Página 1 dos resultados de 74 itens digitais encontrados em 0.006 segundos

Effect of cerium (IV) ions on the anticorrosion properties of siloxane-poly(methyl methacrylate) based film applied on tin coated steel

SUEGAMA, P. H.; SARMENTO, V. H. V.; MONTEMOR, M. F.; BENEDETTI, A. V.; MELO, H. G. de; AOKI, I. V.; SANTILLI, C. V.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.59%
This work investigates the influence of the addition of cerium (IV) ions on the anticorrosion properties of organic-inorganic hybrid coatings applied to passivated tin coated steel. In order to evaluate the specific effect of cerium (IV) addition on nanostructural features of the organic and inorganic phases of the hybrid coating, the hydrolytic polycondensation of silicon alkoxide and the radical polymerization of the methyl methacrylate (MMA) function were induced separately. The corrosion resistance of the coatings was evaluated by means of linear polarization, Tafel type curves and electrochemical impedance measurements. The impedance results obtained for the hybrid coatings were discussed based on an electrical equivalent circuit used to fit the experimental data. The electrochemical results clearly showed the improvement of the protective properties of the organic-inorganic hybrid coating mainly when the cerium (IV) was added to the organic phase solution precursor, which seemed to be due to the formation of a more uniform and densely reticulated siloxane-PMMA film. (C) 2010 Elsevier Ltd. All rights reserved.; FAPESP[05/51851-4]; FAPESP[07/53073-4]; CNPq[310860/2005-9]; CNPq[300728/2007-7]; CNPq[305073/2008-7]; CAPES[BEX-3167-08-9]

Preparação e caracterização de filmes híbridos orgânico-inorgânicos para a proteção de aço inoxidável; Preparation and characterization of organic-inorganic hybrid films for stainless steel protection

Messaddeq, Sandra Helena
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 27/07/1998 PT
Relevância na Pesquisa
76.38%
Filmes inorgânicos de ZrO2 e filmes híbridos orgânico-inorgânicos de ZrO2-PMMA, preparados pelo método sol-gel, foram estudados como protetores contra a corrosão de aço inoxidável em meio ácido. Os sóis foram preparados a partir de uma solução submetida à irradiação de ultra-som e contendo o alcóxito metálico correspondente como precursor, álcool como solvente e ácido acético glacial como agente quelante para modificar a reatividade do alcóxito metálico. Várias concentrações de PMMA foram adicionadas aos sóis e estes foram caracterizados através de reometria, espectroscopia na região do infravermelho (FTIR), calorimetria explanatória diferencial (DSC) visando estudar a evolução de suas características morfológicas durante o envelhecimento. Os filmes de ZrO2 e ZrO2-PMMA foram depositados, utilizando-se a técnica de imersão, sobre lâminas de aço inoxidável 316L (AISI 316L), densificados a 200°C e o tempo de tratamento térmico foi variado de 5 a 180 minutos. Os filmes foram caracterizados por espectroscopia de reflexão especular na região do infravermelho; a morfologia, composição e textura superficiais foram determinadas por microscopia eletrônica de varredura (MEV), dispersão de energia de raios X (EDS) e perfilometria...

Effect of cerium (IV) ions on the anticorrosion properties of siloxane-poly(methyl methacrylate) based film applied on tin coated steel

