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Utilização de uma matriz híbrida orgânica-inorgânica na dinâmica de liberação controlada de fármacos

Lopes, Leandro
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 113 f. : il.
POR
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Pós-graduação em Química - IQ; As condições de preparação de matrizes híbridas siloxano0polióxido de etileno (POE) e siloxano0polióxido de propileno (POP) contendo fármacos foram estabelecidas nessa dissertação. A capacidade de liberação do diclofenaco de sódio por essas matrizes foi estudada a partir de curvas de liberação obtidas em meio aquoso. A caracterização das amostras foi realizada utilizando0se as técnicas de DSC, TG0DTA, DMA, DRX, SAXS, RMN do 13 C, 29 Si e do 23 Na e espectroscopia Raman. O estudo de liberação revelou que é possível controlar a velocidade de saída do fármaco a partir da variação da massa molecular da cadeia polimérica e da concentração do diclofenaco de sódio ou da combinação de precursores híbridos de diferentes classes. As medidas de SAXS “in situ” mostraram que o intumescimento é acompanhado por um relaxamento da matriz polimérica, conduzindo a um afastamento dos grupos siloxano constituintes da molécula. Esse relaxamento também é observado quando se acrescenta fármaco à matriz híbrida polimérica. As medidas de DSC indicaram a existência de interações entre as matrizes híbridas POE e o diclofenaco...

Plataforma inorgânica a base de apatitas de interesse biológico visando à liberação controlada de fármacos

Almeida Filho, Edson de
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Tese de Doutorado Formato: 121 f. : il.
POR
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Pós-graduação em Química - IQ; Recobrimentos de apatitas foram realizados em superfícies de titânio modificadas por feixe de laser Yb:YAG a pressão e atmosfera ambiente. As apatitas foram depositadas pelo método biomimético usando três soluções SBF (Simulated Body Fluid) diferentes que simulam a concentração de sais dos fluídos corpóreos para obtenção das apatitas. As superfícies de titânio submetidas ao processo de fusão e solidificação rápida (ablação) foram imersas na solução de SBF, as quais permaneceram por 4 dias a 37 ºC. As amostras foram caracterizadas pelas técnicas de DRX, refinamento de Rietveld, FTIR, MEV e solubilidade. Os espectros de FTIR mostram bandas referentes às ligações químicas confirmadas pela análise de DRX e quantificadas pelo método de Rietveld. Os recobrimentos de apatitas foram submetidas ao teste de solubilidade em água destilada utilizando-se eletrodo de íons seletivos e titulação complexométrica a fim de estudar a cinética de liberação para as fases se apatitas; Apatite coatings were deposited on titanium surfaces modified by an Yb:YAG laser beam under ambient pressure and air. The apatites were deposited by a biomimetic method using three different SBF (simulated body fluid) solutions that mimic the concentration of salts in the body fluids to obtain the apatites. The titanium surfaces subjected to the process of rapid fusion and solidification (ablation) were immersed in the SBF solutions...

Materiais híbridos argila-poli(metil metacrilato) obtidos através do método grafting

Suzana, Ana Flávia
Fonte: Universidade Estadual Paulista (UNESP) Publicador: Universidade Estadual Paulista (UNESP)
Tipo: Dissertação de Mestrado Formato: 75 f. : il. -
POR
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Pós-graduação em Química - IQ; Some materials formed by an organic phase dispersed in an inorganic phase present new properties that are not limited to the sum of the properties of their separated components, but are the result of the synergism between the phases at molecular level. These materials are known as organic-inorganic hybrids and has received broad scientific attention in recent decades because of its multifunctional nature. As a part of the study of these materials, the surface modification of clay minerals has become lately an important way to improve or create new properties in hybrid materials. The grafting method, for example, consists in the surface reaction between the silanol groups and the reactive groups of the organic compounds (chloride, alkoxide or hydride) which has the function of bind to the inorganic surface and make it compatible with the organic phase, usually a polymer. These organic compounds are referred as coupling agents, since they have the function of coupling to the organic phase with the inorganic one. Thus, the focus of this work was based on nanocomposites organic-inorganic hybrid material obtaining using the grafting method where the inorganic phase is composed by the sodic montmorillonite clay and the organophilizated clay Cloisite® 10A and the organic by poly(methyl methacrylate) (PMMA). The first step of the nanocomposites obtaining was the separation of a fraction of clay particles of uniform size by centrifugation in various aqueous solutions clay; thereby...

