Carbon nanofibers (CNFs) show a high electrical conductivity but a reduced specific surface area that limits their use as electrode materials for supercapacitors. In this work, amorphous CNFs, with a relatively high electrical conductivity are easily activated in KOH, using certain KOH/CNF weight ratios. Activation does not produce any important change in the shape, surface roughness, diameter, graphene sheet size, and electrical conductivity of starting nanofibers. However, activation leads to new micropores and larger surface areas as well as a higher content of basic oxygen groups. They clearly enhanced the specific capacitance, attaining values higher than those reported for other activated CNFs. In this study, the effects of micropore size and oxygen content on the specific capacitance are discussed for three electrolytes: H 2 SO 4 , KOH, and (CH 3 CH 2 ) 4 NBF 4 . Moreover, a good cycle life is found for the most activated CNFs.

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The purpose of this study has been to advance in knowledge of the chemical composition, structure and thickness of the thin native oxide film formed spontaneously in contact with the laboratory atmosphere on the surface of freshly polished commercial AZ31 and AZ61 alloys with a view to furthering the understanding of protection mechanisms. For comparative purposes, and to more fully describe the behaviour of the native oxide film, the external oxide films formed as a result of the manufacturing process (as-received condition) have been characterised. The technique applied in this research to study the thin oxide films (thickness of just a few nanometres) present on the surface of the alloys has basically been XPS (X-ray photoelectron spectroscopy) in combination with ion sputtering. Corrosion properties of the alloys were studied 2 in 0.6M NaCl by measuring charge transfer resistance values, which are deduced from EIS (electrochemical impedance spectroscopy) measurements after 1 hour of exposure. Alloy AZ61 generally showed better corrosion resistance than AZ31, and the freshly polished alloys showed better corrosion resistance than the alloys in as-received condition. This is attributed to a combination of (1) higher thickness of the native oxide film on the AZ61 alloy and (2) greater uniformity of the oxide film in the polished condition. The formation of an additional oxide layer composed by a mixture of spinel (MgAl 2 O 4) and MgO seems to diminish the protective properties of the passive layer on the surface of the alloys in as-received condition.

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El Hadad, Amir A., et al. Preparation of sol-gel hybrid materials from gammamethacryloxypropyltrimethoxysilane and tetramethyl orthosilicate: study of the hydrolysis and condensation reactions. Colloid and Polymer Science, 2011, 289(17-18) Si NMR spectroscopy. The hydrolysis of the prepared sol was also evaluated by liquid state 13 C NMR spectroscopy. The results indicated that under the adopted synthesis strategy conditions, the hydrolysis process require four hours to be completed.

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