number of gate circuits with the block, a rigorous derivation of a new complete stochastic wire length distribution for an on-chip random logic network is described. This distribution is compared to actual data for modern microprocessors and to previously described distributions. A methodology for estimating the complete wire length distribution for future GSI products is proposed. The new distribution is then used to enhance the critical path model that determines the maximum clock frequency of a chip; to derive a preliminary power dissipation model for a random logic network; and, to define an optimal architecture of a multilevel interconnect network that minimizes overall chip size. In essence, a new complete stochastic wiring distribution provides a generic basis for maximizing the value obtained from a multilevel interconnect technology.
Corrosion Phenomena on the Grain Boundary of AlCu FIlms After Plasma Etching
Authors: Kim C. L. , Kwon K. H. , Yu S. J. , Kim H. J. , Chang E. G.
Published: June 2019

The effect of grain boundary on the corrosion of Al(Cu 1%) etched using SiCl4/Cl2/He/CHF3 gas plasma has been evaluated with XPS (X-ray photoelectron spectroscopy), SEM (scanning electron microscopy) and AES (Auger electron spectroscopy). It was found with SEM that the surface of Al(Cu 1 %) mainly corroded at the grain boundary. Using AES point analysis, the cause of selective corrosion at the grain boundary of Al(Cu 1 %) has been investigated. The results of AES indicated that the contents of F and Cl have made a difference at the analyzed positions. This seems to result from the imperfect crystalline structure of Al(Cu 1%) grain boundary. It was also confirmed that F has passivated the Cl at the grain boundary. The SEM and XPS results implied that Cl incorporated in the grain boundary of polycrystalline Al(Cu 1%) film accelerated the corrosion and could not be easily removed by the subsequent SF6 plasma treatment.
Effects of Local Interfacial Debonding on the Stress Evolution in Aluminum Interconnects
Authors: Shen Y. -L.
Published: June 2019

The evolution of thermal stresses in aluminum interconnects, with the presence of local debonded areas between the aluminum line and the surrounding dielectric, is studied numerically. Local interfacial debonding is presumably due to contamination during the line patterning process. Various geometrical features of the interconnect and the debond segment are assumed, and the resulting stress fields are examined by recourse to two- and three-dimensional finite element analyses. Implications of the findings to the interconnect reliability, particularly stress-induced voiding in aluminum lines, are discussed.
Performance and Reliability of Scaled Gate Dielectrics
Authors: Paulson W. M. , Tobin P. J. , Tseng H-H. , Maiti B. , Gelatos C. , Hegde R. I. , Anderson S. G. H.
Published: June 2019

Gate dielectrics for advanced ULSI circuits are rapidly scaling below 10 nm. Thinner dielectrics and smaller lateral dimensions are essential to produce high performance transistors for memories, microprocessors and microcontrollers. In this overview we will discuss the factors that affect the performance and reliability of scaled gate dielectrics. Process parameters that affect oxide and oxynitride dielectrics include substrates, pre-gate cleaning, growth parameters and growth techniques as well as oxide and oxynitride dielectric materials. Thin dielectrics require new or modified measurement methods and extensive use of physical analysis techniques such as SIMS, XPS, AFM and TEM to characterize these materials. Boron diffusion through thin gate oxides, HCI stress, and process induced damage can degrade dielectric quality and affect long term reliability. These factors will affect the performance and reliability of circuits with scaled gate dielectrics.
Synthesis of Ultra-thin stacked oxides using low pressure single furnace cluster process
Authors: Roy P. K. , Brady D. , Chetlur S. , Ma Y. , Morse K.
Published: June 2019

