Los autores agradecen a M. Leboeuf para obtener ayuda con el AFM Lee, W. para el maestro de aluminio texturado anódicamente y la Oficina Federal Suiza de Energía y la Swiss National Science Foundation para su financiación. Una parte de este trabajo se llevó a cabo en el marco del proyecto FP7 &quot;Fast Track&quot;, financiado por la CE en virtud del acuerdo de subvención no 283501.

1. Fabricación de Moldes Usamos nuestra instalación de fabricación casera nanoimpresión para la fabricación del molde Ref siguiente negativos. 6, pero cualquier configuración de nanoimpresión alternativa tendrán ningún problema. Alternativamente, un funcionalizado polidimetilsiloxano (PDMS) moho también podría funcionar. <ol><li> Fabricar o comprar un maestro de transporte adecuada el patrón de escala nanométrica para ser transferidos. En principio, cualquier maestro adecuado para nanoimpresión hará el trabajo. Usamos una textura capa de ZnO sobre una lámina de vidrio (Schott, AF32 eco, 41 mm x 41 mm x 0,5 mm) depositado como se describe en 3,1 como una estructura principal para ilustrar el método. </li><li> Aplicar una capa anti-adhesión sobre la estructura principal como se describe en 2. </li><li> Limpiar un naftalato de polietileno (PEN) hoja (Goodfellow, 82 mm x 41 mm x 0,125 mm) en un baño de acetona ultrasonidos durante 2 min seguido por un baño de ultrasonidos isopropanol durante 2 min más. Lavar una vez más con isopropanol y secar con nitrógeno. </li><li> Depósito de una capa bombardeada Cr adherencia (nm 5-10) en la hoja de PEN. </li><li> Spin-capa de la resina curable por UV (Microresist, Ormocer, 1-2 ml) en la hoja de PEN a 5.000 rpm para obtener una cobertura uniforme. </li><li> Realizar una precocido durante 5 min en una placa caliente a 80 ° C para evaporar el disolvente, mejorar la uniformidad de la película y la adherencia a la lámina de PEN. </li><li> Utilice la configuración de nanoimpresión para acabar con el modelo maestro en la resina de curado UV. Aunque no es obligatorio, realizamos hora bajo vacío para evitar inclusiones de burbujas mediante la aplicación de una presión homogénea de 1 bar a una membrana de silicona flexible. En nuestra configuración, la membrana de silicona separa la cámara de vacío en dos sub-compartimentos. La presión se genera por descompresión del compartimiento superior, mientras que el compartimiento inferior permanece bajo vacío. Ventilación empuja la membrana flexible hacia la parte inferior de iniciar el estampado. </li><li> Exponer la resina a la luz UV para provocar la reacción de reticulación de la resina. Aplicamos una luz moderadaintensidad de 1,4 mW / cm 2 en una longitud de onda de 365 nm proporcionados por varios LED. El tiempo de exposición a través de la hoja de PEN es típicamente 15-20 min. </li><li> Con cuidado, desmoldar manualmente pelar el molde de la estructura principal. </li><li> Como la resina puede someterse ligera contracción durante la deposición del material funcional, que puede conducir a la exfoliación espontánea, se realiza un secado suave mensaje térmico a 150 ° C durante 6-8 horas en un horno con atmósfera ambiente antes de su procesamiento posterior. </li></ol> 2. Capa antiadherente Para el éxito del desmoldeo, la capa anti-adhesión se debe adaptar a los materiales y la rugosidad patrón. En general, los patrones difíciles requieren bajos coeficientes de fricción. Bajos coeficientes que se pegan sobre los patrones lisos pueden conducir a la exfoliación del material funcional del molde. Altos coeficientes que se pegan sobre los patrones en bruto puede resultar en el desprendimiento de la resina de la hoja de PEN durante la fabricación del molde como la adherence de la resina para el maestro es más fuerte. <ol><li> Cubrir el molde (o maestro) con una capa de cromo pulverizado (nm 5-10) para promover la adhesión del agente anti-adherencia. Para los patrones lisos dejamos caer este paso. En algunos casos la capa de cromo puede evitar que el agente anti-adhesión para grabar la estructura principal. </li><li> Aplicar una pequeña gota de agente