| SiC，Si_3N_4晶须的制备方法与显微结构研究 | |
| 周延春 | |
| Subtype | 博士 |
| Thesis Advisor | 师昌绪 |
| 1990 | |
| Degree Grantor | 中国科学院金属研究所 |
| Place of Conferral | 中国科学院金属研究所 |
| Keyword | Sic晶须 Si_3n_4晶须 合成 显微结构 复合材料 |
| Abstract | 本文研究了 SiC，Si_3N_4晶须的制备方法并对SiC，Si_3N_4和SiC/ Si_3N_4复合晶须的显微结构进行了研究。主要涉及SiC，Si_3N_4晶须的制备工艺，SiC晶须中的缺陷，双晶SiC晶须的界面结构，SiC晶须中Fe杂质对SiCw/Al复合材料界面的影响，SiC晶须在热处理过程中的变化，Si_3N_4晶须的缺陷，双晶界面结构和分叉现象，SiC/Si_3N_4复合晶须的界面结构等。结果表明，以SiO_2和C为原料在只改变个别工艺参数的情况下，用同一方法即可以制备SiC晶须又可以制备Si_3N_4晶须。在SiC晶须中有高密度的层错，孪晶等缺陷。一维无序的SiC晶须是由不同 厚度的SiC多型体薄层构成，而竹节状的SiC晶须则由一维无序的与节β-SiC节孪生相连。β-SiC节内有平行于生长前沿的{111}层错，孪晶和不全位错等缺陷。孪晶面平行于晶须轴向的双晶SiC晶须具有{221} - {221}型的二次孪晶关系。由于两个或两个以上的生长方向（〈111〉_β）同时得到满足或形成又晶晶须使SiC昌须容易分叉。SiC晶须中的Fe 杂质在SiCw/6061Al复合材料的界面生成金属间化合物的颗粒相。在热处理过程中SiC晶须的形貌和结构都将发生变化。SiC晶须在1800 ℃以上不稳定并发生球化。这一工作从一个方面解释了制备温度对陶瓷基复合材料韧性的影响。α-Si_3N_4晶须的生长方向分别为{101-bar0}，{101-bar1}和{0001}。{101-bar0}晶须的一侧有小结晶体，{101-bar1}晶须中有大量的复合面缺陷；而{0001}晶须中有高密度的与晶须轴向垂直的面缺陷。α-Si_3N_4晶须容易分叉，其机理和SiC晶须类似。β-Si_3N_4晶须的生长方向为{101-bar0}。在β-Si_3N_4晶须中几乎观察不到任何缺陷。SiC/Si_3N_4复合晶须中SiC/Si_3N_4的界面是晶格与晶格直接匹配的，界面上无非晶层。 |
| Other Abstract | SiC and Si_3N_4 whiskers were prepared and the microstructure of SiC, Si_3N_4 and SiC/Si_3N_4 composite whiskers were characterized in this investigation. It mainly concerned about method for the synthesis of SiC and Si_3N_4 whiskers; defects in SiC whiskers; interfacial structure of bicrystalline SiC whiskers; influence of Fe in SiC whiskers on the interface of SICw/Al composites; the microstructure change of SiC whiskers after high temperature annealing; defects in α-Si_3N_4 whiskers; interface in bicrystalline α-Si_3N_4 whiskers and branched phenomena in α-Si_3N_4 whiskers. The interfacial structure in SiC/Si_3N_4 composite whiskers. It was shown that both SiC and Si_3N_4 whiskers could be synthesised by the same method using SiO_2 and C as raw materials. High density of stacking faults and microtwins were observed in SiC whiskers. One dimensional disordered SiC whiskers were consisted of SiC polytypes with different thickness. In SiC whiskers with "bamboon joint" morphology, β-SiC parts were jointed with one dimensional disordered parts by {111}, twin bourdaries. In β-SiC parts, partial dislocations, stacking faults and microtwins were observed. Second order twin joint with twin boundary parallel to the whisker axis was analysed, and the nature of the interface was {221} - {221} type. Branching of the whiskers was due to the formation of bicrystalline whiskers or growth conditions were satisfied for more than one growth directions. Intermetallic compound particles were formed at interface of SiCw/6061Al composites due to the presence of impurity Fe. The morphology and structure of the SiC whiskers changed during high temperature annealing. SiC whiskers sphericized at temperatures higher than 1800 ℃. This observation explained the influnce of processing temperatures on the toughness of ceramic composites from one point of view. The growth directions of α-Si_3N_4 whiskers were {101-bar0}, {101-bar1} and {0001}, repectively. A targe number of micrograins were observed on one side of {101-bar0} whiskers; and composite planar faults could be identified in {101-bar1} whiskers. In {0001} α-Si_3N_4 whiskers there were high density planar faults. A great amount of branched α-Si_3N_4 whiskers were observed and the mechanism for the formation of the branched whiskers was the same as that for SiC whiskers. The growth direction of β-Si_3N_4 whiskers was {101-bar0}. And almost no defects could be identified in β-Si_3N_4 whiskers. In SiC/Si_3N_4 composite whiskers, the SiC/Si_3N_4 interface was tatice-lattice direct matching without amorphous layer. |
| Pages | 125 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.imr.ac.cn/handle/321006/17499 |
| Collection | 中国科学院金属研究所 |
| Recommended Citation GB/T 7714 | 周延春. SiC，Si_3N_4晶须的制备方法与显微结构研究[D]. 中国科学院金属研究所. 中国科学院金属研究所,1990. |
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