Thesis ESTUDIO DE MÉTODOS ALTERNATIVOS DE PRODUCCIÓN DE GRAFENO
Date
2018
Authors
ORELLANA GOMEZ, CHRISTIAN ANTONIO
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Abstract
El grafeno es un material cristalino bidimensional, formado por una mono capa de átomos de carbono en una estructura tipo panal de abeja. Fue aislada por primera vez el año 2004 [1] y desde entonces ha llamado la atención de la comunidad científica por sus excepcionales propiedades físicas y químicas. Ellas han inspirado el desarrollo de aplicaciones en una amplia gama de campos no obstante, la adopción del grafeno en la sociedad dependerá en gran medida de encontrar métodos de producción eficientes, escalables y seguros. En virtud de lo anterior la presente tesis se centró en el estudio de métodos alternativos a los tradicionales para la producción de grafeno, en especial en aquellos con alto potencial de escalabilidad. Específicamente se exploró el uso del método de llama, dado que ha demostrado resultados sobresalientes en las síntesis de otras nano-estructuras, sin embargo en la producción de grafeno aún quedan desafíos por abordar. Se estudió sistemáticamente el crecimiento de material grafítico a través del método de llama de difusión inversa. A partir de este estudio se desarrolló una nueva vía de crecimiento de grafeno sobre láminas de cobre, esta vez basado en la deposición de vapores químicos a presión atmosférica (AP-CVD), empleando metano como gas precursor. El nuevo método de síntesis se desarrolla en condiciones extremadamente desfavorables para el crecimiento de grafeno, tales como cámara abierta y sin la adición de hidrógeno, gas imprescindible para el crecimiento de grafeno por AP-CVD, como agente reductor y co-catalizador. Esto se consiguió a través de una novedosa configuración del substrato el cual está constituido por dos láminas cobres paralelas y separadas por cierta distancia. En ellas se descompone el metano presente, cuando son calentadas vía inducción electromagnética a una temperatura cercana a los 1000 °C. Las especies de la descomposición, específicamente hidrógeno, se enriquece en la zona entre las láminas, debido a termo difusión o efecto Soret. Considerando el fuerte gradiente térmico entre los sustratos y la cámara, y la ingente diferencia en masas de los componentes gaseosos. Ello resulta en la presencia hidrógeno en cantidades suficientes para reducir el óxido nativo de la superficie del cobre e inhibir la acción de especies oxidativas, siempre presentes en la cámara, lográndose así el crecimiento de grafeno en las caras internas de estas láminas. Con el nuevo método, se reducen los costos de síntesis y los riesgos en la manipulación de hidrógeno gaseoso altamente explosivo. En conclusión, se facilita la producción de grafeno a nivel industrial. Como resultado de esta investigación se ha presentado una solicitud de patente de inversión para el método/sistema desarrollado en la presente tesis, en el Instituto de propiedad industrial (INAPI). Adicionalmente parte de los resultados experimentales derivados de este trabajo se presentaron en la revista internacional Aip Advances, bajo el título "Single step vacuum-free and hydrogen-free synthesis of graphene".
Graphene is a two-dimensional crystalline material, formed by a mono layer of carbon atoms in a honeycombed structure. It was isolated for the first time in 2004 and since then it has attracted the attention of the scientific community for its exceptional physical and chemical properties. It has inspired the development of applications in a wide range of fields, however, the wider adoption of graphene in our society will depend to a great extent on finding efficient, scalable and safe production methods. By virtue of the above, this thesis is focused on the study of alternative methods for the production of graphene, especially those with high scalability potential.Specifically we have explored the use of the flame method, since it has shown outstanding results in the synthesis of other nano-structures, however, the production of graphene are still presents challenges to be addressed. The growth of graphitic material was studied systematically through the reverse diffusion flame method. From this study, a new path of graphene growth on copper sheets was developed, this time based on the deposition of chemical vapors at atmospheric pressure (AP-CVD), using methane as the precursor gas. The new synthesis method proceeds under extremely unfavorable conditions for the growth of graphene. It takes place in an open reactor with no hydrogen gas added during synthesis. This is different to standard CVD, in which hydrogen is an essential gas for the growth of graphene, both as reducing agent and co-catalyst. This peculiar result was achieved through a novel substrate configuration, constituted by two parallel copper sheets separated by a few mm. Between these sheets, heated by electromagnetic induction, methane is decomposed at a temperature close to 1000 ° C. The species of decomposition, specifically hydrogen, is enriched in the area between the sheets, due to thermo-diffusion or Soret effect. This phenomenon is important due to the strong thermal gradient between the substrates and the surrounding chamber and the enormous difference in masses of the gaseous components. This results in the presence of hydrogen in sufficient quantities to reduce the native oxide of the copper surface and inhibit the action of oxidative species, always present in the chamber. Graphene growth is achieved only in the internal faces of the Cu sheets. With the new method, the costs of synthesis and the risks in the handling of highly explosive hydrogen gas are reduced. In conclusion, the production of graphene at an industrial level is facilitated. As a result of this investigation, a patent application for the method / system developed in this thesis was presented to the Industrial Property Institute, Chile (INAPI). Additionally, part of the experimental results derived from this work were published by the international journal Aip Advances, under the title "Single step vacuum-free and hydrogen-free synthesis of graphene".
Graphene is a two-dimensional crystalline material, formed by a mono layer of carbon atoms in a honeycombed structure. It was isolated for the first time in 2004 and since then it has attracted the attention of the scientific community for its exceptional physical and chemical properties. It has inspired the development of applications in a wide range of fields, however, the wider adoption of graphene in our society will depend to a great extent on finding efficient, scalable and safe production methods. By virtue of the above, this thesis is focused on the study of alternative methods for the production of graphene, especially those with high scalability potential.Specifically we have explored the use of the flame method, since it has shown outstanding results in the synthesis of other nano-structures, however, the production of graphene are still presents challenges to be addressed. The growth of graphitic material was studied systematically through the reverse diffusion flame method. From this study, a new path of graphene growth on copper sheets was developed, this time based on the deposition of chemical vapors at atmospheric pressure (AP-CVD), using methane as the precursor gas. The new synthesis method proceeds under extremely unfavorable conditions for the growth of graphene. It takes place in an open reactor with no hydrogen gas added during synthesis. This is different to standard CVD, in which hydrogen is an essential gas for the growth of graphene, both as reducing agent and co-catalyst. This peculiar result was achieved through a novel substrate configuration, constituted by two parallel copper sheets separated by a few mm. Between these sheets, heated by electromagnetic induction, methane is decomposed at a temperature close to 1000 ° C. The species of decomposition, specifically hydrogen, is enriched in the area between the sheets, due to thermo-diffusion or Soret effect. This phenomenon is important due to the strong thermal gradient between the substrates and the surrounding chamber and the enormous difference in masses of the gaseous components. This results in the presence of hydrogen in sufficient quantities to reduce the native oxide of the copper surface and inhibit the action of oxidative species, always present in the chamber. Graphene growth is achieved only in the internal faces of the Cu sheets. With the new method, the costs of synthesis and the risks in the handling of highly explosive hydrogen gas are reduced. In conclusion, the production of graphene at an industrial level is facilitated. As a result of this investigation, a patent application for the method / system developed in this thesis was presented to the Industrial Property Institute, Chile (INAPI). Additionally, part of the experimental results derived from this work were published by the international journal Aip Advances, under the title "Single step vacuum-free and hydrogen-free synthesis of graphene".
Description
Catalogado desde la version PDF de la tesis.
Keywords
CVD , DISPOSICION DE VAPORES QUIMICOS , GRAFENO