【作者】 何顺爱；

【导师】 李懋强；

【作者基本信息】 中国建筑材料科学研究总院 ， 材料学， 2008， 博士

【摘要】 本研究以部分稳定的超细氧化锆微粉制备的水基泥浆为原材料,通过挤出—聚凝成型工艺成功制备了氧化锆陶瓷纤维。论文对该工艺制备氧化锆纤维的成型机理,氧化锆纤维制备过程的影响因素以及在烧结过程中氧化锆陶瓷纤维内的晶粒生长动力学和以及氧化锆陶瓷纤维烧结动力学进行了深入的研究。通过上述研究,获得主要成果如下:提出了一种新的氧化锆纤维成型方法,即挤出—聚凝法。该成型方法的工艺原理为:通过挤压作用,使稳定悬浮的氧化锆泥浆通过喷丝头微孔挤出成细柱状泥浆,降低细柱泥浆中氧化锆颗粒周围液相的介电常数,使颗粒周围双电层急剧变薄,颗粒间静电斥力减小,颗粒之间的作用力失去平衡,从而发生氧化锆微粉颗粒之间聚集,从流态变成固态,并保留了柱状泥浆的长径比。另外,氧化锆泥浆细流中的水基本上被聚凝剂所萃取掉,凝固下来的氧化锆纤维表面包覆的是表面张力很小的聚凝剂,避免了氧化锆纤维纤维在烘干过程中互相之间发生粘结而导致纤维断裂。对纤维表面的粗糙和纤维中心部位的小孔的成因进行了解释:①当泥浆接触聚凝剂的时候,由于聚凝剂与泥浆的界面张力很小,氧化锆颗粒周围水化膜中的水被聚凝剂瞬间萃取,泥浆因为失去颗粒表面水化膜中的水而失去了恢复光滑表面的驱动力,使挤出过程中形成的不均匀表面得以保留;②由于聚凝剂对水的萃取作用,使泥浆已经固化的部分和泥浆内部没有固化的部分形成水的浓度差,水在浓差作用下,不断的从内部向表面运动,从而形成无数的水流通道,宏观表现为表面的粗糙;③泥浆内储存的压应力使泥浆细流离开喷丝孔后发生微小的膨胀,使固化的表面产生裂隙。这些裂隙在宏观上也表现为表面的粗糙;④由于浓差作用,泥浆内部的水分不断向聚凝剂中运动,带动纤维内部流体中被水包围的氧化锆颗粒向已经固化的表面方向运动,形成中空结构。成功地制备出成功制备出密度为6.05g╱cm~3氧化锆陶瓷纤维。并提出挤出—聚凝成型制备氧化锆纤维的最佳工艺参数:泥浆的固相含量为47vol%,分散剂加入量为氧化锆微粉的0.7%(质量分数),球磨时间为24小时、聚凝剂为丙酮,挤出压力在3.28 KPa～4.92 KPa之间,烧结温度为1530℃,保温时间为300min。根据烧结过程中氧化锆纤维晶粒尺寸与烧结温度和保温时间的变化规律,研究了氧化锆纤维的晶粒生长动力学,根据烧结时的氧化锆纤维的密度变化,对氧化锆纤维的烧结动力学进行了研究,提出氧化锆纤维的烧结与块状材料的烧结情况相同观点。实验还发现,氧化锆纤维集合体在高温下有很大的收缩,纤维之间有烧结颈部出现:已经烧结致密的氧化锆陶瓷纤维组成的集合体,在高温下有一定的收缩,但是纤维之间很难看到烧结的颈部。更多还原

【Abstract】 In this paper, Zirconia fiber green body was prepared with extrusion-conglomeration molding sucessfully, using Zirconium water based slurry made of partial stabilized Zirconia super fine powder. The molding mechanism, influence factors on preparation of Zirconia fiber, grains growth kinetic and sintering kinetics of Zirconia fiber during sintering were studied systematically.All of achievements of this study were obtained as follows: extrusion-conglomeration molding for forming Zirconia fiber was put forward for the first time. The molding mechanism was discussed at the same time. When the Zirconium slurry was displaced into conglomerating solvent with low dielectric constant and mutual solubility to water, Zirconia particles would conglomerate because of the electric double layer being thin rapidly, static repulsive falling and equipment breaking among Zirconia particles. When the conglomeration generated continuously, zirconium slurry passed through spinneret orifice changed from fluid state to solid state and become Zirconia fiber with slenderness ratio. In addition, water in Zirconia slurry was extracted and remained little, and conglomerating solution with minute surface tension around Zirconia fiber. During drying process, adhesion between two Zirconia fibers was avoided.The explain of forming coarseness on Zirconia fiber green body surface was given as follows: first, the interfacial tension between organic solvent and Zirconia slurry result in water in film around grains surface was extracted instantly and driver force for decreasing surface area and forming a smooth surface became faintness result in minute surface tension of conglomerating solvent. So that the non-uniform surface created by slurry flowing was kept. Second, when Water, extracted from fiber interior by conglomerating solvent continuously, numerous capillary generated and they looked like minute protuberance at macroscopic. Third, slurry streamlet expanded slightly for the reason of the Barus effect after leaving the spinneret orifice. This expander made the coagulated surface cracked and generated some minute crannies and they looked like minute protuberance at macroscopic as well.The hole appeared in fiber center was because of that the particles were carried by water from slurry center to surface due to water differential concentration between solvent and interior of slurry. On the other hand, the slurry exterior surface was solidified already, so the shrinkage generated just from interior to surface of fiber.Forming optimum parameters of preparation of Zirconia fiber were given such as, In 47vol% slurry, the amount of dispersant agent PAANH4 was about 0.7 wt.% of Zirconia powder and milling time was about 24h. Acetone was used as the conglomerating agent. Extrusion press was from 3.28 KPa to 4.92 KPa. The Zirconia fiber was sintered at 1530℃for soaking 300min and it’s density is about 6.05g/cm~3.Zirconia fiber’s grain growth kinetic was studied and the grain growth activation energy was calculated according to the law of Zirconia fiber’s grain size change during sintering. Further more, the sintering kinetic of Zirconia fiber was studied via the change of fiber density during sintering. The result shows that sintering process of Zirconia fiber is similar to block materials.The sintering of Zirconia fiber aggregation was also studied in this paper. The result showed that, neck between two pieces of fiber could be observed after sintering in aggregation made of Zirconia fiber green body. If the aggregation made up of Zirconia fiber fired at 1530℃for soaking 300min, there were small shrinkage of aggregation but the neck between two pieces of fibers was observed hardly.更多还原