（毕业设计论文）《ZrB2／SiCw复合材料的制备工艺和力学性能的探索和研究》.docVIP

PAGE 摘要 ZrB2属于超高温陶瓷中的一种，具有低的体积密度，另外其还具有一系列优良性能，比如高强度，高硬度，高温抗氧化性，耐腐蚀性，在高温结构材料方面有很好的应用前景。但ZrB2陶瓷应用中存在着脆性大的问题。目前，改善这一缺点的可能途径之一就是在ZrB2基体中加入SiC晶须，使其具有较好的韧性和强度。致密ZrB2陶瓷材料需要在1900o℃或更高的温度，20-30MPa或更高的压力下烧结，这是由于ZrB2为共价键、高温扩散速率低造成的。然而，SiC晶须的使用温度必须低于1900℃，另外在高温下SiC晶须易与ZrB2颗粒表面的氧化物杂质反应造成晶须损伤，从而达不到理想的增韧作用。为了解决这些问题，我们用液态聚碳硅烷（LPCS）来包裹ZrB2-SiCw粉体，降低烧结温度，并减少SiC晶须的界面反应。 首先，将ZrB2和SiC晶须（0-20vol%）在酒精介质下球磨混合5小时，然后烘干，再加入14.29wt.%LPCS和适量丙酮充分混合。由此制得的不同配比（0-20vol%SiCw）的粉体在1750℃真空条件下热压烧结，保温时间为1小时。实验结果表明：ZrB2-SiCw陶瓷材料的力学性能受晶须体积分数影响：抗弯强度、断裂韧性、弹性模量随着体积分数增大而升高，维氏硬度却有所减小。由断面SEM图片可知，断面处明显可有晶须拔出。可以推断纤维拔出是SiCw增韧ZrB2基陶瓷材料的机理。 关键词： ZrB2-SiCw，液态聚碳硅烷（LPCS），晶须增韧，显微组织，力学性能 ABSTRACT Zirconium diboride (ZrB2) belongs to the family of ultra-high temperature ceramic, which has the lowest bulk density. Furthermore, it also has a series of excellent properties, such as high strength, high hardness, high temperature oxidation resistance, corrosion resistance, which renders them as high temperature structural materials. However, one defection of ZrB2 ceramic is its brittleness. At present, one possible solution way is adding SiC whiskers into the ZrB2 powders to improve their strength and toughness. Usually, the densification temperatures for ZrB2-based ceramics are over 1900oC with a pressure of 20-30MPa or higher due to their covalent bonding and low diffusivity at high temperatures. However, SiC whisker will be severely damaged at temperatures over 1900oC. Moreover, SiC whiskers are easier to react with the oxide impurities on the surface of ZrB2 powders at high temperatures, which will degrade whiskers. To solve these problems, liquid Polycarbosilane (LPCS) is added into ZrB2-SiCw powders to decrease the sintering temperatures and to reduce the interfacial reaction of SiC whiskers. Firstly, ZrB2 powder was mixed with SiC whiskers (0-20vol %) by ball-milling with ethanol as grinding media for 5 hours. After being dried, the powders were mixed with 14.29wt.% LPCS and acetone. The as-prep