Self-assembly process under a solid-state reaction of β-Si 3 N 4 /austenitic stainless-steel composites: stirring conditions and material texture

Abstract

In the self-assembly process of β-Si₃N₄ (SN)/316L stainless-steel (SUS316L) composite materials tailored via sintering of powder mixtures, the formation of a SN agglomerate resulting from condensation–dispersion reactions during the stirring of SN/SUS316L was found to play an important role in improving the thermal conductivity. Moreover, the obtained SN secondary particle groups connected to form a network through diffusion-limited aggregation. In particular, it was shown that the sample prepared at the milling speed of 150 r/min has a similar particle group area (about 1.38 μm²) to that at 120 r/min, but a higher κ (increased from 9.5 W m⁻¹ K⁻¹ to 11.5 W m⁻¹ K⁻¹). To quantitatively evaluate the microstructural morphology of the texture of the self-assembled composite material, global parameters τ(q) and D _q and local parameters α(q) and f(α) were determined via multifractal analysis. These characteristics of the anisotropy, dispersion, and cohesiveness of the particle network in the material texture could be analyzed together with the capacity dimension D₀, information dimension D₁ (configuration entropy), correlation dimension D₂, and α(q) (related to internal energy). The results suggest that α(q) reflects the differences in the cohesion of the additive particle agglomeration that constitutes the self-assembly process under the solid-state reaction.