Resinas de silicona a base de silsesquioxanos: síntese, estudo estrutural, morfológico e avaliação do comportamento térmico

Luis Antonio Sanchez de Almeida Prado
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em //2001 PT
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Neste trabalho estudou-se a síntese, estrutura, a morfologia e o comportamento térmico de resinas de silicona do tipo T e TD, preparadas a partir de feniltriclorossilano ou feniltrietoxissilano; n-octiltrietoxissilano ou n-dodeciltrietoxissilano como fontes de unidades T e poli(dimetilsiloxano) ou 1,3-dietoxitetrametildissiloxano como fontes de unidades D. Foram preparadas duas séries de resinas: a primeira constituída de amostras de poli(fenilsilsesquioxano), PPSQ, obtidas em diferentes condições sintéticas e experimentais, e a segunda constituída de resinas T e TD, preparadas pelo processo sol-gel. Neste última série, obteve-se resinas... T, T e T, na ausência de solventes, e resinas TD, contendo no máximo 50% em mols de unidades D, correspondentes a segmentos longos, D, ou curtos, D, de dimetilsiloxano, empregando-se tolueno como solvente. O aspecto físico das amostras de PPSQ variou de vidros resinosos a pós brancos. Os filmes obtidos pelo processo sol-gel foram transparentes, para os derivados de T, e os demais translúcidos, com exceção de TD. A estrutura molecular destas resinas foi caracterizada por FTIR e Si MAS NMR. Observou-se uma dependência da porcentagem de sítios T e T com as condições de preparação...

Síntese e caracterização de materiais nanoporosos para pirólise catalítica de óleos pesados

Costa, Maria José Fonseca
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Dissertação Formato: application/pdf
POR
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The present work reports the study of nanoporous structures, aiming at their use in research directed to the current demand of the petroleum industry to value heavy oil. Initially, two ways were chosen for the synthesis of porous structures from the molecular sieves of type Si-MCM-41. In the first way, the structure MCM-41 is precursory for heteroatom substitutes of silicon, generating catalyst of the type Al-MCM-41 from two different methods of incorporation of the metal. This variation of the incorporation method of Aluminum in the structure of Si-MCM-41 was carried out through the conventional procedure, where the aluminum source was incorporated to the gel of synthesis, and the procedure post-synthesis, where the Aluminum source was incorporated in catalyst after the synthesis of Si-MCM-41. In the second way, the MCM-41 acts as a support for growth of nanocrystals of zeolite embedded in their mesoporous, resulting in hybrid MCM-41/ZSM-5 catalyst. A comparative analysis was carried through characterizations by XRD, FTIR, measures of acidity through n-butylamine adsorption for TGA, SEM-XRF and N2 adsorption. Also crystalline aluminosilicate with zeolitic structure MFI of type ZSM-5 was synthesized without using organic templates. Methodologies to the preparation of these materials are related by literature using conventionally reactants that supply oxides of necessary silicon and aluminum...

Análise química de produtos de incrustação em dutos de petróleo por espectometria de fluorescência de raios X

Sena, Caio Patrício de Souza
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Dissertação Formato: application/pdf
POR
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The quantitative chemical characterization of the inorganic fraction of scale products is very relevant in studying, monitoring and controlling corrosive processes of oil pipelines. The X-ray fluorescence spectrometry (XRF) is a very versatile analytical technique, which can be used in quantitative analysis in solid samples at low concentrations of the chemical element, in the order of few ppm. A methodology that involves sample preparation diluted in the proportion of 1:7 (one portion of the sample for seven of wax), pressed as pellets was used in the XRF calibration for chemical analysis of scale products from oil pipelines. The calibration involved the preparation of reference samples from mixtures of P.A. reagents, aiming to optimize the time consumed in the steps of sample preparation and analysis of Al, Ba, Ca, Fe, K, Mg, Mn, Na, P, S, Si, Sr and Ti, using the same pressed pellet for trace and major elements analysis; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior; A caracterização química quantitativa da fração inorgânica de produtos de incrustação é de grande relevância no estudo, monitoramento e controle de processos corrosivos em dutos de petróleo. A espectrometria por fluorescência de raios X (EFRX) é uma técnica analítica muito versátil...

