Nanosized lead lanthanum titanate (PLT) ceramic powders synthesized by the oxidant peroxo method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of thickness coating on the electrochemical behaviour of thermal spray Cr3C2-NiCr coatings

Thermally sprayed HVOF coatings are increasingly being used in industrial applications where high wear and corrosion resistance are needed [1,2]. In this paper, electrochemical ac and de experiments were used in order to obtain the corrosion resistance of coated steel with different numbers of Cr3C2-NiCr layers. This work has been performed in order to determine the role of coating thickness in the corrosion behaviour of a steel protected with cermet thermally sprayed coatings. It is known that a thicker layer protects better against corrosion when a metallic coating is evaluated. But cermet coatings, such as Cr3C2-NiCr, contain higher levels of porosity and residual stresses than metallic coatings, which really could influence the corrosion resistance of the deposited layer. Electrochemical measurements, such as Open-Circuit Potential (E-Osubset of), Polarisation Resistance (RP) and Cyclic Voltammetry (CV), were performed in an aerated 3.4 NaCI media (%wt.). Electrochemical Impedance Measurements (EIS) were also done in order to obtain a mechanism that explains the corrosion process. Structural Characterisation was carried out by means of Optical and Scanning Electron Microscopes (OM, SEM) with an Energy Dispersive Spectrometry analyser (EDS). Results show that the corrosion resistance of the complete system is mainly influenced by the substrate behaviour. The application of a higher number of deposited layers did not substantially increase their anticorrosive properties. Stress generation during the spraying deposition process plays an important role in the behaviour of the coated steel against corrosion phenomena. (C) 2002 Elsevier B.V. B.V All rights reserved.

Synthesis and characterization of antimony tartrate for ceramic precursors

Synthesis and characterization of antimony tartrate used as a precursor of ceramic powders obtained by Pechini's method were carried out. Antimony tartrate was chosen as a substitute for the antimony citrate commonly used in this chemical processing, because of difficulties in preparing the citrate. FTIR and TGA/DTA analysis showed that antimony tartrate, H-2[Sb-2(C4H2O6)(2)]. forms a polymeric structure. The procedure described indicates that the antimony chelate obtained is adequate for Pechini's method.

Nanopore size growth and ultrafiltration performance of SnO2 ceramic membranes prepared by sol-gel route

Supported ceramic membranes have been produced by the sol-casting procedure from aqueous colloidal suspensions prepared by the sol-gel route. Coatings on a tubular alumina support have been successfully performed leading to crack free layers. Samples have been sintered at 400, 500 and 600 degreesC, and the effect of heating treatment on the nanostructure and on the ultrafiltration properties are analyzed. The characterization has been done by high resolution scanning electron microscopy, nitrogen adsorption-desorption isotherms, water permeation and cut-off determination using polyethylene glycol standard solutions. The micrographs have revealed that grains and pore size increase with the temperature, whereas their shape remains invariant. This results is in agreements with N-2 adsorption-desorption analyses, which have revealed that the mean pore size diameter increases from 4 to 10 nm as the sintering temperature increases from 400 to 600 degreesC, while the total porosity remains constant. Furthermore, the tortuosity, calculated from water permeability, is essentially invariant with the sintering temperatures. The membranes cut-off, determined with a retention rate equal to 95%, are 3500, 6500 and 9000 g . mol(-1) for 400, 500 and 600 degreesC, respectively, showing that the permeation properties of SnO2 ultrafiltration membranes can easily be controlled by sintering condition.

Influence of oxygen atmosphere on crystallization and properties of LiNbO3 thin films

Thin films of lithium niobate were deposited on the Pt/Ti/SiO2 (111) substrates by spin coating from the polymeric precursor method (Pechini process). Annealing in static air and oxygen atmosphere was performed at 500 degreesC for 3 h. The films obtained were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The dielectric constant and dissipation factor were measured in frequency region from 10 Hz to 10 MHz. Electrical characterization of the films pointed to ferroelectricity via hysteresis loop. The influence of oxygen atmosphere on crystallization, morphology and properties of LiNbO3 thin films is discussed. (C) 2003 Elsevier Ltd. All rights reserved.

