Analysis of degradation process during the incorporation of ZrO2:SiO2 ceramic nanostructures intro polyurethane coatings for the corrosion protection of carbon steel

Three different molar ratios of ZrO2:SiO2 mixed oxides (25:75, 50:50, 75:25) were produced by the sol-gel technique and sintered at different temperatures (400, 600, 800, and 1000 °C) in order to analyze differenjces in mechanical and electrochemical properties of a wide variety of organic-inorganic hybrid coatings on AISI 1018 commercial carbon steel. For this purpose, 2, 4, and 6, wt% of the obtained ZrO2:SiO2 nanoparticles were incorporated to the polymeric matrix under vigorous stirring and spread on metallic substrates to reach between 40a and 55 um of dry film

Synthesis and Characterization of Poly(2-vinylpyridine) and Poly(4-vinylpyridine) with Metal Oxide (TiO2, ZnO) Films for the Photocatalytic Degradation of Methyl Orange and Benzoic Acid

In this study, composite material films of pyridine-based polymer and metal oxides (ZnO and TiO2) were successfully deposited by spin coating method for environmental remediation. Firstly, the polymers poly(2-vinylpyridine) P(2-VP), and poly(4-vinylpyridine) P(4-VP) were synthesized via solution polymerization. The analysis by grazing incidence X-ray diffraction (GIXRD) reveals semicrystalline nature and scanning electron microscopy (SEM) indicates that the poly(vinylpyridines) clusters of particles were observed on the surface of the films. It was also shown that the morphology of composite materials is completely dependent on the chemical nature of the oxide. In the case of P(2-VP)-TiO2 and P(4-VP)-TiO2, some channels or pathways of TiO2 on the surface of films were observed. However, the surface morphology of the polymer composites formulated with ZnO shows a homogeneous distribution in P(2-VP) and P(4-VP) matrix. The effectiveness of the composite materials in the photodegradation of methyl orange (MO) was evaluated by photocatalysis. According to the results, the P(4-VP)-ZnO composite exhibited the highest photodegradation of MO, allowing the separation of photogenerated species required for the photocatalytic reaction. The P(4-VP)-ZnO composite was also tested in benzoic acid (BA) photodegradation in water. The presence of some scavengers in the reaction system reveals that hydroxyl radicals (OH•), superoxide radicals (O2-•) and holes (h+) are responsible for the BA reduction by photocatalysis

Analysis of degradation process during the incorporation of ZrO 2:SiO2 ceramic nanostructures into polyurethane coatings for the corrosion protection of carbon steel

Three different molar ratios of ZrO2:SiO2 mixed oxides (25:75, 50:50, 75:25) were produced by the sol-gel technique and sintered at different temperatures (400, 600, 800, and 1000 C) in order to analyze differences in mechanical and electrochemical properties of a wide variety of organic-inorganic hybrid coatings on AISI 1018 commercial carbon steel. For this purpose, 2, 4, and 6 wt% of the obtained ZrO2:SiO2 nanoparticles were incorporated to the polymeric matrix under vigorous stirring and spread on metallic substrates to reach between 40 and 55 μm of dry film. Light microscopy, scanning electron microscopy, confocal laser scanning microscopy studies, atomic force microscopy, and nanoindentation tests were used to evaluate morphological, topographical, and mechanical properties; whereas atmospheric corrosion and electrochemical impedance spectroscopy (EIS) were performed using a 3 wt% NaCl medium in continuous immersion for 226 days. The crystallite size of the as-prepared ZrO2:SiO2 nanoparticles changed according to the sintering temperature from 4 to 9 nm. It was found that an adequate dispersion and homogeneity was achieved when 2 wt% of sintered ZrO2:SiO2 nanoparticles were mechanically mixed with polymer (MDI) to produce hybrid coatings on the metallic substrate. Free-bubble surface and hardness enhancement can be achieved by adding nanostructures assuming fact that the particles are capable of occupying the gas bubble sites. Atmospheric corrosion in the coatings without reinforced particles was more severe than that observed in hybrid coatings, and for these, corrosion was higher according to the increasing zirconia molar ratio. The EIS studies indicated that the synergetic effect between the organic-inorganic phases to seal the surface enhances the barrier properties on this metallic substrate. © 2012 Springer Science+Business Media, LLC

Improvement of adhesion and barrier properties of biomedical stainless steel by deposition of YSZ coatings using RF magnetron sputtering

The AISI 316L stainless steel (SS) has been widely used in both artificial knee and hip joints in biomedical applications. In the present study, yttria stabilized zirconia (YSZ, ZrO2 + 8% Y2O3) films were deposited on AISI 316L SS by radio-frequency magnetron sputtering using different power densities (50-250 W) and deposition times (30-120 min) from a YSZ target. The crystallographic orientation and surface morphology were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of the surface modification on the corrosion performance of AISI 316L SS were evaluated in phosphate buffered saline (PBS) solution using an electrochemical test on both the virgin and coated samples. The YSZ coatings have a (111) preferred orientation during crystal growth along the c-axis for short deposition times (30-60 min), whereas a polycrystalline structure forms during deposition times from 90 to 120 min. The corrosion protective character of the YSZ coatings depends on the crystal size and film thickness. A significant increase in adhesion and corrosion resistance by at least a factor of 46 and a higher breakdown potential were obtained for the deposited coatings at 200 W (120 min). © 2014 Elsevier Inc