Análise sobre diferentes abordagens de configuração eletrônica de elementos apresentados em livros de química

Santos, Jackson da Silva
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Dissertação Formato: application/pdf
POR
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This study aimed to identify and review of the conceptual differences presented by authors of books, focusing on the theme of electronic configuration. It shows the changing concepts of electronic configuration, its implications for the cognitive development of students and their relations with the contemporary world. We identified possible obstacles in books generated in the search for simplifications, situations of different concepts of energy in the electron configuration for sublevels. For this analysis was carried out in several books, and some other general chemistry and inorganic chemistry without distinguishing between level of education, whether secondary or higher. It was found that some books for school books corroborated with higher education, others do not. To check the consistency of what was discussed, it was a survey of 30 teachers, it was found divergent points of responses, particularly with respect to the energy sublevels and authorship of the diagram which facilitated the electron configuration. It was found that the total 22professores, ie, 73,33% answered correctly on the energy sublevel more calcium (Ca) and 80%, ie, 24 teachers responded incorrectly on the iron. As for the authorship of the diagram used to facilitate the electronic configuration...

Estudo de titanatos nanoestruturados obtidos por tratamento hidrotérmico de óxido de titânio em meio alcalino; Studies on nanostructured titanates obtained by alkali hydrothermal treatment of titanium oxide

Morgado Júnior, Edisson
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Tese de Doutorado Formato: application/pdf
POR
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TiTanate NanoTubes (TTNT) were synthesized by hydrothermal alkali treatment of TiO2 anatase followed by repeated washings with distinct degrees of proton exchange. TTNT samples with different sodium contents were characterized, as synthesized and after heattreatment (200-800ºC), by X-ray diffraction, scanning and transmission electron microscopy, electron diffraction, thermal analysis, nitrogen adsorption and spectroscopic techniques like FTIR and UV-Vis diffuse reflectance. It was demonstrated that TTNTs consist of trititanate structure with general formula NaxH2−xTi3O7·nH2O, retaining interlayer water in its multiwalled structure. The removal of sodium reduces the amount of water and contracts the interlayer space leading, combined with other factors, to increased specific surface area and mesopore volume. TTNTs are mesoporous materials with two main contributions: pores smaller than 10 nm due to the inner volume of nanotubes and larger pores within 5-60 nm attributed to the interparticles space. Chemical composition and crystal structure of TTNTs do not depend on the average crystal size of the precursor TiO2-anatase, but this parameter affects significantly the morphology and textural properties of the nanostructured product. Such dependence has been rationalized using a dissolution-recrystallization mechanism...

Obtenção e caracterização físico-química de blendas poliméricas, baseadas em POE e PMMA, dopadas com dióxido de titânio

Lima, Elias Januário de
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Dissertação Formato: application/pdf
POR
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The study of polymer blends has been an alternative method in the search field of new materials for obtaining materials with improved properties. In this work blends of poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO) doped with titanium dioxide (TiO2) were studied. The PEO is a polymer semicrystalline structure varying between, 70 and 84% crystallinity, while the PMMA exhibits behavior amorphous in their structure. The use of TiO2 is related to corrosion-resistant of titanium as well as good heat transfer and other characteristics. The study of these polymer blends doped TiO2 gives the properties junction organic (polymer) and inorganic (oxide) which leads to modification of the properties of the resultant material. The blends were doped TiO2 (POE/PMMA/TiO2) in different proportions of the PMMA with the PEO and TiO2 fixed. The ratios were: 90/10/0,1; 85/15/0, 1; 80/20/0,1, 75/25/0,1 and 70/30/0,1. The resulting material was obtained in powder form and being characterized by Fourier Transformed Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Electrochemical Impedance Spectroscopy (EIS). The infrared spectra (IR) for the blends in different ratios showed a band at 1744 cm-1...

Caracterização estrutural de Perovskitas Lax-1AxCoO3 (x=0 e 0,2) ,dopadas com cálcio e bario, por espectroscopia de absorção de raios X (XAS).

