Síntese e caracterização de niobiosilicatos para produção de biocombustível

The mesoporous materials has been an special attention, among them was discovered in the 1990´s the mesoporous molecular sieve of SBA-15 type. The good features of the SBA- 15 makes this material very promising in catalysis, however, due to the absence of native active sites, it has low catalytic activity. In this way, different metals and oxides have been included in this molecular sieve as a means of introducing active sites and increase its catalytic activity. Among the oxides that are being researched, there is the niobium oxide, which presents strong acid sites and exists in abundance. Brazil is the largest producer of the mineral. On the other hand, the production of biofuels has been desired, but it requires the development of new catalysts for this purpose. The aim of this work was to develop silicate of niobium by impregnation and by new synthesis method for application in the cracking of moringa oil. The methodology consisted of inserting the niobium oxide either by postsynthesis process using wet impregnation and direct insertion. For direct insert a new method was developed for pH adjustment, being tested different pH, and the pH 2.2 was used different ratios of Si/Nb. The materials were characterized by different techniques such as: XRD, N2 adsorption, SEM, EDS, UV-visible, TG/DTG, DSC, TEM, acidity by thermodesorption of n-butilamine and FTIR. After this part of the catalysts developed by the two methods were tested in the thermocatalytic cracking of moringa oil, being used a simple distillation. All silicates of Niobium obtained showed a highly ordered structure, having high specific areas, good distribution of pore diameters, beyond present a morphology in the form of fibers. In the catalysts after synthesis was observed that the niobium inserted has so as octahedrally and tetrahedrally coordinated, demonstrating that there were also oxides formed on the external surface of SBA-15. The materials obtained in the direct synthesis are only tetrahedrally coordinated. The new synthesis method of pH adjusting by using the buffer solution for it, proved to be very efficient for the production of such materials, because the materials obtained showed characteristics and structures similar to the molecular sieve of SBA-15 type. Among the pH tested the material that presented better characteristics was synthesized at pH 2.2. The application of these materials in catalytic cracking showed a higher formation of organic liquids when compared to thermal cracking, in addition to significantly reducing the acidity and residues formed, demonstrating that the use of silicates of Niobium increases both the conversion and the selectivity of the products.

Síntese e reatividade de derivados de quinoxalina visando aplicações como quimiossensores e estudo cinético por análise de imagens

Synthesis of heterocyclic compounds, as quinoxaline derivatives, has being shown to be relevant and promissor due to expressive applications in biological and technological areas. This work was dedicated to the synthesis, characterization and reactivity of quinoxaline derivatives in order to obtain new chemosensors. (L)-Ascorbic acid (1) and 2,3-dichloro-6,7- dinitroquinoxalina (2) were explored as synthetic precursors. Starting from synthesis of 1 and characterization of compounds derived from (L)-ascorbic acid, studies were performed investigating the application of products as chemosensors, in which compound 36 demonstrated selective affinity for Cu2+ íons in methanolic solution, by naked-eye (colorimetric) and UVvisible analyses. Further, initial analysis suggests that 39 a Schiff’s base derived from 36 also presents this feature. Five quinoxaline derivatives were synthesized from building block 2 through nucleophilic aromatic substitution by aliphatic amines, in which controlling the experimental conditions allows to obtain both mono- and di-substituted derivatives. Reactivity studies were carried out with two purposes: i) investigate the possibility of 47 compound being a chemosensor for anion, based on its interaction with sodium hydroxide in DMSO, using image analysis and UV-visible spectroscopy; ii) characterize kinetically the conversion of compound 44 into 46 based on RGB and multivariate image analysis from TLC data, as a simple and inexpensive qualitative and quantitative tool.

