Boron Nitride Ceramic Threaded Bushing BN Ceramic Parts

                                                                                                Product Details                                                                                       

Overview of Pyrolytic Boron Nitride (PBN) Ceramic Tubes

1.1 General introduction
Pyrolytic Boron Nitride (PBN) ceramic tube is a high-performance hollow cylindrical ceramic with prominent anisotropic properties, ultra-high vacuum tightness, outstanding high-voltage insulation and directional thermal conductivity. It delivers precise directional heat control, radiation resistance and low gas release, widely adopted in ultra-high vacuum, semiconductor and high-temperature precision testing equipment, as an irreplaceable advanced ceramic different from alumina, AlN and hot-pressed boron nitride.

1.2 Chemical Composition & Microstructure

• Single-phase pure boron nitride ceramic, ultra-high purity crystal structure formed by vapor deposition, minimal impurity elements.
  
• Distinct layered hexagonal crystal lattice, showing obvious anisotropy on thermal and mechanical performance between a-axis and c-axis directions.
  
• Apparent density: 2.10–2.15 g/cm³ for plate blanks, 2.15–2.19 g/cm³ for crucible tubes; dense pore-free structure with extremely low helium transmittance.
  

2. Manufacturing Process

2.1 Vapor Deposition Raw Material Preparation

High-purity boron source and nitrogen carrier gas are precisely proportioned, purified to eliminate particle impurities, strictly controlled gas flow to guarantee uniform crystal deposition and stable layered lattice growth.
Step A: High-temperature vapor reaction under sealed furnace at controlled thermal gradient.
Step B: Slow layered crystal deposition to form complete uniform hexagonal BN layers.
Step C: Form integrated compact PBN tube blank without internal pores or microcracks.
Step D: Strictly constant temperature curve to avoid deformation and internal stress during deposition.

2.2 Precision Cutting & Controllable Machining

Step A: Mould forming of hollow tubular blanks via self-designed fixture after deposition.
Step B: Slow programmed cutting to eliminate uneven internal stress inside tube bodies.
Step C: Cooled tube blanks maintain complete round shape without deformation before post-processing.
Secondary annealing treatment to release residual forming stress, improve tube body toughness and avoid cracking during precision machining.

2.3 Blank Cutting & Stock Shaping
Saw large sintered PBN blank into standard semi-finished tubular stock; grind inner & outer tube surfaces to uniform dimensional standards for commercial inspection tubes for internal defect detection, annealing treatment eliminates surface residual stress, visual rejecting defective blanks. These semi-finished tubular stock is raw material supply to component manufacturers.

3. Core Performance Profile (Defining Feature)

3.1 Distinct Anisotropic Thermal Performance

• Directional thermal conductivity: 60 W/m·k along a-axis & only 2.60 W/m·k along c-axis at 200℃, realizing one-way heat conduction & vertical heat insulation for precision temperature control scenarios.
  
• Stable long-term service under alternating hot & cold cycles, excellent thermal shock resistance without cracking or deformation.
  
• Ultra-low helium transmittance at 1×10⁻¹⁰ cm³/s, perfect compatibility with ultra-high vacuum (UHV) chambers.
  

3.2 Excellent Electrical Insulation

• Volume resistivity reaches 3.11×10¹¹ Ω·cm, maintains stable insulation across wide temperature & frequency ranges.
  
• Extra-high dielectric strength up to 56 KV/mm at room temperature, reliable isolation under ultra-high voltage working conditions.
  
• Stable insulation property under continuous high-frequency radiation, far superior to polymer plastics which degrade rapidly under high temperature & radiation.
  

3.3 Chemical & Vacuum Compatibility

• Inert to most acids, alkalis, organic solvents and oils; only slightly corroded by hydrofluoric acid and strong molten alkali metals.
  
• Zero gas release under ultra-high vacuum, non-polluting to semiconductor wafer and optical component processing environments.
  
• Outstanding radiation stability against X-ray, gamma and particle irradiation, suitable for nuclear energy and aerospace precision fixtures.
  

3.4 Mechanical & Safety Performance

• Anisotropic mechanical strength: bending strength 243.63 N/mm² (force parallel to c-axis), 197.76 N/mm² (force perpendicular to c-axis), flexible machinability for complex tube profiles.
  
• Knoop microhardness 691.88 N/mm², moderate hardness allowing easy cutting, drilling and turning without severe tool abrasion.
  
• Non-toxic inorganic material without volatile organics, safe for electronic, medical and nuclear industry equipment.
  
• Dense seamless tube wall structure, long service life under continuous fluid or gas flushing in vacuum furnaces.

4. Key Limitations

• Not suitable for long-term working under molten strong alkali metal environment, slight surface corrosion will occur.
  
• Thermal conductivity differs sharply between two crystal directions, directional layout design must be reserved in fixture drawing.
  
• Higher material cost than hot-pressed boron nitride, not the first choice for low-cost ordinary high-temperature insulation parts.
  

5. Main Industrial Applications
5.1 Vacuum & Semiconductor
UHV chamber isolation sleeves, wafer heating directional thermal barriers, electron beam equipment insulation tubes, semiconductor film deposition crucible liners.
5.2 Aerospace & Radiation Testing
Satellite precision thermal isolation sleeves, space radiation shielding structural brackets, particle accelerator high-voltage insulation tubes.
5.3 High-Voltage Precision Electronics
Radio frequency coil isolation sleeves, high-frequency power supply insulation liners, laser resonant cavity temperature control tubes.
5.4 Optics & Precision Instruments
Optical base heating sleeves, electron microscope internal isolation fittings, precision metrology equipment temperature-controlled fixture tubes.
5.5 Medical & Nuclear Industry
Radiation shielding test jigs, non-contaminating laboratory positioning sleeves, nuclear reactor low-loss radiation protection insulation tubes.

6. Material Positioning
Pyrolytic Boron Nitride (PBN) ceramic tube fills the performance gap between ordinary hot-pressed BN and aluminum nitride ceramics. It provides ultra-high vacuum tightness, anisotropic thermal control and superior radiation resistance. Compared with hot pressed BN, PBN features zero air permeability and much higher dielectric strength; compared with AlN, PBN achieves one-way heat isolation while retaining full high-frequency insulation stability. It is the preferred high-performance hollow tube material for customized precision components working under ultra-high vacuum, strong radiation and precise temperature gradient environments.

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