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PREPARATION AND CHARACTERIZATION OF MICROWAVE LOSSY MATERIALS
by
SAYED MOHAMMAD ABBAS
Department of Physics
Submitted in fulfillment of the requirements of the degree of
Doctor of Philosophy
to the
Indian Institute of Technology Delhi
February, 2007
CERTIFICATE
This is to certify that the thesis entitled''Preparation and Characterization
of Microwave Lossy Materials" being submitted by Mr. S. M. Abbas, has been
prepared under our supervision in conformity with rules and regulations ofthe Indian
Institute of Technology Delhi. We further certify that the thesis has attained a
standard required for the award of a degree of Doctor of philosophy of the institute.
This work, or any part thereof, has not been submitted elsewhere for the award of any
other degree or diploma.
Associate Professor Physics Department Indian Institute ofTechnology Delhi New Delhi i 10016, India
Prof. T. C. Godl
Director BITS一 Pilani Goa Campus Zuari Nagar Goa 403726, India
ACKNOWLEDGEMENTS
I am extremely grateful to my Ph. D. supervisors, Dr. Ratnamala Chatterjee and
T. C. Geo]. Specially, to Dr. Ratnamala Chatteりee for her guidance and persuasions
to complete this work successfully. Her targeted suggestions and valuab1e discussions
gave me impetus to complete the experimental works in time and also for 四od
publications. Her patience to critically examine the thesis work is really admirable. I owe
her for putting and pushing me on right track.
I am highly indebted to Prof. T. C. Goel for his valuable guidance and constant
encouragement since beginning of my Ph.D. programme. Apart fflom the work, it was my
great pleasure and enlightening experience to have been associated with his multi-faceted
persona]ity during his stay in lIT
I gratefully acknowledge
recommendations and support through
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Director, DMSRDE Kanpur for his
thePh.D. work. I wish to thank Dr. M. Nasim,
Sciectist 'F' for sparing me to complete the thesis work.
I take this opportunity to thank my colleagues at DMSRDE, Mr. Abok Dixit, Dr.
A. B. Ramesh Kumar, Mr. Mahesh Chardra, Mr. Ratnakar Awasthi, Mr. Shilendra
助mar, Shankar Dayal, A. K. Misra for their help and s叩port.
It has been a good experience to interact with Prof D. C. . I take this
opportunity to thank him for allowing me to use his cavity perturbation set up. I am also
thankful to Dr. Anjali Verma for her help in cariメng out 面crowave measurement
through cavity perturbation technique.
I express my sincere thanks to my 伍ends Dr. Radheshyam, Dr. Pawan Kumar
and Dr. Sonali Chopra, Mr. Vijay Srivastava, Mr. Anupinder Singh, Mr Abhishek Path叱
Mr. Manoj Kumar, Ms. Arti Gupta, Mr. Saurabh Srivastava, Ms. Prita and Mr. Rohit of
Advanced ceramics and Magnetic laboratory for their co-operation and help during my
stay over here. I take the privilege of thanking Mr. Vijay Pratap Rathi for his prompt
services whenever it was required.
I extend my thanks to my 街ends in other Lab,, Ms. Kanwal Preet Bhatti, Mr.
Gopinathan, Mr Ranga Rao, Mr. Tarshem, Mr. Ravinder, Mr. Deepak, Mr. Rakesh Singh,
Mr. Maneesh, Mr. Manoj and others for their direct! indirect help and support.
I wish to thank Mr. Raja Ram of IDDC for his assistance in mould fabrication. I
extend my thanks to Mr.助anna of Physics Dept. for helping me in TEM experiment,
Mr. Khattar ofTextile Dept. for helping in ca呼ng out DSC, and Mr. Pathania of AIIMS
for SEM experiments. I would like to express my appreciation and thanks to Mr. P. N.
Prasad of drawing section, works dept. for making beautiful M6ssbauer and XRD
diagram・
Finally, I offer my sincere gratitude to my mother whose blessings have given me
the strength to complete this work. My wife Talat, daughter Afsah and son Meza need
special mention. OEe patience, understanding and un-due support shown by them are
beyond comparison. I express my sincere thanks for being with me in all 叩s and downs
during my Ph.D. work.
