Cerâmicas elétricas de Ba2In2O5 foram preparadas pelo método convencional de mistura de óxidos, e pela mistura e cristalização dos nitratos metálicos, para verificar o efeito do tamanho inicial das partículas na transição de fase ordemdesordem e na condutividade elétrica. Foram feitas substituições utilizando os cátions Gd3+ e Er3+, para verificar o efeito destes cátions na condutividade elétrica do indato de bário. Foi também preparado o óxido de índio pela técnica de complexação de cátions, e as nanopartículas obtidas foram caracterizadas por diversas técnicas. As principais técnicas de caracterização utilizadas foram: análise térmica, espectroscopia de absorção na região do infravermelho com transformada de Fourier, microscopia eletrônica de varredura, microscopia eletrônica de transmissão, difração de raios X convencional e utilizando radiação síncrotron, espalhamento de raios X a baixos ângulos, espectroscopia de energia dispersiva, espectroscopia Raman e medida da condutividade elétrica por espectroscopia de impedância. Os principais resultados mostraram que os tratamentos térmicos de calcinação e sinterização exercem forte influência na obtenção da fase Ba2In2O5. Fases espúrias são facilmente formadas no Ba2In2O5 também decorrentes da interação deste com a umidade. Um menor tamanho inicial de partículas favorece a redução na temperatura de transição de fase de segunda ordem. A introdução do Er, em teores relativamente baixos, produziu aumento na condutividade elétrica e simultânea redução na temperatura de transição de fase. Altos teores de Er e Gd dão origem a múltiplas fases. Na decomposição térmica do citrato de índio é formado um composto intermediário. A calcinação do citrato de índio produziu um material particulado com tamanho nanométrico, mesmo para temperaturas de até 900 ºC. / The Ba2In2O5 conducting ceramic was prepared by the conventional powder mixing technique and by the crystallization of a mixture of metallic nitrates. The main purpose of this work was to verify the particle size effect on the electrical conductivity and phase transition temperature of sintered ceramics. Gd3+ and Er3+ were used to study the effect of dopant cations in the electrical conductivity behavior of Ba2In2O5. Finally, indium oxide was prepared by the cation complexation technique, and the obtained nanoparticles were characterized by several techniques. The main characterization techniques used in this work were: thermal analyses, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy, energy dispersive X-ray analysis, conventional X-ray diffraction and non-conventional X-ray diffraction using síncroton radiation, small angle X-ray diffraction, Raman spectroscopy and electrical conductivity by impedance spectroscopy. The main results show that special care should be taken in order to obtain single phase Ba2In2O5 powders, especially with thermal treatments of calcination and sintering of powders and compacts. The temperature for the second order phase transition decreased with reduction of the initial particle size. An increase of the electrical conductivity along with decrease in the temperature for phase transition was observed for small amounts of Er. Large contents of both Gd and Er give rise to more complexes phases. An intermediate compound was formed during the thermal decomposition of indium citrate. Calcination of this precursor up to 900 ºC gave rise to nanosized particles.