This work describes the development of a new grow-deposit-grow cluster process to grow ultra-thin stacked oxides. Two approaches for stacked oxide synthesis are discussed, namely thermal and chemical stacked oxides. Fabrication of chemical stacked oxide involves forming the first grown layer chemically after pre-gate cleaning, subsequent deposition of a TEOS-SiO2 layer and final densification/oxidation in a single low pressure (LP) furnace operation. In comparison, all three steps for thermal stacked oxide are accomplished by the LP cluster operation. Both processes offer the advantages of reduced cycle time and higher throughput to the stacked gate technology that produces superior Si/SiO2 interfaces and exhibits higher resistance to plasma-damage during ultra large scale integrated circuit (ULSI) processing. The quality and electrical characteristics of the stacked oxides are discussed.
In-Situ Stress Measurements During Dry Oxidation of Silicon
Authors: Yu Chia-Liang , Flinn Paul A. , Bravman John C.
Published: June 2019

In this study, we present results of both in-situ and ex-situ measurements of stress generated during dry oxidation of silicon. We show that the mechanical stress in as-grown dry oxides is a strong function of oxidation temperature and oxide thickness, but a weak function of oxygen partial pressure. We have identified a structural relaxation phenomenon after the oxide is formed, and found that the viscosity of the oxide increases with its age; consequently, the stress relaxation slows down due to this increase of viscosity. In this paper, we present a one-dimensional mechanical model to simulate the stress generation and relaxation during dry oxidation of silicon. The simulations of both in-situ and ex-situ tests are in good agreement with the experimental measurements.
Creating Data Packages For Aircraft Resupply
Authors: Yancey R. N.
Published: June 2019

The service of many military aircraft is being extended far beyond original design lives. When the C-130 is eventually retired, for example, it will have been in service for 79 years, well beyond its planned life expectancy of 40 years. Similarly, the line of KC-135's is presently expected to remain operational for 86 years, and the venerable B-52 an astounding 94 years! Not only are inventories of parts in short supply, but it may be necessary to acquire parts no one ever expected to replace. The first step in any reprocurement activity is the creation of a data package that can be submitted to suppliers for bid. If no computer-aided design (CAD) model exists, which is likely with older parts, the demands of modern electronic commerce dictate that one be created. If the original alloy is no longer obtainable, which is also likely with older parts, the demands of functional equivalence dictate that a suitable substitute be found and certified. Computed tomography (CT) offers an ideal way to obtain dimensional and material data critical to reverse engineering efforts. Industrial CT systems have progressed to the point where they can nondestructively measure part dimensions to an accuracy competitive with coordinate measuring machines and a speed competitive with laser scanners. Of the existing methods for obtaining part coordinates, only CT can dimension interior surfaces. Moreover, only CT has the ability to densitometrically quantify internal defects — a key consideration for computer-aided engineering activities. This paper describes the use of CT to help create data packages for resupply efforts and examples are presented.
Non-Destructive Evaluation of the Interface in Reinforced Concrete Using Phase Measurement Interferometry
Authors: Ghandehari Masoud , Krishnaswamy Sridhar , Shah Surendra
Published: June 2019

Studying the behavior of steel and concrete as a composite is of fundamental importance to the understanding of the cracking of reinforced concrete structures. In this article, a technique leading toward the development of a constitutive model for the interaction of steel and concrete is described. Experiments are based on pull-out specimens, where the shear stress and the two displacement components at the interface are measured. Phase Measurement Interferometry is used for accurate surface displacement measurement, and crack growth detection. The normal stress is then deduced using the measured crack length and crack opening displacements, along with a fracture mechanics based numerical simulation.
Paint As a Corrosion Sensor; Acrylic Coating Systems
Authors: Zhang J. , Frankel G. S.
Published: June 2019

Paint systems containing color-change or fluorescing compounds have been found to be sensitive to underlying corrosion processes by reacting to the pH increase associated with the cathodic reaction that accompanies corrosion. The sensitivity of these coating systems for detection of cathodic reactions associated with corrosion was determined by applying constant cathodic current and measuring the charge at which color change or fluorescence is detected. Visual observation of coated samples with the unaided eye can detect changes resulting from a charge corresponding to a hemispherical pit with depth on the order of 3–15 microns. Electrochemical Impedance Spectroscopy was also performed to test the influence of the indicating compound addition on the coating corrosion protectiveness.
Measurement Challenges Associated With Irradiated Reactor Components
Authors: Doctor Steven R.
Published: June 2019

