Recycling E-Waste Into a Coating for Steel
takyon writes:
Recycling Electronic Waste to Make Hybrid Materials
Electronic waste could get recycled into strong, protective coatings for steel, a new study finds.
Recycling typically converts large quantities of items made of a single material, such as aluminum cans or glass bottles, into more of the same. However, this approach is not feasible for complex garbage such as electronic waste, or e-waste, because it contains many different materials that cannot be easily separated.
[...] In the new study, researchers investigated the properties of copper and silica compounds often found in old printed circuit boards and computer monitors. They suspected that after these substances were extracted from e-waste, they could get combined to create a durable new hybrid material potentially useful for protecting metal surfaces against corrosion and wear.
First the researchers heated glass and plastic powder from old computer monitor screens and shells to 1,500 degrees C, generating silicon carbide wires 10 to 50 nanometers (billionths of a meter) in diameter. They next combined these ceramic nanowires with copper recovered from ground-up circuit boards, placed the mix on a steel surface, and then heated it up to 1,000 degrees C. This melted the copper to form a thin film 1 micron thick atop the steel. (The scientists noted this width could get adjusted to range from a few nanometers to a few hundred microns.)
This structural bonding of different elements creates new properties that are superior to the parent materials. "Say, for example, the metal structure has a good toughness but a poor hardness. In contrast, a ceramic has a high hardness but it's very brittle," Sahajwalla says. "Combining these two structures together successfully by the judicious choice of temperature after understanding the the raw material can create a completely new hybrid material that has a ceramic-like hardness and metal-like toughness. And surprisingly, all this could be done from waste sources, which can prevent these resources going to a landfill."
The scientists found the micron-thick hybrid layer increased the surface hardness of the steel by about 125%. In addition, microscope images revealed that when this hybrid layer was struck with a nano-sized indenter, it remained firmly bonded to the steel without cracking or chipping.
Material Microsurgery: Selective Synthesis of Materials via High-Temperature Chemistry for Microrecycling of Electronic Waste (open, DOI: 10.1021/acsomega.0c00485) (DX)
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