From graphene learned to make a flexible and durable thread
Although graphene itself is a very durable material, it is not easy to use this strength at the macro level. Although there are options for using the mechanical properties of graphene in the form of flakes in the thickness of the material, which make it stronger, playing the role of "reinforcement", the prospect of making fibers and filaments from graphene, from which you can make ultrastrong fabric or ropes with same, conductive properties.
Scientists from the University of Pennsylvania and Shinshu University in Japan managed to make a thread of graphene oxide , comparable in strength to Kevlar, and at the same time very flexible and elastic, with a smooth surface and a regular internal strukutra. Such threads can be easily twisted and knit knots on them - this is a unique result, because all previous attempts have given though strong, but hard and brittle fibers. After annealing, as a result of which graphene oxide loses oxygen and transforms into pure graphene, the filaments become more brittle, but they acquire high electrical conductivity.
The technology of making threads is quite simple. A suspension of graphene oxide flakes is poured onto a Teflon plate and smoothed to a uniform thickness using a Teflon bar and two adhesive tape along the edges, which define the thickness of the layer. Then the layer of suspension dries out and a thin (2.9 micron) film of stuck flakes forms in its place. The long strips of such a film are then twisted into filaments from hundreds of micrometers to one and a half millimeters thick. The key moment of this technology is that a completely dry film is twisted into a thread, whereas in previous attempts the twisting occurred when the film had not dried yet. The fact is that the film, which dried out without tension, has many small wrinkles that remain in the thickness of the thread after twisting and play the role of “springs” that make the thread elastic.
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Various additives can be added to the original graphene suspension, which alter the properties of the filaments, for example, nylon fibers, making the filaments softer and more flexible, or silver nanowires, which significantly increase the electrical conductivity of the filaments. After annealing at high temperature, the conductivity of such a graphene alloy doped with silver is comparable to copper wire, only the thread is much lighter and stronger.
An article describing the technology and properties of the obtained yarns was published in the May issue of ACSNano magazine.
Scientists from the University of Pennsylvania and Shinshu University in Japan managed to make a thread of graphene oxide , comparable in strength to Kevlar, and at the same time very flexible and elastic, with a smooth surface and a regular internal strukutra. Such threads can be easily twisted and knit knots on them - this is a unique result, because all previous attempts have given though strong, but hard and brittle fibers. After annealing, as a result of which graphene oxide loses oxygen and transforms into pure graphene, the filaments become more brittle, but they acquire high electrical conductivity.
The technology of making threads is quite simple. A suspension of graphene oxide flakes is poured onto a Teflon plate and smoothed to a uniform thickness using a Teflon bar and two adhesive tape along the edges, which define the thickness of the layer. Then the layer of suspension dries out and a thin (2.9 micron) film of stuck flakes forms in its place. The long strips of such a film are then twisted into filaments from hundreds of micrometers to one and a half millimeters thick. The key moment of this technology is that a completely dry film is twisted into a thread, whereas in previous attempts the twisting occurred when the film had not dried yet. The fact is that the film, which dried out without tension, has many small wrinkles that remain in the thickness of the thread after twisting and play the role of “springs” that make the thread elastic.
')
Various additives can be added to the original graphene suspension, which alter the properties of the filaments, for example, nylon fibers, making the filaments softer and more flexible, or silver nanowires, which significantly increase the electrical conductivity of the filaments. After annealing at high temperature, the conductivity of such a graphene alloy doped with silver is comparable to copper wire, only the thread is much lighter and stronger.
An article describing the technology and properties of the obtained yarns was published in the May issue of ACSNano magazine.
Source: https://habr.com/ru/post/228189/
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