Ni-Co/Al2O3 composites with alumina particles below 0.53 µm in size were electrochemically deposited on carbon steel AISI-O1 substrates. The influence of current density (2, 3, 4 and 5 mA/cm2) on the microstructure and adhesion behavior was investigated. It was found that the micro-hardness of the surface increased in 90% with respect to the plain substrate. SEM examination revealed an increased thickness from 3.7 to 10.7 µm at current density of 2 and 5 mA/cm2, respectively. The Co/Ni weight ratio in the coatings was determined by atomic absorption spectroscopy (AAS); the content of Co and Ni at 2 mA/cm2 were 42.4 %Co and 57.6 %Ni, while at 5 mA/cm2 were 44.5%Co and 55.5%Ni. The adhesion of the coatings was evaluated qualitatively according to the VDI 3198 norm; in all the cases, the adhesion was more than acceptable since no cracks or detachments were observed in the periphery of the marks. Details on the synthesis and properties of the Ni-Co/Al2O3 composite coatings are presented together with the excellent properties they show despite of their thin thickness.

Chitin nanowhiskers were obtained with the purpose to be used as astaxanthin protectors against the photo and thermal degradation. These nanostructures were generated by a freezing/thawing procedure using two stirring methods: mechanical and sonication, which were named as FTM and FTS respectively. Morphological and spectroscopic studies were carried out on chitin nanowhiskers by scanning electronic microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Through a SEM analysis, chitin fibers were found uniformly spaced and oriented with the width ranged from of 20-40 nm. Furthermore, the nanowhiskers obtained by FTM showed long and flattened structures and bundles of homogeneous sizes, which have the capacity of being sites of stress concentration. In contrast, by FTS, the nanowhiskers showed coarse fibers exhibiting numerous peaks. By comparing the two methods is appreciated that FTS method provides more surface area, giving more sites for functionalization. Fourier transform infrared spectroscopy (FTIR) allowed the determination of free movement of functional groups on the surface of samples obtained by FTM and FTS methods. Significant differences of signals in the spectra indicate that there were more unassociated amides in the nanowhiskers obtained by FTS than by FTM.

The current work reports the effect of particle size on the rheological behavior of polymer modified asphalt PMA. The modified asphalt was generated with AC-20 asphalt precursor provided by Pemex Salamanca and Solprene® 416 provided by Dynasol Mexico. Solprene® 416 is a SBS star-type copolymer with 4 poly(b-styrene-b-butadiene) arms and Mw = 2.36X105 g/gmole. Modified asphalt samples were prepared with 3 wt % of SBS via hot mix process. Mixing time and temperature were kept constant at 4h and 180 °C. This study also varied the agitation in the mixing process: 500, 1000 and 1500 rpm. All PMAs shown sphere-shaped polymer particles as observed via fluorescent microscopy using a Carl Zeiss KS-300 system. Base asphalt and PMAs were also characterized through rheological measurements using a TA Instruments AR-G2 rheometer. Shear viscosity (η) and tan δ data shown that the flow resistance of the PMA increases as the size its polymer particles decreases. Since the size of the polymer particles decreases with the increase of the stirring speed, it is concluded that the stirring speed of the process determines the size of the polymer particles and so the mechanical resistance of the PMA.

The present work is a study on alkali activation of Mexican blast furnace slag, using sodium silicate. The aim is to produce an optimal specimen, homogeneous without carbonation, and with small fraction of crystalline phases, similar to CSH, which provide mechanical properties suitable to use in the construction industry. The samples were prepared using sodium silicate activator solutions with modulus (SiO2/Na2O) of 1.25, 1.5, and 1.75. The weight percentage of Na2O in the activator solutions was added at 4, 6 and 8% relative to the slag weight. The prepared samples were stored in sealed molds, at room temperature (20°C), during 7 days. The X-ray diffraction has revealed the presence of an amorphous phase, semi crystalline clinotobermorite phase and signals of calcium carbonate for the samples of 4 and 6 % of Na2O; in contrast with the 8% Na2O, where the latter signals almost disappeared. The specimen selected as optimal was prepared with an activator concentration of 8% of Na2O /Slag, and SiO2/Na2O of 1.25. A specimen under these optimal conditions was prepared with accelerated curing (40°C, humidity, 48 hours), and a compressive strength test was attained, with an average value of 52 MPa at 3 days.

