【作者】 包旭东；

【导师】 雷玉成；

【作者基本信息】 江苏大学 ， 材料加工工程， 2005， 硕士

【摘要】 六方氮化硼（h-BN）是一种片状结构陶瓷材料,具有高熔点,热膨胀系数小,热导率高等优点,但是其烧结性能较差,目前六方氮化硼陶瓷制品的主要制备方法是采用热压烧结的方法,但是热压烧结的方法对制品的几何尺寸有明显的限制。并且六方氮化硼作为一种瘠性材料,其复杂形状坯体成型非常困难,传统的成型方法难以获得复杂形状的坯体。因此六方氮化硼陶瓷的无压烧结和新型成型技术研究是六方氮化硼陶瓷材料实际应用的基础。 陶瓷凝胶注模成型工艺是一种新颖的成型工艺,具有很好的应用前景。它将高分子化学单体聚合的思路引入到陶瓷成型工艺中,可制备高强度、高均匀性的陶瓷坯体。本课题针对h-BN陶瓷的凝胶注模成型工艺中的低粘度且高固相体积分数浓悬浮体的制备,对比研究了PAA（聚丙烯酸）和PMAA（聚丙烯酸铵改性）对h-BN浆料流变特性的影响。结果表明:对于该体系用PAA（聚丙烯酸）分散剂比PMAA（聚丙烯酸铵改性）更有效。 同时,对六方氮化硼复杂形状陶瓷件采用凝胶注模工艺成型进行了研究,着重就有机单体含量与配比对胶体性状的影响、料浆加入引发剂后的凝胶固化行为、催化剂对凝胶固化性能的影响、以及单体和引发剂加入量对坯体干燥性状的影响等进行了研究。 考虑到近来t-BN被认为是解决六方氮化硼烧结致密化困难的一个有效途径,我们以尿素、硼酸为原料合成一种六方氮化硼,即t-BN（turbostratic boron nitride）粉体。用XRD、SEM及激光粒度分析等手段对所制备氮化硼粉体进行研究。发现所制备的氮化硼粉体是较纯的t-BN,且为平均粒径在亚微米尺寸的球形颗粒。 同时本文探讨了以六方氮化硼为基体,Al₂O₃,Y₂O₃和B₂O₃为添加剂,在略高于一个大气压的N₂气氛下,于1700℃～1850℃左右进行无压烧结。研究结果表明,随Y₂O₃和Al₂O₃的含量的增加,烧结体的致密度明显提高,强度明显上升。并且B₂O₃作为一种烧结助剂可以有效地提高烧结体的致密度、降低材料的烧结温度。更多还原

【Abstract】 Hexagonal boron nitride is a kind of ceramic materials with flat structure, having high melting points, low hot expansion coefficient, high thermal conductance rate. But its sintering performance is relatively bad. The main sintering method of hexagonal nitrogen boron ceramics is hot pressing sintering at present, but the geometry of the products is obvious restricted by hot pressing sintering method. And as a lean material, hexagonal boron nitride is difficult to form complex shape, it is difficult to get complex shape green by conventional forming technology. So pressureless sintering process and new forming technology of hexagonal boron nitrogen is necessary to study at present.By introducing the concept of organic monomer polymerization chemistry into the ceramic forming techniques, gel-casting of ceramics has become a novel forming method by which a ceramic green body with good uniformity and high strength can be prepared. In the paper, in order to prepare a concentrated suspension with low viscosity and high solid volume content is studied. The rheological properties of h-BN suspensions with two dispersants, PAA and modified PMAA-NH4, were compared. The results show that PAA is more effective than modified PMAA-NH4 which is used frequently.The complex shape green body of hexagonal boron nitride obtained by Gel-Casting forming technology is studied in this paper, it is focused on effect of organic monomer content and proportion on colloid character, collide gelling behavior of slurry added initiator, effect of activator on gel gelling performance, effect of monomer and initiator content on green body gelling character as well as.Thinking about t-BN has been considered to be the effective method to resolve the h-BN pressureless sintering densification question. We synthesis t-BN （turbostratic boron nitride） powder by urea and boric acid. The t-BN powder was analyzed by XRD, SEM and laser granularity analyzer. The results indicated that the BN powder synthesized was pure t-BN and particle size was sub- micron. The particle shape was globular.This paper has researched the pressureless sintering performance of hexagonal boron nitride,with Al₂O₃, Y₂O₃ and B₂O₃ as the additive, under N₂ atmosphere, pressureless sintering at about 1800 °C degrees. Result of study indicates that with increase of the content of Y2O3 and Al₂O₃, the density and the intensity of sintering body更多还原