bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of Limnocorrals in Evaluating the Effects of Pesticides on Zooplankton Communities
Authors: Kaushik NK , Solomon KR , Stephenson GL , Day KE
Published: December 2008

Enclosures of three sizes (large, 1000 m3; medium, 125 m3; small, 20 m3) designed and constructed specifically to facilitate the evaluation of the impact of pesticides in freshwater ecosystems are described. Uniform mixing of permethrin in a corral was possible within an hour using a pump system that had no adverse effects on entrapped organisms. Methoxychlor applied to surface waters with a back-pack spray system penetrated the column of water within 24 h. Both application methods produced replicable concentrations close to the desired nominal concentration. As a result of the impact of permethrin (0.5 and 5.0 μg L−1) and methoxychlor (5 and 50 μg L−1), densities of macrozooplankton populations decreased and rotifer populations increased in numbers. As the macrozooplankton populations recovered, rotifer numbers decreased.

The large corrals possessed a distinctive edge zone that extended 1.0 m from the corral wall and was usually characterized by greater densities of macrozooplankton than the center zone. No such edge zone existed in the small or medium corrals. We recommend that the spatial distribution of zooplankton in each size of corral be defined before establishing a sampling regime; thus more precise population estimates may be attained.

The impact of methoxychlor on enclosed zooplankton populations differed in the three sizes of limnocorrals. The toxicity of 20 μg methoxychlor L−1 to zooplankton increased with increasing size of corral, primarily because of the decreasing ratio of surface area of limnocorral walls to water volume. Methoxychlor adsorbs readily to polyvinyl chloride; thus the concentration in the water of the larger enclosures was higher for a longer period of time than that in the smaller corrals.
Leaching Test Characterization of Iron and Steel Industry Waste
Authors: Philipp JA , Endell R , Raguin J , Dechelette O
Published: December 2008

The iron and steel industry generates considerable tonnages of solid waste, and although much of it is to a large extent valorized, some 50 kg of waste to every tonne (1000 kg) of steel have to be discharged or disposed of as waste. A good environmental protection policy calls for a ban on dumping of special waste materials, which there are strong grounds for fearing may be of a toxic and dangerous nature. Except in specific cases, it is difficult to tell from the composition of a waste material whether or not it is of a “special” nature. Characterization simulations have to be made to ascertain the extent to which the waste material can release harmful elements, such as heavy metals, when in contact with rainwater and in some cases other waste materials. Such is the object of the leaching tests, which have or are being developed in many countries at the instigation of the authorities and industrialists: Federal Republic of Germany, South Africa, Australia, France, Great Britain, Italy, Japan, the United States, and so forth. The International Iron and Steel Institute (IISI) has, within its Environment Committee, made a comparison of the results obtained with different national tests using the same specimens.
Testing Methodologies for Landfill Codisposal of Municipal and Industrial Wastes
Authors: Pohland FG , Gould JP
Published: December 2008

The results of a two-year pilot-scale investigation on codisposal of an industrial metal treatment sludge with municipal refuse under the influence of leachate containment and recycle are used to reveal the environmental consequences of heavy metals on such a landfill management practice. Comparisons between landfill simulators with and without varying metal sludge admixtures have provided an opportunity for examination of selected testing methodologies and parameters descriptive of inherent physical-chemical and microbially mediated reactions prevailing throughout the progress of landfill stabilization. Collectively, these analyses were sufficient to determine landfill assimilative capacity in terms of several controlling mechanisms including: potential inhibition of waste stabilization by mobilized heavy metals; precipitation, immobilization, and detoxification of heavy metals by entrapment and filtration; encapsulation and isolation of heavy metals by reaction with carbonates and sulfides; and formation of less toxic metal complexes with humiclike substances and potential for remobilization without transport phase regulation. On the basis of these results, a method for the determination of sludge loadings and their effects at both present and future landfill codisposal sites could be proposed.
An Approach for Evaluating Long-Term Leachability from Measurement of Intrinsic Waste Properties
Authors: Côté P , Bridle TR , Benedek A
Published: December 2008

This paper presents a radically new approach for evaluating hazardous waste leachability. In the past, leachability has been measured through conductance of laboratory leaching tests, either batch or column, using experimental conditions that attempt to simulate field conditions. An approach is proposed in which measured intrinsic properties of a waste are used in mathematical models to infer the long-term leachability.

To provide background information, laboratory leaching tests are reviewed with emphasis on interpretation of the results. It is argued that results of bench-scale tests are difficult to scale up to field disposal conditions and that they do not lend themselves to extrapolation over time.

Leaching from wastes takes place via solubilization of contaminants inside the matrix and transport through the matrix pore system to the surrounding aqueous solution. Intrinsic properties that determine leaching rates can be categorized as chemical or transport phenomenon. Chemical properties include those factors that determine a contaminant's solubility, for example, chemical speciation, precipitation, adsorption, kinetics of reaction, buffering capacity, and so forth. Transport properties include structure of the pore system, factors affecting diffusion of ions in the pores, and hydraulic conductivity. Laboratory methods to measure these properties are briefly described.

