omposition and structure
Cubic boron nitride single crystal:
a compound formed by nitrogen atoms and boron atoms bonded by covalent bonds. In its crystal structure, boron atoms and nitrogen atoms are arranged alternately and connected by BN covalent bonds to form a tetrahedral structure.
Diamond:
a single substance of carbon, a typical atomic crystal, each carbon atom is connected to the other four carbon atoms by covalent bonds in the form of sp³ hybrid orbitals to form a tetrahedral structure.
Physical properties
Hardness:
The Mohs hardness of cubic boron nitride single crystal is 9.7, and the microhardness is 8000-9000kg/mm²; diamond is the hardest substance in nature, with a Mohs hardness of 10 and a microhardness of 10000kg/mm².
Thermal stability:
Cubic boron nitride single crystal can withstand cutting temperatures above 1200℃; diamond oxidizes at 600°C in the atmosphere and turns into graphite at 1300℃-1400℃ in a vacuum.
Thermal conductivity:
The thermal conductivity of cubic boron nitride single crystal is 79.54 W/m・K, and it will gradually increase with the increase of cutting speed; the thermal conductivity of diamond is as high as 146.5 W/m・K, which is one of the best thermal conductivity materials known.
Color and transparency:
Pure cubic boron nitride single crystal is colorless and transparent, but usually due to factors such as synthesis conditions and impurities, it will appear black, amber, etc.; diamond is usually colorless and transparent, but natural diamond may have various colors such as yellow, blue, green, etc. due to impurities.
Chemical properties
Chemical stability:
Cubic boron nitride single crystal has good chemical inertness to iron, steel and oxidizing environment. It does not react with iron metals below 1150℃. In an oxidizing environment, a thin layer of boron oxide will be formed, which further increases its chemical stability, but it will react chemically when it encounters alkaline aqueous solution; diamond has a strong affinity with transition metals such as iron, cobalt, and nickel. At high temperature, iron atoms can easily react with carbon atoms in diamond to convert it into graphite structure.
Anti-oxidation:
Cubic boron nitride will not oxidize at 1000℃; diamond is easily oxidized at high temperature in the atmosphere.
Preparation and Source
Cubic boron nitride single crystal:
usually prepared by artificial synthesis methods such as high temperature and high pressure catalyst method or seed temperature gradient method. There are almost no natural cubic boron nitride single crystals in nature.
Diamond:
There are natural diamonds and artificial diamonds. Natural diamonds are formed under high pressure and high temperature conditions deep in the earth and are brought to the surface through geological action; artificial diamonds are synthesized in the laboratory by simulating the conditions for the formation of natural diamonds or using methods such as chemical vapor deposition.
Application Field
Cubic boron nitride single crystal: mainly used for processing various hardened steels, cold-hardened steels and other iron-based difficult-to-process materials, making grinding tools, cutting tools, etc., and can exert the self-sharpening characteristics of abrasives in high-speed and ultra-high-speed grinding and polishing.
Diamond:
Widely used in processing hard and brittle materials such as cemented carbide, ceramics, glass, etc. It also has important applications in jewelry, cutting tools, drilling tools, optical devices, semiconductors and other fields.
