The monitoring of corrosion in reinforced concrete structures is considered an important preventive factor against the corrosive damage. The present paper shows the design and construction of a device which performs remote measurements of the polarization resistance of reinforcing steel, this was made using the electrochemical technique of linear polarization resistance as a method to obtain the information of the corrosive process. The development was carried out by implementing a potentiostat based on a free development platform. The design allows to store all the data on a physical memory and to send the results through the mobile network to a web server, where the measured values can be analyzed using an internet connection.

The linear polarization resistance measurements were made in cylindrical concrete specimens with rebars of ½ ”, each one instrumented with embedded electrodes of Copper/Copper sulfate and graphite. The specimens were subjected to a saturated environment of chlorides (3.5%) where the corrosive process was monitored with the developed system. The results were compared with tests performed on a commercial potentiostat / galvanostat, where the values obtained have an mean of 4.83%.

Nowadays the aeronautical industry keeps strict quality standards in its dimensional specifications, mechanical properties and microstructural characteristics. Therefore, the involved manufacturing processes require keeping high standards. The nickel based superalloys are present in many components of the jet engines, being the Inconel 718MR superalloy the most common, making up to 50% of the jet engine. This is designed to resist high temperatures, corrosion and creep. The process of rotary forging is a manufacturing process that is currently under scientific and technological development in the aeronautical industry. An Avrami model coupled with a commercial FEM platform (DEFORMTM 3D) was developed to evaluate the average grain size, as a function of the working conditions at 980 °C and 1000 °C. The results provide a better understanding of the influence of temperature in the grain size evolution during the rotary forging process, compared with previous reports.

New organic materials with semiconductor behavior were prepared from diphenyldiacetylene and aromatic amines with withdrawing groups by Reisch-Schulte reaction and characterized by IR, RMN spectroscopy. The obtained materials share the property of having electron withdrawing groups joint to the attached aromatic ring, it seems this feature accounts in large fashion to improve the semiconducting behavior of this kind of substances, this topic was studied by means theoretical calculations and the results are also discussed. The calculations were carried out by means the Gaussian09 software and all the involved species were geometrically optimized.

Equipment wear is caused by the disintegration of material due to the contact between the machines components and the ore, resulting in stress to the surface of the material. Wear causes loss of efficiency, vibration, misalignment and, in severe cases, cracks that may lead to fracture and damage to the equipment. In mining, wear is caused by operational problems in which generate high costs. Some researchers studied white cast iron alloys with high chromium and the addition of niobium for wear plates manufacturing and therefore, plates to protect structural parts of the equipment have been developed. This study presents the characterization of the microstructure of two alloys of white cast iron with high chromium containing 3.8 wt.% C and 27.1 wt.% Cr and the addition of 0.9 wt.% Nb (alloy 1) and 1.6 wt.% Nb (alloy 2), respectively. Samples of the two alloys were subjected to metallographic tests, microhardness and abrasion type rubber wheel tests, according to the ASTM: G65-91 standard. Complexes carbides have been identified in both alloys. The results of microhardness and wear resistance tests were correlated and identified the effect of niobium addition. The findings suggest that the addition of niobium in these alloys contributes to the formation of NbC and increase of Cr in the matrix; consequently increase in the hardenability of the material. The wear resistance of alloy 2 was 47.95% higher than alloy 1 in abrasion type rubber wheel tests. It demonstrates that the increase of niobium in the alloy has contributed to improve wear resistance due to the substantial change in the microstructure and distribution of NbC carbides.

In recent decades conducting polymers have attracted attention due to their promising and versatile applications in different fields. There is a considerable interest in the application of nanotubes multilayer carbon (MWCNT) because of their unique structure, high electrical conductivity, high chemical stability, and high surface-to-volume ratio. These properties make MWCNT extremely attractive for fabricating sensors. Composites based on a matrix of a biopolymer such as the chitosan (CS) with a lot of conductive polymers or (MWCNT), have received increasing attention due to their attractive structural, mechanical and electrical properties that could have applications in different fields such as tissue engineering, biomedicine, and manufacture of sensors and biosensors. Have been reported conducting polymer composites with an extensive range of interesting mechanical and electrical properties, which is reported in this paper to obtain films by ultrasonic bath mixing of Chitosan 3% w/v using polypyrrole (PPy) and multilayer carbon nanotubes. Surface characterization was performed using scanning electron microscopy (SEM). The electrical properties were analyzed using electrochemical impedance spectroscopy (EIS) in a frequency range 0.01 - 10E+5 Hz to 10 mV AC. The results show that the films of CS/PPy/MWCNT have a homogeneous distribution where the chitosan envelops the loads, while for EIS retention load was observed within the matrix observing these materials in accordance with the equivalent circuit of Warburg showing diffusional process.

