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Superparamagnetic Ni:SiO(2)-C nanocomposites films synthesized by a polymeric precursor method

Fonseca, Fabio Coral; Jardim, Renato de Figueiredo; Escote, Marcia Tsuyama; GOUVEIA, P. S.; LEITE, E. R.; LONGO, E.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
1010.8323%
In this work, we report on the magnetic properties of nickel nanoparticles (NP) in a SiO(2)-C thin film matrix, prepared by a polymeric precursor method, with Ni content x in the 0-10 wt% range. Microstructural analyses of the films showed that the Ni NP are homogenously distributed in the SiO(2)-C matrix and have spherical shape with average diameter of similar to 10 nm. The magnetic properties reveal features of superparamagnetism with blocking temperatures T (B) similar to 10 K. The average diameter of the Ni NP, estimated from magnetization measurements, was found to be similar to 4 nm for the x = 3 wt% Ni sample, in excellent agreement with X-ray diffraction data. M versus H hysteresis loops indicated that the Ni NP are free from a surrounding oxide layer. We have also observed that coercivity (H (C)) develops appreciably below T (B), and follows the H (C) ae [1 - (T/T (B))(0.5)] relationship, a feature expected for randomly oriented and non-interacting nanoparticles. The extrapolation of H (C) to 0 K indicates that coercivity decreases with increasing x, suggesting that dipolar interactions may be relevant in films with x > 3 wt% Ni.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Brazilian agency FAPESP/CEPID; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Brazilian agency CNPq/PRONEX; Brazilian agency CAPES; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Er : YAB nanoparticles and vitreous thin films by the polymeric precursor method

MAIA, Lauro J. Q.; IBANEZ, Alain; ORTEGA, Luc; MASTELARO, Valmor Roberto; HERNANDES, Antonio Carlos
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
1015.96766%
The synthesis of Y(0.9)Er(0.1)Al(3)(BO(3))(4) crystalline powders and vitreous thin films were studied. Precursor solutions were obtained using a modified polymeric precursor method using D-sorbitol as complexant agent. The chemical reactions were described. Y(0.)9Er(0.1)Al(3)(BO(3))(4) composition presents good thermal stability with regard to crystallization. The Y(0.9)Er(0.1)Al(3)(BO(3))(4) crystallized phase can be obtained at 1,150 degrees C, in agreement with other authors. Crack- and porosity-free films were obtained with very small grain size and low RMS roughness. The films thickness revealed to be linearly dependent on precursor solution viscosity, being the value of 25 mPa s useful to prepare high-quality amorphous multi-layers (up to similar to 800 nm) at 740 degrees C during 2 h onto silica substrates by spin coating with a gyrset technology.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[02/13748-9]; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); CAPES[455/04-1]

Study of ethanol electro-oxidation in acid environment on Pt(3)Sn/C anode catalysts prepared by a modified polymeric precursor method under controlled synthesis conditions

SOUZA, R. F. B. De; PARREIRA, L. S.; RASCIO, D. C.; SILVA, J. C. M.; Teixeira Neto, Erico; CALEGARO, M. L.; SPINACE, E. V.; Oliveira Neto, Almir; SANTOS, M. C.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
1010.8323%
A carbon-supported binary Pt(3)Sn catalyst has been prepared using a modified polymeric precursor method under controlled synthesis conditions This material was characterized using X-ray diffraction (XRD). and the results indicate that 23% (of a possible 25%) of Sn is alloyed with Pt, forming a dominant Pt(3)Sn phase. Transmission election microscopy (TEM) shows good dispersion of the electrocatalyst and small particle sizes (3 6 nm +/- 1 nm) The polarization curves for a direct ethanol fuel cell using Pt(3)Sn/C as the anode demonstrated Improved performance compared to that of a PtSn/C E-TEK. especially in the intrinsic resistance-controlled and mass transfer regions. This behavior is probably associated with the Pt(3)Sn phase. The maximum power density for the Pt(3)Sn/C electrocatalyst (58 mW cm(-2)) is nearly twice that of a PtSn/C E-TEK electrocatalyst (33 mW cm(-2)) This behavior is attributed to the presence of a mixed Pt(9)Sn and Pt(3)Sn alloy phase in the commercial catalysts (C) 2009 Elsevier B V All rights reserved; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq[474742/2008-8]; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); CAPES; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[05/59992-6]; FAPESP[08/58789-0]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP[08/58788-4]; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); UFABC; UFABC

