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Dirmyer, Matthew R.

Publications and source records attributed to Dirmyer, Matthew R..

9 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Silicone Elastomers with Novel Modified Filler for Increased Radiation Resistance

Radiation induced chemical aging behavior in filled silicone elastomers results in a decreased mechanical performance over time. This report describes chemical methodologies to reduce radiation aging via a surfacemodified filler. Four different modified fillers were incorporated into a silicone polymer matrix and subjected to accelerated radiation aging. Fillers modified with aryl group such as phenyl, styrl, and napthyl functionality should improve the radiation aging behavior of the composite material. A series of analytical methodologies were applied to determine the efficacy of the modified filler approach as a mitigation strategy for radiation damage. The results support that phenyl and napthyl modified fillers mitigated radiation damage when compared to control samples and samples with hexyl (non-aryl) modified filler.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Evaluation of MS-122 mold releases

Miller Stephenson polytetrafluoroethylene-based mold releases were evaluated; the mold releases include MS-122E, MS-122SE, MS-122AD, MS-122ADL, and MS-122XD. The mold releases were tested for cure inhibition of Sylgard 184 90/10. These mold releases were also tested for sheer flow stability through a defined gap on a uranium alloy surface. Mold releases MS-122E, MS-122SE, MS-122AD, MS-122ADL, and MS-122XD were all tested. SEM images comparing the lay down of each mold release on a flat silicon surface were also compared. MS-122 XD showed signs of cure inhibition of Sylgard 184 90/10. All mold releases were detected on uranium alloy surfaces via Infrared Spectroscopy (FT-IR) after flowing Sylgard 184 90/10 across the uranium surface indicating the mold release coating is stable under flow. All SEM images of the mold releases studied are comparable showing rough surfaces with micron-sized particles.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Structural differences between single crystal and polycrystalline UBe 13

Here, we report on observations of structural and chemical differences between samples of UBe 13 that were synthesised using two different methods. Unexplained discrepancies in properties between samples with differing synthesis had previously been found in this heavy fermion superconductor. A polycrystalline UBe 13 sample was made by arc-melting the constituents. Single crystals were grown using an aluminium flux and had a consistently slightly larger lattice parameter than the polycrystals, which merited further study. Neutron diffraction data were collected at the Lujan Center at LANSCE on the HIPPO diffractometer. Aluminium was detected by inductively coupled plasma mass spectrometry (ICP-MS) in the flux-grown single crystal (0.803 wt%), and small amounts (~0.2 wt%) of thorium were detected in the UBe 13 polycrystalline sample. In order to probe the implications of the presence of Al, calculations by spin-polarised DFT-GGA+U show that the incorporation of Al onto the 96i site (the lowest symmetry site in the structure) is energetically more favourable than on other sites. In general, the trends calculated by DFT for bond lengths and lattice parameter increases are consistent with bond lengths experimentally observed by neutron diffraction, but specific percentage changes with aluminium incorporation may be obscured by the unexpected thorium in the polycrystalline sample. The aggregate of our initial observations suggests that incorporation of aluminium from the flux into single crystal UBe 13 is significant.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Chemical analysis of DC745 Materials: DEV Lot 1 reinvestigation; barcodes P053387, P053388, and P053389

This report serves as a follow up to our initial development lot 1 chemical analysis report (LA-UR-16-21970). The purpose of that report was to determine whether or not certain combinations of resin lots and curing agent lots resulted in chemical differences in the final material. One finding of that report suggested that pad P053389 was different from the three other pads analyzed. This report consists of chemical analysis of P053387, P053388, and a reinvestigation of P053389 all of which came from the potentially suspect combination of resin and curing agents lot. The goal of this report is to determine whether the observations relating to P053389 were isolated to that particular pad or systemic to that combination of resin and curing agent lot. The following suite of analyses were performed on the pads: Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FT-IR), and Solid State Nuclear Magnetic Resonance (NMR). The overall conclusions of the study are that pads P053387 and P053388 behave more consistently with the pads of other resin lot and curing agent lot combinations and that the chemical observations made regarding pad P053389 are isolated to that pad and not representative of an issue with that resin lot and curing agent lot combination.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Synthesis and characterization of surrogate nuclear explosion debris: urban glass matrix

Surrogate nuclear explosive debris was synthesized and characterized for major, minor, and trace elemental composition as well as uranium isotopics. The samples consisted of an urban glass matrix, equal masses soda lime and cement, doped with 500 ppm uranium with varying enrichments. The surface and cross section morphology were measured with SEM, and the major elemental composition was determined by XPS. LA-ICP-MS was used to measure the uranium isotopic abundance comparing different sampling techniques. Furthermore, the results provide an example of the utility of LA-ICP-MS for forensics applications.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2017

Comparative Assessment of Copper-Coated Kapton: Analysis of Microclad from Several Manufacturing Lots

Microclad is a composite material consisting of a thin copper coating applied on a single side over a Kapton substrate. Kapton is the commercial designator for polyimide supplied by DuPont. Microclad is a key material in detonator manufacture and function. Detonators which utilize Microclad function when a large current applied through a thin bridge etched into the copper produces a plasma, accelerating a Kapton flyer into an explosive (PETN) pellet. The geometry and properties of the Microclad are a critical element of this process.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Comparison of femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry for uranium isotopic measurements

Feasibility tests were conducted using femtosecond and nanosecond laser ablation inductively coupled plasma mass spectrometry for rapid uranium isotopic measurements. The samples used in this study consisted of a range of pg quantities of known 235/238 U solutions as dried spot residues of 300 pL drops on silicon substrates. The samples spanned the following enrichments of 235 U: 0.5, 1.5, 2, 3, and 15.1%. In this direct comparison using these particular samples both pulse durations demonstrated near equivalent data can be produced on either system with respect to accuracy and precision. There is no question that either LA-ICP-MS method offers the potential for rapid, accurate and precise isotopic measurements of U10Mo materials whether DU, LEU or HEU. The LA-ICP-MS equipment used for this work is commercially available. The program is in the process of validating this work for large samples using center samples strips from Y-12 MP-1 LEU-Mo Casting #1.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

The Density of Uranium Hydride Formed Under Mechanical Load

The conversion of uranium metal (ρ = 19 g/cc) to uranium hydride (theoretical ρ = 11 g/cc) results in a large volumetric expansion due to both the density decrease and the substantial porosity of the hydride if not volumetrically constrained. This transformation from a monolithic solid to a particulate material can generate substantial forces when the growing hydride impacts a nearby target. The resulting displacement of the target is dependent upon both its resistance to motion and the strength of the growing hydride. We have observed columns of growing uranium hydride apply forces of hundreds to thousands of pounds to flex high-strength cantilever beams, and have measured applied forces of over 5000 pounds when growing hydride columns impacted rigid targets. The force/displacement behavior of growing uranium hydride was originally modeled by finite element methods to develop an elastic, perfectly plastic constitutive model of UH 3 . The UH 3 constitutive model was then applied to simulate the response of components impacted by growing uranium hydride. More recently we have used an experimental apparatus that simultaneously and independently provides measurement of applied force and target displacement during uranium hydride formation. These efforts confirm previous work and allow for increased confidence in modeling results. The design, testing, and experimental results using such an apparatus over a variety of system stiffnesses and with a variety of sample sizes has been completed. This work extended our understanding of UH 3 growth dynamics and mechanics and enabled the development of a higher fidelity constitutive Drucker-Prager model for UH 3 , and greater confidence in predictions of component behavior in systems impacted by uranium hydride formation.

36 MATERIALS SCIENCE↗