Gomes, Washington Charles de Macedo
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Tese de Doutorado Formato: application/pdf
POR
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In this work, the structures of LaCoO3, La0,8Ba0,2CoO3 and La0,8Ca0,2CoO3 perovskites were characterized as a function of temperature (LaCoO3 structure being analyzed only at room temperature). The characterization of these materials were made by X-Ray Absorption Spectroscopy (XAS), in the cobalt K-edge, taking into account the correlated Einstein model X-ray absorption fine structure (EXAFS). The first part of the absorption spectrum corresponded the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). These materials were prepared by the combustion method. The combustion products were calcinated at 900 0C, for 6 hours in air. Noted that the sample LaCoO3 at room temperature and samples doped with Calcium and Barium in the temperature range of 50 K to 298 K showed greater distortion to monoclinic symmetry with space group I2/a. However, the sample doped with barium at the temperatures 50 K, 220 K, and 260 K showed a slight distortion to rhombohedral symmetry with space group R-3c. The La0,8Ca0, 2CoO3 structure was few sensitive to temperature variation, showing a higher local distortion in the octahedron and a higher local thermal disorder. These interpretations were in agreement with the information electronic structural on the XANES region and geometric in the EXAFS region; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior; Neste trabalho foram investigados estruturas de perovskitas LaCoO3...

Síntese de catalisadores nanoporosos na ausência total e parcial de direcionadores orgânicos para pirólise catalítica de óleos pesados e intermediários

Costa, Maria José Fonseca
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Tese de Doutorado Formato: application/pdf
POR
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The processing of heavy oil produced in Brazil is an emergency action and a strategic plan to obtain self-sufficiency and economic surpluses. Seen in these terms, it is indispensable to invest in research to obtain new catalysts for obtaining light fraction of hydrocarbons from heavy fractions of petroleum. This dissertation for the degree of Doctor of Philosophy reports the materials preparation that combine the high catalytic activity of zeolites with the greater accessibility of the mesoporosity, more particularly the HZSM-5/MCM-41 hybrid, done by synthesis processes with less environmental impact than conventional ones. Innovative methodologies were developed for the synthesis of micro-mesoporous hybrid material by dual templating mechanism and from crystalline zeolitic aluminosilicate in the absence of organic template. The synthesis of hybrid with pore bimodal distribution took place from one-single organic directing agent aimed to eliminate the use of organic templates, acids of any kind or organic solvents like templating agent of crystalline zeolitic aluminosilicate together with temperature-programmed microwave-assisted, making the experimental procedures of preparation most practical and easy, with good reproducibility and low cost. The study about crystalline zeolitic aluminosilicate in the absence of organic template...

Aplicabilidade da voltametria de pulso diferencial na quantificação de ácido fólico e ácido oxálico: um método comparativo

Araujo, Eliane Gonçalves de
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Tese de Doutorado Formato: application/pdf
POR
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The development of more selective and sensitive analytical methods is of great importance in different areas of knowledge, covering, for example, food, biotechnological, environmental and pharmaceutical sectors. The study aimed to employ the technique electroanalytical differential pulse voltammetry (DPV) as an innovative and promising alternative for identification and quantification of organic compounds. The organic compounds were investigated in this study oxalic acid (OA) and folic acid (FA). The electrochemical oxidation of oxalic acid has been extensively studied as a model reaction in the boundary between the organic and inorganic electrochemistry. Since the AF, an essential vitamin for cell multiplication in all tissues, which is essential for DNA synthesis. The AF has been investigated using analytical techniques, liquid chromatography and molecular absorption spectrophotometry. The results obtained during the experimental procedure indicated that the process of electrochemical oxidation of oxalic acid is strongly dependent on the nature of the anode material and the oxidation mechanism, which affects their detection. Efficient removal was observed in Ti/PbO2 anodes, graphite, BDD and Pt 90, 85, 80 and 78% respectively. It was also shown that the DPV employing glassy carbon electrode offers a fast...

