The positive temperature coefficient of resistivity (PTCR) sensors is resistor materials that undergo a sharp change in resistivity at a designed Curie temperature due to its unique structure and chemical composition. This effect serves important control functions in a wide variety of electronic circuitry and similar applications. Conventional calcining of mixed oxides method (CMO) is used for fabricating lanthanum doped barium titanate (BaTiO3) for PTCR behaviour through solid-state-sintering route, at 1100°C, 1350°C. Two batches of samples were fabricated at low and high sintering temperatures of 1100°C, 1350°C respectively. The effect of different concentrations of donor dopant on BaTiO3 on the electrical properties of Ba(1-x)LaxTiO3 with x= 0.0005, 0.001, 0.002, 0.0025, 0.003 mol%, is investigated at low sintering temperature. The influence of lantanum doping with Al2O3+SiO2+TiO2 (AST) as sintering aids on the electrical properties of Ba(1-x)LaxTiO3 with x= 0.0005, 0.001, 0.003 mol%, is also investigated. The results of the electrical characterization for the first batch of samples showed an increase in room temperature resistance with increaisng donor concentration. Also the results of the electrical characterization for the second batch of samples also showed the same increase in room temperature resistance with increasing donor concentration. For first batch of sensors the high room temperature resistance keeps the jump small and these materials showed V-shaped NTCR-PTCR multifunctional cryogenic sensor behavior with a strong negative coefficient of resistance effect at room temperature.Where as the second batch of sensors showed few orders of magnitude rise in resistivity values. The La-doped BaTiO3 ceramics co-doped with Mn gives an enhanced PTCR effect which can be exploited for various sensor applications.

The electronics industry is shifting its emphasis from reducing transistor size and operational frequency to increasing device integration, reducing form factor and increasing the interface of electronics with their surroundings. This new emphasis has created increased demands on the electronic package. To accomplish the goals to increase device integration and interfaces will undoubtedly require new materials with increased functionality both electrically and mechanically. This thesis focuses on developing new interconnect and printable conductive materials capable of providing power, ground and signal transmission with enhanced electrical performance and mechanical flexibility and robustness. More specifically, we develop: 1.) A new understanding of the conduction mechanism in electrically conductive composites (ECC). 2.) Develop highly conductive stretchable silicone ECC (S-ECC) via in-situ nanoparticle formation and sintering. 3.) Fabricate and test stretchable radio frequency devices based on S-ECC. 4.) Develop techniques and processes necessary to fabricate a stretchable package for stretchable electronic and radio frequency devices. In this thesis we provide convincing evidence that conduction in ECC occurs predominantly through secondary charge transport mechanism (tunneling, hopping). Furthermore, we develop a stretchable silicone-based ECC which, through the incorporation of a special additive, can form and sinter nanoparticles on the surface of the metallic conductive fillers. This sintering process decreases the contact resistance and enhances conductivity of the composite. The conductive composite developed has the best reported conductivity, stretchability and reliability. Using this S-ECC we fabricate a stretchable microstrip line with good performance up to 6 GHz and a stretchable antenna with good return loss and bandwidth. The work presented provides a foundation to create high performance stretchable electronic packages and radio frequency devices for curvilinear spaces. Future development of these technologies will enable the fabrication of ultra-low stress large area interconnects, reconfigurable antennas and other electronic and RF devices where the ability to flex and stretch provides additional functionality impossible using conventional rigid electronics.

A new route to a well-defined block copolymer with alternating PEO-solubilising groups and fluorinated distyrylbenzene units was established. The Horner Wittig reaction was used as the polycondensation reaction. The non-fluorinated analogue of this block copolymer was prepared via the Wittig reaction. Both polymers were soluble in chloroform and free-standing films could be cast from solution. The position of the HOMO and LUMO energy levels of these two materials were determined by a combination of cyclic voltammetry, UV photoelectron spectroscopy and UV/Vis absorption spectroscopy. The presence of fluorine substituents on the distyrylbenzene unit had no influence on the HOMO-LUMO band-gap (3.0 eV). However, the position of these two energy levels relative to the vacuum level was shifted to higher energies (0.85 eV shift) in the case of the fluorinated block copolymer. The photoluminescence quantum efficiency of the fluorinated block copolymer was 17%, that of the non-fluorinated block copolymer was 34%. The former was used as the electron conducting layer in a light emitting diode with poly(p-phenylene vinylene) as the emissive layer. The latter was used as the emissive layer in light emitting diodes. Luminances over 2000 cd/m(^2) were observed for devices based on the non-fluorinated block copolymer using indium tin oxide as the anode and aluminium as the cathode. The luminescence efficiency of such devices was as high as 0.5 cd/A, corresponding to an internal quantum efficiency of 1.1%.Furthermore, an oligo(p-phenylene vinylene) was synthesised that contained two terminal fluorinated benzene rings and two central non-fluorinated benzene rings, all connected by vinylene bridges. This material aggregated in a 'brickwall' motif, where each molecule overlaps with two halves of molecules in the row above and below. The structure of this J aggregate is due to aryl-fluoroaryl-interactions and was demonstrated by X-ray crystal structure analysis.

