The present study was carried out to evaluate the microstructures and mechanical properties of severely deformed Ni-30Cr alloy. Cross-roll rolling (CRR) as severe plastic deformation (SPD) process was introduced and Ni-30Cr alloy sheets were cold rolled to a 90% thickness reduction and subsequently annealed at 700 °C for 30 min so as to obtain the recrystallized microstructure. For the analysis of grain boundary character distributions (GBCDs), electron back-scattered diffraction (EBSD) technique was introduced. CRR on Ni-30Cr alloy was effective to enhance the grain refinement through heat treatment; consequently, average grain size was significantly reduced from 33 μm in initial material to 0.6 μm in CRR processed material. This grain refinement directly affected the mechanical properties improvement, in which yield and tensile strengths were significantly increased than those of initial material. In this study, we systematically discussed the grain refinement, accompanying with increase in mechanical properties, in terms of the effective strain imposed by CRR, comparing with conventional rolling (CR).

The isothermal oxidation-sulfidation of Fe-40Al based intermetallics alloys in N2/SO2 gas mixture at 625, 700 and 775°C were evaluated. Fe40Al, Fe40Al+0.1B, Fe40Al+0.1B+10Al2O3 alloys were produced by atomization and deposition. Isothermal gas exposition was reached during 48 hours. FeAl based alloys showed good sulfidation resistance, presenting both small weight gain and weight change fluctuations. At 625°C, the Fe40Al+0.1B alloy had the biggest weight gain; on the other hand the Fe40Al alloy exhibited the biggest sulfidation resistance. At 700 and 775°C, the Fe40Al+0.1B alloy presented the smallest weight gain, however Fe40Al alloy presented higher weight gain, that is to say, the smallest sulfidation resistance at those temperatures. The variation in the weight gain curves were discussed in terms of formation and detachment of sulfides, and by local attack on the alloy surface as the temperature increasing. The results are supplemented with characterization by SEM and analysis of X-rays dispersion.

To establish a promising method for the purification of air containing volatile organic compounds, TiO2 nanoparticles with interesting physicochemical properties were prepared by the sol-gel method to perform the photocatalytic decomposition of acetaldehyde. The obtained samples were characterized by the x-ray diffraction -Rietveld refinement, transmission electron microscopy (TEM) and the Brunauer, Emmet and Teller (BET) model. According to the results, the sample that presented the highest activity (96.4%) in the photocatalytic oxidation of acetaldehyde was the one annealed at 200 °C. This material showed the presence of a mixture of the anatase (higher proportion) and brookite phases, nanometric crystal size (7.03 nm) and high surface area (189 m2g-1). The physicochemical properties present in the TiO2-P-200°C nanoparticles suggest that they may establish a photoassisted reaction process for air purification, in which volatile organic compounds are photocatalitically decomposed.

In this research we studied the fracture of a cast iron drum for 3.5 ton trucks, and it seeks to determine the causes that led to a series of cracks in different areas of the part of drum brake during the manufacturing process, casting or machining. The work followed the methodology usually used in failure analysis; we used the following analytical techniques: visual inspection, penetrating liquids, fractography, metallography, chemical analysis and mechanical testing of hardness. The analysis of the automotive part surface is divided into four sections which are the flange, track, belt and covers powders which were evaluated by the above techniques to determine the failure of the piece. Metallography analysis in each section of the piece showed different microstructure on gray cast iron; showing that pieces works with different cooling conditions during manufacture, giving a mechanism of failure-prone fragile.