A mathematical model, developed to predict leaching of toxic metals from solidified wastes under acidic conditions, is described. The model uses measured properties of wastes to predict leaching rates under a variety of conditions. Verification experiments are presented and the merits and limitations of the model for long-term predictions are discussed.
Pentachlorophenol Adsorption on Soils and Its Potential for Migration into Ground Water
Authors: Banerji SK , Piontek K , O'Connor JT
Published: December 2008

The adsorption of pentachlorophenol (PCP) on Missouri soils was studied to determine its potential for migration into ground water. The adsorption data obtained, using low concentrations (0.1 to 10 mg/L) of pentachlorophenol, fit the Freundlich isotherm form. Pentachlorophenol, a weak organic acid, was found to adsorb more completely to Missouri soils as pH decreased, converting PCP to its acid form. High soil organic content was found to strongly increase PCP adsorption. However, most (84%) of the PCP adsorption was reversible. Overall, at the pH values observed (5.7, 6.7), Missouri soils would be expected to retard the movement of pentachlorophenol through adsorption.
Effect of Pore Fluid pH on the Dynamic Shear Modulus of Clay
Authors: Du BL , Mikroudis GK , Fang H-Y
Published: December 2008

This paper presents the laboratory test results on the dynamic shear modulus of clay mineral mixture with sand under dynamic torsion loading. Various pore fluids, as reflected by pH values ranging from 2.0 to 12.0, were introduced in the soil mixtures. Both shear modulus and maximum shear modulus were computed. Consolidation pressures varying from 34.5 to 276 kPa were used. All test results are presented in graphical and tabulated forms. Comparisons of various pH values with normal conditions are made. Finally, physico-chemical concepts are used to examine the soil-pollutants interaction.
The Complex Matrix in Environmental Chemistry for the Petrochemical Industry
Authors: Rohlik AR
Published: December 2008

This paper presents specific examples of problem solving involving the complex matrix. The purpose is to encourage development and comparison of methods with the goal of creating systematic analytical protocols for many waste types.

Complex matrix chemistry is becoming more important in environmental analysis. Many waste matrices are unique to an industrial process and common worldwide. Only recently has analysis of many complex wastes been attempted, primarily because of environmental concerns and regulations. The complex matrix can be multiphase, chemically unstable, and contain analytical interferences. Complicating factors include waste aging and total versus releasable constituents.

Multiphase wastes can contain organic compounds, water, and solids. Examples of centrifugation and extraction of sludges are shown to simplify analysis. The extracts are more uniform and can be analyzed separately with more reproducible results. However, careful attention must be paid to mass, volume, and specific gravity of the separated fractions to be able to reconstruct the original samples. Anaerobic bacteria in petroleum refinery sludges can rapidly generate sulfide in a sample and lead to misleading conclusions about the real hazard of the waste.

Analysis for sulfide immediately after sampling is recommended. Other changes in chemically active wastes, including oxidation, often occur naturally in the disposal environment. These changes caused by aging are shown to confound analytical results and make interpretation of environmental impact difficult.

Matrix interferences in sulfur analyses can be overcome with appropriate analytical techniques. Matrix effects are explained, and comparisons of X-ray fluorescence and combustion are made. The sulfur result is also shown to present a problem in heat content calculation. The success of total assay of metals is dependent on specimen preparation. A comparison of three methods is given and a recommendation made. New test methods under development by ASTM for environmental modeling are presented as future options. The use of background information is recommended to optimize analytical techniques and provide the most useful data.
Waste Immobilization in Cement-Based Grouts
Authors: Gilliam TM , Dole LR , McDaniel EW
Published: December 2008

This paper shows that immobilization of industrial and hazardous wastes in cement-based grouts is technically feasible and offers an improved method of waste disposal. Experiments were performed on four simulated waste streams immobilized in cement-based grouts: (1) fly ash; (2) spent limestone scrubber solids; (3) pickling liquor and recovery sludge containing arsenic, cadmium, chromium, copper, manganese, and lead; and (4) a vacuum pump oil containing polychlorinated biphenols (PCBs), Lindane (hexachlorocyclohexane), pentachlorophenol, and 9-9′-dichlorofluorene. The classes of organic compounds represented by this fourth waste are (1) PCB, chlorinated cyclohexane, chlorinated phenol, and PNA, respectively. Leach tests were performed with a simulated ground water typical of aquifers found in Maryville limestone.
Evaluation of Paint Filter Test Method to Determine Free Liquid in Waste Samples
Authors: Rinaldo-Lee MB
Published: December 2008

This paper presents the results from a round-robin testing program to evaluate the paint filter test method developed by the U.S. Environmental Protection Agency (EPA) to determine whether a waste contains “free” liquid. Regulations prohibiting disposal of waste containing “free” liquids in landfills were the impetus for developing the test method. Six laboratories performed the paint filter test on four waste samples to determine (1) whether the waste contained “free” liquid and (2) the percent “free” liquid released by the waste. The four waste samples were from two wastes; one waste was mixed with three different amounts of water to provide three waste samples.

