From an early age, Howard Tracy Hall always wanted to work for General Electric and only two months after receiving his doctorate, he began working at the Research Laboratory that this company had in Schenectady, New York. He joined the "Project Superpressure" team, led by engineer Anthony Nerad, with the goal of making a synthetic diamond.
As on many other occasions, the circumstances surrounding Hall's synthesis have always been controversial. What is certain is that he manufactured synthetic diamonds on December 16, 1954 with a reproducible, verifiable and witnessed process, using a press of his own design.
According to Hall's account, for almost 4 years, this group of half a dozen researchers had a succession of failed experiments and impatience, rivalries and divisions within the team appeared.
He claimed his success was due to his determination to go his own way with a redesign of the press employing a rock-shaped tie ring that exerted pressure on the sample chamber via two curved conical pistons. He called his first steel design “Pirate” which didn't work, but he managed to get funding to use a harder material, Carboloy (cobalt dispersed tungsten carbide and also known as Widia). However, his experiments were “relegated” to using a small, old, leaky 400-ton press instead of the newer, more expensive 1,000-ton press used by other team members. Therefore, the composition of the starting material in the sample chamber, the catalyst for the reaction, and the required temperature and pressure were no more than guesswork.
The conditions of his experiment were:
- Iron sulfide and a form of powdered carbon as starting material
- Tantalum discs to conduct electricity in the cell for heating
- Pressure = 100,000 atmospheres
- Temperature = 1,600°C
It took about 38 minutes and when the sample was cracked open, the octahedral crystal assemblies were found on the metal disks of tantalum that had acted as a catalyst. In this way, the first synthetic diamonds were achieved, which today have many industrial applications.
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