Pollution Falls with Graphene Balls
For the average car, 15 percent of fuel consumption is spent overcoming friction in the engine and transmission.
Gears have to work harder to move when friction is high, which increases emission levels and fuel consumption. Although oil reduces engine friction, oil additives can greatly enhance oil lubricating performance.
Crumpled graphene balls show promise as an additive for pollution reduction and higher fuel efficiency.
At Northwestern University, associate professor Jiaxing Huang and his team discovered that crumpled graphene balls outperform some commercial lubricants by 15 percent. Friction and the degree of wear on steel surfaces were reduced.
"Every year, millions of tons of fuel are wasted because of friction," said Huang, "It's a serious problem.”
When car engines are improperly lubricated, fuel consumption increases, which negatively affects the environment and a drivers’ hold on cash.
The ultra-fine particles resemble crumpled paper balls. By drying tiny water droplets with graphene-based sheets, the idea for a new additive was born. Eager to share the discovery, Huang explained it to Yip-Wah Chung, professor of materials science and engineering at NU, during a lunch in Hong Kong by crumpling a napkin and juggling it.
"When the ball landed on the table, it rolled," Chung recalled. "It reminded me of ball bearings that roll between surfaces to reduce friction."
Previous additive studies showed limited dispersion in oil; particles clumped together, which is less effective for lubrication. In addition, severe aggregation increased gear wear and friction. Researchers tried modifying particles with surfactants to make them disperse, but the problem persisted.
Crumpled graphene balls self-disperse without needing surfactants. Their pointy surfaces maintain a fair distance between them. If squeezed together, they separate easily when disturbed.
The graphene additive has also been proven to ignore changes in the concentration of oil, guaranteeing stability in performance.
Huang explains that for other carbon additives, performance is very sensitive to concentration and so it is important to find a sweet spot.
“The problem with finding a sweet spot is that, during operation, the local concentration of particles near the surfaces under lubrication could fluctuate," Wang added. "This leads to unstable performance for most other additive particles."
Corrosion Inhibition and Further Research
Since graphene balls have a high surface area and open spaces, uses can expand to carrying materials for corrosion inhibition.
New experiments will test the benefits of crumpled graphene balls in oil.