颗粒级配对选区激光烧结打印结合常压固相烧结制备碳化硅陶瓷性能的影响

Effect of Particle Grading on Properties of Silicon Carbide Ceramics Prepared by Selective Laser Sintering Printing Combined with Solid-phase Sintering at Atmospheric Pressure

SiC陶瓷因其独特的热学、电学性能及优异的力学性能,被广泛应用于航空航天、核能、化工、半导体等国防与工业重大领域,但是传统的成型方法无法满足大尺寸复杂构件的制备需求。选区激光烧结(SLS)打印具有无需支撑、材料利用率高、加工效率高等优势,能高效成型复杂陶瓷结构零部件。本研究采用颗粒级配SiC的方法,系统研究了冷等静压(CIP)、前驱体浸渍热解(PIP)、CIP结合PIP后常压固相烧结等工艺对级配和中位径82μm未级配体系SiC陶瓷的影响。研究发现,级配粉末成型坯体的体积密度和抗弯强度比未级配坯体均提升了20%以上,级配体系CIP后常压固相烧结体的相对致密度达到了90%以上,实现了致密化烧结,而未级配体系烧结体的相对致密度仅为89%,这是由颗粒级配后坯体的堆积密度提升所致,且级配烧结体的抗弯强度(136.8 MPa)比未级配(99.4 MPa)提升了37%以上。采用多次重复PIP结合常压固相烧结的方法制备高致密的SiC陶瓷,发现SLS打印成型的坯体经四次PIP后致密度可达到CIP堆积致密的效果,但四次PIP后常压固相烧结体的体积密度仅为2.29 g/cm^(3),抗弯强度为59.6 MPa。

Silicon carbide(SiC)ceramics are widely used in critical industries such as aerospace,nuclear energy,chemical processing,and semiconductor manufacturing due to their unique thermal and electrical properties coupled with excellent mechanical properties.Nevertheless,conventional forming methods often fall short when it comes to producing large-sized and complex components.Selective laser sintering(SLS)printing has the advantages of no support,high material utilization,high processing efficiency,etc.,endowing it suitable for the precise fabrication of ceramic structural components with complicated shape.Here,the particle grading approach was employed to systematically investigate the impacts of processes such as cold isostatic pressing(CIP),precursor impregnation pyrolysis(PIP),and the combination of CIP with PIP followed by solid-phase sintering at atmospheric pressure.The results revealed that the graded powders significantly enhanced both the bulk density and the flexural strength of the formed body by over 20%compared to non-graded systems.Relative density of the graded system after CIP and subsequent solid-phase sintering at atmospheric pressure was over 90%,confirming successful densification during sintering.In contrast,the non-graded sintered body only achieved a density of 89%.Implementation of the particle grading led to an increase in bulk density,and it was beneficial for achieving higher densification during sintering.Consequently,the flexural strength of the grading-sintered body was significantly improved,reaching 136.8 MPa-a gain of over 37%compared to the non-graded counterpart whose flexural strength was only 99.4 MPa.Meanwhile,high-density SiC ceramics could be achieved by repeating PIP for four cycles combined with solid-phase sintering of which SiC ceramics density was comparable to that of CIP compacts.However,the bulk density of solid-phase sintered body after four PIP cycles was only 2.29 g/cm^(3),which was accompanied by a flexural strength of 59.6 MPa.