Saving energy in buildings is of great importance because about 30 to 40 % of the energy in the world is used in buildings. An electrochromic window (ECW), which makes it possible to regulate the inflow of visible light and solar energy into buildings, is a promising technology providing a reduction in energy consumption in buildings along with indoor comfort. A polymer electrolyte is positioned at the center of multi-layer structure of an ECW and plays a significant role in the working of the ECW. In this study, polyethyleneimine: lithium (bis(trifluoromethane)sulfonimide (PEI:LiTFSI)-based polymer electrolytes were characterized by using dielectric/impedance spectroscopy, differential scanning calorimetry, viscosity recording, optical spectroscopy, and electrochromic measurements. In the first part of the study, PEI:LiTFSI electrolytes were characterized at various salt concentrations and temperatures. Temperature dependence of viscosity and ionic conductivity of the electrolytes followed Arrhenius behavior. The viscosity was modeled by the Bingham plastic equation. Molar conductivity, glass transition temperature, viscosity, Walden product, and iso-viscosity conductivity analysis showed effects of segmental flexibility, ion pairs, and mobility on the conductivity. A connection between ionic conductivity and ion-pair relaxation was seen by means of (i) the Barton-Nakajima-Namikawa relation, (ii) activation energies of the bulk relaxation, and ionic conduction and (iii) comparing two equivalent circuit models, containing different types of Havriliak-Negami elements, for the bulk response. In the second part, nanocomposite PEI:LiTFSI electrolytes with SiO2, In2O3, and In2O3:Sn (ITO) were examined. Adding SiO2 to the PEI:LiTFSI enhanced the ionic conductivity by an order of magnitude without any degradation of the optical properties. The effect of segmental flexibility and free ion concentration on the conduction in the presence of SiO2 is discussed. The PEI:LiTFSI:ITO electrolytes had high haze-free luminous transmittance and strong near-infrared absorption without diminished ionic conductivity. Ionic conductivity and optical clarity did not deteriorate for the PEI:LiTFSI:In2O3 and the PEI:LiTFSI:SiO2:ITO electrolytes. Finally, propylene carbonate (PC) and ethylene carbonate (EC) were added to PEI:LiTFSI in order to perform electrochromic measurements. ITO and SiO2 were added to the PEI:LiTFSI:PC:EC and to a proprietary electrolyte. The nanocomposite electrolytes were tested for ECWs with the configuration of the ECWs being plastic/ITO/WO3/polymer electrolyte/NiO (or IrO2)/ITO/plastic. It was seen that adding nanoparticles to polymer electrolytes can improve the coloring/bleaching dynamics of the ECWs. From this study, we show that nanocomposite polymer electrolytes can add new functionalities as well as enhancement in ECW applications.

The Earth's magnetic field is generated in its fluid outer core through dynamo action. In this process, convection and differential rotation of an electrically conducting fluid maintain the magnetic field against its ohmic decay. Using numerical models, we can investigate planetary dynamo processes and the importance of various core properties on the dynamo. In this thesis, I use numerical dynamo models in Earth-like geometry in order to understand the influence of inner core electrical conductivity and the choice of thermal and velocity boundary conditions on the resulting magnetic field. I demonstrate how an electrically conducting inner core can reduce the frequency of reversals and produce axial-dipolar dominated fields in our models. I also demonstrate that a strong planetary magnetic field intensity does not imply that the dynamo operates in the strong field regime as is usually presumed. Through a scaling law analysis, I find that irrespective of the choice of thermal or velocity boundary conditions, the available power determines the magnetic and velocity field characteristics like the field strength, polarity and morphology. Also, whether a dynamo model is in a dipolar, transitional or multipolar regime is dependent on the force balance in the model. I demonstrate that the Lorentz force is balanced by the Coriolis force in the dipolar dynamo regime models resulting in magnetostrophically balanced dynamos whereas the Lorentz force is balanced by the Inertial force (and not the Coriolis force) in the multipolar dynamo regime models resulting in a non-magnetostrophically balanced dynamo. The generation mechanism differs between the regimes and depends on the velocity boundary conditions. The zonal flows of the stress-free models are stronger than in the no-slip models, and bistability is more prominent when stress-free boundary conditions are used. A single scaling law may be feasible for all the models, but there does appear to be some variation for models with different thermal and velocity boundary conditions. The results presented in this thesis are not only applicable to the geodynamo, but will also aid in understanding the dynamos of other planets and exoplanets.