Síntese, estrutura e propriedades de polímeros de coordenação à base de íons lantanídeos e ácidos benzenodicarboxílicos

Metal Organic Frameworks (MOFs) are hybrids materials, often crystalline, consisting of metal or metal clusters, connected by polytopic organic ligands repetitively, leading to structures, usually porous. In this work, MOFs based on lanthanide ions (La3+ and Gd3+) and dicarboxylate type of ligands (isophthalic and terephthalic acids), were synthesized by hydrothermal, solvothermal and hydro(solvo)thermal methods. The effects of the synthetic route as well as the type of heating, conventional or by microwave, on the structure and properties of MOFs were studied. The powder samples obtained were characterized by X-ray diffraction, infrared spectroscopy, thermal analysis and scanning electron microscopy. The results suggest that the addition of an organic or inorganic base is needed to promote the deprotonation of the ligand, since in the samples prepared by the hydrothermal method, without the use of a base, no formation of the metalorganic framework was observed. On the other hand, the presence of DMF as solvent or cosolvent, afforded the deprotonation of the ligand with the consequent formation of MOFs. At least two different crystalline structures were identified for the samples prepared with terephthalic acid. These samples are isostructural with those reported for phases Eu(1,3-BDC)DMF, Eu2(1,4-BDC)3 (DMF)2 and Tb(1,4-BDC)H2O. The presence of water in the reaction medium in the hydro(solvo)thermal method, provoked the growth of the structure different from that observed in the absence of water. This can be explained by the difference in the coordination mode of water and DMF to lanthanide ions. Although not identified by XRD, the samples prepared with isophthalic acid, also present metalorganic structures, which was confirmed by the presence of the characteristic displacement of the carbonyl group band in their infrared spectra, compared to the spectrum of the pure ligand. This shift was also observed in the samples prepared with terephthalic acid. Thermal analisys shows that the metal organic frameworks do not collapse occurs at a temperature below 430°C.The analysis of scanning electron microscopy suggests that the morphology of powders is highly dependent on the type of heating used, conventional or by microwave.

Estudo da obtenção de cerâmica composta de alumina e beta alumina sódica utilizando-se resíduo cerâmico de velas de ignição e pó químico de extintores de incêndio

Ceramic materials the alumina base are large industrial applications. They are required for these products, specific characteristics obtained by following strict criteria during the manufacturing process. However, after life, not always these products are reused by a suitable waste management process. In ceramist context, advance research aimed at the reuse of waste aimed at obtaining ceramics and composite materials, with marked reduction of conventional raw materials. Aiming to generate scientific, technological and environmental contribution, this work studied to obtain a composite of alumina ceramic (Al2O3) and sodium beta alumina (NaAl11O17 ), and as starting materials the residue of the ceramic insulator of spark plugs, as a source alumina (Al2O3) powder and unusable sodium bicarbonate (NaHCO3) of fire extinguishers, as a source of sodium oxide (Na2O). The final ceramic product was obtained from a conventional mixture of sodium aluminum oxide in appropriate molar proportions. Sample spark plugs were obtained, discarded by lifetime, specific to a manufacturer, which, after passing through mechanical stress (grinding, magnetic purification, washing, drying and grinding the high energy), which resulted in residue powder with ceramic content of 84.34 % alumina (Al2O3), found by FRX chemical analysis, the phases present and identified by DRX. The dry chemical fire extinguisher, baking soda-based (NaHCO3) with expired, was obtained through direct collection of the waste generated during maintenance. Subjected to heat treatment at 120 °C , the NaHCO3 powder was decomposed in sodium oxide ( Na2O), which, subjected to chemical analysis (FRX) and mineralogical (DRX) revealed a content of 86.62 % sodium oxide (Na2O) . In the following steps the experimental procedure, chemical formulations were made on a molar basis of the starting material (1:9, 1:10 and 1:11 de Na2O/ Al2O3) inclusion of additives, milling parameters, sieve analysis, dilatometry, conformation of specimens, sintering in firing steps at 800 °C , 1000 °C and 1.200 °C with varying stays 30 , 60 and 120 minutes in each of the levels. The characterization of the final product was made by the following physical tests: water absorption, porosity, linear shrinkage, mineralogical analysis by DRX and microstructural analysis by MEV. A higher formation of sodium beta alumina (NaAl11O17), in sintered specimens in levels of 1.200 °C and 120 minutes, despite the prevailing coexistence of alpha phase alumina (Al2O3). From the results obtained opens up prospects for the reuse of waste studied in this work, the potter context and in other technological areas.