anti-adhesión (Sigma-Aldrich, (1H, 1H, 2H, 2H-Perfluoroctyl)-trichlorsilane) sobre un portaobjetos de vidrio. Coloque el portaobjetos de vidrio junto con el molde en una cámara de vacío y la bomba hacia abajo. El agente anti-adherencia se evapora y deposita como una monocapa molecular sobre el molde. </li><li> Anclar el agente anti-adhesión a través de recocido durante 1-2 horas a 80 ° C. </li></ol> 3. Material de deposición Se demuestra aquí tres técnicas de deposición adecuadas para la deposición de material para ilustrar la versatilidad de nanomoulding. Otras técnicas de deposición también puede ser aplicado. El tercer ejemplo se describe la faLUBRICAClON de un total de película delgada de células solares de silicio. <ol><li> La deposición química de vapor (CVD) de óxido de zinc: Ponga el molde sobre la placa de calentamiento del reactor ECV calentó a 180 ° C. Utilizar un marco de metal para evitar la flexión del molde PEN durante la deposición de ZnO. Cierre el reactor, la bomba y deje termalización. Admitir los gases precursores (H 2 O y (C 2 H 5) Zn 2). Además contamos dosis pequeñas cantidades de B 2 H 6 por dopaje. El espesor de la capa de ZnO es proporcional al tiempo de deposición. Utilizamos ZnO espesores de capa típicamente 1-5 micras. Los detalles sobre los parámetros de deposiciones típicas se pueden encontrar en la referencia. 7 </li><li> Deposición física de vapor (PVD) / pulverización catódica de plata: Poner el molde en el sistema de PVD. Cierre el sistema y la bomba hacia abajo. Admitir gas argón proceso. Encienda el generador de corriente continua. El espesor de la capa de Ag es de nuevo proporcional al tiempo de deposición. Usamos capa de Ag espesores de típicamente 1 m. P deposición típicaarameters son una presión de argón de 5.5x10 -3 mbar y una potencia DC configuración específica de 250 W dando una tasa de deposición de aproximadamente 45 nm / sec. </li><li> Mejorada por plasma deposición de vapor químico (PE-CVD): Depósito ZnO como en 3,1). Ponga el molde en el reactor PE-CVD se calentó a 200 ° C. Cierre el reactor, la bomba y deje termalización. Admitir los gases precursores (SiH 4 y H 2). Además hemos dosis pequeñas cantidades de B (CH 3) 3 y PH 3 para lograr dopaje p-y n-tipo, respectivamente. Para aumentar la tensión en circuito abierto de las células solares, también se utilizan pequeñas cantidades de CH 4 y CO 2 para las capas dopadas. Después de la deposición de la pila de células de silicio amorfo pin solar, depositaremos un backcontact ZnO como se describe en 3.1. </li><li> Evitar la flexión excesiva del molde, como la flexión podría causar el desprendimiento de la capa depositada. </li></ol> 4. La capa de transferencia Utilizamos glass de diapositivas (Schott eco AF32, 41 mm x 41 mm x 0,5 mm) como sustrato final. Pero otros sustratos, incluyendo láminas de metal o láminas de polímeros, podría ser utilizado alternativamente. <ol><li> Limpie las láminas de vidrio con acetona e isopropanol y secar con nitrógeno. </li><li> Spin-capa de resina curable por UV (Microresist, Ormocer, 1-2 ml) sobre el portaobjetos de vidrio a 5.000 rpm. </li><li> Utilice la configuración de nanoimpresión para anclar el molde llevando las capas depositadas sobre el sustrato final. Como para el estampado, realizamos anclaje al vacío mediante la aplicación de una presión homogénea de 1 bar. </li><li> Exponer la resina a la luz UV para provocar la reacción de reticulación. Se aplica una intensidad moderada de 1,4 mW / cm 2 en una longitud de onda de 365 nm proporcionados por varios LED. El tiempo de exposición a través de la lámina de vidrio es sólo 1-3 min debido a la mayor transmisión de UV de vidrio en comparación con PEN. </li><li> Desmoldeo por pelado manualmente el molde del portaobjetos de vidrio. </li></ol> 5. Ejemplo de Caracterización <ol&gt; <li> Use su favorito técnica morfológica, eléctrica u óptica para caracterizar las muestras nanomoulded. Aquí caracterizar nuestras muestras nanomoulded mediante microscopía electrónica de barrido (SEM) y microscopía de fuerza atómica (AFM). </li></ol>

