Periodic Reporting for period 1 - SUPERYARN (Study and Understanding of gas Phase Entangled Reactions for Yarn Assembly via Robust Nanomaterial aerogelation)
Reporting period: 2022-01-01 to 2023-12-31
Since the arrival of nanotechnology, it was realized that material performance could be tremendously enhanced by using quantum mechanical properties of materials. Nanomaterials come in different forms and shapes, powder, thin films or fibers, each format with pros and cons. Nanowires and nanotubes are natural candidates for exploiting the axial quantum mechanical properties and have great potential for producing super strong fibers, such as carbon nanotubes (CNTs), or high performance materials, such as silicon nanowires (SiNWs) for the production of advanced electrodes in high density batteries, so necessary for sustainable energetics and for advancing towards the green transition, a priority for the European Commission under the European Green Deal for making Europe climate neutral by 2050. And even silicon carbide nanowires (SiCNWs) useful for high temperature semiconductors, sensors and optoelectronics. These are all incredible materials. However, their synthesis is still expensive and their utilization is limited to niche applications, primarily due to the lacking understanding on how to efficiently, selectively and cleanly produce them in a cheap and environmentally friendly way. One of the best ways to do this is by using the floating catalyst chemical vapor deposition methodology (FCCVD), which occurs at high velocities, floating in the gas phase and does not require solvents. This methodology is inheritably fast, enabling industrial scale up for economical production and does not produce toxic waste. Towards this goal, the project SUPERYARN was focusing on providing a framework to better understand the reaction mechanisms for the synthesis of these outstanding one dimensional nanomaterials (1D-NMs) via FCCVD. The reaction mechanism, is a worthwhile effort since it is the key to designing an effective reactor and factory for the inexpensive, clean and efficient synthesis of these materials.
SUPERYARN allowed to build a spark discharge generator (SDG), which is currently one of the best devices for stable and reproducible synthesis of nanoparticles in the form of aerosols. The SDG is flexible for synthesizing nanoparticles of virtually the whole periodic table of the elements. A study was published on how different electronic and process variables affect the properties of the aerosol in terms of its size distribution, concentration and yield, as well as a description of the transient high voltage (HV) fluctuations that are present during the sparking phenomenon. An explanation on the connection of HV variables to the actual aerosol generation provides a bridge between electrical engineering and aerosol science.
Another important activity was the construction of a kinetic reactor composed of two connected, but fully independently functional furnaces with its separate mass flow controllers for precursor and carrier gas injection at the inlet, and sampling at the outlet of each reactor, which could also be operated together. In these reactors, wall losses and sintering studies were executed and are on the way of being published. Particle losses were tested for different tube diameters, lengths, materials, concentrations and size of nanoparticles. It was observed that the main dependence of particle wall losses was on residence time. The reactors were also used to test the synthesis of SiNWs and they successfully showed that SiNWs could be synthesized in these horizontal reactors. Nevertheless, more work is necessary to improve their selectivity towards high purity products.
Another interesting work developed was the synthesis for the first time of SiCNWs using the FCCVD method. The task in this case was much more challenging than for synthesizing CNTs and SiNWs, as for SiCNWs, it is necessary that both Si and C precursors reach the catalyst and become available at the right stoichiometry for the SiCNW to extrude properly.
The results of SUPERYARN were presented in 6 national and international conferences and 2 workshops. The research was well received and raised important points in the synthesis of 1D-NMs via FCCVD, it also showed future worthwhile taking directions. Also 3 papers have been published with full acknowledgment to SUPERYARN, one has been submitted and 5 more are in different stages of preparation.
Another important activity was the construction of a kinetic reactor composed of two connected, but fully independently functional furnaces with its separate mass flow controllers for precursor and carrier gas injection at the inlet, and sampling at the outlet of each reactor, which could also be operated together. In these reactors, wall losses and sintering studies were executed and are on the way of being published. Particle losses were tested for different tube diameters, lengths, materials, concentrations and size of nanoparticles. It was observed that the main dependence of particle wall losses was on residence time. The reactors were also used to test the synthesis of SiNWs and they successfully showed that SiNWs could be synthesized in these horizontal reactors. Nevertheless, more work is necessary to improve their selectivity towards high purity products.
Another interesting work developed was the synthesis for the first time of SiCNWs using the FCCVD method. The task in this case was much more challenging than for synthesizing CNTs and SiNWs, as for SiCNWs, it is necessary that both Si and C precursors reach the catalyst and become available at the right stoichiometry for the SiCNW to extrude properly.