Estudo da obtenção de cerâmica composta de alumina e beta alumina sódica utilizando-se resíduo cerâmico de velas de ignição e pó químico de extintores de incêndio

Ceramic materials the alumina base are large industrial applications. They are required for these products, specific characteristics obtained by following strict criteria during the manufacturing process. However, after life, not always these products are reused by a suitable waste management process. In ceramist context, advance research aimed at the reuse of waste aimed at obtaining ceramics and composite materials, with marked reduction of conventional raw materials. Aiming to generate scientific, technological and environmental contribution, this work studied to obtain a composite of alumina ceramic (Al2O3) and sodium beta alumina (NaAl11O17 ), and as starting materials the residue of the ceramic insulator of spark plugs, as a source alumina (Al2O3) powder and unusable sodium bicarbonate (NaHCO3) of fire extinguishers, as a source of sodium oxide (Na2O). The final ceramic product was obtained from a conventional mixture of sodium aluminum oxide in appropriate molar proportions. Sample spark plugs were obtained, discarded by lifetime, specific to a manufacturer, which, after passing through mechanical stress (grinding, magnetic purification, washing, drying and grinding the high energy), which resulted in residue powder with ceramic content of 84.34 % alumina (Al2O3), found by FRX chemical analysis, the phases present and identified by DRX. The dry chemical fire extinguisher, baking soda-based (NaHCO3) with expired, was obtained through direct collection of the waste generated during maintenance. Subjected to heat treatment at 120 °C , the NaHCO3 powder was decomposed in sodium oxide ( Na2O), which, subjected to chemical analysis (FRX) and mineralogical (DRX) revealed a content of 86.62 % sodium oxide (Na2O) . In the following steps the experimental procedure, chemical formulations were made on a molar basis of the starting material (1:9, 1:10 and 1:11 de Na2O/ Al2O3) inclusion of additives, milling parameters, sieve analysis, dilatometry, conformation of specimens, sintering in firing steps at 800 °C , 1000 °C and 1.200 °C with varying stays 30 , 60 and 120 minutes in each of the levels. The characterization of the final product was made by the following physical tests: water absorption, porosity, linear shrinkage, mineralogical analysis by DRX and microstructural analysis by MEV. A higher formation of sodium beta alumina (NaAl11O17), in sintered specimens in levels of 1.200 °C and 120 minutes, despite the prevailing coexistence of alpha phase alumina (Al2O3). From the results obtained opens up prospects for the reuse of waste studied in this work, the potter context and in other technological areas.

Síntese e caracterização de complexos de Co(II) e Ni(II) com l-dopa, carbidopa e benzimidazol

Were synthesized in this work in the following aqueous solution coordination compounds: [Ni(LDP)(H2O)2Cl2].2H2O, [Co(LDP)Cl2].3H2O, [Ni(CDP)Cl2].4H2O, [Co(CDP)Cl2].4H2O, [Ni(BDZ)2Cl2].4H2O and [Co(BDZ)2Cl2(H2O)2]. These complexes were synthesized by stoichiometric addition of the binder in the respective metal chloride solutions. Precipitation occurred after drying the solvent at room temperature. The characterization and proposed structures were made using conventional analysis methods such as elemental analysis (CHN), absorption spectroscopy in the infrared Fourier transform spectroscopy (FTIR), X-ray diffraction by the powder method and Technical thermoanalytical TG / DTG (thermogravimetry / derivative thermogravimetry) and DSC (differential scanning calorimetry). These techniques provided information on dehydration, coordination modes, thermal performance, composition and structure of the synthesized compounds. The results of the TG curve, it was possible to establish the general formula of each compound synthesized. The analysis of X-ray diffraction was observed that four of the synthesized complex crystal structure which does not exhibit the complex was obtained from Ldopa and carbidopa and the complex obtained from benzimidazole was obtained crystal structures. The observations of the spectra in the infrared region suggested a monodentate ligand coordination to metal centers through its amine group for all complexes. The TG-DTG and DSC curves provide important information and on the behavior and thermal decomposition of the synthesized compounds. The molar conductivity data indicated that the solutions of the complexes formed behave as a nonelectrolyte, which implies that chlorine is coordinated to the central atom in the complex.