The results show a large variance between the laboratories. The large variance is attributed mainly to sample preparation. The participating laboratories noted two other major problems with the test: (1) separation of the mesh from the cardboard filter holder during testing and (2) differences in filter design, which could influence test results.
Laser Damage Studies of Several Methacrylate Polymeric Materials
Authors: O'Connell RM , Ellis RV , Romberger AB , Deaton TF , Siegenthaler KE , Shaffer AA , Mullins BW , Saito TT
Published: December 2008

The bulk damage resistance of several acrylic polymers was investigated with a 1.06 μm wavelength pulsed Nd:YAG laser having a pulse length of 8–9 ns and a spot size of 33 μm. These materials were synthesized in bulk form using either thermal or ultraviolet initiation after extensive distillation and/or filtration at the monomers with sub-micron porosity membrane filters. Samples of pure poly(methyl)methacrylate, poly(ethyl)methacrylate and poly(cyclohexyl)methacrylate as well as plasticized polymers were studied. Details of synthesis methods and results of the damage measurements are presented, and the influence of synthesis methods on damage properties is discussed. In addition, a simple technique that uses scattered, depolarized helium-neon laser light to quickly estimate the impurity content of these samples is described and its ability to predict simple-shot damage resistance is discussed. Finally, a somewhat different method of analyzing multiple-shot damage data is applied and the results are discussed.
The Effect of Defects on the Laser Damage Performance of Metal Mirror Surfaces
Authors: Hurt HH
Published: December 2008

From a laser damage standpoint, the optical surface is not isotropic as evidenced by the selected area damage phenomenon. This is because the modern processes that generate specular surfaces and coatings inherently introduce defects and damage into the bulk material. These defects then act as preferential sites for the onset of laser damage, and the distribution of these defects appears to affect almost all laser damage parameters. This paper presents the development of high resolution electron microscopy methods to identify deleterious imperfections in typical metal-mirror surfaces. Pulsed-laser damage testing of identical surfaces shows systematic changes in the damage resistance of the material that can be correlated directly to defects in the near-surface region. By this method, it is possible to identify trace impurities that are deleterious to high fluence optical components. In addition, one can now specify process parameters that will control not only surface roughness and figure, but will also control laser damage resistance.
Automated Pulsed Testing Using a Scatter-Probe Damage Monitor
Authors: Franck JB , Seitel SC , Hodgkin VA , Faith WN , Porteus JO
Published: December 2008

This paper describes automated pulsed testing of infrared mirrors based on scatter-probe detection of laser damage. Advantages of our approach are (1) ability to monitor minute changes in surface condition without an observer, (2) rapid sampling of a large matrix of test fluences and test positions on the mirror, (3) automatic selection of test fluences, (4) automatic control of laser intensity drift, and (5) compatibility with a vacuum test environment.

Automated determination of damage frequencies and relative damage onsets will be described for single-layer-coated and uncoated metal and semiconductor mirrors. Tests were performed at 2.7 and 10.6 μm with 1/e2 focal spot diameters of 150 and 240 μm, respectively, using a nominal 100-ns pulse length in all cases. Results obtained with the scatter probe will be compared with those obtained from Nomarski postdamage analysis.
High-Precision Damage-Resistant Multiple-Pass Ultraviolet Reflectometer
Authors: Jolin LJ , Foltyn SR
Published: December 2008

A multiple-pass cell was reported by John White in 1942 [1]. Since then, it has been adapted for use as a high-precision reflectometer. The multiple-pass reflectometer has been studied and reported by Arnon and Baumeister [2].

Here, a reflectometer which is similar is described. It utilizes a uv laser operating at λ = 351 nm as the source and the White-cell mirrors are high-reflection dielectric coatings designed for that wavelength. Because of the low-loss reflectors used in the cell, a high number of traversals, reflections, can be achieved; R ≥ 239. The use of dielectric mirrors also improves the damage resistance of the apparatus which is important when a uv laser beam is used.

The results of reflectance measurements performed on several ultraviolet high reflectors are also reported. These include conventional dielectric coatings as well as a hybrid coating consisting of Al2O3, HfO2, and SiO2 layers.
Charge Emission and Accumulation in Multiple-Pulse Damage of Silicon
Authors: Jhee YK , Becker MF , Walser RM
Published: December 2008

To contribute to further understanding of damage mechanisms of silicon surfaces induced by picosecond Nd:YAG 1.06 μm laser pulses, damage at laser intensities below the 1-on-1 damage threshold has been studied. By using a biased charge collector or an electron multiplier tube, one can detect the charge emitted during small pit formation which may be considered as the initial damage morphology. The investigation of the accumulation period has been conducted by observing the first charge emission which indicates its termination. This accumulation time is analogous to the lifetime of the solids subject to a repeated mechanical load and is characterized by processes that are irreversible for at least 3 seconds. This suggests that the damage precursors are long-lived excitations or an accumulation of permanent states. The heterogeneous nature of the nucleation of damage suggests that these precursor states act as nucleation seeds to the laser induced damage. Charge emission after the incubation period was also studied. Positive and negative particles are emitted equally after damage initiation, probably due to thermal evaporation of silicon from small regions. The charge emission follows the Arrhenius relation. Experimentally, this result was independent of pulse repetition period up to at least 10 seconds.
Surface Damage Mechanisms in Nontransparent Media
Authors: Fauchet PM , Siegman AE
Published: December 2008

We review our experimental and theoretical work on surface transformations produced on amorphous and crystalline semiconductors and metals by single or multiple ultrashort laser pulses. In addition to melting and vaporization, two phenomena have attracted our attention: the formation of surface ripples and transformations due to repetitive subthreshold illumination.