The results of SUPERYARN were presented in 6 national and international conferences and 2 workshops. The research was well received and raised important points in the synthesis of 1D-NMs via FCCVD, it also showed future worthwhile taking directions. Also 3 papers have been published with full acknowledgment to SUPERYARN, one has been submitted and 5 more are in different stages of preparation.
The spark discharge generator (SDG) was studied for the effects of different electronic variables, providing some of the most comprehensive and systematic description of the SDG behavior as a function of current, flow rate, electrode gap, capacitance, inductance and resistance. Furthermore, it was found that a resistor in the circuit could, contrary to the expectation that it would reduce efficiency by dissipating energy, actually increase the efficiency of nanoparticle formation at specific resistance values.
Additionally, the studies performed on each of the 3 model materials for 1D-NM synthesis. i.e. CNTs, SiNWs and SiCNWs, have advanced our understanding in the field in terms of mechanistic understanding, conditions to favor selectivity (reaction producing primarily the desired product, few or no by-products) and reaction feasibility. Specifically, we measured for the first time the relationship between the amount of sulfur added and the mean length of the CNTs produced. Also, the number of layers of each CNT increased as more sulfur was available in the reaction. This information showed that the total number concentration of CNTs produced, as well as the volume of C content in each of them was rather constant across the whole range of sulfur tested (spanning over 3 orders of magnitude). This is evidence that the rate limiting step of CNT synthesis is in the kinetics of the decomposition of carbonaceous precursors as well as its arrival into the iron catalyst, rather than any diffusion, liquefaction, solidification process occurring at the iron catalyst.
Furthermore, due to the great demand of data acquisition, and the exploration of wide ranges of variables for finding narrow operating windows, a certain degree of automation in the reactors as well as on data acquisition and processing was developed. This development allows to increase the scientific productivity for developing the FCCVD methodology much faster for the sample materials (SiNWs, CNTs and SiCNWs) as well as for making 1D-NMs from additional materials, as we believe that the whole periodic table of the elements and numerous compounds might be suitable candidates for it.
The socioeconomical contributions of SUPERYARN are also important as one patent is attributable to it and also substantial know-how and interactions with the startup of the host institute, Floatech, which is trying to commercialize SiNW electrodes for making batteries much lighter and with higher energy density, which is essential to make electric vehicles commercially feasible and achieve the green deal of the European Union. Furthermore, numerous technicians, Bsc, MSc and PhD students and postdocs were trained in the skills of the trade, helping them advancing in their careers. Additionally, high school students visited the lab and received inspiration in choosing a technical career by seeing the SDG in action at the beautiful plasma operating mode, and hearing the experiences of the grantee.
Additionally, the studies performed on each of the 3 model materials for 1D-NM synthesis. i.e. CNTs, SiNWs and SiCNWs, have advanced our understanding in the field in terms of mechanistic understanding, conditions to favor selectivity (reaction producing primarily the desired product, few or no by-products) and reaction feasibility. Specifically, we measured for the first time the relationship between the amount of sulfur added and the mean length of the CNTs produced. Also, the number of layers of each CNT increased as more sulfur was available in the reaction. This information showed that the total number concentration of CNTs produced, as well as the volume of C content in each of them was rather constant across the whole range of sulfur tested (spanning over 3 orders of magnitude). This is evidence that the rate limiting step of CNT synthesis is in the kinetics of the decomposition of carbonaceous precursors as well as its arrival into the iron catalyst, rather than any diffusion, liquefaction, solidification process occurring at the iron catalyst.
Furthermore, due to the great demand of data acquisition, and the exploration of wide ranges of variables for finding narrow operating windows, a certain degree of automation in the reactors as well as on data acquisition and processing was developed. This development allows to increase the scientific productivity for developing the FCCVD methodology much faster for the sample materials (SiNWs, CNTs and SiCNWs) as well as for making 1D-NMs from additional materials, as we believe that the whole periodic table of the elements and numerous compounds might be suitable candidates for it.
The socioeconomical contributions of SUPERYARN are also important as one patent is attributable to it and also substantial know-how and interactions with the startup of the host institute, Floatech, which is trying to commercialize SiNW electrodes for making batteries much lighter and with higher energy density, which is essential to make electric vehicles commercially feasible and achieve the green deal of the European Union. Furthermore, numerous technicians, Bsc, MSc and PhD students and postdocs were trained in the skills of the trade, helping them advancing in their careers. Additionally, high school students visited the lab and received inspiration in choosing a technical career by seeing the SDG in action at the beautiful plasma operating mode, and hearing the experiences of the grantee.