Suegama, P. H.; Sarmento, V. H. V.; Montemor, M. F.; Benedetti, A. V.; de Melo, H. G.; Aoki, I. V.; Santilli, C. V.
Fonte: Pergamon-Elsevier B.V. Ltd Publicador: Pergamon-Elsevier B.V. Ltd
Tipo: Artigo de Revista Científica Formato: 5100-5109
ENG
Relevância na Pesquisa
56.57%
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); Processo FAPESP: 05/51851-4; Processo FAPESP: 07/53073-4; This work investigates the influence of the addition of cerium (IV) ions on the anticorrosion properties of organic-inorganic hybrid coatings applied to passivated tin coated steel. In order to evaluate the specific effect of cerium (IV) addition on nanostructural features of the organic and inorganic phases of the hybrid coating, the hydrolytic polycondensation of silicon alkoxide and the radical polymerization of the methyl methacrylate (MMA) function were induced separately. The corrosion resistance of the coatings was evaluated by means of linear polarization, Tafel type curves and electrochemical impedance measurements. The impedance results obtained for the hybrid coatings were discussed based on an electrical equivalent circuit used to fit the experimental data. The electrochemical results clearly showed the improvement of the protective properties of the organic-inorganic hybrid coating mainly when the cerium (IV) was added to the organic phase solution precursor...

Improvement of the corrosion resistance of polysiloxane hybrid coatings by cerium doping

Hammer, P.; Schiavetto, M. G.; dos Santos, F. C.; Benedetti, A. V.; Pulcinelli, S. H.; Santilli, C. V.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 2606-2612
ENG
Relevância na Pesquisa
46.04%
Polysiloxane hybrid films were deposited on stainless steel by dip-coating using a sol prepared by hydrolytic co-polycondensation of tetraethoxysilane (TEOS) and 3-methacryloxy propyltrimethoxysilane (MPTS), followed by radical polymerization of methacrylic moieties. The TEOS/MPTS ratio was chosen equal to 2 and the Ce/Si ratio varied between 0.01 and 0.1. The effects of cerium concentration and valence (Ce(III) and Ce (IV)) on the structural features of polysiloxane films were studied by X-ray photoelectron spectroscopy (XPS) and (29)Si nuclear magnetic resonance (NMR). The corrosion protection of stainless steel by the hybrid coatings was investigated by XPS, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves, after immersion in saline and acid solutions. The NMR results have shown for Ce(IV) doped films a high degree of polycondensation of up to 89%. Electrochemical analysis has evidenced that hybrid films with the lowest Ce concentration act as an efficient diffusion barrier by increasing the corrosion resistance and reducing the current densities up to 3 orders of magnitude compared to bare stainless steel. The analysis of structural effects induced by Ce(III) and Ce(IV) species, performed by XPS...

Lanthanide-Containing Light-Emitting Organic-Inorganic Hybrids: A Bet on the Future

Carlos, Luis D.; Ferreira, Rute A. S.; Bermudez, Veronica de Zea; Ribeiro, Sidney J. L.
Fonte: Wiley-v C H Verlag Gmbh Publicador: Wiley-v C H Verlag Gmbh
Tipo: Artigo de Revista Científica Formato: 509-534
ENG
Relevância na Pesquisa
46.1%
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); Interest in lanthanide-containing organic-inorganic hybrids has grown I considerably during the last decade, with the concomitant fabrication of materials with tunable attributes offering modulated properties. The potential of these materials relies on exploiting the synergy between the intrinsic characteristics of sol-gel derived hosts (highly controlled purity, versatile shaping and patterning, excellent optical quality, easy control of the refractive index, photosensitivity, encapsulation of large amounts of isolated emitting centers protected by the host) and the luminescence features of trivalent lanthanide ions (high luminescence quantum yield, narrow bandwidth, long-lived emission, large Stokes shifts, ligand-dependent luminescence sensitization). Promising applications may be envisaged, such as light-emitting devices, active waveguides in the visible and near-IR spectral regions, active coatings, and bio-medical actuators and sensors, opening up exciting directions in materials science and related technologies with significant implications in the integration...

