Este trabajo fue apoyado por el Departamento de Química y Wake Forest Wake Forest Centre de Energía, Medio Ambiente y Sostenibilidad (CEES). Agradecemos a Charles Mooney y el Fondo para Instrumentación Analítica de la Universidad Estatal de Carolina del Norte para obtener ayuda con imágenes SEM.

1. Preparación de pellets de xerogel <ol><li> gel de síntesis <ol><li> Añadir una barra de agitación magnética 25 mm y 113 ml de agua desionizada a un vaso de precipitados de 500 ml. Magnéticamente agitar el agua desionizada a la tasa más alta que no forma un vórtice. </li><li> Añadir lentamente 13,05 g (0,056 mol) de cloruro de circonio anhidro al agua desionizada en pequeños incrementos. Después de todo el cloruro de circonio anhidro se ha disuelto, añadir 53,29 g (0,296 mol) de glucosa a la solución. </li><li> Después de toda la glucosa se ha disuelto en la solución, añadir 3,73 g (0,01 mol) de hexahidrato de nitrato de itrio a la solución. Aumentar la tasa de agitación magnética a ~ 700 rpm y esperar a que todo el hexahidrato de nitrato de itrio de disolver en solución. </li><li> Añadir 42 ml de óxido de propileno a la solución. Continuar la agitación a ~ 700 rpm para el óxido de propileno para mezclar con la solución acuosa. Una vez que el óxido de propileno se mezcla con la solución acuosa (~ 10 s), disminuir la magnética t agitarO ~ 150 rpm. </li><li> Continuar agitando hasta que la barra de agitación magnética ha dejado de moverse debido a la formación del gel. El gel se forma típicamente a menos de 3 min. NOTAS: Adición de cloruro de circonio anhidro a agua desionizada es una reacción altamente exotérmica y el cloruro de circonio anhidro se plume si se añade demasiado rápidamente. La formulación proporcionada en la Sección 1.1. corresponde a una glucosa a los metales totales (circonio + itrio) relación molar de 4,5: 1. La sección de resultados representativo incluye datos para la glucosa a las relaciones de metales molar total de 0: 1, 2,25: 1, y 4,5: 1. La cantidad de glucosa en la formulación sólo está limitado por la solubilidad de la glucosa en la solución. Para referencia, la solubilidad máxima de la glucosa en agua a 20 ° C es 47,8% en peso. 15 </li></ol></li><li> El envejecimiento y el lavado del gel <ol><li> Estrechamente cubrir el vaso de precipitados que contiene el gel con Parafilm y se deja edad durante 24 h dejando el vaso de precipitados tapado a temperatura ambiente. </li><li> Retire la tapa del vaso de precipitados y decantar el líquido en la parte superior del gel. </li><li> Añadir 300 ml de etanol absoluto al vaso de precipitados que contiene el gel, fuertemente Cubrir el vaso con Parafilm, y dejar el vaso de precipitados cubierto a temperatura ambiente durante 24 h. </li><li> Repita el paso 1.2.3 dos veces más para un total de tres lavados de etanol durante un periodo total de 72 h. </li></ol></li><li> Secar el gel en un xerogel <ol><li> Retire el gel del vaso de precipitados y colocarlo en un plato de evaporación 2 L porcelana (24 cm fuera de la parte superior de diámetro) usando una espátula de laboratorio. </li><li> Romper el gel en aproximadamente 1 cm x 1 cm pedazos con una espátula y hacia fuera las piezas sobre la superficie de la cápsula de evaporación. </li><li> Deje que las piezas de gel se secan en condiciones ambiente durante una semana o hasta que el gel se seque. El gel se considera seco cuando se puede moler en un polvo fino. </li><li> Triturar todo el xerogel en un polvo fino con un mortero y mano de mortero. NOTA: Una vez que el gel se seque, esconsiderado un xerogel porque se