Cuts both ways

A flexible ceramic thermal barrier that can be cut and moulded to coat irregular shapes is undergoing final testing by UK materials technologists.

Plasma-sprayed coatings specialist Zircotec has developed a flexible version of its ceramic coating that can be applied to a 100 microns-thick aluminium foil using a similar method to the one the company already employs to coat rigid systems such as performance car exhausts. Ceramic material is fed into equipment resembling a gas welding torch and kinetic energy blasts it onto the foil. As it hits the substrate, it solidifies and cools into droplets known as ‘splats’ of the ceramic with small air gaps in between. The layers of coating are then built up to the required thickness.

The new product, provisionally named Performance SuperFlex, employs a modified patented technique to form a mesh pattern that prevents it cracking when bent.

Peter Whyman, spokesman for Zircotec, said: ‘We usually supply a service to a company requiring a coating, but we see this more as a product. Between the heat shielding and the substrate is a very flexible bond coat that holds whichever shape you put to it. You can cut it with a pair of scissors and mould to the form you want. Thermally it is as efficient as many of the mainstream heat shields out there at the moment, but a lot lighter and more flexible to fit onto unusual shapes.’

So far, Zircotec has only produced small sheets of the new material and is currently in the process of proving the production of larger elements. Company researchers are carrying out in-house testing of its thermal capabilities and its pull-off and shear strength. Once these steps are complete the company plans to launch the material commercially.

Zircotec is also investigating a multi-layered option. ‘The product is very thin and flexible and provides a good thermal barrier,’ said Whyman. ‘But if a customer needs an even better thermal barrier but doesn’t need as much flexibility we could make a sandwich, so we’re looking for an adhesive we can put between layers that still give a high degree of flexibility without affecting the thermal barrier.’

Zircotec was originally part of the former Atomic Energy Authority and the spray coating process was initially developed for the thermal management of hot pipes. The company moved into the automotive and motorsport sectors in 1993, when it was approached by the Subaru world rally team. It has since gone on to work with F1 and other performance car developers.

The thermal barrier is used to protect heat-sensitive components in cars, including the manifold, tailpipe, catalytic converters and turbo-housing for the comfort of the driver and to reduce the risk of fire in motorsport. It also reduces under-bonnet temperatures giving improved performance and, according to its producer, can also be used to allow classic cars, which exhibit poor thermal properties, to continue to run for much longer.

The coating can be applied to any metal and some non-metal substrates such as carbon composites and glass fibre — as used in F1 — Kevlar and high-temperature plastics using exactly the same process. Zircotec tweaks the spraying parameters accordingly as some components need to be kept cool as the flame burns at several thousand degrees centigrade.

According to Whyman, the main market for the new product will still be automotive, but its flexibility means it could also be used for aerospace applications and even in clothing for emergency services personnel. Although Zircotec’s thermal coating cannot be sprayed directly on cloth, a layer of the new material could be sandwiched between two layers for firefighters, for example.