advanced composite materials · 2016-09-19 · 3.6 some important advanced ceramics 121 3.6.1...

Advanced Composite Materials

Scrivener Publishing

100 Cummings Center, Suite 541J

Beverly, MA 01915-6106

Advanced Materials Series

The Advanced Materials Series provides recent advancements of the fascinating

field of advanced materials science and technology, particularly in the area of

structure, synthesis and processing, characterization, advanced-state properties,

and applications. The volumes will cover theoretical and experimental

approaches of molecular device materials, biomimetic materials, hybrid-type

composite materials, functionalized polymers, supramolecular systems,

information- and energy-transfer materials, biobased and biodegradable or

environmental friendly materials. Each volume will be devoted to one broad

subject and the multidisciplinary aspects will be drawn out in full.

Series Editor: Ashutosh Tiwari

Biosensors and Bioelectronics Centre

Linköping University

SE-581 83 Linköping

Sweden

E-mail: [email protected]

Managing Editors: Sachin Mishra and Sophie Thompson

Publishers at Scrivener

Martin Scrivener ([email protected])

Phillip Carmical ([email protected])

Advanced Composite Materials

Edited by

Ashutosh Tiwari, Mohammad Rabia Alenezi

and Seong Chan Jun

Copyright © 2016 by Scrivener Publishing LLC. All rights reserved.

Co-published by John Wiley & Sons, Inc. Hoboken, New Jersey, and Scrivener Publishing LLC, Beverly,

Massachusetts.

Published simultaneously in Canada.

No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or

by any means, electronic, mechanical, photocopying, recording, scanning, or other wise, except as permit-

ted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior writ-

ten permission of the Publisher, or authorization through payment of the appropriate per-copy fee to

the Copyright Clearance Center, Inc., 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax

(978) 750-4470, or on the web at www.copyright.com. Requests to the Publisher for permission should be

addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030,

(201) 748-6011, fax (201) 748-6008, or online at http://www.wiley.com/go/permission.

Limit of Liability/Disclaimer of Warranty: While the publisher and author have used their best efforts

in preparing this book, they make no representations or warranties with respect to the accuracy or

completeness of the contents of this book and specifically disclaim any implied warranties of merchant-

ability or fitness for a particular purpose. No warranty may be created or extended by sales representa-

tives or written sales materials. The advice and strategies contained herein may not be suitable for your

situation. You should consult with a professional where appropriate. Neither the publisher nor author

shall be liable for any loss of profit or any other commercial damages, including but not limited to spe-

cial, incidental, consequential, or other damages.

For general information on our other products and services or for technical support, please contact

our Customer Care Department within the United States at (800) 762-2974, outside the United States at

(317) 572-3993 or fax (317) 572-4002.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may

not be available in electronic formats. For more information about Wiley products, visit our web site

at www.wiley.com.

For more information about Scrivener products please visit www.scrivenerpublishing.com.

Cover design by Russell Richardson

Library of Congr ess Cataloging-in-Publication Data:

ISBN 978-1-119-24253-6

Printed in the United States of America

10 9 8 7 6 5 4 3 2 1

http://www.copyright.com

http://www.wiley.com/go/permission

http://www.wiley.com

v

Contents

Preface xv

1 Composite Materials for Application in Printed Electronics 1

Kamil Janeczek1.1 Introduction 11.2 Filler Materials 51.3 Conductive Polymers 91.4 Preparation of Electronics Materials for Printing 101.5 Overview of Application Fields 13

1.5.1 RF Applications 131.5.2 Sensors 251.5.3 Electrodes 28

1.6 Conclusions 30References 31

2 Study of Current-limiting Defects in Superconductors Using Low-temperature Scanning Laser Microscopy 45

Pei Li and Dmytro Abraimov2.1 Introduction 462.2 Introduction of Low-temperature Scanning

Laser Microscopy and Its Application in Defect Studies in Superconductors 502.2.1 Basic Principle of LTSLM 502.2.2 Visualization of Defect-induced Dissipation

and Spatial Jc Distribution 51

2.2.3 Thermoelectric Responses from LTSLM 572.2.4 Experimental Setup of LTSLM System 60

vi Contents

2.3 Case Studies of Using LTSLM to Study Defects in Superconductors 642.3.1 REBCO-coated Conductors Based on

Rolling-assisted Biaxially Textured Substrate 642.3.2 MOCVD/IBAD REBCO-coated Conductors 712.3.3 Polycrystalline Iron-based Superconductor 762.3.4 The Application of LTSLM in Study of Grain

Boundaries in Superconductors 812.4 Conclusions 85Reference 86

3 Innovative High-tech Ceramics Materials 93

Hüsnügül Yılmaz Atay3.1 Introduction 933.2 Ceramic Structure 100

3.2.1 Oxide Structures 102 3.2.1.1 Rock Salt Structure 102 3.2.1.2 Wurtzite Structure 102 3.2.1.3 Zinc Blende Structure 102 3.2.1.4 Spinel Structure 103 3.2.1.5 Corundum Structure 103 3.2.1.6 Rutile Structure 103 3.2.1.7 Cesium Chloride Structure 104 3.2.1.8 Fluorite Structure 104 3.2.1.9 Antifluorite Structure 1043.2.1.10 Perovskite Structure 1043.2.1.11 Ilmenite Structure 104

