: Liquid-phase reactor experiments were performed with commercial products and decontaminants to identify viable dual-use products for the decontamination of the chemical warfare agents HD, GD, and VX. The chemical reactivity of the agents in the absence of mass transport limitations (e.g., dissolution of neat agent) was evaluated using a dilute liquid-phase reactor method. When coupled with material testing, the reactor results were used to determine the decontamination modes of action occurring within materials. Evaluation of the data indicated several agent-specific and several broad-spectrum (multiple agent) reactive decontaminants. The reactor analysis was used to identify several commercial products that may provide reactivity with multiple chemical warfare agents in the solution phase. The results indicated that HD was susceptible to oxidation under acidic and alkaline conditions, GD was reactive under alkaline conditions for several decontaminant chemistries, and VX was reactive under acidic and alkaline oxidation chemistries with buffer components. The results suggest that a highly reactive decontaminant for all agents could be achieved with a buffered, alkaline oxidative chemistry that maintains pH levels above 10. This study provides the foundation to enable the interpretation of the mode of decontamination (i.e., reaction or extraction) of chemical warfare agents from materials.

: Decontamination of materials involves the physical and chemical interactions among several components including the agent, material, and decontaminant. The two-way interactions of each component (agentmaterial, agentdecontaminant, and decontaminantmaterial) contribute to the decontaminant performance and the resulting post-decontamination hazards associated with the material. Decontamination involves coupled transport and reaction mechanisms. Mass transfer processes limit the accessibility of the agent to the decontaminant and significantly influence performance. Three modes of action contribute to the decontamination of a material: chemical reactivity, agent extraction, and decontaminant penetration. Each mode contributes to the rate and extent of agent removal. A novel approach was developed to integrate liquid-phase reactor data and material testing to identify the modes of action that may occur for specific agentmaterialdecontaminant combinations. This approach illustrates that chemical reactivity does not necessarily correlate with agent removal from materials and indicates potential directions for future decontamination formulation approaches.

Chemical warfare agents (CWA) can be absorbed by variety of materials including polymeric coatings like paints through bulk liquid contact, thus presenting touch and vapor hazards to interacting personnel. In order for accurate hazard assessments and subsequent decontamination approaches to be designed, it is necessary to characterize the absorption and distribution of highly toxic species, as well as their chemical simulant analogs, in the subsurface of engineered, heterogeneous materials. Using a combination of judicious sample preparation in concert with scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), it should be possible to directly measure the uptake and distribution of CWA simulants in the subsurface of complex multilayer coatings. Polyurethane and alkyd coatings were applied to aluminum and silicon substrates and contaminated with 2-chloroethyl ethyl sulfide (CEES) and dimethyl methylphosphonate (DMMP). The surfaces and cross-sectional interfaces of the contaminated coatings were probed with SEM-EDS to provide imaging, spectral, and elemental mapping data of the contaminant-material systems. This work demonstrated SEM-EDS capability to detect and spatially resolve unique elemental signatures of CWA simulants within military coatings. The visual and quantitative results provided by these direct measurements illustrate contaminant spatial distributions, provide order-of-magnitude approximations for diffusion coefficients, and reveal material characteristics that may impact contaminant transport into complex coating materials. It was found that contaminant uptake was significantly different between the topcoat and primer layers.

The ability to directly characterize chemical transport and interactions that occur within a material (i. e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals ( such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX.

A combination of vacuum-based vapor emission measurements with a mass transport model was employed to determine the interaction of chemical warfare agents with various materials, including transport parameters of agents in paints. Accurate determination of mass transport parameters enables the simulation of the chemical agent distribution in a material for decontaminant performance modeling. The evaluation was performed with the chemical warfare agents bis(2-chloroethyl) sulfide (distilled mustard, known as the chemical warfare blister agent HD) and O-ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (VX), an organophosphate nerve agent, deposited on to two different types of polyurethane paint coatings. The results demonstrated alignment between the experimentally measured vapor emission flux and the predicted vapor flux. Mass transport modeling demonstrated rapid transport of VX into the coatings; VX penetrated through the aliphatic polyurethane-based coating (100 μm) within approximately 107 min. By comparison, while HD was more soluble in the coatings, the penetration depth in the coatings was approximately 2× lower than VX. Applications of mass transport parameters include the ability to predict agent uptake, and subsequent long-term vapor emission or contact transfer where the agent could present exposure risks. Additionally, these parameters and model enable the ability to perform decontamination modeling to predict how decontaminants remove agent from these materials.

Chemical warfare agent simulants are often used as an agent surrogate to perform environmental testing, mitigating exposure hazards. This work specifically addresses the assessment of downwind agent vapor concentration resulting from an evaporating simulant droplet. A previously developed methodology was used to estimate the mass diffusivities of the chemical warfare agent simulants methyl salicylate, 2-chloroethyl ethyl sulfide, di-ethyl malonate, and chloroethyl phenyl sulfide. Along with the diffusivity of the chemical warfare agent bis(2-chloroethyl) sulfide, the simulant diffusivities were used in an advection-diffusion model to predict the vapor concentrations downwind from an evaporating droplet of each chemical at various wind velocities and temperatures. The results demonstrate that the simulant-to-agent concentration ratio and the corresponding vapor pressure ratio are equivalent under certain conditions. Specifically, the relationship is valid within ranges of measurement locations relative to the evaporating droplet and observation times. The valid ranges depend on the relative transport properties of the agent and simulant, and whether vapor transport is diffusion or advection dominant.

