Over the years, extensive research has proved that the unique physical and chemical properties of diamond make it an ideal material for a broad range of scientific and technological applications. Diamond is the hardest and stiffest material known, has the highest room-temperature thermal conductivity and one of the lowest thermal expansion coefficients of known materials, and is radiation-hard and chemically inert to most acidic and basic reagents.1
A diamond is formed deep inside Earth's upper mantle by re-crystallization of carbon, a process in which carbon atoms bond to each other growing into a strong tetrahedral structure where each carbon atom is bonded to four other carbon atoms, resulting in diamond growth.
To accomplish the same natural re-crystallization process above ground, scientists developed two techniques to grow single crystal diamonds:
- High pressure High Temperature (HPHT) technique and
- Chemical Vapor Deposition (CVD) technique using microwave plasma (MPCVD)
In the High-pressure High-temperature (HPHT) technique, diamonds are formed in a growth environment by exposing a diamond seed to high pressure and temperature conditions. The diamonds growth in HPHT machines, developed in the 1950's by GE, and the technique has since remained largely the same.