Ethanol oxidation reaction on PtCeO(2)/C electrocatalysts prepared by the polymeric precursor method

SOUZA, R. F. B. De; FLAUSINO, A. E. A.; RASCIO, D. C.; OLIVEIRA, R. T. S.; TEIXEIRA NETO, E.; CALEGARO, M. L.; SANTOS, M. C.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
1010.8323%
This paper presents a study of the electrocatalysis of ethanol oxidation reactions in an acidic medium on Pt-CeO(2)/C (20 wt.% of Pt-CeO(2) on carbon XC-72R), prepared in different mass ratios by the polymeric precursor method. The mass ratios between Pt and CeO(2) (3:1, 2:1, 1:1, 1:2, 1:3) were confirmed by Energy Dispersive X-ray Analysis (EDAX). X-ray diffraction (XRD) structural characterization data shows that the Pt-CeO(2)/C catalysts are composed of nanosized polycrystalline non-alloyed deposits, from which reflections corresponding to the fcc (Pt) and fluorite (CeO(2)) structures were clearly observed. The mean crystallite sizes calculated from XRD data revealed that, independent of the mass ratio, a value close to 3 nm was obtained for the CeO(2) particles. For Pt, the mean crystallite sizes were dependent on the ratio of this metal in the catalysts. Low platinum ratios resulted in small crystallites. and high Pt proportions resulted in larger crystallites. The size distributions of the catalysts particles, determined by XRD, were confirmed by Transmission Electron Microscope (TEM) imaging. Cyclic voltammetry and chronoamperometic experiments were used to evaluate the electrocatalytic performance of the different materials. In all cases...

Influence of the pH on Al2O3:CuO pigments prepared by a polymeric precursor method

Marques, Carolina Hernandes; Mesquita, Alexandre; Araújo, Vinicius Dantas; Bernardi, Maria Inês Basso
Fonte: Universidade Federal de São Carlos - Departamento de Engenharia de Materiais; São Carlos Publicador: Universidade Federal de São Carlos - Departamento de Engenharia de Materiais; São Carlos
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
1017.6515%
Copper (II) aluminate, CuAl2O4, which is known to be an inverse spinel contains a d9 metal ion and possesses interesting electronic, magnetic and catalytic properties and is used in industry as ceramic pigments, coatings and catalysts. Al2O3 with 10 mol% Cu (AlCu10) was synthesized by the polymeric precursor method varying the pH of the precursor solution with addition of ammonium hydroxide and ethylenediamine. It was shown that the pyrolysis of the polymeric chain occurs in higher temperatures for samples prepared in higher values of pH. The colorimetric coordinates exhibit dependence with pH and with the increase of annealing temperature. AlCu10 samples prepared with higher values of pH present lower values of colorimetric coordinates, indicating alterations in its color. The luminosity parameters L* increase also as a function of pH.; CNPq; FAPESP

Structural characterization of phase transition of Al2O3 nanopowders obtained by polymeric precursor method

Cava, S.; Tebcherani, S. M.; Souza, I. A.; Pianaro, S. A.; Paskocimas, C. A.; Longo, Elson; Varela, José Arana
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 394-399
ENG
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1012.5385%
Nanocrystalline Al(2)O(3)powders have been synthesized by the polymeric precursor method. A study of the evolution of crystalline phases of obtained powders was accomplished through X-ray diffraction, micro-Raman spectroscopy and refinement of the structures through the Rietveld method. The results obtained allow the identification of three steps on the gamma-Al2O3 to alpha-Al2O3 phase transition. The single-phase alpha-Al2O3 Powder was obtained after heat-treatment at 1050 degrees C for 2 h. A study of the morphology of the particles was accomplished through measures of crystallite size, specific surface area and transmission electronic microscopy. The particle size is closely related to gamma-Al2O3 to alpha-Al2O3 phase transition. (c) 2007 Elsevier B.V. All rights reserved.

