Papers by Keyword: Pechini Method

Abstract: Carbon steel is widely used in the industry due to its mechanical properties and low cost, but in contrast it resists poorly to corrosion, leading to economic losses and mechanical issues. The use of surface treatment is essential to extend the life of the metallic material. In this context, niobium is being studied for its great corrosion resistance properties. The aim of this paper was to produce and evaluate the corrosion protection of a niobium-based coating produced by the Pechini Method. The resin was applied in the metallic surface by dip-coating and then calcinated at 450 oC for 1 hour. The coated material was analyzed electrochemically by open circuit potential and potentiodynamic polarization, and morphologically by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The electrochemical analyses showed that the deposition of the coating increased the corrosion resistance and the morphological analyses indicated a homogenous coating with the presence of phases of NbO and NbO₂.

Abstract: Solid electrolytes such as lithium lanthanum zirconate have shown a lot of promise in an all-solid-state Lithium-based battery since the discovery of its highly conductive cubic garnet structure. In this study, different concentrations of Al-doped Lithium Lanthanum Zirconate (Al-doped LLZ) having the formula of Li_7-.3xAl_xLa₃Zr₂O₁₂ with x = 0.1,0 .2, 0.3, were synthesized via modified Pechini method and the effect of sintering temperatures, 1150 and 1200 °C, on the resulting properties were investigated. X-ray diffraction results have shown that cubic Al-doped LLZ can be obtained at a lower temperature using Pechini method. Significant effect to the conductivity on the different sintering temperatures was observed for the 0.1 Al-doped LLZ. With the different studied compositions synthesized via modified Pechini method, it was revealed that the 0.2 Al doped LLZ sintered either at 1150 or 1200 °C showed the highest conductivity of about 1.4x10^-4 S/cm.

Abstract: The aim of this work was to synthesize lead zirconate titanate, Pb(Zr_0.52Ti_0.48)O₃ (PZT) via Pechini method, to characterize the polymeric precursor through differential thermal analysis and thermogravimetric analysis, as well as to characterize the PZT powder through x-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy. In this work, the metallic precursors used during the PZT synthesis were titanium IV isopropoxide, zirconyl nitrate and lead nitrate; citric acid and ethylene glycol were used as chelating and polymerizing agents, respectively. The polymeric precursor was calcined at 800°C for two hours in a muffle oven. The main results showed that the polymeric precursor undergoes decomposition at approximately 316°C and PZT is crystallized around 722°C. It was confirmed that the PZT powder has chemical composition in the morphotropic phase boundary and its morphology consists of agglomerates of particles. Finally, it was proved that the PZT powder is crystalline, with the predominance of the tetragonal phase.

Abstract: Lithium niobate nanostructured thin films were deposited on (100) N-type Si substrates. Spin coating technique was used employed the polymeric precursor method (Pechini process) . The prepared films were Annealing in static air and oxygen atmosphere was performed at 500 _C for 2 h. X-ray diffraction analysis and SEM properties was carried out for films prepared at different mol concentration (0.25,0.50,0.75,1.00) Mol%. The results show a good enhancement in both structural and surface morphology of the films with increasing the concentration

Abstract: In the past few years there is a considerable interest in the study and application of the mullite, due to its chemical, physical and mechanical properties, in which are correlated with the synthesis method used. Aiming to achieve better structural and morphological properties, many synthesis methods are being studied, in which the Pechini method is highlighted, which is today one of the most viable methods and successful technique used in the preparation of nanosized materials. Thus, this study proposes the production of mullite powders by the Pechini method. The influence of different routes of synthesis was investigated. The material was sintered at 1100oC/2h, 1200oC/2h and 1400/2h, and characterized by X ray diffraction (XRD) and thermal analysis (TG/DTG and DTA). The results showed that the synthesis route did not interfere in the formation of the formed phases, and the mullite for both routes, was formed from 1200oC.

