Boron Nitride (BN) Machinable Ceramics

Table of Contents

Introduction
Chemical Composition, Properties and Applications
Physical Properties of Hot-Pressed Boron Nitride
About Ceramic Substrates and Components

Introduction

Boron Nitride is a synthetic, technical ceramic material, which is available in powder, solid, aerosol and liquid forms. In solid form, it can be machined easily with commonly used metalworking tools. Boron Nitride has outstanding thermal characteristics including high thermal conductivity and excellent thermal shock resistance. Boron Nitride in solid form is available in three grades, each having different characteristics

The most common grade, HPBN is manufactured by hot pressing. Its crystal structure is hexagonal. The anisotropy of the HPBN platelet structure is created using the uniaxial densification technique. As a result of the anisotropy, different physical properties are observed parallel or perpendicular to the pressing direction. HPBN is non toxic and can be easily machined.

Chemical Composition, Properties and Applications

The chemical composition, properties and applications of Boron Nitride are tabulated bellow:

Applications
Properties
Chemical Composition
Electrical insulators for high temperature applications
Excellent thermal shock behaviour
Boron
Nitrogen
Oxygen
40-42.6%
49-52.9%
3-5%
Thermocouple tubes
High electrical resistivity
Calcium
SiO2
2-3%
0.2%
Crucibles and nozzels for molten metals
Chemically stable
B203
Others
0.4
0.03%
Rolls and support elements in the glass manufacturing industries
Extraordinary thermo cycling properties
 
 
 
High temperature material
 
 

Standard shapes and maximum dimensions:

  • HPBN is hot-pressed in block shapes up to 280mm diameter and 300mm height.

Physical Properties of Hot-Pressed Boron Nitride

Pressing Direction
 
 
Parallel
Perpendicular
Compressive Strength  
MPa
30
48
Young's modulus RT
GPa
34.1
75.2
Flexural Strength RT
MPa
43.7
60.2
  1000°C
 
12.5
17.4
  1500°C
 
11.8
17.0
Density  
g/cm³
1.9-1.95
1.9-1.95
Vickers Hardness  
kg/mm²
12.01
10.88
Thermal Expansion RT-350°C
x10-6K-1
0.0
0.0
  RT-700°C
 
0.67
0.0
  RT-1500°C
 
2.95
0.87
Thermal Conductivity RT
W/mK
27.22
30.98
  300°C
 
23.03
27.22
  500°C
 
21.77
26.38
  1000°C
 
20.52
25.54
Max usage temperature
Inert atmosphere
 
°C
1500
1500
Oxide atmosphere  
 
850
850
Volume resistivity  
Ω.cm
 
 
  RT
 
1.7x1014
4.0x1014
  150°C
 
1.7x1014
1.9x1014
Dielectric Strength  
KV/mm
>39.4
>39.4

 

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