3.2.2 Silicate Structures 104 3.2.2.1 Orthosilicates 105

3.2.3 Clay Minerals 1053.2.4 Other Structures 106

3.2.4.1 Gibbsite 106 3.2.4.2 Graphite 106 3.2.4.3 Carbides 107 3.2.4.4 Nitrides 107

3.2.5 Glasses 1073.3 Raw Materials 1083.4 Processing of Ceramics 111

3.4.1 Forming and Firing 1123.4.2 Melting and Solidification 1143.4.3 Newer Fabrication Techniques 114

Contents vii

3.5 Properties 1183.6 Some Important Advanced Ceramics 121

3.6.1 Insulating Ceramics/High Thermal Conductive Ceramics 121

3.6.2 Semiconductive Ceramics 122 3.6.2.1 PTC Thermistors 122 3.6.2.2 NTC Thermistors 122 3.6.2.3 Ceramic Varistors 123

3.6.3 Ionic Conductors/Oxygen Sensors 124 3.6.3.1 Oxygen Sensors for Automobiles 124 3.6.3.2 Thick-film-type Oxygen Sensor 124 3.6.3.3 Universal Exhaust Gas Oxygen Sensor 125 3.6.3.4 NO

x sensor 125

3.6.3.5 Oxygen Sensors for Industry 126 3.6.4 Ceramic Fuel Cells 126 3.6.5 Piezoelectric Ceramics 127 3.6.6 Dielectric Ceramics 129

3.6.6.1 Ceramic Capacitors 129 3.6.7 Magnetic Ceramics 130 3.6.8 Optoelectroceramics 131 3.6.9 Superconductive Ceramics 1333.6.10 High-temperature High-strength Ceramics 1343.6.11 Porous Ceramics for Filtration 1363.6.12 Ceramic Bearing 1373.6.13 Cutting Tools 1373.6.14 Ceramics for Biomedical Applications 139

3.6.14.1 Ceramics for Artificial Joints 139 3.6.14.2 Ceramics for Artificial Bone 140 3.6.14.3 Bioactive Cements 141 3.6.14.4 Ceramics for In Situ Radiotherapy of

Cancers 141 3.6.14.5 Ceramics for In Situ Hyperthermia

Therapy of Cancer 1413.6.15 Decorative Ceramics 1423.6.16 Ceramic Materials for Energy Systems 143

3.6.16.1 Li-ion Batteries 1433.6.17 Extruded Cordierite Honeycomb Ceramics for

Environmental Applications 1433.6.18 Composites 144

3.6.18.1 Al2O

3–TZP Composites 145

3.6.18.2 SiC–Si3N

4 Composites 145

viii Contents

3.6.18.3 Whisker Composites 145 3.6.18.4 SiC Whisker–Al

2O

3 Matrix Composites 146

3.6.18.5 SiC Whisker–Si3N

4 Matrix Composites 146

3.6.18.6 Continuous Fiber Composites 147 3.6.18.7 Glass Matrix Composites 147 3.6.18.8 Carbon/Carbon Composites 148 3.6.18.9 SiC/SiC Composites 1483.6.18.10 Oxide/Oxide Composites 1493.6.18.11 Eutectic Composites 149

3.7 Conclusions 149References 150

4 Carbon Nanomaterials-based Enzymatic Electrochemical Sensing 155

Rooma Devi, Lipsy Chopra, C.R. Suri, D.K. Sahoo

and C.S. Pundir4.1 Introduction 1554.2 Carbon Nanomaterials 157

4.2.1 Graphene 159 4.2.1.1 Graphene-based Enzyme Biosensors 159

4.2.2 Carbon Nanotubes 161 4.2.2.1 Single-walled Carbon Nanotubes 162 4.2.2.2 Multi-walled Carbon Nanotubes 164

4.3 Carbon Nanotubes Paste Electrodes 1654.4 Carbon Nanotube-based Electrodes with Immobilized

Enzymes 166 4.4.1 Enzymes Adsorption 167 4.4.2 Covalent Attachment 168 4.4.3 Affinity Binding 170 4.4.4 Electropolymerization 170 4.4.5 Encapsulation or Entrapment 173

4.5 Fullerene-modified Electrode 173 4.6 Carbon Nanoonion (CNO)-modified Electrode 174 4.7 Carbon Nanodiamond-modified Electrode 174 4.8 Carbon Nanohorns-modified Electrode 174 4.9 Carbon Nanofibers-based Electrode 1754.10 Carbon Nanodot-based Electrode 1764.11 Electrochemical Biosensor 177

4.11.1 Glucose 177 4.11.2 Dopamine 182

Contents ix

4.11.3 Cholesterol 183 4.11.4 Creatinine 183 4.11.5 Bilirubin 185 4.11.6 Ascorbic Acid 187 4.11.7 Xanthine 187 4.11.8 Hypoxanthine 189 4.11.9 Uric Acid 190 4.11.10 Amino Acid 191

4.12 Conclusions 1924.13 Future Developments 194Acknowledgment 195References 195

5 Nanostructured Ceramics and Bioceramics for Bone Cancer Treatment 209

B. Palazzo, S. Scialla, F. Scalera, N. Margiotta

and F. Gervaso15.1 Overview 2105.2 General Concepts onto Bone Cancer and

Bone Metastases 2105.2.1 Bone Cancer Etiology and Pathogenesis 2125.2.2 Current and Innovative Therapeutic Treatments

and Related Drawbacks 2145.2.3 Chemotherapy: Traditional and Innovative

Chemotherapeutic Drugs 2185.3 Intrinsically Anticancer Nanoceramics 224

5.3.1 Colloidal Nanoceramics for Hyperthermia 2255.3.2 Magnetic Nanoparticles: Properties, Structures

and Fabrication Methods 2275.3.2.1 Superparamagnetic Core 2285.3.2.2 Protective Coating 2325.3.2.3 Additional Surface Functionality 232

5.3.3 Application of Iron Oxides Magnetic Nanoparticles as Anticancer Agents 234

5.3.4 Nanoceramics for Radiotherapy 2365.4 Imprinting Anticancer Properties to Bioceramics by

Chemotherapeutic Functionalization 2385.4.1 Calcium Phosphates-based Biomaterials