Síntese e caracterização de complexos de Co(II) e Ni(II) com l-dopa, carbidopa e benzimidazol

Were synthesized in this work in the following aqueous solution coordination compounds: [Ni(LDP)(H2O)2Cl2].2H2O, [Co(LDP)Cl2].3H2O, [Ni(CDP)Cl2].4H2O, [Co(CDP)Cl2].4H2O, [Ni(BDZ)2Cl2].4H2O and [Co(BDZ)2Cl2(H2O)2]. These complexes were synthesized by stoichiometric addition of the binder in the respective metal chloride solutions. Precipitation occurred after drying the solvent at room temperature. The characterization and proposed structures were made using conventional analysis methods such as elemental analysis (CHN), absorption spectroscopy in the infrared Fourier transform spectroscopy (FTIR), X-ray diffraction by the powder method and Technical thermoanalytical TG / DTG (thermogravimetry / derivative thermogravimetry) and DSC (differential scanning calorimetry). These techniques provided information on dehydration, coordination modes, thermal performance, composition and structure of the synthesized compounds. The results of the TG curve, it was possible to establish the general formula of each compound synthesized. The analysis of X-ray diffraction was observed that four of the synthesized complex crystal structure which does not exhibit the complex was obtained from Ldopa and carbidopa and the complex obtained from benzimidazole was obtained crystal structures. The observations of the spectra in the infrared region suggested a monodentate ligand coordination to metal centers through its amine group for all complexes. The TG-DTG and DSC curves provide important information and on the behavior and thermal decomposition of the synthesized compounds. The molar conductivity data indicated that the solutions of the complexes formed behave as a nonelectrolyte, which implies that chlorine is coordinated to the central atom in the complex.

La cerámica del yacimiento arqueológico de Castillejo del Bonete (Terrinches, Ciudad Real). Estudio morfológico y tecnólogico

El presente trabajo incluye el estudio de un amplio conjunto cerámico perteneciente al yacimiento arqueológico de la Edad del Cobre y Edad del Bronce de Castillejo del Bonete. La muestra fue recuperada de distintas áreas del asentamiento durante la campaña de excavación de 2012. La investigación ha tenido como fin conocer mejor la relación forma-función de las vasijas, su proceso de fabricación, así como el modelo productivo y las posibles manifestaciones simbólicas presentes en el repertorio analizado. La metodología utilizada para cumplir con los objetivos se ha basado en la recopilación de datos, considerando una serie de variables morfológicas y tecnológicas, y su procesamiento con el empleo de técnicas estadísticas sencillas.

Cerâmica de Santo Antônio do Potengi: entre tradição e modernidade

In the Rio Grande do Norte, the craftsmanship is generating of economy, it involves a significant number of people and is diversified in its raw materials and particular type. As reference of the craft local, the ceramics supplied the primary necessities in the utilitarian domestic servants, acquired piety in the religious figures, were toy in infantile amusements and, finally, gained status of pure ornament. By its historical representation, the district of Santo Antônio do Potengi is considered the most important center of manufacture of craftpottery in the State. The work of the potters continues in that locality anchored between the familiar inheritance and the participation each more influential time of the public politics destined to the sector situation verified for visible alterations in the shape of the pottery from the decade of 1990 with the implantation of a cooperative destined to the collective production. We observe in this passage, that such actions in the measure where they objectify to structuralize conditions ideal to support the artisan making, do not benefit in significant way the social development them craftsmen. It is important not to lose of sight that exists some involved dimensions in this process and that these surpass the common interest for the object and the consequent economic connotation of its commercialization. They are knowledge that imply in the access to raw materials, in the peculiar of the formal aspects and productive methods, in the contextual relations organized to defend the survival of the activity

