Xinyue Guo,Huanv Mao,Chunyan Bao,Decheng Wan,Ming Jin
In this work, three dyes based on fused carbazole–coumarin–ketone structures were designed and synthesized. These dyes were named CCK–Me, CCK–Ph, and CCK–Tol in accordance with their different substituents. Their excellent absorption properties can match the wavelength band of visible light-emitting diodes (LEDs) (i.e., 405–450 nm). Density functional theory calculations, steady-state photolysis, and electron spinning resonance spin trapping experiments were performed to explain the photophysical and photochemical mechanisms of the dyes. These dyes are available as one- or two-component type II photoinitiators (PIs). Both kinds can efficiently initiate the polymerization of acrylate monomers via two different mechanisms under 405–450 nm LED irradiation. Notably, CCK–Tol exhibited excellent photobleaching ability when initiated alone, making it ideal for deep curing. The polymeric samples were up to 57 mm thick. Remarkably, the photolysis product of CCK–Tol showed satisfactorily low cytotoxicity. The above excellent properties showed the great potential application of the dyes in various photocuring materials, especially dental materials and thick three-dimensional structures.
The vat photopolymerization (VPP) technology offers exceptional flexibility in design and manufaction of high-performance piezoceramic structures. However, due to the high refractive index and strong UV absorption characteristics of Pb-based ceramics, ceramic slurries are required to have a low solid content in for efficient deep-curing. This limitation often results in sintering distortion, cracking, low density, and deteriorated piezoelectric properties. To address these challenges, a heat treatment process was initially employed to spheroidize the PZT powder, which effectively decreased light scattering and absorption. Subsequently, high-refractive-index and highly reactive photosensitive resins were introduced to enhance the penetration of UV light and reduce the critical exposure energy of the slurry. Additionally, a hindered amine light stabilizer is added to capture the peroxy radicals to overcome the oxygen inhibition effect and further increase the curing depth. As a result, a PZT slurry with a high solid content of 45 vol.%, was successfully formulated, facilitating the manufacturing of PZT ceramics with complex structures. The sintered samples achieved a high relative density of 96.5% and a d 33 value of 573 pC/N. These optimized strategies provide a solid foundation for the development of high-performance PZT devices with intricate geometries.
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