Structural changes of electroactive species during electrochemical reactions cannot be determined from the electroanalytical technique alone. By incorporating spectroscopic techniques with electrochemistry, additional information about analyte structure and composition of the double layer can be obtained during electrochemical processes. Several spectroscopic methodologies have been tailored for this purpose including electronic and vibrational spectroscopies. Mid-infrared ATR spectroscopy is especially interesting as it provides in-situ information about adsorbates at the electrode surface. Mass transport limitations present in mid-infrared (mid-IR) external reflection and transmission spectroelectrochemistry are circumvented with attenuated total reflectance (ATR) spectroelectrochemistry. However, limitations of appropriate electrode materials for internal reflection configurations have hindered widespread adoption of the technique. The work described in this thesis focuses on the development and coupling of electrically conducting DLC films with mid-IR transparent multi-reflection waveguides for ATR spectroelectrochemistry. Conducting diamondlike carbon (DLC) thin films were developed utilizing pulsed laser deposition systems in collaboration with Joanneum Research (Leoben, Austria) and at the University of North Carolina (Chapel Hill). Nitrogen doping and incorporation of noble metal nanoclusters were investigated as approaches aimed at improving the electrical conductivity of DLC. Detailed compositional studies of nitrogen-doped DLC layers showed that sp2-hybridized carbon is responsible for the observed electrochemical activity. Optical transparency of thin (~ 40 nm) DLC layers in the mid-IR regime was confirmed by transmission-absorption measurements upon deposition on zinc selenide ATR waveguides. Additionally, the first spectroelectrochemical application of conducting DLC films was demonstrated via the electropolymerization of polyaniline onto coated ATR elements. Metal-DLC nanocomposite layers were investigated with various analytical techniques obtaining detailed compositional information. Improved electrochemical activity of metal-DLC demonstrated their suitability as electrode materials. Sufficient mid-IR transmissivity of metal-DLC coated germanium waveguides was displayed to enable spectroelectrochemical application. Finally, electropolymerization of poly(4-vinylpyridine) in acetonitrile was pursued to produce highly cross-linked ion-exchange membranes for spectroelectrochemical sensing. The composition of the pre-polymerization mixture and deposition conditions were tailored to obtain uniform semipermeable membranes. Diffusion of cations to electrodes is restricted by performing the electropolymerization as established herein. By employing the described electropolymerization procedure at DLC-coated waveguides, spectroelectrochemical sensing strategies can now be extended into the mid-IR regime.

The positive temperature coefficient of resistivity (PTCR) sensors is resistor materials that undergo a sharp change in resistivity at a designed Curie temperature due to its unique structure and chemical composition. This effect serves important control functions in a wide variety of electronic circuitry and similar applications. Conventional calcining of mixed oxides method (CMO) is used for fabricating lanthanum doped barium titanate (BaTiO3) for PTCR behaviour through solid-state-sintering route, at 1100°C, 1350°C. Two batches of samples were fabricated at low and high sintering temperatures of 1100°C, 1350°C respectively. The effect of different concentrations of donor dopant on BaTiO3 on the electrical properties of Ba(1-x)LaxTiO3 with x= 0.0005, 0.001, 0.002, 0.0025, 0.003 mol%, is investigated at low sintering temperature. The influence of lantanum doping with Al2O3+SiO2+TiO2 (AST) as sintering aids on the electrical properties of Ba(1-x)LaxTiO3 with x= 0.0005, 0.001, 0.003 mol%, is also investigated. The results of the electrical characterization for the first batch of samples showed an increase in room temperature resistance with increaisng donor concentration. Also the results of the electrical characterization for the second batch of samples also showed the same increase in room temperature resistance with increasing donor concentration. For first batch of sensors the high room temperature resistance keeps the jump small and these materials showed V-shaped NTCR-PTCR multifunctional cryogenic sensor behavior with a strong negative coefficient of resistance effect at room temperature.Where as the second batch of sensors showed few orders of magnitude rise in resistivity values. The La-doped BaTiO3 ceramics co-doped with Mn gives an enhanced PTCR effect which can be exploited for various sensor applications.