General Features 2385.4.2 Calcium Phosphates-based Biomaterials as

Anticancer Drugs Carriers 241

x Contents

5.4.3 Silica-based Biomaterials General Features 2445.4.4 Silica-based Biomaterials as Chemotherapeutic

Drugs Releasing Agents 2475.4.5 Calcium Phosphates and Silica-based

Biomaterials as Injectable Bioceramics 2485.5 Composite Magnetic Bioceramics 249

5.5.1 Calcium Phosphates-based and Silica-based Magnetic Bioceramics 250

5.5.2 Magnetically Triggered Drug Release Nanodevices 253

5.6 Conclusions and Outlook 254Acknowledgements 256References 256

6 Therapeutic Strategies for Bone Regeneration: The Importance of Biomaterials Testing in Adequate Animal Models 275

P.O. Pinto, L.M. Atayde, J.M. Campos, A.R. Caseiro,

T. Pereira, C. Mendonça, J.D. Santos and A.C. Maurício6.1 Introduction 276

6.1.1 Autografts 2766.1.2 Allografts 2776.1.3 Xenografts 2776.1.4 Synthetic Bone Grafts 2786.1.5 The Role of Morphology in Biological Behavior

of the Biomaterials 2836.1.5.1 Porosity 2856.1.5.2 Pore Size 2866.1.5.3 Total Porous Volume 2896.1.5.4 Interconnectivity 2896.1.5.5 Percent Porosity 290

6.1.6 Steam Sterilization 2916.2 Animal Models Used for In Vivo Testing Bone

of Grafting Products 2926.3 Histomorphometric Analyses 2986.4 Histologic Analysis 3016.5 Conclusions 303Acknowledgments 306References 306

Contents xi

7 Tuning Hydroxyapatite Particles’ Characteristics for Solid Freeform Fabrication of Bone Scaffolds 321

F. Miculescu, A. Maidaniuc, G.E. Stan, M. Miculescu,

S.I. Voicu, A. Cîmpean, V. Mitran and D. Batalu7.1 Introduction 3227.2 Powder-based Solid Freeform Fabrication of

Naturally Derived Ceramic Components 3267.2.1 Preliminary Steps 326

7.2.1.1 Preparation of Naturally Derived Ceramics 326

7.2.1.2 Ceramic Powder Processing 3297.2.2 Powder-based Solid Freeform Fabrication

Techniques 3327.2.2.1 Short Introduction on Solid

Freeform Fabrication 3327.2.2.2 Powder Bed Fusion

(Selective Laser Sintering) 3397.2.2.3 Binder Jetting (Tridimensional Printing) 3437.2.2.4 Material Extrusion (Robocasting) 344

7.2.3 Additives and Accessories for Solid Freeform Fabrication 3457.2.3.1 Lasers 3457.2.3.2 Binders 3467.2.3.3 Coatings 347

7.2.4 Ceramic Materials Used in Solid-free Fabrication 3477.2.4.1 Requirements for Ceramic Powders

Used in Solid Freeform Fabrication 3477.2.4.2 Calcium Phosphates for

Bone Substitution 3517.2.5 Current Challenges and Future Steps

for Solid Freeform Fabricated Medical Devices 3567.2.5.1 Solid Freeform Fabricated Structures for

Medical Applications 3567.2.5.2 Porosity’s Influence on

Vascularization 3587.2.5.3 Sterilization’s Influence on

Final Products’ Characteristics 359

xii Contents

7.3 Tuning of Naturally Derived Calcium Phosphates for Solid Freeform Fabrication 3627.3.1 Phase-tuning by Specific Heat-treatment

of Bovine Bone 3637.3.1.1 The Heating Rate and Holding

Time Influence 3637.3.1.2 Temperature’s Influence 3647.3.1.3 Heating Environment’s Influence 3667.3.1.4 Cooling Conditions Influence 368

7.3.2 Biocompatibility Evaluation of Naturally Derived Biphasic Calcium Phosphates 3727.3.2.1 Non-clinical Trials 3737.3.2.2 In Vitro Testing of Biphasic Calcium

Phosphates Developed for Additive Manufacturing 376

7.3.2.3 Challenges Associated with Biocompatibility Testing: In Vivo Trials Ethics 381

7.4 Conclusions 383Acknowledgments 384References 384

8 Carbon Nanotubes-reinforced Bioceramic Composite: An Advanced Coating Material for Orthopedic Applications 399

D. Gopi, E. Shinyjoy, L. Kavitha and D. Rajeswari8.1 Introduction 4008.2 Materials and Method 407

8.2.1 Chemicals 4078.2.2 Specimen Preparation 4078.2.3 Functionalisation of CNTs 4088.2.4 Preparation of Electrolyte Solution for

CNTs-reinforced Bioceramic Composite Coatings on Ti 4088.2.4.1 CNTs-reinforced HAP Composite 4088.2.4.2 CNTs-reinforced Strontium-substituted

HAP (SrHAP), Magnesium-substituted HAP (MgHAP), Zinc-substituted HAP (ZnHAP), and CNTs-reinforced M(Sr+Mg+Zn) HAP Composite 408

Contents xiii

8.2.5 Electrodeposition of CNTs-reinforced Bioceramic Composite Coatings 410

8.2.6 Pulsed Electrodeposition of CNTs/MHAP 4108.2.7 Characterization of CNTs-reinforced

Bioceramic Composite Coatings 4108.2.7.1 Fourier Transform Infrared

Spectroscopic Studies 410 8.2.7.2 X-ray Diffraction Studies 411 8.2.7.3 Scanning Electron Microscopic Studies 411 8.2.7.4 Energy-dispersive X-ray

Analysis (EDX) 411 8.2.7.5 Transmission Electron

Microscopic Studies 412 8.2.7.6 X-ray Photoelectron Spectroscopic

Studies 412 8.2.7.7 Electrochemical Characterization 412 8.2.7.8 Mechanical Characterization 414 8.2.7.9 Inductively Coupled Plasma Atomic

