bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of Thin Films Using Total Internal Reflection Microscopy
Authors: Williams FL , Carniglia CK , Pond BJ , Stowell WK
Published: March 2009

The application of total internal reflection microscopy (TIRM) to the inspection of subwavelength optical features on surfaces has been well documented.1–3 This paper discusses recent experiments testing the feasibility of using TIRM to study dielectric coatings in the nucleation stage. Samples were coated with thin films of different thicknesses to allow optical scattering levels to be determined as a function of coating thickness. An increase was observed in scatter levels with increasing coating thickness, and is assumed to be related to thin film microstructure. Thus, TIRM provides a means of detecting film defects in the early stages of coating growth, as well as identifying possible precursors to nodules that are often observed in thin and thick films.
Scattering Characterization of Materials in Thin Film Form
Authors: Amra C
Published: March 2009

The “scattering characterization” that was developed in Marseilles enables us today, with the help of complementary tools (causal model, isotropy degree, …), to point out the origin of micro-roughness in optical coatings without any ambiguity. Each material can be associated to a key parameter that characterizes its scattering. These parameters can be determined through measurements performed on one single layer, and then can be used to predict scattering in more complex systems.

Experimental results (IAD, IP) are presented and show that in most cases, scattering measurement of substrate is sufficient to predict scattering from any coating with a high accuracy. However, at very low scattering levels (under 10-6), this prediction is limited by the presence of local defects in the coatings.
Interfacial Stability in Optical Coatings
Authors: Lewis KL , Pitt AM , Cullis AG , Welford K , Muirhead IT
Published: March 2009

As optical coatings become more complex, partly due to improved deposition processes and more stringent design criteria, the number of layers in the coating increases, with a corresponding risk of interfacial instability. This can lead to partial film delamination, arising from residual stress effects, from interdiffusion of different chemical species across the film boundaries, or from the presence of impurity species at the interface itself. These effects are very relevant to the application of such coatings in laser systems, especially where the newer digital techniques are used to synthesise graded designs. One useful way of exploring the effect is to incorporate a large number of interfaces within a Fabry-Perot etalon cavity, and to temperature cycle the structure, whilst measuring its spectral response. The changes observed can be correlated with information derived from X-ray photoelectron spectroscopic examination of discrete interfaces specifically fabricated to simulate those present in the etalon cavity.
Laser Conditioning of Optical Thin Films
Authors: Wolfe CR , Kozlowski MR , Campbell JH , Rainer F , Morgan AJ , Gonzales RP
Published: March 2009

Results are presented that show the damage thresholds of e-beam deposited multilayer HfO2/SiO2 thin films can be permanently increased by a factor of 2 to 3 by illumination with subthreshold fluences of laser light. This sub-threshold illumination procedure is referred to as “laser conditioning”. The films used in this study were prepared by three different physical-vapor-deposition techniques: ion-beam sputtering, plasma plating and e-beam evaporation. Only the e-beam deposited films showed consistent and significant improvement with laser conditioning. Of the material pairs examined (HfO2/SiO2, ZrO2/SiO2 and TiO2/SiO2), HfO2/SiO2 gave the greatest and most consistent damage improvement with conditioning. The number of layers and the reflective or transmissive characteristics of the HfO2/SiO2 films were found to have little impact on laser conditioning of the film. The results show that the damage thresholds of a wide range of e-beam deposited coatings (e.g. HR's, polarizers, etc.) can be improved by laser conditioning. Several possible conditioning mechanisms are examined.
Damage Threshold Measurements of Reflective and Transmissive Optics at 130 nm
Authors: Muller CH , Hamilton CE
Published: March 2009

The GLORIA VUV facility at Spectra Technology, Inc. has been used to measure the damage threshold and reflectivity of first surface Al+MgF2 mirrors and second surface MgF2+Al+MgF2 mirrors. The mirrors were illuminated by high power VUV coherent radiation at 130 nm. Mirror reflectivity was monitored for several thousand pulses for each optic studied. Two nanosecond long pulses and energy densities as high as 20 mJ cm-2 were used for the measurements. In addition, measurements of “color center” formation rates in transmissive optics have been obtained. The GLORIA VUV facility, experimental measurement system, and damage results will be discussed in detail.
Laser Induced Damage Thresholds of Dielectric Coatings at 193 nm and Correlations to Optical Constants and Process Parameters
Authors: Kolbe J , Müller H , Schink H , Welling H , Ebert J
Published: March 2009

Laser-induced damage thresholds of dielectric single layers and reflectors were measured at 193 nm. Layers of Al2O3 and SiO2 were prepared by electron beam evaporation and by ion beam sputtering; layers of NaF, AlF3, MgF2, GdF3, LaF3, NdF3 and YF3 were prepared by thermal evaporation. Spectrophotometric methods were used to evaluate optical constants and inhomogeneity coefficients in the spectral range between 150 nm and 250 nm. The dependence of refractive indices and absorption coefficients on process parameters and deposition methods was analyzed in order to prepare low loss reflectors for 193 nm and 157 nm.
Angular Dependence of Thin-Film Dielectric Coating Damage Thresholds Revisited
Authors: Boyer JD , Foltyn SR , Mauro BR , Sanders VE
Published: March 2009