Este trabalho de pesquisa apresenta a avaliação de uma sonda TDR helicoidal para estimar o teor de umidade dos solos, em diferentes profundidades, através da técnica da reflectometria no domínio do tempo (TDR). Essa sonda, desenvolvida especificamente para esse fim, foi devidamente calibrada em laboratório para diferentes tipos de solo. O processo de calibração consistiu na determinação da constante dielétrica aparente (Ka) e condutividade elétrica volumétrica (ECb) de um mesmo solo com diferentes teores de umidade. Posteriormente foram buscadas correlações entre Ka e o teor de umidade gravimétrico (w), obtido em estufa. São propostas correlações entre w e Ka, entre w e \'KA POT. 1/2\' e entre teor de umidade volumétrico (\'teta\') e Ka. Também foram consideradas as correlações propostas por Yu e Drnevich (2004), visando estimar também a massa específica seca dos solos. Foram realizados ensaios de campo para a validação das equações de calibração. Os valores dos teores de umidade estimados através da técnica da reflectometria no domínio do tempo, tanto em laboratório como em campo, foram comparados com os valores de teor de umidade obtidos com o método da estufa. Com base nos resultados foram determinados os erros referentes às calibrações. Nos ensaios de campo, os teores de umidade obtidos através da correlação entre w e \'KA POT. 1/2\' apresentaram melhores resultados, quando comparados com aqueles estimados com as outras correlações. Pelos resultados obtidos conclui-se que a técnica TDR é uma alternativa viável para a estimativa em campo do teor de umidade em grandes profundidades. / In this work is presented the evaluation of a recently developed helicoidal probe used for estimating the soil water content through the time domain technology (TDR). This probe has been calibrated in laboratory for different types of soils. The calibration process consisted in assessing the values of the apparent dielectric constant (Ka) and the bulk electric conductivity (ECb) of a specific soil at different levels of water content (w). Subsequently, correlations between the apparent dielectric constant and the water content have been established. The same has done with the bulk electric conductivity. Correlations between Ka and w, \'KA POT. 1/2\' and w, \'teta\' (volumetric water content) and Ka have been proposed. Also, the correlations proposed by Yu and Drnevich (2004) have been considered. To validate the proposed correlations, tests using the helicoidal probe were performed in the field. Estimated values of field water content, using the TDR technology have been compared to the correspondent oven water content values. Based on these comparisons, errors regarding the calibrations have been calculated. In the field tests, the correlations between \'KA POT. 1/2\' and w have presented more accurate results than those obtained with the other correlations. Experimental results have shown that the TDR technology for estimating water content at different depths in the field is feasible and expedite.

The intensive nature of land uses in the Strzelecki Ranges poses significant threats to landscape values and water quality. A comprehensive catchment strategy was developed based on sustainability science concepts incorporating the careful management of landscape values, proper land management approaches, and government policy and legislative change to ensure that agriculture, forestry and other land uses become sustainable in this sensitive environment. The readily measurable water quality indicators of turbidity, flow, electrical conductivity, and water temperature were used to determine the impacts of the major land uses in the Strzeleckis. From a water quality perspective, there was a trend of decreasing water quality with increasing intensity in land management. However, from a total sediment load perspective, the forest area contributed the highest total sediment load due to higher volumes of steam flow suggesting that natural processes in the Strzeleckis may remain the principal mechanisms for sediment movement within the catchment. An incidental but significant finding was extensive bioturbation along the riparian zone of the plantation area, the extent of which was not observed in the other catchments. This finding suggested that bioturbation may have been the most significant contributor to poorer water quality flowing from in the plantation catchment. The project developed insights into the major environmental processes active in the upper catchment of the Morwell River. Understanding of the contributions to total sediment loads from natural erosional processes and bioturbation, findings related to the impacts on water quality from agricultural practices, and encountering negligible impacts from conservative timber harvesting practices demonstrate that catchment management approaches need to be tailored to achieve sustainability in land uses across the landscape. Key recommendations include the re-establishment and protection of riparian zones in agricultural catchments, the careful assessment and setting of stream buffer zone widths for timber harvesting operations, and the need for further work to map the extent of natural processes such as bioturbation and stream bank erosion. To mitigate these issues, government policy and legislation will need to focus on the preservation and enhancement of the Crown land riparian zones. Recommended changes to current administrative land management arrangements for these sensitive areas include a move from licensing riparian zones for agricultural practices such as grazing to conservation.

