BAE systems Pressure Assisted Densified (“PAD”) Silicon Nitride (Si3N4) is a fine grained, ceramic material having exceptional thermal and mechanical properties. BAE Systems produces three grades of “PAD” Si3N4 with diameters up to 560µm. BAE Systems NSG is a very fine grain Si3N4 with exceptionally high strength and good corrosion resistance. It is appropriate for demanding structural and wear resistant applications.
BAE Systems CI is a high strength Si3N4 with excellent high temperature mechanical properties. This material is excellent for wear and cutting tool applications. BAE systems SC-2 is high purity Si3N4 appropriate for the semiconductor industry. The following chart lists typical properties.
| Grade of PAD Si3N4 | SC-2 | NSG | CI | |
| Bulk Density (min) | g/cm^3 | 3.17 | 3.25 | 3.30 |
| Average Grain Size |
μm |
1-2 | 0.6 | 0.5 |
| Flexural Strength, (4-Pt MOR) | Ksi | 92 | 130 | 123 |
| @RT | MPa | 640 | 900 | 850 |
| Characteristic Strength | MPa | 675 | 930 | 865 |
| Flexural Strength, (4-Pt MOR) | Ksi | - | - | 115 |
| 1000°C | MPa | - | - | 810 |
| Weibull Modulus (m) |
9 |
10 | 12 | |
| Elastic Modulus (E) | GPa | 320 | 300 | 310 |
| Poisson's Ratio (n) | 0.27 | 0.27 | 0.27 | |
| Hardness (Knoop 0.3 kg) | kg/mm^2 | 1650 | 1450 | 1500 |
| Fracture Toughness (Chevron Notch) | MPa-m^1/2 | 4.9 | 5.5 | 6.0 |
| Thermal Expansion (RT-1000°C) | 10-6/°C | 3.3 | 3.3 | 3.3 |
| Thermal Conductivity @RT | (W/m-K) | 30 | 20 | 30 |
| Electrical Resistivity |
Ω-cm |
>10^14 | >10^14 | >10^14 |
