The combination of epoxy resin and "super" graphene foam material invented in Rice Lab of chemist James Tour is much stronger than pure epoxy resin, and has better conductivity than other epoxy resin composite materials, while maintaining the material's Low density. By adding conductive fillers, epoxy resins that can weaken the material structure in current use can be improved.
The American Chemical Society journal ACS Nano details this new material.
Epoxy resins are themselves insulators and are commonly used in coatings, adhesives, electronics, industrial tools, and structural composites. Metal or carbon fillers are often added for applications that require conductivity, such as electromagnetic shielding applications.
But there is a trade-off: more fillers bring better conductivity at the cost of weight and compressive strength, and composites become more difficult to process.
Rice's lab solution replaces metal or carbon powder with a three-dimensional foam made of nanoscale graphene, a thin sheet of carbon with a thickness of only one carbon atom.
Tour Lab collaborated with Rice University's material scientists Pulickel Ajayan, Rouzbeh Shahsavari, Beijing University of Aeronautics and Astronautics, Lou Jun and Zhao Yan to draw inspiration from epoxy resin injection into three-dimensional scaffolding projects including graphene aerogels, foams and various Craft bracket.
The new solution technology uses polyacrylonitrile (PAN) to make a stronger stent. Polyacrylonitrile is a powdery polymer resin used as a carbon source and mixed with nickel powder. In a four-step process, they cold-pressed the material to make it dense, heated in a furnace to make PAN into graphene, chemically treated the resulting material to remove nickel, and used a vacuum to pull epoxy into existing porous materials.
"Graphene foam is single-layer graphene," Tour said. "So, in fact, the entire foam is a large molecule. When the epoxy penetrates the foam and then hardens, any bending of the epoxy in one location will stress the monolith elsewhere because of the embedded graphene scaffold. . This will eventually harden the entire structure. "
According to researchers, this spherical composite with a foam content of 32% is slightly denser but has an electrical conductivity of about 14 Siemens per centimeter (a measure of electrical conductivity or reverse ohms). Foam does not increase the weight of the compound, but makes it 7 times more compressive than pure epoxy.
Simple interlocking between graphene and epoxy also helps stabilize graphene's structure. Tour said: "When the epoxy penetrates the graphene foam and then hardens, the epoxy is captured in micron-sized areas of the graphene foam."
The lab raised the stakes by mixing multi-walled carbon nanotubes into graphene foam. Researchers said that nanotubes act as a reinforcing material combined with graphene, making the composite material hardness 1732% higher than pure epoxy resin, and nearly three times the conductivity, which is about 41 Siemens / cm, which is much higher. Almost all stent-based epoxy composites reported to date.
Tour expects the process to be expanded for industrial scale. "People just need a furnace large enough to produce the final part," he said. "But it's always been like this, cold pressing and then heating to make large metal parts."
He said the material may initially replace carbon composite resins, which are used to pre-impregnate and strengthen fabrics in materials ranging from aerospace structures to tennis rackets.