Newnam et al. [1] reported experiments showing that the angular dependence of 351-nm laser damage thresholds in HfO2/SiO2 multilayer dielectric reflectors was much weaker than even the 1/cosθ expected from simple geometric fluence dilution. Several plausible explanations were suggested, but none were convincing. We propose a simple geometric model based on a cylindrical form for the coating defect responsible for damage initiation. We have measured 248-nm damage thresholds for bare fused silica, evaporated aluminium films, and HfO2/SiO2 and Al2O3/SiO2 dielectric reflectors at angles out to 85°. The measured data agree well with our simple model.
Pulse-Width Dependence of Optical Coating Damage at 1052 nm
Authors: Yoshida K , Ikunishi S , Yoshida H , Kato Y , Nakai S
Published: March 2009

Pulse-width dependence of optical coating damages at 1053 nm laser wavelength is studied. Quarterwave-thick single layer films of high-index materials of A12O3, ZrO2 and TiO2, and low-index materials of MgF2 and SiO2 were tested. Damage thresholds of the MgF2 and SiO2 films follow the square root dependence on the pulse-width τ (√τ scaling) over the pulse widths of 0.35-90 ns. Although the damage thresholds of the A12O3, ZrO2 and TiO2 films followed the √τ scaling from 0.35 to 1 ns, they become independent of the pulse-width for the pulse-widths longer than 6 ns. That is, the pulse-width dependence of the damage threshold is determined by the absorption property of the coating layer, which controls the damage mechanism.
Damage Resistant Optical Coatings Prepared Using High Temperature, Plasma Chemical-Vapor-Deposition
Authors: Campbell JH , Emmett JL , Brusasco RM , Rainer F , Kersten RT , Paquet V , Etzkorn H-W
Published: March 2009

Multilayer dielectric optical coatings, nominally consisting of 1000 or more optical-quarterwave layers, have been prepared by reacting SiCl4 and a halogenated dopant (e.g. GeCl4) with O2 in a microwave-driven plasma. The dopant concentration is such that the index difference (An) between adjacent quarterwave layers is about 0.02 or less. The deposition is carried out at high substrate temperatures (850 to 1100°C) producing a fully dense, fused silica coating. Surface damage thresholds of high reflectivity (HR) coatings prepared by this plasma process are comparable to those for fused silica. For example, at 1.06 μm and 16-ns we measure surface damage thresholds greater than 45 J/cm2 compared to about 45–60 J/cm2 for super-polished optical fused silica.
A High Temperature, Plasma-Assisted Chemical Vapor Deposition System
Authors: Brusasco RM , Britten JA , Thorsness CB , Scrivener MS , Unites WG , Campbell JH , Johnson WL
Published: March 2009

We have designed and built a high-temperature, plasma-assisted, chemical vapor deposition system to deposit multilayer optical coatings of SiO2 and doped-SiO2 on flat substrates. The coater concept and design is an outgrowth of our recent work with Schott Glaswerke demonstrating the use of plasma assisted CVD to prepare very high damage threshold optical coatings. (That work is reported in a companion paper at this Symposium).
The Evolution of Molecular Beam Deposition (MBD) from Laboratory to Production Usage
Authors: Hale CCH , Muirhead IT , Fisher SP , Mathew GJH
Published: March 2009

The use of molecular beam technology (MBD) under ultra high vacuum conditions (UHV) has proved to be a highly controllable process capable of producing dense films which are free of porosity, low in impurities and having bulk like optical properties. These distinctions are requisite for coatings which require a high laser damage threshold, low scatter and stable spectral characteristics. The application also lends itself to the formation of novel distributed Bragg reflectors (DBR) and rugate structures which require a highly controllable deposition process to form the many, often very thin, layers involved.

In order to further the research in this field and produce advanced optical coatings for applications requiring stringent specification beyond the capability of conventional technology, a VG Semicon V90H MBE system has been installed at OCLI, Scotland, purchased and operated under a joint venture between OCLI Ltd and Heriot Watt University. This facility can provide a thickness uniformity of better than +/- 0.5% over a 4" substrate.

This paper will review the current results from this unique deposition facility and describe the advances made in depositing complex multilayer coatings.
Investigation and Modelling of Laser Damage Properties of Fabry-Perot Filters
Authors: McInnes A , MacDonald CM , Gibson DR , Wilson AD
Published: March 2009

The electric field distribution within a fabry-perot etalon is readily variable by changing the angle of incidence or the thickness of the etalon. The laser damage threshold (LDT) of Fabry-Perot etalons was measured as a function of electric field distribution, monitored through the transmittance. Two types of etalon were used — thin film Fabry-Perot devices with high finesse were investigated at 1.064μm, and a simple dielectric slab etalon (Germanium) was investigated at 10.6μm.

In the latter case the results show a correlation between the LDT and the inverse square of the calculated peak electric field (1/E2) in the sample. For the thin film Fabry-Perot, the correlation is between the LDT and 1/E2 at the spacer boundaries. Subsequent sample analysis also suggests that damage was initiated at spacer boundaries.