The Earth's magnetic field is generated in its fluid outer core through dynamo action. In this process, convection and differential rotation of an electrically conducting fluid maintain the magnetic field against its ohmic decay. Using numerical models, we can investigate planetary dynamo processes and the importance of various core properties on the dynamo. In this thesis, I use numerical dynamo models in Earth-like geometry in order to understand the influence of inner core electrical conductivity and the choice of thermal and velocity boundary conditions on the resulting magnetic field. I demonstrate how an electrically conducting inner core can reduce the frequency of reversals and produce axial-dipolar dominated fields in our models. I also demonstrate that a strong planetary magnetic field intensity does not imply that the dynamo operates in the strong field regime as is usually presumed. Through a scaling law analysis, I find that irrespective of the choice of thermal or velocity boundary conditions, the available power determines the magnetic and velocity field characteristics like the field strength, polarity and morphology. Also, whether a dynamo model is in a dipolar, transitional or multipolar regime is dependent on the force balance in the model. I demonstrate that the Lorentz force is balanced by the Coriolis force in the dipolar dynamo regime models resulting in magnetostrophically balanced dynamos whereas the Lorentz force is balanced by the Inertial force (and not the Coriolis force) in the multipolar dynamo regime models resulting in a non-magnetostrophically balanced dynamo. The generation mechanism differs between the regimes and depends on the velocity boundary conditions. The zonal flows of the stress-free models are stronger than in the no-slip models, and bistability is more prominent when stress-free boundary conditions are used. A single scaling law may be feasible for all the models, but there does appear to be some variation for models with different thermal and velocity boundary conditions. The results presented in this thesis are not only applicable to the geodynamo, but will also aid in understanding the dynamos of other planets and exoplanets.

Polymer electrolyte membrane fuel cells (PEMFCs) have the potential to play a major role as energy generators for transportation and portable applications. One of the current barriers to their commercialization is the cost of the components and manufacturing, specifically the bipolar plates. One approach to preparing PEMFCs for commercialization is to develop new bipolar plate materials, related to mass production of fuel cells. Thermoplastic/carbon filler composites with low filler loading have a major advantage in that they can be produced by a conventional low-cost injection molding technique. In addition, the materials used are inexpensive, easy to shape, and lightweight. An optimal bipolar plate must possess high surface and bulk electronic conductivity, sufficient mechanical integrity, low permeability, and corrosion resistance. However, it is difficult to achieve high electrical conductivity from a low-cost thermoplastic composite with low conductive filler loading. Concerns over electrical conductivity improvement and the injection processability of composites have brought forth the idea of producing a polypropylene/three-carbon-filler composite for bipolar plate application. The thesis addresses the development of synergistic effects of filler combinations, investigating composite conductive materials and using composite bipolar plate testing in PEMFCs. One significant effect of conductive network formation is the synergetic effects of different carbon filler sizes, shapes, and multiple filler ratios on the electrical conductivity of bipolar plate materials. A polypropylene resin combined with low-cost conductive fillers (graphite, conductive carbon black, and carbon fibers with 55 wt% of filler loading) compose the main composite for all investigations in this research. Numerous composite formulations, based on single-, two-, and three-filler systems, have been created to investigate the characteristics and synergistic effects of multiple fillers on composite conductivity. Electrical conductivity measurements corresponding to PEMFC performance and processing characteristics were investigated. Experimental work also involved other ex-situ testing for the physical requirements of commercial bipolar plates. All combinations of fillers were found to have a significant synergistic effect that increased the composite electrical conductivity. Carbon black was found to have the highest influence on the increase of electrical conductivity compared to the other fillers. The use of conjugated conducting polymers such as polypyrrole (PPy) to help the composite blends gain desirable conductivities was also studied. Electrical conductivity was significantly improved conductivity by enriching the conducting paths on the interfaces between fillers and the PP matrix with PPy. The conductive network was found to have a linkage of carbon fibers following the respective size distributions of fibers. The combination of Fortafil and Asbury carbon fiber mixture ameliorated the structure of conductive paths, especially in the through-plane direction. However, using small fibers such as carbon nanofibers did not significantly improve in electrical conductivity. The useful characteristics of an individual filler and filler supportive functions were combined to create a novel formula that significantly improved electrical conductivity. Other properties, such as mechanical and rheological ones, demonstrate the potential to use the composites in bipolar plate applications. This research contributes a direction for further improvement of marketable thermoplastic bipolar plate composite materials.