Emission Spectroscopy 4148.2.7.10 Evaluation of Biological Properties 414

8.3 Results and Discussion 4178.3.1 CNTs-reinforced Hydroxyapatite Composite

Coatings on Ti 417 8.3.1.1 Surface Characterization 417 8.3.1.2 Morphological Characterization 418 8.3.1.3 Bioresistance of CNTs/HAP

Composite-coated Ti 421 8.3.1.4 Mechanical Characterization 425 8.3.1.5 In vitro Cytotoxicity Studies with

L929 Mouse Fibroblast Cells 4268.3.2 CNTs-reinforced Minerals-substituted

Hydroxyapatite Composite Coatings on Ti 426 8.3.2.1 Surface Characterization 426 8.3.2.2 Morphological Analysis of the

Composite Coatings 429 8.3.2.3 Bioresistance of CNTs-reinforced

Mineralized Composite Coatings on Ti 430 8.3.2.4 Biocompatibility of the

CNTs-reinforced Mineralized HAP Composite Coatings 432

8.3.2.5 ICPAES Analysis 434

8.3.3 CNTs-reinforced Multiminerals-substituted Hydroxyapatite Composite Coatings on Ti by Pulsed Electrodeposition 435 8.3.3.1 Morphological Results and

Elemental Mapping Analysis 435 8.3.3.2 Mechanical Characterizations 437 8.3.3.3 Biological Characterizations 437

8.4 Conclusion 444Acknowledgments 445References 445

Index 453

xiv Contents

Preface

The term “composites” is a simplified way of describing the combining of unique properties of different materials to produce synergistic effects. A combination of materials is needed so that certain properties can be adapted to any area of application. There has been an everlasting desire for composite materials to be made stronger, lighter or more durable than traditional materials. Carbon materials are known to be attractive for com-posites due to a combination of their chemical and physical properties. Recently, carbon allotropes, such as graphene, graphene oxide and carbon nanotubes, have been used in electrochemical biosensors to provide highly sensitive and selective detection.

Included in this book are innovative fabrication strategies and uti-lization methodologies frequently adopted in the advanced composite materials community with respect to developing appropriate compos-ites to efficiently utilize macro- and nanoscale features. Its general read-ership are those from interdisciplinary backgrounds across the fields of physics, chemistry, materials science and engineering, nanoelectronics, electrochemical sensing, biomaterials science, nanobiotechnology and, most importantly, the biomedical materials-related life science communi-ties. The comprehensive overview of state-of-the-art research on compos-ite materials presented herein will be of interest to scientists, researchers, students and engineers in materials science/nanotechnology research, composite systems and nanodevices, sensors, carbon nanomaterials, gra-phene, nanobiomaterials, advanced biomaterials applications, and also industrial sectors intending to utilize composite materials in different technologies via cutting-edge techniques. Interdisciplinary PhD can-didates will also find this book useful for developing their fundamental understanding on the subject and it will also be appropriate for master and undergraduate level courses on composite materials processing, properties and applications in physics, chemistry, materials science, nanotechnology,

xv

xvi Preface

biomaterials and biomedical engineering, among others. In conclusion, we would like to thank all the contributors whose preparation of such high quality chapters is greatly appreciated and the production team for their dedicated work to ensure the birth of this book.

Editors Ashutosh Tiwari, PhD, DSc

Mohammad Rabia Alenezi, PhD Seong Chan Jun, PhD

July, 2016

1

Ashutosh Tiwari, Mohammad Rabia Alenezi and Seong Chan Jun (eds.) Advanced Composite

Materials, (1–44) © 2016 Scrivener Publishing LLC

1

Composite Materials for Application in Printed Electronics

Kamil Janeczek

Tele and Radio Research Institute, Warsaw, Poland

AbstractFurther development of printed electronics requires investigations of new

advanced composite materials that can be used to produce different types of

devices on flexible or rigid substrates. Among these printed devices, organic light-

emitting diodes, organic photovoltaic cells, radio frequency identification tags,

sensors, and capacitors can be mentioned. To achieve their high performance,

materials used for their fabrication should exhibit excellent electrical as well as

thermal and mechanical properties to be not susceptible to environmental factors,

in particular to bending cycles. In this study, recently developed different materials

used in printed electronics for fabrication of various types of devices are discussed.

These materials contain graphene, graphite nanofibers, carbon nanotubes, silver

nanopowder, or silver flakes. Properties of layers produced from these materials

were discussed, i.e. based on the results obtained using scanning electron micro-

scopy, atomic force microscopy, profilometers, and their durability after thermal

and mechanical tests was assessed by measurement of their resistance and analysis

of their surface and microstructure.

Keywords: Printed electronics, graphene, carbon nanotubes, silver nanopowder,

graphite nanofibers

1.1 Introduction

In recent years, development of modern electronics technologies has been influenced by eco-friendly approach that consists in limitation of

Corresponding author: [email protected]

2 Advanced Composite Materials

hazardous substances and waste created during production of electronics devices. In effect of this approach, the Directive on the restriction of the use of certain hazardous substances in electrical and electronic equipment (in short: Restriction of Hazardous Substances Directive – RoHS) was introduced. Its aim was to restrict the use of the following six substances: lead (Pb), mercury (Hg), cadmium (Cd), hexavalent chromium (Cr6+), polybrominated diphenyl ether (PBDE), and polybrominated biphenyls (PBB) [1].

Another manifestation of the eco-friendly approach in electron-ics industry was development of printed electronics which is also called organic, plastic, polymer, or organic electronics [2]. This new branch is based on polymer materials that allow to fabricate light-weight, flexible, cheap, and disposable devices. Among them, organic light-emitting diodes (OLEDs) [3–6], organic photovoltaic cells [7–9], radio frequency identi-fication (RFID) tags [10–12], memories [13–15], batteries [16–17], smart textiles [18–19], and sensors [20–23] can be named.