Characterization of amorphous niobium silicates powders synthesized by polymeric precursor method

Bertolini, M. J.; Zaghete, M. A.; Gimenes, R.; Paiva-Santos, C. O.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 3196-3199
ENG
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In this paper 4.5SiO(2)-3Al(2)O(3-x)Nb(2)O(5)-2CaO powders have been synthesized using a chemical process the Polymeric Precursor Method. The process of glass formation has been investigated by XRD and DTA, the results confirm that the prepared powders are glasses. Experimental data show that amount of Nb2O5 had a considerable effect on the T-g values. The structures of glasses prepared. have been determined by Si-29 and Al-27 MAS NMR and the results indicated that the network is formed by SiO4 and AlO4 tetrahedral linked and probably Si-O-Nb bonds are present in the vitreous network. (C) 2005 Elsevier B.V. All rights reserved.

Microstructural and ferroelectric properties of PbZr1-xTi(x)O(3) thin films prepared by the polymeric precursor method

Nunes, MSJ; Leite, E. R.; Pontes, F. M.; Duboc, N. M.; Longo, Elson; Varela, José Arana
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 365-370
ENG
Relevância na Pesquisa
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The polymeric precursor method was employed in the preparation of PZT thin films on Pt(111)Ti/SiO2/Si(100) substrates. X-ray diffraction patterns revealed the polycrystalline nature of the PZT (53:47) thin films, which had a granular structure and a grain size of approximately 70 nm. A 350-nm thick film was obtained by running three cycles of the dip-coating/heating process. Atomic force microscopy (AFM) analyses showed the surface of these thin films to be smooth, dense and crack-free with low surface roughness (= 2.0 nm). The PZT (53:47) thin films annealed at 700 degreesC showed a well-saturated hysteresis loop. The C-V curves of perovskite thin film displayed normal ferroelectric behavior, while the remanent polarization (2P(r)) and coercive field (E-e) of the film deposited and measured at room temperature were 40 muC/cm(2) and 110 kV/cm, respectively. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Ba1-xSrxTiO3 thin films by polymeric precursor method

Pontes, F. M.; Longo, Elson; Rangel, J. H.; Bernardi, M. I.; Leite, E. R.; Varela, José Arana
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 249-253
ENG
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Stoichiometric Ba1-xSrxTiO3 (BST; x = 0.4) thin films were prepared by the polymeric precursor method. High quality polycrystalline films of BST with low roughness (approximate to 3 nm) were obtained from a Pt/Ti/SiO2/Si substrate deposited by spin-coating technique. Microstructure and morphological evaluation were done using grazing incident X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Grazing incident angle XRD characterization of these films showed that BST phase crystallizes at 600 degrees C from an inorganic amorphous matrix. No intermediate crystalline phase was identified. A linear relationship between roughness and grain size was observed. (C) 2000 Elsevier B.V. B.V. All rights reserved.

Low temperature synthesis and electrical properties of PbTiO3 thin films prepared by the polymeric precursor method

Pontes, F. M.; Rangel, JHG; Leite, E. R.; Longo, Elson; Varela, José Arana; Araujo, E. B.; Eiras, J. A.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 232-236
ENG
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Ferroelectric PbTiO3 thin films were successfully prepared on a Pt(111)Ti/SiO2/Si(100) substrate for the first time by spin coating, using the polymeric precursor method. X-ray diffraction patterns of the films indicate that they are polycrystalline in nature. This method allows low temperature (500 degrees C) synthesis and high electrical properties. The multilayer PbTiO3 thin films were granular in structure with a grain size of approximately 110-120 nm. A 380-nm-thick film was obtained by carrying out four cycles of the spin-coating/heating process. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses showed the surface of these thin films to be smooth, dense and crack-free with low surface roughness (=3.4 nm). At room temperature and at a frequency of 100 kHz, the dielectric constant and the dissipation factor were, respectively, 570 and 0.016. The C-V characteristics of perovskite thin film prepared at low temperature show normal ferrolectric behavior. The remanent polarization and coercive field for the films deposited were 13.62 mu C/cm(2) and 121.43 kV/cm, respectively. The high electrical property values are attributed to the excellent microstrutural quality and chemical homogeneity of thin films obtained by the polymeric precursor method. (C) 2000 Elsevier B.V. S.A. All rights reserved.