Nanoesferas magnéticas: estudo do sistema maghemita/sílica; Magnetic nanospheres: study of the maghemita, silica, stober

Caiado, Kely Lopes
Fonte: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Química (IQ); Instituto de Química - IQ (RG) Publicador: Universidade Federal de Goiás; Brasil; UFG; Programa de Pós-graduação em Química (IQ); Instituto de Química - IQ (RG)
Tipo: Tese de Doutorado Formato: application/pdf
POR
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In this work, we synthesized core/shell magnetic composite type consisting of maghemite nanoparticles covered with a coating layer of amino-functionalized silica. The experimental procedure was based on four steps: i) synthesis of magnetite nanoparticles and subsequent oxidation to maghemite, ii) preparation of aqueous colloidal dispersions (ferrofluids), from maghemite nanoparticles with modal diameter of 8.4 nm or 7.2 nm functionalized with citrate ion, iii) preparation of silica magnetic nanospheres (NMS) by the modified Stöber method using different amounts of ferrofluids and tetraethoxysilane (TEOS), and iv) functionalization of silica nanospheres with amino groups using aminopropyltrimethoxysilane (APTS). Sample characteristics of NMS were determined from the iron content measurements, from high-resolution transmission electron microscopy (HRTEM) and from vibrating sample magnetometry (VSM) and they were evaluated on the basis of the synthetic parameters employed, these being the content of magnetic material (nFe/nTEOS = 0.05, nFe/nTEOS = 0.01 e nFe/nTEOS = 0.002) and the type of used ferrofluid; a freshly prepared ferrofluid or an aged ferrofluid. The study of ferrofluids by static magnetic birefringence (SMB) showed that both had aggregates of magnetic nanoparticles...

Electro-catalytic performance of 60%NiO/Ce0.9Zr0.1O2 cermets as anodes of intermediate temperature solid oxide fuel cells

Zimicz, Maria Genoveva; Núñez, P.; Ruiz Morales, J. C.; Lamas, Diego German; Larrondo, Susana Adelina
Fonte: Elsevier Publicador: Elsevier
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
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This paper analyses the electrocatalytic performance of a 60%NiO/Ce0.9Zr0.1O2 anode under reducing atmospheres, using a symmetric cell configuration, [anode/electrolyte/anode], with Samaria doped Ceria (SDC) as electrolyte. This anode exhibited excellent performance in H2 atmosphere in comparison with conventional anode materials. A dual chamber solid oxide fuel cell with 60%NiO/Ce0.9Zr0.1O2 anode, SDC electrolyte, and Pt cathode was constructed and tested under H2 atmospheres at intermediate temperatures. Good values of power densities were obtained, indicating the good performance of 60%NiO/Ce0.9Zr0.1O2 in the operating conditions.; Fil: Zimicz, Maria Genoveva. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas de las Fuerzas Armadas. Centro de Investigaciones en Sólidos; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - CONICET - Bahía Blanca. Instituto de Física del Sur; Argentina;; Fil: Núñez, P.. Universidad de la Laguna. Departamento de Química Inorgánica; España;; Fil: Ruiz Morales, J. C.. Universidad de la Laguna. Departamento de Química Inorgánica; España;; Fil: Lamas, Diego German. Universidad Nacional del Comahue. Facultad de Ingeniería. Departamento de Mecánica; Argentina;; Fil: Larrondo...

Mebendazole Mesylate Monohydrate: A New Route to Improve the Solubility of Mebendazole Polymorphs

de Paula, Karina; Camí, Gerardo Enrique; Brusau, Elena Virginia; Narda, Griselda Edith; Ellena, Javier
Fonte: Wiley Publicador: Wiley
Tipo: info:eu-repo/semantics/article; info:ar-repo/semantics/artículo; info:eu-repo/semantics/publishedVersion Formato: application/pdf
ENG
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Mebendazole mesylate monohydrate, a new stable salt of mebendazole (MBZ), has been synthesized and fully characterized. It was obtained from recrystallization of MBZ forms A, B, or C in diverse solvents with the addition of methyl sulfonic acid solution. The crystal packing is first organized as a two-dimensional array consisting of rows of alternating MBZ molecules linked to columns of mesylate ions by hydrogen bonds. The three-dimensional structure is further developed by classical intermolecular interactions involving water molecules. In addition, nonclassical contacts are also found. The vibrational behavior is consistent with the crystal structure, the most important functional groups showing shifts to lower or higher frequencies in relation to the MBZ polymorphs. Thermal analysis indicates that the compound is stable up to 50◦C. Decomposition occurs in five steps. Solubility studies show that the title compound presents a significant higher performance than polymorph C.; Fil: de Paula, Karina. Universidade of São Paulo. Physics Instituto of Sao Carlos; Brasil;; Fil: Camí, Gerardo Enrique. Universidad Nacional de San Luis. Facultad de Química, Bioquímica y Farmacia. Laboratorio de Química Inorgánica; Argentina; Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico San Luis. Instituto de Investigaciones en Tecnología Química; Argentina;; Fil: Brusau...

