NIST Standard Reference Database 30
Last Update to Data Content: 2002
"High Thermal Conductivity in Silicon Nitride with Anisotropic Microstructure," K. Hirao, K. Watari, M.E. Brito, M. Toriyama, and S. Kanzaki, Journal of the American Ceramic Society, Vol. 79 [9], pp. 2485-2488 (1996), published by American Ceramic Society.Language: English
"The seed particles used in this study were composed of rodlike β-Si3N4 single crystals with a mean diameter of 1 µm and a mean length of 10 µm. Powders of α-Si3N4 (E-10 grade, Ube Industries, Japan) with 5 wt% Y2O3 (purity > 99.9%, BET 27 m2/g, Hokko Chemicals, Japan) and 3 wt% dispersing agent were planetary milled using a 4:1 mixed solvent of toluene and 1-butanol as the mixing medium. The seed particles were mixed with the above slurry by ball milling. The amounts of added seed particles were 5% in volume. Furthermore, poly(vinyl butyral) resin and dioctyl adipate, an organic binder and a plasticizer, respectively, were dissolved in the above mixture by ball milling to obtain the final slurry for tape casting. Green sheets were formed by the use of laboratory-scale doctor-blade equipment, adjusting the sheet thickness to about 120 µm. ... Subsequently, the green sheets were punched into a rectangular shape (50 mm x 55 mm) and stacked at 120 °C under a pressure of 10 MPa, aligned in the casting direction. The stacked sheets were then calcined at 600 °C under a flow of N2-5% H2 gas mixture, followed by calcining at 400 °C under a dry air flow, to remove the organic components. The green compact was hot pressed at 1800 °C for 2 h under a pressure of 40 MPa in a flowing nitrogen atmosphere. The green compact could be densified to near full density (> 99% of theoretical density). Hot pressed specimens were annealed at 1850 °C for 2-66 h under a nitrogen pressure of 0.9 MPa, in a BN coated carbon crucible filled with a powder mixture of 70% silicon nitride and 30% boron nitride."
"The thermal diffusivity (α) and the specific heat (Cp) of the specimen were measured at room temperature by a laser flash method using a thermal constant analyzer (TC-3000, ULVAC, Japan). The thermal conductivity (k) was calculated from the equation" k = αCp d where d is the bulk density measured by the Archimedes method.
| Direction | Annealing Time ( h ) | Thermal Conductivity ( W m-1 K-1 ) |
|---|---|---|
| Parallel | 0 | 75 |
| Parallel | 2 | 87 |
| Parallel | 10 | 93 |
| Parallel | 21 | 114 |
| Parallel | 66 | 122 |
| Perpendicular | 0 | 42 |
| Perpendicular | 2 | 51 |
| Perpendicular | 10 | 50 |
| Perpendicular | 20 | 59 |
| Perpendicular | 66 | 59 |
"The thermal conductivity was measured parallel and perpendicular to the casting direction." No values for the measured α, Cp, and d were reported. Data were digitized from Fig. 5 of the reference.