A. Mohammadpour, S. M. Mirkazemi, A. Beitollahi,
Volume 12, Issue 3 (9-2015)
Abstract
In the present study, the feasibility of α-Fe ferromagnetic phase formation in glass and glass-ceramic by
reduction in hydrogen atmosphere have been investigated. The glass with the composition of 35Na
2
O–24Fe2O3–20B
2O3
–
20SiO
2
–1ZnO (mol %) was melted and quenched by using a twin roller technique. As quenched glass flakes were heat
treated in the range of 400-675 °C for 1-2 h in hydrogen atmosphere, which resulted in reduction of iron cations to α-Fe
and FeO. The reduction of iron cations in glass was not completely occurred. Saturation magnetization of these samples
was 8-37 emu g -1
. For the formation of glass ceramic, As quenched glass flakes heat treated at 590 °C for 1 h. Heat
treatment of glass ceramic containing magnetite at 675°C in hydrogen atmosphere for 1 h led to reduction of almost all of
the iron cations to α-Fe. Saturation magnetization of this sample increased from 19.8 emu g
-1
for glass ceramic to 67 emu
g
-1
N. Akhlaghi, G. Najafpour, M. Mohammadi,
Volume 17, Issue 4 (12-2020)
Abstract
Modification of MnFe2O4@SiO2 core-shell nanoparticles with (3-aminopropyl) triethoxysilane (APTES) was investigated. The magnetite MnFe2O4 nanoparticles with an average size of ~33 nm were synthesized through a simple co-precipitation method followed by coating with silica shell using tetraethoxysilane (TEOS); that has resulted in a high density of hydroxyl groups loaded on nanoparticles. The prepared MnFe2O4@SiO2 nanoparticles were further functionalized with APTES via silanization reaction. For having suitable surface coverage of APTES, controlled hydrodynamic size of nanoparticles with a high density of amine groups on the outer surface, the APTES silanization reaction was investigated under different reaction temperatures and reaction times. Based on dynamic light scattering (DLS) and zeta potential results, the best conditions for the formation of APTES-functionalized MnFe2O4@SiO2 nanoparticles were defined at a reaction temperature of 70 °C and the reaction time of 90 min. The effectiveness of our surface modification was established by X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Fourier transforms infrared spectroscopy (FTIR), and vibrating sample magnetometer (VSM). The prepared magnetite nanostructure can be utilized as precursors for synthesizing multilayered core-shell nanocomposite particles for numerous applications such as medical diagnostics, drug, and enzyme immobilization, as well as molecular and cell separation.
