Fabrication of Ultrastrong 700 Gigapascal Fused Double-walled Carbon Nanotubes

The Clean Energy Research Foundation has discovered a method of manufacturing the worlds strongest and toughest materials. Fused double-walled carbon nanotube (DWNT) fibers were made with a strength of a 700 GPa Young’s modulus. This strength was seen in prior experiments, in 2010 and 2011, where electron beams welded DWNTs in microscopic bundles together and the fused bundles had 700 GPa tensile strength. There is now an effort to scale up production of ultrahigh strength material using high temperatures (1700-2300 C) and about 800 atmospheres of pressure instead of an expensive and time-consuming process using high-voltage e-beams. The electron dose available from commercial e-beam facilitaties is so low that processing macroscopic DWNT materials would take months instead of half an hour or less. The same thermal treatment process will enable manufacturing wires that have the highest conductivity of all carbon nanotube wires.

NASA wants the highest conductivity wires for their space probes and satellites where their weight is critical. In current nanotube wires, there is resistance that results from nanoscopic spaces between the nanotubes. Electric currents have to jump that gap to pass from one nanotube to the next. The reason for that is that carbon nanotubes in bundles are locked into place by Van der Waals force fields. Neil Farbstein the inventor says “It is amazing to see that double-walled carbon nanotubes are actually levitating a small distance away from each other. Fused DWNT will have vastly increased connectivity and we will compete successfully with competitors. The Juno space probe has carbon nanotube wires in it to reduce its weight.”

US Patent 10,059,595 is for Ultra High Strength Nanomaterials And Methods Of Manufacture.

In the first experiments at Clean Energy Research Foundation, the bulk hot-pressed double-walled carbon nanotube material was not of record-breaking hardness or toughness. But that’s because the material wasn’t pure enough. They are now planning to reperform the experiment with funds from the air force and other agencies using finer higher quality nanoparticles.

The patent also details use of supersonic cold spray to manufacture diamond-like-carbon (DLC) and superhydrophobic fluorinated DLC coatings at atmospheric pressure in nitrogen and in air using a spray gun. That much simpler process will be less costly than plasma vapor deposition, which is currently used.

The diamond-like-carbon coatings can be built up by 3-D printers to manufacture solid diamond-like-carbon objects. DLC is inert at high temperatures. The coatings can be useful in chemical processing equipment, jet engines, gas turbines, and all types of moving machinery since they are almost as hard as diamonds and as lubricating, and provide corrosion protection. They can be used in heat transfer equipment and cooling devices. Smartphones can be cooled by DLC coated circuit boards and other heat radiator components and DLC can also be useful in cooling computer data centers. Computer data centers generate a tremendous amount of waste heat that can be dissipated by DLC heat exchangers.

Clean Energy Research Foundation is manufacturing prototype silicon carbide nanoceramics in a contract research laboratory using the methods in patent US10059595B1. Those nanostructured ceramics begin with graphene and carbon nanotubes and exceedingly small and pure silicon particles and result in aligned composites with extraordinary material properties. They expect the silicon carbide to have used in slip bearings and machine tools and in jet engine turbines.

Ultra-high strength graphene nanopaper and bulk amounts of aligned carbon nanotube films can already be used for ballistic armor and other applications. Fused double-walled carbon nanotube materials will be the ultimate in high strength materials with 700 GPa or greater Young’s modulus and 17 GPa tensile strength. Graphene-carbide composite nanopaper will replace carbon fiber composites in wind turbines, space planes, jet engines, and other applications. Their diamond-like-carbon composite material has higher heat conductivity than graphite and copper. It will be useful for heat sinks in electronics and also in the $1 billion dollars dental implant industry. Clean Energy Research Foundation Inc is looking for research and development and investment partners for all of those applications.