Among the obstacles for the commercialization of the MoltenCarbonate Fuel Cell (MCFC), the dissolution of thestate-of-the-art lithiated NiO cathode is considered as aprimary lifetime limiting constraint. Development ofalternative cathode materials is considered as a main strategyfor solving the cathode dissolution problem. LiFeO2and LiCoO2had earlier been reported as the most promisingalternative materials; however, they could not satisfactorilysubstitute the lithiated NiO. On the other hand, ternarycompositions of LiFeO2, LiCoO2and NiO are expected to combine some desirableproperties of each component. The aim of this work was todevelop alternative cathode materials for MCFC in the LiFeO2-LiCoO2-NiO ternary system. It was carried out byinvestigating electronic conductivity of the materials, firstin the form of bulk pellets and then in ex-situ sinteredporous-gas-diffusion cathodes, and evaluating theirelectrochemical performance by short-time laboratory-scale celloperations. Materials in the LiFeO2-NiO binary system and five ternary sub-systems,each with a constant molar ratio of LiFeO2:NiO while varying LiCoO2content, were studied. Powders withcharacteristics appropriate for MCFC cathode fabrication couldbe obtained by the Pechini method. The particle size of LiFeO2-LiCoO2-NiO powders considerably depends on thecalcination temperature and the material composition. Theelectrical conductivity study reveals the ability of preparingLiFeO2-LiCoO2-NiO materials with adequate electricalconductivity for MCFC cathode application. A bimodal pore structure, appropriate for the MCFC cathode,could be achieved in sintered cathodes prepared usingporeformers and sub-micron size powder. Further, this studyindicates the nature of the compromise to be made between theelectrical conductivity, phase purity, pore structure andporosity in optimization of cathodes for MCFC application. Cellperformance comparable to that expected for the cathode in acommercial MCFC could be achieved with cathodes prepared from20 mole% LiFeO2- 20 mole% LiCoO2- 60 mole% NiO ternary composition. It shows aniR-corrected polarization of 62 mV and a iR-drop of 46 mV at acurrent density of 160 mAcm-2at 650 °C. Altogether, this study revealsthe possibility of preparing LiFeO2-LiCoO2-NiO cathode materials suitable for MCFCapplication. Keywords: molten carbonate fuel cell (MCFC), MCFC cathode,LiFeO2-LiCoO2-NiO ternary compositions, electrical conductivity,porous gas diffusion electrodes, polarization, electrochemicalperformance, post-cell characterization.

<p>One of the most powerful aspects of conducting polymers is their ability to be nanostructured through innovative, synthetically manipulated, transformations, such as to tailor-make the polymers for specialized applications. In the exponentially increasing wide field of nanotechnology, some special attention is being paid to innovative hybrid dendrimer-core based polymeric smart materials. Star copolymers are a class of branched macromolecules having a central core with multiple linear polymer chains extending from the core. This intrinsic structural feature yields a unique 3D structure with extended conjugated linear polymer chains, resulting in star copolymers, which have higher ionic conductivities than their corresponding non-star conducting polymer counterparts. In this study an in-depth investigation was carried out into the preparation and characterization of specialized electronic &lsquo / smart materials&rsquo / . In particular, the preparation and characterization of novel conducting dendrimeric star copolymers which have a central poly(propylene imine) (PPI) dendrimer core with conducting polypyrrole (PPy) chains extending from the core was carried out. This involved, first, the preparation of a series of dendrimeric polypyrrole poly(propylene imine) star copolymers (PPI-co-PPy), using generations 1 to 4 (G1 to G4) PPI dendrimer precursors. The experimental approach involved the use of both chemical and electrochemical synthesis methods. The basic procedure involved a condensation reaction between the primary amine of a diamino functional PPI dendrimer surface and 2-pyrrole aldehyde, to afford the pyrrole functionalized PPI dendrimer (PPI-2Py). Polymerization of the intrinsically contained monomeric Py units situated within the dendrimer backbone was achieved via two distinctly different routes: the first involved chemical polymerization and the second was based on potentiodynamic oxidative electrochemical polymerization. The star copolymers were then characterized using various sophisticated analytical techniques, in-situ and ex-situ. Proton nuclear magnetic resonance spectroscopy (1HNMR) and Fourier transform infrared spectroscopy (FTIR) were used to determine the structures. Scanning electron microscopy (SEM) was used to determine the morphology. Themogravimetric analysis (TGA) was used to study the thermal stability of the prepared materials. X-ray diffraction analysis (XRD) was used to study the structural make-up of phases, crystallinity and amorphous content. Hall effect measurements were carried out to determine the electrical conductivity of the chemically prepared star copolymers. The PPI-co-PPy exhibited improved thermal stability compared to PPI-2Py, as confirmed by TGA. SEM results showed that the surface morphology of the functionalized dendrimer and star copolymer differed. The surface morphology of the chemically prepared star copolymers resembled that of a