الفهرس 
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Abstract
Nanotechnology is the most important technology in recent years that deals with
the synthesis of materials, structures and/or devices having dimensions up to ῀
100nm with new properties. where they are used in many industrial applications
like spinel nanomaterials.Spinel compounds used in various technological fields
such as electronic deviced, electrical and magnetic industries, communication
technology and microwave due to effect of composition and cation distribution on
their magnetic properties between octahedral and tetrahedral sites. so the structural
and physical properties of pure and doped Cobalt-Manganese Ferrite nano particle
for super capacitor application have been studied
Supercapacitors are called chemical capacitors; ultra-capacitor or hybrid capacitors
are electrochemical capacitors that have unusually high energy densities compared
to common capacitors.
Transition metal oxides show high electrochemical activity and good discharge
performance on the nanoscales due to their high specific surface area so they are
widely considered as possible electrode materials for electrochemical capacitors
during the development of new supercapacitors technology, spinal oxide-type
materials are considered as competent materials due to their extraordinary physical,
chemical, electronic and magnetic properties. Nevertheless, developing
supercapacitors Co (Ⅱ) and Mn (Ⅲ) based ferrite nanoparticles with required
properties (structural, morphology and electrical) to meet the given application is
challenging. Various synthesis methods have been reported for obtaining CoxMn1-
xFe2O4 mixed ferrites such as the co-precipitation process, ceramic process, heating
of layered doubled hydroxide process, thermal decomposition , sol-gel method,
chemical auto combustion and the hydrothermal routes. However, most of these
synthesis routes require special processing and/or unusual inputs (high
temperature, organic solvent, and post synthesis treatments) which often result in
Co-Mn ferrites with considerable higher particle size. Thus, the synthesis of
supercapacitors Co-Mn ferrites at a lower temperature to avoid particle growth
becomes the most compelling and challenging task. Additionally, the design and
development of efficient methods for the synthesis of high quality CoxMnx-1Fe2O4
for abroad range of electron and electrochemical application continue to be an
active area of research .therefore, motivated by these scientific challenges, in the
present work an attempt has been made to synthesized CoxMn1-xFe3O4 (x: 0.1 to
0.9, CMFO) nanoparticles through an innovative simple, economic and ecofriendly
combustion route using white egg as a biofuel.
Notably, compared to other conventional methods, eco-friendly combustion
synthesis route is a simple one with a high rate of reaction while maintaining a low
operating temperature, resulting in a uniform size distribution. This method is
easily scalable to industrial applications. Furthermore, as reported in this work,
synthesis of CMFO NPs without any surfactant or capping agent by the wellrecognized
green approach which is based on white egg as fuel that is easier to
conduct, is interesting for fundamental scientific reasons. Thus, chemical
engineering of CMFO NPs through the chemical substitution allows designing
materials with controlled structure, morphology and electrochemical behavior for
integration into supercapacitors applications.
In the work reported here, Cobalt Manganese ferrites nanoparticles with different
concentration of metal oxide of Co and Mn were synthesized by combustion route
using egg white as biofuel. Five main samples were prepared which named S1, S2,
S3, S4 and S5 respectively. Then Study the effect of egg white concentration,
calcinations time and variation of calcinations temperature, and variation of white
egg concentration on one sample (S2).
Also, prepare cobalt manganese ferrites nanoparticles doped with different
concentration of Al.
The characteristics of their physical properties and their electrical (ac and dcconductivity)
and dielectric properties studies for their performance as
supercapacitors electrode active materials are detailed.
Chapter 1: review the history and development of supercapacitors technology.
The principle of energy storage mechanisms is explained through double layer
capacitance. Pseudo capacitance and hydride capacitor. This chapter also includes
general introduction about the nanomaterials and their classification. The third part
of this chapter gives a brief about ferrite, its types, synthesis ferrite by different
preparation technique, its applications and electrical properties of ferrite are
discussed in detail.
Chapter 2: introduce the experimental details that are relevant to the entire
research work including the materials and chemicals used in the synthesis and
electrical properties testing and the various characterization techniques used in this
thesis (XRD, TEM, UV and electrochemical measurements). A brief description
explaining the operating principle of each facility is also given in this chapter. In
addition, this chapter deals with the preparation by the combustion technique using
egg white as biofuel of nanostructures cobalt manganese ferrite powders with
enhanced specific capacitance.
