الفهرس 
Characterization of the glass samplesOnly 14 pages are availabe for public view
 |  | from | 190 |  |  |
| | | from | 190 | | |
Abstract
Due to their unusual physical properties, magnetic nanoparticle materials have
gained the interest of a number of researchers. They have been used for
different technological applications such as electronic devices, transformer
cores, switching devices, magnetic devices, recording tapes and as a hard disc
recording media. Magnetic nanoparticles embedded into materials were
suggested to improve material properties. Incorporation of magnetic
nanoparticles into suitable host matrices gives rise to a class of composite
materials that have application in photonic devices as light waveguides and
optical switches. Glass has attracted a great interest for it can serve as a source
for nano-structured systems with good optical nonlinear properties. Moreover,
its high flexibility fabrication, inexpensive, and the composition of the glass
can also be well designed and tuned according to the needs of the
encompassed photonic components. Silicate glass has an important role in a
variety of technically orientated glass application. Compared to SiO2 glasses,
Borosilicate glasses based on the Na2O B2O3 SiO2 system play an important
role in various applications from chemically and thermal resistant technical
glass to optical, sealing and nuclear waste.
In this work, a series of high iron content sodium borosilicate glasses having
composition 10 SiO2-40 B2O3-50 Na2O: x (CoO-Fe2O3); 0 wt% were
prepared by conventional melt quench method. Density of these glasses was
found to increase in the range of 2.47-3.03 g/cm3, along with increasing glass
molar volume. FTIR showed the gradual conversion of BO3 units to BO4 units
along with enhanced B-O-Si linkage with the increasing of (CoO-Fe2O3)
content. AC electrical conductivity and dielectric properties were investigated
at room temperature within frequency range 100 Hz to 100 KHz. Dielectric
parameters such as dielectric constants
conductivity ac were found to increase with the increasing of (CoO-Fe2O3) content. The increase in ac conductivity with iron content is likely to arise due
to structural changes of the glass network. Magnetic hysteresis loops were
traced at room temperature using VSM and values of saturation magnetization
MS and coercive field HC were determined. The obtained results revealed that
a ferrimagnetic behavior was observed and as (CoO-Fe2O3) concentration
increases the values of MS increases whereas that of HC dramatically
decreased from 271.12 to 179.23Oe.
Further, the glass sample 10 SiO2 - 40 B2O3 - 50 Na2O : 50 (CoO-Fe2O3) is
annealed at temperatures 500, 525, 550, 575, 600 oC, according to the
determined Tg-values, for 2 hrs and at 575 oC from 1 hr to 5 hrs in order to
precipitate in them nanocrystalline CoFe2O4 phase. The annealing
temperatures were always clearly above the glass transition temperatures: Tg =
493 °C for this glass sample. The phase composition and microstructure of the
annealed glass samples are studied by X-ray diffraction and electron
microscopy. X-ray diffraction patterns reveal the formation of a unique
magnetic crystalline phase (CoFe2O4), embedded in an amorphous matrix. The
particle was found to have a spherical shape and highly monodispersed and
increased with increasing annealing time and temperature with an average
size10-19nm and 19-22nm as a function of annealing temperature and
annealing time respectively as analyzed from transmission electron
microscopy (TEM). Annealing temperature, annealing time and frequency
dependent dielectric properties of the prepared samples have been measured at
room temperature in the frequency range 100 Hz-100 kHz. The conductivity is
found to increase with increasing annealing temperature. Dielectric constant
and dielectric loss decrease with increasing the frequency. The variations of
conductivity and dielectric properties with frequency and composition are also
discussed. The values of saturation magnetization MS and coercive field HC.