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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]

The crystal structure models of O doped CsPbX 3 (X=Cl, Br, I). [Display omitted] • O doped perovskite CsPbX 3 was studied by first principles. • New optical property of CsPbX 3 doped by O are predicted. • O changes the position of the valence band top and conduction band bottom. The electronic structures of perovskite CsPbX 3 (X = Cl, Br, I) and O doped CsPbX 3 have been studied by first principles based on density functional theory (DFT). The theoretical calculation results show that O doping leads to narrow band gap width of perovskite CsPbX 3. For pure CsPbX 3, it is found that the 6p states of Pb determines the position of the conduction band bottom and the p states of halogen determines the position of the valence band top; and for O doped CsPbX 3 , it shows that the incorporation of O is the fundamental reason for the narrowing of band gap and light absorption edge redshifting compared with that of pure CsPbX 3. [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]

Geopolymers have high application potential due to their outstanding ion exchange ability. A novel direct ink writing (DIW) geopolymer adsorption sieve (GAS) preparation strategy was proposed. The preparation and optimization of DIW inks and the adsorption properties and mechanism of GAS for methylene blue (MB) were systematically investigated by characterization and density functional theory (DFT) calculation. The GASs exhibited desired adsorption rates for MB in both dynamic (83.6% at 200 min) and static (97.1% in 7 days) states. The adsorption kinetic was fitted well by the pseudo-first-order model at the early stage and eventually was transformed to fit well by the pseudo-second-order model and indicated the boundary liquid layer diffusion and intraparticle diffusion were all rate-limiting factors. The exploration of adsorption mechanism confirmed that the adsorption of GAS for MB was affected by the coordination of electrostatic action, hydrogen bonds and electrons transfer. The proposed strategy provides a promising reference for design and preparation of eco-friendly 3D printing adsorbent systems. [Display omitted] • A novel strategy for geopolymer adsorption sieve based on direct ink writing was proposed. • The geopolymer adsorption sieves with high molding accuracy and good pore distribution were successfully prepared. • The geopolymer adsorption sieves exhibit considerable dynamic and static adsorption properties. • The adsorption mechanism was proposed based on experiments and DFT calculation. [ABSTRACT FROM AUTHOR]

Water remediation using semiconductor photocatalysts under visible light (VL) irradiance appears as a more sustainable technology option due to the greater penetration depth. Consequently, the overall band spectrum of VL has received significant attention to providing solutions to secure clean water resources over the past few decades. This research developed an innovative approach to enhancing the visible light susceptibility of semiconductor-based photocatalytic composites Ag 10 Si 4 O 13 /TiO 2 (ASO/TO). The intrinsic properties of TO and electron donor ability of ASO lend synergistically to the generation of a narrow bandgap semiconductor. A feasible wet-chemistry method was found to engineer the electronic properties of ASO/TO under VL for rapid decolorization of methylene blue (MB). Inhibition experiments with several agents confirmed that the decolorization proceeds through the generation of hydroxyl radical species assisted by hole carrier generation at the ASO junction. The rate of MB decomposition followed a pseudo-first-order kinetic profile (98.2% within 35 mins under ambient conditions with 5 ppm of 2:1 ASO/TO and 20 ppm of MB). The XRD/XPS spectroscopic analysis confirms the electronic polarization of distorted SiO 4 tetrahedral units coordinated to Ag-O, forming a double dumbbell double-helical structure. The staggered bandgap of these composite photocatalysts is associated with the Ag-Ag d10/sp hybridization and dispersive conduction band. At the same time, the 2p orbitals of TiO 2 showed a less dispersive band due to the availability of d -orbitals. The generated Ag 10 Si 4 O 13 (ASO) based ferroelectric materials allow amplifying its frequency due to internal polarization along the c-axis. The electrochemical evaluation also showed that the interface charge transfer resistance was lowered relative to TiO 2 , facilitating the efficacy of photocatalytic reactivity, where the generation of holes as charge carriers was the rate-limiting step. The novel nano-engineering strategy providing highly active photocatalysis can open new horizons for VL applications. [Display omitted] • Unique d10 and sp/p configurations in its electronic structure, yield high photocatalysis. • Ferroelectric p-block photocatalyst fabrication, by bandgap engineering. • The efficient charge due to electric field in ASO from distorted SiO 4 chain structure. [ABSTRACT FROM AUTHOR]

An embedded dense coating was fabricated on the direct ink writing Si 2 N 2 O porous ceramic by impregnating the SiO 2 -sol and in-situ sintering. The influence of different heat-treatment atmosphere and temperature on the microstructure, phase composition, mechanical properties and water resistance was studied systematically. A relatively flat and dense seal layer was obtained in the air atmosphere. The crystallization of SiO 2 was inhibited by nitrogen atmosphere. The resulting embedded coatings effectively improved the mechanical properties and water resistance of Si 2 N 2 O porous ceramic, and the specimens treated in air exhibited better comprehensive performance due to the higher densification. This strategy provides a reference for in-situ surface reinforced components with complex structures. Unlabelled Image • A strategy for fabricating embedded dense coating on complex structure ceramic was provided. • The samples heat-treated in air exhibits better sealing effect than that in nitrogen. • The crystallization of SiO 2 was inhibited by nitrogen atmosphere. • Mechanical properties and water resistance are improved due to the good sealing effect. [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]

Ag x Si y O z has the potential to inhibit the recombination of photoinduced electron hole pairs via an internal electric field induced by asymmetrical Si–O tetrahedral chains. The strength of the [SiO 4 ] tetrahedral produces a very strong internal electric field for Ag 10 Si 4 O 13. Here, a novel and convenient synthetic strategy for nano-Ag 10 Si 4 O 13 based on a sol-gel method is proposed. A small band gap, an internal electric field and a small size ensure good efficiency for nano-Ag 10 Si 4 O 13 during all chemical dynamical processes, including charge excitation, charge separation and charge transfer. [ABSTRACT FROM AUTHOR]

