R&D of Highly Oriented Graphite Block made from Graphitization of Multi-Polyimide Films with Addition of Guest Element

为了获得高性能的石墨单色器，在聚酰亚胺薄膜中添加和掺杂硼或稀土元素，制备了高取向石墨块。从第一年的研究中发现，在1500 ℃-2500 ℃热处理时，添加硼或镧的聚酰亚胺薄膜的石墨化比未添加的薄膜进行得更多，但添加的薄膜的取向度略有下降。厚度为25 μ m的较薄的膜比厚度为125 μ m的膜的结晶度和取向性好得多。在第二年的研究中，采用热压法制备了高取向石墨块。在石墨模具中放置硼或镧的多层聚酰亚胺薄膜，在真空条件下于1500 ℃退火，然后在热压条件下于2000 ℃热处理。硼或镧的加入也加速了石墨化程度。膜与膜之间的连接比没有添加客体元素的膜更好。在热压条件下，硼或镧原子的扩散促进了膜间的连接。热压后的样品在常压条件下于2500 ℃再次热处理以获得高石墨化度。然而，观察到膜之间的一些分离。本研究为高性能石墨单色仪的研制提供了新的工艺。如何获得无缺陷的高取向石墨块是今后的研究方向。

Fabrication of highly oriented graphite block was carried out from polyimide films with addition and doping of boron or rare earth elements for the purpose of obtaining a high performance graphite monochrometer. From the research of the first year it was found that graphitization of polyimide films with addition of boron or La proceeded more than the films with no addition by heat treatment at 1500ﾟC - 2500ﾟC.But degree of orientation was degraded slightly for the films with addition. Thinner film of 25 mum in thickness was much better for crystallinity and orientation than those film with thickness of 125mum. In the research of the second year fabrication of highly oriented graphite block was fabricated by hot-pressing method. Multi-layrs polyimide film with addition of boron or lanthanum was set in a graphite mold and carbonized at 1500ﾟC under vacuum condition, and then heat-treated at 2000ﾟC under hot-press coundition. Degree of graphitization was also accelerated by boron or lanthanum addition. Joining between films was better than the films without guest element addition. Joining between films was thought to be promoted by diffusion of boron or lanthanum atoms under hot-press condition. After hot pressing the sample was heat-treated again at 2500ﾟC under normal pressure condition for obtaining high degree of graphitization. However, some separation between films was observed. New processing for highly performance graphite monochrometer could be developed through this research. To obtain perfect highly oriented graphite block without any flaw is future research subject.