Synthesis and Magnetic Properties of Nanostructured Maghemite

Abstract

Nanocrystalline maghemite, γ–Fe2O3, can be synthesized in a microwave plasma using FeCl3 or Fe3(CO)12 as the precursor. Electron microscopy revealed particle sizes in the range of 5 to 10 nm. In general, this material is superparamagnetic. The magnetic properties are strongly dependent on the precursor. In both cases the production process leads to a highly disordered material with the consequence of a low magnetization. The assumption of a disordered structure is also supported by electron energy loss (EEL) and Mössbauer spectroscopy. The structure of this material shows a nearly identical number of cations on tetrahedral and octahedral lattice sites.

Microwave Plasma Synthesis of Materials—From Physics and Chemistry to Nanoparticles: A Materials Scientist’s Viewpoint

“…Commercial powders usually contain nanoparticles of sizes ranging from around 5 nm to approximately 200 nm. Similar, broad particle size distributions are observed, when using microwave torches [52,103,109,110], whereas the powders synthesized in low pressure microwave plasma are often characterized by a very narrow particle size distribution [105,107,108,198]. This can be observed for several commercially available nanoscaled powders, like Fe 2 O 3 , ZrO 2 , SnO 2 , or TiO 2 .…”

“…The found data on magnetization and particle sizes fit quite well in the general trends of size dependent magnetic properties (Figure 7). Those particles made from a chloride precursor [107,108] deviate from the trend. According to the indicated particle sizes, the saturation magnetization should be higher.…”

“…Reference data for particle size dependent saturation magnetization (all symbols in black color) are taken from Han et al [220], Morales et al [222], and de Montferrand et al [227], and finally the bulk reference value is taken from [228], page 993. Literature data of the diverse plasma synthesized F 2 O 3 nanoparticles (colored symbols) are taken from Table 7 (David et al [102,109], Nadeem et al [105], Vollath et al [107,108], Banerjee et al [114], Lei et al [115]). The bars herein are not error bars; they show the spread of indicated particle sizes.…”

A Linear Trap for Studying the Interaction of Nanoparticles with Supersaturated Vapors

“…Small nanoparticles of 2-4-nm radius are produced in a microwave discharge particle source by mixing a volatile metal-organic precursor gas with oxygen and a superabundance of helium, and exposing the mixture to a microwave discharge (Chou and Phillips 1992;Vollath et al 1997;Janzen et al 2002;Szab o 2013). The resulting nanoparticles are introduced into the vacuum system via an aerodynamic lens optimized for particles of that size (Meinen et al 2010a,b).…”

Dispersibility, Shape and Magnetic Properties of Nano-Fe<sub>3</sub>O<sub>4</sub> Particles

“…Besides this, many techniques have been used to synthesize magnetite such as thermal decomposition [4] hydrothermal synthesis [5], coprecipitation of an aqueous solution of ferrous and ferric ions by a base [6][7][8],oxidation of the ferrous hydroxide gels using KNO 3 [9], γ-ray irradiation [10], microwave plasma synthesis [11] sol-gel [12], nonaqueous route [13][14][15] etc. Many applications depend on their size and stoichiometry of particles, however the dispersibility and shape of prepared particles varies with the hydrolysis condition, the additive surfactant [4] and organic compound [5], most of them exhibit nano spherical particles [16][17][18].…”