The yield stress evaluation as a function of water content for slip-prone clayey soils due to rainfall is studied in this work, particularly, the clayey soil from the region Teziutlán-Puebla-México. Yield stress was calculated as a function of water content using the slump test in cylindrical geometry. Results show a critical point of water content where yield stress decreases dramatically, and those values were related to the historical daily rain data. It was found a maximum precipitation millimeters that triggers the landslide, but still is low compared with the historical reported data.

Cathodic protection has been applied for many years as the best method to prevent the corrosion in systems which transported hydrocarbon pipelines. However, it has found the presence of stress corrosion cracking (SCC) in steel pipelines with high concentrations of carbonates and bicarbonates with pH final (9 to 11). The resistance to the stress corrosion cracking of the API X-52 and API X-65 steels was evaluated on compact modified wedge opening specimens (WOL). The specimens were loaded of 95% of the yield strength. The resistance of crack propagation and the corrosion rate were evaluated with different applied potentials (-850 and -650 mV), this with respect to a saturated copper/copper sulfate reference electrode. The used electrolytes were simulated soils (carbonate-bicarbonate solution). Evidence of crack propagation of the API X-52 and API X-65 steels were carried out by scanning electron microscopy. The obtained result showed susceptibility to SCC on specimens with cathodic protection. The cathodic protection applied (-850 mV vs Cu/CuSO4 electrode) decreases considerably the corrosion rate on the evaluated steels. In this work the loaded stress showed to be a very important variable on the susceptibility to SCC.

A summary of experimental findings on the luminescence from conical bubble collapse, CBL is presented. Spatial, temporal, and spectral features of luminescence were investigated. In the experimental runs, two inert gases (Ar, Xe) and 1,2-Propanediol, PD, as work liquid were used. Single and multiple light emission events were recorded. Results show that there is a spectral evolution inside each pulse and through the whole experimental sequence. The average spectra consist of a broad continuum background, on which line emissions of OH°, CN, Na+, K+, and Swan lines are superimposed. An increase in continuum intensity from 300 to 860 nm was observed. The molecular and atomic lines as well as the continuum emission arise from different chemical pathways that take place during the bubble compression. Pathways come from the degradation of the liquid due to the repetition of the compression process, resulting in changes of the thermo-chemical conditions inside the cavity, such that each collapse was different. This becomes evident, by using low gas pressures, in which the luminescence was spatially and temporally non uniform. On the other hand if Xe instead of Ar is used the intensity of the luminescence increased one order of magnitude. These findings indicate that several components are presents in the bubble, besides the residual air and inert gas, vapor and liquid droplets, and within the latest water vapor, inert gas and alkali solutions are dissolved.

An Al58Cu25Fe17 alloy composition was produced by conventional casting technique. In order to take advantage from the hydrogen-environmental embrittlement reaction, which affects these alloys, this research was carried out subjecting prealloyed powders to wet-ball milling. Through these experiments it has been possible to evaluate the particle size reduction as consequence of hydrogen fracture and milling energy. The morphological and structural characteristics of the samples were performed using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The experimental results indicate that the samples with higher contents of humidity have a good particle size reduction. With the increment of milling time, the particle size was diminished even more reaching nanometer size scale.

Nowadays, Si3N4 coatings are used to increase the hardness of 316L-type stainless steel for a wide variety of applications. These coatings are normally prepared by chemical vapor deposition (CVD) or variant techniques such as the hybrid solid-gas precursor system chemical vapor deposition (HYSYCVD), where Na2SiF6 is used as a solid precursor. Within the reaction chamber the Si-F gas species interact with nitrogen precursors to form Si3N4; however, during silicon nitride formation there is always certain amount of residual Si-F gas species which may affect the integrity of the steel surface. Therefore, in this work the effect of the Si-F species on the surface of 316L type stainless steel under argon atmosphere has been investigated. Stainless steel samples were prepared under two surface conditions (abraded and mirror polished), and were exposed to Si-F species considering various parameters such as: argon gas flow rate equal to 10 cm3/min, different temperatures (300, 500, 700, 900°C), and three exposure times (30, 60, 90 minutes). After exposure, the substrates were characterized by X-ray diffraction (XRD) and by scanning electron microscopy (SEM). The results show that the FeF2 phase is formed at low temperatures while the formation of different oxides is directly related to the processing temperature. What is more, these oxides are also strongly influenced by processing time; however temperature is the parameter that most significantly influences the oxides formation.

