Since 1975 Mound has been examining the surface structure of high energy materials and the interaction of these materials with various metal containers. The high energy materials that have been studied include: the pyrotechnic TiH /KCIO^, the AI/CU2O machinable thermite, the PETN? HMX and RDX explosives, and two plastic bonded' explosives (PBX). Aluminum and alloys of Fe, Ni and Cr have been used as the containment materials. Two aims in this research are: (1) the elucidation of the mechanism of pyrotechnic ignition and (2) the compatibility of high energy materials with their surroundings. Exciting and new information has been generated by coupling Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) with thermal data. In particular, AES and XPS studies on the pyrotechnic materials and on thermites have ^hown the mechanism of ignition to be nearly independent of the type of oxidizer present but directly related to surface chemistry of the fuels. In studies on the two PBX's, PBX-9407 and LX-16, it was concluded that the Exon coating on 9407 was complete and >̂ 10oA; whereas in LX-16, the coating was <100A or even incomplete. AES and scanning Auger have been used to characterize the surface composition and oxide thickness for an iron-nickel alloy and showed the thicker oxides to have the least propensity for atmospheric hydrocarbon adsorption. Data will be presented and illustrations made which highlight this new approach to studying ignition and compatibility of high energy materials. Finally, the salient features of the X-SAM-800 purchased by Mound will be discussed in light of future studies on high energy materials.

Recent work on a new glass-ceramic/alloy for pyrotechnic components is discussed. A newly developed family of austenitic stainless steels has been hermetically sealed to a widely used lithia-alumina-silica (LAS) glass-ceramic. These alloys, originally developed for high oxidation resistance, contain 4-5 wt% Al. The presence of Al offers several advantages from a glass or glass/ceramic sealing point of view: presence of a tenacious, stable oxide (Al{sub 2}O{sub 3}) on the alloys` surface as well as the fact that they can be strengthened during sealing via precipitation of a secondary phase, NiAl. In addition these new alloys offer lower material and machining costs and improved weldability compared to the widely used Ni-base superalloys.

The fabrication of glass-ceramic to metal components has classically been a two-dimensional process based on the control of time and temperature to yield high-quality components. The implementation of hot isostatic pressing (HIP) to the manufacturing of glass-ceramic to metal seals adds a third dimension (i.e., pressure) to the process. HIP processing of a multiconstituent, lithia-alumina-silica glass at high pressures, up to 207 MPa (30 000 psi), was shown to control the crystalline phases that form in the glass-ceramic. In addition, the high-pressure processing of components fabricated with the glass-ceramic and several high tensile strength alloys, Inconel 718, Hastelloy C-276, Inconel 625, and Nitronic 40, was found to yield superior pore-free interfacial seals with improved hermeticity.

Efforts are being made within the nuclear weapons complex (National Nuclear Security Administration) of the Department of Energy (DOE) to replace Resource Conservation and Recovery Act (RCRA) regulated solvents, (flammable, toxic, corrosive and reactive) and ozone-depleting chemicals (ODC) with more benign alternatives.

Beryllium has found applications in the nuclear industry as components in weapons and nuclear reactors, in the aerospace industry for special structural applications and in precision navigational instruments such as gyroscopes, The purity of the beryllium is known to have a large impact on its mechanical and chemical properties, including its corrosion resistance, Although chlorinated solvents have long been used to degrease and clean beryllium parts, not much has been reported about the potential effects of residual cleaning and processing agents left on the surface of beryllium, Recently, samples from some of the beryllium cladding that has been used in the nuclear industry have been found to contain corrosion promoters, e.g. chlorides. In addition, machined surfaces of more recent beryllium metal, e.g. S200 grades, were found to include chlorides, This paper involves using K-ray photoelectron spectroscopy to examine the effects of residual chlorinated solvents on beryllium under near-ambient conditions. Interpretation of the data concludes that these chlorinated solvents react with the beryllium metal surfaces to produce chlorides. Thermodynamic calculations are used to corroborate these results. A mechanism is proposed to explain the loss of the native protective oxide which exposes a reactive surface to the chlorine in the solvents to produce a chloride. Copyright (C) 1999 John Wiley & Sons, Ltd.

X-ray photoelectron spectroscopy (XPS) is a surface sensitive analytical technique that measures the binding energy of electrons in atoms and molecules on the surface of a material. XPS was used to determine the distribution of the oligosaccharide side chains in the glycoprotein, MUC1 mucin. Low-resolution XPS spectra provided elemental composition of MUC1 mucin (fully glycosylated), mucin polypeptide (nonglycosylated), and carbohydrates found in mucin. The nitrogen content of MUC1 mucin was determined to be intermediate between the mucin polypeptide and the carbohydrates. Assuming a uniform distribution of carbohydrate on MUC1 mucin, the average thickness of the carbohydrate layer was calculated to be 4.9 nm using the low-resolution N 1s signals. High-resolution XPS spectra give detailed information about the chemical bonding of the surface molecules. Calculations based on the high-resolution O 1s spectra showed a carbohydrate thickness of 6.6 nm. These experimentally determined values agree reasonably well with an estimated 5 nm of carbohydrate thickness from a simple model which assume that the core protein is a rodlike molecule approximately 5 nm in diameter. Although the carbohydrate coating on the MUC1 mucin appears to be thick enough to cover the core protein entirely, fully glycosylated breast milk MUC1 mucin is susceptible to proteolytic digestion without removal of any oligosaccharide side chain, suggesting areas of exposed core protein. A possible explanation is that the oligosaccharide side chains may form patches of carbohydrate along the core protein with regions of exposed core protein.

