abstract
Nanoparticles of magnetite (Fe3O4) were obtained by reacting ferric chloride with sodium sulphite, through the reduction-precipitation method. The effects of adding tetramethylammonium hydroxide (TMAOH) during or after the precipitation of the iron oxide were studied in an attempt to obtain well-dispersed magnetite nanoparticles. Accordingly, the following experimental conditions were tested: (i) precipitation in absence of TMAOH (sample Mt), (ii) the same as (i) after peptizing with TMAOH (Mt1), (iii) TMAOH added to the reaction mixture during the precipitation of magnetite (Mt2). Analyses with transmission electron microscopy (TEM), X-ray diffraction, Mossbauer spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), zeta potential, and magnetization measurements up to 2.5 T revealed that magnetite was normally formed also in the medium containing TMAOH. The degree of particles agglomeration was monitored with laser diffraction and technique and inspection of TEM images. The relative contributions of Neel and Brownian relaxations on the magnetic heat dissipation were studied by investigating the ability of suspensions of these magnetite nanoparticles to release heat in aqueous and in hydrogel media. Based on ATR-FTIR and zeta potential data, it is suggested that the surfaces of the synthesized magnetite particles treated with TMAOH become coated with (CH3)(4)N+ cations.
keywords
IRON-OXIDE NANOPARTICLES; NANOSIZED TITANIA POWDERS; HYDROTHERMAL SYNTHESIS; GAMMA-FE2O3 NANOPARTICLES; FLUID HYPERTHERMIA; PHASE; PH; DISPERSIONS; FERROFLUID; DEXTRAN
subject category
Science & Technology - Other Topics; Materials Science
authors
Andrade, AL; Fabris, JD; Ardisson, JD; Valente, MA; Ferreira, JMF
our authors
José Maria da Fonte Ferreira
Retired Professoracknowledgements
This work was supported by CNPq (Brazil including Grants nos. 202212/2007-6 and 302479/2010-4), FAPEMIG (including Grantd no. PPM 00419-10 and no. APQ-00651-11) (Brazil) and by CICECO, (University of Aveiro, Portugal). CAPES (Brazil) grants the Visiting Professor PVNS fellowship to JDF at UFVJM.