Influence of cerium (IV) ions on the inorganic and organic phase for preparation of a siloxane-PMMA based film on tin plate substrate

Sarmento, V. H V; Diniz, R. N.; Benedetti, A. V.; Santilli, C. V.; Suegama, P. H.; Aoki, I. V.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 2138-2147
ENG
Relevância na Pesquisa
46.53%
Tinplate is one of the most widely used food canning materials, however, there are significant problems related to the use of tinplate cans, such as alterations in sensory features affecting food quality and corrosion phenomena of the canning material. To avoid corrosion problems different methods have been used for the passivation of tinplate such protective lacquers or different kinds of corrosion inhibitors (chromate and dichromate). However, chromates and dichromates are extremely harmful to the environment and can cause carcinogenic tumors to humans. An option, protective coatings obtained by the sol-gel process, act as a physical barrier, which isolates the surface of metal protecting from the corrosive agents. The aim of this work is to study the influence of addition of cerium (IV) ions in the inorganic and organic part of sol-gel processing in the formation of hybrid coatings based on siloxane-PMMA on tin plate. The coatings were obtained by dip-coating technique and evaluated by open circuit and impedance measurements, linear polarization and polarization curves obtained in 3.5% NaCl solution. The results have clearly shown the improvement on the protective properties of the Ce 4+ modified film when added into the organic phase...

Novel cellulose/NbOPO 4.nH 2O hybrid material from sugarcane bagasse

Pereira, Paulo Henrique Fernandes; Voorwald, Herman Jacobus Cornelis; Cioffi, Maria Odila Hilario; da Da Silva, Maria Lucia Caetano Pinto
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 867-878
ENG
Relevância na Pesquisa
36.3%
In recent years studies concerning the applications of lignocellulosic/ inorganic couples have resulted in the development of an interesting class of functional materials. In this work a cellulose/NbOPO 4.nH 2O hybrid using cellulose from surgacane bagasse was prepared and characterized in order to test for adsorption applications. The preparation process was conducted by carrying out metallic niobium dilution in hydrofluoric acid in the presence of nitric acid, then adding boric acid to form the complex and, finally, the cellulose sugar cane bagasse was added. Concentrated phosphoric acid was also inserted to precipitate hydrous niobium phosphate particles in the cellulose fiber. This material was characterized by X-ray diffractometry (XRD), thermogravimetry (TG/DTG), and scanning electronic microscopy (SEM) connected to an energy dispersive spectrophotometer (EDS). Results by SEM/EDS show that NbOPO 4.nH 2O was present in structure of the cellulose. During the preparation of the material, using boric acid it was observed that the formation of precipitate occurred in a shorter time than the material prepared without boric acid.

Avaliação de revestimentos hibridos organo-inorganicos e de resinas polissiloxanas aplicadas sobre aço galvanizado e sobre camadas de Zn-Fe; Organic-inorganic hybrid coatings and polysiloxanes resins for corrosion protection of galvanized steel and electroplated ZnFe steel

Maria Eliziane Pires de Souza
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 23/02/2006 PT
Relevância na Pesquisa
66.34%
As características protetoras das superfícies de aços galvanizados são geralmente intensificadas através da passivação por cromo hexavalente (Cr+6). Porém, por ser este um elemento tóxico, vários estudos visando a substituição do procedimento de cromatização vêm sendo realizados. As resinas de polissiloxanos e materiais híbridos organo-inorgânicos preparados pelo processo sol-gel, podem vir a ser um excelente substituinte ao processo de cromatização. Neste trabalho, filmes híbridos organo-inorgânico e filmes de silicone foram aplicados em aço galvanizado e em camadas de Zn-Fe. Os revestimentos foram então avaliados através de Espectroscopia de Impedância Eletroquímica. Os dados obtidos pela Espectroscopia foram modelados através de um circuito equivalente, permitindo a obtenção dos parâmetros eletroquímicos para os sistemas avaliados. Além disso, o potencial em circuito aberto, para os diferentes sistemas, foi monitorado durante processo de desgaste em sistema pino-disco em solução de NaCI 3%. Os revestimentos foram comparados em termos de resistência à corrosão e coeficiente de fricção. Os resultados mostram um bom desempenho para os revestimentos como protetores de corrosão e o comportamento destes mostraram-se dependente do tipo de revestimento metálico que foi aplicado no aço.; Chromating pre-treatments have been widely used to improve galvanized steel corrosion resistance. However...

