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h-BN can withstand temperatures of up to 2000°C in an inert atmosphere and remains stable in an oxidizing environment up to 900°C.
c-BN does not convert to h-BN below 1400°C.
h-BN has better thermal conductivity than aluminum oxide (parallel to c-axis: 400 W/m·K, perpendicular to c-axis: 30 W/m·K).
It exhibits a low coefficient of thermal expansion (h-BN: parallel to c-axis -2.7×10⁻⁶/°C, perpendicular to c-axis 38×10⁻⁶/°C).
h-BN has a low hardness (Mohs hardness ~2) and excellent machinability; c-BN has a hardness second only to diamonds.
h-BN exhibits excellent thermal shock resistance due to its low elastic modulus.
h-BN is a high-quality insulator (resistivity > 10¹⁴ Ω·cm, dielectric constant ~ 4).
c-BN is a wide-bandgap semiconductor (bandgap width ~ 6.4 eV).
Resistant to corrosion by molten metals (such as aluminum and copper), and does not react with acids/bases (except for concentrated sulfuric acid and molten alkali).
h-BN has exceptional high-temperature stability. It can withstand temperatures up to 2000°C in inert atmospheres and remains highly stable in oxidizing environments up to 900°C.
h-BN exhibits better thermal conductivity than aluminum oxide. Its thermal conductivity is highly anisotropic, reaching 400 W/m·K parallel to the c-axis and 30 W/m·K perpendicular to the c-axis.
h-BN is soft with a Mohs hardness of approximately 2, offering excellent machinability and thermal shock resistance. Conversely, Cubic Boron Nitride (c-BN) is extremely hard, second only to diamonds.
h-BN is a high-quality electrical insulator with a resistivity greater than 10¹⁴ Ω·cm and a dielectric constant of approximately 4. On the other hand, c-BN behaves as a wide-bandgap semiconductor with a bandgap width of about 6.4 eV.
Boron Nitride exhibits excellent chemical inertness. It is highly resistant to corrosion by molten metals like aluminum and copper, and does not react with standard acids or bases, with the exception of concentrated sulfuric acid and molten alkali.
