Jacek J. Swiatkiewicz

Processing and Ignition Characteristics of Aluminum-Bismuth Trioxide Nanothermite System

During the past few years, significant progress has been made in the development of new nanoenergetic materials consisting of mixtures of metal and oxidizer nanopowders. It has been found that such reacting mixtures release energy by 2 to 3 orders of magnitude faster than similar systems consisting of micron-size reactants. In some cases, combustion-front velocities reach hundreds of meters per second. These new reacting systems find applications in both civilian and military sectors, including fast vaporization of active chemical components, fast heating of thermal batteries and main ingredients of new environmentally benign percussion primers or electric matches. This paper presents experimental results on ignition and combustion front propagation characteristics in the Al-Bi 2 O 3 nanothermite system. The effect of different coatings and inhibitors of the reaction of aluminum with water in the presence and without the presence of bismuth trioxide is discussed. In addition, thermodynamic analysis of the Al-Bi 2 O 3 reacting system and reaction kinetics measurements using differential scanning calorimetry are presented. Electrostatic discharge sensitivities of Al-Bi 2 O 3 , Al-MoO 3 , and Al-Fe 2 O 3 nanothermite systems were determined. It was found that all investigated nanothermite systems showed very high levels of electrostatic discharge sensitivity in the form of dry and loose powder.

The Effect of Nanopowder Attributes on Reaction Mechanism and Ignition Sensitivity of Nanothermites

Nanothermite composites have several properties that are not typical of conventional thermites. The nanoscale size of individual reactants is responsible for the significant differences in these properties, especially the rate of energy release and mechanism of combustion front propagation. Several thermite mixtures were investigated, including Al-Fe 2 O 3 , Al-CuO, Al-MoO 3 , and Al-Bi 2 O 3 . Previous studies have reported on the behavior of these mixtures during unconfined burning and on the characterization of particle attributes such as particle size, surface area, and reactive metal content. This study was focused on several other attributes, including mixing of nanoreactants in water and measurements of reaction kinetics and combustion front propagation characteristics under confined conditions. The nanoscale nature of the thermite components also has an effect on the kinetics of the reaction. Differential scanning calorimetry was used to determine activation energy of these reacting systems. Several experimental setups were used to monitor the nanothermite mixtures during combustion. The mixtures were monitored during combustion in small diameter tubes using high speed video technology and a pressure sensor system. These tests were used to characterize combustion propagation under confined conditions and to determine the effect of pressure and mixture density on propagation rate. Experiments were also performed using both a closed volume pressure cell and recoil force cell to measure the reactive energy of the mixtures.

In situ densification of SHS composites from nanoreactants

The primary objective of this investigation was focused on in-situ densification of SHS composites synthesized from nanoreactants. Simultaneous combustion synthesis and densification technique was utilized and it was found to be an effective method to form dense intermetallic-ceramic composites. In this research study, two nanoreactant energetic systems, Al-TiO2 and Ni-Al-Al2O3, were explored. In-situ combustion synthesis and densification experiments were conducted in a uniaxial press with densification pressures up to 200 MPa and preheating capability of 1500K. The experiments were conducted in both vacuum and Ar atmosphere. Samples of titanium aluminides-alumina composites with density in the range of 95–98% have been obtained at a preheating temperature of 860°C and pressure of 100 MPa. Reactants and SHS-produced materials were characterized by SEM, XRD, BET, and DSC/TGA. In addition, more fundamental studies of the reaction kinetics as a function of average particle size of aluminum nanopowders were conducted using DSC.

The effect of gaseous additives on dynamic pressure output and ignition sensitivity of nanothermites

In this paper we present experimental results of dynamic pressure profiles and ignition delays times at the constant laser heat flux for the following nanothermite systems: a) Al-Bi2O3, b) Al- Fe2O3 and c) Al-Bi2O3-Fe2O3.