Functional alkali tantalate 2D structures for microelectronics and related applications

Alkali tantalates and niobates, including K(Ta / Nb)O3, Li(Ta / Nb)O3 and Na(Ta / Nb)O3, are a very promising ferroic family of lead-free compounds with perovskite-like structures. Their versatile properties make them potentially interesting for current and future application in microelectronics, photocatalysis, energy and biomedics. Among them potassium tantalate, KTaO3 (KTO), has been raising interest as an alternative for the well-known strontium titanate, SrTiO3 (STO). KTO is a perovskite oxide with a quantum paraelectric behaviour when electrically stimulated and a highly polarizable lattice, giving opportunity to tailor its properties via external or internal stimuli. However problems related with the fabrication of either bulk or 2D nanostructures makes KTO not yet a viable alternative to STO. Within this context and to contribute scientifically to the leverage tantalate based compounds applications, the main goals of this thesis are: i) to produce and characterise thin films of alkali tantalates by chemical solution deposition on rigid Si based substrates, at reduced temperatures to be compatible with Si technology, ii) to fulfil scientific knowledge gaps in these relevant functional materials related to their energetics and ii) to exploit alternative applications for alkali tantalates, as photocatalysis. In what concerns the synthesis attention was given to the understanding of the phase formation in potassium tantalate synthesized via distinct routes, to control the crystallization of desired perovskite structure and to avoid low temperature pyrochlore or K-deficient phases. The phase formation process in alkali tantalates is far from being deeply analysed, as in the case of Pb-containing perovskites, therefore the work was initially focused on the process-phase relationship to identify the driving forces responsible to regulate the synthesis. Comparison of phase formation paths in conventional solid-state reaction and sol-gel method was conducted. The structural analyses revealed that intermediate pyrochlore K2Ta2O6 structure is not formed at any stage of the reaction using conventional solid-state reaction. On the other hand in the solution based processes, as alkoxide-based route, the crystallization of the perovskite occurs through the intermediate pyrochlore phase; at low temperatures pyrochlore is dominant and it is transformed to perovskite at >800 °C. The kinetic analysis carried out by using Johnson-MehlAvrami-Kolmogorow model and quantitative X-ray diffraction (XRD) demonstrated that in sol-gel derived powders the crystallization occurs in two stages: i) at early stage of the reaction dominated by primary nucleation, the mechanism is phase-boundary controlled, and ii) at the second stage the low value of Avrami exponent, n ~ 0.3, does not follow any reported category, thus not permitting an easy identification of the mechanism. Then, in collaboration with Prof. Alexandra Navrotsky group from the University of California at Davis (USA), thermodynamic studies were conducted, using high temperature oxide melt solution calorimetry. The enthalpies of formation of three structures: pyrochlore, perovskite and tetragonal tungsten bronze K6Ta10.8O30 (TTB) were calculated. The enthalpies of formation from corresponding oxides, ∆Hfox, for KTaO3, KTa2.2O6 and K6Ta10.8O30 are -203.63 ± 2.84 kJ/mol, - 358.02 ± 3.74 kJ/mol, and -1252.34 ± 10.10 kJ/mol, respectively, whereas from elements, ∆Hfel, for KTaO3, KTa2.2O6 and K6Ta10.8O30 are -1408.96 ± 3.73 kJ/mol, -2790.82 ± 6.06 kJ/mol, and -13393.04 ± 31.15 kJ/mol, respectively. The possible decomposition reactions of K-deficient KTa2.2O6 pyrochlore to KTaO3 perovskite and Ta2O5 (reaction 1) or to TTB K6Ta10.8O30 and Ta2O5 (reaction 2) were proposed, and the enthalpies were calculated to be 308.79 ± 4.41 kJ/mol and 895.79 ± 8.64 kJ/mol for reaction 1 and reaction 2, respectively. The reactions are strongly endothermic, indicating that these decompositions are energetically unfavourable, since it is unlikely that any entropy term could override such a large positive enthalpy. The energetic studies prove that pyrochlore is energetically more stable phase than perovskite at low temperature. Thus, the local order of the amorphous precipitates drives the crystallization into the most favourable structure