It is concluded that the laser damage properties of such etalons are in agreement with theoretical expectations, and that their damage behaviour can be described by a single parameter.
High Damage Threshold AlO.OH-SiO2 HR Coatings Prepared by the Sol-Gel Process
Authors: Thomas IM
Published: March 2009

Our study of highly reflective (HR) dielectric coatings prepared by the sol-gel process has indicated that hydrated alumina and silica are the materials of choice for the high and low index components respectively.

We can now prepare 32–36 quarter-wave-layer samples from colloidal suspensions of the relevant oxides by spin coating at room temperature. These have reflectivities of about 99% and damage thresholds in the range 30–40 J/cm2 at 1064 nm with 16 ns pulses at 30 Hz. This threefold improvement in threshold over that reported earlier for this system was attributed to an improvement in the preparative technique particularly in regard to cleanliness. Coatings have been prepared recently on substrates up to 8” in diameter and scale-up development continues.
Structural Modification of D2O/H2O-Dosed CaF2 Optical Thin Films
Authors: Franck JB
Published: March 2009

Unusual behavior has been reported for D2O/H2O-dosed CaF2 optical thin films. This behavior includes resistance to laser-induced damage at 2.7-μm radiation, improved damage morphology, and reduced optical absorption in the water band for even H2O-dosed CaF2 optical thin films. Analysis of the films strongly suggests that the modification of film properties is not the result of inclusion of the D2O/H2O into the film matrix or chemical contamination. Rather, the act of dosing has modified the structural properties of the films, thus producing the effects observed.
Non-Avalanche Dielectric Breakdown in Wide-Band-Gap Insulators at DC and Optical Frequencies
Authors: Braunlich P , Jones SC , Shen XA , Casper RT , Cartier E , DiMaria DJ , Fischetti MV , Kelly P
Published: March 2009

It is the purpose of this paper to put recent novel experimental efforts to understand dielectric breakdown in wide-band-gap materials in various fields into a common framework and outline significant changes in the understanding of dielectric breakdown at optical frequencies and free electron heating under DC conditions. New experimental techniques used to measure multiphoton absorption and energy deposition in wide-band-gap alkali halides in the prebreakdown regime have led to hard evidence refuting the avalanche model of laser-induced damage at visible laser wavelength. The experiments show that virtually all lattice heating occurs via nonlinear absorption of laser photons by multiphoton excited free electrons. Direct measurements of free electron heating by DC fields in thin SiO2-films and direct measurements of electron-phonon scattering rates of energetic free electrons impose a new understanding of carrier heating. The scattering of free electrons with non-polar acoustic phonons is found to be the dominant interaction in preventing the free carriers from reaching energies high enough to cause impact ionization and initiate avalanche breakdown. These results unambiguously show that the role of avalanche breakdown under DC conditions has been overestimated in the past.
The Response of Multilayer Dielectric Coatings to Low Fluence Ultraviolet Light Exposure
Authors: Sanders VE , Early JW , Leamon W
Published: March 2009

Multilayer dielectric high-reflectance coatings were investigated for potential application in a high-average-power, 1-μm wavelength, free-electron laser oscillator. Of concern are the ultraviolet harmonics of the primary wavelength generated within the oscillator that tend to degrade the dielectric coatings. These coatings are required to be high reflecting and low absorbing with respect to the 1-μm wavelength and resist degradation/damage from the ultraviolet harmonics.

A KrF excimer laser was used to generate the low fluence ultraviolet light at 248-nm wavelength, a wavelength that simulates the fourth harmonic of the 1-μm free-electron laser. A variety of candidate dielectric oxide thin film materials are compared in this report. In each multilayer dielectric high reflector measured, a candidate high-index dielectric material is used in combination with SiO2 as the low-index material. Damage test measurements are reported for the 248-nm wavelength with HfO2 being the high-index material with significantly the best results.
Radiation Damage in Single Crystal CsI(Tl) and Polycrystal CsI
Authors: Barnouin O , Procoli A , Chung H , Miley GH
Published: March 2009

Radiation damage in single crystal CsI(Tl) and polycrystal CsI was assessed by measuring the changes in radioluminescent intensity caused by successive neutron and gamma ray pulses from a TRIGA nuclear reactor. The radioluminescent intensity from the single crystal decreases within nine pulses by 30% in the near infrared range (0.7–4.5 μm) and by 25% in the visible range (0.2–1 μm) before staying constant. For the polycrystal CsI, the emission in the visible range decreases by 60% within 6 pulses and then remains constant, whereas no measurable emission is observed in the infrared. Finally, a heating and cooling cycle is shown to repair the damage for both crystals.
Effects of Thermal Conductivity and Index of Refraction Variation on the Inclusion Dominated Model of Laser-Induced Damage
Authors: Fuka MZ , McIver JK , Guenther AH
Published: March 2009

