History of the production of diamonds grown in a lab

Recently we looked at the history of the production of diamonds grown in a lab and watched as it began in the late 1800s. Although the equipment for growing diamonds has improved immensely over the past few decades, the current methodology is not very different from what it was in the 1950s, when GE first began mass production of synthetic quality diamonds. Currently, there are two main methods of producing diamonds, which most people in the industry are familiar with. But there are other processes that are now expensive and can not be used for mass production of diamonds of any quality. But with the improvement of technology and, As for the production of diamonds will begin to apply other technologies designed for other industries, we can still see new achievements. Let's take a closer look at how diamonds are synthesized in laboratories at the present time.

The method of high pressure at high temperatures (HPNT) is the most common at present for the production of diamonds. In fact, it was with this method that the very first researchers experimented. As the name suggests, the HPNT method attempts to recreate the pressure and temperature existing in the interior of the Earth where diamonds are formed. This usually requires a pressure of more than 5 GPa (gigapascal) and temperatures above 1500 ° C. For the HPHT method, a seed crystal is necessary, on which subsequent layers of carbon will grow until it reaches the desired size, simulating the actual growth process in the interior of the Earth. The carbon source is introduced into the metal solution. When the metal is heated, the carbon melts and dissolves, which solidifies into diamond under enormous pressure.

Currently, there are three basic designs of presses used in the production of diamonds by the HPHT method. The first is a tape press, originally designed by Tracy Hall, GE engineer, in 1954. In a belt press, two plates pressurize the top and bottom of the tape of compressed steel strips, and at the same time electric current is passed through the steel. In more modern tape presses, the opposite hydraulic pressure, rather than steel strips, is used to control the lateral pressure force. The current tape presses are usually much larger than those used by GE in the 1950s, but the principle is basically the same. The second design of the press is a cubic press in which six plates simultaneously apply force to a cubic capacity, Containing a diamond seed and a metal medium. A cubic press can create a diamond quite quickly compared to a strip press, but it is less effective in producing large diamonds due to the exponential increase in pressure required when the volume of the medium in a cubic capacity increases. 

Probably the most common design of the press is a BARS-type device, or a "halved sphere". It turned out to be the most economical, compact and effective design of the press for use in the cultivation of diamond crystals, and is also effective for the cultivation of large diamonds, sometimes larger than 10 carats. Initially invented by Russian scientists in the late 1980s, it can reach pressures of about 10 GPa and a temperature of up to 2500 ° C. In the center of the "sphere" is a cylindrical capsule, which can reach a size of up to one cubic inch and is made of materials that transmit pressure. This capsule is surrounded by six inner plates of tungsten carbide, which are well adapted to form a two-sided pyramid. This pyramid itself is placed in another set of steel plates, Forming two hemispheres (hence the term "halved sphere"). The whole device is placed in the body in the form of a toroidal chamber with a diameter of one meter. This body is then filled with oil heated to extremely high temperatures. The expansion of the oil creates the necessary force and presses the device in order to cause the growth of the diamond. ( ehudlaniado.com )