<ol>
	<li>Geissler, M., Xia, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patterning:+Principles+and+Some+New+Developments.">Patterning: Principles and Some New Developments.</a> Advanced Materials. 16 (15), 1249-1269 (2004).</li><li>Guo, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nanoimprint+Lithography:+Methods+and+Material+Requirements.">Nanoimprint Lithography: Methods and Material Requirements.</a> Advanced Materials. 19, 495-513 (2007).</li><li>Ahn, S. H., Guo, L. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large-Area+Roll-to-Roll+and+Roll-to-Plate+Nanoimprint+Lithography:+A+Step+toward+High-Throughput.">Large-Area Roll-to-Roll and Roll-to-Plate Nanoimprint Lithography: A Step toward High-Throughput.</a> Application of Continuous Nanoimprinting. ACS Nano. 3 (8), 2304-2310 (2009).</li><li>Battaglia, C., Escarr&#233;, J., 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=Nanoimprint+Lithography+for+High-Efficiency+Thin-Film+Silicon+Solar+Cells.">Nanoimprint Lithography for High-Efficiency Thin-Film Silicon Solar Cells.</a> Nano Letters. 11, 661-665 (2011).</li><li>Battaglia, C., Escarr&#233;, J., 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=Nanomoulding+of+Transparent+Zinc+Oxide+Electrodes+for+Efficient+Light+Trapping+in+Solar+Cells.">Nanomoulding of Transparent Zinc Oxide Electrodes for Efficient Light Trapping in Solar Cells.</a> Nature Photonics. 5, 535-538 (2012).</li><li>Escarr&#233;, J., S&#246;derstr&#246;m, K., 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=High+Fidelity+Transfer+of+Nanometric+Random+Textures+by+UV+Embossing+for+Thin+Film+Solar+Cells+Applications.">High Fidelity Transfer of Nanometric Random Textures by UV Embossing for Thin Film Solar Cells Applications.</a> Solar Energy Materials &amp; Solar Cells. 95, 881-886 (2011).</li><li>Fa&#255;, S., Feitknecht, L., Schl&#252;chter, R., Kroll, U., Vallat-Sauvain, E., Shah, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rough+ZnO+layers+by+LP-CVD+process+and+their+effect+in+improving+performances+of+amorphous+and+microcrystalline+silicon+solar+cells.">Rough ZnO layers by LP-CVD process and their effect in improving performances of amorphous and microcrystalline silicon solar cells.</a> Solar Energy Materials and Solar Cells. 90, 2960-2967 (2006).</li><li>Zhao, X. -. M., Xia, Y., Whitesides, G. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+of+Three-Dimensional+Micro-Structures:+Microtransfer+Molding.">Fabrication of Three-Dimensional Micro-Structures: Microtransfer Molding.</a> Advanced Materials. 8, 837-840 (1996).</li><li>Hampton, M. J., Williams, S. S., 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=The+Patterning+of+Sub-500+nm+Inorganic+Oxide+Structures.">The Patterning of Sub-500 nm Inorganic Oxide Structures.</a> Advanced Materials. 20, 2667-2673 (2008).</li><li>Bass, J. D., Schaper, C. D., 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=Transfer+Molding+of+Nanoscale+Oxides+Using+Water-Soluble+Templates.">Transfer Molding of Nanoscale Oxides Using Water-Soluble Templates.</a> ACS Nano. 5 (5), 4065-4072 (2011).</li><li>Escarr&#233;, J., Nicolay, S., 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=Nanomoulded+front+ZnO+contacts+for+thin+film+silicon+solar+cell+applications.">Nanomoulded front ZnO contacts for thin film silicon solar cell applications.</a> , (2012).</li><li>Sontheimer, T., Rudigier-Voigt, E., Bockmeyer, M., Klimm, C., Schubert-Bischoff, P., Becker, C., Rech, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Large-area+fabrication+of+equidistant+free-standing+Si+crystals+on+nanoimprinted+glass.">Large-area fabrication of equidistant free-standing Si crystals on nanoimprinted glass.</a> Phys. Status Solidi. RRL. 5, 376-379 (2011).</li></ol>

No hay conflictos de interés declarado.

