Sodium catalysis is a novel and sustainable method for synthesizing carbon nanotubes (CNTs) on glass substrates at a low temperature. CNTs are nanomaterials with extraordinary properties that have applications in various fields, such as energy, electronics, aerospace, and medicine. However, the conventional methods for CNT synthesis require high temperatures and metal catalysts, which pose challenges for cost-effectiveness, scalability, and biocompatibility. Sodium catalysis overcomes these limitations by using sodium as a catalyst and plasma as a source of energy.
Sodium catalysis: a breakthrough in CNT synthesis
Researchers at the Institute of Advanced Study in Science and Technology (IASST), an autonomous institute of the Department of Science and Technology (DST), Government of India, have discovered a new method for sodium catalyzed synthesis of CNTs on glass substrates at a temperature of 750 °C . This method uses the Plasma Enhanced Chemical Vapour Deposition Technique (PECVD), where plasma is generated using a specially designed spiral-shaped fused hollow cathode source. This process eliminates the need for metal catalysts and reduces the temperature requirement compared to the conventional methods. Moreover, this synthesis is performed under atmospheric pressure, which adds to its cost-effectiveness and feasibility.
The key factor that enables this novel synthesis is the presence of sodium (Na) in the glass substrate, which acts as a catalyst for initiating CNT growth. The researchers found that the pre-plasma treatment of the glass substrate at an elevated temperature enhances the surface area and exposes more Na to the surface. The Na then reacts with the carbon source (acetylene gas) to form CNTs on the glass substrate. The researchers also observed that the Na present in the as-grown CNTs can be easily removed by washing them with deionized water .
The researchers have characterized the morphology, structure, and composition of the sodium catalyzed CNTs using various techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDX). They have confirmed that the CNTs are mostly single-walled or double-walled with diameters ranging from 1 to 5 nm and lengths up to several micrometers. They have also verified that the CNTs are free of any metal impurities and contain only carbon and traces of sodium .
Advantages and applications of sodium catalyzed CNTs
The sodium catalyzed CNTs have several advantages over the conventional CNTs synthesized using metal catalysts. First, they are cleaner and more biocompatible, as they do not contain any metal impurities that may cause toxicity or interfere with biological functions. Second, they are more flexible and transparent, as they can be grown on glass substrates that have high optical transmittance and mechanical strength. Third, they are more versatile and tunable, as they can be grown with different diameters, lengths, and orientations by controlling the plasma parameters and substrate temperature .
These advantages make the sodium catalyzed CNTs suitable for various applications in energy research, biomedical fields, and optoelectronics. For example, they can be used as electrodes for rechargeable batteries and supercapacitors that require high conductivity and large surface area. They can also be used as sensors and actuators for biomedical devices that require biocompatibility and flexibility. Furthermore, they can be used as transparent conductors and emitters for optoelectronic devices that require transparency and luminescence .
Some of the specific applications of sodium catalyzed CNTs are:
- Rechargeable batteries: Sodium catalyzed CNTs can be used as anodes for lithium-ion batteries (LIBs) that offer high capacity, long cycle life, and fast charge/discharge rates . They can also be used as cathodes for sodium-ion batteries (SIBs) that offer low cost, high safety, and environmental friendliness .
- Flexible electronics: Sodium catalyzed CNTs can be used as flexible electrodes for organic light-emitting diodes (OLEDs) that offer high brightness, low power consumption, and wide viewing angle . They can also be used as flexible substrates for organic photovoltaics (OPVs) that offer low cost, easy fabrication, and light weight .
- Aerospace: Sodium catalyzed CNTs can be used as structural composites for aerospace applications that require high strength, low density, and corrosion resistance . They can also be used as thermal management materials for spacecraft that require high thermal conductivity, low thermal expansion, and radiation resistance .
Conclusion
The sodium catalyzed synthesis of CNTs is a revolutionary method that offers a cleaner, cheaper, and easier way to produce high-quality CNTs on glass substrates. This method opens up new possibilities for exploiting the unique properties of CNTs in various technological domains. The researchers have filed a patent for this process and are working on scaling up the production and exploring more applications of sodium catalyzed CNTs .
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