Grain boundary processes play a major role in controlling different rate processes in yttria stabilized tetragonal zirconia. The present study concentrated on rate processes in tetragonal zirconia, which were significantly influenced by the grain boundary processes. In this present study, nanocrystalline zirconia with grain size as low as 66 nm and density as high as 98.5% was processed using a two steps sintering-sinterforging process in the temperature range of 1473K to 1373K. Significant suppression of grain growth was noted in the second step of the two step process. It was observed that two step sintering-sinterforging process can reduce the processing time by an order of magnitude compared to the two step sintering process. A high grain size dependency of 3.3 indicated grain boundary controlled process dominating this technique. The dense nanocrystalline zirconia was used for microstructural and deformation characterization. An influence of electric field on grain growth behaviour was studied by annealing the specimens at 1573K for 10 hours under an applied field of 4 V/cm to 80 V/cm. It was noticed that grain growth was significantly retarded under a very weak field and the magnitude of retardation dependent on the applied voltage, an extensive grain growth was observed on the other occasion when the applied voltage crossed the threshold value of 3.5V. It was proposed that electrical boundary resistance provides minima in the grain boundary energy during annealing and that retards the grain growth. This technique presented a huge potential application in ceramic processing involving rate process. Again the grain boundary process was reported to control this phenomenon. Low temperature creep properties of nanocrystalline zirconia were investigated in great detail in the present study. Grain boundary sliding was noted as the mode of deformation at 1423 K. Study on the specimens with wide range of grain sizes (65 nm to ~0.4 µm) suggested that the deformation mechanism of the nanograin is similar to that of the submicron grain zirconia. A study on the segregation of yttrium ions to the grain boundaries showed that the segregation behaviour of nanograin and submicron grain 3YTZ was similar, which again indicated towards the possibility of nanocrystalline tetragonal zirconia to be superplastic as the scaling law was applicable from submicron to nanocrystalline 3YTZ. Grain boundary sliding is the mode of deformation of 3YTZ at high temperatures. This study aimed at understanding the influence of grain boundary sliding on rate processes at the boundary namely grain boundary diffusion. Grain boundary diffusivity of the deformed specimens was measured using secondary ion mass spectroscopy. The study revealed that the sliding process is much slower compared to the atomic jumps causing grain boundary diffusion, hence no significant influence of the grain boundary sliding on grain boundary diffusion was observed. This present study demonstrated new techniques which have a huge potential application in processing ceramics at low temperatures. This study also developed an understanding of the grain boundary processes which involved in low temperature rate processes of nanocrystalline zirconia.

La cascarilla cerámica es un material que se emplea principalmente para la realización de moldes en fundición. Esta investigación demuestra que la cascarilla cerámica puede ser empleada para la realización de escultura con una definición excepcional en su acabado. La investigación ha permitido identificar una serie de ventajas que presenta el material para afrontar las dificultades de un artista durante la realización de una escultura. La investigación se ha desarrollado en cinco etapas: En la primera etapa se recogió información sobre la cascarilla como material de proceso. Este fue el punto de partida para la investigación. En la segunda etapa se estableció la composición adecuada de la papilla, tanto en porcentajes como en tipo de aglutinante, y la curva de cocción. Para ello, se valoró sus características para la aplicación, el espesor, el secado, la resistencia mecánica, el coeficiente de reducción y la porosidad. En la tercera etapa se verificó que la cascarilla se adapta a todo tipo de materiales que ejercen de soporte. Se comprobó también que la papilla puede ser empleada con distintos procedimientos escultóricos: modelado, moldeado mediante molde de silicona o escayola, encofrado, con armazón metálico interno, etc. Además se establecieron métodos para reparar y modificar la cascarilla mediante herramientas manuales y eléctricas. En la cuarta etapa hemos comprobado distintas maneras de modificar la superficie de la cascarilla mediante otro tipo de minerales que no afectan la estructura: introducción de limadura de cobre, bronce y hierro en la papilla cerámica, distintos procedimiento de coloración en frío o caliente, mediante esmalte, engobe, etc. En la quinta etapa se realizaron esculturas empleando los métodos que se establecieron en las etapas anteriores, para verificar dicha hipótesis. / The ceramic shell is a material mainly used for making foundry molds. This research demonstrates that ceramic shell can be used for making sculptures with exceptional definition in its finish. The research has identified a number of advantages of the material to meet the challenges of an artist during the making of a sculpture. The research has been developed in five stages: In the first stage data were collected from the chaff as the process material. This was the starting point for research. In the second stage, we have set the appropriate composition of the slurry, both in percentage and type of binder, and firing curve. To this end, we evaluated the application characteristics, thickness, drying, mechanical strength, the reduction coefficient and porosity. In the third stage it was observed that the husk is suitable for all types of materials acting as support. It was also found that the slurry can be used with various sculptural processes: modeling, molding using silicone or plaster mold, shuttering, with internal metal frame, and so on. In addition, we have established methods to repair and modify the husk by hand and power tools. In the fourth stage we have found ways to modify the surface of the husk with other minerals that affect the structure: introduction of filing of copper, bronze and iron in the slurry ceramics, different staining procedure in hot or cold, by enamel slip, and so on. In the fifth stage sculptures were made using the methods established in the previous stages, to verify this hypothesis.

