Materials for black chip resistant ceramic

[eng3000]

Can anyone help with the following brief? For a jewellery and decoration application I'm trying to find some ideas on a formulation for a black or grey (for aesthetic reasons,) non-toxic/irritant ceramic which is hard, preferably quite chip resistant (through droping,) and does not fail explosively or in shards when it goes (i.e. fails benignly).

To give some further clarification, there is a reference at

http://en.wikipedia.org/wiki/Ceramic

to an (unhelpfully named) "High-tech ceramic" used in watches. There also exists a Black Vitreous Ceramic (BVC) used in telescope mirror production, the full properties of which are unclear.

I thought about some iron oxide or other transition metal oxide composition but need some more technical data first (Nickel, some Chromium options etc are likely ruled out on allergy & toxicity grounds). I'd like to pre press/form or cast the parts into shape and have presently a firing temperature limitation of 1300 Celcius.

If it's the only practical solution, I'd consider a coating, but accept that some compromises will be necessary.

A pointer to a good ceramic materials reference book, with materials properties and some chemistry and a technical rather than art and crafts approach would also be of help.

Many thanks in advance.

 

[EdStainless]

Variations of zirconium oxide (TTZ, or TMZ) are the toughest ceramics that you will find. They are naturally off-white or cream colored. To make them black they are re-fired with a doped material that diffuses into the base. I don't know what is used in the doping. If I had access to a RADO watch I could analyze it and tell you. but mine is a fake.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[unclesyd]

Some of the ceramic looking black warch bezels are carbon fiber. They are also making rings and things from the fiber.

Sometime ago I made some earrings and pendents from glassy (vitreous) carbon. It is a little expensive but I got mine from as cast offs from the lab where I worked. I was going good until the lady that supplied the findings moved to California and I lost contact. I also experimented with some high density carbon foams by depositing different metals and cutting and polishing different shapes.

 

[eng3000]

Thanks for the suggestions, regarding vitreous carbon, I have read it is quite brittle. Are different grades (with varying properties,) therefore available? Carbon fibre, though interesting, wouldn't be suitable for this application.

On the zirconium oxide option, I'm willing to experiment but this leads to a few further questions as I can only reach 1300 Celcius at present. What does one get from heating ZrO2 and for example Y2O3 over 1170 C (and not over 1300 C)? Stabilised cubic, stabilised tetragonal or just a mess on the floor of the furnace? And what if I introduce some transition metal oxide or ferrite for colouring purposes? Isn't this likely to destroy the structure at useful concentrations or might this work as a surface dopant?

 

[EdStainless]

I have some pieces of TTZ from Coors. You might contact them and see if you can get some samples to play with. They might even know how to get it black.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube