Production of fine metal powder with BN enhanced atomization process
Introduction
Metal micro powders are essential materials in various industrial applications, including aerospace, automotive, biomedical, and many others. The atomization method is one of the most effective techniques to produce fine metal powders with high purity and homogeneous composition. This process involves the spraying of molten metals through nozzles or crucibles at high-speed gas or liquid stream to form droplets which subsequently solidify into the desired powder. The properties of the produced powder such as particle size distribution, morphology, and chemical composition depend heavily on the atomization conditions and material selection. One key component in this process is the nozzle or crucible, which plays a crucial role in determining the quality of the resulting powder.
Boron Nitride as a Material for Atomization Nozzle or Crucible
Boron nitride is a unique material that has excellent thermal and chemical stability, along with outstanding mechanical properties. It is an ideal material for applications that involve high-temperature environments because of its high thermal conductivity, electrical insulation, and chemical inertness (1). Boron nitride exhibits a high degree of corrosion resistance and can withstand repeated thermal cycling without degradation (2). Its wide bandgap makes it an electrically insulating material, ensuring minimal contamination of impurities when used in high-temperature processes.
Boron nitride material
Nozzle Selection and Its Effect on Powder Quality
The geometry and material of the nozzle play an essential role in the production of metal micro powders by atomization method. The nozzle diameter, shape, and angle impact the droplet formation, velocity, and trajectory, influencing the size distribution and morphology of the resulting powder. Hence, selecting the proper nozzle design is critical to achieving a specific particle size distribution required for a given application. Moreover, the wear resistance of the material composing the nozzle is essential in preventing particle contamination and increasing equipment lifetime. Non-oxide ceramics demonstrate superior durability, strength, and temperature resistance compared to other materials commonly used in the production of atomization nozzles, such as graphite and alumina.
Crucible Selection and Its Effect on Powder Quality
The characteristics of crucibles used in the atomization process also have significant influences on the quality of the resulting metal micro powder. Similar to the material selection for nozzle design, the material selected for the crucible must meet specific requirements related to high-temperature, chemical stability, non-reactivity, and durability. Corrosion resistance is crucial because contact with the molten metals occurs during the atomization process. Boron nitride is an optimal material choice due to its strong covalent bonds and chemical inertness against various materials, therefore leading to a minimal risk of contamination. Additionally, boron nitride has excellent thermal properties that impart greater precision and consistency during the atomization process when compared to alternative materials (2).
Advantages of Using Boron Nitride in Atomization Process
Using boron nitride materials for nozzle or crucible construction enables several improvements over traditional materials. The use of boron nitride-composed components provides higher likelihoods of successful atomization due to its unique composition. It exhibits superior erosion resistance, demonstrating long operational lifetimes, and the potential for more precise control over particle size distribution and morphology. Moreover, the geometrical tolerance of boron nitride components is extremely high, allowing for further improvements in the uniformity of particle sizes produced by atomization.
Applications of Metal Micro Powders Produced Through Boron Nitride-Nozzle Atomization Method
Due to their unique surface properties, high strength-to-weight ratio, and homogeneous chemical compositions, micro powders derived from boron nitride-nozzle atomization techniques are useful across several industries and applications, including metal-metal bonding, additive manufacturing, coatings, biomedical implants, and other uses requiring controlled or rapid material dispersion.
Composite boron nitride nozzle
Conclusions
In conclusion, the atomization method is a powerful way to produce metal micro powders with high purity and homogeneity. Using boron nitride for nozzle or crucible fabrication in this process presents numerous advantages, such as minimal impurity contamination, excellent thermal stability, and outstanding corrosion resistance. Moreover, using boron nitride materials provides a more controlled and uniform method to derivative powders when compared to traditional materials. The application of boron nitride material in atomization techniques can enhance various industrial applications, including the biomedical industry and the electronics industry for use in air and water purification systems and ammonia production. It is increasingly likely that these materials will become more widely utilized for producing high-quality powders in forthcoming years.
References:
Kevan Westcott M., Purcell S.T. (2008). Boron Nitride: Properties, Synthesis and Applications. Inorganic Materials: A Series of Monographs on Inorganic Chemistry, Volume 42.
Williams, P., & Choong, G. (2017). Metal Powder Production by Gas Atomization and Spray Forming. Journal of Materials Engineering and Performance, 26(3), 914-928.