A detailed theoretical model that explains successfully the formation and the major properties of the surface ripples has been developed and we illustrate the agreement by many examples. However, we also present experimental results which suggest that to describe the interaction between the incident beam and the surface diffracted waves, a perturbative approach is not always sufficient. A phenomenological explanation is presented for these nonstandard ripples.

Repetitive subthreshold illumination can produce the same surface transformations as single pulse illumination above threshold. We present universal growth curves and determine a safe level for multiple shot exposure in various materials. Our results are compared to several models, including accumulation of plastic deformation, creation of microcrystallites, and the early stages of ripple formation.
Picosecond-Pulse Damage Studies of Diffraction Gratings
Authors: Gill DH , Newnam BE
Published: December 2008

Diffraction gratings are frequently used in dye-laser cavities as wavelength-tuning elements. These gratings often limit the maximum laser output energy because of their low damage thresholds. We have measured the damage characteristics of both ruled and holographically produced gratings, under a variety of conditions. Using the single-shot-persite mode, the samples were irradiated by 30-ps, 1.064-μm pulses having a spot size of 0.5-mm radius.

It was found that holographic gratings have damage thresholds from 1.5 to 5.0 times higher than similar ruled gratings. Thresholds for S-polarized light (E parallel to grooves) were higher by factors of 1.5 to 6. For the same type grating, gold coatings yielded higher thresholds than aluminum, although this is wavelength dependent. For holographic gratings, replicas have slightly higher thresholds than masters. Dependence upon groove spacing was weak.

Data are presented to show a variety of comparisons between different types of gratings, including two different manufacturers and usage at higher orders of incidence.
Assessment of Optical Coatings Prepared by Molecular Beam Techniques
Authors: Lewis KL , Savage JA , Cullis AG , Chew NG , Charlwood L , Craig DW
Published: December 2008

Thin films of ZnSe and other materials have been produced by molecular beam techniques in an ultra-high vacuum facility dedicated to the examination of fundamental aspects of thin film technology as applied to optical coatings. The ZnSe films have negligible values of absorptance at 10.6 μm and have laser damage thresholds in the range 35–38J/cm2, a significantly higher energy density than hitherto reported for ZnSe films. Examination of the films in cross section by high resolution transmission electron microscopy has revealed a polycrystalline columnar morphology, with the crystallite size dependent on deposition temperature. A complete absence of intergranular voids is noted which renders the film impervious to the ingress of water and other impurities when exposed to the atmosphere. This feature, together with the inherently high purity of the film is believed to be the factor responsible for the enhancement in laser damage threshold.

The electron micrographs do however reveal sub-grain structure in the form of stacking faults and twin planes which are potential sinks for residual impurities in the material. Further improvements in damage threshold may be possible by elimination of this sub-grain structure.
High Damage Threshold Porous Silica Antireflective Coating
Authors: Thomas IM , Wilder JG , Lowdermilk WH , Staggs MC
Published: December 2008

A quarterwave-thick, narrow-bandwidth, antireflective coating for fused silica optical components and KDP crystals has been developed. The coating consists of porous silica prepared from a silica sol in ethanol. It is applied by dip or spin from a solution at room temperature and requires no further treatment. The damage threshold levels are about equal to the surface damage thresholds of the uncoated substrates.
Characterization of Aluminum Nitride/Aluminum Oxide Reactively Sputtered Antireflection Coatings
Authors: Koshigoe LG , Johnson LF , Donovan TM , Marrs CD
Published: December 2008

Aluminum nitride/aluminum oxide multilayer protective antireflection coatings are being developed for use on laser windows. These materials have been shown to be relatively stable and scratch resistant, thus demonstrating their applicability for this use. Both two- and three-layer coatings were designed at the wavelength 0.500μm. The design techniques utilized, as well as the resulting transmission spectra, are discussed. Single-layer films have been deposited on fused quartz and calcium fluoride substrates, and a three-layer film has been deposited on a fused quartz substrate. Studies of the resistance of these films to various environmental conditions including laser radiation, fluorine, electron beam irradiation, and humidity are presented. Surface analysis techniques such as scanning Auger microscopy (SAM), scanning electron microscopy (SEM), energy dispersive X-ray microanalysis (EDX), X-ray photoelectron spectroscopy (XPS), and Nomarski microscopy were used to examine coating composition and stoichiometry. Preliminary measurements on the laser resistance of the materials indicate that damage at defects is the predominant failure mode.
Crystallization of Titania Films by Thermal Heating
Authors: Rujkorakarn R , Hsu LS , She CY
Published: December 2008

