The demand for more accurate measurements is increasing in today’s industry. One reason for this is to optimize production and thus maximize profits. Another reason is that in some cases government regulations dictate that supervision of certain parameters must be followed. At Preemraff Lysekil there are basically four reasons for measuring skin temperatures inside fired process heaters, namely; because of government regulations, in order to estimate the load of the fired process heater, to estimate the lifetime of the tubes inside the fired process heater and finally, to determine the need of decoking. However, only the first three of these reasons are applied to H2301/2/3. The current skin thermocouple design has been in use for many years and now the question of how well it measures surface temperature has risen. Furthermore a new weld-free design is under consideration to replace the old skin thermocouple design. Another question is therefore how well the new design can measure the surface temperature under the same operating conditions as the old one. In order to evaluate this, three–dimensional computer simulations were made of the different designs. As this thesis will show, the differences in calculated skin thermocouple temperature and calculated surface temperature is about the same for the two designs. However, the current design will show a lower temperature than the surface temperature, while the new design will show a higher temperature. Regarding the core of the skin thermocouple designs, namely the thermocouple, no hard conclusions can be drawn, although the industry appears to favor type ’N’ over type ’K’.

In this work, patterns in the behavior of different classes and types of thermoelectric materials are observed, and an alchemy that could help engineer a highly efficient thermoelectric is proposed. A method based on cross-correlation of Seebeck waveforms is also presented in order to capture physics of magnetic transition. The method is used to compute Curie temperature of LaCoO3 with an accuracy of 10K. In total, over 26 systems are analyzed, and 19 presented: Chalcogenides (PbSe, PbTe, Sb2Te3, Ag2Se), Skutterudites and Clathrates (CoSb3, SrFe4Sb12, Cd (CN)2, CdC, Ba8Ga16Si30*), Perovskites (SrTiO3, BaTiO3, LaCoO3, CaSiO3, Ce3InN*, YCoO3*), Half-Heuslers (ZrNiSn, NbFeSb, LiAlSi, CoSbTi, ScPtSb*, CaMgSi*), and an assorted class of thermoelectric materials (FeSi, FeSi2, ZnO, Ag QDSL*). Relaxation time is estimated from experimental conductance curve fits. A maximum upper bound of zT is evaluated for systems that have no experimental backing. In general, thermoelectric parameters (power factor, Seebeck coefficient and zT) are estimated for the aforementioned crystal structures. Strongly correlated systems are treated using LDAU and GGAU approximations. LDA/GGA/L(S)DA+U/GGA+U approach specific errors have also been highlighted. Densities of experimental results are estimated.

Intermetallic clathrates have long been of interest for materials science research. The promise these materials hold for useful applications ranges from thermoelectrics to photovoltaics and optoelectronics to potentially ultra-hard materials and magnetic cooling applications. Their unique physical properties are intimately related to their intriguing structural properties. Thus a fundamental understanding of the chemistry and physics of inorganic clathrates offers the possibility to assess their potential for use in the various applications mentioned above. The purpose of the current work is to expand the current knowledge of the synthetic routes for obtaining clathrate materials, their structural, chemical, and physical properties, particularly those that from in the type I, II and VIII crystal structures. New synthesis routes are presented and used for preparation of single crystals of Na 8Si46 and Na 24Si136. Single-crystal X-ray analysis, and resistivity, Seebeck coefficient and thermal conductivity measurements are presented. In addition, two "inverse" clathrates with compositions Sn 24P19.3Br8 and Sn17Zn7P22Br8 have been characterized in terms of their transport properties. Since the magnetic refrigeration based on the magnetocaloric effect is a topic of great interest, type VIII Eu 8Ga16Ge30 clathrates are also explored in terms of their application for magnetic cooling.

