Gerardo Ines Pangilinan

Time-resolved optical measurements of the post-detonation combustion of aluminized explosives

The dynamic observation and characterization of light emission following the detonation and subsequent combustion of an aluminized explosive is described. The temporal, spatial, and spectral specificity of the light emission are achieved using a combination of optical diagnostics. Aluminum and aluminum monoxide emission peaks are monitored as a function of time and space using streak camera based spectroscopy in a number of light collection configurations. Peak areas of selected aluminum containing species are tracked as a function of time to ascertain the relative kinetics (growth and decay of emitting species) during the energetic event. At the chosen streak camera sensitivity, aluminum emission is observed for 10μs following the detonation of a confined 20g charge of PBXN-113, while aluminum monoxide emission persists longer than 20μs. A broadband optical emission gauge, shock velocity gauge, and fast digital framing camera are used as supplemental optical diagnostics. In-line, collimated detection is ...

Atmospheric Effects on the Combustion of Detonating Aluminized Explosives

The detonation and subsequent combustion of aluminized explosive formulations depend heavily on the oxidation reactions of aluminum. Fuel‐rich formulations require oxygen from an external source (nominally an oxygen‐containing atmosphere or detonation products) to burn the fuel to completion. Dynamic spectroscopic measurements are made for an aluminized explosive (PBXIH‐135) to investigate the effect of changing atmospheres on the combustion properties of aluminum. The explosive formulation is tested under normal atmospheric conditions and in an atmosphere of nitrogen. Light emission (from 350–550 nm) from the explosive event is collected in a spectrometer and dispersed temporally in a streak camera. Aluminum emission (centered at 396 nm) is commonly observed in each atmosphere although the emission persists longer in nitrogen. Aluminum nitride (AlN) is observed as an intermediate in the oxidation of aluminum when oxygen is removed from the atmosphere. New, nitrogen‐containing species (near 387 and 418 nm...

Structural Studies and EOS of Diaminodinitroethylene (DADNE, FOX‐7) under Static Compression

Structural and molecular changes in diaminodinitroethylene compressed to static pressures up to 4.2 GPa were investigated. Angle‐dispersive x‐ray diffraction experiments were performed with synchrotron radiation to monitor the compression and any phase changes. The results indicated higher compression along the b‐axis than along the a‐ or c‐ axis. In addition, the ambient temperature isothermal equation of state of FOX‐7 was generated from this data. Raman spectroscopy covering a 300 to 3400 cm−1 range showed expected hardening of most vibrational modes. However, two modes in the energy regions corresponding to N‐O stretching and H wagging, softened with pressure. This indicates the possible increase of intermolecular H bonding within the zigzagging planes of FOX‐7 at increased pressures.

Novel Optical Fiber‐Based Gauge for Measuring Transient Pressures

While methods for determining transient pressures in shocked condensed matter are available, the need has arisen for new gauges whose quality of data, ease of use, and cost make them more appropriate for studying underwater shocks. A novel optical technique for measuring transient pressures in water or other fluids is being developed. One end of an optical fiber is submerged in the fluid of interest, allowing remote operation using a laser light source. The intensity of reflected light from the tip can be related to the optical properties of the fluid at the fiber/fluid interface and thus the pressure experienced by the fluid at a given time. This novel method has the benefits of avoiding electrical interference, permitting fast time resolution, and requiring only a photodiode and oscilloscope as detection electronics. Application of this gauge to studies of shock compression of water produced by detonation of energetic materials will be presented.

Measurements of Aluminum Combustion in Energetic Formulations

Aluminum combustion plays an important role in tailoring energy release rates of energetic materials. The intimate mixing between Al and oxidizers from the formulation itself or from the surrounding atmosphere is key to effecting combustion. We infer combustion processes in detonated aluminized energetic formulations PBXIH‐135 and PBXN‐111 in air using time‐resolved spectroscopy. We recorded spectral emissions from Al and AlO emanating from the surface of each sample for up to 100 μs. We observe differences in metal combustion between the oxidizer deficient PBXIH‐135 and the oxygen‐rich PBXN‐111. We will discuss phases of combustion that each formulation exhibits and possible reaction processes.

A New Method for Determining Material Thermal Properties at Static High Pressures

The response of materials under shock loading is strongly dependent on the mechanical and thermal properties of materials at high pressures. Despite the availability of several methods that quantify mechanical properties of materials at high pressures and loading rates, only a few existing techniques can measure heat capacity or thermal conductivity at high pressures. A new method is proposed to determine the thermal transport properties of materials in gem anvil cells (GAC). The test material and a ruby sphere were enclosed in a GAC and brought to pressure. The ruby was heated at a constant rate by a pulse of light whose intensity had a square wave temporal profile. Time‐resolved ruby fluorescence spectra were recorded with a spectrometer and a streak camera. The temperature profile of the ruby during both the heating and cooling (following removal of the laser light) periods was sensitively dependent on the thermal transport properties of the surrounding material. A pressure‐dependent set of results is presented for sodium chloride (NaCl) and Teflon, utilizing this new technique. The data is compared to simulations using previously published data.