Nuclear reactor components are known to degrade as reactors age. The reactor pressure vessel and the reactor internals are subjected to the highest radiation fields and thus, age faster. Some boiling water reactors are experiencing extensive cracking of the core shroud and some pressurized water reactors are experiencing a reduction in their fracture toughness. This paper provides background information on reactor pressure vessel materials, fabrication, and construction practices. It identifies some of the challenges that are associated with the nondestructive measurement of changes in material properties associated with these components. The inspection environment, surface conditions and designs are also discussed.
Energy-Microcrack Growth Measurments for Mortar Cylinders in Compression
Authors: Nagy E. N. , Landis E. N.
Published: June 2019

A high resolution three-dimensional scanning technique called x-ray microtomography was applied to measure internal damage and crack growth in small mortar cylinders loaded in compression. Tomographic scans were made at different load increments in the same specimen. Three-dimensional image analysis was used to measure internal crack growth during each load increment. Load-deformation curves were used to measure the work of the external load on the specimen. Non-recoverable work of load was related to measured crack growth to estimate work of fracture in three dimensions. Initial results indicate a roughly linear relationship between work of load and internal crack area.
Development of a Capacitor Probe to Detect Subsurface Deterioration in Concrete
Authors: Diefenderfer B. K. , Al-Qadi I. L. , Yoho J. J. , Riad S. M. , Loulizi A.
Published: June 2019

Portland cement concrete (PCC) structures deteriorate with age and need to be maintained or replaced. Early detection of deterioration in PCC (e.g., alkali-silica reaction, freeze/thaw damage, or chloride presence) can lead to significant reductions in maintenance costs. However, it is often too late to perform low-cost preventative maintenance by the time deterioration becomes evident. By developing techniques that would enable civil engineers to evaluate PCC structures and detect deterioration at early stages (without causing further damage), optimization of life-cycle costs of the constructed facility and minimization of disturbance to the facility users can be achieved.

Nondestructive evaluation (NDE) methods are potentially one of the most useful techniques ever developed for assessing constructed facilities. They are noninvasive and can be performed rapidly. Portland cement concrete can be nondestructively evaluated by electrically characterizing its complex dielectric constant. The real part of the dielectric constant depicts the velocity of electromagnetic waves in PCC. The imaginary part, termed the “loss factor,” describes the conductivity of PCC and the attenuation of electromagnetic waves.

Dielectric properties of PCC have been investigated in a laboratory setting using a parallel plate capacitor operating in the frequency range of 0.1 to 40.1MIHz. This capacitor set-up consists of two horizontal-parallel plates with an adjustable separation for insertion of a dielectric specimen (PCC). While useful in research, this approach is not practical for field implementation. A new capacitor probe has been developed which consists of two plates, located within the same horizontal plane, for placement upon the specimen to be tested. Preliminary results show that this technique is feasible and results are promising; further testing and evaluation is currently underway.
Nde of Tendon Ducts in Concrete Using 3D-Saft
Authors: Krause M. , Wiggenhauser H. , Müller W. , Schmitz V.
Published: June 2019

Prestressed or post-tensioned concrete structures are vulnerable to hazardous corrosion, if the tendon ducts are not fully injected with grout. Also compaction faults reduce the concrete strength. Advanced ultrasonic testing techniques and data analysis have been utilized to evaluate ducts in concrete members nondestructively. A laser Doppler vibrometer is used as an ultrasonic receiver to automatically collect the data. With this method ducts could be investigated which are not accessible by other methods as radiography or impact-echo. Encouraging results on different specimens are presented.
Practical Optical Characterization Of Fretted Surfaces
Authors: Gustafson S. C. , Mehta J. R. , Frantziskonis G. N.
Published: June 2019

