Unlike natural diamonds which are created by geological processes over several thousands of years, synthetic diamonds are created within weeks in a laboratory using an artificial process.
Synthetic diamonds are also referred to as HPHT diamond or CVD diamond after the two common production methods, i.e. high-pressure high-temperature and chemical vapor deposition methods, respectively.
How is Synthetic Diamond Produced?
There are several methods used to produce synthetic diamond. High-pressure and high-temperature (HPHT) method is the most widely used as it is comparatively low cost. In this method, there are three main press designs that are used to supply the pressure and temperature required to produce synthetic diamond - the belt press, the cubic press and the split-sphere (BARS) press. These presses can weigh hundreds of tons to produce a pressure of 5 GPa at 1500°C (2732°F).
The chemical vapor deposition (CVD) method is used to grow synthetic diamond from a hydrocarbon gas mixture. This method is preferred in laboratory research as it is simple and flexible to setup. The other advantages of this method are the possibility of growing synthetic diamonds over large areas and on different substrates, and the precise control over the chemical impurities. The CVD method does not require as much pressure as the HPHT method.
The ultrasound cavitation method is primarily used to manufacture micron-sized diamond crystals. Micron-sized diamond crystals can be created from a suspension of graphite in organic liquid at atmospheric pressure and room temperature using ultrasonic cavitation.
Properties of Synthetic Diamond Compared to Natural Diamond
The properties of synthetic diamond depend on the details of the manufacturing processes.
The key properties of synthetic diamonds are as follows:
- Mechanical properties - The exceptional hardness of synthetic diamond and very low coefficient of friction make these diamonds advantageous in mechanical applications such as extending tool life, reducing downtime and decreasing operating costs and carbon footprints. An example of a very tough kind of synthetic diamond is polycrystalline diamond (PCD). Synthetic diamonds can also be manufactured to have an ultra-fine edge for very high precision.
- Optical properties - The spectral band of synthetic diamond is the widest of any material, extending from UV to far infrared and the millimetre- wave microwave band.
- Thermal properties - Synthetic diamonds are known to have the highest known resistance to thermal shock and the highest known thermal conductivity which is about four times higher than copper. They are a favoured material for thermal management applications requiring optimum performance. They also have low thermal expansion
- Electronic properties - Synthetic diamonds possess high electrical carrier mobility, very good electrical insulator properties, low dielectric constant and loss, and a wide electronic band gap, which means that they can carry very low current even under high voltages.
- Acoustic properties - Synthetic diamonds have excellent acoustic properties that help CVD diamond tweeters to achieve frequencies of 70 kHz, resulting in an unmatched clear and transparent sound reproduction.
- Electrochemical properties - Synthetic diamonds are chemically and biologically inert, thereby allowing them to be used in extreme chemical, physical, and radioactive environments that would destroy minor materials. Efficient oxidation of organic and inorganic compounds is possible due to their good electrochemical properties. Synthetic diamond anodes can facilitate ozone production on a scale that is appropriate for homes, hotels, and hospitals. This method is considered more efficient and more reliable than any other technology currently available.
Companies Involved in Synthetic Diamond
Some companies involved in the business of synthetic diamonds are listed below with a brief introduction:
- Wonderstone Ltd is 100% owned by Assore Ltd and has been mining a uniquely pure pyrophyllite deposit 300 km west of Johannesburg since 1937. They supply the material to synthetic diamond manufacturers around the world.
- Element Six, which was formerly known as De Beers Industrial Diamond, is a company specialised in providing synthetic diamond.
- Scio Diamond Technology Corporation is a manufacturer of synthetic diamonds located in South Carolina, USA.
Applications of Synthetic Diamond
Synthetic diamonds are widely used in various fields. The key areas of application are as follows:
- PCDs are widely used in oil and gas drills as no other material is capable of handling the extreme conditions. Large economic benefits are gained by rig drilling operators due to the use of these diamonds.
- Ideal ‘window’ material for several industrial, R&D, defence and laser applications
- All types of electronic and electrical applications in which build-up of heat can severely impair performance or destroy delicate circuitry
- As a ‘heat sink’ for sensitive components used in the telecommunications industry and in microelectronic devices.
- In the production of laser optics where synthetic diamond provides optimum exit windows for CO2 lasers, such as those used in automotive cutting applications
- Synthetic diamond-based products are being used in industrial and household water treatment
- In advanced healthcare applications such as therapy for eye cancer patients where synthetic diamond-based radiation detectors ensure the delivery of the correct dosage to precisely target only the cancer-affected tissue and not the healthy tissue around it
- As surgical scalpel in ophthalmic and neuro surgery
- Researchers are trying to develop synthetic diamond-based quantum computer technology that could enable faster data processing and secure communication
- In the solid state particle detectors used at the Large Hadron Collider at CERN in Switzerland
- Polycrystalline CVDs are an essential component in high performance loudspeakers
- As consumer diamond gemstones.