Chapter 3: This chapter contains the characterization and structural data we have
and their discussion as well.
from XRD
-Spectral pattern ensure that investigated samples are face centered cubic spinal
type structure with no traces of preliminary material phases demonstrating high
purity of the prepared materials. The particle size was calculated by Scherer’s
formula using half width of the peak maximum (311) plane. The crystal size in the
range of nano size from 18-46 nm of all prepared samples.
-also the effect of egg white concentration on the crystal structure of the prepared
nano- composites was studied and show that the formation of Co Mn ferrites
increases as fuel content increase. The maximum formation of the ferities was
observed in S7 samples. However, XRD pattern confirms that the as prepared
samples consist entirely of Co0.3Mn0.7Fe2O4 as single face with a good crystalline.
The crystallite size of S6, S7 and S8 were calculated by using Scherer equation are
20, 15 and 10 nm respectively.
- Effect of calcination time on the crystal structure of the prepared nanocomposites
was studied and show that figures no traces of preliminary material
phases are seen in observed patterns demonstrating the high purity of the prepared
materials. The intensity of the peak height for CoMnFe2O4 increase when
increasing the calcinations time from 1 hour to 2 hours then the intensity of peak
height decreases when the calcinations time reach to 4 hours, so the best condition
of calcinations time is 2 hours. The crystallite size of S9, S10 and S11 were
calculated by using Scherer equation are 137, 57 and 103 nm respectively.
- Effect of calcinations temperature on the crystal structure of the prepared nanocomposites
was studied and shows that, the intensity of the peak height for
CoMnFe2O4 increase when increasing the calcinations temperature from 600 ℃ to
800℃ then the intensity of peak height also increase when the calcinations
temperature reach to 1000 ℃, so we can say the intensity of peak height increase
by increasing calcinations Temperature but the particle size decrease when
increasing calcinations temperature until 800℃ then particle size increasing again
when reach to 1000℃. The crystallite size of S12, S13 and S14 were calculated by
using Scherer equation are 57, 26 and 117 nm respectively.
- Study the effect of aluminum doping on formation of Co0.3Mn0.7Fe2O4
crystallites was studied and show that no un reacted oxides are seen in the
observed patterns demonstrating the height purity of the prepared materials. The
intensity of the peak height for CoMnFe2O4 increase by increasing the
concentration dopant.
from UV
-UV –Vis spectral study confirmed that all of the prepared cobalt manganese
ferrites nanoparticles are semiconductors materials where band gap energy ranged
from 1.35 e V to 1.4 e V.
from TEM
-Transmission electron microscope images used to study the morphology of the
prepared cobalt manganese ferrite nanoparticles .the images showed that the
prepared ferrites have cubic particles with a crystal size in nanometer scale.
- We noted also by increasing the Co content wt% led to decrease in the particle
size.
-some agglomerations of investigation particles were observed.
-Selected area indicates formation of polycrystalline particles.
from Electrical measurement
The study of dc –electric conductivity plots reveals that the conductivity fits well
with Arrhenius mechanism. The activation energy (Δ Ea) was calculated using
Arrhenius equation and its values confirmed the semiconducting behavior of the
prepared cobalt manganese ferrites nanoparticles.
Moreover, Ac-electrical conductivity is studied in detail. It is noticed that acconductivity
increased with increasing of both frequency and temperature.
Through this study we declared that the conductivity mechanism is a hopping
conductivity in CMFO NPS spinal oxides which arise through polaron hopping.
In addition, the values of dielectric constant ε’ are calculated and reported for all
the prepared cobalt manganese ferrite samples by studying the dielectric behavior.
It is noticed that all samples have semiconducting behavior with high value of
dielectric constant at both radio and microwave frequencies. The recorded high
values of dielectric constant at low frequency are mainly due to the space charge
polarization and rotation direction polarization. The prepared cobalt manganese
ferrites nanoparticles have dielectric constant value lies in the range (1.2X109to
5.9X102) this high value of ε’ called ultrahigh dielectric constant is at least three
order of magnitude higher than any materials that have previously been tested,
indicating that this ferrites materials can be used to make electrostatic
supercapacitors with energy storage capacity that are significantly superior to the
best electrode double layer capacitors (EDLC).