Advanced Thermoelectric Materials for Energy Harvesting Applications

Electrical energy consumption is negatively affecting our environment and contributing to climate change. Therefore the research and industrial communities are working hard to minimize energy consumption using promising energy-efficient and renewable energy technologies. We know that it is possible to convert heat energy into electrical energy using thermoelectric devices; this heat energy can be from the sun or from an electro-mechanical device. However, thermoelectric devices traditionally suffer from lower efficiencies of energy conversion. This book, Advanced Thermoelectric Materials for Energy Harvesting Applications, is a researchintensive textbook consisting of eight chapters organized into three sections. Section 1 consists of Chapters 2, 3, and 4, which cover advanced thermoelectric materials and the topics of organic/inorganic thermoelectric materials, quantum theory of the Seebeck coefficient for the advancement of thermoelectric superconducting material, and the limits of Bismuth Telluride-based thermoelectric materials. Section 2, containing Chapters 5 and 6, evaluates behaviors and performance of thermoelectric devices. Section 3, containing Chapters 7 and 8, focuses on energy harvesting applications of thermoelectric devices. This book will be of interest to a wide range of individuals, such as scientists, engineers, researchers, and undergraduate and postgraduate students in the field of advanced thermoelectric materials

DESIGN OF SMART SENSORS FOR DETECTION OF PHYSICAL QUANTITIES

Microsystems and integrated smart sensors represent a flourishing business thanks to the manifold benefits of these devices with respect to their respective macroscopic counterparts. Miniaturization to micrometric scale is a turning point to obtain high sensitive and reliable devices with enhanced spatial and temporal resolution. Power consumption compatible with battery operated systems, and reduced cost per device are also pivotal for their success. All these characteristics make investigation on this filed very active nowadays. This thesis work is focused on two main themes: (i) design and development of a single chip smart flow-meter; (ii) design and development of readout interfaces for capacitive micro-electro-mechanical-systems (MEMS) based on capacitance to pulse width modulation conversion. High sensitivity integrated smart sensors for detecting very small flow rates of both gases and liquids aiming to fulfil emerging demands for this kind of devices in the industrial to environmental and medical applications. On the other hand, the prototyping of such sensor is a multidisciplinary activity involving the study of thermal and fluid dynamic phenomenon that have to be considered to obtain a correct design. Design, assisted by finite elements CAD tools, and fabrication of the sensing structures using features of a standard CMOS process is discussed in the first chapter. The packaging of fluidic sensors issue is also illustrated as it has a great importance on the overall sensor performances. The package is charged to allow optimal interaction between fluids and the sensors and protecting the latter from the external environment. As miniaturized structures allows a great spatial resolution, it is extremely challenging to fabricate low cost packages for multiple flow rate measurements on the same chip. As a final point, a compact anemometer prototype, usable for wireless sensor network nodes, is described. The design of the full custom circuitry for signal extraction and conditioning is coped in the second chapter, where insights into the design methods are given for analog basic building blocks such as amplifiers, transconductors, filters, multipliers, current drivers. A big effort has been put to find reusable design guidelines and trade-offs applicable to different design cases. This kind of rational design enabled the implementation of complex and flexible functionalities making the interface circuits able to interact both with on chip sensors and external sensors. In the third chapter, the chip floor-plan designed in the STMicroelectronics BCD6s process of the entire smart flow sensor formed by the sensing structures and the readout electronics is presented. Some preliminary tests are also covered here. Finally design and implementation of very low power interfaces for typical MEMS capacitive sensors (accelerometers, gyroscopes, pressure sensors, angular displacement and chemical species sensors) is discussed. Very original circuital topologies, based on chopper modulation technique, will be illustrated. A prototype, designed within a joint research activity is presented. Measured performances spurred the investigation of new techniques to enhance precision and accuracy capabilities of the interface. A brief introduction to the design of active pixel sensors interface for hybrid CMOS imagers is sketched in the appendix as a preliminary study done during an internship in the CNM-IMB institute of Barcelona

Online learning of physics during a pandemic: A report from an academic experience in Italy