secó en condiciones ambientales. </li></ol></li><li> Al pulsar el xerogel en un gránulo <ol><li> Colocar 1 g de polvo de xerogel en una matriz cilíndrica pellet de prensa con un diámetro de 13 mm. </li><li> Usando una prensa hidráulica, se aplican 22 kN de fuerza de 90 s para presionar el gel xerogel en un gránulo. </li><li> liberar lentamente la fuerza aplicada por la prensa. expulsar lentamente la pastilla fuera de la matriz de pellets y luego retirar cuidadosamente el sedimento. </li></ol></li></ol> 2. sinterización del xerogel de pellets en una atmósfera inerte <ol><li> Coloque el pellet xerogel sobre una alúmina o una placa de zirconia estabilizada con itria y cargar la placa en el centro de un horno de tubo. </li><li> Flujo de argón a una velocidad de un tercio del volumen del tubo de trabajo por minuto. Esto corresponde a una tasa de flujo de argón de 750 ml · min-1 para el tubo de trabajo utilizado en este trabajo. Vent la salida de gas a una campana de humos. </li><li> Flujo de argón durante al menos 15 min bntes de empezar a calentar el horno de tubo. </li><li> Mientras que fluye continuamente argón a una velocidad constante, el programa del controlador de temperatura horno de tubo con el siguiente programa de calentamiento: <ol><li> Mantenga a temperatura ambiente durante 15 min. </li><li> Calentar a 850 ° C a una velocidad de rampa de 5 ° C · min-1. </li><li> Calentar a la temperatura de sinterización deseada a una velocidad de rampa de 2 ° C · min-1. </li><li> Se mantiene a la temperatura de sinterización deseada durante 2 h. </li><li> Enfriar a 850 ° C a una velocidad de rampa de 2 ° C · min-1. </li><li> Enfriar a temperatura ambiente a una velocidad de rampa de 5 ° C · min-1. </li></ol></li><li> Iniciar el programa y de doble comprobación de que el horno de tubo está calentando siguiendo el esquema proporcionado en la sección 2.3. </li><li> Eliminar pellet desde el horno de tubo después de que el programa de calentamiento se ha completado. </li></ol> 3. Determinación de concentración de molde Carbon <ol><li> Cortar una pieza mg ~ 50 fuera de lapellet xerogel sinterizado con un cuchillo y se muele en un polvo fino con un mortero de ágata y mano de mortero. </li><li> Place ~ 50 mg del polvo fino en una copa de muestra de alúmina para el análisis termogravimétrico. </li><li> El uso de un analizador termogravimétrico (TGA), calentar la muestra a una velocidad de 10 ° C · min -1 desde temperatura ambiente hasta 1200 ° C, mientras que fluye aire sobre la muestra a una velocidad de 100 ml · min-1. </li><li> Calcular el porcentaje de cambio en el peso que se produce entre ~ 350 ° C y ~ 700 ° C. Este porcentaje en peso corresponde al contenido total de carbono en la muestra. NOTA: Si se produce un aumento de peso en el 350 ° C a 700 ° C gama, una fase de carburo se ha formado y el cálculo del contenido de carbono es más compleja. Para este caso, por favor refiérase a los cálculos descritos en la literatura. 14 Carbon análisis elemental se ha utilizado para confirmar que el contenido de carbono se puede calcular a partir de mediciones de TGA. </li></ol> 4. Preparación de alta Superficie YSZ Andamios de la eliminación de carbono plantilla <ol><li> Coloque el pellet xerogel sinterizado en un crisol de alúmina. </li><li> Colocar el crisol en un horno de caja a 700 ° C durante 2 h. </li><li> Retirar con cuidado el crisol caliente desde el horno de caja con pinzas de crisol de acero inoxidable y permitir que se enfríe a temperatura ambiente durante una hora antes de retirar el porosa, andamio YSZ blanco. </li></ol>