flaky, waxy material, compared to the ordered morphology of the electrochemically grown star copolymers, which resembled that of whelk-like helixes. In the case the electrochemically grown star copolymers, SEM images recorded at higher magnifications showed that the whelk-like helixes of the star copolymers were hollow tubes with openings at their tapered ends, and had an average base diameter of 2.0 &mu / m. X-ray diffraction analysis of the first generation star copolymer G1PPI-co-PPy revealed a broadly amorphous structure associated with PPy, and crystalline peaks for PPI. Cyclic voltammetry (CV), square wave voltammetry (SWV) and electrochemical impedance spectroscopy (EIS) techniques were used to study and model the electrochemical reactivity of the star copolymer materials. Electrochemical impedance spectroscopy data showed that the G1PPI-co-PPy exhibited slightly higher ionic conductivity than pristine PPy in lithium perchlorate. The second generation star copolymer G2PPI-co-PPy electrochemically deposited on a platinum (Pt) electrode had a lower electrochemical charge transfer resistance compared to electrodeposited polypyrrole (PPy) on a Pt electrode, and bare Pt. The decrease in charge transfer resistance was attributed to an increase in the conjugation length of the polymer as a result of the linking of the highly conjugated PPy to the PPI dendrimer. Bode impedimetric analysis indicated that G2PPI-co-PPI was a semiconductor, with a maximum phase angle shift of 45.3&deg / at 100 MHz. The star copolymer exhibited a 2- electron electrochemistry and a surface coverage of 99%. Results of Hall effect measurements showed that the star copolymer is a semiconducting material, having a conductivity of 0.7 S cm-1, in comparison to the 1.5 S cm-1 of PPy. To the best of my knowledge, these new star copolymers have not been reported in the open literature. Their properties make them potentially applicable for use in biosensors.</p>

The aim of this study was to improve the mechanical and electrical properties of conductive polymer composites. For this purpose, different studies were performed in this dissertation. In order to investigate the effects of the carbon nanotube (CNT) surface treatment on the morphology, electrical and mechanical properties of the composites, poly(ethylene terephthalate) (PET) based conductive polymer composites were prepared by using as-received, purified and modified carbon nanotubes in a twin screw extruder. During the purification of carbon nanotubes, surface properties of carbon nanotubes were altered by purifying them with nitric acid (HNO3), sulfuric acid (H2SO4), ammonium hydroxide (NH4OH) and hydrogen peroxide (H2O2) mixtures. Electron Spectroscopy for Chemical Analysis (ESCA) results indicated the removal of metallic catalyst residues from the structure of carbon nanotubes and increase in the oxygen content of carbon nanotube surface as a result of purification procedure. Surface structure of the purified carbon nanotubes was also modified by treatment with sodium dodecyl sulfate (SDS), poly(ethylene glycol) (PEG) and diglycidyl ether of Bisphenol A (DGEBA). Fourier Transformed Infrared Spectroscopy (FTIR) spectra of the carbon nanotube samples indicated the existence of functional groups on the surfaces of carbon nanotubes after modification. All composites prepared with purified and modified carbon nanotubes had higher electrical resistivities, tensile and impact strength values than those of the composite based on as-received carbon nanotubes, due to the functional groups formed on the surfaces of carbon nanotubes during surface treatment. In order to investigate the effects of alternative composite preparation methods on the electrical and mechanical properties of the composites, in-situ microfiber reinforced conductive polymer composites consisting of high density polyethylene (HDPE), poly(ethylene terephthalate) and carbon nanotubes were prepared in a twin screw extruder followed by hot stretching of PET/CNT phase in HDPE matrix. Composites were produced by using as-received, purified and PEG treated carbon nanotubes. SEM micrographs of the hot stretched composites pointed out the existence of in-situ PET/CNT microfibers dispersed in HDPE matrix up to 1 wt. % carbon nanotube loadings. Electrical conductivity values of the microfibrillar composites were higher than that of the composites prepared without microfiber reinforcement due to the presence of continuous PET/CNT microfibers with high electrical conductivity in the structure. To investigate the potential application of conductive polymer composites, the effects of surfactant usage and carbon nanotube surface modification / on the damage sensing capability of the epoxy/carbon nanotube/glass fiber composite panels during mechanical loadings were studied. Surface modification of the carbon nanotubes was performed by using hexamethylene diamine (HMDA). 4-octylphenol polyethoxylate (nonionic) (Triton X-100) and cetyl pyridinium chloride (cationic) (CPC) were used as surfactants during composite preparation. Electrical resistivity measurements which were performed during the impact, tensile and fatigue tests of the composite panels showed the changes in damage sensing capabilities of the composites. Surface treatment of carbon nanotubes and the use of surfactants decreased the carbon nanotube particle size and improved the dispersion in the composites which increased the damage sensitivity of the panels.

