None more black

In the immortal words uttered by Nigel Tufnel of spoof 80s band Spinal Tap, “It’s like, how much more black could this be? And the answer is, none. None more black.” Justin Cunningham finds a material that is laying claim to the sentiment.

Spinal Taps’ Nigel Tufnel was of course talking about the bands all-black album cover. But had he foreseen the recent developments at Surrey NanoSystems, he’d have known that ‘more black’ was, in fact, possible.

Vantablack is the most effective light-suppression material available. Applied as a functional coating, developers say it absorbs 99.96% of light and is the closest anybody will come to looking into a black hole.

The material is unsurprisingly being targeted for application needing ultra high-emissivity, where there is demand to radiate energy as efficiently as possible. The company says Vantablack has both the highest thermal conductivity and lowest mass-volume of any material suitable for such applications, and it can be used over a wide temperature range without impacting properties.

It’s produced using a proprietary photo-thermal chemical vapour deposition process (PTCVD) to create a highly-columnated vertically aligned nanotube array that can be applied directly to substrates. The result is an extremely effective trap for any incident radiation.

The PTCVD process enables synthesis of carbon nanotubes and other nanostructures at temperatures compatible with widely-used engineering alloys and lightweight, temperature sensitive structures such as aluminium.

The manufacture of `super-black` carbon nanotube-based materials has traditionally required high temperatures, preventing their direct application to sensitive electronics or materials with relatively low melting points. This, along with poor adhesion, prevented their application to critical space and air-borne instrumentation.

However, the two year development and test programme by Surrey NanoSystems successfully transferred its low-temperature manufacturing process from silicon to aluminium structures and pyroelectric sensors.

This has allowed it to be deposited in micrometre-scaled patterns at temperatures compatible with chip processing makes it highly-effective as an absorber in integrated-circuit transducers (microbolometers) used to convert incident infrared (IR) radiation to electrical signals for image processing.

In addition, the ability to modify both the density and length of the tubes allows the reflectance characteristics of the material to be tuned for a particular use.

Vantablack was originally intended for use solely within the IR spectrum, where it exhibits a very low (less than 0.15%) total hemispherical reflectance (THR) across wavelengths ranging from 1 to 15µm.

It is therefore used as the functional coating in IR systems such as thermal cameras, calibration targets, analytical instruments and large-scale scientific experiments where absorption of incident radiation defines performance limits.

This high-emissivity is further required for calibration sources for both terrestrial and space-borne instruments, including Earth observation instruments.

Ben Jensen, chief technology officer of Surrey NanoSystems, says: “Vantablack is a major breakthrough by UK industry in the application of nanotechnology to optical instrumentation.

“For example, it reduces stray-light, improving the ability of sensitive telescopes to see the faintest stars, and allows the use of smaller, lighter sources in space-borne black body calibration systems.”

Vantablack has virtually undetectable levels of outgassing and particle fallout, eliminating a key source of contamination in sensitive imaging systems. It withstands launch shock, staging and long-term vibration, and is suitable for coating internal components, such as apertures, baffles, cold shields and Micro Electro Mechanical Systems (MEMS) –type optical sensors.

“We are now scaling up production to meet the requirements of our first customers in the defence and space sectors, and have already delivered our first orders,” says Jensen. “Our strategy includes both the provision of a sub-contract coating service from our own UK facility, and the formation of technology transfer agreements with various international partners.”

Vantablack to be applied to flat and three-dimensional structures in precise patterns with sub-micron resolution.Vantablack is manufactured using Surrey NanoSystems’ NanoGrowth-Catalyst systems at the company's state of the art R&D centre in East Sussex, UK.

Perhaps future customers will include Spinal Tap, to reissue that infamous all black album cover, that this time, you’ll be able to say it can get, ‘none more black.’

Justin Cunningham

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I'd need to see a picture of it...

Comment Dean Hopkins, 10/12/2015

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