【作者】 张祎；

【导师】 贾德昌；

【作者基本信息】 哈尔滨工业大学 ， 材料与化工（专业学位）， 2023， 硕士

【摘要】 航空航天及空间应用中的材料往往面临高温、高压、强辐射、腐蚀、冲击与氧化等复杂的极端环境,将现有材料不断推向其物理极限。聚合物转化陶瓷因非凡的高温热稳定性、可调的电学性能及优异的力学性能,使其在高温、高压及富氧等环境中有着得天独厚的优势。近年来,因对各种异型构件的巨大需求推动了陶瓷增材制造技术的蓬勃发展,利用3D打印技术实现复杂陶瓷构件的制备逐渐成为热点。本文结合直写3D打印与前驱体PBSZ,通过加入BN和纳米气相Si O₂填料调控其流变性能,成功实现了BN/SiBCN复相陶瓷的3D打印成型。浆料流变性能的研究结果表明,BN、纳米气相Si O₂以及二者的复合填料均可增加浆料的表观粘度,并且随着剪切速率的增大,浆料的粘度不断降低,证明这几种浆料均具有剪切稀变的非牛顿流体行为。基于此,分别调配出四种不同BN含量（10 wt%、15 wt%、20 wt%、25 wt%）的复合浆料,通过对该复合浆料进行模量测试,其结果均展现出较大的屈服应力值,表现出一定的粘弹性特征行为。不同BN含量的BN/SiBCN复相陶瓷的结构及性能研究结果表明:h-BN作为一种片层状结构,通过3D打印可实现对其微观结构的有效控制。随着BN含量的增多,复相陶瓷的弯曲强度、维氏硬度及弹性模量不断降低。当BN含量从10 wt%升至25 wt%,复相陶瓷的弯曲强度从209 Mpa降低至144 Mpa,维氏硬度从651.61 HV降低至195.85 HV,弹性模量从69.69 GPa降低至33.95 GPa。此外,介电损耗呈现出先降低后增大的非单调变化趋势。当h-BN的添加量为15 wt%时,BN/SiBCN复相陶瓷的介电损耗降低效果最明显,介电损耗最低可达0.003左右,此时其弯曲强度和弹性模量分别为194 MPa、52.65 GPa。不同热解温度下BN/SiBCN复相陶瓷的结构及性能研究结果表明:随着热解温度的提升,结晶化转变使复相陶瓷的力学性能恶化,导致其弯曲强度减小。在1100～1400℃,复相陶瓷的弯曲强度从122 MPa上升至136 Mpa,当热解温度提升至1600℃,弯曲强度降低至124 MPa。随着热解温度从1100℃增大至1500℃,15wt%BN/SiBCN复相陶瓷的介电损耗从0.04增大至0.13左右,呈单调增大趋势。当热解温度升高至1600℃,介电损耗降低至0.12左右。更多还原

【Abstract】 Materials in aerospace and space applications are often exposed to complex and extreme environments such as high temperature,high pressure,strong radiation,corrosion,impact and oxidation,pushing existing materials to their physical limits.Polymer-transformed ceramics are uniquely suited for high temperature,high pressure and oxygen-rich environments due to their extraordinary high-temperature thermal stability,tunable electrical properties and excellent mechanical properties.In recent years,the huge demand for various shaped components has driven the booming development of ceramic additive manufacturing technology,and the preparation of complex ceramic components using 3D printing technology has gradually become a hot spot.In this paper,we combined direct-write 3D printing with precursor PBSZ and successfully achieved 3D printing and molding of BN/SiBCN complex-phase ceramics by adding BN and nano-gas phase Si O₂ fillers to regulate their rheological properties.The results show that BN,nano-vapor phase Si O₂ and their composite fillers can increase the apparent viscosity of the slurry,and the viscosity of the slurry decreases with the increase of shear rate,which proves that these kinds of slurry have shear thinning non-Newtonian fluid behavior.Based on this,four kinds of composite pastes with different BN content（10 wt%,15 wt%,20 wt%,25 wt%）were prepared respectively.Through the modulus test of the composite pastes,the results all show large yield stress values and certain viscoelastic characteristic behaviors.The structure and properties of BN/SiBCN multiphase ceramics with different BN content show that h-BN,as a lamellar structure,can be effectively controlled by3D printing.With the increase of BN content,the bending strength,Vickers hardness and elastic modulus of multiphase ceramics decrease continuously.When BN content increases from 10 wt%to 25 wt%,the bending strength of the composite ceramics decreases from 209 Mpa to 144 Mpa,the Vickers hardness decreases from 651.61 HV to 195.85 HV,and the elastic modulus decreases from 69.69 GPa to 33.95 GPa.In addition,the dielectric loss shows a non-monotonic trend of decreasing first and then increasing.When the addition of h-BN is 15 wt%,the dielectric loss reduction effect of BN/SiBCN composite ceramics is the most obvious,the lowest dielectric loss can reach about 0.003,and the bending strength and elastic modulus are 194 MPa and52.65 GPa,respectively.The results of the study on the structure and properties of BN/SiBCN composite ceramics at different pyrolysis temperatures show that the mechanical properties of BN/SiBCN composite ceramics deteriorate with the increase of pyrolysis temperature,resulting in a decrease in bending strength.At 1100℃to 1400℃,the bending strength of multiphase ceramics increases from 122 MPa to 136 Mpa.When the pyrolysis temperature is increased to 1600℃,the bending strength decreases to 124MPa.With the pyrolysis temperature increasing from 1100℃to 1500℃,the dielectric loss of 15wt%BN/SiBCN composite ceramics increases from 0.04 to about0.13,showing a monotonically increasing trend.When the pyrolysis temperature rises to 1600℃,the dielectric loss decreases to about 0.12.更多还原