Nominally smooth surfaces subjected to repeated contact may develop characteristic fretted textures. An important example concerns fretted surfaces that may develop on disk dovetail joints that secure fan blades in turbine engines. These surfaces may form sites for crack nucleation and subsequent catastrophic disk and engine failure. Thus a practical and reliable method for the nondestructive evaluation of such fretted surfaces is critically needed. In this paper straightforward optical techniques are considered for identifying and quantifying fretted (and other surface damaged) regions. For example, digital images of candidate surfaces may be processed to separate fretted from unfretted regions and to evaluate the relative degree of fretting. Ideally, optical characterization should be rapid, convenient, inexpensive, reliable, and insensitive to details of lighting and image capture.
Pulsed Eddy-Current Measurements of Corrosion and Cracking in Aging Aircraft
Authors: Moulder J. C. , Bieber J. A.
Published: June 2019

Pulsed, or transient eddy-current methods are an effective tool for quantitative characterization of hidden corrosion and cracking in multi-layer aircraft structures. Eddy currents are the method of choice for this task, since they penetrate multiple layers of metal, whether or not the layers are mechanically bonded. The pulsed eddy-current technique is an important advance over conventional eddy-current methods because it rapidly acquires data over a wide range of frequencies, thereby providing more information than a conventional, single-frequency eddy-current instrument. We have combined a pulsed eddy-current instrument with a portable two-axis scanner to produce an instrument capable of rapidly scanning aircraft lap splices in situ, producing pseudo-color images that reveal hidden corrosion or cracking. A unique feature of time-domain eddy-current data is the ability to selectively filter clutter from the image by time-gating the pulsed signal. Time-gating permits the user to select the inspection depth, thereby eliminating interference from upper layers, air gaps, lift-off variation and fasteners. By using a theoretical model of the pulsed eddy-current system, it is possible to interpret the data quantitatively, yielding quantitative maps of corrosion damage. Some of the same advantages of the pulsed eddycurrent technique apply to the characterization of hidden fatigue cracks as well, although the tieory for crack signals is less advanced.
Electromagnetic Acoustic Resonance To Assess Creep Damage In 2.25Cr-lMo Steel
Authors: Hirao M. , Ogi H. , Ohtani T. , Morishita T.
Published: June 2019

Method of electromagnetic acoustic resonance (EMAR) was applied to the noncontact measurement of the shear wave attenuation during the creep test of 2.25Cr-1Mo steels. Two electromagnetic acoustic transducers were manufactured for this purpose, which generate the polarized shear waves through the magnetostriction effect. The attenuation coefficient increased with the creep deformation. The evolution range of the attenuation was beyond 0.1 μs−1 before the failure, which was much larger than the attenuation variation among the samples.
Ultrasonic Quantification Of Corroded Surfaces
Authors: Mullins W. M. , Shamachary S. S.
Published: June 2019

The surface damage introduced by general corrosion attack of surfaces is considered deleterious to long term structural integrity. As a result, the quantification of this damage represents an interest in the NDE community. In this document, the chemical kinetics of general attack are used to model the morphology of the surface as a function of time of exposure. Timeof- flight ultrasonic data for corroded surfaces are presented which appear to agree with the model predictions. The experimental results are critically reviewed with respect to the practical limitations of the ultrasonic experiments. The effect of exposure on surface morphology and surface stress concentration are shown and related to the classic ultrasonic measurement techniques. The relationships are used to suggest potentially important ultrasonic measurement techniques and to underline the inherent limitations of many classical ultrasonic measurements.
Thermal Wave Imaging For Characterizing Structures In Aging Aircraft
Authors: Han Xiaoyan , Favro L. D. , Thomas R. L.
Published: June 2019

We present examples of the application of thermal wave imaging to the detection of structural defects in aging aircraft. Examples include the imaging of bonded and disbonded internal doublers, together with quantitative corrosion thinning measurements made from thermal wave images of aircraft fuselages and wing skins. We also show example images of impact damage, disbonds and delaminations in composite aircraft materials.
The Role Of Grain Noise In Eddy Current Inspection Of Titanium Alloys
Authors: Blodgett M. P. , Nagy P. B.
Published: June 2019