Unlike conventional technologies, e.g. etching used in production of printed circuit boards, printed electronics belongs to additive manu-facturing techniques. This means that a produced component is formed by printing different types of materials directly on a substrate, whereas in subtractive techniques some parts of materials are removed to create a designed element. In this way, unwanted waste is produced when subtrac-tive techniques are used. This waste has negative impact on environment and it increases production cost because it is necessary to pay for its utili-zation [24]. Printed electronics allows to avoid creating as big amount of waste as it is generated in conventional technological processes and with respect to this ability printed electronics can be assessed as eco-friendly. Its additional advantage is less complexity compared for instance to etching, e.g. to produce electronic circuits smaller number of technological steps is required [25]. To see this aspect better, a few chosen printing techniques and etching technique for comparison are described below.

There are many different printing techniques which can be utilized for fabrication of electronics devices. Among them, screen printing, ink-jet, gravure, and flexography can be specified. The first one is a well-known and popular manufacturing technique in which a paste is transferred onto a substrate through a mesh made from polyester, steel, or polyimide. The mesh is stretched on a metal frame. In order to get a required thickness of a printed pattern, it is necessary to choose suitable force and speed of a squeegee and distance between mesh and substrate. After the printing process, the fabricated pattern is cured using elevated temperature or ultra-violet (UV) [26].

Composite Materials for Application in Printed Electronics 3

Another printing technique is ink-jet, which has been rapidly devel-oped in the recent years. Its two different groups can be named: drop-on-demand (DoD) and continuous ink-jet (CIJ). In the DoD process, a single ink droplet is jetted through a nozzle when pressure within a reservoir grows or due to vibration of a piezo element or a bubble created as a result of rapid evaporation of the heated ink [26–28]. In industrial application, size of generated droplets varies from 15 to 55 μm, drop speed is typically equal to 3–15 m/s, and printing frequencies are up to 100 kHz [29]. In the CIJ process, a stream of fine droplets is ejected out of the nozzle under the pressure inside the reservoir which is undergoing vibration. The generated droplets pass through a charged electrode, and then two perpendicular electric fields can deflect them in two directions. The droplets which are not intended to be printed are collected into a gutter [30]. Typically, CIJ produces droplets with a diameter of 80–100 μm moving at speed of 20 m/s with drop frequencies even above 250 kHz. For both mentioned ink-jet groups, thermal, piezoelectric, and electromagnetic actuators are usually utilized [29].

In comparison to screen printing, ink-jet method makes possible to produce much thinner layers (below 1 μm) [27] and higher resolution (250 lines per cm) [26]. Moreover, it is not necessary to use in-between forms, such as stencils, what is significant advantage of ink-jet printing.

In the classical gravure method, a number of cavities with raster struc-ture are created in a cylindrical metal printing form covered with a thin chrome layer to ensure resistance and hardness to wear. During printing process, the cylinder rotates in an ink reservoir, and the excess amount of ink is wiped away by a doctor blade. Then, the ink remaining in the cavi-ties is transferred to the substrate under pressure created by an impression cylinder. Gravure inks may be solvent- or water-based or UV-curing. Their viscosities can vary in the range of 0.01–0.05 Pa.s [26, 31].

The advantage of the gravure method is highly resistant cylindrical form in comparison to flexography or offset printing. It can be useful when thin layers from low-viscosity inks containing a large amount of aggres-sive organic solvents are fabricated. However, gravure printing shows some limitations. The first one is relatively high pressure in the contact area and very rigid form surface which limit application of this method to flexi-ble substrates and which cause considerable difficulties when multilayer devices are manufactured. The other limitation is connected with observed deformation of printed pattern which varies depending on the position of printed elements relatively to the axis direction of the cylinder [31, 32].

Another advantage of gravure printing is its capability to be used for the mass production of printed electronics. Large cylinders are capable of


producing up to 2000 feet per minute, much more than it is possible to print with ink-jet which is suitable for a small production of printed devices. Furthermore, in gravure method, cavities are constantly refilled with an ink when the cylinder rotates what sustains long print runs and prevents against ink clogging. The latter is a common problem in ink-jet printing [33].

Apart from gravure, flexography can be used for the mass production of printed components. In the recent years, it is often assessed as the most promising roll-to-roll method suitable for printed electronics (initially, it was developed for packaging industry). In flexography method, a printing unit comprises anilox, cylinder holding a flexible printing form and print-ing cylinder which presses a substrate material against the form. Anilox roller is used to precisely supply a quantity of ink onto the print form [31].

The main drawback of flexography, as a potential technique for produc-tion of printed devices, is uneven printing (irregularity on the edges) which is caused by a structure of the thresholds between raster cavities. However, its advantage is capability to produce thin layers and to use a wide vari-ety of substrates, such as corrugated cardboard, paper, board, flexible and rigid polymers, glass, and metals. The ink viscosities can be in the range of 0.01–0.1 Pa.s, and the printed elements can have 10 μm in diameter and 20 μm in width [26, 31].

All above-described techniques belong to additive manufacturing processes. Currently, subtractive techniques are also very popular and used commonly in electronic industry, in particularly wet etching. In this method, liquid chemicals or etchants are utilized to remove unwanted metallic parts in the following steps: deposition of photoresist on the metal-lic surface, exposure of photoresist to UV light through a photomask protecting a desired pattern on the substrate and finally removing of unwanted metallic areas and photoresist layer [34].

During etching process, only a small part of material is used and the rest is either thrown away or recycled. Thus, a lot of waste materials and chemi-cals are created what makes etching technique environmental-unfriendly method.

Bearing in mind capability of printed electronics and its advantages against conventional electronics technologies, it may seem that possibi lity to fabricate different electronics components, devices, or even systems with printing techniques should revolutionize the modern electronic branch and contribute to its rapid development, i.e. in the field of low-cost, dispos-able consumer electronics. However, its further development is hindered by lack of materials or its limited availability or its high price.