Magnetic oxides have become of interest source for spin transport devices due to their high spin polarization. But the real applications of these oxides remains unsatisfactory up to date, mostly due to the change of properties as a result of nano structuring. Magnetite (Fe3O4) is one such a material. High Curie temperature and the half metallicity of Fe3O4 make it a good potential candidate for spin transport devices. Studies have shown that the nano structuring Fe3O4 changes most of it's important properties. This includes high saturation magnetization and drop of conductivity by a few orders of magnitude in Fe3O4 thin films. In this study, we have successfully grown Fe3O4 by reactive sputtering and studied the effect of transition metal buffer layers on structural, transport, and magnetic properties of Fe3O4. It is shown that the lattice strain created by different buffer layers has major impacts on the properties of Fe3O4 thin films. Also for the first time the magnetic force microscopic measurements were carried out in Fe3O4 thin films through Verwey transition. MFM data with the magnetization data have confirmed that the magnetization of Fe3O4 thin films rotate slightly out of the plane below the Verwey transition. Fe3O4 thin films were also successfully used in fabricating spin valve structures with Chromium and Permalloy. Here, the Fe3O4 was used to generated the spin polarized electrons through reflection instead of direct spin injection. This is a novel method that can be used to inject spins into materials with different conductivities, where the traditional direct spin injection fails. Also the effect of growth field on Fe3O4 and Fe3O4/Cr/Py spin valves were investigated. In Fe3O4 the growth field induced an uni-axial anisotropy while it creates a well defined parallel and anti-parallel states in spin valves. Magneto thermal phenomenon including spin dependent Seebeck effect, Planar Nernst effect, and Anomalous Nernst effect were measured in ferromagnetic thin films and spin valves. Spin dependent Seebeck effect and planar Nernst effect were directly compared with the charge counterpart anisotropic magneto resistance. All the effects exhibited similar behavior indicating the same origin, namely spin dependent scattering.

Computers and their constituent electronics continue to shrink. The same amount of work can be done with increasingly smaller and cheaper components that need less power to function than before. In wireless sensor networks, the energy needed by one sensor node borders the amount that is already present in its immediate surroundings. Equipping the electronics with a micro generator or energy harvester gives the possibility that it can become self-sufficient in energy. In this thesis two kinds of energy harvesters are investigated. One absorbs vibrations and converts them into electricity by means of piezo-electricity. The other converts heat flow through a semiconductor to electricity, utilizing a thermoelectric effect. Principles governing the performance, actual performance of off-the-shelf components and design considerations of the energy harvester have been treated. The thermoelectric micro generator has been measured to output power at 2.7 mW and 20°C with a load of 10 W. The piezoelectric micro generator has been measured to output power at 2.3 mW at 56.1 Hz, with a mechanical trim weight and a load of 565 W. In these conditions the power density of the generators lies between 2-3 W/m2.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2017-12-12T19:14:15Z No. of bitstreams: 1 NeymarPereiraDaCosta_TESE.pdf: 7528094 bytes, checksum: a890acb318c8748f5765c7a2bb15e3c4 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2017-12-14T18:05:44Z (GMT) No. of bitstreams: 1 NeymarPereiraDaCosta_TESE.pdf: 7528094 bytes, checksum: a890acb318c8748f5765c7a2bb15e3c4 (MD5) / Made available in DSpace on 2017-12-14T18:05:44Z (GMT). No. of bitstreams: 1 NeymarPereiraDaCosta_TESE.pdf: 7528094 bytes, checksum: a890acb318c8748f5765c7a2bb15e3c4 (MD5) Previous issue date: 2017-09-14 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / A presente tese traz um m?todo de produ??o de alvos semicondutores cujo material ? proveniente de m?dulos termoel?tricos comerciais. Os alvos t?m a finalidade e foram utilizados em sistema magnetron sputtering. Os materiais que comp?em os alvos s?o ligas tern?rias semicondutoras, uma de telureto de bismuto e antim?nio, que se caracteriza como tipo P e a outra ligada ? um seleneto de bismuto e tel?rio, cuja composi??o o caracteriza como tipo N. Estas ligas dos sistemas Bi2Te3-ySey e Bi2-xSbxTe3 apresentam propriedades termoel?tricas de alto desempenho dentro da faixa de temperatura entorno da ambiente. A partir desses alvos, foram produzidos filmes termoel?tricos de espessura nanom?trica, em dois lotes, cujas amostras foram submetidas a tratamentos t?rmicos ap?s sua produ??o. Foram investigadas as propriedades termoel?tricas dos filmes, ? temperatura ambiente, no sistema de medidas de propriedades f?sicas, o PPMS. Para isso foi utilizado a op??o de transporte t?rmico TTO, o qual possibilita a aquisi??o de dados de grandezas f?sicas como o coeficiente Seebeck ?, a condutividade t?rmica ? e a resistividade el?trica ?. Com essas grandezas reunidas, foi calculado o Fator de Pot?ncia e a Figura de M?rito que ? um fator adimensional que determina o quanto o material ? promissor para aplica??es em convers?o de energia e refrigera??o termoel?trica. Medidas de voltagem por corrente pelo m?todo quatro pontas colinear, foram realizadas e mostraram um indicativo de utiliza??o para o semicondutor tipo P como sensor de chaveamento t?rmico. Uma importante perspectiva ? o desenvolvimento de um substrato, utilizando os filmes como termoelementos planares e assim, funcionar como dispositivo termoel?trico, capaz de promover gradientes t?rmicos em aplica??es a outros sistemas como os magneto galvanom?tricos.