Place: IlT Delhi (S. M. ABBAS)
Date: 23 Feb., 2007
ABSTRACT
Microwave lossy /absorbing materials absorb the electromagnetic (EM) wave in
microwave (0.3 一 30 GHz) frequency regions and convert it into heat. Interest in these
materials has existed for many years. In recent years, the microwave lossy I absorbing
materials have drawn more attention because of their widespread applications for
suppression of electromagnetic interference (EMI) and electromagnetic compatibility
(EMC) purposes. These are also in great demand in different GHz frequency ranges, due
to their strategic applications in stealth technology i.e. reduction of radar cross-section
(RCS). Por present thesis, sintered ferrite absorbers as well as composite absorbers out of
M type, U type hexaferrites, polyaniline, BaTiO3, carbon black, and their combination of
filers were prepared in polyurethane (PU) resinsf neoprene rubber matrices.
Polyaniline in nano size has been prepared by controlled wet chemical method at
low temperatures and characterized by FUIR, DSC, XRD and TEM. The particle size in
the range of 15 to 20 nm is established by TEM and also ascertained by XRD data using
Sche叩r's formula. BaTiO3, M type and U type hexafe市te series are prepared by
standard solid-state reaction technique at higher temperatures. XRD and SEM are ca市ed
out to check the phase formation and grain's morphology respectively. M6ssbauer
spectroscopy was done to look at the different valances of iron ions in M type
hexaferrites. EM, and absorption properties in the absorber samples were measured using
the vector network analyzer (HP/Agilent, PNA E8364B) in the Xeehand (8.2 一 12.4 GHz)
frequency range. A computer code was developed to calculate the reflection loss in the
"
absorber samples, based on a theoretical modet for a single layered plane wave absorber
using the measured values of complex perinittivity and complex permeability.
Chapter 1 (Introduction) introduces the fleld of microwave absorbers and gives
short review of literature surveyed on microwave lossy/absorbing materials, explains
electromagnetic (EM) wave materials interaction, describes different materials used for
absorber preparation, different absorber geometries and their principle of absorption.
Lastly, it describes the aim and motivation for the present work.
Chapter 2 (Experimental details) describes the preparation of nano size
polyaniline by wet chemical method. It also gives the procedure ofpreparing the BaTiO3,
M type&U type hexaferrites by standard solid-state reaction technique. Characterization
techniques like FTIR, DSC, XRD, SEM f
M6ssbauer etc, that are used to
characterize these materials, have been briefly described in this Chapter. Preparation of
absorbers and their evaluations by 面crowave measurement techniques like cavity
perturbation or the standard S-parameter techniques are also described. Finally, the basis
for devel ent of the computer code to theoretically simulate the reflection loss using
measured complex ittivities and complex pemeabi]ities is given.
Chapter 3 (Dielectric absorber) presents results of EM and めSorption
properties: dielectric constant (Er'), dielectric loss and reflection loss (RL) for
v面ous dielectric absorbers based on synthesized polyaniline/ BaTiO3, commercial
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polyaniline/ BaTiO3 and carbon black in polyurethane (PU) resin. Structural rties of
the synthesized polyanfiine i BaTiO3 are also given.
Chapter 4 (M type hexaferrite based magnetic absorber) presents the results
of electromagnetic (EM) and absorption properties for different magnetic absorbers
(sintered た市tes and ferrite-PU composites) based on (Co2+-Si軒)substituted M type Ba-
hexafe市te series BaCo2+x民+2y'14+ x+y民+3,2-2x-2yOI9; (X=0.3, y=0.0; x=0.6, y=0.0; x
=0.9, y=0.0; X=0.9, y=0.05; and x=0.9, y=o・2)・ OEe structural properties and
M6ssbauer spectra to show the 釦reed conversion of 民3+ to 民2+ to increase the losses in
the ferrite has also been given.
