In this investigation, the effect of the parameters during vacuum brazing of wide-gaps (0.6 to 1.8 mm) in a Nickel-based super alloy Inconel 738, were studied. The temperatures used were 1120 °C and 1150 °C with times of 120 and 240 min. The filler metal was a mix of Ni-11Cr-3.5Si-2.25B-3.5Fe paste with Inconel 738 powder with a particle size of 73µm. From observations with Scanning Electron Microscopy, three microstructural zones were identified: Athermally Solidified Zone (ASZ), Isothermally Solidified Zone (ISZ) and Diffusion-Affected Zone (DAZ). The eutectic compounds identified by X-Ray Energy Dispersive Spectroscopy in the ASZ were of the Fe-Cr-Si type. When the brazing time was increased to 240 min and the temperature to 1150 °C with a gap of 0.6 mm and the application of a mixture ratio of 80/20 (Ni paste and Inconel powder, respectively), the volumetric fraction of eutectics decreased in the ASZ favoring isothermal solidification, diffusion of B and Si in the Ni matrix; hardness reached 260 HV, while the width of the DAZ decreased by 39% on average. The latter indicates that an adequate selection of brazing parameters allows to obtain better joints, with a reduced process time and a decrease in intermetallics, which are the main reason of cracks and fractures.
The study of the interaction between vanadium oxide and the HY-zeolite using molecular dynamics interaction was carried out for two systems: i) when vanadium oxide penetrates a zeolite ring at its center, and ii) when vanadium oxide impacts the zeolite surface model. The dynamical effects are used to investigate the reduced activity and eventual degradation of the catalyst for the vanadium oxide presence. In the first case, we observe the breaking of an OH-bond that belongs to the acid site. This is related to an initial loss activity stage of the catalyst. In the second case, vanadium oxide is weakly adsorbed onto the zeolite surface velocity depending. Density functional theory, with nonlocal exchange and correlation functional and the basis set of double numerical accuracy, is used to analyze the electronic structure. It was used in combination with Born-Oppenheimer dynamics to perform calculations.
Se sintetizaron nanopartículas de TiO2 dopadas con iones de tierras raras (1%w Ce2O3-TiO2, 5%w Ce2O3-TiO2, 1%w Sm2O3- TiO2 y 5%w Sm2O3- TiO2) por el método sol-gel, bajo condiciones controladas utilizando tetraisopropóxido de titanio (C12H28O4Ti) corno precursor de TiO2, los materiales fueron caracterizados por difracción de rayos X, microscopia de fuerza atómica (AFM). Los patrones de difracción de rayos X mostraron que los nanornateriales preparados presentan la fase tetragonal anatasa del TiO2. La fotoactividad de los catalizadores sintetizados se probó en la degradación fotocatalítica de una solución de rodarnina B expuesta a las siguientes longitudes de onda de radiación (254 nrn y 405 nrn). De acuerdo a la evaluación catalítica de los materiales relacionada con el tamaño de partícula de cada uno, se llega a la conclusión que los materiales con tamaño de partícula fino (:S::39 nrn) y con distribución homogénea son los mejores para la fotodegradación de la rodarnina B por tanto, el material que presenta el mejor cornportarniento fotocatalítico en la región visible ( 405 nrn) es 1 %w Sm2O3/TiO2, lo cual fue demostrado por las diferentes técnicas usadas y en particular gracias a la técnica de espectroscopia de fluorescencia.
The fatigue strength evaluation and fracture behavior for a dual phase steel-AA6061-T6 bonded joints with three different adhesives (DC-80, Betamate 120 and MP55420) are presented in this paper. Single lap shear tests were used to determine maximum shear loads, for the single lap shear testing for 5.0 mm overlap length were 2 to 3.5 times higher in comparison to the 12.7 mm overlap length specimens. The results for the strain measurement revealed that higher strain-stress were developed in the 6061-T6 aluminum alloy adherend and in all cases they were lower than the adherends yield strength. Fatigue testing was carried out at 30, 50 and 70 % of the maximum shear load, 0.1 of reversibility load ratio (R) and 30 Hz of frequency. After
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