They all purchase carbon coated ampoules from Sandfire Scientific Ltd. Other interested customers in our carbon coated ampoules hail from India and Ireland. When it comes to manufacturing quartz ampoules with a layer of pyrolyzed carbon, Sandfire Scientific’s reputation spans the globe.
Why put a layer of carbon inside your ampoule? The main reason is to prevent adhesion of material to the glass. The other reason is that open-ended ampoules can be reused, instead of breaking the glass to get the product out, as in the case of crystal growth using a Bridgman furnace. The Bridgman–Stockbarger technique is named after Harvard physicist Percy Williams Bridgman (Nobel Laureate in Physics, 1946) and MIT physicist Donald C. Stockbarger. Bridgman came up with the idea of a two-zone process; melting and growth in a preheated oven. Stockbarger’s approach was to load the material, in a boat or ampoule for example, either vertically or horizontally and gradually insert it in the oven.
And the “traditional” method of coating an ampoule is to use an oven and bake the carbon inside said ampoule. Only problem with that method is that the set up and completion of the work takes a long time. The ampoule has to be washed and rinsed two dozen times in between etching with Acids. The etching alone takes about 7 hours. Fill and back fill with Argon and Nitrogen at varying degrees in a kiln. Because the ampoule is resting inside an oven, you have to have all sorts of valves, bubbler, hoses and fittings to take the gases to the ampoule. You have to play with the oven temperatures. And it goes on and on. After all that, because the carbon is actually baked inside the ampoule sitting in the oven, the results are not always desirable. Before you have even had time to use it, your brand new ampoule may crack during the cooling off period. Therefore, this method can turn out to be quite expensive. It will certainly put a dent in your budget if you order carbon coated ampoules by the dozen. We are not knocking the traditional method. We simply want to save you time and money.
Sandfire Scientific has developed a method of applying light, medium or heavy layers of carbon without breaking the bank. It’s almost as easy as one, two, three. 1) you take the tube. 2) you make the ampoule. 3) you apply a layer of pyrolyzed carbon inside the ampoule.
So far, our customers have asked us to manufacture and carbon coat ampoules that have a diameter of 4mm ID to 130mm ID, and lengths of up to 500mm. Would you like plugs with your order? If you do, there is a 4th step, which is to remove the layer of carbon to your specified distance in order to facilitate sealing the ampoule with a plug. But more about plugs, and how to seal them in your ampoules, in a future blog. Give us a call.