Materials for extreme electrical contacts need to have high electrical conductivity coupled with good structural properties. Potential applications include motor contacts, high power switches, and the components of electromagnetic launch (EML) systems. In particular, the lack of durability of these materials in rail components limits practical EML implementation. These rails experience significant amounts of Joule heating, due to extreme current densities, and subsequent thermally-assisted wear. New more durable materials solutions are needed for these components. A systematic materials selection study was executed to identify and compare candidate materials solutions. Several possible candidate non-dominated materials as well as hybrid materials that could potential fill the "white spaces" on the Ashby charts were identified. A couple potential candidate materials were obtained and evaluated. These included copper-tungsten W-Cu, "self-lubricating" graphite-impregnated Cu, and Gr-W-Cu composites with different volume fractions of the constituents. The structure-property relations were determined through mechanical and electrical resistivity testing. A unique test protocol for exposing mechanical test specimens to extreme current densities up to 1.2 GA/m2 was developed and used to evaluate these candidate materials. The systematic design of multi-functional materials for these extreme electrical contacts requires more than an empirical approach. Without a good understanding of both the tribological and structural performance, the optimization of the microstructure will not be quickly realized. By using micromechanics modeling and other materials design modeling tools coupled with systematic mechanical and tribological experiments, the design of materials for these applications can potentially be accelerated. In addition, using these tools, more complex functionally-graded materials tailored to the application can be systematically designed. In this study, physics- and micromechanics-based models were used to correlate properties to the volume fraction of the constituents of the evaluated candidate materials. Properties correlated included density, elastic modulus, hardness, strength, and electrical resistivity of the W-Cu materials.

Electrically conductive polymer composites are suitable for use in the manufacture of antistatic products and components for electronic interconnects, fuel cells and electromagnetic shielding. The most widely used processing techniques for producing electrically conductive polymer composites place an inherent constraint on the geometry and architecture of the part that can be fabricated. Hence, this thesis investigates selective laser sintering (SLS), a rapid prototyping technique, to fabricate and characterize electrically conductive nanocomposites of Nylon-12 filled with 4% by weight of carbon black. The objective of the dissertation was to study the effects of the SLS process on the microstructure and properties of the nanocomposite. The effect of laser power and the scan speed on the flexural modulus and part density of the nanocomposite was studied. The set of parameters that yielded the maximum flexural modulus and part density were used to fabricate specimens to study the tensile, impact, rheological and viscoelastic properties. The electrical conductivity of the nanocomposite was also investigated. The thermo-mechanical properties and electrical conductivity of the nanocomposites produced by SLS were compared with those produced by extrusion-injection molding. The structure and morphology of the SLS-processed and extrusion-injection molded nanocomposites were characterized using gas pycnometry, gel permeation chromatography, differential scanning calorimetry, electron microscopy, polarized light microscopy and x-ray diffraction. Physical models were developed to explain the effects of the processing technique on the structure and properties of the nanocomposites. Finally, a one-dimensional heat transfer model of the SLS process that accounted for sintering-induced densification and thermal degradation of the polymer was implemented in order to study the variation in part density with respect to the energy density of the laser beam. This dissertation demonstrated that SLS can be successfully used to fabricate electrically conductive polymer nanocomposites with a relatively low percolation threshold. This capability combined with the ability of SLS to fabricate complicated three-dimensional objects without part-specific tooling could open up several new opportunities.

