Elvio De Campos - Academia.edu (original) (raw)

Papers by Elvio De Campos

Polymers and Polymer Composites, 2013

A cellulose acetate/TiO2 composite was prepared by dissolving cellulose acetate in acetone:acetic... more A cellulose acetate/TiO2 composite was prepared by dissolving cellulose acetate in acetone:acetic acid (70:30 in volume) and adding quantities of titanium(IV) tert-butoxide to obtain varying oxide content after phase inversion, which was achieved by adding water to this mixture. Regardless the quantity of titanium(IV) tert-butoxide, were obtained composites containing about 4 wt.% of TiO2 as anatase, indicated by XRD and Raman spectroscopy. They showed thermal stability up to 250 °C. Adsorption isotherms of methylene blue revealed a maximum adsorption of 11 μmolg-1. This material proved to be an efficient catalyst for the photodegradation of MB under artificial or solar ultraviolet radiation.

RSC Advances, 2017

We report non-conventional silver nanoparticle growth on the surface of lead–germanate oxide glas... more We report non-conventional silver nanoparticle growth on the surface of lead–germanate oxide glasses by thermal annealing under a N2 atmosphere.

DOAJ (DOAJ: Directory of Open Access Journals), Jan 19, 2012

Orbital-The Electronic Journal of Chemistry-is a new peer-reviewed online journal published by th... more Orbital-The Electronic Journal of Chemistry-is a new peer-reviewed online journal published by the Department of Chemistry of the Center for Science and Technology of the Universidade Federal de Mato Grosso do Sul, Brazil. Original contributions (in Portuguese ...

Cerâmica, 2005

Neste trabalho biomateriais à base de Na2O-CaO-SiO2-P2O5 foram obtidos pelo método clássico de fu... more Neste trabalho biomateriais à base de Na2O-CaO-SiO2-P2O5 foram obtidos pelo método clássico de fusão e os biovidros submetidos ao tratamento térmico a diferentes temperaturas. A porosidade das peças foi controlada pela adição de serragem e/ou glucose de milho.A porosidade e a cristalinidade das amostras sintetizadas foram acompanhadas com auxílio das técnicas de Microscopia Eletrônica de Varredura e difração de raios X, respectivamente. Amostras tratadas termicamente a 800 °C mostraram uma reorganização estrutural e conseqüente aumento da dureza. Observou-se que em ambas as cerâmicas tanto a adição de serragem quanto de glucose de milho aumentou a porosidade das peças. Contudo, a estrutura mais organizada e poros mais homogêneos foram obtidos para a mistura vidro/glucose de milho.

Talanta, 2005

The efficiency of niobium(V) oxide as a sorbent phase for solid phase microextraction (SPME) was ... more The efficiency of niobium(V) oxide as a sorbent phase for solid phase microextraction (SPME) was investigated. The thin glass-ceramic rod was coated with niobium(V) oxide using chemical vapor deposition and Nb 2 O 5 as a chemical precursor. Optimum conditions for the preparation and conditioning of the fibers are presented. The fibers were used for the extraction of a mixture of alcohols and a mixture of phenols from the headspace samples. The results obtained proved the suitability of niobium(V) oxide as a new SPME fiber. The calibration graphs for alcohols and phenols in a concentration range of 50-1000 g l −1 were linear (r > 0.995) and the detection limits were below 0.8 g l −1 level. The repeatability for one fiber (n = 6) under similar conditions was between 3 and 10.4%. The fiber-to-fiber reproducibility (n = 6) was between 5 and 15%.

Talanta, 2010

Li 2 O-ZrO 2-BaO-SiO 2 glass fibers were produced and their surfaces were coated with zinc oxide.... more Li 2 O-ZrO 2-BaO-SiO 2 glass fibers were produced and their surfaces were coated with zinc oxide. The fibers' surface morphology was examined by scanning electron microscopy and the zinc oxide layer was characterized by mapping the K ␣ and L ␣ lines of zinc by energy dispersive X-ray spectroscopy. The results indicated that a homogeneous and porous layer of ZnO was formed on the fibers' surface. This layer was subjected to a simultaneous determination of trihalomethanes using headspace-solid phase microextraction-gas chromatography. The study was conducted after evaluating the ideal time of incubation (15 min), extraction (15 min) and desorption (10 min), as well as the effect of the addition of salt (15%, m/v) on the analytical response. A good linear dynamic range was observed individually for trihalomethanes aqueous solutions containing 20 g L −1 and 500 g L −1 of trichloromethane, 15 g L −1 and 250 g L −1 of dichlorobromomethane and dibromochloromethane and 10 g L −1 and 100 g L −1 of tribromomethane, with all the compounds showing correlation coefficients higher than 0.9900.

