Creator:Tracy Hall
Date Created:May 17, 1976
Place Created:Chagrin Falls, Ohio
Keywords:diamond synthesis
Context:letter to William Harshaw
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William A. Harshaw II 6020 Deer Run Drive Chagrin Falls, Ohio 44022
Dear Dr. Harshaw:
17 May 1976
Now that I have your letter of May 11th, I am in a better position to comment than wtimi talking on the telephone with you. Thermodynamic data on the properties of substances at high pressure and elevated temperature are generally unavailable. Consequently, calculations on your proposed pressure device can not be made. Howecer, from experieyxence, I express it as an opinion that a phase change or the thermal expansion of UFg in a confined constant volume will not generate a very high pressure at all. UF^ is a molecular "soft" compound and will be very highly compressiblw. You would need to use a "hard" substance with very strong atomic bonds (network-type structure). I do not know of a substance that would meet this and all the other requirements necessary for your proposed system to reach the pressures that you seek. With respect to ^ooir proposed fixed volume container, you should read P. W. Bridgman's book, "Physics of High Pressure". He will explain why building cylinders of larger and larger diameter is ineffective in confining unHW«.in&. The same would be true for spheres or other shapes. Also, the nickel or any other metal that you might use for your spheres are too highly compressible. The inner parts of your confining chamber must be made of highly incompressible substances such as tungsten carbide or even diamond for the pressures you desire.
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Your idea of using carbon of the amorphous variety and of U3ing efctruding, forging and other methods used for salts seems novel if applied to diamond. Diamond with its network structure and the most untractable substance known ( the strongest three dimensional bonding network known) may offer you some challenges, however, when you treat it the way you tre«t sodium chloride.
I ammnot in a position to consult on your project or to fcecoramend it or to enter into a cooperative arrangement with you but wish you luck and success.
Very truly yours, H. Tracy Hall