Two types of low-loss, low-scatter submicron thick titania films, deposited by ion-sputtering at room temperature, were thermally annealed in air. Upon heating to about 350°C, these amorphous films show evidence of crystallization. Using a sensitive Raman spectroscopic technique, the crystalline structures are identified as anatase in one case (Type A) and rutile in the other (Type B). This amorphous-crystalline transformation coincides with a decrease in optical transmission and small changes in refractive index and energy gap of the film, along with a dramatic increase (∼100-fold) in elastic light scattering. Further heating of Type A films beyond 900°C shows a second phase transformation to anatase-rutile mixtures.
Time Resolved Raman Studies of Laser Induced Damage in TiO2 Optical Coatings
Authors: Exarhos GJ , Morse PL
Published: December 2008

Molecular information available from Raman scattering measurements of sputter deposited TiO2 on silica substrates has been used to characterize crystalline phases, thickness, and surface homogeneity. A two laser technique is described for investigating transient molecular changes in both coating and substrate which result from pulsed 532 nm laser irradiation. Single layer and multilayer coatings of both anatase and rutile phases of TiO2 have been probed by Raman spectroscopy immediately following the damage pulse (nanoseconds) and at longer times. Transient measurements are designed to follow surface transformation/relaxation phenomena; measurements at longer times characterize the equilibrium damage state. The anatase coatings were found to be more susceptible to laser damage than rutile coatings and exhibited irreversible changes during the damage process. Rutile coatings exhibited a reversible phase transition to the anatase form followed by recrystallization to the rutile phase (milliseconds). Loss of coating material from all damaged surfaces is inferred from decreased Raman scattering intensity. Substrate damage characterized by laser induced scrambling of polarized light was also observed. Raman results and molecular structural information are used to formulate a possible damage mechanism for TiO2 coatings.
Ultraviolet Thin Film Coating Characterization
Authors: Stewar AF , Gallant DJ
Published: December 2008

Multilayer dielectric high reflectance coatings designed for 351nm were fabricated using ion beam sputtering and electron beam deposition on super polished silicon substrates. These optics were evaluated in terms of total integrated scatter levels, absorption, reflectance and laser induced damage thresholds. Ion beam sputtering was found to produce optics with the lowest losses while electron beam deposited coatings demonstrated higher laser damage thresholds.
Effect of Anisotropic Stress on Thin Flim Damage Thresholds
Authors: Heiney AJ , Eastman J , Gabel CW
Published: December 2008

Damage thresholds for silica/titania multilayer reflectors are measured using single, 30 ps, Nd:YAG laser pulses to study the effect of anisotropic stress on thin film performance. Damage testing sites near the edges of coatings were used to spatially correlate damage with reproducible anisotropic stress profiles taken parallel to the edge.

Anisotropic stress in a coating is stress which has a directional dependence in the plane of the film. A microscope based modulated ellipsometer is used to measure anisotropic stress via induced birefringence. The damage testing system centers around a vertical illumination microscope. The damage pulse is directed by a 45° high reflector in the microscope tube section through a low power objective. The sample surface is viewed through the same objective used to focus the laser to 8 μm FWHM in the center of the viewing field. The goal is to spatially relate this data with microscopic stress measurements.

In most cases, negative anisotropic stress areas are found to have lower damage thresholds while positive anisotropic stress correlates well with high damage threshold. Damage thresholds for uniform striplike areas of film are found to change dramatically compared to adjacent strips. In one case average damage threshold changed from 1.3 to 6.9 J/cm2 within 100 μm. The width of measured threshold bands in this work ranged from 0.5 to 2.5 J/cm2.
Design of High Power Laser Coatings for Grazing Incidence Mirrors
Authors: Southwell WH
Published: December 2008

Several interesting features occur for high reflectance (HR) coatings at near-grazing incidence: the existence of a Brewster's angle, a double-valued effective index for the p-polarization (enabling a MacNeille-type polarizer to be constructed in air), and a half-wave retarder. It is shown that HR coatings can be designed which have high reflectance and, as compared to normal-incidence designs, extremely low internal E-field standing waves for both s- and p-polarization components. Such mirrors should exhibit considerably less thermal distortion due to decreased laser absorption.
Angular Dependence of Multilayer-Reflector Damage Thresholds
Authors: Newnam BE , Foltyn SR , Gill DH , Jolin LJ
Published: December 2008

The damage resistance of HfO2/SiO2 multilayer dielectric reflectors was measured as a function of angle of incidence with 351-nm XeF-laser irradiation. The laser produced nominal 10-ns pulses at a repetition rate of 35 pps. A series of reflectors designed for 0°, 30°, 45°, 60°, 75°, and 85° was tested with an S-plane polarized beam. To account for variations in the separate coating depositions, some of the coating designs were tested at two angles of incidence. At large angles of incidence, we did not observe the anticipated large increases in damage threshold predicted theoretically on the basis of spatial dilution (1/cosθ) of the intensity at the reflector surface and standing-wave electric fields. For example, the threshold for a reflector designed and tested at 85° was only a factor of 2.5 larger than that of normal-incidence reflectors tested at 0°. Several possible mechanisms to explain this discrepancy were considered.
Survey of Laser Damage Thresholds for High Reflector Films at 1.315 Microns
Authors: Deaton TF
Published: December 2008

We present the results of a survey of laser-induced damage measurements for high-reflector films at 1.315 microns. A pulsed atomic iodine laser with a maximum output energy of 5 Joules in a pulsewidth of approximately 8 microseconds was used, with a spot diameter at the sample of about 2.8 mm. All the thresholds reported are for single shot per site illumination. The pulse energy, temporal profile, and spatial profile information were monitored for each shot.

