Membranas inorgánicas e híbridas orgánico-inorgánicas para pilas de combustible de intercambio de protones

Tesis doctoral de la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química Inorgánica. Fecha de lectura: 26 de mayo de 200

Corrosion Protection of 304 Stainless Steel with Melting Gels Coatings

Methyl-substituted melting gels were used to coat AISI 304 stainless steel substrates. Crack-free coatings up to 1 mm in thickness were obtained. SEM micrographs of cross-sections con fi rm good adhesion to the surface. Samples were subjected to structural characterization using FT-IR, and Raman spectroscopy. Mechanical properties were investigated by micro-scratch tests. Electrochemical analyses (anodic polarization and electrochemical impedance spectroscopy) were performed in 3.5% NaCl solutions. Electrochemical tests show excellent performance of the coatings against corrosion with no sign of degradation after several months of immersion

29Si NMR and SAXS investigation of the hybrid organic-inorganic glasses obtained by consolidation of the melting gels

This study is focused on structural characterization of hybrid glasses obtained by consolidation of melting gels. The melting gels were prepared in molar ratios of methyltriethoxysilane (MTES) and dimethyldiethoxysilane (DMDES) of 75%MTES-25%DMDES and 65%MTES-35%DMDES. Following consolidation, the hybrid glasses were characterized using Raman, 29Si and 13C Nuclear Magnetic Resonance (NMR) spectroscopies, synchrotron Small Angle X-Ray Scattering (SAXS) and scanning electron microscopy (SEM). Raman spectroscopy revealed the presence of Si–C bonds in the hybrid glasses and 8-membered ring structures in the Si–O–Si network. Qualitative NMR spectroscopy identified the main molecular species, while quantitative NMR data showed that the ratio of trimers (T) to dimers (D) varied between 4.6 and 3.8. Two-dimensional 29Si NMR data were used to identify two distinct types of T3 environments. SAXS data showed that the glasses are homogeneous across the nm to micrometer length scales. The scattering cross section was one thousand times lower than what is expected when phase separation occurs. The SEM images show a uniform surface without defects, in agreement with the SAXS results, which further supports that the hybrid glasses are nonporous

Transparent Glass-Ceramics Produced by Sol-Gel: A Suitable Alternative for Photonic Materials

Transparent glass-ceramics have shown interesting optical properties for several photonic applications. In particular, compositions based on oxide glass matrices with fluoride crystals embedded inside, known as oxyfluoride glass-ceramics, have gained increasing interest in the last few decades. Melt-quenching is still the most used method to prepare these materials but sol-gel has been indicated as a suitable alternative. Many papers have been published since the end of the 1990s, when these materials were prepared by sol-gel for the first time, thus a review of the achievements obtained so far is necessary. In the first part of this paper, a review of transparent sol-gel glass-ceramics is made focusing mainly on oxyfluoride compositions. Many interesting optical results have been obtained but very little innovation of synthesis and processing is found with respect to pioneering papers published 20 years ago. In the second part we describe the improvements in synthesis and processing obtained by the authors during the last five years. The main achievements are the preparation of oxyfluoride glass-ceramics with a much higher fluoride crystal fraction, at least double that reported up to now, and the first synthesis of NaGdF4 glass-ceramics. Moreover, a new SiO2 precursor was introduced in the synthesis, allowing for a reduction in the treatment temperature and favoring hydroxyl group removal. Interesting optical properties demonstrated the incorporation of dopant ions in the fluoride crystals, thus obtaining crystal-like spectra along with higher efficiencies with respect to xerogels, and hence demonstrating that these materials are a suitable alternative for photonic applications.This work was supported by MINECO under projects MAT2013-48246-C2-1-P, MAT2013-48246-C2-2-P, and MAT2017-87035-C2-1-P/-2-P (AEI/FEDER, UE) and Basque Country Government IT-943-16 and PPG17/07. The authors are grateful for access to the Spanish Beamline (SpLine) at the ESRF facilities in Grenoble to perform experiments MA-3350 and 25-01-1014. Jose Joaquin Velazquez also acknowledges MINECO for Grant FPDI-2013-16895

Thickness-properties synergy in organic–inorganic consolidated melting-gel coatings for protection of 304 stainless steel in NaCl solutions

Homogeneous and crack-free methyl-substituted organic–inorganic hybrid glass coatings (thickness up to 10 μm) were deposited on AISI 304 stainless steel. Different hybrid glasses obtained fromconsolidation of the diluted melting gels with various methyltriethoxysilane (MTES)/dimethyldiethoxysilane (DMDES) ratios were evaluated considering chemical structure, coating adhesion and corrosion protection. The 70MTES/30DMDES (molar%) melting-gel coating provided improved corrosion protection for this steel due to the synergy of different properties: a highly cross-linked inorganic structure, a coating plasticity based on the hybrid network, and a good adhesion to the substrate through hydroxyl groups. Electrochemical results showa good barrier film with a passive range of 500 mV, a lowanodic current density (0.03 nA cm−2) and impedance values of 109.5Ωcm2 after two months of immersion in 3.5 wt.% NaCl solution