This paper discusses the role electrical anisotropy plays in the structural integrity assessment of polycrystalline titanium alloys from the standpoint of fatigue crack detection and the related issue of microstructural noise. In eddy current inspection of noncubic crystallographic classes of polycrystalline metals the electric anisotropy of individual grains produces an inherent microstructural variation or noise that is very similar to the well-known acoustic noise produced by the elastic anisotropy of both cubic and noncubic materials in ultrasonic characterization. The presented results demonstrate that although the electrical grain noise is detrimental in eddy current nondestructive testing for small flaws, it can be also exploited for characterization of the microstructure in noncubic polycrystalline materials such as titanium alloys in the same way acoustic grain noise is used for ultrasonic characterization of the microstructure in different materials.
Early Fatigue Damage In Carbon Fiber Composites Observed By Electrical Resistance Measurement
Authors: Wang Shoukai , Shui Xiaoping , Fu Xuli , Chung D. D. L.
Published: June 2019

Early fatigue damage during the first tenth (or less) of the fatigue life was observed in carbon fiber composites by DC electrical resistance measurement. The damage was most severe in the first loading cycle and the incremental damage in each subsequent cycle diminished cycle by cycle. For the continuous carbon fiber carbon-matrix composite, the resistance increased irreversibly during early fatigue due to matrix damage and possibly fiber fracture as well. For the short carbon fiber polymer-matrix and cement-matrix composites, the resistance decreased irreversibly during early fatigue due to matrix damage near the junction of adjacent fibers and the resulting increase in the chance that adjacent fibers touched one another.
Surface Roughness Characterization of al Films by Spectroscopic Ellipsometry
Authors: Blanco J. R. , Vedam K. , McMarr P. J. , Bennett J. M.
Published: June 2019

Well characterized rough surfaces of aluminum films have been studied by the nondestructive technique of Spectroscopie Ellipsometry (SE). The roughness of the aluminum specimens had been characterized earlier by Total Integrated Scattering and Stylus Profilometry techniques to obtain numerical estimates of ras roughness and autocovariance lengths. The present SE measurements on these specimens were carried out at a number of angles of incidence in the range 30–80° and at a number of discrete wavelengths in the spectral range 300–650nm. The SE results were then analyzed by the scalar theory of diffraction from random rough surfaces by treating the surface as a simple random rough surface. The results of such analyses of the SE measurements are compared with the results of the earlier characterization techniques.
Experience in Reconstructive Surgery of Craniomaxillofacial Deformities: With Osteomesh, Eleven Years Experience
Authors: Habal Mutaz B. , Leake Donald L.
Published: June 2019

The best possible implantable biomaterial for bony contour abnormalities is autogenous bone grafts. However, some conditions may be present that require use of alloplastic materials. Such alloplastic material must be inert and there should be no reaction in the body to it. The composite graft described in this chapter is a combination of the two different materials described. To have a better take, the bone graft used is ground with a craniotome, and then mixed with blood. This produces an inductive matrix that promotes osteoneogenesis. The alloplastic material is a tray or a template where the bone is placed “in”, “on”, or “under” the implant to allow for complete solidification and better healing. The material used is polyetherurethane-impregnated terephthalate (Dacon) also referred to as osteomesh (R) (Xomed Corporation, Jacksonville, Florida). In a few instances the osteomesh was removed and we noted complete solidification of the bone (resembling skull in the case of the skull defect). For over eleven years, since the success in the experimental animal [1], this composite graft was used in clinical situations with good success [2] in over 100 patients. These patients treated were selected and a strict set of indications and contraindications were instituted and implemented, prior to the applications of this treatment in the individual patient.
Mechanisms of Failure of Arterial Prostheses
Authors: Wesolow M. D. Adam
Published: June 2019

