Optimization of Graphene-Modified Silicon-Based Ceramic Photopolymerization Curing Model and Ultra-High Precision Forming Strategy

Vat photopolymerization (VPP) 3D printing technology, owing to its high design freedom, is well suited for fabricating complex ceramic cores. However, addressing the issue of lateral over-curing width during the forming process is of critical importance. Recently, Professor Xiqing Xu from Chang’an University, together with Professor Shuxin Niu from the Key Laboratory of Advanced High-Temperature Structural Materials at the Beijing Institute of Aeronautical Materials and their team, published a study in “Virtual and Physical Prototyping” (Impact Factor: 10.2) entitled “Optimisation of Curing Models and Ultra-high-precision Forming Strategy in Vat Photopolymerization of Silica-based Ceramic Modified by Graphene”. This research introduces graphene into silica-based ceramic cores for VPP 3D printing to investigate its effects on forming and sintering, and proposes an ideal curing factor to evaluate the accuracy of single-layer forming.

In this study, graphene was employed as a photo-absorber to systematically investigate the influence of graphene content on the forming accuracy and sintering performance of ceramic cores. An ideal curing factor was proposed to evaluate the single-layer forming accuracy. Under conditions of identical curing depth and exposure time, a theoretical model was established to elucidate the combined effects of curing depth and curing sensitivity. Furthermore, the effects of graphene on the flexural strength and surface quality of VPP-printed ceramic components were clarified, and the findings were validated through analyses of double-bond conversion and microstructural morphology. High forming accuracy and excellent performance were successfully achieved in the fabrication of ceramic cores.

The following section presents the research methods and experimental data:

Figure 1. Characteristics of graphene morphology: (a) SEM image; (b) Raman spectrum; (c, d) TEM images; (e) AFM image; (f) line roughness

Figure 2. Debinding–sintering process of the silica-based ceramic core

Figure 3. (a) Curing depth; (b) Schematic illustration of lateral over-curing width measurement

Figure 4. Curing performance of the slurry under identical printing conditions (5 s, 10 mW/cm²): (a) curing depth and (b) lateral over-curing width. Effects of graphene content and exposure power on curing performance: (c) curing depth; (d) lateral over-curing width

Figure 5. Optical microscopy images of slurries with different graphene contents after curing for 5 s under 10 mW/cm²: (a) 0.0 wt‰; (b) 0.2 wt‰; (c) 0.4 wt‰; (d) 0.6 wt‰; (e) 0.8 wt‰; (f) 1.0 wt‰

Figure 6. Beer–Lambert law fitting results: (a) curing depth; (b) lateral over-curing width; (c) linear fit between lateral over-curing width and curing depth; (d) ideal curing factor

Figure 7. Confocal laser scanning microscopy (CLSM) and optical microscopy images showing surface quality and profiles of printed components at a constant curing depth with different graphene contents: (a–a1) 0.2 wt‰; (b–b1) 0.4 wt‰; (c–c1) 0.6 wt‰; (d–d1) 0.8 wt‰; (e–e1) 1.0 wt‰

Figure 8. SEM images showing the cross-sectional microstructure of green bodies at a constant curing depth with different graphene contents: (a) 0.2 wt‰; (b) 0.4 wt‰; (c) 0.6 wt‰; (d) 0.8 wt‰; (e) 1.0 wt‰

Figure 9. (a) Effect of different graphene contents on the flexural strength of green bodies; (b) FTIR spectra of green bodies with varying graphene contents.


Figure 10. (a–e) TEM and SAED images of the green body with 0.6 wt‰ graphene; (f) point elemental analysis

Figure 11. Relationship between polynomial fitting and Sₑ: (a) flexural strength; (b) surface roughness

Figure 12. (a) Schematic illustration of the effect of graphene incorporation on the interaction between UV light and the material; (b) Schematic illustration of the influence of graphene content on the curing process; (c) Schematic illustration of surface quality and profile variations of VPP-3D-printed ceramic parts with different graphene contents


Figure 13. Surface microstructure of VPP-3D-printed ceramic cores after sintering at 1200°C with different graphene contents: (a) 0.2 wt‰; (b) 0.4 wt‰; (c) 0.6 wt‰; (d) 0.8 wt‰; (e) 1.0 wt‰

Figure 14. Cross-sectional microstructure of VPP-3D-printed ceramic cores after sintering at 1200°C with different graphene contents: (a) 0.2 wt‰; (b) 0.4 wt‰; (c) 0.6 wt‰; (d) 0.8 wt‰; (e) 1.0 wt‰

Figure 15. (a) Elemental distribution at the fracture of a ceramic core with 0.6 wt‰ graphene after sintering at 1200°C; (b) EDX spectra at the fracture of the same ceramic core; (c) XRD patterns of ceramic cores with different graphene contents


Figure 16. Effects of graphene content on properties of ceramic cores: (a) apparent porosity and bulk density after sintering at 1200°C; (b) flexural strength at room temperature and high temperature (1540°C) after sintering at 1200°C; (c) shrinkage after sintering at 1200°C; (d) high-temperature (1540°C) deflection

Figure 17. (a) Design of the Oct structure; (b) SEM image of the micro-lattice structure with 0.6 wt‰ graphene; (c) EDS analysis of the micro-lattice structure with 0.6 wt‰ graphene; (d) sintered complex structural model

Research Content

This study proposes an innovative high-precision control strategy that effectively addresses the low accuracy issue of high-solid-loading ceramic slurries. By comprehensively considering absorption characteristics, surface quality, data fitting, double-bond conversion, and sintering performance, the optimal graphene content was determined, and an appropriate curing factor was introduced to evaluate single-layer forming accuracy. On this basis, the influence mechanism of curing sensitivity on forming accuracy and material properties was further clarified. A theoretical curing model, incorporating the combined effects of curing depth and curing sensitivity, was proposed to elucidate the influence of different graphene contents on flexural strength and surface quality under identical curing depths. This work provides valuable guidance for optimizing VPP ceramic 3D printing.

At a constant curing depth, a reduction in graphene content results in diminished surface quality and forming accuracy of the printed components, while stress concentration induced by irregular defects exerts adverse effects on their physical properties. In contrast, an excessive graphene content also compromises forming accuracy and, due to strong interlayer bonding and a high degree of conversion, increases internal stress within the green body. This elevated stress leads to crack propagation during the sintering process, thereby deteriorating the physical performance. When the graphene content is 0.6 wt‰, the ceramic core exhibits an apparent porosity of 25.64%, a flexural strength of 14.6 MPa, a sintering shrinkage of 3.76%, and a high-temperature deflection of 0.948 mm. These results demonstrate that the ceramic core possesses excellent properties and fully meets the requirements for precision casting.