that is the pyrochlore one with similar local organization; the distance between nearest neighbours in the amorphous or short-range ordered phase is very close to that in pyrochlore. Taking into account the stoichiometric deviation in KTO system, the selection of the most appropriate fabrication / deposition technique in thin films technology is a key issue, especially concerning complex ferroelectric oxides. Chemical solution deposition has been widely reported as a processing method to growth KTO thin films, but classical alkoxide route allows to crystallize perovskite phase at temperatures >800 °C, while the temperature endurance of platinized Si wafers is ~700 °C. Therefore, alternative diol-based routes, with distinct potassium carboxylate precursors, was developed aiming to stabilize the precursor solution, to avoid using toxic solvents and to decrease the crystallization temperature of the perovskite phase. Studies on powders revealed that in the case of KTOac (solution based on potassium acetate), a mixture of perovskite and pyrochlore phases is detected at temperature as low as 450 °C, and gradual transformation into monophasic perovskite structure occurs as temperature increases up to 750 °C, however the desired monophasic KTaO3 perovskite phase is not achieved. In the case of KTOacac (solution with potassium acetylacetonate), a broad peak is detected at temperatures <650 °C, characteristic of amorphous structures, while at higher temperatures diffraction lines from pyrochlore and perovskite phases are visible and a monophasic perovskite KTaO3 is formed at >700 °C. Infrared analysis indicated that the differences are due to a strong deformation of the carbonate-based structures upon heating. A series of thin films of alkali tantalates were spin-coated onto Si-based substrates using diol-based routes. Interestingly, monophasic perovskite KTaO3 films deposited using KTOacac solution were obtained at temperature as low as 650 °C; films were annealed in rapid thermal furnace in oxygen atmosphere for 5 min with heating rate 30 °C/sec. Other compositions of the tantalum based system as LiTaO3 (LTO) and NaTaO3 (NTO), were successfully derived as well, onto Si substrates at 650 °C as well. The ferroelectric character of LTO at room temperature was proved. Some of dielectric properties of KTO could not be measured in parallel capacitor configuration due to either substrate-film or filmelectrode interfaces. Thus, further studies have to be conducted to overcome this issue. Application-oriented studies have also been conducted; two case studies: i) photocatalytic activity of alkali tantalates and niobates for decomposition of pollutant, and ii) bioactivity of alkali tantalate ferroelectric films as functional coatings for bone regeneration. Much attention has been recently paid to develop new type of photocatalytic materials, and tantalum and niobium oxide based compositions have demonstrated to be active photocatalysts for water splitting due to high potential of the conduction bands. Thus, various powders of alkali tantalates and niobates families were tested as catalysts for methylene blue degradation. Results showed promising activities for some of the tested compounds, and KNbO3 is the most active among them, reaching over 50 % degradation of the dye after 7 h under UVA exposure. However further modifications of powders can improve the performance. In the context of bone regeneration, it is important to have platforms that with appropriate stimuli can support the attachment and direct the growth, proliferation and differentiation of the cells. In lieu of this here we exploited an alternative strategy for bone implants or repairs, based on charged mediating signals for bone regeneration. This strategy includes coating metallic 316L-type stainless steel (316L-SST) substrates with charged, functionalized via electrical charging or UV-light irradiation, ferroelectric LiTaO3 layers. It was demonstrated that the formation of surface calcium phosphates and protein adsorption is considerably enhanced for 316L-SST functionalized ferroelectric coatings. Our approach can be viewed as a set of guidelines for the development of platforms electrically functionalized that can stimulate tissue regeneration promoting direct integration of the implant in the host tissue by bone ingrowth and, hence contributing ultimately to reduce implant failure.

