الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Spinel ferrites have attracted much attention in technological and scientific field applications due to their remarkable magnetic, electrical and optical properties. Among these ferrites, manganese magnesium ferrites are a most versatile ferrites due to their high DC resistivity, eddy current losses, moderate saturation magnetization, high initial permeability, high dielectric constant, high Neel temperature and low magnetic losses at high frequency. Hence, they have emerged as important materials in magnetic memory,
microwave absorbance, deflection yokes, switching devices, phase shifter, magnetic recording media, radio frequency coil fabrication, transformer cores and rod antenna. The goal of the present study is to investigate the structure, microstructure and magnetic properties of manganese magnesium ferrite powders prepared via two pathways: the sol gel auto-combustion (SGA) and the co-precipitation (CP) routes. Moreover, the effect of reaction parameters ( temperature, time,
pH) and Mn2+, Ni2+ and Cu2+ substituted Mg2+ ion on the crystal structure, microstructure and magnetic properties is also studied. Such a study is important to understand how to control the synthesis conditions of single manganese magnesium ferrite phase powder. The present thesis comprises four chapters: Chapter 1: It includes a brief account on the ferrites and their types which based on the crystal structure. Moreover, it illustrates the structure of spinel ferrites and cations distribution over A- and B- sites. Chapter 2: This chapter is devoted to literature survey for different methods used for preparation of manganese magnesium ferrites powders and films and with different cations substitution in last few years. Meanwhile, properties of manganese magnesium ferrites, which decide the application areas, have been reviewed. Such a survey showed the high trend of scientists for growing
manganese magnesium ferrites due to their applications. Hence, the aim of the
work is cleared.
Chapter 3: This chapter deals with materials, procedures [Sol gel autocombustion
(SGA) and co-precipitation (CP) methods], characterization by
X-ray diffraction (XRD) and scanning electron microscope (SEM) and
magnetization measurements using vibrating sample magnetometer (VSM).
Chapter 4: This chapter deals with the results and discussion: formation of
single phase manganese magnesium ferrite using sol-gel auto-combustion
(SGA) and co-precipitation methods at different synthesis conditions.
The main results are summarized as follows:
1- Synthesis of manganese magnesium ferrite powders by sol-gel autocombustion
(SGA) method:
•Single manganese magnesium ferrites MnxMg1-xFe2O4 phase powders
are synthesized using the sol-gel auto-combustion (SGA) method using
tartaric acid as a fuel.
•Impurity phase of α-Fe2O3 is obtained at pH 7 and annealed at
temperatures 1000 and 1100ºC for 2h. Increasing the annealing
temperature up to 1200ºC, a well-crystallized pure single
Mn0.5Mg0.5Fe2O4 phase is formed.
•The microstructures are found with random distribution, fairly small
grains and open porosity at 1000ºC, intra-granular pores resulting from
discontinuous grain growth at 1100ºC and regular cubic-like structures
with agglomeration with increasing annealing temperature to 1200ºC.
•Saturation magnetization (Ms) is increased from 26.5 to 41.7 emu/g by
increasing annealing temperature from 1000 to 1200ºC respectively.
•A well crystalline single MnxMg1-xFe2O4 phase is formed with x varying
from 0.2 to 0.8 annealed at 1200°C for 2 h.
•The crystallite size, the lattice parameter (a), the unit cell volume and
X-ray density are found to increase with the increasing the Mn2+ ion
insertion.
•The microstructures of the as prepared manganese magnesium ferrite
samples are quasi- spherical particles at x = 0.2 and 0.4, cubic particles
at x = 0.5 and octahedral-like structure with increasing the Mn2+ ion
insertion to 0.6 and 0.8.
•The value of saturation magnetization is increased from 27.8 emu/g at
Mn2+ content of 0.2 to 47.0 emu/g at Mn2+ ion concentration 0.8 which
is related to the change on the crystallite size, the microstructure and
Mn2+ is magnetic ion whereas Mg2+ ion is non-magnetic.
•Magnetic coercivity is reduced from 39.8 to 9.8 Oe which can be
contributed to the increase in the particle size.
•The prepared samples have superparamagnetic properties because the
squareness ratios (Mr /Ms) ranging (0.006–0.04) and can applied in
hyperthermia treatment of cancer.