Carbon nanotubes (CNTs) were synthesized by Chemical Vapor Deposition (CVD) from diethyl ether, butanol, hexane and ethyl acetate. A quartz tube with a stainless steel tube catalyst core with 0.019 m diameter and 0.6 m large formed the reactor. To avoid combustion, argon was used as the carrier gas. Time process ranged 30 to 60 min. The range of CNTs synthesis temperature was 680-850 °C for different precursors. Scanning Electron Microscopy micrographs have demonstrated tangled CNTs growth in all samples, thus presenting difficult length measurement. The CNTs diameters from diethyl ether are 45-200 nm, butanol diameter range from 55-230 nm, hexane diameter range is 50-130 nm and ethyl acetate range from 100 to 300 nm. Carbon content for all samples was higher than 93 %, CNTs from butanol showed carbon concentration up to 99%. FTIR, Raman and X-Ray Spectroscopies spectra for all samples demonstrated the characteristics signals present in carbon nanotubes. This research proposes a simple, effective and innovative method to synthesize CNTs by CVD on iron stainless steel catalyst in combination with diethyl ether, ethyl acetate, butanol and hexane as precursors by applying the principles of green chemistry, sustainability and its ease to be scaled.

Gold nanoparticles can be used as ultimate electrical materials for storing electrons or controlling their flow for the next generation nano-electronic devices. These particles are the core element of assemblies where the electrical current is reduced to the smallest possible since electrons are controlled one by one by using the Coulomb blockade phenomenon. We prepared colloidal gold nanoparticles beteween 4 and 15 nm and grafted them on a grafted organic monolayer (GOM) on silicon. GOM are highly ordered monolayers prepared by hydrosilylation of alkene molecules and subsequently modified with an amine group so that gold nanoparticles can be firmly immobilized on top of the layer. We discuss several electrical properties at a single electron level. Using the conductive tip of KPFM, we were also able to reveal the spontaneous charging behavior of the gold nanoparticles so that the local work function of a 10 nm gold nanoparticle is only 3.7 eV. By placing an STM tip above a nanoparticle, Coulomb blockade allows controlling the number of electrons simultaneously injected in the nanoparticle. This opens the way for new kinds of single electron memories or single electron transistors.

The surface quality of a heat treatable Al-Si-Mg alloy by means compression tests at 450°C was evaluated. Samples were obtained from an ingot with unidirectional solidification in order to obtain a microstructural gradient influenced by the cooling and solidification rate. The samples were heat treated by homogenization at 520°C for 4 hours prior to deformation by compression. Inverted optical and scanning electron microscopes were used to assess the surface damage of deformed samples.

Analysis of deformed surface indicates a greater influence of microstructural refinement on hardening rate. It was found that the samples solidified at high cooling rates showed no defects, but at low cooling rates produced growth of grain size and intermetallic phases and thereby the high incidence of cracks in the surface.

Two machines: The human body and the vehicle motor are made of structural and functional, natural and man-produced materials. They generate energy by chemical oxidation of two fluids: ethanol and gasoline. The characteristics of these fluids: a nutritive beverage and a fuel, providing motion to the vehicle, are described. The damage due to diseases in the body by excessive ethanol consumption and deterioration of the motor by corrosion are treated by means of preventive and curative methods: body rehabilitation and car repair, maintaining both machines in permanent, healthy, working operation. The chemical reactions of ethanol oxidation and gasoline combustion and their effects on the machines and their materials are presented, illustrated and discussed.

We present a set of Molecular Dynamics simulations of the axial elongation of gold nanowires, and the compression of silver decahedral nanowires by a carbon AFM tip. We used Sutton and Chen multibody potentials to describe the metallic interactions, a Tersoff potential to simulate the carbon-carbon interactions, and a 6-12 Lennard-Jones potential to describe the metal-carbon interactions. In the elongation simulations, gold nanowires were subjected to strain at several rates, and we concentrated our attention in the specific case of a wire with an atomistic arrangement based on the intercalation of icosahedral motifs forming a Boerdijk-Coxeter (BCB) spiral, and compare it against results of nanowires with fcc structure and (001), (011), and (111) orientations. We found that the BCB nanowire is more resistant to breakage than the fcc nanowires. In the simulations of lateral compression, we made a strain analysis of the trajectories, finding that when a gold decahedral nanowire is compressed by the AFM tip in a direction parallel to a (100) face, the plastic deformation regime is considerably larger than in the case of compression exerted in a direction parallel to a twin plane, where the fracture of the wire comes almost immediately after the elastic range ends. The strain distribution and elastic response in the compression of nanoparticles with different geometries is also discussed.

There are lessons from recent history of technology introductions which should not be forgotten when considering alternative energy technologies for carbon dioxide emission reductions.

