BNmf-Si3N4w/Si3N4复合材料的制备与性能

Preparation and properties of BNmf-Si3N4w/Si3N4 composites

为制备一种介电性能和力学性能优异的高温透波材料,采用凝胶注模(GC)结合先驱体浸渍裂解(PIP)工艺制备了BN-SiN/SiN复合材料。研究了浸渍裂解次数及BN含量对复合材料的力学性能与介电性能的影响。结果表明:(1)随着PIP循环次数增加,复合材料的密度增大,气孔率降低,氮化硅基体逐渐形成三维网络结构包裹在复相微米增强体周围,复合材料力学性能提升;(2)当BN含量从4vol%增加到12vol%时,弯曲强度从175.5 MPa降低到139.3 MPa,断裂韧性从2.36 MPa·m增加到2.73 MPa·m,介电常数从3.62下降到3.25,介电损耗角正切从0.012下降到0.007;(3) BN-SiN/SiN复合材料的强韧化机制主要为裂纹分叉、裂纹偏转及BNmf及SiN的拔出,三种机制有效降低主裂纹对复合材料的损害。

To prepare a high-temperature wave-transparent material with excellent dielectric and mechanical properties, the BN-SiN/SiNcomposite material was prepared by gel-casting(GC) and precursor infiltration and pyrolysis(PIP) process. The effects of the cycles of PIP and the BNmf content on the mechanical properties and dielectric properties of composite materials were studied. The results show that:(1) As the number of PIP cycles increases, the density of the composite material increases, the porosity decreases, and the mechanical properties improve. The silicon nitride matrix gradually forms a three-dimensional network structure wrapped around the multiphase micro-reinforcement;(2) When the content of BNmf increases from 4vol% to 12vol%, the bending strength decreases from 175.5 MPa to 139.3 MPa, and the fracture toughness increases from 2.36 MPa·mto 2.73 MPa·m,the dielectric constant decreases from 3.62 to 3.25, and the dielectric loss tangent decreases from 0.012 to 0.007;(3) The strengthening and toughening mechanisms of BNmf-SiN/SiNcomposites are mainly crack bifurcation,crack deflection, and pull-out of BNand SiN. Three mechanisms effectively reduce the damage of the main crack to the composite.