Organic-inorganic hybrid coatings for corrosion protection of galvanized steel and electroplated ZnFe steel

Souza, M. E. P.; Ariza, E.; Ballester, M.; Yoshida, I. V. P.; Rocha, L. A.; Freire, C. M. A.
Fonte: Associação Brasileira de Metalurgia e Materiais [etc.] Publicador: Associação Brasileira de Metalurgia e Materiais [etc.]
Tipo: Artigo de Revista Científica
Publicado em /05/2005 ENG
Relevância na Pesquisa
66.54%
The development of hybrids materials by the sol-gel process has been extensively investigated in recent years. The combination a wide variety of compositions and production processes had permit the use of these materials in different applications like coatings for corrosion protection of metals and abrasion resistant coatings. In this work organic-inorganic hybrid materials have been prepared from the hydrolysis of tetraethylorthosilicate (TEOS) and silanol-terminated polidymetilmetoxysilane (PDMS) using a sol-gel process. The composition evaluated was 50% TEOS- 50% PDMS. These materials have been applied on galvanized steel and on steel electroplated with a ZnFe alloy. In order to evaluate the degradation behaviour of these coatings, electrochemical techniques were used. They consisting in the monitoring of the open-circuit potential (Ecorr), and in the realization of potentiodynamic polarization measurements of the samples, which was performed in a 3% NaCl aqueous solution. Additionally, electrochemical impedance spectroscopy (EIS) was used as a complementary technique for the evaluation of the corrosion mechanisms of the coating system. The surface of the samples, before and after the electrochemical tests, have been inspected by SEM and EDS. EIS data was fitted to an equivalent circuit from which the electrochemical parameters were obtained. Results show a good protective character of the hybrid films...

Organic-inorganic hybrid coatings for corrosion protection of galvanized steel and electroplated znfe steel

Souza, M. E. P.; Ariza, E.; Ballester, M.; Yoshida, I. V. P.; Rocha, L. A.; Freire, C. M. A.
Fonte: Universidade do Minho Publicador: Universidade do Minho
Tipo: Conferência ou Objeto de Conferência
Publicado em //2004 ENG
Relevância na Pesquisa
66.54%
The development of hybrids materials by the sol-gel process has been extensively investigated in recent years. The combination a wide variety of compositions and production processes had permit the use of these aterials in different applications like coatings for corrosion protection of metals and abrasion resistant coatings. In this work organic-inorganic hybrid materials have been prepared from the hydrolysis of tetraethylorthosilicate (TEOS) and silanol-terminated polidymetilmetoxysilane (PDMS) using a sol-gel process. The composition evaluated was 50% TEOS- 50% PDMS. These materials have been applied on galvanized steel and on steel electroplated with a ZnFe alloy. In order to evaluate the degradation behaviour of these coatings, electrochemical techniques were used. They consisting in the monitoring of the open-circuit potential (Ecorr), and in the realization of potentiodynamic polarization measurements of the samples, which was performed in a 3% NaCl aqueous solution. Additionally, electrochemical impedance spectroscopy (EIS) was used as a complementary technique for the evaluation of the corrosion mechanisms of the coating system. The surface of the samples, before and after the electrochemical tests, have been inspected by SEM and EDS. EIS data was fitted to an equivalent circuit from which the lectrochemical parameters were obtained. Results show a good protective character of the hybrid films...