The growth of the ecological footprint of a human population about to increase from 7B now to 9B in 2050 raises serious concerns about how to live both more efficiently and with less permanent impacts on the finite world. One present focus is the future of our climate, where the level of concern has prompted actions across the world in mitigation of the emissions of CO2. An examination of successful and failed introductions of technology over the last 200 years generates several lessons that should be kept in mind as we proceed to 80% decarbonize the world economy by 2050. I will argue that all the actions taken together until now to reduce our emissions of carbon dioxide will not achieve a serious reduction, and in some cases, they will actually make matters worse. In practice, the scale and the different specific engineering challenges of the decarbonization project are without precedent in human history. This means that any new technology introductions need to be able to meet the huge implied capabilities. An altogether more sophisticated public debate is urgently needed on appropriate actions that (i) considers the full range of threats to humanity, and (ii) weighs more carefully both the upsides and downsides of taking any action, and of not taking that action.

Newly discovered MAX phases are attractive due to their unique combined properties: mechanical, high temperature, erosion and corrosion resistance. These materials are considered metallic and ceramic at the same time, and they could be the perfect solution for a variety of industrial and scientific applications. In this study, detailed attention has been paid to complex compositions of several transition metals, such as Ti and Cr in TiCrSiCN, whereas Al and Si are recommended for TiAlSiCN. These materials require a combination of both C and N to form the MAX phases (in the “X” position in the formula M(n+1)AXn). The purpose of this study was to investigate the effect of these elements located at the “M”, “A” and “X” positions on the mechanical properties of the materials. The results of the thermogravimetric analysis of TiCrSiCN showed that this phase is stable at temperatures as high as 1400 °C, while the Ti3SiC2 phase is stable up to 1300 °C.

The aerospace and automotive industries demand the development of new manufacturing processes. The productivity during machining of very flexible aerospace and automotive aluminum components is limited for self-excited vibrations. New solutions are needed to suppress vibrations that affect the accuracy and quality of the machined surfaces. Rejection of one piece implies an increase in the manufacturing cost and time. This paper is focused on the design, manufacturing and characterization of a magnetorheological damper. The damper was attached to a thin-floored component and a magnetic field was controlled in order to modify the damping behavior of the system. The dynamics of the machining process was developed by considering a three-degree-of-freedom model. This study was experimentally validated with a bull-nose end milling tool to manufacture monolithic parts with thin wall and thin floor. Experimental tests and characterization of the magnetorheological damper permitted to improve the surface finish and productivity during the machining of thin-floored components. A further aim of this paper was to develop a rheological damper by using magnetorheological fluids (MR) to change the thin floor rigidity with voltage. The stability of the milling process was also analytically described considering one, two or three degrees of freedom, using a mathematical integration model based on the Enhanced Multistage Homotopy Perturbation Method (EMHPM).

Glass-ceramics of eutectic composition in the wollastonite [W, CaO⋅SiO2]- tricalcium phosphate [TCP, β-Ca3(PO4)2] binary system were synthesized by using the glass-crystallization method. The parent glass was crystalized at 800-1300 °C for 0.5-5 h. The in vitro bioactivity of the synthesized glass-ceramics was tested in Kokubo’s Simulated Body Fluid (SBF) for 7-21 days, at pH = 7.4 and 37 °C. All materials were characterized by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM/EDS). The results showed that metastable Apatite phase [Ap, Ca10(PO4)6O], plus W and TCP phases expected according to the binary phase diagram, were formed. Ap was the first phase formed at 900 °C/0.5 h, which was followed by formation of W phase at 900 °C/2 h and of TCP phase at 1200 °C/0.5 h. The relative proportion of the formed crystalline phases was a function of heat treatment temperature and time. A eutectic microstructure was obtained for the materials heat-treated at 1300 °C for 2 or 5 h. All glass-ceramics showed the formation of a hydroxyapatite (HAp)-like layer during the in vitro bioactivity tests. After 21 days of soaking in SBF, the samples treated at 1300 °C/5 h showed a behavior similar to that typically shown by Bioeutectic® material, while the materials heat-treated at lower temperatures tended to form denser HAp-like layers, with similar thicknesses but with higher Ca/P molar ratios.

Highly refractory composites with predominant volume fraction of TiB2, were “in situ” synthesized and consolidated. The production process was carried out using elemental powders by means of self-propagating high-temperature synthesis under pseudo-hot isostatic pressure (SHS-pseudo-HIP). The Ti:B atomic ratio corresponded to TiB2 formation, and Cr:C atomic ratio has been established in (3:2) molar ratio.

Based on scanning electron images (SEI), very high relative density was obtained with nearly full densification in composite with intended 85vol.% of TiB2, which is sufficiently high concentration of boron from the perspective of neutron shielding. However XRD results indicated formation of CrB and TiC, next to TiB2. This clearly indicates no equilibrium in pseudo-binary TiB2-Cr3C2 system. Besides, broadened peaks in XRD patterns as well as gradient of composition in EDS maps may indicate solid solutions, especially (Ti,Cr)C. The existence of (Ti,Cr) solid solutions and ternary compounds is possible, considering Hume-Rothery rules for hypothetical mutual solubility.