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Si 3 N 4 ceramics pose a challenge when it comes to the preparation of light-curing pastes with high depth of cure, elevated solid content, and low viscosity. This challenge is primarily attributed to their inherent characteristics, including high absorbance, a high refractive index, and suboptimal sphericity. Consequently, the application of Si 3 N 4 ceramics in 3D printing remains a complex endeavor. To address the intricacies associated with 3D printing using Si 3 N 4 ceramics, our research focuses on the utilization of Tetramethylammonium Hydroxide (TMAH) for pH adjustment in Si 3 N 4 ceramics. This adjustment aims to enhance the stability, curing depth, and viscosity of the slurry. Subsequently, we employ this Si 3 N 4 light-curing slurry for 3D printing, followed by sintering the printed materials. The evaluation includes testing for porosity, density, and flexural strength of the samples. Notably, our efforts yield porous silicon nitride ceramics boasting an impressive density of 1.8299 g/cm3, porosity measuring 43.718%, and remarkable flexural strength amounting to 275 MPa. [ABSTRACT FROM AUTHOR]

• Hybrid graphene oxide (GO)/carbon nanotubes (CNTs) reinforced cement paste with various hybrid ratios were investigated. • The dispersion properties of hybrid GO/CNTs were improved. • The optimal hybrid ratio for compressive strength reinforcement was determined to be 3:2 (GO:CNTs). • The 3D structure theory of hybrid GO/CNTs and the mechanism of reinforcement were also proposed. This study reports the improved properties of hybrid graphene oxide (GO)/carbon nanotubes (CNTs) reinforced cement paste with various ratios between GO and CNTs (GO:CNTs). The dispersion level of hybrid GO/CNTs was evaluated by UV–vis spectroscopy, sedimentation experiment, zeta potential and dynamic light scattering analysis. Effects of various GO/CNTs ratio was analyzed by comparing the resulting fluidity, compressive and flexural strengths. The improving mechanism was confirmed by the morphology and pore structure analysis. The 3D structure theory of hybrid GO/CNTs and the interaction behavior between hybrid GO/CNTs and cement paste were also proposed. This study reveals that the hybrid GO/CNTs inherent dispersion mechanism showed stronger electrostatic repulsion and reduced particle size of the hybrid GO/CNTs. The hybrid GO/CNTs, with the dosage of 0.05% by weight of cement and the GO:CNTs mass ratio of 3:2, improved the compressive strength by 45.20%, which showed better reinforcing effects than the single addition of GO (28.00%) and CNTs (32.58%) with the same dosage respectively. It is worth noting that no evident synergistic effect was observed in the flexural case. In addition, the hybrid GO/CNTs decreased the fluidity performance up to 70% owing to the heat gained from the ultrasonication treatment and the viscosity of the hybrid GO/CNTs dispersion. [ABSTRACT FROM AUTHOR]

• The influence of hybrid GO/ CNTs on the MKPC paste were investigated. • The dispersion behavior of hybrid GO/CNTs was improved due to stronger electrostatic repulsion and reduced particle size. • The hybrid GO/CNTs improved the properties of MKPC, surpassing GO and CNTs individuals alone. • The mechanism of hybrid GO/CNTs in MKPC could attribute to the promoted hydration process and improved formation of struvite-k. This research reports the effect of hybrid graphene oxide (GO)/carbon nanotubes (CNTs) on the mechanical and microstructural properties of the magnesium potassium phosphate cement (MKPC) paste. The experimental results confirmed that the hybrid GO/CNTs exhibited better dispersion performance than the CNTs and GO individuals by improving the dispersion stability and reducing the diameters of dispersed nanomaterials, making the hybrid GO/CNTs more suitable for nano-modification of cement composites. Furthermore, the addition of GO/CNTs shortened the final setting time and reduced the fluidity of the MKPC paste. The compressive and flexural strength of the MKPC paste was improved by 13.77% and 17.50% respectively by the addition of 0.05% GO/CNTs (by weight of cement). The incorporation of the hybrid GO/CNTs also refined the pore size distribution and improved the crystallization of the hydration products. A higher content of hybrid GO/CNTs and the utilization of polycarboxylate superplasticizer further enhanced the mechanical properties of the MKPC paste. The X-ray diffraction and Fourier transform infrared spectrometer results confirmed the absence of new phases or any chemical bonding between the hybrid GO/CNTs and the pastes. It could be concluded that the hybrid GO/CNTs were relatively promising when compared with the GO or CNTs individuals, possessing great potential for modifying the MKPC paste. [ABSTRACT FROM AUTHOR]