The Experts below are selected from a list of 5583 Experts worldwide ranked by ideXlab platform
John W. Halloran - One of the best experts on this subject based on the ideXlab platform.
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Photopolymerization of powder suspensions for shaping ceramics
Journal of the European Ceramic Society, 2011Co-Authors: John W. Halloran, Vladislava Tomeckova, Susan P. Gentry, Suman Das, Paul Cilino, Dajun Yuan, Rui Guo, Andirudh Rudraraju, Peng ShaoAbstract:Abstract The photopolymerization of suspensions of ceramic powders in monomer solutions is the fundamental step for forming techniques where a liquid suspension is solidified with UV light. The photopolymerization behavior is determined by the properties of the monomer and photoinitiator and by the transport of photons in the suspension. Photon transport in suspensions involves scattering from the particle and absorption by photoinitiators and inert dyes. The photopolymerization behavior is related to the formulation of the suspensions. Proper formulations are discussed for several applications. Techniques for characterization include Cure Depth measurements, photocalorimetry, and photorheology.
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Cure Depth for photopolymerization of ceramic suspensions
Journal of The European Ceramic Society, 2010Co-Authors: Vladislava Tomeckova, John W. HalloranAbstract:Abstract The Cure Depth of a series of photopolymerizable SiO2 and Al2O3 ceramic suspensions was measured as a function of energy dose to determine the sensitivity parameter Dp and its dependence on ceramic volume fraction, type and concentration of photoinitiator and inert dye. As predicted by an Absorption Model for Dp, 1/Dp is a linear function of photoinitiator concentration and dye concentration. The molar extinction coefficients derived from the Cure Depth measurements using an Absorption Model were compared with coefficients determined via spectrophotometry.
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predictive models for the photopolymerization of ceramic suspensions
Journal of The European Ceramic Society, 2010Co-Authors: Vladislava Tomeckova, John W. HalloranAbstract:The photopolymerization of suspensions of ceramic powders in monomer solutions is the fundamental step in several rapid prototyping forming techniques based on photocuring. Exposure to an UV dose of energy E causes the monomer to be polymerized to a certain Cure Depth, with the relation between Cure Depth and energy dose dependant on two properties of the photosuspension, the sensitivity and the critical energy dose. We present simple models for sensitivity in terms of the attenuation of the UV beam by absorption and scattering, and demonstrate the applicability of the model with experimental data for a UV laser, UV lamps and direct spectrophotometry. We also present a model for the critical energy dose in terms of the relative number of photo-generated radicals and the concentration of inhibitors.
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scattering of ultraviolet radiation in turbid suspensions
Journal of Applied Physics, 1997Co-Authors: Michelle L Griffith, John W. HalloranAbstract:A Beer’s law expression for the penetration Depth of ultraviolet radiation in a concentrated suspension of scattering particles is used to model the Depth of Cure for a suspension of ceramic particles in a medium of photocurable monomers. The Cure Depth is predominantly controlled by the square of the refractive index difference between the ceramic particles and the medium, Δn2=(np−n0)2. A secondary effect on the Cure Depth is the ratio of the interparticle spacing to the ultraviolet wavelength. Theoretical results agree with experimental data for 0.40–0.50 volume fraction ceramic-filled suspensions.
Shang-hua Wu - One of the best experts on this subject based on the ideXlab platform.
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Cure behavior of colorful zro2 suspensions during digital light processing dlp based stereolithography process
Journal of The European Ceramic Society, 2019Co-Authors: Yan Hui Li, Hai-dong Wu, Minglang Wang, Fupo He, Yong Chen, Shang-hua WuAbstract:Abstract In this study, the light absorption of the pure ZrO2 and three types of colorful ZrO2 mixtures were investigated. It was found that the absorbance of colored ZrO2 powder increases with the colorant content, and the yellow-colored powder has the strongest absorbance at the wavelength of 405 nm compared with the other two types of colored ZrO2 powder. The Cure behavior investigation on the ceramic suspensions of the above four types of ZrO2 powders during DLP process shows that as the colorant content increases, the Cure Depth and excess Cure width both decrease due to the ceramic absorbance. The Cure Depth of colored suspensions is linear with logarithm of incident energy, consistent with Beer-Lambert model, while the further research into the Cure width shows that the excess Cure width increases nonlinearly with logarithm of incident energy, which is inconsistent with Quasi-Beer-Lambert model. Additionally, colorful ZrO2 accessories were successfully fabricated.
