Ceramic Materials and Their Properties
There are a variety of different ceramic materials, each with their own capabilities, advantages and disadvantages; their use in bearing and rolling element applications was pioneered by many of the space agencies and continues to be at the forefront of engineering technology.
| Ceramic Material | 99.5%-AL2O3 | SiC | HP-Si3N4 | GPS-Si3N4 | ZrO2- Y2O3 |
|---|
| Mechanical Properties | Unit | Metric/Imperial | Metric/Imperial | Metric/Imperial | Metric/Imperial | Metric/Imperial |
|---|---|---|---|---|---|---|
| Density | g/cm3 (lb/ft3) | 3.89(242.8) | 3.1 (193.5) | 3.29(205.4) | 3.27(204) | 6.04 (205.4) |
| Porosity | %(%) | 0(0) | 0 (0) | 0(0) | 0(0) | 0(0) |
| Color | — | ivory | black | black | black | ivory |
| Flexural Strength | MPa (lb/in2x103) | 379(55) | 550 (80) | 830(120.4) | 689(100) | 900(120.4) |
| Elastic Modulus | GPa (lb/in2x103) | 375(54.4) | 410 (59.5) | 310(45) | 310(45) | 200(45) |
| Shear Modulus | GPa (lb/in2x106) | 152(22) | — | — | — | — |
| Bulk Modulus | GPa (lb/in2x106) | 228(33) | — | — | — | — |
| Poisson’s Ratio | — | 0.22(0.22) | 0.14 (0.14) | 0.27(0.27) | 0.24(0.24) | — |
| Compressive Strength | MPa (lb/in2x103) | 2600(377) | 3900 (566) | — | — | — |
| Hardness | Kg/mm2 | 1440 | 2800 | 1580 | 1450 | 1300 |
| Fracture Toughness KIC | MPa•m1/2 | 4 | 4.6 | 6.1 | 5.7 | 13 |
| Maximum Use Temperature (no load) |
°C(°F) | 1750(3180) | 1650 (3000) | 1000(1830) | 1000(1830) | 1500 (2730) |
| Thermal | Unit | Metric/Imperial | Metric/Imperial | Metric/Imperial | Metric/Imperial | Metric/Imperial |
|---|---|---|---|---|---|---|
| Thermal Conductivity | W/m°K (BTU•in/ft2•hr•°F) | 35(243) | 120 (830) | 30(208) | 29(201) | 2 (13.9) |
| Coefficient of Thermal Expansion | 10–6/°C (10–6/°F) | 8.4(4.7) | 4.0 (2.2) | 3.3(1.8) | 3.3(1.8) | 10.3 (5.7) |
| Specific Heat | J/Kg•°K (Btu/lb•°F) | 880(0.21) | 750 (0.18) | — | — | — |
| Electrical | Unit | Metric/Imperial | Metric/Imperial | Metric/Imperial | Metric/Imperial | Metric/Imperial |
|---|---|---|---|---|---|---|
| Dielectric Strength | ac-kv/mm (volts/mil) | 16.9(420) | semiconductor semiconductor | — | — | |
| Dielectric Constant | @ 1 1 MHz | 9.8(9.8) | — | |||
| Volume Resistivity | ohm•cm | >1014 | 102–106 | — | >1010 |