CAPES / A investigação científica na área de tecnologia de sementes é baseada em técnicas que visem a redução de custos e de tempo, padronização, aperfeiçoamento e estabelecimento dos métodos de análise, mantendo um alto nível de confiabilidade dos resultados. O presente estudo buscou elucidar a confiabilidade dos testes de condutividade elétrica e pH do exsudato comparado com o teste clássico de germinação, sendo este desenvolvido na forma de dois estudos separados, porém interrelacionados entre si, quanto aos seus objetivos finais. O material experimental do presente estudo foi composto por sementes das espécies Aspidosperma parvifolium (guatambu), Aspidosperma polyneuron (peroba-rosa), Cabralea canjerana (canjerana), Cariniana legalis (jequitibá), Gallesia integrifolia (pau-d'alho), Handroanthus chrysotrichus (ipê-amarelo), Lonchocarpus campestris (rabo-de-bugio) e Pterogyne nitens (amendoim-do-campo). A qualidade fisiológica das sementes das espécies estudadas foi avaliada por meio dos teste de condutividade elétrica e pH do exsudato pelos métodos massal e individual, sendo comparados e correlacionados com o resultado obtido no teste de germinação. Desta forma, as mesmas sementes avaliadas foram postas para germinar permitindo a comparação dos resultados entre os testes. Além dos métodos testados, foram avaliados os períodos de embebição das sementes para leitura da condutividade e do pH, as quais corresponderam a 2, 4, 6, 8, 24 e 48 horas. O teste de condutividade elétrica se mostrou eficiente em ambos os métodos utilizados para avaliação da qualidade fisiológica das sementes das espécies estudadas quando comparado ao teste padrão de germinação. O teste de pH do exsudato aplicado pelo método individual se mostrou mais eficiente e criterioso para avaliação da qualidade fisiológica das sementes das espécies estudadas, do que o método massal. Para as espécies Gallesia integrifolia, Cariniana legalis e Lonchocarpus campestris os testes de pH do exsudato não foram eficientes devido a fraca ou inesixtente correlação entre a germinação e o pH do meio. / The scientific research in seed technology is based on techniques that aim the reduction of costs and time, standardization, improvement and establishment of analytical methods while maintaining a high level of reliability of the results. This study sought to elucidate the reliability of electrical conductivity and pH of the exudate compared to the classic germination test, which was developed in two separate studies, however interrelated with each other, as to their final goals. The experimental material of this study consisted of seeds of the species Aspidosperma parvifolium (guatambu), Aspidosperma polyneuron (peroba-rosa), Cabralea canjerana (canjerana), Cariniana legalis (jequitibá), Gallesia integrifolia (pau-d'alho), Handroanthus chrysotrichus (ipê-amarelo), Lonchocarpus campestris (rabo-de-bugio) and Pterogyne nitens (amendoim-do-campo). The physiological quality of the studied seed species was evaluated through the electrical conductivity and pH test of the exudate by mass and individual methods being compared and correlated with the results obtained in the germination test. In addition to the tested methods, imbibition periods of the seeds were evaluated for conductivity and pH, which corresponded to 2, 4, 6, 8, 24 and 48 hours. The electrical conductivity test was efficient in both of the used methods to evaluate the physiological quality of the studied seed species when compared to the standard germination test. The pH test of the exudate applied by the individual method was more efficient and thorough to evaluate the physiological quality of the studied seed species, than the mass method. For the species Gallesia integrifolia, Cariniana legalis and Lonchocarpus campestris the pH tests of the exudate tests were not efficient due to poor or absent correlation between germination and pH.