Magistriniame darbe tyrinėjamos elektroninės savybės įvairioms puslaidininkinėms medžiagoms. Tarp jų eksperimentiškai ir teoriškai tirti SbSI - tipo kristalai. Išmatuotos jų voltamperinės charakteristikos įvairiose temperatūrose bei srovės temperatūrinės priklausomybės esant skirtingai įtampai. Iš matavimų paskaičiuotas tarp metalo ir puslaidininkio susidarantis barjero aukštis, kuris vėliau buvo panaudotas teorinių – eksperimentinių rezultatų palyginimui. Eksperimentiniams elektrinio laidumo matavimams paaiškinti remtasi įvairiomis fononais stimuliuoto tuneliavimo teorijomis, kurių taikymui papildomai apskaičiuota elektronų ir fononų sąveikos konstanta esant skirtingoms temperatūroms. Taip pat įvertinti kiti, nemažiau elektriniame laidume svarbius, parametrai. Darbe parodyta, kad fononais stimulioto tuneliavimo teorijos efektyviai aprašo elektrinį laidumą tirtose medžiagose prijungiant prie jų metalo kontaktus. / In this work experimental and theoretical investigations of the high electric field electrical properties in semiconductors with Schottky barrier are presented. Experimental research is given for SbSI – type crystals. Theoretical calculations and comparison with experimental data were made using electrical phonon-assisted tunnelling model (PhAT), which is usable for explanation of temperature-field dependent conductivity in wide branch of materials: semiconductors, dielectrics, inorganic, organic and other materials. PhAT model were used including well determined parameters: effective mass of the charge carrier, participating phonon energy, barrier height and electron-phonon interaction. Barrier height was experimentally measured and found for SbSI, SbSe0.2S0.8I, SbSe0.5S0.5I, SbSeI crystals. The results of the temperature dependence of electron–phonon (e–ph) interaction in the inquiring semiconductors were also calculated. It is shown that these semiconductors have kin e–ph interaction. It varies nearly for about ~ 2.6. It has been shown that the temperature dependent I-V characteristics of SbSeI crystals can be explained by the phonon-assisted tunnelling of charge carriers from the states located in the high electric field region at the electrode-crystal junction. The electron tunnelling probability W(E, T) from traps of the apparent depth to the conduction band was computed using evaluated electron-phonon interaction constant and effective mass of the polaron. The... [to full text]

Disertacijoje yra nagrinėjama, kokią įtaką ličio katijonų ir deguonies vakansijų (Vo) kietųjų elektrolitų elektrinėms savybėms daro jų struktūra ir elementinė sudėtis. Darbe yra aprašomos technologinės superjoninių junginių (SJ) keramikų ir sluoksnių gamybos sąlygos, lemiančios jų mikrostruktūrą, bei pateikiami SJ paviršių, temperatūrinio stabilumo ir elektrinių savybių tyrimo rezultatai. Li+ SJ priklauso monoklininei, ortorombinei arba romboedrinei singonijoms. Keramikų mikrostruktūra labiausiai priklauso nuo jų kepinimo temperatūros. LiCe2/3PO4 keramiką paveikus elektriniu lauku, XPS buvo parodyta, kad šioje medžiagoje vyksta Li+ jonų pernaša. Kompleksinės varžos spektroskopijos tyrimai parodė, kad sistemose Li1+xScxZr2-x(PO4)3, Li1+xZr2-2xAlxTix(PO4)3 ir Li1+xGe2-2xAlxTix(PO4)3 (čia x = 0,1, 0,2, 0,3), didinant x, didėja kristalitiniai keramikų laidžiai, o jų aktyvacijos energijos mažėja. Li3Sc2–xBx(PO4)3 junginiuose vykstančio superjoninio fazinio virsmo temperatūra priklauso nuo x. Li3-xSc2-x-yYyZrx(PO4)3 sistemoje kai x = 0,1, y = 0, 0,1 temperatūrinėse kristalitinio laidžio prieklausose yra stebimos anomalijos, susijusios su superjoniniais faziniais virsmais šiose medžiagose, o kai x = 0,2 tirtame temperatūrų intervale faziniai virsmai nevyksta. Magnetroninio dulkinimo metodu suformuotų YSZ storųjų sluoksnių joninis laidis ir šio laidžio aktyvacijos energija priklauso nuo jų paruošimo technologinių sąlygų. Didinant NiO-CGO sluoksnių, suformuotų purškimo pirolizės... [toliau žr. visą tekstą] / The influence of the structure and elemental composition of lithium ions’ and oxygen vacancies’ (Vo) solid electrolytes (SE) on their electrical properties are investigated in the dissertation. The technological conditions of SE ceramics’ and films’ fabrication, which influence their microstructure, are described. The results of the investigation of the surfaces, temperature stability, and electrical properties are presented. Li+ SE belong to monoclinic, orthorhombic, or rhombohedral symmetries. The microstructure of the ceramics is mainly influenced by the temperature of their sintering. It has been shown by XPS that LiCe2/3PO4 ceramic is Li+-ion conductor. Complex impedance spectroscopy investigation showed that the increase of x in the systems Li1+xScxZr2-x(PO4)3, Li1+xZr2-2xAlxTix(PO4)3, and Li1+xGe2-2xAlxTix(PO4)3 (where x = 0.1, 0.2, 0.3) leads to the increase of bulk ionic conductivity of the ceramics and to the decrease of its activation energy. Phase transition temperature in Li3Sc2–xBx(PO4)3 compounds depends on x. The anomalies of temperature dependencies of bulk conductivity of Li3-xSc2-x-yYyZrx(PO4)3 system were observed when x = 0.1, y = 0, 0.1. The anomalies are related to superionic phase transitions in the materials, but no phase transitions have been detected for x = 0.2 compound in the studied temperature range. Ionic conductivity and its activation energy of YSZ thick films prepared by magnetron sputtering depend on their preparation’s technological... [to full text]

