激光功率对激光选区烧结制备多孔Si_(3)N_(4)陶瓷性能的影响

Effects of laser power on properties of porous Si_(3)N_(4) ceramics prepared by selective laser sintering

针对现有激光选区烧结技术多使用高分子黏结剂,存在素坯易坍塌、烧结时间长等问题,提出使用无机黏结剂,为改善陶瓷坯体烧结质量提供新方法.以Si_(3)N_(4)聚空心微球为原材料,纳米Al N为无机黏结剂,Al_(2)O_(3)和Y_(2)O_(3)为烧结助剂,采用激光选区烧结技术直接成形多孔Si_(3)N_(4)陶瓷,并分析了激光功率对多孔Si_(3)N_(4)陶瓷微观结构及力学性能的影响.结果表明:随着激光功率的增加,陶瓷素坯中Si_(3)N_(4)聚空心微球表面的“绒毛”结构减少;在高温烧结过程中,纳米Al N促进了共晶液相的产生,断裂方式从沿球断裂转变为穿球断裂;Si_(3)N_(4)聚空心球陶瓷的相对密度与抗弯强度随着激光功率的增大呈现先升高再降低的趋势;当激光功率为8 W时,1 800℃烧结后的多孔Si_(3)N_(4)陶瓷获得44.6%的孔隙率及24.6 MPa的抗弯强度;采用激光选区烧结技术为多孔Si_(3)N_(4)陶瓷的激光选区烧结成形及其应用提供了新的思路.

The existing selective laser sintering(SLS) technology mostly uses polymer binder,which has some problems such as easy collapse of green bodies and long sintering time.Inorganic binder provides a new method to improve the sintering quality of ceramics.Porous Si_(3)N_(4)ceramics were prepared by direct selective laser sintering technology,where Si_(3)N_(4)poly hollow microspheres(PHMs) was used as raw material,nano-AlN as inorganic binder,Al_(2)O_(3)and Y_(2)O_(3)as sintering additives.The effects of laser power on the microstructure and properties of porous Si_(3)N_(4)ceramics were analysed. Results show that with the increase of laser power,the microvilli on the surface of the Si_(3)N_(4)poly hollow microspheres decrease. During the high temperature sintering,nano-AlN promotes the formation of eutectic liquid,which leads to the fracture mode changes from fracturing along poly hollow microspheres to fracturing across poly hollow microspheres.Additionally,the relative density and flexure strength of porous Si_(3)N_(4)ceramics increase at first and then decrease.The porous Si_(3)N_(4)ceramics sintered at 1 800 ℃ with selective laser sintering laser power of 8 W have a porosity of 44.6% and a flexural strength of 24.6 MPa. This study provides a new idea for selective laser sintering forming and application of porous Si_(3)N_(4)ceramics.