Nanomoulding permite la transferencia de nanopatterns arbitrarias en materiales funcionales. La comparación de los pasos de procesamiento individuales en la Figura 1 y 2 revela la estrecha relación entre nanomoulding y nanoimpresión. La principal diferencia entre nanomoulding y nanoimpresión es el paso adicional de material de deposición en la Figura 2e. El flujo de proceso restante es idéntica. Nanomoulding por lo tanto se puede realizar en cualquier configuraci?...

Nanoestampación ha adquirido una enorme importancia en muchos campos de la nanotecnología y las ciencias aplicadas. Generación de patrones es el primer paso y puede llevarse a cabo mediante enfoques desde arriba, como la litografía por haz de electrones o enfoques de abajo a arriba sobre la base de métodos de auto montaje, tales como la litografía de nanoesferas o de copolímero de bloque litografía 1. Tan importante como la generación de patrones es la replicación de patrones. Además de fotolitografía, nanoimpresión (Figura 1) ha surgido como una alternativa prometedora en particular adecuado para alto rendimiento de gran superficie patrones a nanoescala a bajo costo 2-4. Mientras que la fotolitografía requiere una máscara estampada, nanoimpresión se basa en una estructura maestro prefabricado. Transferencia del patrón desde el maestro se realiza con frecuencia en un termoplástico o un polímero curable por UV o térmicamente. Sin embargo, hay muchos casos, donde es deseable para transferir el patrón directamente sobre un material funcional. &lt;clase p = &quot;jove_content&quot;&gt; Aquí se describe un método de replicación basada en nanomoulding y capa de transferencia (Figura 2), que se presentó recientemente en la referencia. 5 para transferir patrones funcionales a nanoescala sobre electrodos de óxido de zinc. Nuestro método nanomoulding se puede implementar fácilmente si una configuración de nanoimpresión es disponible. Nanomoulding ofrece el potencial de ser generalizada a muchos otros materiales funcionales, pilas de materiales y dispositivos incluso completas, siempre que el material del molde se elige de manera que sea compatible con el proceso de deposición de material (es). Como ejemplo presentamos aquí nanomoulding de conductor transparente de óxido de zinc (ZnO) electrodos depositados por deposición química de vapor (CVD), que encuentran su aplicación para mejorar la retención de la luz en las células solares 5.

<table border="1"><tbody><tr><td> Nombre del reactivo </td><td> Empresa </td><td> Número de catálogo </td><td> Comentarios (opcional) </td></tr><tr><td> Nanoimpresión resina </td><td> Microresist </td><td> Ormostamp </td><td></td></tr><tr><td> (1H, 1H, 2H, 2H-Perfluoroctyl)-trichlorsilane, anti-adherencia agente </td><td> Sigma Aldrich </td><td> 448931-10G </td><td></td></tr><tr><td> Portaobjetos de vidrio </td><td> Schott </td><td> AF32 eco </td><td> 0,5 mm </td></tr><tr><td> Naftalato de polietileno (PEN) hojas </td><td> Goodfellow </td><td> ES361090 </td><td> 0,125 mm </td></tr><tr><td> (C 2 H 5) 2 Zn </td><td> Akzo Nobel </td><td></td><td></td></tr><tr><td> Ag sputter 4N objetivo </td><td> Heraeus </td><td> 81062165 </td><td></td></tr><tr><td> B 2 H 6, SiH 4, H 2, B (CH 3) 3, PH 3, CH 4, CO 2 </td><td> Messer </td><td></td><td></td></tr><tr><td></td><td></td><td></td><td> EQUIPO </td></tr><tr><td> Nanoimpresión sistema </td><td> Home-construido </td><td></td><td></td></tr><tr><td> LP-CVD sistema </td><td> Home-construido </td><td></td><td></td></tr><tr><td> PVD sistema </td><td> Leybold </td><td> Univex 450 B </td><td></td></tr><tr><td> PE-CVD reactor </td><td> Indeotec </td><td> Pulpo I </td><td></td></tr><tr><td> SEM </td><td> JEOL </td><td> JSM-7500 TFE </td><td></td></tr><tr><td> AFM </td><td> Instrumentos Digitales </td><td> Nanoscope 3100 </td><td></td></tr></tbody></table>

nanomoulding of functional materials, a versatile complementary pattern replication method to nanoimprinting

Se describe una técnica que permite nanomoulding bajo costo patrones a nanoescala de materiales funcionales, pilas de materiales y dispositivos completos. Nanomoulding combinada con la capa de transferencia permite la replicación de los patrones superficiales arbitrarias de una estructura maestro sobre el material funcional. Nanomoulding se puede realizar en cualquier configuración de nanoimpresión y se puede aplicar a una amplia gama de materiales y procesos de deposición. En particular, se demuestra la fabricación de electrodos transparentes estampadas de óxido de zinc para aplicaciones de captura de luz en las células solares.

<html> La figura 3 resume algunos ejemplos ilustrativos de estructuras nanomoulded. Una estructura maestra ZnO crecido por CVD sobre vidrio se muestra en (a). El correspondiente nanomoulded ZnO réplica se muestra en (d). La comparación de la altura local (g) y el ángulo (j) histogramas extraídos de imágenes de AFM revelan la alta fidelidad de la nanomoulding proceso. Análogos resultados se muestran para una rejilla unidimensional fabricado por litografía interferencia (b, e, h, k) y aluminio anód...

Watch this Scientific Journal Video about Nanomoulding of Functional Materials, a Versatile Complementary Pattern Replication Method to Nanoimprinting at JoVE.com

Nanomoulding of Functional Materials, a Versatile Complementary Pattern Replication Method to Nanoimprinting

Se describe una técnica que permite nanomoulding bajo costo patrones a nanoescala de materiales funcionales, pilas de materiales y dispositivos completos. Nanomoulding se puede realizar en cualquier configuración de nanoimpresión y se puede aplicar a una amplia gama de materiales y procesos de deposición.

Nanomoulding de Functional Materials, un versátil método complementario para la replicación de patrones para nanoimpresión

We describe a nanomoulding technique which  allows low-cost nanoscale patterning of functional materials, materials stacks  and full devices. Nanomoulding ...

nanomoulding-functional-materials-versatile-complementary-pattern

Research

JoVE Journal

Engineering

11.6K vistas.  Ecole Polytechnique Fédérale de Lausanne (EPFL). Se describe una técnica que permite nanomoulding bajo costo patrones a nanoescala de materiales funcionales, pilas de materiales y dispositivos completos. Nanomoulding se puede realizar en cualquier configuración de nanoimpresión y se puede aplicar a una amplia gama de materiales y procesos de deposición.

Video: Nanomoulding of Functional Materials, a Versatile Complementary Pattern Replication Method to Nanoimprinting

Using Neutron Spin Echo Resolved Grazing Incidence Scattering to Investigate Organic Solar Cell Materials

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped crystallites. Neutrons are passed through two well defined regions of magnetic field; one before and one after the sample. The two magnetic field regions have opposite polarity and are tuned such that neutrons travelling through both regions, without being perturbed, will undergo the same number of precessions in opposing directions. In this case the neutron precession in the second arm is said to &#34;echo&#34; the first, and the original polarization of the beam is preserved. If the neutron interacts with a sample and scatters elastically the path through the second arm is not the same as the first and the original polarization is not recovered. Depolarization of the neutron beam is a highly sensitive probe at very small angles (&#60;50&#160;&#956;rad) but still allows a high intensity, divergent beam to be used. The decrease in polarization of the beam reflected from the sample as compared to that from the reference sample can be directly related to structure within the sample.
In comparison to scattering observed in neutron reflection measurements the SERGIS signals are often weak and are unlikely to be observed if the in-plane structures within the sample under investigation are dilute, disordered, small in size and polydisperse or the neutron scattering contrast is low. Therefore, good results will most likely be obtained using the SERGIS technique if the sample being measured consist of thin films on a flat substrate and contain scattering features that contains a high density of moderately sized features (30 nm to 5 &#181;m) which scatter neutrons strongly or the features are arranged on a lattice. An advantage of the SERGIS technique is that it can probe structures in the plane of the sample.