Improvement of adhesion and barrier properties of biomedical stainless steel by deposition of YSZ coatings using RF magnetron sputtering

The AISI 316L stainless steel (SS) has been widely used in both artificial knee and hip joints in biomedical applications. In the present study, yttria stabilized zirconia (YSZ, ZrO2 + 8% Y2O3) films were deposited on AISI 316L SS by radio-frequency magnetron sputtering using different power densities (50-250 W) and deposition times (30-120 min) from a YSZ target. The crystallographic orientation and surface morphology were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The effects of the surface modification on the corrosion performance of AISI 316L SS were evaluated in phosphate buffered saline (PBS) solution using an electrochemical test on both the virgin and coated samples. The YSZ coatings have a (111) preferred orientation during crystal growth along the c-axis for short deposition times (30-60 min), whereas a polycrystalline structure forms during deposition times from 90 to 120 min. The corrosion protective character of the YSZ coatings depends on the crystal size and film thickness. A significant increase in adhesion and corrosion resistance by at least a factor of 46 and a higher breakdown potential were obtained for the deposited coatings at 200 W (120 min). © 2014 Elsevier Inc

Enhanced Naproxen Elimination in Water by Catalytic Ozonation Based on NiO Films

This study evaluates naproxen (NP) degradation efficiency by ozonation using nickel oxide films (NiO(F)) as a catalyst. The NiO films were synthesized by chemical vapor deposition and characterized by X-ray diffraction, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. NP degradation was conducted for 5 min using 10 films of NiO(F) comparing against ozonation using 100 mg/L NiO powder in suspension (NiO(S)) and conventional ozonation (O3-conv). Total organic carbon analysis demonstrated a mineralization degree of 12% with O3-conv, 35% with NiO as powder and 22% with NiO(F) after 60 min of reaction. The films of NiO(F) were sequentially used 4 times in ozonation demonstrating the stability of the synthesized material, as well as its properties as a catalyst for ozonation. A proposed modeling strategy using robust parametric identification techniques allows the comparison of NP decomposition pseudo-monomolecular reaction rates

Sponge cake microstructure, starch retrogradation and quality changes during frozen storage

The effect of frozen storage (6 months) on the microstructure (microscopy, flatbed scanning and image analysis), quality (texture, moisture and specific volume) and starch retrogradation of the cake crumb were evaluated. After 2 months of storage, texture (firmness, cohesiveness and resilience) was significantly (P < 0.05) affected and starch retrogradation was observed, while by the fourth month, the crystallinity increased and crumb fractures were noticeable. Additionally, the shrinkage of starch granules was observed as the starch circularity (Sc) values significantly decreased (P < 0.05) by the sixth month of storage. Although structural changes were not detected by image analysis, it was demonstrated that cake microstructure damage is related to physical changes because the Sc was significantly correlated (P < 0.05) with moisture and specific volume and therefore with the cake quality and texture. Moreover, sugar re-crystallisation occurred during frozen storage, and it was significantly correlated (P < 0.05) with the deterioration in cake quality.Fil: Díaz-Ramírez, Mayra. Universidad Autónoma Metropolitana; MéxicoFil: Calderón-Domínguez, Georgina. Instituto Politécnico Nacional; MéxicoFil: Salgado-Cruz, María de la Paz. Consejo Nacional de Ciencia y Tecnología; MéxicoFil: Chanona-Pérez, José J.. Instituto Politécnico Nacional; MéxicoFil: Andraca-Adame, José A.. Instituto Politécnico Nacional; MéxicoFil: Ribotta, Pablo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones en Bioquímica Clínica e Inmunología; Argentin

Thermal, Mechanical and UV-Shielding Properties of Poly(Methyl Methacrylate)/Cerium Dioxide Hybrid Systems Obtained by Melt Compounding

Thick and homogeneous hybrid film systems based on poly(methyl methacrylate) (PMMA) and CeO2 nanoparticles were synthesized using the melt compounding method to improve thermal stability, mechanical and UV-shielding properties, as well as to propose them for use in the multifunctional materials industry. The effect of the inorganic phase on these properties was assessed by using two different weight percentages of synthesized CeO2 nanoparticles (0.5 and 1.0 wt %) with the sol–gel method and thermal treatment at different temperatures (120, 235, 400, 600 and 800 °C). Thereafter, the nanoceria powders were added to the polymer matrix by single screw extrusion. The absorption in the UV region was increased with the crystallite size of the CeO2 nanoparticles and the PMMA/CeO2 weight ratio. Due to the crystallinity of CeO2 nanoparticles, the thermal, mechanical and UV-shielding properties of the PMMA matrix were improved. The presence of CeO2 nanostructures exerts an influence on the mobility of PMMA chain segments, leading to a different glass transition temperature