A simple optical characterization technique is developed for to find the amplitude and phase modulation modes for the twisted nematic liquid crystal display (TN-LCD). The developed technique is based on intensity and pixel shift measurements of the interference pattern obtained from the TN-LCD sandwiched between two polarizers in a modified Young's experiment. Particularly, specimen LC2002 Holoeye is characterized and its amplitude and phase modulation curves as a function of image's gray level, bright B and contrast C are presented.

A lot of duplex and super duplex stainless steels are prone to secondary phases but with different sequence and kinetic which depend on the chemical composition and thermo-mechanical history of the steel. In this paper the results of secondary phase's determination in a welding grade 2510 duplex steel, heat treated at 850–1050°C for 3–30 min are presented. The precipitation stars at grain boundaries with a consistent ferrite transformation for short times. The noses of the TTP curves are at 1000°C (sigma phase) and at 900°C (chi phase) with a partial transformation of chi to sigma, as evidenced in 2205 and 2507 grades.

Extracted samples of L3 vertebrae, the healthy, osteopenic and osteoporotic from Mexican men, were fixed to carry out measurements of the modulus of elasticity (ME) and the minerals content, on the trabecular zone to study their behavior as a function of age.

To determine the ME the immersion ultrasonic method (IUM) was used, X-ray dispersion was applied to know the chemical element concentration (Ca++, Na++, P, and Mg++) and computerized axial tomography (CAT) to obtain bone mineral density (BMD).The samples were organized in four groups by decade. The samples in the range of 30-39 years revealed: a normal BMD and a concentration [% w/w] between pairs of Ca++/P, Ca++/Mg++, P/Mg++ and Mg++/ Na ++ with correlation positive due to the strong dependence between them.

The average ME results were: 2.79±0.326, 2.68±0.45, 2.66±0.43 and 2.70±0.397 [GPa] for each decade respectively. The ME profiles show a nonlinear behavior as a function of age, indicating a minimum value in the third decade, similar behavior is observed in the Ca++. An exponential behavior between ME and T-score was obtained. The plotted Ca++ and ME as a function of area showed a homogeneous distribution for the first and a non homogeneous for the second.

Brazing process is a cost effective technique to repair wide gap cracks in turbine components made from difficult to weld nickel base superalloys. In this process boron and silicon are used as melting point depressants, however, form hard and brittle intermetallic compounds with nickel (eutectic phases) which are detrimental to the mechanical properties of brazed joints. In this paper the effect of brazing parameters such as temperature and time on final microstructure of brazed joint of nickel base superalloy Inconel 738 using a commercial filler metal alloy (Ni-11Cr-3.5Si-2.25B-3.5Fe) was investigated. The microstructure of the joint layer was characterized by optical and scanning electron microscopy; chemical composition was carried out by energy dispersive X-ray spectrometry (EDS) microanalysis and microhardness testing. The results showed that the formation of eutectic microconstituents, within the joint regions, was significantly influenced by the brazing parameters and gap size, also that formation of eutectic constituents decreased by allowing a sufficient amount of time for a complete isothermal solidification to take place at the brazing temperature.