<ol>
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D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+highly+conductive+oxide+anode+for+solid+oxide+fuel+cells.">A highly conductive oxide anode for solid oxide fuel cells.</a> Electrochem. Solid-State Lett. 14 (1), B1-B5 (2011).</li><li>Vo, N. M., Gross, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+vanadium+deficiency+on+the+stability+of+Pd+and+Pt+catalysts+in+lanthanum+strontium+vanadate+solid+oxide+fuel+cell+anodes.">The effect of vanadium deficiency on the stability of Pd and Pt catalysts in lanthanum strontium vanadate solid oxide fuel cell anodes.</a> J. Electrochem. Soc. 159 (5), B641-B646 (2012).</li><li>Sholklapper, T. Z., Jacobson, C. P., Visco, S. J., De Jonghe, L. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+dispersed+and+contiguous+nanoparticles+in+solid+oxide+fuel+cell+electrodes.">Synthesis of dispersed and contiguous nanoparticles in solid oxide fuel cell electrodes.</a> Fuel Cells. 8 (5), 303-312 (2008).</li><li>Jiang, Z., Xia, C., Chen, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nano-structured+composite+cathodes+for+intermediate-temperature+solid+oxide+fuel+cells+via+an+infiltration/impregnation+technique.">Nano-structured composite cathodes for intermediate-temperature solid oxide fuel cells via an infiltration/impregnation technique.</a> Electrochim. Acta. 55 (11), 3595-3605 (2010).</li><li>Zhan, Z., Bierschenk, D. M., Cronin, J. S., Barnett, S. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+reduced+temperature+solid+oxide+fuel+cell+with+nanostructured+anodes.">A reduced temperature solid oxide fuel cell with nanostructured anodes.</a> Energy Environ. Sci. 4, 3951-3954 (2011).</li><li>Gross, M. D., Vohs, J. M., Gorte, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Recent+progress+in+SOFC+anodes+for+direct+utilization+of+hydrocarbons.">Recent progress in SOFC anodes for direct utilization of hydrocarbons.</a> J. Mater. Chem. 17, 3071-3077 (2007).</li><li>Gross, M. D., Carver, K. M., Deighan, M. A., Schenkel, A., Smith, B. M., Yee, A. Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Redox+stability+of+SrNbxTi1-xO3-YSZ+for+use+in+SOFC+anodes.">Redox stability of SrNbxTi1-xO3-YSZ for use in SOFC anodes.</a> J. Electrochem. Soc. 156 (4), B540-B545 (2009).</li><li>Savaniu, C. D., Irvine, J. T. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=La-doped+SrTiO3+as+anode+material+for+IT-SOFC.">La-doped SrTiO3 as anode material for IT-SOFC.</a> Solid State Ionics. 192 (1), 491-493 (2011).</li><li>Choi, S., Shin, J., Kim, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+electrochemical+and+thermodynamic+characterization+of+PrBaCo2-xFexO5+&#948;+(x=0,0.5,1)+infiltrated+into+yttria-stabilized+zirconia+scaffold+as+cathodes+for+solid+oxide+fuel+cells.">The electrochemical and thermodynamic characterization of PrBaCo2-xFexO5+&#948; (x=0,0.5,1) infiltrated into yttria-stabilized zirconia scaffold as cathodes for solid oxide fuel cells.</a> J. Power Sources. 201, 10-17 (2012).</li><li>Kungas, R., Kim, J. S., Vohs, J. M., Gorte, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Restructuring+porous+YSZ+by+treatment+in+hydrofluoric+acid+for+use+in+SOFC+cathodes.">Restructuring porous YSZ by treatment in hydrofluoric acid for use in SOFC cathodes.</a> J. Am. Ceram. Soc. 94 (7), 2220-2224 (2011).</li><li>Jung, W., Dereux, J. O., Chueh, W. C., Hao, Y., Haile, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+electrode+activity+of+nanostructured,+columnar+ceria+films+for+solid+oxide+fuel+cells.">High electrode activity of nanostructured, columnar ceria films for solid oxide fuel cells.</a> Energy Environ. Sci. 5, 8682-8689 (2012).</li><li>Cottam, M., Muhoza, S., Gross, M. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preserving+nanomorphology+in+YSZ+scaffolds+at+high+temperatures+via+in+situ+carbon+templating+of+hybrid+materials.">Preserving nanomorphology in YSZ scaffolds at high temperatures via in situ carbon templating of hybrid materials.</a> J. Amer. Ceram. Soc. 99 (8), 2625-2631 (2016).</li><li>Alves, L. A., Silva, J. B. A., Giulietti, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solubility+of+D-Glucose+in+Water+and+Ethanol/Water+Mixtures.">Solubility of D-Glucose in Water and Ethanol/Water Mixtures.</a> J. Chem. Eng. Data. 52, 2166-2170 (2007).</li><li>Thommes, M., Smarsly, B., Groenewolt, M., Ravikovitch, P. I., Neimark, A. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adsorption+hysteresis+of+nitrogen+and+argon+in+pore+networks+and+characterization+of+novel+micro-+and+mesoporous+silicas.">Adsorption hysteresis of nitrogen and argon in pore networks and characterization of novel micro- and mesoporous silicas.</a> Langmuir. 22, 756-764 (2006).</li><li>Chervin, C. N., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+non-alkoxide+sol-gel+method+for+the+preparation+of+homogeneous+nanocrystalline+powders+of+La0.85Sr0.15MnO3.">A non-alkoxide sol-gel method for the preparation of homogeneous nanocrystalline powders of La0.85Sr0.15MnO3.</a> Chem. Mater. 18, 1928-1937 (2006).</li><li>Clapsaddle, B. J., Sprehn, D. W., Gash, A. E., Satcher, J. H., Simpson, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+versatile+sol-gel+synthesis+route+to+metal-silicon+mixed+oxide+nanocomposites+that+contain+metal+oxides+as+a+major+phase.">A versatile sol-gel synthesis route to metal-silicon mixed oxide nanocomposites that contain metal oxides as a major phase.</a> J. Non-Crystalline Solids. 350, 173-181 (2004).</li><li>Gash, A. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Use+of+epoxides+in+the+sol-gel+synthesis+of+porous+iron+(III)+oxide+monoliths+from+Fe(III)+salts.">Use of epoxides in the sol-gel synthesis of porous iron (III) oxide monoliths from Fe(III) salts.</a> Chem. Mater. 13, 999-1007 (2001).</li></ol>