abstract: This study analyzes the thermoelectric phenomena of nanoparticle suspensions, which are composed of liquid and solid nanoparticles that show a relatively stable Seebeck coefficient as bulk solids near room temperature. The approach is to explore the thermoelectric character of the nanoparticle suspensions, predict the outcome of the experiment and compare the experimental data with anticipated results. In the experiment, the nanoparticle suspension is contained in a 15cm*2.5cm*2.5cm glass container, the temperature gradient ranges from 20 °C to 60 °C, and room temperature fluctuates from 20 °C to 23°C. The measured nanoparticles include multiwall carbon nanotubes, aluminum dioxide and bismuth telluride. A temperature gradient from 20 °C to 60 °C is imposed along the length of the container, and the resulting voltage (if any) is measured. Both heating and cooling processes are measured. With three different nanoparticle suspensions (carbon nano tubes, Al2O3 nanoparticles and Bi2Te3 nanoparticles), the correlation between temperature gradient and voltage is correspondingly 8%, 38% and 96%. A comparison of results calculated from the bulk Seebeck coefficients with our measured results indicate that the Seebeck coefficient measured for each suspension is much more than anticipated, which indicates that the thermophoresis effect could have enhanced the voltage. Further research with a closed-loop system might be able to affirm the results of this study. / Dissertation/Thesis / M.S. Mechanical Engineering 2010

The development of a complete thermoelectric generator and its application on a display polarizer film was successfully accomplished in this thesis. A systematic study of the prospective thermoelectric materials, PEDOT:PSS-based and ${ZnON}$, used for the present application is presented. To the best of our knowledge, this is the first exploration of the thermoelectric parameters of ${ZnON}$ reported here. Thin-film deposition of these materials was performed via both solution- and vacuum-based techniques. In addition, certain doping mechanisms were tested in an attempt to further understand the correlation between electrical conductivity and Seebeck coefficient. A maximum power factor of $42{\mu}Wm^{-1}K^{-2}$ was achieved for the PEDOT:PSS-based thin film at room temperature. It was initially doped via 5vol% of DMSO and sequentially treated with ethylene glycol. Specifically, its electrical conductivity displayed a 2-fold increase after EG treatment, reaching a value of about 1632 Scm$^{-1}$. Systematic studies performed on the association between thin-film thickness and its Seebeck coefficient shows a decrease in the latter as the number of multilayers printed increases. Among the different $O_{2}/N_{2}$ ratios that were tested for ${ZnON}$ thin films, a maximum power factor value of 163${\mu}Wm^{-1}K{-2}$ was achieved with the lowest $O_{2}$ flow rate configuration. In contrast to PEDOT:PSS-based thin films, the ${ZnON}$ displayed the opposite effect on the relation of the Seebeck coefficient with respect to thin-film thickness. Furthermore, a heterostructure was also developed by implementing ${ZnO}$ nanowires into the ${ZnON}$ thin film. ${ZnO}$ nanowires have been fabricated through the hydrothermal method on inkjet-printed patterns of zinc acetate dihydrate. It has been demonstrated that with the right inkjet-printing parameters and substrate temperature, ${ZnO}$ nanowires can be effortlessly fabricated in accordance with the desired pattern variations under low temperature and mild conditions. Finally, a complete device of the thermoelectric generator was fabricated using the above materials and a special set-up developed in order to test the device on the polarizer. The power output achieved from a 1-thermoelectric couple under normal backlight illumination and ambient conditions was 23pW. Overall, it is thought that the particular design and proof of concept presented here can be the basis of a prospective energy harvesting scheme via thermoelectrics in future display-based handheld devices.

