Low temperature co-sintering simulation and properties analysis of 3D printed SiO2-B2O3 nanoparticles based on molecular dynamics simulation

CY Liang and J Huang and W Guo and HX Gong, COMPUTATIONAL MATERIALS SCIENCE, 210, 111447 (2022).

DOI: 10.1016/j.commatsci.2022.111447

3D printing (3DP) permits the integrated precise and rapid molding of low-temperature co-fired ceramics (LTCC). However, the relationship between microstructure and characteristics during sintering remains a challenge. The multi-nanoparticle sintering behavior of the ultra-low dielectric constant LTCC combination SiO2-B2O3 is reproduced by using molecular dynamics (MD) simulation. A trustworthy equivalent model to extract the effective dielectric constant (epsilon eff) of multiphase structures is developed based on fractal verification with the experimental picture. The simulated 3DP-formed 8 nm sample leads to an ultra-low dielectric constant of even lower than 3 due to the high through-hole ratio. Uniaxial tension testing of the sintered structures demonstrated the contribution of pre-pressing on the mechanical properties. The ultimate strength of the 6 nm sample formed by 3DP is approximately 1.71 Gpa, which is an increase of over 44% compared to the 8 nm sample (1.18 Gpa), but still below the yield point of the pre- pressed 6 nm sample (3.28 Gpa). Further combined with strain distribution revealed that the B2O3 aid particles, as the primary stress-bearing phase, have a significant impact on the mechanical properties. In addition, the thermal conductivity (TC) and linear thermal expansion coefficient (TEC) are evaluated to assess thermal stability. Detailed modeling of the SiO2/B2O3 interface exhibit a significant mismatch between the phonon spectra of the SiO2 and B2O3 layers in the vibrational range of 27-40 THz, which leads to differences in thermal conductivity between the 3DP formed and pre-pressed samples.

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