Assessment of anodic and cathodic potentials on stress corrosion cracking (SCC) of API X52 pipeline steel through slow strain rate tests (SSRT) was studied. The SSRT were carried out in a NS4 solution to simulated dilute ground water that has been found to be associated with SCC of pipelines. SSRT were performed and evaluated in air and in the NS4 solution at room temperature at an extension rate of 1×10-6 in/sec. Tests were performed at controlled electrochemical polarization potentials, both anodic and cathodic (100, 200, 400 mV) versus the open circuit corrosion potential. The results of reduction in area ratio (RAR), time to failure ratio (TFR) and plastic elongation ratio (PER) of the specimens tested in the soil solution indicate that X52 pipeline steel was susceptible to SCC at cathodic potentials. These specimens showed a brittle type of fracture with transgranular appearance. The SCC proceess and mechanism of X52 steel in the NS4 solution is mixed-controlled by both anodic dissolution and the hydrogen involvement. At positive potentials the SCC is based mainly on the anodic dissolution mechanism. When the applied potentials shifted negatively, the SCC on the steel follows mainly hydrogen embrittlement mechanism. This mechanism was confirmed through the internal cracks observed in the specimens.

We report thermal diffusivity measurements for samples of silicon, gallium arsenide and cupper by means of the photoacoustic technique in a heat transmission configuration in order to obtain a comparison between the results obtained with the use of the conventional RG-model and our SP-model (based in a square periodical heat source) in the fitting process to the experimental data. Our results show that our SP-model is accurate to obtain a good fitting with the experimental data and it improves notably the results obtained with the RG-model.

Zinc peroxide (ZnO2) nanocrystals were directly produced by hydrothermal process. The nanocrystals were synthesized using zinc acetate as precursor and hydrogen peroxide as oxidant agent. The ZnO2 powders were characterized by X-ray powder diffraction and transmission electron microscopy. The results of transmission electron microscopy indicated that the ZnO2powders consisted of nanocrystals with diameters below to 20 nm and a faceted morphology. High resolution electron microscopy observations have been used in order to the structural characterization. ZnO2 nanocrystals exhibit a well-crystallized structure.

The polylactic acid (PLLA) is commonly used in the biomedical application. The physical and mechanical properties of PLLA depend on the molecular weight, crystallinity, and synthesis. In this work, we study the PLLA crystallization kinetics. One of the main attractive of these polymers is that its degree of crystallinity can easily be modified, from amorphous state to a high crystallinity degree. In this study a new technique is applied to follow the crystallization kinetic. An optical microscope with cross polarizers, warming plates and video camera were used. A series of images were obtained under isothermal conditions to observe the growth spherulite. Since an image is composed by pixels and each pixel has a value from 0 to 255, which represents gray intensity, being zero for black and 255 are white. Then, the pixels average versus time was plotting and from the plots crystallization kinetic and secondary crystallization are easily obtained.

The first steps in the synthesis of nanostructures are followed through UV-Vis and correlated with photoluminescence and images taken by SEM and TEM. Colloids permit the control in the atomic arrangement and the formation of nanostructures used to build cluster of materials. The size of the cluster in the colloid is around 5 nm. After the formation of the colloid a hydrothermal growth and microwave heating allows the formation of an ensemble of nano-sheet. This work is aim in the direction to controls the synthesis and the properties of materials with potential applications as active optical materials.

The porous structure of aluminum foams was quantitatively monitored in terms of pore density, pore area, and shape and size distribution using image analysis; then, related to density and expansion profiles by interrupted experiments. This practice offers important information in the control and reproducibility of foams. The aluminum foams were produced by the powder compact melting method at 800°C. The foamable precursors consisted in uniaxial cold pressed Al-TiH2 mixtures compacted at 387 MPa; the pressure applied and particle size distribution of the mixture originated preforms with 95.9% densification. This procedure eliminated the traditional hot-compaction step; besides, the amount of foaming agent was kept to a minimum of 0.5 wt.% TiH2. A volume expansion of 215 to 236% and densities from 0.7730 to 0.8206 g/cm3were obtained in a time window of 420 to 570 s. The calculated shape factors and Feret diameters defined how the roundness of pores varies with size all along the foaming process.

