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Fiberglass-reinforced ultraviolet cured-in-place pipe (UV–CIPP) composite material is one of the most trenchless materials for underground pipelines’ rehabilitation. In this paper, the bending resistance and damage evolution mechanism of glass fiber-reinforced UV-CIPP composites were investigated under the influence of glass fiber structure, the number of layers of glass fibers, the angle of fiber layups, and the thickness of the material by high-definition video, SEM and infrared thermal imaging. The results indicate that the damage evolution modes of UV-CIPP materials mainly include: (1) fiber pull-out and overall fiber bundle tensile failure caused by strong interfacial bonding, (2) fiber/matrix debonding and delamination, fiber fracture, and matrix cracking caused by weak interfacial bonding. Furthermore, among the seven different fiberglass structures of UV-CIPP materials, the [0°/90°] warp-knit axial/short-cut felt fiberglass fabric exhibit the best flexural performance, with a bending strength of 412 MPa and a bending modulus of 16.1 GPa for the 4 layers glass fiber fabric. Moreover, in the bending process of UV-CIPP materials, the surface temperature rises primarily due to fiber break, the temperature transition aligning with the stress transition. Finally, the energy release is mainly caused by the failure of the glass fibers, but the resin contributed comparatively little. This study provides a scientific reference for the structural design and optimization of UV-CIPP materials.

Abstract High crosslinking and low shrinkage stress are difficult to reconcile in the preparation of performance-enhancing photopolymer materials. Here we report the unique mechanism of upconversion particles-assisted NIR polymerization (UCAP) in reducing shrinkage stress and enhancing mechanical properties of cured materials. The excited upconversion particle emit UV-vis light with gradient intensity to the surroundings, forming a domain-limited gradient photopolymerization centered on the particle, and the photopolymer grows within this domain. The curing system remains fluid until the percolated photopolymer network is formed and starts gelation at high functional group conversion, with most of the shrinkage stresses generated by the crosslinking reaction having been released prior to gelation. Longer exposures after gelation contribute to a homogeneous solidification of cured material, and polymer materials cured by UCAP exhibit high gel point conversion, low shrinkage stress and strong mechanical properties than those cured by conventional UV polymerization techniques.

Abstract In the three-dimensional printing process of ceramic with low-angle structures, additional supporting structures are usually employed to avoid collapse of overhanging parts. However, the extra supporting structures not only affect printing efficiency, but the problems caused by their removal are also a matter of concern. Herein, we present a ceramic printing method, which can realize printing of unsupported multi-scale and large-span ceramics through the combination of direct ink writing and near-infrared induced up-conversion particles-assisted photopolymerization. This printing technology enables in-situ curing of multi-scale filaments with diameters ranging from 410 µm to 3.50 mm, and ceramic structures of torsion spring, three-dimensional bending and cantilever beam were successfully constructed through unsupported printing. This method will bring more innovation to the unsupported 3D manufacturing of complex shape ceramics.

During the ceramic photocuring 3D printing process, the penetration ability of incident light is hindered by the extinction effects of ceramic powders in ceramic slurry. This limitation in light penetration negatively impacts printing efficiency, especially in ceramic slurries with high solid contents. In this work, an in-situ photothermal dual crosslinking strategy, which capitalizes on the combined benefits of near-infrared photothermal energy, was proposed to realize precise and efficient direct ink writing of high solids ceramic slurries. The in-situ curing of ceramic slurries with an alumina content of up to 90 wt% (74.5 vol%) was successfully achieved by integrating photochemical and photothermal crosslinking strategies to recycle excess heat to enhance the energy utilization of near-infrared light. Under near-infrared irradiation (538.25 W/cm2, 3 s), the high solids ceramic photothermal dual curing slurry achieved a curing depth of 2.79 mm, which improved the printing rate and printing throughput compared with the photocuring slurry (2.34 mm) and the thermocuring slurry (0.98 mm). The sintered samples showed a sinter shrinkage of 8.85 % and relative density of 95.08 %. This method has great potential for application in the manufacturing of thick composite materials and high solid content slurry printing.

The exfoliation of bulk two-dimensional metal–organic framework (MOF) into few-layered nanosheets has attracted much attention recently. In this work, an environmental-friendly route has been developed for layered-MOF (MAMS-1) delamination using deep eutectic solvent (DES), which is more sustainable and efficient alternative than conventional organic solvents for MOF nanosheet preparation. Under sonication condition, DES as solvents, the highest exfoliation rate of MAMS-1 is up to 70% with two host layers via poly(vinylpyrrolidone) (PVP) surfactant-assisted method. The presence of tert-butyl exteriors and the atomically thickness endow the MOF nanosheets stable suspension for at least one month. Due to the 2D structure and excellent stability, MAMS-1 nanosheet (MAMS-1-NS) was chosen as a good candidate to encapsulate Eu3+ cations. The obtained Eu3+@MAMS-1-NS acts as a multi-responsive luminescent sensor through fluorescence quenching, and can specifically recognize Fe3+ (LOD = 0.40 μM, KSV = 1.05 × 105 M−l), Hg2+ (LOD = 0.038 μM, KSV = 5.78 × 106 M−l), Cr2O72− (LOD = 0.33 μM, KSV = 1.55 × 105 M−l) and MnO4− (LOD = 0.088 μM, KSV = 4.49 × 105 M−l). Compared with bulk Eu3+@MAMS-1, the sensitivity of Eu3+@MAMS-1-NS is greatly improved owing to its ultrathin nanosheet morphology and highly accessible active sites on the surface.

Crystallization kinetics of metal-organic frameworks in conventional organic solvents are usually very slow. Here, the authors show that an ionic liquid medium accelerates considerably the formation of Zr-based metal-organic frameworks that are active catalysts in the Meerwein-Ponndorf-Verley reaction.