The inclusion-dominated model of laser-induced damage is reexamined in light of recent measurements of thin film thermal conductivities. In particular, the effects of varying the thermal conductivity and imaginary part of the index of refraction are explored. Two different values of the index of refraction are shown to be associated with a given damage threshold, and physical mechanisms are proposed for each value. Thermal conductivity is demonstrated to affect only weakly the value of the imaginary part of the index of refraction corresponding to a particular damage threshold.
Theoretical Determination of the Nonlinear Optical Properties of Inorganic Polymers
Authors: Risser SM , Ferris KF
Published: March 2009

Third order hyperpolarizabilities were calculated using the Huckel Hamiltonian and third order perturbation theory for a series of phosphonitrilic compounds, (X2P-N)n, as a function of bond length alternation, ligand substitution and backbone conformation. Phosphonitrilic compounds show hyperpolarizabilities comparable to those reported for organic species, and are modulated by ligand group electronegativity. In contrast to organic polyenes, the difference in π orbital energy between phosphorus and nitrogen is critical to determining the onset of saturation and the magnitude of the hyperpolarizability. Conformation effects are smaller than those seen in polyenes.
Relation Between n2 and Two-Photon Absorption
Authors: Sheik-Bahae M , Hagan DJ , Van Stryland EW , Wei TH , Said AA , Canto E , Miller A
Published: March 2009

We present evidence from nonlinear refractive index measurements, two-photon absorption measurements, and fourwave mixing measurements on semiconductors showing that the bound electronic nonlinearity can be calculated from two-photon absorption dispersion via a simple Kramers-Kronig analysis. This analysis shows n2 changing from positive to negative as the photon energy approaches the band-gap energy, consistent with observations. Additionally, this simple calculation, which assumes two parabolic bands, gives good agreement with measured values of n2 in wide-gap dielectrics that are 2 to 3 orders of magnitude smaller than in semiconductors.
Formation of a Pregiven Reflecting Surface Topography by Elastic Deformation of the Mirror Substrate. New Concept of Adaptive Optical System
Authors: Apollonov VV , Chetkin SA , Ivanova EA , Prokhorov AM , Vdovin GV
Published: March 2009

Complete model of a multiactuator flexible mirror,made as a thin plate with discrete piezo-actuators is described. Experimental results validated the efficiency of proposed model are presented.New concept of adaptive optical system with flexible mirror and linear wavefront sensor is developed.
Effects of Adhesive Thickness, Open Time, and Surface Cleanness on the Peel Strength of Adhesive-Bonded Seams of EPDM Rubber Roofing Membrane
Authors: Watanabe H , Rossiter WJ
Published: March 2009

A laboratory study was conducted to examine the effects of adhesive thickness, open time, and surface cleanness on T-peel strength of EPDM (ethylene propylene diene terpolymer) rubber seam specimens. Seam specimens bonded with butyl-based contact adhesive were tested after a 2-week cure time. The peel strength generally showed a positive dependency on the adhesive thickness except that it tended towards a plateau value for thick adhesive layers. The leveling of peel strength at large thickness might result from the presence of small voids in the adhesive layer. The peel strength was not dependent on the open times used in this study. Increased levels of surface contamination lowered the peel strength and changed the failure mode from cohesive to adhesive.
Performance Study of Single Ply Roof Membranes in the Northeast United States
Authors: Peterson RH
Published: March 2009

Single Ply roof membranes have been in extensive use inthe Northeast Region of the United States for a period of over twelve years. Although numerous systems and application procedures have been employed there has been limited publication of field performance data on in-situ systems. This study involves the review of both EPDM roof membranes and PVC roof membrane systems that were placed in service between 1977 and 1984. The roof systems included in the study are all reroofing systems of known construction, contractors, materials manufacturers and design. The performance study included a review of the documented history of each roof from design through construction and post construction. Warranty claims, if applicable, were reviewed as well as all other available recorded data.

Building occupants/Owners were interviewed to provide additional undocumented data. All roof systems in the study were inspected to establish existing conditions and to evaluate the level of deterioration of the various roof system components.

Accumulated data from documented history, interviews and field observations will be analyzed in this paper and defects will be summarized. Causation of defects and deterioration were also considered and classified into one or more of the catagories of design defficiency, material performance, improper workmanship and/or lack of appropriate and regular maintenance.

Conclusions relative to the performance of the systems studied will be presented and considerations given to the effect on performance by known system changes.
A Preliminary Investigation of the Biaxial Load-Strain Testing of Selected Roofing Sheet Materials
Authors: Wells JR , Tilton JA
Published: March 2009

The roofing industry has seen increasing efforts to move toward performance standards rather than prescriptive standards for roofing materials. In order to better understand the performance of the materials, testing should represent the material service environment as closely as possible. When in service, roofing materials are stressed biaxially. Therefore, load-strain testing to evaluate performance of roofing materials should be biaxial. Selected membrane sheet materials are tested, and the results reveal significant reductions in elongations to failure as well as failure strength.
Finite Element Analysis of Roofing Systems
Authors: Easter M
Published: March 2009

Finite Element Analysis has been used for almost 30 years by areospace and automobile industries to design parts and systems. Finite Element Analysis, or FEA breaks a part up into small elements in order to find the stresses on the whole. This paper describes how the method was applied to single ply roofing. Standard wind test assemblies were analyzed for verification and then a corner area of a typical roof was analyzed.
Dynamics of Roofing Membranes in Wind
Authors: Zarghamee MS
Published: March 2009