Designing efficient visible light photocatalysts is targeted to improve the solar utilization to ameliorate environmental problems. Ag 10 Si 4 O 13 has great application potential due to a narrow band gap and the existence of internal electric field（spontaneous polarization electric field inside the crystal）. Here, a novel and convenient synthetic strategy based on sol-gel method and template method was proposed to fabricate 3D sponge-like hierarchical pore Ag 10 Si 4 O 13 (HPA) microblock with enhanced photocatalytic activities. The group multiple coordination is conducive to further improve the dispersion of Ag 10 Si 4 O 13 precursor around polystyrene (PS) microsphere. Weak sintering between nano-Ag 10 Si 4 O 13 particles ensured the formation of sponge skeleton structure. Compared with Ag 10 Si 4 O 13 , HPA showed enhanced separation efficiency of electron hole pairs due to the carbon doping. And the uniform and well-developed pore structures further improved the photocatalytic performance. As a result, HPA (P-5) exhibited a degradation efficiency of 98.98% at 30 min under visible light, and an excellent cycle performance were obtained. The proposed strategy provides an important reference for the preparation of easily recoverable microblock photocatalyst. [Display omitted] • Green synthesis methods, keeping synthesis and environmental impact to a low threshold. • Multi-coordination between Ag 10 Si 4 O 13 precursor and PS resulting in a 3D sponge-like hierarchical pore. • Dual function of internal electric field and C doping enhanced photogenerated carrier separation efficiency of Ag 10 Si 4 O 13. [ABSTRACT FROM AUTHOR]

Surface modification of oxygen evolution reaction (OER) cocatalysts is a promising approach to improve PEC water oxidation activity by accelerating the surface charge injection efficiency and catalytic reaction kinetics. However, the PEC performance is still restricted by inefficient charge transfer at the semiconductor/cocatalyst interface. In this study, ultrathin Ti3C2 nanosheets, serving as a highly efficient hole transport layer, were introduced into the Fe2O3/CoAl-layered double hydroxide (LDH) interface. The obtained Fe2O3–Ti3C2–CoAl photoanodes exhibited a significantly improved photocurrent density of 2.1 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (RHE) under AM 1.5G illumination. In this system, the Ti3C2 nanolayer not only suppresses the interfacial recombination of photogenerated carriers but also facilitates efficient hole transfer from Fe2O3 to the OER cocatalyst, thus promoting the PEC performance. This study provides a new guideline for optimizing the charge transfer at the semiconductor/cocatalyst interface. [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]

The performance of carbon-based materials as negative electrodes for supercapacitors can be effectively enhanced through the method like increasing the surface area and active sites as well as heteroatoms doping, while the limited capacitance caused by the surface adsorption mechanism restricts the further improvement of capacitance. Herein, we design hollow and porous FeP spheres (H-FeP) in-situ encapsulated into 3D honeycomb-like porous graphitic N, P-codoping carbon (PGNPC) by a unique post-annealing strategy. The post-annealing process acts as an efficient modification strategy in two aspects: the formation of a porous graphitic carbon framework during the catalytic reaction between iron oxide with carbon and the morphology changing from solid to hollow by introducing the Kirkendall diffusion process. With the synergetic effect of introducing hollow FeP into carbon, the N, P-codoping and 3D porous graphitic carbon framework ensure the as-prepared materials with enhanced performance for negative electrodes. Thus, H-FeP@PGNPC materials display outstanding specific capacitance (696 F g−1), high rate capacity and cycling stability. Using multi-shelled Mn 3 O 4 encapsulated in rGO as the positive electrode, the assembled asymmetric supercapacitor exhibits high specific capacitance and energy density with negligible capacity loss (retain 90% after 5000 cycles). [Display omitted] • Novel in-situ encapsulated hollow FeP into N,P-codoped porous graphenic framework obtained through a high-yield process. • The catalytic reaction caused by the post-annealing process provides extra pseudocapacitive contributions. • The porosity and hollow structure of FeP manipulated by Kirkendall effect. • Porous graphenic framework simultaneously acts as the buffer layer and expressway for electrons transport. [ABSTRACT FROM AUTHOR]

Post heat treatment has been considered as an essential process to relieve residual stress, tailor the microstructure and obtain desired mechanical properties of the parts manufactured by selective laser melting (SLM) technology. The present work comparatively investigated the effect of heat treatment on microstructure evolution and mechanical properties of the SLM-fabricated Ti–6Al–4V alloy (Ti64) and 2 vol% TiB/Ti–6Al–4V titanium matrix composite (TMC). Microstructure analysis indicated that the as-built and heat treated TMC samples showed profoundly different microstructures compared to that of Ti64 samples. With heat treatment temperature increasing, the dominant acicular α′ martensite of Ti64 was decomposed into fine (α+β) lamella and microstructure coarsening occurred. A finer (α+β) dual-phase matrix microstructure, compared to that of Ti64, was achieved for TMC samples when heat treatment temperature exceeded 850 °C. The densely dispersed clusters of parallel nanoscale TiB precipitates of the TMC grew into individually separate TiB whiskers with larger nanoscale and sub-microscale size through a stacking up process of (100) planes based on an Ostwald ripening process. Mechanical testing results showed that the hardness and yield strength values of TMC samples before and after heat treatment were all higher than that of the Ti64 samples. A superior comprehensive mechanical performance with relatively high yield strength (1345 MPa) and significantly improved fracture strain from 17.6% to 31.3% was achieved for the TMC sample after heat treatment at 850 °C. [ABSTRACT FROM AUTHOR]