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Si 2 N 2 O composites were achieved via direct ink writing technique and pressureless sintering. The design and optimization of inks and the effect of mass ratio of Si 3 N 4 and SiO 2 on the phase composition, microstructure, mechanical properties and dielectric properties of composites were systematically investigated. The inks exhibit superior stability and printability. Increasing SiO 2 content facilitated densification and enhancement of mechanical property. The generation of β-Si 3 N 4 and Si 2 N 2 O and the nucleation of cristobalite were restrained by high content SiO 2. The ceramic composites with the flexural strengths from 74.1MPa to 104.9MPa and low dielectric constant (≤4.68) were fabricated. This strategy provides a systematic reference for synthesis of high-performance porous Si 2 N 2 O composites based on the DIW. [ABSTRACT FROM AUTHOR]

Porous Si 2 N 2 O ceramics strengthened by directional β-Si 3 N 4 are fabricated by direct ink writing technique and seeding method. Slurries prepared with different contents of β-Si 3 N 4 grains exhibited superior printing behavior. The degree of orientation of β-Si 3 N 4 grains increased with the increase of grains content. The mechanical properties of the porous Si 2 N 2 O ceramic are effectively improved by interspersed β-Si 3 N 4 grains and present anisotropy. This novel strategy provides a reference for fabricating high-performance anisotropic complex structure ceramics. [ABSTRACT FROM AUTHOR]

A novel, efficient, versatile strategy was carried out to fabricate highly porous ceramic parts based on the combination of strong colloidal gel ink fabricated with high boiling point organic solvents and DIW technique. The preparation and optimization of inks and the effect of heating temperature on the phase composition, microstructure, mechanical properties and dielectric properties of ceramic parts were systematically investigated. The strong colloidal ink exhibits excellent ambient stability and printability. The sintering temperatures bring about the evolution of phases, structural mechanical properties and dielectric properties of ceramic parts. Ultimately, Si 2 N 2 O single wall ceramic parts with a frame density of 1.07˜1.14 g/cm3 and an apparent porosity of 53.13 ± 1.29% were successful fabricated. The dielectric constant and dielectric loss of Si 2 N 2 O sample (1650℃) are only 4.24 and 0.0049, respectively. This strategy provides a reference for in-situ synthesis of high-performance porous ceramic components based on the DIW. [ABSTRACT FROM AUTHOR]

A convenient direct ink writing porous ceramic preparation strategy incorporating green body strengthening measure was provided. Different hydrogen bond interactions between particles in polar and nonpolar solvents have been successfully applied to regulate the rheological properties of 3D printing ink. Inks with different (NH 4)H 2 PO 4 content were systematically optimized, which exhibited acceptable ambient stability and superior printing behavior. The phosphoric acid generated by decomposition of (NH 4)H 2 PO 4 reacts with silica or oxide layer of silicon nitride to form Si–O–P binder by a pretreatment at low temperature to strengthen the green body. The compressive strength of green body fabricated by ink with 0.2 g/mL (NH 4)H 2 PO 4 was increased by 415%. The Si 2 N 2 O single wall frame structure parts with a compressive strength of 3.33 ± 0.14 MPa under a frame density of 1.14 ± 0.05 g/cm3 were fabricated. The dielectric constants of the developed ceramic parts range from 3.57 to 4.21. A systematic study of design and preparation of ink and quantization of molding parameters provide a reference for in-situ reinforced the ceramic green body of silica, silicon nitride and their composites, as well as fabrication of their corresponding highly porous ceramic components based on the direct ink writing. Image 1 • A strategy for direct ink writing of high-strength Si 2 N 2 O green bodies as well as their ceramic components was provided. • The rheological properties of inks were regulated by the different hydrogen bond interactions between particles in C 10 H 22 O 5 and H 2 O. • The phosphorus elements introduced by (NH 4)H 2 PO 4 aqueous solution were evenly distributed in green body and ceramic part. • The compressive strength of Si 2 N 2 O green body was increased up to 415% due to the strengthening of Si–O–P binder. [ABSTRACT FROM AUTHOR]

The practicability of nano-powder photocatalyst is limited by the difficulty of its recovery. 3D monolithic TiO 2 photocatalyst (MTP) was printed by direct ink writing (DIW) using TiO 2 nanoparticles as solutes of tetrabutyl titanate precursor to configure printing slurry to achieve integrated regulation of microscopic and macroscopic pore structure. The SEM verified that the surfaces of skeleton-TiO 2 particles were uniformly covered by the TiO 2 nanoparticles derived from calcining gel. And a highly connected hierarchical pore structure was formed by the skeleton-TiO 2 particles and the designed 3D printing macroscopic pores, which laid the foundation for rapid capture and efficient in situ degradation of antibiotics. The nano TiO 2 powders prepared by calcined gel have narrow band gap width, which is easier to generate electrons and holes and have low recombination rate. Therefore, the core-shell structure constructed by nanoparticles derived from gel and commercial TiO 2 can effectively optimize the photocatalytic performance of MTP. The removal of tetracycline hydrochloride (TCCH) in water by MTP was used to verify the application effect of macro structure in practice, and the synergistic effect of adsorption and degradation kinetics was summarized. The dynamic adsorption effect of MTP reached 97.44 % at pH 7 for 5 h. Under simulated sunlight, MTP exhibited a synergistic adsorption-degradation effect, reaching equilibrium at 210 min. The cycle test shows that the removal rate of TCCH by MTP remains 91 % after 4 cycles. This strategy provides a good reference for the assembly of nanosemiconductor materials into environmentally friendly 3D structured systems. [Display omitted] • A novel strategy for 3D TiO 2 photocatalyst based on direct ink writing was proposed. • The 3D TiO 2 photocatalyst with high molding accuracy and good pore distribution were successfully prepared. • The microstructure of 3D TiO 2 photocatalyst is a core-shell structure in which small particles wrap large particles. • The 3D TiO 2 photocatalyst exhibit considerable dynamic adsorption and degradation properties. [ABSTRACT FROM AUTHOR]