Organic materials are ubiquitous in the geologic environment, and can exert significant influence over the interfacial properties of minerals. However, due to the complexity in their structure and interaction with soil solids, their impact has remained relatively unquantified. This study investigated the engineering behaviors of organoclays, which were synthesized in the laboratory using naturally occurring clay minerals and quaternary ammonium compounds of controlled structure and density of loading. Organic cations were chosen to study the effects of functional group structure and size. The laboratory investigation showed that the presence of the organic cations on the mineral surfaces led to increased hydrophobicity of all clays tested. Conduction studies on the electrical, hydraulic, and thermal properties of the organoclay composites suggested that increasing the total organic carbon content resulted in decreased electrical and thermal conductivity, but increased hydraulic conductivity, due to the reduced swelling of the base clay mineral phase. Electrokinetic properties of the organoclays illustrated that compared with the clay's naturally occurring inorganic cations, exchanged quaternary ammonium cations were more likely bound within a particle's shear plane. Consequently, organoclays had less negative zeta potential than that of unmodified bentonite. Increasing the length of one carbon tail was more effective at binding organic cations within the shear plane than increasing the size of the cation, when compared on the basis of total organic carbon content. In terms of large strain strength, the modified organic clays exhibited increased shear strength, in part owing to the reduction in water content caused by the presence of the hydrophobic organic layering. Shear strength increased with single carbon tail length or with cation size, although the latter effect tended to reach a plateau as the length of the four short cation tails increased from 2 to 4. In terms of small strain behavior, the shear modulus was shown to be a function of the total organic carbon content. It is believed that number of particle contacts increased as the organic carbon content increased. Stiffness increased as either the size of the cation or the total organic carbon content was increased. Damping also increased as the organic loading was increased, with the organic phase acting as an energy dissipation mechanism.

<p>Among the obstacles for the commercialization of the MoltenCarbonate Fuel Cell (MCFC), the dissolution of thestate-of-the-art lithiated NiO cathode is considered as aprimary lifetime limiting constraint. Development ofalternative cathode materials is considered as a main strategyfor solving the cathode dissolution problem. LiFeO₂and LiCoO₂had earlier been reported as the most promisingalternative materials; however, they could not satisfactorilysubstitute the lithiated NiO. On the other hand, ternarycompositions of LiFeO₂, LiCoO₂and NiO are expected to combine some desirableproperties of each component. The aim of this work was todevelop alternative cathode materials for MCFC in the LiFeO₂-LiCoO₂-NiO ternary system. It was carried out byinvestigating electronic conductivity of the materials, firstin the form of bulk pellets and then in ex-situ sinteredporous-gas-diffusion cathodes, and evaluating theirelectrochemical performance by short-time laboratory-scale celloperations.</p><p>Materials in the LiFeO₂-NiO binary system and five ternary sub-systems,each with a constant molar ratio of LiFeO₂:NiO while varying LiCoO₂content, were studied. Powders withcharacteristics appropriate for MCFC cathode fabrication couldbe obtained by the Pechini method. The particle size of LiFeO₂-LiCoO₂-NiO powders considerably depends on thecalcination temperature and the material composition. Theelectrical conductivity study reveals the ability of preparingLiFeO₂-LiCoO₂-NiO materials with adequate electricalconductivity for MCFC cathode application.</p><p>A bimodal pore structure, appropriate for the MCFC cathode,could be achieved in sintered cathodes prepared usingporeformers and sub-micron size powder. Further, this studyindicates the nature of the compromise to be made between theelectrical conductivity, phase purity, pore structure andporosity in optimization of cathodes for MCFC application. Cellperformance comparable to that expected for the cathode in acommercial MCFC could be achieved with cathodes prepared from20 mole% LiFeO₂- 20 mole% LiCoO₂- 60 mole% NiO ternary composition. It shows aniR-corrected polarization of 62 mV and a iR-drop of 46 mV at acurrent density of 160 mAcm^-2at 650 °C. Altogether, this study revealsthe possibility of preparing LiFeO₂-LiCoO₂-NiO cathode materials suitable for MCFCapplication.</p><p>Keywords: molten carbonate fuel cell (MCFC), MCFC cathode,LiFeO₂-LiCoO₂-NiO ternary compositions, electrical conductivity,porous gas diffusion electrodes, polarization, electrochemicalperformance, post-cell characterization.</p>