Influence of experimental parameters using the dip-coating method on the barrier performance of hybrid sol-gel coatings in strong alkaline environments

Figueira, R. B.; Silva, Carlos J. R.; Pereira, Elsa V.
Fonte: MDPI Publicador: MDPI
Tipo: Artigo de Revista Científica
Publicado em //2015 ENG
Relevância na Pesquisa
56.42%
Previous studies have shown that the barrier effect and the performance of organic-inorganic hybrid (OIH) sol-gel coatings are highly dependent on the coating deposition method as well as on the processing conditions. However, studies on how the coating deposition method influences the barrier properties in alkaline environments are scarce. The aim of this experimental research was to study the influence of experimental parameters using the dip-coating method on the barrier performance of an OIH sol-gel coating in contact with simulated concrete pore solutions (SCPS). The influence of residence time (Rt), a curing step between each dip step and the number of layers of sol-gel OIH films deposited on hot-dip galvanized steel to prevent corrosion in highly alkaline environments was studied. The barrier performance of these OIH sol-gel coatings, named U(400), was assessed in the first instants of contact with SCPS, using electrochemical impedance spectroscopy and potentiodynamic methods. The durability and stability of the OIH coatings in SCPS was monitored during eight days by macrocell current density. The morphological characterization of the surface was performed by Scanning Electronic Microscopy before and after exposure to SCPS. Glow Discharge Optical Emission Spectroscopy was used to investigate the thickness of the U(400) sol-gel coatings as a function of the number of layers deposited with and without Rt in the coatings thickness.

Characterization of organic-inorganic hybrid coatings for corrosion protection of galvanized steel and electroplated ZnFe steel

Souza,Maria Eliziane Pires de; Ariza,Edith; Ballester,Margarita; Yoshida,Inez Valéria Pagotto; Rocha,Luis Augusto; Freire,Célia Marina de Alvarenga
Fonte: ABM, ABC, ABPol Publicador: ABM, ABC, ABPol
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/03/2006 EN
Relevância na Pesquisa
66.46%
The development of hybrids materials has been extensively investigated in recent years. The combination of a wide variety of compositions and production processes had permitted the use of these materials in different applications like coatings for corrosion protection of metals. In this work organic-inorganic hybrid materials have been prepared from the hydrolysis of tetraethylorthosilicate and silanol-terminated polidymetilmetoxysilane using a sol-gel process. These materials have been applied on galvanized steel and on steel electroplated with a ZnFe. In order to evaluate the degradation behavior of these coatings, electrochemical techniques (Electrochemical Impedance Spectroscopy and Potentiodynamic Polarization) were used. EIS data was fitted to an equivalent circuit from which the electrochemical parameters were obtained. Results show a good protective character of the hybrid films, when compared with uncovered specimens. The overall performance of the coating systems appears to be highly dependent on the kind of metallic coating applied to the steel.

Biomimetic mineralization of metal-organic frameworks as protective coatings for biomacromolecules

Liang, K.; Ricco, R.; Doherty, C.M.; Styles, M.J.; Bell, S.; Kirby, N.; Mudie, S.; Haylock, D.; Hill, A.J.; Doonan, C.J.; Falcaro, P.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em //2015 EN
Relevância na Pesquisa
46.19%
Enhancing the robustness of functional biomacromolecules is a critical challenge in biotechnology, which if addressed would enhance their use in pharmaceuticals, chemical processing and biostorage. Here we report a novel method, inspired by natural biomineralization processes, which provides unprecedented protection of biomacromolecules by encapsulating them within a class of porous materials termed metal-organic frameworks. We show that proteins, enzymes and DNA rapidly induce the formation of protective metal-organic framework coatings under physiological conditions by concentrating the framework building blocks and facilitating crystallization around the biomacromolecules. The resulting biocomposite is stable under conditions that would normally decompose many biological macromolecules. For example, urease and horseradish peroxidase protected within a metal-organic framework shell are found to retain bioactivity after being treated at 80 °C and boiled in dimethylformamide (153 °C), respectively. This rapid, low-cost biomimetic mineralization process gives rise to new possibilities for the exploitation of biomacromolecules.; Kang Liang, Raffaele Ricco, Cara M. Doherty, Mark J. Styles, Stephen Bell, Nigel Kirby, Stephen Mudie, David Haylock...

