6 research outputs found
Imaging indicator for ESD safety testing.
This report describes the development of a new detection method for electrostatic discharge (ESD) testing of explosives, using a single-lens reflex (SLR) digital camera and a 200-mm macro lens. This method has demonstrated several distinct advantages to other current ESD detection methods, including the creation of a permanent record, an enlarged image for real-time viewing as well as extended periods of review, and ability to combine with most other Go/No-Go sensors. This report includes details of the method, including camera settings and position, and results with wellcharacterized explosives PETN and RDX, and two ESD-sensitive aluminum powders
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FLASHFOAM : a triboluminescent polymer foam for mechanical sensing.
The formulation and processing of a brittle polyurethane foam containing triboluminescent powder additives is described. Two powder additives, known to exhibit triboluminescence, were individually examined: triethylammonium tetrakis (dibenzoylmethanato) europate [NEt3H][Eu(DBM)4] and ordinary table sugar (sucrose, C12H22O11). In each instance, the powders were mixed into the polyol component of the foam. When combined with the isocyanate component, the resulting foams had these powders incorporated into their cellular structure so as to induce a triboluminescent response upon crushing during impact testing. The triboluminescent response of foam specimens containing each of these powder additives was characterized by measuring: the time rate of change in the optical output (measured as Watts), the peak optical output, the total integrated output (Watt-seconds), during the impact event. Foams containing the europate compound were found to yield several orders of magnitude higher output when compared to the sugar-containing foam. Strain rate and concentration of the powder (in the foam) were important variables with respect to optical output. Both the peak and total triboluminescent output increased with increasing powder concentration. Peak output was also found to increase with increasing strain rate. However, the total output was found to be roughly constant for a given concentration regardless of strain rate (over the strain rate range: 20 sec-1< e& < 150 sec-1). At very low strain rates, no triboluminescent response was measured
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Protection of alodine coatings from thermal aging by removable polymer coatings.
Removable polymer coatings were evaluated as a means to suppress dehydration of Alodine chromate conversion coatings during thermal aging and thereby retain the corrosion protection afforded by Alodine. Two types of polymer coatings were applied to Alodine-treated panels of aluminum alloys 7075-T73 and 6061-T6 that were subsequently aged for 15 to 50 hours at temperatures between 135 F to 200 F. The corrosion resistance of the thermally aged panels was evaluated, after stripping the polymer coatings, by exposure to a standard salt-fog corrosion test and the extent of pitting of the polymer-coated and untreated panels compared. Removable polymer coatings mitigated the loss of corrosion resistance due to thermal aging experienced by the untreated alloys. An epoxide coating was more effective than a fluorosilicone coating as a dehydration barrier
Synthesis, characterization and reactivity of some permethyltantalocene alkylidenes and unusually stable metallaoxetanes
Several tantalaoxetanes have been prepared and the X-ray crystal structure of O-exo-Cp_2*Ta(OCHPhCH_2)CH_3 is reported (Cp* = η^5-C_5Me_5). The kinetic products of the reactions of Cp_2*Ta(=CH_2)CH_3 with paraformaldehyde or benzaldehyde are O-endo-Cp_2*Ta(CH_2CH_20)CH_3 and O-endo-Cp_2*Ta(CH_2CHPhO)CH_3, respectively. These tantalaoxetanes undergo an acid and base-catalyzed isomerization to O-exo-Cp_2*Ta(OCH_2CH_2)CH_3 and O-exo-CP_2*Ta(OCHPhCH_2)CH_3 followed by thermal decomposition to Cp_2*Ta(=O)CH_3 and the appropriate olefin. Cp_2*Ta(=CH_2)H deoxygenates epoxides to form Cp_2*Ta(=O)CH_3 and olefin. No intermediates are observed in this deoxygenation under conditions where the appropriate tantalaoxetanes are stable and would have been spectroscopically observed. Stereolabeled epoxides were deoxygenated to probe the mechanism for the possible intermediacy of a 1,4-biradical. Retention of stereochemistry of the resulting olefin was observed and is indicative of a concerted mechanism. These results and their implications for the mechanism of olefin epoxidation are discussed.
Treatment of Cp*_2 TaCI_2 with a variety of substituted benzyl potassium reagents affords an equilibrium mixture of CP*_2 Ta(=CHC_6H_5)H, 1, and Cp*_2 Ta(o-CH_2C_6H_4)H, 2, which interconvert presumably via the unstable 16 electron intermediate [Cp*_2Ta(CH_2C_6H_5)]. Several derivatives substituted at the phenyl ring have been prepared to explore the effect of both sterics and electronics on the a-hydrogen migration equilibrium. Trapping of the benzyl intermediate by methylenetrialkylphosphoranes results in methylene transfer to give Cp*_2 Ta(=CH_2)CH_2C_6H_5. The substituted benzyl derivatives have provided a system to determine the influence of phenyl sUbstituents on migratory aptitude of the benzyl group
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Imaging indicator for ESD safety testing.
This report describes the development of a new detection method for electrostatic discharge (ESD) testing of explosives, using a single-lens reflex (SLR) digital camera and a 200-mm macro lens. This method has demonstrated several distinct advantages to other current ESD detection methods, including the creation of a permanent record, an enlarged image for real-time viewing as well as extended periods of review, and ability to combine with most other Go/No-Go sensors. This report includes details of the method, including camera settings and position, and results with wellcharacterized explosives PETN and RDX, and two ESD-sensitive aluminum powders
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Assuring ultra-clean environments in microsystem packages : irreversible and reversible getters.
A new generation of irreversible, chemically reacting getters specifically targeted toward assuring the integrity of the local environment within microsystem packages were developed and evaluated. These reactive getters incorporate volatile species into a polymer through covalent bonds, thus producing a non-volatile product. These reactive getters will be combined with getters that rely on absorption media (e.g. zeolites and high surface area carbon fibers) to scavenge non-reactive species, like solvents. Our getter systems will rely on device packaging to limit exchange between the microsystem and the global environment. Thus, the internal getters need only provide local environmental control within the microsystem package. A series of experiments were conducted to determine uptake rates and capacities absorption and reactive-based getters. Diffusion rates through the binder used to hold the getter particles together were also investigated. Getters were evaluated in environments with a saturated headspace and with a limited amount of the volatile species of interest. One- and two-dimensional numerical models and analysis techniques have been developed and used to predict the transport of contaminant species within a representative microsystem package consisting of an open gas-filled volume adjacent to a polymer layer containing embedded particles of getter. The two-dimensional model features explicit representation of the individual getter particles while the one-dimensional treatment assumes a homogeneous distribution of getter material within the getterlpolymer layer. Example calculations illustrate the dependence of getter performance on reaction rates, polymer diffusivity, and getter particle volume fraction. In addition, the model is used to deduce surface reaction rates, solid phase diffusivities, and maximum-loading densities by least-squares fitting of model predictions to measured histories of gas-phase contaminant concentration and getter weight gain