Thermal and structural investigation of SnO2/Sb2O3 obtained by the polymeric precursor method

de Melo, Danniely S.; Santos, M. R. C.; Santos, Ieda M. G.; Soledade, L. E. B.; Bernardi, M. I. B.; Longo, Elson; Souza, A. G.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 697-701
ENG
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SnO2-based materials are used as sensors, catalysts and in electro-optical devices. This work aims to synthesize and characterize the SnO2/Sb2O3-based inorganic pigments, obtained by the polymeric precursor method, also known as Pechini method (based on the metallic citrate polymerization by means of ethylene glycol). The precursors were characterized by thermogravimetry (TG) and differential thermal analysis (DTA). After characterization, the precursors were heat-treated at different temperatures and characterized by X-ray diffraction. According to the TG/DTA curves basically two-step mass loss process was observed: the first one is related to the dehydration of the system; and the second one is representative to the combustion of the organic matter. Increase of the heat treatment temperature from 500 to 600 degrees C and 700 degrees C resulted higher crystallinity of the formed product.

Superparamagnetic Ni:SiO2-C nanocomposites films synthesized by a polymeric precursor method

Fonseca, F. C.; Jardim, R. F.; Escote, M. T.; Gouveia, P. S.; Leite, E. R.; Longo, Elson
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica Formato: 703-710
ENG
Relevância na Pesquisa
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); In this work, we report on the magnetic properties of nickel nanoparticles (NP) in a SiO2-C thin film matrix, prepared by a polymeric precursor method, with Ni content x in the 0-10 wt% range. Microstructural analyses of the films showed that the Ni NP are homogenously distributed in the SiO2-C matrix and have spherical shape with average diameter of similar to 10 nm. The magnetic properties reveal features of superparamagnetism with blocking temperatures T (B) similar to 10 K. The average diameter of the Ni NP, estimated from magnetization measurements, was found to be similar to 4 nm for the x = 3 wt% Ni sample, in excellent agreement with X-ray diffraction data. M versus H hysteresis loops indicated that the Ni NP are free from a surrounding oxide layer. We have also observed that coercivity (H (C)) develops appreciably below T (B), and follows the H (C) ae [1 - (T/T (B))(0.5)] relationship, a feature expected for randomly oriented and non-interacting nanoparticles. The extrapolation of H (C) to 0 K indicates that coercivity decreases with increasing x...

LiNbO3 thin films prepared from a polymeric precursor method

Bouquet, V.; Leite, E. R.; Longo, Elson; Varela, José Arana
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 1143-1146
ENG
Relevância na Pesquisa
1013.89375%
LiNbO3 thin films were prepared from polymeric precursor method by dip coating. The precursor films, deposited on Si(111) substrates, were heat-treated from 400°C to 900°C in order to study the heat treatment influence on the crystallinity and microstructure of the final film. The X-ray diffraction patterns showed, in particular, that these films crystallize at low temperature (450°C) and present no preferential orientation. The scanning electron microscopy studies showed that the film microstructure is strongly influenced by the annealing temperature. © 1997 Trans Tech Publications.

Preparation and properties of ferroelectric BaTiO3 thin films produced by the polymeric precursor method

Lee, E. J. H.; Pontes, F. M.; Leite, E. R.; Longo, Elson; Varela, José Arana; Araujo, E. B.; Eiras, J. A.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 1457-1459
ENG
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Ferroelectric barium titanate thin films were produced by the polymeric precursor method. In this technique, the desired metal cations are chelated in a solution using a hydroxycarboxylic acid as the chelating agent. Barium carbonate and titanium IV isopropoxide were used as precursors for the citrate solution. Ethylene glycol and citric acid were used as polymerization/complexation agents for the process. The crystalline structure of the film annealed at 700 °C had a single perovskite phase with a tetragonal structure. The BaTiO3 film showed good P-E hysteresis loops and C-V characteristics due to the switched ferroelectric domains.