The present invention provides methods of manufacturing inorganic nanopaper, laminates, fibers, coatings, films and solid materials with increased strength. The methods include the generalized steps of densifying carbon nanoparticles to put them into physical contact with each other and treating the materials to provide fused structures with dense aggregations of covalent bonds connecting the nanoparticles to each other. One embodiment takes advantage of the coalescence phenomenon observed when bundles of pure double-walled carbon nanotubes were heated to temperatures ranging from of 2100° C.-2500° C.

The bundles were observed to fuse by coalescence of their outer walls—forming structures containing two single-walled nanotubes enclosed by a single outer wall, graphene nanoplatelets, and other structures. Adding 0.05% boron to double-walled carbon nanotubes resulted in similar fused structures linking the bundles and the formation of welded triple junctions and quadruple junction structures derived from intersecting double-walled carbon nanotubes heated at temperatures ranging from 1600° C.-2100° C. The advantage of using double-walled carbon nanotubes is that they coalesce without expensive radiation treatments. Heating them to weld them to each other into bulk materials is easier and cheaper.

In one embodiment divulged in the patent here, pure double-walled carbon nanotube powder is mixed with elemental boron at concentrations sufficient to cause fusion of nanotube walls and welded multiple junction linkages, and compressed in a vacuum hot press at approximately 1700° C. Double-walled carbon nanotubes have an interesting property of coalescing when heated to a certain temperature. They have inner tubes and outer tubes. When heated high enough, the outer walls weld together. That process also creates three way and fourway junctions. Welding the nanotubes together yields much stronger material.

Prior Work at Other Labs by Other Researchers

Journal of Applied Physics – Reinforcing multiwall carbon nanotubes by electron beam irradiation (2010)

Advanced Materials – Ultrahigh Strength and Stiffness in Cross-Linked Hierarchical Carbon Nanotube Bundles (2011)

Nanoletters – Atomic Nanotube Welders: Boron Interstitials Triggering Connections in Double-Walled Carbon Nanotubes (2005)

DWNTs in a bundle with gaps between them and kept apart by Van der Waals forces.

Electron irradiation induced covalent cross-linking at multiple length scales within double-walled nanotube
bundles is was demonstrated to lead to ultrahigh effective strength and stiffness. In situ transmission electron microscopy, tensile testing showed both order of magnitude enhancements in the mechanical properties as well as distinct failure mechanisms of cross-linked versus un-crosslinked bundles.

The picture above shows that a bundle of unfused DWNTs can be fused to each other by boron and that the
intertube connections will reduce electrical resistance in the resulting materials. Copper wires and cables
account for approximately a fifth of the weight in jet aircraft and Neil Farbstein, the President of Clean Energy Research Foundation Inc., believes that the fused DWNT wire product with higher conductivity will compete successfully with other companies working to lower aircraft and satellite weight.

The mechanical properties of carbon nanotubes reveal them as one of the strongest
materials in nature. Carbon nanotubes (CNTs) are long hollow cylinders of graphene. CNTs are very strong in the axial direction. CNT’s have Young’s modulus on the order of 1.09 TPa and tensile strength of 63 GPA was obtained. (From The Nanotube Site- https://web.pa.msu.edu/cmp/csc/ntproperties/ Further studies were conducted. Various measurements show carbon nanotube Young’s module strength in the 1.09 to 1.26 Terapascal range.

Macroscopic Materials With 80 GPa of Tensile Strength Made in China in 2018

Recently, macroscopic quantities of carbon nanotube bundles were created in China that had tensile strength of 80 GPa. The tensile strength of CNTBs (Carbon nanotube bundles) is at least 9–45 times that of other materials. A synchronous tightening and relaxing (STR) strategy improved the alignment of the carbon nanotubes to increase the strength. If a more rigorous engineering definition is used, the tensile strength of macroscale CNTBs is still 5–24 times that of any other types of engineering fiber, indicating the extraordinary advantages of ultralong carbon nanotubes in fabricating superstrong fibers.

Neil Farbstein, the inventor of ultra high strength nanomaterials and methods of manufacture claims his methods can increase the Young’s modulus of fused carbon nanotube fibers to 700 GPa.

Written by – Brian Wang at Nextbigfuture.com