This paper presents the results of a study performed to predict the effect of the dynamic component of wind pressure on an inflated single-ply roofing membrane and its attachment mechanism. The calculation is performed based on the measured power spectra of wind pressure at points on the roof of a square plan building in a boundary layer wind tunnel. The transient response factor, defined as the ratio of the fluctuating component of pressure,difference across the membrane thickness to the fluctuating component of external wind pressure, is shown to depend strongly on the ease of air flow to the space underneath the membrane and to the size of the building. Specific recommendations are tentatively proposed for the design of single-ply roofing systems against wind uplift.
Porosity of Glass Fiber Felts Used in Built-Up Roofing
Authors: Cash CG
Published: March 2009

This paper describes a test method for measuring the relative porosity of asphalt coated glass fiber felts. For this paper, porosity is defined as flow through felt.

I tested the effect of the relative porosity of the felt using a computer model to calculate the flow of coal-tar pitch through the felts in an ideal membrane, exposed to normal Boston, Mass, and Miami, Fla. temperatures.

These data show the relative porosity of the glass fiber felts is highly variable. The mass of the built-up roofing aggregate presses the glass fiber felts to the bottom of the membrane.

I recommend, based on my field observations, our laboratory tests and the calculations reported in this paper, that only steep asphalt, ASTM D 312, Types 3 or 4, be used between the plies of asphalt coated glass fiber felts in the construction of built-up roofing membranes. Coal-tar pitch and dead level asphalt should not be used with glass fiber felts until dependable test methods and standards for the relative porosity of the glass fiber felts are established.
Statistics from Built-Up Roofing Sample Analyses
Authors: Cash CG , Henshell J
Published: March 2009

This paper presents data from over 1,000 built-up roofing membrane samples analyzed by the contributing laboratories. These data were assembled in Task Force D 8.20.15, chaired by Justin Henshell, to determine the typical values that can be expected from the quantitative analysis of built-up roofing membranes.

These data are evaluated by standard statistical methods to determine the type of distribution, mean, standard deviation, range (95% confidence) and the typical values. For this paper the typical range is defined as the range that includes more than 50% of the samples.

The range of the typical values calculated are broader than the recommendations by the roofing material manufacturers, but not as broad as the recommendations of the National Roofing Contractors Association.
Resistance of Structural Silicones to Creep Rupture and Fatigue
Authors: Sandberg LB , Rintala AE
Published: March 2009

Structural silicone sealants are subjected to repeated wind and thermal load cycles and, in certain applications, to sustained loads. Data from two types of creep tests are presented, one using constant loading and the other ramp loading. Both were done on an acetoxy silicone. Fatigue data are reported for tension on a neutral cure sealant, tension on a two-part silicone in insulating glass joints, and shear on an acetoxy silicone. All fatigue testing used full reversal, constant load amplitude cycling. Regression analyses on failure stress versus time or cycles to failure and on stress versus the logarithm of time or cycles to failure are discussed in relation to current design practice. Some of the problems associated with creep and fatigue testing of silicone sealants are explained.
Sealant Stresses in Structural Glazing: A Mathematical Model
Authors: Vallabhan CVG , Chou GD
Published: March 2009

Silicone sealants are used to structurally connect the glass plates of an insulating glass (IG) unit and they are used between the IG unit and the supporting mullion. Thus, the sealants become an integral part of the overall glazing system. Design engineers have to compute stresses and deformations of the glass plates as well as the forces in the sealants when the overall system is subjected to lateral pressures such as wind. By use of von Karman' s nonlinear theory of plates and Boyle's law of ideal gas, the complex interaction between the plates, the air trapped inside the IG unit, and the elastic behavior of the sealants is modelled mathematically. Some numerical examples are shown as illustrations.
Structural Silicone Sealant Requirements for Attaching Stone Panels for Exterior Applications
Authors: Carbary LD
Published: March 2009

This paper attempts to discuss the requirements for an adhesive attachment for stone panels 1.25–3 cm in thickness used in exterior applications. Adhesion requirements are discussed and tensile adhesion testing is suggested through various environments such as heat and humidity cycling, freeze thaw cycling and acid rain exposure. Structural perimeter seals, stiffeners and bedding applications are discussed. ASTM C-880 is discussed with modifications to properly identify if the stone used on a project is proper for the exterior application. Limitations through fire are discussed and recommendations to the design professional are suggested.
Comparison of European and U.S. Testing/Qualification Procedures for Structural Glazing Silicone Sealants
Authors: Iker J , Wolf AT
Published: March 2009

The paper reports on the state-of-the-art test methods and qualification procedures for SSG sealants currently applied in Europe and compares those to the ASTM C-24 proposal. The test data generated show that the 50°C water immersion required by some European building code authorities results in a much lower success rate in the adhesion test than the 1 week room temperature immersion applied by the silicone sealant manufacturers in the U.S. The paper also describes the efforts to consolidate the different national test and requirement standards into one European standard and directive on structural glazing by 1992.
Behavior of Fillet Sealant Joints
Authors: Myers JC
Published: March 2009

