Esta dissertação aborda fundamentalmente a formação de eletretos de Teflon FEP em múltiplas camadas com carregamento por descargas impulsivas de alta tensão. Devido a suas excelentes qualidades piezoelétricas, eles serão destinados a sensores de pressão em múltiplas aplicações. Este tipo de eletreto foi escolhido por se utilizar materiais com grande disponibilidade no mercado e de custo bastante reduzido. O processo de carregamento por altas tensões impulsivas também foi escolhido devido à sua simplicidade, segurança e tempo reduzido. Para se obter maior valor de constantes piezoelétricas foi utilizado o processo de formação de eletretos por multicamadas, e a metodologia empregada utiliza verniz tanto na união das folhas de Teflon FEP quanto na junção dos eletrodos de alumínio. Dessa forma, microbolhas de ar são criadas entre os materiais, que carregadas eletricamente, formando o eletreto. Com tal artifício, é possível obter coeficientes piezoelétricos d33 elevados sem o uso de materiais de alta tecnologia ou de restrita tecnologia. O método de obtenção do eletreto apresenta um custo extremamente reduzido - pelo emprego de materiais simples e de fácil obtenção - e a diversidade de possibilidades de aplicações, o que torna o método bastante atraente, podendo, ainda, tornar o país independente de tecnologia importada. / This dissertation approaches fundamentally the formation of electrets of Teflon FEP in multiple layers by impulsive discharges. Due to their excellent piezoelectric qualities, they will be destined to sensors of pressure in multiple applications. This electret type was chosen due to its easiness of obtaining, by using low-cost common materials easily found in the market. The process of loading by high impulsive tensions was chosen due to its simplicity, safety and reduced necessary time. To reach higher values of piezoelectrics constant the process of electrets formation in multilayers was used, and the methodology employed varnish in the union of both FEP Teflon films and aluminum electrodes. In this way, micro bulbs of air is created among the materials, which were later loaded electrically, forming the electret. With such artifice, it is possible to obtain high piezoelectrics d33 coefficients without using materials of high or restricted technology. The simplicity of the method of electret obtaining, the extremely reduced cost - by the use of simple and easy - of - obtaining materials - and the diversity of application possibilities, make the method quite attractive. By using such method, the country may even become independent of imported technology.

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Du, Xiaona. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 65-74). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.iii / ACKNOWLEDGEMENTS --- p.iii / TABLE OF CONTENTS --- p.iv / LIST OF FIGURES --- p.xi / LIST OF TABLES --- p.ix / Chapter CHAPTER ONE --- INTRODUCTION --- p.1 / Chapter 1.1 --- Background --- p.2 / Chapter 1.1.1 --- Development of portable devices --- p.2 / Chapter 1.1.2 --- Energy harvesting --- p.2 / Chapter 1.1.3 --- Piezoelectric energy harvesting --- p.5 / Chapter 1.1.4 --- Impact based piezoelectric energy harvester --- p.10 / Chapter 1.1.5 --- Operation of piezoelectric materials --- p.14 / Chapter 1.2 --- Research Objective --- p.16 / Chapter 1.3 --- Thesis Organization --- p.19 / Chapter CHAPTER TWO --- DESIGN AND MODELING OF AN EXTENDED ROTARY ENERGY HARVESTER --- p.20 / Chapter 2.1 --- Design Considerations of an Extended Rotary Energy Harvester --- p.20 / Chapter 2.2 --- Models of Rotary Energy Harvesters --- p.24 / Chapter 2.3 --- Simulation Results --- p.33 / Chapter 2.4 --- Chapter Summary --- p.37 / Chapter CHAPTER THREE --- "PROTOTYPE, TESTING AND OUTPUT POWER OF EXTENDED ROTARY ENERGY HARVESTER" --- p.38 / Chapter 3.1 --- Prototype and Experiment --- p.38 / Chapter 3.2 --- Output Power --- p.44 / Chapter 3.2.1 --- Maximum tip displacement on output power --- p.44 / Chapter 3.2.2 --- Rotational frequency on output power --- p.47 / Chapter 3.3 --- Chapter Summary --- p.50 / Chapter CHAPTER FOUR --- COMPARISON BETWEEN E-REH AND REH --- p.51 / Chapter 4.1 --- Force on Output Power --- p.52 / Chapter 4.2 --- Rotational Frequency on Output Power --- p.54 / Chapter 4.3 --- Comparison on Design Space --- p.59 / Chapter 4.4 --- Chapter Summary --- p.62 / Chapter CHAPTER FIVE --- CONCLUSION AND FUTURE WORK --- p.63 / Chapter 5.1 --- Conclusion --- p.63 / Chapter 5.2 --- Future Work --- p.64 / BIBLIOGRAPHY --- p.65

In this thesis, a new model is formulated for a piezoelectric membrane and fluid motion in a microchannel heat engine. A new slug flow model is developed for droplet motion in a circular cross-section channel. The model includes friction, pressure, viscous and thermocapillary forces on the droplet. This thesis examines the concept of a piezoelectric device at one end of the channel to generate electricity from thermocapillary pumping of the droplet within the microchannel. The slug flow model is used to predict the flow energy needed to convert the thermocapillary pumping into electrical energy. A thin membrane design of a piezoelectric device is developed and modelled with the slug flow approximation. The deformation of the piezoelectric membrane is analyzed. The deformation is found to be a function of the air pressure in the closed microchannel and the displacement of the droplet along the microchannel. This was formulated based on the bending of a thin plate (representing the membrane). The displacement relates to the final output voltage of the design. The direct piezoelectric effect was also examined to determine a relationship between the output voltage and induced stress on the membrane by the force of air. Results are presented for a micro heat engine configuration containing a single membrane on one side of the droplet. It was found that the deformation of the membrane and the output voltage were directly proportional to the displacement of the droplet. A relatively small output voltage was gained from a complete cycle of the droplet. A sensitivity study was performed by varying the channel dimensions along with the dimensions of the piezoelectric membrane. The coupling factor of the piezoelectric membrane was varied to examine its effect on the output voltage. It was found that a larger channel and thinner membrane resulted in a larger output voltage. Materials with a large piezoelectric constant were found to have the largest output voltage, as opposed to those with a lower dielectric constant. / UOIT

Thesis (M.S.)--Ohio University, November, 1999. / Title from PDF t.p.

Thesis (Ph. D.)--Washington State University, May 2009. / Title from PDF title page (viewed on Apr. 2, 2009). "School of Mechanical and Materials Engineering." Includes bibliographical references.

Thesis (M.S. in Materials Science and Engineering)--Washington State University. / Includes bibliographical references.

Thesis (M.S.)--School of Materials Science and Engineering, Georgia Institute of Technology, 2005. Directed by Robert Snyder. / Shrout, Thomas, Committee Member ; Snyder, Robert, Committee Member ; Speyer, Robert, Committee Chair. Includes bibliographical references.