Chapter 4 (U type hexaferrite based magnetic absorber) presents the results of
the EM and absorption properties for different magnetic absorbers (sintered ferrites and
ferrite-Neoprene rubber composites) based on Ni substituted Co2U hexaferrite
compositions BaCo2.xNixFe36Oo or Co2-xNixU (x=0.0, 0.5, 1.0, 1.5&2). Structural
properties are also given.
Chapter 6 (Conclusions and scope 加r future work) presents the summary of
results in tabular forms with conclusions, as described in Chapters 3, 4 and 5. It also
discusses the works that may be n up in future.
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TABLE OF CONTENTS
CERTIFICATE
A CKNOWLEDGEMENTS
ABSTRACT
LIST OF FIGURES
LIST OF TABLES
Chapter 1: INTRODUCTION
I . 1 Electromagnetic wave -Matenal Interaction
I . 2 Types of Materials for Absorber Preparation
1.2.1 Conducting Carbons
i .2.2 Conducting Polymers
i .2.3 Barium Titanate/ Titania
L2.4 Ferrite Materials
1.2.4.1 Spinel Ferrites
i .2.4.2 Hexaferrites
I .2.5 Magnetic Metallic Materials
I .3 Fabrication Geometries for Absorber
1.3.1 Graded Impedance Type Absorber
1.3.1.1 Geometrically Shaped Absorber
i .3. 1 .2 Graded Interface Absorber
1.3.2 Resonant Absorber
1.3.2.1 Salisbury Screen and Jaumann Absorbers
I .3.2.2 Dallenbach Layer Absorber
I .4 Principle of Operation of Dallenbach Layer Absorber
i .5 Advances in the fleld of microwave absorbers
i .6 Motivation and Plan of Work
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Chapter 2: EXPERIMENTAL DETAILS
2.1 Synthesis of Materials
2.1.1 Synthesis ofPolyaniline
2.1,2 Synthesis of Hexafetrites and Barium Titanate
2.2 Materials Ch釘叩ten zation
2.2.1 FTIR and DSC Experiments
2.2.2 X-Ray Diffraction
2.2.3 SEM/TEM
2.2.4 M6ssbauer Spectroscocy
2.3 Absorber Preparation
2.4 Microwave Measurements
2.4. 1 Cavity Perturbation Technique
2.4.2 S-Parameter Technique
2.4.3 Reflection loss Measurement
2.4.4 Development of Software Code for Reflection loss
Chapter 3: DIELECTRIC ABSORBER
3. 1 Structural Properties
3.2 Complex Permittivity Spectra
3.2.1 PU matrix and Polyaniline-PU Composite
3.2.2 Polyaniline+BaTiO3-PU Composite
12.3 Polyaniline+BaTiO3+Carbon-PU Composite
3.3 Microwave absorbing properties
3.3.1 Polyaniline-PU Composite Absorber
3.3.2 Polyaniline+BaTiO3- PU Composite Absorbers
3.3.3 Polyaniline+BaTiO3+Carbon -PU Composite Absorbers
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Chapter 4: M-TYPE HEXA皿RIまTE BASED
MAGNETIC ABSORBER
4. 1 StructuraI Properties
4.2 M6ssbauer spectra
4.3 Electromagnetic 倉operties of sintered fe市tes
4.4 Absorption Properties of Sintered feボtes
4.5 Electromagnetic Properties of Ferrite-Polymer Composites
4.6 Absorption Properties of Ferrite-polymer Composites
Chapter 5: U-TYPE HEXAFERRITE BASED MAGNETIC ABSORBER
5.1 S加ctural Properties
5.2 Electromagnetic Properties of U Type Sintered Hexafe市tes
5.3 Absorption Properties ofU Type Sintered Hex水rn tes
5.4 Electromagnetic Properties of U ferrites-Rubber Composite
5.5 Absorption Properties of U fe市tes-Rubber Composites
Chapter 6: CONCLUSIONS AND SCOPE FOR FUTURE WORK
6.1 Summary and Conclusions
6.2 Scope for Future Work
APPENDIX I LIST OF PUBLICATIONS
AUTHOR'S BRIEF BIO-DATA
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