Made available in DSpace on 2014-10-09T12:46:40Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:06Z (GMT). No. of bitstreams: 1 07610.pdf: 4151963 bytes, checksum: 44edae9437590a9401a9113766dec153 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Novel applications for calix[4]recorcinarene (C[4]RA) sensing membranes have been investigated. A comprehensive deposition study was carried out, encompassing casting, spin coating and Langmuir Blodgett (LB) deposition. The spin coating thickness depended on the angular velocity w, following the description of d = c.wx with coefficients of x - 0.44 and - 0.48 for concentrations of 1 mg/ml and 2mg/ml respectively. The analysis of the LB deposited films established a thickness of 0.95 nm for a monolayer. Furthermore the C[4]RA, was successfully employed as a deposition matrix for a non surface active polymer, poly-ortho-methoxy aniline (POMA), which can otherwise not be deposited by LB. The composite film showed good homogeneity and based on thickness and UV measurements a structural model for it was developed, in which two polymer strands aligned themselves per C[4]RA layer, resulting in a monolayer thickness of 2.1 - 2.2 nm. The response of the C[4]RA and the composite membranes to a variety of organic and inorganic gaseous pollutants was investigated by Surface Plasmon Resonance studies, conductivity and capacitance measurements and UV spectroscopic studies. The integration of cast films into the gate of a charge flow transistor, is the first application of pure calixarenes in a conduction based sensor. The turn on response of the transistor is modulated by a variety of organic vapours, at the saturation vapour pressure, showing selectivity between polar and non-polar solvents, i.e. chloroform, methanol, acetone and hexane, with no cross sensitivity to water vapour. The modulation lies within factors of 45 for CHCI3 and 13 for CH3OH. The conductivity increase is partially attributed to micro-condensation of the vapours inside the micro-porous membrane. A successful application of this implementation as an explosion guard sensor for acetone is demonstrated. Gold electrodes with and without C[4]RA LB films have been characterised using impedance spectroscopy and cyclic voltammography. The modification of the gold electrodes by the C[4]RA film changes their constant phase element impedance, given by 1/(w.Q)" with w being the angular velocity. The observed values were from Q =0.725-10 -5 Farad and n = 0.87 to Q = 0.828-10-6 Farad and n = 0.82. Organic analyteslike, chloroform and acetone in water can be successfully detected with these electrodes. It is shown by cyclic voltammetry, that the permeability of the C[4]RA LB films is modulated by the organic solvents.

The development degree of a society depends mainly on the available natural resources for its development, in second level to the technology and the culture. The soil and the hydrics resources are very important natural resources for the humanity from where is extracted the sustenance of the societies, the quality and the amount of the natural resources are very relative, it depends on natural factors and the technology used for it exploration. In that way, it s very important to take in consideration the soil preservation and of the hydrics resources since they are a great indicator of the society life quality. In the last decades, we observing that the capitalist market are concerned with the amount and the quality of his products and put away linked subjects to productive systems sustainability and just worried in obtaining fast profit. Due to concern with the quality of the hydrics resources linked with the type and the way of the earth use, this work has as central objective to verify if you varied of the water bodies depend on the relief and in the ways of the earth use, appraised for remote sensing and field work from where were extracted information as: amount of sediments, electric conductivity, potential of hydrogen and temperature of the water bodies. It was observed that the areas of the hydrographic basins possess great relationship with all the limnological variables. In the hydrographic basins the potential of hydrogen is more related with the area size and the amount of forests contained in it. The total of sediments in suspension mainly depends on the size of the hydrographic basin area, but there are other factors that influence in the percentage of sediments in suspension as the largest steepness than 47% and the steepness among 12% to 47% with the presence of fields. The electric conductivity verified in the hydrographic basins studied possesses a strong relationship with the steepness classes among 12% to 47%, with the total area hydrographic basin, with fields, pastures and exposed soil. / O grau de desenvolvimento de uma sociedade depende principalmente dos recursos naturais disponíveis para o seu desenvolvimento, em segundo a tecnologia e a cultura. O solo e os recursos hídricos são recursos naturais muito importantes para a humanidade de onde se extrai o sustento das sociedades, a qualidade e a quantidade dos recursos naturais são muito relativas, dependem de fatores naturais e a tecnologia utilizada para a sua exploração. Dessa forma é muito importante levar em consideração a preservação do solo e dos recursos hídricos já que é um grande indicador de qualidade de vida de uma sociedade. O que vem se observando, nas ultimas décadas, que o mercado capitalista preocupado com quantidade e qualidade dos produtos acabou deixando de lado questões vinculadas a sustentabilidade dos sistemas produtivos, preocupou-se apenas em obter lucro rápido. Apreensivo com a qualidade dos recursos hídricos que estão vinculados com o tipo e o modo de uso da terra, este trabalho tem como objetivo central verificar se variáveis dos corpos de água dependem do relevo e das formas de uso da terra, avaliado por sensoriamento remoto e trabalho de campo de onde foram extraídas informações como: quantidade de sedimentos, condutividade elétrica, potencial de hidrogênio e temperatura dos corpos de água. Observou-se que as áreas das microbacias hidrográficas possuem grande relação com todas as variáveis limnológicas. O potencial de hidrogênio nas microbacias hidrográficas está mais relacionado com o tamanho da área e a quantidade de matas nas microbacias hidrográficas. O total de sedimentos em suspensão depende principalmente do tamanho da área da microbacia hidrográfica, mas há outros fatores que influenciam na porcentagem de sedimentos em suspensão como as declividades maiores que 47% e as declividades entre 12% a 47% com a presença de campos. A condutividade elétrica verificada nas águas das microbacias hidrográficas estudadas possui forte relação com a declividade de 12% a 47%, com a área total da microbacia, dos campos, das pastagens e do solo exposto.