No tenemos nada que revelar.

Con este enfoque de plantillas de carbono in situ, se puede crear y preservar nanomorphology en-metálicos mixtos-óxidos a temperaturas tradicionales andamio de sinterización de cerámica. Las áreas superficiales resultantes son hasta 80 veces más alto que los andamios tradicionalmente sinterizados y hasta 4 veces más altos que los andamios fabricados por técnicas de deposición de complejos. 14 El sistema de gel de óxido de propileno-glucosa es muy flexible para el ajuste de la c...

La célula de combustible de óxido sólido (SOFC) es una gran promesa como una tecnología alternativa de conversión de energía para la generación eficiente de energía eléctrica limpia. Se ha hecho un progreso considerable 1 en la investigación y el desarrollo de esta tecnología; Sin embargo, las mejoras en el rendimiento del electrodo siguen siendo necesarios para lograr la comercialización fiable. El electrodo a menudo comprende un andamio de cerámica porosa con partículas electrocatalíticas decorados en la superficie del andamio. Un gran cuerpo de investigación se ha centrado en aumentar el área superficial de las partículas electrocatalíticas para aumentar el rendimiento, 2, 3, 4, 5, 6, 7, 8, pero hay muy poca investigación en el aumento de la superficie del andamio. El aumento de la superficie del andamiozona es difícil debido a que se sinterizan a altas temperaturas, 1100 ° C a 1500 ° C. Los andamios procesados por sinterización tradicional típicamente tienen un área de superficie específica de 0,1-1 m 2 · g -1. 8, 9, 10, 11 Hay unos pocos informes sobre el aumento de la superficie del andamio. En un caso, el área superficial de un andamio tradicionalmente sinterizado se mejoró por disolución y precipitación de la superficie de andamio utilizando ácido fluorhídrico, el logro de un área superficial específica de 2 m 2 · g -1. 12 En otra, las altas temperaturas se evitaron por completo mediante el uso de deposición por láser pulsado, el logro de un área de superficie específica de 20 m 2 · g -1. 13 La razón de ser del desarrollo de nuestra técnica era crear una fabricación de bajo costeproceso que proporciona áreas de superficie de andamio sin precedentes y utiliza temperaturas de sinterización tradicionales para que el proceso se puede adoptar fácilmente. Con la técnica informó aquí, áreas de superficie andamio de hasta 80 m 2 · g -1 se han demostrado mientras que se procesa a temperaturas de sinterización tradicionales. 14 Nuestra investigación está motivada principalmente por la ingeniería electrodo de SOFC, pero la técnica es más ampliamente aplicable a otros campos y aplicaciones. Generalmente, el método de plantillas de carbono in situ es un enfoque flexible que puede producir nanoestructurado, de metal mixto materiales cerámicos de alta área superficial en la forma de polvo o armazón poroso. Es flexible porque la composición cerámica-metal mixto, área superficial, porosidad y tamaño de poro se pueden todos ser sintonizado de manera sistemática. Las altas temperaturas son a menudo necesarios para formar la fase deseada en cerámica-metálicos mixtos, y este enfoque conserva nanomorphology cerámica while que permite a uno elegir esencialmente cualquier temperatura de procesamiento. Este método implica la síntesis de un gel a base de propileno-óxido inorgánico-orgánico híbrido, con una estequiometría bien definir de iones de metal y la proporción de inorgánico a contenido orgánico. El gel se seca en condiciones ambientales para formar un xerogel. El xerogel se sinteriza en una atmósfera de argón a la temperatura deseada. Tras el calentamiento, el componente orgánico se descompone dejando atrás una plantilla de carbono in situ, que se mantiene durante la duración de la sinterización. La plantilla de carbono se elimina posteriormente por oxidación a baja temperatura en el aire, resultando en una nanoestructurado, de alta área de superficie cerámica.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Zirconium (IV) chloride, 99.5+%</td>
			<td>Alfa Aesar</td>
			<td>12104</td>
			<td>Air sensitive</td>
		</tr>
		<tr>
			<td>Yttium (III) nitrate hexadydrate, 99.9%</td>
			<td>Alfa Aesar</td>
			<td>12898</td>
			<td>Oxidizer</td>
		</tr>
		<tr>
			<td>D+ Glucose Anhydrous, &#8805; 99.5%</td>
			<td>US Biological Life Sciences</td>
			<td>G3050</td>
			<td></td>
		</tr>
		<tr>
			<td>(&#177;)-Propylene Oxide, &#8805; 99%</td>
			<td>Sigma Aldrich</td>
			<td>110205</td>
			<td>Extremely flammable</td>
		</tr>
		<tr>
			<td>Ethanol 200 Proof</td>
			<td>Decon Laboratories, Inc.</td>
			<td>2716GEA</td>
			<td></td>
		</tr>
		<tr>
			<td>Argon, (99.997%)</td>
			<td>Airgas</td>
			<td>AR 300</td>
			<td>Industrial grade</td>
		</tr>
	</tbody>
</table>

high temperature fabrication of nanostructured yttria-stabilized-zirconia (ysz) scaffolds by in situ carbon templating xerogels

Demostramos un método para la fabricación de alta temperatura de poroso, nanoestructurado estabilizada con itria-zirconia (YSZ, 8% en moles de itria - 92% en moles de óxido de circonio) andamios con sintonizables áreas superficiales específicas de hasta 80 m 2 · g -1. Una solución acuosa de una sal de circonio, la sal de itrio, y la glucosa se mezcla con óxido de propileno (PO) para formar un gel. El gel se seca en condiciones ambientales para formar un xerogel. El xerogel se presiona en gránulos y después se sinteriza en una atmósfera de argón. Durante la sinterización, un YSZ formas fase cerámica y los componentes orgánicos se descomponen, dejando tras de carbono amorfo. El carbono formado in situ sirve como molde duro, la preservación de una nanomorphology área YSZ alta superficie a la temperatura de sinterización. El carbono se elimina posteriormente por oxidación en aire a baja temperatura, resultando en una poroso, andamio nanoestructurado YSZ. La concentración de la plantilla de carbono y el área final superficie andamio puede ser sistemáticaLy sintonizada variando la concentración de glucosa en la síntesis de gel. La concentración de molde de carbono se cuantificó mediante análisis termogravimétrico (TGA), la distribución de área superficial y tamaño de poro se determinó mediante mediciones de adsorción física, y la morfología se caracterizó usando microscopía electrónica de barrido (SEM). pureza de fase y tamaño de los cristalitos se determinó usando difracción de rayos X (XRD). Este enfoque de fabricación proporciona una novela, plataforma flexible para la realización de zonas de superficie de andamio sin precedentes y nanomorphologies para aplicaciones de conversión de energía electroquímica a base de cerámica, por ejemplo de células de combustible de óxido sólido (SOFC) electrodos.

