Publication: Synthesis of carbon nanomaterials by catalytic chemical vapor deposition: growth mechanisms on metal powders and foils
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2017-01
Defense date
2017-01-13
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Abstract
Actualmente, las excelentes propiedades proporcionadas a escala nanométrica por los nanomateriales de carbono, como nanotubos y grafeno, motivan la propuesta teórica de un gran número de aplicaciones. Estos nanomateriales se pueden producir por deposición química en fase vapor (CVD), que consiste en la descomposición térmica de hidrocarburos sobre catalizadores metálicos. La técnica de CVD permite, a través del control de las condiciones de síntesis y la composición y morfología del catalizador, la producción controlada de estructuras altamente organizadas como nanotubos de carbono verticalmente alineados o formando una fibra continua, así como películas de un único átomo de espesor. Sin embargo, la producción de catalizadores altamente controlados requiere técnicas de alto coste y difícilmente escalables a nivel industrial. Una alternativa es la síntesis directa y de bajo coste empleando catalizadores metálicos comerciales en forma de polvo o placa para la producción de nanomateriales de diferentes morfologías y cristalinidades. A pesar de que esta alternativa ya se ha demostrado con anterioridad, la mayoría del trabajo experimental publicado se centra en la caracterización del carbono producido, y existe una necesidad de estudios experimentales enfocados en el mecanismo de crecimiento de nano-estructuras sobre estos catalizadores. En este trabajo, se presenta el uso de polvos metálicos de base níquel y de placas de acero y cobre, como catalizadores de bajo coste para la producción de nanomateriales de carbono por la técnica de CVD. Se demuestra la obtención de nanofibras, nanotubos verticalmente alineados y películas delgadas, así como los mecanismos de crecimiento en cada una de los catalizadores empleados. Finalmente, se demuestra un proceso de producción de películas poliméricas compuestas de películas delgadas de carbono amorfo con alto potencial de escalado industrial, lo que amplía la lista de carbonos nano-estructurados disponibles con potencial uso como superficies multifuncionales.
Carbon nanomaterials such as carbon nanotubes (CNTs) or monolayer graphene are proposed for a wide variety of theoretical applications due to the superior properties provided at the nanoscale. They can be produced by chemical vapor deposition (CVD), which consists on the thermal decomposition of hydrocarbons over metal catalysts. Highly ordered structures like CNTs arrays and fibres as well as large-area monolayer graphene films can be grown in a highly controlled manner at laboratory scale by selecting the proper CVD conditions, the metal catalyst composition and morphology. However, the highly controlled catalysts needed for their synthesis are currently produced by expensive techniques which are hard to scale. Alternatively, the use of commercially available bulk metal catalysts like powders, foils and meshes are shown to be a fast and low cost approach for the production of carbon nanomaterials with several morphologies and crystallinities. This alternative is already demonstrated in the literature, however most of the experimental work on synthesis on bulk metals focuses on the carbon produced, and there is a need of experimental work focused on growth mechanisms of carbon nanomaterials on these metal catalysts. We used nickel-based powders and stainless steel and copper foils for the production of carbon fibres, nanofibres, CNTs arrays and thin films by CVD, providing supported explanations on the carbon nanostructure growth mechanisms. Highly scalable processing developments in the production of graphene-based composite thin films are also presented, which expand the available portfolio of nanostructured carbon materials with potential applications in multifunctional surfaces.
Carbon nanomaterials such as carbon nanotubes (CNTs) or monolayer graphene are proposed for a wide variety of theoretical applications due to the superior properties provided at the nanoscale. They can be produced by chemical vapor deposition (CVD), which consists on the thermal decomposition of hydrocarbons over metal catalysts. Highly ordered structures like CNTs arrays and fibres as well as large-area monolayer graphene films can be grown in a highly controlled manner at laboratory scale by selecting the proper CVD conditions, the metal catalyst composition and morphology. However, the highly controlled catalysts needed for their synthesis are currently produced by expensive techniques which are hard to scale. Alternatively, the use of commercially available bulk metal catalysts like powders, foils and meshes are shown to be a fast and low cost approach for the production of carbon nanomaterials with several morphologies and crystallinities. This alternative is already demonstrated in the literature, however most of the experimental work on synthesis on bulk metals focuses on the carbon produced, and there is a need of experimental work focused on growth mechanisms of carbon nanomaterials on these metal catalysts. We used nickel-based powders and stainless steel and copper foils for the production of carbon fibres, nanofibres, CNTs arrays and thin films by CVD, providing supported explanations on the carbon nanostructure growth mechanisms. Highly scalable processing developments in the production of graphene-based composite thin films are also presented, which expand the available portfolio of nanostructured carbon materials with potential applications in multifunctional surfaces.
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Metals, Chemical vapor deposition, Carbon nanomaterials