Ceramic membrane processes are a rapidly emerging technology for water treatment, yet virtually no information on the performance and fouling mechanisms is available to the industry. Ceramic microfiltration of model feed solutions and a synthetic river water was examined, and a systematic comparison with polymeric counterpart was performed. The results suggested that the models which have been applied to polymeric membranes agreed well with the ceramic membrane filtration data. The fouling was characterized by the initial pore blocking mechanism and transition to the cake filtration mechanism at a later phase. Cake resistance was dominant and readily removable by physical cleaning. The effects of solution chemistry including ionic strength, divalent ion concentration and pH on the flux behavior were comparatively evaluated for ceramic and polymeric ultrafiltration of synthetic water containing model natural organic matter. Experimental evaluations further included resistance-in-series model analysis, organic matter fouling visualization using quantum dots, batch adsorption test, and contact angle measurement, and provided a quantitative a quantitative comparison of fouling characteristics between ceramic and polymeric membranes. The results collectively suggested that the effects of solution chemistry on the fouling behavior with ceramic membranes were mostly similar with polymeric membranes in terms of trends, while the extents varied depending on water quality parameters. Less fouling tendency and better cleaning efficiency were observed with the ceramic membranes, which was a promising finding for ceramic membrane application to surface water treatment. The study further examined a coagulation-ceramic membrane process as a robust option for surface water treatment. The performance of the hybrid system was evaluated using selected surface waters by varying coagulation conditions and types of coagulants. Results suggested that ceramic membranes experienced relatively less fouling and had better cleaning efficiency than polymeric counterpart. The results of this study provide critical information to guide the industry practitioners, consultants, and regulatory agents considering early adoption of this new technology as well as fundamental knowledge upon which further in-depth studies can be built.

Systemic inflammation involves a complex array of cytokines that can result in organ dysfunction. Mortality remains high despite the vast amount of research conducted to find an effective biomarker. The cause of systemic inflammation can be broad and non-specific; therefore, this research investigates using transendothelial electrical resistance (TEER) measurements to better define systemic inflammatory response syndrome (SIRS)/sepsis within a patient. Results show a difference in TEER measurements between healthy individuals and SIRS-rated patients. This research also displays correlations between TEER measurements and biomarkers currently studied with systemic inflammation (tumor necrosis factor-α, C- reactive protein, procalcitonin). Furthermore, this research also presents the groundwork for developing a microfluidic cell-based biosensor using low temperature co-fired ceramic materials. An LTCC TEER-based microfluidic device has the potential to aid in a more effective treatment strategy for patients and potentially save lives.

The inherent thermal resistance of ceramic membranes allows for treatment of industrial waters at elevated temperatures. Traditionally, the high temperature of wastewater has been an issue compromising the integrity of polymeric membrane systems or requiring the temperature to be lowered for further treatments. In ceramic membrane systems, a decrease in viscosity with increasing temperature, however, can be utilized, which increases the permeate flux. In this study, the fouling of ceramic ultrafiltration by feed solutions containing colloidal silica was evaluated at temperatures between 25 – 90 °C seen in various industries. Ceramic membranes were able to perform well at elevated temperatures up to 90 ºC with sustained mechanical and chemical integrity. Results showed net benefit of filtration at elevated temperatures on permeate flux in spite of increasing total fouling resistance with temperature. When the temperature increased from 25 to 90 °C, there was a 90% increase in steady-state permeate flux. The dominant resistance was physically removable fouling, and the increase in fouling with feed temperature was supported by force balance analyses. This study provides a foundation from which further studies can be developed including pilot-scale testing, use of real wastewater, and the effects of operating conditions.

