Spectroscopy of carbon nanotube synthesis processes
Lead Research Organisation:
University of Cambridge
Department Name: Engineering
Abstract
The aims of the project are to implement Cavity-Enhanced Raman Spectroscopy (CERS) for gas phase analysis and detection of main precursors in Floating Catalyst Chemical Vapour Deposition (FCCVD) process for continuous Carbon Nanotube (CNT) synthesis. The immediate goals are to implement a feedback lock-in amplifier for the optical signal to enhance the output of the Raman scattered signal.
Pending the outcome of a feasibility phase, the diagnostic will be expanded to implement it with the non-reacting, and then reacting flows. Alternatively, the project will pursue other types of diagnostics relevant to the FCCVD/CNT synthesis, including in-situ particle scattering and laser induced fluorescence.
Pending the outcome of a feasibility phase, the diagnostic will be expanded to implement it with the non-reacting, and then reacting flows. Alternatively, the project will pursue other types of diagnostics relevant to the FCCVD/CNT synthesis, including in-situ particle scattering and laser induced fluorescence.
Organisations
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/N509620/1 | 01/10/2016 | 30/09/2022 | |||
| 1776816 | Studentship | EP/N509620/1 | 01/10/2016 | 31/07/2020 | Maxim Kuvshinov |
| Description | The objective of the project was the development of a non-invasive optical technique capable of providing information on carbon nanotube aerogel growth via floating catalyst chemical vapour deposition method. Two separate approaches were investigated. First, we have developed a model that describes a performance of a Cavity Enhanced Raman spectroscopy (CERS) system and allows its users to compare its signal amplification to a typical free space spontaneous Raman spectroscopy set-up. The results were experimentally validated by carrying out free space and Cavity-Enhanced Raman Spectroscopy (CERS) for gas phase measurements of nitrogen and oxygen in ambient air. Real time analysis capabilities, and continuous Raman signals with low power diodes, make the technique non-invasive, affordable, compact and applicable for usage in non-reacting flows. The derived comprehensive model allowed for estimation of photon emission for both free space and cavity-based signals and its supplementary text discussed trade-offs in how to organize the cavity geometry for maximum gain relative to free space. Experimental measurements in both free and cavity configurations were compared to the theoretically expected signals, demonstrating the usefulness of the model in predicting amplification. Therefore, the model can serve as a quick guide on how to use low power continuous wave lasers in a cavity setup to obtain enhanced laser induced spontaneous Raman scattering. However, as the main goal was an application of an optical diagnostic in a reactive flow, a separate experimental set-up has been devised, as CERS was not suitable due to possible contamination of mirrors' surfaces and Laser beam drift due to thermal gradients inside of the reactor. A new Raman spectroscopy set-up was built, consisting of a pulsed laser with a 300 ns long pulse width, that is crucial for extracting high quality Raman signal. The reactive flow was located in an open-ended quartz tube, placed inside a modified clam shell furnace, making up the basis of the reactor. The quartz tube has on-axis arms going off its centre, perpendicular to its radial axis. Overall, the reactor structure resembled a cross. The arms were sealed off with purging flanges which contained optical quartz windows in their centre. A continuous optical access inside of the reactor was provided with the use of purging flows, which prevented the deposition of any impurities on the window surfaces that were created during the reactions in the flow. Additionally, the laser beam passed freely through the reactor, allowing for the use of other spectroscopic techniques, simultaneously, with minimal modifications to the set-up. The work was focused on the study of the decomposition of the precursors used in the carbon nanotube synthesis, such as thiophene and ferrocene, at different temperatures and flow rates. The results determined the breakdown temperatures of those compounds, along with the resultant products, such as CH4, H2S, Si-H and Si-H2 , along their dependencies on inlet reactant concentrations. Furthermore, to the author's' knowledge, first Raman spectra of products were successfully acquired during carbon nanotube synthesis via floating catalyst chemical vapour deposition method, making the created setup serve as a great foundation for further optical diagnostics work. |