Glass-ceramic to metal seals are used in pyrotechnic actuators and ignitors. Metals that have been successfully demonstrated for this application include several nickel-based alloys and a family of Al-containing austenitic stainless steels. Seals made between a lithia-alumina-silica (LAS) glass-ceramic and nickel-based alloys show excessive metal attack by the glass. This is also true of the Al-containing alloys but the etching action of the glass is less severe. This attack will cause reactions to occur at the glass-ceramic/metal interface. Not all reactions are detrimental to the seal, but some are and these unwanted reactions can cause the formation of pores and the subsequent loss of hermeticity. In this paper, LAS glass-ceramic will be sealed to Al-containing alloys that were first oxidized prior to sealing-called “preoxidation.” Results will be given that show “preoxidation” of the alloys substantially reduces the probability of glass/metal reactions during seal formation. The reduction in the amount of reaction products that are created improves the overall quality of the interface without loss of seal bond strength. In addition, the mechanism of surface oxide formation on these Al-containing steels is discussed. Auger data are presented that show the composition of the resulting oxides to be a function of the oxidation temperature. There are two theories that exist on the mechanism of oxidation; one is that oxidation occurs at the air/oxide interface (Ref. 10) and the other is that oxidation takes place at the oxide/metal interface (Ref. 11). In order to study which theory is correct for the Al-containing alloys, oxidation of the alloys was performed, first in pure 16O2, and then followed by pure 18O2, Secondary ion mass spectroscopy (SIMS) imaging results showed no layered structure but did show a mixture of oxides. Thus, the mechanism of oxidation of these alloys is not simple and must be occurring in such a manner as to allow oxygen to have access at all stages of the oxidation process.

Carbon foams have been manufactured at EG&G Mound Applied Technologies through the use of a salt replica process [1,2] that has been modified by a Mound propriety process [3]. Applications of these foams have been described in an early publication [4]. In the basic process [1,2] of manufacturing the foams, salt is pressed into bars; the bars are then cured, infused with polymer and cured again. The salt is then removed by copious solvent rinsings and finally carbonized into very porous and light-weight, briquette-like material [2,5]. In this paper, the carbon density and the carbon distribution in various foams were determined either by bulk measurements of weight and volume or by x-ray computed tomography (CT).

Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface chemistry of three BORAZON* materials: Type I, 510, and 550. Samples were examined in the as-received'' condition and following heat treatments in air. Boron oxides were found on the Type I and 550 BORAZON crystals; oxide thicknesses were estimated to be 15A. The titanium-coated product, 510, was found to have a discontinuous titanium coating with a TiO{sub 2} layer that was approximately 20A thick. Following heat treatment at 800{degrees}C for 1 hr in air, the boron oxide layer on the Type I crystals was found to increase in thickness to approximately 30A. The same heat treatment on the 510 crystals yielded a multi-layered structure consisting of an enriched outer layer of B{sub 2}O{sub 3} over a predominantly TiO{sub 2} one. The entire initial titanium coating was oxidized, and segregated patches of B{sub 2}O{sub 3} ( islands'') were observed. The segregated patches can be explained in terms of the coalescence of liquid B{sub 2}O{sub 3} (melting point = 450{degrees}C). The 550 crystals were oxidized at 500{degrees}C. The oxide formed at this temperature was B{sub x}O (x > 0.67). These results were interpreted in terms of theirmore » potential use in sealing BORAZON to glass in vitreous bonding.« less

An austenitic stainless steel alloy that contains 4.5 wt% Al was oxidized in air at 1200°C. The resultant oxide layer, characterized by Auger, EDS, and TEM, was found to be primarily α-Al2O3, with a thin outer layer of mixed oxides of Fe, Cr, and Ni. The crystalline α-Al2O3 had a grain size of between 0.2 and 0.5 μm; the mixed oxide had a grain size approximately one-hundredth the size of the Al2O3 grains. The Al2O3 film thickness was determined by Auger depth profiling and TEM cross-section imaging to be between 1 and 3 μm.

ABSTRACTTwo NDT techniques were used to characterize low-density, microcellular, carbon foams fabricated from a salt replica process. The two techniques are x-ray computed tomography (CT) and ion microtomography (IMT); data are presented on carbon foams that contain high-density regions. The data show that densities which differ by <10% are easily observable for these low density (<100 mg/cm3) materials. The data reveal that the carbon foams produced by this replica process have small density variations; the density being ∼30% greater at the outer edges than when compared to the interior of the foam. In addition, the density gradient is found to be rather sharp, that is the density drops-off rapidly from the outer edges to a uniform one in the interior of the foam. This edge build-up in carbon density was explained in terms of polymer concentrating on the foam exterior during drying which immediately followed a polymer infusion processing step. Supporting analytical data from other techniques show the foam material to be >99.9 % carbon

Mound Laboratoires has been investigating pyrotechnic materials for several years. Prior studies on the mechanism of ignition have been performed on Ti/KCIO 4 and Ti/2B mixtures. These studies have shown the importance of the surface oxides of these materials in determining the mechanism of ignition. In the present study, XPS spectra of fused metal, oxidized fused boron and boron metal powder have been recorded. The spectra are interpeted by including the presence of a continuous boron suboxide layer. The results presented here are different from those previosuly reported, which suggests that the formation of boron oxide occurs in islets. The predominant suboxide will be shown to be B x O y , where x / y = 3. This oxide was found to be present independent of the degree of oxidation. Including this oxide in thickness calculations shows the oxidation of powders to be five layers or so thick, and also aids in understanding Ti/2B ignition.