L’objet de la présente étude relève d’une approche technologique du domaine ibérique à la fin de l’Âge du Fer. L’orientation donnée à notre étude est celle d’un intérêt porté à l’origine d’une innovation : les pratiques de cuisson de la céramique ibérique. Il s’agit d’identifier les modalités selon lesquelles s’articulent matières disponibles, techniques et matériaux fabriqués et de mettre en évidence les jeux d’actions et de rétroactions qui existent entre ces trois composantes au sein de la vallée de l’Èbre. L’étude du matériel issu d’un centre de production – l’atelier de potiers du Mas de Moreno (Foz-Calanda, Teruel, Espagne ; iiie-ier s. av. J.-C.) – revêt dans ce cadre un intérêt particulier : en s’attachant à ce qui relève du raté, il devient possible d’isoler les causes du refus et, par contraste, de mettre en évidence les choix caractérisant une situation normale de production. L’analyse des matériaux fabriqués au sein de l’atelier permet alors d’illustrer la complexité des mécanismes en jeu. En s’attachant à l’articulation entre la gestion des aspects thermiques liés à la cuisson et la mise en œuvre d’une matière argileuse aux qualités particulières, il est possible de proposer une restitution des modalités de gestion du risque au cours de la production. L’acceptation d’une part de risque apparaît alors comme un des moteurs de l’innovation, autorisant une évolution progressive des pratiques de cuisson et l’adoption de techniques nouvelles. / This work aims to understand the technological history of Iron Age Iberia, particularly by focusing on Iberian ceramic firing practices. By highlighting feedbacks and interconnections, main objectives of this thesis are the investigation of the links between the pathways of row material, knowhow and products evolution in the Ebro valley. Details investigations were conducted on the potter workshop of the Mas de Moreno (Foz-Calanda, Teruel, Spain; 3rd-1st c. BC). Here the examination of the variety of defects and failures during the production process allowed a specification of the ideal process. The overall complexity of the production process was evaluated by chemical and mineralogical material analysis. Thermal details of ceramic firing and peculiar properties of the used clayey material enabled us, for the first time, to propose a hypothesis on the production risk management. It appears that the acceptance of risk was the driving force for innovation, allowing for a gradual and steady evolution of the firing practices and the adoption of new techniques.

O tungstato de zircônio (ZrW2O8) é um material cerâmico que exibe diversos compor-tamentos incomuns: expansão térmica negativa, amorfização induzida por altas pressões (entre 1,5 GPa e 2,0 GPa) e recristalização endotérmica quando aquecido a temperaturas superiores a 600 C. A relaxação estrutural exotérmica e irreversível é o fenômeno que precede a recristalização da fase amorfa do composto e é caracterizada por um espectro contínuo de energia de ativação. Este trabalho tem como objetivo principal explorar o mecanismo de relaxação estrutural da fase amorfa do tugnstato de zircônio, em particular, determinar se este fenômeno envolve a quebra das ligações W-O formadas durante a amorfização. Com esta finalidade, foram utilizadas as técnicas de ressonância magnética nuclear de estado sólido do núcleo 17O (RMN), espectroscopia Raman e espectroscopia na região do infravermelho longínquo (FT-FAR-IR). Além disso, como objetivo secundário, foi calculado, por meio de medidas de calorimetria exploratória diferencial modulada (MDSC) o espectro de energia de ativação deste processo. Esse cálculo envolveu a resolução do problema inverso originado do modelo cinético utilizado, que resulta em uma equação integral de Fredholm do primeiro tipo. O espectro obtido apresenta uma distribuição assimétrica de probabilidade de que processos cinéticos ocorram como função da energia com dois máximos em aproximadamente 1.4 eV e 2.7 eV, indício de que dois processos com mecanismos distintos ocorrem durante a relaxação. A evolução da estrutura amorfa durante a relaxação foi acompanhada por RMN do estado sólido do núcleo 17O e por meio das técnicas de espectroscopias vibracionais. Os resultados indicam que durante a relaxação estrutural da fase amorfa do ZrW2O8 não ocorre quebra das ligações W-O formadas durante a amorfização, mas apenas um rearranjo local dos átomos de oxigênio. Somente na temperatura de recristalização é fornecida energia suficiente para que ocorra o rompimento destas ligações. