Energy release characteristics of the nanoscale aluminum-tungsten oxide hydrate metastable intermolecular composite

Abstract

Son, "Energy release characteristics of the nano-scale aluminum tungsten-oxide hydrate metastable intermolecular composite," Journal of Applied Physics, 101(6): 064313, 2007. dx.doi.org/10.1063/ 1.2435797 Energy release characteristics of the nanoscale aluminum-tungsten oxide hydrate metastable intermolecular composite Tungsten oxides are of interest as an oxidant for metals in metastable intermolecular composites ͑MICs͒, a reactive nanoscale powder useful for such applications as electric matches and gun primers. Smaller particles typically lead to fast reaction rates in this class of energetic material, and we have synthesized nanoscale WO 3 ·H 2 O using wet chemistry. Analysis by electron microscopy and small angle x-ray scattering revealed an approximately 100-nm-wide by 7-nm-thick platelet morphology. X-ray diffraction verified the orthorhombic structure and composition of the hydrate. A MIC material was formulated using 44 nm Al as the fuel. Performance was measured using a pressure cell where total enthalpy change and energy release rate was measured. This report includes the thermodynamic analysis of the pressure cell ͑calorimetry͒ that allows the determination of these metrics. Accuracy of the technique is discussed. Performance of the hydrate was found to significantly exceed that of MIC formulated with dehydrated tungsten oxide for one formulation, having an energy release of approximately 1.8 MJ/ kg at a rate of approximately 215 GW/ m 2 , compared to around 1.1 MJ/ kg at a rate of around 130 GW/ m 2 for the dehydrated formulation. The data show that the enhanced behavior of the hydrated MIC formulation resulted from the reaction of aluminum with the interstitially bound water, which had additional energy release and generated hydrogen gas.

Metal-based reactive nanomaterials

“…One substantial difficulty in interpreting the experimental data is the production of transient, or semi-stable gas species. Examples of this kind of system are: Bi vapor in combustion of thermites using Bi 2 O 3 as an oxidizer [51,101], production of hydrogen and water using hydrated oxides as oxidizers [94], production of nitrogen if nitrates are used as oxidizers [121], etc.…”

“…Standard vessels for oxygen bomb calorimetry [94,140] as well as smaller [51,88,101] and larger [120] vessels have been used and combined with different igniters and pressure transducers. In this approach, the experiment can be considered as nearly adiabatic and the pressure increase can be related to the energy produced in combustion [94]. One substantial difficulty in interpreting the experimental data is the production of transient, or semi-stable gas species.…”

“…Another experimental technique aimed at the assessment of the combustion performance of reactive nanocomposite materials is based on a pressure measurement in a confined chamber or pressure cell [51,88,94,101,120,140]. Standard vessels for oxygen bomb calorimetry [94,140] as well as smaller [51,88,101] and larger [120] vessels have been used and combined with different igniters and pressure transducers.…”

“…Literature data are available for many mixes of n-Al with nanosized metal oxide powders; including Fe 2 O 3 , MoO 3 , CuO, Bi 2 O 3 , and others. These thermite compositions made of nanosized components were termed MIC (for metastable intermolecular composites or metastable interstitial composites) or superthermites [92][93][94][95][96][97]. A superthermite is commonly prepared by ultrasonic mixing the nanosized components in a bath of hexane [98][99][100][101], isopropyl alcohol [100,101], or another liquid carrier, which is subsequently evaporated.…”

Nanocomposite thermite powders prepared by cryomilling

“…[2][3][4][5][6][7][8]. Among different techniques used to prepare such nanocomposite materials, Arrested Reactive Milling (ARM) method offers an inexpensive and scalable technique that is very versatile and can be applied to a wide range of reactive material compositions [9][10][11][12][13][14].…”