【作者】 彭珍珍；

【导师】 吴厚政； 蔡舒；

【作者基本信息】 天津大学 ， 材料学， 2004， 硕士

【摘要】 氧化铝/碳化硅纳米复合陶瓷表现出优异的力学性能和表面性能,被陶瓷界称为纳米复合陶瓷的“纳米效应”。为了进一步探讨上述“纳米效应”存在的广泛性,即是否存在于大规模工业化生产的低纯度氧化铝中,本研究以工业生产中广泛使用的85氧化铝陶瓷原料粉为基础料,添加不同含量的亚微米级碳化硅,在C粉和SiC粉形成的还原性气氛下,采用控制无压烧结的方法制备了85氧化铝/碳化硅纳米复合陶瓷。密度及力学性能测试表明,还原性气氛有利于复合陶瓷的烧结致密化,当SiC含量小于10%时,容易制得结构致密且力学性能显著高于85氧化铝陶瓷的85Al2O3/SiC纳米复合陶瓷。研究的重点为85Al2O3/SiC纳米复合陶瓷的表面性能,包括表面抛光行为和表面耐磨损性能。在抛光行为研究中,对用不同尺寸磨粒抛光的材料表面进行了光学显微观察,采用抛光百分率定量化评价对比了85氧化铝陶瓷和纳米复合陶瓷的表面抛光质量。结果表明,添加1~10%纳米碳化硅的纳米复合陶瓷显示出比纯85Al2O3陶瓷更好的表面抛光响应,其中以添加了10%纳米SiC的纳米复合陶瓷的抛光性能最好。材料的磨损性能是在自行设计的耐磨损试验机上进行的,实验还对比测试了85氧化铝和85Al2O3/SiC纳米复合陶瓷在一定时间内的磨损率和磨损速率,结果表明添加10%纳米碳化硅可以使材料的耐磨损性能提高近1倍。断口以及磨削与磨损表面的SEM分析表明,纳米碳化硅的加入改变了材料的断裂方式,由85氧化铝陶瓷的以沿晶断裂为主转变为复合陶瓷的穿晶断裂为主。正是这种断裂方式的转变,使材料的抛光与磨损去除由大范围的深层晶粒拔出和晶间开裂,转变为局部塑性变形和小尺寸以至原子级的材料去除。文中还将研究得出的85Al2O3/SiC纳米复合陶瓷的“纳米效应”和前人对高纯氧化铝/碳化硅纳米复合陶瓷的研究结果作了对比讨论。更多还原

【Abstract】 85Al2O3/SiC nanocomposites, in which different amount of nano-scale SiC particles were dispersed in 85Al2O3 matrix, were prepared by presureless sintering in reduced atmosphere formed by C powder and coarse SiC grits in a limited space. Densities and mechanical properties of the nanocomposites were measured. Fracture surfaces of the nanocomposites were characterized by SEM. The results revealed that SiC particles had great influences on the microstructure and mechanical properties of nanocomposites. Nanocomposites with low SiC content(≤10%) could be fully densified in reduced atmosphere without applying pressure. However, high SiC content(>10%) would greatly inhibit the sintering process and lead to low density. SEM observation of the fracture surface showed that there was an obvious change of facture mode from mainly intergranular fracture in 85Al2O3 to transgranular fracture in the nanocomposites by the addition of nanosized SiC particles. The polishing behavior and wet erosive wear resistance have been studied to evaluate the surface mechanical properties of 85Al2O3/SiC nanocomposites. For polishing behavior, the polished surface with various grit sizes were investigated by optical microscope, and the surface quality was quantified by the relative areas of smooth polished regions as apposed to darker rough regions. It was found that nanocomposites with 1~10% SiC had a better surface finish than 85Al2O3 at all stages of progressively polishing treatment. For wet erosive wear tests, the wear rates of nanocomposites with different amount of SiC nano-particles were measured and compared with 85Al2O3 ceramics. The results showed that 85Al2O3/1-10%SiC nanocomposites had lower wear rates than the pure 85Al2O3. Both results from polishing reponses and erosive wear resistance demonstrated much improved surface mechanical properties for nanocomposites over the 85Al2O3 ceramics. The material removal mechanisms of 85Al2O3 and 85Al2O3/SiC nanocomposites were dicussed based on the SEM observation of the ground and erosive wear surfaces. It was found that, during polishing and erosive wearing, the material removal processes are different for the two types of material. In 85Al2O3 ceramics, grain pullout and intergranular cracking are main removal processes, while local plastic deformation and fine scale removal might be main removal processes in nanocomposites.更多还原