Understanding the Differences Between HPHT and CVD Diamonds
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High-pressure high-temperature (HPHT) and chemical vapor deposition (CVD) are both non-thermal diamond growth methods. Both involve the deposition of carbon on a surface as a diamond. Both HPHT and CVD diamonds have properties that make them suitable for different applications. Let’s take a closer look at the differences between HPHT vs CVD:

What is HPHT Diamond Growth?

High-pressure high-temperature (HPHT) diamond growth is a process that involves applying extremely high pressure and temperatures to a carbon source. In this process, the carbon source is subjected to high pressure and then heated in a high-pressure vessel. The carbon source is compressed to about 2.5 million atmospheres (25 gigapascals, GPa) and heated to about 2,000 degrees Celsius (°C) for several hours. At these conditions, carbon atoms become liquid and form a “carbon melt.” HPHT diamond growth is the same process used to produce synthetic diamonds for use in industrial cutting tools and other applications that require extremely high hardness.

What Is CVD Diamond Growth?

In chemical vapor deposition (CVD) diamond growth, carbon is “grown” on a surface as diamond. A carbon source is placed near the surface of a heated substrate. The carbon source reacts with the surface of the substrate and is deposited as diamond. CVD diamonds are typically deposited on a substrate surface using methane, ethane, or acetylene as the carbon source. These diamonds are grown at relatively low temperatures (about 850–900°C) and pressures of about 10% of the HPHT process. To grow CVD diamonds, the carbon source is placed in a controlled atmosphere chamber and then heated. CVD diamonds tend to have different properties than HPHT diamonds. They exhibit much lower hardness but higher toughness than HPHT diamonds.

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What Are the Differences Between HPHT and CVD Diamonds http://www.pearltrees.com/susan95/new-collection-2022/id48274929/item444352559?

There are a number of differences between HPHT and CVD diamonds. Let’s take a look at the most important ones: Hardness: HPHT diamonds have a hardness of about 10 on the Mohs scale, which is about 10 times harder than natural diamonds. In comparison, CVD diamonds have a hardness of about 7 on the Mohs scale. This means that HPHT diamonds are much harder than CVD diamonds. Growth rate: The growth rate of CVD diamonds is significantly higher than that of HPHT diamonds. CVD diamonds grow at a rate of about 1 micrometer per hour vs. HPHT diamonds, which grow at a rate of about 0.1 micrometer per hour. Price: HPHT diamonds are significantly more expensive than CVD diamonds. The price difference is due primarily to the growth rate of the two types of diamonds. The higher growth rate means that CVD diamonds are much cheaper than HPHT diamonds. The lower hardness and toughness of CVD diamonds makes them more suitable for jewelry.

Which Type of Diamond Should You Choose?

HPHT diamonds are best for applications requiring extremely high hardness and toughness. Examples include tools used in mining and other heavy industry applications. CVD diamonds are best for applications requiring a high level of toughness and low hardness. Examples include jewelry or other decorative items. Now that you know the differences between HPHT and CVD diamonds, you can make a more informed decision when purchasing synthetic diamonds for an industrial application or for jewelry.

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