Formation of TiO2 ceramic foams from the integration of the sol-gel method with surfactants assembly and emulsion

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of cerium on structure modifications of a hybrid sol-gel coating, its mechanical properties and anti-corrosion behavior

An organic-inorganic hybrid coating was developed to improve the corrosion resistance of the aluminum alloy AA 2024-T3. Organic and inorganic coatings derived from glycidoxypropyltrimethoxysilane (GPTMS) and aluminum tri-sec-butoxide Al((OBu)-Bu-s)(3), with different cerium contents, were deposited onto aluminum by dip-coating process. Corrosion resistance and mechanical properties were investigated by electrochemical impedance measurements and nano-indentation respectively. An optimal cerium concentration of 0.01 M was evidenced. To correlate and explain the hybrid coating performances in relation to the cerium content, NMR experiments were performed. It has been shown that when the cerium concentration in the hybrid is higher than 0.01 M there are important modifications in the hybrid structure that account for the mechanical properties and anti-corrosion behavior of the sol-gel coating. (C) 2012 Elsevier Ltd. All rights reserved.

Sol-gel synthesis and characterization of Fe(2)O(3) center dot CeO(2) doped with Pr ceramic pigments

Undoped x center dot alpha-Fe(2)O(3) y center dot CeO(2) and doped with praseodymium ceramic pigments were obtained by the sol-gel method after heat treatment at 800 degrees C for 2 h. These pigments were characterized by XRD, nitrogen adsorption, scanning electron microscopy, ultraviolet-visible absorption spectroscopy and colorimetrical measurements. Red and brown colors with several tonalities were observed after changes with Ce and Pr concentration.

Evaluation and Application of TS-FF-AAS System Using Ceramic Tube as Atomization Cell for Tin Determination in Canned Foods

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Filmes de titânio-silício preparados por spin e dip-coating

The conditions for the preparation of luminescent materials, consisting of Eu3+ ions entrapped in a titanium matrix, in the forma of a thin film, using the sol-gel process, are described. The films were obtained from sols prepared with TEOS and TEOT, in the presence of acetylacetone as the hidrolysis-retarding agent, using the dip-coating and spin-coating techniques. The influence of these techniques on the films based on titanium and silicon are presented. The Eu3+ was used as a luminescent probe. The films have been characterized by luminescence, reflection and transmittance. The thickness of the films could be related to the preparation procedure. Transparent thin films have been prepared by dip-coating technique.

External polyacrylate-coating as alternative material for preparation of photopolymerized sol-gel monolithic column

Photopolymerized sol-gel monolithic columns for use in capillary electrochromatography were prepared in 125 mu m i.d. polyacrylate-coated fused-silica capillaries. The polyacrylate-coating, unlike the polyimide one, is transparent to the radiation used (approximate to 370 nm), and thus, no coating removal is necessary. This is a very important particularity since intrinsic capillary column characteristics, such as flexibility and mechanical resistance, are unchanged. A mixture containing metacryloxypropyltrimethoxysilane (MPTMS) as the polymeric precursor, hydrochloric acid as the catalyst, toluene as the porogen and bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide (Irgacure 819) as the photoinitiator was irradiated at 370 nm for 20 min inside the capillaries to prepare the columns through sol-gel approach. The versatility and viability of the use of polyacrilate as a new capillary external coating were shown through preparation of two columns under different conditions, which were tested in electrochromatography for separation of standard mixture containing thiourea (marker compound), propylbenzene, phenanthrene and pyrene. (C) 2008 Elsevier B.V. All rights reserved.

Optical Fiber Relative Humidity Sensor Based on a FBG with a Di-Ureasil Coating

In this work we proposed a relative humidity (RH) sensor based on a Bragg grating written in an optical fiber, associated with a coating of organo-silica hybrid material prepared by the sol-gel method. The organo-silica-based coating has a strong adhesion to the optical fiber and its expansion is reversibly affected by the change in the RH values (15.0-95.0%) of the surrounding environment, allowing an increased sensitivity (22.2 pm/%RH) and durability due to the presence of a siliceous-based inorganic component. The developed sensor was tested in a real structure health monitoring essay, in which the RH inside two concrete blocks with different porosity values was measured over 1 year. The results demonstrated the potential of the proposed optical sensor in the monitoring of civil engineering structures.

Influência de diferentes materiais de cobertura no conforto térmico de instalações para frangos de corte no oeste paulista

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Mineralogical characterization of clays used in the structural ceramic industry in west of S. Paulo State, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Aço inox bactericida

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)