Pureza de fase se confirmó por difracción de rayos X (XRD) como se informó anteriormente por Cottam et al. 14 YSZ andamio área superficial específica como una función de la concentración de plantilla de carbono se muestra en la Figura 1. La concentración se muestra como el porcentaje en volumen de sólidos totales en el sedimento xerogel sinterizado. La concentración de molde de carbono aumenta sistemáticamente con el aumento de...

Watch this Scientific Journal Video about High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels at JoVE.com

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

Se presenta un protocolo para la fabricación de andamios porosos, nanoestructurado estabilizada con itria-zirconia (YSZ) a temperaturas entre 1000 ° C y 1400 ° C.

Alta Fabrication Temperatura de-estabilizada con itria-óxido de circonio andamios nanoestructurados (YSZ) por<em&gt; In Situ</em&gt; carbono Templating xerogeles

We demonstrate a method for the high temperature fabrication of porous, nanostructured yttria-stabilized-zirconia (YSZ, 8 mol% yttria - 92 mol% zirconia) ...

high-temperature-fabrication-nanostructured-yttria-stabilized

Universidad San Sebastian

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JoVE Journal

Engineering

High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia (YSZ) Scaffolds by In Situ Carbon Templating Xerogels

10.5K vistas.  Wake Forest University.  Se presenta un protocolo para la fabricación de andamios porosos, nanoestructurado estabilizada con itria-zirconia (YSZ) a temperaturas entre 1000 ° C y 1400 ° C. 

Video: High Temperature Fabrication of Nanostructured Yttria-Stabilized-Zirconia YSZ Scaffolds by In Situ Carbon Templating Xerogels

Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. 
Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3.

We present methods for fabrication of patterned microstructures of vertically aligned carbon nanotubes (CNTs), and their use as master molds for production of polymer microstructures with organized nanoscale surface texture. The CNT forests are densified by condensation of solvent onto the substrate, which significantly increases their packing density and enables self-directed formation of 3D shapes.

Fabricación, densificación, y la réplica de Moldeo por inyección de microestructuras 3D nanotubos de carbono

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip ...

