Síntesi de pólvores de superconductors d’alta temperatura : YBa2Cu3O7 i GdBa2Cu3O7 per via de dissolució-polimerització

L’objectiu del projecte és obtenir pólvores dels superconductors d’alta temperatura YBa2Cu3O7 i GdBa2Cu3O7 per la via de dissolució-polimerització. Aquestes pólvores seran obtingudes a partir d’òxids (Itri o Gadolini i Coure) i carbonat de bari amb àcid nítric en una dissolució aquosa de Polietinenglicol (PEG), per tal de convertir aquests òxids en nitrats coordinats amb les cadenes de PEG. Aquest producte intermedi es sotmetrà a una piròlisis per tal d’obtenir òxids i carbonats, però amb una mida més reduïda respecte als productes inicials i un grau de barreja més íntim, permetent que reaccionin entre ells amb més facilitat. Finalment, per tal d’obtenir els superconductors YBa2Cu3O7 i GdBa2Cu3O7 es farà un últim tractament tèrmic a alta temperatura en el qual es produirà la reacció desitjada. Durant tot el procés es duran a terme anàlisis d’aquest per mitjà de tècniques de Termogravimetria (TGA), d’Anàlisi Tèrmica Diferencial (DTA), espectroscòpia Infraroja (IR) i la difracció de raig X (DRX) . També s’analitzaran els diferents productes que es van obtenint (intermedis i finals) amb l’ajuda de l’espectrometria IR i la difracció de pólvores. En base a aquests resultats, es variaran els paràmetres de la reacció (concentracions, temperatures, etc.) i dels tractaments tèrmics (atmosfera, temperatura, temps, etc.) per tal d’optimitzar el producte

Entalpia reticular, entalpia de fusão e temperatura de fusão de adutos: algumas correlações empíricas utilizando DSC

By using DSC data is shown that there are empirical correlations between lattice enthalpy, melting enthalpy and the temperature of melting for adducts, and that is possible, using only a single DSC curve, estimate the value of DM Hmq.

Estudio de laboratorio del efecto de las concentraciones de calcio y caseína, el pH y la temperatura sobre la incorporación de proteínas lácteas al coágulo obtenido por acción enzimática

The effect of casein concentration, Ca2+ concentration, temperature and pH on the amount and size of protein aggregates (fines) in the whey produced by enzimic coagulation of nonfat milk was studied in laboratory conditions. Casein concentrations about 0.3 g/L showed a minimal amount of caseins in the whey, with presence of small aggregates of casein micellles. Ca2+ concentrations higher than 5 mM were neccesary to reduce the whey protein to a minimum constituted by protein particles smaller than casein micelles. The coagulation temperature, in the 35 - 45oC range, produced almost no variations in the whey proteins. The obtention of a minimum amount of whey proteins was possible only in a narrow pH range around 6.4. These results pointed to casein concentration and pH as important variables to be controlled in connection with the process yield.

Estado da arte da cromatografia gasosa de alta resolução e alta temperatura

The developments in stationary phase synthesis and capillary column technology, have opened new perspectives in analysis of high molecular mass compounds (³600 daltons) and thermolabile organic compounds by High Temperature High Resolution Gas Chromatography (HT-HRGC). HT-HRGC is a new analytical borderline and its application to the analysis of high molecular mass compounds is still in its infancy. The apolar and medium polar gum phases can now be operated at temperatures up to 400-480ºC, being used for the analysis of n-alcanes up to C-100, lipids, oligosaccharides, industrial resins, polyglycerols, cyclodextrins, porphyrins, etc. This technique should play a leading role as a powerful tool, for many different analysis types, in multidisciplinary fields of Science.

Caracterização de catalisadores Cu/CeO2/Al2O3 por redução a temperatura programada e atividade para oxidação de CO

The kinetic parameters for the CO oxidation reaction using copper/alumina-modified ceria as catalysts were determined. The catalysts with different concentrations of the metals were prepared using impregnation methods. In addition, the reduction-oxidation behaviour of the catalysts were investigated by temperature-programmed reduction. The activity results show that the mechanism for CO oxidation is bifunctional : oxygen is activated on the anionic vacancies of ceria surface, while carbon monoxide is adsorbed preferentially on the higher oxidation copper site. Therefore, the reaction occurs on the interfacial active centers. Temperatures-programmed Reduction patterns show a higher disperdion when cerium oxide is present.

Control de la temperatura i el llum mitjançant dispositius sense fils

El concepte Internet de les Coses va néixer fa molt poc, cap a l’any 2010, i es refereix a la connexió d’objectes a Internet, de manera que puguin interactuar en xarxa entre ells o amb les persones per transmetre o rebre informació, i realitzar, així, les accions programades en funció de les dades disponibles. Des de llavors la gran majoria d’institucions, tant públiques com privades, s’han interessat en aquest concepte, ja que pot suposar un augment molt important de la qualitat de vida de les persones, un estalvi de recursos i beneficis econòmics. D’aquí neix aquest Treball Final de Grau, ja que des de la Fundació Eduard Soler de Ripoll tenen el desig d’introduir-se en aquest camp. L’objectiu principal d’aquest Treball Final de Grau és crear una xarxa sense fils que pugui controlar la temperatura i la il·luminació de l’edifici C de la Fundació Eduard Soler i que, a més, es pugui connectar a Internet. Una de les conclusions a què he arribat gràcies a aquest treball és que la utilització d’eines de baix cost (Arduino, Xbee, MySQL, PHP...) permet introduir-se en l’apassionant món de l’Internet de les Coses i, a més, aconseguir molt bons resultats.

