Boron Nitride Crucible

Boron nitride crucibles produced by hot-pressing process provide exceptional properties for high-temperature applications. They are essential instruments in the fields of metallurgy, ceramics, and materials research because of their thermal stability, chemical resistance, and electrical insulating properties.

Tags Boron Nitride Crucible

Boron nitride is an advanced ceramic material that comes in six different crystal forms, the most common of which are cubic boron nitride (c-BN) and hexagonal boron nitride (h-BN). c-BN is similar to diamond and is primarily used to produce cutting tools; h-BN is a white powder with a layered structure and lattice parameters comparable to graphite, also known as white graphite, possessing outstanding thermal conductivity and insulating properties, making it the most valued crystal form. Based on the varying preparation techniques, boron nitride can be divided into hot-pressed boron nitride and pyrolytic boron nitride.

Hot-pressed boron nitride is an excellent electrical insulator with exceptional lubricity and high temperature stability; even at extremely high temperatures, it can retain its lubricity and inertness. Despite the relatively poor mechanical properties of boron nitride, it offers high heat capacity, great thermal conductivity, exceptional dielectric strength, and is simple to machine. Boron nitride is a perfect high-temperature thermal insulation material since it can withstand temperatures above 2000 °C in an inert atmosphere.

Furthermore, hot-pressed boron nitride is anisotropic. When the atomic arrangement is perpendicular to the pressure direction, strong bonds are created, exhibiting outstanding strength, thermal, and electrical properties. When the arrangement of atoms is parallel to the direction of pressure, weak bonds are formed, resulting in exceptional lubricity. According to the above characteristics, taking advantage of the excellent chemical stability of boron nitride, it can be used as crucibles for melting and evaporating metals, boats, liquid metal delivery pipes, crucibles for synthesizing GaAs crystals, rocket nozzles, high-power device bases, pipes for melting metals, pump components, cast steel die, insulating materials, etc.

On the other hand, boron nitride produced through high-temperature pyrolysis reaction possesses excellent properties like high thermal conductivity, high mechanical strength, good electrical insulation, non-toxicity, etc., as well as chemical inertness, superior structure and performance, making it an ideal container for element purification, compound and composite semiconductor crystal growth. The primary applications include high temperature and high vacuum equipment insulation board, semiconductor single crystal growth (VGF, LEC) crucible, molecular beam epitaxy (MBE) evaporation crucible, MOCVD heater, polycrystalline synthesis boat and OLED evaporation unit, etc.

Features

High Melting Point: Boron nitride crucibles may be utilized at very high temperatures because of its very high melting point of around 3000°C.
High temperature thermal stability of boron nitride crucibles is remarkable; they are resistant to structural alterations or thermal breakdown.
great Thermal Conductivity: The speedy and uniform heating of the material is facilitated by the great thermal conductivity of boron nitrate.
Chemical Inertness: Most chemicals are not readily reacted with by boron nitride, which is also very resistant to molten metals.
Low thermal expansion coefficient: The crucible's form and dimensional stability are preserved at high temperatures in part because of the low thermal expansion coefficient of boron nitride.
High hardness and outstanding wear resistance make boron nitride crucibles appropriate for usage in harsh environments.
Electrical Insulation: Where electrical insulation is needed in high-temperature settings, boron nitride is a great material.
Self-lubricating: The self-lubricating qualities of boron nitride aid to lower friction and crucible wear during operation.
Non-toxicity: The environment and human body find boron nitride material to be benign.
Good thermal shock resistance and the ability to tolerate sharp temperature swings characterize boron nitride crucibles.

Application Areas

In many different scientific disciplines, boron nitride crucibles find significant use, including but not limited to:
Melting alloys and high melting point metals is achieved via a technique called smelting at high temperatures.

The container is used for chemical reactions in the process of chemical synthesis. This is particularly true in situations requiring high temperatures and chemical stability.
High-performance materials include, among others, ceramics, composite materials, and other materials that may be synthesised and treated with the help of material science.
Another term for the processes of heat treating, alloying, and refining metals is metal processing. Many times, metal processing is used interchangeably with metalworking.
acting as a container for high temperature laboratory experiments, used for scientific research.

Because of its similar structure to graphite, hexagonal boron nitride (h-BN) is also known as white graphite. Boron nitride (BN) is the primary component of boron nitride crucibles, which are crucial in the field of high temperature and chemical processing.

