Michael Irvin White

Selective stress-based microcantilever sensors for enhanced surveillance.

Assessment of component aging and degradation in weapon systems remains a considerable challenge for the Integrated Stockpile Evaluation program. Analysis of weapon atmospheres can provide degradation signatures and indicate the presence of corrosive vapors. However, a critical need exists for compatible in-situ sensors to detect moisture and other gases over stockpile lifetimes. This inhibits development of both “self-aware weapons” and fully instrumented weapon test platforms that could provide in-situ data to validate high-fidelity models for gases within weapons. We developed platforms for on-demand weapon atmosphere surveillance based on static microcantilevers (SMC) and surface accoustic wave (SAW) devices coated with nanoporous metal organic frameworks (MOFs) to provide selectivity. SMC detect analytes via adsorbate-induced stress and are up to 100X more sensitive than resonant

Precision Moisture Generation and Measurement

In many industrial processes, gaseous moisture is undesirable as it can lead to metal corrosion, polymer degradation, and other materials aging processes. However, generating and measuring precise moisture concentrations is challenging due to the need to cover a broad concentration range (parts-per-billion to percent) and the affinity of moisture to a wide range surfaces and materials. This document will discuss the techniques employed by the Mass Spectrometry Laboratory of the Materials Reliability Department at Sandia National Laboratories to generate and measure known gaseous moisture concentrations. This document highlights the use of a chilled mirror and primary standard humidity generator for the characterization of aluminum oxide moisture sensors. The data presented shows an excellent correlation in frost point measured between the two instruments, and thus provides an accurate and reliable platform for characterizing moisture sensors and performing other moisture related experiments.

Identification of volatile butyl rubber thermal-oxidative degradation products by cryofocusing gas chromatography/mass spectrometry (cryo-GC/MS).

Chemical structure and physical properties of materials, such as polymers, can be altered as aging progresses, which may result in a material that is ineffective for its envisioned intent. Butyl rubber formulations, starting material, and additives were aged under thermal-oxidative conditions for up to 413 total days at up to 124 °C. Samples included: two formulations developed at Kansas City Plant (KCP) (#6 and #10), one commercially available formulation (#21), Laxness bromobutyl 2030 starting material, and two additives (polyethylene AC-617 and Vanax MBM). The low-molecular weight volatile thermal-oxidative degradation products that collected in the headspace over the samples were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). The majority of identified degradation species were alkanes, alkenes, alcohols, ketones, and aldehydes. Observations for Butyl #10 aged in an oxygen-18 enriched atmosphere ( 18 O2) were used to verify when the source of oxygen in the applicable degradation products was from the gaseous environment rather than the polymeric mixture. For comparison purposes, Butyl #10 was also aged under non-oxidative thermal conditions using an argon atmosphere. UNCLASSIFIED UNLIMITED RELEASE (UUR) UNCLASSIFIED UNLIMITED RELEASE (UUR) 4 ACKNOWLEDGMENTS The authors gratefully acknowledge the contributions of Donald R. Bradley for his assistance in sample preparation and aging. We would also like to thank Mark Wilson for providing the butyl rubber samples as developed by him at Kansas City Plant. Funding was provided by the Enhanced Surveillance Campaign (ESC). Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DEAC0494AL85000. UNCLASSIFIED UNLIMITED RELEASE (UUR) UNCLASSIFIED UNLIMITED RELEASE (UUR) 5 CONTENTS

Surface plasmon sensing of gas phase contaminants using optical fiber.

Fiber-optic gas phase surface plasmon resonance (SPR) detection of several contaminant gases of interest to state-of-health monitoring in high-consequence sealed systems has been demonstrated. These contaminant gases include H{sub 2}, H{sub 2}S, and moisture using a single-ended optical fiber mode. Data demonstrate that results can be obtained and sensitivity is adequate in a dosimetric mode that allows periodic monitoring of system atmospheres. Modeling studies were performed to direct the design of the sensor probe for optimized dimensions and to allow simultaneous monitoring of several constituents with a single sensor fiber. Testing of the system demonstrates the ability to detect 70mTorr partial pressures of H{sub 2} using this technique and <280 {micro}Torr partial pressures of H{sub 2}S. In addition, a multiple sensor fiber has been demonstrated that allows a single fiber to measure H{sub 2}, H{sub 2}S, and H{sub 2}O without changing the fiber or the analytical system.