title: Nickel ferrite aerogels with monodisperse nanoscale building blocks--the importance of processing temperature and atmosphere.
abstract: Using two-step (air/argon) thermal processing, sol-gel-derived nickel-iron oxide aerogels are transformed into monodisperse, networked nanocrystalline magnetic oxides of NiFe(2)O(4) with particle diameters that can be ripened with increasing temperature under argon to 4.6, 6.4, and 8.8 nm. Processing in air alone yields poorly crystalline materials; heating in argon alone leads to single phase, but diversiform, polydisperse NiFe(2)O(4), which hampers interpretation of the magnetic properties of the nanoarchitectures. The two-step method yields an improved model system to study magnetic effects as a function of size on the nanoscale while maintaining the particles within the size regime of single domain magnets, as networked building blocks, not agglomerates, and without stabilizing ligands capping the surface.
authors.affiliation: Surface Chemistry Branch (Code 6170), U.S. Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, D.C. 20375, USA.
authors.forename: Katherine A
authors.initials: KA
authors.lastname: Pettigrew
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Long
authors.forename: Everett E
authors.initials: EE
authors.lastname: Carpenter
authors.forename: Colin C
authors.initials: CC
authors.lastname: Baker
authors.forename: Justin C
authors.initials: JC
authors.lastname: Lytle
authors.forename: Christopher N
authors.initials: CN
authors.lastname: Chervin
authors.forename: Michael S
authors.initials: MS
authors.lastname: Logan
authors.forename: Rhonda M
authors.initials: RM
authors.lastname: Stroud
authors.forename: Debra R
authors.initials: DR
authors.lastname: Rolison
mesh_terms: D000388:Air; D003460:Crystallization / Q000379:methods*; D005290:Ferric Compounds / Q000737:chemistry*; D005782:Gels / Q000737:chemistry; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D036103:Nanotechnology / Q000379:methods*; D009532:Nickel / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D013696:Temperature
chemical_list: D005290:Ferric Compounds; D005782:Gels; D046911:Macromolecular Substances; C001215:ferrite; D009532:Nickel