In this chapter, recent advances in the field of composite materials used for manufacturing of printed electronics devices (mainly with using screen


printing and ink-jet printing) are discussed. These materials comprise differ-ent types of fillers, such as recently discovered graphene, carbon nanotubes (CNTs), graphite nanofibers (GNFs), silver nanopowder, or well-known and widely utilized in commercial application silver flakes. Properties of layers fabricated from these materials will be described, i.e. based on results obtained from scanning electron microscopy (SEM), atomic force micros-copy (AFM), and surface profilometry. Their thermal and mechanical dura-bility will also be discussed as it is crucial factor from practical point of view. Assuming that a device printed on flexible substrate, such as display, is considered it should be taken into account that it can undergo cyclic bending when is rolled up und then unrolled and it should withstand this type of exposure to be ready for commercialization. Moreover, this display should also exhibit high durability on thermal shocks because it may be used indoors and outdoors and temperature in these two zones can vary considerably, especially in countries with very hot and very cold climates.

1.2 Filler Materials

One of the most interesting filler materials developed in the recent years is graphene. For groundbreaking investigations of its properties, Andre Geim and Konstantin Novoselov from University of Manchester were awarded the Nobel Prize in physics in 2010. From that time graphene has been widely examined in almost every field of science and engineering. As a result, novel materials based on this type of filler are supposed to find application in optoelectronic and electronic devices, nanocomposites, energy storage, and authentication systems.

In general, graphene is an infinite two-dimensional layer built from sp2-bonded carbon atoms which are formed in a two-dimensional honey-comb lattice consisting of two interpenetrated triangular sub-lattices. The atoms of one sub-lattice are at the center of the triangles determined by the other with a C–C inter-atomic length of 1.42 Å. The unit cell consists of two carbon atoms and is unchanging at an angle of 120° around any atom. It is worth to mention that there are also other pseudo-two-dimensional sp2-hybridized carbon structures, such as bilayer and few-layer graphene. These pseudo-structures exhibit different properties than graphene or graphite [35].

Electrical properties of graphene depend on the number of layers. For few-layer graphene, there is a linear band where the number of layers is odd. When this number grows, the band structure is getting more complicated, i.e. valence and conduction bands overlap substantially and


numerous charge carrier appear [36, 37]. It was also reported [38] that electrical properties of multilayer graphene are strongly dependent on stacking order or disorder.

Electrical properties of graphene are also determined by mechanical stresses. During bending of 1 mm (in diameter) graphene, its resistance in the bent direction grows approximately one order of magnitude. Similar behavior was observed when graphene was stretched. Difference of one order of magnitude was noticed between resistance measured in perpen-dicular and in parallel to stretching direction [39]. When mechanical strength of an individual graphene sheet is concerned, it was reported in [40] that a breaking strength of this sheet is 200 times larger than of steel with a Young’s modulus of approximately 1 TPa.

Thermal properties of graphene were recently discussed in [41, 42]. According to data presented in the literature, a suspended graphene sheet could exhibit high thermal conductivity in the range of 4840–5300 W/m·K. It is noteworthy that these values are higher than for diamond (3320 W/m·K). Thus, graphene can find application in polymer composites with high thermal conduction as a filler material.

Another interesting filler material that has attracted attention of many research teams is CNT. The most often investigated are its two types: single-wall (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) [43]. The first type is an individual graphene sheet rolled into a tube and consisted of hexagonal rings of carbon atoms. Its diameter is equal to a few nanometers (typically about 1.4 nm), and length is even up to 105 μm. MWCNTs are composed of concentric graphene layers with a constant space of 0.34 nm between each layers. Their diameters are in the range of 10–200 nm, and lengths are up to hundreds of microns [44].

CNTs exhibit unusual properties, i.e. tensile strength – 45 billion Pa (high-strength steel alloys break at approximately 2 billion Pa), current carrying capacity – about 1 billion A/cm2 (copper wires are damaged at about 1 million A/cm2), field emission – phosphors activation at 1–3 V assuming that electrodes are spaced 1 μm apart (fields of 50–100 V/m are required for molybdenum tips), temperature stability – up to 750 °C in air and up to 2800 °C in vacuum (metal wires in microchips melt above 600 °C), and heat transmission – 6000 W/m·K (3320 W/m·K for nearly pure diamond) [45]. These unique properties of CNTs make them ideal candidate to be filler materials in polymer composites used to fabrication of antennas, transistors, sensors, and supercacitors [46–51].

In relation to printed electronics, high tensile strength of CNTs seems be one of the most important properties of CNTs. It can be expected that this property contributes to achieving high mechanical durability of layers


printed with polymer composites reinforced with CNTs. This issue will be discussed widely in the section.

It is also noteworthy that SWCNTs are found to be metallic or semicon-ducting depending on their atomic structure [52, 53]. Metallic SWCNTs can be used as electrodes or wires with nanometer size, in transparent conducting films and as interconnects for integrated circuits, whereas semiconducting SWCNTs have potential to find application as conduc-tive channels of field effect transistor with high ON/OFF ratios [54]. From practical point of view, it would be recommended to have uniform metallic or semiconducting CNTs. Unfortunately, current synthesis meth-ods cannot successfully produce uniform SWCNTs. It is a big challenge to perform post-synthetic separation of this type of CNTs. Some results of research efforts have been reported in this field, and some separation approaches were proposed with using different electric conductivity and dielectric constants as well as various chemical methods. Their complex review can be found in [55].

Similarly to graphene sheets, electrical properties of CNTs under influ-ence of mechanical deformation have been investigated theoretically and experimentally by several groups. Theoretical considerations showed that nanotube conductance was changing slightly under small bending angles. At larger bending exposure (about 45°), conductance of a metallic SWCNT decreased up to 10-fold what was attributed to development of some sp3 bonding characteristic at the bent in consequence of increased curvature under bending exposure [44, 56].

