H. Tracy Hall

American physical chemist

• Born: October 20, 1919
• Birthplace: Odgen, Utah
• Died: July 25, 2008
• Place of death: Provo, Utah

Hall invented the experimental method for producing synthetic diamond, which is used for numerous industrial applications, electronics, and the jewelry business. Known as the “father of man-made diamond,” Hall was granted nineteen patents that included inventions dealing with high-pressure, high-temperature equipment, as well as various methods for making diamond and other hard chemical compounds.

Primary field: Chemistry

Primary invention: Synthetic diamond

Early Life

Howard Tracy Hall, the son of Howard and Florence Tracy Hall, was reared with his four brothers on a farm in Marriott, Utah, a rural town north of Ogden. As a young boy, Hall learned the value of hard work on the family farm and enjoyed roaming the surrounding fields in Marriott. When his family traveled to Ogden to obtain supplies, Hall and his brothers would spend time at the Ogden City Library, where Hall became highly interested in reading about great scientists, particularly Thomas Alva Edison. At the age of nine, Hall decided that sometime in his future he would work as a scientist for Edison’s company, General Electric (GE).

In 1939, Hall earned his associate degree in science from Weber College in Ogden. He then attended the University of Utah. There he met Ida-Rose Langford, marrying her in 1941. After completing his B.S. degree in chemistry in 1942, he earned his master’s degree from the University of Utah the following year under the direction of G. Victor Beard. Beard was the first scientist to encourage Hall to follow his passion—conducting experiments dealing with diamond synthesis.

From 1944 to 1946, Hall served as a Navy ensign in World War II. After returning to the University of Utah in 1946, Hall, under the tutelage of famed chemist Henry B. Eyring, began thinking more about the theory associated with the conversion of carbon to diamond. He earned his Ph.D. in physical chemistry from the University of Utah in 1948. Two months later, Hall accepted a position as a chemist at the General Electric Research Laboratory in Schenectady, New York, a fulfillment of his childhood dream.

In 1951, GE announced that it would tackle the problem of producing synthetic diamond because of its great value in industrial applications. Volunteers were sought to help with the project, known as Project Superpressure. Hall volunteered and, along with fellow chemist Robert H. Wentorf and a group of physicists led by Herbert M. Strong and Francis P. Bundy, pursued the problem. After thoroughly analyzing a variety of questions related to the chemistry of diamond, Hall decided that the first barrier to overcome was the invention of high-temperature, high-pressure equipment that could convert either graphite or the carbon in carbonates into diamond.

Life’s Work

Initial experiments conducted during Project Superpressure used a Carver press, a modified twenty-ton automobile jack. After the research group designed a new, versatile press that would take about two years to build, Hall pursued experimentation using a small bench press and a modified water-operated Watson-Stillman press that leaked water profusely. Although resisted by other scientists in the group who felt that he was intruding into their areas of expertise, Hall continued to develop unique variations of piston-cylinder devices that were formulated by the group but that were not working because of mechanical failure at the junction of the walls and the bottom of the cylinder bore. Hall finally solved the problem by eliminating the cylinder bottom altogether by placing two conical-shaped semi-pistons back-to-back. Internal pressure was confined radially by a belt of prestressed steel bands. Hall was eventually granted a U.S. patent for the high-pressure, high-temperature belt apparatus in 1960. It could generate 120,000 atmospheres of pressure and sustain a temperature of 1,800 Celsius in a working volume of about one-tenth of a cubic centimeter for intervals of several minutes at a time.

Although it was thought that the extreme pressure and temperature conditions available in the belt apparatus were more than sufficient to directly transform graphite into diamond, experiments proved otherwise. Since direct transformation to diamond did not occur, Hall tried hundreds of indirect approaches using various catalysts to speed up the transformation. After numerous failures, GE was considering abandoning the project to produce synthetic diamond.

With only a few days remaining before GE was to scrap Project Superpressure, on December 16, 1954, Hall used his belt apparatus made with a tungsten carbide chamber to run an experiment that used graphite, along with troilite (iron sulfide) to act as a catalyst; a disk made of tantalum was used to conduct electricity into the cell containing the sample. The pressure in the belt apparatus was near 70,000 atmospheres (about one million pounds per square inch) and the temperature was near 1,600 Celsius. Upon breaking open the cell after several hours of run time, Hall observed numerous shiny, octahedral crystals cleaving to the tantalum disk. After regaining his composure, Hall examined the crystals under a microscope and found that they contained structures that looked like natural diamonds. Further analysis showed that the crystals scratched sapphire, burned in oxygen to produce carbon dioxide, and had the density and refractive index of natural diamond. An X-ray diffraction pattern produced a few days later confirmed that the crystals were diamond. During December 17-30, Hall experimented with varying the pressure and temperature to determine the best pressure-temperature range in which diamond would form. On December 31, GE physicist Hugh Woodbury duplicated Hall’s results and also produced synthetic diamonds.

