Self-Cleaning Materials and Surfaces E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 635

Veröffentlichungsjahr: 2013

Beschreibung

With increasing demand for hygienic, self-disinfecting and contamination free surfaces, interest in developing self-cleaning protective materials and surfaces has grown rapidly in recent times.  This new title comprises of invited chapters from renowned researchers in the area of self-cleaning nano-coatings and the result is a comprehensive review of current research on both hydrophobic and hydrophilic (photocatalytic effect) self-cleaning materials. 

Leseprobe

Contents

Cover

Title Page

Copyright

List of Contributors

Preface

Part I: Concepts of Self-Cleaning Surfaces

Chapter 1: Superhydrophobicity and Self-Cleaning

1.1 Superhydrophobicity

1.2 Self-Cleaning on Superhydrophobic Surfaces

1.3 Materials and Fabrication

1.4 Future Perspectives

References

Part II: Applications of Self-Cleaning Surfaces

Chapter 2: Recent Development on Self-Cleaning Cementitious Coatings

2.1 Introduction

2.2 Atmospheric Pollution: Substances and Laws

2.3 Heterogeneous Photocatalysis

2.4 Self-Cleaning Surfaces

2.5 Main Applications

2.6 Test Methods

2.7 Future Developments

References

Chapter 3: Recent Progress on Self-Cleaning Glasses and Integration with Other Functions

3.1 Introduction

3.2 Theoretical Fundamentals for Self-Cleaning Glasses

3.3 Self-Cleaning Glasses Based on Photocatalysis and Photoinduced Hydrophilicity

3.4 Inorganic Hydrophobic Self-Cleaning Glasses

3.5 Self-Cleaning Glasses Modified by Organic Molecules

3.6 The Functionality of Self-Cleaning Glasses

References

Chapter 4: Self-Cleaning Surface of Clay Roofing Tiles

4.1 Clay Roofing Tiles and Their Deterioration Phenomena

4.2 Protective and Self-Cleaning Materials for Clay Roofing Tiles

References

Chapter 5: Self-Cleaning Fibers and Fabrics*

5.1 Introduction

5.2 Photocatalysis

5.3 Photocatalytic Self-Cleaning Surface Functionalization of Fibrous Materials

5.4 Application of Photocatalytic Self-Cleaning Fibers

5.5 Limitations

5.6 Future Prospects

5.7 Conclusions

References

Chapter 6: Self-Cleaning Materials for Plastic and Plastic-Containing Substrates

6.1 Introduction

6.2 TiO2 Thin Films on Polymers: Sol–Gel-Based Wet Coating Techniques

6.3 TiO2–Polymer Nanocomposites Review: Casting (Mixing) Techniques

6.4 TiO2 Sputter-Coated Films on Polymer Substrates

6.5 TiO2 Thin Films on PET and PMMA by Nanoparticle Deposition Systems (NPDS)

6.6 Photo-Responsive Discharging Effect of Static Electricity on TiO2-Coated Plastic Films

6.7 Recent Achievements

Acknowledgements

References

Part III: Advances in Self-Cleaning Surfaces

Chapter 7: Self-Cleaning Textiles Modified by TiO2 and Bactericide Textiles Modified by Ag and Cu

7.1 Introduction

7.2 Self-Cleaning Textiles: RF-Plasma Pretreatment to Increase the Binding of TiO2

7.3 Self-Cleaning Mechanism for Colorless and Colored Stains on Textiles

7.4 Self-Cleaning Textiles: Vacuum-UVC Pretreatment to Increase the Binding of TiO2

7.5 XPS to Follow Stain Discoloration on Cotton Modified with TiO2 and Characterization of the TiO2 Coating

7.6 Bactericide /Ag/Textiles Prepared by Pretreatment with Vacuum-UVC

7.7 DC-Magnetron Sputtering of Textiles with Ag Inactivating Airborne Bacteria

7.8 Inactivation of E. coli by CuO in Suspension in the Dark and Under Visible Light

7.9 Inactivation of E. coli by Pretreated Cotton Textiles Modified with Cu/CuO at the Solid/Air Interface

7.10 Direct Current Magnetron Sputtering (DC and DCP) of Nanoparticulate Continuous Cu-Coatings on Cotton Textile Inducing Bacterial Inactivation in the Dark and Under Light Irradiation

