Abstract
ABSTRACT Iron oxide is a polymorphous crystalline mineral, including hematite, a-Fe 2 O 3 , magnetite, Fe 3 O 4 and maghemite, g-Fe 2 O 3 . In the area of solid propulsion, nanoparticulate materials such, hematite and maghemite, exhibit high performance on thermal decomposition of ammonium perchlorate (AP).The best catalytic effect of metallic iron oxide nanoparticles was attributed to its small particle size, more active sites and high surface area, which prove most gas adsorption of released products during the thermal reactions of oxidizer. Nowadays, metallic iron nanoparticles can be synthesized via many methods, by co-precipitation, sol-gel, microemulsion, or thermal decomposition. Although there are data on these synthetic methods in the literature, there is a lack of details in nanoparticulate oxides and on the characterization techniques used. In this context, this short review presents methods for obtaining nanoparticulate iron oxides and characteristics of the different characterization techniques and decomposition of these nanomaterials. The morphologies and structures can be characterized by transmission electron microscopy, scanning electron microscopy, X-ray powder diffraction, and FT- IR spectroscopy and the textural properties by physical adsorption.
Highlights
In the last two decades, nanotechnology has attracted great interest in several areas of research for the development of nanoscale materials which can be obtained through different techniques, such as physical or chemical methods
When comparing the two samples of iron oxide, it was observed that the system sample (w/o) presents a smaller specific surface area (147 m2.g–1) and pore size (18 nm) than that from system (o/w). These results indicate that microemulsion synthesis parameters, such as the ratio of oil and water and surfactant concentration, directly influence the characteristics of nanometer scale iron oxide catalysts, such as specific surface area and pore size (Okoli et al 2012)
The present article briefly presents the characteristics of nanosized metallic iron oxides, as well as their methods of synthesis, main techniques of characterization and their application in thermal decomposition of AP, contributing to researches in composite solid propellants field
Summary
In the last two decades, nanotechnology has attracted great interest in several areas of research for the development of nanoscale materials which can be obtained through different techniques, such as physical or chemical methods. Iron oxide is a mineral compound which occurs abundantly in nature It presents more than one crystal structure and different structural and magnetic properties (Cornell and Schwertmann 2000; Machala et al 2011). Magnetite (Fe3O4), at room temperature, presents ferromagnetic properties (Teja and Koh 2009), which differs from other iron oxides forms as its structure has both bivalent and trivalent iron. One of the most important objectives of the study of iron’s solid chemistry state is to understand the mechanisms and the kinetics of polymorphous transformation (kinetics of the transition crystaline phase) (Callister Jr 2012) of iron oxides These issues use to control these processes, mainly because different polymorphic states present particular properties and a range of potential applications in several fields (Machala et al 2011)
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