Both in the industrial and scientific research communities, boron nitride crucibles are indispensable. Their chemical stability and superior performance at high temperatures account for this. Because of advancements in science and technology as well as a growing need for novel materials, boron nitride crucibles are predicted to find even more applications. A wide variety of procedures that occur in high-temperature settings rely on them because they are reliable and can tolerate high temperatures for a long time.

Boron nitride materials are used in crucibles for melting metals, pipes for transporting liquid metals, and molds for casting steel due to their unique combination of properties, including low thermal expansion coefficient, high thermal conductivity, good thermal shock resistance, excellent high-temperature chemical stability, good peeling of solidified matter, and no infiltration with molten metal like molten steel, etc.

Boron nitride crucible's highest operating temperature is 2000°C. It won't crack after repeatedly cool it from 1500°C to room temperature rapidly for 100 times. In some situations, it is a perfect substitute for graphite or alumina crucibles due to its high anti-oxidation temperature of 900°C. On the other hand, boron nitride crucibles can be used to sinter and melt metals, rare earths, ceramics, and other materials.

Materials Available for Boron Nitride Crucible

1. Ferrous metals such as iron, copper, aluminium, nickel, magnesium, bismuth, zinc, etc., as well as alloys like Fe-Co-Ni-Si and Co-Zr-NB.

2. Materials that do not react with water and acid at room temperature, and can be slowly hydrolyzed to boric acid and ammonia by co-boiling with water.

3. Rare earths and nitrides.

Material Unavailable for Boron Nitride Crucible

1. Arsenic trioxide, molybdenum trioxide, antimony trioxide, chromium heptoxide, titanium carbide, etc.

2. High-lead glass glaze cannot be used in boron nitride crucible because it will corrode BN when melted in the air at 800-950℃, but it won't react when protected by nitrogen or inert gas.

3. Boron phosphate cannot be used in boron nitride crucibles because it will corrode boron nitride at 1400℃ in nitrogen and react with hot concentrated or molten alkali, as well as hot chlorine.

Boron nitride material is widely used for making crucibles for melting metals due to its low thermal expansion coefficient, high thermal conductivity, good thermal shock resistance, excellent high temperature chemical stability, good peeling of solidified substance, no infiltration with molten metals such as molten steel, and ease of machining, etc.

Using a boron nitride crucible needs particular guidelines to ensure its normal operation and service life. Some general steps for effectively using a boron nitride crucible are as follows:

Preparing the Crucible

Inspect the crucible for any visible defects or cracks before use. If any are found, it is suggested that the crucible be replaced to avoid failure during operation. In addition, clean the crucible with a soft brush or compressed air to remove any dust or debris.

Loading the Material

Determine the right amount of material to be placed in the crucible. Avoid overloading, since it may cause overflow or inadequate melting. Place the materials into the crucible, ensuring they are uniformly distributed and do not exceed the suggested capacity.

Handling

To avoid burns or injury, always wear proper personal protection equipment (PPE) when handling hot crucibles. This may include heat-resistant gloves and safety goggles. When moving the crucible, please ensure a firm hold and utilize tongs or tools made specifically for high-temperature applications.

Heating the Crucible

Place the loaded crucible into the heating apparatus, such as a furnace or kiln, making sure it is supported and stable. Gradually increase the temperature according to the unique requirements of the materials being processed. To avoid thermal shock, it is advisable to adhere to the suggested heating rate. Throughout the heating process, attentively monitor the temperature to prevent overheating or thermal runaway.

Cooling

Using the proper tools or tongs, carefully remove the crucible from the heating apparatus once the desired processing or melting has been completed. Allow the crucible to cool naturally by placing it on a suitable heat-resistant surface, such as a ceramic pad or insulating material. Avoid abrupt temperature changes or exposure to water, since it may result in thermal stress and potential cracking.

Cleaning and Maintenance

Inspect the crucible for any residue or solidified material when it cools. Remove any debris carefully using a soft brush or compressed air. When not in use, keep the crucible in a clean and dry environment to avoid contamination or damage.

It is crucial to keep in mind that depending on the application and materials involved, the specific procedures when using the crucible may vary. To guarantee correct use and safety precautions, always refer to the manufacturer's instructions and guidelines for the specific crucible you are using.