Surface Engineering, 2012

In this study, the chemical vapour deposition (CVD) technique is used to modify the surface of Li... more In this study, the chemical vapour deposition (CVD) technique is used to modify the surface of Li 2 O-ZrO 2-BaO-SiO 2 glass fibre with Nb 2 O 5 , using NbCl 5 as the precursor. Glass fibres were coated as follows: without thermal pretreatment but followed by air exposure after the reaction with NbCl 5 ; without thermal treatment followed by water hydrolysis, with thermal treatment at 300uC for 2 h and air exposure; and finally, with thermal treatment and hydrolysis in water. The best result was obtained with the fibre chemically modified with Nb 2 O 5 after heat treatment followed by water hydrolysis. This procedure resulted in fibres coated with a homogeneous layer of Nb 2 O 5 without cracks. The fibres were characterised by scanning electron microscopy and energy dispersive X-ray spectroscopy. The fibres were evaluated in the qualitative determination of a mixture of methanol, ethanol and 1-butanol by solid phase microextraction and gas chromatography, yielding better results than those of the fibre coated with Nb 2 O 5 prepared by metallo-organic decomposition.

Química Nova, 2002

Recebido em 11/8/00; aceito em 29/8/01 CHEMICAL DURABILITY OF THE Li 2 O-ZrO 2-BaO-SiO 2 GLASS-CE... more Recebido em 11/8/00; aceito em 29/8/01 CHEMICAL DURABILITY OF THE Li 2 O-ZrO 2-BaO-SiO 2 GLASS-CERAMIC TREATED WITH ACIDIC AND BASIC SOLUTION.The chemical durability of the Li 2 O-ZrO 2-BaO-SiO 2 system was examined by determination of the Vickers hardness. The dependence of hardness and of the chemical resistance with BaO addition was investigated. The experimental results indicate that the hardness increases with the BaO content. The samples surface's morphology submitted to the chemical treatment in acidic (H 2 SO 4) and basic (KOH) solution was accompanied by scanning electron microscopy. The chemical durability of the materials with BaO showed better than the glass ceramic without this content. These materials treated with H 2 SO 4 solution showed a preferential attack to the silica rich sites.

Materials Research, 2002

Differential thermal analysis and scanning electron microscopy were used to determine the influen... more Differential thermal analysis and scanning electron microscopy were used to determine the influence of the addition of BaO on the crystallization mechanism of Li2O-ZrO2-SiO2 systems. As the concentration of BaO in the samples increased, a transition occurred in the predominant crystallization mechanism, which passed from superficial to volumetric. To determine the maximum nucleation rate, the crystallization kinetics of the sample containing 20 mole % BaO, which showed the most uniform crystallization, was studied by counting the nuclei with an image analyzer. The first nuclei appeared at the first endothermic inflection point (at the start of Tg, at 440 °C), while the maximum number of nuclei was counted at the midpoint of the glass transition region (446 °C). These results are similar to those observed for other materials that crystallize in volume, and confirm scanning electron microscopy data.

Journal of Radioanalytical and Nuclear Chemistry, 2006

Composite solid propellants have been used as fuel in the propulsion of rockets. Transition metal... more Composite solid propellants have been used as fuel in the propulsion of rockets. Transition metal oxides such as copper chromite (CuCr 2 O 4) are important catalysts added to the propellants to increase the combustion rates. The content of Cu in samples of copper chromite is normally determined by electrogravimetry and the content of Cr by volumetry. Considering that the content of Cu is important for the determination of the catalytic activity of copper chromite and that electrogravimetry and volumetry are very laborious and time consuming, Fourier transformed infrared spectroscopy (FT-IR) was implemented as an alternative fast method in the Aerospace Technical Center (CTA, Brazil). Here, instrumental neutron activation analysis (INAA), as an independent technique of high metrological level, was employed to validate Cr and Cu determination by FT-IR. The results from FT-IR were comparable to those determined by INAA.

Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2005

Fiberglass with a composition of 29% Li2O, 1% ZrO2, 5% BaO, and 65% Si2O was coated with Nb2O5 us... more Fiberglass with a composition of 29% Li2O, 1% ZrO2, 5% BaO, and 65% Si2O was coated with Nb2O5 using the metallo-organic decomposition (MOD) technique. The morphology and coating homogeneity of the fibers was evaluated, using the scanning electron ...

Chromatographia, 2005

The efficiency of a glass-ceramic rod as a base for the preparation of SPME fibers using sol-gel ... more The efficiency of a glass-ceramic rod as a base for the preparation of SPME fibers using sol-gel technology was investigated. Glass-ceramic rod was coated with PDMS using sol-gel reaction, and its surface characteristic was determined for SEM. Optimum conditions for the preparation of the fiber are presented. The same procedure was used for coating the fused silica rod. The fibers thickness and absorption capacity were compared. The proposed fiber was used for the extraction of a mixture of BTEX, from aqueous samples. The results obtained proved the superiority of glass-ceramic as a new base for SPME fiber, resulting in a thickness of 44lmagainst44 lm against 44lmagainst6 lm for fused silica base. The calibration graphs for BTEX were linear (r > 0.998) and the detection limits were below 0.8 lg L)1 .

