Del grafito al grafeno. El renacimiento de un clásico

Conferencia del Programa "Embajadores" del CENIMEl aislamiento de la lámina de grafeno, el material más delgado y resistente del mundo, por Geim y Novoselov en 2004, ha producido una auténtica revolución científica y mediática. Se espera que encuentre aplicación en campos tan diversos como el sector energético, electrónico, comunicaciones y salud, entre otros. Existen distintos procedimientos para la producción de grafeno que van directamente ligados al trinomio calidad-precio-cantidad. No obstante, más que de grafeno vamos a hablar de materiales grafénicos, dada la amplia variedad de materiales que se pueden obtener con una estructura próxima al grafeno. No todas las aplicaciones tienen el mismo grado de exigencia de perfección estructural ni demandan las mismas propiedades, de este modo, materiales grafénicos “más modestos” pueden ser producidos en grandes cantidades a precios competitivos y utilizados en campos que van desde el sector energético al de la salud. Dentro de este contexto, el grafito juega un papel extraordinariamente importante porque su utilización como materia prima permite la producción de grafeno y una amplia variedad de materiales grafénicos para un amplio rango de aplicaciones.N

Coal-Tar Pitch Utilization

Coal tar pitch has been traditionally used in the aluminium and graphite industry as a binder for anode and electrode manufacture. Further, coal-tar pitches have been studied as matrix precursors in carbon-carbon composites for carbon foam preparation and for energy storage carbons among others. The possibility of obtaining a wide range of carbon materials of different structure and properties,depending on the characteristics of the parent pitch, or even from the same pitch by simply changing the experimental conditions, makes pitch a very suitable product for the tailoring of carbon materials. Currently, improved coal-based pitches are in the process of being developed from tar fractions, such as anthracene-oil with no QI, with the aim of obtaining graphitic materials. This paper offers an overview of traditional uses of coal tar pitches, their main markets and their potential as carbon material precursors.Peer reviewe

Grafito y grafeno

págs.: 109-137Capítulo incluido en el libro: Desarrollo y aplicaciones de materiales avanzados de carbón. Miguel Ángel Álvarez Merino, Francisco Carrasco Marín, Francisco José Maldonado Hódar (Editores). Sevilla: Univeridad Internacional de Andalucía, 2014. ISBN: 978-84-7993-247-3. Enlace: http://hdl.handle.net/10334

Comparison of coal chars prepared in different devices at similar temperature

The characteristics of chars prepared in both a drop tube furnace (DTF) and a flat flame burner (FFB) at 1300 ºC from seven coals of different rank and maceral composition are the subject of this study. Coal samples sized and sieved to 36-75 μm were fed. The flame temperature of the FFB was achieved with a mixture of methane, air and oxygen whereas two different gas compositions were used in the DTF to account for sub-stoichiometric (2.5% O2) and close to stoichiometric (10% O2) oxygen levels. Determination of micropore surface area was carried out by CO2 adsorption isotherms at 0°C and char reactivity to air was measured at 550 °C in a thermogravimetric analyser (TGA). Overall similar combustion trends were obtained in both devices with burnout decreasing as coal rank increases and CO2 surface areas decreasing up to the medium volatile bituminous coal rank and increasing again for the anthracites. The results reveal a reasonable agreement between burnouts of FFB chars and low oxygen DTF chars whereas higher burnouts were obtained for higher oxygen DTF chars. The CO2 surface areas of the chars reasonably scattered without any systematic trend. The intrinsic reactivities of both series of chars from the DTF were similar to the corresponding FFB chars. Increasing coal rank, intrinsic reactivity of chars from the different combustion conditions decreased.The Principality of Asturias (Principado de Asturias), Project PC04-03 and the Ministry for Education (Ministerio de Educación), Project PSE2-2005Peer reviewe

High dielectric constant in Barium titanate-graphene composites around the percolation threshold

Resumen del trabajo presentado a la 14th International Conference of the European Ceramic Society, celebrada en Toledo (España) del 21 al 25 junio de 2015.Peer Reviewe

Supercapacitor modified with methylene blue as redox active electrolyte

MWCNT-based supercapacitors (SC) containing methylene blue (MB) as redox active electrolyte were studied. MWCNTs were employed as model of electrode active material due to their ideal double-layer behavior facilitates the investigation of the energy storage mechanisms involved. MB led to a cell capacitance enhancement equal to 4.5 times the original cell capacitance of MWCNTs in sulphuric acid with a capacitance reduction of only 12% after 6000 charge–discharge cycles. The potential evolution of each electrode during galvanostatic cycling revealed that MB redox reaction develops in both electrodes simultaneously in the voltage range of 0–0.104 V and that this is the main cause of cell capacitance enhancement. Beyond this voltage range, the Faradaic contribution from the MB redox reaction decreases because the anode behaves as a capacitative electrode with a rather reduced charge-capacity due to the small surface area of MWCNTs. By means of a modified assembly composed of a Nafion membrane and MB and sulfuric acid solutions located in the cathode and anode compartments, respectively, it was demonstrated the limiting role of the capacitative electrode in the cell charge-capacity in this type of hybrid devices.The authors acknowledge the financial support of the MICINN (Project MAT2010-20601-C02-01). Silvia Roldán thanks MICINN for a FPI predoctoral research grant.Peer reviewe

Evaluating capacitive deionization for water desalination by direct determination of chloride ions

Ionic conductivity and capacitance measurements are widely used methods for evaluating the desalination efficiency in capacity deionization processes. In this study, these methods are revised and several problems associated to them are identified and evaluated. Furthermore, a new method based on the determination of the chloride ion concentration by means of a chloride selective electrode is proposed as a more reliable alternative for evaluating the desalination performance in these systems. This method has been shown not only to be precise in a wide range of salt concentrations but also to be independent of pH, one of the main limitations of the determinations based on ionic conductivity measurements.The authors thank MICINN and the European Union (project MAT2010-20601-C02-01) for the financial support provided. Patricia Díaz thanks MICINN for a FPI predoctoral research grant (FPI: BES-2011-045394).Peer reviewe

Método de obtención de oxido de material pregrafítico, oxido de grafeno o grafeno a partir de materiales pregrafíticos y productos obtenidos por dicho método

Método de obtención de óxido de material pregrafítico, óxido de grafeno o grafeno a partir de materiales pregrafíticos y productos obtenidos por dicho método. Método de obtención de un producto seleccionado del grupo que consiste en óxido de material pregrafítico, óxido de grafeno y grafeno, caracterizado porque comprende transformar al menos un material pregrafítico en el producto sin tratamiento de grafitización. Preferiblemente, el material pregrafítico es coque (comercial o preparado a partir de breas, tanto de petróleo como de carbón o sintéticas)Peer reviewedConsejo Superior de Investigaciones CientíficasB1 Patente sin examen previ