Electromechanical properties of CNTs were also studied in [57] with using AFM tip. It was revealed that nanotube conductance was lowered after AFM tip pushed this CNT down, but when the tip retracted conduc-tance changed to its initial value. The change in electrical properties of CNTs was caused entirely by mechanical deformation of the SWCNT.

Apart from electromechanical properties, thermal conductivity of CNTs was examined as well. As it was stated above, theoretical heat transmission of CNTs is about 6000 W/m·K, but it is still challenging to measure its exact value due to technological limitations connected with nanoscale dimen-sions of CNTs [58]. Furthermore, its value is dependent on many factors, such as diameter and length of CNTs, their atomic arrangement, number of structural defects, morphology, and presence of impurities. Influence of these factors on thermal properties of CNTs was discussed in [59]. Recent studies showed that thermal conductivity of a single SWCNT is above 2000 W/m·K and of a single MWCNT is about 3000 W/m·K [60, 61].

The third promising filler material is GNFs which are built from gra-phene layers oriented parallel, perpendicular, or skewly relative to the long


axis of the nanofiber [62]. In the literature, this carbon nanomaterial is divided into three types: platelet, ribbon, and herringbone. Their length is in order of nanometers, and their diameter is in the range of some tens of nanometers up to about 200 nm. In comparison CNTs, GNFs are similar in terms of electrical and mechanical properties, but at the same time their dimensions and graphite ordering is controlled well [63]. Their additional advantage compared to CNTs is much higher number active groups on outer walls and edge sites what constitutes them the ideal candidate for fabrication of bio- and electrochemical sensors [64]. GNFs are suitable for easy mass production, and thus, their price is much lower than for CNTs [65]. This shows their potential in elaboration of polymer composites with low unit price which can be reduced in some applications by the fact that GNFs have more microstructural defects than CNTs. In consequence, this can have impact on mechanical properties of layers printed with compos-ites reinforced with GNFs [66], but still mechanical and physical properties of GNFs (i.e. tensile strength – 3 GPa, Young’s modulus – 500 GPa, electri-cal conductivity – 103 S/cm, and thermal conductivity – 1900 W/m·K [67]) make them a promising filler material for advanced composites.

Mechanical properties of GNFs were also reported in [62]. Three different nanofibers were tested using nanoindentation. The obtained results revealed that their average hardness varied from 1.2 to 1.5 GPa, and average reduced elastic modulus was in the range of 88–97 GPa. In turn, thermal properties of GNFs were investigated in [68]. It was showed that thermal conductiv-ity in the axial, transverse in the crease direction, and transverse normal to the crease directions for a five-layer herringbone GNFs with a crease angle of 45° was computed to be equal to 27, 263, and 1500 W/m·K, respectively.

Aside from the above-described carbon nanofillers, there are also metal-lic filler materials useful for printed electronics. Among these filler materi-als, the most popular is silver which in the tested so far composites was in micro- or nanoscale depending on printing techniques used [69]. Silver is cheaper than gold, stable in high temperature, and it is melting in lower temperature compared to gold. Its main competitor is copper which exhib-its similar electrical properties, but copper has a tendency to oxidize in air what causes increase of its resistivity. Despite this obstacle, recently copper inks were also studied to be used in printed electronics (see Section 1.5.1).

Recently, wide attention has been attracted to silver nanoparticles, which finds application in inks utilized for fabrication of printed components with ink-jet. In [70], colloidal silver particles with a diameter of 20 and 100 nm were prepared by wet chemical synthesis and mixed with water to obtain ink for ink-jet-printing process of a cathode layer in OLEDs. SEM analysis revealed that in order to achieve high densely packed structure it is


recommended to use two different sizes of silver particles. Other investiga-tions presented in [71] concerned elaboration of silver nanopowder with a particle size varied from 5 to 55 nm suitable for application in thick-film paste for screen-printing technique. The printed layers with a thickness of 2–3 μm revealed to be dense and well sintered in 300 °C, exhibit good resistance to elevated temperatures and good adhesion to alumina, Kapton foil, glass, and silicon.

1.3 Conductive Polymers

Conductive polymers are an interesting group of materials which have been examined as promising materials for fabrication of many differ-ent devices. Three professors, Alan J. Heeger, Alan G. MacDiarmid, and Hideki Shirakawa were awarded the Nobel Prize in chemistry for 2000 for their discovery and development. Since that time, the mentioned polymers have been used in computer displays, fuel cells, microsurgical tools, and biomaterials [72].

Great advantage of conductive polymers is ability to merge positive properties of conventional polymers and metals (i.e. good electrical and optical properties, ability to conduct current) with ease of synthesis and flexibility in processing [73].

There are many different conductive polymers, such as polyani-line (PANI), polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3-hexylthiophene) (PTh), polyacetylene (PAc), poly (isothianaphthene) (PITN), poly(3-octylthiophnene-3- methylthiophene) (POTMT), and so on. Among them, the most often investigated is the poly(3,4- ethylenedioxythiophene) which demonstrates good chemical, electrical, and environmental stability and better thermal and electrical properties than polypyrrole [74]. Because PEDOT is insoluble in most solvents, poly(styrenesulfonate) (PSS) is used as counter ion and in effect PEDOT can be dispersed in water. Commercial dispersion of PEDOT:PSS, produced, e.g. by Agfa, are utilized as hole injection layer in organic devices due to good transparency, high work function, and high hole affinity [75].

It is worth to mention that it is possible to improve electrical properties of PEDOT:PSS by addition of solvents. The investigations reported in [75] revealed considerable increase in PEDOT:PSS conductivity by up to two or three order of magnitude after its mixing with glycerol, ethylene glycol (EG), dimethyl sulfoxide (DMSO), and sorbitol.

