Archive for the 'science' Category

29
May
13

brand new all metal composite material

wwIt’s not often you can say that you are part of a team that has developed a brand new material, but so far as I am aware we have done just that, in partnership with the Max Planck Institute for Plasma Physics (IPP) at Garching near Munich. The new material in question is a tungsten fibre reinforced tungsten metal. What is so wonderful about that? Well if you carefully tailor the interface between the fibres and the matrix, you can turn an brittle material into a material with considerable toughness. This is particularly useful in high temperature environments where high thermal stresses cause solid tungsten to crack up. An example being a fusion power plant such as ITER currently under construction on Caderache in France.

The tungsten fibre is the same as that you find in old fashioned filament light bulbs and the matrix material is deposited using ATL’s specialism chemical vapour infiltration or CVI for short.

You can read more about it here: http://phys.org/news/2013-05-brittle-material-toughened-tungsten-fibre-reinforced-tungsten.html

07
Mar
13

A bit more rocket science

1-s2.0-S0094576504001614-gr1

So the 6-month Pathfinder Project has wound up. The work done, the reports written, the grant money paid: Thank you very much Astrium/UKSA!

And the results?

Well, like most research, as many new questions asked as old ones answered. Here is the summary of the public report:

The project made significant steps in coating iridium onto C103 niobium alloy to provide a high temperature thruster material.

Initial coating trials with a refractory metal interlayer were successful, but coatings of iridium onto the substrate were problematic. However, the experiments and analysis showed that a duplex layer of refractory metal and iridium could be deposited on a modified substrate. Due to the scientific potential of the material combination and its commercial interest, work will continue on the coatings under the ESA HTAE project until May 2013.

Summary of the summary: There are a few problems, but some results are promising and as the prize is big, we continue to work towards it.

If you want to know more, please get in contact.

18
Aug
11

Some Rocket Science

We have just started a new project. It’s for the European Space Agency and we are part of a group designing a new engine for missions to Mars and exciting stuff like that. Interesting stuff.

Our particular brief is to look at high-temperature materials an amazing number of which are made by CVD or CVI: For instance, W, Re, Ir, Nb, Ta, SiC, HfC & TaC

19
Jun
09

Hafnium Carbide

Carbon Fibre Reinforced Composite (CFC)Hafnium carbide is the most refractory binary compound known to man with a melting point of 3890degC. 480 degrees higher than tungsten! The mixed carbide tantalum hafnium carbide has an even higher melting point of 4215degC. Considering the surface of the sun is ‘only’ 5500degC or so, that’s pretty mind-blowing!

Just like its better known fellow Group4a elements, titanium and zirconium, it can (of course) be deposited by CVD by the reaction of hafnium tetrachloride with methane in the presence of hydrogen.

As a CVD coating HfC, just like its close relative, titanium carbide, TiC, is used on cutting tools, but more interestingly it is also used as a barrier layer to protect the fibres in carbon fibre reinforced carbon composites (CFCs) from oxidation at high temperatures. At first sight this seems pretty odd because HfC by itself has a poor oxidation resistance, but in combination with a carbon underlayer and a silicon carbide over-layer (both also deposited by CVD) a great protective thin film of mixed oxides is formed.

AFAIK nobody has tried to deposit Ta4HfC5 by CVD. Perhaps I should try it!

02
Jun
09

Tungsten

Free-standing CVD W shapes

Free-standing CVD W shapes

I love tungsten! At 3410 degrees C, it has the highest melting point of all metals. This makes it an incredibly useful metal, even if the green lobby manage to get rid of all the ordinary light bulbs out there. Electrical contacts, x-ray targets, windings & heating elements, space, missile, tools and any number of high temperature applications.

Tungsten’s very high melting point is also its weakness: It makes it very hard to work: Melting & casting is practically impossible, sawing, machining & forming very difficult.

Luckily tungsten is easily deposited by CVD, normally by the reaction of tungsten hexafluoride with hydrogen. This can be achieved at the modest temperature of 500 degrees C. Many different materials can be coated with a layer of tungsten from a micron to a few millimeters thick.

The relatively low deposition temperature means that steels can be coated (with a suitable interlayer) without distortion or the need for post-coating re-hardening.

By depositing a thick coating onto a removable/dissolvable/meltable/burnable mould, free-standing CVD tungsten shapes can be created. Thin-walled, boats, tubes, crucibles in 100% dense, high purity tungsten can be made. This is practically impossible by any other route.

If wou want to know more check out www.cvd.co.uk/othercoatings.html

30
Apr
09

Hello world!

Welcome

Welcome

Welcome to my first ever blog!

For the uninitiated CVD in this instance stands for Chemical Vapour Deposition as opposed to Cardio Vascular Disease (or Clyde Valley Drilling or Commercial Vehicles Direct or even Charterhouse Voice and Data).

If you Google ‘CVD’ you’ll soon find the Wiki for ‘Chemical Vapor Deposition’ obvious written by an American friend: Why DO they insist on changing perfectly good spellings?? Nonetheless an accurate piece even if it was written by an expert from the semiconductor industry with an obsession for acronyms. There are however many fields other than semiconductors where CVD finds applications. Nuclear, machine tools, automotive, oils & gas, aerospace, solar power, glass, electronic, medical and military to name but a few. Somewhere at the bottom of page 1 of your ‘CVD Google’ you will find www.cvd.co.uk . This is the website of my Company, Archer Technicoat Ltd, ATL.  Based in the UK, we specialise in the process of CVD and its application across as wide a spectrum of industries as possible.

What I hope to achieve with this blog is to regularly mention a particular coating or application, where hopefully a colleague in a different sector might think “I never knew you could do that with CVD” or a non-specialist might think ” Wow, that’s a pretty cool thing”.

I’ve got a few things in mind to kick off with but no doubt as time passes, things will get harder, so if something occurs to you, please feel free to contribute!

Cheers

John




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