[ad_1]
Scientists have developed a low density epoxy for electronic applications that would be much stronger than pure epoxy and more conductive than other epoxy composites.
The advance of Rice University in Texas combines epoxy and graphene foam invented in the laboratory of chemist James Tour and could improve the current epoxides that weaken the structure of the material by adding conductive fillers. The new material is detailed in ACS Nano.
The epoxy is an insulator used in coatings, adhesives, electronics, industrial tooling and structural composites. Metallic or carbon fillers can be added for applications where conductivity is desired, but more fillers provide better conductivity at the expense of weight and compressive strength, and the composite becomes more difficult to process.
The rice solution replaces the metal or carbon powders with a three-dimensional foam made of nano-sized graphene sheets.
The Tour laboratory, in collaboration with scientists Pulickel Ajayan, Rouzbeh Shahsavari, Jun Lou and Yan Zhao from Beijing Beihang University, specializing in rice materials, is inspired by epoxy injection projects in 3D scaffolding, in particular graphene aerogels, foams and skeletons from various processes.
The new system would produce much stronger scaffolds made of polyacrylonitrile (PAN), a powdered polymer resin that they use as a carbon source, mixed with nickel powder. In the four-step process, they cold-press the materials to make them dense, heat them in an oven to turn the PAN into graphene, chemically treat the material obtained to remove the nickel and use a vacuum to suck the epoxy in the now. porous material.
"Graphene foam is a unique piece of multi-layered graphene," said Tour. "In fact, all foam is a big molecule. When the epoxy infiltrates into the foam and then hardens, any bending of the epoxy at one place will force the monolith to many other places due to embedded graphene scaffolding. This finally stiffens the whole structure.
According to the researchers, the washer-shaped composites containing 32% foam were slightly denser but had an electrical conductivity of about 14 IS per centimeter. The foam did not add significant weight to the compound but gave it a compressive strength seven times greater than that of a pure epoxy.
The easy coupling between graphene and epoxy has also helped stabilize the structure of graphene. "When the epoxy infiltrates into the graphene foam and then hardens, it is captured in areas the size of a micron of graphene foam," Tour said.
The laboratory then mixed multiwall carbon nanotubes into the graphene foam. Nanotubes acted as reinforcing bars that bonded to graphene and made the composite 1.732% stiffer than pure epoxy and almost three times more conductive, at about 41 IS per centimeter, far more than almost all epoxy composites based on scaffolding reported to date. , according to the researchers.
Tour believes that the process will evolve for the industry. "You just need a furnace big enough to produce the ultimate piece," he said. "But this is done all the time to make large metal parts by pressing cold and then heating them."
He added that the material could initially replace the composite carbon resins used to pre-impregnate and reinforce fabrics used in materials ranging from aerospace structures to tennis rackets.
CLICK FOR NEWS
Source link