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Fabrication of complex shaped ceramic parts with surface-oxidized Si3N4 powder via digital light processing based stereolithography method
Ceramics International, 2019Co-Authors: Rong-ji Huang, Qiang Guo Jiang, Wen Yong Liu, Xin Xin Lu, Yan Hui Li, Hai-dong Wu, Shang-hua WuAbstract:Si3N4 ceramic is difficultly fabricated by digital light processing (DLP) based stereolithography method, due to a large refractive index difference between Si3N4 powder and resin. In this paper, a surface oxidation approach of Si3N4 powder for improving Cure Depth is proposed. The results showed that, the amorphous SiO2 layer was uniformly attached onto the surface of Si3N4 powder by surface oxidation, and the absorbance of Si3N4 powder decreased as increasing oxidation degree. Moreover, the Cure Depth of the suspension significantly increased because of a smaller absorbance and a refractive index difference at the interface between oxidized Si3N4 powder and resin. At the exposure energy of 500 mJ/cm2, the Cure Depth of the raw Si3N4 powder was 34 µm. After oxidizing at 1150 °C and 1200 °C for 1 h, the Cure Depth effectively increased to 42 µm and 51 µm, respectively. Finally, the complex-shaped Si3N4 parts were successfully fabricated using surface-oxidized Si3N4 powder via DLP method.
Vladislava Tomeckova - One of the best experts on this subject based on the ideXlab platform.
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Photopolymerization of powder suspensions for shaping ceramics
Journal of the European Ceramic Society, 2011Co-Authors: John W. Halloran, Vladislava Tomeckova, Susan P. Gentry, Suman Das, Paul Cilino, Dajun Yuan, Rui Guo, Andirudh Rudraraju, Peng ShaoAbstract:Abstract The photopolymerization of suspensions of ceramic powders in monomer solutions is the fundamental step for forming techniques where a liquid suspension is solidified with UV light. The photopolymerization behavior is determined by the properties of the monomer and photoinitiator and by the transport of photons in the suspension. Photon transport in suspensions involves scattering from the particle and absorption by photoinitiators and inert dyes. The photopolymerization behavior is related to the formulation of the suspensions. Proper formulations are discussed for several applications. Techniques for characterization include Cure Depth measurements, photocalorimetry, and photorheology.
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Cure Depth for photopolymerization of ceramic suspensions
Journal of The European Ceramic Society, 2010Co-Authors: Vladislava Tomeckova, John W. HalloranAbstract:Abstract The Cure Depth of a series of photopolymerizable SiO2 and Al2O3 ceramic suspensions was measured as a function of energy dose to determine the sensitivity parameter Dp and its dependence on ceramic volume fraction, type and concentration of photoinitiator and inert dye. As predicted by an Absorption Model for Dp, 1/Dp is a linear function of photoinitiator concentration and dye concentration. The molar extinction coefficients derived from the Cure Depth measurements using an Absorption Model were compared with coefficients determined via spectrophotometry.
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predictive models for the photopolymerization of ceramic suspensions
Journal of The European Ceramic Society, 2010Co-Authors: Vladislava Tomeckova, John W. HalloranAbstract:The photopolymerization of suspensions of ceramic powders in monomer solutions is the fundamental step in several rapid prototyping forming techniques based on photocuring. Exposure to an UV dose of energy E causes the monomer to be polymerized to a certain Cure Depth, with the relation between Cure Depth and energy dose dependant on two properties of the photosuspension, the sensitivity and the critical energy dose. We present simple models for sensitivity in terms of the attenuation of the UV beam by absorption and scattering, and demonstrate the applicability of the model with experimental data for a UV laser, UV lamps and direct spectrophotometry. We also present a model for the critical energy dose in terms of the relative number of photo-generated radicals and the concentration of inhibitors.
Yan Hui Li - One of the best experts on this subject based on the ideXlab platform.