Al65Cu15Co20 and Al67Cu13Co20 (% at.) alloys with composition near to the quasicrystalline decagonal phase was produced by melting in an induction furnace and solidified at room temperature. The structural characterization was carried out by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM). For the structural model of decagonal quasicrsytals, it is important to know which crystalline phases have a structural relationship on the formation and decomposition of this type of phases. In the present investigation, the decagonal phase usually coexist with small amounts of the Al(Cu,Co) cubic phase of B2 type. Then, the quasicrystalline (QC) phase is outside of a single-phase region under equilibrium conditions at room temperature. DSC and TGA techniques showed the thermal stability of the alloy system up to 1000 °C.

Polymerized organic thin films were synthesized on a variety of substrates by Plasma Enhanced Chemical Vapor Deposition (PECVD) technique using isopropanol as precursor. Hydrogen peroxide, ammonium hydroxide, and iodine dissolved in isopropanol were used as dopants and chlorobenzene as copolymerization precursor. The structural, optical and electrical properties of the films were studied as functions of the dopant type and concentration.

The polymeric films were characterized by variable angle ellipsometry (VAE), atomic force microscopy (AFM), Fourier Transform Infrared spectroscopy (FTIR), ultraviolet-visible transmission spectroscopy and photoluminescence. The electrical film behavior was explored by the four points probe method.

The growth rate, refractive index, optical bandgap, chemical structure and resistivity of the films strongly depend on the concentration and type of dopant added. The AFM microphotographs showed smooth surfaces with RMS roughness less than 10 nm. The optical bandgap values of the films were in the range of 2.6 to 3.26 eV, the resistivity was in the order of 103 – 104 ohm-cm. The photoluminescence response of the polymerized films was obtained in the visible region, by exciting with a UV laser.

Zinalco alloy (Zn-21mass%Al-2mass%Cu) specimens were deformed superplastically with a strain rate (ε) of 1×10-3 s-1 at homologous temperature (TH) of 0.68 (5 ). It was observed neck formation that indicate nonhomegeneus deformation. Grain size and grain boundaries misorientation changes, due superplastic deformation, were characterized by Orientation Imagining Microscopy (OIM) technique. It was studied three regions in deformed specimens and the results were compared with the results for a specimen without deformation. Average grain size of 1 mm was observed in non-deformed specimen and a fraction of 82% for grain boundary misorientation angles with a grain boundaries angles between 15° and 55° was found. For deformed specimen, the fraction of angles between 15° and 55° was decreced to average value of 75% and fractions of low angle (<5°) and high angle (>55°) misorientations were 10% and 15% respectively. The grain size and high fraction of grain boundary misorientation angles between 15° and 55° observed in the alloy without deformation, are favorable for grain rotation and grain boundary sliding (GBS) procces. The changes observed in the fraction of favorable grain boundary angles during superplastic deformation, shown that the superplastic capacity of Zinalco was reduced with the deformation.

Corrosion study of the API X52 pipeline steel immersed in seawater without biocide and with 0.25, 0.5 and 0.75 ppm of biocide, under static and dynamic (turbulent flow) conditions was carried out at room temperature and atmospheric pressure. The hydrodynamic conditions were controlled by a rotating cylinder electrode (RCE) and the rotation speed was 1000 RPM. I order to analyse the corrosion process, linear polarization resistance (LPR), and polarization curves (PC) were made. This work investigation shown that the corrosion rate is higher under turbulent flow conditions than static conditions. A localized corrosion attacks was found in the superficial analysis.

Nanocrystals of zinc oxides have demonstrated to be very important materials for several applications in many fields, particularly in catalysis. Nanocrystalline zinc peroxide (ZnO2), which is a precursor of zinc oxide (ZnO), has been prepared by means of a hydrothermal process from zinc acetate dehydrates. On the other hand, it is of great interest to have a detailed structural characterization, in order to correlate it with the catalytic properties of the synthesized material. In this work, some results are presented about the nanostructure of the prepared zinc peroxide. By using X-ray diffraction followed of a pattern refinement by the Rietveld techniques, refined average cell parameters and crystallite size were calculated and, from these refined values, crystallite morphology was simulated in an averaged manner. With the aim to get a more complete characterization, besides these results, some micrographs of the crystalline structure of ZnO2, observed by TEM, were also included in this work.