The arrival of the Sars-Cov II has opened a new window on teaching physics in academia. Frontal lectures have left space for online teaching, teachers have been faced with a new way of spreading knowledge, adapting contents and modalities of their courses. Students have faced up with a new way of learning physics, which relies on free access to materials and their informatics knowledge. We decided to investigate how online didactics has influenced students’ assessments, motivation, and satisfaction in learning physics during the pandemic in 2020. The research has involved bachelor (n = 53) and master (n = 27) students of the Physics Department at the University of Cagliari (N = 80, 47 male; 33 female). The MANOVA supported significant mean differences about gender and university level with higher values for girls and master students in almost all variables investigated. The path analysis showed that student-student, student-teacher interaction, and the organization of the courses significantly influenced satisfaction and motivation in learning physics. The results of this study can be used to improve the standards of teaching in physics at the University of Cagliar

Selected problems of materials science

The stamp was provided by the Methodical Council Igor Sikorsky KPI (protocol № 8 from 24.06.2021) at the request of the Academic Council of the Institute of Physics and Technology (protocol № 12 of 14.06.2021)The textbook discusses the physical foundations and practical application of functional dielectrics and simiconductors. Theories, experimental data and also specifications of basic materials, necessary for practical application, are considered. The results of modern research in the field of microelectronics and nanophysics are taken into account, with a special attention paid to the influence of the internal structure on the physical properties of materials and prospects for their use. The textbook is based on the authors' many years of experience in teaching physical materials science, intended for the students of higher educational institutions with specializations in the fields of "Applied Physics" and "Microelectronics". The book can also be used by the graduate students, engineers and researchers specializing in materials science.У навчальному посібнику розглядаються фізичні основи та практичне застосування функціональних діелектриків та напівпровідників. Розглянуто теорії, наведені експериментальні дані, а також специфікації основних матеріалів, що необхідні для практичного застосування. Беруться до уваги результати сучасних досліджень у галузі мікроелектроніки та нанофізики, при цьому особлива увага приділяється впливу внутрішньої структури на фізичні властивості матеріалів і перспективи їх використання. Навчальний посібник заснований на багаторічному досвіді авторів у викладанні курсу фізичного матеріалознавства, призначеного для студентів вищих навчальних закладів із спеціалізаціями в галузях «Прикладна фізика» та «Мікроелектроніка». Книга також може бути використана аспірантами, інженерами та дослідниками, що спеціалізуються в галузі матеріалознавства

3D Freeze Printing of Functional Aerogels

Doctor of PhilosophyDepartment of Industrial & Manufacturing Systems EngineeringDong LinAerogels are a class of highly porous materials made from almost any material compositions. The exotic properties of the aerogels including low thermal conductivity, transparency, flexibility, extremely high porosity, low weight and density, large surface area, etc. attracted the attention of many researchers working in various fields. Incorporating 3D printing technology in aerogel fabrication provided a great freedom in the design of the final product as well as a great capability of tailoring the materials properties. Yet, the 3D printing methods used for fabrication of aerogels suffer from the printability requirements, lack of appropriate support material that can be removed without harsh chemical/thermal post-processes, and lack of ability to simultaneously engineer the macrostructure of the aerogels along with their microstructure. 3D Freeze Printing (3DFP), developed by our group, has shown a great promise to address those issues in our previous studies. However, our group’s previous process investigation studies relied on only optical imaging techniques, which provided information on the material deposition, but not the solidification step. This limits the depth of information that we have about the process since solidification is a very important step. Besides, feasible materials for 3DFP method were limited with graphene and silver nanowires. Considering the wide range of materials used for 3D printed aerogels, different materials need to be introduced to 3DFP method to realize its full potential in the area. In addition, , a fully functioning device using 3DFP method has never been built and evaluated for its performance compared to the devices fabricated by other methods. Moreover, there is a need for a fabrication method which can fabricate aerogels with non-monolithic predesigned microstructures (e.g. pores of various sizes located in certain regions of the aerogels), especially for applications in the field of controlled drug-delivery, bone tissue engineering, selective liquid sorption, and so on. In this thesis, based on the motivation listed above, 3DFP method has been studied in the course of realizing its full potential in the field. Firstly, a process investigation has been performed to simultaneously observe the material deposition and solidification (freezing) using the sophisticated X-ray imaging facilities in SLAC National Accelerator Laboratory. This investigation helped to develop a mathematical model for the geometry of the deposited material, observe the material deposition and solidification concurrently, and understand the effects of different process parameters (e.g. jetting frequency, print head speed, and substrate temperature) on the phase change as well as the quality of the printed constructs. Then, aerogels based on novel materials (cellulose nanocrystals (CNC) and MXenes) for 3DFP method were fabricated and characterized. By incorporating different additives in the ink formulation, different functionalities have been achieved for 3D printed CNC aerogels. Functional devices were developed using the 3D printed MXene aerogels, an enhancement in their performance was achieved by engineering the microstructure, and eventually their performance was compared with other reported devices fabricated by different methods. Finally, a novel method for fabrication of aerogels having non-monolithic micropore morphologies was developed. By achieving local temperature gradients on the substrate used for unidirectional freeze casting and 3DFP processes, a predesigned microstructure where the location of large and small pores can be precisely controlled is obtained. This method has a great potential for applications such as drug delivery, bone tissue engineering, photo catalysis, selective absorption, etc. where a predesigned non-monolithic micropore morphology can be an asset