7.11 Future Trends

References

Chapter 8: Liquid Flame Spray as a Means to Achieve Nanoscale Coatings with Easy-to-Clean Properties

8.1 Gas-Phase Synthesis of Nanoparticles

8.2 Aerosol Reactors

8.3 Liquid Flame Spray

8.4 Liquid Flame Spray in Synthesis of Easy-to-Clean Antimicrobial Coatings

8.5 Summary

References

Chapter 9: Pulsed Laser Deposition of Surfaces with Tunable Wettability

9.1 Introduction

9.2 Basic Theory of Wetting Properties of Surfaces

9.3 Roughening a Flat Surface

9.4 Switchable Wettability

9.5 Concluding Remarks

References

Chapter 10: Fabrication of Antireflective Self-Cleaning Surfaces Using Layer-by-Layer Assembly Techniques

10.1 Introduction

10.2 Antireflective Coatings

10.3 Solution-Based Layer-by-Layer (LbL) Assembly Techniques

10.4 Mechanisms of Self-Cleaning

10.5 Fabrication of Antireflective Self-Cleaning Surfaces Using Electrostatic Layer-by-Layer (ELbL) Assembly of Nanoparticles

10.6 Fabrication of Superhydrophobic Self-Cleaning Surfaces Using LB Assembly of Micro-/Nanoparticles

10.7 Characterization of As-Fabricated Surfaces

10.8 Challenges and Future Development

10.9 Conclusion

References

Part IV: Potential Hazards and Limitations of Self-Cleaning Surfaces

Chapter 11: The Environmental Impact of a Nanoparticle-Based Reduced Need of Cleaning Product and the Limitation Thereof

11.1 Introduction

11.2 Titania and Amorphous Silica Nanoparticles and Carbon Nanotubes Can Be Hazardous and May Pose a Risk

11.3 Environmental Impact of a Reduced Need of Cleaning Product

11.4 Limiting the Direct Environmental Impact of a Nanoparticle-Based Reduced Need of Cleaning Product, Including Limitation of Risks Following from Exposure to Nanoparticles

11.5 Conclusion

References

Index

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Library of Congress Cataloging-in-Publication Data

Self-cleaning materials and surfaces : a nanotechnology approach / edited by Walid A. Daoud.   pages cm  Includes bibliographical references and index.  ISBN 978-1-119-99177-9 (cloth) 1. Coatings. 2. Surface active agents. 3. Materials–Cleaning. 4. Nanostructured materials. I. Daoud, Walid A.  TA418.9.C57S45 2013  667'.9–dc23

2013016955

A catalogue record for this book is available from the British Library.

ISBN: 9781119991779

List of Contributors

Mikko Aromaa, Aerosol Physics Laboratory, Department of Physics, Tampere University of Technology, Finland

Walid A. Daoud, School of Energy and Environment, City University of Hong Kong, Hong Kong

Daniele Enea, Department of Architecture, University of Palermo, Italy

John Kiwi, Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland

Baoshun Liu, State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, PR China and School of Material Science and Engineering, Wuhan University of Technology, PR China

Jyrki M. Mäkelä, Aerosol Physics Laboratory, Department of Physics, Tampere University of Technology, Finland

Evie L. Papadopoulou, Institute of Electronic Structures and Lasers, Foundation for Research and Technology-Hellas, Greece. Current address: Istituto Italiano di Tecnologia, Genova, Italy

Joe A. Pimenoff, Beneq Oy, Vantaa, Finland

Cesar Pulgarin, Institute of Chemical Sciences and Engineering, Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland

