Hexagonal Boron Nitride Powder

1. Introduction to Hexagonal Boron Nitride Powder

Hexagonal boron nitride (hBN) powder is a synthetic material composed of boron and nitrogen atoms arranged in a hexagonal lattice structure. It is commonly referred to as BN Powder, hBN Powder, or Boron Nitride Powder, with the term "hexagonal boron nitride powder" providing the most specific designation for this material . Notably, hBN is also known as 'White Graphite' due to its structural similarities to graphite, which features a hexagonal crystal structure. 

The layered hexagonal lattice structure, which hBN shares with graphite, is fundamental to many of its characteristics, most notably its lubricity. However, a crucial distinction exists between these two materials: while graphite is a well-known electrical conductor and appears black, hexagonal boron nitride is typically an electrical insulator and presents as a white powder. This difference in electrical properties underscores the unique utility of hBN in applications where electrical insulation is paramount, even in conjunction with properties like lubricity or high thermal conductivity.  

Hexagonal boron nitride powder possesses a remarkable combination of properties that make it valuable across a wide spectrum of applications. These key properties include high thermal conductivity, excellent electrical insulation, high-temperature stability, remarkable chemical inertness, and superior lubricity. Consequently, hBN powder finds extensive use in diverse industries such as electronics, personal care and cosmetics, aerospace, automotive, and various material processing sectors. The sheer breadth of these applications highlights the material's versatility, which arises from its unique combination of thermal, electrical, mechanical, and chemical attributes.   

2. Physical and Chemical Properties

2.1 Physical Properties

The fundamental structure of hexagonal boron nitride powder is characterized by a hexagonal lattice. Similar to graphene, it exhibits a layered structure where boron and nitrogen atoms are covalently bonded within each layer. These individual layers are held together by weak van der Waals forces , a characteristic that is primarily responsible for the material's excellent lubricity. The typical morphology of hBN crystals is that of platelets.   

The Tap Density of Cersol hexagonal boron nitride powder is from 0.1 g/cm³ to 0.6g/cm³ , it depends on the different grade. The material has a high melting point of around 3000°C, at which temperature it also dissociates. Notably, at this temperature, hBN undergoes sublimation, transitioning directly from a solid to a gaseous state. It demonstrates stability up to approximately 3000°C when in an inert atmosphere. On the Mohs hardness scale, hBN has a hardness of 1-2 , indicating it is relatively soft, even if harder than graphite. This softness contributes to its non-abrasive nature.   

Cersol Hexagonal boron nitride powder is available in a wide spectrum of particle sizes, ranging from 300nm to 45μm. The suitability of a particular particle size is often application-dependent ; for instance, finer particles are commonly used in cosmetic formulations, while larger particles might be preferred as fillers in composite materials. The color and appearance of hBN powder are typically white to off-white, leading to its designation as "white graphite". The powder's visual characteristics can vary from a matte white to a more translucent or shiny appearance, influenced by the particle size and morphology.   

In terms of thermal properties, hexagonal boron nitride exhibits high thermal conductivity, often comparable to some metals. This thermal conductivity is anisotropic, meaning it differs depending on the direction of measurement relative to the crystal structure. It is significantly higher in-plane (along the layers, with values like 300 W/mK reported ) compared to the through-plane direction (perpendicular to the layers, e.g., 0.08 cal/cm.sec.K ). This anisotropic behavior is particularly relevant in applications such as thermal interface materials. Hexagonal boron nitride is also characterized by its high thermal stability, remaining stable at elevated temperatures up to 1000°C in air, 1400°C in vacuum, and 1800°C in an inert atmosphere. In some scenarios even greater stability, up to 3000°C in inert environments. Furthermore, hBN possesses a low coefficient of thermal expansion , which is advantageous in applications where dimensional stability under varying temperatures is critical. It also demonstrates excellent thermal shock resistance , allowing it to withstand rapid temperature fluctuations without structural damage.   

Hexagonal boron nitride is an excellent electrical insulator, exhibiting high electrical resistance or resistivity. Its room temperature resistivity can reach values as high as 10¹⁶~10¹⁸ Ω.cm. It also has a high dielectric breakdown strength. The material has a low dielectric constant, typically around 4 at MHz frequencies , and exhibits low dielectric loss. Additionally, hexagonal boron nitride is transparent to microwaves.   

The lubricating properties of hBN are notable, with a low coefficient of friction ranging from 0.15 to 0.70 , making it highly effective as a lubricant. This lubricity is attributed to its layered structure, similar to graphite, which allows for easy shearing between the layers due to the weak van der Waals forces.   

2.2 Chemical Properties

The chemical formula of hexagonal boron nitride is BN , and its molecular weight is approximately 24.82 g/mol , sometimes cited as 24.81 g/mol. It is typically produced with high purity levels, often exceeding 99%. Depending on the grade and the manufacturing process, trace amounts of impurities such as Boron Oxide (B₂O₃), Calcium Oxide (CaO), and Carbon (C) may be present.   

Chemically, hexagonal boron nitride is highly inert. It demonstrates resistance to most organic solvents, corrosive chemicals, acids, alkalis, and salt solutions. Generally, it does not readily react with molten metals.   

Hexagonal boron nitride exhibits good oxidation resistance, particularly at elevated temperatures, maintaining stability up to around 900°C in air , which is superior to that of graphite. It also possesses non-wetting properties with respect to most molten metals and glasses , a crucial characteristic for its application as a mold release agent. Furthermore, hBN has the capacity for strong neutron absorption , suggesting potential applications in nuclear technology.   

