膨胀石墨的形貌、成分与结构变化研究

Investigation on Variation of Morphology,Composition and Structure of Expanded Graphite

膨胀石墨是重要的工业应用材料,但其微观形貌、成分与晶体结构随膨胀倍率的变化规律认识仍不足。选择H2SO4+HNO3+KMnO4+FeCl3作为插层氧化体系,通过对鳞片原料石墨化学氧化制备出可膨胀石墨,分别在400℃、600℃、800℃、1000℃下膨化处理获得不同的膨胀石墨。针对上述几种石墨,采用OM、SEM、EDS、XRD等技术对比研究了其形貌、成分与结构的变化。结果表明,原料石墨、可膨胀石墨与膨胀石墨分别呈现层片状、褶皱状和蠕虫状的微观形貌,插层物主要由S与O组成,膨胀石墨的S与O含量显著低于可膨胀石墨,且其含量随着膨化温度提高逐渐降低。这些石墨具有相同的密排六方结构,其中可膨胀石墨的晶格常数显著大于原料石墨,反映出插层后石墨结晶度的严重劣化。膨胀石墨的结晶度稍差于原料石墨,但压片处理后得到改善,更高温度膨化的石墨改善更加明显,且优于原料石墨,这预示着高温膨化石墨的应用可塑性更强,具有更好的应用前景。

Expanded graphite （EG）is a type of material with significant industrial applications,but it is neces-sary to grasp the insight into the change of the morphology,composition and crystal structure as its expanding ratio. Different EGs were achieved by the expansion of expansible graphite （EBG）,at 400 ℃,600 ℃,800 ℃ and 1000 ℃respectively,which was derived from chemical oxidation of raw flake graphite （RFG）with H2 SO4 ＋HNO3 ＋KMnO4 ＋FeCl3 as the intercalating and oxidizing system.These different graphites were investigated through the combination of OM,SEM,EDS and XRD techniques.It is shown that the RFG,EBG and EG were formed into lamellar,wrinkle and worm-like shapes respectively.The intercalation agents mainly consisting of S and O were substantially more abundant in the EBG than in the EGs,and meanwhile the contents of S and O in the EGs decreased gradually as the in-crease of expanding temperature applied.Among all these graphites formed into a hcp structure,the crystallinity of the RFG was distinctly better than that of the EBG affected by the intercalation while the crystal lattice constant of the former was much smaller than that of the latter;the crystallinities of the EGs were inferior to that of the RFG,but were able to promote after being suppressed to be higher than the latter and the promoted crystallizing quality became higher and higher when increasing the expansion temperature,predicting that the EG produced by high temperature expansion would possess improved fabricability for broader perspective application.