HMX-based explosives LX-10 and PBX-9501 were heated through the β-δ phase transition. Ultra-small angle x-ray scattering (USAXS) and molecular diffraction were simultaneously recorded as the HMX was heated. Mesoscale voids and structure dramatically change promptly with the β-δ phase transition, rather than with other thermal effects. Also, x-ray induced damage, observed in the USAXS, occurs more readily at elevated temperatures; as such, the dose was reduced to mitigate this effect. Optical microscopy performed during a similar heating cycle gives an indication of changes on longer length scales, while x-ray microtomography, performed before and after heating, shows the character of extensive microstructural damage resulting from the temperature cycle and solid-state phase transition.

Plasma polymerization and deposition of linear, cyclic and aromatic fluorocarbons on (100)-oriented single crystal silicon substrates Interfacial force microscopy ͑IFM͒ is used to measure the electrical contact properties of electroplated gold thin films of the type used in microelectromechanical system relays. Force and current levels consistent with those present in metal-metal contact switches are examined in an atmospheric-pressure, dry-nitrogen ambient at room temperature, and the nature of a nonmetallic contamination layer which limits contact resistance and lifetime is explicitly examined mechanically, electrically and chemically. The electrical and mechanical properties of the contamination layer on the gold substrate are observed by IFM both before and after being exposed to ozone for an extended period of time. The contamination film is characterized by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry, and found to consist mostly of hydrocarbons; the film remains relatively stable in both composition and thickness following ozonation. However, some subtle chemical changes in the contamination layer induced by the ozonation process are found to profoundly affect the electrical properties of the gold-gold contact, reducing the resistance by more than 3 orders of magnitude and considerably reducing variability in the contact resistance between contact events. These results clearly demonstrate the critical role both positive and negative of the latent contamination present on the contact surfaces.

This work links the structural and electrical properties of thin polycrystalline silicon films at the level of individual grains. A four point “transparent probe” technique was developed which allowed a small number of grains to be isolated and measured electrically in test structures which can be nondestructively prepared for direct imaging in a transmission electron microscope (TEM). By measuring the temperature dependence of electrical resistance in many test structures, the distribution of individual grain boundary activation energies for resistance was determined. After electrical measurements, grains in the test regions were imaged by TEM. Grain size, shape and crystallographic grain boundary character were measured and the distribution of relative grain misorientations was found. Measured boundaries were compared to coincident-site lattice-related boundaries whose character has been the subject of single boundary studies. Single grain boundaries were characterized both electrically and structurally. Electrical results from the transparent probe structures were compared with standard energy band theory developed for blanket film properties and with results from a Monte Carlo model of a network of thermally activated resistors. These results demonstrate how a distribution of grain structures and orientations fundamentally determines the electrical properties of the blanket film.

Diamond has a unique combination of physical properties for the inertial confinement fusion ablator application, such as appropriate optical properties, high atomic density, high yield strength, and high thermal conductivity. Here, we present a feasible concept to fabricate diamond ablator shells. The fabrication of diamond capsules is a multi-step process, which involves diamond chemical vapor deposition on silicon mandrels followed by polishing, microfabrication of holes, and removing of the silicon mandrel by an etch process. We also discuss the pros and cons of coarse-grained optical quality and nanocrystalline chemical vapor deposition diamond films for the ablator application.2