Compósitos de polímero-cerâmica para condensadores incorporados

A necessidade de produção de dispositivos eletrónicos mais eficientes e a sua miniaturização tem sido um dos principais desígnios da indústria eletrónica. Assim surgiu a necessidade de melhorar o desempenho das designadas placas de circuito impresso, tornando-as simultaneamente mais flexíveis, com menos ruído, mais estáveis face a variações bruscas de temperatura e que permitam operar numa vasta gama de frequências e potências. Para tal, uma das estratégias que tem vindo a ser estudada é a possibilidade de incorporar os componentes passivos, nomeadamente condensadores, sob a forma de filme diretamente no interior da placa. Por forma a manter uma elevada constante dielétrica e baixas perdas, mantendo a flexibilidade, associada ao polímero, têm sido desenvolvidos os designados compósitos de matriz polimérica. Nesta dissertação procedeu-se ao estudo do comportamento dielétrico e elétrico da mistura do cerâmico CaCu3Ti4O12 com o copolímero estireno-isoprenoestireno. Foram preparados filmes com diferentes concentrações de CCTO, recorrendo ao método de arrastamento, em conjunto com o Centro de Polímeros da Eslováquia. Foram também preparados filmes por spin-coating para as mesmas concentrações. Usaram-se dois métodos distintos para a preparação do pó de CCTO, reação de estado sólido e sol-gel. Foi realizada a caraterização estrutural (difração de raios-X. espetroscopia de Raman), morfológica (microscopia eletrónica de varrimento) e dielétrica aos filmes produzidos. Na caracterização dielétrica determinou-se o valor da constante dielétrica e das perdas para todos os filmes, à temperatura ambiente, bem como na gama de temperatura entre os 200 K e os 400 K, o que permitiu identificar existência de relaxações vítreas e subvítreas, e assim calcular as temperaturas de transição vítrea e energias de ativação, respetivamente. Foram realizados testes de adesão e aplicada a técnica de análise mecânica dinâmica para o cálculo das temperaturas de transição vítrea nos filmes preparados pelo método de arrastamento. Estudou-se ainda qual a lei de mistura que melhor se ajusta ao comportamento dielétrico do nosso compósito. Verificou-se que é a lei de Looyenga generalizada a que melhor se ajusta à resposta dielétrica dos compósitos produzidos.

Síntese de ésteres graxos a partir da biomassa da microalga Chlorella sp. por hidrólise “in situ” seguido de esterificação

Neste trabalho, a produção de ésteres graxos da biomassa úmida da microalga Chlorella sp. foi investigada pelo método de hidrólise seguido de esterificação e comparado com o método convencional de extração/transesterificação. Na primeira etapa do processo de hidrólise “in situ” seguido de esterificação ocorreu à hidrólise, onde a água presente na biomassa (50 e 100% em massa) reagiu com os lipídios de reserva, na presença de H2SO4 (20, 40 e 60% em massa), sendo obtidos os ácidos graxos brutos. Na segunda etapa do processo, os ácido graxos foram submetidos à reação de esterificação por 1 ou 4 h na presença de metanol, na razão molar de 30:1 álcool:AG, com H2SO4 10% em massa a 60 ou 100 °C. De acordo com os resultados obtidos no processo de hidrólise/esterificação, os melhores rendimentos – cerca de 7,3±0,8% de FAMEs, em relação a biomassa inicial – foram obtidos na presença de 60% de catalisador e 50% de umidade, na etapa de hidrólise e 100 °C por 4 h na etapa de esterificação. No método convencional de extração-transesterificação, os melhores rendimentos – 7,1±1,8% de FAMEs em relação à biomassa seca – foram obtidos utilizando a mistura de clorofórmio:metanol 2:1 v/v. Em resumo os rendimentos obtidos nos dois métodos de produção de ésteres graxos foram próximos. No entanto, o processo de hidrólise “in situ” seguido de esterificação possui vantagens como a utilização da biomassa úmida.