Investigación

Ingeniería

Fabrication of Silica Ultra High Quality Factor Microresonators

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the quality factor (Q) of the cavity, can be in excess of 500ns for cavities with Q factors above 100 million. As a result of their low material losses, silica microcavities have demonstrated some of the longest photon lifetimes to date1-2. Since a portion of the circulating light extends outside the resonator, these devices can also be used to probe the surroundings. This interaction has enabled numerous experiments in biology, such as single molecule biodetection and antibody-antigen kinetics, as well as discoveries in other fields, such as development of ultra-low-threshold microlasers, characterization of thin films, and cavity quantum electrodynamics studies.3-7
The two primary silica resonant cavity geometries are the microsphere and the microtoroid. Both devices rely on a carbon dioxide laser reflow step to achieve their ultra-high-Q factors (Q&gt;100 million).1-2,8-9 However, there are several notable differences between the two structures. Silica microspheres are free-standing, supported by a single optical fiber, whereas silica microtoroids can be fabricated on a silicon wafer in large arrays using a combination of lithography and etching steps. These differences influence which device is optimal for a given experiment.
Here, we present detailed fabrication protocols for both types of resonant cavities. While the fabrication of microsphere resonant cavities is fairly straightforward, the fabrication of microtoroid resonant cavities requires additional specialized equipment and facilities (cleanroom). Therefore, this additional requirement may also influence which device is selected for a given experiment.
Introduction
An optical resonator efficiently confines light at specific wavelengths, known as the resonant wavelengths of the device. 1-2 The common figure of merit for these optical resonators is the quality factor or Q. This term describes the photon lifetime (&tau;o) within the resonator, which is directly related to the resonator's optical losses. Therefore, an optical resonator with a high Q factor has low optical losses, long photon lifetimes, and very low photon decay rates (1/&tau;o). As a result of the long photon lifetimes, it is possible to build-up extremely large circulating optical field intensities in these devices. This very unique property has allowed these devices to be used as laser sources and integrated biosensors.10
A unique sub-class of resonators is the whispering gallery mode optical microcavity. In these devices, the light is confined in circular orbits at the periphery. Therefore, the field is not completely confined within the device, but evanesces into the environment. Whispering gallery mode optical cavities have demonstrated some of the highest quality factors of any optical resonant cavity to date.9,11 Therefore, these devices are used throughout science and engineering, including in fundamental physics studies and in telecommunications as well as in biodetection experiments. 3-7,12
Optical microcavities can be fabricated from a wide range of materials and in a wide variety of geometries. A few examples include silica and silicon microtoroids, silicon, silicon nitride, and silica microdisks, micropillars, and silica and polymer microrings.13-17 The range in quality factor (Q) varies as dramatically as the geometry. Although both geometry and high Q are important considerations in any field, in many applications, there is far greater leverage in boosting device performance through Q enhancement. Among the numerous options detailed previously, the silica microsphere and the silica microtoroid resonator have achieved some of the highest Q factors to date.1,9 Additionally, as a result of the extremely low optical loss of silica from the visible through the near-IR, both microspheres and microtoroids are able to maintain their Q factors over a wide range of testing wavelengths.18 Finally, because silica is inherently biocompatible, it is routinely used in biodetection experiments.
In addition to high material absorption, there are several other potential loss mechanisms, including surface roughness, radiation loss, and contamination loss.2 Through an optimization of the device size, it is possible to eliminate radiation losses, which arise from poor optical field confinement within the device. Similarly, by storing a device in an appropriately clean environment, contamination of the surface can be minimized. Therefore, in addition to material loss, surface scattering is the primary loss mechanism of concern.2,8
In silica devices, surface scattering is minimized by using a laser reflow technique, which melts the silica through surface tension induced reflow. While spherical optical resonators have been studied for many years, it is only with recent advances in fabrication technologies that researchers been able to fabricate high quality silica optical toroidal microresonators (Q&gt;100 million) on a silicon substrate, thus paving the way for integration with microfluidics.1
The present series of protocols details how to fabricate both silica microsphere and microtoroid resonant cavities. While silica microsphere resonant cavities are well-established, microtoroid resonant cavities were only recently invented.1 As many of the fundamental methods used to fabricate the microsphere are also used in the more complex microtoroid fabrication procedure, by including both in a single protocol it will enable researchers to more easily trouble-shoot their experiments.

We describe the use of a carbon dioxide laser reflow technique to fabricate silica resonant cavities, including free-standing microspheres and on-chip microtoroids. The reflow method removes surface imperfections, allowing long photon lifetimes within both devices. The resulting devices have ultra high quality factors, enabling applications ranging from telecommunications to biodetection.

La fabricación de sílice de alta calidad Ultra microresonators Factor

Whispering gallery resonant cavities confine light in circular orbits at their periphery.1-2 The photon storage lifetime in the cavity, quantified by the ...

Preparation and Reactivity of Gasless Nanostructured Energetic Materials

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the balls. Among other applications, it is a versatile technique that allows for effective preparation of gasless reactive nanostructured materials with high energy density per volume (Ni+Al, Ta+C, Ti+C). The structural transformations of reactive media, which take place during HEBM, define the reaction mechanism in the produced energetic&#160;composites. Varying the processing conditions permits fine tuning of the milling-induced microstructures of the fabricated composite particles. In turn, the reactivity, i.e., self-ignition temperature, ignition delay time, as well as reaction kinetics, of high energy density materials depends on its microstructure. Analysis of the milling-induced microstructures suggests that the formation of fresh oxygen-free intimate high surface area contacts between the reagents is responsible for the enhancement of their reactivity. This manifests itself in a reduction of ignition temperature and delay time, an increased rate of chemical reaction, and an overall decrease of the effective activation energy of the reaction. The protocol provides a detailed description for the preparation of reactive nanocomposites with tailored microstructure using short-term HEBM method. It also describes a high-speed thermal imaging technique to determine the ignition/combustion characteristics of the energetic materials. The protocol can be adapted to preparation and characterization of a variety of nanostructured energetic composites.

This protocol describes the preparation of gasless nanostructured energetic materials (Ni+Al, Ta+C, Ti+C) using the short-term high-energy ball milling (HEBM) technique. It also describes a high-speed thermal imaging method to study the reactivity of mechanically fabricated nanocomposites. These protocols can be extended to other reactive nanostructured energetic materials.

Preparación y reactividad de sin gas Nanoestructurados materiales energéticos

High-Energy Ball Milling (HEBM) is a ball milling process where a powder mixture placed in the ball mill is subjected to high-energy collisions from the ...

Fabrication of Low Temperature Carbon Nanotube Vertical Interconnects Compatible with Semiconductor Technology

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive thin-films. Due to the low growth temperature, the process allows integration with modern low-&#954; dielectrics and some flexible substrates. The process is compatible with standard semiconductor fabrication, and a method for the fabrication of electrical 4-point probe test structures for vertical interconnect test structures is presented. Using scanning electron microscopy the morphology of the CNT bundles is investigated, which demonstrates vertical alignment of the CNT and can be used to tune the CNT growth time. With Raman spectroscopy the crystallinity of the CNT is investigated. It was found that the CNT have many defects, due to the low growth temperature. The electrical current-voltage measurements of the test vertical interconnects displays a linear response, indicating good ohmic contact was achieved between the CNT bundle and the top and bottom metal electrodes. The obtained resistivities of the CNT bundle are among the average values in the literature, while a record-low CNT growth temperature was used.