Investigation of thermopower waves based energy sources

Miniaturisation of energy sources is critical for the development of the next generation electronic devices. However, reduction in dimensions of none of the commonly used energy generation technologies including batteries, fuel cells, heat engines and supercapacitors have resulted in efficient and reliable energy sources with high specific powers (power-to-mass ratio). Recently, the new concept of energy generation based on thermopower waves has shown promise for miniaturization. In such sources, exothermic chemical reactions of a reactive fuel are coupled to charge carriers of a thermoelectric (TE) material in its affinity, resulting in an intense thermal wave that self-propagates along the surface of the TE materials. This wave simultaneously entrains charge carriers, resulting in a large current. If the TE material also has a high Seebeck coefficient, a large output voltage and subsequently large specific power output are obtained. As the thermal wave results in a power output, it is called a thermopower wave. In the first stage of the PhD research, the author demonstrated thermopower wave systems based on thin films of Bi 2 Te 3 . Bi 2 Te 3 was implemented due to its high S (~ –200 μV/K) and σ (10 5 S/m). As Bi 2 Te 3 exhibits a low κ , the author devised a novel strategy by placing it on thermally conductive alumina (Al 2 O 3 ) substrate to compensate for this deficiency. The Bi 2 Te 3 based thermopower wave sources generated voltages and oscillations higher (at least 150 %) than the previously reported multi-walled carbon nanotube (MWNT) based thermopower wave sources, while maintaining a high specific power in the order of 1 kW/kg. In the second stage, the author implemented a novel combination of p-type Sb 2 Te 3 and n-type Bi 2 Te 3 as the core TE materials with complimentary semiconducting properties, to show the generation of voltage signals with alternating polarities. In the third stage, the author implemented zinc oxide (ZnO), which is a TE transition metal oxide (TMO), for the first time as the core material in thermopower wave sources. It was shown that both S (~ –500 μV/K at 300 °C) and σ (~ 4×10 3 S/m at 300 °C) of ZnO increased at elevated temperatures. By incorporating ZnO as the core TE material, the PhD candidate obtained voltages and oscillation amplitudes at least 200 % higher than any previously demonstrated thermopower wave systems (in the order of > 500mV), while maintaining a high specific power (~ 0.5 kW/kg). In the final stage, in order to exceed voltages larger than 1 V, the PhD candidate identified that manganese dioxide (MnO 2 ), which is another TE TMO, can exhibit exceptionally large S and moderate σ at elevated temperatures. As a result, the author implemented MnO 2 as the core TE material. It was shown that the S of MnO 2 increased dramatically with temperature, exhibiting a peak value of approximately –1900 μV/K at 350 °C. Consequently, voltages large enough (~1.8 V) to drive small electronic circuits were obtained, while maintaining high specific powers in the order of 1 kW/kg

EUROSENSORS XVII : book of abstracts

Fundação Calouste Gulbenkien (FCG).Fundação para a Ciência e a Tecnologia (FCT)