PBN Properties
Performance PBN is a non-porous, opaque material with mechanical properties that are actually enhanced at high temperatures. Its crystalline structure- consisting of layers of hexagons composed of boron and nitrogen atoms stacked on top of each other in parallel planes-gives it good flexural strength, high compression strength and high fracture resistance.
The bonds between the boron and nitrogen atoms vary with crystal direction, giving Performance PBN aniosotropic properties. In each ring in the planar ("a") direction, the nitrogen and boron atoms bond covalently. In the perpendicular ("c") direction, the bonds are formed by the weaker van der Waal's forces.
Directional Properties of PBN
| Property | "a" Direction | "c" Direction |
|---|---|---|
| Termal conductivity | Good | Low |
| Electrical resistivity | High | Highest |
| Thermal expansion | Low | 24X "a" Direction |
| Compressive strength |
High (High tensile strength also) |
High |
| Dielectric constant | Moderate | Low |
| Loss tangent | Low | Low |
Chemical Properties Of Performance PBN
Performance PBN is non-toxic, non-wetting and inert to nearly all other compounds. It will not react with acids, alkalies, organic solvents, molten metals or graphite. Performance PBN is extremely pure. Bulk impurity levels are less than 100 parts per million with metallic impurities less than 10 parts per million.
Summary of Chemical Purity Data
| Property | Value |
|---|---|
| Non toxic | |
| Non porous | |
| Non wetting | |
| Total impurities | <100 ppm |
| Metalic impurities typical elements | |
| Ca | <1 ppm |
| Al | <1 ppm |
| Mg | <1 ppm |
| Ti | <1 ppm |
| Cu | <1 ppm |
| Si | <5 ppm |
| Total metalic | <10 ppm |
| Total carbon (by LECO WR-12) | < 100 ppm |
| Oxidation rate standard air @700°C | 1.8 x 10-5 mg/cm²•min |
| Oxidation rate standard air @900°C | 3.8 x 10-4 mg/cm²•min |
| Oxidation rate standard air @1200°C | 1.6 x 10-2 mg/cm²•min |
| Outgassing total system pressure 1300° C, system base pressure 1 x 10-10 torr |
<1 x 10-10 Torr |
Summary of Electrical Properties
| Property | Value |
|---|---|
| Resistivity "a" and "c"directions @25°C | 1 x 1015 ohm•cm |
| Resistivity "a" direction @1000°C | 3 x 107 ohm•cm |
| Resistivity "a" direction @1500°C | 1 x 104 ohm•cm |
| Resistivity "c" direction @1000°C | 5 x 109 ohm•cm |
|
Resistivity "c" direction @1500°C |
3 x 105 ohm•cm |
| Dielectric strength "c" direction @25°C | 2 x 105 VDC/mm |
|
Dielectric constant @ 8GHz "a" direction @25°C |
4.97 |
|
Dielectric constant @ 8GHz "a" direction @1200°C |
5.07 |
|
Dielectric constant @ 8GHz "c" direction @25°C |
3.67 |
|
Dielectric constant @ 8GHz "c" direction @1200°C |
3.75 |
|
Loss tangent "a" and "c" directions, @25°C to 600°C 1KHz to 12 GHz |
< 9 x 10-4 |
|
Loss tangent "a" and "c" directions, @1200°C, 12 GHz |
.001 |
Summary of Mechanical Properties
| Property | Value |
|---|---|
| Average density | 2.185 g/cc |
| Gas permeability (Helium) | 2 x 10-11 cm² / sec |
| Compression strength "a" direction @25°C | 37, 000 PSI |
| Compression strength "a" direction @1200°C | 35, 000 PSI |
| Compression strength "c" direction @25°C | 48, 000 PSI |
| Compression "c" direction @1200°C | 54, 000 PSI |
| Tensile strength "a" direction @25°C | 21, 000 PSI |
| Flexural strength @25°C | 28, 000 PSI |
| Flexural strength @1200°C | 27, 000 PSI |
| Torsional shear strength @25°C | 93, 000 PSI |
| Young's modulus "a" direction @25°C | 3.4 x 106 |
| Poisson's ratio "a" direction @25°C | .086 |
| Flexural modulus @25°C | 3.2 x 106 PSI |
| Flexural modulus @1200°C | 3.2 x 106 PSI |
| Hardness taken on surface of "a" plane knoop hardness # | 75 |
| "a" Directional Compressive Stress vs. Strain | Specific Heat vs.Temperature |
|---|---|
 |
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Thermal Properties Of Performance PBN - Summary of Thermal Properties
| Property | Value |
|---|---|
| Thermal conductivity "a" direction @25°C | 0.25 cal/cm•sec•°C |
| Thermal conductivity "a" direction @500°C | 0.17 cal/cm•sec•°C |
| Thermal conductivity "a" direction @1000°C | 0.15 cal/cm•sec•°C |
| Thermal conductivity "c" direction @25°C | 0.004 cal/cm•sec•°C |
| Thermal conductivity "c" direction @500°C | 0.005 cal/cm•sec•°C |
| Thermal conductivity "c" direction @1000°C | 0.006 cal/cm•sec•°C |
| Thermal expansion "a" direction @500°C | 0.001 mm/mm |
| Thermal expansion "a" direction @1000°C | 0.0025 mm/mm |
| Thermal expansion "c" direction @500°C | 0.013 mm/mm |
| Thermal expansion "c" direction @1000°C | 0.027 mm/mm |
| Coefficient of thermal expansion "a" direction above @500°C |
3 x 10-6 mm/mm•°C |
| Coefficient of thermal expansion "c" direction @500°C |
30 x 10-6 mm/mm•°C |
| Resistance to thermal shock: 1200°C into liquid nitrogen |
no damage |
| Specific heat @25°C | 0.2 cal/gm•°C |
| Specific heat @500°C | 0.4 cal/gm•°C |
| Specific heat @1000°C | 0.47 cal/gm•°C |
Performance PBN shows no melting point. It can withstand 1800° C in vacuum and 2000° C in nitrogen. This makes it an excellent choice for furnace components and melting vessels. Performance PBN is resistant to thermal shock. Crucibles heated to 1200° C can be plunged into liquid nitrogen without visible damage.
Performance PBN's thermal conductivity in the "a" direction is similar to that of cast iron, surpassing that of beryllia. For this reason, the compound can conduct heat while acting as an electrical insulator. Thermal conductivity in the "a" direction is almost 66 times greater than thermal conductivity in the "c" direction. Conductivity in the "c" direction increases slightly with increasing temperatures.
Thermal expansion vs. temperature
| Thermal condusctivity vs. temperature "a" direction | Thermal conductivity vs. temperature "c" direction |
|---|---|
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