Materials World Network: Novel Catalyst Systems for Carbon Nanotube (CNT) Synthesis and their Underlying Mechanisms

Lead Research Organisation: University of Cambridge
Department Name: Engineering

Abstract

Chemical vapor deposition (CVD) techniques employing nano-particulate catalysts and catalyst films have proven to be versatile and effective methods for synthesizing carbon nanostructures, such as nanotubes (CNTs) and graphene. CVD enabled extensive investigation of these structures as well as opened routes towards their application in integrated circuits, energy storage, transparent conductors, thermal management surfaces, hierarchical composites, sensors, drug delivery and biomimetics. Despite these successes, the detailed mechanisms of catalytic CVD remain poorly understood and the CVD process lacks deterministic control, in particular regarding CNT chirality. Common catalysts, such as Ni and Fe, are active in their metallic state and hence are prone to coarsening and support interactions at the elevated temperatures required for CVD. We recently demonstrated that nano-particulate zirconia catalyses CNT growth at moderate temperatures, whereby it neither reduces to a metal nor forms a carbide. The low reactivity and limited restructuring of oxides promise a high level of control for the CVD process. We propose to study a range of oxides as CVD catalysts. We plan to use in-situ X-ray photoemission spectroscopy and environmental transmission electron microscopy to explore the mechanism(s) of graphene formation and nanotube nucleation on pre-treated oxide films and size-selected oxide nanoparticles. We will analyse the chiral selectivity of oxide-assisted CNT CVD and explore the possibility of large area graphene CVD on oxide films.

Planned Impact

We anticipate that our research will enable the controlled, scalable synthesis of carbon nanostructures. Such nanostructures and their handling are seen as key to future technological developments in the International Technology Roadmap for Semiconductors. Our research impacts the use of nanotechnologies in widely diverse industries, such as energy storage, pharmaceuticals, advanced structures and aero- and astronautics. In particular, the U.S. project partner of this proposal is leading an industry-funded Consortium including Airbus and Lockheed Martin, and we infer that our results and collaboration could progress advanced materials applications in the UK and secure employment in this area. Our research offers several advantages beyond synthesis control and efficiency: (1) a greater-than-50% reduction in energy requirements, (2) reduced input of feedstock precursor molecules, (3) orders-of-magnitude reductions in the emission of regulated toxicants. Recent reports have highlighted the need for improved understanding of the environmental, health, and safety risks associated with nanomaterials and their fabrication. This is an important point for policy makers and regulators to consider. Our proposed research can mitigate the environmental impact of the production of nanostructures at industrial level. Environmentally benign manufacturing is an important requirement to the advancement of industrial development in this area. Our proposed work overlaps with the field of catalysis and our results can of significant benefit to the bulk chemical synthesis, and green-fuel industries.

Publications


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Kidambi P (2011) Hafnia nanoparticles - a model system for graphene growth on a dielectric in physica status solidi (RRL) - Rapid Research Letters

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Kidambi P (2012) The Parameter Space of Graphene Chemical Vapor Deposition on Polycrystalline Cu in The Journal of Physical Chemistry C


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Kidambi PR (2014) In Situ Observations during Chemical Vapor Deposition of Hexagonal Boron Nitride on Polycrystalline Copper. in Chemistry of materials : a publication of the American Chemical Society






 
Description The research was carried out within a collaborative Materials World Network program between MIT (2 PhD students) and the University of Cambridge (1 PhD student) jointly funded by the NSF and EPSRC. The project explored novel catalyst systems for graphene and carbon nanotube formation, whereby the work at Cambridge particularly focussed on the investigation of the detailed growth mechanisms by using novel in-situ characterisation techniques. Significant new insights into graphene formation on metal and oxide surfaces and the subsequent device interfacing and integration were achieved, as highlighted by the 12 high impact journal publications that so far resulted from this project. The market for these new materials and all commercialisation strategies are currently limited by a lack of scalable manufacturing pathways, in particular regarding applications in the lucrative high-tech market. Hence the knowledge created of how graphene nucleates and forms is hugely important to increase the industrial relevance of these advanced materials. The results led to close interactions and collaborations with a number of companies, including Aixtron, Philips and Thales, that constitute the full supply chain of beneficiaries. The project involved a number of student exchanges and PI visits between the UK and US partners, providing training and skill exchange. This led to an active partnership and it is hoped that this research network can be continued. The work on oxide catalyst systems required dedicated preparation and growth equipment to avoid possible metal contamination, which led to a delay of this work within the program. The amount of work it takes to find a suitable model system to fundamentally investigate these materials is generally underestimated. We have now identified a number of new model systems, incl. 2 dimensional oxides and hexagonal BN, which opened up many new research directions in particular regarding the controlled growth of nano-heterostructures.
Exploitation Route Our research established a new, much more detailed understanding of graphene and carbon nanotube growth. The results will unlock new, scalable and more efficient and sustainable routes of carbon nanostructure manufacture. Our findings are of direct benefit and can be taken forward by a broad and interdisciplinary academic community that grows and utilises these nanomaterials, as well as by industry that wants to expand the range of commercial products based on these materials, in particular regarding integrated processing in the lucrative high-tech market.
Sectors Aerospace, Defence and Marine,Digital/Communication/Information Technologies (including Software),Electronics,Energy,Manufacturing, including Industrial Biotechology
URL http://www-g.eng.cam.ac.uk/hofmann/
 
Description Our research addressed key questions of industrial materials development for carbon nanomaterials. We widely disseminated (12 journal publications, oral presentations at more than 7 main international conferences) our new growth understanding, hence the knowledge can be taken forward by the academic community and industry to improve growth recipes and device integration. The world-wide project partnership and the training on experimental skills provided by us to many researchers further ensures that the knowledge can be effectively applied. The project also led for instance to student projects in the cross-disciplinary Nano Science & Technology Doctoral Training Centre at Cambridge (NanoDTC). Producing such a cadre of interdisciplinary nanoscientists is crucial for the UK to develop both the new academic directions and the industrial capabilities to capitalise on the ideas emerging. The international project research network offered and continues to offer an excellent opportunity to develop the academic careers of young researchers involved. A clear pathway to impact also resulted from the close interactions and collaborations with a number of companies, including Aixtron, Philips and Thales. Aixtron, for instance, now sells growth reactor that is optimised based on our insights. The innovation achieved in our project strengthened for instance the position of Aixtron UK in the market (see key findings), fostering the economic competitiveness. The knowledge created and the people trained are highly valuable assets across academia and industry, acting as transformers and integrators, helping the UK to be internationally competitive particularly in the high-tech sector and will help to continue progressing our knowledge-based society surrounded by a high-tech global economy.
First Year Of Impact 2011
Sector Aerospace, Defence and Marine,Agriculture, Food and Drink,Digital/Communication/Information Technologies (including Software),Electronics,Manufacturing, including Industrial Biotechology
Impact Types Societal,Economic