Functional and Smart Materials

Chander Prakash, Sunpreet Singh, J. Paulo Davim, Chander Prakash, Sunpreet Singh, J. Paulo Davim

• Publisher: CRC Press
• Year: 2020
• Print ISBN: 9780367275105
• eBook ISBN: 9781000193275
• Topic: Technology & Engineering
• Subtopic: Mechanics
• Index: Technology & Engineering

This book presents a comprehensive and broad-spectrum picture of the state-of-the-art research, development, and commercial prospective of various discoveries conducted in the real world of functional and smart materials.

This book presents various synthesis and fabrication routes of function and smart materials for universal applications such as material science, mechanical engineering, manufacturing, metrology, nanotechnology, physics, biology, chemistry, civil engineering, and food science. The content of this book opens various scientific horizons proved to be beneficial for uplifting the standards of day-to-day practices in the biomedical domain. Myriad innovations in the materials science and engineering are transforming our
everyday lives in extraordinary ways.

This book captures the emerging areas of materials science and advanced manufacturing engineering and presents recent trends in research for researchers, field engineers, and academic professionals.

1 Electrochromics for Smart Windows

Oxide-Based Thin Films

A. Henni

Kasdi Merbah University

Y. Bouznit

Université de Jijel

D. Zerrouki and D. Selloum

Kasdi Merbah University

CONTENTS

1.1 Introduction

1.2 The Energy Efficiency of Chromogenic Fenestration

1.3 History and Applications

1.4 Operating Principles and Materials

1.4.1 Transparent Conductive Electrodes

1.4.2 Electrolyte

1.4.3 Electrochromic Layer

1.5 Electrochromic Oxide Films

1.5.1 Anodic Coloured Material: NiO As Reference

1.5.2 Cathodic Coloured Material: WO₃ As Reference

1.6 Conclusions

References

1.1 Introduction

The first civilizations were built using natural materials: wood, stone, leather, bone, horn, linen or hemp. Recently, an emergence of plastics and composites has been observed in the building, automotive, aeronautic, sport and military sectors. But gradually, researchers and engineers have had to use materials with their own functions. Nanotechnology has modified the landscape of energy generation, energy storage and energy saving devices. Architectural fenestration can extensively benefit from green nanotechnologies. Therefore, our habitat will have to evolve technologically, and this will undoubtedly pass through the use of high-tech windows, called smart, also called “smart windows”. These smart windows have the ability to block the heat waves induced by infrared radiation from the sun, and therefore, limit the use of air-conditioning systems while continuing to contribute to the well-being of people working or residing in these buildings.

Amongst them, smart windows are able to control the throughput of visible light and solar radiation into buildings and can impart energy efficiency as well as human comfort by having different transmittance levels depending on dynamic needs. Under the action of a voltage or an electric current, the ECs materials can change their properties. They can be integrated in devices that modulate their transmittance, reflectance, absorptance or emittance. Thus, the electrochromic (EC) phenomenon refers to the formation of a new optical absorption band by the redox process and therefore colour changes in materials. As the redox reaction is reversible, by removing the electric field, the colour of the material will return to the ground state. Electrochromism is known to exist in many types of materials. This chapter deals with devices based on EC metal oxides. There are several promising EC materials such as V₂O₅, [1,2], NiO [3,4] and WO₃ [5,6], which are considered as inorganic or oxide EC material while polyaniline [7] and viologens [8] are common polymer and organic EC materials. The EC phenomenon appears particularly intense by the metal oxides. Of all oxide-based materials, WO₃ has quick response time, high coloration efficiency and long life.

Smart windows are currently used in a growing number of buildings in which some windows are fully colored and others transparent. We note that electrochromism being to the “green” nanotechnologies that are very much in focus today [9].

In this chapter, we will recall a general description of intelligent materials and the different classes. We then describe EC materials in detail, such as their history, interesting properties and some applications of these materials. Also, this chapter discusses oxide-based EC smart windows with emphasis on recent work related to thin films.

1.2 The Energy Efficiency of Chromogenic Fenestration

We start by looking at the world’s population and its interrelationship to our common environment. The population has increased from approximately one billion in 1800 to seven billion in 2019. The result of this evolution is that the strains on the global resources are growing steeply and that there is an unsustainable demand on the resources of all kinds: energy, water, minerals, etc. The large use of fossil fuels generates a large amount of CO₂ by causing the global surface temperature by the greenhouse effect. For this, we try to use the technological power for ecological purposes in order to reduce energy consumption. Since most people spend their time inside buildings, a large portion of energy is consumed inside our buildings to ensure our comfort. Indeed, the energy between 30% and 40% [10] is provided to satisfy our needs in air conditioning, heating, ventilation, etc. It is therefore not surprising that the architectural trend converges towards building design with a growing proportion of windows.

However, from a purely energetic point of view, we find the so-called low-emissivity windows (low-e windows): thin enough to maintain optical transparency; in addition, they are thermal insulators and they block a large part of the infrared electromagnetic radiation. However, this static technology is not adequate for the winter if one wants to take advantage of the solar radiation to warm the house.

In this sense, chromogenic materials (materials that modify their optical properties as a result of an external stimulus) are more promising for use as smart windows. These materials include thermochromic materials that are temperature-activated; photochromic materials that are widely used for ophthalmic lenses that opacify due to exposure to ultraviolet light; and EC materials that stain in the face of electrical current.

The technologies based on other thermochromic and photochromic materials do not offer as much flexibility for the user and depend on the external environment and thus offer no control. For example, being sensitive to UV rays, photochromic materials stain in cloudy weather and staining, and discoloration times are affected by ambient temperature.

On the other hand, the use of EC materials is based on the application of a small potential difference necessary to modulate the colouring state of a smart window, and only a reverse voltage is required to return to the degree of transparency. Thus, a power requirement is minimal for their operation. Moreover, we find that some devices using photovoltaic cells [11]. As clearly shown in Figure 1.1, it is found that the EC materials are the most advantageous since they offer a high modulation both in the visible and in the near IR, thus reducing energy costs in lighting, heating and air conditioning. This technology is also suggested for other applications such as the opening roofs of luxury cars or the portholes...

Table of contents

• Cover
• Half Title
• Series Page
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Editors
• Contributors
• Chapter 1 Electrochromics for Smart Windows: Oxide-Based Thin Films
• Chapter 2 Polymeric Biomaterials in Tissue Engineering
• Chapter 3 Amorphous Semiconductors: Past, Present, and Future
• Chapter 4 Promise of Self-lubricating Aluminum-Based Composite Material
• Chapter 5 Energy Materials and Energy Harvesting
• Chapter 6 Advanced Processing of Superalloys for Aerospace Industries
• Chapter 7 Review on Rheological Behavior of Aluminum Alloys in Semi-Solid State
• Chapter 8 Bio-Nanomaterials: An Inevitable Contender in Tissue Engineering
• Chapter 9 Biomaterials
• Chapter 10 Characterisation and Optimisation of TiO2/CuO Nanocomposite for Effective Dye Degradation from Water under Simulated Solar Irradiation
• Chapter 11 Dual Applicability of Hexagonal Pyramid-Shaped Nitrogen-Doped ZnO Composites As an Efficient Photocatalyst
• Index