One of the most successfully applied classes of biomaterials is the porous textile vascular prosthesis. Experimental and clinical investigations have been continuously conducted during the past thirty years to study tissue healing, clinical longevity and improved design of these prostheses. The vascular device retrieval program has enabled classification of the 40 or more identified mechanisms of failure of arterial prostheses into the following major groupings: A. Failure of diagnosis B. Error in implantation C. Patient contribution D. Complications of healing E. Fabrication failure F. Infection
Carbon Fiber Reinforced Triazin Resin for Endoprostheses
Authors: Esper F. J. , Harms J. , Mittelmeier H. , Gohl W.
Published: June 2019

Metal alloys, ceramics, and thermoplastics are commonly used as materials for endoprostheses, especially artificial hip joints. Prostheses made of these materials still retain disadvantages which have been responsible for failures in the past. A new material, without the abovementioned disadvantages, has been developed. It is a carbon fiber reinforced thermo set based on the triazin resin. Its principle mechanical properties can be matched with those of bone. The new material (referred to as TCF) has a higher bending and fatigue strength than cast metallic alloys if endless fibers are applied. Its creep rate at 37°C under high load (3000 N), as well as its wear rate against metallic or ceramic wear partners, is negligible. Experiments with animals based on ten years of experience show good osteocompatibility of the TCF. Toxic reactions of the tissue caused by the TCF implants themselves, or by fine wear debris found in membranes of connective tissue (or lymph nodes), were not observed at all. Tissue reacts on large particles of TCF wear debris in the same manner as it does on particulates of the same size of polyethylene. It can be expected that the favorable biomechanical and biological properties of the TCF material will make it a good alternative to other materials already in use for construction of endoprostheses, especially hip joints.
Clinical and Laboratory Experience with the use of Titanium and Titanium Type 318 Alloy for Bone and Joint Replacement
Authors: Wright Keith W. J.
Published: June 2019

Commercially pure titanium type T5 and titanium type TAl alloy have been used at Stanmore in major bone and joint replacement prostheses since 1963 and 1971 respectively. Because laboratory studies indicated cast CoCrMo alloy to be a superior bearing material both titanium materials have been joined to cast CoCrMo alloy bearing elements to form composite prostheses with no apparent adverse clinical effects.

Laboratory studies and clinical experience have shown the inadequacy of the fatigue properties of titanium type T5 and cast CoCrMo alloy for highly stressed intramedullary stems. Nevertheless, although titanium type TAl alloy has superior fatigue properties highly stressed components of this material are not immune to fatigue failure.

Wear of U.H.M.W.P.E. appears to be greater when articulated with titanium type TAI alloy than it is when articulated with cast CoCrMo alloy and Al2O3 counterfaces. In addition, capsular tissue which rubs on titanium type TAl alloy can become heavily pigmented. However, to date no clinical complications appear to have resulted from either of these shortcomings. Whether a surface treatment for titanium type TAl alloy such as ion implantation will both improve its wear characteristics with U.H.M.W.P.E. and reduce the amount of metallic material liberated into the soft tissues has yet to be established.
Improvements in the Hardness of Surgical Titanium Alloys by Ion Implantation
Authors: Sioshansi Piran , Oliver Richard W.
Published: June 2019

Titanium is generally recognized as one of the most biocompatible metal species, and as such, titanium based alloys are among the top contenders for the material of choice in orthopaedic prostheses. The questionable wear performance of titanium in abrasive and adhesive wearing conditions has been an impediment for a more widespread use of the alloy up to now. The ion implantation process has been shown to be extremely effective, in laboratory experiments, in enhancing the wear performance of the metal and at the same time reducing the wear of ultra high molecular weight polyethylene (UHMWPE) mating surface in contact with the alloy.

The present paper focuses on the increased hardness of the Ti-6Al-4V alloy as a result of ion implantation. It is generally believed that the wear improvements of titanium as a result of ion implantation are directly proportional to increased hardness of the surface. Thus, hardness data can be useful for the screening of ion implantation parameters to identify the optimum processing conditions. The Knoop hardness of ion implanted Ti-6Al-4V samples has been measured for B, C, N, N2, O and Ne ion species.