Research Gallery
Following are some videos of current topics of research of the group. See our Youtube gallery for more videos of recent work.
Electromagnetic Control of Energetic Material Combustion
The goal of this project is to develop 'smart' energetic materials whose energy output (thrust, light emission, sensitivity) can be controlled dynamically in an 'on-command' nature. We do so by exploiting the electromagnetic properties of energetic materials, development of new nanoscale energetic ingredients used to 'dope' an energetic, and through development of functionally graded energetics through 3D printing and conventional means. The EMCL has developed a number of state-of-the-art techniques enabling electromagnetic coupling with either the gas phase flame of an energetic material or an energetic condensed phase. We are currently developing 3D printing capabilities to develop hierarchically structured energetics with electromagnetically tuned response (e.g. energetic materials with 3D printed energetic 'antennas'). The group is a world leader in the area of electromagnetic controlled energetic material combustion. Following is a listing of a few materials with electromagnetically switchable response that we have developed.
Microwave Plasma Propellant Burning Rate Control Through Alkali Doping
We demonstrate use of a novel alkali metal doping technique in enhancement of microwave coupling to the gas phase of a composite solid rocket propellant flame in order to deposit electromagnetic energy electronically to the propellant flame, producing a microwave-supported plasma and demonstrate the technique's ability to control the burning rate of a composite solid propellant.
On-Command Pyrotechnic Emission Color and Intensity Control
Pyrotechnic flame (500 Hz video acquisition, 5 Hz playback) exposed to 60 Hz modulated 2.45 GHz microwave irradiation within a multimodal cavity. We demonstrate the ability to electromagnetically enhance light emission intensity and color purity in alkali-based pyrotechnics (not shown), and an ability to stimulate molecular emission in other formulations in order to shift emission from gray body continuum type to blue/UV-A molecular emission.
Electromagnetic Switching of Propellant Burning Surface (Eddy Current Loss Wired Propellant)
We develop composite solid rocket propellants with embedded, directional, conductive antenna structures that can absorb microwave energy and generate heat through eddy current loss mechanisms. We demonstrate the ability to use such structures to switch an end burning composite solid propellant strand to a center burning composite solid propellant--effectively enabling control of burning surface area. Video is of propellant light emission from a cylindrical 6 mm diameter propellant strand with an on-axis embedded wire. The propellant+wire is exposed to a 2.45 GHz field modulated at 60 Hz. Video is acquired at 1 kHz, 30 Hz playback. Total video duration is ~3 seconds of real time. Left: Antenna modified propellant without microwave. Right: The same with microwave application.
Graphene Oxide Doped Thermites with Thermally Switchable Microwave Absorptivity
We exploit the microwave reflectivity of graphene oxide (GO), and high microwave absorptivity of thermally reduced graphene oxide (r-GO) at S-band to show that thermal switching of GO to r-GO can enable microwave-facilitated ignition. Using the technique, we are developing microwave--shielded and microwave-ignitable, nanoscale thermites with thermally switchable microwave absorption properties. We have demonstrated the technique capable of switching ignition delay from >60 sec (MW shielded) to < 500 ms (absorber). The technique may suppress microwave absorption of the condensed phase while enabling microwave coupling with high temperature preheat regions of multiphase combustion waves. Video is of light emission (14-bit intensity depth), of ignition of a rGO thin filmn. Emission is mapped to a color scale to prevent downsampling. Acquisition is at 1 kHz rate, playback at 30 Hz.
Microwave Energy Absorption by Aluminum Oxide Features Around Aluminum Particles by Dielectric Loss Thermal Runaway
We demonstrate microwave dielectric energy absorption to high temperature oxide features of an aluminum agglomerate diffusion flame within an aluminized AP composite solid rocket propellant flame as a result of the exponential thermal runaway of the oxide loss tangent. Microwave power is modulated at 60 Hz. Video is recorded at ~20 kHz.
Thermite Stoichiometry Controlled Metal Oxide Thermal Runaway Dielectric Absorption Enhancement of Propellant Combustion
We exploit the aluminum oxide loss tangent thermal runaway by embedding high flame temperature, arrested reactively milled nanocomposite Al/MoO3 thermites with varying stoichiometry (and thermite flame temperature) in order to couple microwave energy to the high temperature oxide products of the flame. Microexplosions of the thermite can also be observed in the video. Video is of light emission (14-bit intensity depth), which is mapped to a color scale to prevent downsampling. Acquisition is at 1 kHz rate, playback at 30 Hz.
RF Sensitive Energetics with 3D Printed, Functionally Graded 'Energetic Antennas'
We demonstrate use of 3D print technology to fabricate composite solid rocket propellants with functionally graded macroscale in order to print within energetics electromagnetically absorptive, reactive antenna structures in order to electromagnetically deposit energy to antenna structures and 'switch' on command the burnign surface of a propellant.
Two-color High-Speed Video Pyrometry of a Microwave-Plasma Enhanced Aluminzed AP Composite Propellant Flame
Spatio-temporal temperature measurement of an aluminized AP composite propellant flame under the influence of 60 Hz modulated microwave irradiation at 2.45 GHz center wavelength. Temperature enhancement in phase with magnetron field application can be observed. Video is acquired using two Phantom v7 monochrome high-speed detectors, using band pass filtering (~10 nm FWHM) of ~650 nm and 750 nm.
High-Heating Rate Ignition of Nanoscale Energetic Materials
Nanostructured energetic materials can have gravimetric and volumetric energy densities that surpasses those of currently used C-H-N-O chemistry energetics. However, nanoscale energetic ignition and reaction rate are slower than molecular energetics (e.g. TNT). Greater diffusion distances within nanostructured energetic materials result spatiotemporal ignition dependencies not prevalent in homogenous energetics. The aim of this work is to explore nanoscale energetic ignition under application-specific conditions of pressure and heating rate. A custom built thermal ignition experiment is utilized to heat energetic materials over a substantial range of heating rates (~100 to ~10^7 °C/s). This large range of achievable heating rates allows study of nanomaterial ignition at heating rates applicable to both propellants and explosives at pressures up to ~21 MPa.
Top left: Temperature vs. time history of the first-generation t-jump device along with image sequences of the heated filament ignition of a nanocomposite energetic material. Bottom left: Video of the ignition of the same. Video is acquired at ~20 kHz, playback is 30 Hz. Right: High-pressure, (~21 MPa) remotely operable windowed combustion bomb fitted with high-heating rate t-jump experiment. The bomb contains an additional vertical ullage volume used for maintaining quasi-static pressure of high gas production experiments.
High Burning Rate Solid Propellants Using Polymer-Capped Nanoscale Lithium Hydride / Nanoaluminum Particles
We report on organometallic composites, containing nanoscale aluminum and lithium-based hydride fuel particles, as solid propellant additives. Replacing aluminum with nanoMetallix capped fuel additives reduces specific impulse, adiabatic flame temperature, condensed-phase products, and hydrochloric acid. Combustion behavior is investigated using high-speed video techniques, including flame emission, laser backlit configurations, and a two-camera ratiometric bandpass emission technique used to detect lithium. Hyperspectral imaging techniques are used to explore loclaization of lithium combustion and laser backlit imaging is used to explore agglomeration at the near burning surface of the propellant.