Determinación de la fracción biodisponible de metales traza en suelos tratados con biosólidos a través de la técnica de la gradiente de difución en capa fina (DGT), cultivo de plantas de ballica y extracción secuencial

Vásquez Sepúlveda, Viviana Andrea
Fonte: Universidad de Chile; CyberDocs Publicador: Universidad de Chile; CyberDocs
Tipo: Tesis
ES
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La aplicación de biosólidos generados en plantas de tratamiento en suelos agrícolas es una de las opciones más factibles para solucionar el problema de su disposición en monorrellenos. Además su alto contenido de materia orgánica, macro y micronutrientes permiten la recuperación de suelos degradados. Sin embargo esto puede traer problemas ambientales, ya que la aplicación de biosólidos trae consigo el aumento en el contenido total de metales traza en el suelo y efectos asociados a la biodisponibilidad, movilidad y asociación química de éstos en el suelo. La fracción biodisponible es aquella utilizable por las plantas, y se puede determinar mediante sistemas biológicos, los cuales requieres tiempo y poseen un alto costo. De aquí nace la necesidad de crear nuevos métodos químicos y físico-químicos para determinar la biodisponibilidad en un laboratorio y obtener respuestas rápidas sobre las condiciones ambientales del sistema. La técnica de Gradiente de Difusión en Capa Fina (DGT) ha demostrado ser una herramienta promisoria para evaluar la biodisponibilidad de los metales pesados en plantas, ya que los dispositivos DGT, al igual que las raíces de las plantas, disminuyen localmente la concentración de la solución de suelo y permiten el transporte por difusión desde la solución de suelo y la fase sólida. Este estudio evaluó el efecto de la aplicación de biosólidos a distintas dosis (0...

Photovoltaic Solar Energy: A Briefly Review; Energia Solar Fotovoltaica: Uma Breve Revisão

Carolina T. Machado; Universidade Federal Fluminense; Fabio S. Miranda; Universidade Federal Fluminense
Fonte: Revista Virtual de Química Publicador: Revista Virtual de Química
Tipo: ; Formato: binary/octet-stream
Publicado em 07/01/2015 PT
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Although the sun sends more energy in one hour than the planet Earth consumes in a year, it is not the most important source of energy powering the planet. Acquiring a photovoltaic system is still expensive and the effectiveness of the most commercial modules is of only 15%. In general, these modules are made of mono or polycrystalline silicon, which are called first generation cells. There are also amorphous silicon cells that have 7% efficiency, and to a lesser extent, there are the CdTe, CIGS (CuInGaSe2) and CIS (CuInSe2) cells that have efficiency around 11%. These are thin film cells, called second-generation cells. There are also third generation cells that are still in the research stage and no commercial cells are available in the market. The third generation cells are the organic cells, dye-sensitized solar cells (DSSC) and solar cells based on quantum dots. Germany is the most developed country in the photovoltaic field and it has established programs to encourage the use of such technology. Despite having high levels of solar radiation and one of the largest quartz reserves, Brazil just took its first steps in this field. Since 2012, after the Resolution Nº 482 of ANEEL (Agência Nacional de Energia Elétrica), a user can inject electricity into the Brazilian grid if the energy is produced by renewable sources and the industry began to develop technology in this area. DOI: 10.5935/1984-6835.20150008; Apesar do sol enviar em uma hora mais energia do que o planeta Terra consome em um ano...