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2016-12-19T16:39:57Z No. of bitstreams: 1 Tese Fernanda Miotto.pdf: 6599930 bytes, checksum: 758989ba90137070ed1f00a6452fd4f6 (MD5) / Made available in DSpace on 2016-12-19T16:39:57Z (GMT). No. of bitstreams: 1 Tese Fernanda Miotto.pdf: 6599930 bytes, checksum: 758989ba90137070ed1f00a6452fd4f6 (MD5) Previous issue date: 2016-12-19 / Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, FAPERGS. / Zirconium tungstate (ZrW2O8) is a ceramic material which exhibits several unusual properties such as negative thermal expansion, amorphization induced by high pressures ( 1.5 GPa and 2.0 GPa) and endothermic recrystallization when heated to temperatures above 600 C. The irreversible exothermic structural relaxation is the phenomenon that precedes the recrystallization of the amorphous phase and is characterized by a continuous activation energy spectrum. This work aims to explore the structural relaxation mechanism of the amorphous phase of zirconium tungstate, in particular, determine whether this phenomenon involves the breakdown of W-O bonds formed during amorphization. To this end, the techniques of 17O solid-state nuclear magnetic resonance (NMR), Raman spectroscopy and far infrared spectrocopy (FT-FAR-IR) were used. As secondary objective, the activation energy spectrum of this process is calculated using modulated di˙erential scanning calorimetry measurements (MDSC). This calculation involved the resolution of the inverse problem originated from the kinetic model used, which results in a Fredholm integral equation of the first kind. The spectrum obtained shows an asymmetric distribution of probability that kinetic processes occur as a function of energy with two maxima at about 1.4 eV and 2.7 eV, evidence that two processes with distinct mechanisms occur during relaxation. The evolution of the amorphous structure during relaxation was monitored by 17O solid-state NMR and vibrational spectroscopy. The results indicate that during structural relaxation of the amorphous phase of ZrW2O8 ther is not breaking of bonds but only a re-arrangement of oxygen atoms. Only at recrystallization temperature enough energy is available to promote the breaking of the W-O bonds formed during amorphization.

Devido à elevada razão superfície/volume dos nanomateriais, estes apresentam propriedades únicas que são consequência das propriedades de suas superfícies. Para estabilizar as nanopartículas, as quais tendem ao crescimento para reduzir o excesso de energia, uma estratégia é a introdução de aditivos que segreguem na superfície e reduzam a energia de superfície. Neste trabalho, o sistema de importância tecnológica SnO2-TiO2 foi estudado. Nanopartículas de Sn1-xTixO2 (0,00 x 1,00) foram sintetizadas pelo método dos precursores poliméricos. Difratogramas de raios X mostram que uma solução sólida com estrutura do tipo rutilo é obtida para x 0,90. A evolução dos parâmetros de rede, os espectros obtidos por perda de energia de elétrons (EELS) e os espectros no infravermelho coletados no modo de refletância difusa (DRIFT) sugerem a segregação do Ti4+ na superfície, que justifica a elevada solubilidade do Ti4+ no SnO2. Os espectros Raman são coerentes com a segregação, mostrando que, mesmo sem a formação de segunda fase, ocorrem regiões ricas em Ti. A segregação está relacionada também à redução do tamanho de cristalito e ao aumento da área de superfície específica devido à redução da energia de superfície (de 1,40 Jm-2 em x = 0,00 até 1,08 Jm-2 em x = 0,50) determinada por calorimetria de adsorção de água e coerente com os dados da calorimetria de dissolução. Para x 0,90, ocorre a formação da fase anatásio além do rutilo e os fenômenos de estabilização dos polimorfos podem ser explicados pela modificação da energia de superfície. Com base na caracterização feita, as atividades fotocatalíticas das nanopartículas foram avaliadas e foi verificado um aumento da eficiência devido à superior área de superfície das amostras aditivadas em relação às amostras puras. / Due to the high surface/volume ratio, nanomaterials have unique properties as a consequence of their surface properties. In order to stabilize the nanoparticles, which tend to grow to reduce their excess energy, one can introduce additives that are prone to segregate at the surfaces and reduce the surface energy. In this work, the technologically relevant SnO2-TiO2 system was studied. Sn1-xTixO2 (0.00 x 1.00) nanoparticles were synthesized by polymeric precursors method. X-ray diffraction patterns show that a rutile-structured solid solution is formed for x 0.90. Lattice parameters evolution, electron energy loss spectra (EELS) and diffuse reflectance infrared spectra (DRIFT) suggest a Ti4+ surface segregation, which explains the high Ti4+ solubility in SnO2. Raman spectra are in accord with the segregation, showing Ti-rich sites in the absence of a second crystalline phase. The segregation is also related to a decrease in the crystallite size and an increase in the surface area due to a decrease in the surface energy (from 1.40 Jm-2 for x = 0.00 to 1.08 Jm-2 for x = 0.50) determined by water adsorption calorimetry and consistent with drop solution calorimetry data. For x 0.90, the formation of anatase occurs in addition to rutile, and the polymorphic stability can be explained according to the surface energy modification. Based on these results, photocatalytic activity of the samples were evaluated, and an increase in the efficiency due to a higher surface area was observed for the samples containing additive compared to pure samples.

