Boron nitride is a crystal composed of nitrogen atoms and boron atoms. In addition to the common hexagonal boron nitride (white graphite), there are also variants such as cubic boron nitride (CBN), rhombohedral boron nitride (RBN), and wurtzite boron nitride (WBN). Scientists have even discovered two-dimensional boron nitride crystals with similar properties to graphene. Different boron nitride variants have different characteristics and applications.
Thermal properties
BN ceramic products can be used in an oxidizing atmosphere of about 900°C and an inert atmosphere of nearly 2100°C. This property is higher in refractoriness than refractory materials such as mullite, alumina, and silicon carbide. At the same time, it has great resistance to thermal shock and will not break even in a rapid cooling and heating environment of 1000°C.
Chemical stability
It does not work with most metals such as liquid iron, aluminum, copper, silicon, potassium arsenide, brass, and cryolite, and the same is true for slag glass, so containers made of boron nitride materials can be used as vessels for the above substances. However, B2O3 is generally hygroscopic, which causes the product to seep out the absorbed water during rapid heating during use, thus causing cracks. One of the effective measures to improve this shortcoming is to add some binders.
Electrical properties
Because BN products have low dielectric constants and dielectric losses, they can be widely used in high-frequency and low-frequency ranges. Its dielectric strength is 4.5 times that of alumina, and its dielectric constant is half that of alumina. Its electrical properties are very different from those of graphite. Like oxide ceramics, it has no conductivity at high temperatures and is an electrically insulating material that can be used in a wide temperature range.
Mechanical properties
h-BN ceramics have a Mohs hardness of two. It can be processed on lathes, milling machines, and other processing equipment, and into thin sheets, spirals, and various complex-shaped parts. BN has low mechanical strength. Although it is superior to graphite at room temperature, it is more brittle than oxide ceramics.
Aerospace field
h-BN has high thermal stability and low dielectric loss and is one of the materials suitable for manufacturing high-temperature antenna covers/windows. Although it has problems such as low hardness and poor rain erosion resistance, h-BN ceramics can be composited with silicon nitride, silicon oxide, etc., which can improve the sintering characteristics while also combining the advantages of each component and can meet the requirements of antenna cover/window components for heat protection, load bearing, wave transmission and other complex performances under high Mach number flight conditions.
Metallurgical industry
h-BN and its composite ceramics have been widely used as high-temperature refractory materials, such as TiB-AlN-BN composite ceramic evaporation boats, special metal high-temperature electrolytic cells, high-temperature collapses, casting shells, etc. With the deepening of research and the expansion of application needs, the performance of this series of ceramic materials has been greatly improved, and the application field has been increasingly broadened.
After experiencing a variety of materials such as traditional refractory materials, fused quartz, and zirconia, h-BN has been recognized as the most promising material.
Electronics industry
h-BN has the characteristics of high insulation and high thermal conductivity and can be used as a heat dissipation management device in electronic circuits. When a single layer or a few layers of h-BN nanomaterials prepared by chemical vapor deposition or liquid phase exfoliation are applied to the surface of a chip, it can not only play a protective role, but also use its special two-dimensional structure to bring about excellent lateral heat transfer capabilities, quickly transfer the heat of local hot spots in high-power electronic devices laterally, reduce the local maximum temperature, and thus improve the life and reliability of the device. In addition, h-BN powder is also an ideal polymer filler. Adding it to materials such as resins, rubbers, and plastics can increase thermal conductivity and improve insulation properties, which plays an important role in the application of polymer materials in flexible electronic devices.
Edgetech Industries Advanced Ceramics Division supplies high-quality boron nitride ceramics, including rods, tubes, plates, rings, gaskets, crucibles, structural parts, etc. Please visit https://www.eticeramics.com for more information about Boron Nitride or other ceramic products.