Electrets In Engineering: Fundamentals and Applications

286 Pages·2000·6.536 MB·English

by  Vladimir N. Kestelman, Leonid S. Pinchuk, Victor A. Goldade (auth.)

ELECTRETS IN ENGINEERING
Fundamentals and Applications
ELECTRETS IN ENGINEERING
Fundamentals and Applications
by
Vladimir N. Kestelman
KVN International, Inc.
King of Prussia, PA 19406
Leonid S. Pinchuk
Metal-Polymer Research Institute
Belarussian Academy of Sciences
Belarus
Victor A. Goldade
Metal-Polymer Research Institute
Belarussian Academy of Sciences
Belarus
SPRINGER-SCIENCE+BUSINESS MEDIA, LLC
Library of Congress Cataloging-in-Publication Data
Kestelman, V. N. (Vladimir Nikolaevich)
Electrets in engineering : fundamentals and applications 1b y Vladimir N.
Kestelman, Leonid S. Pinchuk, Victor A. Goldade.
p.cm.
Includes bibliographical references and index.
ISBN 978-0-7923-7754-2 ISBN 978-1-4615-4455-5 (eBook)
DOI 10.1007/978-1-4615-4455-5
1. Materials. 2. Electrets. 1. Pinchuk, L.S. (Leonid Semenovich) II. Goldade,
V .A. (Viktor Antonovich) ill. Title.
TA403.6 K47 2000
620.1 '1297--dc21
00-040550
Copyright © 2000 by Springer Science+Business Media New York
Originally published by Kluwer Academic Publishers in 2000
Softcover reprint of the hardcover lst edition 2000
AII rights reserved. No part of this publication may be reproduced, stored in a
retrieval system or transmitted in any form or by any rneans, mechanical, photo
copying, recording, or otherwise, without the prior written perrnission of the publisher,
Springer-Science+Business Media, LLC.
Printed on acid-free paper.
CONTENTS
Preface ix
Chapter 1. Electret effect and electric technologies 1
1.1. Polarization of dielectrics. 2
1.1.1. The main notions and terms. 2
1.1.2. Polar and nonpolar dielectrics. 5
1.1.3. Polarization mechanisms. 7
1.2. Electret production and properties. 13
1.2.1. The main types of electrets. 13
1.2.2. Two types of electret charges. 17
1.2.3. Electret materials. 22
1.2.4. Electret properties. 24
1.2.5. Thermally stimulated currents and metal
polymer electret (MPE) formation. 27
1.3. Electricfields as referred to materials
technology. 33
1.3.1. Processing of mineral raw materials. 34
1.3.2. Electrotechnologies for material
processing. 35
1.3.3. Coatings. 38
1.3.4. Polymer and ceramic materials. 41
References 43
Chapter 2. Traditional fields of electret application. 47
2.1. Transducers. 47
2.1.1. Mechanical transducers. 47
2.1.2. Acoustic transducers. 53
2.1.3. Electric transducers. 58
2.1.4. Optical transducers. 61
2.1.5. Heat transducers. 63
2.1.6. Electret-based radiation transducers. 64
2.2. Energy sources. 66
2.3. Filters. 68
vi
2.4. Information recording. 70
References 74
Chapter 3. The principles of engineering electret materials
development. 77
3.1. Technological decisions. 77
3.2. Operation problems. 85
3.3. The problems of electret composite materials
(ECM) development. 89
References 90
Chapter 4. Electrets in anticorrosion technique. 91
4.1. Electret charge effect on corrosion. 91
4.1.1. Corrosion thermodynamics and
electrochemistry. 91
4.1.2. Polymer effect on metal polarization
kinetics in electrolyte solutions. 95
4.1.3. Polymer electret permeability. 96
4.2. Polymer coatings. 100
4.2.1. Electrochemical interaction in metal-
coating systems. 100
4.2.2. Discrete coatings. 105
4.2.3. Electric technologies for coating
formation. 106
4.3. Polymer films. 110
References 116
Chapter 5. Electrets in friction joints. 117
5.1. Physico-chemical processes at friction. 117
5.1.1. Liquid friction. 118
5.1.2. Friction without lubrication. 124
5.2. Metal-polymer friction joints. 126
5.2.1. Electrochemical processes at friction. 127
5.2.2. Polymer tribopolarization. 135
vii
5.2.3. Metal-polymer electret wear. 139
5.2.4. Wear monitoring. 141
5.3. Lubricants. 146
5.3.1. Polymer-containing lubricants. 146
5.3.2. Electrorheological suspensions used as
lubricants. 148
5.3.3. Liquid-crystalline lubricants. 149
5.4. Ceramics. 154
5.4.1. Solid lubricant films. 155