Advanced ceramic composites and coatings via alumoxane nanoparticles

Callender, Rhonda Lynn
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
36.32%
The objective of this research is the development of an environmentally-benign process for the synthesis and fabrication of alumina-based ceramic precursors and advanced ceramic materials. Carboxylate-alumoxanes, [Al(O)x(OH) y(O2CR)z]n, were synthesized by the reaction of boehmite, [Al(O)(OH)]n, with acetic acid (HO2 CCH3), methoxyacetic acid (HO2CCH2OCH 3), methoxyethoxyacetic acid (HO2CCH2OCH 2CH2OCH3) and methoxyethoxyethoxyacetic acid [HO 2CCH2(OCH2CH2)2OCH 3]. Carboxylate-alumoxanes can be considered inorganic-organic hybrid materials consisting of an aluminum-oxygen backbone with carboxylate substituents. These are infinitely stable at ambient conditions in solid and solution. In addition, they show no propensity to segregation or polymerization and are readily processed in aqueous or hydrocarbon medium. Upon thermolysis the carboxylate-alumoxanes are converted to alumina. The physical and spectroscopic properties of the carboxylate-alumoxanes have been determined. The potential environmental impact of the new alumoxane methodology will be discussed. Carboxylate-alumoxanes are reacted with metal acetylacetonate complexes, M(acac)n, to form metal-doped nanoparticles and aluminum acetylacetonate via a transmetalation reaction. This allows the facile formation of highly crystalline materials such as calcium hexaluminate (CaAl12O 19...

An approach to design new coatings for biomedical applications

El-Hadad, Amir Abdel-Samie
Fonte: Universidade Carlos III de Madrid Publicador: Universidade Carlos III de Madrid
Tipo: Tese de Doutorado Formato: application/pdf
ENG
Relevância na Pesquisa
56.72%
Ti6Al4V alloy is widely used as implants for orthopedic and dental applications because of its superior mechanical properties, excellent corrosion resistance and good biocompatibility. However, it takes long period of several months for Ti6Al4V implants to integrate with the bone tissue due to their bio-inert feature in nature. An innovating and incipient method to solve the above mentioned drawbacks consist of the development of new coatings which could improve both the biological and corrosion protection performance of the Ti6Al4V alloy. Thus, a variety of strategies have been implemented to modify the surface of Ti6Al4V-based implants and enhance bone growth and their initial stability. A common approach is the deposition of bioactive hybrid coatings including inorganic and organic units on the surface of the Ti6Al4V alloy via sol-gel method. The sol–gel route is of great interest as it offers the possibility of tailoring the material properties by variation of the relative composition of the precursors used. The aim of this thesis is focused on the development of new coatings, starting with inorganic hydroxyapatite (HAp) deposited onto Ti6Al4V substrate prepared through solgel route. The effect of thermal treatment temperature on both in-vitro bioactivity and corrosion performance has been studied in simulated body fluid solution (SBF). A complete physical-chemical characterization was done in all the thermally treated coatings obtained. In-vitro tests in SBF were carried out in order to investigate the biological performance of the films. Due to the high temperature required for synthesizing HAp in crystalline form...

Preparation of sol-gel hybrid materials from gamma-methacryloxypropyltrimethoxysilane and tetramethyl orthosilicate: study of the hydrolysis and condensation reactions