Progress has been made in utilizing spin echo resolved grazing incidence scattering (SERGIS) as a neutron scattering technique to probe the length-scales in irregular samples. Crystallites of [6,6]-phenyl-C61-butyric acid methyl ester have been probed using the SERGIS technique and the results confirmed by optical and atomic force microscopy.

Uso de neutron spin echo resuelto grazing incidencia dispersión para investigar materiales orgánicos de células solares

The spin echo resolved grazing incidence scattering (SERGIS) technique has been used to probe the length-scales associated with irregularly shaped ...

Investigación

Ingeniería

Casting Protocols for the Production of Open Cell Aluminum Foams by the Replication Technique and the Effect on Porosity

Metal foams are interesting materials from both a fundamental understanding and practical applications point of view. Uses have been proposed, and in many cases validated experimentally, for light weight or impact energy absorbing structures, as high surface area heat exchangers or electrodes, as implants to the body, and many more. Although great progress has been made in understanding their structure-properties relationships, the large number of different processing techniques, each producing material with different characteristics and structure, means that understanding of the individual effects of all aspects of structure is not complete. The replication process, where molten metal is infiltrated between grains of a removable preform material, allows a markedly high degree of control and has been used to good effect to elucidate some of these relationships. Nevertheless, the process has many steps that are dependent on individual &#8220;know-how&#8221;, and this paper aims to provide a detailed description of all stages of one embodiment of this processing method, using materials and equipment that would be relatively easy to set up in a research environment. The goal of this protocol and its variants is to produce metal foams in an effective and simple way, giving the possibility to tailor the outcome of the samples by modifying certain steps within the process. By following this, open cell aluminum foams with pore sizes of 1&#8211;2.36 mm diameter and 61% to 77% porosity can be obtained.

Replication is one of the processing techniques used for the production of porous metal sponges. In this paper one implementation of the method for the production of open celled porous aluminum is shown in detail.

Casting Protocolos para la Producción de célula abierta de aluminio Espumas por la técnica de replicación y el efecto de la porosidad

Metal foams are interesting materials from both a fundamental understanding and practical applications point of view. Uses have been proposed, and in many ...

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 ...

Synthesis and Functionalization of 3D Nano-graphene Materials: Graphene Aerogels and Graphene Macro Assemblies

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. Additionally, most reported graphene assemblies are held together through physical interactions (e.g., van der Waals forces) rather than chemical bonds, which limit their mechanical strength and conductivity. This video method details recently developed strategies to fabricate mass-producible, graphene-based bulk materials derived from either polymer foams or single layer graphene oxide. These materials consist primarily of individual graphene sheets connected through covalently bound carbon linkers. They maintain the favorable properties of graphene such as high surface area and high electrical and thermal conductivity, combined with tunable pore morphology and exceptional mechanical strength and elasticity. This flexible synthetic method can be extended to the fabrication of polymer/carbon nanotube (CNT) and polymer/graphene oxide (GO) composite materials. Furthermore, additional post-synthetic functionalization with anthraquinone is described, which enables a dramatic increase in charge storage performance in supercapacitor applications.

This video method describes the synthesis of high surface area, monolithic 3D graphene-based materials derived from polymer precursors as well as single layer graphene oxide.

Síntesis y funcionalización de 3D Materiales Nano-grafeno: grafeno aerogeles y grafeno Asambleas Macro

Efforts to assemble graphene into three-dimensional monolithic structures have been hampered by the high cost and poor processability of graphene. ...

