Differences in Crystal Structure between Synthetic Diamond and Natural Diamond

1. What is the difference between natural diamond and synthetic diamond?

 

The main differences between natural diamond and synthetic diamond are as follows:.

• (1) Different solvents: Natural diamond grows from silicate melts, where the solubility of carbon is lower, while synthetic diamond grows from metal melts, where the solubility of carbon is much higher than that of silicates;
• (2) The growth temperature of natural diamond (estimated to be 1000-1300 ℃) is lower than that of synthetic diamond (above 1400 ℃);
• (3) The supersaturation during the growth of synthetic diamond is higher than that of natural diamond, so it can be predicted that the surface of synthetic diamond is relatively rough. However, the observed synthetic diamond actually shows a smooth surface;
• (4) The growth spiral observed on artificial diamond crystals is different from that observed on natural diamond. The growth spiral on the {100} surface of artificial diamond is a rectangular parallel {111} with uneven steps, and its height usually exceeds tens of nanometers;
• (5) The morphological differences between natural diamond and synthetic diamond, as well as the differences between theoretically predicted crystal morphology and actual observations, are likely due to the different sizes of growth units.

 

2. What are the quality standards for natural diamond products?

Diamond, as a decorative item, is classified into grades based on the size, quantity, color, and other aspects of defects and impurities. As an industrial diamond, it can be classified based on its impurity content, and the classification of subtypes is mainly based on the difference in impurity nitrogen content. Please refer to the table below for details:

 

3. What is the cleavage plane of diamond?

The surface of a crystal that is most prone to splitting under stress is called the cleavage plane. The best cleavage plane of diamond is the plane that is consistent with the octahedral plane (see figure below). The second most commonly seen cleavage plane is the plane consistent with the rhombic dodecahedron.

 

 

4. How is the crystal form of diamond defined?

Diamond crystal forms can be divided into several types based on their appearance, including intact crystal form, equiaxed crystal form, non equiaxed crystal form, continuous crystal form, and polycrystalline form. The specific meanings are described as follows:

• (1) Any of the following conditions belongs to a complete crystal form: ① Clear crystal planes and edges, and full crystal growth; ② There are no more than two twin or symbiotic crystals; ③ Allow for a quarter of the missing corners and a quarter of the pits on the crystal surface. This type of diamond crystal has good crystal shape, high strength, and impact resistance, making it the most ideal cutting and grinding material.
• (2) Isometric shape: A crystal with a ratio of no more than 1.5:1 between its major and minor axes is called an isometric shape. The quality of this type of diamond is not as good as that of intact crystal diamond, with lower strength but still good shape. At present, this type accounts for a large proportion in synthetic diamonds.
• (3) Non isostructure: A crystal with a ratio of its major axis to its minor axis exceeding 1.5:1 is considered a non isostructure. This type of diamond has poor quality, poor shape, and low strength.
• (4) Continuous crystal: Any crystal with two or more common crystal planes or edges, as well as several incomplete crystals that are connected, is called a continuous crystal. When in use, the connected crystal should be broken into single crystals.
• (5) Polycrystalline: Many tiny crystals randomly aggregate and cluster together, known as polycrystals. This type of diamond has poor quality and low compressive strength.

 

5. What is the crystal structure of synthetic diamond?

Artificial diamond is obtained by transforming graphite under ultra-high temperature and high pressure conditions, with carbon atoms and a small amount of impurities as its constituent elements. Diamond is a crystalline form of carbon. When carbon atoms form diamond, they bond with each other in four identical sp3 hybridized orbitals, forming a tetrahedral structure as shown in the following figure. The tetrahedral structure formed by sp3 hybrid orbitals can exist in both cubic and hexagonal systems, so diamond has two different crystal structures: cubic diamond and hexagonal diamond. Common single crystal forms include hexahedron, octahedron, and rhombic dodecahedron.

 

Quanzhou Huice Tools New Material Co.,Ltd. is an experienced manufacturer of making diamond tools.