The samples tested are part of an extensive survey of currently available coatings from several vendors and represent a wide variety of materials and designs. Each coating was prepared on both silicon and molydbenum substrates. Damage thresholds were defined by the presence of surface pitting visible under Nomarski microscopy. Threshold fluence levels ranged from 10 J/cm2 to 150 J/cm2 with uncertainties of typically ± 15%.
Scanning Electron Microscopy Studies of Laser Damage Initiating Defects in ZnSe/ThF4 and SiH/SiO2 Multilayer Coatings
Authors: Johnson LF , Ashley EJ , Donovan TM , Franck JB , Woolever RW , Dalbey RZ
Published: December 2008

Scanning electron microscopy (SEM) was used to identify four distinct laser damage morphologies in ZnSe/ThF4 multilayer mirrors. There were three types of defect-initiated damage morphologies. Oblong-shaped damage sites oriented perpendicular to the electric field vector of the laser were associated with particulates on or near the surface of the ZnSe/ThF4 multilayers. Circular-shaped damage sites were initiated by particulates embedded beneath the top ZnSe layer. Selective laser damage at pinholes was identified as the third defect-initiated damage morphology. In addition to defect-initiated damage, stress-related damage was indicated by cracks near or within laser damage craters and erosion sites. Selective laser damage at nodular growth defects in SiH/SiO2 multilayers was also observed using SEM. Samples with different numbers of nodules were prepared in-house using RF-diode, reactive sputtering. The low-defect mirror had the highest laser damage onset, and the mirror with the highest number of nodules had the lowest laser damage onset.
Single Pulse Laser Induced Damage in IR Coatings at 10.6 μm
Authors: Deng H , Bass M , Koumvakalis N
Published: December 2008

Results on single pulse laser damage to several reflective and anti-reflective coatings designed for use at 10.6 μm are reported. Samples from two different manufacturers were studied. Nomarski microscopy and TV vidicon detection were used for the characterization of the samples before and after damage. Suggestions about the future use of an improved TV system for the detection of scattering centers in the visible are made.
Light Stripping of UV Dielectric Coatings
Authors: Asmus JF , Oldenettel JR
Published: December 2008

High-performance ultraviolet lasers require optics with a tighter tolerance on surface figure than comparable visible and infrared systems. Consequently, the costs of large-aperture figured substrates can be quite high. When ultraviolet coatings become damaged through exposure to photons and/or halogen radicals, recoating is often performed in order to salvage such substrates. If the coating is not strippable, this entails the expense of regrinding and repolishing. We have found that the remains of damaged coatings of SiO2, LaF3, MgF2, and HfO2 can be removed with pulsed xenon flashlamp radiation. A train of shots at 30 J/cm2 is sufficient to dislodge a coating without damaging fused silica and Zerodur substrates. A pulselength of 600 microseconds was employed. Frequently, photochemical damage involves only the coating and not the substrate. In these instances flashlamp stripping may be employed to salvage the substrate without reworking the surface.
Fatigue Life Improvement by Cold Working Fastener Holes in 7050 Aluminum
Authors: Ozelton MW , Coyle TG
Published: December 2008

The effect of cold working on the fatigue life of 7050-T7451 aluminum that contained fastener holes was investigated. The holes were cold worked using the split sleeve technique. The fatigue life improvement achieved by inserting interference fit fasteners in both cold worked and non-cold worked holes was also determined. Fatigue tests were conducted under constant amplitude loading conditions. Additional evaluations were conducted, including determinations of the effects of precracks emanating from the hole (introduced prior to cold working), specimen orientation, and the amount of material reamed from a hole following cold working. Fractographic and metallographic analyses were undertaken to determine typical crack initiation sites. Cold working of fastener holes in 7050-T7451 increased the fatigue life by a factor of up to five, depending upon the specific cold work and fatigue test parameters employed. The insertion of interference fit fasteners also significantly increased fatigue life. Contributions from interference fit fasteners and cold working of holes were synergistic. The introduction of a precrack prior to cold working the hole reduced fatigue life, though precracked material containing a cold worked hole exhibited a greater fatigue life than if the hole had not been cold worked. The optimum amount of material that should be reamed from a hole after split sleeve cold working to give the maximum fatigue life for given test parameters was determined.
Effect of Load Transfer on Fatigue of Mechanically Fastened Metallic Joints
Authors: Lee EU
Published: December 2008

Mechanically fastened joints are highly susceptible to fatigue cracking especially when varying loads are applied. The fatigue cracking is influenced by load transfer through fasteners.