Miroslava Radeka, Faculty of Technical Sciences, University of Novi Sad, Serbia

Jonjaua Ranogajec, Faculty of Technology, University of Novi Sad, Serbia

L. Reijnders, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, The Netherlands

Paul Roach, Institute for Science and Technology in Medicine, Guy Hilton Research Centre, Keele University, UK

Neil Shirtcliffe, Faculty of Technology and Bionics, Hochschule Rhein-Waal, Germany

Wing Sze Tung, School of Applied Sciences and Engineering, Monash University, Australia

Houman Yaghoubi, Department of Mechanical Engineering/Department of Electrical Engineering, University of South Florida, USA

Yu-Min Yang, Department of Chemical Engineering, National Cheng Kung University, Taiwan

Qingnan Zhao, State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, PR China

Xiujian Zhao, State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, PR China

Preface

With increasing demand for hygienic, self-disinfecting, and contamination-free surfaces, interest in developing efficient self-cleaning, protective surfaces and materials has grown. Due to rising population density, the spreading of antibiotic-resistant pathogens remains a growing global concern. The ability of microorganisms to survive on environmental surfaces makes infection transmission a critical issue, and studies have shown that some infectious bacteria can survive on the surface of various polymeric and textile materials for more than 90 days. Self-cleaning surfaces not only provide protection against infectious diseases but also against odor, staining, deterioration and allergies. Advances in nanotechnologies could make dirt-free (or no-wash) surfaces a reality. This would improve the environment through reduced use of water, energy and petroleum-derived detergents.

Having been an active researcher in self-cleaning nanotechnology since 2002, witnessing a rapidly growing interest in the field of self-cleaning coatings, surfaces and materials from the media, industry, and academia, I felt a compelling need for a book that describes the recent developments and provides a timely account of this topic.

Following an invitation from Wiley, I have approached fellow researchers from across the globe, renowned experts in the field, to contribute to this book with their fascinating achievements covering all areas from the basic and fundamental knowledge of the concepts, potential applications, and recent and future development of self-cleaning nanotechnologies, to their potential hazards and environmental impact.

The book is divided into four parts, starting with the general concepts of self-cleaning mechanisms covering both hydrophobic and hydrophilic surfaces. This is followed by specific applications of self-cleaning surfaces and coatings, such as cementitious materials, glasses, clay roof tiles, textiles and plastics. The third part describes recent achievements in self-cleaning surfaces, using advanced materials and technologies, such as liquid flame spray, pulsed laser deposition, and layer-by-layer assembly. In the last part, the potential hazards, environmental impact, and limitations of self-cleaning surfaces are discussed toward further development.

Many aspects of this book can be used for general public education, further research and development, as well as in the curriculum development of courses in the areas of materials science and engineering, nanotechnology, and textile finishing.

I would like to take this opportunity to express my sincere gratitude to all the authors, my PhD student, Dr Wing Sze Tung, and my research assistant, Ms Stephanie Kung. Special thanks are also due to Wiley editorial staff, Ms Emma Strickland, Ms Sarah Tilley, and the editing team.

Walid A. Daoud

Part I

Concepts of Self-Cleaning Surfaces

1

Superhydrophobicity and Self-Cleaning

Paul Roach1 and Neil Shirtcliffe2

1 Institute for Science and Technology in Medicine, Guy Hilton Research Centre, Keele University, UK

2 Faculty of Technology and Bionics, Hochschule Rhein-Waal, Germany

One of the ways that surfaces can be self-cleaning is by repelling water so effectively that water-borne contaminants cannot attach – by being superhydrophobic. This is demonstrated particularly well by the Indian Lotus, Nelumbo nucifera, which has leaves that remain clean in muddy water. The leaves can be cleaned of most things by drops of water, an effect that has been patented and used in technical systems [1].