Once the achievement of the synthesis of diamond was formally announced by the media on February 15, 1955, Hall was highly sought after, with job offers from numerous high-techology companies. Because of the lack of credit received by Hall from GE for his invention of the apparatus and the method for synthesizing diamond, he accepted a position as a professor of chemistry and director of chemical research at Brigham Young University (BYU) in 1955. At BYU, Hall invented a completely new high-pressure machine for making diamond, known as the tetrahedral press. It contained four anvils (press members) that converged on a tetrahedral volume. He was granted a U.S. patent for the tetrahedral press on December 29, 1959. Hall built and sold tetrahedral presses and invented an improved apparatus, the cubic press, in 1964. The cubic press had six anvils that provided pressure simultaneously onto all the faces of a cube-shaped volume. In 1966, Hall and two other BYU professors, Bill Pope and Duane Horton, formed Megadiamond, a company that manufactured high-pressure equipment and produced synthetic diamond.

In his personal life, Hall was a devoted husband and father. He often said that his greatest accomplishments were his home and family. He was a devoted member of the Church of Jesus Christ of Latter-day Saints, serving as a bishop and in many other positions of responsibility and leadership. During his spare time, he enjoyed farming and growing fruit trees.

Impact

Hall is the epitome of an individual who never gives up no matter what the odds may be. While working at GE, after hundreds of failed experiments, an increasingly impatient management, and intense rivalries and competition among fellow researchers, Hall endured and pursued his dream of making diamond until he succeeded. His inventive genius and perseverance led to his receiving nineteen patents, which included eleven patents for high-pressure, high-temperature apparatuses and five patents for making diamond and diamond composites. Until the late 1990’s, every diamond-making press in the world was based on designs invented by Hall.

The first synthetic diamonds produced by Hall and others were very small, but just right for a variety of industrial applications that involved cutting, grinding, and polishing other materials. By 1954, industry was using about 14 million carats of diamond in manufacturing processes, all coming from natural sources. By 1996, industrial diamond usage had risen to more than 505 million carats, with more than 90 percent being produced synthetically using Hall’s inventions. Human-made diamonds are used for applications in the aerospace, mining, manufacturing, petroleum, and automotive industries. They can be found in drill bits, masonry saws, cutting tools, and polishing machinery.

As Hall improved his tetrahedral and cubic presses, electronic applications soon emerged, followed by the production of diamonds large enough to be used in the jewelry business, starting in 1970. Industrial diamond instruments made dental work safer, faster, cheaper, and less painful and allowed eyeglasses to be made in an hour or less. In place of using jackhammers, saws made with synthetic diamond blades became the primary tool used for repairing roads.

In 1970, Hall received the Chemical Pioneers Award from the American Institute of Chemists. Two years later, he was presented the American Chemical Society Award for Creative Invention for being the first scientist to invent a reproducible process for manufacturing synthetic diamond. In 1994, Hall was awarded the Governor’s Medal for Science and Technology.

Bibliography

Barnard, Amanda. The Diamond Formula: Diamond Synthesis—A Gemmological Perspective. Boston: Butterworth-Heinemann, 2000. A comprehensive history of synthetic diamonds that highlights the contributions of Hall. An exhaustive work on diamond manufacturing and testing, it brings together research, achievements, theories, and experimental and analytical data.

Bridgman, Roger. One Thousand Inventions and Discoveries. New York: Dorling Kindersley, 2006. Bridgman reviews some of the most important inventions and discoveries in history, including Hall’s synthesis of diamond. The entries are written primarily for younger readers, with descriptions and cross-references to valuable resources.

Hazen, Robert M. The Diamond Makers. New York: Cambridge University Press, 1999. An excellent review of the historical developments that led to the production of synthetic diamond. Readers are introduced to the brilliant pioneers of high-pressure, high-temperature research and the extraordinary technological advances and the devastating failures of the synthetic diamond industry. Hazen believes that Hall should have received the Nobel Prize for his work in inventing the equipment and method for producing synthetic diamond.

Shigley, James E., ed. Gems and Gemology in Review: Synthetic Diamonds. Carlsbad, Calif.: Gemological Institute of America, 2008. Discusses the inventions and work of Hall and gives up-to-date information on high-pressure, high-temperature production of synthetic diamonds. The production and identifying characteristics of such diamonds are detailed in the text, which includes two full-size wall charts.