BMW created a bit of a buzz in August when it announced that it would be unveiling a special version of its 2020 BMW X6 at the Frankfurt Motor Show in September. What was unique about this car was its colour: Vantablack.
For the uninitiated, Vantablack was (at the time), the blackest version of black in the world and is capable of absorbing more than 99 per cent of visible light. BMW had partnered with Vantablack maker, Surrey Nano Systems, to create the world's blackest car.
Vantablack was so incredibly black that it made details of the car very difficult to make out. Indeed, when you look at anything covered in Vantablack it almost looks like you are looking into a void.
Vantablack is not actually a paint but a coating of carbon nanotubes, which has the ability to absorb light almost completely, so much so that when you view objects coated with Vantablack, they look somewhat two-dimensional. This is due to spatial depth being lost due to the non-reflection of light.
Interestingly, the month BMW showcased its Vantablack car, MIT engineers reported that they had come up with a material that is 10 times blacker than anything previously reported!
(It captures at least 99.995 per cent of any incoming light, making it the blackest material on record).
Like Vantablack, it is made from carbon nanotubes, or CNT’s (microscopic filaments of carbon), grown on a surface of chlorine-etched aluminium foil. The researchers had published their findings in the journal ACS-Applied Materials and Interfaces.
BLACKEST OF BLACK
The MIT had actually discovered this blackest of black material by accident. The team was experimenting with ways to grow carbon nanotubes on electrically-conducting materials such as aluminium, to boost their electrical and thermal properties.
But in attempting to grow CNTs on aluminium, they ran up against a barrier: a layer of oxide that coats aluminium when it is exposed to air acts as an insulator, blocking rather than conducting electricity.
The solution for that could be found in salt. They discovered that if they soaked aluminium foil in saltwater, they could remove the oxide layer. The researchers were then able to grow carbon nanotubes on the aluminium.
The team was surprised at how incredibly dark the material was. Test results showed that the material absorbed at least 99.995 per cent of incoming light, from every angle. In other words, it reflected 10 times less light than all other super-black materials, including Vantablack.
Apparently, the team has no plans to give the material a catchy name to rival Vantablack. Nor are they keeping it to themselves. Instead, they are now focused on MIT's mission to create and disseminate knowledge by making the material available for art and science applications.
So, what could such blackness be used for? Not for making a car, it seems. The BMW show car will most likely be a one-off sample because of the huge difficulty involved in making Vantablack or the MIT’s version of it suitably durable for everyday automotive use.
Coating the car with those materials would also be extremely expensive, not to mention questionable in terms of road safety due to its remarkable ability to absorb light. Other cars might simply not see it at night.
Among the practical uses of super black material include optical blinders that reduce unwanted glare to help space telescopes spot orbiting exoplanets. “There are optical and space science applications for very black materials,” says Brian Wardle, professor of aeronautics and astronautics at MIT, who co-wrote this report.
Oon Yeoh is a consultant with experiences in print, online and mobile media. Reach him at [email protected].