| 3D printing technology is also known as additive manufacturing,a layer-by-layer fabrication method controlled by computer.Compared with 3D printing of polyermer or metal materials,a small amount of researches focus on the additive manufacturing of ceramics.3D printing process of ceramic materials based on photo-curable resins became a hot issue recently.Aimed at the disadvantages of resin systems made up of photo-curable resin and ceramic particles,this dissertation used pure preceramic resin systems to avoid the problem of sedimentation,low solid content and low printing accuracy caused by ceramic particles.This academic dissertation focused on optimization of different constituents in the preceramic resin system,3D printing of optimized resin systems,and the pyrolysis properties of printed samples.The main conclsions were as follows:(1)In the first part,the research on selection of resin formula was carried out.Aimed at the resin requirements,such as fast curing speed,low shrinkage ratio,great mechanical properties and high ceramic yield of stereolighography technology,the optimization on kinds and contents of photo initiator was made.The properties of cured samples from different prepolymer kinds and amounts of photo-curable resins were explored.The resin formula which could meet the requirements of 3D printing was figured out.Study found that when photo initiator was 819 with 2.0wt%content,the waveband matching,curing speed,crosslinking degree of mixed resin was comparatively better.Then research found that when vinyl-siloxane was set as P171prepolymer,the resin system had fast curing speed(6s),low shrinkage ratio(6.82%),high tensile strength(1.06MPa)and high ceramic yield(38.11wt%).Results showed that with the rising of DPHA content,curing speed became faster,shrinkage ratio increased,shape retention and ceramic yield decreased.Thus,the three resin systems were all meeting the requirements of 3D printing and were all tested in the later experiments;(2)In the second part,the research on the process parameters optimization(including light strength,exposure time,curing depth and critical exposure energy)of resin systems was performed.Aimed at the requirements of high printing accuracy and long preservation time of resin systems,the photosensitizer additives were added and optimized.The reaction mechanism was explored and the process paratmeters of three resin systems were optimized.Besides,the transmission depth and critical exposure energy of different systems were also explored.The samples were fabricated successfully through 3D printing process using optimized parameters.Research found that the add of Sudan Red with content of 200ppm and the Tinuvin 123 with content of2.0wt%could solve the problem of low printing accuracy and unstable properties of resin system.Then the parameters optimization of three systems with different DPHAcontents(30wt%,40wt%and 50wt%)was performed.The results showed under the light intensity of 250,the best exposure time of single layer was 3s,6s and 5s.Next,the research on depth of transmission and critical exposure energy was carried out.The results illuminated that the critical exposure energy of three systems were 24.91mJ/cm~2,41.28 mJ/cm~2 and 37.89 mJ/cm~2,respectively.The reaction mechanism of system was also explored to be the polymerization of thiol-ene groups.Finally,the samples with complex shapes were fabricated using the preceramic resins and optimized parameters successfully.(3)In the third part,the post curing methods and pyrolysis properties of printed samples were explored.Aimed at the defects of large volume shrinkage and low ceramic yield during the high temperature treatment,the post curing methods were tested and optimized.The research of different temperature and heat increasing rate on macromorphology,shape retention,microstructure and ceramic yield were carried out.The best post curing method,pyrolysis paratmeters and pyrolyzed ceramic samples were obtained.The study results showed that post curing by heat was comparatively better than by exposure and the best post curing treatment was heated to 200℃for 1h.Research found that after 1000℃treatment,the pyrolyzed sample had the ceramic yield of 30.05wt%,shape retention of 62.76%,compression strength of 1.86MPa.The best heating speed was 1℃/min,under which condition sample had the excellent macro-morphology,mechanical property and shape retention.The post curing and pyrolysis treatment using the optimized process parameters were carried out.The results showed with the rise of DPHA content,the ceramic yield and shape retention decreased,with more cracks appearing.Study found that the best DPHA content should be set as40wt%in the thiol-ene siloxane system according to the experimental results. |
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