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Ammonium perchlorate (AP) is the most abundant ingredient in many solid rocket motors and presents a thermal runaway hazard. The addition of metal oxides (MOs) can alter motor performance but may affect decomposition behavior. In this work, a total of 14 MOs, mostly transition metal oxides, were mixed with AP and subjected to isothermal thermogravimetric analysis (TGA). MOs commonly incorporated into AP-based propellants can alter AP decomposition rates, the extent of reaction, and the particle size of the AP itself. Partially decomposed AP showed significant changes in terminal particle size. There is an inverse correlation between MO lattice energy and peak reaction rates of AP/MO mixtures. The objective of this work is not to provide definitive details of mechanisms, but rather to report observations and interactions with a wide variety of MOs, often ones that were not previously reported. The findings have implications for the safe storage of AP and the development of insensitive motors. [ABSTRACT FROM AUTHOR]

Abstract: The properties of TiO2 nanoparticles synthesized using the flame stabilized on a rotating surface method (FSRS) are investigated. The method uses a laminar, premixed, stagnation flame, combining particle synthesis and film deposition in a single step. The current study examines the effects of flame properties on particle characteristics. Synthesized particles were characterized using X-ray diffractometry, Transmission Electron Microscopy and UV–vis spectrometry in order to quantify the effects of equivalence ratio and precursor loading on particle size, crystallinity and optical band-gap. Results show that flame stoichiometry significantly affects crystal phase, but it has little to no effect on particle size and light absorption band edge. In addition, precursor loading impacts both the particle size and the crystal phase. The study demonstrates the potential of the FSRS method for producing tailored nanoscale TiO2 particles for a variety of applications. [ABSTRACT FROM AUTHOR]

Abstract: A new method is proposed to fabricate nanocrystalline titania (TiO2) films of controlled crystalline size and film thickness. The method uses the laminar, premixed, stagnation flame approach, combining particle synthesis and film deposition in a single step. A rotating disc serves as a combination of substrate-holder and stagnation-surface that stabilizes the flame. Disc rotation repetitively passes the substrates over a thin-sheet, fuel-lean ethylene–oxygen–argon flame doped with titanium tetraisopropoxide. Convective cooling of the back side of the disc keeps the substrate well below the flame temperature, allowing thermophoretic forces to deposit a uniform film of particles that are nucleated and grown via the flame stabilized just below the surface. The particle film grows typically at ∼1μm/s. The film is made of narrowly distributed, crystalline TiO2 several nanometers in diameter and forms with a 90% porosity. Analysis shows that the rotation of the stagnation-surface does not reduce the stability of a stagnation flame, nor does it affect the fundamental chemistry of particle nucleation and growth that occurs between the flame and the stagnation surface. [Copyright &y& Elsevier]