Abstract: Yttrium doped barium cerate is considered a promising electrolyte material for solid oxide fuel cell applications due to its excellent proton conductivity. The proton conductivity characteristics of the ceramic material can be influenced by the different synthesis processing parameters. This study aimed to obtain yttrium doped barium cerate BaCe_1-xY_xO_3-δ (x = 0.15, 0.20) using a sol-gel modified Pechini method. The phase formation and surface morphology of the yttrium doped barium cerate were investigated using x-ray diffraction and scanning electron microscopy. The thermal decomposition of the calcined ceramic material was examined using thermogravimetric analysis. Diffraction analysis confirmed the formation of perovskite crystalline structure with the presence of secondary phase yttrium doped ceria. Larger grain size with homogeneous distribution and coalescence was observed in the sintered BaCe_0.80Y_0.20O_3-δ.

Abstract: The solid oxide fuel cell are an alternative of production clean and efficient energy, because converts chemical energy in electrical energy. A fuel cell is formed basically by an electrolyte, a cathode and an anode. The main electrolyte used for SOFC manufacturing is the ZrO₂-Y₂O₃. The materials for electrode manufacturing must possess thermal expansion characteristics close to electrolyte and have high electrical conductivity in operating temperature. Recently, the perovskite LaNi_0,6Fe_0,4O_3-δ, has attracted interest for application as cathode in SOFC ́s for has a high electronic conductivity and a thermal expansion coefficient whish for the zirconia electrolyte. This work aimed to LaNi_0,6Fe_0,4O_3-δ obtained by Pechini method. The powders were characterized by differential thermal analysis, thermogravimetric analysis, x-ray diffraction, energy dispersion X-ray fluorescence spectroscopy, helium pycnometry and scanning electron microscopy. The results showed powders obtained with perovskite formation when calcined 600°C during 2 hours.

Abstract: The traditional Ni-based anodes are capable of providing a good power output using H₂ and CO fuels, but sulfur contamination in any hydrocarbon fuel is a problem. Thus, perovskite structure materials containing lanthanum have been widely studied as electrodes for solid oxide fuel cells (SOFCs), due to its electrical properties. In this work was investigated the obtain of the perovskite structure LaCr_0.5Ni_0.5O₃, by Pechini method, and its suitability as SOFC anode. The choice of this composition was based on the stability provided by chromium and the catalytic properties of nickel. After preparing the resins, the samples were calcined at 300oC, 600oC, 700oC and 850oC. The resulting powders were characterized by X-ray, X-ray fluorescence spectroscopy, He pycnometry, specific surface area by BET isotherm and scanning electronic microscopy. The obtaining of the powders of LaCr_0.5Ni_0.5O₃ through the Pechini method proved to be effective for temperatures above 850oC.

Abstract: Through the constant search by researchers to obtain materials with improved properties, literature has presented an annual increase in the number of articles that seek to optimize in the methodology used to prepare nanopowders. In this way, the aim of this work is to study how the calcined temperature (500, 600, 700, 800, 900, 1000, 1100 and 1200oC) changes the final properties of the alumina synthesized by Pechini method with citric acid: metallic cation ratio of 2:1. The alumina was characterized by thermal analysis, X-ray diffraction, particle size analysis and scanning electron microscopy. The results showed a total of mass loss of 61.6%. The alumina phase appear at 800°C of temperature, however the α-alumina only appear at 1100oC. The increase in the calcined temperature increases the crystallite size and the crystallinity of the alumina and the great value reached for the agglomerates diameter was 13μm for the alumina calcined at 1200oC. In relation to the morphology of the alumina, it was observed heterogeneous particles with different size and irregular geometry, with aspect of high density.

Abstract: Given the opportunities that aluminas present in relation to the broad field of applications to which they refer, the literature has reported great diversity in methodology to obtain these materials in the search of generating the best properties. In this way, the aim of this work is to evaluate the use of different citric acid and metallic cation ratio on the structural and morphological characteristics of the alumina synthesized by Pechini method and calcined at 1100°C. The samples were characterized by X-ray diffraction, thermal analysis, particle size and scanning electron microscopy. The results showed a large amount of loss of mass after pyrolysis. The α-alumina phase was achieved for the two studied ratio reaching values for crystallite size of 41.4 and 52.5 nm, crystallinity of 88 and 91.2%, agglomerates size of 12.3 and 14μm, for the synthesized samples 2:1 and 3:1, respectively. According to the SEM images, the changes in the citric acid: metallic cation ratio did not significantly modify the morphology of the alumina.