Ni/Mg/Al mixed oxides were obtained from hydrotalcite-like precursors by thermal decomposition at 400º, 600º and 800ºC using co-precipitation method at pH 7. The mixed oxides were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Energy-dispersive X-ray spectroscopy (EDS) techniques. XRD analysis revealed the formation of NixMg1-xO (x = 0 - 1), α-Al2O3 and traces of MgAl2O4 (NiAl2O4) phases. The diffraction peak positions for MgO or NiO oxides were shifted towards 2θ values higher than simulated for pure bulk oxides that can be attributed to the possible presence of lattice vacancies or surface compressive stress. The evaluated grain size by XRD technique was about 8 -10 nm. It was also detected the presence of microstrains that can be associated with the presence of extended defects in the grains. SEM observations showed that the particles of oxides are formed as agglomerates with the particle sizes of 50 nm up to 200 nm. EDS detected the presence of Mg2+, Ni2+, and Al3+ cations and oxygen in all particles independently on their size. The obtained results revealed the presence of mixture of Ni/Mg/Al oxides in each particle obtained. The oxides calcined at temperatures of 400º and 600ºC were unstable and under air storage they revert to the precursor. The incorporation of Ni2+ in Mg-Al mixed oxides leads to stability of the compounds calcined at 800ºC.

Deposition conditions that provided low absorption related to both band tail and deep localized states have been found for both materials Ge:H and Si1YGeY:H. Phosphorous incorporation on Si0.01Ge0.99:H films and boron incorporation on Ge:H films were deposited by low frequency plasma-enhanced chemical vapour deposition (LF PECVD). The phosphorous incorporation in solidphase was observed to preferential with the increase of the doping in the gas phase to 2.5 %, and 2.5% to 4% was observed preferential Si0.01Ge0.99 film, boron incorporation in solid phase increase linearly with the increase of the doping gas phase. The content of solid phase was characterized by Secondary ion mass spectrometry (SIMS) profiling. Hydrogen concentration in the films was determined from Fourier transform infrared spectroscopy (FTIR) and SIMS measurements. Optical measurements provided optical gap, localized states, and band tail. A significant reduction of both band tail and deep localized states were observed at boron incorporation in solid phase = 0.004% on Ge:H films and the same were observed at phosphorous incorporation in solid phase = 0.29% on Si0.01Ge0.99:H films.

An electrochemical study was carried out in order to obtain the effects of the turbulent flow condition on the stainless steel corrosion immersed in natural seawater using an electrochemical corrosion technique like electrochemical impedance spectroscopy (EIS). A three-electrode electrochemical glass cell was used to obtain the electrochemical measures, where a cylinder of the AISI 410 stainless steel was used as working electrode, a saturated calomel electrode as reference electrode and a synthesised graphite rod as auxiliary electrode. 24 hours was the total exposure time. In order to control the hydrodynamic conditions a rotating cylinder electrode (RCE) was used and, a scanning electron microscope (SEM) was used in order to obtain the superficial analyses of the metallic surface after tests. The results of the electrochemical techniques shown that at 1000 rpm of the rotation speed, the corrosion rate (CR) increased as the exposure time also increased. In additions, in the other rotations speed (2000, 3000 and 5000 rpm), the CR was affected by the corrosion products formed on metallic surface. t is important to point out that the corrosion morphology found in the steel sample was localized corrosion.

Nickel base superalloys, which are gamma prime γ‘(Ni3Al, Ti) precipitation strengthened, is largely responsible for the elevated-temperature strength of the material and the higher resistance to creep deformation. The amount of γ’ depends on the chemical composition and temperature, heat treatment, these alloy are widely used in hot sections of aero-engines, land based turbines, stator parts, nozzle guide vanes, blades and integral wheels, due to its excellent elevated temperature strength and hot corrosion resistance. The γ‘ size decreases not only by the high temperature of heat treatment solution (1120 °C), the cooling environment and cooling rate are important parameter to decrease γ’ size to 0.65 μm. This paper presents the effect of heat treatment solution in base nickel IN 738 superalloy under service conditions, on the size and morphology of the gamma phase γ’ Ni3 (Al, Ti), main phase in the nickel base superalloys. Also shown coarse carbide and precipitates gamma prime size distributed and improve interdentritic spacing in the matrix after heat treatment solution.