El enfoque local en la cooperación al desarrollo un estudio de casos en Argelia: cerámica tradicional y vitivinicultura

El objetivo principal de la investigación es el estudio y la validación práctica en territorios del sur del mediterráneo de metodologías de intervención basadas en el marco teórico del desarrollo local, que establecen el fortalecimiento del capital territorial de un espacio/comunidad como elemento de partida a partir del cual desplegar con éxito estrategias de desarrollo eficaces y efectivas. Este objetivo principal pretende dar respuesta a necesidades que surgen tanto desde el punto de vista científico y geográfico, como profundización en un orden científico que proporcione nuevos conocimientos sobre las características de determinados territorios y comunidades, como desde el punto de vista de la investigación prospectiva, como respuesta a la necesidad de testar la aplicabilidad y pertinencia de ciertos enfoques y métodos de trabajo en territorios y comunidades del sur de cara a establecer los cimientos de una adecuada intervención en el territorio. El estudio se ha desarrollado desde la óptica investigación-acción aprovechando la participación en el diseño y ejecución de diferentes proyectos financiados en Argelia por la Agencia Española para la Cooperación Internacional al Desarrollo con el objeto de poner en marcha procesos de activación y puesta en valor del saber hacer ligado a actividades tradicionales que forman parte del patrimonio cultural mediterráneo como la cerámica y el vino. La investigación ha seguido un planteamiento constructivista, respaldado por la metodología cualitativa, que entiende el conocimiento como el resultado de la interacción de los actores y su ambiente llevándolo a un escenario en donde los actores recobran su protagonismo. Se trata de un método adecuado para analizar procesos y estrategias de desarrollo como el que nos ocupa y que exige considerar las múltiples conexiones socioespaciales que existen entre los elementos estudiados, para lo cual es conveniente que la investigación adopte una visión sistémica de la realidad que permita identificar las diferentes entidades y actores que la conforman y estudiar las relaciones estructurales existentes entre ellas. El predominio de un enfoque cualitativo que articule el grueso de la investigación permite recoger y analizar toda una serie de factores inmateriales y de difícil cuantificación que tienen gran importancia en procesos económicos y sociales como los que estamos estudiando. Las técnicas utilizadas han sido la entrevista en profundidad de carácter amplio y no estructurado, tanto en su variante individual como de grupo y la observación directa en la idea de que la suma de ambas técnicas permite una mejor comprensión de las factores que alimentan o frenan los procesos de dinamización y puesta en valor de los recursos de un determinado territorio, y de cómo las acciones emprendidas dentro de una estrategia de desarrollo a medio plazo alcanzan con éxito los resultados esperados o fracasan en la consecución de los objetivos propuestos...

Síntese, caracterização e cinética da decomposição térmica dos materiais cerâmicos PrMO3 (M = Ni ou Co)

In this work have been studied the preparation, characterization and kinetic study of decomposition of the polymerizing agent used in the synthesis under non-isothermal condition ceramics PrMO3 of general formula (M = Co and Ni). These materials were obtained starting from the respective metal nitrates, as a cations source, and making use of gelatin as polymerizing agent. The powders were calcined at temperatures of 500°C, 700°C and 900°C and characterized by X-ray Diffraction (XRD), Thermogravimetric Analysis (TG / DTG/ DTA), Infrared Spectroscopy (FTIR), Temperature Programmed Reduction (TPR) and Scanning Electron Microscopy (SEM). The perovskite phase was detected in all the X-rays patterns. In the infrared spectroscopy observed the oxide formation as the calcination temperature increases with the appearance of the band metal - oxygen. The images of SEM revealed uniform distribution for the PrCoO3 and particles agglomerated as consequence of particle size for PrNiO3. From the data of thermal analysis, the kinetics of decomposition of organic matter was employed using the kinetics methods called Model Free Kinetics and Flynn and Wall, in the heating ratios 10, 20 and 30° C.min-1 between room temperature and 700°C. Finally, been obtained the values of activation energy for the region of greatest decomposition of organic matter in samples that were determined by the degree of conversion (α)

Síntese e caracterização de nanocompósitos de carbon-dot e lantanídeos

Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, 2015.