Hydrazine (CAS 302-01-2); Hidrazina (CAS 302-01-2)

Vanessa G. Oliveira; Universidade Federal Fluminense; Nathalia M. C. Tolentino; Universidade Federal Fluminense; Pedro Henrique R. de Oliveira; Universidade Federal Fluminense
Fonte: Revista Virtual de Química Publicador: Revista Virtual de Química
Tipo: ; Formato: binary/octet-stream
Publicado em 08/07/2015 PT
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This article presents information about the physico-chemical properties of hydrazine, as well as its toxicity, industrial synthesis and its application in industry and organic synthesis. DOI: 10.5935/1984-6835.20150086; Este artigo contém informações sobre as propriedades físico-químicas da hidrazina, bem como sua toxicidade, síntese industrial e aplicações na indústria e na síntese orgânica. DOI: 10.5935/1984-6835.20150086

Recovering and Applying Potassium Dichromate from Sulphochromic Waste; Recuperação e Aplicação do Dicromato de Potássio Proveniente do Resíduo de Sulfocrômica

Thallis M. Souza; Universidade Federal de Lavras; Adelir Aparecida Saczk; Universidade Federal de Lavras; Zuy Maria Magriotis; Universidade Federal de Lavras; Robson Augusto Pereira; Universidade Federal de Lavras; Felipe M. Pinto; Universidade Federal de
Fonte: Revista Virtual de Química Publicador: Revista Virtual de Química
Tipo: ; Formato: application/pdf
Publicado em 28/02/2014 PT
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A simple procedure for recovering potassium dichromate (K2Cr2O7) from treatment of residual sulphochromic solution  was proposed in the present work by means of cooling crystallization. The decrease of temperature favored the crystallization of K2Cr2O7 due to the decrease of solubility.  5.0 L of sulphochromic wastes containing 48.08 g L-1 of Cr(VI) were treated and the process of crystallization was performed in three steps until crystals were not formed anymore.  On each step the content of Crtotal was determined by flame atomic absorption spectrometry and Cr(VI) by colorimetric method with 1,5- diphenylcarbazide, resulting in the removal of 91% and 92% of Crtotal and Cr(VI), respectively. After the last step, the remaining Cr(VI) in the solution was reduced to Cr(III) from the addition of NaHSO3, recovering via precipitation in pH 8 approximately 36.13 g of Cr(OH)3. The final supernatant was discarded since chromium content was below the maximum limit established by the Brazilian legislation for effluents discharge, which corresponds to 0.10 and 1.0 mg L-1 of Cr(VI) and Cr(III), respectively. 628.4 g of K2Cr2O7 were recovered and the salt was characterized by X-ray diffraction and differential thermal analysis. Its  applicability was compared to the standard K2Cr2O7 when determining the soil organic matter...

Analysis of Petroleum Oily Sludge Produced from Oil-Water Separator; Análise de Borra Oleosa de Petróleo Proveniente do Separador Água e Óleo

Cícero S. Lima; Universidade Federal do Rio Grande do Norte; Regineide O. Lima; Universidade Federal do Rio Grande do Norte; Edjane Fabiula B. Silva; Faculdade Estácio de Natal; Késia Kelly V. Castro; Universidade Federal do Rio Grande do Norte; Osvald
Fonte: Revista Virtual de Química Publicador: Revista Virtual de Química
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Publicado em 01/11/2014 EN
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The petroleum oily sludge is formed during the production, transportation, and storage processes as well as in the oil refinery plant. The elemental analysis was performed with samples of petroleum oily sludge collected in the State of Rio Grande do Norte. For the carbon and hydrogen elements, small differences were observed between them, but for the oxygen element, bigger differences between the sludge samples were noticed. They have presented differences in the chemical composition of inorganic and organic parts. The sludge from oil-water separator (OWS) 2 showed a high amount of oil (94.88%), being considered a high value-added residue by the oil industry. In the analyses of saturated, aromatics, resins, and asphaltenes (SARA) components, the sludge from the unloading had a high amount of saturates. The inorganic material separated from the sludge of the OWS 2 was characterized, and presented a lot of sulfur (41.57%). The sludge analyzed showed a high value of organic components, thus such material can be handled and reprocessed in processing units within the oil industry. DOI: 10.5935/1984-6835.20140076; As borras oleosas são formadas durante as operações de produção, transporte, armazenamento e na refinaria de petróleo. A análise elementar foi realizada com amostras de borra oleosa de petróleo coletadas no Estado do Rio Grande do Norte. Para o elemento carbono e o hidrogênio foram observadas pequenas diferenças entre os mesmos...