1. HPHT

1.1 Overview

HPHT is a technology that simulates the natural conditions under which diamond form. It converts carbon sources into diamond through high-temperature and high-pressure environments.

1.2 Process

Raw material preparation:

High-purity carbon sources (e.g., graphite) and metal catalysts (e.g., nickel, iron, cobalt) are used.

High-temperature high-pressure environment

Reactions occur at 5-6GPa pressure and 1300-1600℃ temperature.

Crystal growth

Carbon atoms rearrange under the action of the catalyst to form diamond crystals.

Cooling and separation

After the reaction, the temperature is slowly reduced, and diamond crystals are separated.

1.3 Characteristics

Fast growth rate

Suitable for producing large-grain diamonds.

High cost

Complex equipment and high energy consumption.

Wide applications

Mainly used for industrial diamonds and gem-grade diamonds.

2. CVD

2.1 Overview

CVD is a technology that deposits diamond films on substrate surfaces through gas-phase chemical reactions.

2.2 Process

Gas preparation

Carbon-containing gases (e.g., methane) and hydrogen are used.

Reaction chamber setup

The substrate is placed in the reaction chamber, and reactions gases are introduced.

Chemical reactions

At 800-1200 ℃, the gases decompose and form diamond films on the substrate surface.

Films growth

Uniform diamond film growth is achieved by controlling gas flow and temperature.

2.3 Characteristics

High purity

Can produce high-purity diamond films.

Complex shapes

Can deposit on substrates with complex shapes.

Lower cost

Relatively simple equipment and lower energy consumption.

Wide applications

Used in electronics, optics, tool coatings, and more.

3. Comparison of HPHT and CVD

Feature	HPHT	CVD
Growth speed	Fast	Slower
Cost	High	Lower
Product type	Large-grain diamonds	Diamond films
Applications	Industrial and gem-grade diamonds	Electronics, optics, tool coatings, etc.
Equipment Complexity	Complex	Relatively simple

4. Conclusion

HPHT and CVD are two major diamond synthesis technologies, each with its own advantages. HPHT is suitable for produced large-grain diamonds, while CVD excels in high-purity films and complex-shaped depositions. With technological advancements, the application prospects of both methods will continue to expand.