Light-cured 3D printing technology has always had a series of advantages such as high precision, fast forming speed and low cost compared with other printing technologies. Since the invention of Stereo lithography Appearance(SLA) printing technology in 1986, light-cured 3D printing has been developing rapidly, and has been derived into Digital Light Processing (DLP), Laser cladding deposition (LCD), Continuous Liquid Interface Production (CLIP), etc. Object: The roughness of the printed products of various photocurable printers was evaluated by the surface morphology of the printed products on the micro level, Compared with the original digital file model, the dimensional accuracy of printed products of various types of photo-curing printers is evaluated. Materials and Methods: A digital 3D model was obtained by scanning the adult maxillary teeth with a 3shape mouth scanner. Save the upper digital three-dimensional model as an STL file and print it as a physical model using three different 3D printers(UNIZ (LCD), Han’s laser SLA 6000 (SLA) and Han’s laser DLP (DLP)). Again, use 3shape to scan the physical model into a 3D digital model and use the Dental Cad to compare the accuracy. Test blocks (20mm*10mm*5mm) were printed using three different printers, and the surface topography was observed using a KEYENCE optical microscope, and data comparison was performed using DANTAL CAD for file fitting. Results and Conclusion: On the Z direction, the surface bump SLA was 185.1 micron mum, the LCD 105.4 mum, and the DLP 95.2 mum. SLA<LCD<DLP. The model fit DLP was 0.07 mm, the LCD was 0.10 mm, and the SLA was 0.14 mm. In terms of print accuracy, DLP > LCD > SLA. The surface roughness of the test block was DLP>SLA>LCD. Conclusion: DLP performs well in all aspects.
The neodymium cluster evolution in fluorite crystals has been unknown for nearly 60 years, which hindered further exploration of rare-earth-doped fluorite materials. In this work, the first-principles calculation is coupled with the synchrotron X-ray absorption near-edge structure and extended X-ray absorption fine structure (EXAFS), as well as the dielectric spectra to study the neodymium-doped and yttrium-codoped strontium fluorite crystals. The results reveal that the monomers will emerge first and work as basic units. Then, the units aggregate to become the cubic sublattice centers and the cubic sublattice centers further transform to become square antiprism structure clusters as the neodymium concentration rises. The evolution from the monomers to high order clusters will be accelerated by the codopant of yttrium ions. There are about 100% of square antiprism centers that could be obtained when tailored with yttrium ions. The EXAFS spectra further show that the square antiprism centers consist of about 74.2% of SAP-9CN and 25.8% of SAP-8CN polyhedrons, which is in good agreement with the calculated pentamer and hexamer cluster structures. The spectroscopic parameters of neodymium-doped fluorites could be tuned in large scale by the evolution, which presents us a methodology for designing new rare-earth-doped fluorite materials.
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