Effect of Pore-forming Agent Type on the Properties of Porous Si3N4 Ceramics Prepared by Digital Light Processing

Porous Si3N4 ceramics were widely used in aerospace and other fields due to their excellent properties. Adding pore‑forming agent is an effective method to prepare porous Si3N4 ceramics. Porous Si3N4 ceramics are prepared using digital light processing (DLP) technology combined with pore forming agent method, and the effects of four pore‑forming agents (starch, rice husk powder, polystyrene (PS) and polymethyl methacrylate (PMMA)) on the properties of porous Si3N4 ceramics are systematically investigated. It is shown that the difference in the specific surface area of the pore‑forming agent powder particles had an effect on the viscosity of the slurry, among which the rice husk powder had the largest specific surface area and its slurry viscosity is the smallest. Meanwhile, the increase of the volume fraction of solid particles in the ceramic slurry led to a decrease in the depth of cure; while an increase in the average particle size of solid particles reduced the scattering of ultraviolet light, resulting in an increase in the depth of cure. In addition, the difference in physical properties and morphology of the pore‑forming agent affected the micro‑morphology of the green body and the sintered samples, but would not affect the phase transition process and fracture mode of the porous Si3N4 ceramics. The flexural strength of porous Si3N4 ceramics decreased with the increase of porosity, which was closely related to the physical properties of the pore‑forming agent and the characteristics of the formed pores. Considering the influence of different pore‑forming agents on the viscosity and curing depth of ceramic paste, the quality of body green and the properties of sintered sample, it was more appropriate to choose PMMA as the pore‑forming agent. The addition of 10 wt% PMMA as the pore‑forming agent resulted in a better overall performance of porous Si3N4 ceramics with a bulk density of 2.66 g/cm3, a porosity of 20.10%, and a flexural strength of 463.43 MPa. © 2024 Chinese Mechanical Engineering Society. All rights reserved.