5.4.2. Composites based on ceramic matrix. 158
5.4.3. Strengthening of ceramic articles surface
layer. 159
References 163
Chapter 6. Electrets in sealing systems. 167
6.1. Electret field effect on medium permeation. 167
6.1.1. Diffusive permeation. 167
6.1.2. Phase permeation. 170
6.2. Electret seals. 173
6.2.1. Deformation model. 173
6.2.2. Wetting and spreading. 175
6.2.3. Examples of design. 177
6.3. Hermetic coatings. 180
6.3.1. Tightness and toughness. 180
6.3.2. Hermetizing methods. 183
6.3.3. Industrial applications. 185
6.4. Filtering materials. 186
6.4.1. Melt-blowing technique. 186
6.4.2. Modifications of melt-blowing
technology . 190
6.4.3. Electret materials and articles. 195
References 201
Chapter 7. Biological and medical applications of
electrets. 203
7.1. Electrets in biotechnology. 203
7.1.1. Conteporary trends in biotechnology. 204
7.1.2. Bioe1ectret effect. 208
7.1.3. Electric nature of biotechnological processes 210
viii
7.1.4. Bioelectronics. 214
7.1.5. Electret materials in biotechnology. 218
7.2. Electret application in medicine. 223
7.2.1. Endoprostheses. 223
7.2.2. Regulated drug transport. 231
7.2.3. Electrotherapy. 239
References 244
Chapter 8. Ecological and economic aspects of electret
Application. 249
8.1. Terms of electret charge preservation. 249
8.1.1. Charge relaxation. 250
8.1.2. Effect of additions. 252
8.1.3. Effect of irradiation. 255
8.2. Spontaneous electret effects. 257
8.3. Electret materials and ecology. 261
8.4. Economic aspects of electret application. 268
References 272
Index 275
PREFACE
Recently a new sphere in materials science· has formed which
subject is structure and properties of electret materials used in engineering,
medicine, biotechnology and other branches. It is characterized by specific
methods of experimental investigations based on recording charge transfer,
polarization and depolarization of dielectrics and involves original
techniques and physico-mathematical aids where notions that exist at the
interface of several natural and technical sciences are concentrated. It
embraces a vast area of applications mainly in engineering, instrument
making, electronics, medical technique, biotechnology, and etc., has a
specialized technological base for electric polarization of dielectrics
composed of uncommon technological methods, equipment and
instrumentation.
Apparently, future fundamental investigations in the domain of
electret materials science are to be developed at the interface of computer
simulation, physics and physical chemistry of dielectrics. Elaboration of a
model for electric polarization of solid media with uneven charge density
distribution, complicated by surface phenomena, outer electromagnetic,
heat, chemical and other effects, presents a grave methodological problem.
The simulation of structures in which polarization follows diffusion
mechanism of chemically active molecules or their fragments, and the
development of calculation methods for polarized charge relaxation and
regularities of dielectric nonlinear properties, are the most urgent objectives
of current research. Success in bioelectret effect studies is anticipated to
result in profound widening of natural science knowledge.
The results of fundamental investigations have found a wide area of
technical applications. This includes all industrial branches from general
engineering to microelectronics, medicine and biotechnology The
development of nanotechniques for thin electret film production (Langmure
Blodgett technique) efficiently used in microelectronics, nonlinear optics
and biotechnology, inspires hope that through commercial production
improvements in technology, labor productivity and product quality will be
attained. This confidence is rooted in experience obtained from rapidly
developing computer and measuring facilities, communications, and other
engineering branches, which roots are built from of advances in electret
materials science.