Advanced Experimental Methods for Low-temperature Magnetotransport Measurement of Novel Materials

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film synthesis) for the purpose of exploratory materials research. Certain materials pose a challenge wherein the traditional bulk Hall bar device fabrication method is insufficient to produce a measureable device for sample transport measurement, principally because the single crystal size is too small to attach wire leads to the sample in a Hall bar configuration. This can be, for example, because the first batch of a new material synthesized yields very small single crystals or because flakes of samples of one to very few monolayers are desired. In order to enable rapid characterization of materials that may be carried out in parallel with improvements to their growth methodology, a method of device fabrication for very small samples has been devised to permit the characterization of novel materials as soon as a preliminary batch has been produced. A slight variation of this methodology is applicable to producing devices using exfoliated samples of two-dimensional materials such as graphene, hexagonal boron nitride (hBN), and transition metal dichalcogenides (TMDs), as well as multilayer heterostructures of such materials. Here we present detailed protocols for the experimental device fabrication of fragments and flakes of novel materials with micron-sized dimensions onto substrate and subsequent measurement in a commercial superconducting magnet, dry helium close-cycle cryostat magnetotransport system at temperatures down to 0.300 K and magnetic fields up to 12 T.

We describe the methodology of mechanical exfoliation and deposition of flakes of novel materials with micron-sized dimensions onto substrate, fabrication of experimental device structures for transport experimentation, and the magnetotransport measurement in a dry helium close-cycle cryostat at temperatures down to 0.300 K and magnetic fields up to 12 T.

Avanzados métodos experimentales para baja temperatura magnetotransporte Medición de Nuevos Materiales

Novel electronic materials are often produced for the first time by synthesis processes that yield bulk crystals (in contrast to single crystal thin film ...

Standardized Method for Measuring Collection Efficiency from Wipe-sampling of Trace Explosives

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common procedure for collecting traces of explosives, and standardized measurements of collection efficiency are needed to evaluate and optimize sampling protocols. The approach described here is designed to provide this measurement infrastructure, and controls most of the factors known to be relevant to wipe-sampling. Three critical factors (the applied force, travel distance, and travel speed) are controlled using an automated device. Test surfaces are chosen based on similarity to the screening environment, and the wipes can be made from any material considered for use in wipe-sampling. Particle samples of the explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) are applied in a fixed location on the surface using a dry-transfer technique. The particle samples, recently developed to simulate residues made after handling explosives, are produced by inkjet printing of RDX solutions onto polytetrafluoroethylene (PTFE) substrates. Collection efficiency is measured by extracting collected explosive from the wipe, and then related to critical sampling factors and the selection of wipe material and test surface. These measurements are meant to guide the development of sampling protocols at screening venues, where speed and throughput are primary considerations.

Optimized sampling protocols and the development of new wipe materials can be facilitated by standardized measurements of collection efficiency from wipe-sampling. Our approach for sampling trace explosives uses an automated device to control speed, force, and distance during wipe-sampling followed by extraction of collected explosives.

Método normalizado para medir la eficiencia de colección Wipe-muestreo de trazas de explosivos

One of the limiting steps to detecting traces of explosives at screening venues is effective collection of the sample. Wipe-sampling is the most common ...

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and forging. Adoption of this technique is proceeding despite disagreement concerning the underlying mechanism responsible for EAD. The experimental procedure described herein enables a more explicit study compared to previous EAD research by removing thermal effects, which are responsible for disagreement in interpreting previous EAD results. Furthermore, as the procedure described here enables EAD observation in situ and in real time in a transmission electron microscope (TEM), it is superior to existing post-mortem methods that observe EAD effects post-test. Test samples consist of a single crystal copper (SCC) foil having a free-standing tensile test section of nanoscale thickness, fabricated using a combination of laser and ion beam milling. The SCC is mounted to an etched silicon base that provides mechanical support and electrical isolation while serving as a heat sink. Using this geometry, even at high current density (~3,500 A/mm2), the test section experiences a negligible temperature increase (&#60;0.02 &#176;C), thus eliminating Joule heating effects. Monitoring material deformation and identifying the corresponding changes to microstructures, e.g. dislocations, are accomplished by acquiring and analyzing a series of TEM images. Our sample preparation and in situ experiment procedures are robust and versatile as they can be readily utilized to test materials with different microstructures, e.g., single and polycrystalline copper.