O presente trabalho apresenta o desenvolvimento de uma bancada didática de baixo custo para estudo dos materiais termoelétricos para a realização de ensaios de obtenção de curvas de desempenho dos módulos termoelétricos no que se refere a geração de energia pelo Efeito Seebeck e resfriamento através do Efeito Peltier de forma a difundir os conhecimentos nas áreas afim em escolas de Engenharia, refletindo na compreensão dos princípios e funcionalidades destas tecnologias. O sistema proposto permite ler simultaneamente até 3 geradores termoelétricos, e é composto por dois principais circuitos eletrônicos: sendo um estágio aquisição de dados compostos por 3 canais para leitura de tensão, 3 canais para corrente e 6 canais para aquisição do sinal dos termopares (<400°C) além de sistema térmico que terá as funções de aquecimento e resfriamento. Os dados medidos são adquiridos para um computador com um software customizado a aplicação que permite o monitoramento das grandezas envolvidas (tensão, corrente, potência e temperatura) para acompanhamento do ensaio dos materiais termoelétricos, tanto por meio de uma indicação numérica como gráfica. O sistema de aquisição de dados possui precisa o para temperatura de ±2,5%, para tensão de ±2,5% e para corrente de ±1,5%. / The present work describes the development of a low cost didactic bench for Study of thermoelectric materials for performing obtaining performance curves testing of thermoelectric modules in regard to energy generation effect Seebeck and cooling via Peltier Effect order to disseminate knowledge in areas related to engineering schools, reflecting the understanding of the principles and features of these technologies. The proposed system can be read simultaneously up to 3 thermoelectric generators, and consists of two main electronic circuits: being a stage data acquisition composed of 3 channels for reading voltage and 3 channels for current using ACS712 instrumentation amplifiers and 6 channels signal acquisition thermocouples (<400 ° C) as well as thermal system will have the heating and cooling functions. The measured data is acquired to a computer with software developed in Delphi language, which allows monitoring of the quantities involved (voltage, current, power and temperature) to monitor the testing of thermoelectric materials, either through a digital display as a graphic . The data acquisition system has a temperature accuracy to ± 2,5% to ± 2.5% voltage and current of ± 1.5%.

O presente trabalho apresenta o desenvolvimento de uma bancada didática de baixo custo para estudo dos materiais termoelétricos para a realização de ensaios de obtenção de curvas de desempenho dos módulos termoelétricos no que se refere a geração de energia pelo Efeito Seebeck e resfriamento através do Efeito Peltier de forma a difundir os conhecimentos nas áreas afim em escolas de Engenharia, refletindo na compreensão dos princípios e funcionalidades destas tecnologias. O sistema proposto permite ler simultaneamente até 3 geradores termoelétricos, e é composto por dois principais circuitos eletrônicos: sendo um estágio aquisição de dados compostos por 3 canais para leitura de tensão, 3 canais para corrente e 6 canais para aquisição do sinal dos termopares (<400°C) além de sistema térmico que terá as funções de aquecimento e resfriamento. Os dados medidos são adquiridos para um computador com um software customizado a aplicação que permite o monitoramento das grandezas envolvidas (tensão, corrente, potência e temperatura) para acompanhamento do ensaio dos materiais termoelétricos, tanto por meio de uma indicação numérica como gráfica. O sistema de aquisição de dados possui precisa o para temperatura de ±2,5%, para tensão de ±2,5% e para corrente de ±1,5%. / The present work describes the development of a low cost didactic bench for Study of thermoelectric materials for performing obtaining performance curves testing of thermoelectric modules in regard to energy generation effect Seebeck and cooling via Peltier Effect order to disseminate knowledge in areas related to engineering schools, reflecting the understanding of the principles and features of these technologies. The proposed system can be read simultaneously up to 3 thermoelectric generators, and consists of two main electronic circuits: being a stage data acquisition composed of 3 channels for reading voltage and 3 channels for current using ACS712 instrumentation amplifiers and 6 channels signal acquisition thermocouples (<400 ° C) as well as thermal system will have the heating and cooling functions. The measured data is acquired to a computer with software developed in Delphi language, which allows monitoring of the quantities involved (voltage, current, power and temperature) to monitor the testing of thermoelectric materials, either through a digital display as a graphic . The data acquisition system has a temperature accuracy to ± 2,5% to ± 2.5% voltage and current of ± 1.5%.