【作者】 汪彩芬；

【导师】 刘家臣；

【作者基本信息】 天津大学 ， 材料学院， 2012， 硕士

【摘要】 本论文主要进行了石英/漂珠复合多孔陶瓷的制备及其与石英纤维编织体的连接实验,目的是利用石英基多孔陶瓷的轻质、隔热性及纤维编织体的可压缩性,制备高温密封隔热构件。实验首先以漂珠为造孔剂,采用凝胶注模成型工艺制备石英/漂珠多孔陶瓷,研究了漂珠量、烧结温度等因素对制品强度、密度等性能的影响,并最终确定连接用石英基轻质复合隔热材料的最佳配方;然后研究了石英纤维及其编织体在不同温度下的力学性能,以确定石英纤维编织体合适的的连接、使用温度;最后实验选择了三种中间层物质进行连接实验,研究了不同中间层对连接性能的影响,并探讨了各自的连接机理;论文还用有限元分析了同样两种材料连接时采用陶瓷/编织体连接和陶瓷/陶瓷连接时各自的应力分布,尝试总结了陶瓷/纤维编织体连接体系与现有陶瓷连接体系的异同。实验表明:通过添加45 wt.%的漂珠,采用凝胶注模成型,可以成功制备密度为0.94 g/cm³、强度为15.6 MPa、气孔率达60%、常温热导率0.21 W/ （m·K）的轻质隔热材料;漂珠在制品中不仅起到造孔剂的作用,还能促进石英烧结,搭建的莫来石晶须骨架能够对制品起到增强作用;体积分数为45%的三维四向石英纤维编织体最大可压缩60%,800℃仍具有5%回弹量;采用硅酸钠600-800℃可以实现基体与编织体的良好连接,连接机理为扩散烧结,连接件强度为基体强度3倍,应变量是原来的6倍,断裂发生在纤维层;采用B₂O₃为中间层可通过B₂O₃与基体的低共熔实现连接,但B₂O₃对纤维损害大,采用B₂O₃/SiO₂混合物做中间层可减小损害程度,连接温度随SiO₂含量增加而增大;采用Na₂CO₃为中间层,可通过800℃Na₂CO₃与基体反应及粉末烧结实现连接,但连接强度低,断裂发生在中间层;陶瓷/纤维编织体连接体系与其它连接体系相比,主要区别在于纤维编织体结构的疏松多孔性,纤维编织体疏松多孔的结构一方面导致对液态浆料的吸附性较强,另一方面能一定程度减小基体材料的热应力。更多还原

【Abstract】 This paper prepared silica based porous composites and realized the joining between the s ilica ba sed composite a nd quartz fiber w aves t o make a s ealed component w ith good heat insulation at high temperature. Firstly, silica based porous composites were prepared by gel-casting with fused silica as raw material and fly ash cenosphere （FAC） as pore-forming agent. And the effects of FAC on the properties of silica based composites were discussed to obtain the optimal formula of s ilica/FAC composites. Secondly, the mechanical pr operties o f q uartz fiber a nd q uartz fiber waves treated at different temperatures were studied to determine the temperature at which for joining and working. And then, the joining between silica based composite and quartz fiber waves was made with three materials （B₂O₃, Na₂CO₃ and Na₂SiO₃） as interlayers. At last, the ceramic/fiber wave joint was compared with the existing joint systems.Results showed that the silica based light-weight porous composite with the density of 0.94 g/cm³, the bending strength of 15.6 MPa, the porosity of 60% and the conductivity of 0.21 W/（ m·K） was prepared by adding 45 wt.% fly ash cenonsphere after s intered a t 1200℃. In t he p rocess o f s intering, FACs not o nly a cted a s a pore-forming agent but also as a sintering aid to promote the densification o f s ilica. An interlaced microstructure of lath-like and needle-like mullite crystals was found in the composites, which was a beneficial factor for strengthening of framework. Quartz fiber’s strength decreased as the temperatures i ncreased. There w as still 60% compressibility and 5% resilience in 3D silica fiber braid when treated at 800℃. During three interlayer materials （B₂O₃, Na₂CO₃, Na₂SiO₃）, the joint with Na₂SiO₃ performed best as its easy process, high joining intensity and small damage to quartz fiber. The joining mechanism of using Na₂SiO₃ as joining interlayer was diffusion sintering bonding （600-800℃）, and it was brazing for B₂O₃ and B₂O₃/SiO₂ mixed powders i nterlayer and reaction j oining （ 800℃） for Na₂CO₃ interlayer. What’s different about ceramic/fiber wave joint was that the loose and porous structure in fiber wave could release the stress in the joining substrate.更多还原