El Hadad, Amir; Carbonell, Diógenes; Barranco, V.; Jiménez Morales, Antonia; Casal, Blanca; Galván Sierra, Juan Carlos
Fonte: Springer Publicador: Springer
Tipo: info:eu-repo/semantics/submittedVersion; info:eu-repo/semantics/article Formato: application/pdf
Publicado em 01/12/2011 ENG
Relevância na Pesquisa
46.1%
Organic-inorganic hybrid materials suitable for the development of sol&-gel coatings for metallic surfaces were prepared by hydrolysis and condensation of gamma-methacryloxypropyltrimethoxysilane (MAPTMS) and tetramethyl orthosilicate (TMOS). The hydrolysis of MAPTMS/TMOS was carried out in an ethanol/water solution. The prehydrolysis stage of MAPTMS/TMOS system was monitored by Fourier transform infrared spectroscopy (FTIR) and liquid-state 29Si and 13C nuclear magnetic resonance (29Si and 13C NMR). FTIR analysis indicated that the hydrolysis of MAPTMS/TMOS was accomplished as far as the (SiOMe) band corresponding to unhydrolyzed silane disappeared. The concentration of the alkoxy groups and the extent of self-condensation of mono-, di-, and trisubstituted siloxanes (T species) in the sol were estimated by using liquid-state 29Si NMR spectroscopy. The hydrolysis of the prepared sol was also evaluated by liquid-state 13C NMR spectroscopy. The results indicated that under the adopted synthesis strategy conditions, the hydrolysis process requires 4 h to be completed.; This work has been supported by the Ministry of Science and Innovation of Spain (Projects MAT2006-04486 and MAT2009-13530) and the Regional Community of Madrid (Project 2009/MAT-1585). AA El hadad acknowledges a predoctoral contract JAE financed by CSIC...

Triethylphosphite as a network forming agent enhances in-vitro biocompatibility and corrosion protection of hybrid organic-inorganic sol-gel coatings for Ti6Al4V alloys

El Hadad, Amir; Barranco, V.; Jiménez Morales, Antonia; Hickman, G. J.; Galván, J. C.; Perry, C. C.
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article
Publicado em /10/2014 ENG
Relevância na Pesquisa
76.51%
The biocompatibility and life of metallic implants can be enhanced through improving the biocompatibility and corrosion protection characteristics of the coatings used with these materials. In this study, triethylphosphite (TEP) was used to introduce phosphorus into organic-inorganic hybrid silica based sol-gel coatings prepared using gamma-methacryloxypropyltrimethoxysilane and tetramethylorthosilicate. Addition of TEP dramatically increased the rate of intermolecular condensation and resulted in materials showing greater cross-linking. Protein (fibrinogen) uptake, osteoblast in vitro biocompatibility and corrosion resistance was enhanced in coatings containing TEP. Although higher concentrations of phosphorus supported the greatest improvement in biocompatibility, a compromise in the phosphorus concentration used would be required if corrosion resistance was most desirable parameter for optimisation. Films prepared by dip coating on Ti6Al4V alloys from these sols offer a promising alternative to wholly metallic prostheses.; This work was supported by the Ministerio de Economía y Competitividad (Project MAT2012-30854).; In Press, Accepted Manuscript

The design and characterisation of sol–gel coatings for the controlled-release of active molecules

Hernández Escolano, M.; Juan-Díaz, M.; Martínez Ibáñez, M.; Jiménez Morales, Antonia; Goñi, I.; Gurruchaga, M.; Suay, J.
Fonte: Springer Publicador: Springer
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article
Publicado em /11/2012 ENG
Relevância na Pesquisa
46.04%
The controlled release of active agents from a matrix has become increasingly important for oral, transdermal or implantable therapeutic systems, due to the advantages of safety, efficacy and patient convenience. Controlled-release hybrid (organic-inorganic) sol-gel coating synthesis has been performed to create a sol with an active molecule included (procaine). Synthesis procedures included acid-catalysed hydrolysis, sol preparation, the addition of a procaine solution to the sol, and the subsequent gelation and drying. The alkoxide precursors used were triethoxyvinylsilane and tetraethyl-orthosilicate (TEOS) in molar ratios of 1:0, 9:1, 8:2 and 7:3. After the determination of the optimal synthesis parameters, the material was physicochemically characterised by silicon-29 nuclear magnetic resonance (²⁹Si-NMR) and Fourier transform infrared spectroscopy, contact angle analysis and electrochemical impedance spectroscopy tests. Finally, the materials were assayed in vitro for their ability to degrade by hydrolysis and to release procaine in a controlled manner. The sustained release of procaine over a 3-day period was demonstrated. A close correlation between release and degradation rates suggests that film degradation is the main mechanism underlying the control of release. Electrochemical analysis reveals the formation of pores and water uptake during the degradation. The quantity of TEOS is one of the principal parameters used to determine the kinetics of degradation and procaine release.; The supports of the Spanish Ministry of Economy and Competitiveness through project IPT-010000-2010-004 and of the University of the Basque Country (UPV/EHU) through ‘‘UFI11/56’’ are kindly acknowledged