Made available in DSpace on 2014-06-11T19:28:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-07-25Bitstream added on 2014-06-13T19:16:31Z : No. of bitstreams: 1 sotogonzales_jl_me_jabo.pdf: 308779 bytes, checksum: 5145ae6e7c3cbcbb34d37f4d6766a506 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Essa pesquisa teve como objetivo estudar a variabilidade da germinação e caracteres biométricos e da qualidade fisiológica de sementes entre matrizes de farinha-seca [Albizia hassleri (Chod.) Burkart.] – Foram empregadas 16 matrizes de farinha-seca coletadas nas rodovias de acesso à cidade de Jaboticabal, SP. O estudo de biometria de sementes constou da avaliação do tamanho (comprimento, largura e espessura), da massa fresca e do número de sementes por quilograma. O teste padrão de germinação foi conduzido em diferentes temperaturas (20, 25, 30, 20-30 e 25-35 ºC), sobre papel, por 19 dias e fotoperiodo de 8 h. O teste de condutividade elétrica (CE) foi conduzido em cinco repetições de 20 sementes, embebidas em 75 mL de água destilada, por períodos variando de 2 a 120 h embebição, a 25ºC. O teste de envelhecimento acelerado (EA), foi conduzido a 42 ºC por 48 h pelo método do gerbox, com quatro repetições de 25 sementes. De acordo com os resultados obtidos, concluiuse que: há considerável variabilidade entre as matrizes quanto aos caracteres biométricos das sementes; o teste padrão de germinação pode ser conduzido a 30, 20- 30 e 25-35 ºC por 19 dias; o teste de CE conduzido a 25 ºC, por períodos de 2 a 120 h de embebição em 75 mL de água destilada, não foi eficiente para discriminar as matrizes quanto a qualidade das sementes; o teste de EA conduzido a 42 ºC por 48 h, pelo método do gerbox, foi eficiente para avaliação da qualidade fisiológica das sementes de diferentes matrizes. Houve ampla variabilidade entre as matrizes quando ao processo germinativo, apresentando distintos níveis de vigor. / This research had the objective to study the variability of germination and biometrics characters and the physiological quality of seeds between mother trees of [Albizia hassleri (Chod.) Burkart.] -. Were used 16 mother trees of dry flour collected in the access of highways around the city of Jaboticabal, state of São Paulo, Brazil. The seed biometry were evaluated by the fruit size (length, width and thickness), the fresh weight and the number of seeds for kilogram. The germination test was performed at different temperatures (20, 25, 30, 20-30 and 25-35 ºC), on paper, for 19 days and 8 hours photoperiod. The electric conductivity test (EC) was made in five replications of 20 seeds, in 75 mL of distilled water, for periods varying from 2 to 120 hours of imbibition at 25 ºC. The accelerated aging test (AA). was made at 42 ºC for 48 hours with the method of gerbox, with four replications of 25 seeds. According to the results was concluded that: there was considerable variability between the mother trees in relation to the seeds biometrics characters; the germination can be performed at 30 , 20-30 and 25-35 ºC, for 19 days; the EC test conducted at 25 ºC, for the periods of 2 a 120 hours of imbition in 75 mL of distilled water, was not efficient to discriminate the mother trees in relation to the seed quality; the accelerated aging test was efficient for evaluate the seeds physiological quality; there was a high variability between the mother trees in relation to germination and was observed different vigor levels.