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Cure behavior of colorful zro2 suspensions during digital light processing dlp based stereolithography process
Journal of The European Ceramic Society, 2019Co-Authors: Yan Hui Li, Hai-dong Wu, Minglang Wang, Fupo He, Yong Chen, Shang-hua WuAbstract:Abstract In this study, the light absorption of the pure ZrO2 and three types of colorful ZrO2 mixtures were investigated. It was found that the absorbance of colored ZrO2 powder increases with the colorant content, and the yellow-colored powder has the strongest absorbance at the wavelength of 405 nm compared with the other two types of colored ZrO2 powder. The Cure behavior investigation on the ceramic suspensions of the above four types of ZrO2 powders during DLP process shows that as the colorant content increases, the Cure Depth and excess Cure width both decrease due to the ceramic absorbance. The Cure Depth of colored suspensions is linear with logarithm of incident energy, consistent with Beer-Lambert model, while the further research into the Cure width shows that the excess Cure width increases nonlinearly with logarithm of incident energy, which is inconsistent with Quasi-Beer-Lambert model. Additionally, colorful ZrO2 accessories were successfully fabricated.
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Fabrication of complex shaped ceramic parts with surface-oxidized Si3N4 powder via digital light processing based stereolithography method
Ceramics International, 2019Co-Authors: Rong-ji Huang, Qiang Guo Jiang, Wen Yong Liu, Xin Xin Lu, Yan Hui Li, Hai-dong Wu, Shang-hua WuAbstract:Si3N4 ceramic is difficultly fabricated by digital light processing (DLP) based stereolithography method, due to a large refractive index difference between Si3N4 powder and resin. In this paper, a surface oxidation approach of Si3N4 powder for improving Cure Depth is proposed. The results showed that, the amorphous SiO2 layer was uniformly attached onto the surface of Si3N4 powder by surface oxidation, and the absorbance of Si3N4 powder decreased as increasing oxidation degree. Moreover, the Cure Depth of the suspension significantly increased because of a smaller absorbance and a refractive index difference at the interface between oxidized Si3N4 powder and resin. At the exposure energy of 500 mJ/cm2, the Cure Depth of the raw Si3N4 powder was 34 µm. After oxidizing at 1150 °C and 1200 °C for 1 h, the Cure Depth effectively increased to 42 µm and 51 µm, respectively. Finally, the complex-shaped Si3N4 parts were successfully fabricated using surface-oxidized Si3N4 powder via DLP method.
Hai-dong Wu - One of the best experts on this subject based on the ideXlab platform.
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Cure behavior of colorful zro2 suspensions during digital light processing dlp based stereolithography process
Journal of The European Ceramic Society, 2019Co-Authors: Yan Hui Li, Hai-dong Wu, Minglang Wang, Fupo He, Yong Chen, Shang-hua WuAbstract:Abstract In this study, the light absorption of the pure ZrO2 and three types of colorful ZrO2 mixtures were investigated. It was found that the absorbance of colored ZrO2 powder increases with the colorant content, and the yellow-colored powder has the strongest absorbance at the wavelength of 405 nm compared with the other two types of colored ZrO2 powder. The Cure behavior investigation on the ceramic suspensions of the above four types of ZrO2 powders during DLP process shows that as the colorant content increases, the Cure Depth and excess Cure width both decrease due to the ceramic absorbance. The Cure Depth of colored suspensions is linear with logarithm of incident energy, consistent with Beer-Lambert model, while the further research into the Cure width shows that the excess Cure width increases nonlinearly with logarithm of incident energy, which is inconsistent with Quasi-Beer-Lambert model. Additionally, colorful ZrO2 accessories were successfully fabricated.
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Fabrication of complex shaped ceramic parts with surface-oxidized Si3N4 powder via digital light processing based stereolithography method
Ceramics International, 2019Co-Authors: Rong-ji Huang, Qiang Guo Jiang, Wen Yong Liu, Xin Xin Lu, Yan Hui Li, Hai-dong Wu, Shang-hua WuAbstract:Si3N4 ceramic is difficultly fabricated by digital light processing (DLP) based stereolithography method, due to a large refractive index difference between Si3N4 powder and resin. In this paper, a surface oxidation approach of Si3N4 powder for improving Cure Depth is proposed. The results showed that, the amorphous SiO2 layer was uniformly attached onto the surface of Si3N4 powder by surface oxidation, and the absorbance of Si3N4 powder decreased as increasing oxidation degree. Moreover, the Cure Depth of the suspension significantly increased because of a smaller absorbance and a refractive index difference at the interface between oxidized Si3N4 powder and resin. At the exposure energy of 500 mJ/cm2, the Cure Depth of the raw Si3N4 powder was 34 µm. After oxidizing at 1150 °C and 1200 °C for 1 h, the Cure Depth effectively increased to 42 µm and 51 µm, respectively. Finally, the complex-shaped Si3N4 parts were successfully fabricated using surface-oxidized Si3N4 powder via DLP method.