O tungstato de zircônio (ZrW2O8) é um material cerâmico que exibe diversos compor-tamentos incomuns: expansão térmica negativa, amorfização induzida por altas pressões (entre 1,5 GPa e 2,0 GPa) e recristalização endotérmica quando aquecido a temperaturas superiores a 600 C. A relaxação estrutural exotérmica e irreversível é o fenômeno que precede a recristalização da fase amorfa do composto e é caracterizada por um espectro contínuo de energia de ativação. Este trabalho tem como objetivo principal explorar o mecanismo de relaxação estrutural da fase amorfa do tugnstato de zircônio, em particular, determinar se este fenômeno envolve a quebra das ligações W-O formadas durante a amorfização. Com esta finalidade, foram utilizadas as técnicas de ressonância magnética nuclear de estado sólido do núcleo 17O (RMN), espectroscopia Raman e espectroscopia na região do infravermelho longínquo (FT-FAR-IR). Além disso, como objetivo secundário, foi calculado, por meio de medidas de calorimetria exploratória diferencial modulada (MDSC) o espectro de energia de ativação deste processo. Esse cálculo envolveu a resolução do problema inverso originado do modelo cinético utilizado, que resulta em uma equação integral de Fredholm do primeiro tipo. O espectro obtido apresenta uma distribuição assimétrica de probabilidade de que processos cinéticos ocorram como função da energia com dois máximos em aproximadamente 1.4 eV e 2.7 eV, indício de que dois processos com mecanismos distintos ocorrem durante a relaxação. A evolução da estrutura amorfa durante a relaxação foi acompanhada por RMN do estado sólido do núcleo 17O e por meio das técnicas de espectroscopias vibracionais. Os resultados indicam que durante a relaxação estrutural da fase amorfa do ZrW2O8 não ocorre quebra das ligações W-O formadas durante a amorfização, mas apenas um rearranjo local dos átomos de oxigênio. Somente na temperatura de recristalização é fornecida energia suficiente para que ocorra o rompimento destas ligações. / Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, FAPERGS. / Zirconium tungstate (ZrW2O8) is a ceramic material which exhibits several unusual properties such as negative thermal expansion, amorphization induced by high pressures ( 1.5 GPa and 2.0 GPa) and endothermic recrystallization when heated to temperatures above 600 C. The irreversible exothermic structural relaxation is the phenomenon that precedes the recrystallization of the amorphous phase and is characterized by a continuous activation energy spectrum. This work aims to explore the structural relaxation mechanism of the amorphous phase of zirconium tungstate, in particular, determine whether this phenomenon involves the breakdown of W-O bonds formed during amorphization. To this end, the techniques of 17O solid-state nuclear magnetic resonance (NMR), Raman spectroscopy and far infrared spectrocopy (FT-FAR-IR) were used. As secondary objective, the activation energy spectrum of this process is calculated using modulated di˙erential scanning calorimetry measurements (MDSC). This calculation involved the resolution of the inverse problem originated from the kinetic model used, which results in a Fredholm integral equation of the first kind. The spectrum obtained shows an asymmetric distribution of probability that kinetic processes occur as a function of energy with two maxima at about 1.4 eV and 2.7 eV, evidence that two processes with distinct mechanisms occur during relaxation. The evolution of the amorphous structure during relaxation was monitored by 17O solid-state NMR and vibrational spectroscopy. The results indicate that during structural relaxation of the amorphous phase of ZrW2O8 ther is not breaking of bonds but only a re-arrangement of oxygen atoms. Only at recrystallization temperature enough energy is available to promote the breaking of the W-O bonds formed during amorphization.

