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Chihuahua, Mexico

The effect of thermal annealing of poly(3-octylthiophene) (P3OT) and polystyrene (PS) blend coatings on the corrosion inhibition of stainless steel in a 0.5 M NaCl solution was investigated. P3OT was synthesized by direct oxidation of the 3-octylthiophene monomer with ferric chloride (FeCl 3) as oxidant. Stainless steel electrodes with mirror finish were coated with P3OT/PS blend by dropcasting technique. In order to study the temperature effect on the function like physical barrier against the corrosive species of P3OT/PS polymeric blend, the coatings were thermally annealed at three different temperatures (55°C, 80°C, and 100°C). The corrosion behavior of P3OT/PScoated stainless steel was investigated in 0.5 M NaCl at room temperature, by using potentiodynamic polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy. The LPR values indicated that, at 100°C, P3OT/PS coatings showed a better protection of the 304 stainless steel in 0.5 M NaCl; the corrosion rate diminished in two orders of magnitude with regard to the bare stainless steel. The superficial morphology of the coatings before and after the corrosive environment was researched by atomic force microscopy, optic microscopy, and scanning electronic microscopy. Morphological study showed that the increased temperature benefited the integration of the two polymeric phases, which improved the barrier properties of the coatings. The coating/metal adhesion and the coating thickness were evaluated. The temperature increases the adhesion degree coating/substrate; thus, the coating annealed at 100°C showed the best adhesion. © Springer-Verlag 2009.


Background: Chemicals generically referred to as flavonoids belong to the group of phenolic compounds and constitute an important group of secondary metabolites due to their applications as well as their biochemical properties. Flavonoids, which share a common benzo- γ-pyrone structure, constitute a kind of compound which are highly ubiquitous in the plant kingdom.Findings: The M06 family of density functionals has been assessed for the calculation of the molecular structure and properties of the Naringenin flavonoid. The chemical reactivity descriptors have been calculated through Conceptual DFT. The active sites for nucleophilic and electrophilic attacks have been chosen by relating them to the Fukui function indices and the dual descriptor f(2)(r). A comparison between the descriptors calculated through vertical energy values and those arising from the Koopmans' theorem approximation have been performed in order to check for the validity of the last procedure.Conclusions: The M06 family of density functionals (M06, M06L, M06-2X and M06-HF) used in the present work leads to the same qualitatively and quantitatively similar description of the chemistry and reactivity of the Naringenin molecule, yielding reasonable results. However, for the case of the M06-2X and M06-HF density functionals, which include a large portion of HF exchange, the calculations considering the validity of the Koopmans' theorem lead to negative electron affinities. © 2013 Glossman-Mitnik; licensee Chemistry Central Ltd.


Sanchez-Dominguez M.,CIMAV | Pemartin K.,CIBER ISCIII | Boutonnet M.,KTH Royal Institute of Technology
Current Opinion in Colloid and Interface Science | Year: 2012

In this review, the synthesis of inorganic nanoparticles using oil-in-water (O/W) microemulsions as confined reaction media is discussed. Synthesis using (O/W) microemulsions has been demonstrated for a great variety of inorganic nanoparticles: metallic (Pt, Pd, Rh, Ag), single metal oxides (CeO 2, ZrO 2, TiO 2, Fe 2O 3), mixed and doped metal oxides (Ce 0.5Zr 0.5O 2, Ce 0.99Eu 0.01O 2, Zr 0.99Eu 0.01O 2, and Fe 2Mn 0.5Zn 0.5O 4), semiconductors (PbS, CdS, Ag 2S, ZnS, CdSe, PbSe, Ag 2Se), fluorides (CaF 2, YF 3, NdF 3, PrF 3), phosphates (CePO 4, HoPO 4), and chromates (BaCrO 4 and PbCrO 4). There are two synthetic strategies: 1) the use of oil-in water (O/W) microemulsions, in which the precursor is an ionic salt which is dissolved in the continuous aqueous phase; and 2) use of O/W microemulsions, in which the precursor is an organometallic salt dissolved in the oil droplets of the microemulsion. The latter approach keeps more resemblance to the typical W/O microemulsion reaction method, as it has the greatest level of precursor confinement. © 2012 Elsevier Ltd.


Glossman-Mitnik D.,CIMAV
Procedia Computer Science | Year: 2013

The M06 family of density functionals has been assessed for the calculation of the molecular structure and properties of the Rhodamine B molecule. The chemical reactivity descriptors have been calculated through Conceptual DFT. The active sites for nucleophilic and electrophilic attacks have been chosen by relating them to the Fukui function indices and the dual descriptor f (2)(r). A comparison between the descriptors calculated through vertical energy values and those arising from the Koopmans' theorem approximation have been performed in order to check for the validity of the last procedure. © 2013 The Authors. Published by Elsevier B.V.


Garay-Tapia A.M.,CINVESTAV | Garay-Tapia A.M.,CIMAV | Romero A.H.,CINVESTAV | Barone V.,Central Michigan University
Journal of Chemical Theory and Computation | Year: 2012

We have studied Li adsorption on graphene for Li concentrations ranging from about 1% to 50% by means of density functional theory calculations. At low adsorbant densities, we observe a strong ionic interaction characterized by a substantial charge transfer from the adatoms to the substrate. In this low concentration regime, the electronic density around the Li adatoms is well localized and does not contribute to the electronic behavior in the vicinity of the Fermi level. For larger concentrations, we observe the formation of a chemically bound Li layer characterized by a stronger binding energy as well as a significant density of states above the Fermi level coming from both graphene and the two-dimensional Li sheet. © 2012 American Chemical Society.

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