This paper investigates the behavior of fillet (triangular) sealant joints using tensile and cyclic tests and finite element analyses. Fillet sealant joints with diagonal bond breakers have greater movement capability and lower peak stresses than fillet sealant joints with flat bond breakers and than square and rectangular joints. Design of fillet joints with diagonal bond breakers should follow current rectangular joint design procedures, with the required bond breaker size based on the horizontal projected length of the concealed face of the joint.
Design of Sealant Joints
Authors: O'Connor TF
Published: March 2009

Often, thermal movement and other factors are inadequately considered in the design of sealant joints. Deficient design results in premature failure of the sealant and usually water damage to the building and its contents. Performance factors that affect sealant joint design are described, including: thermal movement; moisture movement; live and dead loads; creep, elastic frame shortening, and shrinkage of concrete structures; and material, fabrication, and erection tolerances. Three examples, including calculations, will be presented of joints that accommodate movement: (1) expansion joints in masonry walls, (2) joints that occur between different building systems, and (3) multi-story curtainwalls with floor line expansion joints.
Temperature and Moisture Effects on the Engineering Properties of Silicone Sealants
Authors: Tock RW
Published: March 2009

Physical property changes for two structural silicone rubber sealants were studied to determine the effects of expected variations in environmental temperature and moisture. Test coupons were subjected to uniaxial tensile forces at different isotherms and moisture levels. The elastic modulus at zero strain, stress at a function of extension, and relaxation times were determined for the two sealants.

For extensions of zero to thirty percent, and for temperatures over a range of 0°C to 30°C, both sealants were found to behave as ideal elastomers. The use of the model for an ideal rubber allowed the cross link density, tensile modulus, and stress to be quantified for a given isotherm. Normal, environmental temperature variations did not compromise sealant performance.

Moisture (immersion in water) appeared to have little effect on the measured mechanical properties. The pH of the water over a range of 5 to 12 also appeared not to affect sealant performance. However, strong sulfuric acid solutions (pH < 2.0) seriously compromised the integrity of both materials.
Adhesive Properties of Silicone Sealants
Authors: Gutowski WS
Published: March 2009

It is shown in this paper, that the strength of adhesion between the sealant and substrate depends upon surface properties of these materials expressed in terms of specific components of their surface energies and the acid-base interactions.

The predictive model regarding the relationship between the bond strength and the energy of acid-base interaction presented in this paper may be applicable in both dry and humid/wet environments.
The Water Resistance of Sealants for Construction
Authors: Beech J , Mansfield C
Published: March 2009

When sealants are exposed to water in the service environment a number of distinct phenomena may occur which can influence their performance, and may contribute to the failure of the sealant to perform the intended functions. The primary effects with which we are concerned are first, the absorption of water by the sealant, which may cause either softening or enhanced cure, depending upon the chemical nature of the sealant, its cure mechanism and state of cure at the time it is first exposed to moisture. Secondly, the diffusion of liquid water to the sealant/primer/substrate interfaces may impair the adhesive bond of the sealant to the joint surfaces. The laboratory evaluation of these effects is based on tensile testing in which the modulus and the extensibility of sealant test joints after varying durations of immersion in water are used as indices of performance. A system of performance evaluation based upon changes in these indices with water immersion is proposed, and discussed in relation to the results of BRE research results, and those of other workers in the UK.
Polyurethane - A Simple Method of Selecting Polyurethane Sealants for Your Particular Application
Authors: Jacob LJ , Payne KJ
Published: March 2009

Numerous polyurethane sealants are available to cover a wide variety of applications. They vary substantially in chemical composition and performance characteristics. This leaves the user with the complex problem of evaluating and identifying the best sealant for a particular application. In this paper, we propose a simple, yet detailed technique to facilitate the selection process. The focus of the test programme is its uniformity and reproducibility. The fundamental feature of this rating chart is the flexibility it offers for a range of applications and types of sealants. Finally, the benefit to the user is the one-value rating which defines the relevant characteristics for a particular application.
Silicon Modified Polyethers for Moisture Cured Sealants
Authors: Timberlake JF
Published: March 2009

Silicon modified polyethers are an intermediate for the preparation of one-part and two-part sealants. Silicon modified polyethers consist of a polyoxypropyl-ene backbone with methyldimethoxysilane end groups. Curing with moisture in the presence of catalysts gives flexible polymers with siloxane bonds connecting the poly-ethers. The primary application for these silicon modified polyethers is in construction sealants.