1.1 Superhydrophobicity

1.1.1 Introducing Superhydrophobicity

Superhydrophobicity is where a surface repels water more effectively than any flat surface, including one of PTFE (Teflon®). This is possible if the surface of a hydrophobic solid is roughened; the liquid/solid interfacial area is increased and the surface energy cost increases. If the roughness is made very large, water drops bounce off the surface and it can become self-cleaning when it is periodically wetted. To understand more about this type of self-cleaning it is necessary to consider how normal surfaces become wetted and become dirty. The effect has been a focus of much recent research and has been reviewed recently [2–7]. A good mathematical explanation can be found in a recent book chapter by Extrand [8].

1.1.2 Contact Angles and Wetting

When a liquid rests on a surface the “contact angle” is measured through the droplet between the solid/liquid and liquid/air interfaces. The equilibrium angle that forms is known as Young's angle after a theory proposed by Young, but not actually formulated in his work [9]. Young's equation can be considered as a force balance of lateral forces on a contact line. In a perfect system the contact line cannot sustain any lateral force, so will always move to a position where the forces balance. This is achieved mathematically by taking the components of each force in the plane of the surface, at right angles to the contact line, as shown in Figure 1.1.

(1.1)

where is the interfacial tension and the subscripts refer to solid, liquid and gas, for example, is the interfacial tension between solid and liquid.

Figure 1.1 Cross-section of a drop on a flat surface with the contact angle θ. Contact angles also form at the edge of larger pools of water, in tubes, at bubbles on underwater surfaces and any other configuration where a liquid interface meets a solid.

Young's equation can also be derived from the surface and interfacial energies and their changes. The contact angle is an important measure of the interaction between the three phases, one solid, a liquid and another fluid, which may be a liquid or a gas. For small drops on a flat surface the drops form spherical caps, spheres intersecting the surface. External factors, such as electric fields, may also influence the drop shape, with gravity playing a role in distorting larger droplets. At the contact line the angle tends to the Young angle except when the contact line is moving relatively rapidly. In most systems there is a certain uncertainty in contact angle known as contact angle hysteresis.

1.1.3 Contact Angle Hysteresis

In practice the equilibrium angle is often difficult to measure because there are a small range of angles on every surface that are stable. These are often described as local energy minima close to the global energy minimum. In practice the contact line therefore often behaves as though it were fixed over a small range of angles close to the equilibrium angle [10]. Traditionally, the equilibrium contact angle was approached by vibrating the surface to supply the energy for the drop to escape the local minima. Although the static angle can vary, the contact line begins to move at a certain angle when the liquid front is advanced and at a different angle when it recedes. These values are simpler to measure so it is often the greatest stable angle and the lowest stable angle that are measured, known as the advancing and receding angles. The angles commonly quoted are those measured at a very low speed as the measured angles are affected by the speed of motion of the contact line. This is usually carried out by injecting liquid slowly into a drop and removing it again. Often the advancing and receding angles are of more practical use than the equilibrium angle, although the equilibrium value can be used to derive surface energies. It is sometimes possible to determine the equilibrium angle if both advancing and receding angles are measured. This still assumes that hysteresis is not very large and the surface is reasonably flat [11].

The difference between the advancing and receding angles, or rather the difference between the cosines of the angles governs whether liquids will stick to a surface or slide or fall off. A drop on a vertical sheet can have the advancing angle at the bottom and the receding angle at the top without moving (Figure 1.2). Surfaces with low hysteresis allow drops to slide over them whatever the equilibrium contact angle. The energy required for a drop to move can be calculated as [12],

(1.2)

where r is the base radius of the drop. The contact angle itself enters the equation in two ways: first the cosine function enhances differences near 90°; secondly the value of the contact radius r, for a given volume depends upon the contact angle.

Figure 1.2 A drop on a vertical surface sliding slowly with advancing angle at the front and receding angle at the back, in practice geometrical factors and speed of movement will change the angles away from the actual advancing and receding angles.