Tests were conducted using zero, low, medium, and high load transfer specimens of 7475-T7351 aluminum. The fatigue crack initiation and growth and the final fracture behaviors were investigated. The fatigue crack initiation life, Ni, and the total fatigue life, Nf, are reduced by increasing stress range, Δσ, and load transfer level, L. The relationship is defined by the equations of the form logN=C−BΔσ−DLH where C, B, D, and H are constants. The fatigue crack growth rate, da/dN, is related to the stress intensity factor range, ΔK, by the equation da∕dN=(2.36×10−7)·(ΔK)2.89mm×cycle The crack initiation portion of the total fatigue life, Ni/Nf, is greater with lower stress range, Δσ, and longer total fatigue life, , is greater with lower stress range, Δσ, and longer total fatigue life, Nf, and it is reduced by load transfer.
Enhanced Stop-Drill Repair Procedure for Cracked Structures
Authors: Landy MA , Armen H , Eidinoff HL
Published: December 2008

A repair technique for cracked structures that consists of stop drilling the crack tip is examined. This repair procedure is enhanced by cold expanding the stop-drill hole and by installation of an interference-fit fastener. An experimental and analytical investigation of the effectiveness of the enhanced stop-drill procedure is presented. The analysis consists of elastic-plastic stress analysis utilizing the finite element approach to determine residual stress distributions, stress intensity factors around the stop-drill holes due to cold expansion, and stress intensity factors along the fatigue crack paths followed by crack initiation and crack growth life predictions. Comparisons of the life predictions and fatigue test data are also presented. The results indicate that cold expansion and interference-fit fastener installation improve the fatigue performance of stop-drill holes through crack tips by factors ranging from 3 to 20.
A New Cladding Alloy for Coolant-Side Corrosion Protection of Vacuum-Brazed Aluminum Radiators
Authors: AC Scott
Published: December 2008

K805, a nonvolatile aluminum-tin cladding alloy, was developed to provide coolant-side corrosion protection in vacuum-brazed aluminum automobile radiators and heat exchangers. Its performance was evaluated in laboratory glassware corrosion tests of coupon specimens, and a 80 470-km (50 000-mile) simulated service test of vacuum-brazed production automobile radiators. The alloy provided adequate cathodic protection to 3000-series core alloys in corrosive water and depleted glycol automotive coolants. The performance of K805 cladding is compared to that of aluminum-zinc cladding alloys (for example, 7072), the protective properties of which are degraded in vacuum-brazing applications because of the volatility of zinc.
A Demonstration of Aluminum Transport Deposition
Authors: LK Beard , JJ Conville , JC Wilson
Published: December 2008

The Ford procedure, “Engine Test for Coolants in Aluminum Systems,” was used to demonstrate aluminum transport deposition in a Ford Escort engine with a silicate-containing coolant. Evidence of aluminum transport was gathered from physical and chemical analysis of coolant samples, corrosion specimen weight losses, and inspection of cooling system components. The loss of hot surface aluminum protection corresponded with the depletion of silicate from solution during the test. Corrosion of heat-rejecting aluminum surfaces led to the presence of aluminum in solution, and the resultant deposition of aluminum phosphate in the radiator. Inspection of the coolant passages of the aluminum cylinder head at the completion of the test showed evidence of extensive corrosion.

In a second dynamometer test, it was shown that aluminum transport deposition can be prevented by the use of a coolant with adequate silicate stability. In this case, the silicate concentration remained high enough to insure hot surface aluminum protection throughout the test. Evaluation of the radiator at the completion of the test showed essentially no loss of heat rejection capacity. Inspection of the cylinder head showed no signs of corrosion.
Propylene Glycol, A New Base Fluid for Automotive Coolants
Authors: FE Mark , W Jetten
Published: December 2008

Propylene glycol is, because of its favorable toxicological properties, used as a base material for automotive engine coolant formulations in a number of European countries. In the present paper propylene glycol and ethylene glycol are compared with respect to relevant engine coolant properties like heat transfer characteristics, freezing protection, cavitation and erosion-corrosion, rubber compatibility, and toxicological properties. These properties are largely determined by the chemical and physical properties of the coolant base material rather than by the additive package which controls mainly corrosion inhibition.

Propylene glycol offers distinct advantages over ethylene glycol as a coolant base fluid as regards its toxicological and environmental properties and its cavitation resistance. With respect to the other properties both types of glycols behave very similarly.
Evalution of Engine Coolants by Electrochemical Methods
Authors: Chance RL , Walker MS , Rowe LC
Published: December 2008

