在室温条件下,以不同浓度的HNO_3溶液(质量分数分别为10,20,30 and 40%)为氧化介质处理沥青球,而后直接进行高温炭化处理,利用FT-IR、XPS、SEM和元素分析表征HNO_3氧化沥青球及其炭化样的化学结构和表面形貌.结果表明:用30% HNO_3氧化12 h的沥青球在900 ℃高温炭化后能够保持良好的球形度和表面形貌;HNO_3处理引入的-NO_2官能团在400 ℃前转化为胺基,促进了沥青分子的交联,保证了沥青球炭化过程的顺利进行;当炭化温度为900 ℃时,胺基进一步发生了环化和芳构化反应,氮原子以吡啶氮和季氮形式存在.
Pitch spheres were stabilized by HNO_3 oxidation at room temperature using HNO_3 solutions of 10,20,30,and 40% mass fraction.The chemical structure and morphology changes of the oxidized pitch spheres and their carbonized samples were investigated by FT-IR,XPS,elemental analysis,and SEM.Results showed that the pitch spheres oxidized by 30% HNO_3 for 12 h could be carbonized at 900 ℃ to produce carbonized spheres without any change in shape.The successful carbonization can be ascribed to the contribution of nitrogen functional groups in the form of -NO_2,which were introduced in the HNO_3 oxidation process.In the early stage of the heat treatment around 400 ℃,the transformation of -NO_2 groups to amine groups occurred,which promoted the cross-linking of pitch molecules.As the pitch spheres were carbonized at 900 ℃,cyclization and aromatization reactions led to the formation of pyridine and quaternary nitrogen groups.
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