Ignition of Nanoscale Titanium/Potassium Perchlorate Pyrotechnic Powder: Reaction Mechanism Study

Abstract

The reaction mechanism and ignition characteristics of the pyrotechnic composite of titanium nanoparticles and micron-sized potassium perchlorate was investigated under rapid heating conditions (∼5 × 105 K/s) by temperature jump (T-Jump) time-of-flight mass spectrometry. X-ray photoelectron spectroscopy surface analysis and transmission electron microscopy (TEM) characterization of titanium nanoparticles show a reactive oxide layer (∼6 nm) composed of amorphous TiO2 and roughly 20% crystalline TiN and titanium oxynitride. The T-Jump and thermogravimetric analysis reveals the oxide layer to be responsible for catalysis of oxygen release from KClO4, resulting in ignition temperatures as low as 720 K in atmospheric pressure argon. Fast and slow in situ heating TEM corroborate the findings of oxygen atmosphere ignition characteristics, which illustrate KClO4 melting and coating of titanium nanoparticles immediately before oxidizer decomposition and titanium oxidation. Unlike aluminum, which has been shown to have a rapid loss of surface area before combustion as a result of sintering, Ti retained its high surface area. A combination of a reactive shell and the preservation of titanium nanostructure under rapid heating may lead to enhanced oxygen diffusion and increased potential for transient energy release.

Rapid Laser Pulse Synthesis of Supported Metal Nanoclusters with Kinetically Tunable Size and Surface Density for Electrocatalytic Hydrogen Evolution

“…The principle and details of T-Jump/TOFMS can be found in the Experimental Section and in our previous studies. 22 Briefly, a small amount of metal salt precursor was deposited onto a platinum wire probe. Once loaded into the TOFMS vacuum chamber, the platinum wire probe coated with metal salt precursor was resistively heated by a direct current voltage supply which delivers a rapid heating rate as fast as 10 5 K/s.…”

“…Previous thermogravimetric analysis with a slow heating rate (10 K/s) revealed that chloroplatinic acid decomposes to volatile PtCl 2 at 415 °C, which further decomposes to metallic Pt at 510 °C: Temperature-jump/time-of-flight mass spectrometry (T-Jump/TOFMS, see Figure S1) was used to study precursor decomposition under a fast heating rate (10 5 K/s). The principle and details of T-Jump/TOFMS can be found in the Experimental Section and in our previous studies . Briefly, a small amount of metal salt precursor was deposited onto a platinum wire probe.…”

Submicron Potassium Perchlorate: a Key Component to Reach Detonation in Binary Mixtures with Titanium Hydride

“…Rudloff and Freeman also reported that metallic oxides including TiO 2 , lower the decomposition temperature of potassium perchlorate [15]. More recently, Rehwoldt et al have shown that in mixtures of titanium nanoparticles (50-80 nm) and fine potassium perchlorate powder (0.1-1.5 μm), the shell of Ti particles composed of TiO 2 , TiON and TiN catalyzes the melting, the decomposition, and the final reaction of KClO 4 with Ti [16]. In the micron-sized TiH 2 particles, the oxidation of titanium is likely to be the driving force of the reaction process: the heat released by the early step of metal oxidation, along with the production of TiO 2 and KCl accelerates the decomposition of KP.…”

Thermal Shock Synthesis of Metal Nanoclusters within On-the-Fly Graphene Particles

“…Metal nanoclusters (1–10 nm) with unique size- and shape-dependent properties have drawn attention because of their potential applications in electronics, catalysis, nanomedicine, and energy storage. − Technological utility of metal nanoclusters is hindered however by the difficulties of synthesizing and handling these ultrasmall particles arising from their unstable and easy-aggregation nature. Although various kinds of synthesis approaches have been reported, manufacturing those small particles in large quantities to enable their utility is still challenging.…”