This paper is a review of electrochemical techniques as they were applied at the authors' research laboratories in investigations of corrosion phenomena associated with automotive cooling system metals in ethylene glycol solutions. Studies were conducted in the laboratory, in simulated service test assemblies, and in a moving vehicle. Investigations included the measurement of corrosion rates of cooling system metals during simulated and actual vehicle service; of component parts, such as a water pump and thermostat housing, during simulated service; of aluminum at heat-rejecting surfaces and in cavitating solutions; and of brass in inhibited solutions. The measuring and monitoring of corrosion rates was accomplished mostly by linear polarization (polarization resistance) methods. Other studies involved the use of either anodic polarization measurements or continuous current measurements at constant potential. Results show the applicability of electrochemical techniques to the study of practical automotive cooling system corrosion problems.
Solder Bloom Corrosion Analysis Based on Field Survey Data, Potential Causes, and Resolution
Authors: Park KH
Published: December 2008

A method to analyze field survey data on the solder bloom corrosion in copper/brass radiators is presented. In an effort to distinguish various manufacturers' radiator products according to their solder bloom corrosion performance, a corrosion index number is introduced (Park's Solder Bloom Corrosion Index). Using this technique, the solder bloom corrosion susceptibility of various manufacturers' radiators can be forceranked as a function of miles-in-service and months-in-service.

Potential causes for the solder bloom corrosion in the copper/brass radiators are analyzed from the standpoint of coolant type used, solder type used, different soldering processes, various internal rinse systems, and so forth. Based on the data analysis, a number of recommendations are presented for the potential resolution of solder bloom corrosion.
Corrosion Behavior Diagram of Aluminum 319 Alloy in Automotive Coolants
Authors: Weir TW
Published: December 2008

Polarization resistance (PR) and corrosion behavior diagram (CBD) measurements are described which provide a rapid means of determining the effectiveness of inhibitors for aluminum corrosion in automotive coolants. The polarization resistance measurement gives a direct measure of the general corrosion rate of aluminum. The area of the hysteresis loop in the CBD is shown to be very sensitive to the degree of pitting of aluminum in a given coolant environment. The combined PR and CBD measurements take about 40 min to perform.
The MIT Miniaturized Disk Bend Test
Authors: Harling OK , Lee M , Sohn D-S , Kohse G , Lau CW
Published: December 2008

A miniaturized disk bend test (MDBT) using transmission electron microscopy specimens for the determination of various mechanical properties is being developed at MIT. Recent progress in obtaining strengths and ductilities of highly irradiated metal alloys is reviewed. Possibilities exist for applying the MDBT approach to the determination of other mechanical properties. Progress in fatigue testing and in determination of the ductile-to-brittle transition temperature is reviewed briefly.
Disk-Bend Ductility Tests for Irradiated Materials
Authors: Klueh RL , Braski DN
Published: December 2008

Because irradiation is known to cause a decrease in the ductility of numerous structural alloys, a simple test to determine the ductility of small irradiated specimens would be extremely useful. A mechanical test designed for this purpose was developed by Hanford Engineering Development Laboratory (HEDL). Changes in the ductility of an alloy are determined by bending a transmission electron microscopy disk (3 mm diameter by 0.25 mm thick) in a hemispherical punch and die. We modified the HEDL test machine and are using it to qualitatively screen alloys that are susceptible to embrittlement caused by irradiation. Tests designed to understand the disk-bend test in relation to a uniaxial tensile test are discussed. Selected results of tests after neutron irradiation are also presented.
Design and Use of Nonstandard Tensile Specimens for Irradiated Materials Testing
Authors: Panayotou NF , Atkin SD , Puigh RJ , Chin BA
Published: December 2008

Miniature, nonstandard, tensile-type specimens have been developed for use in radiation effects experiments at high energy neutron sources where the useful radiation volume is as small as a few cubic centimeters. The end result of our development is a 12.7-mm-long sheet-type specimen, with a 5.1-mm-long, 1.0-mm-wide gage section, which is fabricated from 0.25-mm-thick sheet stock by a punching technique. Data obtained using miniature specimens of an austenitic, a ferritic and a precipitation hardened alloy are in good agreement with data obtained using much larger specimens. This finding indicates that miniature tensile specimen data may be used for engineering design purposes and that miniature tensile specimen technology may be applicable to fields other than the study of radiation effects. This paper reviews the miniature specimen technology which was developed and reports the data which were obtained.
Miniature Center-Cracked-Tension Specimen for Fatigue Crack Growth Testing
Authors: Ermi AM , James LA
Published: December 2008

A miniature specimen was developed to characterize the effects of neutron irradiation on the fatigue crack growth behavior of candidate fusion reactor first-wall materials. During the developmental effort, questions regarding thickness, buckling, excessive plasticity, accuracy of crack length measurements, length-to-width ratio, and proximity of welds to the notch (for welded specimens) were systematically addressed. This investigation led to the miniature center-cracked-tension specimen, consisting of a notched insert (nominally 0.61 mm thick by 25.4 mm wide by 12.7 mm long) which is irradiated, and two end grips (28.6 mm long) which are welded to the insert after irradiation. Fully assembled, the specimen has dimensions which are very similar to those of the standard center-cracked-tension specimen described in ASTM Test for Constant-Load-Amplitude Fatigue Crack Growth Rates Above 10−8 m/Cycle (E 647). The specimen is used with an electrical potential technique for monitoring the crack length, miniature high-temperature fatigue crack growth rate testing machines, and a computerized data acquisition system for unattended around-the-clock testing.