A method for the growth of low temperature vertically-aligned carbon nanotubes, and the subsequent fabrication of vertical interconnect electrical test structures using semiconductor fabrication is presented.

Fabricación de Baja Temperatura de nanotubos de carbono Interconexiones verticales Compatible con la tecnología de semiconductores

We demonstrate a method for the low temperature growth (350 &#176;C) of vertically-aligned carbon nanotubes (CNT) bundles on electrically conductive ...

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices have used devices prepared by spin coating, a process that is not amenable to large-scale fabrication. This mismatch in device fabrication makes it difficult to translate quantitative results obtained in the laboratory to the commercial level, making optimization difficult. Using a mini-slot die coater, this mismatch can be resolved by translating the commercial process to the laboratory and characterizing the structure formation in the active layer of the device in real time and in situ as films are coated onto a substrate. The evolution of the morphology was characterized under different conditions, allowing us to propose a mechanism by which the structures form and grow. This mini-slot die coater offers a simple, convenient, material efficient route by which the morphology in the active layer can be optimized under industrially relevant conditions. The goal of this protocol is to show experimental details of how a solar cell device is fabricated using a mini-slot die coater and technical details of running in situ structure characterization using the mini-slot die coater.

Printing Fabrication of Bulk Heterojunction Solar Cells and In Situ Morphology Characterization

Here, we present a protocol to fabricate organic thin film solar cells using a mini-slot die coater and related in-line structure characterizations using synchrotron scattering techniques.

La fabricación de la impresión a granel heterounión células solares y<em&gt; In Situ</em&gt; Morfología Caracterización

Polymer-based materials hold promise as low-cost, flexible efficient photovoltaic devices. Most laboratory efforts to achieve high performance devices ...

Fabrication of 3D Carbon Microelectromechanical Systems (C-MEMS)

A wide range of carbon sources are available in nature, with a variety of micro-/nanostructure configurations. Here, a novel technique to fabricate long and hollow glassy carbon microfibers derived from human hairs is introduced. The long and hollow carbon structures were made by the pyrolysis of human hair at 900 &#176;C in a N2 atmosphere. The morphology and chemical composition of natural and pyrolyzed human hairs were investigated using scanning electron microscopy (SEM) and electron-dispersive X-ray spectroscopy (EDX), respectively, to estimate the physical and chemical changes due to pyrolysis. Raman spectroscopy was used to confirm the glassy nature of the carbon microstructures. Pyrolyzed hair carbon was introduced to modify screen-printed carbon electrodes ; the modified electrodes were then applied to the electrochemical sensing of dopamine and ascorbic acid. Sensing performance of the modified sensors was improved as compared to the unmodified sensors. To obtain the desired carbon structure design, carbon micro-/nanoelectromechanical system (C-MEMS/C-NEMS) technology was developed. The most common C-MEMS/C-NEMS fabrication process consists of two steps: (i) the patterning of a carbon-rich base material, such as a photosensitive polymer, using photolithography; and (ii) carbonization through the pyrolysis of the patterned polymer in an oxygen-free environment. The C-MEMS/NEMS process has been widely used to develop microelectronic devices for various applications, including in micro-batteries, supercapacitors, glucose sensors, gas sensors, fuel cells, and triboelectric nanogenerators. Here, recent developments of a high-aspect ratio solid and hollow carbon microstructures with SU8 photoresists are discussed. The structural shrinkage during pyrolysis was investigated using confocal microscopy and SEM. Raman spectroscopy was used to confirm the crystallinity of the structure, and the atomic percentage of the elements present in the material before and after pyrolysis was measured using EDX.

Fabrication of 3D Carbon Microelectromechanical Systems C-MEMS

Long and hollow glassy carbon microfibers were fabricated based on the pyrolysis of a natural product, human hair. The two fabrication steps of carbon microelectromechanical and carbon nanoelectromechanical systems, or C-MEMS and C-NEMS, are: (i) photolithography of a carbon-rich polymer precursor and (ii) pyrolysis of the patterned polymer precursor.

Fabricación de sistemas microelectromecánicos de carbono 3D (C-MEMS)

A wide range of carbon sources are available in nature, with a variety of micro-/nanostructure configurations. Here, a novel technique to fabricate long ...

Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of gamma rays created when neutrons interact with soil elements. The main parts of the INS system are a pulsed neutron generator, NaI(Tl) gamma detectors, split electronics to separate gamma spectra due to INS and thermo-neutron capture (TNC) processes, and software for gamma spectra acquisition and data processing. This method has several advantages over other methods in that it is a non-destructive in situ method that measures the average carbon content in large soil volumes, is negligibly impacted by local sharp changes in soil carbon, and can be used in stationary or scanning modes. The result of the INS method is the carbon content from a site with a footprint of ~2.5 - 3 m2 in the stationary regime, or the average carbon content of the traversed area in the scanning regime. The measurement range of the current INS system is &#62;1.5 carbon weight % (standard deviation &#177; 0.3 w%) in the upper 10 cm soil layer for a 1 hmeasurement.

Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures.

Mediciones de carbono del suelo por neutrón-Gamma análisis en estática y modos de exploración

The herein described application of the inelastic neutron scattering (INS) method for soil carbon analysis is based on the registration and analysis of ...

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic glasses (MGs). Despite their amorphous nature, the identification of hyperfine interactions unveils faint structural modifications. For this purpose, we have employed two techniques that utilize nuclear resonance among nuclear levels of a stable 57Fe isotope, namely M&#246;ssbauer spectrometry and nuclear forward scattering (NFS) of synchrotron radiation. The effects of heat treatment upon (Fe2.85Co1)77Mo8Cu1B14 MG are discussed using the results of ex situ and in situ experiments, respectively. As both methods are sensitive to hyperfine interactions, information on structural arrangement as well as on magnetic microstructure is readily available. M&#246;ssbauer spectrometry performed ex situ describes how the structural arrangement and magnetic microstructure appears at room temperature after the annealing under certain conditions (temperature, time), and thus this technique inspects steady states. On the other hand, NFS data are recorded in situ during dynamically changing temperature and NFS examines transient states. The use of both techniques provides complementary information. In general, they can be applied to any suitable system in which it is important to know its steady state but also transient states.

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Here, we present a protocol to describe ex situ and in situ investigations of structural transformations in metallic glasses. We employed nuclear-based analytical methods which inspect hyperfine interactions. We demonstrate the applicability of M&#246;ssbauer spectrometry and nuclear forward scattering of synchrotron radiation during temperature-driven experiments.

Métodos Ex Situ e In Situ las investigaciones de las transformaciones estructurales: el caso de la cristalización de vidrios metálicos

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic ...

Radio Frequency Magnetron Sputtering of GdBa2Cu3O7&#8722;&#948;/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 (STO) Single-crystal Substrates

Here, we demonstrate a method of coating ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on (001) SrTiO3 (STO) single-crystal substrates by radio frequency (RF) magnetron sputtering. LSMO nanoparticles were deposited with diameters from 10 to 20 nm and heights between 20 and 50 nm. At the same time, (Gd) Ba2Cu3O7&#8722;&#948; ((Gd) BCO) films were fabricated on both undecorated and LSMO nanoparticle decorated STO substrates using RF magnetron sputtering. This report also describes the properties of GdBa2Cu3O7&#8722;&#948;/ La0.67Sr0.33MnO3 quasi-bilayer films structures (e.g., crystalline phase, morphology, chemical composition); magnetization, magneto-transport, and superconducting transport properties were also evaluated.

Radio Frequency Magnetron Sputtering of GdBa2Cu3O7ÃƒÆ’Ã‚Â¢Ãƒâ€¹Ã¢â‚¬Â 'ÃƒÆ’Ã…Â½ Â´/ La0.67Sr0.33MnO3 Quasi-bilayer Films on SrTiO3 STO Single-crystal Substrates

Here, we present a protocol to grow LSMO nanoparticles and (Gd) BCO films on (001) SrTiO3 (STO) single-crystal substrates by radio frequency (RF)-sputtering.

Radio frecuencia de magnetrón Sputtering de GdBa2Cu3O7−δ/ La0.67Films Sr0.33MnO3 cuasi-bicapa sobre sustratos de monocristal SrTiO3 (STO)

Here, we demonstrate a method of coating ferromagnetic La0.67Sr0.33MnO3 (LSMO) nanoparticles on (001) SrTiO3 (STO) single-crystal substrates by radio ...

Hybrid Printing for the Fabrication of Smart Sensors

A method to combine additively manufactured substrates or foils and multilayer inkjet printing for the fabrication of sensor devices is presented. First, three substrates (acrylate, ceramics, and copper) are prepared. To determine the resulting material properties of these substrates, profilometer, contact angle, scanning electron microscope (SEM), and focused ion beam (FIB) measurements are done. The achievable printing resolution and suitable drop volume for each substrate are, then, found through the drop size tests. Then, layers of insulating and conductive ink are inkjet printed alternately to fabricate the target sensor structures. After each printing step, the respective layers are individually treated by photonic curing. The parameters used for the curing of each layer are adapted depending on the printed ink, as well as on the surface properties of the respective substrate. To confirm the resulting conductivity and to determine the quality of the printed surface, four-point probe and profilometer measurements are done. Finally, a measurement set-up and results achieved by such an all-printed sensor system are shown to demonstrate the achievable quality.

Here we present a protocol for the fabrication of inkjet-printed multilayer sensor structures on additively manufactured substrates and foil.

Híbrido de la impresión para la fabricación de sensores inteligentes

A method to combine additively manufactured substrates or foils and multilayer inkjet printing for the fabrication of sensor devices is presented. First, ...