End-of-life Glass Fibers Are Converted Into Silicon Carbide! Another New Method Of Recycling Glass Fibers Has Been Developed Abroad
Glass fiber reinforced plastics (GFRP) are used in a wide variety of applications, from aircraft components to wind turbine blades. However, precisely because of its robustness and versatility, glass fiber is also very difficult to dispose of. As a result, most fiberglass waste is buried in landfills after it reaches the end of its useful life.
To address this problem, Rice University researchers and collaborators have developed a new, energy-efficient upcycling method that converts GFRP into silicon carbide, which is widely used in semiconductors, sandpaper and other products. The research is published in the journal Nature Sustainability.
"GFRP is used to make very large things, and in most cases we end up burying the entire wing structure of an airplane or the blades of a wind turbine in a landfill," said James Tour, a professor of chemistry and materials science and nanoengineering at Rice." Disposing of GFRP in this way is not sustainable. So far, there are no good recycling methods."
1. GFRP Waste Management
With increasing pressure from regulatory agencies to modify and improve end-of-life vehicle recycling methods, there is a critical need for better ways to manage GFRP waste. While some have tried to develop ways to treat GFRP using incineration or dissolution, Yi Cheng, a postdoctoral assistant researcher working in the Tour Lab and a junior fellow at Rice College, says these methods aren't ideal because they're resource-intensive and cause environmental pollution.
"This material has plastic on the fiberglass surface, and incinerating the plastic produces a lot of toxic fumes," Cheng says." Trying to dissolve GFRP is also problematic because solvents produce large amounts of acid or alkali waste. We wanted to find a more environmentally friendly way to deal with this material."
2. Silicon carbide for sandpaper and semiconductors
Tull's lab has already made headlines for developing new waste treatment and recycling applications using flash joule heating technology. Flash Joule heating is a technology that passes an electric current through a material of moderate electrical resistance to rapidly heat it to super-high temperatures and convert it to other substances. tour says that when he learned about the problems involved in GFRP processing from colleagues at the U.S. Department of Defense's Advanced Research Projects Agency, he thought this kind of turbo-heating could convert GFRP to silicon carbide, which is widely used in semiconductors and sandpaper.We already knew that if we heated a mixture of metal chloride and carbon by flash-joule heating, we could get metal carbides - and in one demonstration, we made silicon carbide," Tour says. So we were able to use this work to come up with a process to transform GFRP into silicon carbide."
This new process grinds GFRP into a mixture of plastic and carbon; more carbon is added if necessary to make the mixture electrically conductive. The researchers then apply high voltage using two electrodes to raise its temperature to 1,600 ~2,900°C. "The high temperature promotes the conversion of plastic and carbon to silicon carbide," explains Tour." We can make two different kinds of silicon carbide, which can be used for different purposes. In fact, one of the silicon carbides shows excellent capacity and rate performance as a battery anode material."
3. Scaling up the low-cost process is underway
While this initial research was a proof-of-concept test at bench-scale in the lab, Tour and colleagues have begun working with outside companies to scale up the process for wider use. Recycling GFRP has an operating cost of less than $0.05 per kilogram, which is much cheaper and more environmentally friendly than incineration or dissolution. It will take time and some good engineering to properly scale up this new method, but Tour says he's excited that his lab has been able to develop a sustainable method for converting GFRP waste into silicon carbide.
