E-waste coating

Attacking e-waste with ‘material microsurgery’

Australian researchers have reported early success with an innovative idea for recycling old electronic devices or e-waste.

They call the small-scale, targeted process “material microsurgery” and say they have used it to convert old printed circuit boards and monitor components into a strong protective coating for metal.

The “radical, new approach”, described in a paper in the journal ACS Omega by Veena Sahajwalla and Rumana Hossain from the University of NSW, involves leveraging high-temperature reactions. It was inspired, they say, “by the principles used by medical surgeons when operating on the human body”.

Recycling e-waste ticks lots of boxes because it contains small amounts of many different valuable materials – but it is challenging for just that reason.

“Glass, metals and plastics are embedded in e-waste in such a manner that it is not feasible to separate them and remove contamination for conventional recycling,” the researchers write.

“Conventional recycling also requires a large input volume of like materials, which is not possible to obtain from many e-waste sources such as printed circuit boards (PCBs).”

The new project built on previous studies showing it is possible to selectively break and reform chemical bonds in waste to form new, environmentally friendly materials. In this way, researchers have turned a mix of glass and plastic into silica-containing ceramics and recovered copper from circuit boards.

Based on the properties of copper and silica compounds, Sahajwalla and Hossain suspected that, after extracting them from e-waste, they could combine them to create a durable new hybrid material ideal for protecting metal surfaces.

To do this, they first heated glass and plastic powder from old computer monitors to 1500 degrees Celsius, generating silicon carbide nanowires. They then combined the nanowires with ground-up circuit boards, put the mix on a steel substrate and heated it again.

This time the thermal transformation temperature selected was 1000 degrees, melting the copper to form a silicon-carbide enriched hybrid layer atop the steel.

Microscope images revealed that, when struck with a nanoscale indenter, the hybrid layer remained firmly affixed to the steel, without cracking or chipping. It also increased the steel’s hardness by 125%.

“This technique… has the potential to transform waste materials into new hybrid surface coatings, which endows the base materials with superior properties to those seen in the source materials,” the researchers write.

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