A novel experimental and computational methodology has been developed for estimating Fickian mass transport parameters of organic molecules through stagnant mediums such as air, paints, or polymeric substrates. Dynamic contact angle experiments were performed to measure the droplet volume evolution with the chemical warfare agent bis(2-chloroethyl) sulfide (distilled mustard, known as the chemical warfare agent HD) on military-relevant substrates. A finite element model for simultaneous evaporation and absorption was used to analyze the experimental data and determine the mass transport parameter values of the agent in the absorptive material. The computational model was validated by comparison with the results of a complementary experimental technique involving testing for HD vapor emission from the contaminated material. The model predicted HD vapor emission rates from a silicone elastomer substrate for contamination conditions not directly tested. The simulation results show that the model parameters c...

The "island dynamics" numerical method was used to investigate kinetically limited nucleation and growth during copper electrodeposition in the presence of additives. The system geometry consisted of a metal substrate initially patterned with a square array of Cu seed clusters. The simulations used estimated values of the reaction rate constants associated with an additive system consisting of acid sulfate electrolyte containing "accelerator" and "suppressor" species. Numerical results were obtained for the probability distributions for nearest-neighbor distance and for distance of nuclei from the seed Cluster, and were compared with comparable experimental data reported in Part I of this series. Numerical results were in qualitative agreement with experimental trends associated with variations in additive composition, array spacing, and applied potential. Conditions that favored formation of high nucleation density were high chloride (Cl(-)) and high poly(ethylene glycol) (PEG) concentrations; in this case, it was found that 90% of the Au Surface was covered by Cu upon passage of 0.1 mC/cm(2). Conditions that favored deposition onto pre-existing seed clusters were low (Cl(-)) concentration, moderate (PEG) concentration, and closely spaced clusters. The results reported here provide a foundation for developing improved parameter estimation procedures based on optimization methods. (C) 2009 The Electrochemical Society. [DOL 10.1149/1.3183505] All rights reserved.

Nucleation and growth in the presence of additives during Cu electrodeposition on ordered arrays of Cu seed Clusters oil a polycrystalline An film were investigated. The seed Clusters, formed by an E-beam lithography method, were 25 nm in diameter and positioned in square arrays (100, 200, or 300 nm spacing) with overall dimensions of 20 x 20 mu m. Electrodeposition was carried out in acid sulfate solutions (0.6 M CuSO4 and 1.0 M H2SO4) containing various concentrations of additives [0.1-10 ppm Cl-, 3-3000 ppm poly(ethylene glycol), and 3-50 ppm bis(3-sulfopropyl) disulfide]. Image analysis methods were used to extract quantitative information oil the effect of additives, array spacing, and potential on the probability of finding Cu nuclei at a given distance from a Cu seed cluster as well as finding the nearest neighbor to any deposited Cu nucleus. The level of chloride concentration was found to mediate the extent of seed growth vs wild nucleation. Low levels of chloride (0.1 ppm) yielded growth predominantly at the Cu seeds with virtually no wild nuclei. Progressively higher levels of chloride (1 and 10 ppm) yielded lower deposition rates at the Cu seeds and proportionally higher levels of wild nucleation. Experimental results are compared with numerical simulations in Part II [Stephens et al., J. Electrochem. Soc., 156, D385 (2009)]. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3183502] All rights reserved.

Electron-beam-induced deposition was used to create an ordered array of Pt seed clusters on a Au film onto which Cu was subsequently electrodeposited in the presence of additives. The Pt seed clusters were 25-30 nm diameter, positioned in square arrays of 200, 300, or 400 nm spacing, with overall dimensions of 5 x 5 mu m. Electrodeposition was carried out in an acid sulfate bath containing additives. Image analysis methods were used to evaluate the probability of finding Cu nuclei at a given distance from a Pt seed cluster, as well as finding the nearest neighbor to any deposited Cu nucleus. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.2992705] All rights reserved.

In this paper, a novel, high throughput experimental and theoretical technique was developed to extract additive influences on the dual-kinetic deposition of a metal onto a foreign substrate based on key transition points in chronopotentiometry curves. A finite difference (FD) 1-D growth mode simulation was developed to predict the overgrowth of an electrodeposited metal onto a resistive substrate in the presence of additives based on the experimental results. The simulations were employed to study thin film overgrowth on the wafer scale. Results indicated that the deposit profile was more uniform over a broader range of deposition rates as the rate on the coalesced deposit (ξCu) decreased. Other key parameters forpromoting thin film growth included a low coalescence thickness, high substrate conductivity, and an intermediate applied current.