The influence of the structure and elemental composition of lithium ions’ and oxygen vacancies’ (Vo) solid electrolytes (SE) on their electrical properties are investigated in the dissertation. The technological conditions of SE ceramics’ and films’ fabrication, which influence their microstructure, are described. The results of the investigation of the surfaces, temperature stability, and electrical properties are presented. Li+ SE belong to monoclinic, orthorhombic, or rhombohedral symmetries. The microstructure of the ceramics is mainly influenced by the temperature of their sintering. It has been shown by XPS that LiCe2/3PO4 ceramic is Li+-ion conductor. Complex impedance spectroscopy investigation showed that the increase of x in the systems Li1+xScxZr2-x(PO4)3, Li1+xZr2-2xAlxTix(PO4)3, and Li1+xGe2-2xAlxTix(PO4)3 (where x = 0.1, 0.2, 0.3) leads to the increase of bulk ionic conductivity of the ceramics and to the decrease of its activation energy. Phase transition temperature in Li3Sc2–xBx(PO4)3 compounds depends on x. The anomalies of temperature dependencies of bulk conductivity of Li3-xSc2-x-yYyZrx(PO4)3 system were observed when x = 0.1, y = 0, 0.1. The anomalies are related to superionic phase transitions in the materials, but no phase transitions have been detected for x = 0.2 compound in the studied temperature range. Ionic conductivity and its activation energy of YSZ thick films prepared by magnetron sputtering depend on their preparation’s technological... [to full text] / Disertacijoje yra nagrinėjama, kokią įtaką ličio katijonų ir deguonies vakansijų (Vo) kietųjų elektrolitų elektrinėms savybėms daro jų struktūra ir elementinė sudėtis. Darbe yra aprašomos technologinės superjoninių junginių (SJ) keramikų ir sluoksnių gamybos sąlygos, lemiančios jų mikrostruktūrą, bei pateikiami SJ paviršių, temperatūrinio stabilumo ir elektrinių savybių tyrimo rezultatai. Li+ SJ priklauso monoklininei, ortorombinei arba romboedrinei singonijoms. Keramikų mikrostruktūra labiausiai priklauso nuo jų kepinimo temperatūros. LiCe2/3PO4 keramiką paveikus elektriniu lauku, XPS buvo parodyta, kad šioje medžiagoje vyksta Li+ jonų pernaša. Kompleksinės varžos spektroskopijos tyrimai parodė, kad sistemose Li1+xScxZr2-x(PO4)3, Li1+xZr2-2xAlxTix(PO4)3 ir Li1+xGe2-2xAlxTix(PO4)3 (čia x = 0,1, 0,2, 0,3), didinant x, didėja kristalitiniai keramikų laidžiai, o jų aktyvacijos energijos mažėja. Li3Sc2–xBx(PO4)3 junginiuose vykstančio superjoninio fazinio virsmo temperatūra priklauso nuo x. Li3-xSc2-x-yYyZrx(PO4)3 sistemoje kai x = 0,1, y = 0, 0,1 temperatūrinėse kristalitinio laidžio prieklausose yra stebimos anomalijos, susijusios su superjoniniais faziniais virsmais šiose medžiagose, o kai x = 0,2 tirtame temperatūrų intervale faziniai virsmai nevyksta. Magnetroninio dulkinimo metodu suformuotų YSZ storųjų sluoksnių joninis laidis ir šio laidžio aktyvacijos energija priklauso nuo jų paruošimo technologinių sąlygų. Didinant NiO-CGO sluoksnių, suformuotų purškimo pirolizės... [toliau žr. visą tekstą]

