الفهرس 
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Abstract
Nanostructure ferrites have become an important area of research in
magnetism, catalysis technological applications and in biosciences.
Nanoparticle ferrites are among the most important magnetic materials that
can be widely used in many fields, such as high-density information storage,
ferrofluids, magnetic devices , flexible recording media, sensors, color
imaging, bimolecular separation and so on . Furthermore, spinel ferrites are
well known catalysts for various processes like oxidative dehydrogenation
of hydrocarbons, decomposition of alcohols, and selective oxidation of
carbon monoxide. These properties are strongly dependent on their shape,
size, crystallinity and the distribution of the cations among the tetrahedral
and octahedral sites of the spinel structure.
It is a well-known fact that the properties of ferrite materials are
strongly influenced by the material’s composition and microstructure, which
are sensitive to the preparation method used in their synthesis . In addition,
the sintering conditions employed and the impurity levels present in or
added to these materials also change their properties. The usual
conventional ceramic method of preparing ferrites, gives inhomogeneous
final microstructure with low surface areas. The recently developed low
temperature co-precipitation method yields homogeneous and fine ferrite
powders with high surface areas and catalytic activity.
Why copper manganese ferrite?
Mn containing ferrites have various applications such as transformers,
electromagnetic interference, asymmetric digital subscriber line etc. These
properties of ferrites mainly depend upon chemical composition, method of
preparation, sintering time and temperature. By introducing small amount of
foreign ion can change the electrical and magnetic properties of the ferrite.
Copper ferrites have attracted the attention of investigators, for its
uniqueness condition. It shows remarkable effect in structural resistivity.
Several studies have been reported on the addition of Mn4+ ions in copper
ferrite and other ferrites. In the present work, a detailed investigation of the
manganese doped copper ferrite with composition and temperature
dependence of surface and catalytic activity properties and thermoelectric
power were carried out.
The prevailing investigation comprises a trial of correlating the
catalytic activity of the above mentioned spinels that have the general form
CuxMn1-x Fe2O4, where (x=0.0, 0.2, 0.4, 0.6, 0.8, 1) with its structure and
texture towards the decomposition of ethanol.
1) The parent materials were prepared by the interaction between
aluminum oxide and the metal nitrates (in presence of urea as a
precipitating agent). Interaction process was affected by impregnation
and the calcination is affected in air atmosphere at a range of
temperatures 600-1200°C for 5 hours.
2) In this work different coordinated physicochemical techniques have
been used in order to characterize the different catalysts and identify
the nature and different types of acid sites. These physicochemical
techniques include i) phase changes and structural investigation of the
catalysts were achieved by X-ray diffractometer. Thus, it was possible
to define phase changes accompanying annealing in air as well as to
assert spinel formation being ferrite, and ii) absorption and/or
adsorption of volatile amine such as pyridine have been used to
identify qualitatively the nature of acid sites on solid catalysts.
3) Nitrogen sorption isotherms were measured on the parent mixtures
and their calcination products. Applying the BET equation the
corresponding specific surface areas were calculated and the values
obtained were discussed in terms of influencing of x values for the
different mixtures. Furthermore, analysis of sorption isotherms was
performed. Va-t plots were constructed, and it was possible to
investigate the porosity of the various adsorbents. Pore size
distribution analysis from cumulative calculations was also done
according to de Boer’s method. The necessary calculations were run
through a computer programme designed for this purpose.
4) The catalytic activity of the different catalyst series calcined at 600 up
to 1200°C, was tested for the catalytic decomposition of ethanol,
using a standard flow system, in which the reactor was heated by
fixed bed technique. The catalytic experiments, in the temperature
range 250-450°C, showed that diethyl ether, ethylene and
acetaldehyde are the products of both dehydration and
dehydrogenation reactions, respectively. Eventually, the surface
structures were correlated with the catalytic activity, where the
catalyst selectivity towards the dehydration and dehydrogenation
pathways was also taken in consideration. The activity patterns for the
different spinels were understood in terms of the total acidity of the
catalysts.
5) The appropriate reaction mechanism for both the surface dehydration
and dehydrogenation reactions was postulated.