Preparation of lanthanum doped Bi4Ti3O12 ceramics by the polymeric precursor method

Simões, A. Z.; Quinelato, C.; Ries, A.; Stojanovic, B. D.; Longo, Elson; Varela, José Arana
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 481-485
ENG
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Lanthanum-modified bismuth titanate, Bi4 - xLaxTi3O12 (BLT) ceramics, with x ranging from 0 to 0.75 were prepared by the polymeric precursor method. Orthorhombicity of the system is decreased with the increase of lanthanum content in the bismuth titanate (BIT) crystal lattice. No secondary phases were evident after lanthanum addition. Increasing lanthanum content causes a structural distortion in the bismuth titanate lattice. The shape of the grains is strongly influenced by the lanthanum added to the system. © 2005 Elsevier B.V. All rights reserved.

Luminescent properties of hybrid materials prepared by the polymeric precursor method

Oliveira, Larissa H.; Moura, Ana Paula de; Longo, Elson; Varela, José Arana; Rosa, Ieda L.V.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 227-235
ENG
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Rare earth complexes (RE) can be incorporated in silica matrixes, originating organic/inorganic hybrid materials with good thermal stability and high rare earth emission lines. In this work, the hybrid material was obtained by the polymeric precursor method and ultrasonic dispersed with spherical silica particles prepared by the Stöber Method. The Raman spectra indicated that the Eu3+ ions are involved in a polymeric structure formed as consequence of the chelation and polyesterification reactions of this ion with citric acid and ethylene glycol. After the ultrasonic stirring, 2-hydroxynicotinic ligand will also compose this polymeric rigid structure. The TGA/DTA analysis showed that this polymeric material was thermal decomposed at 300 °C. Moreover, this process allows the chelating process of the 2-hydroxynicotinic acid ligand to the Eu3+ ions. The 29Si NMR showed that the ultrasonic dispersion of the reactants was not able to promote the functionalization of the silica particles with the 2-hydroxynicotinic acid ligand. Moreover, heat treatment promotes the [Eu(HnicO2)3] complex particles incorporation into silica pores. At this temperature, the TGA curve showed that only the thermal degradation of ethylene glycol and citric acid used during the experimental procedure occurs. The silica and hybrid materials are composed by spherical and aggregated particles with particle size of approximately 450 nm...

Mechanisms of phase formation along the synthesis of Mn-Zn ferrites by the polymeric precursor method

Martins, Murillo Longo; Florentino, Ariovaldo de Oliveira ; Cavalheiro, Alberto Adriano; Silva, Rafael Innocenti Vieira da; Santos, Dayse Iara dos; Saeki, Margarida Juri
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 16023-16031
ENG
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1013.89375%
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Considering the wide application of crystalline Mn-Zn ferrites microparticles, understanding synthesis routes that allow the achievement of such materials is a constant need. In this work, Mn-Zn ferrites, Mn(1-x)ZnxFe2O4 (0.15 <= x <= 0.30), were synthesized by the polymeric precursor method in well-cohtrolled steps and the mechanisms of phase formation under different thermal treatments were studied. Such investigation was performed by means of thermal analysis (TG/DTA), synchrotron X-ray powder diffraction (SXPD) (including in-situ and anomalous scattering experiments) and scanning electron microscopy (SEM). The ferrite precursor powders present the spinel as single crystalline phases whose cell parameters increase as Mn is substituted by Zn, indicating possible Fe deficiencies into the structure. The crystallization degree of these samples is also affected by the Mn substitution and reaches a maximum for x=0.25. Further thermal treatments in air at 700 degrees C and 1100 degrees C lead to additional events also related to the Zn content, such as carbonates elimination and crystallization of the contaminant phase hematite. Thermal treatments under N-2 atmosphere at 700 degrees C allow the achievement of powders with only the spinel phase...

