Key Takeaways & Executive Findings
- •• Optimized Si3N4 slurry formulation achieves 50 vol% solid content with low viscosity (2.48 Pa·s) and excellent stability, enabling high-precision DLP 3D printing. • Gas-pressure sintering dramatically enhances flexural strength from ~109 MPa to ~618 MPa, while maintaining high hardness (16.59 GPa) and improved fracture toughness (4.45 MPa·m1/2). • Crack deflection and bridging are identified as dominant toughening mechanisms, along with pull-out of rod-like β-Si3N4 grains, effectively mitigating crack propagation. • The study provides a pathway for fabricating complex Si3N4 ceramic components with superior mechanical properties via DLP, offering significant potential for advanced engineering applications.
Abstract
Digital light processing (DLP) is a crucial additive manufacturing (AM) technique for producing high-precision ceramic components. This study aims to optimize the formulation of Si3N4 slurry to enhance both its performance and manufacturability in the DLP process, and investigate key factors such as particle size distribution, photopolymer resin monomer ratios, and dispersant types to improve the slurry’s rheological properties. Through these optimizations, a photosensitive Si3N4 slurry with 50vol% solid content was developed, exhibiting excellent stability, and low viscosity (2.48 Pa·s at a shear rate of 12.8 s−1). The effects of gas-pressure sintering on the material’s phase composition, microstructure, and mechanical properties were further explored, revealing that this technique significantly increases the flexural strength of the green sample from (109 ± 10.24) to (618 ± 42.15) MPa. The sintered ceramics exhibited high hardness ((16.59 ± 0.05) GPa) and improved fracture toughness ((4.45 ± 0.03) MPa·m1/2). Crack trajectory analysis revealed that crack deflection, crack bridging, and the pull-out of rod-like β-Si3N4 grains, are the main toughening mechanisms, which could effectively mitigate crack propagation. Among these mechanisms, crack deflection and bridging were particularly influential, significantly enhancing the fracture toughness of the Si3N4 matrix. Overall, this research highlights how monomer formulation and gas-pressure sintering strengthen the performance of Si3N4 slurry in the DLP three-dimensional printing technique. This work is expected to provide new insights for fabricating complex Si3N4 ceramic components with superior mechanical properties.
1. Introduction
Si3N4 ceramic is a key structural material with high strength, outstanding thermal stability, excellent high-temperature performance, and remarkable resistance to corrosion, wear, and thermal shock [1–2]. Its applications cover bone grafts, ball bearings, engine components, and cutting tools, playing significant roles in aviation, electronics, medicine, and defense. Recently, there has been growing interest in Si3N4 materials with high solid content [3–6]. Common methods for molding Si3N4 include injection molding, slip casting, tape casting, gel casting, and extrusion [7–9]. However, these methods are costly, wasteful, slow, and limited in forming complex shapes. Selecting the proper preparation method is crucial for the successful application of Si3N4 ceramics.
Additive manufacturing (AM), also known as three-dimensional (3D) printing or rapid prototyping, first proposed by Blanther, has become increasingly popular [10]. This technology is based on the “discrete–deposition” principle, where the design is discretized using computer technology and then guided by a 3D model, and raw materials are deposited using AM equipment to form a three-dimensional structure. AM technology is not limited by structural shapes, making it suitable for the integrated manufacturing of multi-material or multifunctional structures, and has brought about revolutionary changes in material processing methods [11]. The common 3D printing technologies include photopolymerization (such as stereolithography (SLA), laser induced slip (LIS), digital light processing (DLP), liquid crystal display (LCD)), material extrusion (such as direct ink writing (DIW), robotic casting, fused deposition modeling (FDM)), and other additive manufacturing techniques (such as binder jetting (BJ), 3D printing (3DP), laminated object manufacturing (LOM)) [12]. Among these techniques, photopolymerization-based DLP technology has attracted widespread attention. DLP 3D printing builds 3D structures layer by layer using liquid resin, offering the advantages of high resolution, fast speeds, and low energy use at a low cost, regardless of volume or complexity [13]. It is both cost-effective and environmentally friendly, promoting sustainable development compared to traditional methods [14]. DLP 3D printing can utilize...
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Qing Qin, Gang Xiong, Lin Han, Yujuan Zhang, Zhen Shen, Changchun Ge (2025). Enhancing rheology and mechanical properties of DLP 3D-printed Si3N4 materials via composition optimization and gas-pressure sintering. Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报). https://doi.org/10.1007/s12613-025-3106-x
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Frequently Asked Questions
What is the main objective of this study?
The main objective is to optimize the formulation of Si3N4 slurry for DLP 3D printing to enhance its rheological properties and manufacturability, and to investigate the effects of gas-pressure sintering on the mechanical properties of the printed ceramics.
What are the key improvements achieved in the Si3N4 slurry?
The optimized slurry achieved a 50 vol% solid content with excellent stability and low viscosity (2.48 Pa·s at a shear rate of 12.8 s−1), which is crucial for high-precision DLP printing.
How does gas-pressure sintering affect the mechanical properties?
Gas-pressure sintering significantly increases the flexural strength from (109 ± 10.24) MPa to (618 ± 42.15) MPa, while also improving hardness to (16.59 ± 0.05) GPa and fracture toughness to (4.45 ± 0.03) MPa·m1/2.
What are the main toughening mechanisms identified?
The main toughening mechanisms are crack deflection, crack bridging, and pull-out of rod-like β-Si3N4 grains, with crack deflection and bridging being particularly influential in enhancing fracture toughness.
What is the significance of this research?
This research provides new insights into fabricating complex Si3N4 ceramic components with superior mechanical properties using DLP 3D printing, which is expected to benefit applications in aerospace, electronics, medicine, and defense.
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