Silicon modified polyethers give soft sealants which have excellent weatherability and durability (joint movement) with little changes in properties after four years under normal use conditions. Weathering data demonstrate that these sealants will last for many years in outdoor exposure. The sealants show good adhesion to most substrates including aluminum, mortar, and stone. Good curing rates are observed in both one-part and two-part sealants over a range of temperatures. The sealants are nonstaining on stone and can be easily painted.
Corrosion—A Problem of International Importance
Authors: Baboian R
Published: March 2009

Corrosion is a problem of international importance because it affects public safety and is costly. The problem has escalated due to a number of factors including an increasing demand on the performance of materials and increasingly aggressive environments. Examples used to demonstrate the magnitude of the problem include: (1) deterioration of the infrastructure; (2) effects on transportation; (3) underground corrosion; (4) reliability of electrical and electronics equipment; and (5) concern over the fate of outdoor artistic and historic works. Corrosion testing and evaluation play an important part in solving corrosion problems. Typical concerns are listed, and the importance of planning and preparation is emphasized.
Computerization of Corrosion Data
Authors: Anderson DB
Published: March 2009

Computerization of the wealth of available corrosion data facilitates both data access and interpretation to address specific user needs. Data collection and compilation can be enhanced by adoption of format standards which define guidelines for common terminology, documentation of performance measurement for both metals and nonmetals, data output and presentation, and for assessing data quality. Well-defined programs, using a variety of established computerization techniques, can serve as effective tools for selection of corrosion resistant materials, assessing material limitations, selection and design of corrosion control methods, and for gaining a better understanding of the significance and theoretical considerations relating to operative corrosion mechanisms.
Correlation of Failure Analysis Corrosion Testing
Authors: Nekoksa G
Published: March 2009

Several test methods and procedures applicable to corrosion failure analysis of pipelines, tanks, concentric neutral (CN) cables, underground transformers, potable water pipes, cooling water systems, and plant components are examined. Correlation of different test results from the field and laboratories is shown on three case histories.
Choice of Testing, Evaluation Methods, and Quality Criteria in Corrosion Engineering
Authors: Bartoň K , Knotková D , Holler P
Published: March 2009

This paper proposes a general scheme for the design of test programs to assess corrosion resistance in a meaningful way. Any metallic material or coated metal product that is to be used in a specific set of conditions may suffer corrosion. The chemical and physical factors of the service application, together with the metallic material, determine the type and extent of corrosion damage encountered. Corrosion science can be used to specify the critical environmental factors in the test method.

The test program can provide results that are important for the following: the development of new materials and coatings; the choice of protective systems for new equipment designs; the development of quality control programs and quality acceptance tests. Statistical methods are essential to determine the significance levels of results and the corresponding material specifications.
Stress-Corrosion Cracking of Mn-Bronze Castings and Test Specimens in New York City Water Distribution Shafts
Authors: Andersen GA , Donnellan PB
Published: March 2009

Stress-corrosion cracking (SCC) has been found to be the cause of failure of 48-in. (1219.2-mm) and 30-in. (762-mm) diameter manganese bronze gate valve bodies, a 48-in.-diameter shaft cap, and 1½-in. (38-mm)-diameter nuts. All of these in-service failures occurred in New York City distribution shafts for Water Tunnels Nos. 1 and 2. The valves and shaft cap, which were made of Copper Development Association (CDA) Alloy C86500, failed in predominantly transgranular mode with some intergranular cracking. The nuts, made of CDA Alloy C86300, cracked in an intergranular mode only.

With numerous manganese bronze castings presently in service in all 37 water distribution shafts in New York City, a stress-corrosion cracking test program has recently been initiated. The specimens used were of the modified compact wedge-loaded type made of CDA Alloy C86500. The purpose of the test was not only to find which distribution shafts contained an aggressive SCC environment, but to identify any corrosive agents in the shafts. All 37 shaft environments produced cracking in one or more of the specimens tested in 15 to 63 days. Most of the cracking occurred with the pH in the range from 7.5 to 9.5.

The spillage of elemental mercury from flowmeters in the shafts plus the introduction of chemicals used for mercury cleanup accelerated the SCC investigation. Mn-bronze specimens were tested in jars containing ammonia, mercury, water, trisodium phosphate, and commercial mercury cleaning solutions. All chemical induced cracking in the specimens in a range from 1 to over 300 days, except mercury and trisodium phosphate.

Scanning electron microscopy was used to characterize the crack pattern of several in-service failures and SCC test specimens. Energy-dispersive analysis was used to identify the corrosion products on the crack surfaces.
Erosion-Corrosion Measuring Devices
Authors: Schorr M , Weintraub E , Andrasi D
Published: March 2009

Two instruments for the study and measurement of erosion-corrosion (EC) were developed and built: the erosion-corrosion unit (ECU) and the erosion-corrosion tester (ECT). These instruments simulate the shear and impact forces acting on industrial equipment to evaluate the corrosive wear effects of the fluid on the equipment and their interaction. The specimen in the ECU consists of a cylinder rotated about a vertical axis while a jet of slurry impinges continuously onto its curved surface through an interchangeable nozzle. The ECT applies rotational sliding abrasion by the slurry on a static disk specimen. In both devices, a three-electrode system (working, reference, and counter electrodes) is used to evaluate the electrochemical corrosion component by the polarization resistance technique. The contribution of mechanical erosion to the synergetic EC process is measured by weight loss on long-term exposures.

The instruments were applied as follows: in industrial plants to monitor the influence of corrosion parameters during production, in pilot plants and in the laboratory to evaluate and select corrosion-resistant alloys, to assess the corrosivity of the ores and slurries handled, and for analysis of EC failures.

