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

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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

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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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