The aim of this study is to compare the corrosion rate of aluminum alloys for ornamental pieces. Three Fe/Cu relationships were tested in order to improve hardness and brightness in aluminum pieces since these alloys are used in the making of ornamental pieces. The variation on Fe/Cu content could result in modification on corrosion rate, since a metallographic characterization must be carried out identifying the presence of intermetallic phases. The presence of these elements could result in increasing corrosion rate, or even in modification of corrosion morphology, so localized corrosion could be expected.

The assessment of corrosion rate was carried out in saline media, since chlorides are ions that promote localized corrosion. Electrochemical techniques (polarization curves and Tafel plots) were used in order to evaluate the attack in aluminum pieces; electrochemical impedance spectroscopy was also employed with voltage amplitude of 10 mV rms, and a frequency range from 10,000 Hz to 0.01 Hz. A typical three electrodes cell was used, exposing an area of one cm2. Before polarization, open circuit potential was monitored for an hour looking for a steady state. All conditions were tested for triplicate.

The behavior of open circuit potential vs. time, and polarization curves was analyzed; a corrosion mechanism is proposed according to the electrochemical control. Polarization rate was calculated by using Tafel plots and, an electrochemical impedance spectroscopy analysis by using equivalent electric circuits is shown. Electrochemical impedance will yield information about corrosion morphology that is backed with microscopic inspection.

The objective of this study is to compare the corrosion rate of aluminum alloys for ornamental pieces in order to determine the effect of the relationship Fe/Cu on the corrosion mechanism in aluminum parts for ornamental pieces.

Development of polymers with antimicrobial characteristics can avoid deterioration and assist in containing spread of pathogens harmful to human health. This study aimed to compare the antimicrobial and mechanical properties of polymeric matrices containing organic antimicrobial additives. Silver organomodified bentonite (Ag_bentonite) and organochlorine molecule in a masterbatch based polyethylene (Cl_PE) were tested in proportion of 2% in a thermoplastic elastomeric formulation. The polymeric matrices were prepared by melt mixing and evaluated in tensile and antimicrobial properties against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) strains. The additives were characterized by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). The nanoscale of Ag_bentonite was verified by SEM. TGA assay showed that Cl_PE is more sensitive to heat than Ag_bentonite. As a result of this lower thermal stability, the addition of Cl_PE reduced the tensile properties of the compound. The sample with Cl_PE was effective against both bacterial strains, reducing the populations of S. aureus and E. coli in 99 and 96%, respectively. The addition of Ag_bentonite did not affect the tensile strength and decreased in 97 and 40% S. aureus and E. coli populations, respectively. The results indicate that the use of organic additives is promissory, but further modifications in processing must be necessary.

Lately, the investigations of binders from ternary system Portland cement (PC), calcium aluminate cement (CAC) and calcium sulfate ( $C\overline S$ ), have gone through a larger stage of development due to their special properties such as fast setting and rapid hardening, early strength, non-efflorescence, etc. These special properties are ensured by the binder’s microstructure, developed through hydration processes and reactions between hydrate components, which allows us to use them in special environments (aggressive environments with very low or very high level of pH, environments with high temperature, etc.). The binders from this system were simply named “dry mortars”, and provide the final user with an easy processing. In order to explain the mechanical behavior of the specimens exposed in normal curing conditions (T = 20 ± 2 °C and R.H. ≈ 95%), and with different percentages of calcium sulfate (added as hemihydrate or anhydrite), research on the microstructure of the hardened system was performed using SEM and XRD investigation techniques. The analyses have been performed on the binder pastes, hydrated for 1 and 28 days. The tests results showed that the specimen with anhydrous $C\overline S$ content had the best mechanical behavior.