A Novel Method for In Situ Electromechanical Characterization of Nanoscale Specimens

Isolating electrical and thermal effects on electrically assisted deformation (EAD) is very difficult using macroscopic samples. Metallic sample micro- and nanostructures together with a custom test procedure have been developed to evaluate the impact of applied current on the formation without joule heating and evolution of dislocations on these samples.

Un nuevo método para<em&gt; In Situ</em&gt; Caracterización electromecánica de especímenes de nanoescala

Electrically assisted deformation (EAD) is increasingly being used to improve the formability of metals during processes such as sheet metal rolling and ...

A Fabrication and Measurement Method for a Flexible Ferroelectric Element Based on Van Der Waals Heteroepitaxy

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on high-density data storage and low-power consumption capabilities. However, the high-quality oxide based nonvolatile memory on flexible substrates is often constrained by the material characteristics and the inevitable high-temperature fabrication process. In this paper, a protocol is proposed to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica. The versatile deposition technique and measurement method enable the fabrication of flexible yet single-crystalline non-volatile memory elements necessary for the next generation of smart devices.

In this paper, we present a protocol to directly grow an epitaxial yet flexible lead zirconium titanate memory element on muscovite mica.

Una fabricación y método de medición de un elemento ferroeléctrico Flexible basado en heteroepitaxias de Van Der Waals

Flexible non-volatile memories have received much attention as they are applicable for portable smart electronic device in the future, relying on ...

Multiscale Structures Aggregated by Imprinted Nanofibers for Functional Surfaces

Multiscale surface structures have attracted increasing interest owing to several potential applications in surface devices. However, an existing challenge in the field is the fabrication of hybrid micro-nano structures using a facile, cost-effective, and high-throughput method. To overcome these challenges, this paper proposes a protocol to fabricate multiscale structures using only an imprint process with an anodic aluminum oxide (AAO) filter and an evaporative self-aggregation process of nanofibers. Unlike previous attempts that have aimed to straighten nanofibers, we demonstrate a unique fabrication method for multiscale aggregated nanofibers with high aspect ratios. Furthermore, the surface morphology and wettability of these structures on various liquids were investigated to facilitate their use in multifunctional surfaces.

Presented is an easy method to fabricate nano-micro multiscale structures, for functional surfaces, by aggregating nanofibers fabricated using an anodic aluminum oxide filter.

Multiescala estructuras agregadas por nanofibras impreso para superficies funcionales

Multiscale surface structures have attracted increasing interest owing to several potential applications in surface devices. However, an existing ...

Studying Large Amplitude Oscillatory Shear Response of Soft Materials

We investigate the sequence of physical processes exhibited during large amplitude oscillatory shearing (LAOS) of polyethylene oxide (PEO) in dimethyl sulfoxide (DMSO) and xanthan gum in water &#8212; two concentrated polymer solutions used as viscosifiers in foods, enhanced oil recovery, and soil remediation. Understanding the nonlinear rheological behavior of soft materials is important in the design and controlled manufacturing of many consumer products. It is shown how the response to LAOS of these polymer solutions can be interpreted in terms of a clear transition from linear viscoelasticity to viscoplastic deformation and back again during a period. The LAOS results are analyzed via the fully quantitative Sequence of Physical Processes (SPP) technique, using free MATLAB-based software. A detailed protocol of performing a LAOS measurement with a commercial rheometer, analyzing nonlinear stress responses with the freeware, and interpreting physical processes under LAOS is presented. It is further shown that, within the SPP framework, a LAOS response contains information regarding the linear viscoelasticity, the transient flow curves, and the critical strain responsible for the onset of nonlinearity.

We present a detailed protocol outlining how to perform nonlinear oscillatory shear rheology on soft materials, and how to run the SPP-LAOS analysis to understand the responses as a sequence of physical processes.

Estudio de respuesta de cizalla oscilatoria de amplitud grande de materiales blandos

We investigate the sequence of physical processes exhibited during large amplitude oscillatory shearing (LAOS) of polyethylene oxide (PEO) in dimethyl ...