Iron Oxide Nanopowder
Introduction To Iron Oxide Nanopowder
They have the diameters between 1 to 100 nm and are broadly categorized into two main types that is, magnetite and its oxidized form maghemite. Magnetite is written as Fe3O4 and maghemite as &gamma-Fe2O3 in the short forms. This powder is irritant in nature and can cause skin, eye or respiratory irritations and hence should be handled with care. Iron oxide nanopowders have gained extensive popularity because of their supermagnetic properties. They have a widespread scope in many fields. Researchers are constantly making advancements in finding new applications for Iron oxide powders in biological, chemical and industrial areas.
Maghemite differs from magnetite as most of the iron is in the trivalent state (Fe3+) and by the presence of cation vacancies in the octahedral sites. Maghemite has a cubic unit cell in which each cell comprises 32 O ions, 21*1/3 Fe3+ ions and 2*2/3 vacancies.
Properties Of Iron Oxide Nanopowder
It is denoted by Fe2O3 and belong to group: Oxygen 16 and iron. The electronic configuration is Iron [Ar] 3d6 4s2 Oxygen [He] 2s2 2p4. It has 69.93% iron and 30.03 oxygen.
The unpaired electrons make a material magnetic, iron oxide is less magnetic than iron and therefore is called a paramagnetic material. The paramagnetic properties of iron oxide powder are not changed from the bulk material except that these minute particles can go where larger particles cannot.
The superparamagnetic behaviour of iron oxide powder can be attributed to their particle size. When the size gets small enough that is
Due to its 4 unpaired electrons in 3d shell, an iron atom has a strong magnetic moment. Therefore, when crystals are formed from iron atoms or ions Fe2+ and Fe3+ they can be in ferromagnetic, antiferromagnetic or ferrimagnetic states. They have a comparative magnetic permeability greater than one. When the applied field is detached the magnetic moment drops to zero. But in a ferromagnetic material, all the atomic moments are aligned even without an external field. A ferrimagnetic material is similar to a ferromagnet but has two different types of atoms with opposite magnetic moments. The material has a magnetic moment because the opposing moments have dissimilar strengths. If they have the same magnitude, the crystal is antiferromagnetic and possesses no net magnetic moment.
Synthesis Of Iron Oxide Nanopowder
The preparation method has an impact on the shape, size distribution, and surface chemistry of the powder. It also determines to the extent to which the distribution and type of structural defects or impurities are present in the particles. The combination of these factors affects the magnetic behaviour.
The most widely used method is Coprecipitation. This method can be further divided into two types. In the first, ferrous hydroxide suspensions are partially oxidized with different oxidizing agents. The other method involves ageing stoichiometric mixtures of ferrous and ferric hydroxides in aqueous media, yielding spherical magnetite particles that are homogeneous in size.
A microemulsion is a stable isotropic dispersion of 2 immiscible liquids consisting of Nano sized domains of one or both liquids in the other stabilized by an interfacial film of surface-active molecules. Microemulsions may be categorized further as oil-in-water (o/w) or water-in-oil (w/o), depending on the dispersed and continuous phases.
High-Temperature Decomposition Of Organic Precursors
The decomposition of iron precursors in the existence of hot organic surfactants results in samples with good size control, narrow size distribution (5-12 nm) and good crystallinity and they can be easily dispersed.
For biomedical applications like magnetic resonance imaging or magnetic cell separation where the particle size is very crucial, powders produced by this method are very useful.
Iron Oxide Nanopowder Applications
- It is used in magnetic resonance imaging to provide enhanced contrast at very low concentrations in the Nanomolar range for studies related to tumours.
- It is also used as a targeted delivery vehicle and as a drug delivery coating for nanoscale anti-cancer drugs.
- Lithium batteries distribution.They are widely used in magnetic data storage.
- In coatings, plastics, nanowires, nanofibers, and textiles and in specific alloy and catalyst applications.
- Used as contrast agents for Magnetic Resonance Imaging (MRI).
- Iron oxide powders can be used as gene carriers for gene therapy.
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