Volume 108, Issue 3, 01 August 2010
Index of content:
Time-resolved measurements of near infrared emission spectra from explosions: Pure pentaerythritol tetranitrate and its mixtures containing silver and aluminum particles108(2010); http://dx.doi.org/10.1063/1.3437056View Description Hide Description
Measurements of chemical transients and thermodynamic conditions are difficult to obtain yet fundamentally important in understanding the behavior of explosives. We have constructed a fast near infrared (NIR) spectrometer and have made temporally and spectrally-resolved emission measurements during postdetonation combustion of pure pentaerythritol tetranitrate (PETN) charges and PETN charges doped with 10 wt % microparticles composed of silver(Ag) and aluminum(Al). We have observed postdetonation PETN emission spectra between 750 and 1500 nm at rates up to 46 992 spectra/s. The instrument captures the highly structured spectra immediately following breakout as well as the longer-lived broadband NIR emission signals from hot particles. The early spectra reveal spectral signatures related to PETN and the reacting constituents of the particles. The later spectra provide a means to infer the gray-body temperature history of the particles.
108(2010); http://dx.doi.org/10.1063/1.3437079View Description Hide Description
Atomically sharp high-density tungsten nanotip arrays are fabricated by nanocasting using a patterned template. The fabrication involves mainly top-down processes making it fully compatible with today’s Si technology. The obtained tungsten nanotip arrays show atomically sharp tips (radius of curvature smaller than 1 nm), high emitter density , perfect tip alignment, and excellent field emission properties with a turn-on field of and a field enhancement factor of 3334. The unique fabrication process flow leads to the highly uniform height of the W nanotips, allowing for submicron cathode-anode spacing, which very much relaxes the requirement of vacuum level and makes it possible for low vacuum operation.