Another important conductive polymer is polyaniline, known as aniline black. It has different forms among which emaraldine is the most stable


and conductive. PANI is a low-cost, stable environmentally and easy to synthesize polymer, but at the same time its application is limited by its low processability, non-biodegradability, and lack of flexibility [76]. Despite these disadvantages, polyaniline has been successfully utilized, e.g. for fab-rication of sensors [77–79].

Good solubility in organic solvents, excellent electrical properties, and environmental stability can be achieved by using poly(3-hexylthio-phene) [80]. This polymer has been utilized in organic photovoltaics applications [81, 82].

In general, electrical conductivity of polymers is the result of electron hopping within and between polymer chains and, in fact, depends on a combination of many factors. The key factor is doping process which allows to convert conductivity of a pristine polymer from insulating to metallic. The conductivity increase is combined with growth of doping level. To induce an insulator–metal transition, p-type (electron accepting) and n-type (electron donating) dopants have been used [72]. Further analysis of conduction phenomenon in electronics polymer can be found in [83].

Thermal properties of conductive polymers were investigated in [84] on the example of polyaniline doped with different levels of camphor sul-fonic acids. It was found that its thermal conductivity is less dependent on the doping level than its electrical properties. The maximum thermal and electrical conductivities were achieved for the doping level of 60% inter-preted as the molar ratio of camphor sulfonic acid to phenyl-N repeat unit of PANI. Another studies concerned doping of PEDOT showed that light doping of this polymer causes much higher of its thermoelectric properties compared to the heavily doped PEDOT [85]. Moreover, it was revealed as well that thermal conductivity of PEDOT:PSS films is anisotropic. Its value in a trough-plane direction was estimated to 0.15 W/m·K and in an in-plane direction to 0.84 W/m·K [86].

1.4 Preparation of Electronics Materials for Printing

The above-described filler materials and conductive polymers can be used for preparation of electronics materials to be suitable for different print-ing techniques. To produce a paste or ink, it is usually necessary to mix a filler with a polymer matrix using some of these processes: grinding in mortar, treatment with sonotrode, sonication, centrifugation, stir and extrusion, ball milling, and three-roll-milling (calendaring). The detailed description of this method can be found in [87]. It was shown in [88] that despite ultrasonic energy provided by sonotrode causes breaking of


CNT agglomerates and it also destroys CNTs by cutting them into shorter segments.

However, during mixing a certain filler with a selected polymer matrix, a huge problem with achieving satisfied dispersion of the filler can appear. As it was stated in [89], CNTs tend to form agglomerates due to strong van der Waals’ forces. Similar phenomenon was reported for other carbon nanofillers because of their high surface energy resulting from nanoscale diameters and high aspect ratio [65, 90]. Some examples of SEM images presented inhomogeneous dispersion in polymer composites with CNTs and GNFs are presented in Figure 1.1.

Particle dispersion was discussed in [91] where it was reported that dis-persion degree is dependent on, e.g. size of filler particles and their size distribution. In order to obtain more homogeneous dispersion, many researchers proposed treatment of CNTs with EG, DMSO, 1-methyl-2-pyrrolidone (NMP), or dimethylformamide (DMF) [92, 93]. Ndiaye et al. [94] investigated comparatively influence of an organic solvent,

Figure 1.1 SEM images of CNTs (a) and GNFs (b) dispersed in a conductive polymer

PEDOT:PSS.

(a)

(b)


chloroform (CHCl3), and a surfactant, sodium dodecylbenzene sulfonate

(NaDDBs), on dispersion of SWCNTs. It was revealed that the surfactant debundled CNTs more effectively than the organic solvent. Influence of two kinds of surfactants (cationic and anionic) was discussed further in [90]. The cationic surfactants, such as octadecyl trimethylammonium bromide (OTAB), cetyltrimethylammonium chloride (CTAC), and cetyl-trimethylammonium bromide (CTAB), introduce a positive charge on CNTs and help preventing flocculation. On the other hand, the anionic surfactants, such as nafion, introduce a negative charge to CNTs. In this way, the positively charged metal ions are repelled what also facilitate to receive layers with uniform dispersion of CNTs [88].

Many investigations have been performed on a method to break agglo-merates of carbon nanofibers. In order to achieve homogeneous disper-sion of GNFs, it was proposed to combine mechanical mixing with sonication and diluting a polymer matrix with solvents [95, 96]. As it was stated in [97], the most widely utilized dispersion method for GNFs is melt mixing because of its simplicity, availability, and low price. In this method, high shear force needs to be used, and in consequence, the aspect ratio of GNFs is reduced during the mixing process what deteriorates some properties of this filler material. Therefore, it is a big challenge to elaborate the melt mixing method with the use of relatively low shear mixing.

When thermosetting polymers are mixed with GNFs, a solution approach combined with sonication can be used. In this process, GNFs are dispersed in a liquid epoxy with using sonication before a hardener is added to the mixture. To improve effectiveness of sonication process, acetone or other solutions are usually utilized. Moreover, to prevent from temperature increase during the sonication step, external cooling should be provided [97].

In terms of graphene, its dispersion was investigated in aqueous solutions with addition of different surfactants [98, 99] or in epoxy resin [100, 101]. In [98], cationic (tetradecyltrimethylammonium bromide – CTAB), anionic (sodium dodecyl sulfate – SDS), non-ionic (polyoxy ethylene (40) nonylphenylether – CO890), and polymer (polycarboxylate – H14N) sur-factants at various concentrations were tested. The best dispersion was achieved by using the non-ionic surfactant at a concentration of about 200–300 ppm. When epoxy resin was used [100], it was revealed that dis-persion techniques have impact on structural properties of graphene and cause defects in its particles. Sonication resulted in higher residual stresses in a prepared composite compared to other methods used and in wrinkled graphene sheets, whereas three-roll-milling separated stacked nanoplate-lets and entailed extension of graphene sheets. Thus, it was concluded

advanced composite materials · 2016-09-19 · 3.6 some important advanced ceramics 121 3.6.1...

Documents