Electrochemical Properties of Melting Gel Coatings

Organic-inorganic melting gel coatings were applied to titanium alloy substrates to decrease their corrosion and extend their lifetime in an electrochemical application. Melting gels containing phenyl substitutions were coated onto the substrates. The ratio of diphenyl dimethoxysilane (DPhDMS) to methanol was varied to change the thickness of the coatings. The coatings were inspected visually to see that there is good adhesion between the coating and the substrate. Nanoindenter tests were performed to determine hardnes

ANALISIS PENGARUH MOTIVASI KERJA DAN FAKTOR KOGNISI PEKERJA TERHADAP KEMAMPUAN KERJA SERTA DAMPAKNYA TERHADAP PERFORMANSI KERJA (STUDI KASUS DI PT. SANKEN INDONESIA-BEKASI)

Makalah ini bertujuan untuk memperkirakan berapa besar pengaruh yang diberikan dari variabel Motivasi Kerja dan Kognisi Pekerja terhadap Kemampuan Kerja serta dampaknya terhadap Performansi di PT. SANKEN INDONESIA dengan menggunakan analisis jalur (Path Analysis), dengan tujuan menerangkan akibat langsung dan tidak langsung seperangkat variabel sebagai variabel penyebab (eksogenus) terhadap seperangkat variabel lainnya yang merupakan variabel akibat (endogenus). Berdasarkan pengolahan data dengan menggunakan analisis jalur menunjukkan bahwa pengaruh antara variabel Motivasi Kerja dan Kognisi Pekerja terhadap Kemampuan Kerja memberikan kontribusi sebesar 38 %, sedangkan faktor lain diluar variabel penelitian yang tidak teridentifikasi oleh model penelitian dan dapat mempengaruhi peningkatan serta penurunan Kemampuan Kerja adalah sebesar 62%. Sedangkan pengaruh antara variabel Motivasi Kerja (X1), Kognisi Pekerja (X2) dan Kemampuan Kerja (Y) terhadap Performansi Kerja (Z) adalah sebesar 56%, sedangkan faktor lain diluar variabel penelitian yang tidak teridentifikasi oleh model penelitian dan dapat mempengaruhi peningkatan serta penurunan Performansi Kerja (Z) adalah sebesar 44 %. Kata Kunci : Ergonomi Industri, Analisis Jalur, Faktor Kognisi, Ergonomi Kogniti

New direct alcohol and hydrogen fuel cells for naval and aeronautical applications (PILCONAER)

In the current context of demand for reliable, low cost and low environmental impact energy sources, many countries and companies are mostly focused on fuel cells (FC) in fields as transportation and stationary power generation and portable devices. Lately, FCs have begun to be applied in naval and aeronautical systems due to its high efficiency, low noise and environmental advantages. These applications could range from propulsion systems to auxiliary power units(APU). The main problems associated with the use of FCs in these areas are the current high cost due to the materials used, i.e. Nafion and Pt, the lack of durability testing in these specific conditions, security issues to flammability and high H2 pressures and low availability as a fuel, or the toxicity of methanol used as a fuel, and specific parameters such as weight in aircraft applications and volume in marine applications. Currently it is working on each of these issues, and at this point the ethanol as direct fuel is considered crucial. The use of ethanol as fuel has the advantage of easy transportation, storage and refueling, and is nontoxic. Bioethanol is a promising energy source, produced from raw materials containing sugar or starch. These raw materials exists in all parts of the world and is renewable, which involves the use of local energy sources contributing to the diversification of energy supply, reducing import dependence, increasing security of supply and generating new opportunities for agriculture. The main objective of the project is the development of low power stacks (stacks) fed with methanol (DMFC)and ethanol (DEFC) based on the development of new catalysts and membranes. PILCONAER aims contributing to the development of a sustainable use technology, further commitment to the restoration of the natural environment and biodiversity conservation

Blend Hybrid Solid Electrolytes Based on LiTFSI Doped Silica-Polyethylene Oxide for Lithium-Ion Batteries

Organic/inorganic hybrid membranes that are based on GTT (GPTMS-TMES-TPTE) system while using 3-Glycidoxypropyl-trimethoxysilane (GPTMS), Trimethyletoxisilane (TMES), and Trimethylolpropane triglycidyl ether (TPTE) as precursors have been obtained while using a combination of organic polymerization and sol-gel synthesis to be used as electrolytes in Li-ion batteries. Self-supported materials and thin-films solid hybrid electrolytes that were doped with Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were prepared. The hybrid network is based on highly cross-linked structures with high ionic conductivity. The dependency of the crosslinked hybrid structure and polymerization grade on ionic conductivity is studied. Ionic conductivity depends on triepoxy precursor (TPTE) and the accessibility of Li ions in the organic network, reaching a maximum ionic conductivity of 1.3 × 10−4 and 1.4 × 10−3 S cm−1 at room temperature and 60 °C, respectively. A wide electrochemical stability window in the range of 1.5–5 V facilitates its use as solid electrolytes in next-generation of Li-ion batteries