Porous silicon (PSi) combines the potential of miniaturization with a very large surface area. The PSi surface can be chemically modified resulting in a high sensitivity (low detection threshold) device for chemical and biomolecular sensing. In previous work, we have shown that redox proteins and fluorescent ligands can be infiltrated into PSi (PSiMc) structures. The hybrid devices have shown interesting new properties produced by the coupling of the individual properties of PSi nanostructures and the modifiers. In this work, we have obtained a PSiMc/redox protein bioelectrode, which presents a quasi-reversible electrochemical response. This effect was attributed to the semiconducting nature of the PSi substrate and to the functional groups of the crosslinking molecules (MPTS), which together produce a capacitive effect on the device. On the other hand, the chemical modification of PSiMc with fluorescent ligands allowed us to fabricate fluorescent PSi hybrid nanostructures, which were tested for the detection of environmental pollutants such as heavy metals (specifically Hg2+). We found that the selectivity of this optical device depends on the selected recognizing molecule. The captured metal induces the formation of a metallic complex that shows higher fluorescence compared with the sensor device. These results demonstrate the viability of using porous silicon as optical sensors and electrochemical biosensors. The infiltration of fluorescent recognizing molecules and proteins into the PSi matrix were evaluated by specular reflectance, FTIR spectroscopy, fluorescence spectroscopy and cyclic voltammetry.

The main purpose of this research was to establish the effectiveness of the V844 corrosion inhibitor for seawater on various metallic materials: carbon steel, aluminum and copper alloy at different concentrations via colloid formation. The changes in both physical and chemical properties of seawater, including pH, total hardness, alkalinity, total dissolved solids (TDS) and conductivity at different concentrations of V844 were assessed, too. The test procedure involves dissolving the V844 corrosion inhibitor powder provided by Magna International Private Limited in seawater to obtain a stock solution of 4% V844 in seawater, which was further diluted to obtain the remaining concentrations. The analysis of parameters begun when various metal species, polished beforehand, were placed into the solutions. The analysis was observed over a period of 26 days and a total of 9 sets of readings were obtained. From our observation and analysis, it was concluded that the inhibitor worked best at 0.05% concentration for carbon steel.

A very realistic 1:17 scale physical model of a 140-ton gas-stirred industrial steel ladle was used to evaluate flow patterns measured by Particle Image Velocimetry (PIV), considering a three-phase system (air-water-oil) to simulate the argon-steel-slag system and to quantify the effect of the slag layer on the flow patterns. The flow patterns were evaluated for a single injector located at the center of the ladle bottom with a gas flow rate of 2.85 l/min, with the presence of a slag phase with a thickness of 0.0066 m. The experimental results obtained in this work are in excellent agreement with the trends reported in the literature for these gas-stirred ladles. Additionally, a mathematical model was developed in a 2D gas-stirred ladle considering the three-phase system built in the physical model. The model was based on the Eulerian approach in which the continuity and the Navier Stokes equations are solved for each phase. Therefore, there were three continuity and six Navier-Stokes equations in the system. Additionally, turbulence in the ladle was computed by using the standard k-epsilon turbulent model. The agreement between numerical simulations and experiments was excellent with respect to velocity fields and turbulent structure, which sets the basis for future works on process analysis with the developed mathematical model, since there are only a few three-phase models reported so far in the literature to predict fluid dynamics in gas-stirred steel ladles.

The main purpose of coatings is to increase the lifetime of cutting tools, to perform continuous and economical material removal process, reducing the frequency of sharpening or replacement of the tool, which contributes to increase quality of product. Therefore, hafnium nitride (HfN) single layer coatings were deposited on High-speed steel by Magnetron Sputtering physical vapour deposition (PVD). The machining on AISI 1020 steel samples were carried out in a computer numerical control (CNC) machine, using coated and uncoated tools, the temperature of the different components were measured (steel bar and tool), due to continuous temperature measurement help to predict tool wear and the quality of finished piece [1] . In order to evaluate wear resistance and performance, not only temperature data were compared, the tool wear morphological analysis for flank wear was carried using Scanning Electron Microscopy (SEM), and work pieces roughness were checked through their surfaces in an Atomic Force Microscopy (AFM). In most of the parameters evaluated differences between the tools were identified, and results reveals that on HfN coating, occurs less wear, due the proportionality between the energy transfer and the tool deterioration, also the coating improves surface finish of the machined part; all of them are reflected in changes on process temperatures. The use of single layer HfN coating on cutting tools could increase their lifetime, improve the quality of the work piece, and even reduce process time and cost.