| dc.description |
At first, I fervently express all of my admiration and devotion to the almighty
ALLAH, the most beneficial who has enabled me to perform this research work and to submit
this thesis.
With much pleasure, I respectfully express my earnest gratitude to my honorable teacher and
supervisor Major Brajalal Sinha, PhD, Department of Science and Humanities, Military Institute
of Science and Technology (MIST) for his scholastic guidance, instructions, valuable advice,
suggestions, relentless patience and continuous encouragement throughout my voyage of
research.
I express my profound gratitude to my honorable co-supervisor Professor Dr. Mohammed Abdul
Basith, Department of Physics, Bangladesh University of Engineering and Technology (BUET),
for his constant direction, constructive criticism and inspiration in pursuing the whole
investigation of the present research. Words are always insufficient to express his working
capacities and unending enthusiasm for scientific rigorousness for innovative investigations. This
always becomes everlasting source of inspiration for his students.
I would also like to express my humblest thanks to Dr. Sri Ramulu Torati, Research Professor,
Department of Emerging Materials Science, DGIST, South Korea for providing me with
experimental facilities to carry out XRD, FESEM, EDS and VSM measurements of my samples
during this research.
Next, I offer my gratefulness to Captain M Ziaul Ahsan (retired), BN, Ex-Head, Department of
Science and Humanities and Wing Commander Md Nurul Huda, Head, Department of Science
and Humanities, MIST for their kind permission to perform this work. I thank my respected teacher
V
Major Md. Mahabubar Rahman Shah, PhD for his constant help throughout the completion of the
degree. I am also grateful to MIST authority for providing the financial grant for this research.
I am also grateful to Mr. Galib Hashmi who is a PhD student in Department of EEE at University
of Dhaka and also my undergrad project supervisor for his guidance, inspiration and
encouragement. I wish to give special thanks to Arif Khan and Lieutenant Sonjibone Sudha, (ND),
BN my fellow M.Phil. Researchers for their constant support. I also thank all the staffs of Physics
lab for their constant help while conducting my experimental works.
I am earnestly thankful to The World Academy of Sciences, Italy for supporting our work with
Grant 14-024 RG/PHY/AS_I-UNESCO FR: 324028590.
Finally, I would mention a very special gratefulness for the moral support and sustaining
inspiration provided by my family members. |
en_US |
| dc.description.abstract |
FexNi100-x and FexCo100-x (x = 20, 40 and 80) alloy nanoparticles (NPs) were synthesized by
sonofragmentation process, a facile one-step technique to produce NPs directly from bulk
powders. The structural properties were studied by using X-ray Diffraction (XRD). The
XRD shows the crystalline structure of the alloy samples and the size of the crystallites
were calculated 35 nm and 19.3 nm for Fe-Ni and Fe-Co respectively with significant
amount of phase purity. The compositions of Ni, Fe and Co in the alloy are confirmed from
energy dispersive spectroscopy (EDS). It also reveals that there is no unwanted element
in the alloys. Scanning electron microscopy (SEM) reveals the aggregation or cluster of
spherical NPs with wide size distribution from 20 to 50 nm for all compositions of
nanoalloys. The vibrating sample magnetometer (VSM) illustrates the superparamagnetic
behavior of the alloys. The saturation magnetization (Ms) is found to be 57, 66 and 105
emu/g for Fe20Ni80, Fe40Ni60 and Fe80Ni20 NPs alloys respectively. The values of Ms were
found to be 107, 131, and 153 emu/g for Fe20Co80, Fe40Co60 and Fe80Co20 NPs alloys
respectively. However, the coercivity (Hc) is observed 73, 64 and 57 Oe for Fe20Ni80,
Fe40Ni60 and Fe80Ni20 respectively. The value of Hc is also observed 128, 113 and 72 Oe
for Fe20Co80, Fe40Co60 and Fe80Co20 respectively. It can be noticed that with increasing Fe
content magnetization increases whereas corercivity decreases. The increasing
magnetization may be ascribed to the incorporation of higher magnetic moments into the
compositions. Such compositional dependent nature shows an important approach to attain
tunable magnetic properties of Fe-Ni and Fe-Co NPs for their many practical applications.
Moreover, the synthesized high magnetization Fe-Ni and Fe-Co nanoalloy can be used for
XV
various potential applications, and also this simple and environment friendly technique can
be extended to synthesize other nanostructures. |
en_US |