•A well crystalline single cubic structure of MnxMg1-xFe2O4 phase is
formed using tartaric, citric or oxalic acids as fuel and organic
precursor at annealing temperature 1200oC for 2 h.
•Maximum saturation magnetization (49.4 emu/g) is achieved for the
formed Mn0.5Mg0.5Fe2O4 phase at pH 7 annealed at 1200ºC for 2h using
citric acid as organic acid precursor.
•The optimum conditions for preparing MnxMg1-xFe2O4 ferrite powders
using tartaric acid as organic acid precursor are formed at pH 7 and
annealed at 1200ºC for 2h.
•Single Ni substituted Mn0.5Mg0.5−yNiyFe2O4 ferrite phase powders are
successfully synthesized using the sol-gel auto-combustion (SGA)
method.
•The lattice parameter of the produced Ni substituted
Mn0.5Mg0.5−yNiyFe2O4 ferrite powder is gradually decline with
increasing nickel content from 0.1 to 0.3.
•The morphologies of Mn0.5Mg0.5-yNiyFe2O4 powders were cubic
particles with some extent agglomeration and the grain boundary size
was increased with the Ni content.
•Saturation magnetization is increased from 55 emu/g at Ni2+ content of
0.1 to 58.9 emu/g at Ni2+ ion concentration 0.3.
2- Synthesis of manganese magnesium ferrite powders by coprecipitation
method:
•Manganese magnesium ferrites MnxMg1-xFe2O4 powders are
successfully synthesized using coprecipitation method using Na2CO3
as a base.
•Impurity phase of α-Fe2O3 is obtained at low annealing temperatures
1000oC and slowly disappear at 1100°C. At 1200°C, a well-crystallized
pure single MnxMg1−xFe2O4 phase is formed.
•The lattice parameter and the unit cell volume of the produced spinel
were varied by increasing the annealing temperature.
•At annealing temperature 1000oC, the microstructure had random
distribution and unclear microstructure fairly small grains. At 1100oC,
the presence of intra-granular pores are resulting from discontinuous
grain growth.
•Increasing the annealing temperature to 1200oC, well-clear grain
growth and particles with regular triangle-like structure are produced.
•Saturation magnetization are increased from 25.3 to 49.2 emu/g by
increasing the annealing temperature from 1000oC to 1200oC
respectively.
•The influence of annealing time ranging from 1 and 4 h on the crystal
structure, microstructure and the crystallite size of Mn-Mg ferrite is
investigated using Na2CO3 at pH 10 and annealed at 1200oC. the
results depicts that the crystallite size and crystallinity are increased
with increasing the time
•As annealing time increased from 1 to 4, the general trend of saturation
magnetization (Ms) is increased from 27.1 to 50.9 emu/g whereas
coercivity (Hc) is decreased from 20.5 to 12.2Oe.
•The morphology of the polycrystalline Mn-Mg ferrite particles appears
as triangular plate-like structure. Moreover, the average particle size is
increased with increasing Mn-content.
•Superparamagnetic properties are possessed by the prepared samples at
different Mn molar ratios where the squareness ratios (Mr /Ms) ranging
(0.021-0.029).
•Highest saturation magnetization (54.2 emu/g) is accomplished for the
formed Mn0.8Mg0.2Fe2O4 phase at pH 10 annealed at 12000C for 2h.
•Single Cu substituted Mn0.5Mg0.5−zCuzFe2O4 ferrite phase powders are
successfully synthesized using the co-precipitation (CP) method.
•The lattice parameter of the produced Cu substituted
Mn0.5Mg0.5−zCuzFe2O4 ferrite powder is gradually increased with
increasing copper content from 0.1 to 0.3.
•Saturation magnetization is increased from 46.3 emu/g at Cu2+ content
of 0.1 to 50.1 emu/g at Cu2+ ion concentration 0.3.
In conclusion, Mn-Mg ferrites powders have been successfully prepared via
the sol-gel auto-combustion (SGA) and low cost co-precipitation (CP) with
good superparamagnetic properties. Such properties would qualify them for
several potential applications including electronic devices and hyperthermia
treatment and as contrast agents in magnetic resonance imaging (MRI)