6 indicators to judge the quality of synthetic diamonds

1. Impact Strength

In past decades, China's synthetic diamond industry has been using static pressure strength to measure the quality of diamonds, but this test method has poor representation, large human error, and unscientific test mechanism. At present, the impact strength is basically used in the industry, and Ti (impact strength at room temperature) is to simulate the actual state of the impact and friction of diamond in use, so as to test the cold punch strength. TTi (thermal shock strength) is to heat the diamond to 1100 degrees, and measure Ti after cooling, which takes into account the frictional heat generated by the cutting of the diamond after it is made into a saw blade. Impact strength is a scientific and comprehensive quality indicator.

2. Magnetic Susceptibility

Due to the use of metal as a catalyst in the synthesis of diamond, it contains different diamond impurities, especially the inclusions inside the crystal, which makes diamond magnetic. It is of great practical value to characterize the impurity, toughness, strength, specific gravity, thermal stability and other properties of diamond by measuring the magnetic susceptibility easily and non-destructively. The smaller the impurity content, the smaller the magnetic susceptibility, the smaller the specific gravity, the lighter the color, the better the transparency, the higher the impact toughness and the smaller the brittleness.

3. Color

The color of diamond crystals is affected by temperature and chemical environment. When the temperature is low, the diamond crystals grow darker, and when the temperature is high, the color is lighter. Various trace elements (impurities) as the crystal grows determine the color of the diamond. For example, a trace amount of boron will make the diamond crystal appear sky blue, and a large amount of boron will make it black (commonly known as black diamond). Nitrogen enters the diamond crystal to form yellow diamond, which is mostly synthetic diamond. Aluminum prevents nitrogen from entering the growing diamond crystal. Makes diamond crystals colorless. (natural diamond color).

4. Particle Size

The concentration, uniformity and tolerance range of diamond particle size are also an important indicator for judging the quality of diamond. The particle size can be seen through the microscope, and it cannot be too large or too small. The particle size concentration should be high, and the tolerance range has a great influence on electroplating diamond tools. In electroplating tools, if tolerance requirements are involved, the relevant tolerance requirements cannot be less than the range in this table, otherwise only the error of the diamond itself will cause the tool The overall requirements are not up to standard.

5. Transparency

When diamond is synthesized at high temperature and high pressure, the crystal nucleus first grows at the junction of graphite and metal catalyst. If the crystal grows too fast, the metal will be wrapped in the diamond crystal, forming small black spots of impurities. Due to the poor thermal stability of impurities, the diamond will expand and crack from the inside when heated, thereby affecting the strength of the diamond.

6. Crystal form

The growth rate and shape of diamond crystals are more sensitive to pressure, with high pressure, more nucleation, fast growth, and easy formation of octahedral crystals. Diamond crystals grown under different pressure and temperature conditions have different morphologies. Therefore, stable pressure and stable temperature are important factors for crystal shape.