Today's electret engineering includes multitude of microphones,
telephones, sensors and many other systems without which man's life would
be inferior. Fields of electret application stretch from household filter for
running water to spa~e vehicles, and from mebrane separating bacteria to
endoprostheses. Engineering challenges to increase pressure, speed and
x
temperature while simultaneously reducing machine mass are to a great
degree supported by successes in electret materials science.
All natural processes including metabolism, rock fonnation,
hydrological cycle, etc. are connected by the electret effect. The
investigation of bioelectricity and geophysical fields promote a more
comprehensive understanding of processes taking place in nature and
outlines new prospects in their rational management.
Advances in electret techniques spur the expanded nomenclature of
electret materials. Their creation encounters, as a rule, preconceptions
towards feasibilities of these materials. Nevertheless, their production
techniques, compositions and optimum variants of application are
innovatory and competitive. A number of electret systems are referred to as
smart ones, i.e., systems able to adapt to operation conditions and effect
properties of conjugated parts, articles or components of technological
process.
Thus, electrets are a vast class of promising materials showing wide
prospects for applications in engineering, medicine and biotechnology, and
indicating high level of a large group of engineering articles. The range of
investigations in materials science has shifted to the creation of
multifunctional materials involving those being physical field sources. Their
role in technical progress is continuously growing.
With developing electret materials science and growing significance
of electric polarization as a technological process, the activities connected
with development and utilization of electret articles start to be specialized.
The combination of specific for electret new systems of knowledge,
methodology, tooling, specialized techniques and professional skills has led
to fonnation of a special teaching course of electret materials science in
educational institutions and public recognition of specialists in the field of
electrets.
All aspects of electret application cannot be fully reflected here in a
single book. Concepts which have not yet received universal recognition but
adequately reflect contemporary trends in electret development, are
disclosed by the authors along with traditional representations. The authors
attempted to objectively show a number of viewpoints, even disputable ones
and hope the present book will stimulate new investigations in the domain of
electret effect application.
CHAPTERl
ELECTRET EFFECT AND ELECTRIC
TECHNOLOGIES.
First investigations of electret effects were undertaken at the begin
ning of the twentieth century by a Japanese physicist Eguchi in 1919 [1].
Theoretically the existence of electrets as a "permanently polarized dielec
tric" was forecasted already in 1892 by the British physicist Heaviside. An
electret was produced by Eguchi by melting a mixture of camauba wax,
rosin and beeswax and cooling it to solidification in a static electric field. He
has noticed that charges on the specimen surface immediately upon its for
mation were opposite in their sign to those of the adjacent electrodes. The
charge was named by Eguchi a heterocharge. The electret can change its
charge with time for the opposite. This one reached upon stabilization was
named a homocharge.
It was supposed initially, that the electret effect was conditioned by
"freezing" of the field-oriented dipolar molecules. After the field removal
the remanent polarization and the related surface charge begin to slowly re
duce with time. Later (in the 50-s) Gross has established, that along with
polarized charges found in electrets there are charges involved from the out
side during polarization. He has also shown that remanent polarization can
emerge through both dipolar molecule freezing and space charge formation
during ion and electron migration in electric field. In the 60-70-s Sessler,
Perlman and others were studying the homocharge origin by examining ki
netics of the charge carrier recombination in the electret traps.
The electret effect is generally described by the phenomenological
theory which basic statements were formulated by Adams [2] and Swann [3].
The recent state of the phenomenological theory of electrets has been re
ported by Gubkin [4], Sessler [5] and other authors [6, 7]. The last digest of
literature on electrets, charged and poled dielectrics and their application
was given in [8].
When speaking about electrets we imply dielectrics which preserve
electric charges of both or one sign for a long period. It can be asserted now,
that electrets have been formed from practically all dielectric materials and
the electret effect itself is a universal phenomenon like polarization or con
duction. To produce the electret state it is necessary for a dielectric to have
sufficiently deep trapping levels for electrons and adequately deep potential
wells for ions and dipole molecules, while electric conductance of the mate
rial should not exceed 10-8 - 10-10 Ohm-tcm-t.