Orientador: Yoshitaka Gushikem / Texto em inglês / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-21T20:29:33Z (GMT). No. of bitstreams: 1 Rahim_Abdur_D.pdf: 2383649 bytes, checksum: 98658562d78717c6e16d2a66e1d8cfa6 (MD5) Previous issue date: 2013 / Resumo: Este trabalho descreve as sínteses, caracterizações e as aplicações dos materiais carbono cerâmicos mesoporosos identificados como: SiO2/20wt%C (SBET= 160 mg) e SiO2/50wt%C (SBET= 170 mg), em que C corresponde ao carbono grafite. Tais materiais foram preparados através do método sol-gel e empregados como matrizes para o desenvolvimento de sensores e biosensores eletroquímicos. Imagens obtidas através da microscopia eletrônica de varredura (MEV) acoplada com a espectrosocopia de energia dispersiva (EDS) mostraram que, com relação as resoluções utilizadas, não foram detectadas segregação de fases. Os materiais que contem 20 e 50 wt% de C apresentaram condutividades elétricas de 9,2 x 10 S cm e 0,49 S cm, respectivamente. Esses materiais foram utilizados como matrizes para suportar ftalocianinas de: cobalto (CoPc), cobre (CuPc) e manganês (MnPc), as quais foram preparadas in situ ao longo de suas superfícies de forma que fosse assegurada dispersão homogênea dos complexos eletroativos nos poros das matrizes. As densidades superficiais da ftalocianina de cobalto em ambas as superfícies da matriz foram: 0,014 mol cm e 0,015 mol cm, para os materiais contendo 20 e 50 % m/m de C, respectivamente. Foram empregados como eletrodos de trabalho pastilhas preparadas a partir dos eletrodos carbono cerâmicos, considerando-se os seguintes materiais: SiO2/C/CoPc, SiO2/C/CuPc e SiO2/C/MnPc. A técnica de XPS foi usada para determinar as proporções de Mn/Si atómicos dos materiais MnPc modificados. O material SiO2/C/CoPc foi testado como um sensor de ácido oxálico e de oxigenio, e os materiais e SiO2/C/CuPc e SiO2/C/MnPc foram testados como sensores para a dopamina e nitrito, respectivamente. Esses materiais tem se mostrado como alternativas promissoras para o desenvolvimento de sensores eletroquímicos e de biosensores, atuando como substratos robustos e versáteis para a construção de novos eletrodos carbono cerâmicos. / Abstract: This work describes the synthesis, characterization and applications of mesoporous carbon ceramic materials identified as: SiO2/20wt%C (SBET = 160 mg) and SiO2/50wt%C (SBET= 170 mg), where C represents the carbon graphite. These materials were prepared by the sol-gel method and used as support for the development of electrochemical sensors and biosensors. Images obtained by scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS) showed that, within the magnification used, no phase segregation was detectable. The materials containing 20 and 50 wt% of C presented electric conductivities of 9.2×10and 0.49 S cm, respectively. These materials were used as matrices to support manganese phthalocyanines (MnPc), cobalt phthalocyanines (CoPc), and copper phthalocyanines (CuPc), prepared in situ on their surfaces, to assure homogeneous dispersion of the electroactive complex in the pores of matrices. The surface densities of cobalt phthalocyanine on both matrix surfaces were: 0.014 mol cm and 0.015 mol cm, for materials containing 20 and 50% wt% of C, respectively. The pressed disk carbon ceramic electrode: SiO2/C/MnPc, SiO2/C/CoPc, and SiO2/C/CuPc were used as working electrode. XPS was used to determine the Mn/Si atomic ratios of the MnPc-modified materials. The material SiO2/C/CoPc was tested as a sensor for oxalic acid and oxygen and the materials SiO2/C/CuPc and SiO2/C/MnPc were tested as sensors for dopamine and nitrite, respectively. These materials have shown to be promising alternative in the development of electrochemical sensors and biosensor, acting as a robust and versatile conducting substrate for the construction of new carbon ceramic electrodes. / Doutorado / Quimica Inorganica / Doutor em Ciências