Efeito da temperatura no desempenho catalítico de óxidos de ferro contendo cobre e alumínio

Aluminum and copper doped hematite was evaluated in the high temperature shift (HTS) reaction at several temperatures in order to find catalysts that can work in different operational conditions. It was found that the catalysts work in kinetic regime in the range of 300-400 ºC. Both copper and aluminum increases the activity and selectivity. Aluminum acts as textural promoter whereas copper acts as structural one. The most promising catalyst is that with both copper and aluminum which showed higher activity and selectivity than a commercial sample. This catalyst has the advantages of being non toxic and can work at low temperatures.

Um banho termostático de baixo custo (temperatura ambiente até 0ºC)

Thermal baths to decrease ambient temperature are an indispensable tool for most research and teaching laboratories, especially those in tropical or equatorial regions. A simple and inexpensive thermal bath has been developed based on a scratched compressor. It has three possible setups for cooling: sample immersed into the bath, sample flowing through the bath, and cooling liquid flowing in a jacket around the sample. It has been tested for 40 months. The temperature ranges from room temperature to 0 °C, when using water. The repeatability is better than 3% and the precision varies from 0.5% to 2%.

Extração de matéria orgânica aquática por abaixamento de temperatura: uma metodologia alternativa para manter a identidade da amostra

In this work was developed an alternative methodology to separation of aquatic organic matter (AOM) present in natural river waters. The process is based in temperature decreasing of the aqueous sample under controlled conditions that provoke the freezing of the sample and separation of the dark extract, not frozen and rich in organic matter. The results showed that speed of temperature decreasing exerts strongly influence in relative recovery of organic carbon, enrichment and time separation of the organic matter present in water samples. Elemental composition, infrared spectra and thermal analysis results showed that the alternative methodology is less aggressive possible in the attempt of maintaining the integrity of the sample.

Remoção de metais pesados de efluentes aquosos pela zeólita natural escolecita - influência da temperatura e do pH na adsorção em sistemas monoelementares

Cation exchange capabilities of a Brazilian natural zeolite, identified as scolecite, were evaluated for application in wastewater control. We investigated the process of sorption of chromium(III), nickel(II), cadmium(II) and manganese(II) in synthetic aqueous effluents, including adsorption isotherms of single-metal solutions. The natural zeolite showed the ability to take up the tested heavy metals in the order Cr(III) > Cd(II) > Ni(II) > Mn(II), and this could be related to the valence and the hydration radius of the metal cations. The influence of temperature (25, 40 and 60 ºC) and initial pH value (from 4 to 6) was also evaluated. It was found that the adsorption increased substantially when the temperature was raised to 60 ºC and that maximum adsorption capacity was observed at pH 6. These results demonstrate that scolecite can be used for removal of heavy metals from aqueous effluents, under optimized conditions.

Otros factores físicos de importancia para los seres vivos : luz, temperatura, corriente

Capítol 9 del llibre 'Conceptos y técnicas en ecología fluvial' que es refereix a la influència de factors com la temperatura de l'aigua, la disponibilitat de llum i la velocitat de la corrent en els organismes que viuen en els sistemes fluvials

Influência da temperatura do ar de secagem sobre o teor e a composição química do óleo essencial de Lippia alba (Mill) N. E. Brown

Leaves of Lippia alba were submitted to six different drying treatments, using air at ambient temperature and heated up to 80 °C. The essential oil was extracted by steam distillation and analyzed by GC-MS. For the dried leaves, the oil content was reduced by 12 to 17% when compared with the fresh plant (0.66%). The major oil component was citral, representing 76% for the fresh plant, and varying from 82 to 84% for the dried material. These results showed that L. alba can be submitted to a drying process of up to 80 ºC without degradation and/or loss of the major, [LC1] active component.

Estudo termogravimétrico do efeito da temperatura e da atmosfera na absorção de dióxido de enxofre por calcário

Thermogravimetry was applied to investigate the effects of temperature and atmosphere on conversion of sulfur dioxide (SO2) absorbed by limestone. Ranges of temperature and particle size were studied, typical of fluidized-bed coal combustion. Isothermal experiments were performed at different temperatures (between 750 and 950 ºC) under local atmospheric pressure (~ 697 mmHg) in dynamic atmospheres of air and nitrogen. The maximum conversion was 29% higher in nitrogen atmosphere than in air atmosphere. The optimum conversion temperature was found at 831 ºC in air atmosphere and at 894 ºC in nitrogen atmosphere.

Otimização e validação da técnica de extração líquido-líquido com partição em baixa temperatura (ELL-PBT) para piretróides em água e análise por CG

The liquid-liquid extraction with the low temperature partition technique was developed for the analysis of four pyrethroids in water by CG. Using a factorial design the extraction technique was optimised evaluating the effect of the variables ionic strength, contact time and proportion between sample and solvent volumes. The validation parameters sensitivity, precision, accuracy and detection and quantification limits were evaluated. The LOD and LOQ of the method varied from 1.1 to 3.2 µg L-1 and 2.7 to 9.5 µg L-1, respectively.

Nióbia magnética como adsorvente de contaminantes orgânicos em meio aquoso: efeito da temperatura e do pH

This work describes novel materials based on pure iron oxide and iron oxide/niobia composite to produce a magnetic adsorbent. These materials were prepared with synthetic iron oxide and characterized by powder XRD, SEM, FTIR, TPR and Mössbauer spectroscopy. Results showed that the main iron oxides formed were goethite (aFeOOH) and maghemite (gFe2O3) with small particle size. The iron oxide and iron oxide/niobia composite showed high adsorption ability for organic compounds. The positive enthalpy indicated an endothermic adsorption process suggesting physical adsorption.