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Since their discovery in 1991, carbon nanotubes have been developed for use in several applications. Research exploring their full potential has been intense, with teams globally investigating how to exploit the material’s unique properties.
Carbon nanotubes have excellent electrical conductivity and very high thermal conductivity, they can also withstand high working temperatures and are stiff, tough, and strong. They have the highest strength-to-weight ratio of any material that we know of. Already, carbon nanotubes have been successfully developed for applications in numerous industries, from clean energy to healthcare. They are used to clean polluted water, enhance solar energy by a factor of 10,000, increase the efficiency of electrical transmission lines, build molecular syringes, probes, bioelectronic noses, and more.
Currently, there are numerous methods for synthesizing carbon nanotubes, from laser methods and ball milling to catalyzed chemical vapor deposition. However, a new method has emerged that demonstrates the ability to create carbon nanotubes from mining waste, allowing troublesome waste products to find another use.
A Team in Bratislava Innovates New Method to Create Carbon Nanotubes
In 2017, scientists in Bratislava, Slovakia, published a paper discussing an innovative new method they developed where they conduct carbon nanotube synthesis using mining waste. Currently, mining waste remains a major focus for the mining industry, as it presents a significant problem to the companies in the industry, the environment, and the communities surrounding mining sites. Mining generates many waste materials from the intense excavation required to extract the desired minerals. The formation of huge deposits of waste poses a threat to the surrounding environment. Given that there are over 3500 active mining waste facilities worldwide, and that these facilities generate an estimated 100 billion tonnes of solid waste each year, any innovation that finds a use for this waste is welcomed.
That’s exactly what the Slovakian team did, they found a way to utilize unwanted mining waste and repurpose it to create much-in-demand carbon nanotubes. To do this, they used zero-valent iron to create iron shavings. These shavings were then used to treat the water flowing from a closed and abandoned mining site. When introduced into the water, the shavings became coated with a precipitate made mostly from compounds of arsenic, antimony, manganese, nickel, and iron. The team used this coating as the substrate to synthesize carbon nanotubes. After collecting the coating, they added the substrate onto a silicon plate and conducted hot filament chemical vapor deposition (HFCVD).
In 2008, a team at the University of Illinois reported that both nanodiamonds and carbon nanotubes could be grown with the HFCVD method. The HFCVD technique was first reported in 1979 after being developed for the synthesis of amorphous silicon films from silane gas. The procedure involves heating a coiled wire to decompose the precursor reactants that exist in a gas mixture. The decomposed reactants are then transferred as a film over the substrate surface which is kept close to the filament at lower temperatures.
The Slovakian team has proven that the HFCVD method can successfully synthesize carbon nanotubes from mining waste. This assists the needs of two industries, they create a reliable method of creating an in-demand material for the scientific community, and they address the problem of waste for the mining community. However, the extent that the method will help with the mammoth problem of mining waste is likely to be minimal.
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