The ongoing search for energy conservation in built structures and during the construction process prompted this thesis work to explore the use of sustainable technologies for floor heating systems. The thesis work explores the use of thermoplastic material as a sustainable substitute material for future floor heating systems. Concrete materials are presently used extensively for floor heating systems. Thermoplastic materials are seldom used for floor heating and the primary focus of this thesis is to explore the suitability & adaptability of thermoplastics as an innovative energy saving floor heating material. A thorough study of energy demands and the impact on environment due to greenhouse gas emissions has been done. Thermoplastic materials are environmental friendly and light weight. They exhibit high thermal conductivity which is favourable for the floor heating systems. A design technique has been developed for the use of thermoplastic materials as an energy efficient floor heating material. The present technique creates a new modular floor heating system. The design technique uses thermoplastic material of size 2.4m x1.2m with embedded electric heaters. Thermoplastic foam panels act as a single building block. A numerical simulation has been carried out to study the heat transfer characteristics of the proposed material. Limited experiments were conducted to verify the validity of the simulation results. The results from the experiments indicate good agreement with simulation results. The energy savings from the thermoplastic floor heating systems have been compared with that of electrical floor heating systems. The adaptability of the new floor heating system in terms of energy savings and cost benefit analysis is also discussed. / sustainable floor heating system

Detailed soil and water data are essential to ensure the optimum long-term management of fields. The objective of this study was to estimate water table depths, spatially variable and layered soil properties using electromagnetic induction methods. Soil samples were collected and analyzed within two wild blueberry, a soybean-barley and a pasture fields. Observation wells were installed. The DualEM-2 was calibrated to predict the soil properties and groundwater depths. The apparent ground conductivity (ECa) and water table depths were measured simultaneously from each well, before and after every significant rainfall for three consecutive days. Comprehensive surveys were conducted in selected fields to measure ECa with DualEM-2. Survey data were imported in C++ program to estimate layered soil properties using mathematical models. Regression models were developed to predict soil properties and groundwater depths. The predicted soil properties and groundwater table maps were generated. This information can help to develop variable rate technologies.

The A2Mo3O12 family, where A3+ is a large trivalent cation, can show interesting thermal properties such as negative thermal expansion, also known as thermomiotic behavior, where the overall volume of the material contracts with increasing temperature. A selection of compounds in this family, namely HfMgMo3O12, In2Mo3O12, Y2Mo3O12, Al2Mo3O12, In(HfMg)0.5Mo3O12, and In1.5(HfMg)0.25Mo3O12, have been synthesized using solid-state and mechanical activation techniques as well as a simplified sol-gel approach (Al2Mo3O12). Coefficients of thermal expansion were found to range from large-negative to low-positive in the orthorhombic phase, including near-zero in In(HfMg)0.5Mo3O12 and In1.5(HfMg)0.25Mo3O12. This set of materials provided insight into the role of low-frequency phonon modes in open-framework materials. Low-temperature heat capacity and thermal conductivity measurements confirmed that low-frequency modes were active in thermomiotic materials, and also present to some extent in all members of the open-framework A2Mo3O12 family examined. A clear correlation exists between the magnitude and sign of the coefficient of thermal expansion in the orthorhombic phase and the contribution of low-energy modes to the low-temperature heat capacity, with negative thermal expansion materials having a larger contribution. The low-frequency phonon modes result in low thermal conductivity and reduced phonon mean free paths when compared to conventional ceramics and indicate that these low values are characteristic of open-framework materials in NTE families even if the materials in the families are not thermomiotic themselves.