| Exploitation Route | The model can be used by others to help with the design of the cavity for their specific application. Previously, in related research a fair amount of geometrical parameters of the cavity seemed to have been chosen arbitrarily, sometimes resulting in inadequate performance in an outlined task. By using the model, the optical cavities can be tailored to be sensitive to a specific chemical compound, making them ideal for its detection and over-time monitoring. Additionally, in comparison to other Raman spectroscopy devices on the market, the cost of a CERS set-up is quite cheap and it can have variable footprint sizes, making it applicable for remote sensing operations. This makes CERS a promising technique to be used in emissions, environmental, healthcare and food sectors. The findings acquired from the pulsed Laser Raman set-up will provide crucial data, that is currently missing, to the theorists who work on modelling of the Carbon nanotube synthesis via the floating catalyst chemical vapour deposition method. Additionally, the set-up can be used by others to study any reacting flows of interest inside a heated environment as the issues of continuous optical access are solved. The set-up is not limited to Raman spectroscopy, as multiple spectroscopic techniques can be used due to the fact that the Laser beam is able to cleanly enter and exit the quartz tube reaction chamber. |
| Sectors | Agriculture, Food and Drink,Chemicals,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology,Security and Diplomacy |
| URL | https://doi.org/10.17863/CAM.73878 |
| Title | CERS Model |
| Description | A comprehensive model for estimation of photon emission for both free space and cavity enhanced Raman spectroscopy based signals that helps to plan the cavity geometry for maximum gain relative to a free space set-up. |
| Type Of Material | Computer model/algorithm |
| Year Produced | 2019 |
| Provided To Others? | Yes |
| Impact | The users can utilise the model in order to help in construction and assembly of their cavity enhanced Raman spectroscopy set-up. This allows to tailor the se-up to be sensitive to a particular chemical compound, increasing the set-up's efficiency in detection and monitoring. |
| URL | https://doi.org/10.1364/AO.99.099999 |
| Description | 2018 Imaging and Applied Optics Congress |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | A presentation was given at a conference in front of specialists specialising in laser applications to chemical, security and environmental analysis. This resulted in a discussion after the presentation about the potential future applications of the technology presented. From this discussion we were invited to submit a paper describing our funding to a special issue of an 'Applied Optics' journal. |
| Year(s) Of Engagement Activity | 2017,2018 |
| URL | https://www.osapublishing.org/abstract.cfm?uri=lacsea-2018-LW3C.2&origin=search |
| Description | ANAM biannual industrial meetings |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | International |
| Primary Audience | Industry/Business |
| Results and Impact | Biannual meetings of advanced nanotube application and manufacturing initiative's industrial and academic members, with on average 35 people participating. The work presented in those meetings always generates discussions about the current state of the researched technology and its potential applications towards carbon nanotubes' synthesis. The meetings allow various research groups to share their new knowledge and ideas with each other and converse with the industrial partners regarding the aspirations towards the initiative and the goals they would like us to achieve. |
| Year(s) Of Engagement Activity | 2017,2018,2019 |
| URL | https://www.anam.eng.cam.ac.uk/ |
| Description | Cambridge Particle Meeting and Combustion Aerosol Conference 2018 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Industry/Business |
| Results and Impact | A poster presentation about ongoing research of particle size measurement in an aerosol using laser light scattering. Poster generated some discussion and prompted industrial members to express interest in the further development of the technology. The candidate's entry was sudden and quite late, resulting in it missing from the webpage. |
| Year(s) Of Engagement Activity | 2018 |
| URL | http://www.cambridgeparticlemeeting.org/2018 |
| Description | Sensors PhD Showcase 2017 |
| Form Of Engagement Activity | A talk or presentation |
| Part Of Official Scheme? | No |
| Geographic Reach | National |
| Primary Audience | Postgraduate students |
| Results and Impact | I brief talk was given in front of 55-60 people, which has resulted further questions and discussion after the presentation. The speaker was approached by industry and academic members to further elaborate in the future of research of this project. |
| Year(s) Of Engagement Activity | 2017 |
| URL | https://cdt.sensors.cam.ac.uk/events/past-events-1/sensors-cdt-showcase/phd-student-showcase-program |