Journal of Non-Crystalline Solids, 2015

Glass stability (GS) parameters based on typical temperatures obtained by differential thermal an... more Glass stability (GS) parameters based on typical temperatures obtained by differential thermal analysis were determined for glasses composed of Li 2 O:BaO:SiO 2 :nucleant, using TiO 2 , V 2 O 5 , ZrO 2 and Nb 2 O 5 as nucleants. The GS parameter proposed by Saad and Poulain, S, showed values of 21.26 for ZrO 2 , 13.77 for Nb 2 O 5 , 11.42 in the glass without nucleating agent, 6.91 for V 2 O 5 and 6.29 in that containing TiO 2. GS was also inferred from the apparent activation energy of crystallization, A E , and these values of the compositions, in kJ mol −1 , were 355 in the glass without nucleating agent, 322 for TiO 2 , 254 for ZrO 2 , 278 for V 2 O 5 and 300 for Nb 2 O 5. A surface crystallization mechanism was observed, and thermal treatment yielded crystalline Li 2 Si 2 O 5 and Li 2 SiO 3. The time-temperature-transformation diagrams, TTT diagrams, were consistent with the obtained GS parameters.

An entry from the Cambridge Structural Database, the world's repository for small molecule cr... more An entry from the Cambridge Structural Database, the world's repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Neste trabalho encontram-se descritas a preparacao e a caracterizacao de dois compositos orgânico... more Neste trabalho encontram-se descritas a preparacao e a caracterizacao de dois compositos orgânicos/inorgânicos, obtidos a partir de matrizes celulosicas e de pentoxido de niobio. O composito de celulose e Nb205 (Cel/Nb2O5) foi preparado na forma de fibras pelo tratamento da celulose suspensa em CCl4 com Nb(5-n)(OC2H5)n em atmosfera de nitrogenio, seguido da evaporacao do solvente e da hidrolise ao ar .Obteve- se compositos com percentuais de oxido, em massa, de 4,5%, 10,2% e 16,0 %. Observou-se o aumento do grau de cristalinidade das fibras em relacao ao polimero puro, devido a reacao do reagente precursor do oxido com a fase amorfa da matriz. As analises de XPS e SEM indicaram que as particulas de oxido dispersaram-se uniformemente sobre as fibras de celulose e a presenca de sitios acidos de Lewis e de Brfnsted foi detectada com o uso de piridina como molecula sonda. Membranas do composito acel/Nb205 (onde acel e o acetato de celulose) foram preparadas a partir da adicao do NbCl5 a uma solucao de acetato de celulose dissolvido numa mistura de acetona e acido acetico. As membranas foram obtidas pelo metodo da inversao de fase seguido da hidrolise do metal em atmosfera umida. Obtiveram-se membranas com os teores percentuais de oxido em massa de 1,1%, 6,1%, 9,8%, 15,6% e 20,9%. Observou-se a diminuicao da estabilidade termica do acetato de celulose com o aumento do teor de Nb2O5 disperso, em relacao a estabilidade termica do polimero puro. As micrografias obtidas por microscopia eletronica de varredura e pelo mapeamento com microssonda de raio- X dispersivo mostraram que as particulas do oxido encontram-se homogeneamente dispersas na matriz polimerica. Os espectros eletronicos de absorcao indicaram que as particulas do oxido disperso sao formadas por unidades monomericas e/ou oligomericas, nao havendo a formacao de grandes aglomerados de Nb2O5. A investigacao da acidez superficial destas particulas, usando-se piridina como molecula sonda, mostrou que a quantidade de sitios acidos de Lewis aumenta diretamente com o teor de Nb2O5, indicando que nao ocorre a saturacao do numero de coordenacao do metal, em todos os compositos preparados. Aos sitios acidos de Lewis do composito acel/Nb2O5, adsorveu-se hematoporfirina IX. As quantidades de hematoporflfina IX e de metal adsorvidos foram de 43 mmol.g e 39,5 mmol.g, respectivamente, correspondendo a complexacao total dos nitrogenios iminicos da porfirina com cobalto. O espectro eletronico do material com o cobalto adsorvido indicou a formacao de um complexo de cobalto(Il) e o estudo de EPR mostrou haver a formacao de especies com e sem oxigenio molecular coordenado axialmente. Este material foi utilizado na construcao de um eletrodo quimicamente modificado e a propriedade eletroquimica do complexo porfirinico de cobalto adsorvido foi estudada, a fim de se verificar a possibilidade de utilizacao do sistema como sensor eletroquimico de oxigenio. A reducao eletrocatalitica do O2 ocorreu a -390 mV em KCl 1M e pH 1. A intensidade da corrente de eletrorreducao do O2 variou linearmente com a concentracao de oxigenio em solucao. Abstract