Structural properties of cerium doped siloxane-PMMA hybrid coatings with high anticorrosive performance

Harb, S. V.; Santos, F. C. dos; Caetano, B. L.; Pulcinelli, S. H.; Santilli, C. V.; Hammer, P.
Fonte: Royal Soc Chemistry Publicador: Royal Soc Chemistry
Tipo: Artigo de Revista Científica Formato: 15414-15424
ENG
Relevância na Pesquisa
36.31%
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); This study reports on the characterization of cerium doped organic-inorganic hybrid coatings by correlating their structural properties with the corrosion protection efficiency of coated carbon steel. The films were prepared via the sol-gel route from radical polymerization of methyl methacrylate (MMA) with 3-methacryloxy propyltrimethoxysilane (MPTS) followed by acidic hydrolysis and condensation of tetraethoxysilane (TEOS). After identifying the optimum proportion of polymeric and silica phase for the formation of a highly ramified structure (MMA/TEOS = 4), increasing concentration of Ce(IV) ions (0.1% < Ce/Si < 5%) was added to the inorganic precursor to enhance the passivating character of the films. Nuclear magnetic resonance, X-ray photoelectron spectroscopy, small angle X-ray scattering, atomic force microcopy and thermogravimetry were used to characterize the structural properties and electrochemical impedance spectroscopy, potentiodynamic polarization curves and field emission scanning electron microscopy were employed to evaluate the corrosion resistance of the coated samples in a standard saline environment. Structural analysis revealed a high degree of connectivity of the hybrid network...

EIS Study of Amine Cured Epoxy-silica-zirconia Sol-gel Coatings for Corrosion Protection of the Aluminium Alloy EN AW 6063

Fontinha,I. Rute; Salta,M. Manuela; Zheludkevich,Mikhail L; Ferreira,Mário G.S.
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/11/2013 EN
Relevância na Pesquisa
36.46%
The organic-inorganic hybrid sol-gel films, the structure of which comprises interconnected inorganic and organic networks have been reported as an environmentally friendly anti-corrosion pre-treatment for several metals, including aluminium alloys. In this paper, an epoxy-silica-zirconia hybrid sol-gel coating was synthesized from glycidoxypropyltrimethoxysilane (GPTMS) and zirconium npropoxide (TPOZ) precursors and applied to EN AW-6063 alloy by dip-coating. To promote the organic network formation through the epoxy group polymerization at room temperature, two types of amine crosslinkers were added during synthesis: diethylenetriamine (DETA), in different concentrations, and a tri-functional aminosilane. The evolution of the curing process and the corrosion behaviour of the coated aluminium alloy specimens were evaluated by Electrochemical Impedance Spectroscopy (EIS) in 0.5 M NaCl. The morphology and surface chemistry of the hybrid coatings were characterized by Energy Dispersive Spectroscopy (EDS) coupled with Scanning Electron Microscopy (SEM) and by Fourier Transform Infrared Spectroscopy (FTIR). The results obtained revealed that the sol-gel coatings with lower amine ratios required longer curing times, but showed the best anticorrosive performance with time. The increase in amine concentration has led to a more cross linked organic network...