The mechanism of structural transformation during combustion of nickel nitrate (oxidizer)−glycine (fuel) system is investigated by using different in situ techniques, including time-resolved X-ray diffraction (TRXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) with dynamic mass spectrometry (MS), and high-speed infrared thermal imaging. It is shown that for initial compositions with a relatively large fuel-to-oxidizer ratio (φ), pure Ni phase forms directly in the combustion front. For fuel-lean conditions, only NiO phase can be detected. Analysis of the obtained data, including transmission and scanning electron microscopy (TEM−SEM) studies of the quenched reaction fronts, allows us to suggest the intrinsic mechanism of pure metal formation in the investigated system. It is shown that the combustion front propagates because of the reaction between N 2 O and NH 3 , which are the products of decomposition of the oxidizer and fuel. The excess of NH 3 gas produced in fuel-rich conditions rapidly (<0.2 s) reduces nickel oxide to pure metal in the reaction front.

A template-assisted combustion-based method is developed to synthesize the ultrasmall (below 5 nm) α-Fe 2 O 3 nanoparticles. The iron and ammonium nitrate are used as oxidizers, glycine as a "fuel" and mesoporous silica (SBA-15) as a template. Because of the ultralow sizes and high crystallinity, the combustion-derived α-Fe 2 O 3 nanoparticles exhibit superparamagnetism in the temperature range of 70−300 K. The high specific surface area (132 m 2 /g) of α-Fe 2 O 3 indicates the important role of surface magnetic spins resulting in remarkably high magnetization (21 emu/g) at 300 K.

Solution combustion synthesis (SCS) is typically used to produce nanostructured oxides and bulk metallic materials for a variety of application including catalysis. Here, we report in situ, one-step SCS of high surface area (155 m 2 /g) Ni catalysts supported on fumed silica (SiO 2 ). Time-resolved X-ray diffraction is used to investigate the dynamics of phase formation during combustion of nickel nitrate−glycine−ammonium nitrate reactive gels impregnated onto porous SiO 2 . It is shown that highly dispersed nickel nanoparticles (5 nm) formed in the reaction front are followed by their rapid oxidation by air oxygen. To prevent the undesired oxidation process, the synthesis was conducted in an inert atmosphere (argon, helium). It is demonstrated that low concentration oxygen impurity (less than 0.001 wt %) in the inert gas passivates the Ni nanoparticles through the formation of a thin amorphous oxide layer. The thus prepared Ni/SiO 2 supported catalyst possesses high activity during the ethanol decomposition toward hydrogen at low temperatures (200°C) and excellent stability toward deactivation with essentially no change of catalyst activity over 100 h of operation.

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