Selective Infiltration of Fine Pores in Molecular Size by Use of CVI

化学气相渗透现在被用于生产用于航空航天应用的先进材料。它也适用于碳，以提高抗氧化性。本文以电极级石墨、电极级炭、焦炭和活性炭为原料，采用氮气吸附法研究了甲烷热解过程中亚孔（直径<1.5nm）、中孔（d<2nm）和中孔（d<50 nm）的结构变化。这些细孔比大孔（d> 50 nm）的比表面积大，在内烧条件下，氧化主要发生在细孔中，因此认为细孔在氧化动力学中起着重要作用。此外，在氧化过程中，这些孔的打开速率被延迟到原始样品的约1/3。因此，微孔是活性炭和其它炭抗氧化性能提高的主要原因，用压汞仪测量了大孔和细孔的变化，但认为大孔对活性炭抗氧化性能的提高影响不大。

Chemical vapor infiltration is now being used to produce advanced materials for aerospace applications. It is also applicable to carbons to enhance the resisitance against oxidation. In the present study, methane pyrolysis was conducted for several kinds of carbons such as electrode-grade graphite electrode-grade carbon, coke and activated charcoal.The structural change of the fine pores : submicropore (diameter<1.5nm), micropore (d<2nm), mesopore (d<50nm), was investigated by use of nitrogen adsorption method. Those fine pores oreconsidered to have an important role for oxidation kinetics because in the case of inner burning, oxidation is considered mainly to occur in such fine pores due to their larger specific surface area comparing to those of macropores (d>50nm).The measured results indicates that the size of micropores decreases extremely for the infiltrated activated charcoal. Additionally, the opening rate of these pores are retarded to about 1/3 of the original sample during the oxidation. Therefore, it is concluded that the micro pores are attributed to the enhancement of oxidation resistance for activated charcoal as well as other carbons.The change of macropores measured by mercury porosimeter is compared with that of fine pores but is considered to have little effect on the enhancement of resistance.