Effect of the iron doping on the thermal decomposition of the polymeric precursor for the titanium dioxide powder synthesis

Lopes, Silvanice A.; Cruz, Natali A.; Manfroi, Daniela C.; Dias, Rafael Gomes; Silva, Margarete S.; Zaghete, Maria Aparecda; Anjos, Ademir dos; Cavalheiro, Alberto A.; Oliveira, Lincoln C.S.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 211-216
ENG
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922.271%
The Polymeric Precursor Method has proved suitable for synthesizing reactive powders using low temperatures of calcination, especially when compared with conventional methods. However, during the thermal decomposition of the polymeric precursor the combustion event can be releases an additional heat that raises the temperature of the sample in several tens of degrees Celsius above the set temperature of the oven. This event may be detrimental to some material types, such as the titanium dioxide semiconductor. This ceramic material has a phase transition at around 600 ° C, which involves the irreversible structural rearrangement, characterized by the phase transition from anatase to rutile TiO2 phase. The control of the calcination step then becomes very important because the efficiency of the photocatalyst is dependent on the amount of anatase phase in the material. Furthermore, use of dopant in the material aims to improve various properties, such as increasing the absorption of radiation and in the time of the excited state, shifting of the absorption edge to the visible region, and increasing of the thermal stability of anatase. In this work, samples of titanium dioxide were synthesized by the Polymeric Precursor Method in order to investigate the effect of Fe (III) doping on the calcination stages. Thermal analysis has demonstrated that the Fe (III) insertion at 1 mol% anticipates the organic decomposition...

Ethanol electrooxidation using Ti/(RuO2)(x) Pt(1-x) electrodes prepared by the polymeric precursor method

Freitas,R. G; Marchesi,L. F. Q. P; Forim,M. R; Bulhões,L. O. S; Pereira,E. C; Santos,M. C; Oliveira,R. T. S
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2011 EN
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This work describes a detailed study of the ethanol electrooxidation on Ti/(RuO2)(x)Pt(1-x) electrodes using several compositions prepared by the polymeric precursor method. The results obtained using cyclic voltammetry and chronoamperometry showed that the best composition of Ti/(RuO2)(x)Pt(1-x) electrodes for CO and ethanol oxidation processes is Ti/(RuO2)0.50Pt0.50. On this electrode composition the onset of CO and the ethanol oxidation occurred at 380 mV and 220 mV more negative than on Ti/Pt, respectively. Besides, there was an increase of 2.5-fold in the current density for ethanol electrooxidation under constant potential polarization. The Ti/(RuO2)0.50Pt0.50 electrodes produced lower amount of acetic acid compared to Ti/Pt and polycrystalline Pt electrodes using in situ HPLC spectrometric analysis. Also, a non common product from ethanol oxidation could be observed on higher RuO2 loads: ethyl acetate. Finally, the impedance data showed that Ti/(RuO2)0.50Pt0.50 electrode composition had the smallest charge transfer resistance for ethanol oxidation among those compositions investigated

Influence of the pH on Al2O3:CuO pigments prepared by a polymeric precursor method

Marques,Carolina Hernandes; Mesquita,Alexandre; Araújo,Vinicius Dantas; Bernardi,Maria Inês Basso
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/02/2013 EN
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1017.6515%
Copper (II) aluminate, CuAl2O4, which is known to be an inverse spinel contains a d9 metal ion and possesses interesting electronic, magnetic and catalytic properties and is used in industry as ceramic pigments, coatings and catalysts. Al2O3 with 10 mol% Cu (AlCu10) was synthesized by the polymeric precursor method varying the pH of the precursor solution with addition of ammonium hydroxide and ethylenediamine. It was shown that the pyrolysis of the polymeric chain occurs in higher temperatures for samples prepared in higher values of pH. The colorimetric coordinates exhibit dependence with pH and with the increase of annealing temperature. AlCu10 samples prepared with higher values of pH present lower values of colorimetric coordinates, indicating alterations in its color. The luminosity parameters L* increase also as a function of pH.