The instruments are described and their characteristics compared. The results obtained in several environments are presented and their significance discussed.
Advanced Laboratory and Field Exposure Systems for Testing Materials
Authors: Spence JW , Edney EO , Haynie FH , Stiles DC , Corse EW , Wheeler MS , Cheek SE
Published: March 2009

ABSTRACT: A unique laboratory exposure system for exposing materials to complex air mixtures that simulate atmospheric conditions has been developed for studying the aerodynamic and chemical processes controlling atmospheric degradation of materials. Runoff studies using covering-spray devices were also developed to provide insight into the effects of atmospheric acidity on materials in the early stage of field exposure. Using these facilities, exposure studies of galvanized steel panels have shown that the deposition of sulfur dioxide (SO2) is controlled by the gas phase resistance of the atmosphere during periods of surface wetness. The delivery of SO2 to the galvanized steel surface is controlled by the atmosphere. Each molecule of SO2 that deposits to the wet surface will react with one zinc (Zn) atom to form zinc sulfate (ZnSO4). During periods of surface dryness, the surface density of SO2 corresponds to the formation of a saturated monolayer of SO2. The deposition of nitrogen dioxide (NO2) is an order of magnitude less than SO2 during periods of surface wetness and appears to be controlled by the surface resistance of galvanized steel. The delivery of NO2 is limited to its solubility within the aqueous surface film. Of the atmospheric gases, nitric acid (HNO3) readily deposits during periods of surface wetness and dryness. Rain acidity contributes to the corrosion of zinc according to the stoichiometric relationship 2(H+) = Zn2+. The corrosion film that forms on zinc is soluble in rain due to dissolved atmospheric carbon dioxide (CO2). The dissolution of the corrosion film depends on the residence time of rainwater on the surface of the galvanized steel panel.
Atmospheric Factors Affecting the Corrosion of Zinc, Galvanized Steel, and Copper
Authors: Cramer SD , McDonald LG
Published: March 2009

The Bureau of Mines, as part of the National Acid Precipitation Assessment Program, studied the atmospheric corrosion of zinc, galvanized steel, and copper at five sites in the eastern United States for periods up to five years. Air quality, meteorology, precipitation chemistry, and pariculate chemistry were monitored at each site. Long-term (steady-state) corrosion rates were measured by mass loss and by determining the rate that corrosion products were removed in precipitation runoff. A three-term runoff flux model fit long-term field corrosion data well, giving R2 values greater than 0.95. The model was based on the fluxes of precipitation volume, wet-deposited hydrogen ion, and dry-deposited sulfur dioxide that are available from regional environmental monitoring activities. The parameter values obtained from this model agreed with values obtained by direct measurement, indicating they are physically significant. These parameters are the dry deposition velocity of sulfur dioxide to the metal, the number of hydrogen ions needed to release a metal ion from the corrosion product, and a product of residence time and the solubility of the corrosion product in precipitation. Experimental evidence suggests the model needs a fourth term for the dry deposition of particulates that deposit on the metal and neutralize a fraction of the acidic species subsequently deposited. Damage to zinc, galvanized steel, and copper from wet and dry acidic deposition was estimated to be 50% or more of the total damage at each of the five sites. Damage to zinc at the Ohio site by acid deposition was more than 80% of the total damage. for copper, damage from the wet deposition of hydrogen ions was greater than that from the dry deposition of sulfur dioxide at four of the five sites.
A Comparison of Sulfide Stress Cracking Tests
Authors: Treseder RS
Published: March 2009

Sulfide stress cracking, a form of hydrogen embrittlement, first became a serious problem in the oil industry in 1951. Subsequent improvements in the metallurgy of steels for high-pressure gas and oil wells and improved selection methods for high-strength alloys have been based on laboratory test methods. Of the large number of test methods that have been used, five have survived: the Shell bent beam test, the uniaxial load tension test, the double-cantilever-beam test, the C-ring test, and the slow strain rate test. Major features of these tests are compared in terms of their applicability to specific sulfide stress cracking problems. In addition, a general comparison is made of the testing requirements for the sulfide stress cracking system and for anodic stress corrosion cracking systems involving hydrogen sulfide. These comparisons illustrate the need to design environmental cracking tests which reflect both corrosion mechanism factors and application requirements.
Stress Corrosion Cracking in Alloy 400 (UNS NO4400) at Room Temperature
Authors: Everhart LG , Price CE
Published: March 2009

Selective pitting studies were used to determine environments likely to cause stress corrosion cracking (SCC) in Alloy 400. Slow strain rate tests were performed on waisted specimens, with solution composition and concentration, strain rate, grain size, and prior cold work as variables. It was found that environments which caused pitting also caused SCC; examples include ammonium hydroxide, ammonium persulfate, and hydrofluoric acid in the presence of an oxidizer.

As in the case of both hydrogen and liquid metal embrittlement of Alloy 400 and other nickel-base alloys, the SCC at low strain levels was intergranular with a transition to transgranular at higher strains. The fractography of the SCC resembled that of the other embrittling environments.