Date of Award

Spring 2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Materials Science and Engineering - (Ph.D.)

Department

Committee for the Interdisciplinary Program in Materials Science and Engineering

First Advisor

Boris Khusid

Second Advisor

Zafar Iqbal

Third Advisor

N. M. Ravindra

Fourth Advisor

Marek Sosnowski

Fifth Advisor

Rao Surapaneni

Abstract

This dissertation focused on the investigation of novel materials that are both energetic and inert in their micron- and nano-scale crystalline form. The characterization of the materials properties and its effects on the ballistic performance when incorporated into a composite material were evaluated as a gun propellant for application in a future weapon system for the US Army. Some of these materials may find dual use in civilian applications. Applications in small and medium arms, artillery, tank, aircraft, and shipboard gun systems will all benefit from these advancements. Not only will gun system performance be improved for greater stand-off range and accuracy, but the ability to perform consistently across a broad temperature range. Additionally, an improved performance and longer gun barrel life achievable by tailoring the combustion products, lowering the propellant flame temperature, minimum sensitivity of burning velocity to pressure, temperature and gas velocity (erosive burning) and with munitions that are insensitive to outside stimulus attack will give such systems a significant advantage during military use. In addition, "green" chemistry and lower lifecycle cost were taken into consideration during this research.

The approach to be taken was to incorporate these novel materials into a gun propellant formulation by using nitramine-based micron scale cyclotrimethylene trinitramine (RDX) explosives in combination with synthesized novel ingredients in nanoscale crystalline form, characterize the material properties and predict the ballistic performance across the ballistic temperature range. The nano-scale crystalline materials evaluated consisted of polymeric nitrogen stabilized in single wall carbon nanotubes (SWNTs), nitrogenated boron nanotubes / nanofibers (BNNTs/BNNFs), nano-aluminum, and titanium dioxide. The polymeric nitrogen and the nitrogenated boron nanotubes / nanofibers (BNNTs/BNNFs), should provide an enhancement in the propellant burn rate by achieving the burn rate differential goal of 3:1 between the fast and the slow burning propellant and at the same time improve the gun propellant performance by lowering the CO/CO2 ratio and raising the N2 / CO ratio for mitigating gun bore wear and erosion, respectively.

For the synthesis approaches of polymeric nitrogen stabilized in carbon nanotubes, the following synthesis method were performed, optimized and compared: Electrochemical Reactions, Microwave Induced Electrochemical Chemical Reactions and Plasma Enhanced Chemical Vapor Deposition (PE-CVD). The Electrochemical Reaction process has proven to be the most efficient synthesis approach for the polymeric nitrogen based on analytical results obtained through Raman Spectroscopy, Laser Ablation Mass Spectroscopy, Scanning Electron Microscope, Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) and Differential Scanning Calorimeter/Thermal Gravimetric Analysis (DSC/TGA). The PE-CVD is the second recommended synthesis approach to synthesize the polymeric nitrogen although a cost benefit economic analysis has to be performed which is beyond the objectives of this research work.

For the synthesis of the nitrogenated boron nanotubes, the use of the magnesium borohydride to initiate the reaction has proven to be the most optimized process due to a much lower reaction temperature which is approximately 500°C when compared with the reaction temperature of 950°C when using Magnesium Boride (MgB2) in the thermally induced CVD process. The small scale synthesis of boron nanotubes /nanofibers carried out using MgB2 powder, Nickel Boride (Ni2B) powder catalysts and mesostructured hexagonal framework zeolite powder was successfully achieved at 950C. The quality of the nanotubes produced was checked by Raman spectroscopy and transmission electron microscope analysis. The TEM data shows the production of 10-20 nm boron nanotubes using the MgB2, Ni2B and Mobile Crystalline Material (MCM-41) in the synthesis process.

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