Preface

Plasma as the fourth state of matter differs from solid, liquid, and gaseous states and is an ionized gas consisting of both negative and positive ions, electrons, neutral atoms, radicals, and ultraviolet photons. Plasma plays a crucial role in a wide variety of applications in material processing, environmental control, semiconductor manufacturing, biomedicine, green energy, and many more. Generally, plasma can be divided into two categories, namely low-pressure and atmosphericpressure plasma. Compared to low-pressure plasma, atmospheric-pressure plasma overcomes the drawbacks associated with vacuum, which makes it the most sought-after plasma process in industrial applications. Over the last few decades, atmospheric-pressure plasmas have started to attract increasing attention from both scientists and industry due to a variety of potential applications. Because of increasing interest in this topic, the focus of this book is on providing engineers and scientists with a fundamental understanding of the physical and chemical properties of different atmospheric-pressure plasmas via plasma diagnostic techniques and their applications.

The book has been organized into two parts. Part I focuses on the latest achievements in advanced diagnostics of different atmospheric-pressure plasmas and contains three chapters. Chapter 1 introduces advanced optical diagnostics to visualize the physical and chemical properties of atmospheric-pressure plasmas. Optical diagnostic techniques include optical emission spectroscopy, Schlieren imaging or shadowgraph, and invasive methods of active laser spectroscopy, including laser-induced fluorescence, laser or broadband absorption, cavity ring-down spectroscopy, and laser scattering. Chapter 2 not only reviews electrical diagnostic techniques to measure charge-voltage signals of atmospheric-pressure dielectric barrier discharges (DBD) but also provides information at length on the interpretation of charge-voltage diagram results from different practical cases. It is a great reference for those who work on charge-voltage measurement techniques to understand or solve the problems they encounter. Chapter 3 is focused on the development of a model for charge accumulation on the surface of epoxy materials, which is an important problem in the development of insulators for high-voltage applications and electrical power transmission lines.

Part II from Chapter 4 to Chapter 6 focuses on the applications of different atmospheric-pressure plasmas and the measurement of plasma properties, which are of key importance for plasma applications, including the use of plasma in the biomedical field. Chapter 4 demonstrates the various applications of DBD microplasma from indoor air purification and skin treatment for drug delivery, to particle removal and the plasma actuator for flow control, while Chapter 5 reviews atmospheric/thermal-plasma spray processes and their applications in the formation of nanostructure coatings. Chapter 6 discusses diverse chemical approaches to detect reactive oxygen and nitrogen species induced in aqueous media by atmosphericpressure plasma in regard to the biomedical application of plasmas.

We hope that with this book the readers will be introduced to the exciting world of plasma applications and plasma diagnostics, where numerous discoveries for both fundamental and applied science are foreseen for future studies.

#### **Dr. Anton Nikiforov**

Department of Applied Physics, Ghent University, Belgium

#### **Dr. Zhiqiang Chen**

Section 1

Plasma Diagnosctics

1

Institute for Frontier Materials, Deakin University, Australia Section 1
