(546e) Nanocomposite Thermite Powders with Improved Flowability Prepared By Mechanical Milling

Authors: 
Nguyen, Q. - Presenter, New Jersey Institute of Technology
Huang, C., New Jersey Institute of Technology
Schoenitz, M., New Jersey Institute of Technology
Sullivan, K., Lawrence Livermore National Laboratory
Dreizin, E., New Jersey Institute of Technology
Nanocomposite thermite powders are of interest to develop variety of reactive parts and components. Manufacturing these components requires tailoring such properties of the thermite powders as their particle size distributions, particle shapes, and powder flowability. For example, an improved flowability is desired to use such powders as feedstock in additive manufacturing. Arrested reactive milling (ARM) offers a versatile and practical approach for preparing various nanocomposite thermites with fully dense particles, which will retain their structures and mixedness between reactive components while being stored, handled, and processed. However, ARM products usually have broad particle size distributions, rock-like particle shapes, and poor flowability. Here, ARM is modified to include an additional milling stage to tune the shapes and flowability of the prepared powders. Experiments are performed with aluminum-rich Al·Fe2O3 thermites. After the initial nanocomposite thermite is prepared in a planetary mill, it is additionally milled at a reduced rotation rate, replacing milling balls with smaller glass beads, and adding different liquid process control agents. Powders with modified particle shapes and size distributions are obtained, which have substantially improved flowability compared to the initial material. Ignition temperature is obtained via filament ignition experiment performed in air. The rate of ignition and combustion are evaluated using electro-static discharge (ESD) experiment while combustion performance is tested using constant-volume explosion (CVE) experiment. A reaction kinetics study is performed at various heating rates using differential-scanning-calorimetry (DSC). The wire ignition set-up is modified with a copper plate mounted under the heated filament wire to capture igniting particles, thus enabling us to observe the products of partially burned individual particles for different prepared samples. In a modified ESD set-up, an aluminum foils is attached to also capture igniting particles at difference distances. The morphology of particles captured on foils are analyzed via scanning-electron-microscope (SEM) and compared for the same powders ignited using different heat sources (heated wire and ESD). The reactivity of the modified powders is not diminished; instead, an improved reactivity is observed for selected samples. Detailed results will be further discussed in the talk.