3. Application Industries of Hexagonal Boron Nitride Powder

· The Electronics and Semiconductor Industry is a major consumer of hexagonal boron nitride powder. Its high thermal conductivity and electrical insulation properties are critical for thermal management in semiconductors and LEDs. It is also used as a substrate for semiconductors and graphene-based devices , as an electrical insulator in electronic devices , and as electronic packaging insulators. Additionally, its microwave transparency allows for its use in microwave transparent windows , and it finds application in capacitors and wires. The increasing demand for smaller and more powerful electronic devices continues to drive the need for hBN in this sector.   

· The Cosmetics and Personal Care Industry increasingly utilizes hexagonal boron nitride powder for its smooth and silky texture, enhancing the feel and application of various products. It is a key ingredient in foundations, powders, eye shadows, lipsticks, blushers, kohl pencils, and skincare products. Its inert and non-toxic nature makes it suitable for sensitive skin applications, and it provides a desirable soft-focus effect in high-performance cosmetics.   

· In the Aerospace Industry, hexagonal boron nitride powder is essential for thermal management systems and as a high-performance insulator. It is used in coatings designed to withstand extreme temperatures and harsh environments , and in specialized applications like the plasma chamber in Hall Effect thrusters for satellite propulsion. Its high-temperature stability also makes it suitable for rocket engine components and heat shields for spacecraft.   

· The Automotive Industry benefits from the use of hBN powder in thermal management, particularly in electric vehicles and high-performance engines. It is also used as a lubricant additive in engine oils , in sealing oxygen sensors , and for brake lubrication.   

· In Metallurgy and Material Processing, hBN powder serves as an effective mold release agent for molten metals and is added to ceramics, alloys, plastics, and rubbers to provide self-lubricating properties. It is used in the production of crucibles and reaction vessels for handling molten metals and in high-temperature coatings for tools and components. It also finds application in hot isostatic pressing (HIP) processes.   

· The Paints and Coatings industry incorporates hBN powder as an additive to enhance thermal conductivity, chemical resistance, and lubricity. It is used in protective coatings for various industrial applications , including advanced bullet coatings and anti-corrosive coatings.   

· In Glass Manufacturing, hBN powder is utilized as a mold release agent for glass forming and as a non-wetting agent in various glass manufacturing processes.   

· The Energy Sector is also exploring the benefits of hBN powder as a component in batteries and energy storage technology and for thermal management in renewable energy systems. Its potential as a proton conductor in fuel cells is also being investigated.   

· The Cutting Tool Industry uses hBN powder as an additive to enhance the performance and longevity of cutting tools.   

Contact Cersol now to request your TDS and Grade recommendation.

4. Cersol Boron Nitride Powder Spec

5. Frequently Asked Questions (FAQs) about Hexagonal Boron Nitride Powder

What is the difference between hexagonal and cubic boron nitride? Hexagonal boron nitride (hBN) possesses a crystal structure similar to graphite, making it a soft material suitable for use as a lubricant and additive. In contrast, cubic boron nitride (cBN) has a structure akin to diamond, rendering it the second hardest known material, primarily used as an abrasive.   

How should I choose the appropriate BN Powder particle size?

If you are using it as a mold release agent for aluminum casting, CPW-02 is a general choice. If you are using it as a diamond grinding wheel additive, you can choose CPW-05. The above are just suggestions. Choose according to your past experience! You can also contact Cersol for more details.

Is hexagonal boron nitride powder toxic? While generally regarded as non-toxic , safety data sheets indicate potential hazards such as irritation upon inhalation, skin contact, or eye contact, and it may be harmful if ingested. Therefore, proper handling precautions are essential.   

What are the typical particle sizes available? Hexagonal boron nitride powder is available in a wide range of particle sizes, from nanometers (e.g., 70 nm, 100-400 nm) to micrometers (e.g., 0.5 µm to 30-40 µm). Specific sizes are often tailored to meet the requirements of different applications.   

How should hexagonal boron nitride powder be stored? It should be stored in a dry, well-ventilated area, in tightly closed containers. It is important to keep it away from strong oxidizing agents and strong acids and to protect it from electrostatic charges.   

What are the temperature limitations for using hBN powder? Hexagonal boron nitride powder is stable up to 1000°C in air, 1400°C in vacuum, and 1800°C in an inert atmosphere. Certain grades can withstand even higher temperatures, up to 3000°C, in inert environments.   

What are the advantages of using hBN over graphite? Compared to graphite, hBN offers higher thermal stability, especially in oxidizing atmospheres (up to 900°C for hBN vs. below 500°C for graphite). It also provides electrical insulation, unlike conductive graphite , and is white in color. Furthermore, hBN is considered non-toxic and chemically inert.   

How is hexagonal boron nitride powder manufactured? Common manufacturing methods include Chemical Vapor Deposition (CVD), the Borax-Urea method, and the Hydrothermal method. ¹ Each of these processes yields powder with distinct characteristics in terms of purity, particle size distribution, and morphology.   

What is the typical concentration of hBN used in different applications? The concentration of hBN varies significantly depending on the intended application. For instance, in cosmetics, it may range from 3 to 10%. In polymers used for thermal conductivity, a higher loading is often necessary to achieve effective percolation of the particles. The specific concentration is typically determined by the formulator based on the desired performance outcomes.